Photocatalytic removal of acid orange 7 azo dye by suspended and immobilized zinc oxide (original) (raw)

2020, DESALINATION AND WATER TREATMENT

Acid Orange 7 (AO7) is one of the most widely used azo dye for textile industry and not easily removed via conventional biological wastewater treatment process. The photocatalytic process combining ultraviolet (UV) and zinc oxide (ZnO) in the suspended state or immobilized on the concrete plate was used to remove AO7 in this study. The effects of initial pH (2-11), UV lamp power (8-40 W), ZnO dosage (2.58-25.8 g/L for suspended reactor and 20-200 g/m 2 for immobilized reactor) and initial AO7 concentration (10-200 mg/L) on AO7 removal were systemically investigated in batch tests. Under the optimum conditions (neutral pH of 7, UV lamp power of 32 W, ZnO dosage of 10.32 g/L for suspended reactor and 80 g/m 2 for immobilized reactor, initial AO7 concentration of 50 mg/L), AO7 removal reached 97% and 98% after 60 and 360 min for suspended and immobilized reactors, respectively. AO7 removal followed by first-order reaction kinetics with decreasing rate constant and energy consumption with increasing initial AO7 concentration for both reactors. The photocatalytic efficiency of UV/ZnO in the immobilized reactor was significantly lower than in the suspended reactor but could be improved via increasing ZnO coated concrete plate area (i.e., ZnO active surface area).