Recovery of palladium as nanoparticles from waste multilayer ceramic capacitors by potential-controlled electrodeposition

Abstract

Recycling palladium from waste multilayer ceramic capacitors (MLCCs) has attracted much attention recently. The existing recycling methods have many shortcomings including pollution, low purity and recovery rate of palladium. This study proposed to separate and purify palladium from waste MLCCs by electrodeposition technology efficiently based on the difference in reduction potentials of metal ions in HNO3 solution. The electrochemical behavior of palladium at titanium electrode was studied, which showed higher concentration of HNO3 decreased the peak current of palladium and the corresponding potential shifted negatively. Besides, a mathematical model was established to describe the electrodeposition process at different agitation speeds. The diffusion coefficient and thickness of diffusion region were calculated. Furthermore, the optimal conditions for electrodeposition were determined as applied potential of −0.25 V, agitation speed of 240 rpm and HNO3 concentration of 0.5 M, under which high-purity palladium (>99%) was recovered with the recovery rate of 99.02%. The morphology analysis showed the electrodeposited palladium was nanoparticles. Finally, an efficient process combining enrichment and electrodeposition for recycling waste MLCCs was proposed in an environmentally friendly way. The results of this study can provide reliable information for efficient recycling of palladium resource from waste MLCCs.