Efficiency of neonicotinoids photocatalytic degradation by using annular slurry reactor

Abstract

© 2015 Elsevier B.V. This article is concerned with the kinetics of the photocatalytic degradation of four neonicotinoids insecticides as active ingredients (AIs) in their commercial formulations by using the annular slurry reactor (ASR). For all AIs, more effective photodegradation was achieved by UVA than by visible light irradiation. The most efficient degradation was observed in the case of thiacloprid, which degraded completely after two hours of irradiation using UVA, and 59% using visible light irradiation. On the other hand, the most stable appeared to be acetamiprid, whereby during the same time of irradiation it was degraded 42% using UVA, and only 4% using visible light irradiation. Because of that the efficiency of a number of advanced oxidation processes was examined in the case of acetamiprid. It was found that the presence of H2O2 in ZnO, 7.8Fe/ZnO, and 7.2Fe/TiO2 systems using UVA did not bring significant changes in the efficiency of degradation. However, using visible light irradiation the presence of H2O2 in ZnO and 7.8Fe/ZnO systems significantly increases efficiency of acetamiprid degradation. Also, by adjusting pH to 2.80 in the system 7.2Fe/TiO2/H2O2 using both type of irradiation resulted in a significant increase of the degradation efficiency. For the first time, for ZnO/H2O2 system a general reaction mechanism in the dark, as well as in the presence of visible light irradiation was proposed. The electrical energy consumption of ASR was estimated for the most efficient visible light irradiation system using the figure-of-merit electrical energy per order and compared with batch and laminar falling film slurry reactor.