title: Bacterial removal of chromium (VI) and (III) in a continuous system.
abstract: The capacity of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans to reduce different concentrations of hexavalent chromium in shake flask cultures has been investigated. A. ferrooxidans reduces 100% of chromium (VI) at concentrations of 1, 2.5 and 5 ppm, but in the presence of 10 ppm only 42.9% of chromium (VI) was reduced after 11 days of incubation. A. thiooxidans showed a lower capacity to reduce this ion and total reduction of chromium (VI) was only obtained for concentrations of 1 and 2.5 ppm, whereas 64.7% and 30.5% was reached for 5 and 10 ppm, respectively, after 11 days. A continuous flow mode system was subsequently investigated, in which A. thiooxidans was immobilized on elemental sulphur and the acidic medium obtained was employed to solubilize chromium (III) and to reduce chromium (VI) present in a real electroplating waste [30% of chromium (III) and 0.1% of chromium (VI)]. The system enabled the reduction of 92.7% of hexavalent chromium and represents a promising way to treat this type of waste in the industry.
authors.affiliation: Department of Chemical Engineering, Food Technology and Environmental Technologies, University of Cadiz, Puerto Real 11510, Spain. gema.cabrera@uca.es
authors.forename: Gema
authors.initials: G
authors.lastname: Cabrera
authors.forename: Marisa
authors.initials: M
authors.lastname: Viera
authors.forename: Jose M
authors.initials: JM
authors.lastname: Gómez
authors.forename: Domingo
authors.initials: D
authors.lastname: Cantero
authors.forename: Edgardo
authors.initials: E
authors.lastname: Donati
mesh_terms: D042763:Acidithiobacillus / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D002857:Chromium / Q000302:isolation & purification* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction
chemical_list: D002857:Chromium