Effect of ethylene diamine tetra‐acetic acid and functional monomers on the structure and adsorption properties of copper ( II ) ion‐imprinted polymers

Development of Adsorptive Membranes for Selective Removal of Contaminants in Water

The presence of arsenic and ammonia in ground and surface waters has resulted in severe adverse effects to human health and the environment. Removal technologies for these contaminants include adsorption and membrane processes. However, materials with high selectivity and pressure stability still need to be developed. In this work, adsorbents and adsorptive membranes were prepared using nanostructured graphitic carbon nitride decorated with molecularly imprinted acrylate polymers templated for arsenate and ammonia. The developed adsorbent removed arsenate at a capacity and selectivity similar to commercial ion-exchange resins. Ammonia was removed at higher capacity than commercial ion exchange resins, but the adsorbent showed lower selectivity. Additionally, the prepared membranes removed more arsenate and ammonia than non-imprinted controls, even in competition with abundant ions in water. Further optimization is required to improve pressure stability and selectivity.

Preparation, Characterization of Cd(II) Ion-Imprinted Microsphere and Its Selectivity for Template Ion

Cadmium is one of the many toxic elements for humans even at low concentrations, and it could exist in the environment for a long time. The ion imprinting technique has gained much attention due to its selective recognition performance. In this study, a cadmium ion imprinted maleic acid-co-acrylonitrile polymeric microsphere (Cd-I-MA-co-AN) was synthesized via precipitation polymerization using Cd(II) as a template ion, acrylonitrile and maleic acid as functional monomers, divinylbenzene as a cross-linker, and potassium persulfate as an initiator. UV–vis, SEM and FTIR were used for characterization, and the adsorption conditions were observed and optimized. The adsorption capacity and selectivity of Cd-I-MA-co-AN for Cd(II) were analyzed by flame atomic absorption spectrometry (FAAS). The results documented that the optimal pH, flow rate and eluent were 6, 2 mL min−1 and 1 mol L−1 nitric acid, respectively. Compared with the non-ion imprinted maleic acid-co-acrylonitrile polymeric microsphere (NI-MA-co-AN), Cd-I-MA-co-AN had a higher adsorption capacity. The saturated adsorption capacities of Cd-I-MA-co-AN and NI-MA-co-AN were 20.46 mg g−1 and 7.64 mg g−1, respectively. The adsorption behavior of Cd-I-MA-co-AN fitted with the Freundlich isotherm model. The relative selectivity coefficients of Cd-I-MA-co-AN for Cd(II) in the presence of Cu(II), Mn(II), Ni(II) and Pb(II) were 3.79, 3.39, 3.90 and 3.31, respectively. The Cd-I-MA-co-AN showed good selectivity for Cd(II). In addition, a reusability study showed that Cd-I-MA-co-AN can be recycled ten times and has high recovery in natural water samples.

A Note about Crosslinking Density in Imprinting Polymerization

Imprinting polymerization is an exciting technique since it leads to specific binding sites, which are the basis of a variety of applications, such as sensors, detectors, and catalysts. The specific binding sites are created using templates and then fixing the structure of the binding site with crosslinking. The literature review of imprinting polymerizations shows that the crosslinking density governs the physical properties of the resulting molecularly imprinted polymer (MIP). It is also a factor governing the capacity and the selectivity of MIPs. Reviewing polymer science data and theory, the crosslinking density commonly used in MIP synthesis is unusually high. The data reviewed here suggest that more research is needed to determine the optimal crosslinking density for MIPs.