Sulfuroxidation

Sulfuroxidation is the chemical process by which reduced forms of sulfur or sulfur-containing compounds are oxidized to higher oxidation states, most commonly to sulfate (SO4^2−). In natural systems this oxidation can occur abiotically in the presence of oxygen and water, or biologically mediated by sulfur-oxidizing microorganisms.

Biotic sulfuroxidation is carried out by chemolithoautotrophic bacteria such as Acidithiobacillus and Thiobacillus species. These organisms derive energy from electrons donated by reduced sulfur compounds and transfer them to electron acceptors like oxygen or nitrate, producing sulfate and acidity as byproducts.

Pathways include oxidation of sulfide (S^2−) and elemental sulfur (S) to sulfate, and partial oxidation to intermediates such as thiosulfate (S2O3^2−) or sulfite (SO3^2−). The exact products depend on the substrate, redox conditions, and microbial community involved.

Applications and implications: in geology and environmental science, sulfuroxidation drives weathering of sulfide minerals, contributing to acid mine drainage and the mobilization of metals. In industry and mining, controlled sulfuroxidation is exploited in biomining and bioleaching to extract metals from sulfide ores; related oxidation pathways are also connected to the production of sulfuric acid in industrial processes. Overall, sulfuroxidation is a key component of the global sulfur cycle, influencing acidity, mineral dissolution, and metal mobility in both natural and engineered systems.