Optimization of preparation conditions of ZnO-SiO2 xerogel by sol-gel technique for photodegradation of methylene blue dye

The ZnO-SiO2 xerogel photocatalyst was prepared via the sol-gel technique and applied for photodegradation of methylene blue (MB) dye. The optimum conditions for preparation of ZnO-SiO2 gel is 30:70 ZnO:SiO2 molar ratio and TEOS:C2H5OH:H2O:HNO3 is 1:16:12:0.04 molar ratios at 30 degrees C for 30 min, at these conditions the photoactivity of ZnO-SiO2 xerogel was 99% at a surface area of 500 m(2)/g after 60 min. The optimum loading of ZnO-SiO2 photocatalyst was 0.050 wt% that gives 99% MB dye removal efficiency after 40 min. The overall kinetics of photodegradation of MB dye using ZnO-SiO2 photocatalyst was found to be of the first order.