Degradation of Aqueous CONFIDOR® Pesticide by Simultaneous TiO2 Photocatalysis and Fe-Zeolite Catalytic Ozonation

Abstract

Due to the importance of water for human survival and scarcity of freshwater resources, wastewater treatment has become very important recently. Some persistent pollutants, such as pesticides, are not removed even after multiple conventional wastewater treatment techniques. Advanced oxidation processes (AOPs) are one of the novel techniques that can be used to treat these persistent compounds. Photocatalytic ozonation is a promising AOP that combines photocatalysis and ozonation for synergistic effects and faster degradation of persistent pollutants. However, usually, only a photocatalyst is used while combining photocatalysis and ozonation. In this work, both a photocatalyst and ozonation catalyst have been simultaneously used for the degradation of commercially available CONFIDOR® pesticide, a Bayer product with Imidacloprid as the active ingredient. TiO2 is employed as a photocatalyst, and Fe-coated Zeolite is employed as an ozonation catalyst. The results show that the reaction rate increases by 1.4 times if both catalysts are used as compared to the use of one photocatalyst only. Almost complete removal (>99%) of pollutant is achieved after 20 min with the simultaneous use of a catalyst when imidacloprid with an initial concentration of 100 mg/L is subjected to 250 W/m2 UV of a wavelength of 253.7 nm and 100 mg/h ozone, where it takes 30 min if only one photocatalyst is used. The paper also explores the effect of initial concentration, UV intensity, catalyst dose and catalyst reuse while also briefly discussing the kinetics and mechanism.