Capturing Cadmium(II) Ion from Wastewater Containing Solid Particles

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Capturing Cadmium (II) Ion from Wastewater Containing Solid Particles and Floccules Using Ion-imprinted Polymers with Broom Effect Xu-Biao Luo, Yu Xi, Haiyan Yu, Xiaocui Yin, and Shenglian Luo Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b04030 • Publication Date (Web): 08 Feb 2017 Downloaded from http://pubs.acs.org on February 14, 2017

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Industrial & Engineering Chemistry Research

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Capturing Cadmium (II) Ion from Wastewater Containing Solid Particles and Floccules Using Ion-imprinted Polymers with Broom Effect Xubiao Luo†*, Yu Xi†, Haiyan Yu†, Xiaocui Yin†, Shenglian Luo†*

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†

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Recycle, Nanchang Hangkong University, Nanchang 330063, P.R. China

Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources

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ACS Paragon Plus Environment


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ABSTRACT: Cavities and adsorption sites in adsorption materials can be easily

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blocked in complex media containing solid particles and floccules, which limit the

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applicability of these materials. This study demonstrates the synthesis of cadmium (II)

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ion-imprinted polymers (Cd-IIPs) and non-ion-imprinted polymers (NIPs) via

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reversible

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(RAFTPP). Microspheres of IIPs and NIPs were modified by grafting bi-component

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polymer brushes with different ratios of a hydrophilic component, hydroxyethyl

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methacrylate (HEMA) and a rigid component, styrene. The maximum adsorption

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capacities of the IIPs and NIPs in pure water are 65.5 and 24.5 mg/g, respectively.

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Specifically, the 9:1-IIP exhibits excellent anti-blockage and anti-interference

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performance, with an adsorption capacity considerably higher than those of IIPs in

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simulated wastewater, including SiO2 solid particles and floccules. This higher

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performance suggests that the 9:1-IIP has the rigidity to resist chaff interference from

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different aqueous media and also possesses good water-compatibility. The 9:1-IIP has

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a high recognition ability and high selectivity (α > 5.9) to Cd(II) although the surface

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is grafted with bi-component polymer brushes. Furthermore, the steric hindrance due

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to the styrene on the bi-component polymer brushes, in addition to van

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der Waals interactions with the interfering chaff, was confirmed to result in a “broom

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effect”. The developed sorbents demonstrate the expected adsorption capacities when

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applied to environmental samples from factories, indicating that IIP microspheres

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grafted with polymer brushes have significant potential for application in complex

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wastewater treatment.

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Keywords: Cd(II), ion-imprinted anti-blockage, anti-interference

addition-fragmentation

chain

transfer

polymer,

precipitation

polymer


polymerization

brushes,

adsorption,

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INTRODUCTION

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Ion imprinting polymers (IIPs) have proven to be novel sorbents that are widely

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used to remove heavy metals from aqueous media. They are easy to synthesize, are

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environmentally stable and exhibit high selectivity toward target ions due to their

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tailor-made recognition sites.1,2 The development of IIPs holds significance due to

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their applicability for the removal of heavy metals from different aqueous media, such

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as pure water,3 pure milk,4 synthetic nuclear power reactor effluents,5 neutral

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analytes,6 and steel pickling waste liquor.7 In our research group, the use of

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copper,8─10 lead,11,12 lithium,13 and cadmium14,15 as template ions for ion-imprinting

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technology has resulted in considerable advancements in wastewater treatment.

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However, despite the advantages of water compatibility and multiple applications,

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previously developed IIPs also present the challenge that their adsorption sites are

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easily blocked when template ions diffuse to their surface during adsorption from

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complex aqueous matrices from factories.16─19 Such blockage significantly limits their

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practical application in wastewater treatment. In fact, special attention must be paid to

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the development of novel IIPs with anti-interference performance in complex-matrix

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water samples from the environment, such as those containing solid particles and

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floccules.

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Recently, increasing attention has been focused on reversible addition

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-fragmentation chain transfer (RAFT) polymerization, which is a highly exploited

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living radical polymerization (LRP) technique, widely studied and utilized for the

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production of well-defined polymers with controllable molecular weight and

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composition.20─26 Polymer brushes synthesized by RAFT polymerization have been

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used to make surfaces with a variety of mechanical and chemical properties.27─31

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Surface modification using polymeric systems that respond to a variety of stimuli,

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such as pH, thermal stimuli, cosolvents, and magnetic fields,32 has been applied in the

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field of molecular imprinted polymers (MIPs).33─35 Grafting of surfaces with the

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polymer 2-(dimethylamino) ethylmethacrylate (PDMAEMA) can make the material

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responsive to the pH of aqueous environments;36,37 thermo-responsive poly (N-isopro

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pylacrylamide) (PNIPAM) can be used to make a material either hydrophilic or



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hydrophobic, depending on the temperature of water;38─43 and polymer hydroxyethyl

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methacrylate (PHEMA) can improve the hydrophilicity of the material.44─47

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Herein, we introduce the concept of the “broom effect”. A broom is a well-known

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cleaning tool typically consisting of rigid fibers attached to a long handle, used for

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such purposes as sweeping dirt off sidewalks. Similarly, polymers grafted onto the

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surface of IIP microspheres act as a broom because they can resist chaff interference

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in IIP cavities during adsorption from complex water samples. The anti-blockage and

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anti-interference performance of such IIPs grafted with polymer brushes is referred to

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as the “broom effect” here due to its similarity to the cleaning action of brooms.

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However, such polymer brushes have not been applied for the modification of IIP

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microspheres48 but our research group,49 as it is more challenging to graft polymer

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brushes onto IIP surfaces than onto MIPs for two reasons. First, the removal of metal

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ions from IIPs requires organic ligands that must have not only strong binding energy

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but also good coordination ability such that they can complex with the metal ions

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during polymerization. Second, it is necessary for the organic ligand to have a double

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bond to be used as a monomer for graft polymerization. Therefore, we chose

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3-allylrhodanine as the functional monomer due to its good complexing ability with

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cadmium and because it has not yet been applied before as a complexing agent for the

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removal of metal ions.50, 51

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In this study, we also hope to maintain or improve the hydrophilicity of Cd-IIP/NIP

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microspheres, with the polystyrene (PS) possessing the dual purpose of being a rigid

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building block for modification and the hydrophobic component. A mixture of HEMA

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and styrene was used as the bi-component copolymer for grafting onto IIP

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microspheres, which imparts them good water-compatibility and the rigidity to resist

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chaff interference from complex water samples. To our knowledge, this is the first

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study of IIPs grafted with polymer brushes. A series of adsorption experiments were

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conducted in pure water, simulated wastewater containing solid particles and floccules,

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and different real wastewater samples from factories to verify the “broom effect” on

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the adsorption property, anti-blockage and anti-interference performance.


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MATERIALS AND METHODS Material and instrumentation. All details regarding the materials and instrumentation are provided in the Supporting Information (SI).

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Synthesis of Cd-IIP/NIP microspheres with different ratios of surface-grafted

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bi-component polymer brushes. The IIP microspheres with surface-immobilized

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dithioester groups52 were synthesized by RAFT precipitation polymerization

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(RAFTPP), as described in the SI. For comparison, NIP microspheres were prepared

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and treated under identical conditions without adding the Cd(II).

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The Cd-IIP/NIP microspheres grafted with bi-component polymer brushes were

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synthesized by a surface-initiated RAFT polymerization procedure, as shown in the SI.

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The resulting solid products were then dried at 30 °C under vacuum until they reached

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a constant weight, leading to light pink Cd-IIP/NIP microspheres grafted with

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bi-component polymer brushes. The increases in weight due to grafting are listed in

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Table 1.

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Batch Adsorption Experiments. The equilibrium adsorption experiments carried

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at a pH of 7.0 ± 0.2, with initial Cd(II) concentrations ranging from 100 to 600 mg/L

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in pure water. Competitive adsorption of RAFT-IIP/NIP and Cd-IIP/NIP were also

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conducted in pure water, Zn(II), Ni(II), Co(II), and Cu(II) were chosen as competitor

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ions due to their identical charges and similar sizes to Cd(II). The aqueous solutions

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(pH = 7.0 ± 0.3) of Cd(II), Zn(II), Ni(II), Cu(II), and Co(II) all had an initial

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concentration of 500 mg/L. All the adsorption experiments in paper were mixed 50

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mg sorbents and 50 ml adsorbate solution to incubator shaker.

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The adsorptions of the developed sorbents were first studied in different samples of

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simulated wastewater to investigate the broom effect, namely, the anti-blockage and

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anti-interference performance of the bi-component polymer brushes. Here, we have

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synthesized three kinds of particle sizes range of SiO2 (Figure S1: 1 ~ 3 nm, 20 ~ 60

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nm, 70 ~ 400 nm), which cover a wide particle sizes in simulated wastewater, so that

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we can approach to the solid distribution in real wastewater as much as possible. SiO2

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particles were homogenized in water at a concentration of 1.0 mg/mL. Additionally,



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several industrial-grade pure flocculating agents, common exist in wastewater,

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including sodium carboxymethyl cellulose (CMC), poly-aluminium chloride (PAC),

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and polyacrylamide (PAM), were added either single-component or pairwise

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orthogonal flocculating agents addition was used to form floccules. The concentration

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of Cd(II) in all aqueous samples was 500 mg/L. used to simulated.

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All the sorbents have adsorption experiments in real wastewater. Wastewater from

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the tin-removal process was obtained from Hongtai Tin Industry Co. Ltd. (Shenzhen,

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China), the wastewater contained suspended white floccules with a Cd(II)

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concentration of approximately 4.0 g/L and a pH of 1.35 at room temperature.

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Lithium battery wastewater, obtained from Dingxin Metal Chemical Co. Ltd.

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(Shangrao, China), contained approximately 2.5 g/L of Cd(II) and 50 mg/L of solids,

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with a pH of 7.5 at room temperature. The particle sizes of real wastewater are shown

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in Figure S1, we adjust pH of real wastewater to 7.0 ± 0.2 before adsorption so as to

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investigated the performance of sorbents in real wastewater.

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RESULTS AND DISCUSSION

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Morphology characterization. The morphologies of both IIP and 9:1-IIP

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microspheres were characterized by SEM. The IIP (Figure 1a) and 9:1-IIP (Figure 1b)

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both consist of independently dispersed spherical particles with particle size

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distributions in the range of 5.5-2.7 µm. A comparison of the magnified images of the

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IIP (Figure 1c) and 9:1-IIP (Figure 1d) shows that the 9:1-IIP surface contains many

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bumps and is considerably rougher than the surface of IIP, indicating that polymer

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brushes have been grafted onto the 9:1-IIP surface.

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Hydrophilicity of IIP/NIP and Cd-IIP/NIP microspheres. After the ultrasonic

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dispersion of the sorbents in pure water (1 mg/mL), the dispersed mixtures were

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allowed to settle for different times at 20 °C. Figure S2 shows typical photographs of

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the resultant solutions, taken after different sedimentation times. These clearly show

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that all the sorbents take a rather long time (more than 4 h) to settle down, which is

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attributed to their hydrophilicity, particularly for IIPs and NIPs. A comparison of the

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details from Figure S2c shows that sedimentation occurs more rapidly in the presence


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of the IIP and Cd-IIP than in the presence of the NIP and Cd-NIP, which are ascribed

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to imprinting cavities in IIP and Cd-IIP, result in its densities lower to NIP and Cd-NIP,

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respectively.

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Characterization of the grafted polymer brushes. The samples for the

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characterization experiments were chosen to have different polymer brush: Cd-IIP

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ratios but the same number of graft sites (dithioester groups) to maintain the same

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quantity of initiators43. The free polymers obtained in our study were characterized by

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gel permeation chromatography (GPC)53. As shown in Table 1, the evaluated

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number-average molecular weights (Mn,

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polymer brushes on the surface of the IIP/NIP microspheres are in the ranges of

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26,378–17,282 and 1.14–1.00, respectively. In contrast, the number-average

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molecular weight of polymer brushes for the 9:1-IIP (Mn, GPC = 26,378) is 0.27% and

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10.21% higher than those for the 8:2-IIP and 7:3-IIP, and the molecular weight of

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polymer brushes for the 9:1-NIP (Mn, GPC = 25564) is 19.57% and 32.39% higher than

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those for 8:2-NIP and 7:3-NIP, indicating that 9:1-IIP/NIP possess longer polymer

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brushes. Additionally, the rates of weight gain (ΔW = (mCd-IIP－mIIP)/mIIP, (%)) of the

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resultants from the synthetic reaction, listed in Table 1, show that 9:1-IIP/NIP

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(10.92%/11.52%) microspheres are considerably heavier than 8:2 and 7:3-IIP/NIP

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microspheres, which confirm that surface-initiated RAFT polymerization has took

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place and polymer brushes were grafted on the Cd-IIP/NIP microspheres.

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GPC)

and polydispersity indices (PDIs) of

Cd(II) Adsorption Capacity Experiments.

Figures 2 and S3 show the

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equilibrium adsorption results of the IIP/Cd-IIP and the NIP/Cd-NIP toward Cd(II),

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which were used to investigate the adsorption capacities of the developed materials

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and determine the adsorption performance after the grafting of IIPs/NIPs with

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polymer brushes containing different ratios of HEMA and styrene. The correlation

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coefficient (R2) values demonstrate that the Langmuir model is more suitable than the

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Freundlich model for describing the adsorption process. The adsorption reaches

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equilibrium at a concentration of 500 mg/L. Both the IIP and Cd-IIP are found to take

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up more Cd(II) than their corresponding NIP and Cd-NIP (QIIP = 65.5 ± 1.6 mg/g,

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QNIP = 23.0 ± 0.8 mg/g), as seen from a comparison with the adsorption capacities



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reported in previous studies. As a monomer, 3-allylrhodanine has higher complexing

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ability with Cd(II) than cadmium ion-imprinted polymers prepared with

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carboxymethyl chitosan54 (Q = 20.7 mg/g) and polysaccharide55 (Q = 33.4 mg/g) as

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monomers. IIP exhibits better adsorption than Cd-IIP (Q9:1-IIP = 58.0 ± 1.5 mg/g) in

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pure water because identical weights of Cd-IIP-grafted polymer brushes have fewer

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adsorption sites for Cd(II). Further, the 9:1-IIP has a considerably higher adsorption

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capacity, 1.5 and 1.7 times higher than those of the 8:2-IIP and 7:3-IIP, respectively.

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These results suggest that the quantity of hydrophobic styrene in bi-component

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polymer brushes has an effect on the adsorption capacity. The 9:1-IIP has the best

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adsorption performance among the grafted microspheres due to the following two

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reasons. First, the polymer brushes bearing more of the hydrophilic component

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HEMA show good affinity with aqueous media. Second, the less rigid (hydrophobic)

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component styrene provides steric hindrance, which obstructs chaff interference from

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accessing imprinted cavities but still allows sufficient space for Cd(II).

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Competitive experiments. Figures 3 and S4 show the uptake capacity of Cd(II),

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Zn(II), Ni(II), Cu(II), and Co(II) by IIP/NIPs and Cd-IIP/NIPs. Combined with the

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data in Tables 2 and S1, the NIP and Cd-NIP sorbents exhibit considerably lower

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adsorption capacity and selectivity (β > 1.1, Table 2) than the IIP and Cd-IIP,

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respectively, in competitive experiments, furthermore, IIP and Cd-IIP showed poor

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adsorption to Zn(II), Ni(II), Cu(II), and Co(II) (α > 1). These contrasts in the

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adsorptions indicate that imprinted cavities and Cd(II) specific binding sites in a

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predetermined orientation are formed in the IIP and Cd-IIP. The IIP shows higher

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selectivity to Cd(II) (minimum α = 3.8) than materials reported in previous studies15

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(maximum α = 3.05). Thus, the monomer in this study, 3-allylrhodanine, has a higher

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complexing ability with Cd(II). Additionally, the 9:1-IIP has a rather high selectivity

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to Cd(II) (minimum αCd/Ni = 5.9 among the metal ions in Table 2) compared with

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those shown by the 8:2-IIP and 7:3-IIP, which confirms that the 9:1-IIP still retains a

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high recognition ability compared to other Cd-IIP ratios. The reason is the styrene

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content in polymer brushes would affects the adsorption performance because of

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its hydrophobicity and steric hindrance.


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Adsorption experiments in simulated wastewater. We chose SiO2 as a

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representative interfering solid particle and three common types of flocculants (CMC,

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PAM, and PAC) to simulate floccules to ensure that the components of the simulated

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wastewater were consistent with those of industrial wastewater. Adsorption

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experiments were first performed in complex aqueous samples (simulated wastewater)

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to study the “broom effect” of bi-component polymer brushes on the Cd-IIP/NIP. The

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broom effect is defined as the combination of two actions: anti-blockage performance

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in solid particle media, prevention of imprinted cavities from being blocked by solid

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particles and the performance in floccules media, which is to stop the floccules from

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wrapping the adsorption sites of sorbents.

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Figures 4 and S5 show the adsorptions in media containing different particle sizes

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of SiO2 (1~400 nm). Batch adsorption studies reveal that the IIP and Cd-IIP adsorbed

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more Cd(II) than the corresponding NIP and Cd-NIP in aqueous samples containing

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different particle sizes of SiO2. The adsorption capacity of the 9:1-IIP (Q 9:1-IIP = 54.2

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± 1.0 mg/g) is 2.38 times that of the 9:1-NIP, and 2.17 and 2.16 times those of the 8:2

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and 7:3 sorbents, respectively, in media containing 1~3 nm SiO2. This suggests that

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tailor-made recognition sites for target ions, such as those present in adsorbents

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synthesized by imprinting technique, exist in IIP and Cd-IIP microspheres.

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For the IIP/NIP, higher adsorption capacities were seen in media with larger

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particles of SiO2 (Q1~3nm < Q20~60nm < Q70~400nm). In particular, the IIP shows 57.86%

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lower adsorption in media with 1~3 nm SiO2 than in pure water because the particle

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size of SiO2 is sufficiently small for it to easily access the pores of sorbents. In

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contrast, the situation is completely reversed for the Cd-IIP/NIP, which exhibits a

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higher adsorption capacity as the particle size of SiO2 is decreased. For example, the

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9:1-IIP shows an adsorption capacity of 54.2 ± 1.1 mg/g in media with 1~3 nm SiO2,

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and this drops to 49.4 ± 0.9 and 37.0 ± 1.0 mg/g in media with 20~60 nm and 70~400

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nm SiO2 particles, respectively. This indicates that the adsorption performance

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decreases as the intensity of interference in the adsorption environment increases.

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Q9:1-IIP is 1.96 times higher than that of QIIP (27.6 ± 0.7 mg/g) in 1~3 nm SiO2 media,

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and the following trend is observed in the adsorption performances of Cd-IIP/NIP:



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Q9:1 > Q8:2 > Q7:3. These results demonstrate that the extent of hydrophobicity of

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styrene in the bi-component polymer brushes influences the adsorption capacity. The

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9:1-IIP shows outstanding anti-blockage performance because its bi-component

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polymer brushes have adequate rigidity and hydrophilicity; due to these properties,

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the corresponding Cd-IIP shows the “broom effect” and prevents solid particles from

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accessing the imprinted cavities in sorbents.

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Additionally, the adsorptions of PHEMA-IIP/NIP and PS-IIP/NIP were studied for

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comparison. In pure water, the adsorption capacity of PHEMA-IIP/NIP is higher than

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that of the 9:1-IIP/NIP but lower than that of the IIP/NIP because there is no sterically

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hindered (styrene) to prevent Cd(II) from accessing the imprinted cavities and an

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identical weight of PHEMA-IIP/NIP grafted with polymer brushes has fewer

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adsorption sites than an IIP/NIP. However, the following trend is observed when

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adsorption is carried out in media containing solid SiO2 particles: QIIP/NIP
QCMC > QPAC+CMC)

273

for Cd(II) adsorption onto the IIP/NIP and Cd-IIP/NIP were observed. However, as

274

shown in Figures 5b and S6b, PAM-containing media show only a slight decrease in

275

adsorption capacity because the viscidity of PAM-containing adsorbents hinders

276

uniform dispersal. In general, floccules were separated out of microspheres by

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polymer brushes such that efficient adsorption sites were maintained for the target ion

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Cd(II).

279

Analysis of the mechanism. EDX analysis was performed on the 9:1-IIP after the

280

adsorption of Cd(II) in media containing SiO2 particles (Figure S7a) and floccules

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(Figure S7b). The results confirm that the template Cd(II) was successfully bound to

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the imprinted cavities of 9:1-IIP microspheres, as shown by the strong cadmium peaks

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in the EDX spectrum after adsorption in media containing SiO2 particles and floccules.

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This suggests that ion-imprinted polymer microspheres grafted with bi-component

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polymer brushes maintain their adsorption ability for Cd(II). Additionally, the

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elements Si and Al were also detected on the surface of grafted 9:1-IIP microspheres,

287

verifying that Cd(II) adsorption occurs in media with solid particles and floccules.

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The chemical composition of the IIP/NIP and 9:1-IIP/NIP after the adsorption of

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Cd(II) was measured by XPS. As shown in Figures 6a and S8a, the peak

290

corresponding to Cd 3d, S 2p, C 1s, and O 1s of sorbents are observed in the

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high-resolution spectrum. The 9:1-IIP/NIP shows no clear peaks for Cd 3d in wide

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scans because the XPS probe can test the microsphere surface only down to 10 nm,

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indicating that the 9:1-IIP/NIP microspheres have been successfully grafted with

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bi-component polymer brushes. Cd 3d peaks were obtained in the narrow scope

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sweep, and the two peaks with binding energies of 404.9 eV and 411.6 eV are

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attributed to Cd 3d5/2 and Cd 3d3/2,56 respectively, on the surface of IIP microspheres,

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as shown in Figure 6e. The peaks at 405.8 eV and 412.5 eV are assigned to Cd 3d5/2

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and Cd 3d3/2 of Cd(II) absorbed on 9:1-IIP microspheres, as shown in Figure 6f. These

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results indicate that both the IIP and 9:1-IIP adsorb Cd(II). The presence of Cd in the

300

product further validates its affinity to the IIP and 9:1-IIP.

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Adsorption occurring on the IIP/NIP and 9:1-IIP/NIP can be checked by the shifts



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of S. The analysis of results for the IIP shows peaks at approximately 163.6, 164.3 eV

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before adsorption, corresponding to S－C bonds (S1/2p and S3/2p), whereas the peaks at

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approximately 164.8 and 165.5 eV correspond to S=C bonds (S1/2p and S3/2p),57 as

305

shown in Figure 6c. The binding energies of S－C sites are shifted to lower values of

306

163.3 and 163.8 eV after Cd(II) adsorption whereas the S=C sites are shifted to lower

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values of 164.5 and 165.0 eV. Additionally, the S binding energy of the 9:1-IIP/NIP is

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changed after the adsorption process, as shown in Figure 6d. The shifts in core levels

309

indicate an electron transfer in the valence band involving the reaction between Cd

310

and S. These findings indicate that the S－C and S=C groups play a critical role in

311

Cd(II) adsorption.

312

To elucidate the anti-interference mechanism of the 9:1-IIP polymer brushes, the

313

adsorptions of the IIP and 9:1-IIP were studied in media containing floccules made

314

with PAC. This test was performed in the absence of Cd(II) to determine how the

315

interfering species affect the chemical state of the elements in the sorbent. An IIP with

316

no bi-component polymer brushes was used as the blank control. Figure S9 suggests

317

the coexistence of S 2p, C 1s, O 1s, and Al 2p in the as-prepared sorbents. The O 1s

318

spectrum (Figure S9c) of the IIP can be fitted to three characteristic peaks: the peaks

319

at 531.77 and 532.49 eV are attributable to oxygen in the IIP of O－C=O, whereas the

320

peak at 533.83 eV is associated with the oxygen from CO2 in air58. After grafting with

321

bi-component polymer brushes in the 9:1-IIP, the peak at 531.96 eV is assigned to Al

322

－OH in the polymer brushes. The high intensity of the Al－OH peak verifies the

323

presence of a large quantity of OH in the polymer brushes. The peaks at 532.82 and

324

533.85 eV, associated with oxygen in the O－C=O groups of the 9-1-IIP, indicate that

325

van der Waals forces are an effective way for the bi-component polymer brushes to

326

prevent interfering species from accessing imprinted cavities. The other way is by the

327

“broom effect” produced by the steric hindrance from benzene rings in styrene.

328

Application in real wastewater. Figures 7 and S10 show the results for

329

applications of IIP/NIP and Cd-IIP/NIP in real wastewater. The results indicated that

330

for IIP/NIP, all the possible sites are not available as effective adsorption sites for

331

Cd(II) because the pores in the microspheres are blocked by chaff interference in real


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332

wastewater. The solid particle sizes in lithium battery wastewater were considerably

333

larger than those in the wastewater from tin removal (see Figure S1), 9:1-IIP showed

334

nice adsorption performance in both lithium battery wastewater and wastewater from

335

tin removal, which might due to the intensity of interference in real wastewater lower

336

than simulation wastewater, 9:1-IIP can dispose it although bigger particle size. Other

337

ratios showed different adsorption capacity, these adsorption rules can benefit the

338

application of these materials in industrial wastewater. Additionally, in contrast to the

339

IIP, the 9:1-IIP has a considerably higher adsorption capacity in real wastewater,

340

which proves that the bi-component polymer brushes can still display the “broom

341

effect” in a real wastewater environment.

342

Reusability. The stability and reusability of IIP and 9:1-IIP is key factors for

343

improving the process economics (Fig. S11). The regenerated IIP and 9:1-IIP were

344

reused for five cycles of adsorption-desorption. It can be observed that the adsorption

345

capacity of IIP and 9:1-IIP were stable within the five cycles with little decrease in the

346

adsorption capacity for Cd(II), but their adsorption capacity of were approximately

347

15.42% and 8.96% loss in the fifth cycles, respectively. It can be concluded that IIP

348

and 9:1-IIP exhibits relatively good adsorption efficiency after regeneration, and ion

349

imprinted polymer grafted polymer brushes also can protect material be destroyed

350

from eluent.

351

CONCLUSIONS

352

Cd-IIP adsorbents exhibiting the broom effect were utilized to treat heavy metal

353

wastewater, which can prevent solid particles and chaff interference in wastewater

354

from blocking the imprinting cavities. Appropriately rigid styrene introduced in

355

bi-component polymer brushes can provide moderate steric hindrance and enhance

356

the anti-blockage ability toward solid particles in complex wastewater. HEMA

357

brushes can provide adsorbents with good hydrophilicity and anti-interference ability

358

toward chaff interference, using van der Waals force to ensure that the adsorption

359

capacity is preserved in complex wastewater. This study provides fundamental

360

insights to enhance the anti-blockage and anti-interference ability of IIPs. It is critical

361

for the broad application of IIP technology to recycle valuable metals from complex



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

362

wastewater and reduce the cost of wastewater treatment by obtaining valuable

363

products.

364

365

Supporting Information

366

Material and instrumentation. Synthesis methods of IIP/NIP microspheres and

367

Cd-IIP/NIP. More detailed information on adsorption capacity and competitive

368

adsorption parameters calculation. Additional adsorption chart of non ion imprinting

369

polymers. This material is available free of charge via the internet at

370

http://pubs.acs.org.

371

372

Corresponding author

373

*(L.X.B.) Tel.: +86 791 3953372; Fax: +86 791 395373; E-mail: [email protected],

374

*(L.S.L.) E-mail: [email protected].

375

Notes

376

The authors declare no competing financial interest.

377

378

This study was financially supported by the National Science Fund for Excellent

379

Young Scholars (51422807), the Natural Science Foundation of China (51238002,

380

51678285), the Key Project of Science and Technology Department of Jiangxi

381

Province (20143ACG70006) and the Cultivating Project for Academic and Technical

382

Leader of Key Discipline of Jiangxi Province (20153BCB22005).

383

384 385

ASSOCIATED CONTENT

AUTHOR INFORMATION

ACKNOWLEDGMENTS

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1 2

3 4 5

TOC



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

6 7 8

Table captions Table 1. Polymerization conditions for synthesis of different ratios of grafted Cd-IIP/NIP via RAFT polymerization and their properties.

9 10

Table 2. Selectivity adsorption experiments parameters for IIP and Cd-IIP.

11 12


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13

Table 1. Polymerization conditions for synthesis of different ratios of Cd-IIP/NIP

14

via RAFT polymerization and their properties. Cd-IIP/NIP

Brush reactant (mmol) HEMA Styrene 9 1 9 1 8 2 8 2 7 3 7 3

9:1-IIP 9:1-NIP 8:2-IIP 8:2-NIP 7:3-IIP 7:3-NIP

ΔW(%)

Mn,GPC

PDI

10.92 11.52 9.57 7.05 7.88 6.52

26378 25564 26307 20561 23685 17282

1.14 1.04 1.07 1.06 1.00 1.08

15 16 17 18 19

Table 2. Selectivity adsorption experiments parameters for IIP and Cd-IIP. metal ions

IIP KD

α

9:1-IIP β

KD

α

8:2-IIP β

124.5

KD

α

7:3-IIP β

78.0

KD

α

β

Cd( II )

138.4

Zn( II)

36.4

3.8

1.1

20.0

6.2

1.7

14.3

5.4 2.6

18.0

3.4

1.2

Ni( II )

26.9

5.1

1.8

21.1

5.9

2.6

12.8

6.1 2.8

14.3

4.3

1.2

Cu( II )

21.3

6.5

2.5

13.4

9.3

3.3

25.9

2.7 1.0

13.9

4.5

1.2

Co( II )

13.3

10.4

3.5

17.8

7.0

2.1

10.9

7.2 2.4

17.0

3.6

1.4

20


62.0


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

21

Figure captions

22

Figure 1. SEM images of (a) IIP and (c) their magnified detail, (b) 9:1-IIP grafted

23

copolymer brushes and (d) their magnified detail.

24 25

Figure 2. Equilibrium adsorption experiments for IIP and Cd-IIP.

26 27

Figure 3. The selectivity of Cd(II) adsorption among Zn(II), Ni(II), Cu(II), and Co(II)

28

mixture solution by IIP and Cd-IIP.

29 30

Figure 4. Adsorption experiments of IIP and Cd-IIP performed in simulated

31

wastewater which contains three kind different particle sizes of SiO2.

32 33


34

wastewater which contains three kinds of flocculating agents CMC, PAC, and PAM

35

by adding single-component or pairwise orthogonal.

36 37

Figure 6. XPS spectra of (a) IIP and (b) 9:1-IIP survey; (c), (d) S 2p, and (e), (f) Cd 3d

38

for IIP and 9:1-IIP.

39 40 41

Figure 7. Adsorption experiments with IIP and Cd-IIP in real wastewater: Tin removal wastewater and Lithium battery wastewater.


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42 43

44 45

Figure 1. SEM images of (a) IIP and (c) their magnified detail, (b) 9:1-IIP grafted

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copolymer brushes and (d) their magnified detail.

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Figure2. Equilibrium adsorption experiments for IIP and Cd-IIP.

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Figure3. The selectivity of Cd(II) adsorption among Zn(II), Ni(II), Cu(II), and Co(II)

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mixture solution by IIP and Cd-IIP.

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55 56


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wastewater which contains three kind different particle sizes of SiO2.

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wastewater which contains floccules: (a) two kinds flocculating agents CMC, PAC,

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and the mixture of two (b) PAM, the mixture of PAM and PAC, the mixture of with

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PAM and CMC.

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Figure 6. XPS spectra of (a) IIP and (b) 9:1-IIP survey; (c), (d) S 2p, and (e), (f) Cd

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3d for IIP and 9:1-IIP.

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Figure 7. Adsorption experiments with IIP and Cd-IIP in real wastewater: Tin

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removal wastewater and Lithium battery wastewater.

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Capturing Cadmium(II) Ion from Wastewater Containing Solid Particles

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