Leaching of platinum group metals (PGMs) from spent automotive catalyst using electro-generated chlorine in HCl solution

摘要

In order to conserve resources without affecting the environment, an energy efficient leaching process has been studied to recover platinum group metals (PGMs) from spent automotive catalyst using electro-generated chlorine as a strong oxidant in a separate reactor. Results: The different process parameters studied showed an increase in the dissolution of PGMs (Pt, Pd, Rh) with HCl concentration, current density, time, and temperature but not pulp density. Leaching efficiencies of 71% Pt, 68% Pd and 60% Rh were obtained under the optimized conditions of 6.0molL~(-1) HCl, 714 A m~(-2) current density, 363K, 20gL~(-1) pulp density, 700rpm agitation speed. The PGMs dissolution kinetics followed ash diffusion control with activation energies for Pt, Pd and Rh of 29.6, 26.4, 20.6 in kJ mol~(-1), respectively over the temperature range 298-363K. The leaching studies carried out after treatment with 20% formic acid at room temperature showed a remarkable increase in dissolution efficiencies to 97% Pt, 94% Pd and 90% Rh. Conclusions: A process for the leaching of PGMs using electro-generated chlorine showed almost total dissolution of PGMs in hydrochloric acid solution after pretreatment of the spent automotive catalyst with formic acid. The proposed leaching system is eco-friendly and has high leaching ability for PGMs from spent materials.