Occurrence Modes of Arsenic in Coal: A Case Study from the Hanshuiquan Coal Mine, Santanghu Coalfield, Xinjiang Province, China

The high concentration of arsenic in coal does great harm to the environment. It is important to research the occurrence mode of As in coal to promote the removal of As in coal and understand the migration and transformation of As in coal. In this work, eleven samples from the Hanshuiquan coal mine, in the Santanghu Coalfield, were tested by X-ray diffraction (XRD) and Scanning Electron Microscopy with an Energy Dispersive Spectrometer (SEM-EDS). The results show that maximum arsenic content in the coal seam was 108.37 μg/g, which was 13 times more than that of the world coal, and 28 times more than that of the Chinese coal. Through X-ray diffraction (XRD) experiments, ojuelaite and scorodite were found in the samples. Scanning Electron Microscopy (SEM) and an Energy Dispersive Spectrometer (EDS) were used to determine the occurrence location of the arsenic elements. In combination with geochemistry and mineralogy theory, the occurrence modes of the arsenic were studied in detail. The occurrence modes of arsenic in coal from the study area are dominated by sulfide-bound arsenic. At the same time, it was found that arsenic in the study area might occur in the form of arsenate containing zinc and organic bound arsenic. Previous studies and this work have shown that (1) arsenic in coal is predominantly in the form of pyrite, and (2) arsenic in coal is associated with organic matter in low-rank coal and to a lesser extent in high-rank coal. Understanding the occurrence modes of arsenic in coal is of great significance because it has significant impacts on coal mining, preparation, combustion, and utilization, and has adverse effects on the environment and human health.