Magnetically separable composite photocatalyst BiOBr/CoFe2O4And preparation method and application thereof
阅读说明：本技术 一种可磁分离的复合光催化剂BiOBr/CoFe2O4及其制备方法和应用 (Magnetically separable composite photocatalyst BiOBr/CoFe2O4And preparation method and application thereof ) 是由 李晓微 毕崇耀 周晋 禚淑萍 于 2020-11-30 设计创作，主要内容包括：本发明公开了一种可磁分离的复合光催化剂,所述复合光催化剂的结构包括BiOBr纳米片,以及负载于所述BiOBr纳米片上粒径大小均一的CoFe-2O-4纳米粒子,二者之间的紧密结合增强了对可见光的响应,加快了光生电子的传输速率,抑制了电子-空穴对的复合,从而赋予了光催化剂很高的催化活性和很好的稳定性,短时间内几乎可以使罗丹明B染料完全降解。本发明还公开了该复合光催化剂的制备方法,其反应条件温和,制备过程简单,生产成本低廉且以水为溶剂对环境友好,符合当代社会发展对生态环境的需求,有利于环境和能源的可持续发展。本发明所述的复合光催化剂在工业印染废水的处理方面具有很强的实用性和广阔的应用前景,可实现工业化大规模应用。(The invention discloses a magnetically separable composite photocatalyst, which structurally comprises a BiOBr nanosheet and CoFe loaded on the BiOBr nanosheet and having uniform particle size 2 O 4 The close combination of the nano particles and the nano particles enhances the response to visible light, accelerates the transmission rate of photoproduction electrons, and inhibits the recombination of electron-hole pairs, thereby endowing the photocatalyst with high catalytic activity and good stability, and almost completely degrading the rhodamine B dye in a short time. The invention also discloses a preparation method of the composite photocatalyst, which has the advantages of mild reaction conditions, simple preparation process and low production cost, takes water as a solvent, is environment-friendly, meets the requirements of modern social development on ecological environment, and is beneficial to the sustainable development of environment and energy. The composite photocatalyst has strong practicability and wide application prospect in the aspect of treatment of industrial printing and dyeing wastewater, and can realize industrial large-scale application.)
1. The magnetically separable composite photocatalyst is characterized by comprising a BiOBr nanosheet and CoFe with uniform particle size loaded on the BiOBr nanosheet2O4Nanoparticles.
2. A magnetically separable composite photocatalyst as claimed in claim 1, wherein the composite photocatalyst is a transparent photocatalystIn the composite photocatalyst, CoFe2O4The mass percentage of the nano particles is 5-15%.
3. A magnetically separable composite photocatalyst as claimed in claim 1, in which the dimensions of the BiOBr nanosheets are from 500nm to 3 μm; CoFe2O4The size of the nano particles is 35-50 nm.
4. The method for preparing a magnetically separable composite photocatalyst according to claim 1, wherein the magnetically separable composite photocatalyst is prepared by a hydrothermal method using water as a solvent.
5. The method of claim 1, comprising the steps of:
1) providing CoFe2O4Nanoparticles;
2) mixing bismuth nitrate pentahydrate and potassium bromide according to the molar ratio of 1:1, adding the mixture into deionized water, and performing ultrasonic dispersion to obtain a white suspension;
3) mixing CoFe2O4Adding the nano particles into the white suspension, performing ultrasonic dispersion, and stirring to obtain a mixed solution;
4) and carrying out hydrothermal reaction on the mixed solution, cooling to room temperature after the reaction is finished, centrifuging, washing and drying to obtain the magnetically separable composite photocatalyst.
6. The method according to claim 5, wherein in step 1), the CoFe2O4The nano particles are prepared by the following method:
mixing cobalt nitrate hexahydrate and ferric nitrate nonahydrate according to the molar ratio of 1:2, dissolving in deionized water, stirring until the cobalt nitrate hexahydrate and the ferric nitrate nonahydrate are completely dissolved, dripping aqueous solution of sodium hydroxide into the mixture to adjust the pH value of the solution to be 12, continuously stirring for a while, carrying out hydrothermal reaction on the mixed solution, naturally cooling to room temperature after the reaction is finished, centrifugally separating, washing and drying precipitates to obtain the CoFe2O4Nanoparticles.
7. The method according to claim 5, wherein in step 3), CoFe2O4The mass ratio of the nano particles to the white suspension is 3.9 multiplied by 10-4-1.3×10-3。
8. The preparation method according to claim 5, wherein in the step 4), the temperature of the hydrothermal reaction is 140 ℃ and the time is 12 h;
preferably, in the step 4), the drying method is vacuum drying, the temperature is 55-60 ℃, and the drying time is 8-10 h.
Preferably, in the step 4), the washing mode is that deionized water and absolute ethyl alcohol are respectively washed for 2 to 3 times.
9. Use of a magnetically separable composite photocatalyst as claimed in claim 1, wherein the composite photocatalyst is used in the degradation of wastewater containing rhodamine B dye.
10. The use of claim 9, wherein the composite photocatalyst is used in an amount of 60-100mg when the volume of the wastewater containing the rhodamine B dye is 100mL and the concentration is 10 mg/L.
Technical Field
The invention relates to the technical field of photocatalysis. More particularly, relates to a composite photocatalyst capable of being magnetically separated, and a preparation method and application thereof.
Background
In recent years, due to the fact that the problems of energy shortage and environmental pollution are increasingly prominent, people are constantly dedicated to developing new clean renewable alternative energy sources, wherein semiconductor photocatalysis is a novel 'green technology', and is favored in the aspect of environmental management because the semiconductor photocatalysis has the advantages of being simple to operate, mild in reaction conditions, low in energy consumption, low in secondary pollution and the like, and more importantly, the technology can directly utilize solar energy to degrade pollutants in the environment into harmless substances so as to solve the two problems of energy shortage and environmental pollution faced by human beings at present. However, the key to achieving this process is to find and design new efficient semiconductor photocatalysts.
In many semiconductor photocatalysts, BiOBr is widely concerned due to unique properties, but the traditional BiOBr photocatalyst generally has the problems of low quantum efficiency, mismatch of forbidden bandwidth and solar spectrum, easy recombination of photon-generated carriers, difficult catalyst recovery and the like, so that the practical application of the traditional BiOBr photocatalyst is limited, and thus, modification or modification of BiOBr is an important method for obtaining the photocatalyst with high visible light activity. CoFe2O4The spinel type ferrite material has magnetism and photocatalytic activity, and the spinel type ferrite material is compounded with the semiconductor photocatalyst matched with an energy band, so that the high-activity photocatalyst can be obtained, and the magnetic separation of the photocatalyst is realizedAnd (5) separating. So far, the composite photocatalytic material BiOBr/CoFe2O4There are few reports.
Disclosure of Invention
Based on the facts, the first purpose of the invention is to provide a composite photocatalyst BiOBr/CoFe capable of being magnetically separated2O4The composite photocatalyst has high catalytic activity, good stability and magnetic separability in the photodegradation reaction of rhodamine B.
The second purpose of the invention is to provide a preparation method of the composite photocatalyst capable of being separated magnetically.
The third purpose of the invention is to provide the application of the composite photocatalyst capable of being separated magnetically.
In order to achieve the first purpose, the invention adopts the following technical scheme:
the composite photocatalyst capable of being magnetically separated structurally comprises BiOBr nanosheets and CoFe loaded on the BiOBr nanosheets and having uniform particle size2O4Nanoparticles.
In the technical scheme, CoFe is used2O4The surface of the BiOBr nanosheet is modified by the nanoparticles, so that the forbidden bandwidth of the photocatalyst is changed, the response to visible light is enhanced, and the separation of photo-generated electrons and holes is promoted, so that the photocatalytic performance is improved. With BiOBr and CoFe2O4Compared with a monomer, the composite material BiOBr/CoFe with the specific morphology2O4The degradation rate of the photocatalyst on rhodamine B is greatly improved, and the rhodamine B can be almost completely degraded in a short time under the action of visible light. In addition, the composite photocatalyst BiOBr/CoFe2O4The photocatalyst has good stability and high magnetic responsiveness, can be conveniently and quickly separated from a reaction system under the action of an external magnetic field for repeated use, has high activity after being repeatedly used for 6 times, and has a degradation rate of more than 91 percent on rhodamine B.
Further, in the composite photocatalyst, CoFe2O4NanoparticlesThe mass percentage of the components is 5-15%. CoFe having a uniform particle size in this range2O4The nanoparticles can be uniformly and tightly loaded on the BiOBr nanosheets.
Further, in the composite photocatalyst, the size of the BiOBr nanosheet is 500nm-3 μm; CoFe2O4The size of the nano particles is 35-50 nm.
In order to achieve the second purpose, the invention adopts the following technical scheme:
a preparation method of a magnetically separable composite photocatalyst is characterized in that water is used as a solvent, and a hydrothermal method is adopted to prepare the magnetically separable composite photocatalyst.
Further, the preparation method comprises the following steps:
1) providing CoFe2O4Nanoparticles;
2) mixing bismuth nitrate pentahydrate and potassium bromide according to the molar ratio of 1:1, adding the mixture into deionized water, and performing ultrasonic dispersion to obtain a white suspension;
3) mixing CoFe2O4Adding the nano particles into the white suspension, performing ultrasonic dispersion, and stirring to obtain a mixed solution;
4) and carrying out hydrothermal reaction on the mixed solution, cooling to room temperature after the reaction is finished, centrifuging, washing and drying to obtain the magnetically separable composite photocatalyst.
Further, in step 1), the CoFe2O4The nano particles are prepared by the following method:
mixing cobalt nitrate hexahydrate and ferric nitrate nonahydrate according to the molar ratio of 1:2, dissolving in deionized water, stirring until the cobalt nitrate hexahydrate and the ferric nitrate nonahydrate are completely dissolved, dripping aqueous solution of sodium hydroxide into the mixture to adjust the pH value of the solution to be 12, continuously stirring for a while, carrying out hydrothermal reaction on the mixed solution, naturally cooling to room temperature after the reaction is finished, centrifugally separating, washing and drying precipitates to obtain the CoFe2O4Nanoparticles.
Further, in the step 1), the temperature of the hydrothermal reaction is 180 ℃ and the time is 10 hours.
Further, in step 1), the concentration of the aqueous sodium hydroxide solution was 3 mol/L.
Further, in the step 1), the dosage of the cobalt nitrate hexahydrate and the ferric nitrate nonahydrate are respectively 1mmol and 2mmol, and the volume of the deionized water is 80 ml.
Further, in the step 2), magnetic stirring is carried out after ultrasonic dispersion, wherein the ultrasonic dispersion time is 10min, and the magnetic stirring time is 30 min.
Further, in step 3), CoFe2O4The mass ratio of the nano particles to the white suspension is 3.9 multiplied by 10-4-1.3×10-3。
Further, in the step 3), the stirring time is 1h after the ultrasonic dispersion. Further, in the step 4), the temperature of the hydrothermal reaction is 140 ℃ and the time is 12 h.
Further, in the step 4), the drying method is vacuum drying, the temperature is 55-60 ℃, and the drying time is 8-10h, so that the influence of oxygen in the air on the photocatalyst in the drying process is avoided.
Further, in the step 4), the washing mode is that deionized water and absolute ethyl alcohol are respectively washed for 2-3 times.
In order to achieve the third purpose, the invention adopts the following technical scheme:
the magnetically separable composite photocatalyst described above as the first object is applied to photocatalytic degradation of wastewater containing rhodamine B dye.
The composite photocatalyst can be used for treating printing and dyeing wastewater on a large scale, and has high practical application value.
Namely, the composite photocatalyst has high degradation efficiency when being used for photocatalytic degradation of wastewater containing rhodamine B dye.
Further, when the volume of the wastewater containing the rhodamine B dye is 100mL and the concentration is 10mg/L, the dosage of the composite photocatalyst is 60-100 mg.
Further, a light source adopted by the photocatalytic degradation is a xenon lamp simulating sunlight, and the power is 300W.
The invention has the following beneficial effects:
the inventionIn the provided composite photocatalyst, CoFe is utilized2O4Composite photocatalyst BiOBr/CoFe prepared by modifying surfaces of BiOBr nanosheets with nanoparticles2O4Has a unique sheet structure (the prior art which is similar to the morphological structure of the composite material is not found at present), and BiOBr and CoFe in the catalyst2O4The close and good contact interface between the two photocatalyst layers not only enhances the response of the photocatalyst to visible light, but also accelerates the movement of photon-generated carriers, inhibits the recombination of electron-hole pairs, and improves the activity of the photocatalyst to a great extent2O4The unique morphology structure and the strong binding force between the two also enable the photocatalyst to have good stability and recycling performance, and CoFe in the photocatalytic reaction process is avoided2O4The nanometer particles are separated from the surface of the BiOBr nanometer sheet to cause the phenomenon of catalyst inactivation.
In addition, the composite photocatalyst BiOBr/CoFe2O4The magnetic separation device also has unique magnetic separation characteristic, and can be separated, recovered and reused by using the magnet, thereby not only simplifying the operation process, but also reducing the experiment cost, and simultaneously overcoming the problems of economic loss, environmental pollution and the like, and undoubtedly laying a solid foundation for subsequent industrialization.
In the preparation method provided by the invention, toxic and harmful organic solvents are not needed, ethylene glycol in the prior art is abandoned, green and environment-friendly water is used as the solvent for the first time, and the novel efficient composite photocatalyst BiOBr/CoFe is prepared by a hydrothermal method2O4Effectively meets the requirements of the modern social development on the ecological environment.
In addition, the composite photocatalyst BiOBr/CoFe prepared by the invention2O4The preparation method is simple, the raw materials are easy to obtain, the cost is low, the environment is protected, the method is suitable for industrial large-scale production, and the method has a very wide application prospect in the technical field of photocatalysis. In the process of preparing the composite photocatalyst, the reaction conditions are milder, the used temperature is reduced, and the reaction time is correspondingly shortened, so that the material preparation process is further reducedResulting in loss of energy consumption.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 shows a composite photocatalyst BiOBr/CoFe synthesized in example 4 of the invention2O4Scanning Electron Micrograph (SEM) of 10%.
FIG. 2 shows a composite photocatalyst BiOBr/CoFe synthesized in example 4 of the invention2O4-Scanning Electron Microscopy (SEM) partial magnification of 10%.
FIG. 3 shows BiOBr and BiOBr/CoFe synthesized in examples 2-5 of the present invention2O4A time-dependent change curve diagram of the degradation rate of the composite photocatalytic material to rhodamine B under the action of visible light.
FIG. 4 shows BiOBr/CoFe synthesized in example 4 of the present invention2O4And (3) a comparison graph of degradation effects of the composite photocatalytic material with the concentration of 10% on rhodamine B, wherein the composite photocatalytic material is recycled for 6 times under the action of visible light.
FIG. 5 shows BiOBr/CoFe synthesized in example 4 of the present invention2O4A magnetic separation effect graph which is rapidly recovered from a reaction system after the photocatalytic reaction of 10 percent of composite photocatalytic material is finished.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
Example 1
Magnetic spinel type ferrite material CoFe2O4Preparing nano particles: dissolving 1mmol of cobalt nitrate hexahydrate and 2mmol of ferric nitrate nonahydrate in 80mL of deionized water, stirring until the cobalt nitrate hexahydrate and the ferric nitrate nonahydrate are completely dissolved, dripping 3mol/L of sodium hydroxide solution into the mixture to adjust the pH value of the solution to 12, continuously stirring for 30min, transferring the mixed solution into a polytetrafluoroethylene high-pressure reaction kettle, reacting for 10h at 180 ℃, naturally cooling to room temperature after the reaction is finished,centrifugally separating the product, washing with deionized water and anhydrous ethanol for 2-3 times, and vacuum drying to obtain CoFe with particle size of 35-50nm2O4Nanoparticles.
Example 2
Preparation of a photocatalyst BiOBr monomer: adding 1mmol of bismuth nitrate pentahydrate and 1mmol of potassium bromide into 30mL of deionized water, carrying out ultrasonic oscillation, stirring for 30min to obtain a white suspension, transferring the white suspension into a polytetrafluoroethylene high-pressure reaction kettle, reacting at 140 ℃ for 12h, naturally cooling to room temperature after the reaction is finished, carrying out centrifugal separation on a product, washing with deionized water and absolute ethyl alcohol for 2-3 times respectively, and carrying out vacuum drying to obtain the material BiOBr.
Example 3
Composite photocatalyst BiOBr/CoFe2O45 percent (namely CoFe in the composite photocatalyst)2O45 percent of the raw materials in percentage by mass) are prepared: (1) mixing 1mmol of bismuth nitrate pentahydrate and 1mmol of potassium bromide, adding the mixture into 30mL of deionized water, performing ultrasonic dispersion, and performing magnetic stirring for 30min to obtain a white suspension; (2) 0.012g of CoFe obtained in example 1 was weighed out2O4Adding the suspension into the suspension, continuing stirring for 1h at room temperature after ultrasonic dispersion for 10min, transferring the mixed solution into a polytetrafluoroethylene high-pressure reaction kettle, reacting for 12h at 140 ℃, naturally cooling to room temperature after the reaction is finished, respectively washing precipitates for 2-3 times by centrifugal separation, deionized water and absolute ethyl alcohol, and drying to obtain the magnetic nano composite photocatalytic material BiOBr/CoFe2O4-5％。
Example 4
Composite photocatalyst BiOBr/CoFe2O410 percent (namely CoFe in the composite photocatalyst)2O410 percent of mass percent) of the raw materials: (1) mixing 1mmol of bismuth nitrate pentahydrate and 1mmol of potassium bromide, adding the mixture into 30mL of deionized water, performing ultrasonic dispersion, and performing magnetic stirring for 30min to obtain a white suspension; (2) 0.026g of CoFe obtained in example 1 was weighed2O4Adding into the suspension, ultrasonically dispersing for 20min, stirring at room temperature for 1 hr, transferring the mixed solution into a polytetrafluoroethylene high-pressure reaction kettleReacting at 140 ℃ for 12h, naturally cooling to room temperature after the reaction is finished, performing centrifugal separation on precipitates, washing with deionized water and absolute ethyl alcohol for 2-3 times respectively, and drying to obtain the magnetic nano composite photocatalytic material BiOBr/CoFe2O4-10％。
Example 5
Composite photocatalyst BiOBr/CoFe2O415 percent (namely CoFe in the composite photocatalyst)2O415 percent of mass percent) are prepared: (1) mixing 1mmol of bismuth nitrate pentahydrate and 1mmol of potassium bromide, adding the mixture into 30mL of deionized water, performing ultrasonic dispersion, and performing magnetic stirring for 30min to obtain a white suspension; (2) 0.041g of CoFe prepared in example 1 was weighed out2O4Adding the suspension into the suspension, continuing stirring for 1h at room temperature after ultrasonic dispersion for 35min, transferring the mixed solution into a polytetrafluoroethylene high-pressure reaction kettle, reacting for 12h at 140 ℃, naturally cooling to room temperature after the reaction is finished, washing precipitates for 2-3 times respectively by centrifugal separation, deionized water and absolute ethyl alcohol, and drying to obtain the magnetic nano composite photocatalytic material BiOBr/CoFe2O4-15％。
Referring to attached figures 1 and 2, the composite photocatalytic material BiOBr/CoFe prepared in example 42O4Scanning electron micrograph of-10%, from which it is clear that CoFe having uniform particle size2O4The nano particles are tightly loaded on the surface of the BiOBr nano sheet, and an 'intimate contact' interface is formed between the BiOBr nano sheet and the BiOBr nano sheet, so that the transfer of photo-generated electrons and the improvement of photocatalytic activity are facilitated.
The properties of the photocatalytic materials obtained in examples 2 to 5 were measured and compared
The materials prepared in the examples 2 to 5 are used as photocatalysts, wastewater containing rhodamine B is used as a simulated pollutant, the photocatalytic activity and the recycling performance of the materials are investigated and compared, and the specific experimental method and conditions are as follows:
100mL of wastewater containing 10mg/L rhodamine B is put into a quartz tube, 0.1g of the photocatalytic material prepared in the embodiment 2 to 5 is weighed and added into the quartz tube for ultrasonic dispersion for 3min, and then the mixture is placed in a photochemical reactionStirring in the dark for 1h to achieve adsorption-desorption balance, irradiating the solution by using a 300W xenon lamp light source, sampling once every 10min, carrying out centrifugal separation on the sampled sample, testing the absorbance of supernatant liquid by using an ultraviolet-visible spectrophotometer, and further calculating the degradation rate of rhodamine B. FIG. 3 shows BiOBr and BiOBr/CoFe synthesized in examples 2-5 of the present invention2O4Degradation rate (1-C/C) of composite photocatalytic material to rhodamine B under the action of visible light0) The time-dependent change of BiOBr/CoFe2O4The activity of the composite photocatalytic material is obviously superior to that of single-phase BiOBr, wherein CoFe2O4When the percentage content of (B) is 10%, BiOBr/CoFe2O4The activity of (A) is optimal. BiOBr/CoFe with optimal activity2O4The-10% of the rhodamine B is a photocatalyst, the recycling performance of the rhodamine B is researched, the details are shown in the attached figure 4, after the rhodamine B is recycled for 6 times, the activity is not greatly reduced, and the degradation rate of the rhodamine B can still reach 92%. In addition, due to the unique magnetism of the composite material, in the recycling process, the composite material can be separated and recycled by using a magnet for the next repeated use, and particularly, the composite material is shown in figure 5.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
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