PHOTOCATALYTIC REMOVAL OF TR I- AND HEXA-VALENT CHROMIUM IONS FROM CHROME-ELECTROPL ATING WASTEWATER

Puangrat Kajitvichyanukul (Department of Environmental Engineering, King Mongkut’s University of Technology Thonburi, Bangkok National Research Center for Environm ental and Hazardous Waste Management, Chulalongkorn University, Bangkok)
Chulaluck Changul (Department of Environmental Engineering, King Mongkut’s University of Technology Thonburi, Bangkok)

ASEAN Journal on Science and Technology for Development
Vol. 22 No. 4 (2005): ASEAN Journal on Science and Technology for Development (AJSTD)

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.