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Remediação de solos contaminados por compostos farmacêuticos
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Orientador(es)
Resumo(s)
O recente surgimento de nanopartículas de ferro valente-zero (nFZV), um
material com elevada capacidade de remediação de solos por via de reacções de
oxidação/redução pode ser uma opção viável para a remoção de fármacos do solo. A
sua aplicação já é uma realidade em alguns tipos de solos contaminados por
compostos específicos e, com este trabalho, procura-se estudar a sua capacidade de
remediação de solos contaminados por compostos farmacêuticos, recorrendo-se a
uma tecnologia “verde” de síntese destas nanopartículas. Esta tecnologia é bastante
recente, ainda não aplicada no campo de trabalho, que se baseia no uso de folhas de
certas árvores para produzir extratos naturais que reduzem o ferro (III) a ferro zero
valente, formando nFZV.
Desta forma procedeu-se, à escala laboratorial, ao estudo da eficiência das
nFZV na degradação de um fármaco – paracetamol – e comparou-se com a eficiência
demonstrada por oxidantes, muito utilizados hoje em dia em casos de remediação in
situ como o permanganato de potássio, o peróxido de hidrogénio, o persulfato de sódio
e o reagente de Fenton. O estudo foi efectuado em dois meios diferentes: solução
aquosa e solo arenoso. De forma muito sucinta, o estudo baseou-se na introdução dos
oxidantes/nFZV em soluções/solos contaminados com paracetamol e consequente
monitorização do processo de remediação através de cromatografia líquida de alta
eficiência.
Nos ensaios com soluções aquosas contaminadas com paracetamol, o
permanganato de potássio e o reagente de Fenton revelaram capacidade para
degradar o paracetamol, atingindo mesmo um grau de degradação de 100%. O
persulfato de sódio também demonstrou uma capacidade de degradação do
paracetamol, chegando a atingir 99% de degradação, mas apenas recorrendo ao uso
de um volume de oxidante elevado quando comparado com os outros dois oxidantes
já referidos. Por outro lado, o peróxido de hidrogénio não demonstrou qualquer
capacidade de degradação do paracetamol, pelo que o seu uso não passou desta
fase. Verificou-se também que o uso de ferro granulado para o tratamento de água
contaminada com paracetamol revelou resultados diferentes dos observados no uso
de nFZV, obtendo-se eficiências de 87%. Existiram dificuldades analíticas na
quantificação do paracetamol, especificamente relacionadas com o uso do extracto de
folhas de amoreira, cuja composição continha substâncias que causaram dificuldades
acentuadas na análise dos cromatogramas. Por fim, um pequeno teste de combinação do reagente de Fenton com os fenómenos de biodegradação resultantes dos
microrganismos presentes em folhas do extracto de chá preto demonstrou que este
pode ser uma área que pode e deve ser mais estudada. Desta forma, a utilização das
nFZV para o tratamento de água contaminada com paracetamol não permitiu a
retirada de conclusões seguras sobre a capacidade que as nFZV produzidas com
extractos de folhas de amoreira e de chá preto têm de degradação do paracetamol.
Nos testes de remediação de solos contaminados os resultados demonstraram
que, mais uma vez, tanto o permanganato de potássio como o reagente de Fenton se
revelam como os melhores oxidantes para a degradação do paracetamol, obtendo-se
a degradação total do paracetamol. Por outro lado, voltou a ser necessário uma
elevada quantidade de persulfato de sódio quando comparada com os dois anteriores,
para que ocorra a degradação desta mesma quantidade de paracetamol,
demonstrando mais uma vez que, apesar de não ideal, o persulfato demonstra
capacidade de degradação do paracetamol.
The recent emergence of zero-valent iron nanoparticles (nZVI), a substance with a high capacity for soil remediation through chemical reduction may be a valid option for the removal of pharmaceutical compounds from the soil. Its application is already a reality in some types of soils contaminated by specific compounds, and this work seeks to study their ability to treat soils contaminated by pharmaceuticals, making use of a fairly recent “green” technology for the synthesis of these nanoparticles, which is not yet applied in the field and relies on the use of leaves of certain trees. The efficiency of nZVI to degrade a pharmaceutical compound - acetaminophen - was explored on a laboratory scale and the obtained efficiency was compared with the efficiency of oxidants which are widely used for in situ chemical oxidation: potassium permanganate, hydrogen peroxide, sodium persulfate and Fenton's reagent. The remediation studies were performed in aqueous solutions and a sandy soil. The experiments were executed by introducing the oxidant/nZVI in solutions/soils contaminated with acetaminophen and the remediation process was monitored through the analysis of the amount of acetaminophen by high performance liquid chromatography. In aqueous solutions contaminated with acetaminophen, potassium permanganate and Fenton's reagent showed degrading capacities of 100%. Although sodium persulfate also degraded acetaminophen (99% efficiency) the amount of reagent needed was much higher than the amount of the other oxidants mentioned above. On the other hand, hydrogen peroxide did not show any degradation capacity of acetaminophen and was therefore not included in the remediation of contaminated soils. It was also found that the use of granulated zero valent iron iron for the treatment of water contaminated with acetaminophen showed different results than those observed when nFZV is used, achieving a 87% degradation. Analytical difficulties in the quantification of acetaminophen, specifically related to the use of the mulberry leaf extracts, were encountered. These difficulties were related to the presence of substances in this extract with the same retention time as acetaminophen. Finally, the combination of Fenton's reagent with the biodegradation phenomena arising from microorganisms present in black tea leaves demonstrated that this may be an area that can and should be studied further. Therefore, there weren’t any secure conclusions about the capacity of nZVI produced using mulberry bush and black tea leaves to degrade acetaminophen in aqueous solution. In the remediation of contaminated soils results showed that again both potassium permanganate and Fenton's reagent are the best oxidants for the degradation of acetaminophen, providing total degradation. On the other hand, once again a large amount of sodium persulfate, compared to the previous two oxidants, was required for the degradation of the same amount of acetaminophen. Therefore, although not ideal, persulfate also shows a degrading capacity of acetaminophen.
The recent emergence of zero-valent iron nanoparticles (nZVI), a substance with a high capacity for soil remediation through chemical reduction may be a valid option for the removal of pharmaceutical compounds from the soil. Its application is already a reality in some types of soils contaminated by specific compounds, and this work seeks to study their ability to treat soils contaminated by pharmaceuticals, making use of a fairly recent “green” technology for the synthesis of these nanoparticles, which is not yet applied in the field and relies on the use of leaves of certain trees. The efficiency of nZVI to degrade a pharmaceutical compound - acetaminophen - was explored on a laboratory scale and the obtained efficiency was compared with the efficiency of oxidants which are widely used for in situ chemical oxidation: potassium permanganate, hydrogen peroxide, sodium persulfate and Fenton's reagent. The remediation studies were performed in aqueous solutions and a sandy soil. The experiments were executed by introducing the oxidant/nZVI in solutions/soils contaminated with acetaminophen and the remediation process was monitored through the analysis of the amount of acetaminophen by high performance liquid chromatography. In aqueous solutions contaminated with acetaminophen, potassium permanganate and Fenton's reagent showed degrading capacities of 100%. Although sodium persulfate also degraded acetaminophen (99% efficiency) the amount of reagent needed was much higher than the amount of the other oxidants mentioned above. On the other hand, hydrogen peroxide did not show any degradation capacity of acetaminophen and was therefore not included in the remediation of contaminated soils. It was also found that the use of granulated zero valent iron iron for the treatment of water contaminated with acetaminophen showed different results than those observed when nFZV is used, achieving a 87% degradation. Analytical difficulties in the quantification of acetaminophen, specifically related to the use of the mulberry leaf extracts, were encountered. These difficulties were related to the presence of substances in this extract with the same retention time as acetaminophen. Finally, the combination of Fenton's reagent with the biodegradation phenomena arising from microorganisms present in black tea leaves demonstrated that this may be an area that can and should be studied further. Therefore, there weren’t any secure conclusions about the capacity of nZVI produced using mulberry bush and black tea leaves to degrade acetaminophen in aqueous solution. In the remediation of contaminated soils results showed that again both potassium permanganate and Fenton's reagent are the best oxidants for the degradation of acetaminophen, providing total degradation. On the other hand, once again a large amount of sodium persulfate, compared to the previous two oxidants, was required for the degradation of the same amount of acetaminophen. Therefore, although not ideal, persulfate also shows a degrading capacity of acetaminophen.
Descrição
Palavras-chave
Nanopartículas de ferro zero valente Paracetamol Remediação de solos Oxidação/redução química Zero valent iron nanoparticles Acetaminophen Soil remediation Chemical oxidation/reduction
Contexto Educativo
Citação
Editora
Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto