Estudo do Processo Sonoeletroquímico Fotoassistido para degradação da Atrazina

Abstract

Contamination of water by pesticides present in effluents from industrial and agricultural activities causes major environmental impacts, and the development of treatment technologies for these effluents is essential. In this study, a combination of three techniques we applied: electrochemical, photochemical and sonochemical - denominated photoassisted sonoelectrochemical degradation, for the degradation of the pesticide atrazine. For this purpose, the system was assembled using a bench scale electrochemical cell with continuous flow, the working electrode was Ti/Ru0,3Ti0,7O2, plate the counter electrode a Ti plate and the supporting electrolyte NaCl. The variables were defined as applied, electric current, NaCl concentration, inter-electrode spacing, applied the experimental design in terms of energy efficiency. The electrochemical system was chosen for implementation of this design, because it was necessary to quantify the species of chlorine in this study. Thus, the most significant variables of the process were obtained and the optimum process conditions were determined to carry out the degradation assays. In photochemical degradation, the irradiation was applied by an ultraviolet light source. For sonochemical treatment, the ultrasonic energy was provided by means of a ultrasound bath. The degradation experiments were monitored by UV-vis spectroscopy, TOC, HPLC and phytotoxicity, and the energy efficiency of the process was evaluated. From the experimental design the most significant variables were the NaCl concentration and the spacing between electrode, and the optimum conditions obtained were and 1.73 mol L-1 and 0.56 cm, respectively. The electric current was kept constant at 0.20 A. The photoassisted sonoelectrochemical degradation process promoted greater generation of highly oxidizing species, allowing for efficient degradation of atrazine, achieving TOC removal of approximately 98%. For the HPLC analysis it is inferred that this process resulted in a removal of atrazine of ~ 100%, and the obtained chromatograms revealed the formation of degradation products. Furthermore, the combination of three techniques showed a higher current efficiency and lower energy consumption. Phytotoxicity tests showed that there was no generation of toxic degradation products using the test organism Lactuca sativa. The results indicated that the photoassisted sonoelectrochemical process proposed by this study can be applied to the degradation of atrazine as an effective and appropriate treatment.