Influence of Particle Size on the Biological Settling Behavior of Hematite Using Bacillus licheniformis

In the present study, the flocculation of fine-grained hematite was investigated in two size ranges using the bacterial cells and metabolic products of Bacillus licheniformis. More than 99% settling for fine and ultrafine particles was observed in the best condition by the bacterial cells in pH 5, and 7, respectively. Settling of fine and ultrafine particles improved by 33% and 18% compared to the control tests. Moreover, adsorption studies revealed that the settling behavior of each size, the fraction was pH-dependent and could be justified very well by the flocculant adsorption. In fact, although for fine hematite, maximum biosurfactant adhesion occurred in an acidic environment, for ultrafine hematite, neutral and basic pH caused the highest flocculant adsorption.