Abstract
The function of microbial contact leaching to pyrite oxidation was investigated by analyzing the differences of residue morphologies, leaching rates, surface products, and microbial consortia under different conditions in this study. This was achieved by novel equipment that can control the redox potential of the solution and isolate pyrite from microbial contact oxidation. The morphology of residues showed that the corrosions were a little bit severer in the presence of attached microbes under 750 mV and 850 mV (vs. SHE). At 650 mV, the oxidation of pyrite was undetectable even in the presence of attached microbes. The pyrite dissolution rate was higher with attached microbes than that without attached microbes at 750 mV and 850 mV. The elemental sulfur on the surface of pyrite residues with sessile microorganisms was much less than that without attached microbes at 750 mV and 850 mV, showing that sessile acidophiles may accelerate pyrite leaching by reducing the elemental sulfur inhibition. Many more sulfur-oxidizers were found in the sessile microbial consortium which also supported the idea. The results suggest that the microbial “contact leaching” to pyrite oxidation is limited and relies on the elimination of elemental sulfur passivation by attached sulfur-oxidizing microbes rather than the contact oxidation by EPS-Fe.
Highlights
Pyrite (FeS2 ) is the most abundant sulfide mineral on the earth
Rod-shaped and spiral-shaped microorganisms could be seen under each redox potential
Pyrite with attached microbes showed no corrosion under 650 mV demonstrating that attached microbes cannot leach pyrite directly and extracellular polymeric substance (EPS)
Summary
Pyrite (FeS2 ) is the most abundant sulfide mineral on the earth. The oxidation of pyrite is an indispensable part of a global circulation of iron and sulfur [1]. Pyrite always intergrows with Cu, Co, and Zn and serves as the most prevalent host of gold. Pyrite bioleaching is useful for the extraction of a variety of useful metals [2]. Bioleaching is used in treating spent catalysts to recover a lot of valuable metal [3,4]. When exposed to the atmosphere, pyrite generates an acidic, metal-enriched effluent, so-called “acid mine drainage” (AMD), which is accelerated by the growth of microbes and is harmful to the environment [5]. Investigating the pyrite leaching mechanisms and microbes’ functions are both vital for mining and environmental protection
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