“Chemistry in a spinneret” to fabricate hollow fibers for organic solvent filtration

Organic solvent filtration (OSF) is a very efficient separation technique with high potential in many branches of industry. Currently the choice of the commercial membranes is limited only to a few flat sheet membranes and spiral wound modules. It is generally known that a membrane in hollow fiber form has several advantages, over a flat configuration, such as high surface to volume ratio and no need of spacers. Consequently more compact and simpler modules and easy to scale up can be built.In this work we explore a new technique called “chemistry in a spinneret”, to fabricate a hollow fiber (HF) for OSF. This technique combines the membrane formation and crosslinking reaction into a single step process. P84 polyimide was chosen as a membrane forming polymer and poly(ethylene imine) (PEI), dissolved in the bore liquid, as a crosslinking agent. In order to obtain a membrane with the best stability and low membrane MWCO, the composition of the bore liquid was systematically varied, including solvent/non-solvent ratio and PEI concentration.The crosslinked membranes have MWCO in the range of 2500–3500 g mol−1 and toluene permeance in the range of 0.2–1.1 l m−2 h−1 bar−1. The most stable crosslinked membrane maintains 80% of its mass after 11 days immersion in N-methyl-2-pyrrolidinone. Due to crosslinking, the HFs become more hydrophilic and therefore attractive for separations in alcohol systems. Preliminary results are in fact presented here using an ethanol/polyethylene glycol model system.

Graphical abstract(a) “Chemistry in the spinneret” for developing crosslinked P84 membranes. (b) SEM images of cross sections of spun hollow fibers.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We fabricate crosslinked P84 polyimide hollow fiber membranes for organic solvent filtration. ► The membranes have MWCO around 3000 Da and toluene permeance in the range of 0.2–1.1 l m−2 h−1 bar−1. ► The fibers are more hydrophilic and attractive for separations in alcohol systems.