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|Title:||Removal of Aqueous Cr(VI) by a Combination of Photocatalytic Reduction and Coprecipitation|
|Source:||Wang, X.,Pehkonen, S.O.,Ray, A.K. (2004-03-31). Removal of Aqueous Cr(VI) by a Combination of Photocatalytic Reduction and Coprecipitation. Industrial and Engineering Chemistry Research 43 (7) : 1665-1672. ScholarBank@NUS Repository.|
|Abstract:||Semiconductor photocatalytic reduction is a relatively new technique for the removal of dissolved toxic metal ions from wastewater. In this paper, adsorption and photocatalytic reduction of Cr(VI) to Cr(III) inaqueous solutions by UV/TiO2 photocatalysis has been investigated. It has been observed that the pH of the solution plays an important role in this reaction. An acidic medium is favorable for Cr(VI) photocatalytic reduction, where 94% of Cr(VI) was photoreduced within 1 h at pH 3 when 2 g/L of TiO 2 was used as the slurry. An adsorption study shows that the photocatalytic reduction mainly occurs on the surface of TiO2. The presence of Fe(III) improved the photocatalytic reduction of Cr(VI) because it was observed that an additional reaction between Fe(II) and Cr(VI) takes place in the UV/TiO2 reduction process. A new combination of photocatalytic reduction and metal ion coprecipitation using Fe(OH)3 for complete removal of aqueous Cr [Cr(VI) as well as Cr(III)] was designed, which reduced the chromium concentration from 30 ppm to 17 ppb for a simulated wastewater. Thermodynamic analysis showed that TiO2 cannot photoreduce Cr(III) to Cr(0), but reduction is possible with ZnS. When kinetic experiments were performed, it was observed that more than 86% of Cr(III) could be photoreduced to Cr(0) in 5 h with a ZnS catalyst.|
|Source Title:||Industrial and Engineering Chemistry Research|
|Appears in Collections:||Staff Publications|
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