Enhancement Mechanism of Stibnite Dissolution Mediated by Acidithiobacillus ferrooxidans under Extremely Acidic Condition

Abstract

Oxidative dissolution of stibnite (Sb2S3), one of the most prevalent geochemical processes for antimony (Sb) release, can be promoted by Sb-oxidizing microbes, which were studied under alkaline and neutral conditions but rarely under acidic conditions. This work is dedicated to unraveling the enhancement mechanism of stibnite dissolution by typical acidophile Acidithiobacillus ferrooxidans under extremely acidic conditions. The results of solution behavior showed that the dissolution of Sb2S3 was significantly enhanced by A. ferrooxidans, with lower pH and higher redox potential values and higher [Sb(III)] and [Sb(V)] than the sterile control. The surface morphology results showed that the cells adsorbed onto the mineral surface and formed biofilms. Much more filamentous secondary minerals were formed for the case with A. ferrooxidans. Further mineral phase compositions and Sb/S speciation transformation analyses showed that more secondary products Sb2O3/SbO2−, Sb2O5/SbO3−, SO42−, as well as intermediates, such as S0, S2O32− were formed for the biotic case, indicating that the dissolution of Sb2S3 and the Sb/S speciation transformation was promoted by A. ferrooxidans. These results were further clarified by the comparative transcriptome analysis. This work demonstrated that through the interaction with Sb2S3, A. ferrooxidans promotes S/Sb oxidation, so as to enhance S/Sb transformation and thus the dissolution of Sb2S3.

Differential Mechanisms of Microbial As(III) and Sb(III) Oxidation and Their Contribution to Tailings Reclamation

“…Consistently, both anoA -containing strain AsSb1 and anoA -encoding MAGs isolated or retrieved from XKS tailing in this study belong to the same order as the family Rhizobiaceae . Further, multiple known Sb­(III) oxidizers, such as Allorhizobium , Ensifer , Agrobacterium , and Rhizobium , were also affiliated with these lineages. ,− On the other hand, other known Sb­(III) oxidizing populations, such as Thiobacillus and Pseudomonas , may utilize different mechanisms for Sb­(III) oxidation. − For instance, the arsO gene encoding a homologue of flavoprotein monooxygenase was reported to mediate Sb­(III) oxidation in various microorganisms, including Thiobacillus and Pseudomonas . Furthermore, the extracellular superoxide has been shown to mediate Sb­(III) oxidation in Pseudomonas . , These observations suggested that various functional genes may be responsible for Sb­(III) oxidation.…”