Development of a bio-based collector by isolating a bacterial strain using flotation and culturing techniques

A microbial bio-based collector was isolated from iron mine soil using a combination of flotation and culturing techniques. Four microbial strains with greater than 75% recovery of pure hematite were separated using the technique. Classification and identification of the 4 strains by 16S rDNA sequences were conducted. Among them only 1 strain, termed F3, can act as a collector for hematite, as it is not pathogenic to humans. The morphology and hematite adsorption (by scanning electron microscopy; SEM), composition, zeta potential and hydrophobicity of strain F3 were further evaluated. Based on the changes in the zeta potential and hydrophobicity of a hematite surface before and after adsorption with F3, its adsorption mechanism was also analysed. The results revealed that the combination technique of flotation and bacterial culturing is a highly effective technique for isolating bio-collectors from iron mine soil. Two flotation stages were required to isolate strain F3, which belongs to the genus Stenotrophomonas. This rod-shaped bacterium had CH2, CH3 and phosphate groups on its cell wall that imparted strong hydrophobicity and negative charge. Adsorption of strain F3 reduced the zeta potential of a hematite surface and enhanced its hydrophobicity. The adsorption of F3 to hematite is presumed to be through chemical adsorption. Therefore, strain F3 can be used as a bio-collector for hematite flotation.