Kinetic model for batch bacterial dissolution of pyrite particles by Thiobacillus ferrooxidans

Abstract

The kinetics of the bacterial dissolution of pure pyrite (FeS 2) particles by Thiobacillus ferrooxidans was studied at different initial particle sizes in a well-mixed batch reactor. Experimental studies were made on the adsorption of bacteria on pyrite particles as well as the bacterial dissolution of pyrite. The Langmuir isotherm was used to fit the adsorption data. The equilibrium constant in the Langmuir equation was independent of the particle size, whereas the maximum adsorption capacity per unit weight of pyrite increased with decreasing particle size. A rate expression for the kinetics of bacterial growth and pyrite dissolution was derived, taking into account the effect of initial particle size. The kinetic parameters appearing in the rate equations, the growth yield and specific growth rate of adsorbed bacteria, were evaluated by curve-matching, using the experimental data obtained at different initial particle sizes. The evaluated kinetic parameters were found to be independent of the initial particle size. This kinetic model was successfully used to predict the bacterial dissolution behavior for the different operating variables, i.e. the initial particle size, the initial cell concentration and the initial pyrite-liquid loading ratio.