Preparation And Performance Study Of Bilayer Mixed Matrix Membrane For Hemodialysis

Currently,more than 2 million ESRD patients worldwide rely on maintenance hemodialysis to extend their lives.Although traditional hemodialysis improves the survival rate of patients,its intermittent dialysis treatment is not effective and restricts the freedom of patients during the treatment process.Therefore,it is not a perfect treatment plan.The miniaturization of traditional hemodialysis equipment into a wearable artificial kidney(WAK)is a new development direction.Because WAK can better simulate the function of the human kidneys,the quality of life of ESRD patients can be further improved through frequent and continuous dialysis,thereby bringing more autonomy to patients.Similar to traditional hemodialysis,the WAK device also has a relatively low removal rate of middle molecular toxins.Therefore,WAK needs an efficient dialysate purification system to remove toxins in the dialysate in time.In this study,hydroxyapatite(HAP)and natural volcanic mud were separately introduced into the separation membrane to prepare a double-layer mixed matrix membrane.Then in the dialyzer,the PES/HAP double-layer mixed matrix membrane improves the removal rate of mid-molecular toxins through combining diffusion and adsorption.In this process,the PES/mud double-layer mixed matrix membrane is used in the dialysate circulation system to remove toxins in the dialysate.HAP was hydrophobically modified by hexadecyltrimethoxysilane,g-HAP-4 and g-HAP-12 were prepared by controlling the reaction time.They were separately blended into the PES lower layer casting liquid,and the double-layer mixed matrix film was prepared by the phase inversion method.The static adsorption capacity of PES/HAP,PES/g-HAP-4 and PES/g-HAP-12 to lysozyme gradually increased to 4.9mg/g,6.7 mg/g and 8.4 mg/g,respectively.In the simulated dialysis experiment,the PES/g-HAP-12 double-layer mixed matrix membrane has a clearance rate of 58.4%for lysozyme,which is significantly higher than that of 40.6%of a single-layer membrane.Because the upper layer of the single-layer membrane and the double-layer membrane are composed of PES and PVP and PVP gives the membrane good hydrophilicity,all membranes show good blood compatibility.Volcanic mud has strong adsorption capacity for urea and lysozyme.Through testing,it was found that the volcanic mud does not contain heavy metal elements such as Pb,Hg,Cd,etc.,which are harmful to the human body.Therefore the volcanic mud can be used as an adsorbent for the purification of dialysate.The volcanic mud of different quality is blended into the lower layer casting liquid,and the three PES/volcanic mud double-layer mixed matrix membranes prepared by the phase inversion method have the volcanic mud content of 29.6 wt%,37.3 wt%and 46.6 wt%.It's found that the membrane with the highest loading of volcanic mud has the best adsorption performance in the experiment.In the static adsorption experiment,its adsorption capacity for urea and lysozyme were 0.120 mg/cm~2 and 0.055 mg/cm~2,respectively;in the ultrafiltration adsorption experiment,its adsorption capacity for urea and lysozyme were 0.205 mg/cm~2 and 0.241 mg/cm~2 respectively.