RESUMO
The present work describes a more efficient methodology for the chlorination of water containing disperse dyes, where the chlorinated byproducts identified by mass spectra are compared. For this investigation, we tested the degradation of CI Disperse Blue 291 dye, 2-[(2-Bromo-4,6-dinitrophenyl)azo]-5-(diethylamino)-4-methoxyacetanilide) a commercial azo dye with mutagenic properties. The present work evaluates the photoelectrocatalytic efficiency of removing the CI Disperse Blue 291 dye from a wastewater of the textile industry. We employed NaCl as a supporting electrolyte. It should be noted that photoelectrocatalytic techniques are non-conventional method of generating chlorine radicals. The by-products formed in this process were analyzed using spectrophotometry, liquid chromatography, dissolved organic carbon, mass spectral analysis and mutagenicity assays. The process efficiency was compared with the conventional chlorination process adopted during sewage and effluents treatment processes. This conventional chlorination process is less efficient in removing color, total organic carbon than the photoelectrochemistry technique. Furthermore, we shall demonstrate that the mutagenicity of the generated by-products obtained using photoelectrocatalysis is completely different from that obtained by the conventional oxidation of chloride ions in the drinking water treatment process.
Assuntos
Compostos Azo/química , Cloro/química , Corantes/química , Mutagênicos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Compostos Azo/efeitos da radiação , Compostos Azo/toxicidade , Catálise , Corantes/efeitos da radiação , Corantes/toxicidade , Eletroquímica , Halogenação , Resíduos Industriais , Mutagênicos/efeitos da radiação , Mutagênicos/toxicidade , Compostos Organometálicos/química , Oxidantes/química , Processos Fotoquímicos , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/genética , Indústria Têxtil , Raios Ultravioleta , Poluentes Químicos da Água/efeitos da radiação , Poluentes Químicos da Água/toxicidade , Purificação da Água/métodosRESUMO
These studies represent the rare use of a TiO2 material as a photocathode and the first application of photoelectrocatalysis for BrO3- removal. Photoelectrocatalytic reduction of BrO3- to Br- can reach 70% at neutral pH under an applied potential of -0.20 V versus SCE (saturated calomel electrode) after 75 min on the irradiated nanoporous thin-film TiO2-coated working electrode, which presented a flat band potential of -0.0274 V versus SCE. Regardless of the potential applied in these experiments, no BrO3- removal was observed in the counter electrode compartment or during electrolysis or photocatalysis, confirming that reduction of BrO3- to Br requires the combination of a negative potential (ideally near -0.20 V) and ultraviolet irradiation of the Ti/TiO2 electrode. The process was selective for BrO3- removal in that this process did not significantly reduce levels of Ca2+ and Mg2+ in drinking waters.
Assuntos
Bromatos/química , Titânio/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Catálise , Técnicas Eletroquímicas , Eletrodos , FotoquímicaRESUMO
The feasibility of the photobleaching of a leather acid dye, acid red 151, simultaneously to degradation of anionic surfactant, Tamol, and reduction of Cr(VI) to the less toxic Cr(III) was investigated by photoelectrocatalytic oxidation. The best experimental conditions were found to be pH 2.0 and 0.1 mol L(-1) sodium sulfate when the nanoporous Ti/TiO2 photo anode was biased at +1.0 V and submitted to UV-irradiation. The photoelectrocatalytic oxidation promotes 100% discoloration, reducing around 98-100% of Cr(VI) and achieving an abatement of 95% of the original total organic carbon. The effect of pH, the applied potential, the Cr(VI) concentration and the complexation reaction between Cr(VI) and acid red dye were evaluated as to their effect on the kinetics of the reaction.