Heterogeneous Photocatalytic Decolourization of Cobalamine in the Presence of Aqueous Titanium Dioxide Suspensions

Abstract

The objective of this research was to investigate experimentally the decolourization of cobalamine (a-(5,6-dimethylbenzimidazolyl) cobamidcyanide with a chemical formula (C₆₃H₈₈N₁₄O₁₄CoP) under different conditions. The photocatalytic decolourization of cobalamine was carried out in aqueous solution of titanium dioxide (TiO₂ Degussa P25) using UVA source of irradiation. The results showed that a complete decolourization was achieved in less than 30 min, however the percent of mineralization was only 80 % after 7 h of irradiation under same conditions. It was noticed that pH of reactants was changed at the end of reaction towards 7 independent on the initial pH. The effect of various parameters, such as photocatalyst amount, cobalamine concentration, addition of H₂O₂ and flow rate of O₂ on photocatalytic oxidation were investigated. The results indicated that the photocatalytic decolourization of cobalamine was well described by pseudo first order kinetics according to the Langmuir-Hinshelwood model. The effect of temperature on the efficiency of photodecolourization of cobalamine was also studied in the range 278-298 K. The activation energy was found to be equal to 22 ± 1 kJ mol^-1.