Surface Thermodynamics and Extended DLVO Theory of Acidithiobacillus ferrooxidans Cells Adhesion on Pyrite and Chalcopyrite

The adhesion of Acidithiobacillus ferrooxidans bacterial cells have been assessed by following the thermodynamic and extended DLVO theoretical approaches. Surface potential, interfacial tension and contact angle parameters that are necessary for the calculation of free energy of adhesion have been determined experimentally. The Hamaker constant involved in the Lifshitz-van der Waals interaction energy has been estimated by microscopic and macroscopic methods. The free energy of adhesion found to be negative on pyrite and chalcopyrite minerals indicating the adsorption of bacterial cells on these minerals. The potential energy diagrams of total interaction energy versus separation distance curves also illustrate the feasibility of bacterial cells adhesion except in a pH region where the bacterial species and minerals possess similar surface charge with high magnitude. The present theoretical analysis of bacterial adhesion on mineral surfaces found to be in good agreement with the experimental results and previous findings in the literature. Thus, the bacterial adhesion behavior on minerals can be judged and explained by considering the physico-chemical interaction forces.