Recovery of platinum (IV) from aqueous solutions using 3-aminopropyl(diethoxy)methylsilane functionalized bentonite

Abstract

Platinum, naturally found in a few parts of the world, is one of the most widely used precious elements and its recycling from waste components is very important due to demand. However, not as much attention has been given toward its recovery from aqueous solutions. This present study is aimed at recovering platinum (Pt(IV)) from aqueous solutions such as mining wastewaters using bentonite functionalized with 3-aminopropyl(diethoxy)methylsilane (APDEMS). The study exploited the novelty of using a cost-effective natural mineral, bentonite, as a support base to which amine groups, that have a high affinity for Pt(IV), could be anchored. The approach involved characterizing the natural and functionalized bentonite. Adsorption experiments were conducted in batch mode under varying conditions, namely: adsorbent dosage, pH, initial concentration, and competing ions. The data were fitted using various kinetic and isothermic models to understand the adsorption mechanism. The results showed that >85% of Pt(IV) in solution was recovered at a dosage of 10 g L−1 of the adsorbent at pH 2, within 90 min of contact. The adsorption of Pt(IV) increased by >5% in the presence of other ions, most likely due to synergistic effects. The adsorption of Pd(II), Ir(III), Rh(III), Os(III), and Ru(III) was also enhanced along with that for Pt(IV). Adsorption was found to proceed via the Langmuir isotherm and the pseudo second-order kinetic model, implying monolayer coverage and chemisorption, respectively. The successful synthesis of APDEMS-functionalized bentonite and its efficiency in adsorbing Pt(IV) from aqueous solutions make it a potential adsorbent for application in the mining industry.