Cinética de degradação de Azitromicina e Claritromicina presentes em efluentes domésticos por processo foto-Fenton em meio homogêneo e heterogêneo
Data
2023-08-04
Autores
Santos, Matheus Gabriel Guardiano dos
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A presença de antibióticos em efluentes provenientes de estações de tratamento de esgotos (ETE) após processo convencional tem recebido grande atenção atualmente devido à constatação dos problemas que esses contaminantes podem causar tanto ao ambiente quanto à saúde humana, como a resistência bacteriana. O presente trabalho estudou a cinética de degradação de dois antibióticos macrolídeos, a azitromicina (AZT) e a claritromicina (CLA), por processo Fenton em meio homogêneo e heterogêneo e comparou-a com a degradação do sulfametoxazol (SMX), pertencente à classe das sulfonamidas. Desenvolveu-se e validou-se métodos analíticos para separação e quantificação simultânea dos macrolídeos, isoladamente do método de quantificação do SMX. A formação de complexos de ferro e cobre com os macrolídeos e a influência da complexação no ciclo redox Fe(II)/Fe(II) e Cu(I)/Cu(II) foi avaliada utilizando a espectrofotometria. A degradação dos fármacos foi realizada em água ultrapura e efluente da ETE contendo 1% de acetonitrila devido à baixa solubilidade dos macrolídeos. A concentração dos fármacos foi monitorada por cromatografia líquida de alta eficiência (HPLC), assim como seus produtos de transformação foram identificados por meio do acoplamento da HPLC com um espectrômetro de massas. Para degradação no processo heterogêneo, foram preparados catalisadores à base de óxido de cobre e ferro. Verificou-se a formação dos complexos de ferro e cobre com os macrolídeos, porém com um efeito redutor dos macrolídeos sobre o Cu(II), gerando complexos de Cu(I) em solução. Embora os complexos de macrolídeos com Fe e Cu influenciem o ciclo redox, apenas os complexos de cobre apresentaram comportamento recalcitrante ao processo foto-Fenton homogêneo. Dentre os catalisadores utilizados no processo heterogêneo, observou-se que o aumento do teor de cobre durante a síntese contribuiu para a maior área específica de CAT1 do que de CAT2, resultando em uma maior atividade de CAT1. A variação do pH afetou a degradação dos macrolídeos, assim como a variação da concentração de H2O2 inicial. Melhores resultados de aplicação do processo foto-Fenton heterogêneo foram obtidos usando 0,125 g L-1 de CAT1, 15 mmol L-1 de H2O2 em pH 5,4. Nos processos em meio homogêneo e heterogêneo, a constante de degradação de SMX foi superior à dos macrolídeos, indicando uma maior recalcitrância dos macrolídeos. Experimentos realizados em efluente de ETE evidenciaram que a matriz não influenciou a degradação de AZT e CLA, porém afetou a degradação do SMX. A matriz interferiu na degradação do SMX por ela ocorrer por combinação dos mecanismos de adição eletrofílica com abstração do átomo de hidrogênio e transferência eletrônica, enquanto os macrolídeos foram menos afetados pela degradação ocorrer por transferência eletrônica apenas. A identificação de produtos de transformação revelou a formação de produtos hidroxilados para os macrolídeos. Experimentos realizados na presença de sequestrantes de radicais hidroxila evidenciaram a importância do •OH na degradação dos macrolídeos, enquanto a degradação do SMX não foi totalmente inibida por não depender apenas do •OH, mas sim de outros radicais como o HO2•, O2•- e 1O2. Os resultados obtidos contribuem para o entendimento do mecanismo de degradação e recalcitrância dos macrolídeos ao processo Fenton.
The presence of antibiotics in effluents from wastewater treatment plants (WWTP) after a conventional process has received great attention due to problems that these contaminants can cause both to the environment and to human health, such as bacterial resistance. The present work studied the degradation kinetics of two macrolide antibiotics, azithromycin (AZT) and clarithromycin (CLA), by Fenton process in homogeneous and heterogeneous medium and compared it with sulfamethoxazole (SMX) degradation, belonging to sulfonamides class. Analytical methods were developed and validated for simultaneous separation and quantification of macrolides, separately from SMX quantification method. The formation of iron and copper complexes with macrolides and the complexation influence on the Fe(II)/Fe(II) and Cu(I)/Cu(II) redox cycle was evaluated using spectrophotometry. Pharmaceuticals degradation was performed in ultrapure water and WWTP effluent containing 1% acetonitrile due to the low solubility of macrolides. Pharmaceuticals concentrations were monitored by high performance liquid chromatography (HPLC) and their transformation products were identified through the coupling of HPLC with a mass spectrometer. For heterogeneous process degradation, catalysts based on copper and iron oxide were used. The formation of iron and copper complexes with the macrolides was verified with reducing effect of the macrolides on Cu(II), generating Cu(I) complexes in solution. Although the complexes of macrolides with Fe and Cu influenced the redox cycle, only the copper complexes showed a recalcitrant behavior to the homogeneous photo-Fenton process. Among the catalysts used in the heterogeneous process, it was observed that the increase in copper content during the synthesis contributed to the surface area of CAT1 being greater than that of CAT2, resulting in a greater activity of CAT1. Variation in pH affected macrolide degradation, as well initial H2O2 concentration. The best results of heterogeneous photo-Fenton process application were obtained using 0.125 g L-1 of CAT1, 15 mmol L-1 of H2O2 at pH 5.4. In all processes (homogeneous and heterogeneous media) the degradation constant of SMX was higher than that of macrolides, indicating greater recalcitrance of AZT and CLA. Experiments carried out on the WWTP effluent showed that the matrix did not influence AZT and CLA degradation, however it affected SMX degradation. The matrix interfered with SMX degradation because it occurs by combining the mechanisms of electrophilic addition with abstraction of the hydrogen atom and electronic transfer, while the macrolides were less affected due to the degradation occurring by electronic transfer only. The transformation products identification revealed the formation of hydroxylated products for both macrolides. Experiments carried out in the presence of hydroxyl radical scavengers showed the importance of •OH in macrolides degradation. SMX degradation was not completely inhibited because it does not depend only on •OH, but also on other radicals such as HO2•, O2•- and 1O2. The obtained results contribute to the understanding of the degradation mechanism and the recalcitrance of macrolide antibiotics to the Fenton process.
The presence of antibiotics in effluents from wastewater treatment plants (WWTP) after a conventional process has received great attention due to problems that these contaminants can cause both to the environment and to human health, such as bacterial resistance. The present work studied the degradation kinetics of two macrolide antibiotics, azithromycin (AZT) and clarithromycin (CLA), by Fenton process in homogeneous and heterogeneous medium and compared it with sulfamethoxazole (SMX) degradation, belonging to sulfonamides class. Analytical methods were developed and validated for simultaneous separation and quantification of macrolides, separately from SMX quantification method. The formation of iron and copper complexes with macrolides and the complexation influence on the Fe(II)/Fe(II) and Cu(I)/Cu(II) redox cycle was evaluated using spectrophotometry. Pharmaceuticals degradation was performed in ultrapure water and WWTP effluent containing 1% acetonitrile due to the low solubility of macrolides. Pharmaceuticals concentrations were monitored by high performance liquid chromatography (HPLC) and their transformation products were identified through the coupling of HPLC with a mass spectrometer. For heterogeneous process degradation, catalysts based on copper and iron oxide were used. The formation of iron and copper complexes with the macrolides was verified with reducing effect of the macrolides on Cu(II), generating Cu(I) complexes in solution. Although the complexes of macrolides with Fe and Cu influenced the redox cycle, only the copper complexes showed a recalcitrant behavior to the homogeneous photo-Fenton process. Among the catalysts used in the heterogeneous process, it was observed that the increase in copper content during the synthesis contributed to the surface area of CAT1 being greater than that of CAT2, resulting in a greater activity of CAT1. Variation in pH affected macrolide degradation, as well initial H2O2 concentration. The best results of heterogeneous photo-Fenton process application were obtained using 0.125 g L-1 of CAT1, 15 mmol L-1 of H2O2 at pH 5.4. In all processes (homogeneous and heterogeneous media) the degradation constant of SMX was higher than that of macrolides, indicating greater recalcitrance of AZT and CLA. Experiments carried out on the WWTP effluent showed that the matrix did not influence AZT and CLA degradation, however it affected SMX degradation. The matrix interfered with SMX degradation because it occurs by combining the mechanisms of electrophilic addition with abstraction of the hydrogen atom and electronic transfer, while the macrolides were less affected due to the degradation occurring by electronic transfer only. The transformation products identification revealed the formation of hydroxylated products for both macrolides. Experiments carried out in the presence of hydroxyl radical scavengers showed the importance of •OH in macrolides degradation. SMX degradation was not completely inhibited because it does not depend only on •OH, but also on other radicals such as HO2•, O2•- and 1O2. The obtained results contribute to the understanding of the degradation mechanism and the recalcitrance of macrolide antibiotics to the Fenton process.
Descrição
Palavras-chave
Antibióticos, Macrolídeos, Tratamento efluente de águas residuais, Complexos (Química), Cromatografia líquida de alta eficiência