The filter membranes are easily contaminated, such as the blocked pores phenomenon or appearance of the formed adhesion layer. For the separation of traditional Chinese medicine, it is necessary to maintain the pore diameter of the medicine in the range of 1 to 5 nanometers.
Then, the medicine should be treated by medium filtration method, like the filter paper or talcum powder. The efficiency and quality of the separation can be greatly improved.
Meanwhile, the filter membrane could also be well protected. Moreover, to effectively alleviate the concentration polarization, the solute concentration on the surface of the membrane should be reduced. In the process of solving this problem, there are two kinds of methods to reduce the viscosity of the Chinese medicine liquid, magnetic stirring, and pulse flow method.