A nitrogen-doped porous carbon material, preparation method and application thereof in new pollutant treatment

Abstract

The present invention relates to the technical field of sewage treatment, discloses a nitrogen-doped porous carbon material, a preparation method and its application in the treatment of new pollutants, and the present invention provides a nitrogen-doped porous carbon material, including graphite nitrogen and pyridine nitrogen. Graphite nitrogen activates persulfate through an electron transfer mechanism, and pyridine nitrogen activates persulfate through non-radical singlet oxygen, rapidly degrading organic pollution, limiting the ratio of the atomic content of graphite nitrogen and pyridine nitrogen to 1: 0.7-2.1, using a dual non-radical pathway (electron transfer and singlet oxygen) can effectively avoid water background interference, and can selectively degrade organic pollutants in complex water bodies; limiting the nitrogen content to 9at%-23at%, good conductivity, conducive to electron transfer, rapid activation of persulfate, and organic pollutant degradation; the present invention not only needs to increase the total amount of nitrogen atoms, but also needs to increase the ratio of graphite nitrogen and pyridine nitrogen content, so that new pollutants can be degraded through dual non-radical pathways.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a nitrogen-doped porous carbon material, a preparation method and application thereof in the treatment of new pollutants. Background Art

[0002] Advanced oxidation processes (AOPs) based on permonosulfate (PMS) show good oxidation efficiency for the treatment of new pollutants in the water environment, but PMS needs to be activated to better exert its oxidation function. Currently, the reagents commonly used to activate PMS are metal catalysts and carbon materials (CMs). Metal catalysts generally activate PMS through free radical pathways, and free radical (sulfate radical and hydroxyl radical) pathways are easily interfered by background ions in water bodies, which is not conducive to the application of actual water bodies; however, CMs can induce non-radical activation, can resist the interference of the background environment of water bodies, avoid the formation of toxic halogenated byproducts, and show higher substrate selectivity in complex environments. However, unmodified CMs have poor conductivity and lack of catalytic active centers, resulting in weak catalytic performance in activating PMS. Therefore, the development of high-performance CMs is of great significance for the removal of new pollutants in the environment.

[0003] Nitrogen-doped porous carbon materials (NPCs) can improve the conductivity of CMs due to the introduction of nitrogen atoms. However, since carbon nitride precursors often produce a large amount of ammonia during pyrolysis, the nitrogen doping amount is limited and the catalytic effect is poor. Graphitic carbon nitride (g-C3N4) is a low-cost, chemically stable carbon-nitrogen polymer. Its rich N content (57.1at%) makes it an ideal precursor for the synthesis of NPCs. Unfortunately, N atoms in g-C3N4 are easily lost during pyrolysis, and only a small amount of N reacts with C groups, resulting in a low N content in NPCs (5.4at%).

[0004] To this end, the related art discloses a method for preparing highly nitrogen-doped carbon materials by molecular-scale confined pyrolysis, wherein 8g-15g of graphite-phase carbon nitride precursor, 0.5g-2g of 2-mercaptobenzimidazole and 50-80g of zirconium oxide ball milling beads are placed in a ball mill and milled for 2h-3h until they are evenly mixed to obtain a solid powder, and the solid powder is transferred to a quartz boat, and the quartz boat is placed in a quartz tube, and then the quartz tube is placed in a tube furnace for high-temperature carbonization treatment, and the temperature is 2°C / min under gas protection. -1 -5℃ / min -1The heating rate is increased to 800℃-1000℃, the carbonization time is controlled at 2h-3h, and the reaction is cooled to room temperature after completion to obtain a high nitrogen-doped carbon material. The purpose of this method is to increase the nitrogen content and use it as a counter electrode in dye-sensitized solar cells. In addition, the current nitrogen-doped carbon material activates PMS mainly with sulfate radicals and hydroxyl radicals, which are greatly interfered by the background of water and are not suitable for complex water bodies.

[0005] Therefore, how to obtain an NPC material that can efficiently activate PMS and thus improve the degradation rate of new pollutants is one of the technical problems that urgently need to be solved in this field. Summary of the invention

[0006] In view of this, the present invention provides a nitrogen-doped carbon material, a preparation method and application thereof in treating new pollutants in wastewater, so as to quickly activate persulfate and achieve degradation of organic pollutants.

[0007] In a first aspect, the present invention provides a nitrogen-doped porous carbon material having a total atomic content of nitrogen of 9 at%-23 at%; the nitrogen-doped porous carbon material comprises graphitic nitrogen and pyridinic nitrogen, and the atomic content ratio of the graphitic nitrogen to the pyridinic nitrogen is 1:0.7-2.1.

[0008] In an optional embodiment, the atomic content of graphitic nitrogen is 5at%-8at%.

[0009] In an optional embodiment, the atomic content of pyridine nitrogen is 4 at%-15 at%.

[0010] In an optional embodiment, the total nitrogen content is 21.4 at %, and the atomic content ratio of the graphitic nitrogen to the pyridinic nitrogen is 1:2.06.

[0011] In a second aspect, the present invention provides a method for preparing the nitrogen-doped porous carbon material, comprising the following steps:

[0012] The graphite phase carbon nitride precursor and the thiol compound are uniformly mixed at a molar ratio of 6-24:1 to obtain a mixture;

[0013] Under the protection of an inert atmosphere, the mixture is heated to cause a thermal polymerization reaction, the reaction temperature is controlled to be 750° C.-850° C., and the reaction time is 2 h-3 h.

[0014] In an optional embodiment, the heating rate is 1°C / min-10°C / min.

[0015] In an optional embodiment, the graphite phase carbon nitride precursor includes at least one of melamine, dicyandiamide, urea and thiourea.

[0016] In an optional embodiment, the thiol compound includes at least one of 2-mercaptobenzimidazole, 2-mercapto-5-benzimidazole carboxylic acid, and 5-amino-2-mercaptobenzimidazole.

[0017] In a third aspect, the present invention also provides an application of the above-mentioned nitrogen-doped porous carbon material in catalytic degradation of new pollutants in water environment.

[0018] In an optional embodiment, the use of the nitrogen-doped porous carbon material in catalytic degradation of new pollutants in water environment comprises the following steps:

[0019] Peroxymonosulfate and the nitrogen-doped porous carbon material are added to an aqueous solution containing new pollutants for reaction, wherein the ratio of the peroxymonosulfate to the nitrogen-doped porous carbon material is 0.25mmol-2mmol: 0.05g-0.4g.

[0020] In an optional embodiment, the nitrogen-doped porous carbon material and the aqueous solution containing the new pollutants are first mixed, and then persulfate is added for degradation.

[0021] In an optional embodiment, the new pollutant includes at least one of bisphenol A, sulfamethoxazole, para-chlorophenol, and bisphenol F.

[0022] In an optional embodiment, the concentration of the new pollutant is 1 mg / L-20 mg / L.

[0023] In an optional embodiment, the mixing time is 40 min-120 min, and the degradation time is 0.5 min-7 min.

[0024] In an optional embodiment, the degradation temperature is 20°C-35°C.

[0025] In an optional embodiment, the degradation reaction is carried out in a dark environment.

[0026] In an optional embodiment, the pH of the aqueous solution is 2-11.

[0027] In an optional embodiment, the aqueous solution also includes SO4 2- 、H2PO4 - 、NO3 - , Cl - , humic acid or at least one of the following.

[0028] In the present invention, at% refers to the ratio of N atoms to the total number of atoms in the NPC.

[0029] In the present invention, new pollutants refer to toxic and hazardous chemical substances that are discharged into the environment, have characteristics such as biological toxicity, environmental persistence, and bioaccumulation, and pose great risks to the ecological environment or human health, but have not yet been included in management or the existing management measures are insufficient.

[0030] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0031] 1. The nitrogen-doped porous carbon material provided by the present invention has a total atomic content of nitrogen of 9 at%-23 at%; the nitrogen-doped porous carbon material includes graphitic nitrogen and pyridinic nitrogen, and the atomic content ratio of graphitic nitrogen to pyridinic nitrogen is 1:0.7-2.1. Nitrogen atom-doped porous carbon material (NPC) benefits from a specific electronic configuration and can strengthen the interaction with persulfate or the electron transfer ability in a π delocalized system. The high or low N content is not the only determining factor. The nitrogen content should have a suitable ratio and a reasonable nitrogen configuration to activate PMS. Specifically, graphite nitrogen can activate persulfate through an electron transfer mechanism, and pyridine nitrogen can activate persulfate through non-radical singlet oxygen to quickly degrade organic pollution. The atomic content ratio of graphite nitrogen and pyridine nitrogen in the present invention is 1:0.7-2.1. The dual non-radical pathway (electron transfer and singlet oxygen) can effectively avoid the interference of water background and can selectively degrade organic pollutants in complex water bodies. At the same time, the nitrogen content is limited to 9at%-23at%, which has good conductivity, is conducive to electron transfer, quickly activates persulfate, and realizes the degradation of organic pollutants. It can be seen that the present invention not only needs to increase the total amount of nitrogen atoms, but also needs to increase the ratio of graphite nitrogen and pyridine nitrogen content, so as to degrade new pollutants through dual non-radical pathways.

[0032] 2. The nitrogen-doped porous carbon material provided by the present invention utilizes an efficient molecular confinement strategy, adopts carbon nitride as the N source, and cleverly utilizes the CSC bond directly formed between it and thiol to successfully prepare ultra-high N-doped nitrogen-doped carbon materials under the effect of molecular confinement. The N content of the nitrogen-doped carbon material is significantly higher than that of most similar existing materials.

[0033] 3. The application of the nitrogen-doped porous carbon material provided by the present invention in the catalytic degradation of new pollutants in the water environment. The nitrogen-doped carbon material activates persulfate under lightless conditions to quickly degrade new pollutants, and exhibits good performance and stability under a wide pH condition, in different water environment background ions, and in actual water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is the XRD diagram of the melamine after polymerization of the present invention.

[0036] Figure 2 It is an X-ray photoelectron spectrum diagram of S2p of the intermediate product obtained at different thermal polymerization temperatures of the present invention.

[0037] Figure 3 It is the X-ray photoelectron spectrum of S2p of the nitrogen-doped carbon materials prepared in Examples 1 to 3 of the present invention.

[0038] Figure 4 3 and 4 are diagrams showing the total N content and N configuration of the nitrogen-doped carbon materials prepared in Examples 1 to 3 of the present invention.

[0039] Figure 5 It is an X-ray photoelectron spectrum of N1s of the nitrogen-doped carbon materials prepared in Examples 1 to 3 of the present invention.

[0040] Figure 6 It is an X-ray photoelectron spectrum of N1s of the nitrogen-doped carbon materials prepared in Examples 1, 6 and 7 of the present invention.

[0041] Figure 7 (a) is the present invention k obs / S BET and N content, (b) is the correlation diagram of k obs / S BET Correlation plot with pyridinic N / graphitic N.

[0042] Figure 8 It is a diagram of the degradation effects of different catalytic systems of the present invention.

[0043] Fig. 9Schematic diagram of the adsorption sites of the present invention; wherein, N1 is pyridine N, N2 is graphite N, C1 is the adjacent C of pyridine N, C2 is the adjacent C of graphite N, C0 is the C not adjacent to N, a1 is NPC1-PMS-N1, a2 is NPC1-PMS-N2, a3 is NPC1-PMS-C1, a4 is NPC1-PMS-C2, a5 is NPC1-PMS-C0, b1 is NPC1-BPA-N1, b2 is NPC1-BPA-N2, b3 is NPC1-BPA-C1, b4 is NPC1-BPA-C2, and b5 is NPC1-BPA-C0.

[0044] Fig.10 It is a diagram showing the degradation effects of different nitrogen-doped carbon material concentrations of the present invention.

[0045] Fig.11 It is a diagram of the degradation effect of different PMS concentrations of the present invention.

[0046] Fig.12 It is a diagram showing the degradation effects of the nitrogen-doped carbon materials prepared in Examples 1, 6 and 7 of the present invention.

[0047] Fig.13 It is a diagram showing the degradation effects of nitrogen-doped carbon materials prepared in Examples 1 to 3 and 8 of the present invention.

[0048] Fig.14 It is a diagram of the degradation effect of adding different free radical quenchers in the present invention.

[0049] Fig.15 It is a diagram of the degradation effect under different pH values ​​of the present invention.

[0050] Fig.16 It is a diagram showing the degradation effects of different organic pollutants of the present invention.

[0051] Fig.17 This is a diagram showing the degradation effects of adding different anions and humic acid in the present invention.

[0052] Fig.18 It is a diagram comparing the degradation effects of different water bodies according to the present invention. DETAILED DESCRIPTION

[0053] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0054] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0055] The present invention is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed by the present invention.

[0056] All catalytic degradation experiments of the present invention were carried out in a multi-channel reactor (PL-SX100A, Princes, China).

[0057] In order to solve the problems existing in the above-mentioned related technologies, the present invention provides an application of a nitrogen-doped porous carbon material in catalytic degradation of new pollutants in a water environment, which specifically comprises the following steps:

[0058] (1) grinding a graphite phase carbon nitride precursor and a thiol compound at a molar ratio of 6-24:1 to obtain a precursor mixture, heating the mixture to 750°C-850°C at a heating rate of 1°C / min-10°C / min in an inert atmosphere for a thermal polymerization reaction for 2h-3h to obtain a nitrogen-doped porous carbon material, wherein the total atomic content of nitrogen is 9at%-23at%; the nitrogen-doped porous carbon material includes graphite nitrogen and pyridine nitrogen, and the atomic content ratio of graphite nitrogen to the pyridine nitrogen is 1:0.7-2.1; the atomic content of graphite nitrogen is 5at%-8at%, and the atomic content of pyridine nitrogen is 4at%-15at%; wherein the graphite phase carbon nitride precursor includes at least one of melamine, dicyandiamide, urea, and thiourea; the thiol compound includes at least one of 2-mercaptobenzimidazole, 2-mercapto-5-benzimidazole carboxylic acid, and 5-amino-2-mercaptobenzimidazole;

[0059] (2) The nitrogen-doped porous carbon material and the aqueous solution containing the new pollutant are first mixed, and then persulfate is added for degradation reaction, the ratio of peroxymonosulfate to nitrogen-doped porous carbon material is 0.25mmol-2mmol:0.05g-0.4g; the new pollutant includes at least one of bisphenol A, sulfamethoxazole, p-chlorophenol, and bisphenol F; the concentration of the new pollutant is 1mg / L-20mg / L; the mixing time is 40min-120min, the degradation time is 0.5min-7min; the degradation temperature is 20℃-35℃, the degradation reaction is carried out in a dark environment, and the pH of the aqueous solution is 2-11; the aqueous solution also includes SO4 2- 、H2PO4 - 、NO3 - , Cl - , humic acid or at least one of the following.

[0060] Calcination of graphite carbon nitride precursor and thiol compounds together can increase the nitrogen content, but the larger the ratio of the two is not necessarily better. Through our research, we found that when the molar ratio of graphite carbon nitride precursor and thiol compounds is 18, the N content is the highest. In addition, electron transfer is also related to the proportion of graphite nitrogen, and the content and configuration of singlet oxygen and pyridine nitrogen. The nitrogen atom-doped porous carbon material (NPC) of the present invention benefits from a specific electronic configuration and can strengthen the interaction with persulfate or the electron transfer ability in a π delocalized system. The high or low N content is not the only determining factor. The nitrogen content should have a suitable ratio and a reasonable nitrogen configuration at the same time to activate PMS. Specifically, graphite nitrogen can activate PMS through an electron transfer mechanism, and pyridine nitrogen can activate PMS through non-radical singlet oxygen to quickly degrade organic pollution. The atomic content ratio of graphite nitrogen and pyridine nitrogen of the present invention is 1:0.7-2.1. The dual non-radical pathway (electron transfer and singlet oxygen) can effectively avoid the interference of water background and can selectively degrade organic pollutants in complex water bodies. At the same time, the nitrogen content is limited to 9at%-23at%, which has good conductivity, is conducive to electron transfer, quickly activates persulfate, and realizes the degradation of organic pollutants. It can be seen that the present invention not only needs to increase the total amount of nitrogen atoms, but also needs to increase the ratio of graphite nitrogen and pyridine nitrogen content, so as to degrade new pollutants through dual non-radical pathways.

[0061] In addition, the reaction temperature, reaction time, and the molar ratio of the graphite phase carbon nitride precursor and the thiol compound will affect the nitrogen configuration and content. The difference in content and configuration directly determines the difference in the activation path of PMS. Unclear N type and configuration are easy to activate PMS through the free radical path, while the free radical path is easily interfered by the background of the water body and is not suitable for actual complex water bodies. In order to realize the dual non-free radical mechanism to activate PMS, there are strict requirements for nitrogen content and nitrogen configuration.

[0062] Example 1

[0063] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, comprising the following steps:

[0064] The precursor melamine and 2-mercaptobenzimidazole were ground at a molar ratio of 18:1 to obtain a precursor mixture. The precursor mixture was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min under a flowing argon environment for thermal polymerization for 2 hours to obtain a high nitrogen-doped carbon material NPC-18.

[0065] Example 2

[0066] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, comprising the following steps:

[0067] The precursor melamine and 2-mercaptobenzimidazole were ground at a molar ratio of 12:1 to obtain a precursor mixture. The precursor mixture was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min in a flowing argon environment for thermal polymerization for 2 hours to obtain a nitrogen-doped carbon material NPC-12.

[0068] Example 3

[0069] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, comprising the following steps:

[0070] The precursor melamine and 2-mercaptobenzimidazole were ground at a molar ratio of 24:1 to obtain a precursor mixture. The precursor mixture was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min in a flowing argon environment for thermal polymerization for 2 hours to obtain a nitrogen-doped carbon material NPC-24.

[0071] Example 4

[0072] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, comprising the following steps:

[0073] The precursor dicyandiamide and 2-mercapto-5-benzimidazole carboxylic acid were ground at a molar ratio of 16:1 to obtain a precursor mixture. The precursor mixture was placed in a tube furnace and heated to 850°C at a heating rate of 1°C / min in a flowing argon environment for thermal polymerization for 2.5 hours to obtain a nitrogen-doped carbon material NPC-16.

[0074] Example 5

[0075] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, comprising the following steps:

[0076] The precursor urea and 5-amino-2-mercaptobenzimidazole were ground at a molar ratio of 20:1 to obtain a precursor mixture. The precursor mixture was placed in a tube furnace and heated to 750°C at a heating rate of 10°C / min in a flowing argon environment for thermal polymerization for 3 hours to obtain a nitrogen-doped carbon material NPC-20.

[0077] Example 6

[0078] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, which is substantially the same as the steps in Embodiment 1, except that melamine is replaced with urea to obtain a nitrogen-doped carbon material NPC-URE.

[0079] Example 7

[0080] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, which is basically the same as the steps in Example 1, except that melamine is replaced by dicyandiamide to obtain a nitrogen-doped carbon material NPC-DCD.

[0081] Example 8

[0082] This embodiment provides a method for preparing a nitrogen-doped porous carbon material, which is substantially the same as the steps of Embodiment 1, except that the molar ratio of the precursors melamine and 2-mercaptobenzimidazole is 6:1.

[0083] Experimental Example 1

[0084] After the precursor melamine was thermally polymerized at 550°C for 2 hours, XDR test was performed. Figure 1 As shown in the figure, it can be seen that melamine can form N-rich g-C3N4 intermediates after thermal polymerization at 550°C.

[0085] In the same process as in Example 1, melamine and 2-mercaptobenzimidazole were thermally polymerized at 550°C, 700°C, and 800°C for 2 h, respectively, and the obtained intermediate products were subjected to S2p test. Figure 2 As shown in the figure, it can be seen that at 700°C, there is an obvious CSC characteristic peak at the binding energy of 164eV. At 800°C, the CSC characteristic peak disappears, indicating that the CSC covalent bond formed by g-C3N4 and 2-mercaptobenzimidazole is confined in the local space.

[0086] The nitrogen-doped carbon materials prepared in Examples 1 to 3 above were subjected to S2p tests. Figure 3 As shown in the figure, it can be seen that during the pyrolysis of g-C3N4, the CSC covalent bonds played a vital role in reducing the loss of nitrogen, leading to the formation of nitrogen-rich NPCs with various types of nitrogen. In this process, the CSC bonds acted as molecular constraints, stabilizing the structure during pyrolysis and eventually decomposing after the reaction was completed at 800 °C.

[0087] The nitrogen-doped carbon materials prepared in Examples 1 to 3 and Examples 6 to 7 were tested for N content and N configuration. Figure 4-Figure 6As shown in the figure, it can be seen that by adjusting the molar ratio of melamine and 2-mercaptobenzimidazole, the nitrogen configuration is consistent, but the content is significantly different; when the molar ratio of melamine and 2-mercaptobenzimidazole increases from 12:1 to 18:1, the N yield increases from 15.9at% to 21.4at%, exceeding most similar catalysts; however, with further increase to 24:1, the nitrogen yield drops to 14.1at%. Therefore, by adjusting the molar ratio of melamine to 2-mercaptobenzimidazole, the formation of CSC bonds can be adjusted, so that the type and doping level of N incorporation can be precisely controlled. In Example 6 and Example 7, by replacing melamine with urea and dicyandiamide, respectively, the nitrogen configuration is consistent with the nitrogen configuration of the nitrogen-doped carbon materials prepared in Example 1 to Example 3.

[0088] In order to determine the potential active sites of the prepared catalysts, the normalized reaction rate constant (k obs / S BET ) and the correlation between pyridinic N and graphitic N contents. Figure 7 (a) is k obs / S BET Correlation between (b) k obs / S BET The correlation between pyridinic N / graphitic N is shown in the figure. The combined content of pyridinic nitrogen and graphitic nitrogen is related to k obs / S BET The correlation coefficient between them is 0.980. In addition, the ratio of pyridinic nitrogen to graphitic nitrogen content is related to k obs / S BET The correlation coefficient between them is 0.994, indicating that both can serve as the main active sites of NPC.

[0089] Experimental Example 2

[0090] The nitrogen-doped carbon material, bisphenol BPA and deionized water prepared in Examples 1 to 3 were respectively placed in a 30 mL quartz reaction tube, so that the concentration of the nitrogen-doped carbon material was 0.2 g / L, the concentration of bisphenol BPA was 5 mg / L, and the pH of the solution was 5.83. The mixture was reacted for 40 min under magnetic stirring at 25°C in the dark to reach adsorption-desorption equilibrium, and then peroxymonosulfate PMS (0.5 mmol / L) was added for catalytic degradation. The solutions after 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, and 7 min of reaction in the quartz tube were collected respectively and filtered through a 0.22 μm polyethersulfone filter, and then an equal volume of methanol (MeOH) was immediately added to mix evenly, and the liquid phase was collected in a small vial and the concentration of BPA was detected by a high performance liquid chromatograph (HPLC, Waters e2695, USA) equipped with an Agilent C-18 column (4.6 mm×250 mm, 5 μm). At the same time, the solution was compared with the case where PMS or nitrogen-doped carbon material was omitted. The results are shown in FIG. Figure 8 shown.

[0091] As can be seen from the figure, in the system with only NPC or PMS, the degradation effect of BPA is negligible. However, after adding NPC and PMS, BPA in all systems showed obvious degradation, especially in the NPC-18 / PMS system, where BPA was completely degraded within 3 minutes, indicating that NPC-18 can efficiently activate PMS to degrade BPA.

[0092] In addition, DFT calculations were performed to identify the active sites and investigate the activation mechanism of PMS, such as Fig. 9 As shown in the figure, it can be seen that the adsorption energy of PMS on the pyridinic N of NPC1 is -2.909eV, and the adsorption energy of PMS on the graphitic N of NPC1 is -3.266eV, indicating that PMS is more easily adsorbed on the graphitic N site of NPC1, proving that the introduction of N element enhances the adsorption and activation of PMS, which is consistent with the results of the catalytic degradation experiment. Similarly, BPA is more easily adsorbed on the pyridinic N site of NPC1. During the catalytic reaction, graphitic N and pyridinic nitrogen are the active sites of PMS and BPA, respectively.

[0093] Experimental Example 3

[0094] The nitrogen-doped carbon material NPC-18, bisphenol BPA and deionized water prepared in Example 1 were respectively placed in 30 mL quartz reaction tubes, so that the concentrations of the nitrogen-doped carbon material were 0.05 g / L, 0.1 g / L, 0.2 g / L, 0.3 g / L and 0.4 g / L, respectively, the concentration of bisphenol BPA was 5 mg / L, and the pH of the solution was 5.83. The mixture was reacted for 40 min under magnetic stirring at 25°C in the dark to reach adsorption-desorption equilibrium, and then peroxymonosulfate PMS (0.5 mmol / L) was added for catalytic degradation. The solutions after 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, and 7 min of reaction were collected in the quartz tube, respectively, and filtered through a 0.22 μm polyethersulfone filter, and then an equal volume of methanol (MeOH) was immediately added and mixed evenly. The liquid phase was collected in a small vial and the concentration of BPA was detected by a high performance liquid chromatograph (HPLC, Waters e2695, USA) equipped with an Agilent C-18 column (4.6 mm×250 mm, 5 μm). The results are shown in FIG. Fig.10 shown.

[0095] As can be seen from the figure, as the dosage of NPC-18 increased from 0.05 g / L to 0.2 g / L, the degradation efficiency of BPA increased significantly, and the degradation rate increased from 63.5% to 100% within 3 min. obs From 0.318min -1 Increased to 1.771min -1 When the dosage of NPC-18 is further increased, the BPA degradation efficiency does not increase significantly, so the preferred dosage of the catalyst of the present invention is 0.20 g / L.

[0096] Experimental Example 4

[0097] This experimental example refers to the degradation steps of Experimental Example 3. The only difference from Experimental Example 3 is that the concentration of nitrogen-doped carbon material is 0.2 g / L, and the concentration of PMS is 0.25 mM, 0.5 mM, 1 mM, 1.5 mM, and 2 mM. The results are shown in Fig.11 shown.

[0098] As can be seen from the figure, when the PMS concentration continues to increase from 0.5 mM, the degradation efficiency of BPA only increases slightly, indicating that the utilization of the active sites of NPC-15 is nearly saturated. Therefore, the preferred dosage of PMS in the present invention is 0.5 mM.

[0099] Experimental Example 5

[0100] This experimental example refers to the degradation steps of Experimental Example 3. The only difference from Experimental Example 3 is that the nitrogen-doped carbon material prepared in Example 1 is replaced by the nitrogen-doped carbon materials prepared in Examples 1-3 and 6-8. The concentrations of the nitrogen-doped carbon materials are 0.2 g / L, respectively. After 7 minutes of degradation, the degradation efficiency of BPA in the nitrogen-doped carbon materials prepared in Examples 6-7 is 100%. The results are as follows: Fig.12 As shown, the nitrogen-doped carbon material prepared in Example 8 has a BPA degradation efficiency of 81% after 7 minutes of degradation. Fig.13 shown.

[0101] Experimental Example 6

[0102] This experimental example refers to the degradation steps of Experimental Example 3, and the only difference from Experimental Example 3 is that the concentration of the nitrogen-doped carbon material is 0.2 g / L, and quenchers are added to the above aqueous solution, methanol (MeOH, 50 mM), tert-butyl alcohol (TBA, 50 mM), p-benzoquinone (p-BQ, 1.5 mM), L-histidine (L-His, 3 mM) as quenchers to identify hydroxyl radicals, sulfate radicals, superoxide radicals and singlet oxygen active species, and the control group is not added with quenchers, such as Fig.14 As shown, after adding MeOH, TBA, and p-BQ to the NPC-18 / PMS / BPA system, the inhibitory effect on BPA degradation was weak, and all three systems were able to achieve complete degradation of BPA within 3 minutes, indicating that hydroxyl radicals, sulfate radicals, and superoxide radicals were not the main active species for BPA degradation. However, after adding L-His, the degradation rate of BPA dropped from 100% to 88.8% in 3 minutes, indicating that singlet oxygen is the active species for BPA degradation. In addition, the addition of L-His did not completely inhibit the degradation of BPA, indicating the existence of an electron transfer mechanism. Therefore, our present invention has implemented the activation of PMS through a dual non-radical (singlet oxygen and electron transfer) mechanism by rationally designing the nitrogen content and nitrogen type.

[0103] Experimental Example 7

[0104] This experimental example refers to the degradation steps of Experimental Example 3. The only difference from Experimental Example 3 is that the concentration of nitrogen-doped carbon material is 0.2 g / L, and the pH of the bisphenol BPA solution is adjusted to 2.00, 4.01, 5.83, 8.00, and 10.02 by adding sodium hydroxide or hydrochloric acid. The degradation effect is shown in Fig.15 As shown in the figure, it can be seen that when the pH is between 2.00 and 10.02, the system can achieve complete degradation of BPA, indicating that the system has strong adaptability to changes in pH.

[0105] Experimental Example 8

[0106] This experimental example refers to the degradation steps of Experimental Example 3. The only difference from Experimental Example 3 is that the concentration of nitrogen-doped carbon material is 0.2 g / L, and bisphenol (BPA) is replaced by chloramphenicol (CAP), bisphenol S (BPS), sulfamethoxazole (SMX), para-chlorophenol (4-CP), bisphenol A, and bisphenol F (BPF). The results are shown in Fig.16 As shown in the figure, it can be seen that the present invention can effectively remove SMX, 4-CP, bisphenol A and bisphenol F, but cannot effectively remove CAP and BPS, indicating that the present invention can selectively degrade electron-rich pollutants in water, while chloramphenicol and bisphenol S with electron-withdrawing substances cannot be effectively removed. Therefore, the present invention can target and degrade electron-rich substances in complex water bodies without being interfered by background ions.

[0107] Example 9

[0108] This experimental example refers to the degradation steps of Experimental Example 3. The only difference from Experimental Example 3 is that the concentration of nitrogen-doped carbon material is 0.2 g / L, 5 mol / L sulfate (SO4 2- )、5mol / L dihydrogen phosphate (H2PO4 - )、5mol / L nitrate (NO3 - )、5mol / L chloride ion (Cl - ) and 5 mol / L humic acid, the results are shown in Fig.17 As shown, it was found that SO4 2- 、H2PO4 - 、NO3 - , Cl - And the inhibitory effect of humic acid on the catalytic degradation process is slight, indicating that the present invention has a strong ability to resist interference from environmental factors.

[0109] Example 10

[0110] This experimental example refers to the degradation steps of Experimental Example 3. The only difference from Experimental Example 3 is that the concentration of nitrogen-doped carbon material is 0.2 g / L, and the bisphenol BPA aqueous solution is replaced by pure water, tap water, river water, and sea water. The results are shown in Fig.18 As shown in the figure, it can be seen that the removal effects are all high, indicating that the present invention is suitable for removing new pollutants in different water bodies.

[0111] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment, characterized in that: The total atomic content of nitrogen is 9at%-23at%; the nitrogen-doped porous carbon material includes graphitic nitrogen and pyridinic nitrogen, and the atomic content ratio of the graphitic nitrogen to the pyridinic nitrogen is 1:0.7-2.1; The new pollutant includes at least one of bisphenol A, sulfamethoxazole, parachlorophenol, and bisphenol F; The method for preparing the nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment comprises the following steps: The graphite phase carbon nitride precursor and the thiol compound are uniformly mixed at a molar ratio of 6-24:1 to obtain a mixture; Under the protection of an inert atmosphere, the mixture is heated to cause a thermal polymerization reaction, the reaction temperature is controlled to be 750° C.-850° C., and the reaction time is 2 h-3 h.

2. The nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment according to claim 1, characterized in that: The atomic content of graphite nitrogen is 5at%-8at%; And / or, the atomic content of pyridine nitrogen is 4 at %-15 at %.

3. The nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment according to claim 1, characterized in that: The total nitrogen content is 21.4 at %, and the atomic content ratio of the graphitic nitrogen to the pyridinic nitrogen is 1:2.

06.

4. A method for preparing the nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment according to any one of claims 1 to 3, characterized in that: The steps include: The graphite phase carbon nitride precursor and the thiol compound are uniformly mixed at a molar ratio of 6-24:1 to obtain a mixture; Under the protection of an inert atmosphere, the mixture is heated to cause a thermal polymerization reaction, the reaction temperature is controlled to be 750° C.-850° C., and the reaction time is 2 h-3 h.

5. The method according to claim 4, characterized in that The heating rate is 1℃ / min-10℃ / min; And / or, the graphite phase carbon nitride precursor includes at least one of melamine, dicyandiamide, urea and thiourea; And / or, the thiol compound includes at least one of 2-mercaptobenzimidazole, 2-mercapto-5-benzimidazole carboxylic acid, and 5-amino-2-mercaptobenzimidazole.

6. Use of the nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment as described in any one of claims 1 to 3 or the nitrogen-doped porous carbon material for catalytic degradation of new pollutants in water environment prepared by the method described in claim 4 or 5 in catalytic degradation of new pollutants in water environment.

7. The use according to claim 6, characterized in that: The steps include: Peroxymonosulfate and the nitrogen-doped porous carbon material are added to an aqueous solution containing new pollutants for reaction, wherein the ratio of the peroxymonosulfate to the nitrogen-doped porous carbon material is 0.25mmol-2mmol: 0.05g-0.4g.

8. The use according to claim 7, characterized in that: The nitrogen-doped porous carbon material is first mixed with an aqueous solution containing new pollutants, and then peroxymonosulfate is added for degradation.

9. The use according to claim 8, characterized in that: The new pollutant includes at least one of bisphenol A, sulfamethoxazole, parachlorophenol, and bisphenol F; and / or, the concentration of the new pollutant is 1 mg / L-20 mg / L; And / or, the mixing time is 40min-120min, and the degradation time is 0.5min-7min; And / or, the degradation temperature is 20°C-35°C; And / or, the degradation reaction is carried out in a dark environment.

10. The use according to claim 8 or 9, characterized in that: The pH value of the aqueous solution is 2-11; And / or, the aqueous solution also includes SO4 2- 、H2PO4 - 、NO3 - , Cl - , humic acid or at least one of the following.

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