Fotodegradação artificial e solar de efluente têxtil : avaliação da atividade fotocatalítica dos catalisadores TiO2, ZnO e Nb2O5

• Ano de defesa: 2014
• Autor(a) principal: Souza, Renata Padilha de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; Departamento de Química; Programa de Pós-Graduação em Química; Maringá, PR; Centro de Ciências Exatas
• Palavras-chave em Português: Química analítica; Efluente têxtil - Degradação artificial e solar; Fotodegradação; Fotocatálise heterogênea; Toxicidade; Ciências Exatas e da Terra; Química
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/4721

Environmental contamination has been pointed as one of the greatest problem of modern society, being the contamination of waters the biggest one. The textile industry is a major source of water pollution due to the generation of large volumes of wastewater. Textile effluents are highly colored and have high values of pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and other toxic chemicals to humans and the environment. In this work, heterogeneous photocatalysis was employed in the treatment of textile effluent from industrial laundry of jeans, in order to reduce their toxic organic load. The TiO2, TiO2 P25 (commercial), ZnO and Nb2O5 catalysts under artificial and solar irradiation were used. The parameters investigated under artificial irradiation, were: solution pH; catalyst concentration and the effect of mixed oxides (TiO2/Nb2O5 e ZnO/Nb2O5). From the optimal condition was performed the photodegradation under solar irradiation. The photocatalytic activity was evaluated by means of the kinetic efficiency (rate constant and half-life time), thermodynamic (decrease in absorbance: 228, 254, 284, 310, 350, 500 and 660 nm), reduction of COD, mineralization in terms of inorganic ions formation (NH4+, NO3-, NO2-, SO42- and Cl-) and toxicity reduction through bioassays with Artemia salina. The results indicated that kinetic and thermodynamic efficiency are affected by solution pH and catalyst concentration. It was found that the photocatalytic degradation of textile effluent at pH 3.0 and catalyst concentration of 0.250 g L-1 gave the best results, being found 95.91%; 87.35%; 86.95% and 59.18% of absorbance reduction at 660 nm (?max), after 300 min of artificial irradiation, for P25 TiO2, Nb2O5; TiO2 and ZnO, respectively. ZnO showed the lowest degradation rate, both under artificial light as in sunlight. The ZnO/Nb2O5 mixed significantly improved the photoactivity of ZnO, yielding approximately 27% of increase in the COD reduction. TiO2 and Nb2O5 were responsible for the reduction of approximately 70 and 66% of COD under artificial light and, 68 and 60% under sunlight, respectively. The photocatalytic activity was very close to TiO2 P25, confirmed by the efficiency in COD reduction, absorbance and inorganic ions formation, due to this, Nb2O5 becomes a promising alternative to replace the commercial TiO2 P25. The Artemia salina bioassays confirmed the efficacy of the treatment indicating that after the photodegradation there was a significant decrease of toxic compounds in wastewater, leading to a reduction in toxicity of 27.59% (in natura) to 77.52% and 131.95% in the presence of Nb2O5 under artificial and solar irradiation, respectively. The photocatalysis reduced the effluent toxicity up to 5 times, indicating that the intermediate and products formed showed no toxic