Effects of grain refinement on microstructure and electrochemical properties of Pb-(0.5wt.%)Ag anodes for zinc electrowinning

Abstract

In this study, Pb-(0.5 wt.%)Ag anodes were prepared using five different preparation techniques, namely, ultrasonic treatment (UST), equal channel angle pressing (ECAP), rolling treatment (RT), cold-rolling (CR), and ultrasonic + rolling treatment (UST + RT). Except for UST, these processes were followed by a subsequent annealing treatment. The microstructure, resistivity, microhardness, and electrochemical performances of the Pb-(0.5 wt.%)Ag anodes prepared under different conditions were investigated and compared in detail. Preparation methods that can be used to obtain anode materials with better comprehensive properties are discussed. The results show that the conductivity, electrochemical properties, and mechanical properties of Pb-(0.5 wt.%)Ag anodes are significantly improved upon treatment using the different processes. Among them, UST + RT is beneficial for obtaining a denser structure and achieving considerably better electrochemical performance compared with the casting, rolling, and ultrasonic processes. Compared with the as-cast Pb-(0.5 wt.%)Ag alloy, the resistivity was reduced by 45 % and the hardness by 2.2 times after UST + RT. In zinc electrowinning experiments, the cell voltage of the Pb-(0.5 wt.%)Ag anode subjected to UST + RT was also significantly reduced, and the current efficiency was increased by 8.63 %. These results will lay the foundation for energy conservation in zinc electrowinning.