Control of the separation order of Au(III), Pd(II), and Pt(IV) achieved by site-controllable carboxyl-functionalized diethylaminoethyl celluloses

Abstract The separation and recovery of Au(III), Pd(II), and Pt(IV) is a challenge in hydrometallurgy, and finding good adsorbents is a way to solve this problem. In this work, two novel adsorbents, carboxymethyldiethylammoniumethyl cellulose (CM-n-DEAEC) and carboxymethyl-2-diethylaminoethyl cellulose (CM-o-DEAEC), were synthesized by changing the grafting site of carboxymethyl on diethylaminoethyl cellulose (DEAEC). The structures and morphologies of the adsorbents were examined by NMR, FT-IR, EA, TGA, and SEM analyses. The effects of adsorbents on the separation performance of Au(III), Pd(II), and Pt(IV) at different adsorption conditions were studied. The performances of stripping and recycling were investigated. At a 3 M chloride ion concentration, CM-n-DEAEC's adsorption rates for Pd(II), Au(III), and Pt(IV) were stabilized at 60%, 30%, and 7% in the pH range of 1.0–3.0 and were unaffected by coexisting metal ions. However, at a 0.1 M chloride ion concentration, CM-o-DEAEC separated Pt(IV) before Au(III) and Pd(II) in the pH range from 1.0 to 2.0 without being affected by coexisting metal ions. In addition, the absorbed metal ions can be easily stripped by a 0.1 M thiourea-0.1 M HCl solution, and the adsorption rate only decreased by 3.0% and 1.8% after seven adsorption–desorption cycles. Therefore, it was shown that CM-n-DEAEC and CM-o-DEAEC are excellent adsorbents that can control the adsorption order of precious metals and can selectively and quickly recover Pd(II) or Pt(IV) from wastes containing Au(III). Graphic abstract