Preperation Of Highly Efficient Carbonbased Gel Adsorbents And Its Coordination With Dialysis Membranes For The Removal Of Protein-bound Toxins-indoxyl Sulfate

Chronic kidney disease is a disease caused by the inability to effectively eliminate toxins due to the disruption of kidney structure and function,which poses a great danger to human health.Due to the limitation of kidney donor and cost,blood purification technology such as hemodialysis and hemoperfusion are currently effective clinical treatments for chronic kidney disease.In the blood of patients with chronic kidney disease,a high accumulation of protein-bound uremic toxins represented by indoxyl sulfate（IS）is observed.Due to their hydrophobicity and binding to human serum albumin（HSA）,these toxins are difficult to be removed by conventional hemodialysis techniques.The current treatment with the highest clearance of protein-bound uremic toxins is hemoperfusion,and common adsorbents include activated carbon,zeolites and metal-organic framework materials.However,these adsorbents have disadvantages such as poor biocompatibility,cumbersome preparation process and dissolution in the physiological environment.Therefore,it remains a challenge to develop a porous,safe,low-cost,efficient and easily recoverable adsorbent,thus further enhancing the clearance of protein-bound uremic toxins,together with the application of adsorbents in combination with dialysis membranes in the field of hemodialysis to achieve the miniaturization and light weight of dialysis equipment.These will open up a new avenue for the development of portable artificial kidneys,which are essential for the treatment of patients with chronic kidney disease and also of profound importance to the field of blood purification.1.We modified activated carbon（AC）by nitric acid hydrothermal method to prepare 60-AC,and mixed with sodium alginate（SA）.SA/AC microspheres were prepared using calcium chloride（CaCl₂）as coagulation bath combined with freeze drying technology.By regulating the mass ratio of 60-AC to SA,we obtained three types of microspheres,among which SA/AC 1:4 had the best adsorption performance.The adsorption of IS by SA/AC 4:1,SA/AC 1:1 and SA/AC 1:4 was in accordance with the Freundlich model,and the maximum adsorption capacity of IS at an initial concentration of 600 mg/L was 48.18 mg/g,97.27 mg/g and 176.81 mg/g,respectively.The whole adsorption process reached equilibrium within 10 h,and the adsorption kinetics accorded with the pseudo-second-order kinetic model.The analysis of the toxin removal mechanism shown that the adsorption of IS on 60-AC and SA/AC was mainly controlled by van der Waals interaction,hydrophobic interaction and hydrogen bonding interaction.The SA/AC microspheres had good adsorption performance and was easy to be recovered,achieving the effect of regeneration of dialysate,which could have good application in the field of portable artificial kidney.2.We proposed a novel strategy of thin-film nanofibrous composite（TNFC）dialysis membrane combined with reduced graphene oxide（rGO）aerogel adsorbents for clinical removal of IS as well as high retention of proteins.To further improve the removal rate of the adsorbent,we used a medium hydrothermal method following by freeze-drying treatment to obtain the rGO aerogel adsorbents.It exhibited excellent adsorption for IS with a maximum adsorption capacity of69.40 mg/g throughπ-πinteraction and hydrogen bonding interaction based on Langmuir isotherm models.Time-dependent absorption experiments showed that it reached adsorption equilibrium within 4 h,which was matched with the hemodialysis time.Subsequently TFNC membrane with good selectivity and permeability were prepared by a combination of electrospinning and coating-reaction method.The coordination was significantly exhibited by introducing rGO aerogel blocks into the dialysate for absorbing the diffused free IS during hemodialysis.Taking the advantages of the TFNC dialysis membrane and the rGO aerogel,the volume of dialysate for hemodialysis was only one-tenth of that without adsorbent blocks but with very comparable dialysis performance（the clearance of IS at 51.8%and the retention of HSA over 98%）,which could lighten conventional hemodialysis effectively and be benefit to realize the miniaturization of the dialysis equipment.Therefore,the coordination of the TFNC dialysis membrane and rGO aerogel adsorbents would open a new path for the development of portable artificial kidney.