Inativação de bactérias em fase gasosa por fotocatálise heterogênea: efeito da adição de metais
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Data
2008-11-10
Autores
Modesto Junior, Olayr [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O controle de microorganismos em determinados ambientes é um fator essencial para a conservação de alimentos e prevenção de patologias humanas. Diversos métodos de controle da presença de microorganismos já foram desenvolvidos e são amplamente utilizados; porém, cada um deles tem uma limitação, suscitando a busca por outros meios. Assim, o objetivo desse trabalho é o de avaliar o efeito da adição de metais de transição (Pd, Ag e Fe) ao TiO2 na desinfecção em fase gasosa pela fotocatálise heterogênea. Os ensaios foram realizados num reator que propiciou uma área de 720 cm2 de fotocatalisador e 16 watts de luz UV; a névoa de microorganismos após tratamento foi colhida em água estéril e sua quantificação foi realizada por semeadura em Plat Cont Agar. Dentre os fotocatalisadores preparados com o TiO2 comercial P25, os melhores resultados foram obtidos empregando-se o TiO2 com paládio fotodepositado, inativando respectivamente, E. coli, S. aureus e B. subtilis numa taxa de 53%, 91% e 90%, contra 46%, 30% e 31% para o TiO2 puro, demonstrando que a interação com o paládio produziu um efeito sinérgico aumentando a eficiência do fotocatalisador puro em até 200%. Considerando-se os fotocatalisadores sintetizados a partir do tetraisopropóxido de titânio, os melhores resultados foram obtidos com o TiO2 dopado com ferro, inativando respectivamente, E. coli, B. subtilis e S. aureus numa taxa de 48%, 48% e 47%, contra 31%, 22% e 25% para o TiO2 puro, mostrando que também neste caso ocorre um efeito sinérgico aumentando a eficiência do fotocatalisador em até 120%. Não há diferenças significativas (teste t) entre as radiações de 254 e 365 nm tanto para os ensaios de controle, utilizando somente radiação UV, quanto aquele com fotocatalisador irradiado, atribuída ao breve período de exposição de 15 segundos.
The control of microorganisms in certain atmospheres is an essential factor for the conservation of foodstuff and prevention of human pathologies. Several methods of control of the presence of microorganisms have already been developed and they are widely used, however, each one of them has a limitation, prompting the search for other alternatives. Thus, the objective of this work is to evaluate the effect of the addition of transition metals (Pd, Ag and Fe) to TiO2 in the disinfection in gaseous phase by heterogeneous photocatalysis. The experiments were carried out in a reactor that provided a photocatalyst area of 720 cm2 and 16 watts of UV light; the mist of microorganisms after treatment was collected in sterile water and its quantification was made by innoculation in Plat Cont Agar. Among the prepared photocatalysts from commercial TiO2 P25, the best results were obtained by the use of TiO2 with Pd, inactiving respectively, E. coli, S. aureus and B. subtilis in a rate of 53%, 91% and 90%, against 46%, 30% and 31% for pure TiO2, demonstrating that the interaction with the Pd produced a synergistic effect increasing the efficiency of the pure photocatalyst up to 200%. Considering the photocatalyst synthesized starting from the titanium tetraisopropoxide, the best results were obtained with TiO2 doped with iron, inactivating respectively, E. coli, B. subtilis and S. aureus in a rate of 48%, 48% and 47%, against 31%, 22% and 25% for pure TiO2, showing that also in this case a synergistic effect increasing the efficiency of the photocatalyst in up to 120% occurs There are no significant differences (test t) between the radiations of 254 and 365 nm either for the control experiments using only UV radiation or those with irradiated photocatalyst, attributed to the brief exposure period of 15 seconds.
The control of microorganisms in certain atmospheres is an essential factor for the conservation of foodstuff and prevention of human pathologies. Several methods of control of the presence of microorganisms have already been developed and they are widely used, however, each one of them has a limitation, prompting the search for other alternatives. Thus, the objective of this work is to evaluate the effect of the addition of transition metals (Pd, Ag and Fe) to TiO2 in the disinfection in gaseous phase by heterogeneous photocatalysis. The experiments were carried out in a reactor that provided a photocatalyst area of 720 cm2 and 16 watts of UV light; the mist of microorganisms after treatment was collected in sterile water and its quantification was made by innoculation in Plat Cont Agar. Among the prepared photocatalysts from commercial TiO2 P25, the best results were obtained by the use of TiO2 with Pd, inactiving respectively, E. coli, S. aureus and B. subtilis in a rate of 53%, 91% and 90%, against 46%, 30% and 31% for pure TiO2, demonstrating that the interaction with the Pd produced a synergistic effect increasing the efficiency of the pure photocatalyst up to 200%. Considering the photocatalyst synthesized starting from the titanium tetraisopropoxide, the best results were obtained with TiO2 doped with iron, inactivating respectively, E. coli, B. subtilis and S. aureus in a rate of 48%, 48% and 47%, against 31%, 22% and 25% for pure TiO2, showing that also in this case a synergistic effect increasing the efficiency of the photocatalyst in up to 120% occurs There are no significant differences (test t) between the radiations of 254 and 365 nm either for the control experiments using only UV radiation or those with irradiated photocatalyst, attributed to the brief exposure period of 15 seconds.
Descrição
Palavras-chave
Química ambiental, Dióxido de titânio, Fotocatálise heterogênea, Environmental chemistry
Como citar
MODESTO JUNIOR, Olayr. Inativação de bactérias em fase gasosa por fotocatálise heterogênea: efeito da adição de metais. 2008. 64 f. Dissertação (mestrado) - Universidade Estadual Paulista, Instituto de Química, 2008.