| Affinity membrane separation (AMS) is a new separation technology combining the advantages of both affinity chromatography and membrane technology. Due to high specificity and output of AMS, the fast separation process under lower pressure drop can be obtained. AMS has many practical applications in chemical engineering, biologic engineering, biomedicine and other fields. The main obstacle for AMS is that its binding capacity and adsorption rate are insufficient to take advantage of the improved transport properties of the membrane. The existing methods for improving adsorption capacity and rate are through enhancing ligand content of affinity membrane. But the high ligand density does not always translate into high ligate capacity. In this work, a novel affinity membrane-affinity electromembrane is fabricated and a new affinity separation method-electrical facilitated adsorption is developed. The main research contents are as follows:1. Preparation and Characterization of the affinity electromembraneThe ATP-immobilized affinity electromembrane is fabricated by chemical oxidizing polypyrrole (PPy) onto porous polycarbonate (PC) track-etch membrane using template method. ATP was selected as both ligand and dopant. Because conductive polymer could dope with cation or anion during the procedure of its polymerization, ATP was incorporated into the conducting polymer during polymer synthesis. By controlling the reaction condition the ATP immobilized affinity electromembrane with ideal structure was obtained. The prepared affinity electromembrane has a uniform conductivity value of 1.29×10-4 S/cm. The ATP content of affinity electromembrane is 20.39 mg/g membrane.2. The adsorption property and mechanism of affinity electromembraneHemoglobin (Hb) was chosen as the adsorbate, BSA as the nonspecific testingprotein. Electrical stimulation of the affinity electromembrane was performed using a TD73000 Electrochemical System in a standard three-electrode cell containing Hb solution. The affinity electromembrane acted as the working electrode, and all the electrical stimulation adsorption experiments were processed at constant current condition. The effects of adsorption time, current value, ion strength and initial concentration of Hb, pH of Hb solution on the adsorption capacity were investigated; the adsorption specificity of the affinity electromembrane was examined; and the adsorption mechanism between the Hb and affinity electromembrane was analyzed. The results show: (1) Hb adsorption capacity and rate are greatly facilitated by electrical stimulation, and the adsorption capacity and rate increase with increasing current value; (2) Higher adsorption capacity can be attained at lower ion intensity, higher initial concentration of Hb and neutral Hb solution (pH6.8); (3) the prepared membrane showed good adsorption specificity for Hb; (4) the mechanisms of Hb adsorption on the affinity electromembrane fitted the Freundlich model well.3. Elution and regeneration of the affinity electromembraneThree different solutions were used to elute the Hb adsorbed membrane, and compared the elution result of the adsorbed membrane with different adsorption method (electrical facilitated adsorption and normal adsorption); after adsorbed and eluted the regeneration experiment was executed under cyclic voltammetry condition. The results show: the Hb adsorbed on the membrane can be totally eluted by the Bis-Tris (pH7.0) buffer; dedoped rate of ATP is 70%, redoped rate by electrochemical method could attain 118%.
|
PDF Full Text Request