Biogenic Synthesis and Reduction of Fe(III)-hydroxysulfates

Reduction of jarosite by Shewanella oneidensis MR-1 and secondary mineralization

“…Except for physical and chemical weathering (Kunda and Veltman, 1979), decomposition of jarosite by bacteria has been proved previously Johnson, 1998, 2000). It is also found that sulfate-reducing bacteria (SRB) can promote the reduction of Fe(III) and the formation of iron sulfides (Li et al, 2006;Gramp et al, 2009), in which the heavy metals and radionuclides released from jarosite can be incorporated into sulfides again. Other than environmental issues, the weathering of jarosite and formation of iron oxides/hydroxides can change the magnetic properties of sediments due to iron minerals transformation (Wills et al, 2000;Papoutsakis et al, 2002).…”

What Do We Really Know about the Role of Microorganisms in Iron Sulfide Mineral Formation?

“…However, determining mineralogy using EDS only can be contentious, as hydrogen sulfide can potentially adsorb onto iron sulfide aggregates, and thus alter the measured Fe:S ratio of the precipitates. X-ray diffraction (XRD), selected area electron diffraction (SAED), or X-ray absorption spectroscopy (XAS), revealed primarily the formation of mackinawite and greigite in microbial cultures to which Fe has been provided as soluble Fe(II) ( Table 1) (Rickard, 1969;Herbert et al, 1998;Benning et al, 1999;Watson et al, 2000;Neal et al, 2001;Li et al, 2004;Williams et al, 2005;Gramp et al, 2009Gramp et al, , 2010Zhou et al, 2014). While greigite is typically found as rod-shaped and 100-to 300-nm platelet structures (Herbert et al, 1998;Gramp et al, 2010), mackinawite does not have a specific morphology, and both minerals appear (via XRD and SEM) to be disordered and poorly crystalline and tend to assemble in µm-sized aggregates (Fortin et al, 1994;Herbert et al, 1998;Benning et al, 1999;Watson et al, 2000;Kim et al, 2015).…”

Crystallization of jarosite in the presence of amino acids

“…The stability of solids in various environments is, however, also linked to their structure, so one could ask whether the presence of microbes induces the formation of jarosites with different structure and therefore properties. Again, early work is showing that jarosites formed in the presence of microbes may have different features [19] suggesting that there are differences between biogenic jarosite and synthetic jarosites [14,20]. There is also the suggestion that particular microbes promote the presence of different phases [8], however, as stated above pH and temperature are also significant contributors to this.…”

“…For the most part, literature is also agreed that below pH 3 jarosite will form [9,14] while above pH 3 and below pH 5 schwertmannite is the product formed. However, this is temperature dependant [10,14]. From an acid mine drainage point of view we find that the bacteria that grow well in the conditions required for jarosite formation must be acidophiles (pH must be below 3).…”