Integration of Biodegradation and Nano-Oxidation for Removal of

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Integration of biodegradation and nano-oxidation for removal of PAHs from aqueous solution Xiaoying Jin, Bing Yu, Jiajiang Lin, and Zuliang Chen ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b00933 • Publication Date (Web): 01 Aug 2016 Downloaded from http://pubs.acs.org on August 7, 2016

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ACS Sustainable Chemistry & Engineering 1

Integration of biodegradation and nano-oxidation for removal of PAHs from aqueous solution

Xiaoying Jin†, Bing Yu†,‡, Jiajiang Lin†, Zuliang Chen*,†,‡

†

School of Environment Science and Engineering, Fujian Normal University, Fuzhou

350007, Fujian Province, China ‡

Global Centre for Environmental remediation, University of Newcastle, Callaghan

NSW 2308, Australia

*Corresponding author. Ph: 61-02-49139748; Email: [email protected]

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering

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ABSTRACT: Despite many reports being published on using biodegradation or Fenton-like oxidation to remove various containments, the integration of these two processes to improve the removal efficiency of contaminants is still challenge. This study attempted to remove naphthalene and phenanthrene from aqueous solution using a sequential biodegradation and Fenton-like oxidation based on green synthesis of iron nanoparticles (Fe NPs). Results showed that after 96 hours, 100% naphthalene was biodegraded, while only 28.9% phenanthrene and 48.3% chemical oxygen demand (COD) were removed, respectively, indicating that the biodegradation was an incomplete process and the degraded metabolites still existed. To improve the removal efficiency of phenanthrene and the degraded metabolites, Fenton-like oxidation based on Fe NPs synthesized using tea extracts under various atmospheres (N2, O2 and air) was employed. Results indicated 100% of phenanthrene was removed, total COD removed increased to 81.5%, 77.2% and 68.7% using N2, O2 and air-Fe NPs, respectively. In addition, Fe NPs were confirmed by scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS). Finally, the degraded metabolites were identified by GC-MS to understand degradation pathway.

KEYWORDS: Bacillus fusiformis (BFN), naphthalene, phenanthrene, Fenton-like oxidation, Green synthesis, FeNPs.


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INTRODUCTION Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds with two or more benzene rings, and this has created many concerns regarding their toxicity, recalcitrance and danger to human health.1 Recently, much tremendous interest has arisen in using biodegradation for eliminating PAHs from wastewater because of their environmental safety and low cost.2 However, biological treatments for PAHs are usually time-consuming and often proved to be incomplete removal processes as well.3 In addition, some of their metabolites may be more toxic and more difficult to degrade than their parent PAHs compounds. 4

To address the limitations of biodegradation and improve removal efficiency of PAHs, advanced oxidation processes (AOPs) have been used as a post-treatment biological process.5 Taking Fenton-like oxidation using nanoscale zero-valent iron (nZVI) as an example, the pertinent property of nZVI is its nanosize, large specific surface and high reactivity. In addition, nZVI can also serve as a slow-releasing source of dissolved Fe2+ in the Fenton system, which activate H2O2 to produce hydroxyl-free radicals.6 Fenton-like oxidation involves several sequential reactions:7 Fe0 + H2O2→Fe2+ +2OH- (1) Fe2+ + H2O2→Fe3+ + OH- + OH• (2) Various chemical and physical methods have been proposed to synthesize nZVI, for example, vacuum sputtering, thermal decomposition, and chemical method.8 However, these methods are usually quite expensive and chemical substances such as NaBH4 and organic solvents are toxic and corrosive.9 Furthermore, nZVI synthesized by the



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mentioned methods tends to form agglomerates, leading to be readily oxidized by non-target compounds.10 Consequently, developing cost-effective and environmental friendly synthesis method is necessary.

Recently, the green synthesis of Fe NPs using plant extracts has become increasingly popular because components such as polyphenols, protein and vitamins extracted from plan materials are nontoxic and biodegradable.8 Moreover, these components can play the role of both reducing and capping agents for nZVI, and thus reduce the oxidation and agglomeration of nZVI to some extent. 11 Reports have been published in green synthesis of Fe NPs by tea extract (GT-Fe NPs): firstly, reductive degradation of chlorinated organic; or secondly, as a Fenton catalyst for the oxidation of methylene blue (MB) and methyl orange (MO) dyes.12, 13

Studies have confirmed that the components of Fe NPs synthesized by plant extract includes zero-valent iron and iron oxide nanoparticles.8,14 Furthermore, their size, reactivity, and proportion have been affected by several factors, such as type of tea extract, temperature and pH.11 However, knowledge is still limited concerning another significant factor, flowing gas atmosphere, which is often necessary to be taken into consideration in the synthesis of nanoparticles.15

Our previous study showed that the Fenton oxidation are limited for those organic contaminants with a poor solubility in aqueous solution, 6 and biological treatments for these low-solubility organic contaminants are often proved to be effective, but


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incomplete removal processes and intermediates have been observed.1 These metabolites are usually with a higher solubility than their parent compounds. 2.3 Herein, to achieve a better degradation and make it more practical for in situ remediation, this sequential biodegradation and Fenton-like oxidation was proposed to degrade PAHs, which is a typical class of organic contaminants with a class of low-solubility. In addition, biodegradation is often accepted as a low cost technology and nano-oxidation using Fe NPs synthesized by plant extract is also more cost-effective comparing with Fe NPs synthesized by chemical method such as NaBH4.8 Hence, development of a new remediation method is required. PAHs are a class of compounds that have more than two aromatic rings in their molecules. Naphthalene and phenanthrene were selected as the targets owing to their often presence in the environment. 1 In views of the fact that phenanthrene is hard to be degraded by biodegradation or Fenton oxidation since there is a three aromatic rings. Hence, it is interesting to test the possibility of intergradation of biodegradation and Nano oxidation used for the degradation of mixed PAHs. The aim of this study is to determine whether this integrated treatment will degrade both naphthalene and phenanthrene completely, and to examine whether the flowing gas atmosphere impacts on the synthesis of Fe NPs and thus affects its Fenton-like reactivity. The following experiments were conducted: (1) investigating the growth of BFN and degree of COD removal to examine biodegradation of both naphthalene and phenanthrene; (2) synthesis of Fe NPs using three different flowing gas atmospheres (N2, O2 and air) and comparing their performance in Fenton-like oxidation; and (3) exploring the possible degradation mechanism by SEM, EDS and GC/MS studies.



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MATRERIALS AND METHODS Microorganisms and chemicals. The BFN strain has been isolated from activated sludge in our previous study.16 The mineral salts medium (MSM) consisted of (g L-1): MgSO4·7H2O 0.3, K2HPO4·2H2O 1.0, (NH4)2SO4 0.3, KH2PO4 1.0, NaCl 5.0, CaCl2 0.020. MSM also included trace elements as follows: (g L-1): FeCl3 2.3, ZnSO4 5.0, (NH4)6Mo7O24 1.0 and MnSO4 5.0. All of the mediums were then sterilized by autoclaving at 121◦C for 20 min.

BFN strain culture was enriched in MSM (50 mL in a 150 mL Erlenmeyer flask) with 100 mg L-1 naphthalene being added as the sole carbon source in a darkened shaking incubator (150 rpm, 30◦C). For the sake of preparing the resting cell, we harvested the culture suspension from the late log phase culture by centrifugation (7000 rpm, 10 min). Following this，the cell pellet was washed three times using sterilized distilled water and finally the cell suspension’s optical density was adjusted to 0.7 (OD at 600 nm) using UV–visible spectroscope (Bio-Tek Instruments, Shanghai, China).

Biodegradation of naphthalene and phenanthrene. Batch experiments of naphthalene and phenanthrene degradation were conducted in 100 mL Erlenmeyer flasks sealed with ground glass plugs to minimize volatilization. Each flask contained 50 mL liquid medium with 0.2% (v/v) inoculums placed in the darkness to avoid possible photolysis. A series of tests was conducted at a fixed naphthalene and phenanthrene concentration (50 mg L-1).

The cultures were incubated in a shaking incubator at 150 rpm, 30◦C. The naphthalene and phenanthrene in samples were extracted twice each with 10 mL n-hexane. The ACS Paragon Plus Environment

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extracts were dried over anhydrous sodium sulphate and evaporated with nitrogen gas to 1 mL for GC analysis. The quantity of naphathalene and phenanthrene was established using gas Chromatograph (Varian CP-3800 series) equipped with CP-Sil 8 CB column (30 m × 0.32 mm id, 0.25µm film thickness) and a flame ionization detector (FID). Nitrogen (Purity >99.999%) served as carrier gas with a steady flow rate of 1.0 mL min-1. The column temperature was programmed as follows: the column temperature was firstly held at 50◦C for 2 min then raised to 250◦C at a speed of 50◦C min-1, and then maintained for 4 min. The temperatures of the injector and detector were held at 250◦C and 300◦C, respectively. UV–visible spectroscope measured cell growth based on absorbance at 600 nm. The water quality detector (LianHua-Tek Instruments, Lanzhou, China) was employed to determine the COD of degraded mediums, sample with known amount of potassium dichromate solution, based on the strong sulfuric acid medium and silver sulfate as catalyst. After high temperature resolution, the COD value is determined by the spectrophotometry. All experiments were done in triplicate to ensure data quality.

Preparation of Fe NPs (N2, O2 and air). The method of Fe NPs synthesis using green tea was described in our previous study.11 In this study, to explore the effect of flowing gas atmosphere on Fe NPs synthesis, three different flowing gas atmospheres (N2, O2 and air) were inserted into the synthesis process, respectively. An extract of green tea was prepared by adding 60 g of processed green tea leaf into 1000 mL distilled water in a water bath heated at 353 K for 1 h. Then the extracts were taken for vacuum filtration after cooling to room temperature. Before 0.10 mol L-1 Fe2SO4 was added to the tea extracts with a ratio volume of 1:2, N2, O2 or air into the synthesis reactor was passed,



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respectively. Having been vacuum-filtered, the mixture reacted completely and was then put into a vacuum drying chamber for 12 h. This made it possible to use the nano solid particles for Fenton-like oxidation reaction.

Fenton-like oxidation experiment. The batch experiments were carried out in 100 mL Erlenmeyer flasks containing 50 mL naphthalene and phenanthrene degradation medium which had been used to cultivate BFN strain for 96 hours. In the initial approach, the Fenton-like process series were operated at constant H2O2 concentration: 10 mmol L-1, temperature: 30◦C，Fe NPs dosage: 0.5 g L-1. Following this procedure, these were then placed on a rotary shaker at 250 r min-1. The residual phenanthrene and COD were measured at different time intervals (0, 5, 15, 30, 60, 90 min). All tests were carried out in triplicate.

Characterization and Analytical method. The samples of BFN strains for SEM analysis using JSM-7500F (JEOL Ltd. Co., Tokyo, Japan) were prepared utilizing the following procedures. Cells were concentrated by centrifugation at 10000 rpm, followed by being washed three times with sterile water. The samples were fixed in 2.5% glutaraldehyde (pH 7.2) for 1 h, and then were rinsed three times with phosphate buffer. A second fixation step was performed using osmium tetroxide for 2 h, followed by dehydration using ethanol at a range of different concentrations (30, 50, 70, 80, 90, and 100% ethanol) for 10 min. At last, the samples were dried overnight at 30◦C to form sample blocks. The particles were subsequently coated with gold powder and attached onto a microscope support with silver glue.17


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SEM images of Fe NPs under N2 (N-Fe NPs), Fe NPs under O2 (O-Fe NPs) and Fe NPs under air (air-Fe NPs) before and after Fenton-like oxidation reaction were acquired using a JSM-7500F to observe the surface morphology and grain size. The powdered samples were first affixed onto adhesive tapes supported on metallic disks and then covered with a thin, electric conductive gold film. Then they were recorded at different magnifications at an operating voltage of 3 kV. The elemental loading on the surface of N-Fe NPs, O-Fe NPs and air-Fe NPs samples before and after reaction were analyzed by INCA EDS (Oxford Instruments, UK) in conjunction with SEM.

Gas chromatography-mass spectrometry (GC–MS, Thermo, USA) with EI mode (70 eV) was also employed to analyze and identify the naphthalene, phenanthrene and their metabolites. For GC–MS analysis, a 30 m capillary column (DB-5; inner diameter, 0.32 mm; film thickness, 0.25 µm) was used for the separation. Helium served as the carrier gas maintaining the column flow at 1.0mL min-1 (at a pressure of 105 kPa). A 2.0 µL sample of the extract was injected and the following were typical temperature programs: DB-5MS column, the column temperature was initially held at 60◦C for 2 min and then programmed by 10◦C min-1 up to 160◦C, which was held for 2 min. This then rose to 240◦C at a rate of 5◦C min-1 for 2 min, and finally to 290◦C at a rate of 30◦C min-1 for 2 min. The mass spectrometer and transfer line was maintained at 290◦C. Statistical analyses. A one-way ANOVA, followed by a Student’s t-test at the 95% confidence level was used to determine the significant differences among different groups.

RESULTS AND DISCUSSION Biodegradation

of

naphthalene

and phenanthrene


by

BFN.

The

initial


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concentrations for naphthalene and phenanthrene in MSM were kept as both 50 mg L-1 to investigate the biodegradation of these two kind of PAHs. The BFN strain’s growth with the incubation time was shown in Figure 1a, where apparently significant cell growth occurred after a brief lag period of 12 hours, and the biomass of BFN increased from 0.012 at the beginning to 0.171(OD600) after 60 hours’ incubation. However, there were no obvious change in cell numbers for the control experiment without the addition of naphthalene and phenanthrene, which confirmed that only MSM could not promote the cells’ metabolism Herein, we can infer that the growth of BFN strain may be attributed to the fact that individual naphthalene, phenanthrene or both of them could serve as a carbon source for the BFN strain.16 Similar results have been reported that Sphingobacterium sp. and Bacillus cereus could be used for biodegradation of phenanthrene.18 Furthermore, a consortium DV-AL could degrade high concentrations of naphthalene has also been observed.19

COD was used to assess the residual amount of organic matter and thus their degradation process was monitored as shown in Figure 1b, where 48.3% of COD was removed after 96 hours, while only 7.5% of COD was degraded in the abiotic control sample. Comparing Figure 1a with Figure 1b, it was evident that COD removal was consistent with the incremental increase in BFN strains’ biomass. COD removal was probably caused by the biodegradation of naphthalene and phenanthrene. BFN strain may biodegrade naphthalene and phenanthrene (with large molecular weight) into some intermediates with smaller molecular weight.20


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11 0.18

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biomass of BFN control

0.03 0.00 0

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(c)

80

PHE PHE control NAP NAP control

60 40 20 0 0

12

24

36

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60

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96

Time (h)

Figure 1 Biodegradation of naphthalene and phenanthrene using BFN strains: (a) biomass of BFN; (b) the removal of COD; and (c) the removal of naphthalene and phenanthrene.

The biodegradation of naphthalene and phenanthrene using the BFN strain with the incubation time was illustrated in Figure 1c, where the percentage of naphthalene removed was 100.0%. However, 71.1% of phenanthrene remained at the end of the 96-hour experiment. In contrast, 90.3% and 94.5% of naphthalene and phenanthrene was observed after 96 hours in the control samples, respectively. Comparing Figure 1a with Figure 1c, it can be concluded that the biodegradation corresponded to the growth



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of BFN strain, indicating that the mass loss of both naphthalene and phenanthrene was degraded by the BFN strain.16 This confirmed that the BFN strain not only degraded naphthalene but also phenanthrene as its carbon source.

Although 100% naphthalene was degraded within 96 hours, only 28.9% phenanthrene and 48.3% chemical oxygen demand (COD) were removed, respectively. It indicates that this biological treatment was an incomplete process. In addition, some intermediate products may emerge during the degradation process which contributed greatly to the value of COD.21 To improve the degradation of phenanthrene and further remove the intermediates, Fenton-like oxidization using Fe NPs synthesized by tea extracts under various atmospheres (N2, O2 and air) as a catalyst was conducted in subsequent experiments.

Heterogeneous Fenton-like oxidation. To determine whether the Fe NPs synthesized using tea extracts under various atmospheres (N2, O2 and air) can be used for oxidative degradation of phenanthrene and intermediates, the use of these synthesized Fe NPs as catalyst was proposed, where the samples were collected after using BFN strain in biodegrading lasting 96 hours. As shown in Figure 2a, only 7.2% phenanthrene was removed after 90 min reaction when experiments were conducted in only the presence of a H2O2 system, and thus the overall amount of phenanthrene removed was only 34.0%, which was similar to the blank sample without adding other chemicals (data not shown). It is evident the phenanthrene was not degraded by H2O2 alone.7 Furthermore, the overall degradation of phenanthrene increased to 37.5% when the subsequent experiments were conducted only adding 0.5 g L-1 Fe NPs to the samples. Subsequently the removal of phenanthrene was probably attributed to the Fe NPs’ surface adsorption.8


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13

100

Fe NPs (O2)+H2O2

100 Fe NPs (O2)+H2O2 Fe NPs (air)+H2O2

80

Fe NPs (N2)+H2O2 H2O2 Fe NPs (O2) Fe NPs (air) Fe NPs (N2)

60

40 (a)

20 0

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30

45

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COD removal degree (%)

PHE removal degree (%)

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Fe NPs (air)+H2O2 Fe NPs (N2)+H2O2 H2O2

80

60

(b)

40 0

15

Time (min)

30

45

60

75

90

Time (min)

Figure 2 Comparison of oxidative degradation efficiency using three kinds of green synthesized Fe NPs as Fenton-like catalysts: (a) phenanthrene; (b) COD.

The experiment with the simultaneous presence of 0.5 g L-1 of Fe NPs and 10 mmol L-1 of H2O2 was conducted as shown in Figure 2a, where a 100% of phenanthrene was removed within 90 min in all Fe NPs/H2O2 systems, indicating the high catalytic capacity of Fe NPs to the H2O2 activation.8,13 Furthermore, it only required 30 min to completely degrade phenanthrene when using N-Fe NPs, while 60 and 90 min were required when employing air-Fe NPs and O-Fe NPs, respectively. As Huang and coworkers had confirmed that particle size plays an important role in the reactivity, where smaller nanoparticle size indicated larger surface area, and thus contributed to higher reactivity.11 This may be explained by the fact that synthesized N-FeNPs (under N2 atmosphere) produced

smaller particle diameter compared with O-Fe NPs (under

O2 atmosphere) and air-Fe NPs, which was also confirmed by the subsequent SEM images,22 while Fe NPs synthesized in the flowing atmosphere of O2 and air may lead to the formation of iron oxide, this will also decrease its catalyst activity. 22

COD was one of the most important parameters to evaluate the degradation process of



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organic matter content in mineral salts medium.21 As shown in Figure 2b, only 6.1% COD was removed after 90 min reaction, leading to 49.4% being removed overall when experiments were conducted in anoxic bottles containing MSM and 10 mmol L-1 H2O2. However, the total removal efficiency of COD reached 81.5%, 77.2%, and 68.7% in the simultaneous presence of 0.5 g L-1 Fe NPs (N-Fe NPs, O-Fe NPs and air-Fe NPs) and 10 mmol L-1 H2O2 within 90 min, respectively. This provided further evidence that Fe NPs could be used as a good catalyst in the Fenton-like system.8, 22

Analytical method and characterization. Surface morphology of the BFN strain after 96 hours of naphthalene and phenanthrene cultivation, determined by SEM, is illustrated in Figure 3. The BFN strain was rod-shaped with an average size of 1 µm×0.5 µm, while the BFN strain’s surface was smooth and plump. Furthermore, cells were rather intensive and grew well, which provided a further insight that both naphthalene and phenanthrene were only minimally toxic to the BFN strain. It is concluded that both of them serve as a carbon source for the metabolism of BFN strains.16 The results obtained from the SEM image agreed well with the growth of BFN strains shown in Figure 1a.

Figure 3 Scanning electron microscope images of BFN strain. ACS Paragon Plus Environment

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The images of N-Fe NPs, O-Fe NPs and air-Fe NPs before and after reaction by SEM are shown in Figure 4. It is clear that all of these synthesized particles were nano-sized with diameters ranging from 20-80 nm, and this is similar to previous reports.11,14 These Fe NPs existed as chain-like aggregates, which may result from the fact that the polyphenols or antioxidants in the tea extracts acted as capping agents.9 Moreover, compared to O-Fe NPs and air-Fe NPs, it was observed that N-Fe NPs dispersed better with a diameter less than 50 nm, which is attributed to N2 atmosphere effectively preventing synthesized nZVI from being oxidized to some iron oxides and hydroxides such as Fe3O4, Fe2O3, Fe (OH)3 and FeOOH.8 After these Fe NPs were employed as a catalyst in heterogeneous Fenton-like oxidation (Figure 4b, d and e), some aggregations and a slight increasing in the dimensions of Fe NPs were observed. This may due to the corrosion of Fe NPs in aqueous solution and more nZVI being converted into iron oxide through this oxidation process.23



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Figure 4 SEM images of N-Fe NPs before (a) and after reaction(b); O-Fe NPs before (c) and after reaction(d); air-Fe NPs before (e) and after reaction (f).

The localized elemental information of synthesized Fe NPs before and after reaction was determined by EDS. As shown in Figure 5a, c and e, there are typically intense peaks of C, O and Fe appearing in all these EDS patterns, where C and O signals originated from some C, O-containing molecules in the tea extracts such as polyphenol groups.11 However, the O signals may also be attributed to the formation of some iron oxide NPs, as the synthesized Fe NPs would not avoid reacting with air or water and thus produce a shell of iron oxide NPs.9 Specifically, the C, O and Fe loadings of N-Fe


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NPs were 52.17 wt%, 26.24 wt% and 21.59 wt%, respectively. Meanwhile they were 49.15 wt%, 34. 77 wt% and 16.08 wt% for O-Fe NPs, and 56.15 wt%, 24.50 wt% and 19.35 wt% for air-Fe NPs, also respectively. Clearly, the weight composition of Fe synthesized in the flowing gas atmosphere of N2 was more than that of in O2 or air atmosphere. This was due to N2 protecting the nZVI from oxidization to some extent.

Figure 5 EDS micrographs of of N-Fe NPs before (a) and after reaction(b); O-Fe NPs before (c) and after reaction(d); air-Fe NPs before (e) and after reaction (f).

Hence, a higher weight composition of Fe can be obtained when Fe NPs were synthesized in N2 atmosphere, which agrees with the above SEM analysis. However,



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after these Fe NPs were used for Fenton-like reacting, the O percentages in all Fe NPs samples increased while the Fe content declined. For example, O loadings of N-Fe NPs rose from 26.24 wt% to 37.93 wt% but Fe loadings decreased from 21.99 wt% to 11.89 wt%. This finding can be explained by the nZVI in GT-Fe NPs acting as a catalyst in heterogeneous Fenton-like oxidation, forming iron oxide such as Fe3O4, Fe2O3 and Fe (OH)3.22

Possible degradation mechanism analysis by GC-MS. As shown in Figure 6a, naphthalene was eluted with a retention time of 4.734 min before reaction, and the retention time of 9.696 min corresponded to phenanthrene. After 96 hours of biodegradation by the BFN strain, the retention time of phenanthrene still maintained at 9.696 min and the peak declined markedly, indicating that biodegradation yields did not impact on the varying of retention time and a remarkable amount of phenanthrene was biodegraded during the biological process. The peak at 4.734 min disappeared, indicating that all of naphthalene was degraded by the BFN strain within 96 hours However, the metabolites in the degradation of both naphthalene and phenanthrene by the BFN strain were not detected through GC-MS. The possible explanation is that that the polarity of some metabolites means they cannot be extracted by solvent. Consequently, they are less detectable by GC-MS,8 and some intermediates may be totally mineralized which was confirmed by the level of COD removal as depicted in Figure 1b.7

After 90 min of Fenton-like reaction, the peak at 9.696 min representing phenanthrene also disappeared, suggesting both naphthalene and phenanthrene were completely degraded by this coupled treatment. Since the majority of nanoparticles in the sample was cleared before GC-MS anlysis, and the retention time of impurities was consistent ACS Paragon Plus Environment

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for these three samples shown in Figure 6a, which indicated that the effect of nanoparticles on the retention time can be ignored. In addition, a metabolite with the retention time of 9.160 min was detected as shown in Figure 6b. It had an M+ at m/z 222 and fragmentation ions at m/z 207 [M+-15, -CH3 loss], 147 [M+-75, -C3H7O2 loss]. Based on fragmentation pattern and in comparison to the Wiley 275.L mass spectra database,

this

product

was

identified

as

Trans-3-(O-Hydroxyphenyl)-1-phenyl-2-propen-1-one. Finally, a possible pathway of phenanthrene being degraded by Fenton-like oxidation was proposed as depicted in Figure 6c.

(a)

(b)

(c) +▪OH

Figure 6 GC-MS analysis of naphthalene and phenanthrene before and after reaction (a); Mass spectral profiles of metabolite (b); the possible degradation pathway of phenanthrene by Fenton-like oxidation.



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CONLUSIONS The present study revealed an integrated approach using sequential biodegradation and Fenton-like oxidation based on green synthesis of Fe NPs provides the potential to remove both naphthalene and phenanthrene completely. In the biodegradation process, 100% of naphthalene was degraded while only 28.9% of phenanthrene and 48.3% of COD were removed within 96 hours. However, the removal efficiency of phenanthrene and COD increased to 100% and 81.5% using N-Fe NPs/H2O2, respectively. Characterization using SEM and EDS fully confirmed that Fe NPs synthesized in the flowing atmosphere of N2 provides the high catalytic activity used in Fenton-like oxidation.

GC-MS

analysis

Trans-3-(O-Hydroxyphenyl)-1-phenyl-2-propen-1-one

confirmed existed

in

the

that Fenton-like

oxidation of phenanthrene and indicated a possible phenanthrene degradation pathway.

ACKNOWLEDGEMENTS The authors thank the financial support by the National Natural Science Foundation of China (No. 41401585) and (No. 41501349).

REFERENCES (1) Yap, C. L.; Gan, S.; Ng, H. K. Fenton based remediation of polycyclic aromatic hydrocarbons-contaminated soils, Chemosphere 2011, 83, 1414-1430. (2) Lu, J.; Guo, C.; Zhang, M.; Lu, G.; Dang, Z. Biodegradation of single pyrene and mixtures of pyrene by a fusant bacterial strain F14, Int. Biodeterior. Biodegrad. 2014, 87, 75-80. (3) Yu, B.; Jin, X.; Kuang, Y.; Megharaj, M.; Naidu, R.; Chen, Z. An integrated ACS Paragon Plus Environment

Page 21 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


biodegradation and nano-oxidation used for the remediation of naphthalene from aqueous solution. Chemosphere 2015, 141, 205-211. (4) Navarro1, V. C.; Brozinski, J.M.; Leppänen, M. T.; Honkanen, J. O.; Kronberg, L.; Kukkonen, J. V. K. Inhibition of pyrene biotransformation by piperonyl butoxide and identification of two pyrene derivatives in Lumbriculus variegatus (Oligochaeta), Environ. Toxicol. Chem. 2011, 30, 1069-1078. (5) Moro, G. D.; Mancini, A.; Mascolo, G.; Iaconi, C. D. Comparison of UV/H2O2 based AOP as an end treatment or integrated with biological degradation for treating landfill leachates, Chem. Eng. J. 2013, 218, 133–137. (6) Li, R.; Jin, X.; Megharaj, M.; Naidu, R.; Chen, Z. Heterogeneous Fenton oxidation of 2, 4-dichlorophenol using iron-based nanoparticles and persulfate system, Chem. Eng. J. 2015, 264, 587-594. (7) Xu, L.; Wang, J. A heterogeneous Fenton-like system with nanoparticulate zero-valent iron for removal of 4-chloro-3-methyl phenol, J. Hazard. Mater. 2011, 186, 256-264. (8) Kuang, Y.; Wang, Q.; Chen, Z.; Megharaj, M.; Naidu, R. Heterogeneous Fenton-like oxidation of monochlorobenzene using green synthesis of iron nanoparticles, J. Colloid Interface Sci. 2013, 410, 67-73. (9) Wang, T.; Lin, J.; Chen, Z.; Megharaj, M.; Naidu, R. Green synthesized iron nanoparticles by green tea and eucalyptus leaves extracts used for removal of nitrate in aqueous solution, J. Clean Prod. 2014, 83, 413-419. (10) Machado, S.; Pinto, S. L.; Grosso, J. P.; Nouws, H. P. A.; Albergaria, J. T.; Delerue-Matos, C. Green production of zero-valent iron nanoparticles using tree leaf



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extracts, Sci. Total. Environ. 2013, 445-446, 1-8. (11) Huang, L.; Weng, X.; Chen, Z.; Megharaj, M., Naidu, R. Green synthesis of iron nanoparticles by various tea extracts: Comparative study of the reactivity, Spectrochim. Acta. A. 2014, 130, 295-301. (12) Hoag, G. E.; Collins, J. B.; Holcomb, J. L.; Hoag, J. R.; Nadagouda, M. N.; Varma, R. S. Degradation of bromothymol blue by ‘greener’ nano-scale zero-valent iron synthesized using tea polyphenols, J. Mater. Chem. 2009, 19, 8671-8677. (13) Shahwan, T.; Sirriah, S. A.; Nairat, M.; Boyacı, E.; Eroğlu, A. E.; Scott, T. B.; Hallam, K. R. Green synthesis of iron nanoparticles and their application as a Fentonlike catalyst for the degradation of aqueous cationic and anionic dyes, Chem. Eng. J. 2011, 172 258-266. (14) Weng, X.; Huang, L.; Chen, Z.; Megharaj, M.; Naidu, R. Synthesis of iron-based nanoparticles by green tea extract and their degradation of malachite, Ind. Crops Prod. 2013, 51, 342-347 (15) Whittaker, M. L.; Cutler, R. A. Effect of synthesis atmosphere, wetting, and compaction on the purity of AlB2, J. Solid State Chem. 2013, 201 93-100. (16) Lin, C.; Gan, L.; Chen, Z. L. Biodegradation of naphthalene by strain Bacillus fusiformis (BFN), J. Hazard. Mater. 2010, 182, 771-777. (17) Cheng, Y.; Lin, H.; Chen, Z.; Megharaj, M.; Naidu, R. Biodegradation of crystal violet using Burkholderia vietnamiensis C09V immobilized on PVA–sodium alginate–kaolin gel beads, Ecotox. Environ. Safe. 2012, 83, 108-114. (18) Janbandhu, A.; Fulekar, M. H. Biodegradation of phenanthrene using adapted microbial consortium isolated from petrochemical contaminated environment, J.


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Hazard. Mater. 2011, 187, 333-340. (19) Patel, V.; Jain, S.; Madamwar, D. Naphthalene degradation by bacterial consortium (DV-AL) developed from Alang-Sosiya ship breaking yard, Gujarat, India, Bioresour. Technol. 2012, 107, 122–130. (20) Ghoshal, S.; Ramaswami, A.; Luthy, R. G. Biodegradation of Naphthalene from Coal Tar and Heptamethylnonane in Mixed Batch Systems, Environ. Sci. Technol. 1996, 30, 1282–1291. (21) Kallel, M.; Belaid, C.; Mechichi, T.; Ksibi, M.; Elleuch, B. Removal of organic load and phenolic compounds from olive mill wastewater by Fenton oxidation with zero-valent iron, Chem. Eng. J. 2009, 150, 391-395. (22) Lin, J.; Weng, X.; Huang, L.; Jin, X.; Naidu, R.; Chen, Z. RSC Adv. 2015, 5, 70874-70882. (23) Zha, S.; Cheng, Y.; Gao, Y.; Chen, Z.; Megharaj, M.; Naidu, R. Nanoscale zero-valent iron as a catalyst for heterogeneous Fenton oxidation of amoxicillin, Chem. Eng. J. 2014, 255, 141-148.



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Graphic abstract The possible degradation pathway of phenanthrene by Fenton-like oxidation

A graphic in the Table of Contents Integration of biodegradation and nano-oxidation for removal of PAHs from aqueous solution Xiaoying Jin, Bing Yu, Jiajiang Lin, Zuliang Chen*


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Graphic abstract

The possible degradation pathway of phenanthrene by Fenton-like oxidation.

(b)

(c)

(c)

(a)


Integration of Biodegradation and Nano-Oxidation for Removal of

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