Obtenção e caracterização de fotocatalisadores heterogêneos a partir de rejeito da mineração de ferro e sua aplicação de contaminantes emergentes

Abstract

Mining tailings and emerging contaminants such as hormones and dyes characterize two serious environmental problems that have been extensively studied lately. In this work, the waste from iron mining (RS) was used as a precursor for the synthesis of heterogeneous catalysts by the reduction at different temperatures (RS460, RS560, RS660, RS760 e RS860) that were later applied in advanced oxidative processes (Fenton, photo Fenton and photocatalysis) for the degradation of the hormone 17 -ethynilestradiol and the Ponceau S dye. To investigate the iron phases present, all materials produced and the iron tailing were characterized by temperature programmed reduction (TPR), Mössbauer spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). Analyzing the Mössbauer spectra and X-ray diffractograms it was possible to identify goethite and hematite for RS, and hematite and magnetite was identified in the sampletreated at low temperatute, RS460. For all other reduced materials we noticed phases of magnetite and Fe2+. When using these materials as catalysts in the removal of the contaminants 17 -ethynyloestradiol and Ponceau S it was possible to verify the importance of the phases of Fe2+ for the studied processes, since the thermally reduced materials showed to be more effective in relation to the tailings without previous treatment. Among the catalysts tested, RS860 presented the best catalytic activity in all three processes. For each process and pollutant studied, the influence of pH, time of reaction and catalytic capacity were evaluated after several reaction cycles. In general, for the two analytes, the reactions performed at pH 3,0 led to the best results and the best catalysts were RS660 and RS860 with removal percentages above 90,0%.