Dissolution behaviour of platinum by electro-generated chlorine in hydrochloric acid solution

Abstract

Background Depletion of primary resources, stringent environmental regulations, and the requirement for energy efficient and eco-friendly processes have created research interest in recovering Pt from secondary resources using electro-generated chlorine in HCl solution. Results Platinum dissolution rate was found to increase by a factor of 2.5 by increasing the HCl concentration from 3.0 to 5.0 mol L-1 at 70 degrees C, while maintaining total chloride ions at 5.0 mol L-1 with NaCl. Increasing the aqueous chlorine concentration made no improvement to the dissolution rate. A theoretical calculation of distribution for chlorine species showed a predominance of Cl3- ions in comparison with Cl2(aq) upon increasing the acid concentration to above 5.0 mol L-1; raising temperature also increased the dissolution rate. The activation energies of Pt dissolution in the 5.0 mol L-1 HCl solution were 82.3 and 83.5 kJ mol-1 at 5.0 and 15 mmol L-1 aqueous chlorine concentration, respectively. Conclusions Eco-friendly electro-generated chlorine leaching was applied for the dissolution of Pt in hydrochloric acid solutions. Increasing HCl concentration and solution temperature effectively enhanced Pt dissolution during leaching. A quantitative investigation of Pt dissolution rate verified the chemical reaction control of Pt dissolution rather than mass transfer