Biodesulphurization of Indian (Assam) coal using Thiobacillus ferrooxidans(ATCC 13984)

The pyritic sulphur removal from coal and pyrite by Thiobacillus ferrooxida ns was studied in a batch reactor. Microbial oxidation of ferrous iron to t he ferric form, the central step in the biodesulphurization process was fou nd to be affected by the substrate and product concentration. Direct microb ial oxidation of pyrite was dominant during the exponential phase, while in direct electrochemical oxidation was observed at the stationary phase of th e growth. The effect of various parameters, such as pulp density, ferrous a nd ferric iron concentrations on the rate of biodesulphurization was studie d. The rate of pyritic sulphur removal was retarded at higher concentration s of ferrous and ferric iron. Therefore, during the process, the concentrat ions of Fe(II) and Fe(III) iron in the bioreaction mixture need to be contr olled to maintain high rates of pyritic sulphur removal. (C) 1999 Elsevier Science Ltd. All rights reserved.