High-dispersion magnetic nano photocatalyst and preparation method thereof
阅读说明：本技术 一种高分散的具有磁性的纳米光催化剂及制备方法 (High-dispersion magnetic nano photocatalyst and preparation method thereof ) 是由 商亚博 陈美娟 陈科皓 于 2020-12-23 设计创作，主要内容包括：一种高分散的具有磁性的纳米光催化剂及制备方法,向水中加入g-C-3N-4粉末,搅拌超声后,得到均匀分散的悬浊液A；向水中加入Fe～(3+)盐和Zn～(2+)盐,搅拌得到溶液B；将溶液B滴加到悬浊液A中,调节pH值为11.0-13.0后搅拌30min-60min,然后在90℃-110℃下水热反应4h-8h,生成的固体粉末为高分散的具有磁性的复合光催化剂。本发明合成的g-C-3N-4/ZnFe-2O-4纳米光催化剂具有良好的水相分散性,增加了催化剂与污染物的接触/反应面积,光催化反应速率得到显著提高,同时在外加磁场时,可完全从水中分离,不会造成二次污染。(A high-dispersity magnetic nano-photocatalyst is prepared through adding g-C to water 3 N 4 Stirring and ultrasonically treating the powder to obtain uniformly dispersed suspension A; adding Fe to water 3+ Salt and Zn 2+ Salt, and stirring to obtain a solution B; and dropwise adding the solution B into the suspension A, adjusting the pH value to 11.0-13.0, stirring for 30-60 min, and carrying out hydrothermal reaction at 90-110 ℃ for 4-8 h to obtain solid powder which is a highly dispersed magnetic composite photocatalyst. g-C synthesized by the invention 3 N 4 /ZnFe 2 O 4 The nano photocatalyst has good water phase dispersibility, increases the contact/reaction area of the catalyst and pollutants, obviously improves the photocatalytic reaction rate, and can be completely separated from water without causing secondary pollution when a magnetic field is applied.)
1. A preparation method of a high-dispersion magnetic nano photocatalyst is characterized by comprising the following steps:
adding g-C to water3N4Stirring the powder, and carrying out ultrasonic treatment for 30min to 90min under the power of 400W to obtain suspension A of 3g/L to 6 g/L;
adding Fe to water3+Salt and Zn2+Salt, and stirring to obtain a solution B;
adding solution B dropwise into suspension A under stirring at a rate of 0.1-0.3 ml/s to obtain g-C3N4ZnFe in powder and solution B2O4The mass ratio of (1-10) to (1), adjusting the pH to 11.0-13.0 to obtain g-C3N4/ZnFe2O4The precursor solution of (1);
g to C3N4/ZnFe2O4The precursor solution is subjected to hydrothermal reaction for 4 to 8 hours at the temperature of between 90 and 110 ℃ to obtain the highly dispersed magnetic nano photocatalyst.
2. The method as set forth in claim 1, wherein g-C is the amount of the nano photocatalyst3N4The powder was prepared by the following procedure: heating urea to 500-550 ℃ at the speed of 2.5-4.0 ℃/min and calcining for 2-4 h to obtain g-C3N4And (3) powder.
3. The method as set forth in claim 1, wherein Fe is added to the reaction mixture3+The salt being Fe (NO)3)3·9H2O or C15H21FeO6，Zn2+The salt is Zn (NO)3)2·6H2O or Zn (CH)3COO)2，Fe3+And Zn2+The ratio of the amounts of the substances of (a) to (b) is 2: 1.
4. The method as set forth in claim 1, wherein Fe is in solution B3+The concentration of (B) is 2.50mmol/L-50.00mmol/L, Zn2+The concentration of (b) is 1.25mmol/L-25.00 mmol/L.
5. The method according to claim 1, wherein the stirring speed is 400rpm to 800 rpm.
6. The method as claimed in claim 1, wherein the pH of the sodium hydroxide solution is adjusted to 11.0-13.0 mol/L to a concentration of 1.0-2.0 mol/L.
7. A highly dispersed nano photocatalyst having magnetic properties prepared by the method of any one of claims 1 to 6.
Technical Field
The invention belongs to the field of catalyst preparation, and particularly relates to a high-dispersion magnetic nano photocatalyst and a preparation method thereof.
Background
In recent years, antibiotics are used in a large amount in life, are discharged randomly and enter a water environment along with the metabolism of organisms, so that antibiotic organic pollutants in a water body are widely existed, and a serious environmental problem is caused. For example, ciprofloxacin is a third-generation quinolone antibiotic, is difficult to degrade in the environment, can cause bacteria to generate drug resistance genes after being existed in the environment for a long time, and has great threat to the ecological environment and human health. Therefore, how to efficiently remove ciprofloxacin in an aqueous environment is particularly important.
The semiconductor photocatalysis technology is a green and efficient method for treating water environment pollution, and can decompose organic pollutants in water into H by using inexhaustible sunlight as energy2O and CO2. Graphene carbon nitride (g-C)3N4) The catalyst is a novel visible light active catalyst, and has the advantages of narrow band gap (about 2.7eV), low cost, good stability, easy regulation and control of structure and performance and the like. However, with the progress of research, some drawbacks have been found: (1) g-C3N4The photo-induced hole-electron recombination rate is high, the quantum efficiency is low, and the photo-catalytic activity is low; (2) due to g-C3N4For only the wavelength lambda of sunlight<500nm light is absorbed and has limited use of visible light, so g-C alone3N4The photocatalytic performance is not ideal; (3) g to C3N4After the water-soluble organic fertilizer is used in a water environment, the organic fertilizer is difficult to separate from the water environment, and secondary pollution is caused. ZnFe2O4Is a magnetic narrow band gap (1.9eV) semiconductor material, and is prepared from ZnFe2O4And g-C3N4Composite, can be effectively solved byThe above problems. First, ZnFe2O4And g-C3N4The energy level matching of the two can improve the electron-hole separation efficiency and the photocatalytic activity by compounding the two. Second, ZnFe2O4Can absorb the wavelength lambda<The 700nm sunlight (the band gap is 1.9eV) expands the response range of visible light. Finally, g-C3N4/ZnFe2O4The heterojunction has ZnFe2O4The magnetism of the monomer can realize the complete separation and recovery of the catalyst by utilizing an external magnetic field, thereby avoiding secondary pollution.
At present, with respect to g-C3N4/ZnFe2O4Reports of nano-photocatalyst prove that the nano-photocatalyst has good degradation effect on organic pollutants under visible light, but g-C3N4/ZnFe2O4The preparation method has the defects of complex preparation process, high reagent cost, high energy consumption and the like. Yao et al (Yao et al&Engineering Chemistry Research, 2014) prepares g-C capable of degrading organic dye Sudan red by visible light through a three-step synthesis method of' calcining (550 ℃) -calcining (500 ℃) -heating reflux3N4/ZnFe2O4The nano photocatalyst has good effect, the synthesis method needs two steps of high-temperature calcination, and the heating reflux operation adopting the organic reagent is complex. Wu et al (Wu et al, Catalysis Letters, 2018) synthesize g-C by a three-step process of calcination (500 ℃ C.) -hydrothermal (180 ℃ C., 12h) -calcination (400 ℃ C.)3N4/ZnFe2O4The nanometer photocatalyst has good degradation effect on organic dye methylene blue under visible light, the synthesis method adopts twice calcination, in addition, isopropanol is adopted as a solvent of a precursor solution in a hydrothermal process, and the hydrothermal temperature is high (180 ℃) and the hydrothermal time is long (12 h). Zhang et al (Zhang et al&Interfaces, 2013) Synthesis of g-C by calcination (550 ℃) hydrothermal (200 ℃,12h)3N4/ZnFe2O4The nano photocatalyst is used for degrading methyl orange under visible light, shows a good degradation effect, takes an organic reagent triethylene glycol as a solvent in the hydrothermal process, and has high reaction temperature (200 ℃) and long reaction time (12 hours).
In addition, the nano g-C prepared by the existing method3N4/ZnFe2O4When the catalyst is used in a water environment, the catalyst is easy to agglomerate, so that the contact/reaction area of the catalyst and pollutants is reduced, and the reaction rate of the degradation of organic pollutants is not high. If the nano g-C can be increased3N4/ZnFe2O4The dispersibility in the water phase can be increased, namely the nano g-C can be increased3N4/ZnFe2O4The contact/reaction area with the organic pollutants improves the reaction rate of the degradation of the organic pollutants.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a highly dispersed magnetic nano photocatalyst and a preparation method thereof.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for preparing high-dispersion magnetic nano photocatalyst by adding g-C into water3N4Stirring the powder, and carrying out ultrasonic treatment for 30min to 90min under the power of 400W to obtain suspension A of 3g/L to 6 g/L;
adding Fe to water3+Salt and Zn2+Salt, and stirring to obtain a solution B;
adding solution B dropwise into suspension A under stirring at a rate of 0.1-0.3 ml/s to obtain g-C3N4ZnFe in powder and solution B2O4The mass ratio of (1-10) to (1), adjusting the pH to 11.0-13.0 to obtain g-C3N4/ZnFe2O4The precursor solution of (1);
g to C3N4/ZnFe2O4The precursor solution is subjected to hydrothermal reaction for 4 to 8 hours at the temperature of between 90 and 110 ℃ to obtain the highly dispersed magnetic nano photocatalyst.
In a further development of the invention, g-C3N4The powder was prepared by the following procedure: heating urea to 500-550 ℃ at the speed of 2.5-4.0 ℃/min and calcining for 2-4 h to obtain g-C3N4And (3) powder.
In a further development of the invention, Fe3+The salt being Fe (NO)3)3·9H2O or C15H21FeO6，Zn2+The salt is Zn (NO)3)2·6H2O or Zn (CH)3COO)2，Fe3+And Zn2+The ratio of the amounts of the substances of (a) to (b) is 2: 1.
In a further development of the invention, the solution B contains Fe3+The concentration of (B) is 2.50mmol/L-50.00mmol/L, Zn2+The concentration of (b) is 1.25mmol/L-25.00 mmol/L.
The further improvement of the invention is that the stirring speed is 400rpm-800 rpm.
The further improvement of the invention is that the pH value is adjusted to 11.0-13.0 by using sodium hydroxide solution with the concentration of 1.0-2.0 mol/L.
A highly dispersed nano photocatalyst having magnetism prepared according to the above method.
Compared with the prior art, the invention has the beneficial effects that:
1、g-C3N4/ZnFe2O4high water phase dispersibility and high reaction rate: g-C synthesized by the invention3N4/ZnFe2O4The nano photocatalyst has good water phase dispersibility, and the catalyst dispersed in water still disperses uniformly after standing for 18 hours; g-C with dispersibility3N4/ZnFe2O4The reaction rate is improved by 4.3 times compared with the catalyst without dispersion.
2. Magnetic separation: when a magnetic field is applied, g-C3N4/ZnFe2O4The catalyst can be completely separated from the water.
3. Let g-C3N4/ZnFe2O4The regulation and control steps with the dispersibility are simple and easy to realize: by simply regulating and controlling the ultrasonic frequency and time, the dropping speed of the solution and the g-C3N4And ZnFe2O4Is given a mass ratio of g-C3N4/ZnFe2O4The nano photocatalyst has high dispersibility exceeding the ultrasonic frequency and time, the dropping speed of the solution and g-C3N4And ZnFe2O4Quality ofRange of ratio, g-C3N4/ZnFe2O4The dispersibility of the aqueous phase of (2) disappears.
4. g-C of dispersibility with the reported Anhydrous phase3N4/ZnFe2O4In contrast, g-C of the present invention3N4/ZnFe2O4The preparation process has low energy consumption, low reagent cost and safe operation:
(1) the precursor liquid in the hydrothermal process of the invention takes water as solvent, and has low cost and safe operation. In the prior art, organic reagents such as triethylene glycol, isopropanol and the like are mostly adopted as solvents in the hydrothermal process.
(2) The hydrothermal process of the invention adopts the reaction at 90-110 ℃ for 4-8 h, the temperature is low, and the time consumption is short. In the prior art, the temperature of a hydrothermal process is higher than 180 ℃ and the reaction time is longer than 12 h.
Drawings
FIG. 1 is a comparison of the degradation performance of different nano-catalysts on ciprofloxacin under visible light.
FIG. 2 is a graph showing the dispersion of various catalysts after standing dispersed in water and the effect of catalyst dispersion on degradation efficiency, where (a) is g-C3N4/ZnFe2O4(10:1) a dispersion chart after dispersing in water and standing for 18 hours; (b) is W1-g-C3N4/ZnFe2O4(10:1) a dispersion chart obtained by dispersing in water and standing for 10 min; (c) g-C3N4/ZnFe2O4The influence of the aqueous dispersibility of (a) on the degradation reaction rate of ciprofloxacin.
FIG. 3 shows g-C under an applied magnetic field3N4/ZnFe2O4Separating effect in water. Wherein, (a) is before the external magnetic field, and (b) is after the external magnetic field.
FIG. 4 shows g-C3N4、ZnFe2O4And g-C3N4/ZnFe2O4XRD pattern of (a).
FIG. 5 is g-C3N4/ZnFe2O4SEM images of the nano photocatalyst under different times. Wherein (a) is 100.0k, (b) is 150.0k, and (c) is 10.0 k.
Detailed Description
The present invention will be described in detail with reference to the following embodiments and drawings.
The invention provides a preparation method of the catalyst, which has the advantages of simple steps, low reagent cost, low energy consumption and safe operation. Is endowed with g-C3N4/ZnFe2O4The nanometer photocatalyst has good water phase dispersibility. g-C synthesized by the invention3N4/ZnFe2O4The catalyst can be completely separated from water when a magnetic field is applied, and secondary pollution is not caused.
The invention endows g-C with simple and easy scheme by improving the experimental method3N4/ZnFe2O4The nanometer photocatalyst has good water phase dispersibility, and the degradation rate of organic pollutants is improved. The method has the advantages of simple steps, less reagents, low equipment requirement, low reaction energy consumption and low danger coefficient.
The invention comprises the following steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating from room temperature to 500-550 ℃ at the speed of 2.5-4.0 ℃/min, and calcining for 2-4 h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: first, the g-C obtained in (1) is added to water3N4Stirring the powder, then carrying out ultrasonic treatment for 30min-90min under the power of 400W to obtain uniformly dispersed suspension A, standing the suspension A for 12h, and then carrying out g-C3N4Is still uniformly dispersed in water, g-C in suspension A3N4The concentration of (b) is 3g/L to 6 g/L.
Secondly, Fe is added to the water in a mass ratio of 2:13+Salt and Zn2+Salt, stirring to form solution B, and adding Fe in solution B3+The concentration of (B) is 2.50mmol/L-50.00mmol/L, Zn2+The concentration of (b) is 1.25mmol/L-25.00 mmol/L.
Finally, the solution B is added dropwise at a rate of 0.1ml/s to 0.3ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4Mass ofMixed liquor (ZnFe) with ratio of 10:1-1:12O4According to the mass of Fe3+Is completely converted into ZnFe2O4Calculation), then adjusting the pH to 11.0-13.0 with 1.0-2.0 mol/L sodium hydroxide solution, and continuing to stir the mixed solution for 30-60 min to obtain g-C3N4/ZnFe2O4The precursor solution of (1). Wherein, Fe3+The salt being Fe (NO)3)3·9H2O or C15H21FeO6(iron acetylacetonate), Zn2+The salt is Zn (NO)3)2·6H2O or Zn (CH)3COO)2。
(3) Hydrothermal preparation of highly dispersed magnetic g-C3N4/ZnFe2O4Photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into a baking oven with the temperature of 90-110 ℃ for reaction for 4-8 h, and the generated solid powder is the highly dispersed magnetic g-C3N4/ZnFe2O4A nano photocatalyst.
All stirring speeds in the present invention are 400rpm to 800 rpm.
g-C obtained3N4/ZnFe2O4The nano photocatalyst has good dispersibility in water, and can be uniformly dispersed in water after standing for 18 h.
g-C obtained3N4/ZnFe2O4The nanometer photocatalyst can be completely separated from the water phase under the external magnetic field.
If the ultrasonic power and time, the dropping speed of the solution B and the g-C in the experimental scheme are exceeded3N4And ZnFe2O4Mass ratio of (ZnFe)2O4According to the mass of Fe3+Is completely converted into ZnFe2O4Calculation) of g to C prepared3N4/ZnFe2O4No dispersibility is achieved; beyond the time and temperature of the hydrothermal reaction, g-C cannot be synthesized3N4/ZnFe2O4A nano photocatalyst.
The following are specific examples.
Example 1
Synthesis of g-C3N4/ZnFe2O4(10:1) Nano-catalyst (g-C in step (2))3N4And ZnFe2O4The mass ratio is 10: 1).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 550 ℃ at the speed of 2.5 ℃/min, and calcining for 4h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: firstly, g-C obtained in step (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 30min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Is still uniformly dispersed in water, g-C in suspension A3N4The concentration of (2) was 6 g/L. Secondly, Fe (NO) is added to the water in a mass ratio of 2:13)3·9H2O and Zn (NO)3)2·6H2O, stirring to form a solution B, wherein Fe is contained in the solution B3+Has a concentration of 2.50mmol/L, Zn2+The concentration of (B) was 1.25 mmol/L. Finally, solution B was added dropwise at a rate of 0.1ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 10:1, then 1.0mol/L sodium hydroxide solution is used for adjusting the pH value to 11.0, the mixed solution is continuously stirred for 30min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of highly dispersed magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into an oven with the temperature of 100 ℃ for reaction for 6 hours, and the generated solid powder is g-C3N4/ZnFe2O4(10:1) a nano photocatalyst.
The stirring rate throughout the above experiment was 400 rpm.
Example 2
Synthesis of g-C3N4/ZnFe2O4(5:2) Nano-catalyst (g-C in step (2))3N4And ZnFe2O4The mass ratio is 5: 2).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 500 ℃ at the speed of 4 ℃/min, and calcining for 2h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: firstly, g-C obtained in step (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 60min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Is still uniformly dispersed in water, g-C in suspension A3N4The concentration of (2) is 5 g/L. Secondly, Fe (NO) is added to the water in a mass ratio of 2:13)3·9H2O and Zn (NO)3)2·6H2O, stirring to form a solution B, wherein Fe is contained in the solution B3+Has a concentration of 10.00mmol/L, Zn2+The concentration of (2) was 5.00 mmol/L. Finally, solution B was added dropwise at a rate of 0.2ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 10:1, then 2.0mol/L sodium hydroxide solution is used for adjusting the pH value to 12.0, the mixed solution is continuously stirred for 60min, and the g-C preparation can be obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of highly dispersed magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into a baking oven with the temperature of 90 ℃ for reaction for 8 hours, and the generated solid powder is g-C3N4/ZnFe2O4(5:2) a nano photocatalyst.
The stirring rate throughout the above experiment was 600 rpm.
Example 3
Synthesis of g-C3N4/ZnFe2O4(1:1) Nano-catalyst (g-C in step (2))3N4And ZnFe2O4The mass ratio is 1: 1).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 530 ℃ at the speed of 3 ℃/min, and calcining for 3h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: first, the g-C obtained in (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 90min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Is still uniformly dispersed in water, g-C in suspension A3N4The concentration of (2) is 4 g/L. Secondly, C is added to the water in a mass ratio of 2:115H21FeO6And Zn (CH)3COO)2Stirring to form solution B, Fe in solution B3+Has a concentration of 50.00mmol/L, Zn2+The concentration of (2) was 25.00 mmol/L. Finally, solution B was added dropwise at 0.3ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 1:1, then 1.5mol/L sodium hydroxide solution is used for adjusting the pH value to 13.0, the mixed solution is continuously stirred for 60min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of highly dispersed magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into a drying oven with the temperature of 110 ℃ for reaction for 4 hours, and the generated solid powder is g-C3N4/ZnFe2O4(1:1) nanometer photocatalyst.
The stirring rate throughout the above experiment was 700 rpm.
Example 4
Synthesis of g-C3N4/ZnFe2O4(1:1) sodiumRice catalyst (g-C in step (2))3N4And ZnFe2O4The mass ratio is 1: 1).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 520 ℃ at the speed of 3 ℃/min, and calcining for 3h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: firstly, g-C obtained in step (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 50min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Is still uniformly dispersed in water, g-C in suspension A3N4The concentration of (2) is 3 g/L. Secondly, C is added to the water in a mass ratio of 2:115H21FeO6And Zn (CH)3COO)2Stirring to form solution B, Fe in solution B3+Has a concentration of 30.00mmol/L, Zn2+The concentration of (2) was 15.00 mmol/L. Finally, solution B was added dropwise at 0.3ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 1:1, then 1.5mol/L sodium hydroxide solution is used for adjusting the pH value to 13.0, the mixed solution is continuously stirred for 60min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of highly dispersed magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into a drying oven with the temperature of 110 ℃ for reaction for 4 hours, and the generated solid powder is g-C3N4/ZnFe2O4(1:1) nanometer photocatalyst.
The stirring rate throughout the above experiment was 800 rpm.
The following are comparative examples.
Comparative example 1
Synthesis of W1-g-C3N4/ZnFe2O4(101) i.e. g-C of anhydrous phase dispersibility3N4/ZnFe2O4(10:1) a nano catalyst, wherein the solution B in the synthesis step 1(2) is dripped into the continuously stirred suspension A at the speed of 0.5ml/s (exceeding the dripping speed of the invention by the range of 0.1ml/s-0.3 ml/s).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 550 ℃ at the speed of 2.5 ℃/min, and calcining for 4h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: first, the g-C obtained in (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 30min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Still uniformly dispersed in water, g-C in A3N4The concentration of (2) was 6 g/L. Secondly, Fe (NO) is added to the water in a mass ratio of 2:13)3·9H2O and Zn (NO)3)2·6H2O, stirring to form a solution B, and Fe in the solution B3+Has a concentration of 2.50mmol/L, Zn2+The concentration of (B) was 1.25 mmol/L. Finally, the solution B was added dropwise at a rate of 0.5ml/s (out of the range of 0.1ml/s to 0.3ml/s in the present invention) to the suspension A which was continuously stirred, to obtain g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 10:1, then 1.0mol/L sodium hydroxide solution is used for adjusting the pH value to 11.0, the mixed solution is continuously stirred for 30min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into an oven with the temperature of 100 ℃ for reaction for 6 hours, and the generated solid powder is W1-g-C3N4/ZnFe2O4(10:1), the dispersibility of the obtained catalyst is obviously poor, and all the catalyst precipitates after the water phase is kept stand for 10 min.
The stirring rate throughout the above experiment was 400 rpm.
Comparative example 2
Synthesis of W2-g-C3N4/ZnFe2O4(10:1), i.e., g-C of anhydrous phase dispersibility3N4/ZnFe2O4(10:1) nano photocatalyst, wherein the ultrasonic time in the synthesis step 1 and 2 is 10min (the ultrasonic time is 30min-90min beyond the range of the invention).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 550 ℃ at the speed of 2.5 ℃/min, and calcining for 4h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: firstly, adding the g-C obtained in the step (1) into water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 10min (exceeding the ultrasonic treatment time of 30min-90 min) to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Still uniformly dispersed in water, g-C in A3N4The concentration of (2) was 6 g/L. Secondly adding Fe (NO) into the water in a mass ratio of 2:13)3·9H2O and Zn (NO)3)2·6H2O, stirring to form a solution B, and Fe in the solution B3+Has a concentration of 2.50mmol/L, Zn2+The concentration of (B) was 1.25 mmol/L. Finally, the solution B was added dropwise at a rate of 0.3ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 10:1, then 1.0mol/L sodium hydroxide solution is used for adjusting the pH value to 11.0, the mixed solution is continuously stirred for 30min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into an oven with the temperature of 100 ℃ for reaction for 6 hours, and the generated solid powder is W2-g-C3N4/ZnFe2O4(10:1), the dispersibility of the obtained catalyst is obviously poor, and all the catalyst precipitates after the water phase is kept stand for 10 min.
The stirring rate throughout the above experiment was 400 rpm.
Comparative example 3
Synthesis of g-C3N4/ZnFe2O4(1:2), i.e., g-C of anhydrous phase dispersibility3N4/ZnFe2O4(1:2) Nano photocatalyst, Synthesis Process g-C3N4And ZnFe2O4Is 1:2 (out of the range of 10:1 to 1:1 in the present invention).
The method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 550 ℃ at the speed of 2.5 ℃/min, and calcining for 4h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: first, the g-C obtained in (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 30min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Still uniformly dispersed in water, g-C in A3N4The concentration of (2) was 6 g/L. Secondly, Fe (NO) is added to the water in a mass ratio of 2:13)3·9H2O and Zn (NO)3)2·6H2O, stirring to form a solution B, and Fe in the solution B3+Has a concentration of 100.00mmol/L, Zn2+The concentration of (B) was 50.00 mmol/L. Finally, the solution B was added dropwise at a rate of 0.3ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 1:2, then 1.0mol/L sodium hydroxide solution is used for adjusting the pH value to 11.0, the mixed solution is continuously stirred for 30min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of magnetic g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into an oven with the temperature of 100 ℃ for reaction for 6 hours, and the generated solid powder is g-C3N4/ZnFe2O4(1:2), the dispersibility of the obtained catalyst is obviously poor, and all the catalyst precipitates after the water phase is kept stand for 10 min.
The stirring rate throughout the above experiment was 400 rpm.
Comparative example 4
Synthesis of g-C3N4/ZnFe2O4(20:1), i.e., g-C of anhydrous phase dispersibility3N4/ZnFe2O4(20:1) Nano-photocatalyst, Synthesis Process g-C3N4And ZnFe2O4Is 20:1 (more than 10:1-1:1 in the claims). And when a magnetic field is applied, the catalyst can not be completely separated from the water phase,
the method comprises the following specific steps:
(1) preparation of g-C by calcination3N4Powder: will CH4N2Placing O (urea) in a muffle furnace, heating to 550 ℃ at the speed of 2.5 ℃/min, and calcining for 4h to obtain g-C3N4And (3) powder.
(2) Preparing a precursor solution: first, the g-C obtained in (1) is added to water3N4Mixing the powders, stirring, and performing ultrasonic treatment at 400W for 30min to obtain uniformly dispersed suspension A, standing for 12 hr, and collecting g-C3N4Still uniformly dispersed in water, g-C in A3N4The concentration of (2) was 6 g/L. Secondly, Fe (NO) is added to the water in a mass ratio of 2:13)3·9H2O and Zn (NO)3)2·6H2O, stirring to form a solution B, and Fe in the solution B3+Is 1.25mmol/L, Zn2+The concentration of (2) was 0.625 mmol/L. Finally, the solution B was added dropwise at a rate of 0.3ml/s to the continuously stirred suspension A to give g-C3N4And ZnFe2O4The mass ratio of the mixed solution is 20:1, then 1.0mol/L sodium hydroxide solution is used for adjusting the pH value to 11.0, the mixed solution is continuously stirred for 30min, and the preparation g-C is obtained3N4/ZnFe2O4The precursor solution of (1).
(3) Hydrothermal preparation of g-C3N4/ZnFe2O4Nano photocatalyst: g to C in the step (2)3N4/ZnFe2O4The precursor solution is put into an oven with the temperature of 100 ℃ for reaction for 6 hours, and the generated solid powder is g-C3N4/ZnFe2O4(20:1), the obtained catalyst has obviously poor dispersibility, precipitates completely after the water phase is kept still for 10min, and cannot be completely separated from the water phase under the action of an external magnetic field.
The stirring rate throughout the above experiment was 400 rpm.
FIG. 1 is g-C3N4、ZnFe2O4And different mass ratios g-C3N4/ZnFe2O4(including 1:2, 1:1, 5:2 and 10:1) of the nano photocatalyst. The degradation conditions are as follows: under the irradiation of visible light, the concentration of ciprofloxacin is 10mg/L, and the dosage of the catalyst is 0.5 g/L. As can be seen from FIG. 1, g-C3N4/ZnFe2O4Heterojunction ratio g-C3N4、ZnFe2O4High photocatalytic efficiency of the monomer, which means that g-C3N4And ZnFe2O4The construction of the heterojunction is an effective way for improving the photocatalytic efficiency. g-C for comparison with different mass ratios3N4/ZnFe2O4Catalyst discovery when g-C3N4And ZnFe2O4When the mass ratio of (1 to 1) is 10:1 to 1:1, g-C3N4/ZnFe2O4The degradation effect on the ciprofloxacin is obviously improved compared with that of a monomer. When g-C3N4And ZnFe2O4The mass ratio of (1) to (2) is less improved in degradation effect.
In FIG. 2, (a) is g-C3N4/ZnFe2O4(10:1) Dispersion map after dispersing in water and standing for 18 hours, and g-C can be seen from the map after standing for 18 hours3N4/ZnFe2O4(10:1) can still be uniformly dispersed in water, which shows that the catalyst has good dispersibility in water; in FIG. 2 (b) is W1-g-C3N4/ZnFe2O4(10:1) dispersion in water, standing for 10min, and W1-g-C after standing for 10min3N4/ZnFe2O4(10:1) completely precipitated to the bottom of the vessel, indicating that the catalyst does not have aqueous phase dispersibility; in FIG. 2, (C) is g-C3N4/ZnFe2O4The influence of the aqueous dispersibility of (a) on the degradation reaction rate of ciprofloxacin. The degradation conditions are as follows: under the irradiation of visible light, the concentration of ciprofloxacin is 10mg/L, and the dosage of the catalyst is 0.5 g/L. As can be seen from FIG. 2(C), W1-g-C having no dispersibility3N4/ZnFe2O4(10:1) ciprofloxacin degradation reaction rate constant k value is 0.003, and g-C with dispersibility3N4/ZnFe2O4(10:1) the reaction rate constant k value for degrading ciprofloxacin was 0.013. After the dispersibility is given, the k value is improved by 4.3 times.
FIG. 3 shows g-C under an applied magnetic field3N4/ZnFe2O4Separating effect in water. It can be seen from fig. 3 (a) and (b) that the catalyst uniformly dispersed in water is completely attracted to the magnet side in the presence of the magnet, indicating that the catalyst can be completely separated from water upon application of a magnetic field.
FIG. 4 shows different ratios g-C3N4/ZnFe2O4XRD pattern of the nano-photocatalyst, it can be seen from FIG. 4 that 13.1 ° and 27.8 ° in the composite catalyst are g-C3N4Has main characteristic peaks of ZnFe at 29.9 degrees, 35.2 degrees and 62.2 degrees2O4With g-C3N4And ZnFe2O4Variation of the mass ratio, g-C3N4Gradually becomes weaker while ZnFe2O4The main characteristic peak of the invention is enhanced, which shows that the invention successfully synthesizes g-C3N4And ZnFe2O4g-C of different mass ratios3N4/ZnFe2O4The nano photocatalyst of (1).
FIG. 5 is a Scanning Electron Microscope (SEM) image of the nano-photocatalyst of the present invention under different magnification. As can be seen from (a), (b), (c) of figure 5,the surface of the catalyst is rough and stacked in a lamellar way, and ZnFe is adhered to the surface2O4And (3) granules.
It should be noted that the above-mentioned embodiments do not limit the present invention in any way, and all technical solutions obtained by means of equivalent or alternative or equivalent changes fall within the protection scope of the present invention.