Comparative assessment of ZnO and TiO2 Nano-particles in solar simulated light mineralization of methylene blue in aqueous media

الملخص EN

Nano-powders of commercial ZnO and TiO2 were investigated as photo-catalysts for mineralization of methylene blue (MB) in aqueous media.

Comparative study was performed under solar-simulated light at room temperature and neutral conditions.

Both systems showed activity and caused complete mineralization of the reacted MB molecules of low concentrations.

The ZnO system showed much higher catalytic efficiency than the TiO2 counterpart.

Spectrophotometric analysis of the reaction mixture showed that up to 100% removal of MB was achieved by ZnO catalyst in 60 min, whereas the TiO2 caused only 50% removal after the same time exposure.

The UV light present in the solar simulator light (with about 5%) was responsible for mineralization of MB.

Due to its higher efficiency, the ZnO system was then considered the catalyst of choice, where effects of different reaction parameters have been studied including: value of pH, temperature, light intensity, catalyst amount and MB concentration.

The catalyst efficiency was measured by calculating values of turn-over number (TN), and quantum yield, after 30 min.

The ZnO catalyst was isolated after reaction cessation and re-used for three times, where the catalyst retained up to 95% of its efficiency.

The results show the potential value of using ZnO as a photo-catalyst for mineralization of MB in water with solar light.