Heavy metals' release behavior in antimony tailings dump and its response to different rainfall conditions

Abstract

Under the influence of natural rainfall, heavy metals (HMs) in Qinglong antimony tailings are easily released into surface or underground runoff, posing a great threat to the ecological environment and human health. In this study, an independently designed rainfall simulation device was used to study the effects of tailings leachate and carbonate rocks on the release behavior and mechanism of HMs under rainfall activities (different rainfall intensities and intermittent rainfall). X-ray diffraction shows that the characteristic minerals of tailings are quartz, gypsum, kaolinite, pyrite, fluorite and calcite, and the main antimony mineral is stibnite. The simulated rainfall shows that lower intensities result in decreased pH, increased EC, higher heavy metal concentrations, and cumulative release amounts positively correlated with rainfall intensity, but has little effect on the leaching mechanism of HMs. The release of Sb is mainly a diffusion mechanism, and the leaching of As, Fe, and Mn is mainly controlled by surface leaching. Intermittent rainfall leaching significantly promoted the release of Sb and As, changing the release control mechanism and increasing concentrations by 109.2 μg/L and 16.6 μg/L, respectively. Carbonate rocks can effectively inhibit release of HMs from tailings while elevating Sb/As/Fe valence states and inducing Sb-As-Fe-Mn release correlations. The kinetic release mathematical model reflects that the release process of HMs is controlled by multiple factors. This work has deepened the understanding of heavy metal leaching under various rainfall conditions and provided a useful reference for managing open-pit tailings in karst mountainous areas.