Preparation of high-purity lead carbonate and lead oxide from spent lead paste

Abstract

Compared with pyrometallurgical recycling, hydrometallurgical recycling of spent lead paste has obvious advantages such as energy saving and emission reduction, however, hydrometallurgical recycling of spent lead paste is also characterized by high levels of impurities (e.g.,Fe, Ba and Cu) in the recovered products. In this study, a green process for the conversion of spent lead paste into high-purity lead carbonate is presented. The process consists of four steps: sulfation, desulfurization leaching, distillation and carbonization to obtain high-purity lead carbonate. The details are as follows: (1) Spent lead paste (mainly composed of lead sulfate, lead dioxide, lead oxide and lead monomers) was converted into sulfated lead paste using sulfuric acid, hydrogen peroxide and sodium chloride. (2) The sulfated lead paste was reacted with ammonium acetate to leach the lead while desulfurizing; the leaching rate was reached 99.94% under the conditions of 30 wt% ammonium acetate concentration, 40 °C reaction temperature and 7.5 min reaction time. (3) Glycerol was added to the mother liquor and distilled to obtain a glycerol solution containing lead acetate. (4) Using ammonium carbonate (aq) as a carbonizing agent, reacting for 20 min under the condition that the molar ratio of CO32−/Pb is 1.10 can make more than 99.9% of lead precipitate to obtain high-purity lead carbonate products. (5) The lead carbonate product decomposed into orthorhombic α-PbO at 350 °C. (6) Recovered lead oxide product has better electrochemical performance than commercial lead oxide. This process prepares high-purity lead carbonate and lead oxide products with reduced energy consumption and recycles the spent lead paste. This study provides a feasible technology for green recycling of spent lead paste.