| According to membrane pore size or molecular weight cut-off (MWCO), ultramicro-porous filtration can be divided to ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). In recent years, membrane separation processes have found wide applications in industry and research laboratories, the development of quantitative predictive models are importance for the successful application of membrane filtration. The primary difference of UF, NF and RO is membrane pore size, and the common defects of the existing models are that they do not consider the change of "meaningful membrane pore size" and therefore, cannot be compatible with each other, in part because of neglecting the interface between solution and membrane. To clarify the real filtrate progress in ultramicro-porous, this study carried out research on reviews and experiments of ultramicro-porous filtration theory.In the filtrate progress, the interface between phases is generated as two phases intersect each other, in which the molecules of two phases are permeating mutually and form a non-uniform layer the existance of interface layer caused actual membrane pores are "samller" and narrowed the solution flow path within pores. Based on the interfacial narrowed pores effect, the ultramicro-porous filtration can be divided into three filtrating model,①primary filtrated model: molecular sieving for big pore UF,②secondary filtrated model:molecular sieving and interface peanetrate for RO and small pore NF, and③) tertiary filtrated model:molecular sieving, interfacial narrowed-pores filtrate and interface peanetrate for small pores UF and big pores NF.Panax notoginseng saponins (PNS) was selected as experimental subject. Notoginsenoside Rl(Rl), Ginsenoside Rgl (Rgl), Ginsenoside Rbl (Rbl) and Ginsenoside Rd (Rd), four main components of PNS, have similar structure and molecular size, but different surface activities. Using series of membranes with different pore sizes, the transmittances of main components of PNS water solution were detected. Using the interfacial thickness difference of the four solute (1.8nm) as evaluation indexes, the values of tendency constan (b), interfacial thickness(Ds) and velocity eqution index (N) of Rl, Rgl, Rbl and Rd were calculated the by using Maple software with data of membrane radius and transmittances and were verified by Matlab R2011b which evaluated by correlation coefficients (r). Results show that Ds of main components of PNS were varied from1.96nm to3.90nm, b varied from0.71to1.95, and N was6. According to the whole method mentioned above, the fitting model of interfacial narrowed pores effect was established to analyze the interfacial characteristics for solutes.With the solution properties affected by organic solvents, surfactants, inorganic salt, tempreture and pH, the solution surface tension, solute transmittance and interfacial composition were changed correspondingly. As the surface tension decreasing, conversely the solutes tranmittance and the proportion of Rbl and Rd were increased. Therefore, under the guidance of interfacial narrowed pores effect, analyzing the relevance among of influened factors, surface tension and tranmittance to get the purposefully retain or reject results by changing the liquid-solid interfacial properties.in the practical application,1,2-propylene glycol was chosen as cosolvent to reduce the interfacial effect and improve borneol solubility and tranmittance of Bingqi injection. Moreover, the solubility and transmittance of baicalin were increased by adjusting pH to7.5, and the10KDa membrane was suitable for Tongluoqingnao powder injection with little loss of baicalin and high rejection of endotoxin.The interfacial composition and thickness of various solutes are different in the same liquid-solid system, and the start inspiring results achieved by ultramicropore will be helpful in revealing the essence of interface effect in nature.Meanwhile, the filtration theory of interface-effect did not challenge the molecular sieving theory, but instead attempt to modify it. The interfacial narrowed-pore effect may exert profound influence on the development of the whole membrane technology and provides a guideline for the application of membrane separation including selecting proper membrane pore size and material, membrane modification, designing specific membrane material and extending the fields of membrane application etc. In addition, the results develop here would be of great value to the future studies on interface by ultramicro-pore method. |
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