Taylor The Support Layer Structures For Optimizing Gas Separation Propeties Of Hollow Fiber Composite

Hollow fiber membranes have many advantages such as high packing density,and large separation area.It has a wide range of applications in the fields of gas separation,water treatment,organic solvent and so forth.Here in this stud,the polyacrylonitrile(PAN)and polysulfone(PSF)hollow fiber porous membranes were prepared by dry-jet wet spinning.In the hollow fiber spinning process,factors including the interaction between polymers,solvents and additives in the casting solution,and the bore fluid flow rate,the take-up speed and the bore fluid formulation were adjusted to optimize the hollow fiber substrate structures.The effects of polymer content,non-solvent content,take-up speed,bore fluid flow rate,and bore fluid composition to the structure and performance of hollow fiber membranes were studied.Scanning electron microscope,gas permeance and selectivity were measured to correlate the relations between membrane structure and performance.The experiments showed that the higher the concentration of the dope solution,the lower the gas permeation rate of the membrane;the addition of non-solvent increased membrane permeation rate.A low bore fluid flow resulted in a low membrane permeance,while a high take-up speed also decreased membrane permeance.When bore fluid contained high water content,membrane exhibited low permeance.Silicone rubber(PDMS)was selected as the coating layer material,and the effect of coating solutions with different concentrations on gas permeance of hollow fiber membranes was studied.Results showed that a high concentration prevented the formation of defects,but an over-high concentration decreased the gas permeance.We studied the soaking times in water bath on the removal efficiency to organic solvent left in the nascent hollow fiber membranes.The water-wet membranes were dried using three methods including freeze-drying,methanol/n-hexane solvent exchanges,and isopropyl alcohol-hexane solvent exchange.The three methods were evaluated by comparing gas permeance in the corresponding dry membranes.The effects of different solvent exchanging times of methanol and n-hexane on the gas permeance of hollow fiber membranes were studied also.The hollow fiber composite membranes with the best gas separation properties were obtained using 1 wt.%PDMS coating solution.The nitrogen permance was 500±5 GPU,the oxygen permeance was 1050+5 GPU,and the carbon dioxide permeance was 5300±10 GPU,which were on par with the best gas separation membranes all over the world.