An environment-friendly process of lead recovery from spent lead paste

Abstract

Spent lead paste, an important secondary resource, calls for recycling at the request of both environmental protection and the sustainable development of lead industry. An environment-friendly process to recover lead from spent lead paste was proposed. The impurities Sb, Ca, Fe and Cu in spent lead paste were firstly removed by H2SO4 at the leaching rate of 92.22%, 86.43%, 87.89% and 94.04%, respectively. And then, 99.9% of PbO2 in spent lead paste was reduced to PbO by the hydrothermal reduction process with glucose as the reductant. In the process of hydrothermal desulfurization by NaOH, 99.46% of S in the reduced lead paste was removed and then the lead paste was converted into a single phase of 3PbO·H2O. Finally, metallic lead, with a purity of 99.978%, was obtained from the single-phase lead paste by a low-temperature reduction smelting process with starch as the reductant under the conditions of Na2O/B2O3 = 1/2, PbO/B2O3 = 5/1, starch/PbO = 1/7.5, smelting temperature 700 °C, and smelting duration 90 min, and the lead recovery is high up to 95.53%. Compared with the traditional lead smelting technology, the smelting temperature was reduced from 1200 °C to 700 °C, helping greatly reduce the energy consumption. The process proposed in this paper guides a new development direction for the utilization of spent lead paste.