TY - JOUR
T1 - A mechanism study of light-induced Cr(VI) reduction in an acidic solution
AU - Wang, Shan Li
AU - Chen, Chung Chi
AU - Tzou, Yu Min
AU - Hsu, Chia Lian
AU - Chen, Jen Hshuan
AU - Lin, Chen Fang
N1 - Funding Information:
This work was financially supported by the National Science Council, ROC under Project No. 95-2313-B-005-047-MY3 and, in part, by the Ministry of Education, R.O.C. under the ATU plan.
PY - 2009/5/15
Y1 - 2009/5/15
N2 - The mechanisms of photo-catalytic reduction of Cr(VI) were investigated in acidic solutions with and without Fe(III). In a system without Fe(III), no Cr(VI) reduction was observed in dark conditions; conversely, under light conditions, the reduction reaction rate increased to 0.011 and 0.020 μM min-1 at pH 2 and pH 1, respectively, indicating the occurrence of Cr(VI) photo-reduction. The Cr(VI) photo-reduction reaction was induced by the photolysis of water molecules, leading to O2 production. Upon the addition of Fe(III), the photo-reduction rate of Cr(VI) was significantly enhanced due to the formation of Fe(II), which is the photolytic product of FeCl2+ and the electron donor for Cr(VI) reduction. However, with the same concentration of FeCl complexes, a strong inhibition of Cr(VI) reduction at pH 2 was observed, compared with pH 1. A possible explanation is that FeOH2+ becomes predominant with increasing pH and that its photolytic product, the OH free radical, is an oxidant for Fe(II) and Cr(III) and can compromise Cr(VI) reduction. The kinetic result of each photo-reduction reaction pathway shows zero-order kinetics, suggesting that the photolysis reaction of H2O or FeCl2+ is the rate-determining step in each pathway. The results also show the potential of developing a homogeneous photo-catalytic method to treat Cr(VI)-containing water.
AB - The mechanisms of photo-catalytic reduction of Cr(VI) were investigated in acidic solutions with and without Fe(III). In a system without Fe(III), no Cr(VI) reduction was observed in dark conditions; conversely, under light conditions, the reduction reaction rate increased to 0.011 and 0.020 μM min-1 at pH 2 and pH 1, respectively, indicating the occurrence of Cr(VI) photo-reduction. The Cr(VI) photo-reduction reaction was induced by the photolysis of water molecules, leading to O2 production. Upon the addition of Fe(III), the photo-reduction rate of Cr(VI) was significantly enhanced due to the formation of Fe(II), which is the photolytic product of FeCl2+ and the electron donor for Cr(VI) reduction. However, with the same concentration of FeCl complexes, a strong inhibition of Cr(VI) reduction at pH 2 was observed, compared with pH 1. A possible explanation is that FeOH2+ becomes predominant with increasing pH and that its photolytic product, the OH free radical, is an oxidant for Fe(II) and Cr(III) and can compromise Cr(VI) reduction. The kinetic result of each photo-reduction reaction pathway shows zero-order kinetics, suggesting that the photolysis reaction of H2O or FeCl2+ is the rate-determining step in each pathway. The results also show the potential of developing a homogeneous photo-catalytic method to treat Cr(VI)-containing water.
KW - Chromium
KW - Photo-reduction
KW - Photolysis
KW - Reaction rate
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U2 - 10.1016/j.jhazmat.2008.07.145
DO - 10.1016/j.jhazmat.2008.07.145
M3 - Article
C2 - 18789578
AN - SCOPUS:61349102414
SN - 0304-3894
VL - 164
SP - 223
EP - 228
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
IS - 1
ER -