Removal of alprazolam from aqueous solutions by heterogeneous photocatalysis: Influencing factors, intermediates, and products (original) (raw)

2017, Chemical Engineering Journal

Efficiency of photodegradation of anxiolytic drug alprazolam by advanced oxidation processes was investigated. The structural and morphological properties of ZnO were investigated in detail. It was found that ZnO has wurtzite structure with crystallite size about 41 nm, specific surface area about 6.5 m 2 /g, and intraparticle system of pores (maximum pore width about 160 nm). The efficiency of photocatalytic degradation of alprazolam was examined as a function of the type of irradiation (UVA, visible, and simulated solar irradiation) and photocatalyst (ZnO, TiO 2 Degussa P25), loading of photocatalyst, pH, as well as the presence of hydroxyl radical scavenger (ethanol and methanol). By examining the effect of types of irradiation and catalysts, it was found that the UVA/ZnO system is the most efficient for alprazolam removal. The optimum catalyst loading was 1.0, and 2.0 mg/mL for ZnO and TiO 2 Degussa P25, respectively. In the case of ZnO, the pH 7 was selected as an optimal condition, while in aqueous suspension of TiO 2 Degussa P25, degradation rate increases in whole investigated pH range (3.4-8.8), but increasing is not as pronounced as in case of ZnO. By studying the effect of hydroxyl radical scavengers, it was found that the heterogeneous catalysis takes place mainly via hydroxyl radicals. The results of total organic carbon and ionic chromatography analysis showed that after 60 min of irradiation using both catalysts alprazolam was completely mineralized. Also, reaction intermediates formed using both catalysts were studied in detail using LC-ESI-MS/MS, whereby the main intermediates were hydroxyl derivates.