Modes of occurrence of arsenic in high-arsenic coal by extended X-ray absorption fine structure spectroscopy

The concentration ranges of As and Sb in six Late Permian high-arsenic coals collected from Xingren and Xingyi, Guizhou Province are 94.1 μg · g^-1-3.2% and 8.1 μg · g^-1-120 μg · g^-1, respectively. Based on the mineralogical analysis, no arsenic and arsenic-bearing minerals are detected in these samples and arsenic occurs in coal macerals. By extended X-ray absorption fine structure(EX-AFS) spectroscopy, we have found that arsenic in these high-arsenic coal samples coordinates with oxygen; the coordination number of As with oxygen for these samples is 4 except one sample(H₉) for which the coordination number of As is 3. Therefore, arsenic in these high-arsenic coals does not occur in sulfide minerals, but occurs in arsenate or arsenite phase, and the preponderance of As is in arsenate of As⁵⁺.