Preparation of a surface-grafted imprinted ceramic membrane for selective separation of molybdate anion from water solutions

Molecularly imprinted polymer composite membranes: From synthesis to diverse applications

This review underscores the fundamentals of MIP-CMs and systematically summarizes their synthetic strategies and applications, and potential developments. MIP-CMs are widely acclaimed for their versatility, finding applications in separation, filtration, detection, and trace analysis, as well as serving as scaffolds in a range of analytical, biomedical and industrial contexts. Also characterized by extraordinary selectivity, remarkable sensitivity, and outstanding capability to bind molecules, those membranes are also cost-effective, highly stable, and configurable in terms of recognition and, therefore, inalienable in various application fields. Issues relating to the potential future for the paper are discussed in the last section with the focus on the improvement of resource practical application across different areas. Hence, this review can be seen as a kind of cookbook for the design and fabrication of MIP-CMs with an intention to expand the scope of their application.

Preparation and permeation recognition mechanism of Cr(vi) ion-imprinted composite membranes

The Cr(vi) ion-imprinted composite membranes (Cr(vi)-IICMs) were prepared by using the surface imprinting method. The template ion was Cr(vi), the functional monomer was 4-vinylpyridine (4-VP), and the nylon filter membrane (nylon-6) was the support membrane. Non-imprinted composite membranes (NICMs) were prepared under the same conditions as the corresponding Cr(vi)-IICM. The adsorption effect of the imprinted membrane can reach 2.4 times that of the corresponding non-imprinted membrane. Meanwhile, the adsorption quantity of Cr(vi)-IICM was 34.60 μmol·g−1. The physical characteristics of membranes were confirmed by Brunauer–Emmett–Teller and scanning electron microscopy. Inductively coupled plasma emission spectrometry was used to analyze their adsorption properties and permeation selectivity. Cr(vi)-IICM and NICM were both mesoporous materials from the structural characterization and performance test results. Their adsorption behavior conformed to the Langmuir isotherm adsorption model. The permeation recognition mechanism of Cr(vi)-IICM was the Piletsky’s gate model. The IICM still has excellent permeability selectivity to Cr(vi) in the presence of competitive ions. The results provided a reference for the isolation and enrichment of Cr(vi).

Molecularly Imprinted Affinity Membrane: A Review

A molecularly imprinted affinity membrane (MIAM) can perform separation with high selectivity due to its unique molecular recognition introduced from the molecular-printing technique. In this way, a MIAM is able to separate a specific or targeted molecule from a mixture. In addition, it is possible to achieve high selectivity while maintaining membrane permeability. Various methods have been developed to produce a MIAM with high selectivity and productivity, with their respective advantages and disadvantages. In this paper, the MIAM is reviewed comprehensively, from the fundamentals of the affinity membrane to its applications. First, the development of a MIAM and various preparation methods are presented. Then, applications of MIAMs in sensor, metal ion separation, and organic compound separation are discussed. The last part of the review discusses the outlook of MIAMs for future development.

The ion-imprinted oyster shell material for targeted removal of Cd(II) from aqueous solution

In order to realize the sustainable utilization of waste oyster shell and develop a targeted removal technology for cadmium. A novel ion-imprinted oyster shell material (IIOS) was prepared by surface imprinting technique. The prepared samples were characterized by scanning electron microscope, Fourier infrared spectrometer, X-ray diffractometer, thermogravimetric analysis and N₂ adsorption-desorption. The adsorption performances of IIOS for Cd(II) from aqueous solution were studied by the single factor sequential batch, kinetics, isotherms, selectivity and recycling experiments. The characterization researches showed that IIOS was successfully prepared. The adsorption experiments indicated that the adsorption process reached equilibrium within 240 min; the maximum adsorption capacity was up to 69.1 mg g^-1 with the initial Cd(II) concentration of 75 mg L^-1 at pH 5; the adsorption process fitted well to the pseudo-second-order model and the Langmuir isotherm model, which revealed the chemisorption characteristic of Cd(II). Moreover, IIOS exhibited a good targeted adsorption of Cd(II) in several binary competition systems owing to the present of these imprinted cavities. The recycling experiment showed that the targeted removal ratio of IIOS for Cd(II) remained above 80% after used six times. The results of this study indicated that it is a promising prospect for waste oyster shell used as IIOS to dispose heavy metals in wastewater.

Selective and rapid removal of Mo(VI) from water using functionalized Fe3O4-based Mo(VI) ion-imprinted polymer

Fe₃O₄ nanoparticles-based magnetic Mo(VI) surface ion-imprinted polymer (Mo(VI)-MIIP) was elaborated employing 4-vinyl pyridine as a functional monomer. The adsorbent preparation was confirmed by Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, vibrating sample magnetometer, thermogravimetric analysis, and surface area analysis. Batch adsorption experiments showed that the maximum adsorption capacity of Mo(VI)-MIIP was 296.40 mg g^-1 at pH 3, while that of the magnetic non-imprinted polymer (MNIP) was only 147.10 mg g^-1. The adsorption isotherm model was well fitted by the Langmuir isotherm model. The adsorption experiments revealed that Mo(VI)-MIIP reached adsorption equilibrium within 30 min, and the kinetics data fitting showed that the pseudo-second-order kinetics model suitably described the adsorption process. Mo(VI)-MIIP exhibited an excellent adsorption selectivity to Mo(VI) in binary mixtures of Mo(VI)/Cr(VI), Mo(VI)/Cu(II), Mo(VI)/H₂PO4₄^-, Mo(VI)/Zn(II), and Mo(VI)/I^-, with relative selectivity coefficients toward MNIP of 13.71, 30.27, 20.01, 23.53, and 15.89, respectively. After six consecutive adsorption-desorption cycles, the adsorption capacity of Mo(VI)-MIIP decreased by 9.5% (from 228.4 mg g^-1 to 206.7 mg g^-1 at initial Mo(VI) concentration of 250 mg L^-1), demonstrating its reusability.

Preparation and performance of poly(4-vinylpyridine)-b-polysulfone-b-poly(4-vinylpyridine) triblock copolymer/polysulfone blend membrane for separation of palladium (II) from electroplating wastewaters

In order to separate palladium (II) from electroplating wastewaters, poly(4-vinylpyridine)-b-polysulfone-b-poly(4-vinylpyridine) (P4VP-PSF-P4VP) / polysulfone blend membranes were fabricated by combining non-solvent induced phase separation, surface segregation and self-assembly of block copolymer. Amphiphilic P4VP-PSF-P4VP was used as the membrane base material, which was synthesized by introducing the functional monomer of 4-vinylpyridine (4-VP), and polysulfone as the additive. Effects of blend ratio and 4-VP content on membrane performance, such as structure, hydrophilicity, pure water flux and adsorption capacity towards Pd (II), were investigated. The membranes exhibited dense surface structure and low roughness due to surface segregation and self-assembly of P4VP-PSF-P4VP. The presence of 4-VP increased hydrophilicity and water flux of membrane, and it also provided good adsorption capacity towards Pd (II) (up to 103.1 ± 5.15 mg/g). Further, the membrane was used to separate Pd (II) from simulated wastewaters during filtration. It showed good rejection ability and high selectivity towards Pd (II) in co-existence of Cu (II) and Ni (II), and selectivity coefficients of Pd/Cu and Pd/Ni are 41.9 ± 1.88 and 97.8 ± 4.32, respectively. In filtration process of actual electroplating wastewater, the membrane also exhibited excellent rejection performance (Pd (II) rejection reached up to 96.8 ± 2.71%). Perhaps it is suitable for future practice applications.

Selective adsorption of molybdate from water by polystyrene anion exchanger-supporting nanocomposite of hydrous ferric oxides

Molybdenum is an essential trace element for humans but can be harmful with excess assimilations or chronic exposures. In this study a polymer-functionalized nanocomposite (HFO-PsAX) was fabricated for selective adsorption of molybdate from aqueous solution. HFO-PsAX was prepared by grafting hydrous ferric oxide nanoparticles (HFOs) into the porous structure of a polystyrene anion exchanger (PsAX) by in situ synthesis method. The resultant HFO-PsAX exhibited greatly enhanced selectivity toward molybdate as compared with the matrix, PsAX, which is also a fair adsorbent for scavenging molybdate. The competitive abilities of the ubiquitous anions, i.e., chloride, carbonate, sulfate, and phosphate, on the adsorption of molybdate by HFO-PsAX followed the order: chloride < phosphate < carbonate < sulfate. The unexpectedly weak competitive ability of trivalent phosphate may be due to incompletely dissociated state and formation of molybdate-phosphate complexes. The optimal pH for the adsorption of molybdate was determined as pH≈4, which is associated with the dissociation constants of molybdic acid; certain adsorption capacities were also observed even under extremely alkaline condition (pH=14) for single-component molybdate solution. Temperature (10, 25, and 40°C) has negligible effect on the adsorption capacities by HFO-PsAX, and Freundlich model and Dubinin-Radushkevich (D-R), Temkin model can describe the adsorption isotherms well. The adsorption potential of Temkin model is calculated as ≈100J/mol, which is between those of physisorption and chemisorption process. Fixed-bed column adsorption experiments validated the potential of HFO-PsAX in treating Mo(VI) contaminated water for practical application, and the exhausted HFO-PsAX can be regenerated by a binary NaOH-NaCl solution (both 5% in mass) without loss in adsorption capacities.