Electrochemical extraction of palladium from spent heterogeneous catalysts of a petrochemical unit using the leaching and flat plate graphite electrodes

Abstract

In this study, electrometallurgy recovery of Pd from the spent petrochemical unit Pd/Al2O3 catalyst has been reported. The electrochemical deposition of Pd from the acid solution (HCl/H2O2) was developed using flat plate graphite electrodes. The effect of the operating variables was assessed and optimized by employing the central composite design of the response surface methodology. The recovery efficiency of Pd was obtained 99.07% at the optimum condition of, reaction temperature of 67.0 °C, electrolysis time of 3.4 h, liquid/solid ratio of 24.7 ml/g, a current density of 196 A/m2 and stirring speed of 572 rpm. The results of the statistical analysis indicated that the anticipated data were in good suitable with the observed ones (R2 = 0.9762), in which the average deviation from experimental data was 0.32% for optimum condition. It indicates that the deposited Pd has spherical nanoparticles shape with a purity of 94.02%. The present study can provide a reliable process for extraction of Pd from the solid waste by the high efficiency and purity.