The Multi-Challenges of the Multi-Ion-Imprinted Polymer Synthesis

Multi-ion-imprinted polymers (MIIPs) are materials with a wide range of applications mainly focused on environmental recovery, mining, technology, sensors, etc. MIIPs can incorporate ions such as heavy metals, transition metals, rare earth elements, radionuclides, and other types of ions. The chemical structures of MIIPs can be designed for different purposes and with certain morphologies, such as gels, crystals, or powders, and the surface area and porosity are also considered. All these properties provide the material with several desirable characteristics, like high selectivity, high specificity, adequate efficiency, good stability, the possibility of reusability, and strategy technology adaptation. In this review, we show the multitude of challenges of multi-ion imprinted polymer chemical synthesis based on the different and interesting methods reported previously.

Application Prospect of Ion-Imprinted Polymers in Harmless Treatment of Heavy Metal Wastewater

With the rapid development of industry, the discharge of heavy metal-containing wastewater poses a significant threat to aquatic and terrestrial environments as well as human health. This paper provides a brief introduction to the basic principles of ion-imprinted polymer preparation and focuses on the interaction between template ions and functional monomers. We summarized the current research status on typical heavy metal ions, such as Cu(II), Ni(II), Cd(II), Hg(II), Pb(II), and Cr(VI), as well as metalloid metal ions of the As and Sb classes. Furthermore, it discusses recent advances in multi-ion-imprinted polymers. Finally, the paper addresses the challenges faced by ion-imprinted technology and explores its prospects for application.

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.

Highly selective recovery of Ni(II) in neutral and acidic media using a novel Ni(II)-ion imprinted polymer

In this work, an original ion-imprinted polymer (IIP) was synthetized for the highly selective removal of Ni(II) ions in neutral and acidic media. First a novel functional monomer (AMP-MMA) was synthetized through the amidation of 2-(aminomethyl)pyridine (AMP) with methacryloylchloride. Following Ni(II)/AMP-MMA complex formation study, the Ni(II)-IIP was produced via inverse suspension polymerization (DMSO in mineral oil) and characterized with solid state ¹³C CPMAS NMR, FT-IR, SEM and nitrogen adsorption/desorption experiments. The Ni(II)-IIP was then used in solid-phase extraction of Ni(II) exploring a wide range of pH (from neutral to strongly acidic solution), several initial concentrations of Ni(II) (from 0.02 to 1 g/L), and the presence of competitive ions (Co(II), Cu(II), Cd(II), Mn(II), and Mg(II)). The maximum Ni(II) adsorption capacity at pH 2 and pH 7 reached values of 138.9 mg/g and 169.5 mg/g, that are among the best reported in literature. The selectivity coefficients toward Cd(II), Mn(II), Co(II), Mg(II) and Cu(II) are also very high, with values up to 38.6, 32.9, 25.2, 23.1 and 15.0, respectively. The Ni(II)-IIP showed good reusability of up to 5 cycles both with acidic and basic Ni(II) eluents.

Selective removal and recovery of Ni(ii) using a sulfonic acid-based magnetic rattle-type ion-imprinted polymer: adsorption performance and mechanisms

It is significant to selectively remove Ni(ii) ions from wastewater. A novel sulfonic acid-based magnetic rattle-type ion-imprinted polymer (Fe₃O₄@void@IIP-Ni(ii)) was designed by taking advantage of the strong interaction between Ni(ii) and sulfonic acid groups. Green polymerization was used to synthesize Fe₃O₄@void@IIP-Ni(ii), which was then investigated using SEM, TEM, FT-IR, VSM, TGA, EDS, and XPS. The adsorption results indicated that the prepared imprinted material had a short adsorption equilibrium time (10 min), good magnetic responsiveness (about 5 seconds) and high adsorption capacity (44.64 mg g^-1) for Ni(ii) at the optimal pH of 6.0. The removal rate of Ni(ii) was up to 99.97%, and the adsorption process was spontaneous and endothermic, following the pseudo-secondary kinetic model and Langmuir model. The selectivity coefficients of the imprinted material were 4.67, 4.62, 8.94 and 9.69 for Ni(ii)/Co(ii), Ni(ii)/Cu(ii), Ni(ii)/Pb(ii) and Ni(ii)/Zn(ii), respectively. The regeneration and application of the imprinted material in actual water samples have been verified. Moreover, the mechanism of selective adsorption for Ni(ii) was investigated by FTIR, XPS and density functional theory (DFT) calculation. The results showed that the imprinted sorbent has a strong binding ability with Ni(ii), and the adsorption of Ni(ii) on Fe₃O₄@void@IIP-Ni(ii) was the result of the co-coordination of O atoms of the sulfonic acid groups and N atoms of -N-C[double bond, length as m-dash]O groups in AMPS with Ni(ii).

Influence of Synthesis Parameters and Polymerization Methods on the Selective and Adsorptive Performance of Bio-Inspired Ion Imprinted Polymers

Ion-imprinted polymers (IIPs) have been widely used in different fields of Analytical Sciences due to their intrinsic selective properties. However, the success of chemical imprinting in terms of selectivity, as well as the stability, specific surface area, and absence of swelling effect depends on fully understanding the preparation process. Therefore, the proposal of this review is to describe the influence of relevant parameters on the production processes of ion-imprinted polymers, including the nature (organic, inorganic, or hybrid materials), structure, properties of the salt (source of the metal ion), ligand, crosslinking agent, porogenic solvent, and initiator. Additionally, different polymerization methods are discussed, the classification of IIPs as well as the applications of these adsorbent materials in the last years (2017–2022).

A comprehensive review on the decontamination of lead(ii) from water and wastewater by low-cost biosorbents

The disadvantages of conventional methods in water and wastewater management including the demand for high energy consumption, the creation of secondary toxic sludge, and operation cost are much too high for developing countries. However, adsorption using low-cost biosorbents is the most efficient non-conventional technique for heavy metals removal. The high adsorption capacities, cost-effectiveness, and the abundance of agricultural waste materials in nature are the important parameters that explain why these biosorbents are economical for heavy metals removal. The present investigation sought to review the biosorption of lead [Pb(ii)] onto low-cost biosorbents to understand their adsorption mechanism. The review shows that biosorption using low-cost biosorbents is eco-friendly, cost-effective, and is a simple technique for water and wastewater treatment containing lead(ii) ions. The batch biosorption tests carried out in most studies show that Pb(ii) biosorption by the low-cost biosorbents is dependent on biosorption variables such as pH of the aqueous solution, contact time, biosorbent dose, Pb(ii) initial concentration, and temperature. Furthermore, batch equilibrium data have been explored in many studies by evaluating the kinetics, isothermal and thermodynamic variables. Most of the studies on the adsorptive removal of Pb(ii) were found to follow the pseudo-second kinetic and Langmuir isotherm models with the thermodynamics variables suggesting the feasibility and spontaneous nature of Pb(ii) sequestration. However, gaps exist to increase biosorption ability, economic feasibility, optimization of the biosorption system, and desorption and regeneration of the used agricultural biosorbents.

Tailoring Nanoadsorbent Surfaces: Separation of Rare Earths and Late Transition Metals in Recycling of Magnet Materials

Novel silica-based adsorbents were synthesized by grafting the surface of SiO₂ nanoparticles with amine and sulfur containing functional groups. Produced nanomaterials were characterized by SEM-EDS, AFM, FTIR, TGA and tested for adsorption and separation of Rare Earth Elements (REE) (Nd³⁺ and Sm³⁺) and Late Transition Metals (LTM) (Ni²⁺ and Co²⁺) in single and mixed solutions. The adsorption equilibrium data analyzed and fitted well to Langmuir isotherm model revealing monolayer adsorption process on homogeneously functionalized silica nanoparticles (NPs). All organo-silicas showed high adsorption capacities ranging between 0.5 and 1.8 mmol/g, depending on the function and the target metal ion. Most of these ligands demonstrated higher affinity towards LTM, related to the nature of the functional groups and their arrangement on the surface of nanoadsorbent.

Selective cobalt and nickel electrodeposition for lithium-ion battery recycling through integrated electrolyte and interface control

Molecularly-selective metal separations are key to sustainable recycling of Li-ion battery electrodes. However, metals with close reduction potentials present a fundamental challenge for selective electrodeposition, especially for critical elements such as cobalt and nickel. Here, we demonstrate the synergistic combination of electrolyte control and interfacial design to achieve molecular selectivity for cobalt and nickel during potential-dependent electrodeposition. Concentrated chloride allows for the speciation control via distinct formation of anionic cobalt chloride complex (CoCl42-), while maintaining nickel in the cationic form ([Ni(H2O)5Cl]+). Furthermore, functionalizing electrodes with a positively charged polyelectrolyte (i.e., poly(diallyldimethylammonium) chloride) changes the mobility of CoCl42- by electrostatic stabilization, which tunes cobalt selectivity depending on the polyelectrolyte loading. This strategy is applied for the multicomponent metal recovery from commercially-sourced lithium nickel manganese cobalt oxide electrodes. We report a final purity of 96.4 ± 3.1% and 94.1 ± 2.3% for cobalt and nickel, respectively. Based on a technoeconomic analysis, we identify the limiting costs arising from the background electrolyte, and provide a promising outlook of selective electrodeposition as an efficient separation approach for battery recycling.

Fabrication of nickel-tagged magnetic imprinted polymeric network for the selective extraction of Ni(II) from the real aqueous samples

A new nickel ion, magnetic imprinted polymer was fabricated through the precipitation polymerization process, using amine-functionalized silica-capped iron oxide particles as a core material, and 4-vinyl pyridine as complexing agent methacrylic acid as functional monomer. The resulted magnetic adsorbent was employed to eliminate toxic Ni²⁺ ions from industrial wastewater. The different parameters were optimized, such as pH, shaking speed, and adsorbent dose, to obtain the maximum adsorption capacity. The synthesized material showed high selectivity coefficient for Ni⁺² ions in the presence of other competitive ions and followed pseudo-second-order kinetics and Langmuir isotherm. A good adsorption capacity of 158.73 mg g^-1 was obtained at optimized pH 6 in the concentration of 5 mg L^-1 nickel ions aqueous solution. The limit of detection, quantification, and the percent relative standard deviation was found to be 0.58, 1.93, and 3.4%. This proves the excellent performance of prepared magnetic Ni(II) ion-imprinted polymer for selective detoxification of Ni²⁺ ions from real aqueous samples. Due to tunable magnetic properties, the prepared MMIPs are highly selective and sensitive and highly porous in nature; due to excellent magnetic properties, there is no need for centrifugation. Just use external magnetic field, it has good reusability. Showing preparation of Ni (II) imprinted magnetic polymer.

Green synthesis of reusable super-paramagnetic diatomite for aqueous nickel (II) removal

Adsorption is an effective method for treating wastewater containing nickel due to its minimal equipment requirements and flexible operation. Therefore, an environmental friendly, inexpensive, efficient and recyclable adsorbent is needed. In this work, a reusable dual-functional super-paramagnetic adsorbent was prepared by combining APTES (3-Aminopropyltriethoxysilane) and EDTA (ethylenediaminetetraacetic acid disodium) with magnetic diatomite for the removal of Ni²⁺. It is named diatomite/CoFe₂O₄@APTES-EDTA (DECFASEs). The synthetic material was characterized and studied by XRD (X-ray Powder Diffractometer), FTIR (Fourier Transform Infrared Spectrometer), SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope), EDS (Energy Dispersive Spectrometer), VSM (Vibrating-Sample Magnetometer), BET (Brunauer-Emmett-Teller) method, Zeta potential analyzer and XPS (X-ray Photoelectron Spectroscopy), respectively. The performance of adsorption Ni²⁺ by DECFASEs was studied on effect of pH, reaction time and initial concentrations. The adsorption and desorption capacity and recyclability of the adsorbent material were estimated. A adsorption kinetic data had a significant correlation with the pseudo second-order kinetic and also adsorption isotherm data corresponded well with Freundlich adsorption isotherm. The maximum adsorption capacity of the adsorbent material was 19.22 mg/g. The Ni²⁺ adsorption capacity of DECFASEs decreased slightly from 9.11 to 8.25 mg/g after 4 recycles. The XPS results of DECFASEs before and after Ni²⁺ uptake showed N and O participated in the complexation of Ni²⁺ in the adsorption process, which verified the chemical interaction between Ni²⁺ and DECFASEs. Modified-diatomite is a promising adsorbent for aqueous Ni²⁺ removal.

Microcrystalline Cellulose from Groundnut Shell as Potential Adsorbent of Crystal Violet and Methylene Blue. Kinetics, Isotherms and Thermodynamic Studies

The isolation of microcrystalline cellulose from a groundnut shell is reported. Adsorption experiments were carried out for the removal of cationic crystal violet and methylene blue and it follows Langmuir model. Positive enthalpy and negative free energy changes have shown endothermic and favorable processes. The results reflect good adsorption process.

CTAB-intercalated molybdenum disulfide nanosheets for enhanced simultaneous removal of Cr(VI) and Ni(II) from aqueous solutions

The treatment of heavy metal pollution in aquatic environment, especially the pollution caused by multiple heavy metal ions, has been a growing global concern for decades. To address this problem, it is urgent to explore effective and low cost adsorbents which can remove multiple heavy metal ions simultaneously. Herein, Cr(VI) and Ni(II) removal from water by MoS₂ with widened interlayer spacing was systematically investigated in comparison with pure MoS₂. A series of techniques, including X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area and porosimetry analysis were applied to characterize the nanocomposites. The XRD results confirmed the enlarged interlayer spacing of MoS₂ by intercalating cetyl trimethyl ammonium bromide (CTAB) into the interlamination. The maximum adsorption capacities of Cr(VI) and Ni(II) for MoS₂/CTAB were 79.4 mg g^-1 and 88.3 mg g^-1, respectively. Moreover, a synergistic effect in the simultaneous removal of Cr(VI) and Ni(II) was observed. A new Cr(VI) removal mechanism involving redox reaction between Cr(VI) and Mo(IV) in MoS₂/CTAB was verified. The removal efficiencies of Cr(VI) and Ni(II) still remained high at the end of fifth cycle, indicating that MoS₂/CTAB has a great potential to remove heavy metals from wastewater.

A Critical Review on the Synthesis and Application of Ion-Imprinted Polymers for Selective Preconcentration, Speciation, Removal and Determination of Trace and Essential Metals from Different Matrices

The presence of toxic trace metals and high concentrations of essential elements in the environment presents a serious threat to living organism. Various methods have been used for the detection, preconcentration and remediation of these metals from biological, environmental and food matrices. Owing to the complexicity of samples, methods with high selectivity have been used for detection, preconcentration and remediation of these trace metals. These methods are achieved by the use of ion-imprinted polymers (IIPs) due to their impressive properties such as selectivity, high extraction efficiency, speciation capability and reusability. Because of the increase of toxic trace and essential metals in the environment, IIPs have attracted great use in analytical chemistry. This review, provide a brief background on IIPs and polymerization method that are used for their preparation. Recent applications of IIPs as adsorbents for preconcentration, removal, speciation and electrochemical detection of trace and essential metal is also discussed.

Synthesis and characterization of a surface-grafted Pb(ii)-imprinted polymer based on activated carbon for selective separation and pre-concentration of Pb(ii) ions from environmental water samples

Even the lowest concentration level of lead (Pb) in the human body is dangerous to health due to its bioaccumulation and high toxicity.

Porous MnFe2O4@SiO2 magnetic glycopolymer: A multivalent nanostructure for efficient removal of bacteria from aqueous solution

The focuses of this research is to prepare an efficient magnetic glycopolymer for bacteria removal from aqueous solution. To perform this idea; porous MnFe₂O₄@SiO₂ was functionalized with glucose and or maltose as an anchors to adhere onto bacteria cell surface. Aminopropyltriethoxysilane was employed to link the saccharides on magnetic nanoparticle surface. The hybrid materials were characterized with XRD, VSM, FT-IR, FESEM, TEM, zeta potential measurement and elemental mapping. Microscopic image showed that MnFe₂O₄ is in cluster form composed from tiny nanoparticles. After saccharide functionalization hybrid composite generate hyper-crosslinked porous structure as a result of polysilicate formation due to hydrolysis of silica source. Escherichia coli and bacillus subtilis were selected as sample pathogens to evaluate the bacteria capturing ability of the magnetic glycopolymer. At the optimum conditions (pH = 6, time of 20 min, dosage of 15 mg) removal efficiency was more than 99% using both saccharide.

Comparative performance of novel magnetic ion-imprinted adsorbents employed for Cd2+, Cu2+ and Ni2+ removal from aqueous solutions

Novel magnetic ion-imprinted polymer was prepared by use of SBA-15 as functional monomer, ethylene glycol dimethacrylate as cross linker, diphenylcarbazide as ligand, and Cd²⁺, Cu²⁺, and Ni²⁺ as the template of ion source. The adsorption capacity of the synthesized adsorbent was 111, 95, and 87 mg g^-1, respectively for cadmium, copper, and nickel. The selectivity of the adsorbents examined in the presence of different cations including Na⁺, K⁺, Ca²⁺, Mg²⁺, Zn²⁺, Co²⁺, Fe²⁺, Mn²⁺, Hg²⁺, and Pb²⁺ indicated that the synthesized ion-imprinted adsorbents were highly selective for the appropriate cations. Kinetic studies indicated that the adsorption process was very fast and the equilibrium was established within 5 min and followed the pseudo-second-order kinetic model. The used ion-imprinted adsorbent was readily regenerated by elution with 2 M HNO₃, and the regenerated adsorbent retained most of its initial capacity. The calculated thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic.

Preparation and adsorption characteristics of an ion-imprinted polymer for fast removal of Ni(II) ions from aqueous solution

A novel Ni(II) ion-imprinted polymer (IIP) was synthesized by bulk polymerization for fast removal of Ni(II) ions from aqueous solution. Effects of preparation conditions on adsorption performance were investigated. Diphenylcarbazide (DPC) and N,N-azobisisobutyronitrile (AIBN) were used as ligand and initiator, respectively. Various monomers, solvents, cross-linking agents and molar ratios of template, monomer and cross-linking agent for polymerization were studied to obtain the largest adsorption capacity. The prepared Ni(II)-IIPs were characterized using Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). The elution process has no influence on the three-dimension network structure observed on the surfaces of Ni(II)-IIPs. Ni(II) ions could be eluted from IIPs successfully with HCl solution. Effects of operating time, pH and initial concentration of Ni(II) in aqueous solution on adsorption performance were investigated too. The adsorption equilibrium was reached within 30min. The maximum adsorption capacity of Ni(II)-IIPs was 86.3mgg^-1 at pH 7.0 with initial Ni(II) concentration of 500mgL^-1. The adsorption by Ni(II)-IIPs followed a pseudo-second-order kinetic and Freundlich isotherm models. The selectivity coefficients for all Ni(II)/interfering ions are larger than one because of the imprinting effect. The Ni(II)-IIPs also showed high reusability and stability.

Synthesis and characterization of a new ion-imprinted polymer for the selective separation of thorium(iv) ions at high acidity

A new ion-imprinted polymer (IIP), which was synthesized with bis(2-methacryloxyethyl) phosphate as functional ligand and Th⁴⁺ as a template ion, can be used in high acidity environment.