KINETIC STUDY OF MICROBIAL COAL DESULFURIZATION USING THERMOPHILIC MICROORGANISMS

Microbial coal desulfurization was investigated using a thermophilic microorganism Sulfolobus acidocaldarius. The rate of ferrous iron oxidation by the microbes was studied. Microbial leaching of iron pyrite from coal was investigated and a kinetic model was proposed. The effects of basal salts, pyrite grain size, prior washing of coal and initial cell density on sulfur removal was experimentally determined. Experimental results showed that both chemical and microbial oxidation of pyritic sulfur were significant. A single dose of basal salts, high cell density (10('8) cells/ml) and fine pyrite grain size (100% < 10 (mu)m) gave 2 to 3 times higher sulfur leaching rates. Cell attachment to coal and other particles was investigated to define the phenomenon of cell-particle interaction. Microbial cells attached to the coal surface at high rates where equilibrium was reached in 5 min and the adsorption isotherms fitted the Langmuir Model in some cases. A kinetic model which assumed a first order rate equation for chemical oxidation of pyrite and the Monod Model for biological oxidation of pyrite along with cell adsorption was proposed to fit the experimental data.