Release Characteristics of Harmful Trace Elements during Dynamic Leaching and Static Immersion of Coal Gangue in Xinjiang

Abstract

Coal gangue has dual attributes of waste residue and resources. Clarifying the release characteristics of harmful trace elements from the coal gangue can provide a theoretical basis for environmental impact and resource utilization. In this study, the characteristics of harmful trace elements released from coal gangue in Xinjiang during dynamic leaching and static immersion experiments were determined using proximate analysis, X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), and inductively coupled plasma mass spectrometry (ICP-MS). The results show that (1) the higher the content of harmful trace elements in coal gangue and the greater the concentration coefficient (CC), the greater the release of elements in dynamic leaching and static immersion experiments. The mode of occurrence of trace elements in the coal gangue determines their transport and release. Elements are associated not only with moisture but also with minerals, such as clays, sulfides, and carbonates, which are readily soluble in water. (2) The release of harmful trace elements was inversely proportional to time in the dynamic leaching experiments, and the main reason for the reduction in element release during the late leaching period was the adsorption effect of clay minerals. In the dynamic leaching experiment, harmful trace elements in the surrounding environment continued to accumulate, and static immersion experiments in water showed that harmful trace elements gradually reached dynamic equilibrium. The concentration of most elements in the late stage of the static immersion experiment was lower than that in the early stage, indicating that the environmental hazards of dynamic leaching were greater than those of the static immersion of coal gangue in Xinjiang.