Galena weathering in simulated alkaline soil: Lead transformation and environmental implications

Alkaline soils are widely distributed around the world. During the mining and transportation processes galena may be exposed to the alkaline soils. Weathering of galenamay lead to the formation of different lead phases having higher bio-accessibility than galena, and thereby increasing the mobility and toxicity of lead. In this study, electrochemical techniques and Raman spectroscopic measurementswere used for the evaluation of the interfacial processes that are involved in the galena weathering under the conditions of simulated saline soil and meadow soil solutions. The results showed that the release of Pb2+ and S-0 took place during initial stage of the oxidation. Thereafter, further transformation to anglesite would take place, even leading to the transformation to beta-PbO and alpha-PbO at higher temperatures. Galena weathering prone to saline soil than that in meadow soil, and has a faster weathering rate in the saline soil at same ambient temperature. Higher temperatures was found to promote the weathering of galena, and the rate constant for the release of Pb (II) was approximate 10(-9) to 10(-8)mol.m(-2).s(-1), while surface reactionwas found to control theweathering kinetics. Based on the surface characterization and evaluation of the thermodynamic and kinetic parameters, the weathering mechanism of galena in the alkaline soil and its environmental implications was suggested. (C) 2020 Elsevier B.V. All rights reserved.