阅读说明：本技术 一种以电纺丝纳米纤维膜为支撑层的复合正渗透膜及其制备方法与应用 (Composite forward osmosis membrane with electrospun nanofiber membrane as supporting layer and preparation method and application thereof ) 是由 于洋 陈达 于�玲 刘海 于 2021-07-05 设计创作，主要内容包括：本发明属于渗透膜材料技术领域,具体公开了一种以电纺丝纳米纤维膜为支撑层的复合正渗透膜及其制备方法与应用。所述方法具体为将具有氧化石墨烯中间层的电纺丝纳米纤维支撑层浸入氯化钙溶液中,随后在水中润洗；再浸入碳酸钠溶液中,随后在水中润洗,再通过间苯二胺和均苯三甲酰氯的界面聚合反应在负载碳酸钙的氧化石墨烯纳米中间层的电纺丝膜基底的表面制备聚酰胺选择分离层,干燥后得到正渗透膜。本发明通过在电纺丝纳米纤维支撑层及其表面氧化石墨烯中间薄层负载碳酸钙颗粒,借助界面聚合过程中产生的H～(+)离子,原位生成二氧化碳纳米气泡,对聚酰胺分离层结构和性能进行调控,制备高渗透通量和高截留率的正渗透膜材料。(The invention belongs to the technical field of permeable membrane materials, and particularly discloses a composite forward permeable membrane taking an electrospinning nanofiber membrane as a supporting layer, and a preparation method and application thereof. The method is to have oxidized stoneImmersing the electrospinning nanofiber supporting layer of the graphene intermediate layer into a calcium chloride solution, and then rinsing in water; and then immersing the membrane into a sodium carbonate solution, then rinsing the membrane in water, preparing a polyamide selective separation layer on the surface of the electrospinning membrane substrate of the calcium carbonate-loaded graphene oxide nano intermediate layer through the interfacial polymerization reaction of m-phenylenediamine and trimesoyl chloride, and drying the polyamide selective separation layer to obtain the forward osmosis membrane. Calcium carbonate particles are loaded in the electrospinning nanofiber supporting layer and the graphene oxide middle thin layer on the surface of the electrospinning nanofiber supporting layer by virtue of H generated in the interfacial polymerization process + And (3) generating carbon dioxide nanobubbles in situ by ions, regulating and controlling the structure and the performance of the polyamide separation layer, and preparing the forward osmosis membrane material with high permeation flux and high rejection rate.)

1. A preparation method of a composite forward osmosis membrane taking an electrospinning nanofiber membrane as a supporting layer is characterized by comprising the following steps: immersing the electrospinning nanofiber supporting layer with the graphene oxide interlayer into a calcium chloride solution, and then rinsing in water; and then immersing the membrane into a sodium carbonate solution, then rinsing the membrane in water, preparing a polyamide selective separation layer on the surface of the electrospinning membrane substrate of the calcium carbonate-loaded graphene oxide nano intermediate layer through the interfacial polymerization reaction of m-phenylenediamine and trimesoyl chloride, and drying the polyamide selective separation layer to obtain the forward osmosis membrane.

2. The method of claim 1, wherein: the concentration of the calcium chloride is 0.01 mmol-0.4 mmol.

3. The method of claim 1, wherein: the concentration of the calcium chloride is 0.05 mmol-0.2 mmol.

4. The method of claim 1, wherein: the concentration of the sodium carbonate solution is 0.01 mmol-0.4 mmol.

5. The method of claim 1, wherein: the concentration of the sodium carbonate solution is 0.05 mmol-0.2 mmol.

6. The method of claim 1, wherein the electrospun nanofiber substrate is prepared by the method comprising: dissolving polyacrylonitrile powder in dimethylformamide, and uniformly mixing to obtain a uniform electrostatic spinning membrane casting solution; and then carrying out electrostatic spinning to obtain the electrospun nanofiber membrane substrate.

7. The preparation method according to claim 1, wherein the immersing time of the electrospun nanofiber supporting layer with the graphene oxide intermediate layer in the calcium chloride solution is 0.5-2 min.

8. The preparation method according to claim 1, wherein the immersion time of the electrospun nanofiber supporting layer with the graphene oxide intermediate layer in a sodium carbonate solution is 0.5-2 min.

9. A composite forward osmosis membrane with an electrospun nanofiber membrane as a supporting layer is prepared by the method of any one of claims 1-8.

10. The composite forward osmosis membrane using the electrospun nanofiber membrane as the support layer according to claim 9, which is applied to the fields of seawater desalination, drinking water treatment and wastewater reuse.

Technical Field

The invention belongs to the technical field of permeable membrane materials, and particularly relates to a composite forward permeable membrane taking an electrospinning nanofiber membrane as a supporting layer, and a preparation method and application thereof.

Background

During application, the actual osmotic pressure difference across the forward osmosis membrane is much lower than ideal, which is mainly caused by the Internal Concentration Polarization (ICP) phenomenon, directly resulting in severe attenuation of the forward osmotic flux. In order to effectively reduce internal concentration polarization and obtain high permeation flux, the forward osmosis membrane support layer should have the structural characteristics of high porosity, low tortuosity pore structure and low thickness. By optimizing the preparation conditions, the electrospinning technology can prepare the electrospinning nanofiber supporting layer which effectively meets the structural characteristic requirements. Research shows that the permeability coefficient of the electrospinning nanofiber composite forward osmosis membrane can be 0.4-3.5 times higher than that of a forward osmosis membrane and a commercial membrane material prepared by a phase inversion method. However, when the electrospun nanofiber membrane is directly used as a supporting layer of a forward osmosis membrane, the structure and performance of a polyamide separation layer can be significantly influenced by the surface open macroporous structure of the electrospun nanofiber membrane, and a thicker polyamide layer with a lower crosslinking degree is formed in pores in the interfacial polymerization process, so that the permeability and the rejection rate of the forward osmosis membrane are influenced. Researchers use a phase inversion method to prepare a porous polyvinylidene fluoride intermediate thin layer on the surface of an electrospinning nanofiber membrane, the smooth and flat intermediate layer is beneficial to improving the stability of a polyamide separation layer, and meanwhile, the fact that the water flux of the composite forward osmosis membrane is positively correlated with the porosity of the intermediate layer is also found. The construction of the intermediate thin layer can reduce the adverse effect of the electrospinning nanofiber supporting layer on the polyamide separating layer, but the regulation and control effect of the polyamide layer is limited.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention mainly aims to provide a preparation method of a composite forward osmosis membrane taking an electrospinning nanofiber membrane as a supporting layer.

The invention also aims to provide the composite forward osmosis membrane which is prepared by the method and takes the electrospinning nanofiber membrane as the supporting layer.

The invention further aims to provide application of the composite forward osmosis membrane taking the electrospinning nanofiber membrane as the supporting layer in the fields of seawater desalination, drinking water treatment and wastewater recycling.

The purpose of the invention is realized by the following scheme:

a preparation method of a composite forward osmosis membrane with an electrospinning nanofiber membrane as a supporting layer comprises the steps of immersing the electrospinning nanofiber supporting layer with a graphene oxide intermediate layer into a calcium chloride solution, and then rinsing in water; and then immersing the membrane into a sodium carbonate solution, then rinsing the membrane in water, preparing a polyamide selective separation layer on the surface of the electrospinning membrane substrate of the calcium carbonate-loaded graphene oxide nano intermediate layer through the interfacial polymerization reaction of m-phenylenediamine and trimesoyl chloride, and drying the polyamide selective separation layer to obtain the forward osmosis membrane.

The electrospinning nanofiber supporting layer with the graphene oxide intermediate layer is preferably prepared by loading graphene oxide nanosheets on an electrospinning nanofiber substrate through a vacuum filtration method.

Preferably, the preparation method of the electrospun nanofiber substrate comprises the following steps: dissolving polyacrylonitrile powder in dimethylformamide, and uniformly mixing to obtain a uniform electrostatic spinning membrane casting solution; and then carrying out electrostatic spinning to obtain the electrospun nanofiber membrane substrate.

More preferably, after completion of the electrospinning process, the obtained electrospun nanofiber membrane substrate is placed in an oven for drying to remove residual solvent, and further subjected to a heat pressing process to improve the mechanical strength of the membrane.

The concentration of the calcium chloride is 0.01 mmol-0.4 mmol, preferably 0.05 mmol-0.2 mmol.

The immersion time of the electrospinning nanofiber supporting layer with the graphene oxide interlayer in a calcium chloride solution is 0.5-2 min, preferably 1 min;

the concentration of the sodium carbonate solution is 0.01 mmol-0.4 mmol, preferably 0.05 mmol-0.2 mmol.

The immersion time of the electrospinning nanofiber supporting layer with the graphene oxide intermediate layer in a sodium carbonate solution is 0.5-2 min, and preferably 1 min.

The rinsing time in water is 0.5-5 min, preferably 1 min.

The composite forward osmosis membrane with the electrospinning nanofiber membrane as the supporting layer is prepared by the method.

The composite forward osmosis membrane with the electrospinning nanofiber membrane as the supporting layer is applied to the fields of seawater desalination, drinking water treatment and wastewater reuse.

Compared with the prior art, the invention has the following advantages and beneficial effects:

calcium carbonate particles are loaded in the electrospinning nanofiber supporting layer and the graphene oxide middle thin layer on the surface of the electrospinning nanofiber supporting layer by virtue of H generated in the interfacial polymerization process⁺And (3) generating carbon dioxide nanobubbles in situ by ions, regulating and controlling the structure and the performance of the polyamide separation layer, and preparing the forward osmosis membrane material with high permeation flux and high rejection rate.

Drawings

FIG. 1 shows the surface topography of a support layer after calcium carbonate loading; wherein a is TFN-0, b is TFN-1, c is TFN-2, and d is TFN-3.

FIG. 2 is a topographical feature of a polyamide separation layer; wherein a is TFN-0, b is TFN-1, c is TFN-2, and d is TFN-3.

Fig. 3 shows the contact angle between the support layer and the surface of the polyamide layer after loading calcium carbonate particles.

FIG. 4 shows the permeation flux of a forward osmosis membrane, wherein AL-FS is the side of a polyamide separation layer facing a feed liquid in the forward osmosis process; AL-DS is the side of the polyamide separation layer facing the draw solution during forward osmosis.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

The reagents used in the examples are commercially available without specific reference.

Example 1

(1) Preparation of electrospun nanofiber substrates

Dissolving polyacrylonitrile powder in dimethylformamide, wherein the concentration of polyacrylonitrile is 10 wt%, and fully stirring at 60 ℃ to obtain a uniform electrostatic spinning membrane casting solution. The electrostatic spinning parameters are set as follows: an applied voltage of 21kV, a collection distance of 15cm, a forwarding flow rate of 0.6mL/h and an electrospinning time of 10 h. After the electrospinning process is completed, the obtained polyacrylonitrile electrospun nanofiber membrane is dried in an oven at 60 ℃ to remove residual solvent, and is further subjected to hot pressing treatment to improve the mechanical strength of the membrane.

(2) Preparation of calcium carbonate-loaded graphene oxide intermediate layer

Preparing a graphene oxide uniform dispersion solution under the ultrasonic assistance condition, respectively loading 0.2mg of graphene oxide nanosheets onto the surface of a polyacrylonitrile electrospinning nanofiber substrate through vacuum filtration, wherein the loading amount of the graphene oxide is 56 mu g/cm². And then, drying the polyacrylonitrile electrospinning nanofiber substrate loaded with the graphene oxide in an oven at 50 ℃ for 30 min.

The calcium carbonate coating is synthesized on a polyacrylonitrile support layer loaded with a thin layer of graphene oxide by an alternative dipping method. Briefly, the support layer with the graphene oxide thin layer was sequentially soaked in 0.05mmol/L calcium chloride solution for 1min, rinsed with deionized water for 1min, soaked in 0.05mmol/L sodium carbonate solution for 1min, and rinsed with deionized water for 1 min. The molar concentration ratio of calcium chloride to sodium carbonate solution was maintained at 1: 1. And then, heating the membrane in an oven at 50 ℃ for 30min to obtain the calcium carbonate-loaded graphene oxide interlayer modified polyacrylonitrile support layer.

(3) Preparation of the Polyamide active layer

The polyamide active layer of the forward osmosis membrane is prepared by interfacial polymerization between m-phenylenediamine and trimesoyl chloride monomers. Briefly, the support layer was soaked in a 2 wt% solution of m-phenylenediamine for 5 min. Subsequently, the excess m-phenylenediamine solution on the surface of the support layer was removed using a squeegee. Next, a certain amount of 0.15 wt% trimesoyl chloride solution (n-hexane as solvent) was poured gently on the surface of the support layer for reaction for 1 min. The excess trimesoyl chloride solution was decanted off and the resulting membrane washed twice with n-hexane. Thereafter, the resulting film was dried in an oven at 50 ℃ for 10min to further carry out interfacial polymerization and promote evaporation of n-hexane. Finally, the prepared forward osmosis membrane was washed 3 times and stored in deionized water.

Example 2

Referring to example 1, except that the concentrations of the calcium chloride solution and the sodium carbonate solution in step (2) were changed to 0.1 mmol/L.

Example 3

Referring to example 1, except that the concentrations of the calcium chloride solution and the sodium carbonate solution in step (2) were changed to 0.2 mmol/L.

The calcium carbonate loadings of the forward osmosis membranes prepared in examples 1-3 were 0.05, 0.1 and 0.2mmol, respectively, and expressed as TFN-1, TFN-2 and TFN-3, respectively. A polyamide selective separation layer is directly prepared on the surface of an original substrate loaded with graphene oxide and is used as a control membrane TFN-0.

Application examples

(1) Characterization of surface morphology of film material

The surface morphology of the substrate and the forward osmosis membrane was observed using a field emission scanning electron microscope (FESEM, S4800, Hitachi).

(2) Characterization of the hydrophilicity of the Membrane surface

The hydrophilicity of the substrate and forward osmosis membrane surfaces was determined using a dynamic contact angle measuring instrument (attention Theta, Biolin Scientific), the measurement was repeated at least at 5 positions for each sample, and the average value was calculated.

(2) Film Performance testing

And (3) measuring the performance of the prepared forward osmosis membrane material by using a self-made forward osmosis experimental device. Deionized water and NaCl solution (0.5-2.0M concentration) were used as feed solution and draw solution, respectively. The membrane material properties were evaluated at room temperature and at a flow rate of 0.15L/min in AL-FS (polyamide selective separation layer towards feed solution) mode and AL-DS (polyamide selective separation layer towards draw solution) mode, respectively. Water flux (J)_w，L/m²h) Determined by measuring the change in volume of the draw solution over a time interval, the calculation formula is as follows:

J_w＝ΔV/(A_m·Δt)

wherein Δ V (L) is the change in volume of the draw solution, A_m(m²) Is the effective membrane area, and Δ t (h) is the time interval.

As can be seen from fig. 1 and 2, after the calcium carbonate particles are loaded, a crystal-like structure can be observed on the surface of the substrate, and the nanofiber imprints on the surface of the corresponding forward osmosis membrane can be attenuated.

As can be seen from fig. 3, after loading the calcium carbonate particles, the contact angle of the substrate and the corresponding forward osmosis membrane decreased, indicating an increased hydrophilicity.

As can be seen from fig. 4, the permeation flux of the forward osmosis membrane was improved after loading calcium carbonate particles.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.