Degradação fotocatalítica artificial e solar de efluentes têxteis por processos oxidativos avançados utilizando TiO2

Abstract

The goal of the present work was to plan the degradation of real samples of textile effluents containing 4 textile dyes used in the textile industry (Brilliant Blue Remazol RN, Black Remazol, Red Procion HE7B and Yellow Procion HE4R) and, after to make the characterization of the evolution of the degradation process by using as parameters the sample mineralization and toxicity decreasing. The obtained results show that the dyes absorbed better in pH 3 and the mineralization occurred in the presence of artificial light (Hg vapor light) as well as in the presence of sun light. Others important factors were: the impossibility of dye degradation in the presence of H2O2, the high efficiency and fast mineralization of the dyes when the association of the catalyser and oxidant agent is carried out. Mixtures of the four colorant dyes were utilized in a factorial study to model the photodegradation conditions and 0.25 9 L-1and 1.10-2 mol L-1 of TiO2 and H2O2, respectively, were selected as the work range because presented the better performance to all the analyzed responses (ABS decaying, COD decreasing, and mineralization in terms of SO42-, NO3- and NH4+ formation). Under these conditions several textile that were collected in different days were degraded to verify the susceptibility to degradation and mineralization. The obtained results to real samples indicated that all the effluents were satisfactory degraded and, high amount of organic matter was removed (90 %) and high formation of ions (up to 93.56 mg L-1 of sulphate and 9.42 mg L-1 of nitrate). The kinetic of the degradation process was pseudo-first order to colorant dyes as well as to effluents and, the degradation velocity constant in terms of color reduction and relevant bands disappearing (254, 284 and 310 nm) was easy calculated. Ouring the photocatalytic process the added hydrogen peroxide was consumed and in the end of the process its concentration was very low or inexistent. Toxicity analysis by using lettuce seeding (Lactuca saliva) and micro-crustaceous (Arlemia salina) confirmed the reduction of the toxicity during the oxidative process, or in other words, the formed products during the degradation process are not toxics, confirming the mineralization chemical data.