Study On Characterization And Mass Transfer Performance Of Hollow Fiber Dialysis Membrane

Chronic kidney disease has become a serious disease in the world nowadays, followingcardiovascular disease, cancer and diabetes. Hemodialysis is an important therapy forend-stage patients as replacementof kidney. Hemodialysis is being applied more and morewidely because of the increasing number of patients. This project compares threerepresentative materials ofhollow fiber membrane. These materials containcellulose triacetate,polyethersulfone and polysulfone, which are commonly used for hollow fiber dialysers.Amass-transfer model is established based on the law of mass conservation and double filmtheory, and the model is used in calculating membrane diffusion coefficient and totalmass-transfer coefficient. Referential suggestions are put forward by analyzing therelationship between mass-transfer performance and structure/characteristics.Main works ofthis project aresummarized as the followings:(1) Fiber surface morphology, density and porosityare tested. According tothe test results,both for density test and porosity test, weighing method is relatively more suitable for hollowfiber membrane, because of the micro porous and hollow structure.(2) Retention ratio and water flux are tested byultrafiltrationdevice. The results areanalyzed combined with membrane surface/structure morphology. Test results showcloserelationshipbetweenmass transfer efficiency and membrane pore structure. The retentionrate of albumin can reach more than99.99%for the three kinds of hollow fiber membrane,meanwhile water, creatinine, urea, phosphate, and vitamin B12can pass smoothly. Test resultsof water flux show that fiber membrane pore size is proportional to the water flux valuewithsimilarporosity.(3)Mass-transfer theory model is established based on the mass-conservation law anddouble-film theory. This model considers multiple affecting factors, such as membrane area,fluid viscosity, fiber diameter, fiber thickness, porosity, etc. Total mass-transfercoefficients总are calculated after dialysis simulate tests. Results show that:a) membrane thickness has great influence on总.Mass-transfer resistance isproportional to thickness of membrane, and inversely proportional to total mass-transfercoefficient.b) increase of concentration gradienthelps to improve dialysis efficiency.(4)Based on the mass-transfer theory model, membrane diffusion coefficients aretested with four different solutes (creatinine, urea, phosphate and vitamin B12).Results areanalyed with membrane surface/structure morphology,excluding membrane area, fiber diameter, fiber thickness and porosity.Membrane diffusion coefficient is proportional to fibermembrane pore size and pore distribution uniformity.Consideringmaterialsmass-transferperformance, polyether sulfone membrane and polysulfone membraneare better than cellulose acetate membrane.