CN111214962A - Folded graphene oxide/nanofiber composite membrane and preparation method and application thereof - Google Patents
Folded graphene oxide/nanofiber composite membrane and preparation method and application thereof Download PDFInfo
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- B01J20/28033—Membrane, sheet, cloth, pad, lamellar or mat
Abstract
The invention provides a folded graphene oxide/nanofiber composite membrane and a preparation method and application thereof. The preparation method of the folded graphene oxide/nanofiber composite membrane comprises the steps of combining a high-molecular spinning solution and a graphene oxide dispersion solution onto the surface of a supporting layer to obtain a composite membrane, and carrying out heat treatment or chemical treatment on the composite membrane to obtain the folded graphene oxide/nanofiber composite membrane; the polymer spinning solution is combined with the supporting layer by using an electrostatic spinning method, and the graphene oxide dispersion liquid is combined with the supporting layer by using an electrostatic spraying method. The electrostatic spraying method shrinks the graphene oxide into three-dimensional graphene oxide clusters which are used as spacing materials to be dispersed among the nanofiber networks, so that the close packing probability of the nanofibers is reduced, the porosity of the electrostatic spinning nanofiber membrane is improved, and the adsorption capacity of the obtained composite membrane is increased.
Description
Technical Field
The invention relates to the field of preparation of adsorption separation materials, in particular to a preparation method of a nanofiber composite membrane, and particularly relates to a folded graphene oxide/nanofiber composite membrane as well as a preparation method and application thereof.
Background
With the rapid development of economy, a large amount of industrial wastewater is discharged, accidents caused by heavy metal and organic pollutant pollution occur frequently, clean water resources are in shortage day by day, and the sustainable development of the society is severely restricted. Most contaminants are difficult to biodegrade, can accumulate in organisms, and are transmitted in the food chain through biological enrichment and concentration, which poses serious threats to the ecological environment and human health. Scientists have developed a number of methods for treating water pollutants including ion exchange, chemical precipitation, membrane separation, and adsorption. The adsorption method has the advantages of simple operation, low energy consumption, low cost and the like, and is a high-efficiency and widely-applied removal method.
The adsorbent plays a decisive role in the adsorption method, common adsorbents comprise active carbon, diatomite, activated alumina, nano materials, porous materials, cellulose, chitosan and other modified high polymer materials, however, in the practical application process, inorganic powder and nano particles are easy to lose, potential secondary pollution is caused, common high polymer materials need to be subjected to functional modification to have a good adsorption effect, and the chemical modification process is complex and has high cost. The nano-fiber material is used as an adsorption material with a very large specific surface area, has strong adsorption force and filterability, and the graphene oxide has a very high specific surface area, is rich in hydroxyl/carboxyl/epoxy active adsorption sites, and is also a good nano-adsorbent.
Electrostatic spinning (Electrospinning) is a simple and convenient method capable of preparing continuous nanofibers, the diameter of the fibers is generally dozens to thousands of nanometers, and the formed non-woven fabric has a structure with nanometer micropores and communicated pores, has the advantages of large specific surface area, high porosity, light weight, high strength and the like, and is a very good adsorption separation material. In addition, the electrostatic spinning nanofiber membrane can be applied to dynamic filtration and adsorption, compared with a fixed bed filled with particles, the through hole structure of the non-woven fabric enables the fluid resistance to be small and the mass transfer to be fast, the engineering application is easy to realize, and meanwhile, the loss of the particles can be avoided.
Electrostatic spraying (electrostatic spraying) is a technology developed based on the principle that conductive fluid generates high-speed spraying under a high-voltage electrostatic field, polymer liquid drops sprayed from a needle are charged through the action of high-voltage static electricity, and then a simple method for preparing polymer micro-nano microspheres through volatilization of a solvent in the liquid drops is adopted. The microsphere prepared by the electrostatic spraying technology has good monodispersity, high purity and diameter reaching micro/nano scale, and can be formed in one step by the electrostatic spraying technology without adding a template and a post-treatment process.
CN102268745A provides a method for preparing porous nanofiber with high specific surface area, which prepares composite nanofiber by preparing a certain proportion of polyacrylonitrile and polyethylene oxide mixed solution and carrying out high-pressure electrostatic spinning on the mixed solution. The porous nanofiber with high specific surface area has high application value in the fields of medical appliances, artificial organs, ultrapure water manufacturing, sewage treatment, recycling and the like.
CN103212382A discloses a self-assembled electrospun cellulose nanofiber membrane for adsorbing heavy metal ions and a preparation method thereof, firstly preparing an electrospun cellulose nanofiber membrane with the average diameter of 88-135nm and the porosity of 30-80% by adopting an electrospinning method, soaking the electrospun cellulose nanofiber membrane in 100% ethanol for 1-2h, then soaking the ethanol-treated electrospun cellulose nanofiber membrane in an alkaline solution for 30-90min, and finally preparing 2-6 layers of polyethyleneimine-assembled electrospun fibroin nanofiber membrane by adopting polyethyleneimine solution treatment. The self-assembled electrostatic spinning cellulose nanofiber membrane prepared by the method has a large specific surface area, can increase the contact area with metal ions, increase the adsorption capacity, shorten the time for reaching adsorption balance, and effectively adsorb heavy metal ions in wastewater.
However, the nanofiber obtained by electrostatic spinning is actually a fiber felt or non-woven fabric formed by overlapping and stacking multiple layers of fibers, and the close-packed structure inevitably sacrifices a lot of effective specific surface area, prevents the target pollutant from diffusing into the adsorption material, and relatively reduces the adsorption performance.
Therefore, how to improve the close packing state of the nanofibers and increase the porosity and specific surface area of the electrospun nanofiber membrane is an urgent problem to be solved in the process of preparing the nanofiber membrane.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a folded graphene oxide/nanofiber composite membrane and a preparation method thereof. In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, a preparation method of a folded graphene oxide/nanofiber composite membrane comprises the following steps:
the method comprises the steps of combining a high-molecular spinning solution and a graphene oxide dispersion liquid on the surface of a supporting layer to obtain a composite film, and carrying out heat treatment or chemical treatment on the composite film to obtain the folded graphene oxide/nanofiber composite film, wherein the high-molecular spinning solution is combined with the supporting layer by using an electrostatic spinning method, and the graphene oxide dispersion liquid is combined with the supporting layer by using an electrostatic spraying method.
In the process of electrostatic spraying, due to the rapid volatilization of the solvent, the two-dimensional graphene oxide nanosheets can shrink into wrinkled three-dimensional graphene oxide groups (like wrinkled paper groups), and meanwhile, good self-dispersion is realized due to charge carrying. The three-dimensional folded graphene oxide clusters are dispersed among the networks of the nanofibers as spacing materials (spacers), the close packing probability of the nanofibers can be reduced, and the porosity and the specific surface area of the electrospun nanofiber membrane can be further improved, so that the diffusion of adsorbed solutes is facilitated, and the adsorption rate is accelerated. In addition, the graphene oxide can be wound and fixed by the polymer nano-fibers, so that the problems of loss in the single use process and secondary reprocessing required by generation of difficultly separated fine slurry are avoided, and the defect of engineering application feasibility is overcome.
As a preferred technical solution of the present invention, the polymer material in the polymer spinning solution is any one or a combination of two or more of Cellulose Acetate (CA), chitosan, polyvinyl alcohol (PVA), polystyrene pyrrolidone (PVP), polyvinylidene fluoride (PVDF), Polyimide (PI), Polyamide (PA), polymethyl methacrylate (pmma), polylactic acid (PLA), Polycaprolactone (PCL), Polycarbonate (PC), Polyaniline (PANI), Polyacrylonitrile (PAN), Polysulfone (PSU), Polyethersulfone (PES), Polystyrene (PS), or polyethylene terephthalate (PET).
Preferably, the mass concentration of the polymer material is 1 to 20%, and may be, for example, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 16%, 18%, or 20%.
Preferably, the solvent in the polymer spinning solution is any one or a combination of two or more of water, ethanol, acetone, tetrahydrofuran, formic acid, N-butanol, 1, 4-dioxane, isopropanol, N-methylpyrrolidone, dichloromethane, N-dimethylformamide, N-dimethylacetamide and acetic acid.
In a preferred embodiment of the present invention, the mass concentration of graphene oxide in the graphene oxide dispersion liquid is 0.01 to 1%, and may be, for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.5%, 0.6%, 0.8%, or 1%.
Preferably, the dispersant in the graphene oxide dispersion liquid is any one or a combination of two or more of water, ethanol, acetone, tetrahydrofuran, formic acid, N-butanol, 1, 4-dioxane, isopropanol, N-methylpyrrolidone, dichloromethane, N-dimethylformamide, N-dimethylacetamide, or acetic acid.
In a preferred embodiment of the present invention, the supporting layer is one or a combination of two or more of polyester fibers, polypropylene fibers, polyamide fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, carbon fibers, glass fibers, and cotton-flax fabrics, and is preferably polyester fibers.
In a preferred embodiment of the present invention, the voltage used in the electrospinning method is 8 to 30kV, and may be, for example, 8kV, 10kV, 12kV, 15kV, 18kV, 20kV, 25kV, 28kV, or 30 kV.
Preferably, the flow rate of the polymeric spinning solution in the electrostatic spinning method is 0.1-6 mL/h, and may be, for example, 0.1mL/h, 0.5mL/h, 1mL/h, 1.5mL/h, 2mL/h, 3mL/h, 4mL/h, 5mL/h or 6 mL/h.
Preferably, the receiving distance of the electrospinning method is 5-15 cm, and for example, may be 5cm, 6cm, 8cm, 10cm, 12cm or 15 cm.
In a preferred embodiment of the present invention, the voltage used in the electrostatic spraying method is 8 to 30kV, and may be, for example, 8kV, 10kV, 12kV, 15kV, 18kV, 20kV, 25kV, 28kV, or 30 kV.
Preferably, the flow rate of the graphene oxide dispersion liquid in the electrostatic spraying method is 0.5-5 mL/h, and may be, for example, 0.5mL/h, 0.6mL/h, 1mL/h, 1.5mL/h, 2mL/h, 3mL/h, 3.5mL/h, 4mL/h or 5 mL/h.
Preferably, the electrostatic spraying method has a receiving distance of 5 to 15cm, for example, 5cm, 6cm, 8cm, 10cm, 12cm or 15 cm.
As a preferred embodiment of the present invention, the bonding of the polymer spinning solution and the graphene oxide dispersion to the surface of the supporting layer is performed by simultaneously electrospinning the polymer spinning solution and electrostatically spraying the graphene oxide dispersion on the surface of the supporting layer, or alternatively electrospinning the polymer spinning solution and electrostatically spraying the graphene oxide dispersion on the surface of the supporting layer.
In the invention, if electrostatic spinning and electrostatic spraying are alternately carried out, the high polymer material and the graphene oxide are alternately deposited to obtain a layered structure with the high polymer material and the graphene oxide spaced; if carry out electrostatic spinning and electrostatic spraying simultaneously, then the macromolecular material that obtains and graphite oxide are each other twine each other and are the alternate mixed homogeneous structure, can not appear the condition that both peeled off, can effectively prevent that the granule from breaking away from, and the effect is better.
In a preferred embodiment of the present invention, the heat treatment temperature is 30 to 200 ℃, and may be, for example, 30 ℃, 50 ℃, 60 ℃, 80 ℃, 100 ℃, 120 ℃, 150 ℃, 180 ℃ or 200 ℃.
Preferably, the time of the heat treatment is 10-180 min, for example, 10min, 40min, 50min, 60min, 80min, 100min, 120min, 150min or 180 min.
Preferably, the degree of vacuum of the heat treatment is 0 to 0.1MPa, and may be, for example, 0.01MPa, 0.02MPa, 0.04MPa, 0.05MPa, 0.06MPa, 0.08MPa or 0.1 MPa.
Preferably, the chemical treatment is to place the composite membrane in a solution or steam containing a cross-linking agent.
Preferably, the chemical treatment time is 0.5-24 h, for example, 0.5h, 1h, 4h, 5h, 6h, 8h, 10h, 12h, 15h, 18h, 20h or 24 h.
Preferably, the cross-linking agent is any one or a combination of more than two of glutaraldehyde, isocyanate, formaldehyde, epichlorohydrin, ethylene glycol, glycerol or trimesoyl chloride.
As a preferable technical scheme of the invention, the preparation method comprises the following steps:
simultaneously carrying out electrostatic spinning on a macromolecular spinning solution and electrostatic spraying of a graphene oxide dispersion liquid on the surface of a supporting layer, or alternatively carrying out electrostatic spinning on the macromolecular spinning solution and electrostatic spraying of the graphene oxide dispersion liquid on the surface of the supporting layer to obtain a composite film;
the mass concentration of the high molecular material in the high molecular spinning solution is 1-20%, the high molecular material is combined with the supporting layer by using an electrostatic spinning method, the voltage used by the electrostatic spinning method is 8-30 kV, the flow rate of the high molecular spinning solution is 0.1-6 mL/h, and the receiving distance is 5-15 cm; the mass concentration of graphene oxide in the graphene oxide dispersion liquid is 0.01-1%, an electrostatic spraying method is used to combine the graphene oxide dispersion liquid with the supporting layer, the voltage used by the electrostatic spraying method is 8-30 kV, the flow rate of the graphene oxide dispersion liquid is 0.5-5 mL/h, and the receiving distance is 5-15 cm;
and then carrying out heat treatment or chemical treatment on the composite film, wherein the heat treatment temperature is 30-200 ℃, the time is 10-180 min, and the vacuum degree is 0-0.1 Mpa, and the chemical treatment is to place the composite film in a solution or steam containing a cross-linking agent for 0.5-24 h to prepare the folded graphene oxide/nanofiber composite film.
In a second aspect, the folded graphene oxide/nanofiber composite membrane prepared by the preparation method of the first aspect is used.
In a third aspect, the invention also provides an application of the folded graphene oxide/nanofiber composite membrane in preparation of a separation material.
The folded graphene oxide/nanofiber composite membrane provided by the invention can be used as an adsorption material or a filter medium, and can be widely applied to the field of separation.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between any of the above-recited numerical ranges not recited, and for the sake of brevity and clarity, the present invention is not intended to be exhaustive of the specific numerical values encompassed within the range.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the folded three-dimensional graphene oxide clusters are used as spacing materials to be dispersed among networks of the nanofibers, so that the close packing probability of the nanofibers is reduced, the porosity and the specific surface area of the electrospun nanofiber membrane are improved, the diffusion of adsorbed solutes is facilitated, and the adsorption rate is accelerated; meanwhile, the adsorption capacity of the composite membrane can be increased due to the functional groups carried by the graphene oxide.
(2) The graphene oxide can be wound and fixed by the polymer nano-fiber, so that the problems of loss in the process of independent use and secondary reprocessing for generating difficultly-separated micro slurry are avoided, the defect of feasibility of engineering application is overcome, the method is simple and feasible, large-scale production is easy to realize, and the obtained material has potential application prospects in the separation fields of adsorption, filtration and the like.
Drawings
Fig. 1 is an electron micrograph (scale 1 μm) of the graphene oxide/nanofiber composite film prepared in example 1.
FIG. 2 is an electron micrograph (scale 1 μm) of the chitosan nanofiber membrane prepared in comparative example 1.
FIG. 3(a) is an electron micrograph (scale 1 μm) of the dispersed graphene oxide particles obtained in comparative example 2,
fig. 3(b) is an electron micrograph (scale 100nm) of the graphene oxide dispersed particles obtained in comparative example 2.
Fig. 4 is a dynamic adsorption curve diagram of the composite membrane obtained in example 1 for adsorbing heavy metal uranium ions.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Example 1
In this embodiment, a preparation method of a folded graphene oxide/nanofiber composite membrane is provided, where the preparation method includes the following steps:
(1) dissolving 2g of chitosan (Zhejiang gold shell biochemistry limited company, molecular weight 30 ten thousand) in 40mL of acetic acid solution with mass concentration of 90% to prepare transparent and uniform chitosan spinning solution;
(2) dispersing 0.1g of graphene oxide (Nanjing Xiapong nano material science and technology Co., Ltd. XF002-3) in 50mL of water, ultrasonically dispersing to prepare a uniform graphene oxide dispersion liquid, then adding 100mL of ethanol, and ultrasonically dispersing;
(3) adding the chitosan spinning solution into electrostatic spinning equipment, and controlling the chitosan spinning solution to be sprayed out by a micro-injection pump, wherein electrostatic spinning parameters are controlled to be 20kV in voltage, 1.8mL/h in flow speed and 8cm in receiving distance;
(4) adding the graphene oxide dispersion liquid into electrostatic spraying equipment, and spraying the graphene oxide dispersion liquid by using a micro-injection pump, wherein electrostatic spraying parameters are controlled to be 20kV in voltage, 3.6mL/h in flow speed and 10cm in receiving distance;
(5) carrying out electrospinning and electrospraying simultaneously, covering polyester fibers on a rolling receiving roller to serve as a supporting layer, and receiving the electrospun chitosan nanofibers and electrosprayed graphene oxide particles on the surface of the polyester fibers;
(6) the composite membrane is placed into glutaraldehyde saturated steam for crosslinking for 12 hours to carry out chemical crosslinking, and the folded graphene oxide/nanofiber composite membrane is prepared, wherein an electron microscope (JSM-6700F scanning electron microscope) of the folded graphene oxide/nanofiber composite membrane is shown in figure 1, and as can be seen from figure 1, dispersed graphene oxide particles are filled among high-molecular spinning yarns of the composite membrane prepared by the preparation method provided by the invention, so that the close packing among the spinning yarns is reduced.
Example 2
In this embodiment, a preparation method of a folded graphene oxide/nanofiber composite membrane is provided, where the preparation method includes the following steps:
(1) dissolving 2g of polyvinylidene fluoride (PVDF) (50-70 ten thousand, Shanghai Sanai Rich New Material science and technology Co., Ltd.) in 50mLN, N-Dimethylformamide (DMF) solution to prepare transparent and uniform PVDF spinning solution;
(2) dispersing 0.2g of graphene oxide in 50mL of water, performing ultrasonic dispersion to prepare a uniform graphene oxide dispersion solution, adding 200mL of ethanol, and performing ultrasonic dispersion;
(3) adding the PVDF spinning solution into electrostatic spinning equipment, and controlling the PVDF spinning solution to be sprayed out by a micro-injection pump, wherein electrostatic spinning parameters are controlled to be 21kV, the flow rate is 2.4mL/h, and the receiving distance is 8 cm;
(4) adding the graphene oxide dispersion liquid into electrostatic spraying equipment, and spraying the graphene oxide dispersion liquid by using a micro-injection pump, wherein electrostatic spraying parameters are controlled to be 21kV in voltage, 3mL/h in flow speed and 12cm in receiving distance;
(5) carrying out electrospinning and electrospraying simultaneously, covering polyester fibers on a rolling receiving roller to serve as a supporting layer, and synchronously receiving the electrospun PVDF nanofibers and the electrosprayed graphene oxide particles on the surface of the polyester fibers;
(6) and (3) putting the composite membrane into a vacuum drying oven with the temperature of 120 ℃ for heat treatment for 1h to prepare the folded graphene oxide/PVDF nano-fiber composite membrane.
Example 3
In this embodiment, a preparation method of a folded graphene oxide/nanofiber composite membrane is provided, where the preparation method includes the following steps:
(1) dissolving 5g of polyamide material (PA6/PA66 particles, Aldrich company, USA, molecular weight is 10,485) in 40mL of formic acid solution to prepare transparent and uniform PA spinning solution;
(2) dispersing 0.6g of graphene oxide in 100mL of water, performing ultrasonic dispersion to prepare a uniform graphene oxide dispersion solution, adding 300mL of acetone according to the volume, and performing ultrasonic dispersion;
(3) adding a polyamide spinning solution into electrostatic spinning equipment, and controlling the polyamide spinning solution to be sprayed out by a micro-injection pump, wherein electrostatic spinning parameters are controlled to be 15kV, the flow rate is 1.2mL/h, and the receiving distance is 8 cm;
(4) adding the graphene oxide dispersion liquid into electrostatic spraying equipment, and spraying the graphene oxide dispersion liquid by using a micro-injection pump, wherein electrostatic spraying parameters are controlled to be 15kV in voltage, 0.1mL/h in flow speed and 15cm in receiving distance;
(5) carrying out electrospinning and electrojetting alternately, covering polyester fibers on a rolling receiving roller to serve as a supporting layer, and receiving the electrospun polyamide nanofibers and the electrojetted graphene oxide particles on the surface of the polyester fibers for 60min each time;
(6) and (3) putting the composite membrane into a vacuum drying oven with the temperature of 80 ℃ for heat treatment for 30min, wherein the vacuum degree is 0.1Mpa, and preparing the folded graphene oxide/nanofiber composite membrane.
Comparative example 1
(1) 2g of chitosan is dissolved in 40mL of acetic acid solution with the mass concentration of 90% to prepare transparent and uniform chitosan spinning solution;
(2) adding the chitosan spinning solution into electrostatic spinning equipment, and controlling the chitosan spinning solution to be sprayed out by a micro-injection pump, wherein electrostatic spinning parameters are controlled to be 20kV in voltage, 1.8mL/h in flow speed and 8cm in receiving distance;
(3) carrying out single electrospinning, covering polyester fibers on a rolling receiving roller to serve as a supporting layer, and receiving the electrospun chitosan nanofibers on the surface of the polyester fibers;
(4) and (3) putting the membrane into glutaraldehyde saturated steam for crosslinking for 12 hours to carry out chemical crosslinking, and preparing the chitosan nanofiber membrane, wherein the structure of the chitosan nanofiber membrane is shown in figure 3. As can be seen from comparison between fig. 1 in example 1 and fig. 2 in comparative example 1, the graphene oxide/nanofiber composite membrane provided by the present invention is more fluffy than a pure chitosan membrane, and the close packing between fibers is significantly reduced.
Comparative example 2
(1) Dispersing 0.1g of graphene oxide in 50mL of water, performing ultrasonic dispersion to prepare a uniform graphene oxide dispersion solution, adding 100mL of ethanol, and performing ultrasonic dispersion;
(2) adding the graphene oxide dispersion liquid into electrostatic spraying equipment, and spraying the graphene oxide dispersion liquid by using a micro-injection pump, wherein electrostatic spraying parameters are controlled to be 20kV in voltage, 3.6mL/h in flow speed and 10cm in receiving distance;
(3) performing electric spraying independently, covering an aluminum foil on a rolling receiving roller (since the aperture of a polyester fiber supporting layer is about 120 microns, graphene oxide cannot be received on the surface of the polyester fiber supporting layer), and receiving graphene oxide particles on the surface of the aluminum foil;
(6) the membrane is put into glutaraldehyde saturated steam for crosslinking for 12 hours to carry out chemical crosslinking, graphene oxide dispersed particles are obtained through preparation, an electron microscope photograph of pure graphene oxide under a scale of 1 mu m and a electron microscope photograph under a scale of 100nm are shown in a picture (a) and a picture (b) in a picture (3), the graphene oxide obtained through single electric spraying is in a fold shape, and the graphene oxide particles are uniformly dispersed due to mutual repulsion of negative charges in the electric spraying process, so that the membrane cannot be formed.
Performance testing
The wrinkled graphene oxide/nano-fiber composite membranes obtained in examples 1-3 and the chitosan nano-fiber membranes obtained in comparative example 1 are used as adsorption beds and are sequentially numbered into 1-4 groups, the adsorption beds of each group respectively contain 15 layers of corresponding composite membranes or fiber membranes, and 3 parallel experiments are arranged in each group. Initial uranium concentration C for each experimental group0The uranium acyl solution is 2mg/L, and the concentration C of uranium in the outflow solution at different times is analyzedtWith Ct/C0Plotting as ordinate and time as abscissa to obtain penetration curve, and setting Ct/C0The time to reach the breakthrough point was calculated for each experimental group as 0.1, the longer the time to reach the breakthrough point, the better the performance of the composite membrane.
Wherein, the penetration curve of the experimental group 1, namely the folded graphene oxide/chitosan nanofiber composite membrane obtained in the embodiment 1, is shown in fig. 4, and the time for reaching the penetration point is 38 min; the time for the experimental group 2 to reach the breakthrough point was 17 min; the time for the experimental group 3 to reach the breakthrough point was 22 min; the time to reach the breakthrough point for experimental group 4, comparative example 1, was 19 min.
In conclusion, the folded graphene oxide/nanofiber composite membrane provided by the invention has the advantages that the time for reaching the penetration point is longer, and the performance of the composite membrane is better. Therefore, the chitosan nanofiber membrane provided by the comparative example has a more compact structure and is not beneficial to the diffusion of the adsorption material to the inside, and the graphene oxide/nanofiber composite membrane and the preparation method thereof provided by the invention can disperse the graphene oxide as a spacer material among networks of nanofibers, reduce the close packing probability of the nanofibers and increase the adsorption capacity of the composite membrane, but the chitosan nanofiber membrane has a functional group, so that the performance of the chitosan nanofiber membrane is superior to that of the chitosan nanofiber membrane in example 2. Therefore, the composite membrane provided by the invention has better adsorption capacity to substances such as heavy metals in a solution, and the adsorption capacity of the composite membrane prepared by simultaneously carrying out electrostatic spinning and electrostatic spraying is better than that of the composite membrane prepared by alternately carrying out preparation.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A preparation method of a folded graphene oxide/nanofiber composite membrane is characterized by comprising the following steps:
combining a high-molecular spinning solution and a graphene oxide dispersion liquid on the surface of a supporting layer to obtain a composite film, and performing heat treatment or chemical treatment on the composite film to obtain the folded graphene oxide/nanofiber composite film;
the polymer spinning solution is combined with the supporting layer by using an electrostatic spinning method, and the graphene oxide dispersion liquid is combined with the supporting layer by using an electrostatic spraying method.
2. The preparation method according to claim 1, wherein the polymer material in the polymer spinning solution is any one or a combination of two or more of cellulose acetate, chitosan, polyvinyl alcohol, polystyrene pyrrolidone, polyvinylidene fluoride, polyimide, polyamide, polymethyl methacrylate, polylactic acid, polycaprolactone, polycarbonate, polyaniline, polyacrylonitrile, polysulfone, polyethersulfone, polystyrene, or polyethylene terephthalate;
preferably, the mass concentration of the high polymer material is 1-20%;
preferably, the solvent of the polymer spinning solution is any one or a combination of more than two of water, ethanol, acetone, tetrahydrofuran, formic acid, N-butanol, 1, 4-dioxane, isopropanol, N-methylpyrrolidone, dichloromethane, N-dimethylformamide, N-dimethylacetamide and acetic acid.
3. The preparation method according to claim 1 or 2, wherein the mass concentration of graphene oxide in the graphene oxide dispersion liquid is 0.01-1%;
preferably, the dispersant in the graphene oxide dispersion liquid is any one or a combination of two or more of water, ethanol, acetone, tetrahydrofuran, formic acid, N-butanol, 1, 4-dioxane, isopropanol, N-methylpyrrolidone, dichloromethane, N-dimethylformamide, N-dimethylacetamide, or acetic acid.
4. The preparation method according to any one of claims 1 to 3, wherein the support layer is any one or a combination of two or more of polyester fibers, polypropylene fibers, polyamide fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, carbon fibers, glass fibers or cotton-linen fabrics, and is preferably polyester fibers.
5. The method according to any one of claims 1 to 4, wherein the electrostatic spinning method uses a voltage of 8 to 30 kV;
preferably, the flow rate of the polymer spinning solution in the electrostatic spinning method is 0.1-6 mL/h;
preferably, the receiving distance of the electrostatic spinning method is 5-15 cm;
preferably, the voltage used by the electrostatic spraying method is 8-30 kV;
preferably, the flow rate of the graphene oxide dispersion liquid in the electrostatic spraying method is 0.5-5 mL/h;
preferably, the receiving distance of the electrostatic spraying method is 5-15 cm.
6. The preparation method according to any one of claims 1 to 5, wherein the bonding of the polymer spinning solution and the graphene oxide dispersion to the surface of the support layer is performed by simultaneously electrospinning the polymer spinning solution and electrostatically spraying the graphene oxide dispersion on the surface of the support layer, or by alternately electrospinning the polymer spinning solution and electrostatically spraying the graphene oxide dispersion on the surface of the support layer.
7. The preparation method according to any one of claims 1 to 6, wherein the temperature of the heat treatment in the preparation method is 30 to 200 ℃;
preferably, the time of the heat treatment is 10-180 min;
preferably, the vacuum degree during the heat treatment is 0-0.1 Mpa;
preferably, the chemical treatment is to place the composite membrane in a solution or steam containing a cross-linking agent;
preferably, the chemical treatment time is 0.5-24 h;
preferably, the cross-linking agent is any one or a combination of more than two of glutaraldehyde, isocyanate, formaldehyde, epichlorohydrin, ethylene glycol, glycerol or trimesoyl chloride.
8. The production method according to any one of claims 1 to 7, characterized by comprising the steps of:
the composite membrane is obtained by simultaneously carrying out electrostatic spinning on the surface of the supporting layer to obtain a high-molecular spinning solution and electrostatic spraying on the graphene oxide dispersion liquid, or alternatively carrying out electrostatic spinning on the surface of the supporting layer to obtain a high-molecular spinning solution and electrostatic spraying on the graphene oxide dispersion liquid,
the mass concentration of the high molecular material in the high molecular spinning solution is 1-20%, the high molecular material is combined with the supporting layer by using an electrostatic spinning method, the voltage used by the electrostatic spinning method is 8-30 kV, the flow rate of the high molecular spinning solution is 0.1-6 mL/h, and the receiving distance is 5-15 cm;
the mass concentration of graphene oxide in the graphene oxide dispersion liquid is 0.01-1%, an electrostatic spraying method is used to combine the graphene oxide dispersion liquid with the supporting layer, the voltage used by the electrostatic spraying method is 8-30 kV, the flow rate of the graphene oxide dispersion liquid is 0.5-5 mL/h, and the receiving distance is 5-15 cm;
and then carrying out heat treatment or chemical treatment on the composite film, wherein the heat treatment temperature is 30-200 ℃, the time is 10-180 min, and the vacuum degree is 0-0.1 Mpa, and the chemical treatment is to place the composite film in a solution or steam containing a cross-linking agent for 0.5-24 h to prepare the folded graphene oxide/nanofiber composite film.
9. The folded graphene oxide/nanofiber composite membrane prepared by the preparation method according to any one of claims 1 to 8.
10. Use of a pleated graphene oxide/nanofibre composite membrane according to claim 9 for the preparation of a separation material.
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