The adsorption of jarosite and the resulting passivation of mineral surfaces can negatively influence metal extraction from sulfidic ores as well as the fate of other elements in biohydrometallurgical processes. Some bioleaching microorganisms mediate dissimilatory iron reduction coupled to sulfur oxidation (DIRSO), a process utilized predominantly in continuously enhanced leaching of metals from sulfide and/or oxidized ores. In this study, the reductive dissolution of jarosite (biosynthesized by the iron-oxidizing archaeon Acidianus manzaensis) catalyzed by the mesophilic acidophilic bacterium Acidithiobacillus (At.) thiooxidans oxidizing different inorganic sulfur compounds was investigated. Kinetic measurements of pH, ORP, iron concentrations, and planktonic cell counts were performed to describe the reductive dissolution of jarosite. Moreover, the solid leaching residues were analyzed using X-ray absorption near edge structure (XANES), Inductively coupled plasma - optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The dissolution rates of jarosite after 34 days of bioleaching by At. thiooxidans with S0, Na2S2O3, and Na2SO3 were 41.7, 76.3, and 98.4%, respectively, while negligible jarosite dissolution was detected in abiotic controls. The presence of Na2S2O3 and Na2SO3 resulted in structural modifications on the jarosite surfaces, but the dissolution of jarosite was not promoted in the absence of At. thiooxidans. In the biotic assays with Na2SO3, jarosite was completely dissolved, indicating that Na2SO3 was the most suitable electron donor (out of those tested) for DIRSO by At. thiooxidans. The findings obtained in this study can contribute to designing suitable bioleaching strategies for oxidized ores. They also highlight the potential of microbially catalyzed DIRSO to mitigate jarosite formation that often hinders bioleaching of sulfidic ores.
- Acidithiobacillus thiooxidans
- iron reduction
- sulfur oxidation