Preparation And Characteristics Research Of Affinity Membrane Based On Anodic Aluminum Oxide (AAO) Membrane

An ideal affinity membrane should own well uniformities.However,most existing microporous membranes were manufactured by phase-inversion method. Membranes produced from this method generally have wide pore size distribution and some thickness variation.These nonunitbrmites may severely degrade the performance of affinity membranes.In this paper,chitosan(CS)-anodic aluminum oxide(AAO) composite membrane and silica(SiO₂)-AAO composite membrane with excellent uniformities,such as narrowpore size and porosity distribution,aswell as uniform membrane thickness,were fabricated,for the first time.Then,through the activation method to coupling different ligands for obtain new model of affinity membrane.The characteristics and adsorption mechanism of affinity membrane were studied.The main research contents are as follows:1.Modification of membrane materials.Select AAO membranes as a matrix,use biological macromolecule of chitosan(CS) and inorganic silica(SiO₂) as modified materials,respectively,by chemical coupling and sol-gel method to obtain organic-inorganic composite membrane(CS-AAO) and inorganic-inorganic composite membrane(SiO₂-AAO).After ligand coupling,the affinity membrane of Cu²⁺-attached and lysine(Lys)-attached were fabricated.The morphologies of composite membrane were observed by SEM,TEM.And,composite membrane retained the morphology of ultra-uniform structure of blank AAO membrane.The contents of CS and Cu²⁺ of Cu²⁺-attached affinity membranes were～49.7 and 27.15mg/g membrane;the contents of Lys of Lys-attached affinity membranes were 5.57 mg/g membrane.2.Adsorption performance of affinity membrane.The Cu²⁺-attached affinity membranes were used to recover a model protein,hemoglobin,from hemoglobin-phosphate solution(batch manner) and from the hemolysate(dynamic manner).The Lys-attached affinity membranes were used to removal lipophilic toxins Bilirubin(BR),through the static adsorption and dynamic adsorption to study the adsorption performance of affinity membrane.Adsorption experiments indicated that: (1) The non-specific adsorption capacity of two different composite membrane reduced significantly;(2) The prepared affinity membranes showed good adsorption specificity for adsorbate;the adsorption capacity decreased with increasing the concentration of NaCl and increased with increasing temperature;(3) Cu²⁺-attached affinity membrane can be attained maximum adsorption from aqueous solutions is observed at Hb pI(pI of Hb:6.8) and significantly lower adsorption capacities were obtained with all affinity membranes in more acidic and in more alkaline pH regions; (4) The adsorption capacity of Lys-attached affinity membrane decreased with increasing the concentration of BSA;(5) The dynamic capacities smaller than the corresponding static adsorption capacities,because some adsorptive capacity remains unused mainly due to slow sorption kinetics and resistance from mass transport rate processes.3.Adsorption mechanisms of affinity membrane.The mechanisms of Hb adsorption on the Cu²⁺-attached affinity membranes fitted the Freundlich model well, and R²=1.The mechanisms of BR adsorption on the Lys-attached affinity membranes fitted the Langmuir model well,and R²=0.9937,q_max=18.08 mg/g membrane.4.Elution and Regeneration of affinity membrane.The adsorbed Hb on the Cu²⁺-attached affinity membranes was desorbed up to 91.2%with 0.5 M imidazole aqueous solution as the desorption agent.The BR adsorbed on Lys-attached affinity membranes can be eluted by the NaOH and BSA,and the elute rate was 95%.In order to show the reusability of the affinity membranes,the adsorption-elution cycle was repeated five times using the same affinity membranes.The adsorption capacity of both Cu²⁺-attached affinity membranes and Lys-attached affinity membranes decrease only 6%.