Preparation Of Modified Nylon Affinity Membranes And Their Performance In Lipophilic Endotoxin Removal

Affinity membrane chromatography (AMC) is a new separation technology combining the advantages of affinity chromatography and membrane technology. High specificity and output of AMC, it can get fast separation process under lower pressure drop. AMC has an application prospect in vitro detoxification. A new kind of affinity membrane system was introduced by using nylon membrane filters as support; coating with hydrophilic macromolecules of chitosan, chitosan derivatives and hydroxyethyl cellulose to enhance the hydrophilicity and immobilizing with a reactive dye namely Cibacron Blue F3GA as ligand, for bilirubin removal.Physical and chemical properties of the affinity membranes were determined. Scanning electronic microscope (SEM) displays the uniform pore structure and pore size distribution, tensile strength revealed good mechanical property, and hydraulic analysis shows fairly large pore size, porosity and pure water permeable flux. FTIR analysis indicates covalent couple of hydrophilic layers and dye release determines the covalent bond of the ligand immobilization. All these characteristics including a hydrophilic layer contents up to 91.6 mg/g and ligand content over 90 μmol/g are suggesting the further applications of the membranes.Effects on the bilirubin adsorption of the membranes were investigated. The adsorption capacity showed to increase with increasing the ligand content and initial bilirubin concentration. It first decreased and then increased of the capacity with the increasing of ionic strength. And first increased then decreased with increasing the pH value of the adsorption medium and a peak appeared at pH range 6.0 to 7.0. The adsorption capacity and the rate increased with the increasing of temperature. And at 37 ℃, the adsorption condition was optimized at the experimental range. Competitive adsorption of the membranes was also investigated. The effect of bovine serum albumin (BSA) might be prononce, while the membranes could still get adsorption capacities up to 20 mg/g even at high molar ratio (50:1) of BSA to bilirubin. And at the molar ratio less than 0.8, the membranes could achieve a strong competitive ability to adsorb bilirubin from BSA-bilirubin complex solution.The adsorption kinetics and isotherm were studied in this dissertation. The adsorption processes were likely to display (pseudo) first-order kinetics in the prior 50 min and a (pseudo) second-order kinetic in the posterior adsorption. The isotherm fitted the Langmuir-Freundlich model well, which indicated a favorable adsorption and the bilirubin adsorption of the membranes were positive cooperated.The breakthrough behaviors of the membrane stacks were studied. The membrane stacks were easily breakthrough at high feeding rate and initial bilirubin concentration. The ligand utilization ratio and the clearance of bilirubin increased with increasing the initial bilirubin concentration, while decreased with the increasing of the feeding rate. The adsorbed bilirubin could be eluted by simply feeding with NaOH aqueous and BSA solution. Regeneration and reuse of the membranes were performed. The regeneration membranes showed good mechanical property and high adsorption capacity. All these suggested a biomedical application prospect.