Separation of antimony from lead-antimony alloy by molten salt electrolysis

Abstract

Lead-acid batteries (LABs) are widely used in electric motorcycles, uninterruptible power systems, and stationary energy storage devices. However, spent LABs should be recycled to reuse lead (Pb) and thereby close the Pb cycle and avoid Pb contamination. In order to reuse the recovered Pb, the purity of recovered Pb should meet the required standard. Since antimony (Sb) is a common alloying element in Pb alloy grid such as the Pb-Sb alloy, separating Sb from the recovered Pb is necessary. In this paper, we proposed a molten salt electrolysis method to separate Sb from liquid Pb-Sb alloys in terms of forming a solid Ca-Sb intermetallic at the top of the liquid Pb-Sb cathode. The electrochemical separation process was performed in molten NaCl-CaCl2. The content of Sb (atomic percent) in the Pb-Sb alloy was reduced from 1% to less than 0.01% (atomic ratio). The recovery principle lies in the different alloying potentials between Ca-Sb and Ca-Pb. Hence, molten salt electrolysis is a promising separation method to recover pure Pb from spent Sb-containing Pb alloys.