A closed-loop sodium glutamate system for leaching of lead sulfate in spent lead-acid batteries

Leaching of PbSO 4 is one of the key steps of waste lead paste via hydrometallurgical process , but its low efficiency and high cost of reagents need to be improved. Sodium glutamate was used as a leaching reagent to leach PbSO 4 from waste lead paste for the first time. Through the coordination reaction between sodium glutamate (Glu) and PbSO 4 , the leaching ratio of PbSO 4 could reach nearly 100 %. The Glu-containing species mainly exist in the form of HGlu - in the leaching solution , and Pb 2+ could combine with the carboxylic groups and the amine group from HGlu - to form a ternary ring chelate with a stable binding energy of −7.5416 eV. Furthermore, the rate-limiting step of PbSO 4 leaching by sodium glutamate was the internal diffusion. Then, high-purity PbCO 3 (99.9896 %) could be obtained from the Glu-Pb solution by using sodium carbonate, and sodium glutamate was regenerated simultaneously. Finally, the effectiveness and stability of the process were verified by sodium glutamate recirculation process, and the PbSO 4 leaching ratio from waste lead paste remained at above 97.31 % within 10 round of recirculation. These findings achieved the high efficiency recovery of waste lead paste, deep purification of impurities and recycling of leaching agents under mild conditions. • A closed-loop sodium glutamate system for leaching of lead sulfate is provided. • PbSO 4 is almost completely leached by sodium glutamate. • Solution thermodynamics model of PbSO 4 leaching by sodium glutamate is established. • PbSO 4 can combine with O and N from sodium glutamate to form a ternary ring chelate. • The internal diffusion is the speed-limiting step of lead sulfate leaching.