Separation of cis-Fatty Acids from Saturated and trans-Fatty Acids by Nanoporous Polydicyclopentadiene Membranes

Abstract

This article describes the separation of mixtures of fatty acid salts using a new organic solvent nanofiltration membrane based on polydicyclopentadiene (PDCPD). Mixtures of free fatty acids could not be separated by the membranes because they permeated at similar rates. When triisobutylamine was added to the fatty acids, the cis-fatty acid salts (oleic, petroselinic, vaccenic, linoleic, and linolenic acid) had slower permeation though the membranes than saturated (stearic acid) and trans-fatty acid (elaidic acid) salts. The reason for the difference in permeation was due to the formation of stable salt pairs between the amine and fatty acids that increased their cross-sectional areas. The fatty acid salts derived from saturated and trans-fatty acids were smaller than the critical area cutoff for the PDCPD membranes, so they readily permeated. In contrast, the fatty acid salts derived from the cis-fatty acids had critical areas larger than critical area cutoff of the PDPCD membranes and had slowed permeation. The partitioning coefficients of fatty acids and fatty acid salts were investigated to demonstrate that they were not responsible for the difference in permeation. The use of pressure was investigated to greatly accelerate the permeation through the membranes. For a solvent mixture of 35/65 (v/v) toluene/hexanes, the permeation of solvent was approximately 39 L m(-2) h(-1). This value is similar to values reported for permeation through membranes used in industry. The separation of a mixture of fatty acids based on the composition of soybean oil was investigated using pressure. The saturated fatty acid salts were almost completely removed from the cis-fatty acid salts when iBu(3)N was used as the amine to form the salt pairs. The separation of the cis-fatty acids found in soybean oil was investigated with Pr(3)N as the amine. The oleic acid salt (oleic acid has one cis double bond) preferentially permeated the membrane while the linoleic (two cis double bonds) and linolenic (three cis double bonds) salts were partly retained. The separation of fatty acids using membranes may have real applications in industry to purify fatty acids on a large scale.

Membrane technology for vegetable oil processing—Current status and future prospects

“…Nonetheless, processing undiluted oils using nonporous membranes has shown moderate selectivity for FFA over TAG but lost entirely upon dilution with hexane (Bhosle et al., 2005). Gupta and Bowden (2013) disclosed an interesting study that showed that the addition of triisobutylamine to the mixture of fatty acids increased the cross‐sectional areas of stable salt pairs between the amine and fatty acids. Consequently, a solvent‐resistant nanofiltration (SRNF) polydicyclopentadiene membrane could separate the cis‐fatty (petroselinic, oleic, linoleic, and linolenic) acid salts from saturated (stearic) and trans‐fatty (elaidic) acid salts in a solvent phase consisting of chloroform and methanol (75:25).…”

Experimental and theoretical investigations on temperature modulated translocation of IgG molecules through nanopore arrays

“…Nanoporous membrane based functional devices are attracting more and more attention because of their broad applications in selective separation, [1][2][3][4][5][6] controlled release, 7,8 drug delivery, [9][10][11] etc. In recent years, nanopore or nanopore arrays based analytical technology has provided potential possibilities to fabricate novel nanofluidic devices for biomolecule sensing.…”

Batchwise extraction of methyl linolenate (18:3, ALA) from fatty acid methyl esters derived from soybean and canola oils using silver nitrate/silica gel

“…A prior study [10] by our group employed a AgNO 3 /SiO 2 -WI solid-phase adsorbent, prepared by wet impregnation (WI) of silica with AgNO 3 , for the extraction of polyunsaturated FAMEs from methyl soyate on a relatively large scale ($1 mL of FAMEs) in comparison to such separations that are typically performed on a much smaller scale by chromatography [11] and other methods [12]. The chromatographic separations are based on the ability of Ag þ ions to co-ordinate to double bonds in the unsaturated FAMEs.…”