Effect of Flux Salts on the Recovery Extent and Quality of Metal Values from Spent Rechargeable Lead Batteries

Abstract

Lead–calcium alloy containing up to 0.10% calcium was recovered from spent rechargeable sealed acid–lead batteries. Two techniques were investigated to explore the effect of flux salts on the extent and quality of the recovered alloy: pyrometallurgical and electrochemical methods. About 10 kg of the spent batteries were collected for testing. The sample was washed with hot water and dried. The plastic cases of the batteries were mechanically cut, the contents were dismantled manually, and the plastic containers were shredded for recycling. The electrode plates were freed from the loose powder and placed in SiC crucible and covered with alkali chloride salts. The loaded crucible was heated in an electronically controlled chamber furnace-type NaberthermC3 at temperatures up to 800 °C. The obtained metals were analyzed. The effect of temperature, rate of heating, atmospheric conditions, composition of the flux salts on the extent and quality of the recovered lead–calcium alloy were studied. Results revealed that the spent rechargeable batteries contain three groups of three plates of Pb–Ca grids, each packed with lead oxides. Direct heating of these plates in a silicon carbide crucible under ambient conditions produces lead metal poor in calcium content (0.07%) due to partial oxidation of the alloying calcium element. Rate of temperature increase has a considerable effect on the yield of the lead alloy composition. Thermodynamically, the activation energy of the alloying process amounts to 5366 kJ/mol. Flux sodium salts benefit the recovery process. Sodium salts are more powerful as compared to potassium salts. Lead calcium alloy meeting the standard specification has been successfully recovered from the spent rechargeable acid–lead batteries with a very competitive cost to that of the same alloy prepared from primary resources.