Study On Polyether Sulfone/Hydroxyapatite Mixed Matrix Membrane

Polyether sulfone(PES)is widely used for polymeric ultrafiltration and microfiltration membranes because of its toughness,good thermal resistance and chemical inertness.Hydroxyapatite(HAP)is an inorganic material,which has good biocompatibility and biological activity.Besides,HAP has good adsorption to protein and mainly used for repairing bone tissue and culturing sclerotin in the medical field.The PES/HAP mixed matrix membranes(MMMs)were prepared by incorporation HAP into a PES porous matrix by phase separation process.A mixed membrane composed of solid particles was formed.Polyvinylpyrrolidone(PVP)was used as pore-forming additive and dimethyl acetamide(DMAc)was used as solvent.The MMMs properties were investigated by scanning electron microscope(SEM)observations,measurements of pure water flux,and bovine serum albumin(BSA)adsorption.The article contents are as follows:1.PES solutions containing HAP were prepared by using DMAc as solvent.The rheological curves of the blend solution with different HAP mass fraction,the effects of HAP,and the temperature of the blend solution on the rheological properties were studied.The results show that non-Newtonian flow index of the blend solutions decrease with temperature and HAP mass fraction increases.PES-HAP blend solutions are non-Newtonian fluid.Flow activation energy of PES/HAP blend solution is significantly greater than pure PES solution.The temperature must be strictly controlled because of the temperature sensitivity during the membrane forming process.2.PES/HAP monolayer MMMs were prepared and the structure and properties of PES/HAP MMM were also studied.Equilibrium data coincide with the Langmuir model by nonlinear least-squares regression analysis.The solid line in the figure is the Langmuir isotherm that best fit the data.PES/HAP MMM prepared in 60%DMAc aqueous solutions has sponge-like structure and has lower flux and lower adsorption to BSA.Pure water flux of MMM increases with pre-evaporation time extending.The adsorption to BSA reaches maximum when MMM was prepared with no pre-evaporation time.The shape of finger-like pores in the cross section changes from straight to oblique with H20 mass fraction increasing and the pure water flux of MMMs decreases.BSA adsorption capacity of MMMs increases gradually along with the increase of PVP K90 content and reaches the maximum(44.4 mg/g HAP)when 5%PVP is added into the casting solutions.It can be seen that the suitable conditions for preparing monolayer MMMs are as following:Os pre-evaporation time,water coagulation bath and 5%PVP K90 content.3.PES/HAP double layer MMMs were prepared by changing the concentration of the upper PES casting solution and the coagulation bath was 60%DMAc water solution.The thickness of the MMMs increases gradually and the structure of the membrane tends to be more dense with the concentration of the upper PES casting solution increasing.The pure water flux and BSA adsorption capacity of MMMs constantly decreases respectively.The shrinkage rate of the double layer MMMs decreases,while the trend of the mean pore size continues to increase.In comparison,the MMMs concentration of the upper PES casting solution(10%)is used for the next step of the experiment.4.The protein adsorption properties of the membrane were compared based on the above selected monolayer MMM and double layer MMM.The BSA adsorption capacity of pure HAP particle,monolayer MMMs,and double layer membranes firstly increase at the same time and then decrease with the pH value increases.The BSA adsorption capacity of MMMs increases gradually,then becomes stable with the extension of time.About the dynamic adsorption of monolayer MMMs,the dialysis BSA capacity is far bigger than adsorption capacity when a piece of membrane was used.The adsorption capacity is far bigger than dialysis capacity and the adsorption ratio greatly improves when two pieces of membrane were used.For the double layer MMMs,the BSA adsorption capacity is bigger than dialysis one.The adsorption ratio of double layer MMMs is bigger than that of monolayer MMM.The BSA desorption of the MMMs gradually increases with the time extending.BSA capacity of desorption becomes stable and reaches the balance state after 15 hours.The maximum BSA desorption capacity and desorption rate of double layer MMMs are slightly lower than monolayer MMMs.The research results provide evidence on the optimization of preparation for PES/HAP mixed membranes.It also provides a potential application for the MMMs on protein adsorption.