Photocatalytic efficiency of ZnO plates in degradation of azo dye solutions

Tape casting method was used to prepare ZnO plates for photocatalytic degradation of Reactive Orange 16 (RO 16) and Reactive Red 180 (RR 180) textile dyes in aqueous solutions. The plates were sintered at 700 °C and 1050 °C and characterized by using TG-DTA, BET and SEM. The sintering process at 700 °C yields relatively high surface area ZnO plates comparing with the plates sintered at 1050 °C. The photocatalytic activity was enhanced when the high surface area plates were used in photocatalytic degradation processes. Up to 95.7% and 88.6% color removal was obtained in 90 min for the RR 180 and RO 16 aqueous solutions, respectively, when the plates were sintered at 700 °C. Total organic carbon (TOC) removal was 43% at 180 min for RR 180 solution. Photocorrosion tendency was observed to some extend during photocatalysis when multiple tests were performed on the same plate. This corrosive effect was recovered by the memory effect when the plates were subjected to dark interval overnight.