The separation performances of polymeric membranes suitable for separation of fluid species in the food and pharmaceutical industry, such as in the Organic Solvent Nanofiltration (OSN) processes, strongly depend on the solubility of the fluids in the polymer membrane. [1-3] The solubility and diffusivity of several pure and mixed liquids of interest for the food and pharmaceutical industry was studied at 35°C into dense films of crosslinked PDMS membrane, that is widely used in membrane separation processes for its good permeation performance and for its resistance to solvents.[4] The effect of the presence of a low molecular weight solvent that swells the matrix on the solubility is analyzed and discussed. The measurement of pure liquid solubility in PDMS was performed gravimetrically, according to the blot and weight method: samples were immersed in vials filled with liquid, placed in a thermostatic bath and weighted at regular intervals with an analytical balance. In this way the mass uptake as a function of time was obtained. In the case of mixed liquids solubility, we considered solutions formed by a volatile component and a second one with negligible vapor pressure. Firstly the measurement of the total mass uptake of the liquid mixture was performed, according to the previously described procedure. Then, the volatile component was allowed to evaporate, until constant weight was obtained. Mass balance calculations provided the separate mass uptake of the volatile and of the non volatile component. In such way we obtained the solubility and diffusivity of a series of pure liquids at 35°C in PDMS: n-alkanes from n-C4 to n-C18, Cyclo-C6, H2O, acetone, linear alcohols from Ethanol to 1-Hexanol, Iso-Butanol and Tert-Butanol, and liquids of interest for the food and pharmaceutical sectors (Ethyl Acetate, PEG 400, Squalene, Limonene, Linalool, Geraniol, Olive oil, Groundnut Oil, Sunflower Oil Oleic acid). The data for homologous classes of penetrants show regular trends which can be explained via entropic and energetic effects. In multicomponent sorption experiments (carried out with mixtures formed by acetone/olive oil, acetone/oleic acid, pentane/olive oil; pentane/oleic acid; pentane/eicosane; tert-butanol/PEG-400; etc.) it was found that the solubility of the less soluble component is deeply enhanced by the presence of the other, more soluble component, that usually is the low molecular weight solvent. For example, the swelling induced by n-pentane promotes the dissolution of eicosane in PDMS, which shows a maximum at an intermediate mass fraction of n-C5 in the mixture. This behavior has been retrieved in many other mixtures and can be properly exploited to tune and design membrane separation processes.
Solubility of pure and mixed liquids for food and pharmaceutical applications in crosslinked polydimethylsiloxane (PDMS) films / G. Cocchi; M.G. De Angelis; F. Doghieri. - STAMPA. - (2014), pp. 56-56. (Intervento presentato al convegno ESAT 2014 tenutosi a Eindhoven, Paesi Bassi nel 6-9 Luglio 2014).
Solubility of pure and mixed liquids for food and pharmaceutical applications in crosslinked polydimethylsiloxane (PDMS) films
COCCHI, GIOVANNI;DE ANGELIS, MARIA GRAZIA;DOGHIERI, FERRUCCIO
2014
Abstract
The separation performances of polymeric membranes suitable for separation of fluid species in the food and pharmaceutical industry, such as in the Organic Solvent Nanofiltration (OSN) processes, strongly depend on the solubility of the fluids in the polymer membrane. [1-3] The solubility and diffusivity of several pure and mixed liquids of interest for the food and pharmaceutical industry was studied at 35°C into dense films of crosslinked PDMS membrane, that is widely used in membrane separation processes for its good permeation performance and for its resistance to solvents.[4] The effect of the presence of a low molecular weight solvent that swells the matrix on the solubility is analyzed and discussed. The measurement of pure liquid solubility in PDMS was performed gravimetrically, according to the blot and weight method: samples were immersed in vials filled with liquid, placed in a thermostatic bath and weighted at regular intervals with an analytical balance. In this way the mass uptake as a function of time was obtained. In the case of mixed liquids solubility, we considered solutions formed by a volatile component and a second one with negligible vapor pressure. Firstly the measurement of the total mass uptake of the liquid mixture was performed, according to the previously described procedure. Then, the volatile component was allowed to evaporate, until constant weight was obtained. Mass balance calculations provided the separate mass uptake of the volatile and of the non volatile component. In such way we obtained the solubility and diffusivity of a series of pure liquids at 35°C in PDMS: n-alkanes from n-C4 to n-C18, Cyclo-C6, H2O, acetone, linear alcohols from Ethanol to 1-Hexanol, Iso-Butanol and Tert-Butanol, and liquids of interest for the food and pharmaceutical sectors (Ethyl Acetate, PEG 400, Squalene, Limonene, Linalool, Geraniol, Olive oil, Groundnut Oil, Sunflower Oil Oleic acid). The data for homologous classes of penetrants show regular trends which can be explained via entropic and energetic effects. In multicomponent sorption experiments (carried out with mixtures formed by acetone/olive oil, acetone/oleic acid, pentane/olive oil; pentane/oleic acid; pentane/eicosane; tert-butanol/PEG-400; etc.) it was found that the solubility of the less soluble component is deeply enhanced by the presence of the other, more soluble component, that usually is the low molecular weight solvent. For example, the swelling induced by n-pentane promotes the dissolution of eicosane in PDMS, which shows a maximum at an intermediate mass fraction of n-C5 in the mixture. This behavior has been retrieved in many other mixtures and can be properly exploited to tune and design membrane separation processes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
