Mixed ZnO-TiO2 Suspended Solution as an Efficient Photocatalyst for Decolonization of a Textile Dye from Waste Water

Introduction: Textile industries produce large volume of colored dye effluents which are toxic and removal of dyes from wastewater is a significant environmental issue. Advanced oxidation process (AOPs) is alternative method for the complete degradation many organic pollutants. ZnO and TiO2 are important photocatalysts with high catalytic activity that have attracted much research attention. Material and Methods: Mixed ZnO/TiO2 was prepared with mixing of ZnO and TiO2 (20, 40, 60, 80 % (w/w)). 20 mL of dye solution (80 mgL-1 for DB71) containing the appropriate quantity of photocatalyst was magnetically stirred under UV irradiation. Photocatalytic study was carried out to evaluate the effect of UV (400 W), ZnO/TiO2 weight percent (20, 40, 60, 80 % (w/w)), pH (2.3 – 9.2), irradiation time of (10 – 70 min), initial dye concentration of (10, 40, 80 mg/L) and ZnO/TiO2 dosage of (0.2 – 1.6 g/L) on removal of dye. Dye concentration was monitored spectrophotometrically by measuring the dye absorbance at 285 nm. Results: In comparison with TiO2 or ZnO as photocatalyst, mixed photocatalyst (ZnO/TiO2) is more efficient catalyst for degradation of dye under UV irradiation Results show that approximately 90 % of Direct Blue 71 has been eliminated after 70 minutes and optimized condition ((pH = 6.4, ZnO/TiO2 (50% w/w, 1.25 g/L). Experiments showed, the noticeable decolorization of dye solution can be done without any oxidation agent with mixed ZnO/TiO2 photocatalyst.