A novel technique based on photocatalysis was applied to eliminate chromium ions, a toxic hazardous environmental pollutant. The photoreduction of each species of chromium (total, hexavalent, and trivalent chromiums) from chrome-electroplating wastewater was investigated using a titanium dioxide suspension under irradiation by a low-pressure mercury lamp. The initial concentration of total chromium was 300 mg/l. The applied conditions were the direct photocatalytic reduction process at pH 3.65 and the indirect photocatalytic reduction with added hole scavengers at the same solution pH. Results from both processes were comparatively discussed. Result show that chromium was not efficiently removed by direct photoreduction. In contrast, with the adding of hole scavengers, which were formate ions, the photoreduction of chromium was very favorable. Both hexavalent and trivalent chromiums were efficiently removed. The photocatalytic mechanism is purposed in this study.


Chen, D. and Ray, A.K. (2001), Removal of Toxic Metal Ions from Wastewater by Semiconductor Photocatalysis, Chemical Engineering Science, vol. 56, pp. 1561-1570.

Chenthamarakshan, C.R., Rajeshwar, K., and Wolfrum, E.J. (2000), Heterogeneous Photocatalytic Reductin of Cr(VI) in UV-Irradiated Titania Suspensions: Effect of Protons, Ammonium Ions, and Other Interfacial Aspects, Langmuir, vol. 16, pp. 2715-2721.

Deng, B. and Stone, A.T. (1996), Surace-Catalyzed Chromium(VI) Reduction: The TiO2-CrVI-Mandelic Acid System, Environmental Science and Technology, vol. 30, pp. 463-472.

Kajitvichyanukul, P., Chenthamarakshan, C.R., Qasim, S.R., and Rajeshwar, K. (2002), Photocatalytic Reactivity of Thallium(I) species in Aqueous Suspensions of Titania, Journal of Electroanalytical Chemistry, pp. 519, 25-32.

Kajitvichyanukul, P. and Vatcharenwong, A. (2004), Influence of pH, Organic and Inorganic Anions on Photocatalytic Reduction of Chromium(VI) With Titania Powders, Asean Journal of Science and Technology for Development (submitted).

Kajitvichyanukul, P., Taweekitwanich, A., Toyam N., and Pongpom, S. (2004), Effect of Organic and Inorganic Ions on Chromium(VI) Adsorption onto TiO2Surface, Asean Journal on Science and Technology for Development, vol.21, pp. 249-258.

Khalil, L.B., Mourad, W.E., and Rophael, M.W. (1998), Photocatalytic Reduction of Environmental Pollutant Cr(VI) over Some Semiconductors under UV/Visible Light Illumination, Applied Catalysis B: Environmental, vol. 17, pp. 267-273.

Ku, Y. and Jung, I-L. (2001), Photocatalytic Reduction of Cr(VI) in Aqueous Solutions by UV Irradiation With the Presence of Titanium Dioxide, Water Research, vol. 35, pp. 135-142.

Lin, W.-Y., Wei, C., and Rajeshwar, K. (1993), Photocatalytic Reduction and Immobilization of Hexavalent Chromium at Titanium Dioxide in Aqueous Basic Media, Journal of Electrochemistry Society, vol. 140, pp. 2477-2482.

Litter, M.I. (1999), Heterogeneous Photocatalysis Transition Metal Ions in Photocatalytic Systems, Applied Catalysis, vol. 23, pp. 89-114.

Rajeshwar, K. and Ibanez, J.G. (1997), Environmental Electrochemistry, Academic Press, San Diego, USA.


Download data is not yet available.