Degradação da atrazina presente em águas pelo processo oxidativo avançado de eletro-foto-ozonização

Abstract

In Brazil, through public policies, the increase in the use of pesticides began in the 1960s. Since then, tons of active ingredients are sold year after year to control pests and obtain highly productive crops, which is a reason for great concern. Part of this concern is due to the fact that most of the pesticides used are considered an endocrine disruptor and end up reaching natural water sources for human consumption. This is the case of atrazine, which is the sixth most sold active ingredient in Brazil. This substance is considered by USEPA as an endocrine disruptor and has high persistence in water bodies and soils. Due to this, a series of treatments have been studied for its degradation and mineralization. Among these, advanced oxidative processes are shown as an alternative, since these processes usually use the hydroxyl radical, a strong oxidizing agent to effectively degraded organic pollutants. The objective of this work is to investigate how the parameters of O3 concentration (mg∙L-1), electric current intensity (A) and pH influence the degradation of atrazine present in water by Electro-Photo-Ozonation. Preliminary tests were performed using random values of the parameters, allowing the choice of a central point and subsequent application of an experimental design of the DCCR type and a Response Surface Methodology (MSR) to obtain the optimal operating conditions. The experiments were carried out with synthetic atrazine effluent at a concentration of 10 mg∙L-1, the value adopted, as it is commonly found in wastewater from washing packaging and pesticide factories, with O3 concentrations ranging from 11.36 to 78, 64 mg∙L-1, current intensity between 0.32 and 3.68 (A) and pH between 2.5 and 7.5. From the DCCR design, the degradation rate was obtained in 15 min (3.88 to 92.07%), 30 min (27.61 to 98.43%) and in 45 min (51.7 to 99.62%). For the maximum degradation identified in 45 min with an O3 concentration of 65 mg∙L-1, Current Intensity of 1A and pH 5, and a residual concentration of 38 ppb. In the MSR, for the degradation in 15 min, it was identified that the linear interactions of O3 and the linear interactions between O3 and current intensity were the parameters that most influenced the degradation of ATZ. As an optimal condition, 45 O3 mg∙L-1, 2 A and pH 5 were found with a reproducibility of 78% to obtain 92.07% of atrazine degradation. The residual concetration of atrazine is above what is established in federal and international legislation, thus, the application of a post-treatment such as nanofiltration and mineralization analysis of ATZ is suggested.