Design And Application Of Ceramic Membrane In Microfiltration Of Chinese Herb Aqueous Extract

Due to excellent material properties, ceramic membranes have been widely usedin many fields, such as chemical industry, petrifaction, metallurgy, biochemistry,environment, food and pharmacy. However, the market share of ceramic membrane isstill far lower than that of organic membrane because of the high price and scarcekind of ceramic membrane. It could be better only if technologies for preparation andapplication of ceramic membrane were improved. Ceramic membrane separation is apromising technology for the innovation of traditional industry because less energy isdemanded. In refinement of traditional Chinese herb, the general method of extractionwith ethanol can be substituted by membrane microfiltration. In order to obtain thebest efficiency the concept on application-oriented design of ceramic membrane wasproposed and explained in details. The relationship between microfiltrationpermeability and membrane microstructure parameters (pore size, thickness andporosity) for colloid systems was built and verified by microfiltration of bovineserum albumin (BSA) solutions and the aqueous extract of Radix Rehmannia,respectively. On basis of the proposed model, the method of membrane design wassuccessfully used in the refining process of traditional Chinese herb compounds.In chapter 2, the study on theory and model of application-oriented design ofceramic membrane was elaborated. According to the size of disperse phase, theapplication system was classified into three simple systems: solution, colloid andsuspension. In this work, microfiltration of colloid was systematically investigated bythe method of membrane design. A new mathematical relation between permeabilityand microstructure parameters was put forward based on the adsorption-concentrationpolarization model. The active layer of ceramic membrane sintered of cumulateparticles was similar to filtration cake, thus the pure water flux (PWF) can bepredicted by the improved Kozeny-Carman(K-C) equation. The microstructureparameters of ceramic membrane were introduced into the improved model byequation of PWF. Therefore, not only permeate flux could be calculated at varioustime, but the effects of membrane microstructure parameters on steady flux could bepredicted. This model was verified by microfiltration of BSA solutions. It laid afoundation for application-oriented design of ceramic membrane in the refiningprocess of traditional Chinese herb. III摘 要In chapter 3, the adsorption behaviors of organic substances in Chinese herbaqueous extract on ceramic membrane of ZrO2 and Al2O3 were discussed. As for atypical traditional Chinese herb, Radix Rehmannia was selected. The adsorption oforganic substances in the aqueous extract on the surface of ceramic particles obeyedthe Langmuir model. The kinetic parameters (p and x) of adsorption were fitted bygeneral kinetic equation with the experiment data at different pH values. Theparameter of p arrived at the maximum when pH was near the isoelectric point (IEP)of ceramic particles where the adsorption velocity was the highest. And at this pHvalue, fouling was the most serious and the steady flux was the lowest inmicrofiltration of the aqueous extract using ZrO2 membrane. The results ofmicrofiltration showed the good correspondence to adsorption. The parameters ofequilibrium and kinetics obtained by adsorption experiments were necessary forsolving the improved model in this work.In chapter 4, design and application of ceramic membrane in microfiltration of acolloid system were studied. The pore size for microfiltration of BSA solution wasoptimized using the relationship between permeability and membrane microstructureparameters. The suitable one was 90 nm. The ceramic membrane with designed poresize was prepared by sintering method and characterized by gas-liquid displacementmethod. In microfiltration of BSA solutions by the designed ceramic membrane thesteady flux was higher than that by other commercial ones. The theory...