Degradação da rodamina B por fotocatálise heterogênea utilizando diferentes catalisadores.

Abstract

The treatment of industrial effluents represents a highly complex problem, due to the generation of waste containing a variety of persistent organic compounds that are not removed by conventional treatment processes. Food, textile, leather and gemstone industries generate a high volume of liquid waste with strong coloration, due to the presence of dyes such as rhodamine B, which strongly impact the aquatic environment. For the effective degradation of this type of persistent organic compounds, the chemical treatments, specifically the POA's (Advanced Oxidative Process), have been attracting a lot of interest. The principle is the use of highly oxidizing species for an effective degradation of the effluent to be treated, allowing in many cases the complete mineralization of these compounds. The heterogeneous photocatalysis is a type of POA, which has as its principle the activation of a semiconductor, through sunlight or ultraviolet light, for the degradation of these compounds into other innocuous compounds such as H2O and CO2. In this work the semiconductors TiO2, Bi2O3 and Bi12TiO20, were tested in photocatalysis processes using UV radiation for degradation of Rhodamine B. Photolysis, adsorption and photocatalysis tests were performed for each oxide. The photolysis test presented a result of 10% of dye degradation only with the light incidence, in a time of 120 minutes. The adsorption tests showed an accumulation of Rhodamine B of 22.5% with TiO2, 16% with Bi2O3 and 15% with Bi12TiO20, in a time of 150 minutes. The results showed that in the photocatalysis assays, TiO2 is efficient in the adsorption and photodegradation of Rhodamine B, because it presents grains in the nanometric order, with high surface area, resulting in an elimination of 62.9% of Rhodamine B from the solution in 180 min. The Bi2O3 was not as efficient as the previous oxide in terms of adsorption, because it presented micrometric sized grains, resulting in an elimination of 41.2% by photocatalysis, with a total of 50.8% of Rhodamine B elimination from the solution in 180 min. For the Bi12TiO20, the grains obtained were of low surface area, providing low adsorption, however, from the point of view of photocatalysis only, the result was very promising, since it presented a high percentage of degradation (46.6%), despite the high granulometry of the grains, eliminating, by both processes, 54.6% of Rhodamine B in the same test time. For this reason, the test with Bi12TiO20 was repeated for a time of 8 hours, presenting 88.6% of Rhodamine B degradation. And so that the photocatalysis tests could be performed, an MDF photocatalytic reactor was built with 3 UVC lamps installed inside.