Studies on TiO2/ZnO photocatalysed degradation of lignin

The photocatalytic degradation of lignin obtained from wheat straw kraft digestion has been investigated by using TiO2 and ZnO semiconductors. ZnO has been found to be a better photocatalyst than TiO2. The different variables studied, include catalyst dose, solution pH, oxidant concentration and initial concentration of the substrate. The degradation of lignin was favorable at pH 11. Optimum values of catalyst dose and oxidant concentration were found to be 1 g/l and 12.2 x 10(-6) M, respectively. The degradation of the organic compound was also evaluated as COD removal and increase in the COD removal was observed with increase in degradation rate. An attempt has also been made to explore the applicability of ZnO in immobilized mode for the degradation of lignin under solar light for industrial scale application. Further the comparative evaluation of ZnO in slurry/immobilized mode has been carried out. (c) 2007 Elsevier B.V. All rights reserved.