Degradação de contaminantes orgânicos em água usando catalisadores de ferro obtidos da indústria de mineração

Abstract

This work aims the evaluation of the catalytic efficiency of iron ore samples in the removal of organic contaminants such as the methylene blue dye (MB), the rhodamine B dye (RhB) and the paracetamol drug (PRC) from water by the heterogeneous Fenton process. In the first chapter, samples were collected at different points in the mining industry: feed, concentrate and waste (A, C e R) and characterized by XRD, FTIR, N2 Physisorption, chemical analysis and TPR. The main crystalline phases present in all the samples are hematite, magnetite, maghemite, goethite, quartz and the iron content differs accordingly with the collection point in the mining plant. The degradation of the RhB dye was optimized by evaluating the pH solution, amount of catalyst and oxidant, addition of acid promoters, as well as the study with radical scavengers to evaluate the reaction mechanism. High reaction rates were observed at pH 3,0 and 9,0 and the addition of formic acid (HFor) thermodynamically favored the organic degradation by the generation of hydroxyl radicals. The highest RhB removal (85% of removal) was reached using 50 mg of catalyst after 75 min of reaction for the waste and 0,1 mL of H2O2 and the reaction mechanism occurred through radical mechanism. A lower MB removal was obtained (33%), in the absence of HFor, and all the samples were active for PRC oxidation in presence of H2O2 (e.g. 66% of removal for the waste). In the second chapter, the waste sample (R) was modified by heat treatment under methane atmosphere (R-CH4) and impregnated with PET powder residue followed by a heat treatment under N2 atmosphere to produce a composite material (R-PET). The samples were characterized by the techniques mentioned in chapter 1, besides TGA and Mössbauer spectroscopy (SM). The catalytic tests showed that the R-CH4 and R-PET presented higher MB, RhB and PRC removals than the waste, which can be attributed to the formation of new mineral phases containing Fe+2 ions, species more active for the Fenton process.