Influence of TiO2 and ZnO photocatalysts on adsorption and degradation behaviour of Erythrosine

The photocatalytic degradation of Erythrosine, an anionic dye (λmax at 526 nm, ɛmax = 7.24 × 104 L mol−1 cm−1), has been investigated over TiO2 and ZnO photocatalysts, irradiated by UV–vis light. Spectrum of the dye has been found, unaffected in the pH range 4.86–11.56. The adsorption over TiO2 and ZnO surface followed Langmuir and Freundlich adsorption isotherms. The extent of adsorption decreased with the rise of pH. But the percent of decolourization fluctuated over this pH range. Increment of initial dye concentration adversely affected the decolourization efficiency but proportionately affected with the catalyst loading until it gets attenuated after 2.0 g/L. The presence of H2O2 in lower concentration (ie, 4 × 10−4 M) with the catalysts decelerated the degradation but accelerated at higher concentration (ie, 300 × 10−4 M). Kinetic studies including order of the reaction, rate constant and half-life have also been performed in the presence of TiO2 and ZnO.