Photocatalysis of methomyl using concentrating solar collector and ultraviolet light

摘要

The photocatalytic oxidation of methomyl, using TiO_2 suspensions under solar radiation and ultraviolet light, has been studied at pilot scale at photodegradation laboratory of University of Antioquia (Medellin, Colombia). Two different reactor designs were tested: a low-concentrating radiation system, Solar-Parabolic-Concentrator Reactor (SPCR), facing south and inclined 6 degrees (geographic position of Medellin: 6 degrees north latitude), and an ultraviolet light system (ULS). Both systems were built in University of Antioquia. In Colombia, methomyl is used as a foliar spray and controls many insects on field crops, fruit crops, and vegetables. Methomyl was dissolved in water to required mg/L levels in a reservoir tank. In both cases, 1 g/L of Lannate (formulation with an active compound: methomyl) was used. TiO_2, in concentrations between 50 mg/L and 250 mg/L, and H_2O_2, between 1 mL (30%)/L and 3 mL (30%)/L, were used. Aliquots of the water samples were taken at different times of irradiation and total organic carbon (TOC) was analyzed. In some experiments, air was used, without H_2O_2, which permitted to compare oxidative efficiency of two oxidant agents (O_2 and H_2O_2); both are very used in photocatalytic processes. 79% of mineralization was obtained using SPCR and 52% using ULS.