Highly Cross-Linked Epoxy Nanofiltration Membranes for the Separation of Organic Chemicals and Fish Oil Ethyl Esters.

Membrane separations are highly desired for the chemical industry because they are inexpensive, avoid the use of heat, can be applied to the purification of a wide range of chemicals, and can be scaled to industrial levels. Separating chemicals with molecular weights between 100 and 300 g mol(-1) remains a significant challenge in the field of organic solvent nanofiltration (OSN) due to their similar sizes and rotational flexibility. In this work, we report the fabrication of poly(epoxy) membranes that show excellent selectivity of over 100:1 for chemicals in this range. The membranes are easily tuned to obtain different flux and selectivity by using interchangeable amine and epoxide monomers. These membranes were used to separate the important nutritional omega-3 fatty acid ethyl esters eicosapentaenoic ethyl ester (EPA-EE) and docosahexaenoic acid ethyl ester (DHA-EE) from each other, despite a small difference in molecular weight (26 g mol(-1)). This is the first example of a separation of EPA-EE and DHA-EE using a membrane process.