Study On Separation Performance Of Ceramic Membrane In Microfiltration Of Protein System

Chinese herb aqueous extract (CHAE)is a very complex system. It contains particles, colloid and compounds with the molecular weight from 100Da to several million Da. During membrane filtration, the foulants are mainly composed of protein, carbohydrate (such as polysaccharides, cellulose, hemicelluloses, amylum, pectin and lignin) and solid particles. In order to analyze the key foulant, the microfiltration of a simple binary system (BSA/Dextran70) and the adsorption of the foulant on the membrane materials were studied. By introducing the property of materials into the"adsorption-concentration polarization"model, an improved model was applied to design the optimal membrane and predict the permeate flux in actual CHAE system (magnolia official aqueous extract).In chapter 2, the flux behavior was examined during cross-flow microfiltration (MF) of the simulative binary system (BSA/Dextran70) using three ceramic membranes (Mean pore size:0.05μm,0.20μm and 0.50μm). Analysis of the results revealed that the separation performances of these membranes were controlled by the gel-layer on the membrane surface formed during the filtration process and the BSA was the key foulant, the larger the ratio BSA was, the more serious the fouling was. The fouling using the ceramic membrane with pore size of 500nm was the most serious.In chapter 3, the static adsorption behaviors of BSA on Al2O3, ZrO2 and TiO2 materials in form of powder or disc membranes were examined. The equilibrium parameters of Langmuir and Freundlich models were obtained. The results declared that the equilibrium adsorbing capacity of the powder materials was 2.75×10-5kg·m-2, 1.50×10-5 kg·m-2 and 1.20×10-5 kg·m-2 for Al2O3, ZrO2 and TiO2 powders respectively; and the equilibrium adsorbing capacity was 1.5×10-4kg·m-2, 5.0×10-4kg·m-2 and 1.0×10-4kg·m-2 for disc membranes respectively. According to the correlation coefficient R, the adsorption behavior of BSA on powder obeyed the Freundlich model, but the adsorption behavior of BSA on membrane obeyed the Langmuir model.