| 1. |
- Trifunovic, Olivera, et al.
(author)
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Mass transport of aliphatic alcohols and esters through hydrophobic pervaporation membranes
- 2006
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In: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 50:1, s. 51-61
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Journal article (peer-reviewed)abstract
- Mass transport in pervaporation of multi-component mixtures of homologous series of alcohols and esters through composite pervaporation membranes has been investigated. Pervaporation experiments were performed in a concentration range relevant for aroma recovery, using a membrane with an active layer of poly (octyl) methylsiloxane (POMS) caste on a porous polyetherimide (PEI) support. The fluxes, selectivities and average diffusion coefficients were determined for each compound studied and were related to the properties of the permeating molecule. The reduction in the selectivity of the higher homologues of the alcohol series with increase in feed concentration was explained by a decrease in diffusion coefficient with respect to feed concentration. There was evidence of a tendency towards aggregation of water molecules, lower homologues of alcohol series and the first two homologues of the ester series, which resulted in a decrease in diffusivity for the polar, lower homologues in both series. (C) 2005 Elsevier B.V. All rights reserved.
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| 2. |
- Trifunovic, Olivera, et al.
(author)
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The influence of permeant properties on the sorption step in hydrophobic pervaporation.
- 2003
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In: Journal of Membrane Science. - 0376-7388. ; 216:1-2, s. 207-216
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Journal article (peer-reviewed)abstract
- Liquid solubility measurements were performed by immersion of poly(octyl)methylsiloxane (POMS) in dilute aqueous solutions of homologous series of aliphatic esters and alcohols with compound specific concentrations of 20, 40, 80 and 120 ppm. Measurements were performed at 20 °C with both single- and multi-compound mixtures and linear sorption isotherms were obtained. By fitting experimentally determined molar solubility coefficients to their liquid molar volumes, exponential relationships were obtained for compounds within the same chemical group. The solubility coefficients of alcohols were smaller than those obtained for esters of approximately the same molecular size due to the hydrophilic hydroxyl group in the former. There was evidence of some coupling effects; in the case of larger esters the solubility was higher when they were sorbed from multi-compound solutions of esters. The solubility of all the alcohols except n-octanol was the same regardless of whether they were sorbed from single- or multi-compound solutions. As far as the n-octanol was concerned, the solubility decreased when other alcohols were present in the solution. One possible explanation of this is that the ability of alcohols to form clusters through hydrogen bonding modifies the polymer phase by reducing its ability to take up n-octanol.
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| 3. |
- Trifunovic, Olivera, et al.
(author)
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The influence of process parameters on aroma recovery by hydrophobic pervaporation
- 2006
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In: Desalination. - : Elsevier BV. - 0011-9164. ; 189:1-3, s. 1-12
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Journal article (peer-reviewed)abstract
- Hydrophobic pervaporation has been shown to be a promising, alternative process for the recovery of volatile organic components from their aqueous solutions, such as the recovery of aroma compounds in the food industry. Until now most of the research on the influence of operating parameters on aroma recovery by pervaporation has been conducted on the laboratory scale. The number of studies dealing with the scaling-up of the pervaporation process for the separation of multi-component mixtures is still relatively small, and usually has a number of limitations. The aim of this study was to investigate module design aspects of pervaporation, using a modified version of an existing pervaporation simulation tool for aroma recovery. By applying the simulation to four aroma compounds, two alcohols and two esters, the influence of major process and module design parameters on the performance of a single module has been investigated. The results of the simulation show that detailed modelling of single module behaviour is an important aspect of the optimisation of pervaporation plant performance.
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| 4. |
- Trifunovic, Olivera, et al.
(author)
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The influence of support layer on mass transport of homologous series of alcohols and esters through composite pervaporation membranes
- 2005
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388. ; 259:1-2, s. 122-134
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Journal article (peer-reviewed)abstract
- In this study the effect of the composite membrane structure on the mass transfer limitations in hydrophobic pervaporation of dilute aqueous solutions of homologous series of alcohols and esters was investigated. Three hydrophobic membranes with poly (octyl)methylsiloxane (POMS) as an active layer were used. The membranes studied varied with respect to the thickness of the active layer and the nature and geometric characteristics of the support layer: polyetherimide (PEI) or polyacrylonitrile (PAN). The transport through the support was modelled by Knudsen diffusion. While the support layer had a moderate effect on mass transfer resistance for homologous series of esters, for the homologous series of alcohols the effects of the support layer depended not only on the geometric characteristics of the support structure, but also on the nature of the support: the membrane with the PEI support exhibited a greater reduction in driving force than membranes with the PAN support. However, regarding selectivity towards the feed mixture the membrane with the PEI support was superior, due to the correct proportions between the thickness of the active layer and the support layer. Further improvement in membrane performance can be obtained by optimizing the geometric characteristics of this support structure in order to minimize the reduction in driving force of pressure-sensitive compounds. (c) 2005 Elsevier B.V. All rights reserved.
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| 5. |
- Trifunovic, Olivera, et al.
(author)
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Transport of diluted volatile organic compounds through pervaporation membranes
- 2002
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In: Desalination. - 1873-4464. ; 149:1-3, s. 1-2
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Journal article (peer-reviewed)abstract
- Over the years, pervaporation has been widely investigated as a technique for separation of liquid mixtures and recovery of organic compounds from diluted solutions. So far, the research has focused on applications in wastewater treatment, in pharmaceutical industry, for removing the products from fermentation broth in bioreactors and for aroma recovery. When it comes to pervaporation of aroma compounds, this technique has shown potential to concentrate these compounds up to several hundreds times their original concentration.
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