A green recycling process of the spent lead paste from discarded lead–acid battery by a hydrometallurgical process

In this study, a green recycling process of discarded lead–acid battery paste, which could avoid both the smelting and electro-winning route has been developed. Leaching reagents containing sodium citrate, acetic acid and hydrogen peroxide were reacted with spent lead paste in aqueous media at the pH of 5–6. Lead paste was leached and formed into lead citrate precursor, which was recrystallized and separated from the solution. The optimal conditions for the leaching process at room temperature were found to be the: concentration of acetic acid solution of 0.92 mol L-1; concentration of sodium citrate solution of 0.478 mol L-1; initial mass ratio of solid spent lead paste to liquid (solid/liquid ratio) of 1/5 g/mL; and reaction time of 2 hours. The results showed that the desulphurization efficiency of lead paste was up to 99.9%. The optimal conditions for lead citrate re-crystallization from the leaching mixed solution were found to be the re-crystallization temperature of 55oC for 5 hours in a water bath. The lead citrate precursor synthesized from discarded lead–acid battery pastes was the chemical formula of Pb3(C6H5O7)2·3H2O with columnar shape in the length of 30–50 μm, which was easily separated from the leaching solution. The results of kilogram-scale experiments made progress easier for obtaining the ultrafine lead oxide product (PbO and Pb) from discarded lead–acid battery paste.

Theoretical and Experimental Investigation on Disposing of Used Lead-Acid Cell Using Citric Acid

Taking the paste of used lead acid batteries as studying object, reaction mechanisms and experiments were investigated between citric acid and PbO, PbO2and PbSO4. The results showed that: three reactions Gibbs function, between the citric acid and the PbO, PbO2and PbSO4, were less than zero, and the reaction could be spontaneous; XRD results showed that: the above three reactions could produce lead citrate, and after roasting of the three kinds of lead citrate precursor, the powders, Pb/PbO as their main ingredients, could be obtained at low reaction temperature.