| 1. |
- Penha, Frederico Marques, et al.
(författare)
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Evaluation of permeation of macauba oil and n-hexane mixtures through polymeric commercial membranes subjected to different pre-treatments
- 2015
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Ingår i: Journal of Food Engineering. - : ELSEVIER SCI LTD. - 0260-8774 .- 1873-5770. ; 155, s. 79-86
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Tidskriftsartikel (refereegranskat)abstract
- Macauba is a Brazilian palm tree with high edible oil productivity and of great interest to many applications. In the oil extraction process, solvent recovery is one point of major concern, due to its high energy consumption and oil quality losses. Those drawbacks can be partially overcome by integration of membrane technology to the usual solvent distillation step. The present work tested four ultrafiltration (UF) and one nanofiltration (NF) membrane (Microdyn-Nadir) on the solvent recovery of synthetic mixtures of macauba oil and n-hexane. Membranes were pre-treated before use with different solvents in specific time lengths, according to preliminary studies. The membrane performance was evaluated by permeate flux and oil retention. Macauba (pulp and kernel) oil was evaluated by determinations of acidity, peroxide value and fatty acid profile. Membranes showed usual flux behaviour, compatible with other studies concerning oil/solvent mixtures permeation, although its values were quite above the expected. Best results for retention (>30%) are related to the membranes with lower molar mass cut-off (MMCO), and the best balance between permeate flux and oil retention was found for the NF membrane (12.4 g m(-2) h(-1), 34.7%).
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| 2. |
- Penha, Frederico Marques, et al.
(författare)
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Influence of different solvent and time of pre-treatment on commercial polymeric ultrafiltration membranes applied to non-aqueous solvent permeation
- 2015
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Ingår i: European Polymer Journal. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0014-3057 .- 1873-1945. ; 66, s. 492-501
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Tidskriftsartikel (refereegranskat)abstract
- Several pre-treatments and solvents were tested through permeation in commercial polymeric membranes (UH004, UP005, UP010 and UH050 - Microdyn-Nadir) with different molar mass cut-offs (4 kDa, 5 kDa, 10 kDa and 50 kDa, respectively), in order to evaluate their efficiency and stability through non-aqueous solvent permeation. After pre-treatments and permeations, membranes were characterised with contact angle, Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electronic Microscopy (FESEM) to evaluate structural integrity. The results of solvent permeation suggest that selectivity of the polymeric matrix depends not only on pore size, but also, in great extent, on the interaction between solvent and polymer. A strong relation can be noted between the conditioning length and permeability for ethanol pre-treatments. Permeability to n-hexane increased from 4 to 18 times after pre-treatment, depending on the time of exposure to ethanol and n-hexane. Characterisation analyses show no significant changes on the membranes surface. In some cases, discrepancies observed among permeate fluxes and contact angles might be an indicative of the occurrence of swelling and plasticisation. However, results suggest the feasibility in the use of these membranes for the recovery of solvents in the oil industry, if suitable process parameters are chosen.
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| 3. |
- Rezzadori, Katia, et al.
(författare)
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Effect of dense CO2 on polymeric reverse osmosis and nanofiltration membranes and permeation of mixtures of macauba oil (Acrocomia aculeata) and CO2
- 2015
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Ingår i: Journal of Membrane Science. - : ELSEVIER SCIENCE BV. - 0376-7388 .- 1873-3123. ; 481, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- The performance of four commercial membranes upon subcritical and supercritical CO2 treatments have been characterised by different methods. The membranes were treated up to 8 h in static process, using two different conditions (18 MPa/313.15 K - supercritical and 8 MPa/293.15 K - subcritical). The possible changes in membrane characteristics were investigated by atomic force microscopy (AFM), contact angle and surface free energy, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM). Membrane performance was also evaluated by measuring CO2 flux ancl macauba oil retention factors. Changes in membrane roughness ancl in contact angles were observed for all membranes after sub and supercritical CO2 treatments. Moreover, the surface free energy and the polar component showed a decrease after CO2 exposure, confirming an increase in surface hydrophobicity of membranes detected from contact angle results. This empowerment of hydrophobicity is associated mainly with the CO2-polymer interaction. Other intra and interchain effects should not affect the thermal stability leaving TGA results unchanged after CO2 exposure. ORAK and NP030 membranes showed high macauba oil retentions; 95% and 85%, respectively in supercritical condition. This latter revealed to cause important changes in the membranes due to the higher solubility of CO2 in polymeric matrix at this condition. However, the selectivity was not changed and it is possible to use commercial polymeric membranes in supercritical systems for CO2 regeneration and partial fatty acid fractioning.
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| 4. |
- Rezzadori, Katia, et al.
(författare)
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Evaluation of reverse osmosis and nanofiltration membranes performance in the permeation of organic solvents
- 2015
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Ingår i: Journal of Membrane Science. - : ELSEVIER. - 0376-7388 .- 1873-3123. ; 492, s. 478-489
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the influence of different solvents and time conditionings in the permeation of n-hexane and oil/n-hexane solutions through several reverse osmosis (ORAK - Osmonics, BW30 - Dow Filmtec) and nanofiltration (NF270 - Dow Filmtec, NP030 - Microdyn Nadir) polymeric membranes. The study of the influence of membrane conditioning on the n-hexane flux was carried out using different solvents (n-hexane, ethanol, n-propanol, iso-propanol and butanol) as pretreating agents in different time intervals. Membrane performance was tested by measuring n-hexane fluxes and rejections of dissolved castor oil. The conditioning with ethanol increased n-hexane fluxes in the polyamide membranes ORAK, NF270 and BW30, while the polyethersullone membrane NP030 did not present any increase in permeability. An increase in contact angle after membrane conditioning was detected, as well as a reduction in free surface energy. This suggests that pretreatment steps alter the surface hydrophilic character. Salt rejections for all the membranes decreased after the pretreatments and permeation with n-hexane for 8 h. These rejections dropped from 87-99% to 72-77% for membranes NF270, NP030 and BW30; and from 99% to 88% for ORAK, which showed better stability to solvent exposure. For castor oil, the highest retention was 60% for reverse osmosis membrane ORAK. The results obtained in this work with commercial RO and NF membranes, normally used in aqueous solutions operations, indicate that most of these membranes do not present adequate stability towards nonaqueous solvents.
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