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O desenvolvimento de métodos de tratamento de águas residuais com origem na indústria petroquímica inclui o estudo de processos de oxidação de poluentes em misturas bifásicas contendo água e hidrocarbonetos. Neste contexto, efetuou-se uma revisão bibliográfica sobre a solubilidade em água e os coeficientes de partição alcano/água de um conjunto selecionado de compostos que participam no processo de peroxidação de poluentes. Foram estudados três poluentes (2-nitrofenol, 3-nitrofenol e 4-nitrofenol) bem como alguns solutos representativos dos produtos das reações de oxidação (4-aminofenol, hidroquinona, p-benzoquinona, catecol, acetamida, ácido oxálico, ácido malónico e ácido málico).
Numa segunda etapa, efetuou-se a medição da solubilidade em água do ácido málico e do ácido malónico entre 298,2 K e 313,2 K, utilizando um método analítico isotérmico, visto haver inconsistência entre os dados já disponíveis na literatura. A partir dos dados obtidos neste trabalho, calcularam-se os valores das propriedades termodinâmicas de solução.
Finalmente, aplicou-se o modelo UNIFAC na previsão dos coeficientes de partição em ciclo-hexano/água, isooctano/água e 1-octanol/água e compararam-se os resultados obtidos com os valores calculados pelo modelo de solvatação de Abraham. O modelo UNIFAC apresentou algumas limitações: não permitiu diferenciar isómeros de posição como os nitrofenóis, ou a hidroquinona e o catecol; não foi possível descrever a molécula p-benzoquinona a partir dos subgrupos disponíveis; os valores de alguns parâmetros de interação energética não se encontram disponíveis.
Por outro lado, o modelo de Abraham descreve de forma muito satisfatória todos os tipos de coeficientes de partição. Para isso contribui o seu carácter semi-preditivo, ao estimar alguns dos seus parâmetros a partir de dados de partição. De qualquer forma, o modelo UNIFAC será sempre uma ferramenta útil numa fase preliminar em que não haja dados experimentais.
The development of treatment methods of wastewaters from the petrochemical industry includes the study of pollutant oxidation processes in biphasic mixtures containing water and hydrocarbons. In this context, a literature review was performed on water solubility and alkane/water partition coefficients of a selected set of compounds participating in the pollutant peroxidation process. Three pollutants (2-nitrophenol, 3-nitrophenol and 4-nitrophenol) as well as some representative solutes of oxidation reaction products (4-aminophenol, hydroquinone, p-benzoquinone, catechol, acetamide, oxalic acid, malonic acid and malic acid) were studied. In a second step, the water solubility of malic acid and malonic acid was measured between 298.2 K and 313.2 K, using an isothermal analytical method, as there is inconsistency between data already available in the literature. From the data obtained in this work, the values of the thermodynamic properties of solution were calculated. Finally, the UNIFAC model was applied to predict the partition coefficients in cyclohexane/water, isooctane/water and 1-octanol/water and the results were compared with the values calculated by the Abraham solvation model. The UNIFAC model had some limitations: it did not allow differentiating position isomers such as nitrophenols, or hydroquinone and catechol; it was not possible to describe the p-benzoquinone molecule from the available subgroups; the values of some energy interaction parameters were not available. On the other hand, Abraham's model describes very satisfactorily all types of partition coefficients. This is due to its semi-predictive character by estimating some of its parameters from partition data. In any case, the UNIFAC model will always be a useful tool at a preliminary stage when no experimental data are available.
The development of treatment methods of wastewaters from the petrochemical industry includes the study of pollutant oxidation processes in biphasic mixtures containing water and hydrocarbons. In this context, a literature review was performed on water solubility and alkane/water partition coefficients of a selected set of compounds participating in the pollutant peroxidation process. Three pollutants (2-nitrophenol, 3-nitrophenol and 4-nitrophenol) as well as some representative solutes of oxidation reaction products (4-aminophenol, hydroquinone, p-benzoquinone, catechol, acetamide, oxalic acid, malonic acid and malic acid) were studied. In a second step, the water solubility of malic acid and malonic acid was measured between 298.2 K and 313.2 K, using an isothermal analytical method, as there is inconsistency between data already available in the literature. From the data obtained in this work, the values of the thermodynamic properties of solution were calculated. Finally, the UNIFAC model was applied to predict the partition coefficients in cyclohexane/water, isooctane/water and 1-octanol/water and the results were compared with the values calculated by the Abraham solvation model. The UNIFAC model had some limitations: it did not allow differentiating position isomers such as nitrophenols, or hydroquinone and catechol; it was not possible to describe the p-benzoquinone molecule from the available subgroups; the values of some energy interaction parameters were not available. On the other hand, Abraham's model describes very satisfactorily all types of partition coefficients. This is due to its semi-predictive character by estimating some of its parameters from partition data. In any case, the UNIFAC model will always be a useful tool at a preliminary stage when no experimental data are available.
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Coeficientes de partição Solubilidade Modelo de solvatação de Abraham Modelo UNIFAC