Surface Modification of Galena Concentrate, Sphalerite Concentrate, and Silica by the Bacterium Citrobacter sp. and Its Application to Green Flotation of Complex Pb–Zn Ores

In the present work, a biosurfactant-producing and sulfur-oxidizing mixotrophic bacterium (identified as Citrobacter sp.) was studied as flotation reagents to substitute for several hazardous chemical reagents to establish a cleaner and greener mineral processing. The mixotrophic bacterium Citrobacter sp. was adapted with galena (PbS) concentrate or sphalerite (ZnS) concentrate or silica (SiO 2 ) mineral to modify the hydrophobicity of mineral surfaces as described by contact angle measurements, scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM–EDS), and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the bacterium application as potential flotation reagents in the bioflotation of complex Pb–Zn ore in a 2.5-l laboratory-scale Denver flotation cell showed that the mixotrophic bacterium could function as flotation bioreagents by producing metabolites apart from its bacterial cells. The bacterial action as flotation bioreagents included collector, frother, and depressant due to its capability in producing biosurfactants and oxidizing sulfur with a moderate capacity in oxidizing iron. Its function yielded the high flotation recovery of lead (Pb: ~ 90%) and zinc (Zn: ~ 80%) and higher Pb and Zn grade in concentrate with respect to pH, conditioning time, and bacterial cell concentration. From an industrial viewpoint, the findings of this study might be very prospective for the improvement of more cost-effective and eco-friendly flotation reagents. Graphical Abstract