CN105603637A - Efficient electrostatic spinning oil-water separation fiber membrane - Google Patents

Abstract

The invention discloses a preparation method of an efficient electrostatic spinning oil-water separation fiber membrane. The preparation method includes the steps that polyamic acid (PPA) is synthesized, a PPA nanofiber membrane is prepared in an electrospinning mode, and the PPA nanofiber membrane is imidized into a polyimide membrane (PI); a cellulose acetate (CA) nanofiber membrane is prepared; coaxial electrospinning is carried out on CA-PAA, and a product is imidized into CA-PI; benzoxazine monomers (BAF-tfa) are synthesized; in-situ immobilization is performed on the CA, PI and CA-PI nanofiber membranes with BAF-tfa and BAF-tfa/silica nanoparticles (SiO2NPs); an oil-water separation experiment is carried out. The preparation method has the advantages that by carrying out surface modification on the fiber membranes, the CA-PI nanofiber membrane which is biodegradable, low in cost, large in oil-water separation flow and high in separation efficiency is obtained; the high-performance membrane material has broad application prospects in oil-water separation, sewage treatment and deepwater oil leak.

Description

Efficient electrospinning fiber membrane for oil-water separation

technical field

The invention relates to a method for preparing an efficient electrospinning oil-water separation fiber membrane, in particular a method for preparing an efficient superhydrophobic and super-oleophilic electrospinning oil-water separation fiber membrane for gravity-driven oil-water separation.

Background technique

By electrospinning, many literatures on nanofibrous membranes such as polystyrene, polycaprolactone, polymethyl methacrylate, polyurethane, and inorganic silica fibers have been reported. However, these fibers have the disadvantages of slow separation speed, low separation efficiency, poor stability, poor strength, and easy to produce secondary pollution. Moreover, the biggest obstacle of slow separation speed, low separation efficiency and poor strength seriously limits their practical application.

Contents of the invention

The present invention proposes a method for preparing an efficient superhydrophobic and superoleophilic electrospun oil-water separation fiber membrane for gravity-driven oil-water separation. Its purpose is to overcome the above-mentioned defects in the prior art. CA and PAA is used as the raw material, and high-molecular-weight poly-PAA is used as the core through high-pressure coaxial electrospinning technology, and CA is used as the shell, and PAA is imidized after temperature programming to obtain biodegradable, low-cost, and significant separation flux. CA-PI nanofiber membranes with high separation efficiency and mechanical strength; functional fiber membrane materials are obtained by modifying the surface of fiber membranes; moreover, this highly efficient super-hydrophobic and super-oleophilic membrane material is used in oil-water separation, sewage treatment and deep-sea petroleum It has broad application prospects in leakage.

Technical solution of the present invention: the preparation method of highly efficient superhydrophobic and superoleophilic oil-water separation nanofibrous membrane comprises the following process steps:

(1) Synthetic polyamic acid (PAA)

(2) Electrospun PAA nanofiber membrane and imidization into polyimide (PI) membrane;

(3) preparing cellulose acetate (CA) nanofiber membrane;

(4) Coaxial electrospinning of CA-PAA and imidization into CA-PI;

(5) Synthesis of benzoxazine monomer (BAF-tfa);

(6) BAF-tfa and BAF-tfa/silica nanoparticles (SiO ₂ NPs) in situ curing CA, PI, CA-PI nanofibrous membranes;

(7) Contact angle experiment

(8) Oil-water separation experiment.

Positive effect of the present invention

a. It has high separation flow rate and separation efficiency, the flow rate reaches 2270Lm ^-2 h ^-1 , and the separation efficiency reaches over 99%. Compared with the oil-water separation membrane bought in the market, the flow rate is increased by 3-4 times, and it also has higher separation efficiency efficiency.

b. It has high strength, the tensile strength reaches more than 200MPa, which is more than 30 times higher than the commonly used CA nanofiber membrane's tensile strength of 6.65MPa;

c. The maximum contact angle of CA-PI nanofiber membranes modified by BAF-tfa with water can only reach 137°, which does not have superhydrophobic and superoleophilic properties; while CA-PI modified by BAF-tfa The maximum contact angle of PI nanofiber membrane with water can reach 161°, and the contact angle of oil can reach 0°. It has super hydrophobic and super lipophilic properties and can be used in oil-water separation process.

d. It has the properties of acid and alkali resistance and high temperature resistance, and can still maintain superhydrophobic properties under different pH and high temperature.

e. It can be used for a long time. After 300 days of storage, the contact angle drops below 5%. After ten cycles of use, the flow rate can still reach about 2000Lm ^-2 h ^-1 and the separation efficiency can reach 98.5%.

Description of drawings

Figure 1 is a schematic diagram of the structure of the electrospun PAA nanofiber membrane device.

Figure 2 is a schematic diagram of the process of coaxial electrospinning CA-PI nanofibrous membranes.

Fig. 3 is a graph showing the change of contact angle between F-PBZ-1/PI and F-PBZ-1/CA-PI and water after 300 days at room temperature.

Fig. 4 is a diagram of the contact angle variation between F-PBZ-1/SNP-4/CA-PI and water at different pH and temperature.

Fig. 5 is a graph of CA, PI, CA-PI flux and separation efficiency after in-situ curing of different concentrations of BAF-tfa and BAF-tfa/SiO ₂ NPs.

Figure 6 is a diagram of the flow and separation efficiency of different types of oil-water mixtures; 10 cycles of F-PBZ-1/SNP-4/CA-PI flow and separation efficiency changes and BAF-tfa/SiO ₂ NPs in-situ solidification with different thicknesses Flow and separation efficiency graphs after CA-PI.

Fig. 7 is a diagram of porosity variation of CA-PI with different thicknesses.

detailed description

The preparation method of the preparation method of the efficient superhydrophobic and superoleophilic oil-water separation nanofiber membrane comprises the following process steps:

(1) synthesis of PAA;

Add biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) respectively 2.9422g and 1.0814g (molar ratio 1:1) into a dry four-necked flask equipped with a mechanical stirrer, a thermometer, and a nitrogen gas inlet and outlet tube, and mix well ; Under strong mechanical stirring, add 40ml of DMAc, react at -15°C-5°C for 24 hours, and then terminate the reaction to obtain PAA.

(2) Electrospun PAA nanofiber membrane and imidization into polyimide (PI) membrane:

Use 1-5% (wt) PAA DMAc solution to spin in a high-voltage electrostatic field with a voltage of 30Kv (+20, -10KV), the receiving distance from the needle tip of the syringe to the flywheel is 10-15cm, and the speed of the flywheel is 1000- 2000 revolutions/min, the speed of electrospinning is 0.5-1ml/h, and the polyamic acid (PAA) nanofiber membrane is spun into, as shown in Figure 1. The electrospun PAA nanofiber membrane was imidized in a tube furnace according to the temperature program of 150°C/1h, 200°C/1h, 250°C/1h, 300°C/1h, 350°C/30mim to obtain a PI film Afterwards, the stress-strain of the PI film was tested at room temperature with the universal material testing machine (CMT-8500 type) of Shenzhen Xinsansi, and the stress-strain was tested.

(3) Preparation of CA nanofiber membrane,

The preparation of CA nanofiber film: with the mixed solution of the dichloromethane of 5-10% (wt) and acetone (2/1 (V/V)), spinning in the high-voltage electrostatic field, the distance from the needle point of the syringe to the cylinder is 10-15cm, the electrospinning speed is 0.5-1ml/h, and it is spun into CA nanofiber membrane. The electrospinning device is the same as that of electrospinning PAA membrane. Model 8500) for stress-strain testing at room temperature.

(4) Coaxial electrospinning of CA-PAA and imidization into CA-PI:

The preparation of coaxial CA-PAA nanofiber film: adopt coaxial needle on the basis of traditional electrospinning device, 1-5% (wt) DMAc solution of PAA is used as core, 5-10% (wt) di A 2:1 (V/V) mixed solution of methyl chloride and acetone was used as a shell, spun in a high-voltage electrostatic field, and the flywheel rotated at high speed to receive CA-PAA nanofibers. The electrospun CA-PAA nanofiber membrane was imidized according to the temperature program of 150°C/2h, 200/3h, 250°C/1h, and 260°C/1h to obtain a CA-PI nanofiber membrane; the obtained nanofiber The film was tested for stress-strain at room temperature using a universal material testing machine (CMT-8500) from Shenzhen Xinsansi. as shown in picture 2.

(5) Synthesis of benzoxazine monomer

1) Add 14.7, 5.3 and 14.1 g of bisphenol AF, paraformaldehyde and m-trifluorotoluidine, respectively, into a four-necked flask equipped with a condensing reflux tube, an electric stirrer, _N2 airway tube, and a thermometer;

2) Heat until the reactant is viscous and difficult to stir, wait for the reactant to cool to room temperature, add CHCl ₃ 200ml to it for dissolving; wash the above-mentioned completely dissolved mixed solution with 2% NaOH solution by mass fraction, wait for the solution to be layered and take lower layer solution. Add 50 ml of CHCl ₃ to the separated solution; add 2 g of anhydrous calcium chloride (CaCl ₂ ) to dehydrate after stirring evenly; dry the dehydrated solution to obtain monomer powder containing fluorobenzoxazine. (6) BAF-tfa and BAF-tfa/silica nanoparticles (SiO ₂ NPs) in situ curing CA, PI, CA-PI nanofibrous membranes;

1) Weigh 0.001g, 0.002g, 0.005g, 0.01g, 0.05g, 0.1g and 0.4g of fluorine-containing benzoxazine BAF-tfa monomer powder, according to the mass fraction of 0.01%, 0.02%, 0.05% %, 0.1%, 0.5%, 1.0%, and 4.0% were dissolved in Butyl Acetate (ButylAcetate) to obtain a completely dissolved and uniformly mixed transparent solution;

2) cutting the prepared CA, PI, CA-PI fiber membranes into experimental samples with a width and length of 2×2 cm, and immersing the fiber membranes in a butyl acetate solution containing fluorobenzoxazine BAF-tfa;

3) Quickly take out the CA, PI, and CA-PI fiber membranes immersed in the mixed solution with a camera, first dry them under natural conditions, and then put them into a vacuum supply box for curing; after cooling to room temperature, take out the F-PBZ /CA, F-PBZ/PI, F-PBZ/CA-PI spare.

4) Weigh 0.001g, 0.002g, 0.005g, 0.01g, 0.05g, 0.1g and 0.4g of BAF-tfa monomer powder, respectively 0.01%, 0.02%, 0.05%, 0.1%, 0.5% by mass fraction %, 1.0%, 4.0% dissolved in butyl acetate (ButylAcetate);

5) Adding SiO ₂ NPs with a mass fraction of 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, 1.0%, and 4.0% to the butyl acetate solution to obtain a completely dissolved and uniformly mixed transparent solution;

6) Cut the prepared CA, PI, CA-PI fiber membranes into experimental samples with a width and length of 2×2cm, and soak the fiber membranes in butyl acetate solution in which BAF-tfa and SiO ₂ NPs are dissolved; finally, Use tweezers to quickly take out the fiber membrane immersed in the mixed solution, first dry it under natural conditions, then put it in a vacuum oven for 2 hours, and then cool it to room temperature, take out the F-PBZ/SNP/CA, F-PBZ/SNP /PI, F-PBZ/SNP/CA-PI standby.

(7) Contact angle experiment,

CA, PI, CA-PI nanofiber membranes modified with different concentrations of benzoxazine and silica nanoparticles, F-PBZ/CA, F-PBZ/PI, F-PBZ/CA- PI and F-PBZ/SNP/CA, F-PBZ/SNP/PI, and F-PBZ/SNP/CA-PI composite fiber membranes were studied for their hydrophobic and lipophilic static contact angles.

(8) Oil-water separation experiment:

1) Measure 10ml of dichloromethane and water respectively, the water is stained with methylene blue, and the oil (dichloromethane) is stained with oil red. After the 200ml oil-water mixed solution was left to stand for 1min, the oil-water separation occurred. The water dyed blue was in the upper layer, the red oil was in the lower layer, and the F-PBZ--1/SNP-4/CA-PI functional fiber membrane was fixed between two glass tubes. Then, pour the layered mixed solution into the upper glass tube for oil-water separation. The red oil quickly permeated the F-PBZ-1/SNP-4/CA-PI fiber membrane and flowed into the beaker below, while the blue water remained in the upper glass tube, and the time for complete separation of oil and water was recorded , and measure the volume of water before and after separation.

2) Select 20ml (1/1( V/V)), carry out the oil-water separation experiment according to 1).

3) CA-PAA films of different thicknesses were electrospun and imidized to obtain CA-PI films, and F-PBZ- ₁ /SNP- 4/CA-PI film. And carry out the oil-water separation experiment according to 1).

4) Select F-PBZ-1/SNP-4/CA-PI membrane, and perform multiple oil-water separations according to 1).

The main purpose of the present invention is to obtain the coaxial CA-PI nanofiber membrane by coaxial electrospinning. The flow rate of CA modified with BAF-tfa and SiO ₂ NPs can only reach 1800Lm ^-2 h ^-1 , and the separation efficiency can reach 96 %, stress 6.65MPa; BAF-tfa and SiO ₂ NPs modified PI, its flow rate and separation efficiency can only reach 400Lm ^-2 h ^-1 and 95%, and when we do it, we give electrospun coaxial CA -PI nanofibrous membrane is like adding a steel wire to CA with relatively poor mechanical properties. After high-temperature imidization, the CA-PI membrane modified by BAF-tfa and SiO ₂ NPs can reach a flow rate of 2270Lm ^-2 h ^-1 , the separation efficiency reaches 99.5%, and the strain is increased by more than 200MPa. Moreover, it is resistant to acid and alkali, high temperature, and can be used for 10 cycles. In the actual application of oil-water separation, it can greatly save the time and cost of oil-water separation. It overcomes the problems of low flow rate, low separation efficiency, poor mechanical properties, not durable, easy to be broken in the process of recycling, and easy to be corroded by strong acid, strong alkali and high temperature harsh conditions in the actual application of oil-water separation. shortcoming. The usable times of the existing oil-water separation membrane are increased, and the economic cost is saved.

Claims (8)

1. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa, is characterized in that comprising following processing step:

(1) synthesizing polyamides acid (PAA)

(2) electrospinning PAA nano fibrous membrane and imines turn to polyimides (PI) film;

(3) prepare cellulose acetate (CA) nano fibrous membrane;

(4) coaxial electrically spun CA-PAA imines turn to CA-PI;

(5) synthetic benzoxazine monomer (BAF-tfa);

(6) BAF-tfa and BAF-tfa/ Nano particles of silicon dioxide (SiO₂NPs) in-situ solidifying CA, PI, CA-PI receiveRice tunica fibrosa;

(7) water-oil separating experiment.

2. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa according to claim 1, described in it is characterized in thatStep (1) synthesizing polyamides acid (PAA); Being housed, mechanical agitator, thermometer, nitrogen derive into dry four of pipeIn mouth flask, add bibenzene tetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PPD) (PDA) difference 2.9422 and 1.0814g (mol ratio1: 1), mix; Under strong mechanical agitation, add DMAc40ml, at-15 DEG C-5 DEG C, react 24h hourAfter, finish subsequently reaction, obtain polyamic acid.

3. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa according to claim 1, described in it is characterized in thatPreparation and the imines of step (2) PAA nano fibrous membrane turn to polyimides (PI) film: with 1-5% (wt) PAADMAc solution, be spinning in the high-voltage electrostatic field of 30Kv (+20 ,-10KV) at voltage, syringe needle point is to flywheelReceiving range is 10-15cm, and the rotating speed of flywheel is turn/min of 1000-2000, and the speed of electrospinning is 0.5-1ml/h, spinningBecome PAA nano fibrous membrane. By PAA nano fibrous membrane good electrospinning according to 150 DEG C/1h of temperature programming, 200 DEG C/1h,250 DEG C/1h, 300 DEG C/1h, the method for 350 DEG C/30mim is carried out imidization and is obtained PI film in tube furnace; Use afterwards darkThe universal testing machine (CMT-8500 type) that ditch between fields is newly thought carefully is at room temperature tested stress one strain of PI film,Test its stress-strain.

4. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa according to claim 1, described in it is characterized in thatThe preparation of step (3) CA nano fibrous membrane: with the carrene of 5-10% (wt) and mixing of acetone (2/1 (V/V))Close solution, spinning in high-voltage electrostatic field, syringe needle point is 10-15cm to the distance of cylinder, electrospinning speed is0.5-1ml/h, is spun to CA nano fibrous membrane, and electric spinning equipment is with the device of electrospinning PAA film, the nano fibrous membrane obtainingThe universal testing machine (CMT-8500 type) of newly thinking carefully with Shenzhen at room temperature carries out test stress-strain.

5. according to claim 1, it is characterized in that described step (4) coaxial electrically spun CA (shell)-PAA (core) alsoThe preparation method of the efficient electrostatic spinning water-oil separating of imidization tunica fibrosa is the preparation of CA-PI tunica fibrosa: traditionalOn the basis of electric spinning equipment, adopt coaxial syringe needle, the DMAc solution of 1-5% (wt) PAA is as core, 5-10% (wt)Carrene and the mixed solution of acetone 2: 1 (V/V) as shell, spinning in high-voltage electrostatic field flies High Rotation SpeedWheel receives CA-PAA nanofiber. By CA-PAA nano fibrous membrane good electrospinning according to 150 DEG C/2h of temperature programming,200/3h, 250 DEG C/1h, the method for 260 DEG C/1h is carried out imidization and is obtained CA-PI nano fibrous membrane; The nanometer fibre obtainingThe universal testing machine (CMT-8500 type) that dimension film adopts Shenzhen newly to think carefully at room temperature carries out test stress one strain.

6. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa according to claim 1, described in it is characterized in thatThe synthetic benzoxazine monomer of step (5):

1) by bisphenol A/F, paraformaldehyde and m-benzotrifluoride amine 14.7g respectively, 5.3g and 14.1g, add successively condensation be housedReturn duct, electric blender, N₂In the four-hole bottle of wireway, thermometer;

2) heating is until reactant thickness is difficult to stir, and question response thing is cooled to room temperature, adds CHCl to it₃200ml entersRow dissolves;

3), with the above-mentioned dissolving of the NaOH solution washing mixed solution completely of mass fraction 2%, treat that solution layering takes off a layer solution.The solution of separating is added to the CHCl of 50ml₃；

4) after stirring, add the anhydrous calcium chloride (CaCl of 2g₂) dehydration;

5) solution after dehydration is dried, obtains the monomer powders of fluorine-containing benzoxazine.

7. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa according to claim 1, described in it is characterized in thatStep (6) BAF-tfa and BAF-tfa/ Nano particles of silicon dioxide (SiO₂NPs) in-situ solidifying CA, PI,CA-PI nano fibrous membrane;

1) take 0.001g, 0.002g, 0.005g, 0.01g, 0.05g, the fluorine-containing benzoxazine BAF-tfa of 0.1g and 0.4g is mono-Body powder, is respectively 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, 1.0%, 4.0% according to mass fraction and dissolvesIn butyl acetate (ButylAcetate), obtain dissolving completely and mix the clear solution of homogeneous;

2) by the laboratory sample of CA, PI, CA-PI tunica fibrosa cutting 2 × 2cm width and the length of preparation, and by this fibreDimension film immersion is in the butyl acetate solution that is dissolved with fluorine-containing benzoxazine BAF-tfa;

3) with taking the photograph son, CA, the PI, the CA-PI tunica fibrosa that are immersed in mixed solution are taken out rapidly, first in natural conditionsUnder dry, then put vacuum into and be cured for case; Be cooled to afterwards room temperature, taking-up F-PBZ/CA, F-PBZ/PI,F-PBZ/CA-PI is for subsequent use.

4) take 0.001g, 0.002g, 0.005g, 0.01g, 0.05g, the BAF-tfa monomer powders of 0.1g and 0.4g, according toMass fraction is respectively 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, 1.0%, 4.0% and is dissolved in butyl acetate(ButylAcetate) in;

5) and to add mass fraction be 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, 1.0%, 4.0% SiO₂NPsIn butyl acetate solution, obtain dissolving completely and mix the clear solution of homogeneous;

6) by the laboratory sample of CA, PI, CA-PI tunica fibrosa cutting 2 × 2cm width and the length of preparation, and by this fibreDimension film immersion is being dissolved with BAF-tfa and SiO₂In the butyl acetate liquid of NPs; Finally, will be immersed in mixed solution with tweezersIn tunica fibrosa take out rapidly, first dry under field conditions (factors), then put vacuum drying oven into and be cured 2h, cooling afterwardsTo room temperature, take out F-PBZ/SNP/CA, F-PBZ/SNP/PI, F-PBZ/SNP/CA-PI for subsequent use.

8. the preparation method of efficient electrostatic spinning water-oil separating tunica fibrosa according to claim 1, described in it is characterized in thatStep (7) water-oil separating experiment:

1) measure respectively carrene and the water of 10ml,Water methylene blue staining, oil (carrene) dyes with oil red. By after the oil mixing with water solution left standstill 1min of 200ml,Profit separates. Be dyed to blue water on upper strata, red oil is in lower floor, F-PBZ--1/SNP-4/CA-PI function fibreDimension film is fixed between two glass tubes. Then, the mixed solution of layering is poured in glass tube above, carried out profitSeparate. Red oil permeates F-PBZ-1/SNP-4/CA-PI tunica fibrosa rapidly, flows in beaker below, and blueWater is still stayed in the glass tube on upper strata, and records the time that profit is separated completely, and measure separate before with separate afterThe volume of water.

2) select respectively different oil water mixtures (carrene-water, bromobenzene-water, carbon tetrachloride-water, chloroform-Water and 1,2-dichloroethanes-water) 20ml (1/1 (V/V)), according to 1) carry out water-oil separating experiment.

3) the CA-PAA film of electrospinning different-thickness imidization obtain CA-PI film respectively, at the BAF-tfa through 1wt%And 4wt%SiO₂NPs in-situ solidifying obtains different-thickness F-PBZ-1/SNP-4/CA-PI film. And by 1) carry out profitSeparating experiment.

4) select F-PBZ-1/SNP-4/CA-PI film, and by 1) carry out repeatedly water-oil separating.