Elimination of pesticides and their formulation products from drinking water using thin film continuous photoreactor under solar radiation

Abstract

There is an urgent need for the development of inexpensive, but reliable and efficient photocatalyst which can work under solar radiation for drinking water application. Hence the treatment options to be tried out for drinking water contaminated with pesticides and their formulation products should be cost effective and affordable. In this study, we developed a cheap and efficient photocatalyst and continuous photoreactor for the removal of pesticides from drinking water under solar radiation. Continuous photodegradation experiments were carried out with synthetically prepared commercial grade methyl parathion (Folidon 50% E.C.), dichlorvos (DDVP 70% E.C.), and analytical grade lindane. Photodegradation of mixed pesticide was carried out using both Degussa P-25 TiO2 and N-doped TiO2 with identical mass concentrations (50μg/L) of all the three pesticides under UV, visible and solar radiation. Continuous reactor was operated for more than 24h (6h each on 4days) for mixed pesticide degradation. N-doped TiO2 showed 100% degradation for all the three pesticide under solar radiation. Photodegradation of mixed pesticide showed methyl parathion, dichlorvos and lindane were degrading simultaneously. However, the rate of reaction was completely different from single pesticide degradation. N-doped TiO2 showed higher photocatalytic activity under solar radiation compared to UV and visible light. GC–MS analysis of mixed pesticide degradation showed more than 16 peaks in the middle of the reaction. Among these peaks, three intermediates such as hexachloro-benzene and para-nitrophenol and dichlorovinyl-O-methyl phosphate were identified in the middle of the reaction. However, at the end of the reaction (reactor outlet) none of the intermediates were observed.