Preparation and adsorption characteristics of an imprinted polymer for selective removal of Cr(VI) ions from aqueous solutions

To achieve a fast adsorption rate and a high adsorption capacity in the selective adsorption of Cr(vi) from wastewater, a novel Cr(vi) ion imprinted polymer (Cr(vi)-IIP) was synthesized by bulk polymerization with ethylene glycol dimethacrylate as a crosslinking agent, azodiisobutyronitrile as an initiator, and acetone as a solvent. Eight functional monomers, including acidic, basic and neutral agents, were investigated in the synthesis of Cr(VI)-IIPs. The Cr(VI)-IIP prepared with 4-vinyl pyridine (4-VP) as a functional monomer provided the highest adsorption capacity, which was characterized by Fourier infrared spectroscopy, zeta potential, Brunauer, Emmett and Teller and scanning electron microscopy. The influences of functional monomer amount, crosslinking agent, initiator, solvent, pH in aqueous solution, initial Cr(vi) concentration, and so on, on adsorption performance were studied. The adsorption process of Cr(VI)-IIP followed a pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The electrostatic interactions between Cr(vi) anion and the protonated N atoms of the functional pyridine groups on prepared IIPs could enhance the adsorption capacity and adsorption rate. Under the optimal operating conditions, the maximum adsorption capacity of Cr(vi)-IIP prepared with 4-VP was up to 338.73 mg g(-1), and the adsorption equilibrium was reached within 3 min. The Cr(VI)-IIPs also showed good selectivity, reusability and stability. The selectivity coefficient was up to 189.05 and 96.56 for Cr(VI)/Cu(II) and Cr(VI)/Cr(III), respectively.