Photocatalytic degradation of methyl-red by immobilised nanoparticles of TiO2 and ZnO

In this work, we report on the degradation of methyl-red (2-(4-Dimethylamino-phenylazo)-benzoic acid - C.I. 13020) under UV irradiation in the presence of nanosized ZnO and TiO₂. Oxide nanocrystals with controlled size were synthesised by using non-hydrolytic approaches and tested for the photocatalysed degradation. The performances of the immobilised nanoparticles were compared with their commercial counterparts after immobilization onto a solid support. The influence of some experimental conditions, namely pH and dye concentration, were investigated by monitoring the dye decoloration spectrophotometrically. Several intermediate by-products were identified by HPLC-MS, showing that two different mechanisms were operative during the photocatalytic oxidation.