Iron solubilization during anaerobic growth of acidophilic microorganisms with a polymetallic sulfide ore

Abstract

Citation: NORRIS, P.R., GOULD, O. and OGDEN, T.J., 2015. Iron solubilization during anaerobic growth of acidophilic microorganisms with a polymetallic sulfide ore. Minerals Engineering, 75, Additional Information:• This paper was accepted for publication in the journal Miner- AbstractAcidithiobacillus ferrooxidans at 30 °C and Sulfobacillus thermosulfidooxidans at 47 °C were selected from a preliminary screening of various acidophiles for their ferric iron reduction capacities during anaerobic, autotrophic growth on sulfur. The selected cultures were used with a polymetallic sulfide ore under anoxic conditions to demonstrate enhanced solubilization of iron during leaching in shaken flasks and enhanced removal of iron from laboratory ore-leaching columns, compared to leaching with continuous aeration. Oreassociated, ferric iron-rich precipitates, which were formed under previously oxidizing conditions, were a potential influence on extraction of target metals and percolation through ore columns and were available as the source of ferric iron for anaerobic sulfur oxidation. Over twice as much iron was removed by moderate thermophiles when anoxic phases were introduced during the leaching. Enhanced removal of iron and some improvement in extraction of base metals from ore fragments were also demonstrated with a selected ''Sulfolobus''-like strain during growth and leaching with alternating periods of aeration and anoxic conditions at 70 °C.

Metallosphaera javensis sp. nov., a novel species of thermoacidophilic archaea, isolated from a volcanic area

“…Like other members of the genus, J1 T was able to oxidize iron (determined by visual inspection of the formation of reddish Fe(III) precipitates in comparison with an abiotic control) [34]. In the presence of sulphur, J1 T reduced 50 mM ferric iron to ferrous iron under anaerobic conditions in one week (results not shown), which is consistent with results from previous studies [11]. Iron reduction has also been observed with M. sedula in connection with H 2 oxidation [35], but has not been described for other species of the genus Metallosphaera.…”

“…The type species of the genus is Metallosphaera sedula [4]. Previously, a potentially novel member of the genus Metallosphaera has been demonstrated to oxidize metal sulphides such as pyrite and chalcopyrite, exhibiting higher copper and solid load tolerances in bioleaching experiments than M. sedula [10,11]. Here we report the characterization of the novel isolate which was previously referred to as strain J1 T and as a potential species of the genus Metallosphaera because of the close relationship of its 16S RNA gene sequence to those of other species of the genus Metallosphaera [12].…”

Ferric Iron Reduction in Extreme Acidophiles

“…Overall, ferric iron reduction was shown for different physiologic groups of acidophilic microorganisms, covering heterotrophs and chemoautotrophs which feature temperature optima ranging from mesophilic to thermophilic adaptations ( Johnson and Bridge, 2002 ). In particular, the ability of acidophiles to mediate reductive dissolution of ferric iron minerals is frequently explored, with emphasis on the applicability prior to elucidation of the exact biochemical mechanism ( Hallberg et al, 2011a ; Nancucheo et al, 2014 ; Norris et al, 2015 ; Marrero et al, 2017 ). However, certain research groups provided insight into the mechanisms of ferric iron reduction that occur in extreme acidophiles at different oxygen concentrations, which will be discussed in more detail.…”

“…Reductive bioleaching was also up to 6 times more effective than acid leaching in processing cobalt-containing limonite from Kazakhstan or the Philippines under aerobic conditions ( Smith et al, 2017 ). Further benefits of reductive bioleaching approaches were shown by an initial anaerobic phase during leaching of polymetallic sulfides which had to some extend positive effects on the base metal recovery and enhanced the iron removal noticeable at both 45 and 70°C ( Norris et al, 2015 ).…”

Bacterial and chemical leaching of copper-containing ores with the possibility of subsequent recovery of trace silver

“…All clean flasks were sterilized by autoclaving using Steam Autoclave VK-75 at 1 atm and 121 °C for 20 min before inoculation. In order to prevent growth of indigenous bacteria in flasks 1-4, 6, benzoic acid (50 mg/l) was immersed to un-inoculated medium (Norris et al, 2015).…”