Leaching of waste battery paste components. Part 2: Leaching and desulphurisation of PbSO₄ by citric acid and sodium citrate solution

In this study, as part of developing a new process that can avoid both smelting and electro-winning, citric acid based reagents were reacted with PbSO₄, in aqueous media for achieving lead recovery simultaneously with desulphurisation. PbSO₄ is the main component in a spent battery paste (accounting for nearly 50% by weight). Recovery of the two oxides PbO and PbO₂, which together account for the remaining 50% of the paste, has been discussed in Part 1 in a separate paper. Leaching of PbSO₄ with a solution containing C₆H₅Na₃O₇·2H₂O alone was neither effective in removing the sulphate or in synthesising uncontaminated lead citrate. When both C₆H₅Na₃O₇·2H₂O and C₆H₈O₇·H₂O reagents were used together, it was possible to achieve effective recovery of lead precursor as lead citrate while simultaneously removing sulphur as Na₂SO₄. The lead citrate product was characterised by SEM and XRD analysis. Conditions for achieving a recovery of 99% of the lead precursor crystallites have been experimentally deduced by varying the concentrations of various reagents, time and temperature of the reaction, and the starting ratio of solid to liquid.