Degradação de antibióticos sulfonamidas por processo foto-Feton: identificação de intermediários
Data
2012-04-20
Autores
Batista, Ana Paula dos Santos [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A degradação foto-Fenton dos antibióticos sulfonamidas sulfadiazina (SDZ) e sulfatiazol (STZ) mediados por Fe(III)-oxalato foi estudada nesse trabalho. A influência da complexação de íons ferro, a concentração de H2O2 e o pH na velocidade inicial de degradação dos antibióticos foi avaliada. A degradação de SDZ e STZ foi melhorada na presença de Fe(III)-oxalato em comparação a Fe(NO3)3, alcançando completa degradação após 8 minutos de irradiação em pH 2,5 na presença de 5 mM H2O2 (equivalente a [H2O2]/[antibiótico] = 50). Também foi possível estender a faixa de pH do processo foto-Fenton na presença de Fe(III)-oxalato alcançando mais de 69% de degradação em pH 6, embora sem significante mineralização. A comparação da cinética de degradação dos antibióticos indicou que a STZ é mais recalcitrante provavelmente devido à baixa densidade eletrônica do seu anel tiazol em relação ao anel pirimidínico na SDZ. Experimentos de fotodegradação das sulfonamidas por irradiação gama da água na presença de N2O foram executados e seus produtos de degradação, identificados por análise LC/MS, foram comparados àqueles formados por processo foto-Fenton. Os intermediários de degradação formados são compostos hidroxilados após entrada de grupos hidroxilas no anel benzênico assim como no anel pirimidínico na molécula da SDZ e no anel tiazol na molécula da STZ, seguido por abertura dos anéis durante processo de descarbonilação
The photo-Fenton degradation of the sulfonamide antibiotics sulfadiazine (SDZ) and sulfathiazole (STZ) mediated by Fe(III)-oxalate was studied in this work. The influence of iron complexation, H2O2 concentration and pH on the initial SDZ and STZ degradation rate was evaluated. Degradation of both antibiotics is improved in the presence of Fe(III)-oxalate in comparison to free iron, achieving complete degradation after 8 min irradiation at pH 2.5 in the presence of 5 mM H2O2 (equivalent to H2O2/antibiotic = 50). It was also possible to extend pH range of the photo-Fenton reaction by the use of Fe(III)-oxalate reaching more the 69% degradation at pH 6, however without significant mineralization. Comparison of the degradation kinetics of both sulfonamides indicated higher recalcitrance of STZ due to the lower electron density of its thiazol ring in relation to pyrimidine ring in SDZ. The sulfonamides photodegradation experiments by water gamma-irradiation in presence of N2O were also executed and their by-products, identified by LC/MS analysis, were compared to that formed from photo-Fenton process. The intermediates of degradation formed are hydroxylated compounds with entrance of hydroxyl group in the benzenic ring as well as in both pyrimidine ring in the SDZ molecule and thiazole group in the STZ ring, followed by rings opening during decarbonylation process
The photo-Fenton degradation of the sulfonamide antibiotics sulfadiazine (SDZ) and sulfathiazole (STZ) mediated by Fe(III)-oxalate was studied in this work. The influence of iron complexation, H2O2 concentration and pH on the initial SDZ and STZ degradation rate was evaluated. Degradation of both antibiotics is improved in the presence of Fe(III)-oxalate in comparison to free iron, achieving complete degradation after 8 min irradiation at pH 2.5 in the presence of 5 mM H2O2 (equivalent to H2O2/antibiotic = 50). It was also possible to extend pH range of the photo-Fenton reaction by the use of Fe(III)-oxalate reaching more the 69% degradation at pH 6, however without significant mineralization. Comparison of the degradation kinetics of both sulfonamides indicated higher recalcitrance of STZ due to the lower electron density of its thiazol ring in relation to pyrimidine ring in SDZ. The sulfonamides photodegradation experiments by water gamma-irradiation in presence of N2O were also executed and their by-products, identified by LC/MS analysis, were compared to that formed from photo-Fenton process. The intermediates of degradation formed are hydroxylated compounds with entrance of hydroxyl group in the benzenic ring as well as in both pyrimidine ring in the SDZ molecule and thiazole group in the STZ ring, followed by rings opening during decarbonylation process
Descrição
Palavras-chave
Quimica analitica, Sulfonamidas, Antibioticos, Antibiotics
Como citar
BATISTA, Ana Paula dos Santos. Degradação de antibióticos sulfonamidas por processo foto-Feton: identificação de intermediários. 2012. 85 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Química de Araraquara, 2012.