Bacterial removal of chromium (VI) and (III) in a continuous system
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.
KeywordsA. ferrooxidans A. thiooxidans Chromium (VI) Chromium (III) Reduction Solubilization
The authors from University of Cádiz wish to express their sincere gratitude to Dr. Donati from Centro de Investigación y Desarrollo en Fermentaciones Industriales (CINDEFI-CONICET), Universidad Nacional de La Plata, Argentina, where part of this research was carried out. This research was supported by Regional Goberment of Andalusia.
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