Platinum group metals removal using expanded vermiculite

Abstract

In this work, a granular expanded vermiculite (GEV) is employed as a sorbent to remove Platinum group metals (PGMs) such as Pt (IV), Rh (III), Ru (III) and Ir (III). Batch adsorption experiments included factors such as metal concentration, pH, GEV dosage and contact time; whereas in a continuous system, the bed height and the desorption process were also investigated. Pseudo-second order was the rate equation that accurately described the adsorption kinetic and adsorption isotherms that were adequately simulated by the Langmuir and Freundlich model. Maximum sorption capacities of GEV in a batch system for Pt (IV), Rh (III), Ru (III) and Ir (III) were 73.01 μg g−1, 157.03 μg g−1, 147.12 μg g−1 and 47.91 μg g−1 at optimal pH values, respectively. Additionally, the adsorption capacities obtained in continuous adsorption experiments for Pt (IV), Rh (III), Ru (III) and Ir (III) were 48.78 μg g−1, 50.11 μg g−1, 51.88 μg g−1 and 37.96 μg g−1. The elution step was accomplished efficiently (71.9-82.5%) using an HCl solution. Hence, the GEV adsorbent could be used as a profitable alternative to remove and recover PGMs from solutions.