Single-atom catalyst Fe-n / BC, and preparation method and application thereof

Abstract

The application provides a monatomic catalyst Fe-N / BC and a preparation method and application thereof, and the preparation method comprises the following steps: step S1, hydrochloric acid is added into bamboo powder, and after stirring, the bamboo powder is filtered and cleaned to obtain a solid; step S2, the solid obtained in the step S1 is added into a 4-12 g / L iron citrate solution, and after ultrasonic treatment, the solid is extracted to obtain impregnated biomass; step S3, the impregnated biomass obtained in the step S2 is mixed with dicyandiamide through ball milling, and then pyrolysis is carried out at 800-1000 DEG C to obtain the monatomic catalyst Fe-N / BC. The monatomic catalyst Fe-N / BC obtained by the technical scheme has good catalytic activity, and has the functions of catalyzing sodium borohydride to reduce nitrobenzene pollutants and catalyzing persulfate to oxidize aniline pollutants.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a single-atom catalyst Fe-N / BC, its preparation method, and its application. Background Technology

[0002] Nitrobenzene contaminants (nitrobenzene, p-nitrophenol, etc.) are common pollutants. Treatment processes for these contaminants can be mainly divided into two categories: chemical reduction and advanced oxidation processes. Chemical reduction methods can remove nitrobenzene using zero-valent iron and catalytic reduction. Advanced oxidation processes can degrade nitrobenzene using Fenton-like, Fenton-like, photocatalytic, and electrocatalytic methods.

[0003] Chemical reduction methods include zero-valent iron (ZV) reduction, which can efficiently reduce nitrobenzene pollutants to aniline pollutants. However, in water, ZV tends to aggregate, and after reducing nitrobenzene pollutants, ZV is oxidized to ferrous (Fe2+) and ferric (Fe3+) iron, making continuous reduction of nitrobenzene impossible. Catalytic reduction methods utilize catalysts to catalyze the reduction of nitrobenzene pollutants. The most common catalytic reduction method is catalytic sodium borohydride (NaBH4). This process can efficiently reduce nitrobenzene pollutants to less toxic aniline pollutants, but it cannot further remove the generated aniline pollutants.

[0004] Advanced oxidation processes use nitro groups as electron-withdrawing groups. Nitrobenzene pollutants are more difficult to oxidize than benzene. However, using advanced oxidation processes to treat nitrobenzene pollutants presents the problem of large oxidant dosages. Furthermore, nitrobenzene pollutants cannot be completely oxidized, resulting in the formation of numerous highly toxic intermediate products.

[0005] The combined process of catalytic reduction and advanced oxidation can effectively treat nitrobenzene pollutants and reduce the generation of toxic byproducts. However, there is currently a lack of catalysts that can be used in both catalytic reduction and advanced oxidation systems. The combined use of two catalysts is required, which makes the process complex and increases operating costs. Summary of the Invention

[0006] To address the above technical problems, this invention discloses a single-atom catalyst Fe-N / BC, its preparation method, and its applications.

[0007] The technical solution adopted by this invention is as follows:

[0008] A method for preparing a single-atom catalyst Fe-N / BC includes the following steps:

[0009] Step S1: Add hydrochloric acid to bamboo powder, stir, filter, wash and obtain solid.

[0010] Step S2: Add the solid obtained in step S1 to a 4-12 g / L ferric citrate solution, sonicate, and then filter to obtain the impregnated biomass.

[0011] Step S3: The impregnated biomass obtained in step S2 is ball-milled and mixed with dicyandiamide, and then pyrolyzed at 800-1000℃ to obtain the single-atom catalyst Fe-N / BC.

[0012] As a further improvement of the present invention, in step S1, 0.003-0.01 mol of hydrochloric acid is used per gram of bamboo powder.

[0013] As a further improvement of the present invention, in step S1, the concentration of hydrochloric acid is 0.5-2 mol / L.

[0014] As a further improvement of the present invention, in step S2, the concentration of the ferric citrate solution is 6-10 g / L. Further, in step S2, the concentration of the ferric citrate solution is 8 g / L.

[0015] As a further improvement of the present invention, in step S3, the amount of dicyandiamide used is 1-3 times the mass of bamboo powder in step S1.

[0016] As a further improvement of the present invention, in step S3, the amount of dicyandiamide used is twice the mass of bamboo powder in step S1.

[0017] As a further improvement of the present invention, in step S3, the ball milling time is at least 1 hour; the pyrolysis time is more than 1 hour. Further, in step S3, the ball milling time is 2 hours, and the pyrolysis time is 2 hours.

[0018] The present invention also discloses a single-atom catalyst Fe-N / BC, which is prepared by the method described above for preparing the single-atom catalyst Fe-N / BC.

[0019] The present invention also discloses the application of the single-atom catalyst Fe-N / BC as described above, wherein the single-atom catalyst Fe-N / BC is used to catalyze the reduction of nitrobenzene pollutants by sodium borohydride and to catalyze the oxidation of aniline pollutants by persulfate.

[0020] The present invention also discloses a method for treating nitrobenzene-containing wastewater, wherein NaBH4 and the single-atom catalyst Fe-N / BC as described above are added to the nitrobenzene-containing wastewater, wherein the amount of NaBH4 is more than 0.5 times the initial concentration of nitrobenzene, and the amount of the single-atom catalyst Fe-N / BC is 0.02-2 times the amount of NaBH4. After reacting for 1 hour, PMS is added, wherein the amount of PMS is 20-50 times the initial concentration of nitrobenzene.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The Fe-N / BC single-atom catalyst obtained using the technical solution of this invention is an iron-nitrogen-doped single-atom catalyst with excellent catalytic activity. It combines the functions of catalyzing the reduction of nitrobenzene pollutants with sodium borohydride (NaBH4) and the oxidation of aniline pollutants with persulfate (PMS). The catalytic reduction-catalytic oxidation combined system using this catalyst can efficiently reduce nitrobenzene pollutants and treat the resulting aniline pollutants. Attached Figure Description

[0023] Figure 1 These are spherical aberration electron microscopy (SEM) images of the single-atom catalyst Fe-N / BC prepared in the embodiments of the present invention, wherein (a) and (b) are SEM images at different positions, and (c) is an SEM image at another magnification.

[0024] Figure 2 This is the result of the effect of catalyst dosage on nitrobenzene removal rate in Example 2 of the present invention.

[0025] Figure 3 This is the result of the effect of NaBH4 dosage on the nitrobenzene removal rate in Example 3 of the present invention.

[0026] Figure 4 This is the result of the concentrations of nitrobenzene and aniline during the catalyst recycling and recycling process in Example 4 of this invention.

[0027] Figure 5 This is the concentration curve of p-nitrophenol and p-aminophenol in water treated by the combined catalytic reduction and catalytic oxidation method in Example 5 of the present invention. Detailed Implementation

[0028] The preferred embodiments of the present invention will be described in further detail below.

[0029] Example 1

[0030] Weigh 2g of bamboo powder into a beaker, add 10mL of 1mol / L hydrochloric acid, and stir on a magnetic stirrer at 350rad / min for 6 hours. Pour the mixture into a vacuum filter, wash three times with pure water, and then transfer the filtered solid to a beaker containing 8g / L ferric citrate solution. Sonicate at 40kHz for 30 minutes, and then filter out the biomass using a vacuum filter. Place the impregnated biomass in a ball mill, add 4g of dicyandiamide, and ball mill for 2 hours. Then, place the mill in a tube furnace and pyrolyze at 900℃ for 2 hours to obtain the catalyst Fe-N / BC.

[0031] The obtained catalyst Fe-N / BC was analyzed by spherical aberration electron microscopy, and the spherical aberration electron microscopy pattern is shown below. Figure 1 As shown in the figure, the bright spots are iron single-atom sites, indicating that the catalyst Fe-N / BC is a single-atom catalyst.

[0032] This Fe-N / BC catalyst is an iron-nitrogen-doped single-atom catalyst that combines the functions of catalyzing the reduction of nitrobenzene pollutants by sodium borohydride (NaBH4) and catalyzing the oxidation of aniline pollutants by persulfate (PMS). It is used for the efficient reduction of nitrobenzene pollutants and the further treatment of the aniline pollutants generated therefrom. The following is a description with reference to specific examples.

[0033] Example 2

[0034] Weigh a certain amount of PMS and NaBH4 and place them in a centrifuge tube to prepare a stock solution of PMS and NaBH4 of a certain concentration; prepare a nitrobenzene solution with a concentration of 10 mg / L.

[0035] Add 100 mL of 10 mg / L nitrobenzene solution to a beaker, set the rotation speed to 350 r / min, add a certain amount of NaBH4 solution, then add 1 mg of Fe-N / BC and start timing. After reacting for 1 hour, add a certain amount of PMS solution and continue the reaction. Take samples of the reaction solution periodically, filter them through a 0.22 μm filter membrane into a liquid chromatography vial pre-filled with 10 μL of sodium thiosulfate solution, and determine the concentration of nitrobenzene and its reduction product aniline using UPLC.

[0036] The effect of catalyst dosage (2, 5, 10, 20, 50 mg / L) on nitrobenzene removal rate was investigated under the conditions of an initial nitrobenzene concentration of 10 mg / L, NaBH4 dosage of 0.1 g / L, and pH value of 7. The results are as follows: Figure 2 As shown.

[0037] from Figure 2 It can be seen that when the Fe-N / BC dosage is 10 mg / L, the nitrobenzene removal rate reaches over 97% after 15 min of reaction.

[0038] Example 3

[0039] Based on Example 2, with an initial nitrobenzene concentration of 10 mg / L, a catalyst dosage of 10 mg / L, and an initial pH of 7, the effect of NaBH4 dosage (0, 0.01, 0.05, 0.1, 0.25, 0.5 g / L) on the nitrobenzene removal rate was investigated. The results are as follows: Figure 3 As shown.

[0040] from Figure 3 It can be seen that when the dosage of NaBH4 is 10 mg / L, the removal rate of nitrobenzene reaches more than 97% after 15 min of reaction.

[0041] Example 4

[0042] Based on Example 2, nitrobenzene was reduced under the conditions of 10 mg / L nitrobenzene, 0.1 g / L NaBH4, and 10 mg / L catalyst. After 1 hour of reaction, the residual sodium borohydride in the system was completely decomposed. No additional catalyst was added subsequently; instead, 0.25 g / L PMS was directly introduced into the system. After the reaction, the catalyst was recovered by filtration through a 0.45 μm filter membrane, washed several times with deionized water, and then dried in a 60°C forced-air drying oven. The dried catalyst was then subjected to the same steps under the same conditions, and the concentrations of nitrobenzene and aniline were measured during the reaction. This cycle was repeated several times, and the results are as follows: Figure 4 As shown.

[0043] from Figure 4 It is evident that the combined NaBH4-PMS catalytic system has a good treatment effect on nitrobenzene. After catalytic reduction, nitrobenzene is almost completely converted into aniline. After the addition of PMS, aniline can be efficiently removed, and the catalyst efficiency remains almost unchanged after five repeated experiments.

[0044] Example 5

[0045] Based on Example 2, nitrobenzene was reduced under the conditions of 10 mg / L p-nitrophenol, 0.1 g / L NaBH4, and 10 mg / L catalyst. After 1 hour of reaction, the residual sodium borohydride in the system was completely decomposed. No further catalyst was added; instead, 0.25 g / L PMS was directly added to the system. The results are as follows. Figure 5 As shown.

[0046] from Figure 5 It is evident that this catalytic reduction-catalytic oxidation combined system can effectively treat p-nitrophenol and its reduction product p-aminophenol.

[0047] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. The application of a single-atom catalyst Fe-N / BC, characterized in that: The single-atom catalyst Fe-N / BC is used to catalyze the reduction of nitrobenzene pollutants by sodium borohydride and the oxidation of aniline pollutants by persulfate. The single-atom catalyst Fe-N / BC is prepared by the following steps: Step S1: Add hydrochloric acid to bamboo powder, stir, filter, wash and obtain solid. Step S2: Add the solid obtained in step S1 to a 4~12 g / L ferric citrate solution, sonicate, and then filter to obtain the impregnated biomass. Step S3: The impregnated biomass obtained in step S2 is ball-milled and mixed with dicyandiamide, and then pyrolyzed at 800~1000 °C to obtain the single-atom catalyst Fe-N / BC; wherein the amount of dicyandiamide is 1-3 times the mass of bamboo powder in step S1; the ball milling time is at least 1 hour; and the pyrolysis time is more than 1 hour.

2. The application of the single-atom catalyst Fe-N / BC according to claim 1, characterized in that: In step S1, 0.003-0.01 mol of hydrochloric acid is used per gram of bamboo powder.

3. The application of the single-atom catalyst Fe-N / BC according to claim 2, characterized in that: In step S1, the concentration of hydrochloric acid is 0.5-2 mol / L.

4. The application of the single-atom catalyst Fe-N / BC according to claim 1, characterized in that: In step S2, the concentration of the ferric citrate solution is 6-10 g / L.

5. The application of the single-atom catalyst Fe-N / BC according to claim 1, characterized in that: In step S3, the amount of dicyandiamide used is twice the mass of bamboo powder used in step S1.

6. A method for treating wastewater containing nitrobenzene, characterized in that: NaBH4 and a single-atom catalyst Fe-N / BC are added to wastewater containing nitrobenzene. The amount of NaBH4 is more than 0.5 times the initial concentration of nitrobenzene, and the amount of the single-atom catalyst Fe-N / BC is 0.02-2 times the amount of NaBH4. After reacting for 1 hour, PMS is added. The amount of PMS is 20-50 times the initial concentration of nitrobenzene. The single-atom catalyst Fe-N / BC was prepared using the following steps: Step S1: Add hydrochloric acid to bamboo powder, stir, filter, wash and obtain solid. Step S2: Add the solid obtained in step S1 to a 4~12 g / L ferric citrate solution, sonicate, and then filter to obtain the impregnated biomass. Step S3: The impregnated biomass obtained in step S2 is ball-milled and mixed with dicyandiamide, and then pyrolyzed at 800~1000 °C to obtain the single-atom catalyst Fe-N / BC; wherein the amount of dicyandiamide is 1-3 times the mass of bamboo powder in step S1; the ball milling time is at least 1 hour; and the pyrolysis time is more than 1 hour.

7. The method for treating nitrobenzene-containing wastewater according to claim 6, characterized in that: In step S1, 0.003-0.01 mol of hydrochloric acid is used per gram of bamboo powder.

8. The method for treating nitrobenzene-containing wastewater according to claim 7, characterized in that: In step S1, the concentration of hydrochloric acid is 0.5-2 mol / L.

9. The method for treating nitrobenzene-containing wastewater according to claim 6, characterized in that: In step S2, the concentration of the ferric citrate solution is 6-10 g / L.

10. The method for treating nitrobenzene-containing wastewater according to claim 6, characterized in that: In step S3, the amount of dicyandiamide used is twice the mass of bamboo powder used in step S1.

Images