Treatment of Cr(VI) and phenol by illuminated TiO2

Industrial wastewater from organic chemical manufacturing and metal plating industries may contain significant amounts of refractory organic matter and heavy metals. Heavy metals such as Cr(VI) and refractory organic matter like phenol were simultaneously removed by reduction and mineralization, respectively, during photocatalytic process. Therefore, this study was carried out to evaluate the effects of phenol on the removal of Cr(VI) in several environmental conditions. Cr(VI) and phenol were more effectively eliminated in UV/TiO2 condition than either by UV or TiO2-alone. The removal efficiencies of Cr(VI) increased as the pH of the TiO2 slurry decreased, the concentration of phenol increased up to 10 mg L-1, and nitrogen gas was used. Otherwise, the removal efficiencies of phenol were higher at O-2-purged system and neutral pH. Without regard to purging gases, complete Cr(VI) removal was observed at pH 4 after 80 min while 90% phenol destruction and 60% mineralization were found after 120 min. It was found that application of photocatalytic reaction by using illuminated TiO2 to treat wastewater containing both Cr(VI) and phenol was possible.