Preliminary study on the mode of occurrence of arsenic in high arsenic coals from southwest Guizhou Province

Coal samples from high arsenic coal areas have been analyzed by electron mi croprobe analyzer (EMPA), scanning electron microscopy with an energy dispe rsive X-ray analyzer (SEM-EDX), X-ray diffraction analysis (XRD), low tempe rature ashing (LTA), transmission electron microscopy (TEM), X-ray absorpti on fine structure (XAFS), instrument neutron activation analysis (INAA) and wet chemical analysis. Although some As-bearing minerals such as pyrite, a rsenopyrite, realgar(?), As-bearing sulfate, and As-bearing clays are found in the high arsenic coals, their contents do not account for the abundance of arsenic in the some coals. Analysis of the coal indicates that arsenic exists mainly in the form of As5+ and As3+ , combined with compounds in the organic matrix. The occurrence of such exceptionally high arsenic contents in coal and the fact that the arsenic is dominantly organically associated are unique observations. The modes of occurrence of arsenic in high As-coa ls are discussed.