Modes of iodine occurrence in bituminous coal and anthracite and their environmental effects

Modes of iodine occurrence in bituminous coal and anthracite were investigated by using inductively coupled plasma mass spectrometry (ICP-MS) and sequential chemical extraction. The results showed that iodine in both these coals occurs in a descending order of organic, bound with Fe-Mn oxide, water-soluble, residue, ion exchangeable, and the fraction bound to carbonate. In bituminous coal and anthracite, the mean relative content values are 47.4%±3.28% and 43.3%±2.42% for iodine bound to organic matter, 36.8%±3.70% and 34.6%±4.77% for the iodine bound to Fe-Mn oxides, respectively; the amounts of water soluble and ion exchangeable iodine are 10.3%±3.00% and 14.3%±3.37%, respectively; the potential leachable rates of iodine are 10.9% and 16.0%, and potential leachable iodine contents 0.9 μg/g and 1.2 μg/g, respectively. These results suggested that iodine leaching from both these coals can lead to an increase of iodine concentration in surface water at the supergene conditions; the effect of iodine in anthracite is more environmentally favorable than that in bituminous coal.