Acidic Peroxidation of Brazilian Coal: Desulfurization and Estimation of the Forms of Sulfur

Abstract

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 HNO 3 (0.1 mol L −1 ). Best results were obtained using 10% H 2 O 2 /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.

Transformation of organic sulfur and its functional groups in nantong and laigang coal under microwave irradiation

“…Using 16% potassium hydroxide solution followed by 10% hydrochloric acid at 95°C, about 22%–35% of total sulfur has been removed . Fallavena et al removed 88% of pyritic sulfur in the coal samples using 10% H 2 O 2 with 0.1 mol L −1 HCl. Although the physical or chemical methods are applicable to the removal of inorganic sulfur, they are ineffective for the desulfurization process of coal that contains highly amount of organic sulfur, as finely dispersed and chemical bonding with coal molecules .…”

Evaluation of Zeolite/Backfill Blend for Acid Mine Drainage Remediation in Coal Mine

“…The findings indicated expected characteristics for this type of sample with high ash content (74.55%) since it is originated from coal tailings that have high levels of mineral matter (∼50%). 5,35,41 Total sulfur content was high (5.33%), with 40% of this total corresponding to pyritic sulfur (2.12%) and 51% to sulfate (2.72%).…”

Application of mass spectrometry in the characterization of chemicals in coal‐derived liquids

“…Oxidation with different oxidants, such as NaOCl, H 2 O 2 , and HNO 3 , has been extensively used for coal desulfurization (Li & Cho, 2005;Carrillo-Pedroza et al, 2009;Fallavena et al, 2012;Shen et al, 2012). Therefore, there should be SCCs present in the products from mild oxidation of coals.…”