Perpustakaan Digital ITB

Bioflotation is a biotechnology by employing microbes, in particular bacteria, for processing ores to separate gangue minerals (undesirable impurities). A biosurfactant-producing and sulfur-oxidizing bacterium, namely Citrobacter youngae strain SKC-4, was studied as an alternative for the replacement of relatively toxic chemical reagents in the flotation process of silicate minerals. Surface properties of the silicate minerals caused by the action of bacteria were characterized using FTIR and contact angle measurement. The study results showed that Citrobacter youngae strain SKC-4 was capable of producing biosurfactants as evidenced by a decrease of the surface tension of the solutions in interaction with silica as a function of time. Surface properties of the silica-bacterial cell complexes which were assessed by water contact angle values (°) showed an increase in the contact angle over time, indicating a hydrophobic property, but their increase remained lower than 10o. Fourier Transform Infrared (FTIR) analyses confirmed the role of bacterial strain in changing the silica surface properties to be more hydrophobic. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) observations on the silica-bacterial cell complexes revealed the presence of bacterial cell aggregation along with silica, where silica particles become embedded in the biofilm matrix. The strain was found to promote the formation of silica-cell complexes due to the generation of surface-active agents (i.e., extracellular polymeric substances (EPS). It is suggested from this study that the bacterium Citrobacter youngae strain SKC-4 could potentially be applicable as the flotation bioreagents for making the silicate flotation processes more economical and environmentally friendly.