Adsorption of Cd2+ and Cu2+ ions from aqueous solutions by a cross-linked polysulfonate–carboxylate resin

Abstract

A new cross-linked polyzwitterion (CPZ) was synthesized through cyclocopolymerization of 3-[diallyl(carboxymethyl)ammonio]propane-1-sulfonate (92.5 mol%), and a cross-linker 1,1,4,4-tetraallylpiperazine-1,4-diium chloride (7.5 mol%) in the presence of tert-butylhydroperoxide. The cross-linked polyzwitterion/anion (CPZA) was obtained by the basification of CPZ with NaOH. The adsorption data fit both Temkin and Freundlich isotherm models. The adsorption trend on CPZA is as Cu2+ > Cd2+ and both followed pseudo-second-order kinetic model. The negative ΔG and positive ΔH values ascertained the spontaneous and endothermic nature of the adsorption process. The effectiveness of a zwitterionic–anionic motif consisting of quaternary nitrogen, sulfonate and carboxylate groups has been tested for the first time for capturing Cd2+ and Cu2+ ions at low concentrations. Keywords: Adsorption, Cross-linked resin, Cadmium, Copper, Metal ion removal