Pyrite Surface after Thiobacillus ferrooxidans Leaching at 30°C

Abstract

In order to investigate the effect of Thiobacillus ferrooxidans on the oxidation of pyrite, two parallel experiments, which employed H2S04 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans, were designed and carried out at 30°C. The initial pH of the two solutions was adjusted to 2.5 by dropwise addition of concentrated sulphuric acid. The surfaces of pyrite before exposure to leaching solutions and after exposure to the HSO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans were observed by scanning electron microscopy (SEM). There were a variety of erosion patterns by Thiobacillus ferrooxidans on the bio-leached pyrite surfaces. A conclusion can be drawn that the oxidation of pyrite might have been caused by erosion of the surfaces. Attachment of the bacteria to pyrite surfaces resulted in erosion pits, leading to the oxidation of pyrite. It is possible that the direct mechanism plays the most important role in the oxidation of pyrite. The changes in iron ion concentrations of both the experimental solutions with time suggest that Thiobacillus ferrooxidans can enhance greatly the oxidation of pyrite.

Microbial Imprints on Sulfide Minerals in Submarine Hydrothermal Deposits of the East Pacific Rise

“…Microbes that oxidize ferrous iron to ferric iron are generally thought to be the largest contributors to pyrite oxidation (Murphy & Strongin, 2009). Mostly, studied microbial species are the iron‐oxidizing bacteria Acidithiobacillus ferrooxidans (Andrews, 1988; Aoki, 1999; Bennett & Tributsch, 1978; Blight et al, 2000; Edwards et al, 2001; Hiltunen et al, 1981; Jiang et al, 2007; Liu & Zhang, 2015; Lu et al, 2006; Mustin et al, 1992, 1993; Ndlovu & Monhemius, 2005) and Leptospirillum ferrooxidans (Rojas‐Chapana & Tributsch, 2004), and the iron‐oxidizing archaeon Ferroplasma acidarmanus (Edwards et al, 2001). The pits within chalcopyrite and pyrite of our samples are generally in accordance with those of biologically induced pits observed in experimental studies in distribution patterns and in pitting morphology and are apparently distinct from those abiotic chemical etching marks (Asta et al, 2008; Lefticariu et al, 2010).…”

“…Their metabolic activities can alter the geochemistry of their surroundings, influencing the weathering of minerals and the cycling of major and minor elements (Newman, 2010). Experimental studies demonstrate that a number of iron‐oxidizing microbes can facilitate the oxidative dissolution of metal sulfide minerals, mostly pyrite, resulting in characteristic pitting patterns within the crystal surface (Andrews, 1988; Aoki, 1999; Bennett & Tributsch, 1978; Blight et al, 2000; Edwards et al, 2001; Hiltunen et al, 1981; Jiang et al, 2007; Liu & Zhang, 2015; Lu et al, 2006; Mustin et al, 1992, 1993; Ndlovu & Monhemius, 2005; Rojas‐Chapana & Tributsch, 2004). However, microbe‐mineral interactions in marine sulfide deposits are poorly known.…”

Surface Characteristic of Pyrrhotite Bio-Oxidized by Acidithiobacillus Ferrooxidans

“…Presently, studies of A. ferrooxidans on sulfide surface and surface morphological changes of mineral have started to receive attention in China. For instance, in a study on the surface morphological change of pyrite before and after oxidation, Lu et al suggested that a direct mechanism might have played an important role in the bio-oxidation of pyrite [10] . With modern biological microscopic approaches and surface morphological and in-situ chemical analyses (scanning electron microscope, transmission electron microscope), we will present in this paper surface characteristic of pyrrhotite during bacterium-assisting oxidation to better understand the bio-oxidation processes of pyrrhotite.…”