Design and application of ion-imprinted chelating polymer for selective adsorption of silver ion

Abstract

A polymeric sorbent material that could selectively capture silver ions (Ag⁺) from aqueous solution was prepared by an ion-imprinting method. First, maleimide-pyridyl-thiosemicarbazide (MATCH), a chelating ligand with a polymerizable maleimide moiety, was synthesized by reacting 1-amino-1H-pyrrole-2,5-dione with 2-pyridyl isothiocyanate. The complex of Ag⁺/MATCH ([Ag(MATCH)(H₂O)₂]) was incorporated into a free radical polymerization with styrene-divinylbenzene to produce an Ag-imprinted polymeric adsorbent (Ag-IIP). The Ag-IIP showed high selectivity for Ag⁺ over Hg²⁺, Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ after acidified thiourea chemical elution. The maximum uptake capacity reached 296 ± 1 mg/g. The adsorption behavior followed the Sips isotherm and pseudo-second-order kinetics, confirming a chemisorption mechanism. The Ag-IIP was further tested on real wastewater from AgZn batteries and achieved an impressively high Ag⁺ removal efficiency of 97 %, far outstripping the uptake of Zn²⁺. Superior selectivity results from the ability of imprinted binding sites for strong AgS and AgN coordination. Conversely, the non-imprinted polymer or NIP has much lower efficiencies of removal simply because there are no specified binding sites for the analytes.