Microbial Desulfurization of Malaysian Coal in Batch Process using Mixed Culture (RESEARCH NOTE)

Abstract

Biodesulfurization of coal has been carried out in batch culture of single strain and mixed culture of sulfur oxidizing bacteria. The pure cultures of Thiobacillus thiooxidans and Thiobacillus ferrooxidans utilized inorganic sulfur content of Malaysian coal. The chemolithotroph bacteria were able to grow on coal and metabolize the coal's sulfur content. The batch cultures of coal with 3-5 percent sulfur were used for growing microorganisms. A few species of bacteria and fungi had potential to utilize coal complex media, which were isolated from coal rice hulls and pharmaceutical wastewater. Asperigillus niger and Thiobacillus species isolated from coal, fungi from rice hulls and Saccharomyces species from wastewater, all microorganisms capable to grow on coal. The main concern was the sulfur oxidizing bacteria were screened out from all non-sulfur reducing bacteria. In the Batch cultures, the biooxidation coal's sulfur was affected by several parameters, such as pH, nutrients, agitation rate, growth stimulants and percentage coal. The trace amount of magnesium and cobaltions, 200 rpm agitation rate with initial pH of 2.6 for mixed culture of Thiobacillus thiooxidans and Thiobacillus ferrooxidans showed maximum growth rate and optimum batch operating conditions. The highest sulfur oxidation was obtained at the optimal Thiobacillus growth rate. More than 75 percent of sulfur was removed from coal. The biooxidation of coal, the kinetic model followed by Monod rate equation with specific growth rate, µmax = 4.8d-1 and rate constant. Ks =16.7 g/L.