Selective recovery of Au(III), Pd(II), and Ag(I) from printed circuit boards using cellulose filter paper grafted with polymer chains bearing thiocarbamate moieties

Abstract

This paper describes selective recovery of Au(III), Pd(II), and Ag(I) from waste printed circuit boards (WPCBs) by CFP-g-PHCTMA, an adsorbent based on cellulose filter paper (CFP) grafted with polymer chains bearing thiocarbamate moieties. As a preliminary study, the adsorption kinetics and the effect of acid concentration on the adsorption processes were studied in detail. The adsorption capacity for Au(III) and Pd(II) was not affected significantly by acid concentration, whereas that for Ag(I) was decreased under higher acid concentration. The adsorption proceeded smoothly, and reached equilibria for Pd(II) and Ag(I) within 90 min, and for Au(III) within 150 min. The selective adsorption toward these precious metal ions was maintained even in multi-element solutions. Only Ag(I), Pd(II), and Au(III) were adsorbed from a mixture containing Ag(I), Cu(II), Zn(II), Ni(II), Co(III), V(V), Cr(III), Fe(III), Mn(II), Cd(II), Au(III), Pd(II), Pt(IV), Ir(III), Os(III), Ru(III), and Rh(III). Encouraged by the fast and selective adsorption ability, the recovery of Au(III), Pd(II), and Ag(I) by CFP-g-PHCTMA was studied for a WPCB leachate in aqua regia. These precious metals were selectively adsorbed with negligible adsorption of coexisting ions contained in excess. This study demonstrates that this cellulose-based CFP-g-PHCTMA is an eco-friendly and economically viable adsorbent for the selective adsorption of precious metals.