Jennifer C. Oraegbunam, Tunde V. Ojumu
Microbial-mineral interactions are critical for understanding how microbial activity influences the surface properties of jarosite precipitate in bioleaching processes. The surface properties of jarosite precipitate is essential to minimize metal entrapment and optimize bioleaching process. This study compared bio- and chemical leaching of pyrite under similar redox condition at different pH (1.9-2.4). The resulting jarosite precipitates were analyzed for phase composition, morphology and elemental composition, functional groups, thermal stability, surface area and surface charge. Kinetic data fitted into Monod model showed an excellent fit (>0.92) and rmaxFe2+ were similar for bi0- and chemical leaching under a given pH. Both leaching processes produced jarosite precipitates containing mixtures of K- and Na-jarosite. Biogenic jarosite was predominantly K-jarosite with increase pH, while chemical jarosite was mainly Na-jarosite. Microbial activity slightly reduced crystallite sizes which displayed stacked rose-flower like aggregates and loosely packed cauliflower-like particles while chemical jarosite showed low crystalline cubic-shaped structure. As pH increased crystalline structure was well-defined. The functional group and thermal stability analysis were consistent across all jarosite types. Most importantly, the study demonstrated that biogenic jarosite exhibited higher surface area, pore volume, and pore diameter compared to chemical jarosite and as pH increased from 1.9 to 2.4, the surface area of all jarosite samples decreased, while the pore size distribution increased. More so, microbial modification led to increased negatively charged surface. The findings from this study could provide a fundamental understanding into the role of microbial activity could potentially inform the optimization and design of bioleaching processes.