Difference in Biological Oxidation Between High-Sulfur Coal and Pure Pyrite at Different pH Levels

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In this study, Acidthiobacillus ferrooxidans LX5 was used as an experimental microbial strain, and differences in biological oxidation between high-sulfur coal and pure pyrite were thoroughly investigated over 18 days in acidic environments with initial pH values of 1.70, 2.00, 2.30, and 2.60. The results showed that the pyrite bio-oxidation efficiency in the coal biological desulfurization system exceeded that in the pure pyrite bio-oxidation system at the same initial pH. The net increase in SO42− concentration in the coal biological desulfurization system increased with increasing initial pH values, consistent with the net increasing trend in SO42− in the pure pyrite biological oxidation system. The net increase in SO42− concentration in the high-sulfur coal biological oxidation system with an initial pH of 2.60 reached 4589.06 mg/L after 18 days. The density of A. ferrooxidans LX5 in both systems increased with increasing initial pH values. With increasing initial pH levels, the inorganic sulfur (pyritic sulfur and sulfate sulfur) removal efficiencies increased in both the coal biological desulfurization and pyrite biological oxidation systems, reaching 88.28% and 9.25%, respectively, at an initial pH of 2.60. The results are of great significance for better understanding the biological desulfurization process of coal.