Kinetic study on recovery of antimony in anode slime from used lead batteries utilizing volatile oxide formation

From the viewpoint of recycling and recovery of metal values from used lead-batteries, especially from lead anode slime, recovery of antimony has been studied experimentally. First, oxidation kinetics has been investigated for pure liquid antimony in the temperature range between 973 and 1373 K to elucidate the reaction mechanism. Since lead anode slime generally consists of antimony, lead and bismuth, oxidation experiments have also been carried out using antimony-lead-bismuth alloy. It was found that gas phase mass transfer step mainly controls the overall oxidation rate. The overall rate was expressed as the sum of antimony oxide and metallic antimony evaporation rates. The oxide evaporation is dominant at lower temperature around 1073 K with higher oxygen partial pressure. In the experiment of the antimony-leadbismuth alloy simulated for anode slime, only the oxide Sb₄O₆ evaporation was observed, indicating that antimony was preferentially oxidized followed by evaporation of antimony oxide. The oxidation rate of the alloy was substantially identical with that of pure antimony. This is the advantage of oxidation treatment for anode slime.