Recovery of palladium and silver from waste multilayer ceramic capacitors by eutectic capture process of copper and mechanism analysis

Abstract

Recycling waste multilayer ceramic capacitors (MLCCs) is significant for environmental protection and resource recovery, which contain rich precious metals including palladium and silver. The existing recycling methods have many shortcomings such as environmental pollution, low recovery efficiency and low purity of precious metals. In view of the special structure of MLCCs and low content of precious metals per unit mass, a novel approach of enrichment for recovering palladium and silver from waste MLCCs by eutectic capture process of copper was proposed, in which process precious metals were separated and enriched for subsequent recovery. The recovery rates of palladium and silver reached 100 % and 87.53 %, respectively under the optimal condition. And the enrichment multiples of palladium and silver were 13.16 and 7.37. The Cu-Pd-Ag alloy was formed in the capture process, of which palladium and copper formed Cu-Pd solid solution, while silver was a separate phase through the analysis of SEM-EDS, XPS and XRD. Besides, the molten residue can be reused to prepare glass-ceramics. Finally, the mechanism was analyzed through thermodynamics, which was divided into two processes: migration of precious metals and alloy formation. This study provides a highly efficient and environmentally friendly method for recycling precious metals from waste MLCCs.