Method for preparing pvdf nanofiber chromatography membrane

Abstract

The application discloses a PVDF nanofiber chromatographic membrane preparation method, and relates to the technical field of membranes, and comprises the following steps: a nanofiber membrane is formed by stacking first electrospinning nanofibers and second electrospinning nanofibers with different diameters; and hydrophilic modification is performed on the fiber surface of the nanofiber membrane through in-situ radical polymerization.Compared with the prior art, the application has the beneficial effects that: the design of stacking electrospinning nanofibers with different diameters optimizes the micropores of the nanofiber membrane to have asymmetry, so that the filtration flux and the number of nanocarriers of the nanofiber membrane are improved; and after the surface of the nanofiber membrane is subjected to hydrophilic modification, when the nanofiber membrane is used as a chromatographic membrane for chromatographic analysis and chromatographic separation processes, the adsorption capacity, separation efficiency and separation purity of the chromatographic membrane are all significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of membrane, in particular to a preparation method of PVDF nanofiber chromatography membrane. BACKGROUND

[0002] Polyvinylidene fluoride (PVDF) has the characteristics of large mechanical strength, high temperature resistance, good chemical stability and biocompatibility, so the manufactured microporous membrane has been widely applied and developed, such as bacteria removal filtration in biopharmaceutical industry, membrane bioreactor in water reuse, and chromatography medium with ion exchange performance.

[0003] Chromatography membrane is a key material in chromatographic analysis and chromatographic separation process, at present, there are still deficiencies in the adsorption capacity, separation efficiency and separation purity of chromatography membrane.

[0004] Therefore, it is necessary to develop a preparation method of PVDF nanofiber chromatography membrane to overcome the above deficiencies. SUMMARY

[0005] The present application aims to disclose a preparation method of PVDF nanofiber chromatography membrane, which forms a nanofiber membrane by optimizing the design of stacking electrospun nanofibers with different diameters, realizes the improvement of the filtration flux and the number of nanofiber membranes, and then prepares a nanofiber chromatography membrane through hydrophilic modification.

[0006] To achieve the above-mentioned application purposes, the present application provides a preparation method of PVDF nanofiber chromatography membrane, which comprises the following steps:

[0007] Stacking the first electrospun nanofiber and the second electrospun nanofiber with different diameters to form a nanofiber membrane;

[0008] Performing hydrophilic modification on the fiber surface of the nanofiber membrane through in-situ free radical polymerization.

[0009] Preferably, the hydrophilic modification comprises the following steps:

[0010] Using a hydroxyl functional alkyl acrylate compound as a monomer, a difunctional acrylate compound as a crosslinking agent, a peroxide compound as an initiation catalyst, and an ethanol aqueous solution as a polymerization solvent to prepare a polymerization and crosslinking solution;

[0011] The nanofiber membrane is subjected to in-situ free radical polymerization in the polymerization and crosslinking solution for 5-30 minutes.

[0012] Preferably, the hydroxyl functional alkyl acrylate compound is one or more mixtures of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate;

[0013] The difunctional acrylate compound is one or more mixtures of triethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and propylene glycol di(meth)acrylate.

[0014] The peroxyl compound is one or more mixtures of ammonium persulfate, t-butyl peroxybenzoate, and benzoyl peroxide.

[0015] Preferably, the hydroxyl functional alkyl acrylate compound is hydroxypropyl acrylate.

[0016] The difunctional acrylate compound is triethylene glycol dimethacrylate.

[0017] The peroxyl compound is ammonium persulfate.

[0018] The reaction formula of the in-situ radical polymerization is:

[0019]

[0020] Preferably, the monomer concentration is 3%-10%, the crosslinking agent concentration is 0.5%-1.5%, and the concentration of the initiation catalyst is 0.5%-1.5%.

[0021] Preferably, the diameter of the first electrospun nanofiber is equal to 2 times the diameter of the second electrospun nanofiber.

[0022] Preferably, the first electrospun nanofiber and the second electrospun nanofiber are layered and stacked to form a nanofiber membrane.

[0023] Preferably, the first electrospun nanofiber and the second electrospun nanofiber are blended and stacked to form a nanofiber membrane.

[0024] Preferably, the method further comprises the following steps:

[0025] The PVDF material is dissolved in a mixed solvent of dimethylformamide and acetone at a volume ratio of 1:1, and a spinning solution with a mass content of 5%-12% is prepared;

[0026] The spinning solution is prepared into first electrospinning nanofibers and second electrospinning nanofibers through an electrospinning process, the first electrospinning nanofibers are prepared from a first spinneret, the second electrospinning nanofibers are prepared from a second spinneret, the electrospinning voltage is 24000V-28000V, the spinning distance is 150mm-200mm, the production speed of the nanofiber membrane is 400mm / min, the first spinneret and the second spinneret adopt stainless steel needles of different models for medical injectors, and the model of the stainless steel needle for the medical injector is No. 7-No. 14.

[0027] Preferably, the model of the spinneret of the first spinneret is a stainless steel No. 12 needle for medical injectors, the arrangement mode of the spinneret of the first spinneret is 4 rows*10 per row, and the first spinneret uses a spinning solution with a mass content of 10%;

[0028] The model of the spinneret of the second spinneret is a stainless steel No. 9 needle for medical injectors, the arrangement mode of the spinneret of the second spinneret is 4 rows*10 per row, and the second spinneret uses a spinning solution with a mass content of 7%.

[0029] Compared with the prior art, the beneficial effects of the present application are:

[0030] The design of the accumulation of electrospinning nanofibers with different diameters optimizes the micropores of the nanofiber membrane to have asymmetry, so that the filtration flux and the number of nanocarriers of the nanofiber membrane are improved; after the surface of the nanofiber membrane is hydrophilically modified, when the nanofiber membrane is used as a chromatographic membrane for chromatographic analysis and chromatographic separation process, the adsorption capacity, separation efficiency and separation purity of the chromatographic membrane are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a sectional view of the PVDF nanofiber membrane of the present application.

[0032] Figure 2 It is a flow comparison graph of the nanofiber membrane of the present application and the existing nanofiber membrane.

[0033] Figure 3 It is a flow comparison graph of the nanofiber membrane of the present application and the existing nanofiber membrane after filtering an aqueous solution of ferric sol.

[0034] Figure 4 It is a spinneret distribution graph of the electrospinning of the present application.

[0035] Figure 5 It is a winding roller circuit graph of the nanofiber membrane of the present application.

[0036] Figure 6 It is a protein adsorption capacity curve per unit volume of the modified PVDF chromatographic membrane of the present application at different pH values.

[0037] Figure 7 Figure 8 is a curve of the change of the adsorption capacity of the PVDF chromatographic membrane to lysozyme protein at different flow rates of the present application.

[0038] Figure 8 Figure 9 is the UV A280 absorption curve and the change curve of the solution ionic strength detected by the Biologic LP instrument of the present application.

[0039] Figure 9 Figure 10 is the SDS electrophoretogram of the present application.

[0040] Wherein, 1, the first nanofiber layer; 2, the second nanofiber layer; 3, the third nanofiber layer; 4, the fourth nanofiber layer; 5, the electrospinning spinneret; 51, the first spinneret; 52, the second spinneret. DETAILED DESCRIPTION

[0041] The present application will be described in detail below with reference to the various embodiments shown in the drawings, but it should be noted that these embodiments are not a limitation on the present application, and equivalent transformations or substitutions of function, method, or structure made by those of ordinary skill in the art based on these embodiments are within the scope of the present application.

[0042] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0043] The specific implementation process of the present application will be described below through multiple embodiments.

[0044] Example I:

[0045] Embodiment one provides a PVDF nanofiber chromatographic membrane preparation method, comprising the following steps:

[0046] Step S1: forming a nanofiber membrane by stacking first electrospun nanofibers and second electrospun nanofibers of different diameters; specifically, the existing electrospinning process uses several stainless steel needles of the same model for spinning, and finally forms a nanofiber membrane with substantially the same diameter. The pores of such a membrane have symmetry, that is, the pores of each layer of the nanofiber membrane are substantially consistent. Such a membrane is called a symmetric pore nanofiber membrane, which results in insufficient filtration flux and nanocarrier number of the current symmetric pore nanofiber membrane. To further improve the filtration flux and nanocarrier number of the nanofiber membrane, the present embodiment uses first electrospun nanofibers and second electrospun nanofibers of different diameters to form an asymmetric pore nanofiber membrane, which has a higher filtration flux and a larger nanocarrier number than the symmetric pore nanofiber membrane.

[0047] It should be further noted that the stacking of the first electrospun nanofibers and the second electrospun nanofibers has two forms. One is that the first electrospun nanofibers and the second electrospun nanofibers are stacked in layers to form a nanofiber membrane. In this stacking form, the diameters of the electrospun nanofibers in the same layer are substantially consistent. Several layers of electrospun nanofibers are stacked to form a nanofiber membrane. According to the requirements of the nanofiber membrane for filtration flux and nanocarrier number, electrospun nanofibers of different diameters are stacked in layers, as shown in Figure 1 The nanofiber membrane includes a first nanofiber layer 1, a second nanofiber layer 2, a third nanofiber layer 3, and a fourth nanofiber layer 4. The first nanofiber layer 1 and the third nanofiber layer 3 are respectively stacked by the first electrospun nanofibers. The second nanofiber layer 2 and the fourth nanofiber layer 4 are respectively stacked by the second electrospun nanofibers. The second is that the first electrospun nanofibers and the second electrospun nanofibers are mixed and stacked to form a nanofiber membrane. In this stacking form, the diameters of the electrospun nanofibers in the same layer are not the same. More accurately, in this stacking form, there is no obvious layered structure, that is, different diameters of electrospun nanofibers are mixed and formed in a certain proportion. The specific mixing ratio is closely related to the required filtration flux and nanocarrier number. For example, the mixing ratio of the first electrospun nanofibers and the second electrospun nanofibers is 7:3-3:7. By mixing and stacking electrospun nanofibers of different diameters, the porosity and void size can be controlled, the specific surface area and mechanical strength can be controlled, and thus the filtration flux and nanocarrier number can be controlled.

[0048] The following is a further description with the diameter of the first electrospun nanofibers being twice the diameter of the second electrospun nanofibers, as shown in Figure 1The thicknesses of the first nanofiber layer 1 and the third nanofiber layer 3 are 5 μm and the diameter of the first electrospun nanofiber is 1.0 μm; the thicknesses of the second nanofiber layer 2 are 5 μm and the thicknesses of the fourth nanofiber layer 4 are 10 μm-20 μm and the diameter of the second electrospun nanofiber is 0.5 μm.

[0049] Referring to Table 1, which shows the layered structure and performance parameters of the asymmetric nanofiber membrane, the asymmetric nanofiber membrane numbered 1 includes a first nanofiber layer 1, a second nanofiber layer 2, a third nanofiber layer 3, and a fourth nanofiber layer 4. The first nanofiber layer 1 and the third nanofiber layer 3 are each formed by stacking first electrospun nanofibers with a diameter of 1 μm, and their stacking thicknesses are both 5 μm. The second nanofiber layer 2 and the fourth nanofiber layer 4 are each formed by stacking second electrospun nanofibers with a diameter of 0.5 μm, wherein the stacking thickness of the second nanofiber layer 2 is 5 μm, and the fourth nanofiber layer 4... The stacking thickness of layer 2 is 20 μm, and the total thickness of the asymmetric nanofiber membrane with serial number 1 is 31 μm. The total thickness is slightly less than the sum of the thicknesses of each layer because the fibers between the layers intersect and the stacking material is a loose material. The difference between the asymmetric nanofiber membrane with serial number 1 and the asymmetric nanofiber membrane with serial number 2 is that the thickness of the fourth fiber nanolayer 4 is 15 μm, and the total thickness of the asymmetric nanofiber membrane with serial number 2 is 28 μm. The difference between the asymmetric nanofiber membrane with serial number 1 and the asymmetric nanofiber membrane with serial number 3 is that the thickness of the fourth fiber nanolayer 4 is 10 μm, and the total thickness of the asymmetric nanofiber membrane with serial number 3 is 25 μm.

[0050] Table 1. Layered structure and performance parameters of asymmetric nanofiber membranes

[0051]

[0052] See Figure 2 The pure water flow rates of the asymmetric nanofiber membrane and the symmetric nanofiber membrane (number 1) were compared. The bubble points of both the asymmetric and symmetric nanofiber membranes after ethanol wetting were 10 kPa-12 kPa. Figure 2The results show that the pure water flow of the asymmetric nanofiber membrane is 85% higher than that of the symmetric nanofiber membrane at a pressure of 1.5 KPa; the pure water flow of the asymmetric nanofiber membrane is 92% higher than that of the symmetric nanofiber membrane at a pressure of 3 KPa; the pure water flow of the asymmetric nanofiber membrane is 80% higher than that of the symmetric nanofiber membrane at a pressure of 5 KPa; the pure water flow of the asymmetric nanofiber membrane is 67% higher than that of the symmetric nanofiber membrane at a pressure of 10 KPa; and the pure water flow of the asymmetric nanofiber membrane is 59% higher than that of the symmetric nanofiber membrane at a pressure of 15 KPa. It can be seen that the asymmetric nanofiber membrane of the embodiment has a larger pure water flow at the same pressure, which can represent that the asymmetric nanofiber membrane of the embodiment has a higher porosity.

[0053] Referring to Figure 3 , the asymmetric nanofiber membrane with serial number 1 and the symmetric nanofiber membrane were selected to compare the flow attenuation of the iron sol aqueous solution, and the water bubble point of the asymmetric nanofiber membrane and the symmetric nanofiber membrane after ethanol wetting was 10 KPa-12 KPa. The average flow of the asymmetric nanofiber membrane at four different positions was taken as the basis, and the average flow of the symmetric nanofiber membrane at four different positions was taken as the basis. From Figure 3 The results show that when 5 L of the iron sol aqueous solution is filtered, the flow of the asymmetric nanofiber membrane and the symmetric nanofiber membrane is 1300 and 680 respectively, and the flow of the symmetric nanofiber membrane is 52% of that of the asymmetric nanofiber membrane; when 20 L of the iron sol aqueous solution is filtered, the flow of the asymmetric nanofiber membrane and the symmetric nanofiber membrane is 970 and 530 respectively, and the flow of the symmetric nanofiber membrane is 55% of that of the asymmetric nanofiber membrane; when 35 L of the iron sol aqueous solution is filtered, the flow of the asymmetric nanofiber membrane and the symmetric nanofiber membrane is 788 and 432 respectively, and the flow of the symmetric nanofiber membrane is 55% of that of the asymmetric nanofiber membrane; and when 50 L of the iron sol aqueous solution is filtered, the flow of the asymmetric nanofiber membrane and the symmetric nanofiber membrane is 593 and 294 respectively, and the flow of the symmetric nanofiber membrane is 50% of that of the asymmetric nanofiber membrane. It can be seen that after the same amount of impurities is intercepted, the flow of the asymmetric nanofiber membrane is much higher than that of the symmetric nanofiber membrane, that is, after the same iron sol aqueous solution is filtered, the flow of the asymmetric nanofiber membrane is still much higher than that of the symmetric nanofiber membrane, which indicates that the asymmetric nanofiber membrane has a higher porosity, flow and loading capacity.

[0054] The process for preparing the nanofiber membrane is further described below by taking an example that the diameter of the first electrospinning nanofiber is equal to 2 times of the diameter of the second electrospinning nanofiber, which includes the following steps:

[0055] Step S11: PVDF material is dissolved in a mixed solvent of dimethylformamide and acetone in a volume ratio of 1:1, and a spinning solution with a mass content of 5%-12% is prepared;

[0056] Step S12: The spinning solution is prepared into first electrospun nanofibers and second electrospun nanofibers by an electrospinning process, the first electrospun nanofibers are prepared by a first spinneret, the second electrospun nanofibers are prepared by a second spinneret, the electrospinning voltage is 24000V-28000V, the spinning distance is 150mm-200mm, and the production speed of the nanofiber membrane is 400mm / min, the first spinneret and the second spinneret use stainless steel needles of different models for medical injectors, and the model of the stainless steel needle for the medical injector is No.7-No.14. It needs to be further explained that the size and inner diameter of the medical injector stainless steel needle of No.7-No.14 have definiteness, the spinning inner diameter of the medical injector stainless steel needle of different models is different, and the diameter of the electrospun nanofibers sprayed is also different.

[0057] To realize the layered accumulation of the first electrospun nanofibers and the second electrospun nanofibers to form the nanofiber membrane, referring to Figure 4 , the nanofiber membrane is driven along several rollers, the spinneret 5 for electrospinning includes a first spinneret 51 and a second spinneret 52, the first spinneret 51 and the second spinneret 52 are aligned to spin the nanofiber membrane to make the nanofiber membrane continuously thicken; the spinneret model of the first spinneret 51 is a stainless steel No.12 needle for medical injectors (No.12 in Figure 4 ), the arrangement mode of the spinneret of the first spinneret 51 is 4 rows*10 per row, that is, the number of spinnerets of each group of the first spinneret 51 is 40, and the first spinneret 51 uses a spinning solution with a mass content of 10%; the spinneret model of the second spinneret 52 is a stainless steel No.9 needle for medical injectors (No.9 in Figure 4 ), the arrangement mode of the spinneret of the second spinneret 52 is 4 rows*10 per row, that is, the number of spinnerets of each group of the second spinneret 52 is 40, and the second spinneret 52 uses a spinning solution with a mass content of 7%.

[0058] The nanofiber membrane is formed by accumulating several layers of electrospun nanofibers, according to the requirements of the nanofiber membrane on the filtration flux and the number of nanocarriers, different diameter electrospun nanofibers are layered and accumulated, referring to Figure 4 , Figure 4 is a schematic diagram of preparing the asymmetric nanofiber membrane with No.1 in Embodiment Two, Figure 5 is Figure 4The winding roller line diagram of the middle-nanofiber membrane, the nanofiber membrane is sequentially passed through two groups of the first group of spinnerets 51, four groups of the second group of spinnerets 52, two groups of the first group of spinnerets 51 and eight groups of the second group of spinnerets 52; the two groups of the first group of spinnerets 51 are used for preparing the first nanofiber layer 1, the first nanofiber layer 1 is stacked by the first electrospinning nanofiber with a diameter of 1 μm, and the stacking thickness is 5 μm; the four groups of the second group of spinnerets 52 are used for preparing the second nanofiber layer 2, the second nanofiber layer 2 is stacked by the second electrospinning nanofiber with a diameter of 0.5 μm, and the stacking thickness is 5 μm; the two groups of the first group of spinnerets 51 are used for preparing the third nanofiber layer 3, the third nanofiber layer 3 is stacked by the first electrospinning nanofiber with a diameter of 1 μm, and the stacking thickness is 5 μm; the eight groups of the second group of spinnerets 52 are used for preparing the fourth nanofiber layer 4, the fourth nanofiber layer 4 is stacked by the second electrospinning nanofiber with a diameter of 0.5 μm, and the stacking thickness is 20 μm.

[0059] Step S2: hydrophilic modification is performed on the fiber surface of the nanofiber membrane through in-situ radical polymerization. Specifically, the hydrophilic modification comprises the following steps:

[0060] Step S21: a polymerization and crosslinking solution is prepared by taking a hydroxyl functional group alkyl acrylate compound as a monomer, a di-functional group acrylate compound as a crosslinking agent, a peroxide compound as an initiation catalyst, and an ethanol aqueous solution as a polymerization solvent; wherein the hydroxyl functional group alkyl acrylate compound is one or more mixtures of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate; the di-functional group acrylate compound is one or more mixtures of triethylene glycol di(meth) acrylate, diethylene glycol di(meth) acrylate, ethylene glycol di(meth) acrylate, tripropylene glycol di(meth) acrylate, dipropylene glycol di(meth) acrylate, and propylene glycol di(meth) acrylate; and the peroxide compound is one or more mixtures of ammonium persulfate, tert-butyl peroxybenzoate, and benzoyl peroxide.

[0061] Step S22: the nanofiber membrane is subjected to in-situ radical polymerization in the polymerization and crosslinking solution for 5 min-30 min, and the in-situ radical polymerization time is preferably 10 min-15 min.

[0062] The process and principle of in-situ radical polymerization are described below by taking hydroxypropyl acrylate as a monomer, triethylene glycol dimethacrylate as a crosslinking agent, ammonium persulfate as an initiation catalyst, and an ethanol aqueous solution as a solvent as examples: the hydroxyl functional group alkyl acrylate compound is hydroxypropyl acrylate; the di-functional group acrylate compound is triethylene glycol dimethacrylate; and the peroxide compound is ammonium persulfate;

[0063] The reaction formula of the in-situ radical polymerization is:

[0064]

[0065] Wherein, the ammonium persulfate contains a peroxyl group (-O-O-, peroxide bridge), and after being heated, the -O-O- bond breaks and splits into two corresponding oxygen radicals, the reaction equation is: -O-O-→2O·, and the persulfate S2O8 -2 E 0 =2.01V, which has very high oxidation initiation ability.

[0066] The hydrophilic property of the modified PVDF nanofiber membrane mainly depends on the degree of covering the hydrophobic groups on the surface of the membrane fibers by the hydrophilic polymer, and this degree is closely related to the reaction concentration of the hydrophilic monomer. And since the PVDF nanofiber membrane is completely covered by the hydrophilic polymer, water can completely spread on the surface of the membrane, so we take the spreading time of water on the surface of the membrane as the index for identifying the hydrophilicity, see Table 2 for details.

[0067] Table 2 Relationship between monomer concentration and water spreading time on the surface of the membrane

[0068]

[0069] The modified PVDF nanofiber membrane needs to ensure sufficient water flux to meet the requirements of sample processing time as a chromatographic medium. By adjusting the concentrations of monomers, cross-linking agents and initiators, the length of the cross-linked hydroxypropyl acrylate polymer molecular chain segment is controlled to ensure the smoothness of the membrane pores. The monomer concentration is 3%-10%, the cross-linking agent concentration is 0.5%-1.5%, and the concentration of the initiating catalyst is 0.5%-1.5%. According to the test results in Table 2, the concentration of the monomer hydroxypropyl acrylate is preferably 7wt%, the concentration of the cross-linking agent triethylene glycol dimethyl acrylate is preferably 1wt%, and the concentration of the initiating catalyst ammonium persulfate is preferably 1wt%, and the water flux of the prepared hydrophilic modified membrane reaches the highest, which is 89% of the modified membrane, and the grafting rate is 0.0874×10 -3 (mol / cm 3 ).

[0070] Next, the nanofiber membrane with serial number 1 in Table 1 is used as the substrate for hydrophilic modification by using the hydrophilic modification solution table with serial number 2 in Table 2. The protein adsorption capacity and separation characteristics of the nanofiber membrane after hydrophilic modification are shown in the following tests and test results.

[0071] The sample solution is selected as 20 mmol / L Tris-HCl buffer with different pH values, and the elution solution is 20 mmol / L Tris-HCl + 1 mol / L NaCl buffer. A series of lysozyme and ovalbumin solutions with different concentrations from low to high are prepared by using several sample solutions with different pH values, and are filtered by using a satorius 0.2 μm filter membrane. The sample solution with different concentrations of lysozyme is loaded, and the adsorption and elution of the protein are monitored by using a Biologic LP (atmospheric pressure chromatography system) and detected by using the Bradford method. According to the experimental results, the lysozyme and ovalbumin solutions are mixed at a suitable ratio to carry out separation and purification experiments, and the purification effect is identified by using SDS protein electrophoresis.

[0072] Adsorption capacity characterization of the PVDF nanofiber chromatography membrane. The lysozyme with an isoelectric point of 11.0 and a molecular weight of 14300 is used to characterize the cation exchange characteristics of the PVDF nanofiber chromatography membrane. Through adsorption and elution experiments, the maximum adsorption capacity is 0.0392 g / ml at pH 9.0, as shown in Figure 6 , which is several times the adsorption capacity of the existing nanofiber membrane.

[0073] The theoretical value of the adsorption capacity of the PVDF chromatography membrane = the number of grafted hydroxyl groups on the unit membrane area * the molecular weight of the protein * the correction coefficient (κ). Assuming that the correction coefficient κ = 1, the theoretical value of the adsorption capacity of the PVDF chromatography membrane is 1.25 g / cm 3 , that is, 1.25 g / ml. Assuming that one hydroxyl group can adsorb one molecular unit of lysozyme, the theoretical adsorption capacity (1.25 g / ml) of the modified PVDF membrane is much higher than the maximum adsorption capacity (0.0392 g / ml) actually measured, indicating that the number of hydroxyl groups provided on the membrane surface has far exceeded the required number of hydroxyl groups, and the number of charges on the surface of the lysozyme plays a decisive role.

[0074] Effect of flow rate on adsorption capacity. According to the experimental conclusion of Figure 6 , the optimal pH value is pH 9.0, which is selected as the reference for the flow rate experiment. Under different flow rates, the changes of the adsorption capacity of the nanofiber chromatography membrane for lysozyme protein are shown in Figure 7 , indicating that changing the flow rate does not affect the adsorption capacity of the membrane for the protein between 0.25 ml / min and 2 ml / min.

[0075] Separation efficiency of the PVDF chromatography membrane. The pH 9.0 lysozyme solution (2.8 mg / ml) and the pH 9.0 ovalbumin solution (1.8 mg / ml) are mixed at a volume ratio of 1:3, and the separation and elution are carried out at a flow rate of 1 ml / min and a pulse sample of 200 μl. The results are shown in Figure 8The UV A280 absorption curve and the solution ion strength change curve detected by the Biologic LP instrument show that the egg white albumin and lysozyme can be well separated in a solution system.

[0076] PVDF chromatography membrane separation and purification effect, Figure 9 A is the mixture of lysozyme and egg white albumin, B is the elution peak collected liquid, and C is the elution peak collected liquid, which is the elution peak collected liquid. Figure 9 It can be seen that the modified PVDF nanofiber membrane can be used to separate lysozyme and egg white albumin, and the separation and purification effect reaches the electrophoretic pure level.

Claims

1. A method for preparing a PVDF nanofiber chromatography membrane, characterized by, Comprising the following steps: An asymmetric-pore nanofiber membrane is formed by mixed accumulation of first electrospinning nanofibers and second electrospinning nanofibers with different diameters, the diameter of the first electrospinning nanofibers being equal to 2 times the diameter of the second electrospinning nanofibers, and the blending ratio of the first electrospinning nanofibers and the second electrospinning nanofibers being 7:3-3:7 by weight; Hydrophilic modification is performed on the fiber surface of the nanofiber membrane through in-situ radical polymerization; the hydrophilic modification comprises the following steps: A polymerization cross-linking solution is prepared with a hydroxyl functional group alkyl acrylate compound as a monomer, a difunctional acrylate compound as a cross-linking agent, a peroxide compound as an initiation catalyst, and an ethanol aqueous solution as a polymerization solvent, the monomer concentration being 3%-10%, the cross-linking agent concentration being 1%-1.5%, and the initiation catalyst concentration being 0.5%-1.5%; The nanofiber membrane is subjected to in-situ radical polymerization in the polymerization cross-linking solution for 10-30 min; the hydroxyl functional group alkyl acrylate compound is one or a mixture of more than one of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate; The difunctional acrylate compound is one or a mixture of more than one of triethylene glycol bis(meth) acrylate, diethylene glycol bis(meth) acrylate, ethylene glycol bis(meth) acrylate, tripropylene glycol bis(meth) acrylate, dipropylene glycol bis(meth) acrylate, and propylene glycol bis(meth) acrylate; The peroxide compound is one or a mixture of more than one of tert-butyl peroxybenzoate and benzoyl peroxide.

2. A method of preparing a PVDF nanofiber chromatography membrane, characterized by, Comprising the following steps: An asymmetric-pore nanofiber membrane is formed by accumulation of a first nanofiber layer, a second nanofiber layer, a third nanofiber layer, and a fourth nanofiber layer, the first nanofiber layer and the third nanofiber layer being respectively formed by accumulation of first electrospinning nanofibers, and the second nanofiber layer and the fourth nanofiber layer being respectively formed by accumulation of second electrospinning nanofibers, the diameter of the first electrospinning nanofibers being equal to 2 times the diameter of the second electrospinning nanofibers; Hydrophilic modification is performed on the fiber surface of the nanofiber membrane through in-situ radical polymerization; the hydrophilic modification comprises the following steps: A polymerization cross-linking solution is prepared with a hydroxyl functional group alkyl acrylate compound as a monomer, a difunctional acrylate compound as a cross-linking agent, a peroxide compound as an initiation catalyst, and an ethanol aqueous solution as a polymerization solvent, the monomer concentration being 3%-10%, the cross-linking agent concentration being 1%-1.5%, and the initiation catalyst concentration being 0.5%-1.5%; The nanofiber membrane is subjected to in-situ radical polymerization in the polymerization cross-linking solution for 10-30 min; the hydroxyl functional group alkyl acrylate compound is one or a mixture of more than one of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate; The difunctional acrylate compound is one or more mixtures of triethylene glycol bis(meth)acrylate, diethylene glycol bis(meth)acrylate, ethylene glycol bis(meth)acrylate, tripropylene glycol bis(meth)acrylate, dipropylene glycol bis(meth)acrylate, and propylene glycol bis(meth)acrylate; The peroxyl compound is one or more mixtures of tert-butyl peroxybenzoate and benzoyl peroxide.

3. The method of claim 1 or 2, wherein the PVDF nanofiber chromatography membrane is prepared by a process comprising: The hydroxyl functional alkyl acrylate compound is hydroxypropyl acrylate. The difunctional acrylate compound is triethylene glycol dimethacrylate. The peroxyl compound is tert-butyl peroxybenzoate. The reaction formula of the in-situ radical polymerization is: 。 4. The method of claim 3, wherein the PVDF nanofiber chromatography membrane is prepared by the steps of: The PVDF material is dissolved in a mixed solvent of dimethylformamide and acetone in a volume ratio of 1:1 to prepare a spinning solution with a mass content of 5%-12%; The spinning solution is prepared into first electrospun nanofibers and second electrospun nanofibers by an electrospinning process, the first electrospun nanofibers are prepared by a first spinneret, the second electrospun nanofibers are prepared by a second spinneret, the voltage of electrospinning is 24000V-28000V, the spinning distance is 150mm-200mm, the production speed of the nanofiber membrane is 400mm / min, the first spinneret and the second spinneret use stainless steel needles of different models for medical syringes, and the model of the stainless steel needle for the medical syringe is 7-14.

5. The method of claim 4, wherein the first spinneret is a stainless steel 12-gauge needle for medical syringes, the first spinneret is arranged in 4 rows with 10 needles per row, and the first spinneret uses a spinning solution with a mass content of 10%; The second spinneret is a stainless steel 9-gauge needle for medical syringes, the second spinneret is arranged in 4 rows with 10 needles per row, and the second spinneret uses a spinning solution with a mass content of 7%. ​ ​

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