Abstract
Processes on wastewater treatment plants (WWTP) are not always efficient for pollutant removal. A new, low-cost, and effective technology is needed. In this work, the photocatalytic degradation of four insecticides, chlorantraniliprole, imidacloprid, pirimicarb, and thiamethoxam, has been examined in different water matrices (irrigation water, leaching waters, and WWTP effluent). Lab experiments were conducted with TiO2 and ZnO, as photocatalysts, with and without Na2S2O8 as an oxidant, exposed to UVA irradiation with LED lamps. Previously, different loadings of TiO2 and ZnO were assessed on the disappearance kinetics of the different insecticides to know the optimal efficiency. The effect of water matrices, susceptible to being contaminated with the target insecticides, was discussed when the photocatalytic system TiO2/Na2S2O8 was applied. The abatement of their main transformation products (TPs) was also monitored during the studied photoperiods. A total of 13 TPs were detected in the different water matrices studied. All of them were formed and eliminated during the photoperiod, except thiamethoxam urea which was present from the beginning of the experiments due to its hydrolysis in water. In conclusion, UVA-LED lamps are a good source to carry out heterogeneous photocatalysis in WWTP, since its high efficiency, low-cost, long lifetime, and effectiveness on pollutant removal.
Highlights
In addition to water scarcity, the presence of a wide range of pollutants in wastewater have triggered the search of new, low-cost, and effective technologies that allow for reusing and recycling these waters in many countries [1]
Among Advanced oxidation processes (AOPs), heterogeneous photocatalysis using semiconductor materials such as TiO2 and ZnO has received the attention of the scientific community due to their photochemical properties and low cost [7,8]
The impact of catalyst concentration on the degradation rates of the studied insecticides for the election of the most appropriate loading to be used in the incoming experiments was previously evaluated
Summary
In addition to water scarcity, the presence of a wide range of pollutants in wastewater have triggered the search of new, low-cost, and effective technologies that allow for reusing and recycling these waters in many countries [1]. Use different processes, such as sedimentation, coagulation, volatilization, biodegradation, or sorption, to eliminate toxic contaminants, including pathogens, nutrients, or suspended solids, from wastewater [2]. These processes are not always efficient to remove pesticides and others organic biorecalcitrant pollutants [3]. Among AOPs, heterogeneous photocatalysis using semiconductor materials such as TiO2 and ZnO has received the attention of the scientific community due to their photochemical properties and low cost [7,8]. Teixeira et al [8], for instance, reused TiO2 and ZnO nanoparticles through an ecofriendly and cost-effective process for water treatment. Semiconductor materials can be irradiated by photons of energy equal or higher to its band gap energy (Eg ), generating electron/hole pairs (e− /h+ )
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