Affinity Modification Of Microporous Polypropylene Membrane And Preparation Of Immobilized Metal Affinity Membrane For Bioseparations

Due to the high mechanical property and chemical stability, microporous PP (Polypropylene) membrane was selected as support matrix. The surface of the PP membrane was modified by oxygen-plasma modification technique under low temperature and by plasma induced-grafting method for facilitating the preparation of affinity membrane. After modification, the active groups could be grafted on the surface of membrane, and the hydrophilicity of PP membrane was improved greatly, which were favorable for affinity membrane preparation. The metal ions were selected as affinity ligands, and a series of immobilized metal ions affinity membranes were prepared. The adsorption equilibrium and dynamics of the prepared affinity membranes were evaluated, and the membranes were applied in biomolecule separation and purification process. Several kinds of electrical capacity coupling plasma-discharge apparatuses for induced-polymerization process had been designed to study the influence of structure parameters of the equipment on discharge performance. The result showed that the suitable parameters of the apparatus were: 7Onini in tube diameter and 31 cm in tube length. The distance between two electrodes should be as close as possibLe. Low temperature oxygen plasma technique was applied in the modification of microporous PP membrane. The SEM showed that the surface of the membrane was etched by oxygen plasma. Under the conditions of low discharge power and short time, the etching was only taken place on the surface of PP membrane, and fragment peeling from the membrane surface was not observed. From- IR spectra and XPS analysis, the polar groups, such as aldehyde, hydroxyl, carboxyl as well as ester groups, had been formed on the surface of PP membrane after low temperature oxygen plasma treatment, among them, the dominated active groups were -OH. The effects of treatment time and discharge-power on adsorption of lysozyme on the affinity membrane were examined and the results showed that, when discharge- 11 power 60?0w and the treatment time 30?Omin, the adsorption capacity of lysozyme on the affinity membrane reached the highest. Four types of metal ions, Fe3~, Ni2~, Cu2~ and Zn2~, were used to form chalets on the surface of plasma modified membranes respectively and the resulted affinity membranes were evaluated by adsorption-desorption experiments of lysozyme. The experimental results showed that adsorption capacity of the membranes with Ni2~ was the highest, followed by Cu2~ and Fe3~, and the adsorption capacity of Zn2~ membrane was the lowest. The repeated use of metal ion affinity membrane was also examined, and the experimental results showed that the adsorption capacity was much lower in the second adsorption-desorption cycle than that in first cycle, but remained stable after the third cycle. A kinetic model for bio-m,olecule adsorption on to stacked flat-sheet affinity membrane was proposed based on adsorption equilibrium and kinetics as well as mass balance equation. The influence of dispersion coefficient, feed concentration, forward direction rate constant, membrane thickness, ligand concentration and flow rate on the breakthrough curves were studied. And a set of data from literature was used to verit~?the reliability of the model. The PP hollow fiber affinity membranes were also prepared by oxygen plasma technique. The PP membrane was...