Poly(N-acryloyl-l-histidine)-modified wood sawdust as an efficient adsorbent for low-level heavy metal ions

Abstract

An amphoteric metal adsorbent, poly(N-acryloyl-l-histidine)-modified sawdust (SD-g-P(A-His)), is prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization of N-acryloyl-l-histidine from modified sawdust. SD-g-P(A-His) possess imidazolyl and carboxyl groups and shows outstanding adsorption performance for heavy metals. The adsorption capacities of SD-g-P(A-His) are 241.8 and 95.7 mg/g for Pb(II) and Cu(II), respectively. Ten tested metal ions, e.g. Au(III), Cr(III), Cu(II), Fe(III), Ni(II), Pb(II), Pd(II), Hg(II), Mg(II) and Zn(II), can be effectively removed from the multi-metal solution at pH > 2.7, while Au(III) and Pd(II) can be selectively recycled from the multi-metal solution by lowering the pH to ≤ 1.0. The adsorption kinetics of Pb(II) and Cu(II) onto SD-g-P(A-His) fit well with the pseudo-second order model. SD-g-P(A-His) can treat the water with low concentration of metal ions down to sub-10 μg/L level to meet the Quality Standards for Drinking Water of China. Moreover, SD-g-P(A-His) can be recycled and maintain high adsorption efficiency (91.5%) even after 5 cycles.