Fotodegradação de contaminantes ambientais pelo processo de foto-Fenton

Abstract

One of the current environmental issues is the contamination by chemical and industrial compounds, including "Emerging Contaminants," which are potentially harmful to most organisms at some level of exposure and absorption. In this context, it is crucial to understand and enhance effective methodologies for the degradation of these compounds, complementing the traditional liquid waste treatment processes already in use. Advanced Oxidative Processes, such as photo-Fenton, emerge as viable alternatives, as they have been described as efficient in the degradation of various pollutant compounds, contributing to the reduction of environmental impacts. However, due to their limited performance at very acidic pH levels, the use of iron complexes can play a crucial role as carriers of Fe2+ ions under conditions closer to those found in real effluents. In this regard, this thesis was divided into two chapters in the form of scientific articles. The objective of the first article was to analyze the efficiency of the photo-Fenton process mediated by Ferrioxalate (FeOx / H2O2 / UV) in the degradation of two pollutant chemical compounds, namely the agrochemicals: Atrazine, and Glyphosate, two herbicides widely used in Brazil. Using a Central Composite Rotatable Design (CCRD) 23 , it was found that the optimal point indicated by the model (FeOx = 2.59 mg / L-1, H2O2 = 64.88 mg / L-1, and pH = 3.40) was effective in degrading the two emerging agroenvironmental contaminants, achieving a degradation rate of 99.04% for Atrazine, and 99.98% for Glyphosate. The objective of the second article was to analyze the efficiency of the photo-Fenton process mediated by Ferrioxalate (FeOx / H2O2 / UV) in the degradation of six contaminant compounds, namely dyes: Methyl Violet, Methylene Blue, Giemsa Stain, Safranin, Fuchsine, and May Grunwald. Using the same optimal point generated by the CCRD in the first article, degradation rates of 96.23% for Methyl Violet, 95.50% for Methylene Blue, 91.89% for Giemsa Stain, 95.06% for Safranin, 97.55% for Fuchsine, and 90.70% for May Grunwald were obtained. The photo-Fenton process mediated by Ferrioxalate in both studies proved to be an excellent alternative for the treatment of the investigated contaminants. Both solar radiation (ex situ) and ultraviolet radiation used in situ yielded similar results. In both methodologies employed in the two articles, the ideal exposure time was 90 minutes. The results obtained in this study demonstrated the high efficiency of the methodology in the oxidation of chemical compounds, and Ferrioxalate played an efficient role in the supply of Fe2+ ions for the reaction.