Degradação fotoeletroquímica dos pesticidas glifosato, atrazina, carbendazim e 2,4-D em água utilizando eletrodos de nanotubos de Ti/TiO2, Ti/TiO2-Ag e Ti/TiO2-Au

Abstract

The intensive use of pesticides has resulted in the contamination of several environmental matrices, such as surface waters, so the development of environmentally and cost viable techniques for the elimination of these compounds is mandatory. Advanced oxidation processes, especially photoelectrocatalysis, have shown promising results in the degradation of organic contaminants. Thus, in the present work the degradation of the main pesticides used State of Mato Grosso, 2,4-D, glyphosate, atrazine and carbendazim was studied using photoelectrocatalysis with bare Ti/TiO2 nanotube electrodes and impregnated with Ag and Au nanoparticles. The photoelectrocatalytic treatment of 2,4-D resulted in 95% degradation of the chromophore group after 3 hours of treatment under optimal conditions (Ti/TiO2-Au, 0.01 mol L-1 NaCl, pH 4, UV irradiation and applied potential of + 1V vs Ag/AgCl), for photocatalysis and photolysis techniques obtained 91% and 42% degradation, respectively, with main by-products formed: 4- dichlorophenol, 1,4-chlorobenzoquinone, phenol, cyclohexadione and acetic acid. Glyphosate was completely degraded after 1 minute of treatment (Ti/TiO2-Au, applied potential + 1V vs. Ag/AgCl, 0.05 mol L-1 NaCl support electrolyte, and pH 2). Photoelectrocatalytic treatment of atrazine (Ti/TiO2- Au, applied potential + 1V vs. Ag/AgCl, 0.05 mol L-1 NaCl support electrolyte, and pH 2). completly degraded the chromophore group after 60 min, with main by-products N-methylmethanimine, 2-isocyanatopropane, 6-nitro-1,3,5- triazine-2,4-diol, hydroxytrazine . Finally, the photoelectrocatalytic treatment of carbendazim under the same conditions as atrazine resulted in 100% degradation of the chromophore group after 10 min of reaction, being observed the main byproducts: benzimidazole isocyanate, N- (1- methoxyvinyl) -1H-diazirin-3-amine, resorcinol, phenol, methyl hydrogen carbonimidate. Therefore, photoelectrocatalysis can be promising for the remediation of pesticide-contaminated waters.