Accelerated removal of cyanides from industrial effluents by supported TiO2 photo-catalysts

This study presents novel supported TiO2 catalysts able to mediate the photo-oxidation of cyanides with an acceptable kinetics. The catalyst preparation was optimized towards cyanide degradation using different TiO2 colloids on glass Raschig rings. The TiO2 during the photo-degradation of cyanides was activated by two different sources of UV light (366 nm). The catalyst used showed long-term stability and was able to degrade the cyanide solution within minutes in a repetitive fashion. The dependence of the cyanides oxidation rate was investigated as a function of: (1) catalyst preparation, (2) cyanide initial concentration, (3) applied light intensity, and (4) nature and concentration of the oxidant (O-2 or/and H2O2). The Langmuir-Hinshelwood mechanistic model was used to fit the experimental data. The by-products observed in solution during the cyanide degradation were identified as cyanates and nitrites. The catalytic efficiency of the best catalyst was tested on real wastewater from the galvanic industry containing similar to400 mg/l of cyanides and 60-70 mg/l of Cu-ions. (C) 2004 Elsevier B.V. All rights reserved.