title: Synthesis of argentojarosite with simulated bioleaching solutions produced by Acidithiobacillus ferrooxidans.
abstract: Argentojarosite (AgFe3(SO4)2(OH)6) is formed as a secondary phase in Ag-catalyzed bioleaching of chalcopyrite (CuFeS2), but to date very little is known about the paragenesis or characteristics of this silver-containing compound. The purpose of this study was to synthesize argentojarosite via biological oxidation of 120mM ferrous sulfate by Acidithiobacillus ferrooxidans. Because of its toxicity to A. ferrooxidans, Ag(+) (as AgNO3) was added to spent culture media (pH2) after complete oxidation of ferrous sulfate. Schwertmannite (ideally Fe8O8(OH)6(SO4)) was precipitated during the iron oxidation phase, and subsequent Ag(+) addition resulted in the formation of argentojarosite. Contact time (8h, 5d, and 14d) and Ag(+) concentration (0, 5, 20, and 40mM) were used as variables in these experiments. Synthesis of argentojarosite, schwertmannite and other mineral phases was confirmed through X-ray diffraction analysis. Additional analyses of solid-phase oxidation products included elemental composition, color and specific surface area. The sample synthesized in the presence of 40mM Ag(+) and with 14d contact time yielded an X-ray diffraction pattern of well crystallized argentojarosite, and its elemental composition closely matched the calculated Ag, Fe, and S contents of ideal argentojarosite. The color and surface area of the remaining samples were influenced by the presence of residual schwertmannite. This phase remained stable over the time course of 14d when no Ag(+) was present in the system. When equilibrations were extended to 42d, partial conversion of reference schwertmannite to goethite was noted in the absence of Ag. In the presence of 20mM or 40mM Ag over the same time course, some formation of argentojarosite was also noted. In this case, schwertmannite was the only source of Fe and SO4 for argentojarosite formation.
authors.affiliation: Department of Microbiology, Ohio State University, 484 West 12(th) Avenue, Columbus, OH 43210, USA.
authors.forename: Chiranjit
authors.initials: C
authors.lastname: Mukherjee
authors.affiliation: School of Environment and Natural Resources, Ohio State University, 2021 Coffey Road, Columbus, OH 43210, USA.
authors.forename: F Sandy
authors.initials: FS
authors.lastname: Jones
authors.affiliation: School of Environment and Natural Resources, Ohio State University, 2021 Coffey Road, Columbus, OH 43210, USA.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Bigham
authors.affiliation: Department of Microbiology, Ohio State University, 484 West 12(th) Avenue, Columbus, OH 43210, USA. Electronic address: tuovinen.1@osu.edu.
authors.forename: Olli H
authors.initials: OH
authors.lastname: Tuovinen
mesh_terms: D042763:Acidithiobacillus / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D058085:Iron Compounds / Q000737:chemistry / Q000378:metabolism; D008903:Minerals / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D012835:Silver Nitrate / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D005296:Ferrous Compounds; D058085:Iron Compounds; D008903:Minerals; D012996:Solutions; C511969:schwertmannite; C012819:chalcopyrite; C020748:ferrous sulfate; D003300:Copper; D012835:Silver Nitrate
keywords: Acidithiobacillus ferrooxidans; Argentojarosite; Iron oxidation; Jarosite; Schwertmannite