Studies On Membrane Fouling In Clarification Of Traditional Chinese Medicine Extract Using Ceramic Membrane

To reduce membrane fouling and promote permeation flux during the applicationof ceramic membranes in clarification of traditional Chinese medicine extract, factorsinfluencing permeation flux, pollution mechanism and cleaning methods weresystematically studied in this thesis. Metropolis aqueous extract, a kind of typical traditional Chinese medicine extract,was chosen as the experiment system. Permeation flux influenced with differentmembrane parameters including pore size, membrane material and support werecompared and the influences of TMP(trans-membrane pressure), concentration ofaqueous extract and CVF(cross velocity of feed)were investigated by experiments inthe same time. The appropriate membrane is Al2O3 membrane with pore size of0.2μm and its permeate flux is about 200L/m2.h at the TMP of 0.15MPa,CVF of 5m/s,temperature of 27℃. With the increase of the CVF and TMP, the steady fluxincreased. And the permeate flux decreased more quickly when the CVF was smallerand the TMP was higher. The proportion of different resistances in the process was calculated with theresistance model. It was concluded that the key factors leading to the decrease ofpermeation flux were the resistance of filter cake and gel; the proportion of totalresistances is 80 percent. The effects of membrane material, trans-membrane pressure,concentration of aqueous extract, CVF on the fouling mechanism were investigated. Most of ingredients leading to membrane fouling were polysaccharide and fewmaterial including inorganic elements, which mainly deposited on the membranesurface. And the result can be confirmed by analyzing with infra-red spectrum (IRspectrum), ultraviolet spectrophotometer, ICP, SEM and EDX etc. The cleaningmethod was given by comparing the effect of various cleaning agents on the recoveryof permeate flux. The effective cleaning method includes: pursing the apparatus withwater, cleaning the membrane with hot water at the temperature of 60℃ for 10min,cleaning the membrane with the 2%NaClO solution for 1h, and then pursing theapparatus with water until the pH value of the permeate was about 7 .