Evaluation of TiO 2, ZnO, CuO and Ga 2 O 3 on the Photocatalytic Degradation of Phenol Using an Annular-Flow Photocatalytic Reactor

Abstract

Even with rigorous environmental regulations, phenol still is a major contaminant. One possible solution is the use of heterogeneous photocatalysis due to low chemical addition, feasibility and reliability to be implanted on cost-effective industrial process. TiO 2 is the most employed photocatalyst because of its favorable (photo) chemical properties and ZnO is considered one of the best alternative for that. Other oxides were tested in lesser proportions, like CuO and Ga 2 O 3 . When the photocatalyst is dispersed as slurry, higher degradation rates are achieved due to high solid to liquid contact area when compared with supported form. The aim of this work was to develop a batch recirculating photocata-lytic reactor and evaluate its efficiency when assisted by the photocatalysts TiO 2 P25, ZnO, CuO and β-Ga 2 O 3 . TiO 2 achieved 95% mineralization after 200 min reaction in an average degradation rate of 0.68 mg·L −1 ·min −1 and ZnO was less efficient (0.41 mg·L −1 ·min −1). Ga 2 O 3 and CuO presented poor performance, mainly due to low surface area for the CuO syntesized and the absorption of the UV radiation by the reactor walls, decreasing Ga 2 O 3 activity. Degradation intermediates were detected in diverse concentrations and at different operational times for each oxide tested, which indicate different degradation mechanisms.