ADHESION OF ESCHERICHIA COLI ONTO OXIDE MINERALS – EXTENDED DLVO THEORY AND FLOTATION BEHAVIOUR

摘要

The adhesion behaviour of Escherichia coli to three oxide minerals (quartz, hematite and corundum) was investigated experimentally. A strain of E. coli was used that contains genes encoding a protein involved in silica precipitation. Maximum cell adhesion was observed at pH <4.3 for quartz and at pH 4.5 - 8.5 for corundum. Cell adhesion to hematite remained low at all pHs. Microbe–mineral adhesion was assessed with an extended DLVO theory approach. The essential parameters used to calculate the energy of the microbe–mineral interaction (Hamaker constants and acid–base components) were experimentally determined. The extended DLVO approach can be used to explain the results of the adhesion experiments. The effect of E coli on the floatability of the three oxide minerals was determined. Our results showed that E coli can act as a selective collector for quartz at acidic pHs, with 90 per cent of the quartz floated at 1.5 × 109 cells/mL. However, only 9 per cent of hematite and 30 per cent of corundum was floated under similar conditions. Using E coli and no reagents, it was possible to separate quartz from a hematite–quartz mixture with a Newton’s efficiency of 0.7. Quartz was removed from a corundum mixture by E coli with a Newton’s efficiency of 0.6.