Microcrystalline structure and surface area of elemental sulphur as factors influencing its oxidation by Thiobacillus albertis

Abstract

The effect of particle size, surface area per unit weight, and molecular composition of S0 on the rate of S0 oxidation by Thiobacillus albertis was studied. Spherical S0 prills varying in size and surface areas were prepared and added as the sulphur source to synthetic salts medium. The rate of S0 oxidation by T. albertis was found to be a function of surface area/unit weight of sulphur. In all these experiments [Formula: see text] was produced in a linear manner with time indicating sterically favorable cell–sulphur oxidation binding sites for bacterial growth. Different powdered forms of S0 (high-purity orthohombic, high-purity polymeric, and mixed molecular sulphur) were oxidized at a significantly faster rate than the prilled S0. Also the initial oxidation was exponential up to 3 days at which point [Formula: see text] production from mixed molecular sulphur utilization fell off substantially with time as compared with similar [Formula: see text] rate curves obtained with high-purity orthorhombic and high-purity polymeric oxidation. It was implied that the increased Sx content in mixed molecular sulphur was responsible for the slower oxidation rate by altering the sulphur crystal lattice formation which affected the number of sterically favorable oxidation binding sites for T. albertis growth. Thiobacillus albertis was shown to colonize S0 surfaces as microcolonies. It was concluded that particle size, surface area/unit weight, and the crystal microstructure of S0 affects the oxidation rate of S0 by T. albertis.