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[摘要]：Existing standard test methods for determining forms of sulfur take a long time, consume a significant amount of reagents, and generate waste. Faced with this problem, an alternative screening method is proposed using hydrogen peroxide in acid medium for the desulfurization of coal and estimation of forms of sulfur in Brazilian raw coal. The detailed characterization of the extracts and the solids was performed at different reaction times. Hydrogen peroxide solutions at different concentrations (3, 10, and 30%) were tested in the presence and absence of the HCl or HNO3 (0.1 mol L-1). Best results were obtained using 10% H2O2/0.1 mol L-1 HCl with removals of 88-98% of pyritic sulfur and 3.5-18% of ash present in the coal samples. The concentration of total dissolved iron measured in extracts approaches the maximum concentration of iron expected for total oxidation of pyrite to sulfate at the end of reaction (240 min). Thus, it can be used to estimate the content of pyritic sulfur, with maximum percent error of 12%. Peroxidation also causes the dissolution of sulfate minerals, which together with sulfate from the oxidation of pyritic sulfur allows estimating the sum of these forms of sulfur (pyrite + sulfate) from the sulfate measured in the leaching extracts with errors <14% for most of the coals studied. It is a characteristic of the Brazilian coals to have low levels of sulfate sulfur and organic sulfur; these forms of sulfur cannot be determined by this method. |
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