Fabrication of high-permeance polyketone (PK) hollow fiber membrane using triple-orifice spinneret via the thermally induced phase separation

The co-extrusion technique employing a triple-orifice spinneret has been found to be an effective method to regulate the membrane pore size and surface structure. This is achieved by simultaneously extruding another solvent at the outer surface of the nascent polymer membrane. In this study, co-extrusion technology was employed to modify the outer surface structure of the polyketone (PK) hollow fiber membrane to enhance membrane permeance. By extruding various solvents at the outermost layer of the triple-orifice spinneret, besides the interaction among PK, diluent, and extruded solvent, it was emphasized that the viscosity of the outer solvent significantly influenced the penetration process and consequently affected the microstructure of the membrane surface. In addition, it was found that the higher water permeance was mainly attributed to the increased surface porosity rather than the slightly increased membrane pore size. The penetration of extrusion solvent propylene carbonate (PC) with low viscosity resulted in a porous outer surface with higher surface porosity, leading to high water permeance (2430 L m(-2)h(-1)bar(-1)). Furthermore, the air gap distance was optimized, and its effects on membrane structure, pore size, water permeance, and strength were discussed. This work provides a guideline for selecting preparation parameters and extrusion solvents to prepare PK membranes with high permeance.