KINETICS AND MECHANISM OF THE ADSORPTION OF SULFOLOBUS-ACIDOCALDARIUS ON COAL SURFACES

The adsorption of Sulfolobus acidocaldarius on five types of coals (with different sulfur contents) was investigated to define the kinetics of the bacterial cell adsorption and to clarify the mechanism of the adsorption involved in biological desulfurization of coals. A kinetic model, in which two stages of adsorption are considered, is proposed on the basis of the experimental results. The estimated values of the maximum cell numbers adsorbed per unit area of coal surface (including internal surface area of pores larger than 0.5-mu-m), [S(m)], showed a good correlation with the pyritic sulfur content of the coals. The mechanism of the adsorption was studied by investigating the effects of pH, zeta potentials of coal particles and the bacteria, a specific inhibitor of membrane-bound ATPase (20 mM NaF), a surfactant (Tween 80, 0.05%), and heat treatment (121-degrees-C, 15 min) of the bacteria. From these observations, it was concluded that the rapid adsorption in the first stage was related with the physical force of hydrophobicity and the adsorption in the second stage was strongly related with the oxidation of pyrite. An electromicrographic study on the erosion of the pyrite surfaces by the bacterial cells was also conducted. The micrographs of the pyrite particles after 5 days of the incubation showed that surfaces of pyrite minerals were eroded by adsorbed cells.