Ion-imprinted Polymer Research Articles

Synthesis and Characterization of Adsorbent Materials Magnetite Mercaptosilicate Ion Imprinted Polymer as Cadmium Ion Adsorbent

Cadmium (Cd) is a toxic heavy metal with the active property of reacting with other components so that cadmium residues can quickly enter the food chain and cause cardiovascular, kidney, and cancer diseases. The purpose was to synthesize the magnetite mercaptosilicate ion imprinted polymer adsorbent material by forming Ion-Imprinted Polymer as a template, to analyze the characterization results using XRD and SEM-EDS, and to determine the adsorption test results for Cd metal ions. The results of the characterization of XRD show that there is a broad peak at a diffraction angle of 2θ= 20-220 with an amorphous structure, which is silica, and there is a high peak at a diffraction angle of 2θ= 35.55140 which indicates magnetite. The results of SEM analysis with magnifications of 500x, 1000x, and 5000x showed that the surface morphology of the particles was not uniform. For the EDS results, it can be seen that the components of the magnetite mercaptosilicate ion imprinted polymer material are elements C, O, Si, S, and Fe, with a mass percentage of 25.0%; 41.2%; 29.9%; 3.28% and 0.8%. The results of the adsorption test for the Magnetite-IIP-Mercaptosilika Material were able to adsorb Cd ions with the highest adsorption capacity of 10.536 mg/g at a concentration of 100 mg/L. Then the selectivity coefficient value of the Ion Cd metal ion is 2.32 greater than 1, indicating that the selectivity of the magnetite mercaptosilicate ion imprinted polymer material is much higher for Ion Cd metal ions than for Cu and Cr ions with a selectivity coefficient of 0.1 and 0.26.

Highly effective and selective recovery of Gd(III) from wastewater by defective MOFs-based ion-imprinted polymer: Performance and mechanism

Highly effective and selective recovery of Gd(III) from wastewater by defective MOFs-based ion-imprinted polymer: Performance and mechanism

Development of an azo-functionalized ion-imprinted polymer for selective recognition of palladium ions

The current work reports the development of a new azo-functionalized ion-imprinted material for specific recognition of palladium ions (Pd2+). The ion-imprinted material was synthesized via a free radical polymerization approach, enabling convenient access to Pd2+. First, a maleimide-phenolic azo-functionalized ligand (MIZOH) was synthesized and combined with Pd2+ to form the corresponding [Pd(MIZO)2] complex. The copolymerization was then proceeded with utilizing 2,2-azobisisobutyronitrile (AIBN) as an initiator with styrene and divinylbenzene crosslinkers in the presence of the [Pd(MIZO)2] monomer complex. A solution mixture of thiourea/HNO3 was used to extract the Pd2+ ions. Various methodologies were employed to investigate the synthesized ligands, complexes, and polymers. Batches were conducted to evaluate the adsorption characteristics, including pH, capacity, contact time, selectivity, and recyclability. The results suggest that at a temperature of 30 °C and a solution pH of 6, the adsorption capacity was around 155 mg/g. The kinetic analyses exhibited a high degree of conformity with the pseudo-second-order kinetics. The Langmuir and Freundlich isothermal equations were constructed using equilibrium data, which exhibited a favorable level of conformity with the Langmuir isothermal model. Interference experiments show that the Pd2+ ion-imprinted polymer has a stronger attraction to Pd2+ than it does to the other ions that could be in the solutions. Additionally, there has been no appreciable decline in the affinity of the wasted polymer after at least five regeneration cycles.

Design of a New Phthalocyanine-Based Ion-Imprinted Polymer for Selective Lithium Recovery from Desalination Plant Reverse Osmosis Waste.

In this study, a novel technique is introduced that involves the combination of an ion-imprinted polymer and solid-phase extraction to selectively adsorb lithium ions from reverse osmosis brine. In the process of synthesizing ion-imprinted polymers, phthalocyanine acrylate acted as the functional monomer responsible for lithium chelation. The structural and morphological characteristics of the molecularly imprinted polymers and non-imprinted polymers were assessed using Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorption data for Li on an ion-imprinted polymer showed an excellent fit to the Langmuir isotherm, with a maximum adsorption capacity (Qm) of 3.2 mg·g-1. Comprehensive chemical analyses revealed a significant Li concentration with a higher value of 45.36 mg/L. Through the implementation of a central composite design approach, the adsorption and desorption procedures were systematically optimized by varying the pH, temperature, sorbent mass, and elution volume. This systematic approach allowed the identification of the most efficient operating conditions for extracting lithium from seawater reverse osmosis brine using ion-imprinted polymer-solid-phase extraction. The optimum operating conditions for the highest efficiency of adsorbing Li+ were determined to be a pH of 8.49 and a temperature of 45.5 °C. The efficiency of ion-imprinted polymer regeneration was evaluated through a cycle of the adsorption-desorption process, which resulted in Li recoveries of up to 80%. The recovery of Li from the spiked brine sample obtained from the desalination plant reverse osmosis waste through the ion-imprinted polymer ranged from 62.8% to 71.53%.

Graphene oxide based ion-imprinted polymers for selective uranium adsorption from seawater

The project for the uranium adsorption from seawater provides a new idea for acquisition of uranium resources. However, the low concentration of uranium in seawater, the presence of multiple metal ions, and the attachment of microorganisms all affect the adsorption of uranium by the material. To solve these problems, graphene oxide (GO)-based uranium imprinted polymers with antibacterial properties and specific selectivity for uranium were prepared. β-1,3 glucan was selected as the functional monomer for grafting GO, followed by the imprinting process with uranyl ions as the target template. After elution of the target ions by hydrochloric acid, the ion-imprinted polymer was prepared (GOG-RE). The results of ion-competition adsorption experiments showed that the imprinted material had a high adsorption selectivity for uranyl ions, the Kd value of 1.28 × 105 mL∙g−1. The calculated maximum adsorption capacity was 806.45 mg·g−1. Antibacterial experiments have proven its significant inhibitory effect on E. coli (Gram-negative), S. Aureus (Gram-positive) and Pseudoalteromonas marina. The above results indicate that GOG-RE has excellent application prospects in the field of uranium adsorption from seawater.

Cadmium ion-imprinted polymers for adsorption and detection of cadmium ions

Cadmium is a typical heavy metal ion. Long-term exposure to cadmium can lead to diseases like renal tubular dysfunction and bone degeneration. Therefore, it is necessary to develop efficient separation methods and detection techniques for cadmium ions. In this paper, adsorption enrichment was combined with detection to rapidly detect cadmium ions in water. Cadmium ion imprinted polymers (Cd(II)-IIPs) were prepared by bulk polymerization using Cd(II) as template ion, itaconic acid (IA) as functional monomer, ethylene dimethacrylate (EGDMA) as cross-linker, 4-(2-pyridylazo)-resorcinol (PAR) as chromogenic ligand, and azobisisobutyronitrile (AIBN) as initiator. The preparation conditions were optimized and the prepared Cd(II)-IIPs were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C nuclear magnetic resonance (13C NMR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). In the adsorption experiment, the adsorption equilibrium was reached within 10 min in a solution of pH 7.0, and the saturation adsorption capacity of IIPs and NIPs were 50.542 mg·g−1 and 33.762 mg·g−1, respectively. The Cd(II)–IIPs exhibited selectivity for Cd(II) ions in the presence of Ni(II), Fe(II), Co(II), Cu(II), and Pb(II) ions; and after eight adsorption–desorption cycles, the adsorption capacity of Cd(II)-IIPs retained > 90%. In addition, the detection performance of the Cd(II)-IIPs was investigated by digital image colorimetric (DIC) and ultraviolet spectrophotometric methods; the detection limits were 1.46 and 1.74 μg·L−1, respectively, and the quantitative detection range was 8–100 μg·L−1. The Cd(II)-IIPs exhibited excellent adsorption properties and an obvious color gradient variation, which could be used for quantitative colorimetric detection over a range of concentrations.

Controllable synthesis of 3D superhydrophilic Cd(II) ion-imprinted polymer microspheres based on OV-POSS and bifunctional monomers synergy with superior selectivity for Cd(II) adsorption

Novel 3D porous Cd(II) ion-imprinted polymer (Cd(II)-IIP) microspheres based on octavinyl polyhedral oligomeric silsesquioxane (OV-POSS) were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization technique combined with the synergistic effect of N-hydroxymethylacrylamide (NMA) and 1-vinylimidazole (1-VI) as bifunctional monomers. RAFT polymerization could achieve a controllable synthesis of polymer networks on OV-POSS. The structure, composition and properties of Cd(II)-IIP were systematically investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscope, water contact angle and thermogravimetric analysis. The results showed that the adsorbent, with a water contact angle of 0 ° and superhydrophilicity, has a high potential for application in aqueous phase systems. Different parameters influencing the sorption performance of Cd(II)-IIP, such as OV-POSS ratio, functional monomers ratio, adsorbent dosage, pH and adsorption time were optimized. Under optimal conditions, the maximum adsorption amount of Cd(II)-IIP for Cd(II) was 80.21 mg/g, and the adsorption equilibrium state could be reached within 40 min. The sorption kinetics proved that the sorption was chemisorption and the rate-limiting step was intraparticle diffusion. Thermodynamic studies showed that Cd(II) sorption was a spontaneous endothermic process. Importantly, XPS analysis, density functional theory (DFT) and frontier molecular orbital (FMO) theory calculations showed that the sorption of Cd(II)-IIP was attributed to the coordination of O and N atoms with Cd(II) on NMA and1-VI, respectively. Actual water sample analysis results indicated that Cd(II)-IIP was an adsorbent of great application potential.

Dinuclear Pb(II) monomer complex: Synthesis, characterization, and application of Pb(II) ion-imprinted polymer as a selective potentiometric microsensor

A Pb(II) centered [Pb2(maa)4(vim)2] complex was synthesized using methacrylic acid (maaH) and 1-vinylimidazole (vim) containing vinylic groups suitable for polymerization. The structure of the Pb(II) monomer complex was elucidated by single-crystal X-ray diffraction method, fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). A new Pb(II) ion-imprinted polymer (Pb(II)-IIP) was prepared with [Pb2(maa)4(vim)2] complex as functional monomer, ethylene glycol dimethacrylate (EGDMA) as crosslinker and 2,2′-azobisisobutyronitrile (AIBN) as initiator, to use in a Pb2+ selective sensor design. The prepared Pb(II)-IIP was characterized by FT-IR, TGA, energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). Pb(II)-IIP was used as an ionophore in the structure of polyvinylchloride (PVC) membrane of the all-solid-state ion-selective microsensor to obtain a selective potentiometric response for Pb2+ ions. The Pb2+-selective microsensor exhibited a highly selective Nernstian response over a wide linear concentration range of 10−6 to 10−2 mol.L−1 with a slope of 29.4 mV per decade (R2 = 0.9987) in the pH range of 3.0 to 7.0. The response time of the microsensor was very short (less than 15 s) and the detection limit was determined as 8.30 × 10−8 mol.L−1. The lifetime of the microsensor was calculated as 45 days.

Thermo-responsive ion imprinted polymer on the surface of magnetic carbon nanospheres for recognizing and capturing low-concentration lithium ion

Ion imprinted polymer (IIP) on the surface of magnetic carbon nanospheres, using N-propylacrylamide and benzo-12-crown 4-ether (B12C4) as bi-functional monomers, is designed and synthesized for the selective recognition and recovery of Li+ from aqueous medium. The adsorption behaviors of Li+-IIP including adsorption kinetics, isotherms, selective recognition, and regeneration are investigated in detail by inductively coupled plasma-optical emission spectroscopy. The adsorption capacity of Li+-IIP towards Li+ reaches a maximum value of 23.46 mg g−1 at 25 ˚C within 60 min. The Langmuir and pseudo-second-order models manifest the apparent adsorption behavior dominated by single layer chemisorption. The Li+-IIP realized selective adsorption of Li+ against Na+, K+, Mg2+, Al3+, and Fe3+ in their coexistence solution. It is reused five times without a significant decrease with the assistance of externally applied magnetic field for solid/liquid separation. The recognition mechanism of Li+-IIP towards Li+ is the combined action of dehydration effect, electrostatic attraction, and size and imprinting effect, as identified by theoretical simulated calculation based on density functional theory and experimental data. The temperature-responsive adsorption of Li+-IIP towards Li+ facilitates the adsorption/desorption operations. Li+-IIP shows good separation from the treated solution by applying an external magnetic field. This work provides new insights into the recovery of lithium.

Ion-imprinted magnetic adsorbents for the selective capture of Cu(II) and their cascade application as heterogeneous recyclable catalysts for Ullmann and Glaser coupling reactions

The selective capture and efficient reuse of Cu(II) from contaminated seawater requires a multifunctional adsorbent with a high Cu(II) selectivity and magnetic properties to facilitate recycling. Moreover, the cascade application of the recycled adsorbent is important but has not been extensively investigated. Accordingly, in this study, ion-imprinted magnetic adsorbents, particularly, copper ion-imprinted polymers (Fe3O4@mSiO2@CIIP) were prepared using magnetic mesoporous silica microspheres (Fe3O4@mSiO2) as carriers, with organosilicon containing hydroxyl and Schiff bases as the polymer backbone to selectively collect Cu(II) from aqueous media. The adsorption isotherms, kinetics, selectivity, and mechanisms were examined under various adsorption conditions. Fe3O4@mSiO2@CIIP-2 shows high selectivity and fast adsorption kinetics, and the equilibrium adsorption amount of Cu(II) is 263.2 mg/g within 30 min. The pseudo-second-order model and the Langmuir model are supported by the adsorption kinetics and isotherms, respectively. Particularly, the adsorption amount of Fe3O4@mSiO2@CIIP-2 could be reused eight times without substantial loss. Additionally, specific functional monomers bound to Fe3O4@mSiO2@CIIP-2 could both selectively adsorb Cu and serve as functional ligands for catalysts that can heterogeneously catalyze the Ullmann and Glaser coupling reactions after adsorbing Cu(II).

Synthesis and characterization of epoxy resin-based ion-imprinted polymer for selective removal of copper ions

Synthesis and characterization of epoxy resin-based ion-imprinted polymer for selective removal of copper ions

Fabrication and characterization of a new bifunctional imprinted polymer as a selective receptor for cobalt ions from aqueous medium

Ion-imprinting methodology was used to fabricate a new cobalt ion-imprinted polymer as a cross-linked copolymer consisting of fumaric acid and 4-vinylpyridine as monomers. Different techniques were used to investigate all of the chemical and morphological changes that occurred during the cobalt ion imprinting process. Furthermore, extraction experiments for cobalt ions using controlled and imprinted polymers were carried out to obtain the essential isotherm, kinetic and thermodynamic parameters. The controlled and imprinted resins had the best agreement with the pseudo-second-order and Langmuir models, with maximum retention capacities of 14.7 ± 2 and 42.0 ± 0.5 mg/g, respectively. In comparison to non-imprinted polymer, the imprinted polymer showed greater affinity for cobalt ions in the presence of other metal ions like Cd2+, Cu2+, Ni2+, La3+, and Y3+. In addition, after the fifth adsorption-desorption cycle, resin regenerates with about 96% of its initial activity, demonstrating its high economic value.

Synthesis and characterization of zinc(II) methacrylate monomer complex and adsorption properties of zinc(II) ion-imprinted polymer

A zinc(II) centred [Zn(maa)2(vim)2] complex was synthesised using methacrylic acid (maaH) and 1-vinylimidazole (vim) containing vinylic groups suitable for polymerization. The structure of the monomer complex was elucidated by Fourier Transform Infrared Spectroscopy (FT-IR), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction methods. A new Zn(II)-based imprinted polymer (Zn(II)-IIP) was prepared with [Zn(maa)2(vim)2] as monomer complex and ethylen glikol dimethacylate (EGDMA) as crosslinker in the presence of 2,2′-azobisisobutyronitrile (AIBN) as initiator to eliminate Zn(II) from aqueous solutions. The prepared Zn(II)-IIP was characterized by FT-IR, TGA, energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The adsorption performance of Zn(II)-IIP in aqueous solutions was investigated too. The maximum adsorption of Zn(II) ions on to the Zn(II)-IIP particles was 41.5 mg/g at pH: 6.0. The zinc(II) ion content of the solutions was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The Langmuir and Freundlich isotherm models were applied comparatively to experimental results.

Construction of 1, 10-phenanthroline functionalized magnetic starch as a lead (II) tagged surface imprinted biopolymer for highly selective targeting of toxic lead ions

In this research 1, 10 - phenanthroline functionalized CaFe2O4 - starch was employed as a magnetic ion-imprinted polymer (IIP) for highly selective targeting toxic Pb2+ ions from aqueous media. VSM analysis revealed that the sorbent has magnetic saturation of 10 emu g−1 which is appropriate for magnetic separation. Moreover, TEM analysis confirmed that the adsorbent is composed of particles with a mean diameter of 10 nm. According to XPS analysis, lead coordination with phenanthroline is the main adsorption mechanism that is along with electrostatic interaction. A maximum adsorption capacity of 120 mg g−1 was obtained within 10 min at a pH of 6 and an adsorbent dosage of 20 mg. Kinetic and isotherm studies showed that lead adsorption followed the pseudo-second–order and Freundlich models, respectively. The selectivity coefficient of Pb (II) relative to Cu(II), Co(II), Ni(II), Zn(II), Mn(II), and Cd(II) was 4.7, 14, 20, 36, 13 and 25, respectively. Moreover, the IIP represents the imprinting factor of 1.32. The sorbent showed good regeneration after five cycles of the sorption/desorption process with an efficiency of >93 %. Finally represented IIP was used for lead preconcentration from various matrices i.e., water, vegetable, and fish samples.

Selective Adsorption Behavior and Mechanism for Cd(II) in Aqueous Solution with a Recoverable Magnetie-Surface Ion-Imprinted Polymer.

A novel recoverable magnetic Cd(II) ion-imprinted polymer was synthesized on the surface of silica-coated Fe3O4 particles via the surface imprinting technique and chemical grafting method. The resulting polymer was used as a highly efficient adsorbent for the removal of Cd(II) ions from aqueous solutions. The adsorption experiments revealed that Fe3O4@SiO2@IIP had a maximum adsorption capacity of up to 29.82 mg·g-1 for Cd(II) at an optimal pH of 6, with the adsorption equilibrium achieved within 20 min. The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model. Thermodynamic studies showed that the adsorption of Cd(II) on the imprinted polymer was spontaneous and entropy-increasing. Furthermore, the Fe3O4@SiO2@IIP could rapidly achieve solid-liquid separation in the presence of an external magnetic field. More importantly, despite the poor affinity of the functional groups constructed on the polymer surface for Cd(II), we improved the specific selectivity of the imprinted adsorbent for Cd(II) through surface imprinting technology. The selective adsorption mechanism was verified by XPS and DFT theoretical calculations.

Field specific capture of Pb(II) in aqueous samples with three channels in-tip microextraction apparatus based on ion-imprinted polymer

On-site specific capture is a critical step in accurate analysis of trace Pb(II) in environmental waters. In this connection, a new Pb(II)-imprinted polymer-based adsorbent (LIPA) was in-situ prepared in pipette tip and used as the extraction medium of laboratory-made portable three channels in-tip microextraction apparatus (TIMA). Density function theory was employed to verify the selection of functional monomers for the preparation of LIPA. The physical and chemical properties of the prepared LIPA were inspected with various characterization techniques. Under the beneficial preparation parameters, the LIPA presented satisfactory specific recognition performance towards Pb(II). Selectivity coefficients of LIPA towards Pb(II)/Cu(II) and Pb(II)/Cd(II) were 6.82 and 3.27 times higher than that of non-imprinted polymer-based adsorbent, respectively, and the adsorption capacity towards Pb(II) was as high as 36.8 mg/g. Freundlich isotherm model fitted well with the adsorption data, revealing that the adsorption of Pb(II) on LIPA was a multilayer process. After optimizing the extraction conditions, the developed LIPA/TIMA was employed to field selectively separate and enrich trace Pb(II) in various environmental waters followed by quantification with atomic absorption spectrometry. The enhancement factor, linear range, limit of detection and RSDs for precision were 183, 0.50–10000 ng/L, 0.14 ng/L and 3.2–8.4%, respectively. Accuracy of the developed approach was inspected by means of spiked recovery and confirmation experiments. Achieved results reveal that the developed LIPA/TIMA technique is good for field selective separation and preconcentration of Pb(II) and the introduced approach can be used to measure ultra-trace Pb(II) in a variety of waters.

Enhanced Selective Adsorption of Lanthanum(III) by Dual-Site Polymeric Ion-Imprinted Nanoparticles from Aqueous Media

Selective recognition and separation of rare-earth elements (REEs) is considered a real challenge for the RE industry. In this work, two dual-site ion-imprinted polymers (IIP-AM and IIP-MAA) were synthesized via a radical copolymerization method for the removal of La(III) from aqueous solutions. The structures of samples were characterized and confirmed with various kinds of techniques, including IR, X-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller, thermogravimetry analysis, and X-ray photoelectron spectroscopy (XPS). Adsorption studies reveal that the pseudo-second-order kinetic model and the Langmuir isotherm model were well-fitted with the adsorption of La(III), showing high adsorption capacities of 45.65 and 50.05 mg/g for IIP-AM and IIP-MAA, respectively, after 120 min at pH = 5.5 and 25 °C. Impressively, the fabricated IIPs possess remarkable selectivity between La(III) and other REEs, as well as excellent reusability after five successive adsorption–regeneration cycles with less than 9% reduction of capacities. The adsorption mechanism indicates that the surface complexation and electrostatic attraction contribute to the adsorption of La(III) based on the characterization analysis of XPS, elemental mapping, and energy-dispersive spectrometry, as well as density functional theory calculations. Accordingly, these samples with tailored ion-imprinted cavities and abundant active O sites entirely exhibit the potentials for the selective recovery of REEs from aqueous solutions.

Synthesis and Application of a Novel Metal-Organic Frameworks-Based Ion-Imprinted Polymer for Effective Removal of Co(II) from Simulated Radioactive Wastewater.

In this work, a novel metal-organic frameworks (MOFs)-based ion-imprinted polymer (MIIP) was prepared to remove Co(II) from simulated radioactive wastewater. The batch experiments indicated that the sorption was well described by the pseudo-second-order kinetic and Langmuir models, and it is monolayer chemisorption. The theoretical maximum sorption capacity was estimated to be 181.5 mg∙g-1, which is by far the reported maximum value of Co(II) sorption by the imprinted materials. The MIIP presented an excellent selectivity for Co(II) in the presence of common monovalent and divalent metal ions, and the selectivity coefficients were 44.31, 33.19, 10.84, 27.71, 9.45, 16.25, and 7.60 to Li(I), K(I), Mg(II), Ca(II), Mn(II), Ba(II), and Cd(II), respectively. The sorption mechanism was explored by X-ray photoelectron spectroscopy (XPS) technology and density functional theory (DFT) calculations, suggesting that Co(II) was adsorbed by the MIIP via the chelation of 4-vinylpyridine (VP) ligands with Co(II), which was a spontaneous process, and the optimal coordination ratio of VP to Co(II) was 6. This work suggested that the MIIP has a high sorption capacity and excellent selectivity for Co(II), which is of great significance for the selective separation of Co-60 from radioactive wastewater.

Synthesis of nanostructured novel ion-imprinted polymer for selective removal of Cu2+ and Sr2+ ions from reverse osmosis concentrated brine

This study aims to prepare an ion-imprinted polymer (IIP) using copper sulfate as a template and potassium persulfate as an initiator to selectively adsorb copper ions (Cu2+) from aqueous solutions and in an attempt to also test its applicability for removing strontium ions (Sr2+). The prepared polymer was denoted by IIP-Cu. Various physical and chemical characterizations were performed for the prepared IIP-Cu. The scanning electron microscopy and transmission electron microscopy analyses confirmed the cavities formed after the removal of the template. It also indicated that the IIP-Cu had a rough and porous topology. The X-ray photoelectron spectroscopy confirmed the successful removal of the Cu template from IIP-Cu. The Brunauer-Emmet-Teller revealed that the surface area of IIP-Cu is as high as 152.3 m2/g while the pore radius is 8.51 nm. The effect of pH indicated that the maximum adsorption of Cu2+ was achieved at pH 8 with 98.7%. Isotherm studies revealed that the adsorption of Cu2+ was best explained using Langmuir models with a maximum adsorption capacity of 159 mg/g. The effect of temperature revealed that an increase in temperature had an adverse impact on Cu2+ removal from the aqueous solution, which was further confirmed by thermodynamic studies. The negative value of standard enthalpy change (−4.641 kJ/mol) revealed that the adsorption of Cu2+ onto IIP-Cu was exothermic. While the continuous increase in Gibbs free energy from −6776 kJ/mol to −8385 kJ/mol with the increase in temperature indicated that the adsorption process was spontaneous and feasible. Lastly, the positive value of the standard entropy change (0.023 J/mol.K) suggested that the Cu2+ adsorption onto IIP-Cu had a good affinity at the solid-liquid surface. The efficiency of the prepared IIP-Cu was also tested by studying the adsorption capacity using Sr2+ and real brine water. The results revealed that IIP-Cu was able to remove 63.57% of Sr2+ at pH 8. While the adsorption studies revealed that the experiment was best described using the Langmuir model with a maximum adsorption capacity of 76.92 mg/g. Additionally, IIP-Cu was applied in a real brine sample, which consisted of various metal ions. The highest percentage of Cu2+ removal was 90.6% and the lowest was 65.63% in 1:4 and 1:1 brine ratios, respectively. However, this study indicates the successful application of IIP-Cu in a real sample when it comes to the effective and efficient removal of Cu2+ in a solution consisting of various competing ions.

Fabrication of surface ion imprinting rice husk-based polymer for selective detection and efficient adsorption of Cu2+ in lake water

With the deepening of the concept of recycling economy and green chemistry, selective detection and capture of Cu2+ from lake water by biosorbent are of great significance. Herein, the Cu2+ ion-imprinted polymers (RH-CIIP) with organosilane containing hydroxyl and Schiff base groups (OHSBG) as ion-receptor, fluorescent chromophores and cross-linking agent, and Cu2+ as template ion, were fabricated via surface ion imprinting technology by employing mesoporous silica MCM-41 (RH@MCM-41) as supporter. The RH-CIIP could be exploited as a fluorescent sensor for Cu2+ with high selective compared with Cu2+ non-imprinted polymers (RH-CNIP). Additionally, the LOD was calculated to be 5.62 μg/L, which is far below WHO standard for Cu2+ in drinking water of 2 mg/L, and more lower than the reported methods. Moreover, the RH-CIIP can also be utilized as an adsorbent for the effective elimination of Cu2+ from lake water with the adsorption capacity of 87.8 mg/g. Besides, the kinetic features of adsorption were well defined by the pseudo-second-order model and the sorption isotherm was in agreement with the Langmuir model. Meanwhile, the interaction of RH-CIIP and Cu2+ was investigated using theoretical calculations and XPS. Finally, RH-CIIP was able to remove almost 99 % Cu2+ in lake water samples that satisfied the drink water standard.