Síntese de catalisadores a base de óxidos mistos de ferro e cobre (Fe/Cu) e seu uso em Processos Oxidativos Avançados

Abstract

In 2015 more than 6 billion textile accessories were produced in Brazil, a country where the textile sector occupies the fifth position in the world ranking. It is estimated that 1% to 15% of the dyes used in textile processes are not treated correctly and are released into the effluents. One of the alternatives that emerged in recent years, with an efficient removal of organic wastewater pollutants, was the Advanced Oxidative Processes (AOP). Heterogeneous photocatalysis and the heterogeneous photo-Fenton reaction are examples of these AOPs, where the degradation of the organic molecule is obtained by the reaction of Fe2+ with H2O2 in the presence of sunlight, generating hydroxyl radicals, which are highly reactive and nonselective species. The objective of this work was to produce a Fe/Cu catalysts in the 60/40 and 80/20 mass proportions, respectively, for the removal of the methylene blue dye from an aqueous solution. The catalysts were produced by a modified Pechini method and calcined at different temperatures. Phases such as copper ferrite, hematite, magnetite and copper oxide were identified in the XRD of the samples. The catalysts were not efficient in photocatalysis, however, they were efficient in the heterogeneous photo-Fenton reaction. The Fe/Cu 60/40 calcined catalyst at 600°C (E3) was the most efficient in the photo-Fenton reaction, removing 100% of the dye in both the first and second cycles at pH 6, showing that the catalyst can be reused in the process. The catalyst produced was more efficient than the pure oxides of copper and iron. The solar radiation has a fundamental role for the catalyst produced, since the velocity constant has a linear relation with the solar radiation on the day of the experiment. The catalyst has high stability and the values of the calculated kinetic constants are close to those obtained experimentally. A mechanism for the heterogeneous photo-Fenton reaction has been proposed in which there is the formation of new sites with the reduced phases and the regeneration of Fe2+ for the continuous removal of the dye.