Avaliação da efetividade de remoção de cor de soluções corantes e efluentes têxteis pelo tratamento fotocatalítico de óxidos de ferro recobertos com dióxido de titânio

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

This work evaluated the use of ferrites encapsuled with titanium dioxide (CoFe2O4@TiO2) for photocatalytic removal of color of dye (Methylene Blue and HRFL Drimaren Blue) solutions and textile effluents. The CoFe2O4@TiO2 and TiO2 used in the tests was synthesized according to the polymeric precursors method, and the solids obtained were characterized by X ray diffraction (XRD), nitrogen adsorption (BET), zero charge point (ZCP), amongst others. During all degradation tests the concentration of catalyst was kept at 140 mg/L. The batch tests were carried out in two reactors: cylindrical (vertical or horizontal) and completely stirred tank reactor (jartest). The experiments in the cylindrical reactor were carried out with methylene blue and showed that the photocatalytic properties of TiO2 and CoFe2O4@TiO2 were only evident with the use of UV lamps when the reactor was in a horizontal position. When the catalysts were kept suspended by the injection of air (vertical configuration) the color removal efficiency was reduced, probably due to the shielding effects which precluded the formation of hydroxyl radicals from dissolved oxygen. The experiments carried out in the CSTRs (5 h HRT) showed that methylene blue was better degraded at pH 12, where 100% of color removal was observed with the UV and fluorescent lamps and ~80% with black light lamp. For the HRFL Drimaren blue, the best results were obtained at pH 2, with 25% of color removal for black and fluorescent lamps and ~85% with UV lamp. As far as the textile effluent is concerned the tests (20 h HRT) showed the best results were obtained with UV lamp at pH 2. Although color removal was evident, it was not observed changes in the effluent chemical oxygen demand (COD), implying that the organic matter was not mineralized during the photocatalytic treatment. Aerobic biodegradability assays were carried out with both raw and photocatalytically treated textile effluent and the results showed that the use of CoFe2O4@TiO2 with UV radiation enhanced the biodegradability of the industrial effluent organic matter. Photocatalytic tests with continous feeding (CSTRs) showed that the color removal of methylene blue solution at 5h HRT was 48% and 70% with, respectively, UV and fluorescent lamps. When the HFRL Drimaren blue was used, a significant degradation (~75%) was observed only with UV lamp. The increase of HRT from 5h to 20h increased color removal for both dyes in any conditions employed. For the HFRL Drimaren blue the presence of CoFe2O4@TiO2 had little impact on color removal, with is at odds with the batch tests results. When the textile effluent was continuously fed to the CSTRs (20 h HRT), the color removal, assessed at 277 nm, 400 nm, 611 nm and 780 nm, was higher (40 to 72%) with UV lamp when compared to fluorescent lamp (8 to 43%) and the catalyst had little impact on color removal.

ASSUNTO(S)

efluente - tratamento indústria têxtil cor na indústria têxtil oxidação saneamento ambiental

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