Effects of TiO2 dosage, pH and initial cyanide concentration on the removal efficiency of cyanide from aqueous solutions with illuminated TiO2 have been investigated. Adsorption and oxidation were recognized as significant processes for the elimination of cyanide. From the Langmuir isotherm, the maximum adsorption capacity was determined as 17.24 mg/g at pH 7. Adsorbed amount of cyanide slightly increased as the TiO2 dosage increased. However, as no significant increase was observed above 1 g/L TiO2, an optimum TiO2 dosage was determined as 1 g/L. Photocatalytic oxidation efficiency of cyanide was greatly affected by the solution pH. It increased as the solution pH decreased. The photocatalytic oxidation efficiency after 120 min was 80.4% at pH 3 while it was only 20.4% at pH 11. Photocatalytic oxidation of cyanide was well described by the second-order kinetics. Photocatalytic reaction with illuminated TiO2 can be effectively applied to treat industrial wastewater contaminated with cyanide.
Keywords: cyanide, kinetics, photocatalysis, TiO2, UV irradiation