Synthesis of a Highly Selective Scavenger of Precious Metals from a Printed Circuit Board Based on Cellulose Filter Paper Functionalized with a Grafted Polymer Chain Bearing -Methyl-2-hydroxyethylcarbamothioate Moieties.

We report the synthesis and practical application of a novel scavenger for precious metals. The scavenger was prepared from cellulose filter paper with grafted chains of poly(glycidyl methacrylate) modified with a novel ligand group of -methyl-2-hydroxyethylcarbamothioate moieties, introduced by the reaction with -1-mercapto-3-phenoxypropan-2-yl -methyl-2-hydroxyethylcarbamothioate. Batch experiments were performed to evaluate the capability of the scavenger in ranges of pH and acid concentration as well as to determine the kinetics and isotherm models. The scavenger was found to adsorb only Ag(I), Pd(II), and Au(III) from an aqueous media in the presence of coexisting ions of different bases and precious metals at wide ranges of pH and acid concentration. The adsorption rates fit a pseudo-second-order kinetic equation, and the adsorption reached equilibrium within 60 min. The isotherm studies indicated that the obtained data were a good fit with the Langmuir model. The maximum adsorption capacities of Ag(I), Pd(II), and Au(III) were 126.95, 124.67, and 230.67 mg g, respectively. Regeneration experiments indicated that the adsorbent maintained 97% of its initial efficiency even after five adsorption/desorption cycles. The scavenger was effectively utilized to recover Ag(I), Pd(II), and Au(III) from an aqua regia solution of waste printed circuit boards.