On the fundamentals aspects of hematite bioflotation using a Gram positive strain

- Fundamental studies of hematite bioflotation using R. erythropolis as biorreagent.
- Cells adhesion onto the mineral surface shifts the hematite zeta potential curve.
- Floatability conditions: pH 5-6, bacteria 150-200 mg/l and particle size −53 + 38 μm.
- This strain was capable to produce a stable froth.
- Bacterial concentration affects the surface tension of suspension-air interface.

The use of microorganisms and/or their metabolic products is becoming an attractive alternative in mineral processing. In that sense, this research deals with the use of the hydrophobic gram positive Rhodococcus erythropolis bacteria as a possible substitute of synthetic reagents used in hematite flotation. Bacterial growth experiments, using culture media of tryptic soy broth (TSB) and yeast and malt extract with glucose (YMG) separately, showed a greater bacterial density for the first one. In addition, it was observed that the isoelectric point (IEP) of hematite was shifted after biomass interaction, suggesting that the bacterial cells were adhered onto the mineral surface. Moreover, bacterial adhesion was higher at acidic pH, which also suggests an electrostatic attraction between the mineral surface and the biomass at this pH range. Microflotation tests were carried out in a modified Hallimond tube achieving a maximum hematite floatability of 83.86% at pH 6. Finally, the kinetics of the process followed a second order model.