CN109468709B

CN109468709B - Preparation method of graphene-doped Co3O4 mesoporous fiber

Info

Publication number: CN109468709B
Application number: CN201811264903.5A
Authority: CN
Inventors: 朱光; 张莉
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2018-10-29
Filing date: 2018-10-29
Publication date: 2021-07-16
Anticipated expiration: 2038-10-29
Also published as: CN109468709A

Abstract

The invention relates to graphene doped Co₃O₄The preparation method of mesoporous fiber is characterized by utilizing electrostatic spinning technology and high-temperature heat treatment method to prepare Co₃O₄Mesoporous fiber, and then preparing Co by microwave method₃O₄a/rGO composite; the steps comprise (1) weighing DMF and PAN, stirring at constant temperature until PAN is completely dispersed in DMF, and weighing Co (CH)₃COO)₂·4H₂Adding O, stirring and dissolving to obtain a spinning solution; (2) adding a solvent, stirring until the solvent is fully dissolved and uniformly mixed; (3) controlling the solution flow in the electrostatic spinning process by using a micro-injection pump, putting the solution on an electrostatic spinning device for spinning, and carrying out high-temperature heat treatment after spinning drying to obtain Co₃O₄Fibers; (4) weighing Co₃O₄Adding the fiber and graphite oxide into deionized water, and performing ultrasonic treatment to obtain Co₃O₄A fiber/graphite oxide dispersion solution. The invention then adopts microwave radiation reaction to prepare Co by reduction₃O₄The doping of the rGO increases the light absorption strength of the material and improves the electron transmission capability, thereby improving the photocatalytic performance of the composite material.

Description

Graphene doped Co3O4Preparation method of mesoporous fiber

Technical Field

The invention relates to the technical field of high polymer materials and electrochemistry, in particular to graphene doped Co₃O₄Preparation method of mesoporous fiber

Background

As the population grows and the water consumption increases, the shortage of fresh water resources is a problem. In the field of water purification, the removal of contaminants in water, including heavy metals, organic contaminants and dyes, is one of the issues that is urgently needed to be addressed. Although a plurality of methods for purifying water exist at present, many processes are too complicated, the treatment effect is not ideal, and the standardized discharge is difficult to realize. The transition metal oxide has good photocatalytic activity, so that the transition metal oxide can be applied to the field of water purification, and some transition metal oxides can be used as catalysts to accelerate the degradation of waste in water so as to realize water purification. Co₃O₄The solid is gray black or black transition metal oxide flaky solid, has high crystal stability, and is widely applied to various fields such as high-efficiency catalysts, supercapacitors and the like. The chemistry for making it is numerous. For example, the chemical precipitation method has good application prospect, but the size of the precipitated particles is difficult to control in the preparation process,A plurality of problems of product impurities, difficult control of reaction and the like; the sol method has high production cost, poor calcinatability and large structural change after drying, and the material prepared by the method is difficult to popularize in industrial production.

The electrostatic spinning technology has the advantages of low cost, simple operation, easy mass production and the like, and has potential application prospect in the preparation field of materials such as photocatalysis, solar cells, super capacitors and the like, thereby attracting the interest of the majority of scientific researchers. Meanwhile, the polymer/transition oxide composite fiber and the inorganic nanofiber material prepared by the electrostatic spinning technology have the advantages of high porosity, large specific surface area and good dispersibility. Recently, the electrostatic spinning technology for preparing Co₃O₄The fiber material is mainly applied to the fields of flexible devices, water treatment and the like. Chinese patent CN102277642A discloses a method for preparing fibers by electrostatic spinning of thermoplastic carboxymethyl cellulose derivatives, which is characterized by comprising the following steps: dissolving sodium carboxymethylcellulose in water, adding an initiator ammonium persulfate to initiate reaction for 0.1-2 hours after swelling, adding methyl acrylate to perform graft copolymerization reaction, and reacting for 0.5-8 hours at 40-85 ℃; then mixing the reacted materials with ethanol, standing, filtering, mixing the solid with acetone, standing, filtering, and drying the solid to obtain thermoplastic cellulose; thermoplastic cellulose is crushed into powder, and the powder is dissolved in an organic solvent to prepare a solution, so that an electrostatic spinning solution is obtained; and (3) carrying out electrostatic spinning on the electrostatic spinning solution through an electrostatic spinning device, and drying to obtain the fiber. The invention effectively solves the problem of spinnability of cellulose material solution, and the prepared fiber can be spun into a film, and is applied to the aspects of wastewater treatment, film permeation and the like, and opens up new application of cellulose derivative materials. Chinese patent CN105214516A discloses a method for preparing an electrostatic spinning nanofiber ultrafiltration membrane with high flux and high rejection rate, which adopts bamboo fiber as a coating liquid raw material, polyethylene glycol diacrylate as a cross-linking agent, ammonium persulfate as an initiator and polyethylene glycol as a protective agent, and adopts an electrostatic spinning technology and a glue homogenizing coating method to prepare the electrostatic spinning nanofiber ultrafiltration membrane by taking a polyethylene glycol layer as a surface protective layer and a reinforced nano cellulose layer as a second layerThe spinning layer is a third layer, and the non-woven fabric is a bottom layer. The nano-fiber ultrafiltration membrane prepared by the method has the advantages of small aperture, high stability, long service cycle, good pollution resistance, high flux and good interception effect. Co in water treatment process₃O₄The fiber material has the problems of easy agglomeration, easy recombination of photon-generated carriers and the like, so that the fiber material has great limitation only depending on the photocatalytic capability of the body. Graphene (rGO) is known as one of the most excellent photocatalyst carriers in the new century, and the doping of the rGO can increase the light absorption intensity of the material and improve the electron transmission capability, so that the photocatalytic performance of the composite material is improved, and the Co is prepared by utilizing an electrostatic spinning technology and a high-temperature heat treatment method₃O₄Mesoporous fiber, and then preparing Co by microwave radiation reaction reduction₃O₄a/rGO composite; and the material is used as a photocatalyst to degrade methylene blue dye, and the photocatalytic performance of the composite material is researched. The experimental results show that: co can be improved by doping graphene₃O₄The light absorption intensity of (1) is increased by the excellent conductivity of the graphene in the process of photocatalytic reaction₃O₄The conductivity is improved, photoproduction electrons in the reaction process are easy to separate, the recombination of photoproduction electrons and holes is effectively inhibited, and the Co is improved₃O₄The photocatalytic properties of the material.

Disclosure of Invention

In order to solve the problems that the Co3O4 fiber material is easy to agglomerate and a photon-generated carrier is easy to recombine in the water treatment process in the prior art, the invention provides a method for preparing Co by utilizing an electrostatic spinning technology and a high-temperature heat treatment method₃O₄Mesoporous fiber, and then preparing Co by microwave radiation reaction reduction₃O₄The doping of the rGO can increase the light absorption strength of the material and improve the electron transmission capability, thereby improving the photocatalytic performance of the composite material.

Graphene doped Co₃O₄The preparation method of the mesoporous fiber is to prepare Co by utilizing an electrostatic spinning technology and a high-temperature heat treatment method₃O₄Mesoporous fiber, then adopting microwave radiation reaction to reducePreparation of Co₃O₄a/rGO composite; the preparation of graphene doped with Co₃O₄Weighing N, N-Dimethylformamide (DMF) and Polyacrylonitrile (PAN) and stirring at constant temperature until the PAN is completely dispersed in the DMF, weighing Co (CH3COO) 2.4H 2O and adding into the solution, and stirring until the Co (CH3COO) 2.4H 2O is completely dissolved to obtain a spinning solution; (2) adding a dissolving agent into the obtained spinning solution, stirring until the dissolving agent is fully dissolved, and uniformly mixing; (3) transferring the spinning liquid into an injector, controlling the solution flow in the electrostatic spinning process by using a micro-injection pump, putting the solution flow on an electrostatic spinning device for spinning, drying the obtained spun yarn, and then putting the dried spun yarn into a muffle furnace for high-temperature heat treatment to obtain Co₃O₄Fibers; (4) weighing Co₃O₄Adding the fiber and the graphite oxide dispersion liquid into deionized water for ultrasonic treatment to obtain Co₃O₄Fiber/graphene oxide dispersion liquid, then transferring the dispersion liquid into a microwave reaction instrument, and carrying out microwave radiation reaction reduction to prepare graphene doped Co₃O₄A mesoporous fiber.

Preferably, DMF is recovered from industrial wastewater by an extraction method and a reduced pressure distillation method, an extracting agent o-sec-butylphenol is added into the industrial wastewater containing DMF, diluents cyclohexane and n-octanol are added into the extracting agent, and the mixture is subjected to constant temperature water bath at 30 ℃; and after layering is finished, absorbing the water phase, carrying out reduced pressure distillation on the oil phase, and collecting the evaporated steam into a liquid collecting bottle through a condensing tube to obtain the DMF.

Preferably, the DMF and the PAN are stirred for 3 hours at the ambient temperature of 70 ℃ by a magnetic stirrer at the speed of 800r/min, so that the PAN is completely dispersed into the DMF; adding Co (CH) into the solution₃COO)₂4H2O, stirring for 2H at 70 ℃ by using a magnetic stirrer at 800r/min, and completely dissolving to obtain a spinning solution; the DMF, PAN and Co (CH)₃COO)₂·4H₂The mass ratio of O is 9:1: 1.

Preferably, the Co (CH)₃COO)₂·4H₂O is prepared by plasma exchange method, and CoCl is adsorbed by ion exchange column₂Solution, filling weak acid cation exchange resin in an ion exchange column,washing with distilled water after adsorption to remove residual non-adsorbed CoCl in the resin₂Washing the resin layer with dilute acetic acid until AgNO is used₃Until no Cl ion in the washing liquid can be detected, eluting the washed resin with acetic acid to obtain a mixture of cobalt acetate and acetic acid, and finally evaporating and crystallizing in vacuum to prepare cobalt acetate and recovering acetic acid.

Preferably, the solvent is one of dichloromethane, chloroform and dioxane, and is uniformly stirred by a magnetic stirrer at 800 r/min.

Preferably, the feed rate of the micro-syringe pump is 0.025 to 0.059 mL/min.

Preferably, the spinning conditions are electrostatic spinning device voltage of 16KV, temperature of 20 ℃, plate interval of 18cm and spinning solution flow rate of 1 mL/h.

Preferably, the prepared spinning is dried for 12h, placed in a muffle furnace, heated to 450 ℃ at the speed of 1 ℃/min by taking nitrogen as shielding gas, and subjected to high-temperature heat treatment for 2h to obtain Co₃O₄A fiber.

Preferably, the graphite oxide is prepared by first using H₂SO₄And NaNO₃Soaking graphite, intercalating the graphite, and adding K₂FeO₄Oxidizing graphite, said H₂SO₄、NaNO₃、K₂FeO₄According to the mass ratio of 1: 5: and 5, forming a graphite oxide dispersion liquid after reaction, and finally adding a reducing agent vitamin C into the graphite oxide dispersion liquid by adopting a microwave radiation reduction method to reduce to obtain the graphene component.

Preferably, the Co is₃O₄Mixing the fibers and the graphene oxide dispersion liquid according to the ratio of 35:3, stirring for 30min at 800r/min by using a magnetic stirrer to form a composite solution, transferring the composite solution into a microwave reaction instrument, carrying out hydrothermal reaction for 5 min at the constant temperature of 180 ℃ under high pressure, naturally cooling to room temperature, mixing and centrifugally washing for 3 times by using secondary deionized water and absolute ethyl alcohol, and finally carrying out vacuum drying for 24h at the constant temperature of 65 ℃ to obtain the graphene Co-doped graphene₃O₄A mesoporous fiber.

Compared with the prior art, the invention has the beneficial effects that:

(1) DMF is recovered from industrial wastewater by an extraction method and a reduced pressure distillation method, and because DMF has strong dissolving capacity and is widely applied to the industrial fields of medicines, pesticides, food additives, leather and the like, a large amount of industrial wastewater containing DMF is generated, the method recovers and prepares DMF, not only can obtain a solvent required by an experiment, but also can play a role in purifying wastewater; the extraction agent o-sec-butylphenol is selected because the boiling point of the solvent is higher than DMF, and the extracted organic phase can be recycled only by distilling DMF out.

(2) DMF and PAN are stirred for 3h at the ambient temperature of 70 ℃ by a magnetic stirrer at the speed of 800r/min, so that PAN can be completely dispersed in DMF, and Co (CH) is added₃COO)₂·4H₂O, stirring for 2 hours at 70 ℃ by using a magnetic stirrer at 800r/min, and completely dissolving to obtain spinning solution, wherein DMF, PAN and Co (CH)₃COO)₂·4H₂The mass ratio of O is 9:1:1, so that the solvent reaction can be completed.

（3）Co(CH₃COO)₂·4H₂O is prepared by plasma exchange method, and CoCl is adsorbed by ion exchange column₂The solution and the ion exchange column are filled with weak acid cation exchange resin, and the resin has the advantages of high exchange capacity, small volume change, high mechanical strength, good chemical stability, pollution resistance, oxidation resistance, high exchange speed, high regeneration efficiency and the like; washing with distilled water after adsorption to remove residual non-adsorbed CoCl in the resin₂Should be Cl^-Can be prepared as CoCl⁺Adsorbed on the resin and not eluted with water, so that the resin layer is sufficiently washed with dilute acetic acid until AgNO is used₃Until no Cl ions in the washing liquid can be detected, eluting the washed resin with acetic acid to obtain a mixture of cobalt acetate and acetic acid, and finally evaporating and crystallizing in vacuum to obtain the cobalt acetate, wherein the acetic acid liquid can be recovered.

(4) The solvent is one of dichloromethane, chloroform and dioxane, and because the volatilization speed is increased after the solvent is added in the electrostatic spinning process, the jet flow drying and curing time is shortened, and the curing is carried out before sufficient stretching, the average diameter of the nano-fiber and the distribution range of the fiber diameter are enlarged, and convenience is provided for the subsequent doping of graphene.

(5) The micro-injection pump can control the spinning time of electrostatic electrospinning, and the proper feeding speed can be adjusted by selecting different solvents according to respective volatilization speeds. Putting the spun yarn into a muffle furnace for high-temperature heat treatment to form Co₃O₄Fibres capable of solidifying their structure and of causing Co₃O₄The fibers are more easily doped with graphene molecules.

（6）H₂SO₄And NaNO₃Soaking graphite, reducing Van der Waals force between graphite flakes under acidic condition, intercalating graphite, increasing interlayer spacing, avoiding potassium chlorate, avoiding toxic gas generation and explosion risk, and adding K₂FeO₄The graphite is oxidized, potassium ferrate is used for replacing potassium permanganate to serve as an oxidant, so that a graphite oxide aqueous solution is obtained, the obtained graphite oxide solution and a solution obtained by a potassium permanganate oxidation method are basically consistent in chemical composition, monolayer rate, size and defect degree, however, an oxidation product is iron ions, compared with manganese ions formed by potassium ferrate, the graphite oxide aqueous solution is more environment-friendly, the potassium ferrate is oxidized more rapidly, the prepared small steamed stuffed bun is improved, and the overall cost is reduced.

（7）Co₃O₄Mixing the fiber and graphite oxide dispersion to obtain composite solvent, and microwave reacting to obtain Co₃O₄The fiber and the graphene dispersion liquid are well fused, and the completely doped graphene doped Co is finally obtained by reduction reaction, cooling and washing₃O₄The mesoporous fiber improves the performance of the composite material.

Drawings

FIG. 1 is Co₃O₄SEM pictures at low resolution;

FIG. 2 is Co₃O₄SEM pictures at high resolution;

FIG. 3 is Co₃O₄SEM pictures of/rGO-1 at low resolution;

FIG. 4 is Co₃O₄SEM pictures of/rGO-1 at high resolution;

FIG. 5 is Co₃O₄SEM pictures of/rGO-2 at low resolution;

FIG. 6 is Co₃O₄SEM pictures of/rGO-2 at high resolution;

FIG. 7 is Co₃O₄SEM pictures of/rGO-3 at low resolution;

FIG. 8 is Co₃O₄SEM pictures of/rGO-3 at high resolution;

FIG. 9 is Co₃O₄SEM pictures of/rGO-4 at low resolution;

FIG. 10 is Co₃O₄SEM pictures of/rGO-4 at high resolution;

FIG. 11 is Co₃O₄The mesoporous fiber nitrogen adsorption-desorption maze and aperture distribution diagram;

FIG. 12 is Co₃O₄And Co₃O₄Raman spectrum of/rGO composite material;

FIG. 13 is Co₃O₄And Co₃O₄XRD spectrogram of/rGO composite material;

FIG. 14 is Co₃O₄And Co₃O₄UV-VIS absorption spectrum of/rGO composite material;

FIG. 15 is Co₃O₄A relation graph of ultraviolet-visible absorption peaks and reaction time of a/rGO-4 composite material photocatalytic degradation dye methylene blue;

FIG. 16 is Co₃O₄And Co doped with GO in different proportions₃O₄A graph of photocatalytic degradation rate of/rGO composite;

FIG. 17 is Co₃O₄Schematic diagram of/rGO photocatalytic degradation.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1:

graphene doped Co₃O₄The preparation method of the mesoporous fiber is to prepare Co by utilizing an electrostatic spinning technology and a high-temperature heat treatment method₃O₄Mesoporous fiber, and then preparing Co by microwave radiation reaction reduction₃O₄a/rGO composite; the preparation of graphene doped with Co₃O₄Weighing N, N-Dimethylformamide (DMF) and Polyacrylonitrile (PAN) and stirring at constant temperature until the PAN is completely dispersed in the DMF, weighing Co (CH3COO) 2.4H 2O and adding into the solution, and stirring until the Co (CH3COO) 2.4H 2O is completely dissolved to obtain a spinning solution; (2) adding a dissolving agent into the obtained spinning solution, stirring until the dissolving agent is fully dissolved, and uniformly mixing; (3) transferring the spinning liquid into an injector, controlling the solution flow in the electrostatic spinning process by using a micro-injection pump, putting the solution flow on an electrostatic spinning device for spinning, drying the obtained spun yarn, and then putting the dried spun yarn into a muffle furnace for high-temperature heat treatment to obtain Co₃O₄Fibers; (4) weighing Co₃O₄Adding the fiber and the graphite oxide dispersion liquid into deionized water for ultrasonic treatment to obtain Co₃O₄Fiber/graphene oxide dispersion liquid, then transferring the dispersion liquid into a microwave reaction instrument, and carrying out microwave radiation reaction reduction to prepare graphene doped Co₃O₄A mesoporous fiber.

An experimental instrument: scanning electron microscope, X-ray diffractometer, Raman spectrometer, electrostatic spinning device, optical reaction instrument, ultraviolet-visible light photometer, vacuum drying oven, muffle furnace, electrothermal constant temperature blast drying oven, ultrasonic cleaning instrument, and N₂An adsorption-desorption specific surface area tester.

Experimental reagent: polyacrylonitrile (PAN), N-Dimethylformamide (DMF), cobalt acetate, anhydrous ethanol, GO solution, methylene blue.

Under the irradiation of ultraviolet light, the photocatalytic performance of the sample is detected by degrading a dye methylene blue solution through a photocatalytic experiment. 0.02 g of samples doped with different proportions are respectively weighed and put into 50 mL of methylene blue solution (10 mg/L), and dark reaction is carried out for 30min to achieve adsorption-desorption balance. And (3) turning on a 300W mercury lamp light source, and carrying out photocatalytic reaction under the irradiation of ultraviolet light. Taking a certain amount of methylene blue solution every 30min, centrifuging and taking supernatant, and taking samples. And measuring the ultraviolet-visible absorption spectrum of the supernatant by using an ultraviolet-visible spectrophotometer according to the sampling sequence, recording the maximum peak absorption intensity and calculating the degradation rate of the methylene blue. And (4) drawing an ultraviolet absorption spectrogram and a degradation efficiency chart according to data obtained by experiments, and analyzing the photocatalytic performance of a plurality of samples.

FIG. 1 to FIG. 10 are Co₃O₄And Co₃O₄Low and high power SEM images of/rGO composite material, Co is shown in FIGS. 3, 5, 7 and 9₃O₄/rGO-1、Co₃O₄/rGO-2、Co₃O₄rGO-3 and Co₃O₄Low power SEM picture of/rGO-4, from which it can be clearly seen that the flake graphene is doped to Co₃O₄In the formation of Co₃O₄a/rGO composite material. FIGS. 4, 6, 8 and 10 are each Co₃O₄/rGO-1、Co₃O₄/rGO-2、Co₃O₄rGO-3 and Co₃O₄High power SEM picture of/rGO-4, it can be seen that rGO is wrapped with Co₃O₄Fibers, forming a loose porous Co₃O₄a/rGO composite structure.

FIG. 11 is Co₃O₄The mesoporous fiber nitrogen adsorption-desorption labyrinth and the pore diameter distribution diagram. Co can be seen in FIG. 11₃O₄The mesoporous fiber shows an obvious IV-type isothermal curve, which shows that Co₃O₄The surface of the dye has a large number of mesopores (2-50 nm), when the relative pressure P/P0= 0.95-1.0, the adsorption curve is nearly vertical, which indicates that a large number of macropores (more than 50 nm) exist, and the existence of the mesopores and the macropores is beneficial to the diffusion and the transfer of dye molecules in the photocatalysis process. As can be seen from the pore size distribution diagram, Co is present at a pore size of 30 nm₃O₄With the largest pore volume, also demonstrating the presence of a large number of mesopores, which is consistent with the results obtained for the adsorption curve. Tested to obtain Co₃O₄The specific surface area of the mesoporous fiber can reach 20.8 m/g, and the adsorption capacity and the photocatalytic performance of the material are relatively strong.

FIG. 12 is Co₃O₄And Co₃O₄Raman spectrum of/rGO composite material. Comparison of spectrum D and G peaks I of rGO_D/I _GThe presence of rGO in the composite material can be known by the ratio. From FIG. 12, it can be seen that Co₃O₄And Co₃O₄Raman spectra of/rGO composite material are all in A (462 cm)^-1）、B（504 cm^-1）、C（668 cm^-1) Shows distinct peaks, which are Co₃O₄Characteristic absorption peaks of Raman spectra. With pure Co₃O₄In contrast, Co₃O₄rGO-1 and Co₃O₄The reason why the characteristic absorption peak of rGO does not appear in the/rGO-2 is that the doping ratio of rGO is too low. Co₃O₄rGO-3 and Co₃O₄the/rGO-4 composite materials are all in 1346 cm^-1And 1588 cm^-1Shows an absorption peak, and the two absorption peaks and an absorption peak (1346 cm) shown by rGO^-1And 1588 cm^-1) The position is the same, at 1346 cm^-1The D band absorption peak appears, and the D peak represents the disordered carbon; at 1588 cm^-1The peak appears as a G band absorption peak, and the G peak represents sp²Hybrid or ordered carbon, from which rGO was successfully doped to Co₃O₄In (1).

FIG. 13 is Co₃O₄And Co₃O₄The XRD spectrogram of the/rGO composite material can be seen from the graph in FIG. 13, the diffraction peaks of the crystal planes of 22.89 degrees and 43.32 degrees of 2 theta of a comparative rGO standard PDF card (PDF # 50-0927) are (113) and (315), and the doped GO can be successfully reduced into the rGO in the composite material by comparing the XRD spectrogram of the rGO; pure Co₃O₄Peaks at 19.00 °, 31.27 °, 36.84 °, 38.55 °, 44.81 °, 55.66 °, 59.35 ° and 65.23 ° 2 θ, for comparative Co₃O₄The standard PDF cards (PDF # 42-1467) are Co3O4 crystal face diffraction peaks of (111), (220), (311), (222), (400), (422), (511) and (440), respectively. Co used in different proportions₃O₄Diffraction peaks of/rGO composites are similar and identical to pure Co₃O₄The standard diffraction peaks of (A) are consistent, which indicates that rGO is not dopedWith change of Co₃O₄Its original crystal form or a new crystal phase is generated. Because the doping ratio of rGO is low, and Co₃O₄The peak intensity of the characteristic peak is strong, so that the XRD spectrum of the composite material does not have the characteristic peak of rGO.

FIG. 14 is Co₃O₄And the ultraviolet-visible absorption spectrum of the Co3O4/rGO composite material. As can be seen from FIG. 14, the absorption wavelength range of 300 nm to 800 nm is similar to that of pure Co₃O₄Co doped with GO in different proportions compared with absorption spectrum₃O₄the/rGO composite material shows a strong absorption peak, and the doped rGO can obviously enhance Co₃O₄Thereby being beneficial to improving the photocatalytic performance of the catalyst.

FIG. 15 is Co₃O₄The graph of the relationship between the ultraviolet-visible absorption peak and the reaction time of the/rGO-4 composite material for photocatalytic degradation of the dye methylene blue can be seen from FIG. 15, the intensity of the ultraviolet-visible absorption peak which is in direct proportion to the concentration of the dye methylene blue gradually weakens along with the lapse of time, which shows that the concentration of the methylene blue in the solution gradually decreases and Co is gradually reduced along with the extension of the degradation time₃O₄the/rGO-4 has excellent performance of degrading methylene blue through photocatalysis. FIG. 16 is Co₃O₄And doping with different proportions of GOCo₃O₄Graph of photocatalytic degradation rate of/rGO composite. From the degradation rate graph of FIG. 16, Co can be seen₃O₄the/rGO-4 has better photocatalytic performance. By experimental data and according to the absorbance calculation formula (the photocatalytic effect is measured by the degradation rate D, the degradation rate D is calculated by the absorbances A0 and A before and after the reaction and the concentrations C0 and C of the dye)

It is known that Co₃O₄、Co₃O₄/rGO-1、Co₃O₄/ rGO-2、Co₃O₄rGO-3 and Co₃O₄After the/rGO-4 is irradiated by ultraviolet light for 180 min, the degradation rates of the dye methylene blue are respectively 16.6 percent, 18.1 percent and 22.1 percent,30.1% and 62.3%, which shows that the Co can be improved by doping graphene₃O₄The rate of degrading methylene blue showed the best degradation effect when the doping amount was 12%, because Co₃O₄Under the irradiation of a mercury lamp, in the process of transferring photoproduction electrons from a valence band to a conduction band, the excellent conductivity of the rGO accelerates the migration rate of the photoproduction electrons to the surface of a reactant (figure 17), so that the photocatalytic degradation rate of the composite material is improved; the doping of the rGO can obviously improve the light absorption intensity of the material (figure 17), inhibit the recombination of photo-generated electrons and holes, improve the photocatalytic quantum efficiency and further improve the photocatalytic performance of the material.

Example 2:

The experimental apparatus, reagents and procedure were the same as in example 1.

While the foregoing description shows and describes the preferred embodiments of the present invention, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as described herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. Graphene doped Co₃O₄The preparation method of mesoporous fiber is characterized by utilizing electrostatic spinning technology and high-temperature heat treatment method to prepare Co₃O₄Mesoporous fiber, and then preparing Co by microwave method₃O₄a/rGO composite; preparation of graphene doped Co₃O₄The mesoporous fiber comprises the following steps: (1) weighing DMF and PAN, and stirring for 3h at the ambient temperature of 70 ℃ by using a magnetic stirrer at the speed of 800r/min to completely disperse the PAN into the DMF; then adding Co (CH)₃COO)₂·4H₂O, stirring for 2 hours at the constant temperature of 70 ℃ by using a magnetic stirrer at the speed of 800r/min, and completely dissolving to obtain a spinning solution; the DMF, PAN and Co (CH)₃COO)₂·4H₂The mass ratio of O is 9:1: 1; (2) adding a solvent into the obtained spinning solution, wherein the solvent is one of dichloromethane, chloroform and dioxane, and stirring by a magnetic stirrer at 800r/min until the solvent is fully dissolved and uniformly mixed; (3) transferring the spinning liquid into an injector, controlling the solution flow in the electrostatic spinning process by using a micro-injection pump, putting the solution flow on an electrostatic spinning device for spinning, drying the obtained spun yarn for 12 hours, putting the dried spun yarn in a muffle furnace, taking nitrogen as protective gas, heating the spun yarn to 450 ℃ at the speed of 1 ℃/min, and carrying out high-temperature heat treatment for 2 hours to obtain Co₃O₄Fibers; (4) weighing Co₃O₄Adding the fiber and the graphite oxide dispersion liquid into deionized water for ultrasonic treatment to obtain Co₃O₄The fiber/graphene oxide dispersion liquid is transferred into a microwave reaction instrument, and the microwave radiation reaction is carried out to reduce and prepare the graphiteAlkene doped with Co₃O₄A mesoporous fiber.

2. The graphene-doped Co as claimed in claim 1₃O₄The preparation method of the mesoporous fiber is characterized in that DMF is recovered from industrial wastewater by an extraction method and a reduced pressure distillation method, an extracting agent of o-sec-butylphenol is added into the industrial wastewater containing DMF, diluents of cyclohexane and n-octanol are added into the extracting agent, and the mixture is subjected to constant temperature water bath at 30 ℃; and after layering is finished, absorbing the water phase, carrying out reduced pressure distillation on the oil phase, and collecting the evaporated steam into a liquid collecting bottle through a condensing tube to obtain the DMF.

3. The graphene-doped Co as claimed in claim 1₃O₄The preparation method of the mesoporous fiber is characterized in that the Co (CH)₃COO)₂·4H₂O is prepared by plasma exchange method, and CoCl is adsorbed by ion exchange column₂Filling weak acid cation exchange resin in the solution and ion exchange column, washing with distilled water after adsorption is completed, and removing residual non-adsorbed CoCl in the resin₂Washing the resin layer with dilute acetic acid until AgNO is used₃Until no Cl ion in the washing liquid can be detected, eluting the washed resin with acetic acid to obtain a mixture of cobalt acetate and acetic acid, and finally evaporating and crystallizing in vacuum to prepare cobalt acetate and recovering acetic acid.

4. The graphene-doped Co as claimed in claim 1₃O₄The preparation method of the mesoporous fiber is characterized in that the feeding speed of the micro-injection pump is 0.025-0.059 mL/min.

5. The graphene-doped Co as claimed in claim 1₃O₄The preparation method of the mesoporous fiber is characterized in that the spinning conditions are that the voltage of an electrostatic spinning device is 16kV, the temperature is 20 ℃, the distance between polar plates is 18cm, and the flow rate of spinning solution is 1 mL/h.