Towards stabilization of supported liquid membranes: preparation and characterization of polysulfone support and sulfonated poly (ether ether ketone) coated composite hollow fiber membranes

A supported liquid membrane (SLM) contains organic solvent and organic extractant as one organic phase, and a porous support structure. It has been widely investigated for separation and purification of various chemical compounds. SLM has high permeability and selectivity, being regarded as one of the most versatile, efficient membrane separation processes. However, due to the gradual loss of organic phase during application, the permeability and selectivity degrade, largely hindering the commercialization of SLM. Our endeavor to achieve a stable SLM is to prepare composite membranes with an ion exchange coating layer based on the tailor-made hydrophobic supports. In this paper, the optimization of spinning parameters in preparing hydrophobic polysulfone (PSf) hollow fiber support membrane is described. A triple orifice-spinneret was utilized to create an open outward surface. The effect of polymer concentration, amount of additive and the NMP content in the bore liquid were investigated. Copper ion, pure water permeability, porosity and pore size distribution were characterized in selection of the support. Suitable support membranes were prepared from solutions of PSf content at 17 wt.% with an approaching ratio of 0.9 and a bore liquid containing 75 wt.% of NMP. The membrane showed much higher copper flux than literature reported values, but still unstable. Based on the tailor-made PSf hollow fiber membranes, a sulfonated poly (ether ether ketone) (SPEEK) layer was dip-coated at the outside layer and the SPEEK composite hollow fiber membranes showed significant improvement in stability.