Degradação de poluentes orgânicos persistentes por processos oxidativos

Abstract

The presence of organic pollutants in aquatic environments has been the subject of numerous researches focused on the evaluation of environmental impacts and the development of treatments. Among the industrial sectors with polluting potential, the textile sector and the agricultural activity deserve to be highlighted by producing effluents with high concentrations of organic pollutants. Conventional water and sewage treatment systems are inefficient in the removal of pollutants such as dyes and pesticides while advanced oxidative processes stand out been highlighted in the treatment of effluents containing such pollutants, as they present higher rates of oxidation of organic matter and less generation of by-products of oxidation. In this work a study was developed to evaluate the degradation of the pesticide profenophous by the process H2O2/UV and the textile dye leucoindigo carmine through the process Photo Fenton. With this objective, were developed photocatalytic reactors, in piston flow, in bench scale. Mercury vapor lamps (254 nm) were used as the radiation source. For analytical control, among other tools, liquid chromatography coupled to mass spectrometry and total organic carbon analyzer were applied. The results showed that treatment of the effluent containing 1 mg/L of the profenophous pesticide was possible through the H2O2/UV process with 100% degradation of the pollutant within 30 minutes of degradation, using a dosage of 0.5 mM H2O2 at pH 8. Results of the by-product analysis indicated that pollutant degradation generated smaller molecules such as m - bromophenol, bromobenzene and phosphorothioic acid, monor toxicity and in low concentrations (0.162 μg/L). Regarding the degradation of the leucoindigo carmine dye, the results indicated that it was possible to remove 100% of the color and 77.5% of the total organic carbon from the studied effluent, which contained 25 mg/L leucoindigo 2+ carmine. These results were obtained using a dosage of Fe 4 mM and H2O2 24 mM at pH 3. The results of the by-product analysis also indicated that degradation of the pollutant molecule occurred in smaller molecules such as Dioxindole And mandelic salt, wif monor toxicity and in low concentrations (12.5 μg/L). The degradation of leucoindigo carmine and profenofós were better adjusted to the pseudo 2nd order kinetic model.