Environmental Application, Fate, Effects, and Concerns of Ionic

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Environmental Application, Fate, Effects and Concerns of Ionic Liquids: A Review Meseret Amde, Jing-fu Liu, and Long Pang Environ. Sci. Technol., Just Accepted Manuscript • Publication Date (Web): 07 Oct 2015 Downloaded from http://pubs.acs.org on October 7, 2015

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Environmental Science & Technology

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Environmental Application, Fate, Effects and

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Concerns of Ionic Liquids: A Review

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Meseret Amde,†,§ Jing-Fu Liu,*,†,‡ and Long Pang#

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Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing 100085, China

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China

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§

State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-

Institute of Environment and Health, Jianghan University, Hubei Province, Wuhan 430056,

College of Resources and Environment, University of Chinese Academy of Sciences, Beijing

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100049, China

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No. 166, Science Avenue, Zhengzhou 450001, China

Department of Material and Chemical Engineering, Zhengzhou University of Light Industry,

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* Corresponding author: E-mail: [email protected]

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Tel: +86-10-62849192

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Fax: +86-10-62849192

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ABSTRACT

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Ionic liquids (ILs) comprise mostly of organic salts with negligible vapor pressure and low

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flammability that are proposed as replacements for volatile solvents. ILs have been promoted as

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“green” solvents and widely investigated for their various applications. Although the utility of

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these chemicals is unquestionable, their toxic effects have attracted great attention. In order to

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manage their potential hazards and design environmentally benign ILs, understanding their

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environmental behavior, fate and effects is important. In this review, environmentally relevant

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issues of ILs, including their environmental application, environmental behavior and toxicity are

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addressed. In addition, also presented are the influence of ILs on the environmental fate and

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toxicity of other co-existing contaminants, important routes for designing non-toxic ILs and the

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techniques that might be adopted for the removal of ILs.

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1. INTRODUCTION

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Ionic liquids (ILs), which are mostly organic salts made of organic cations and organic/inorganic

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anions that are liquids at room temperature, have gained wide recognition as novel solvents for

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various applications especially as a medium for organic synthesis and catalysis.1-5 Many ILs have

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been synthesized from organic cations like imidazolium, pyridinium, phosphonium,

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pyrrolidinium, piperidinium, morpholinium and cholinium. For instance, over 30,000

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imidazolium salts are collected in the CAS database.6 A potentially large number of ILs could be

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prepared by varying the cations and anions combination.7,8 Nowadays, many ILs covering a wide

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range of properties are now commercially available.

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ILs have unique properties including negligible vapor pressure, good thermal stability,

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non-flammability, a wide electrochemical (conductivity) window, tunable miscibility, and good

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extraction capability for various analytes. These exceptional properties merit their potential

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applications.9-15 ILs are widely applicable in extraction, absorption and degradation processes.16-

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20

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distribution coefficients, which may indicate possible applications in heavy metal pollution

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remediation. As an example, the addition of ILs (1–5 wt%) to a diphenyl (dibutyl)

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carbamoylmethylphosphine oxide solution enhance the extraction coefficients of americium from

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nitric acid.24

Task-specific ILs have been also synthesized for metal extraction in water8,21-23 with higher

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Because of their low volatility, atmospheric pollution due to these chemicals is unlikely.

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However, due to their significant solubility in water,25 ILs may enter into the environment

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through industrial wastewater. Consequently, researchers are more concerned about their

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potential impacts on the aquatic and terrestrial environments. To disclose the possible toxic

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effects of ILs, different model organisms have been considered and the toxicity data have been

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extensively reported along with the traditional solvents,26-31 indicating the possible toxicity of

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ILs to the environment. Even though numerous toxicity studies have been published, only few

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review papers have been published.32-34 More importantly, a lot of works have been reported

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since the publication of the most recent review,34 while environmental factors affecting the

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toxicity of ILs like dissolved organic matter (DOM) and salinity were not addressed in previous

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reviews.

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In this paper, we focus on the environmentally relevant issues of ILs, including (i) the

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environmental applications, processes and toxicity of ILs; (ii) the effects of ILs on the fate and

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toxicity of other contaminants; (iii) approaches for designing “green” ILs; and (iv) techniques

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that might be adopted for the removal of ILs.

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2. ENVIRONMENTAL APPLICATION

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2.1. Enrichment of Environmental Pollutants for Analytical Purpose. ILs have been applied

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in sample treatment and pre-concentration processes like single drop microextraction,35-41 hollow

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fiber liquid-phase microextraction,42,43 dispersive liquid-liquid microextraction44-53 and solid

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phase (micro)extraction.54-59 A recent review15 has provided fundamentals, advances, and

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perspectives of ILs in analytical chemistry with detail information.

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IL-based sample pretreatment methods have been applied for the extraction of organic

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analytes like substituted benzene derivatives,60 biofuels,61 polycyclic aromatic hydrocarbons

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(PAHs),35,55,62,63

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antibiotics.46,50,66 Ordinary and task-specific ILs have also been used for the extraction of

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inorganic pollutants.67-70 The superior roles of ILs in analytical and separation sciences have

phenolic

compounds,64

pesticides,16,41,44,53,56,65

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bactericides,48

and

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been well documented elsewhere,15,35,71-77 thus the details are not addressed herein. However, we

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tabulated these applications for quick overview (Table S1).

94 95

2.2. Removal of Environmental Contaminants. Heavy metal pollution has given rise to

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various environmental problems, especially in areas with high anthropogenic stress,78,79 and

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various remedial techniques involving the application of ILs have been reported. 1-Butyl-3-

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methylimidazolium hexafluorophosphate ([C4MIM][PF6]) was found to be effective (80 – 95%

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within ~2 min) for the removal of Cu2+, CuO, and Cu0.80 Kalidhasan et al. proposed the use of

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ultrasound in conjunction with Aliquat 336 IL impregnated Dowex 1×8 resin for effective

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adsorption (efficiency, ≥97%) of Cr (VI).81 Zhang et al.82 suggested the use of ILs for

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biotreatment of uranium. The glucaminium-based ILs was found to be applicable for the removal

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of boron from water.49 1-Dodecyl-3-methylimidazolium chloride ([C12MIM][Cl]) and 1-

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hexadecyl-3-methylimidazolium chloride ([C16MIM][Cl]) were adsorbed on a high charge Ca-

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montmorillonite for the removal of chromate (2.6 mM) from water with high adsorption

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capacity (190 mmol/kg) and efficiency (99.5%).83

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Water soluble organics were separated from produced water, waste water in the extraction

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process of oil/gas, using hydrophobic ILs in aqueous solution.84 Trihexyltetradecylphosphonium

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tetrachloroferrate (III) was proposed for the removal of phenolic compounds efficient extraction

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and removal efficiency.64 ILs were immobilized on to porous ceramic membranes for the

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removal of dioxins from high temperature vapor streams.85 The extraction and removal of

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anionic dyes like methyl orange, eosin yellow and orange G from aqueous phase were achieved

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with imidazolium-based ILs.17

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ILs have also been investigated for the removal of various organic contaminants from soils.

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[C4MIM][PF6] and [C4MIM][Cl] were employed for the extraction of DDT, dieldrin,

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hexachlorobenzene, and pentachlorophenol from glacial till soil and montmorillonite. While

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[C4MIM][PF6] was found to be effective for their extraction from the montmorillonite, both ILs

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were effective for soils possessing abundant organic matter.16 Ma and Hong reviewed the

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potential applications of ILs to control and recycle organic pollutants in waste gas, waste water,

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solid waste and contaminated soils.86

121 122

3. FATE AND TRANSPORT OF ILs IN ENVIRONMENT

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The low volatility of ILs make them an attractive alternative to volatile organic solvents, as they

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are unlikely to act as air contaminants even though some ILs can be distilled at low pressure

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without decomposition.87 However, ILs could contaminate environmental recipients like soils,

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sediments, surface and ground water. Some ILs are relatively stable in environment due to their

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resistant to photodegradation88 and small degree biodegradation,89 though their degradability can

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be modified.90 Therefore, it is essential to have a comprehensive understanding of their fate,

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transport and transformation in terrestrial and aquatic systems (Figure 1).

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3.1. Adsorption Behavior of ILs in Terrestrial System. Some studies have investigated the

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adsorption behavior of ILs to soil and sediments,83,91-95 and proposed different adsorption

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mechanisms. Mrozik et al. reported that for the sorption of imidazolium ILs onto kaolinite, ion-

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exchange and van der Waals interactions are primarily responsible at the beginning of the

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binding process, whereas the later becomes dominant at higher concentrations.92 Another report

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also disclosed that the ionic interaction can affect the sorption and desorption of ILs in soil.93 The

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sorption of [C12MIM][Cl] and [C16MIM][Cl] on montmorillonite was found to be through cation-

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exchange at lower initial concentration (CMC).83 Normally, the sorption mechanism of ILs to soil/sediment depends on their physico-

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chemical properties, including a diversity of sorption related properties of the soil/sediment (e.g.

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organic matter content, accessibility of sorption sites, ion exchange domains) and ambient

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parameters (e.g. temperature and salinity). Markiewicz et al. suggested that processes like

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adsorption of monomers with alkyl chains, formation of small aggregates, and formation of a

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double layer are involved in the adsorption of imadazolium ILs.96

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The sorption strength depends on the physicochemical properties of the IL, which in various

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ways is dependent on their chemical structure. Insignificant effect of side chain length was

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reported by Beaulieu et al. using imidizolium-based ILs ([CnRIM][X] (R=H/CH3; n=4,6 and 10;

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X=Cl/Br)) and four types of aquatic sediments. Rather, the positive charge could cause ILs to

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adsorb onto the sediments via electrostatic interactions. The hydrogen atoms on the imidazolium

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ring can form hydrogen-bonds with the polar moieties in sediment organic matter (SOM).91

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Contrasting to this, hydrophobic long chained ILs were found to adsorb much more strongly than

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hydrophilic ILs92,95 and ILs with short and/or hydroxylated derivatives, which are more mobile in

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soils/sediments and therefore probably could be released more readily to surface/ground

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waters.95 The adsorption of ammonium-, phosphonium- and pyrrolidinium-based ILs with

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single/quaternary substitution were tested on soils by Mrozik et al.97 and at lower concentrations,

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single alkyl chained ILs adsorbed more strongly (especially with soils having higher cation

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exchange capacity) than the quad-substituted. On the other hand, because of the double-layer

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formation and induced stronger dipole interaction with previously sorbed molecules, the quad-

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substituted ILs interacted more strongly at higher concentrations, with sorption coefficients

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between 16.8 mL/g (tetrabutylphosphonium chloride) and 1.1 mL/g ([C4MIM][Cl]). This

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indicates that high levels of substitution can also affect the transport of ILs in soil/sediments.

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Soils and aquifer materials with low pH showed limited availability of negatively charged

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active sites that are responsible for electrostatic interaction with IL cations. Contrarily, low pH

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values promote the sorption of anions by anion exchange owing to the formation of neutral and

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positively charged surface sites.98 Increasing pH leads to the deprotonation of anionic soil

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surfaces, enhancing the cation exchange capacity. However, as reported by Gorman-Lewis et

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al.,99 [C4MIM][Cl] adsorb neither onto Bacillus subtilis nor gibbsite (pH 6 – 10) and may travel

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unimpeded to groundwater in areas dominated with these surfaces. Clay minerals typically

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exhibit both pH-dependent and pH-independent sorptions.100 The pH-dependent sorption occurs

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through site-specific surface complexation reactions involving clay edge sites, similar to

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reactions that occur on oxide surfaces.101 The pH-independent sorption occurs through cation-

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exchange reactions in the interlayer, and form electrostatic interactions from the permanent

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charge on the clay.102 In the work of Mrozik et al., the existence of lower sorption potency in

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lower pH was reported.95

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For soils with higher organic carbon (OC), the strong bonding of ILs to soil matrices can

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reduce the migration of the solutes to the solution.94 In a recent study, high affinity of humic acid

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(HA) towards ILs in aqueous solutions was reported.103 Our group also found that the sorption of

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[C4MIM][Cl] and [C8MIM][Cl] to HA significantly reduce their freely dissolved concentration

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and bioavailability.104

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3.2. Transfer Behavior of ILs in Aquatic System. Alkylimidazolium cation, [CnMIM]+, is the

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most widely used IL cation. It has received much attention because of its amphiphilic properties,

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such as aggregation, which is analogous to short-chain cationic surfactants. The aggregation

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behavior of [CnMIM]+-based ILs in aqueous solution has been investigated by Bowers et al.105

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Their result illustrated that [C4MIM][BF4] can be modelled as a dispersion of polydisperse

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spherical aggregates above critical aggregation concentration (CAC), while ILs with longer-

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chain, [C8MIM][I], can be modeled as a system of regularly sized near-spherical charged

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micelles that form above the CMC. However, varying the anions may affect their aggregation

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behavior. Ghasemian et al.106 investigated the effect of electrolytes on surface tension and surface

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adsorption of [C6MIM][Cl] in aqueous solution. From the surface and bulk properties of ILs,

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they revealed that ILs behave surfactant-like and aggregate in aqueous solution, and the

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electrolytes reduce surface tension and CAC of the ILs. Singh and Kumar107 illustrated that the

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aggregation properties of ILs depend on the aromatic ring, alkyl chain length, counter ions, and

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their interaction with water, which agree with the report of Bowers et al.105 As reported by Sastry

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et al.108 on the aggregation behavior of short chain pyridinium-based ILs in water, CAC values

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and area per adsorbed molecule decreases as the alkyl chain length decreases.

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3.3. Degradation of ILs in the Environment.

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3.3.1. Biodegradation. Microorganism based degradation method seems more friendly to the

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environment.109 Coleman and Gathergood90 presented a comprehensive review on ILs

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biodegradation, including methods for the biodegradation assessment, trends observed for

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structurally related ILs, and applications of biodegradable ILs in synthetic chemistry. ILs are

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classified as “readily biodegradable”, corresponding to Organization for Economic Cooperation

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and Development (OECD) standards, for which ≥60% biodegradation level is required in 28

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days.110 Besides, full biodegradation should yield completely non-toxic products.90 Gathergood

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and Scammells89 reported the first investigation on the biodegradability of dialkylimidazolium

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ILs. Imidazolium-based ILs can also be partially degraded in aerobic aqueous solution inoculated

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with soil-bacteria.111 Roughly, protic ILs exhibited higher biodegradability (57 – 95% in 28 days)

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than ordinary aprotic ILs (0.61 – 1.33%) in water.112 In general, ILs showed weak

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biodegradability in the environment and also determination of the degradation products is not

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straight-forward. Therefore, most studies on this area were carried out based on the active slurry.

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This has been addressed under artificial methods for the removal of ILs in this paper.

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3.3.2. Abiotic Hydrolysis. The abiotic hydrolysis of ILs have been studied in relation to anions,

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and the formation of different products have been reported. Hydrolysis of [PF6]- has been

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reported to form volatiles such as HF, [POF3]-, [PO2F2]- and [PO3F2]-.113 Besides,

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[C4MIM][F·H2O] has been identified as one of the hydrolysis products of [C4MIM][PF6] during

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its purification process.114 Baker and Baker115 studied the relative intrinsic hydrolytic stabilities

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of [C4MIM][BF4], [C4MIM][PF6], [C6MIM][(C2F5)3PF3] and [C4MPyr][Tf2N]. Their results

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showed that [C4MIM][BF4] exhibit the fastest degradation kinetics, presumably due to intimate

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contact with water. In contrast, [(C2F5)3PF3]- and [Tf2N]- have shown excellent hydrolytic

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stabilities because the C-F bond is relatively inert to hydrolysis under mild conditions,116 and

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[(C2F5)3PF3]- performed even better than [Tf2N]-. Both [(C2F5)3PF3]- and [Tf2N]- underwent

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hydrolysis after one week at 50 oC,115 which indicates that the anion decomposition may be

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slowed/halted under low temperature. Besides, Steudte et al. studied the hydrolytic stability of

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[N(CN)2]-, [C(CN)3]-, [B(CN)4]-, [(CF3SO2)2N]-, [(C2F5)3PF3]- and [H(C2F4)SO3]-,117 and their

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half-life was reported to be about 1 year at 25 oC and pH 7 – 9.

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Generally, ILs with good hydrolytic stability are desired in industrial applications. However,

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it is not important from ecotoxicity point of view as abiotic hydrolysis inhibit the transport of IL

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anions in aquatic ecosystem, and decreases their ecotoxicity. Besides, the profile of hydrolysis

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products of each anion should be investigated to manage/control the formation/side effects of

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hazardous metabolites.

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4. ENVIRONMENTAL EFFECTS OF ILs

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The toxicity of ILs depends on their interaction with cellular membranes,118-120 which is mainly

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dependent on the ILs type (alkyl chain length, cation family and anion moiety) and morphology

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of the model organisms.120-122 Hitherto, various biological organisms have been utilized as

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representative model organisms (Table S2 – S7). In this section, we discuss ILs toxicity related

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issues.

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4.1. Traditional Solvents vs ILs. ILs have been considered as “green” solvents relative to

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traditional solvents. However, toxicity studies on bacteria,27,123 invertebrates,26,30 algae28-31 and

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cell lines27,118 indicated that they can be equivalent in toxicity, or even more toxic, than

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traditional solvents.

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The biological effects of alkylimidazolium ILs to Vibrio fischeri (logEC50/µM, -0.182 – 3.94)

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were found to be higher than acetone, acetonitrile, methanol, and methyl tert-butyl ether

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(logEC50/µM, 3.89 – 7), except methyl tert-butyl ether which has similar toxicity (logEC50/µM,

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3.89) with the least toxic IL, [C3MIM][BF4], (logEC50/µM, 3.9).27 [C8MIM][Br], [C8MPy][Br]

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and [C6MIM][Br] were reported to be more toxic (EC50, 1.17 – 6.44 mg/L) to the bacteria than o-

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xylene, phenol, toluene, methyl isobutyl ketone, benzene, ethylene glycol, chloroform,

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dichloromethane, ethyl acetate, acetone and methanol (EC50, 9.25 – 101068.5 mg/L).123 In the

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work of Hernandez-Fernandez et al., the toxic effects of [C4MPheIM][MeSO4], [C4MIM][H2SO4]

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and [C4MPy][BF4] (EC50, 7.60 – 30.93 mg/L) were reported to be comparable to that of toluene

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(EC50, 31.94 mg/L) and higher than that of chloroform (EC50, 1193.80 mg/L).124

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The LC50 (mg/L) values of imidazolium-based ILs towards Daphnia magna indicated that

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the ILs are similar in toxicity (8.03 – 19.91) to ammonium (2.90 – 6.93) and phenol (10 – 17),

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but more poisonous than trichloromethane (29), tetrachloromethane (35), benzene (356 – 620),

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methanol (3289) and acetonitrile (3600).26 Wells et al. also found that the toxicities of ILs

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towards Daphnia magna and Selenastrum capricornutum were about 104 – 106 times higher than

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that of methanol.30

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A toxicity study of [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br] on Scenedesmus

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quadricauda and Chlamydomonas reinhardtii showed that these ILs are more/as toxic (EC50,

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0.005 – 13.23 mg/L) than/as acetone, benzene, toluene and phenol.28 The toxicity of

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[C4MIM][Br], [C4MPy][Br], 1-butyl-1-methylpyrrolidinium bromide, tetrabutylammonium

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bromide and tetrabutylphosphonium bromide (logEC50/µM, 2.35 – 4.09) were also reported to be

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2 – 4 orders of magnitude greater than methanol, dimethylformamide and 2-propanol

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(logEC50/µM, 4.37 – 5.85) towards Selenastrum capricornutum.29 The photosynthesis inhibitory

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effects (EC50, mM) of selected imidazolium ILs (3.47 – 23.99, except [C3MIM][Br] which

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showed a value of >1000) and pyridinium (0.055 – 53.7) on Pseudokirchneriella subcapitata was

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found to be higher than methanol (2570), dimethyl-formamide (2089) and 2-propanol (589).31

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Ranke et al. presented the biological effects of imidazolium ILs in leukemia cells (IPC-81)

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and glioma cells (C6), and their toxic effects were reported to be higher than the toxicity of

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acetone, acetonitrile, methanol, and methyl t-butyl ether.27,118

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4.2. Factors Affecting the Toxicity of ILs

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4.2.1. Effect of Structural Modification. The structural composition of the IL, including the

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cation, alkyl chain length and anion can affect the degree of its toxicity.122,125,126 The summary of

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structural modification effect is presented in Figure 2.

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4.2.1.1. Effect of Cations. Based on LC50 (mg/L) values of [C4MIM][PF6] (19.91) and

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[C4MIM][BF4] (10.68), and their corresponding sodium salts, NaPF6 (9344.81) and NaBF4

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(4765.75), towards Daphnia magna, Bernot et al.26 concluded that the toxicity of ILs is explicitly

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associated to the cation entity. A mathematical model-based study on the toxicity of ILs to

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Daphnia magna by means of quantitative structure activity relationship, also indicated that

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cations contribute significant percentage (12 – 48%) to the total toxicity.127 The trend of IL

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toxicity with cation variation is shown in Figure 2.

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Stock et al. presented the inhibition effect of imidazolium, pyridinium and phosphonium ILs

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to acetylcholinesterase, and cations bearing positively charged nitrogen and certain lipophilicity

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inhibited the test organism (Table S2). Specifically, pyridinium-based ILs, [C4MPy][BF4] (EC50,

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34 µM) and [C4MPy][PF6] (EC50, 28 µM), were found to be more toxic than their corresponding

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imidazolium-based ILs, [C4MIM][BF4] (EC50, 105 µM) and [C4MIM][PF6] (EC50, 140 µM).128

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Pyridinium-based ILs were also reported to be slightly more toxic than imidazolium-based ILs

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towards Vibrio fischeri.123 Dicationic cholinium-based ILs showed significantly lower toxicity to

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Vibrio fischeri than monocationic counterparts.129 Similarly, inferior toxicity due to cholinium-

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based ILs (LC50, 2.896 – 9.517 mM) towards Artemia salina was reported in comparison to the

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toxicities of imidazolium and pyridinium ILs (LC50, 0.079 – 0.117 mM).125 The pyrrolidinium-

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based ILs exhibited lower toxicity (EC50, 4588.85 – >29130 mg/L) than imidazolium- and

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pyridinium-based ILs (EC50, 7.6 – 505.64 mg/L) towards Vibrio fischeri.124

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Petkovic et al. assessed the toxicity of sixteen ILs having various head groups towards fungi

301

and the imidazolium-based ILs were found to be the most toxic, followed by pyridinium-,

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pyrrolidinium- and piperidinium-based ILs, while cholinium-based ILs were the least in

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toxicity.130 However, similar toxicity of [C4MIM][Cl] (EC50, 930 – 3742 mg/kg) and [C4MPy][Cl]

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(EC50, 588 – 2890 mg/kg) towards Allium cepa, Lolium perenne and Raphanus sativus plants

305

have been reported.131 This indicates that the toxicity is also affected by susceptibility of the

306

model organisms.

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Bado-Nelles et al.132 reported lower toxicity of imidazolium-based ILs (EC50, 17.3 – 300.8

308

mg/L) than phosphonium-based (EC50, 0.053 – 130.7 mg/L) to Daphnia magna. In the work of

309

Costello et al., pyridinium-based (LC50, 21.4 – 901 mg/L) and imidazolium-based (LC50, 21.8 –

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1290 mg/L) ILs were found to have similar toxicities towards Dreissena polymorpha.133 Choline-

311

based ILs (LC50, 2.896 – 9.001 mM) exhibited lower toxicity on Artemia salina than

312

imidazolium (LC50, 0.079 – 0.114 mM) and pyridinium (LC50, 0.086 – 0.117 mM) ILs.125 A

313

similar toxicity trend was obtained using human cell HeLa.125

314 315

4.2.1.2. Effect of Side Chain Length. The toxicity of ILs has strong correlation with its

316

lipophilicity which may affect their interaction with the surface of the model organisms.128,134 In

317

the work of Stock et al.128 IL with longer alkyl chain length, [C10MIM][BF4] (EC50, 13 µM),

318

showed stronger inhibition to acetylcholinesterase than that of [C3MIM][BF4] (EC50, 189 µM).

319

The proposed toxicity mechanism involves the choline cation binding to the anionic site of the

320

enzyme, such that longer side chain results in an improved fit. Similarly, 105 and 46 µM EC50

14 ACS Paragon Plus Environment

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321

values were reported for the inhibitory effects of [C4MIM][BF4] and [C8MIM][BF4] ILs,

322

respectively towards acetylcholinesterase.134

323

Considering bacterial model organisms (Table S3), the direct correlation between toxicity

324

and lipophilicity of ILs was validated by high susceptibility of the Gram-positive bacterial strains

325

compared to the Gram-negative strains, largely because the former has thicker and more

326

hydrophobic cell wall.135 However, while assessing the antimicrobial activity of imidazolium ILs,

327

Docherty et al. noticed that Gram-positive was both the most and the least resistant strain, but the

328

toxicity nevertheless increased with alkyl chain length.123 In a recent study, Gram-positive

329

Listeria monocytogenes was also found to be more tolerant towards ILs induced toxicity than

330

Gram-negative Escherichia coli. Such strong distinctions in terms of susceptibility might be

331

attributed to the bacterial strategies like efflux pumps, cell membrane variations and increased

332

osmolyte production against stress.136 Increase in ILs toxicity towards Vibrio fischeri was

333

observed with alkyl chain length from [C3MIM][BF4] (logEC50/µM, 3.94) to [C10MIM][BF4]

334

(logEC50/µM, -0.182) except for [C5MIM][BF4] (logEC50/µM, 3.14) and [C6MIM][BF4]

335

(logEC50/µM, 3.18) which had similar toxicity.27 The toxicities of [C4MIM][Cl] (logEC50, 3.39

336

µM), [C6MIM][Cl] (logEC50, 2.18 µM) and [C8MIM][Cl] (logEC50, 0.94 µM) to the Vibrio

337

fischeri supports the trend of direct association between side chain length and ILs toxicity.137 In

338

the work of Peric et al., a long chain IL, [C8MIM][Cl] (EC50, 0.5 mg/L), also exhibited greater

339

toxicity than [C4MIM][Cl] (EC50, 278 mg/L) to Vibrio fischeri.112 Markiewicz et al. also reported

340

elevated ILs toxicity towards activated sludge communities with the elongation of the alkyl

341

chain.138 Toxicities of cholinium-based ILs and its derivatives towards Vibrio fischeri was found

342

to exacerbate with the alkyl/linkage chain length, the number of hydroxyethyl groups and the

343

insertion of carbon–carbon multiple bonds.129 Using bioluminescent bacteria, Ventura et al. also

15 ACS Paragon Plus Environment

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344

showed the increase in toxicity of imidazolium- and phosphonium-based ILs with the alkyl chain

345

length.139

346

Using

algae,

the

effect

of

side

chain

length

on

ILs

toxicity

has

been

347

investigated.28,30,31,112,121,140-142 According to the toxicity data, the cation lipophilicity was found

348

to be a dominant factor influencing the overall toxicity (Table S4). The work of Kulacki and

349

Lamberti indicated increase in the toxicity of imidazolium-based ILs to Scenedesmus

350

quadricauda (EC50, 0.005 – 13.23 mg/L) and Chlamydomonas reinhardtii (EC50, 4.07 – 2138

351

mg/L) with alkyl chain length.28 A high correlation (R2 ≥0.9837) between the EC50 values of

352

[CnMIM]+ ILs towards Chlorella vulgaris and Oocystis submarina with the number of carbons in

353

the alkyl chain was reported.121 The toxicity of [CnMIM][Cl] (n=2,4,6,8 and 10) towards

354

Bacillaria paxillifer (EC50, 0.99 – 34.4 µM) and Geitlerinema amphibium (EC50, 0.02 – 30.9 µM)

355

was also positively affected by the alkyl chain length.143 Similarly, Chen et al. investigated the

356

toxicity of [C4MIM][Cl] (EC50, >1000 µM), [C6MIM][Cl] (EC50, 118.78 µM), [C8MIM][Cl]

357

(EC50, 12.69 µM) and [C10MIM][Cl] (EC50, 0.34 µM) towards Scenedesmus obliquus in which

358

the trend of chain length effect on the toxicity can be easily explored from the EC50 values.142

359

An increase in ILs toxicity towards human carcinoma with IL side chain length was also

360

reported.144 The toxicity of [C4MIM][PF6], [C4MIM][BF4], [C4MIM][Br], [C4MIM][Tf2N],

361

[C5MIM][Tf2N], [C7MIM][Tf2N] and [C10MIM][Tf2N] towards a fish cell line was obtained to

362

be moderate to high (EC50, >10 – 4400 µmol/kg) on Folsomia candida also indicated the relationship of an increasing

376

alkyl chain length on ILs toxicity.134 Swatloski et al. employed Caenorhabditis elegans to

377

examine the putative toxicity of [C4MIM][Cl], [C8MIM][Cl] and [C14MIM][Cl], and it was

378

observed that an increase in the alkyl side chain increased lethality. When exposed to 1.0 mg/L,

379

the lethality went from 0% with [C4MIM][Cl] to 11% with [C8MIM][Cl], and then 97% with

380

[C14MIM][Cl].149 Bernot et al. studied the effects of imidazolium- and pyridinium-based ILs on

381

survivorship and behavior (movement and feeding rates) of Physa acuta, and it was found that

382

the LC50 values with Br- and PF6- counter ions ranged from 1 to 325 mg/L. High toxicity was

383

reported for the ILs with eight-carbon alkyl chains and weakened for shorter alkyl chains,

384

indicating a positive relationship between alkyl chain length and toxicity.150 Similarly, the effect

385

of imidazolium- and pyridinium-based ILs on the mortality and feeding of Dreissena

386

polymorpha was reported to cause acute mortality (LC50, 21.4 – 1290 mg/L), and longer alkyl

387

chained ILs were more toxic.133

388

Various aquatic and terrestrial plants have been also used in investigations of the relationship

389

between ILs toxicity and its side chain length (Table S7). Peric et al. investigated the

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390

comparative terrestrial eco-toxicities of protic and aprotic ILs towards Allium cepa, Lolium

391

perenne and Raphanus sativus, in which ILs with longer anion and cation chain length were

392

observed to exhibite higher toxicity. Namely, [C8MIM][Cl] (EC50, 150 – 561 mg/kg) shown high

393

toxicity than [C4MIM][Cl] (EC50, 930 – 3742 mg/kg).131 In the study of [CnMIM][BF4] toxicity

394

towards Triticum aestivum and Lepidium sativum, increment in growth inhibition with alkyl

395

chain length was observed.151 A similar toxicity trend was reported for [CnMIM][BF4] ILs

396

towards Lemna minor and Lepidium sativum plants.152 [CnMIM][Cl] also affected the growth of

397

Lemna minor112 and Lepidium sativum153 plants, and ILs with longer alkyl chain exhibited higher

398

toxicity. Inhibitory effects of imidazolium-based ILs on Hordeum vulgare growth was found to

399

depend on hydrophobicity, whereby the most toxic was [C10MIM][Br], followed by [C7MIM][Br]

400

and [C4MIM][Br].126

401

Generally, increase in chain length escalates the deleterious effect of ILs (Figure 2). This

402

may be due to the increase in the interaction with the organism, or since short chain ILs are the

403

most soluble, giving rise to less sorption to enzymes and hence more rapid excretion. However, a

404

“cut-off effect” was observed with elongation.30,129,141,154 Further elongation of the side chain154

405

or symmetrical chains128,155 resulted in lower activities, since high steric effect may affect ILs

406

interaction with the cell surface.154

407 408

4.2.1.3. Effect of Anions. IL toxicity is mainly affected by the cations and the side chain length.

409

However, in case of less toxic cations, anions have significant contribution to the overall toxicity.

410

Mainly, more lipophilic/unstable anions play a major role in the toxicity of ILs.134,156

411 412

Matzke et al., reported high toxicity of [(CF3)2N]- (EC50, 40 µM) on acetylcholinesterase compared to Cl-, [BF4]-, [C8OSO3]- and [(CF3SO2)2N]- (EC50, 80 – 100 µM) using [C4MIM]+.134

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413

Ranke et al.27 assessed the influence of [BF4]-, Br-, and p-toluenesulfonate on the toxicity of

414

[C4MIM]+ towards Vibrio fischeri and reported 3.55, 3.07, and 3.52 logEC50/µM values,

415

respectively. Similarly, [C10MIM]+ derivatives of Cl- and [BF4]- ILs exhibited 0.5 and -0.18

416

logEC50/µM, respectively.27 Romero et al. reported the presence of anion effect in IL toxicity

417

with logEC50/µM values of 2.18, 2.11, 0.94 and 0.70 for [C6MIM][Cl], [C6MIM][PF6],

418

[C8MIM][Cl] and [C8MIM][PF6], respectively, indicating the higher toxicity of [PF6]- than Cl-.137

419

Monoatomic anions (Br- and Cl-) were found to contribute less effect than large sized anions.157

420

Similarly, Br- (EC50, 3.27 µM) and Cl- (EC50, 3.34 µM) derivatives of [C4MIM]+ exhibited lower

421

toxicity than [BF4]- (EC50, 3.1 µM) and [PF6]- (EC50, 3.07 µM) to Photobacterium

422

phosphoreum.158 In the work of Mester et al., chaotropic anions were reported to affect the

423

chaotropicity of ILs to Listeria monocytogenes and Escherichia coli by enhancing the surfactant

424

like behavior of cations and chaotropicity itself represents cation independent toxicity of ILs.136

425

Markiewicz et al.138 examined the influence of [B(CN)4]-,

426

[(C2F5)3PF3]- on the toxicity of [C2MIM]+ towards activated sewage sludge (municipal WWTP

427

and industrial WWT). Among the anions, [(C2F5)3PF3]- (logIC50/µM, 3.24 and 3.26 for municipal

428

WWTP

429

(logIC50/µM, >5.00 and 4.39 for municipal WWTP and industrial WWT, respectively) were the

430

least toxic.

and

industrial

WWT,

respectively)

were

the

[N(CN)2]-, [(CF3SO2)2N]- and

most

toxic

and

[N(CN)2]-

431

Cho et al. employed Selenastrum capricornutum to figure out the contribution of Br-, Cl-,

432

[BF4]-, [PF6]-, [CF3SO3]-, [C8H17SO4]- and [SbF6]- to the toxicity of [C4MIM]+-based ILs. Except

433

for [PF6]- (EC50, 1318 µM) and [SbF6]- (EC50, 135 µM), all have low effect on the toxicity (EC50,

434

2137 – 2884 µM). The high toxicity of [SbF6]- may be associated to its ability to undergo

435

hydrolysis in water.159 Among [BF4]-, [DCNA]-, [TFMS]-, [MeSO4]- and [MPEGSO4]-

19 ACS Paragon Plus Environment

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436

derivatives of [C4MIM]+, [BF4]- exhibited higher toxicity (EC50, 425.33 and 707.81 µM,

437

respectively) towards Chlorella vulgaris and Oocystis submarina than others (EC50, 930.81 –

438

2650.98 µM and 897.04 – 3292.98 µM, respectively).121 The high toxicity of [BF4]- based IL

439

might be ascribed to fluoride formation during the hydrolysis of [BF4]- which enhanced the toxic

440

effect.121

441

Bernot et al. employed Daphnia magna to evaluate the toxicity of [C4MIM]+-based ILs with

442

Cl-, Br-, [PF6]-, and [BF4]-. Though the toxic effects were comparable (LC50, 8.03 – 19.91 mg/L),

443

the slight toxicity difference is attributed to the anions.26 Garcia et al.158 also reported difference

444

in [C4MIM]+ toxicity with the counter anions using Daphnia magna.

445

Using IPC-81, Stolte et al. reported the contribution of anions to the total toxicity of

446

imidazolium-based IL [C4MIM]+, showing that the anion [CF3SO3]- exhibited more cytotoxicity

447

(EC50, 1000 µM) than [CH3SO3]- (EC50, 3200 µM). While, because of its vulnerability to

448

hydrolysis, [SbF6]- had the highest cytotoxicity (EC50, 180 µM) than [BF4]- (EC50, 1700 µM) and

449

[PF6]- (EC50, 1300 µM)156 that was also observed by Cho et al. using Selenastrum

450

capricornutum.159 The toxicities of [C8MIM]+ and [Choline-Cn]+ ILs exhibited toxicity variation

451

with [FeCl4]-, [GdCl6]3-, [CoCl4]2- and [MnCl4]2- counter ions on human cell lines. Namely,

452

[CoCl4]2- and [MnCl4]2- derivatives are more prone to generate cytotoxicity.160 Compared to Cl-

453

(EC50, 0.74 µM) with the same alkoxymethyl chain, lower cytotoxicity of saccharinates (EC50,

454

4.2 µM) and acesulphamates (EC50, 3.1 µM) to IPC-81was reported161

455

Anions can also affect IL toxicity to plants (Table S7). Biczak et al. reported the presence of

456

anions could influence the [C3MIM]+-based IL toxicity towards spring barley and common

457

radish plants though regularity within the effect was not observed.162 In the work of Bubalo et al.

458

on the effect of [C4MIM]+-based ILs on the growth of Hordeum vulgare, the effect of counter

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Environmental Science & Technology

459

anions was reported to be in the order of Br->[CH3CO2]->[BF4]-.126 Furthermore, toxicity of

460

[NTf2]- to Triticum aestivum was found to be higher than [BF4]-, Cl- and [HSO4]-, and

461

independent of the soil composition.163

462

Generally, some fluorinated anions like [BF4]-, [PF6]- and [SbF6]- usually induce IL toxicity

463

which might be ascribed to their ability to undergo hydrolysis and yield toxic fluoride containing

464

products.121,134,159 Stable anion, [NTf2]-, exhibits over-additive toxicity effects,156 due to its high

465

lipophilic nature could enhance its ability to destruct phospholipid membranes.164 More or less, it

466

can be said that anions do have some contribution to the toxicity of ILs, particularly for shorter

467

alkyl chained ILs.

468 469

4.2.2. Environmental Factors.

470

4.2.2.1. Dissolved Organic Matter. The more an IL is sorbed to a mineral or organic component

471

of soil or (pore)water, the lower the amount of freely-dissolve ILs is present,104 which implies

472

that less of the ILs within the soil or water system will be bioavailable or able to exert toxic

473

effects. The effect of soil organic matter on the toxicity of [C4MIM][BF4] and [C8MIM][BF4] to

474

Triticum aestivum151 and Lepidium sativum151,153 has been reported and the toxicity effect

475

decreases as the amount of organic matter increases. An increase in the total organic matter by 5%

476

was found to reduce by about 50% of [C4MIM][BF4] and [C8MIM][BF4] toxicity at 500

477

mg/kg.151 Similarly, natural DOM was found to slightly reduce the toxicity of imidazolium

478

cations to Lemna minor.165 Our group104 studied the sorption of ILs to DOM and its effects on

479

toxicity of ILs in the presence and absence of HA, and showed that the freely dissolved

480

concentration of [C4MIM][Cl] and [C8MIM][Cl] apparently decreases in the presence 11 µg/mL

481

DOM (the free fraction of the ILs was decreased to 0.85 and 0.79, respectively). This reduction

21 ACS Paragon Plus Environment

Environmental Science & Technology

482

of freely dissolved concentration gave rise to remarkable reduction of bioavailability and

483

therefore toxicity of the ILs, indicating that DOM may play an important role in determining the

484

environmental fate and toxicity of ILs. Some ILs such as [C8MIM][Cl] can form complexes with

485

DOM below the CMC, which not only affects the solubility and bioavailability of IL, but also the

486

solubility and bioavailability of other organic compounds in soil pore water.166 Therefore, the

487

effects of DOM in the system should be taken into account while assessing the fate and potential

488

effects of ILs in environment.

Page 22 of 55

489 490

4.2.2.2. Salinity. Salinity should also be considered while investigating the toxic effects of ILs.

491

There are different mechanisms for the effect of salinity on IL bioavailability and toxicity,

492

including its effect on the solubility of ILs through salting-in or salting-out effects, competition

493

of IL ions with other ions for the interaction with ionic sorption sites on soils and in

494

tissues/enzymes, the roll of IL on micelle (aggregate formation) by the screening effect, and the

495

presence of ion-pairing environment for the IL cations which prevent their interaction with

496

cellular structures. Latala et al.167 investigated the effect of salinity variations on the toxicity of

497

imidazolium ILs towards Oocystis submarina, Chlorella vulgaris, Geitlerinema amphibium and

498

Cyclotella meneghiniana. Their report indicated that increasing the salinity significantly

499

decreases ILs toxicity (eight–ten times in 0 – 32 practical salinity unit (PSU)), which might be

500

due to the reduced permeability of IL cations through the algal cell walls. Similarly, the control

501

cell density of Oocystis submarina was reduced by 50% after 3 days exposure to [C6MIM][Cl],

502

and the cell growth inhibition was only 30% and 10% at salinity of 8 and 16 – 32 PSU,

503

respectively. For [C4MIM][Cl], 30% and 10% inhibition was observed in fresh water and 16 PSU,

504

respectively, while it was unaffected at 32 PSU.168 In contrast, the toxicity of [C4MIM][Cl] to

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Environmental Science & Technology

505

Skeletonema marinoi was reported to be insignificant at 35 (EC50, 0.12 mM), 25 (EC50, 0.1 mM)

506

and 15 PSU (EC50, 0.14 mM) salinities.169 Kulacki and Lamberti28 also reported opposing result

507

to the work of Latala et al.167,168 as difference in IL effects on Scenedesmus quadricauda was not

508

observed between modified water (375 µS) and ground water (742 µS) media. The difference in

509

these studies might be due to the initial conditions, origin and type of the algal strains and the

510

experimental media.

511 512

4.3. Impacts on the Fate and Toxicity of Co-Existing Environmental Pollutants. ILs may

513

affect the fate and transport of co-existing environmental pollutants. Due to the hydration layer

514

on their surface, metal oxides and clays are not effective sorbents for nonionic organic

515

compounds in aqueous system. However, they can adsorb ionic surfactants of opposite charge

516

and therefore neutralize the surface, which enhance the hydrophobic interactions and thus

517

increase the affinity for non-ionic organic compounds.170-173

518

Pino et al.174 investigated the partitioning behavior of aliphatic hydrocarbons, PAHs, phenols

519

and esters to imidazolium-based IL aggregates (partition coefficients, 30 – 5200). Hydrophobic

520

analytes (KOW >300) such as aliphatic hydrocarbons, esters and PAHs are preferably extracted. In

521

a recent study, the release of PAHs and DOM from soil to water by [C8MIM][Cl] was thoroughly

522

investigated and enhanced release of the materials by sub-CMC IL concentration was reported.

523

In addition, due to the dissolution of soil organic matter, high concentration of DOM was also

524

observed upon addition of sub-CMC IL concentrations.166

525

As mentioned earlier, ILs behave as traditional short-chain surfactants and are prone to sorb

526

to minerals and organic matter. Thus, in the study of subsurface transport of contaminants, they

527

can be sorbed to immobile aquifer media and decrease groundwater pollution. Conversely, ILs

23 ACS Paragon Plus Environment

Environmental Science & Technology

528

aggregate and form colloids in aqueous phase, which could sorb organic and inorganic

529

contaminants and increase amount of the contaminants in groundwater.175

Page 24 of 55

530

In the environment, there can be various multi-contaminant cocktails with different

531

compositions and concentrations. Since it is impossible to study the combined effects of all

532

chemical mixtures, two basic concepts, concentration addition (CA) and independent action (IA),

533

have been used to investigate the effect of ILs on toxicity of various pollutants.176-178 CA is a

534

model based on dilution principle and designed for compounds which share similar functional

535

sites, exhibit similar interaction or similar chemical structures. IA is designed for a mixture of

536

dissimilarly acting compounds. In recent reports, other techniques like mixture information179

537

equipartition ray design180 and integrated CA with IA based on multiple linear regression

538

(ICIM)178 models have been proposed.

539

The study on the mixture of ILs and pesticides showed that all binary mixtures exhibited a

540

similar toxicity action rule: a synergistic interaction (more toxic than expected) in high

541

concentration region; an additive action in medium concentration region; and an antagonistic

542

interaction (less toxic than expected) in low concentration region.177,181 Matzke et al. employed

543

CA and IA concepts to investigate the toxic effect of different IL mixtures ([C4MIM][BF4],

544

[C8MIM][BF4] and [C14MIM][NTf2]), and cadmium to Scenedesmus vcuolatus and Triticum

545

aestivum. The authors obtained underestimated toxicity with both CA and IA, which illustrated

546

the presence of interactions among the compounds or the compounds and other constituents.176

547

In a recent study, the combined toxicity of heavy metals and ILs on Vibrio qinghaiensis was

548

investigated using CA, IA and ICIM models.178 As was found by Matzke et al.,176 the combined

549

toxicities were underestimated by CA and IA models but effectively predicted by ICMA.

550

Accordingly, the mixtures exhibited synergism, and ICIM was proposed as appropriate model.178

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Environmental Science & Technology

551

These findings imply that to objectively assess the ecotoxicological risk of ILs, the complex

552

scenarios of mixture toxicity and pre-pollution assessment should be made.

553 554

5. APPROACHES FOR DESIGNING “GREEN” ILs.

555

Structural modification-based approaches, which yield non-toxic and biodegradable ILs can be

556

followed to design more “green” ILs (Figure 3). As initially proposed by Gathergood et al.,182

557

introduction of polar functional groups, to alkyl side chain significantly decreases the

558

toxicity.33,124,139,141,182-185 Besides, substitution of alkyl group with hydrogen in 1-position of

559

imidazole,185 can reduce its toxicity. However, incorporation of a methyl group or a hydroxyethyl

560

group in an imidazolium ring enhances its antimicrobial activity.186 Furthermore, cytotoxicity is

561

strongly dependent on the position of the polar functional group in the side chain (less toxic as

562

distant from the ring).187

563

Benign ILs can also be synthesized using proper cations (e.g. cholinium)129 and anions (e.g.

564

saccarinate/acesulphamate).161,188 The use of aromatic containing cations148,189 and fluorine

565

containing anions189 increase the toxicity. Egorova et al.190 studied the cytotoxicity of several

566

amino acid-containing ILs, with amino acid-based cations and anions towards cell cultures and

567

compared their toxicity with imidazolium-based ILs. Even though functionalization of natural

568

amino acids was considered to reduce the toxicity, the result of this study gave new insight into

569

biological effects of amino acid-containing ILs and showed that an amino acid residue may make

570

ILs more biologically active. Therefore, attention should be paid to the plausible synergetic

571

effect of ILs combination with biologically active molecules.

572

The inhibitory effect of aprotic ILs (EC50, 8.59 – 14.4 mg/L) were reported to be more

573

significant than protic ILs (EC50, 302 – 8912 mg/L) towards acetylcholinesterase.112 Hence,

25 ACS Paragon Plus Environment

Environmental Science & Technology

574 575 576

Page 26 of 55

protic ILs are recommended as environmentally safer ILs. Based on these findings and recommendations, we have compiled important routes of synthesizing relatively less toxic and more biodegradable ILs (Figure 3).

577 578

6. ARTIFICIAL METHODS FOR THE REMOVAL OF ILs

579

To manage the environmental hazards of ILs, various techniques have been proposed as adequate

580

solution for the issue of disposal of ILs. A summary of methods investigated to remove of ILs is

581

presented in Figure 4 and presented below.

582 583

6.1. Adsorption. Adsorption separation technology based on the accumulation of target entities

584

on to solid surfaces has been used in environment cleanup.109,191 Likewise, adsorption has been

585

employed to remove ILs from aqueous solutions using appropriate adsorbents such as activated

586

carbon (AC),192-198 bacterial biosorbents,199 clays,93,99,200-202 ion-exchange resin,203 and

587

aluminum-based salts.204

588

AC has been used as effective, environmental friendly and non-destructive adsorbent for the

589

removal of various ILs in aqueous solution.192-198 Structural and chemical properties of AC can

590

be conveniently modified for efficient adsorption192,195,198,205 via chemical treatments (acidic and

591

basic), impregnation of foreign materials and modification of its physical characteristics. 206 A

592

study on kinetic aspects of ILs adsorption onto AC showed that the relatively low adsorption rate

593

can be efficiently enhanced by decreasing the adsorbent particle size.197 For ACs, adsorbent

594

porosity, pH, temperature and IL entities (cation, chain length and anion) can affect the

595

adsorption efficiency.194,195 The larger average pore diameter facilitates easy diffusion and

596

sorption of ILs. On the other hand, microporous/narrow mesoporous ACs (with high content of

26 ACS Paragon Plus Environment

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Environmental Science & Technology

597

pores and small diameter) presented highest adsorption capacities (up to 1 g/g of imidazolium-

598

based ILs).195 In basic media, main interactions shift from dispersive to electrostatic, which

599

significantly increases the adsorption process.194 The kind of interactions between organic

600

cations and the carbon surface depends on the amount of oxygenated groups and IL type, and the

601

presence of oxygen groups promote electrostatic interaction which is stronger for more

602

hydrophilic cations.194,198,205 Generally, ACs containing high polar functional groups in their

603

surface and with low polarity are recommended for effective adsorption of hydrophilic and

604

hydrophobic ILs, respectively.195,205

605

Won et al.199 employed Escherichia coli biomass for biosorption of [C2MIM]+ from aqueous

606

solution. At optimal pH (7 – 10), fast (10 min) and efficient adsorption (72.6 mg/g) of the cation

607

was reported. Moreover, acetic acid can easily desorb [C2MIM]+ from the biosorbent. Hence,

608

such non-destructive, environmental friendly and cheap adsorbents seem promising but require

609

extensive research for identification of proper biosorbents for the numerous ILs.

610

Choi et al.203 reported the adsorption of [C2MIM]+ by ion-exchange resins possessing

611

different functional groups. Resins with sulfonic acid functional groups showed the highest

612

sorption abilities (578.2 to 616.2 mg/g). Large bead size led to lower kinetics of [C2MIM]+

613

adsorption, and the bead size and degree of cross-linking of the resins insignificantly affected the

614

sorption performance.

615

Pioneering work on adsorption of [C4MIM][Cl], [C8MIM][Cl], 1-allyl-3-methylimidazolium

616

chloride ([AMIM][Cl]), [C4Py][Br] and [C8Py][Br] to Na-montmorillonite (pH 7, at 25 oC) was

617

reported by Reinert et al., and adsorption capacity was found to closely related to nature of the

618

cation and alkyl chain length ([C4Py][Br] > [C8Py][Br]~[AMIM][Cl]~[C4MIM][Cl] >

619

[C4MIM][Cl]). The involved adsorption mechanism is via cation exchange with the interfoliar

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Na+.201 Another researchers also investigated the existence of pH independent adsorption of

621

[C4MIM][Cl] on to Na-montmorillonite.99

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622 623

6.2. Artificial Degradation Methods of ILs. It is likely ILs will entry into the environment,

624

once they are utilized in industrial application. Thus, degradation methods could play essential

625

role to overcome their potential impacts on the environment, and artificial methods (Figure 4)

626

would be an alternate option.

627 628

6.2.1. Activated Sludge Microorganisms Based Degradation. To reduce incineration and landfill

629

wastes, readily biodegradable chemicals should be utilized. Docherty et al.207 examined the

630

biodegradability of imidazolium-based ([C4MIM][Br], [C6MIM][Br], and [C8MIM][Br]) and

631

pyridinium-based ([C4MPy][Br], [C6MPy][Br], and [C8MPy][Br]) ILs using OECD standard test

632

method. In the report, only [C8MPy][Br] can be classified as readily biodegradable (96%

633

degraded within 25 days), and both butyl substituted cations ([C4MIM][Br] and [C4MPy][Br])

634

exhibited 0% degradation in 43 days. However, the ability of microorganisms to degrade

635

[C4MPy][Br] at low concentration (46.7 µM) was reported.208 Another group, Stolte et al.209 also

636

reported the good biodegradability of pyridinium-based ILs bearing an ester containing

637

substituent and longer alkyl chain length. Liwarska-Bizukojc and Gendaszewska evaluated the

638

biodegradability of [C2MIM][Br], [C6MIM][Br] and [C10MIM][Br], and it was found the

639

degradation was inadequate (90%),

729

[C4MPyr][Br] (>80%) and N-butyl-N-methylmorpholinium bromide (>76%) in aqueous solution

730

by US-ZVI/AC with micro-electrolysis system was reported by Zhou et al.,226 and the

731

degradation pathways were suggested based on the detected intermediates.

732

The efficiency of ILs degradation in Fenton/Fenton like systems can be affected by the type

733

of IL, H2O2 concentration and the background ions. The degradation efficiency decreases as the

734

side chain elongates (e.g., >93% for [C2MIM][Br] and 73.7% for [C10MIM][Br]).228 Similarly,

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735

lengthening the alkyl chain [C4MIM][Cl] to [C8MIM][Cl] lowered the ILs degradation from

736

~100% to ~70%, respectively, under similar conditions.230 Change in H2O2 concentration from

737

100 to 400 mM enhanced [C4MIM][Cl], [C6MIM][Cl], [C8MIM][Cl] and [C4MPy][Cl] ILs

738

degradation from 57 – 84% to 87 – 100% within 60 min.230 Stoichiometric H2O2 dose is

739

recommended for effective conversion of imidazolium-based ILs and to avoid toxic effluents

740

from the system.227 Counter anions may affect the degradation efficiency due to their ability to

741

compete with the target cation towards •OH or form complex with the catalyst which hinder the

742



743

the ILs cation, increasing the stability of cations and interacting with the catalyst. Siedlka et al.

744

investigated the influence of counter ions (Cl-, [C(CN)3]- and [CF3SO3]-) and background ions

745

([C6F11O2]-, [C8F15O2]- and [C10F19O2]-) on the degradation of [C4MIM]+-based ILs in H2O2/Fe3+

746

system, and the effect of counter anions on the degradation rate followed Cl->[C(CN)3]-

747

>[CF3SO3]- order.225

OH formation. The background anions may interfere the degradation process by interacting with

748 749

7. SUMMARY AND FUTURE RESEARCH DIRECTIONS

750

ILs have been considered as “green” solvents and have gained numerous environmental

751

applications, though studies on their environmental fate and toxic effects have brought a question

752

on their greenness. The toxic effects of ILs vary considerably across their type, test conditions

753

and morphology of the model organisms. On the whole, it is recommended to create a database

754

of environmentally benign ILs based on their toxicological and biodegradation data, which

755

should play as crucial role in manufacturing non-toxic and degradable ILs. In addition, the

756

following directions typifies the research gap should be worked on. (i) Systematic study on the

757

effects of ILs on the transport and environmental processes of co-existing pollutants like POPs;

33 ACS Paragon Plus Environment

Environmental Science & Technology

758

(ii) Fundamental understanding on the toxicity mechanism (mode of action) of ILs to various

759

organisms; (iii) Conducting the toxic effects and environmental processes of ILs in real

760

environmental conditions rather than controlled laboratory conditions; (iv) The species and

761

toxicity of degradation products and intermediate products of various ILs; (v) Extensive research

762

on the development of techniques for the removal of ILs; (vi) Design and synthesis of

763

environmentally benign ILs from the green chemistry point of view.

Page 34 of 55

764 765

■ ASSOCIATED CONTENT

766

Supporting Information

767

Additional information Tables S1 to S7 have been cited in the text. This material is available free

768

of charge via the Internet at http://pubs.acs.org.

769 770

■ AUTHOR INFORMATION

771

Corresponding Author

772

*Phone: +86 10 62849192; Fax: +86 10 62849192; e-mail: [email protected]

773

Notes

774

The Authors declare no competing financial interest

775 776

■ ACKNOWLEDGEMENT

777

This work was supported by the Strategic Priority Research Program of the Chinese Academy of

778

Sciences (XDB14020101), and the Chinese Academy of Sciences (YSW2013A01,

779

YSW2013B01). Meseret Amde acknowledges the support of CAS-TWAS President’s

780

Fellowship for his PhD study.

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781 782

■ REFERENCES

783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824

(1) Andrade, C. K. Z.; Matos, R. A. F.; Oliveira, V. B.; Durães, J. A.; Sales, M. J. A., Thermal study and evaluation of new menthol-based ionic liquids as polymeric additives. J. Therm. Anal. Calorim. 2010, 99, 539-543. (2) Hallett, J. P.; Welton, T., Room-temperature ionic liquids: solvents for synthesis and catalysis. 2. Chem. Rev. 2011, 111, 3508-3576. (3) Shi, J.; Liu, W.; Wang, N.; Yang, Y.; Wang, H., Production of 5-hydroxymethylfurfural from mono- and disaccharides in the presence of ionic liquids. Catal. Lett. 2013, 144, 252-260. (4) He, L.; Qin, S.; Chang, T.; Sun, Y.; Gao, X., Biodiesel synthesis from the esterification of free fatty acids and alcohol catalyzed by long-chain Brønsted acid ionic liquid. Catal. Sci. Technol. 2013, 3, 1102-1107. (5) Wu, Q.; Wan, H.; Li, H.; Song, H.; Chu, T., Bifunctional temperature-sensitive amphiphilic acidic ionic liquids for preparation of biodiesel. Catal. Today 2013, 200, 74-79. (6) Holbrey, J. D.; Turner, M. B.; Rogers, R. D., Selection of ionic liquids for green chemical applications. In ionic liquids as green solvents; Rogers, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC. 2003, 856, 2-12. (7) Chiappe, C.; Pieraccini, D., Ionic liquids: solvent properties and organic reactivity. J. Phys. Org. Chem. 2005, 18, 275-297. (8) Visser, A. E.; Swatloski, R. P.; Reichert, W. M.; Mayton, R.; Sheff, S.; Wierzbicki, A.; DavisJr, J. H.; Rogers, R. D., Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg2+ and Cd2+: synthesis, characterization, and extraction studies. Environ. Sci. Technol. 2002, 36, 2523–2529. (9) Rantwijk, F. v.; Sheldon, R. A., Biocatalysis in ionic liquids. Chem. Rev. 2007, 107, 2757-2785. (10) Parvulescu, V. I.; Hardacre, C., Catalysis in ionic liquids. Chem. Rev. 2007, 107, 26152665. (11) Pereiro, A. B.; Araújo, J. M. M.; Martinho, S.; Alves, F.; Nunes, S.; Matias, A.; Duarte, C. M. M.; Rebelo, L. P. N.; Marrucho, I. M., Fluorinated ionic liquids: properties and applications. ACS Sustainable Chem. Eng. 2013, 1, 427-439. (12) Khatri, P. K.; Thakre, G. D.; Jain, S. L., Tribological performance evaluation of taskspecific ionic liquids derived from amino acids. Ind. Eng. Chem. Res. 2013, 52, 15829-15837. (13) Ventura, S. P. M.; Gurbisz, M.; Ghavre, M.; Ferreira, F. M. M.; Gonçalves, F.; Beadham, I.; Quilty, B.; Coutinho, J. A. P.; Gathergood, N., Imidazolium and pyridinium ionic liquids from mandelic acid derivatives: synthesis and bacteria and algae toxicity evaluation. ACS Sustainable Chem. Eng. 2013, 1, 393-402. (14) Stolte, S.; Schulz, T.; Cho, C.-W.; Arning, J.; Strassner, T., Synthesis, toxicity, and biodegradation of tunable aryl alkyl ionic liquids (TAAILs). ACS Sustainable Chem. Eng. 2013, 1, 410-418. (15) Ho, T. D.; Zhang, C.; Hantao, L. W.; Anderson, J. L., Ionic liquids in analytical chemistry: fundamentals, advances, and perspectives. Anal. Chem. 2014, 86, 262-285. (16) Khodadoust, A. P.; Chandrasekaran, S.; Dionysiou, D. D., Preliminary assessment of imidazolium-based room-temperature ionic liquids for extraction of organic contaminants from soils. Environ. Sci. Technol. 2006, 40, 2339–2345. 35 ACS Paragon Plus Environment

Environmental Science & Technology

825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869

Page 36 of 55

(17) Pei, Y. C.; Wang, J. J.; Xuan, X. P.; Fan, J.; Fan, M., Factors affecting ionic liquids based removal of anionic dyes from water. Environ. Sci. Technol. 2007, 41, 5090–5095. (18) Ramdin, M.; de Loos, T. W.; Vlugt, T. J. H., State-of-the-art of CO2 capture with ionic liquids. Ind. Eng. Chem. Res. 2012, 51, 8149-8177. (19) Pinto, A. M.; Rodrí guez, H.; Colón, Y. J.; Arce, A.; Arce, A.; Soto, A., Absorption of carbon dioxide in two binary mixtures of ionic liquids. Ind. Eng. Chem. Res. 2013, 52, 59755984. (20) Quijano, G.; Couvert, A.; Amrane, A.; Darracq, G.; Couriol, C.; Cloirec, P.; Paquin, L.; Carrié, D., Absorption and biodegradation of hydrophobic volatile organic compounds in ionic liquids. Water Air Soil Pollut. 2013, 224, 1528. (21) Papaiconomou, N.; Lee, J.-M.; Salminen, J.; Stosch, M. v.; Prausnitz, J. M., Selective extraction of copper, mercury, silver, and palladium ions from water using hydrophobic ionic liquids. Ind. Eng. Chem. Res. 2008, 47, 5080–5086. (22) Zhu, X.; Jiang, R., Determination of iron (III) by room temperature ionic liquids/surfactant sensitized fluorescence quenching method. J. Fluoresc. 2011, 21, 385-391. (23) Zeeb, M.; Ganjali, M. R.; Norouzi, P., Preconcentration and trace determination of chromium using modified ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction: application to different water and food samples. Food Anal. Methods 2013, 6, 1398-1406. (24) Pribylova, G. A.; Smirnov, I. V.; Novikov, A. P., Effect of ionic liquids on the extraction of americium by diphenyl (dibutyl) carbamoylmethyl phosphine oxide in dichloroethane from nitric acid solutions. J. Radioanal. Nucl. Chem. 2013, 295, 83-87. (25) Ropel, L.; Belveze, L. S.; Aki, S. N. V. K.; Stadtherr, M. A.; Brennecke, J. F., Octanolwater partition coefficients of imidazolium-based ionic liquids. Green Chem. 2005, 7, 83–90. (26) Bernot, R. J.; Brueseke, M. A.; Evans-White, M. A.; Lamberti, G. A., Acute and chronic toxicity of imidazolium-based ionic liquids on Daphnia magna. Environ. Toxicol. Chem. 2005, 24, 87–92. (27) Ranke, J.; Mölter, K.; Stock, F.; Bottin-Weber, U.; Poczobutt, J.; Hoffmann, J.; Ondruschka, B.; Filser, J.; Jastorff, B., Biological effects of imidazolium ionic liquids with varying chain lengths in acute Vibrio fischeri and WST-1 cell viability assays. Ecotoxicol. Environ. Saf. 2004, 58, 396-404. (28) Kulacki, K. J.; Lamberti, G. A., Toxicity of imidazolium ionic liquids to freshwater algae. Green Chem. 2008, 10, 104–110. (29) Cho, C. W.; Jeon, Y. C.; Pham, T. P.; Vijayaraghavan, K.; Yun, Y. S., The ecotoxicity of ionic liquids and traditional organic solvents on microalga Selenastrum capricornutum. Ecotoxicol. Environ. Saf. 2008, 71, (1), 166-171. (30) Wells, A. S.; Coombe, V. T., On the freshwater ecotoxicity and biodegradation properties of some common ionic liquids. Org. Process Res. Dev. 2006, 10, 794-798. (31) Pham, T. P.; Cho, C. W.; Min, J.; Yun, Y. S., Alkyl-chain length effects of imidazolium and pyridinium ionic liquids on photosynthetic response of Pseudokirchneriella subcapitata. J. Biosci. Bioeng. 2008, 105, 425-428. (32) Pham, T. P. T.; Cho, C.-W.; Yun, Y.-S., Environmental fate and toxicity of ionic liquids: A review. Water Res. 2010, 44, 352-372. (33) Petkovic, M.; Seddon, K. R.; Rebelo, L. P.; Silva Pereira, C., Ionic liquids: a pathway to environmental acceptability. Chem. Soc. Rev. 2011, 40, 1383-1403.

36 ACS Paragon Plus Environment

Page 37 of 55

870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913

Environmental Science & Technology

(34) Bubalo, M. C.; Radosevic, K.; Redovnikovic, I. R.; Halambek, J.; Srcek, V. G., A brief overview of the potential environmental hazards of ionic liquids. Ecotoxicol. Environ. Saf. 2014, 99, 1-12. (35) Liu, J.-F.; Jiang, G.-B.; Chi, Y.-G.; Cai, Y.-Q.; Zhou, Q.-X.; Hu, J.-T., Use of ionic liquids for liquid-phase microextraction of polycyclic aromatic hydrocarbons. Anal. Chem. 2003, 75, 5870-5876. (36) Marquez-Sillero, I.; Aguilera-Herrador, E.; Cardenas, S.; Valcarcel, M., Determination of 2,4,6-tricholoroanisole in water and wine samples by ionic liquid-based single-drop microextraction and ion mobility spectrometry. Anal. Chim. Acta 2011, 702, 199-204. (37) Marquez-Sillero, I.; Cardenas, S.; Valcarcel, M., Direct determination of 2,4,6tricholoroanisole in wines by single-drop ionic liquid microextraction coupled with multicapillary column separation and ion mobility spectrometry detection. J. Chromatogr. A 2011, 1218, 7574-7580. (38) Vallecillos, L.; Pocurull, E.; Borrull, F., Fully automated ionic liquid-based headspace single drop microextraction coupled to GC-MS/MS to determine musk fragrances in environmental water samples. Talanta 2012, 99, 824-832. (39) Wen, X.; Deng, Q.; Wang, J.; Yang, S.; Zhao, X., A new coupling of ionic liquid basedsingle drop microextraction with tungsten coil electrothermal atomic absorption spectrometry. Spectrochim Acta A Mol. Biomol. Spectrosc. 2013, 105, 320-325. (40) Jiang, C.; Wei, S.; Li, X.; Zhao, Y.; Shao, M.; Zhang, H.; Yu, A., Ultrasonic nebulization headspace ionic liquid-based single drop microextraction of flavour compounds in fruit juices. Talanta 2013, 106, 237-242. (41) Amde, M.; Tan, Z. Q.; Liu, R.; Liu, J. F., Nanofluid of zinc oxide nanoparticles in ionic liquid for single drop liquid microextraction of fungicides in environmental waters prior to high performance liquid chromatographic analysis. J. Chromatogr. A 2015, 1395, 7-15. (42) Peng, J.-F.; Liu, J.-F.; Hu, X.-L.; Jiang, G.-B., Direct determination of chlorophenols in environmental water samples by hollow fiber supported ionic liquid membrane extraction coupled with high-performance liquid chromatography. J. Chromatogr. A 2007, 1139, 165-170. (43) Abulhassani, J.; Manzoori, J. L.; Amjadi, M., Hollow fiber based-liquid phase microextraction using ionic liquid solvent for preconcentration of lead and nickel from environmental and biological samples prior to determination by electrothermal atomic absorption spectrometry. J. Hazard. Mater. 2010, 176, 481-486. (44) Zhou, Q.; Bai, H.; Xie, G.; Xiao, J., Temperature-controlled ionic liquid dispersive liquid phase micro-extraction. J. Chromatogr. A 2008, 1177, 43-49. (45) Yao, C.; Li, T.; Twu, P.; Pitner, W. R.; Anderson, J. L., Selective extraction of emerging contaminants from water samples by dispersive liquid-liquid microextraction using functionalized ionic liquids. J. Chromatogr. A 2011, 1218, 1556-1566. (46) Hou, D.; Guan, Y.; Di, X., Temperature-induced ionic liquids dispersive liquid–liquid microextraction of tetracycline antibiotics in environmental water samples assisted by complexation. Chromatographia 2011, 73, 1057-1064. (47) Zhang, J.; Gao, H.; Peng, B.; Li, S.; Zhou, Z., Comparison of the performance of conventional, temperature-controlled, and ultrasound-assisted ionic liquid dispersive liquidliquid microextraction combined with high-performance liquid chromatography in analyzing pyrethroid pesticides in honey samples. J. Chromatogr. A 2011, 1218, 6621-6629.

37 ACS Paragon Plus Environment

Environmental Science & Technology

914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957

Page 38 of 55

(48) Zhao, R.-S.; Wang, X.; Sun, J.; Hu, C.; Wang, X.-K., Determination of triclosan and triclocarban in environmental water samples with ionic liquid/ionic liquid dispersive liquidliquid microextraction prior to HPLC-ESI-MS/MS. Microchimica Acta 2011, 174, 145-151. (49) Joshi, M. D.; Chalumot, G.; Kim, Y. W.; Anderson, J. L., Synthesis of glucaminiumbased ionic liquids and their application in the removal of boron from water. Chem. Commun. 2012, 48, 1410-1412. (50) Gao, S.; Yang, X.; Yu, W.; Liu, Z.; Zhang, H., Ultrasound-assisted ionic liquid/ionic liquid-dispersive liquid-liquid microextraction for the determination of sulfonamides in infant formula milk powder using high-performance liquid chromatography. Talanta 2012, 99, 875-882. (51) Vazquez, M. M.; Vazquez, P. P.; Galera, M. M.; Garcia, M. D., Determination of eight fluoroquinolones in groundwater samples with ultrasound-assisted ionic liquid dispersive liquidliquid microextraction prior to high-performance liquid chromatography and fluorescence detection. Anal. Chim. Acta 2012, 748, 20-27. (52) Peng, B.; Yang, X.; Zhang, J.; Du, F.; Zhou, W.; Gao, H.; Lu, R., Comparison of two ultrasound-enhanced microextractions combined with HPLC for determining acaricides in water. J. Sep. Sci. 2013, 36, 2196-2202. (53) Han, D.; Tang, B.; Row, K. H., Determination of pyrethroid pesticides in tomato using ionic liquid-based dispersive liquid-liquid microextraction. J. Chromatogr. Sci. 2014, 52, 232237. (54) Tian, M.; Yan, H.; Row, K. H., Solid-phase extraction of tanshinones from Salvia Miltiorrhiza Bunge using ionic liquid-modified silica sorbents. J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 2009, 877, 738-742. (55) Polo-Luque, M. L.; Simonet, B. M.; Valcarcel, M., Coiled carbon nanotubes combined with ionic liquid: a new soft material for SPE. Anal. Bioanal. Chem. 2012, 404, 903-907. (56) Galán-Cano, F.; Lucena, R.; Cárdenas, S.; Valcárcel, M., Dispersive micro-solid phase extraction with ionic liquid-modified silica for the determination of organophosphate pesticides in water by ultra performance liquid chromatography. Microchem. J. 2013, 106, 311-317. (57) Liu, J.-F.; Li, N.; Jiang, G.-B.; Liu, J.-M.; Jönsson, J. Å.; Wen, M.-J., Disposable ionic liquid coating for headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in paints followed by gas chromatography–flame ionization detection. J. Chromatogr. A 2005, 1066, 27-32. (58) Zhao, F.; Meng, Y.; Anderson, J. L., Polymeric ionic liquids as selective coatings for the extraction of esters using solid-phase microextraction. J. Chromatogr. A 2008, 1208, 1-9. (59) Gao, Z.; Deng, Y.; Hu, X.; Yang, S.; Sun, C.; He, H., Determination of organophosphate esters in water samples using an ionic liquid-based sol-gel fiber for headspace solid-phase microextraction coupled to gas chromatography-flame photometric detector. J. Chromatogr. A 2013, 1300, 141-150. (60) Huddleston, J. G.; Willauer, H. D.; Swatloski, R. P.; Visser, A. E.; Rogers, R. D., Room temperature ionic liquids as novel media for ‘clean’ liquid–liquid extraction. Chem. Commun. 1998, 1765–1766. (61) Lovejoy, K. S.; Davis, L. E.; McClellan, L. M.; Lillo, A. M.; Welsh, J. D.; Schmidt, E. N.; Sanders, C. K.; Lou, A. J.; Fox, D. T.; Koppisch, A. T.; Del Sesto, R. E., Evaluation of ionic liquids on phototrophic microbes and their use in biofuel extraction and isolation. J. Appl. Phycol. 2013, 25, 973-981.

38 ACS Paragon Plus Environment

Page 39 of 55

Environmental Science & Technology

958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002

(62) Liu, J.-F.; Chi, Y.-G.; Peng, J.-F.; Jiang, G.-B.; Jonsson, J. A., Ionic liquids/water distribution ratios of some polycyclic aromatic hydrocarbons. J. Chem. Eng. Data 2004, 49, 1422-1424. (63) German-Hernandez, M.; Crespo-Llabres, P.; Pino, V.; Ayala, J. H.; Afonso, A. M., Utilization of an ionic liquid in situ preconcentration method for the determination of the 15 + 1 European Union polycyclic aromatic hydrocarbons in drinking water and fruit-tea infusions. J. Sep. Sci. 2013, 36, 2496-2506. (64) Deng, N.; Li, M.; Zhao, L.; Lu, C.; de Rooy, S. L.; Warner, I. M., Highly efficient extraction of phenolic compounds by use of magnetic room temperature ionic liquids for environmental remediation. J. Hazard. Mater. 2011, 192, 1350-1357. (65) Wang, S.; Liu, C.; Yang, S.; Liu, F., Ionic liquid-based dispersive liquid–liquid microextraction following high-performance liquid chromatography for the determination of fungicides in fruit juices. Food Anal. Methods 2013, 6, 481-487. (66) Yang, X.; Zhang, S.; Yu, W.; Liu, Z.; Lei, L.; Li, N.; Zhang, H.; Yu, Y., Ionic liquidanionic surfactant based aqueous two-phase extraction for determination of antibiotics in honey by high-performance liquid chromatography. Talanta 2014, 124, 1-6. (67) Wei, G.-T.; Yang, Z.; Chen, C.-J., Room temperature ionic liquid as a novel medium for liquid/liquid extraction of metal ions. Anal. Chim. Acta 2003, 488, 183-192. (68) Visser, A. E.; Swatloski, R. P.; Reichert, W. M.; Davis Jr, J. H.; Rogers, R. D.; Mayton, R.; Sheff, S.; Wierzbicki, A., Task-specific ionic liquids for the extraction of metal ions from aqueous solutions. Chem. Commun. 2001, 135-136. (69) Fischer, L.; Falta, T.; Koellensperger, G.; Stojanovic, A.; Kogelnig, D.; Galanski, M.; Krachler, R.; Keppler, B. K.; Hann, S., Ionic liquids for extraction of metals and metal containing compounds from communal and industrial waste water. Water Res. 2011, 45, 46014614. (70) Shah, F.; Kazi, T. G.; Naeemullah; Afridi, H. I.; Soylak, M., Temperature controlled ionic liquid-dispersive liquid phase microextraction for determination of trace lead level in blood samples prior to analysis by flame atomic absorption spectrometry with multivariate optimization. Microchem. J. 2012, 101, 5-10. (71) Liu, J.-F.; Jiang, G.-B.; Liu, J.-F.; Jönsson, J. Å., Application of ionic liquids in analytical chemistry. Trends Anal. Chem. 2005, 24, 20-27. (72) Han, X.; Armstrong, D. W., Ionic liquids in separations. Acc. Chem. Res. 2007, 40, 1079– 1086. (73) Liu, R.; Liu, J.-F.; Yin, Y.-G.; Hu, X.-L.; Jiang, G.-B., Ionic liquids in sample preparation. Anal. Bioanal. Chem. 2009, 393, 871-883. (74) Sun, P.; Armstrong, D. W., Ionic liquids in analytical chemistry. Anal. Chim. Acta 2010, 661, 1-16. (75) Poole, C. F.; Poole, S. K., Extraction of organic compounds with room temperature ionic liquids. J. Chromatogr. A 2010, 1217, 2268-2286. (76) Aguilera-Herrador, E.; Lucena, R.; Cardenas, S.; Valcarcel, M., The roles of ionic liquids in sorptive microextraction techniques. Trends Anal. Chem. 2010, 29, (7), 602-616. (77) Poole, C. F.; Poole, S. K., Ionic liquid stationary phases for gas chromatography. J. Sep. Sci. 2011, 34, 888-900. (78) Nagajyoti, P. C.; Lee, K. D.; Sreekanth, T. V. M., Heavy metals, occurrence and toxicity for plants: a review. Environ. Chem. Lett. 2010, 8, 199-216.

39 ACS Paragon Plus Environment

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1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046

Page 40 of 55

(79) Wei, B.; Yang, L., A review of heavy metal contaminations in urban soils, urban road dusts and agricultural soils from China. Microchem. J. 2010, 94, 99-107. (80) Huang, H.-L.; Wang, H. P.; Wei, G.-T.; Sun, I.-W.; Huang, J.-F.; Yang, Y. W., Extraction of nanosize copper pollutants with an ionic liquid. Environ. Sci. Technol. 2006, 40, 4761-4764. (81) Kalidhasan, S.; Kumar, A. S.; Rajesh, V.; Rajesh, N., An efficient ultrasound assisted approach for the impregnation of room temperature ionic liquid onto Dowex 1x8 resin matrix and its application toward the enhanced adsorption of chromium (VI). J. Hazard. Mater. 2012, 213-214, 249-257. (82) Zhang, C.; Dodge, C. J.; Malhotra, S. V.; Francis, A. J., Bioreduction and precipitation of uranium in ionic liquid aqueous solution by Clostridium sp. Bioresour. Technol. 2013, 136, 752756. (83) Li, Z.; Jiang, W. T.; Chang, P. H.; Lv, G.; Xu, S., Modification of a Ca-montmorillonite with ionic liquids and its application for chromate removal. J. Hazard. Mater. 2014, 270, 169175. (84) McFarlane, J.; Ridenour, W. B.; Luo, H.; Hunt, R. D.; DePaoli, D. W.; Ren, R. X., Room Temperature ionic liquids for separating organics from produced water. Sep. Sci. Technol. 2005, 40, 1245-1265. (85) Kulkarni, P. S.; Neves, L. A.; Coelhoso, I. M.; Afonso, C. A.; Crespo, J. G., Supported ionic liquid membranes for removal of dioxins from high-temperature vapor streams. Environ. Sci. Technol. 2012, 46, 462-468. (86) Ma, J.; Hong, X., Application of ionic liquids in organic pollutants control. J. Environ. Manage. 2012, 99, 104-109. (87) Earle, M. J.; Esperanca, J. M.; Gilea, M. A.; Lopes, J. N.; Rebelo, L. P.; Magee, J. W.; Seddon, K. R.; Widegren, J. A., The distillation and volatility of ionic liquids. Nature 2006, 439, 831-834. (88) Stepnowski, P.; Zaleska, A., Comparison of different advanced oxidation processes for the degradation of room temperature ionic liquids. J. Photochem. Photobiol. A: Chem. 2005, 170, 45-50. (89) Gathergood, N.; Scammells, P. J., Design and preparation of room-temperature ionic liquids containing biodegradable side chains. Aust. J. Chem. 2002, 55, 557–560. (90) Coleman, D.; Gathergood, N., Biodegradation studies of ionic liquids. Chem. Soc. Rev. 2010, 39, 600-637. (91) Beaulieu, J. J.; Tank, J. L.; Kopacz, M., Sorption of imidazolium-based ionic liquids to aquatic sediments. Chemosphere 2008, 70, 1320-1328. (92) Mrozik, W.; Jungnickel, C.; Skup, M.; Urbaszek, P.; Stepnowski, P., Determination of the adsorption mechanism of imidazolium-type ionic liquids onto kaolinite: implications for their fate and transport in the soil environment. Environ. Chem. 2008, 5, 299–306. (93) Matzke, M.; Thiele, K.; Muller, A.; Filser, J., Sorption and desorption of imidazolium based ionic liquids in different soil types. Chemosphere 2009, 74, 568-574. (94) Studzinska, S.; Kowalkowski, T.; Buszewski, B., Study of ionic liquid cations transport in soil. J. Hazard. Mater. 2009, 168, 1542-1547. (95) Mrozik, W.; Kotlowska, A.; Kamysz, W.; Stepnowski, P., Sorption of ionic liquids onto soils: experimental and chemometric studies. Chemosphere 2012, 88, 1202-1207.

40 ACS Paragon Plus Environment

Page 41 of 55

Environmental Science & Technology

1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091

(96) Markiewicz, M.; Mrozik, W.; Rezwan, K.; Thoming, J.; Hupka, J.; Jungnickel, C., Changes in zeta potential of imidazolium ionic liquids modified minerals--Implications for determining mechanism of adsorption. Chemosphere 2013, 90, 706-712. (97) Mrozik, W.; Jungnickel, C.; Paszkiewicz, M.; Stepnowski, P., Interaction of novel ionic liquids with soils. Water Air Soil Pollut. 2013, 224, 1759. (98) Stepnowski, P.; Mrozik, W.; Nichthauser, J., Adsorption of alkylimidazolium and alkylpyridinium ionic liquids onto natural soils. Environ. Sci. Technol. 2007, 41, 511-516. (99) Gorman-Lewis, D. J.; Fein, J. B., Experimental study of the adsorption of an ionic liquid onto bacterial and mineral surfaces. Environ. Sci. Technol. 2004, 38, 2491-2495. (100) Kraepiel, A. M. L.; Keller, K.; Morel, F. M. M., A model for metal adsorption on montmorillonite. J. Colloid Interface Sci. 1999, 210, 43–54. (101) McKinley, J. P.; Zachara, J. M.; Smith, S. C.; Turner, G. D., The influence of uranyl hydrolysis and multiple site-binding reactions on adsorption of U (VI) to montmorillonite. Clays and Clay Minerals 1995, 43, 586-598. (102) Turner, G. D.; Zachara, J. M.; McKinley, J. P.; Smith, S. C., Surface-charge properties and UO22+ adsorption of a subsurface smectite. Geochimica et Cosmochimica Acta 1996, 60, 3399-3414. (103) Wang, H.; Wang, J.; Fan, M., Extraction of ionic liquids from aqueous solutions by humic acid: an environmentally benign, inexpensive and simple procedure. Chem. Commun. 2012, 48, 392-394. (104) Zhang, Z.; Liu, J.-F.; Cai, X.-Q.; Jiang, W.-W.; Luo, W.-R.; Jiang, G.-B., Sorption to dissolved humic acid and its impacts on the toxicity of imidazolium based ionic liquids. Environ. Sci. Technol. 2011, 45, 1688-1694. (105) Bowers, J.; Butts, C. P.; Martin, P. J.; Vergara-Gutierrez, M. C., Aggregation behavior of aqueous solutions of ionic liquids. Langmuir 2004, 20, 2191-2198. (106) Ghasemian, E.; Najafi, M.; Rafati, A. A.; Felegari, Z., Effect of electrolytes on surface tension and surface adsorption of 1-hexyl-3-methylimidazolium chloride ionic liquid in aqueous solution. J. Chem. Thermodynamics 2010, 42, 962-966. (107) Singh, T.; Kumar, A., Aggregation behavior of ionic liquids in aqueous solutions: effect of alkyl chain length, cations, and anions. J. Phys. Chem. 2007, 111, 7843-7851. (108) Sastry, N. V.; Vaghela, N. M.; Macwan, P. M.; Soni, S. S.; Aswal, V. K.; Gibaud, A., Aggregation behavior of pyridinium based ionic liquids in water-surface tension, 1H NMR chemical shifts, SANS and SAXS measurements. J. Colloid Interface Sci. 2012, 371, 52-61. (109) Siedlecka, E. M.; Czerwicka, M.; J.Neumann; Stepnowski, P.; Fernandez, J. F.; Thoming, J., Ionic liquids: methods of degradation and recovery. In: Kokorin, A. (Ed.), Ionic liquids: theory, properties, new approaches. In Tech, Rijeka. In 2011; pp pp.701–722. (110) OECD Guidelines for the Testing of Chemicals, Guideline 301: Ready biodegradability, Paris, France. 1992. (111) Shefali, K.; Wolfgang, R.; Bertold, S.; Udo, K., On the biodegradation of ionic liquid 1butyl-3-methylimidazolim tetrafluoroborate. Chim. Oggi. Chem. Today 2006, 24, 24-26. (112) Peric, B.; Sierra, J.; Marti, E.; Cruanas, R.; Garau, M. A.; Arning, J.; Bottin-Weber, U.; Stolte, S., (Eco)toxicity and biodegradability of selected protic and aprotic ionic liquids. J. Hazard. Mater. 2013, 261, 99-105. (113) Plakhotnyk, A. V.; Ernst, L.; Schmutzler, R., Hydrolysis in the system LiPF6—propylene carbonate—dimethyl carbonate—H2O. J. Fluor. Chem. 2005, 126, 27-31.

41 ACS Paragon Plus Environment

Environmental Science & Technology

1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136

Page 42 of 55

(114) Swatloski, R. P.; Holbrey, J. D.; Rogers, R. D., Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate. Green Chem. 2003, 5, 361– 363. (115)Baker, G. A.; Baker, S. N., A simple colorimetric assay of ionic liquid hydrolytic stability. Aust. J. Chem. 2005, 58, 174–177. (116) Ignatyev, V. N.; Wlz-Biermann, U., New ionic liquids with advanced properties. Chim. Oggi. 2004, 22, 42-43. (117) Steudte, S.; Neumann, J.; Bottin-Weber, U.; Diedenhofen, M.; Arning, J.; Stepnowski, P.; Stolte, S., Hydrolysis study of fluoroorganic and cyano-based ionic liquid anions – consequences for operational safety and environmental stability. Green Chem. 2012, 14, (9), 2474–2483. (118) Ranke, J.; Cox, M.; Müller, A.; Schmidt, C.; Beyersmann, D., Sorption, cellular distribution, and cytotoxicity of imidazolium ionic liquids in mammalian cells – influence of lipophilicity. Toxicol. Environ. Chem. 2006, 88, 273-285. (119) Gal, N.; Malferrari, D.; Kolusheva, S.; Galletti, P.; Tagliavini, E.; Jelinek, R., Membrane interactions of ionic liquids: possible determinants for biological activity and toxicity. Biochim. Biophys. Acta 2012, 1818, 2967-2974. (120) Mikkola, S. K.; Robciuc, A.; Lokajova, J.; Holding, A. J.; Lammerhofer, M.; Kilpelainen, I.; Holopainen, J. M.; King, A. W.; Wiedmer, S. K., Impact of amphiphilic biomass-dissolving ionic liquids on biological cells and liposomes. Environ. Sci. Technol. 2015, 49, (3), 1870-1878. (121) Latała, A.; Nędzi, M.; Stepnowski, P., Toxicity of imidazolium and pyridinium based ionic liquids towards algae. Chlorella vulgaris, Oocystis submarina (green algae) and Cyclotella meneghiniana, Skeletonema marinoi (diatoms). Green Chem. 2009, 11, 580–588. (122) Ventura, S. P.; de Barros, R. L.; Sintra, T.; Soares, C. M.; Lima, A. S.; Coutinho, J. A., Simple screening method to identify toxic/non-toxic ionic liquids: agar diffusion test adaptation. Ecotoxicol. Environ. Saf. 2012, 83, 55-62. (123) Docherty, K. M.; Kulpa, J. C. F., Toxicity and antimicrobial activity of imidazolium and pyridinium ionic liquids. Green Chem. 2005, 7, 185–189. (124)Hernandez-Fernandez, F. J.; Bayo, J.; Perez de Los Rios, A.; Vicente, M. A.; Bernal, F. J.; Quesada-Medina, J., Discovering less toxic ionic liquids by using the Microtox(R) toxicity test. Ecotoxicol. Environ. Saf. 2015, 116C, 29-33. (125) Gouveia, W.; Jorge, T. F.; Martins, S.; Meireles, M.; Carolino, M.; Cruz, C.; Almeida, T. V.; Araujo, M. E., Toxicity of ionic liquids prepared from biomaterials. Chemosphere 2014, 104, 51-56. (126)Bubalo, M. C.; Hanousek, K.; Radosevic, K.; Srcek, V. G.; Jakovljevic, T.; Redovnikovic, I. R., Imidiazolium based ionic liquids: effects of different anions and alkyl chains lengths on the barley seedlings. Ecotoxicol. Environ. Saf. 2014, 101, 116-123. (127) Hossain, M. I.; Samir, B. B.; El-Harbawi, M.; Masri, A. N.; Mutalib, M. I. A.; Hefter, G.; Yin, C.-Y., Development of a novel mathematical model using a group contribution method for prediction of ionic liquid toxicities. Chemosphere 2011, 85, 990-994. (128) Stock, F.; Hoffmann, J.; Ranke, J.; Stormann, R.; Ondruschka, B.; Jastorff, B., Effects of ionic liquids on the acetylcholinesterase - a structure-activity relationship consideration. Green Chem. 2004, 6, 286–290. (129) FA, E. S.; Siopa, F.; Figueiredo, B. F.; Goncalves, A. M.; Pereira, J. L.; Goncalves, F.; Coutinho, J. A.; Afonso, C. A.; Ventura, S. P., Sustainable design for environment-friendly mono and dicationic cholinium-based ionic liquids. Ecotoxicol. Environ. Saf. 2014, 108, 302-10.

42 ACS Paragon Plus Environment

Page 43 of 55

Environmental Science & Technology

1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181

(130) Petkovic, M.; Ferguson, J.; Bohn, A.; Trindade, J.; Martins, I.; Carvalho, M. B.; Leitão, M. C.; Rodrigues, C.; Garcia, H.; Ferreira, R.; Seddon, K. R.; Rebelo, L. P. N.; Silva Pereira, C., Exploring fungal activity in the presence of ionic liquids. Green Chem. 2009, 11, 889–894. (131) Peric, B.; Sierra, J.; Marti, E.; Cruanas, R.; Garau, M. A., A comparative study of the terrestrial ecotoxicity of selected protic and aprotic ionic liquids. Chemosphere 2014, 108, 41825. (132) Bado-Nilles, A.; Diallo, A. O.; Marlair, G.; Pandard, P.; Chabot, L.; Geffard, A.; Len, C.; Porcher, J. M.; Sanchez, W., Coupling of OECD standardized test and immunomarkers to select the most environmentally benign ionic liquids option--towards an innovative "safety by design" approach. J. Hazard. Mater. 2015, 283, 202-210. (133) Costello, D. M.; Brown, L. M.; Lamberti, G. A., Acute toxic effects of ionic liquids on zebra mussel (Dreissena polymorpha) survival and feeding. Green Chem. 2009, 11, 548–553. (134) Matzke, M.; Stolte, S.; Thiele, K.; Juffernholz, T.; Arning, J.; Ranke, J.; Welz-Biermann, U.; Jastorff, B., The influence of anion species on the toxicity of 1-alkyl-3-methylimidazolium ionic liquids observed in an (eco)toxicological test battery. Green Chem. 2007, 9, 1198–1207. (135) Maeda, T.; Manabe, Y.; Yamamoto, M.; Yoshida, M.; Okazaki, K.; Nagamune, H.; Kourai, H., Synthesis and antimicrobial characteristics of novel biocides, 4,4'-(1,6hexamethylenedioxydicarbonyl) bis(1-alkylpyridinium iodide)s. Chem. Pharm. Bull. 1999, 47, 1020–1023. (136) Mester, P.; Wagner, M.; Rossmanith, P., Antimicrobial effects of short chained imidazolium-based ionic liquids-influence of anion chaotropicity. Ecotoxicol. Environ. Saf. 2015, 111, 96-101. (137) Romero, A.; Santos, A.; Tojo, J.; Rodriguez, A., Toxicity and biodegradability of imidazolium ionic liquids. J. Hazard. Mater. 2008, 151, (1), 268-273. (138) Markiewicz, M.; Piszora, M.; Caicedo, N.; Jungnickel, C.; Stolte, S., Toxicity of ionic liquid cations and anions towards activated sewage sludge organisms from different sources consequences for biodegradation testing and wastewater treatment plant operation. Water Res. 2013, 47, 2921-2928. (139) Ventura, S. P.; Marques, C. S.; Rosatella, A. A.; Afonso, C. A.; Goncalves, F.; Coutinho, J. A., Toxicity assessment of various ionic liquid families towards Vibrio fischeri marine bacteria. Ecotoxicol. Environ. Saf. 2012, 76, (2), 162-168. (140) Ventura, S. P.; Goncalves, A. M.; Goncalves, F.; Coutinho, J. A., Assessing the toxicity on [C3mim][Tf2N] to aquatic organisms of different trophic levels. Aquat. Toxicol. 2010, 96, 290-297. (141) Stolte, S.; Matzke, M.; Arning, J.; Böschen, A.; Pitner, W.-R.; Welz-Biermann, U.; Jastorff, B.; Ranke, J., Effects of different head groups and functionalised side chains on the aquatic toxicity of ionic liquids. Green Chem. 2007, 9, 1170–1179. (142) Chen, H.; Zou, Y.; Zhang, L.; Wen, Y.; Liu, W., Enantioselective toxicities of chiral ionic liquids 1-alkyl-3-methylimidazolium lactate to aquatic algae. Aquat. Toxicol. 2014, 154, 114-20. (143) Latała, A.; Nędzi, M.; Stepnowski, P., Toxicity of imidazolium and pyridinium based ionic liquids towards algae. Bacillaria paxillifer (a microphytobenthic diatom) and Geitlerinema amphibium (a microphytobenthic blue green alga). Green Chem. 2009, 11, 1371–1376. (144) Chen, H.-L.; Kao, H.-F.; Wang, J.-Y.; Wei, G.-T., Cytotoxicity of Imidazole Ionic Liquids in Human Lung Carcinoma A549 Cell Line. J. Chin. Chem. Soc. 2014, 61, (7), 763-769.

43 ACS Paragon Plus Environment

Environmental Science & Technology

1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227

Page 44 of 55

(145) Radosevic, K.; Cvjetko, M.; Kopjar, N.; Novak, R.; Dumic, J.; Srcek, V. G., In vitro cytotoxicity assessment of imidazolium ionic liquids: biological effects in fish channel catfish ovary (CCO) cell line. Ecotoxicol. Environ. Saf. 2013, 92, 112-118. (146) Bubalo, M. C.; Radosevic, K.; Srcek, V. G.; Das, R. N.; Popelier, P.; Roy, K., Cytotoxicity towards CCO cells of imidazolium ionic liquids with functionalized side chains: preliminary QSTR modeling using regression and classification based approaches. Ecotoxicol. Environ. Saf. 2015, 112, 22-8. (147) Ranke, J.; Muller, A.; Bottin-Weber, U.; Stock, F.; Stolte, S.; Arning, J.; Stormann, R.; Jastorff, B., Lipophilicity parameters for ionic liquid cations and their correlation to in vitro cytotoxicity. Ecotoxicol. Environ. Saf. 2007, 67, 430-438. (148) Roy, K.; Das, R. N.; Popelier, P. L., Quantitative structure-activity relationship for toxicity of ionic liquids to Daphnia magna: aromaticity vs. lipophilicity. Chemosphere 2014, 112, 120-7. (149) Swatloski, R. P.; Holbrey, J. D.; Memon, S. B.; Caldwell, G. A.; Caldwell, K. A.; Rogers, R. D., Using Caenorhabditis elegans to probe toxicity of 1-alkyl-3-methylimidazolium chloride based ionic liquids. Chem. Commun. 2004, 668-669. (150) Bernot, R. J.; Kennedy, E. E.; Lamberti, G. A., Effects of ionic liquids on the survival, movement, and feeding behavior of the freshwater snail Physa acuta. Environ. Toxicol. Chem. 2005, 24, 1759–1765. (151) Matzke, M.; Stolte, S.; Arning, J.; Uebers, U.; Filser, J., Imidazolium based ionic liquids in soils: effects of the side chain length on wheat (Triticum aestivum) and cress (Lepidium sativum) as affected by different clays and organic matter. Green Chem. 2008, 10, 584–591. (152) Jastorff, B.; Mölter, K.; Behrend, P.; Bottin-Weber, U.; Filser, J.; Heimers, A.; Ondruschka, B.; Ranke, J.; Schaefer, M.; Schröder, H.; Stark, A.; Stepnowski, P.; Stock, F.; Störmann, R.; Stolte, S.; Welz-Biermann, U.; Ziegert, S.; Thöming, J., Progress in evaluation of risk potential of ionic liquids—basis for an eco-design of sustainable products. Green Chem. 2005, 7, 362–372. (153) Studzinska, S.; Buszewski, B., Study of toxicity of imidazolium ionic liquids to watercress (Lepidium sativum L.). Anal. Bioanal. Chem. 2009, 393, 983-990. (154) Pernak, J.; Sobaszkiewicz, K.; Mirska, I., Anti-microbial activities of ionic liquids. Green Chem. 2003, 5, 52-56. (155) Pernak, J.; Sobaszkiewicz, K.; Foksowicz-Flaczyk, J., Ionic liquids with symmetrical dialkoxymethyl-substituted imidazolium cations. Chem. Eur. J. 2004, 10, 3479-3485. (156) Stolte, S.; Arning, J. r.; Bottin-Weber, U.; Matzke, M.; Stock, F.; Thiele, K.; Uerdingen, M.; Welz-Biermann, U.; Jastorff, B.; Ranke, J., Anion effects on the cytotoxicity of ionic liquids. Green Chem. 2006, 8, 621–629. (157) Couling, D. J.; Bernot, R. J.; Docherty, K. M.; Dixon, J. K.; Maginn, E. J., Assessing the factors responsible for ionic liquid toxicity to aquatic organisms via quantitative structure– property relationship modeling. Green Chem. 2006, 8, 82–90. (158) Garcia, M. T.; Gathergood, N.; Scammells, P. J., Biodegradable ionic liquids : part II. Effect of the anion and toxicology. Green Chem. 2005, 7, 9–14. (159) Cho, C.-W.; Phuong Thuy Pham, T.; Jeon, Y.-C.; Yun, Y.-S., Influence of anions on the toxic effects of ionic liquids to a phytoplankton Selenastrum capricornutum. Green Chem. 2008, 10, 67–72. (160) Frade, R. F.; Simeonov, S.; Rosatella, A. A.; Siopa, F.; Afonso, C. A., Toxicological evaluation of magnetic ionic liquids in human cell lines. Chemosphere 2013, 92, 100-105. 44 ACS Paragon Plus Environment

Page 45 of 55

Environmental Science & Technology

1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272

(161) Stasiewicz, M.; Mulkiewicz, E.; Tomczak-Wandzel, R.; Kumirska, J.; Siedlecka, E. M.; Golebiowski, M.; Gajdus, J.; Czerwicka, M.; Stepnowski, P., Assessing toxicity and biodegradation of novel, environmentally benign ionic liquids (1-alkoxymethyl-3hydroxypyridinium chloride, saccharinate and acesulfamates) on cellular and molecular level. Ecotoxicol. Environ. Saf. 2008, 71, 157-165. (162) Biczak, R.; Pawlowska, B.; Balczewski, P.; Rychter, P., The role of the anion in the toxicity of imidazolium ionic liquids. J. Hazard. Mater. 2014, 274, 181-190. (163) Matzke, M.; Stolte, S.; Arning, J.; Uebers, U.; Filser, J., Ionic liquids in soils: effects of different anion species of imidazolium based ionic liquids on wheat (Triticum aestivum) as affected by different clay minerals and clay concentrations. Ecotoxicology 2009, 18, 197-203. (164) Evans, K. O., Supported phospholipid bilayer interaction with components found in typical room-temperature ionic liquids – a QCM-D and AFM Study. Int. J. Mol. Sci. 2008, 9, 498-511. (165) Larson, J. H.; Frost, P. C.; Lamberti, G. A., Variable toxicity of ionic liquid-forming chemicals to Lemna minor and the influence of dissolved organic matter. Environ. Toxicol. Chem. 2008, 27, 676–681. (166) Markiewicz, M.; Jungnickel, C.; Arp, H. P., Ionic liquid assisted dissolution of dissolved organic matter and PAHs from soil below the critical micelle concentration. Environ. Sci. Technol. 2013, 47, (13), 6951-6958. (167) Latała, A.; Nędzi, M.; Stepnowski, P., Toxicity of imidazolium ionic liquids towards algae. Influence of salinity variations. Green Chem. 2010, 12, (1), 60-64. (168) Latala, A.; Stepnowski, P.; Nedzi, M.; Mrozik, W., Marine toxicity assessment of imidazolium ionic liquids: acute effects on the Baltic algae Oocystis submarina and Cyclotella meneghiniana. Aquat. Toxicol. 2005, 73, 91-98. (169) Samori, C.; Sciutto, G.; Pezzolesi, L.; Galletti, P.; Guerrini, F.; Mazzeo, R.; Pistocchi, R.; Prati, S.; Tagliavini, E., Effects of imidazolium ionic liquids on growth, photosynthetic efficiency, and cellular components of the diatoms Skeletonema marinoi and Phaeodactylum tricornutum. Chem. Res. Toxicol. 2011, 24, (3), 392-401. (170) Zhu, L.; Chen, B., Sorption behavior of p-nitrophenol on the interface between anioncation organobentonite and water. Environ. Sci. Technol. 2000, 34, 2997–3002. (171) Zhu, L.; Chen, B.; Shen, X., Sorption of phenol, p-nitrophenol, and aniline to dual-cation organobentonites from water. Environ. Sci. Technol. 2000, 34, 468-475. (172) Zhu, L.; Ren, X.; Yu, S., Use of cetyltrimethylammonium bromide-bentonite to remove organic contaminants of varying polar character from water. Environ. Sci. Technol. 1998, 32, 3374-3378. (173) Sheng, G.; Xu, S.; Boyd, S. A., Mechanism(s) controlling sorption of neutral organic contaminants by surfactant-derived and natural organic matter. Environ. Sci. Technol. 1996, 30, 1553-1557. (174) Pino, V.; Baltazar, Q. Q.; Anderson, J. L., Examination of analyte partitioning to monocationic and dicationic imidazolium-based ionic liquid aggregates using solid-phase microextraction-gas chromatography. J. Chromatogr. A 2007, 1148, 92-99. (175) McCarthy, J. F.; Zachara, J. M., Subsurface transport of contaminants. Environ. Sci. Technol. 1989, 23, 496–502. (176) Matzke, M.; Stolte, S.; Böschen, A.; Filser, J., Mixture effects and predictability of combination effects of imidazolium based ionic liquids as well as imidazolium based ionic

45 ACS Paragon Plus Environment

Environmental Science & Technology

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Page 46 of 55

liquids and cadmium on terrestrial plants (Triticum aestivum) and limnic green algae (Scenedesmus vacuolatus). Green Chem. 2008, 10, 784–792. (177) Zhang, J.; Liu, S. S.; Liu, H. L., Effect of ionic liquid on the toxicity of pesticide to Vibrio-qinghaiensis sp.-Q67. J. Hazard. Mater. 2009, 170, 920-927. (178) Ge, H. L.; Liu, S. S.; Su, B. X.; Qin, L. T., Predicting synergistic toxicity of heavy metals and ionic liquids on photobacterium Q67. J. Hazard. Mater. 2014, 268, 77-83. (179) Zhang, J.; Liu, S. S.; Liu, H. L.; Zhu, X. W.; Mi, X. J., A novel method dependent only on the mixture information (MIM) for evaluating the toxicity of mixture. Environ. Pollut. 2011, 159, (7), 1941-1947. (180) Dou, R. N.; Liu, S. S.; Mo, L. Y.; Liu, H. L.; Deng, F. C., A novel direct equipartition ray design (EquRay) procedure for toxicity interaction between ionic liquid and dichlorvos. Environ. Sci. Pollut. Res. Int. 2011, 18, (5), 734-742. (181) Zhang, J.; Liu, S. S.; Zhang, J.; Qin, L. T.; Deng, H. P., Two novel indices for quantitatively characterizing the toxicity interaction between ionic liquid and carbamate pesticides. J. Hazard. Mater. 2012, 239-240, 102-109. (182) Gathergood, N.; Scammells, P. J.; Garcia, M. T., Biodegradable ionic liquids : part III. The first readily biodegradable ionic liquids. Green Chem. 2006, 8, 156–160. (183) Alvarez-Guerra, M.; Irabien, A., Design of ionic liquids: an ecotoxicity (Vibrio fischeri) discrimination approach. Green Chem. 2011, 13, 1507–1516. (184) Samori, C.; Malferrari, D.; Valbonesi, P.; Montecavalli, A.; Moretti, F.; Galletti, P.; Sartor, G.; Tagliavini, E.; Fabbri, E.; Pasteris, A., Introduction of oxygenated side chain into imidazolium ionic liquids: evaluation of the effects at different biological organization levels. Ecotoxicol. Environ. Saf. 2010, 73, (6), 1456-1464. (185) Pretti, C.; Chiappe, C.; Baldetti, I.; Brunini, S.; Monni, G.; Intorre, L., Acute toxicity of ionic liquids for three freshwater organisms: Pseudokirchneriella subcapitata, Daphnia magna and Danio rerio. Ecotoxicol. Environ. Saf. 2009, 72, 1170-1176. (186) Demberelnyamba, D.; Kim, K. S.; Choi, S.; Park, S. Y.; Lee, H.; Kim, C. J.; Yoo, I. D., Synthesis and antimicrobial properties of imidazolium and pyrrolidinonium salts. Bioorg. Med. Chem. 2004, 12, 853-857. (187) Stolte, S.; Arning, J. r.; Bottin-Weber, U.; Muller, A.; Pitner, W.-R.; Welz-Biermann, U.; Jastorff, B.; Ranke, J., Effects of different head groups and functionalised side chains on the cytotoxicity of ionic liquids. Green Chem. 2007, 9, 760–767. (188) Hough-Troutman, W. L.; Smiglak, M.; Griffin, S.; Matthew Reichert, W.; Mirska, I.; Jodynis-Liebert, J.; Adamska, T.; Nawrot, J.; Stasiewicz, M.; Rogers, R. D.; Pernak, J., Ionic liquids with dual biological function: sweet and anti-microbial, hydrophobic quaternary ammonium-based salts. New J. Chem. 2009, 33, 26–33. (189) Costa, S. P.; Pinto, P. C.; Lapa, R. A.; Saraiva, M. L., Toxicity assessment of ionic liquids with Vibrio fischeri: an alternative fully automated methodology. J. Hazard. Mater. 2015, 284, 136-42. (190) Egorova, K. S.; Seitkalieva, M. M.; Posvyatenko, A. V.; Ananikov, V. P., An unexpected increase of toxicity of amino acid-containing ionic liquids. Toxicol. Res. 2015, 4, (1), 152-159. (191) Mai, N. L.; Ahn, K.; Koo, Y.-M., Methods for recovery of ionic liquids—A review. Process Biochemistry 2014, 49, (5), 872-881. (192) Palomar, J.; Lemus, J.; Gilarranz, M. A.; Rodriguez, J. J., Adsorption of ionic liquids from aqueous effluents by activated carbon. Carbon 2009, 47, 1846-1856.

46 ACS Paragon Plus Environment

Page 47 of 55

Environmental Science & Technology

1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363

(193) Virtanen, P.; Mikkola, J.-P.; Toukoniitty, E.; Karhu, H.; Kordas, K.; Eränen, K.; Wärnå, J.; Salmi, T., Supported ionic liquid catalysts—from batch to continuous operation in preparation of fine chemicals. Catal. Today 2009, 147, S144-S148. (194) Farooq, A.; Reinert, L.; Levêque, J.-M.; Papaiconomou, N.; Irfan, N.; Duclaux, L., Adsorption of ionic liquids onto activated carbons: effect of pH and temperature. Microporous and Mesoporous Mater. 2012, 158, 55-63. (195) Lemus, J.; Palomar, J.; Heras, F.; Gilarranz, M. A.; Rodriguez, J. J., Developing criteria for the recovery of ionic liquids from aqueous phase by adsorption with activated carbon. Sep. Pur. Technol. 2012, 97, 11-19. (196) Lemus, J.; Neves, C. M.; Marques, C. F.; Freire, M. G.; Coutinho, J. A.; Palomar, J., Composition and structural effects on the adsorption of ionic liquids onto activated carbon. Environ. Sci. Process Impacts 2013, 15, 1752-1759. (197) Lemus, J.; Palomar, J.; Gilarranz, M. A.; Rodriguez, J. J., On the Kinetics of Ionic Liquid Adsorption onto Activated Carbons from Aqueous Solution. Ind. Eng. Chem. Res. 2013, 52, 2969-2976. (198) Qi, X.; Li, L.; Tan, T.; Chen, W.; Smith, R. L., Jr., Adsorption of 1-butyl-3methylimidazolium chloride ionic liquid by functional carbon microspheres from hydrothermal carbonization of cellulose. Environ. Sci. Technol. 2013, 47, 2792-2798. (199) Won, S. W.; Choi, S. B.; Mao, J.; Yun, Y. S., Removal of 1-ethyl-3-methylimidazolium cations with bacterial biosorbents from aqueous media. J. Hazard. Mater. 2013, 244-245, 130134. (200) Stepnowski, P., Preliminary assessment of the sorption of some alkyl imidazolium cations as used in ionic liquids to soils and sediments. Aust. J. Chem. 2005, 58, 170–173. (201) Reinert, L.; Batouche, K.; Lévêque, J.-M.; Muller, F.; Bény, J.-M.; Kebabi, B.; Duclaux, L., Adsorption of imidazolium and pyridinium ionic liquids onto montmorillonite: characterisation and thermodynamic calculations. Chem. Eng. J. 2012, 209, 13-19. (202) Ye, C.; Wang, X.; Wang, H.; Wang, Z., Effects of counter anions on the adsorption properties of 4-methylimidazolium-modified silica materials. Journal of the Taiwan Institute of Chemical Engineers 2014, 45, (6), 2868-2877. (203) Choi, S. B.; Won, S. W.; Yun, Y.-S., Use of ion-exchange resins for the adsorption of the cationic part of ionic liquid, 1-ethyl-3-methylimidazolium. Chem. Eng. J. 2013, 214, 78-82. (204) Neves, C. M. S. S.; Freire, M. G.; Coutinho, J. A. P., Improved recovery of ionic liquids from contaminated aqueous streams using aluminium-based salts. RSC Adv. 2012, 2, 10882– 10890. (205) Qi, X.; Li, L.; Wang, Y.; Liu, N.; Smith, R. L., Removal of hydrophilic ionic liquids from aqueous solutions by adsorption onto high surface area oxygenated carbonaceous material. Chem. Eng. J. 2014, 256, 407-414. (206) Yin, C.; Aroua, M.; Daud, W., Review of modifications of activated carbon for enhancing contaminant uptakes from aqueous solutions. Sep. Pur. Technol. 2007, 52, 403-415. (207) Docherty, K. M.; Dixon, J. K.; Kulpa, C. F., Jr., Biodegradability of imidazolium and pyridinium ionic liquids by an activated sludge microbial community. Biodegradation 2007, 18, 481-493. (208) Pham, T. P. T.; Cho, C.-W.; Jeon, C.-O.; Chung, Y.-J.; Lee, M.-W.; Yun, Y.-S., Identification of metabolites involved in the biodegradation of the ionic liquid 1-butyl-3methylpyridinium bromide by activated sludge microorganisms. Environ. Sci. Technol. 2009, 43, 516–521. 47 ACS Paragon Plus Environment

Environmental Science & Technology

1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407

Page 48 of 55

(209) Stolte, S.; Abdulkarim, S.; Arning, J.; Blomeyer-Nienstedt, A.-K.; Bottin-Weber, U.; Matzke, M.; Ranke, J.; Jastorff, B.; Thoming, J., Primary biodegradation of ionic liquid cations, identification of degradation products of 1-methyl-3-octylimidazolium chloride and electrochemical wastewater treatment of poorly biodegradable compounds. Green Chem. 2008, 10, 214–224. (210) Liwarska-Bizukojc, E.; Gendaszewska, D., Removal of imidazolium ionic liquids by microbial associations: study of the biodegradability and kinetics. J. Biosci. Bioeng. 2013, 115, 71-75. (211) Jastorff, B.; Störmann, R.; Ranke, J.; Mölter, K.; Stock, F.; Oberheitmann, B.; Hoffmann, W.; Hoffmann, J.; Nüchter, M.; Ondruschka, B.; Filser, J., How hazardous are ionic liquids? Structure–activity relationships and biological testing as important elements for sustainability evaluation. Green Chem. 2003, 5, 136-142. (212) Markiewicz, M.; Jungnickel, C.; Markowska, A.; Szczepaniak, U.; Paszkiewicz, M.; Hupka, J., 1-methyl-3-octylimidazolium chloride--sorption and primary biodegradation analysis in activated sewage sludge. Molecules 2009, 14, 4396-4405. (213) Markiewicz, M.; Henke, J.; Brillowska-Dąbrowska, A.; Stolte, S.; Łuczak, J.; Jungnickel, C., Bacterial consortium and axenic cultures isolated from activated sewage sludge for biodegradation of imidazolium-based ionic liquid. Int. J. Environ. Sci. Technol. 2014, 11, (7), 1919-1926. (214) Gao, J.; Chen, L.; He, Y. Y.; Yan, Z. C.; Zheng, X. J., Degradation of imidazolium-based ionic liquids in aqueous solution using plasma electrolysis. J. Hazard. Mater. 2014, 265, 261270. (215) Li, X.; Zhao, J.; Li, Q.; Wang, L.; Tsang, S. C., Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations. Dalton Trans. 2007, 1875–1880. (216) Czerwicka, M.; Stolte, S.; Muller, A.; Siedlecka, E. M.; Golebiowski, M.; Kumirska, J.; Stepnowski, P., Identification of ionic liquid breakdown products in an advanced oxidation system. J. Hazard. Mater. 2009, 171, 478-483. (217) Morawski, A. W.; Janus, M.; Goc-maciejewska, I.; Syguda, A.; Pernak, J., Decomposition of ionic liquids by photocatalysis. . Polish J. Chem. 2005, 79, 1929–1935. (218) Itakura, T.; Hirata, K.; Aoki, M.; Sasai, R.; Yoshida, H.; Itoh, H., Decomposition and removal of ionic liquid in aqueous solution by hydrothermal and photocatalytic treatment. Environ. Chem. Lett 2009, 7, 343-345. (219) Damiano, T.; Morton, D.; Nelson, A., Photochemical transformations of pyridinium salts: mechanistic studies and applications in synthesis. Org. Biomol. Chem. 2007, 5, 2735-2752. (220) Oxley, J. D.; Prozorov, T.; Suslick, K. S., Sonochemistry and Sonoluminescence of Room-Temperature Ionic Liquids. J. Am. Chem. Soc. 2003, 125, 11138-11139. (221) Siedlecka, E. M.; Stolte, S.; Gołębiowski, M.; Nienstedt, A.; Stepnowski, P.; Thöming, J., Advanced oxidation process for the removal of ionic liquids from water: The influence of functionalized side chains on the electrochemical degradability of imidazolium cations. Sep. Purif. Technol. 2012, 101, 26-33. (222) Siedlecka, E. M.; Fabiańska, A.; Stolte, S.; Nienstedt, A.; Ossowski, T.; Stepnowski, P.; Thöming, J., Electrocatalytic oxidation of 1-butyl-3-methylimidazolium chloride: Effect of the electrode material. Int. J. Electrochem. Sci. 2013, 8, 5560 - 5574.

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Page 49 of 55

Environmental Science & Technology

1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431

(223) Fabiańska, A.; Ossowski, T.; Stepnowski, P.; Stolte, S.; Thöming, J.; Siedlecka, E. M., Electrochemical oxidation of imidazolium-based ionic liquids: The influence of anions. Chem. Eng. J. 2012, 198-199, 338-345. (224) Siedlecka, E. M.; Mrozik, W.; Kaczynski, Z.; Stepnowski, P., Degradation of 1-butyl-3methylimidazolium chloride ionic liquid in a Fenton-like system. J. Hazard. Mater. 2008, 154, (1-3), 893-900. (225) Siedlecka, E. M.; Gołębiowski, M.; Kaczyński, Z.; Czupryniak, J.; Ossowski, T.; Stepnowski, P., Degradation of ionic liquids by Fenton reaction; the effect of anions as counter and background ions. Appl. Catal. B: Environ. 2009, 91, (1-2), 573-579. (226) Zhou, H.; Lv, P.; Shen, Y.; Wang, J.; Fan, J., Identification of degradation products of ionic liquids in an ultrasound assisted zero-valent iron activated carbon micro-electrolysis system and their degradation mechanism. Water Res. 2013, 47, 3514-3522. (227) Domínguez, C. M.; Munoz, M.; Quintanilla, A.; de Pedro, Z. M.; Ventura, S. P. M.; Coutinho, J. A. P.; Casas, J. A.; Rodriguez, J. J., Degradation of imidazolium-based ionic liquids in aqueous solution by Fenton oxidation. J. Chem. Technol. Biotechnol. 2014, 89, (8), 1197-1202. (228) Zhou, H.; Shen, Y.; Lv, P.; Wang, J.; Li, P., Degradation pathway and kinetics of 1-alkyl3-methylimidazolium bromides oxidation in an ultrasonic nanoscale zero-valent iron/hydrogen peroxide system. J. Hazard. Mater. 2015, 284, 241-52. (229) Siedlecka, E. M.; Golêbiowski, M.; Kumirska, J.; Stepnowski, P., Identification of 1Butyl-3-methylimidazolium Chloride Degradation Products Formed in Fe(III)/H2O2 Oxidation System. Chem. Anal. (Warsaw) 2008, 53, 943-951. (230) Siedlecka, E. M.; Stepnowski, P., The effect of alkyl chain length on the degradation of alkylimidazolium- and pyridinium-type ionic liquids in a Fenton-like system. Environ. Sci. Pollut. Res. Int. 2009, 16, (4), 453-458.

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1443 1444

Figure Captions

1445

Figure 1. The transport and transformation of ILs in the environmental system

1446

Figure 2. Effects of structural modifications on toxicity of ILs

1447

Figure 3. Some important routes to synthesize less toxic and more biodegradable ILs

1448

Figure 4. Methods for removal of ILs

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TOC Art

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1483 1484

Figure 1.

CO2

Air Water

Aerobic degradation

Suspended particle IL

IL

IL

IL

IL

ILs

IL

1485

IL IL

Suspension IL

IL

IL IL

Sediment/Soil

IL

Uptake

Deposition IL

IL

IL

IL IL

IL

IL

IL

Dissolved NOM

Sorption

Anaerobic degradation

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IL IL

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1497

Anion effect

Increases

• Side chain length (up to “cut off” effect) • Hydrophobicity of the side chain

Cation type

Side chain

Figure 2.

Cation effect

1498

Increases

• Anion lipophilicity • Anion lnstability

Toxicity Increases 1499 1500 1501 1502 1503 1504 1505 1506

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1507 1508

Figure 3.

• • • • •

Use of protic ILs Salts of organic acids Short alkyl side-chains Use of cholinium cations Polar group to the side chain (away from the ring) • Use of saccharinate and acesulphamate anions • Methyl group in 1-position of the imidazole

• Use of protic ILs • Salts of organic acids • Long hydrophobic alkyl sidechains • Use of pyridinium cations • Use of anions like: • Alkyl sulphates • Alkyl sulphonates • Alkyl benzene sulphonates

Recommended

ILs

Less Toxic

More Biodegradable Side chain

Cation

Anion

• Adding methyl or hydroxyethyl in to the imidazolium ring

• Introduction of polar functional groups

• Use of aromatic containing cations

• Fluorine containing ILs

• Using [BF4]-, [PF6]- and [SbF6]anions • Methylation of the pyridinium ring

• Short alkyl side chains

Conflicts/trade-offs

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Figure 4.

Advanced Oxidation

Methods for Removal of ILs

Degradation

Adsorption

Biodegradation

1520

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Enhanced Photodegradation Ultrasonic based degradation Electrolytic based degradation