Mecanismo de fotodegradação de compostos orgânicos catalisada por TiO2

Abstract

CP 6154-13045-970-Campinas-SP Recebido em 13/2/97; aceito em 23/7/97 MECHANISM REACTIONS OF PHOTODEGRADATION OF ORGANIC COMPOUNDS CATA-LYZED BY TiO 2. Conventional technology used in the treatment of wastewater has been pointed as a major environmental problem for sustainable development, since minimization is not addressed accordingly. Advanced oxidation processes (AOP), based on the formation of hydroxyl radical (. OH), a powerful oxidant agent, have been considered to be a potential technology for the destruction of many toxic compounds. Photocatalysis using solar light, an AOP, has been studied for nearly 20 years and recently attracted great interest as a clean-up technology. However, solar detoxification processes have not yet achieved commercial success. This article presents an overview of reaction mechanisms at the surface of semiconductors used as photocatalysts (specially TiO 2), when heterogeneous photocatalysis is used to remove hazardous compounds from contaminated sites.

Study of a Photodegradant Polymeric Composite Containing TiO<sub>2</sub> and Glass Residue

“…Then, the cultivated bacteria were transferred to the Mueller Hinton Agar plates in the same temperature and for the same time, for formation of the colony. After the colony growth, they were suspended in sterile saline solution (0.9% NaCl prepared in distilled water) until 1 × 10 8 CFU concentration approximately or 0.5 Mac Farland scale of turbidity. This contaminated solution was used to contaminate the samples.…”

“…According to [8] To improve photocatalytical activity, there are studies about the use of glass mixed to the material and semiconductor. [9] used crushed recycled waste glass, by-product from drinking bottles, in replacement of part of the aggregate of the superficial layers from a photocatalytical concrete.…”

Degradation of cyanotoxins (microcystin) in drinking water using photoelectrooxidation

“…Activated coal adsorption has been shown to be effective in removing cyanotoxins (Falconer et al, 1989;Donati et al, 1994;Drikas et al, 2001). However, decontamination takes place by pollutant adsorption, and the pollutant is transferred from the liquid to the solid matter; that means that there is only transference of the pollutant phases, but no destruction (Ziolli and Jardim, 1998). Mondardo et al (2006) tested ozonisation and chlorination to remove cyanobacteria.…”

Degradação fotoeletroquímica do herbicida bentazona sobre eletrodos de carbono modificados por TiO2

“…Nesse caso, o melhor reagente é o dióxido de titânio (TiO 2 ), pois apresenta vantagens como sua não toxicidade e estabilidade química numa ampla faixa de pH, boa capacidade de adsorção, além de baixo custo. No mecanismo de ação do TiO 2 como catalisador no processo de fotocatálise heterogênea, proposto por Ziolli et al 21 e Melo et al, 16 a irradiação do óxido metálico promove um estado eletronicamente excitado, no qual um elétron da banda de valência passa para a banda de condução, gerando um par elétron-vacância. O caráter oxidante da vacância da banda de valência gera radicais hidroxila ( • OH) pela oxidação de moléculas de H 2 O adsorvidas na superfície do semicondutor.…”