Catalyst for degrading p-nitrophenol and preparation method thereof

Abstract

The preparation method comprises the following steps: dissolving sodium alginate and carbon black in water, adding polyacrylic acid, and carrying out a stirring reaction so as to obtain a mixture; then adding a CN precursor while heating and stirring, heating to a gel state, and roasting at high temperature to obtain a carbon nitride composite material; dispersing the composite material into water, adding a cobalt chloride solution, carrying out ultrasonic treatment, and adjusting the pH value to 10-11 to obtain a mixture; and adding a NaBH4 solution, reducing to obtain nano particles, filtering, washing and drying to obtain the catalyst. According to the preparation method, the carbon nitride composite carrier with high specific surface area is prepared firstly, then the active component is loaded, and the photocatalytic degradation effect of p-nitrophenol is improved through the synergistic effect of the composite carrier and the active component.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution treatment, and particularly relates to a catalyst for degrading p-nitrophenol and a preparation method thereof. Background Art

[0002] In recent years, the degradation of harmful substance p-nitrophenol in natural environmental water bodies has attracted more and more attention. The reduction product of p-nitrophenol is p-aminophenol which has low toxicity, is easily degradable and has important applications in industry. However, due to the very stable nitro group on the benzene ring, the degradation of p-nitrophenol has always been a difficult problem in wastewater treatment. Therefore, the preparation of a catalyst for catalytically degrading p-nitrophenol into p-aminophenol is of great significance for reducing environmental water pollution.

[0003] As a new type of photocatalytic material, carbon nitride materials have attracted much attention in recent years and can be used as catalyst carriers in different catalytic systems. However, the traditional preparation method is to use urea or melamine for calcination to prepare crystalline phase C3N4 samples, and the specific surface area of the prepared C3N4 samples is relatively low, which limits its application in supported catalysts. Moreover, for p-nitrophenol, its catalytic selectivity also needs to be improved.

[0004] The literature "Preparation and Photocatalytic Reduction of p-Nitrophenol by Au / g-C3N4 Composite Particles" (Yin Rong, Journal of Hebei University of Science and Technology) aimed to solve the problem that the separation difficulty of photogenerated electrons and holes affects the photocatalytic activity of g-C3N4. An in-situ method was used to prepare Au / g-C3N4 composite particles, and the visible-light photocatalytic performance of Au / g-C3N4 composite particles was investigated using the p-nitrophenol reduction reaction as a model. The results showed that: g-C3N4 is a hexagonal crystal with a lamellar stacking structure, and the nano-gold between the lamellae is a face-centered cubic crystal form; the introduction of nano-gold significantly improves the visible-light absorption of the g-C3N4 matrix and the separation efficiency of its photogenerated electron-hole pairs; when the gold content is 0.5% (mass fraction) and the molar ratio of sodium chloroaurate to sodium citrate is 1:3, the activity of the photocatalyst is the highest. However, the catalytic performance of Au / g-C3N4 composite particles is achieved by introducing nano-gold, and the gold content is 0.5%, so the preparation cost is relatively high.

[0005] CN110034306A discloses a preparation method and application of a composite material of nitrogen-doped porous carbon-coated cobalt nanoparticles. The preparation method includes the following steps: uniformly disperse a carbon source precursor, a nitrogen source precursor, and a soluble salt of a transition metal ion in a solvent according to a ratio, and then dry to obtain a solid powder precursor. Calcinate the solid powder precursor under a protective atmosphere to obtain a black powder, which is the composite material. The composite material has high-efficiency oxygen reduction catalytic performance and can be applied to air electrode catalysts of proton exchange membrane fuel cells, alkaline fuel cells, metal-air batteries, etc. This method is achieved by nitrogen-doped porous carbon coating cobalt nanoparticles. The metal nanoparticles coated in the porous carbon will affect their catalytic degradation performance of p-nitrophenol. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a catalyst for degrading p-nitrophenol and a preparation method thereof. The present invention first prepares a carbon nitride composite support with a high specific surface area, and then loads active components. Through the synergistic effect of the composite support and the active components, the photocatalytic degradation effect of p-nitrophenol is improved.

[0007] On the one hand, the present invention provides a preparation method of a catalyst for degrading p-nitrophenol, including the following content:

[0008] (1) Dissolve sodium alginate and carbon black in water, add polyacrylic acid, stir and react for a certain time to obtain a mixture; add a CN precursor under heating and stirring, heat to a gel state, and calcine at a high temperature to obtain a carbon nitride composite material;

[0009] (2) Disperse the composite material in water, add a cobalt chloride solution, perform ultrasonic treatment, and then adjust the pH value to 10-11 to obtain a mixture;

[0010] (3) Add a NaBH 4 solution to the mixture in step (2), reduce to obtain nanoparticles, and obtain the catalyst after filtration, washing, and drying.

[0011] In step (1) of the present invention, the mass ratio of sodium alginate to water is 0.5-2.5:100, preferably 0.5-1.0:100.

[0012] In step (1) of the present invention, the mass ratio of sodium alginate to carbon black is 1:0.03-0.1, preferably 1:0.03-0.06.

[0013] In step (1) of the present invention, the molar ratio of polyacrylic acid to sodium alginate is 1:0.5-2, preferably 1:1-1.2.

[0014] In step (1) of the present invention, stirring can be carried out using conventionally used magnetic or electric stirring equipment. The stirring rate is 500 - 1500 rpm, and the stirring time is 1 - 5 h.

[0015] In step (1) of the present invention, the heating can be carried out by any one of water bath heating, heating with a magnetic stirrer with heating function, heating with a hot plate, etc. The heating temperature is 30 - 60 °C, and the stirring rate is 500 - 1500 rpm.

[0016] In step (1) of the present invention, the CN precursor is selected from at least one of melamine, dicyandiamide, monocyanamide, urea, thiourea, ammonium bisulfate, etc.

[0017] In step (1) of the present invention, the CN precursor is added according to the mass ratio of 10 - 30:1 to carbon black.

[0018] In step (1) of the present invention, it is heated to a gel state and then subjected to high-temperature roasting. The roasting temperature is 400 - 500 °C, and the roasting time is 2 - 10 h. Roasting can be carried out using conventionally used roasting equipment such as a muffle furnace.

[0019] In step (2) of the present invention, the carbon nitride composite is dispersed in water, and the mass-volume ratio of the two is 2 - 10 g:1 L.

[0020] In step (2) of the present invention, the concentration of the cobalt chloride solution is 50 - 150 g / L. The addition amount of the cobalt chloride solution is added according to the mass ratio of cobalt chloride to the carbon nitride composite of 1:89 - 99.

[0021] In step (2) of the present invention, the ultrasonic power is 80 - 300 W, and the ultrasonic time is 15 - 60 min.

[0022] In step (2) of the present invention, the pH is adjusted by adding an alkali, and the alkali is at least one of sodium hydroxide, potassium hydroxide, etc.

[0023] In step (3) of the present invention, NaBH 4 The concentration of the solution is 1.0 - 5.0 mol / L. The volume ratio of the mixture in step (2) to the NaBH 4 solution is 1:1.2 - 1.5.

[0024] In step (3) of the present invention, filtration is carried out by conventional filtration methods such as suction filtration and pressure filtration. The solid obtained by filtration is washed, and it can be washed 3 - 5 times with deionized water, etc.

[0025] In step (3) of the present invention, the drying is carried out by vacuum drying. The vacuum degree is 0.01 - 10 Pa, the drying temperature is 40 - 50 °C, and the drying time is 10 - 60 min.

[0026] In the second aspect of the present invention, a catalyst for degrading p-nitrophenol is provided, which is prepared by the method of the present invention described above. The prepared catalyst uses a carbon nitride composite material as a carrier to load the CoB active component. Based on the mass of the catalyst, the loading amount of CoB is 1% - 10%.

[0027] In the third aspect of the present invention, a method for degrading p-nitrophenol is provided, which uses the catalyst prepared by the method of the present invention described above as a photocatalyst to degrade p-nitrophenol in water.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) In the present invention, a carbon nitride composite support with a high specific surface area is first prepared, and then the CoB active component is loaded. Through the synergistic effect of the composite support and the active component, the photocatalytic degradation effect of p-nitrophenol is improved.

[0030] (2) In the present invention, a mixed solution of sodium alginate, carbon black, and polyacrylic acid is first prepared, and then a CN precursor is added under heating and stirring to obtain a gel. After calcination, amorphous carbon is doped into the crystalline phase C3N4, which improves the specific surface area of the carbon nitride composite material. Compared with the carbon nitride material prepared by the traditional method, the specific surface area is increased by more than 50%, which is beneficial to mass transfer and diffusion and improves the photocatalytic effect.

[0031] (3) The preparation method of the present invention can promote the uniform combination of the active component onto the carbon nitride composite material, avoid the agglomeration of the active component, and improve the activity and stability of the catalyst. Specific Embodiments

[0032] The technical solutions and their effects of the present invention will be further described below through examples. The examples are implemented on the premise of the technical solutions of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0033] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, can all be purchased from biochemical reagent stores. The water used is all deionized water.

[0034] In the examples, a UV-visible spectrophotometer (Shanghai Jingke, L5s) was used to analyze the catalytic performance of the prepared catalyst.

[0035] Example 1

[0036] (1) Weigh 2.5 g of sodium alginate and 0.125 g of carbon black, dissolve them in 500 mL of distilled water, add polyacrylic acid according to the molar ratio of polyacrylic acid to sodium alginate of 1:1, with a stirring rate of 500 rpm, and stir magnetically for 3 h to obtain a mixed solution; under the conditions of heating and stirring, with a heating temperature of 45 °C and a stirring rate of 500 rpm, slowly add 2.5 g of melamine powder, continue heating until gelation occurs, then stop heating, transfer it to a muffle furnace and calcine at 500 °C for 5 hours to obtain a carbon nitride composite material. After testing, the specific surface area of the prepared composite material is 65.3 m 2 / g.

[0037] (2) Disperse the carbon nitride composite material powder in water, with a mass-to-volume ratio of 5 g:1 L for the two, add a cobalt chloride solution with a mass concentration of 100 g / L, add it according to the mass ratio of cobalt chloride to the carbon nitride composite material of 1:94, and treat it with an ultrasonic power of 200 W for 30 min; add NaOH to adjust the pH value of the solution to 10 to obtain a mixture.

[0038] (3) Add 1.0 mol / L NaBH 4 solution to the mixture, with a volume ratio of the mixture to the NaBH 4 solution of 1:1.2, reduce to obtain nanoparticles, filter, wash with deionized water 3 times, and dry at a vacuum of 1 Pa and 40 °C for 30 min to obtain a catalyst.

[0039] Example 2

[0040] (1) Weigh 5.0 g of sodium alginate and 0.2 g of carbon black, dissolve them in 500 mL of distilled water, add polyacrylic acid according to the molar ratio of polyacrylic acid to sodium alginate of 1:1.2, stir magnetically for 4 h with a stirring rate of 500 rpm to obtain a mixed solution. Stir and heat on a magnetic stirrer, with a heating temperature of 35 °C and a stirring rate of 500 rpm. Slowly add 5.0 g of melamine powder, continue heating until gelation occurs, then stop heating, transfer it to a muffle furnace and calcine at 450 °C for 7 hours to obtain a carbon nitride composite material. After testing, the specific surface area of the prepared composite material is 61.7 m 2 / g.

[0041] (2) Disperse the carbon nitride composite material powder in water, with a mass-to-volume ratio of 3 g:1 L for the two, add a cobalt chloride solution with a mass concentration of 70 g / L, add it according to the mass ratio of cobalt chloride to the carbon nitride composite material of 1:89, and treat it with an ultrasonic power of 300 W for 15 min; add NaOH to adjust the pH value of the solution to 10 to obtain a mixture.

[0042] (3) Add 2 mol / L NaBH 4 solution to the mixture, with a volume ratio of the mixture to the NaBH 4The volume ratio of the solution is 1:1.3. Nanoparticles are obtained by reduction, filtered, washed three times with deionized water, and dried at a vacuum of 1 Pa and 40 °C for 30 min to obtain the catalyst.

[0043] Example 3

[0044] (1) Weigh 7.5 g of sodium alginate and 0.75 g of carbon black and dissolve them in 500 mL of distilled water. Add polyacrylic acid according to the molar ratio of polyacrylic acid to sodium alginate of 1:1.1, and stir magnetically for 2 h at a stirring rate of 500 rpm to obtain a mixed solution. Heat and stir on a magnetic stirrer at a heating temperature of 60 °C and a stirring rate of 500 rpm. Add 7.5 g of melamine powder, continue heating until gelling, then stop heating and transfer to a muffle furnace for calcination at 400 °C for 10 hours to obtain a carbon nitride composite material. After testing, the specific surface area of the prepared composite material is 57.4 m 2 / g.

[0045] (2) Disperse the carbon nitride composite material powder in water at a mass-volume ratio of 10 g:1 L, add a cobalt chloride solution with a mass concentration of 150 g / L, and add it according to the mass ratio of cobalt chloride to carbon nitride composite material of 1:99. Treat it with an ultrasonic power of 100 W for 60 min; add NaOH to adjust the pH value of the solution to 11 to obtain a mixture.

[0046] (3) Add a 3 mol / L NaBH 4 solution to the mixture. The volume ratio of the mixture to the NaBH 4 solution is 1:1.5. Nanoparticles are obtained by reduction, filtered, washed three times with deionized water, and dried at a vacuum of 1 Pa and 40 °C for 30 min to obtain the catalyst.

[0047] Example 4

[0048] Same as Example 1, except that: the CN precursor uses urea, and finally a carbon nitride composite material is obtained. After testing, the specific surface area of the prepared composite material is 62.2 m 2 / g. Steps (2) and (3) are the same as in Example 1, and finally a catalyst is obtained.

[0049] Example 5

[0050] Same as Example 1, except that: the CN precursor uses monocyanamide, and finally a carbon nitride composite material is obtained. After testing, the specific surface area of the prepared composite material is 58.4 m 2 / g. Steps (2) and (3) are the same as in Example 1, and finally a catalyst is obtained.

[0051] Comparative Example 1

[0052] Same as Example 1, except that: sodium alginate, carbon black, polyacrylic acid, and melamine are mixed and heated together to finally obtain a composite material. After analysis, the specific surface area of the prepared composite material is 48.2 m 2 / g. Steps (2) and (3) are the same as in Example 1, and finally a catalyst is obtained.

[0053] Comparative Example 2

[0054] Same as Example 1, except that: sodium alginate is not used, and finally a composite material is obtained. After analysis, the specific surface area of the prepared composite material is 40.6 m 2 / g. Steps (2) and (3) are the same as in Example 1, and finally a catalyst is obtained.

[0055] Comparative Example 3

[0056] Same as Example 1, except that: polyacrylic acid is not used, and finally a composite material is obtained. After analysis, the specific surface area of the prepared composite material is 31.7 m 2 / g. Steps (2) and (3) are the same as in Example 1, and finally a catalyst is obtained.

[0057] Comparative Example 4

[0058] Same as Example 1, except that: carbon black is not used, and finally a composite material is obtained. After analysis, the specific surface area of the prepared composite material is 18.6 m 2 / g. Steps (2) and (3) are the same as in Example 1, and finally a catalyst is obtained.

[0059] Comparative Example 5

[0060] Same as Example 1, except that: in step (2), chloroauric acid solution is used to replace cobalt chloride solution, and finally a catalyst is obtained.

[0061] Comparative Example 6

[0062] Same as Example 1, except that: ultrasonic treatment is not used in step (2), and finally a catalyst is obtained.

[0063] Comparative Example 7

[0064] Same as Example 1, except that: the reduction treatment in step (3) is cancelled, and the substance in step (2) is directly filtered, washed, and dried to obtain a catalyst.

[0065] Comparative Example 8

[0066] Same as Example 1, except that: carbon nitride material is directly prepared by calcining melamine, and it is used as a carrier to finally obtain a catalyst.

[0067] Test Example

[0068] The catalysts prepared in the examples and comparative examples of the present invention were subjected to performance tests.

[0069] Using p-nitrophenol as the degradation substrate, the specific experiment is as follows: Add a sodium borohydride solution with a concentration of 10 mg / mL to a 1.5 mmol / L p-nitrophenol solution, and add the catalyst powder in an amount of 10 mg / mL. Start the scanning program of the ultraviolet-visible spectrophotometer, and the ultraviolet-visible spectrophotometer scans within 200 - 500 nm to detect the change in the absorbance of p-nitrophenol over time, and calculate the degradation rate of p-nitrophenol.

[0070] Table 1 Degradation effects of examples and comparative examples

[0071]

[0072]

[0073] From the above test results, it can be seen that the catalyst prepared by the present invention has a better p-nitrophenol removal effect and can maintain good stability after being recycled multiple times. However, the effect of the catalyst prepared without adopting the complete technical solution of the present invention is significantly reduced, and the recycling effect is also not ideal.

Claims

1. Preparation method of catalyst for degrading p-nitrophenol, characterized in that it includes the following contents: (1) Dissolve sodium alginate and carbon black in water, add polyacrylic acid, stir and react for a certain time to obtain a mixture; add a CN precursor under heating and stirring, heat to a gel state, and perform high-temperature calcination to obtain a carbon nitride composite material; (2) Disperse the composite material in water, add a cobalt chloride solution, perform ultrasonic treatment, and then adjust the pH value to 10-11 to obtain a mixture; (3) Add NaBH to the mixture in step (2). 4 The solution is added, and nanoparticles are obtained by reduction. After filtration, washing, and drying, the catalyst is obtained.

2. The method according to claim 1, characterized in that: In step (1), the mass ratio of sodium alginate to water is 0.5-2.5:100, preferably 0.5-1.0:

100.

3. The method according to claim 1, characterized in that: In step (1), the mass ratio of sodium alginate to carbon black is 1:0.03-0.1, preferably 1:0.03-0.

06.

4. The method according to claim 1, characterized in that: In step (1), the molar ratio of polyacrylic acid to sodium alginate is 1:0.5-2, preferably 1:1-1.

2.

5. The method according to claim 1, characterized in that: In step (1), the stirring rate after adding polyacrylic acid is 500-1500 rpm, and the stirring time is 1-5 h.

6. The method according to claim 1, characterized in that: In step (1), the heating is carried out by any one of water bath heating, magnetic stirrer heating with heating function, and hot plate heating; the heating temperature is 30-60 °C, and the stirring rate is 500-1500 rpm.

7. The method according to claim 1, characterized in that: In step (1), the CN precursor is selected from at least one of melamine, dicyandiamide, monocyanamide, urea, thiourea, or ammonium bisulfate.

8. The method according to claim 1, characterized in that: In step (1), the CN precursor is added according to the mass ratio of 10-30:1 to carbon black.

9. The method according to claim 1, characterized in that: In step (1), heat to a gel state for high-temperature calcination, the calcination temperature is 400-500 °C, and the calcination time is 2-10 h.

10. The method according to claim 1, characterized in that: In step (2), disperse the carbon nitride composite material in water, and the mass-volume ratio of the two is 2-10 g:1 L.

11. The method according to claim 1, characterized in that: In step (2), the concentration of the cobalt chloride solution is 50-150 g / L; the addition amount of the cobalt chloride solution is added according to the mass ratio of cobalt chloride to the carbon nitride composite material of 1:89-99.

12. The method according to claim 1, characterized in that: In step (2), the ultrasonic power is 80-300 W, and the ultrasonic time is 15-60 min.

13. The method according to claim 1, characterized in that: In step (2), the pH is adjusted by adding an alkali, and the alkali is at least one of sodium hydroxide and potassium hydroxide.

14. The method according to claim 1, characterized in that: In step (3), the concentration of the NaBH 4 solution is 1.0 - 5.0 mol / L; the volume ratio of the mixture in step (2) to the NaBH 4 solution is 1:1.2 - 1.

5.

15. The method according to claim 1, It is characterized in that: In step (3), filtration is carried out by suction filtration or pressure filtration, and the obtained solid matter is washed 3-5 times with deionized water.

16. The method according to claim 1, It is characterized in that: In step (3), drying is carried out by vacuum drying, the vacuum degree is 0.01-10 Pa, the drying temperature is 40-50 °C, and the drying time is 10-60 min.

17. A catalyst for degrading p-nitrophenol, It is characterized in that it is prepared by the method described in any one of claims 1-16.

18. A method for degrading p-nitrophenol, which is characterized in that a catalyst prepared by the method described in any one of claims 1-16 or the catalyst described in claim 17 is used as a photocatalyst to degrade p-nitrophenol in water.

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