title: Influence of chloride and sulfate on formation of akaganéite and schwertmannite through ferrous biooxidation by Acidithiobacillus ferrooxidans cells.
abstract: Iron (oxyhydr)oxides play important roles in the fixation of toxic elements and also in the distribution of nutrients for plants in soils. Akaganéite and schwertmannite, as the iron oxyhydroxides having an analogous tunnel structure, have been widely recognized in Fe-rich environments. The objective of this study was to examine the formation of akaganéite/ schwertmannite via biooxidation of 0.1 M of ferrous solution containing only Cl-, SO4(2-) or both the anions with a Cl-/SO4(2-) mole ratio of 1, 3, 6, and 10 by chloride-acclimated Acidithiobacillus ferrooxidans cells. Results showed that ferrous iron in chloride/sulfate-containing solutions could be easily biooxidized to ferric iron, and subsequent Fe(III)-hydrolysis/precipitation could result in the formation of large quantity of akaganéite/schwertmannite precipitates. The resulting precipitates were identified to be the pure akaganéite (Fe8O8(OH)7.1(Cl)0.9, the pure schwertmannite (Fe8O8(OH)4.42(SO4)1.79, and the main schwertmannite phase (Fe8O8(OH)(8-2x)(SO4)x, with 1.09 < or = x < or = 1.73), respectively, under different Cl-/SO4(2-) mole ratio conditions. Obviously, sulfate inhibited drastically the bioformation of akaganéite but facilitated schwertmannite phase occurrence in the ferrous solution containing both sulfate and chloride. However, the presence of chloride ion in initial ferrous solution containing sulfate and Acidithiobacillus ferrooxidans cells would affect the morphology and other characteristics of schwertmannite generated.
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Huixin
authors.initials: H
authors.lastname: Xiong
authors.forename: Yuehua
authors.initials: Y
authors.lastname: Liao
authors.forename: Lixiang
authors.initials: L
authors.lastname: Zhou
mesh_terms: D042763:Acidithiobacillus / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D011232:Chemical Precipitation; D002712:Chlorides / Q000494:pharmacology*; D003116:Color; D005290:Ferric Compounds / Q000378:metabolism*; D005296:Ferrous Compounds / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007501:Iron / Q000378:metabolism; D058085:Iron Compounds / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction / Q000187:drug effects; D012996:Solutions; D013055:Spectrophotometry, Infrared; D013431:Sulfates / Q000494:pharmacology*; D013499:Surface Properties / Q000187:drug effects; D013997:Time Factors; D014961:X-Ray Diffraction
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D005296:Ferrous Compounds; D058085:Iron Compounds; D012996:Solutions; D013431:Sulfates; C473845:akaganeite; C511969:schwertmannite; D007501:Iron