Surface chemical studies on galena and sphalerite in the presence of thiobacillus thiooxidans with reference to mineral beneficiation

Adsorption and electrokinetic studies were carried out to examine the surfa ce chemical changes on galena and sphalerite before and after interaction w ith Thiobacillus thiooxidans (T. thiooxidans). The adsorption density of ba cterial cells onto the two sulphide minerals was found to be independent of pH, although an increased number of cells was adsorbed onto galena compare d to sphalerite. The adsorption isotherms of the cells with respect to the two minerals conform to the Langmuir equation. Zeta potential measurements revealed that the isoelectric points of the sulphide minerals were shifted to higher pH values after bacterial interaction, suggestive of specific ads orption. Both the sulphide minerals as well as the cells became less electr onegative as a function of time after interaction with each other. Selectiv e flotation and flocculation studies highlighted that galena could be separ ated from sphalerite after bacterial interaction. These tests confirmed tha t galena was depressed white sphalerite was made hydrophobic after interact ion with the cells. Fourier transform infrared spectroscopic studies provid ed evidence in support of hydrogen bonding for the mineral-cell adsorption process. Possible mechanisms of interaction between galena/sphalerite and t he cells of T. thiooxidans are discussed. (C) 2000 Elsevier Science Ltd All rights reserved.