Monatomic catalyst for high-selectivity generation of superoxide radicals, and preparation method and application thereof

Abstract

The application discloses a monatomic catalyst for high-selectivity generation of superoxide free radicals, and a preparation method and application thereof. x The catalyst comprises nitrogen-doped Ti3C2T x Nanoplate and transition metal monatomic aiming at asymmetric coordination structure. The preparation method comprises mixing Ti3C2T x nanoplate, nitrogen precursor and soluble transition metal salt, self-assembly, centrifugation, freeze-drying and pyrolysis. The monatomic catalyst can realize high-selectivity generation of superoxide free radicals, is a novel catalyst capable of directional generation of superoxide free radicals, high efficiency, low consumption and recycling, and can realize rapid and thorough removal of organic pollutants in water under the condition of low catalyst dosage when used as a catalyst for activation of peroxymonosulfate and treatment of wastewater, can realize effective purification of organic wastewater, and can overcome defects such as large catalyst dosage and low PMS activation efficiency in a heterogeneous catalytic process, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of environmental new materials, and relates to a monatomic catalyst for high-selectivity generation of superoxide radicals and a preparation method and application thereof. BACKGROUND

[0002] In recent years, as a promising green decontamination technology, advanced oxidation process can utilize in-situ generated strong oxidizing active substances for water pollutant remediation, wherein, the Fenton-like technology based on peroxymonosulfate (PMS) has attracted extensive attention in organic wastewater treatment due to high efficiency and economy.

[0003] Under natural conditions, PMS alone only shows limited oxidizability. At present, many monatomic catalysts have been developed and present structure-dependent induction of colorful PMS activation pathways, and these catalysts mainly involve directional regulation of PMS molecules to directly split HO· or SO4· - , or indirectly split non-radicals (such as 1 O2, high-valence iron-oxygen species and electron transfer). However, so far, there is no related report on directional high-selectivity generation of ·O2 - . Therefore, developing a monatomic catalyst for high-selectivity generation of superoxide radicals has important significance for promoting the wide application of the Fenton-like technology based on peroxymonosulfate (PMS) in treating organic wastewater and realizing efficient purification of organic wastewater. SUMMARY

[0004] The technical problem to be solved by the application is to overcome the shortcomings of the prior art and provide a monatomic catalyst for high-selectivity generation of superoxide radicals and a preparation method and application thereof.

[0005] To solve the above technical problems, the application adopts the following technical solutions:

[0006] A monatomic catalyst for high-selectivity generation of superoxide radicals comprises nitrogen-doped Ti3C2T x nanosheets and transition metal monatomic atoms, and the transition metal monatomic atoms are aimed at the nitrogen-doped Ti3C2T x nanosheets in an asymmetric coordination structure.

[0007] The monatomic catalyst, further improved, has a mass percentage of transition metal monatomic atoms in the monatomic catalyst of 0.8% to 1.3%.

[0008] The monatomic catalyst, further improved, has a mass percentage of transition metal monatomic atoms in the monatomic catalyst of 0.9% to 1.2%.

[0009] The monatomic catalyst, further improved, wherein the transition metal atom is one of cobalt atom, manganese atom, iron atom, and copper atom.

[0010] As a general technical concept, the application further provides a preparation method of the monatomic catalyst for high-selectivity generation of superoxide radicals, comprising the following steps:

[0011] S1, mixing Ti3C2T x The nanosheet, the nitrogen precursor, and the soluble transition metal salt solution are mixed to perform a self-assembly reaction, centrifuged, and freeze-dried to obtain a catalyst precursor;

[0012] S2, pyrolyzing the catalyst precursor to obtain the monatomic catalyst for high-selectivity generation of superoxide radicals.

[0013] The preparation method, further improved, in step S1, the Ti3C2T x The mass ratio of the nanosheet, the nitrogen precursor, and the soluble transition metal salt in the soluble transition metal salt solution is 100:100-800:1.2-9.6; the nitrogen precursor is protonated melamine; and the soluble transition metal salt is one of soluble cobalt salt, soluble manganese salt, soluble iron salt, and soluble copper salt.

[0014] The preparation method, further improved, in step S1, the centrifugation is performed at a speed of 4000 r / min-6000 r / min, and the centrifugation is performed for 8 min-15 min; and the freeze-drying is performed for 24 h-48 h.

[0015] The preparation method, further improved, in step S2, the pyrolysis is performed in a nitrogen atmosphere, the temperature is raised at a rate of 3 ℃ / min-8 ℃ / min during the pyrolysis, the pyrolysis is performed at a temperature of 500 ℃-550 ℃, and the pyrolysis is performed for 1 h-4 h.

[0016] The preparation method, further improved, after the pyrolysis, further comprising the following treatment: sequentially washing the pyrolysis product with water and ethanol, and drying the washed pyrolysis product under vacuum.

[0017] As a general technical concept, the application further provides an application of the monatomic catalyst or the monatomic catalyst prepared by the preparation method in treatment of organic wastewater as a catalyst for peroxymonosulfate.

[0018] The application, further improved, comprising the following step: mixing the monatomic catalyst, the peroxymonosulfate, and the organic wastewater to perform a catalytic reaction, and removing the organic matter in the wastewater.

[0019] The application is further improved, and the amount of the monatomic catalyst added is 0.05g-0.15g per liter of the organic wastewater.

[0020] The application is further improved, and the concentration of the monopersulfate in the organic wastewater is 0.3mM-0.9mM.

[0021] The application is further improved, and the concentration of the organic wastewater is 20uM-40uM.

[0022] The application is further improved, and the organic matter in the organic wastewater is p-acetylaminophenol.

[0023] The application is further improved, and the pH value of the organic wastewater is 3-11.

[0024] The application is further improved, and the catalytic reaction is carried out under stirring; the stirring speed is 300r / min-600r / min; and the catalytic reaction time is 3min-5min.

[0025] In the application, the Ti3C2T x The preparation method of the nanosheet comprises the following steps: LiF is added into an HCl solution and stirred uniformly, then Ti3AlC2 is slowly added, and stirring is continuously carried out at 35-45℃ for 24-36 hours; the obtained residue is washed with ultrapure water until the pH value of the supernatant is 5.5-6.5, and the remaining precipitate is subjected to ultrasonic treatment, centrifugation, and freezing drying to obtain the few-layer Ti3C2Tx nanosheet. The ratio of the LiF to the HCl solution is 1g-2g:20mL-40mL; and the mass ratio of the LiF to the Ti3AlC2 is 1-2:1-2.

[0026] In the application, the protonated melamine is a positively charged protonated melamine, and the preparation method comprises the following steps: melamine is added into anhydrous ethanol and stirred for 60min, HCl solution is added and stirring is continuously carried out for 60min, drying is carried out, and the obtained powder is washed with ultrapure water and ethanol alternately and dried, so that the protonated melamine is obtained. The ratio of the melamine to the anhydrous ethanol is 1g-2g:15mL-30mL; and the ratio of the melamine to the HCl solution is 2g-4g:3mL-6mL.

[0027] Compared with the prior art, the application has the following advantages:

[0028] (1) The application provides a monatomic catalyst for generating superoxide radicals with high selectivity, which comprises nitrogen-doped Ti3C2T xNanosheet and transition metal monatomic, wherein the transition metal monatomic is aimed at nitrogen-doped Ti3C2T x nanosheet in an asymmetric coordination structure. x The active site formed by the cooperation of the nanosheet and the transition metal monatomic has a nitrogen and oxygen co-regulated electronic structure and chemical environment, and when the monatomic catalyst formed thereby is used to activate an oxidant, the high selectivity of superoxide radicals is realized for the first time, which is conducive to realizing the efficient removal of organic pollutants in wastewater, is a new type of catalyst capable of directional generation of superoxide radicals, high efficiency, low consumption and recycling, has high use value and good application prospect.

[0029] (2) The application also provides a preparation method of the monatomic catalyst for high-selectivity generation of superoxide radicals. x The nanosheet, a nitrogen precursor and a soluble transition metal salt solution are mixed to perform self-assembly reaction and freeze-drying, and the nitrogen precursor and the transition metal ion are uniformly adsorbed on the Ti3C2T x nanosheet by electrostatic adsorption, and then the catalyst precursor is pyrolyzed, and the nitrogen and the Ti3C2T x nanosheet are coupled to regulate the coordination microenvironment of the transition metal atom, and an asymmetric coordination transition metal monatomic catalyst is formed, which can realize the high selectivity of superoxide radicals, and at the same time, the prepared monatomic catalyst presents a highly wrinkled state, which is conducive to the exposure of the metal active site, and thus the effective contact of the organic pollutants in wastewater, the oxidant and the surface of the monatomic catalyst is enhanced, so that the efficiency and selectivity of the reaction can be improved, and more importantly, the prepared monatomic catalyst has excellent structural stability, is easy to separate, can be recycled, has good cycle performance and wide application prospect.

[0030] (3) The application also provides an application of the monatomic catalyst as a catalyst for peroxymonosulfate in treating organic wastewater, wherein the monatomic catalyst is used to activate the peroxymonosulfate and form a large amount of superoxide radicals with strong oxidizing property, and then the superoxide radicals are used to realize the efficient degradation of organic pollutants, and the method has the advantages of simple process, small catalyst dosage, low cost, high treatment efficiency and good removal effect, can realize the rapid and thorough removal of organic pollutants in water under the condition of low catalyst dosage, can realize the effective purification of organic wastewater, can overcome the defects of large catalyst dosage and low PMS activation efficiency in the heterogeneous catalytic process, and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0032] Figure 1 Scanning electron microscope image of the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in Embodiment 1 of the present application.

[0033] Figure 2 Elemental mapping of the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in Embodiment 1 of the present application.

[0034] Figure 3 XRD pattern of the single-atom catalyst (Co SA -N-Ti3C2T x ), Ti3C2T x nanosheet (Ti3C2T x ), N-Ti3C2T x catalyst (N-Ti3C2T x ) prepared in Comparative Example 2.

[0035] Figure 4 XRD pattern of the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in Embodiment 2 of the present application, Ti3C2T x nanosheet (Ti3C2T x ), Ti3C2T x -anneal catalyst (Ti3C2T x -anneal), N-Ti3C2T x catalyst (N-Ti3C2T x ), Co-Ti3C2T x catalyst (Co-Ti3C2T x ) when used for activating PMS.

[0036] Figure 5 Comparison chart of removal effects of p-acetamidophenol by Co SA -N-Ti3C2T x / PMS system under different quenching agents in Embodiment 3 of the present application.

[0037] Figure 6 Comparison chart of removal effects of p-acetamidophenol by Co SA -N-Ti3C2T xThe removal effect of the / PMS system on p-acetamidophenol is shown in the following figure.

[0038] Figure 7 The Co SA -N-Ti3C2T x The removal effect of the / PMS system on p-acetamidophenol is shown in the following figure.

[0039] Figure 8 The Co SA -N-Ti3C2T x The removal effect of the / PMS system on p-acetamidophenol is shown in the following figure. DETAILED DESCRIPTION

[0040] The present application will be further described in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present application is not limited thereby.

[0041] In the following embodiments of the present application, unless otherwise specified, the materials and instruments used are commercially available, the equipment used is conventional equipment, and the data obtained are the average values of more than three repeated experiments.

[0042] Embodiment 1

[0043] A monatomic catalyst for generating superoxide radicals with high selectivity, comprising nitrogen-doped Ti3C2T x nanosheets and transition metal monomers, wherein the transition metal monomers are targeted on the nitrogen-doped Ti3C2T x nanosheets in an asymmetric coordination structure (N-Ti3C2Tx).

[0044] In this embodiment, the mass percentage content of transition metal monomers in the monatomic catalyst is 1.0%.

[0045] In this embodiment, the transition metal monomers are cobalt atoms.

[0046] A preparation method of the monatomic catalyst for generating superoxide radicals with high selectivity in the above embodiment, comprising the following steps:

[0047] a. Slowly mix 75 mg of Ti3C2T x nanosheets (referred to as Ti3C2T x ), 300 mg of protonated melamine, and a solution containing 3.6 mg of CoCl2.6H2O to carry out a self-assembly reaction to obtain a precursor.

[0048] b. Centrifuge the precursor obtained in step a. at 5000 r / min in a high-speed centrifuge for 10 min, collect the precipitated product, and dry it in a freeze dryer for 36 h.

[0049] c. The solid obtained in step b is pyrolyzed under the protection of high-purity nitrogen at a temperature rising rate of 5℃ / min to 550℃ for 3h, washed with water and ethanol, and dried in a vacuum drying oven at 40℃, and the obtained powder is a monatomic catalyst for generating superoxide radicals with high selectivity, denoted as Co SA -N-Ti3C2T x .

[0050] In the present application, the Ti3C2T x The preparation method of the nanosheet comprises the following steps: 1g of LiF is added into 20mL of an HCl solution, stirred uniformly, 1g of Ti3AlC2 is slowly added, stirred at 40℃ for 24h, washed with ultrapure water until the pH value of the effluent is 6, ultrasonically treated, centrifuged, and the upper ink green solution is obtained, the upper ink green solution is freeze-dried to obtain the few-layer Ti3C2Tx nanosheet.

[0051] In the present application, the protonated melamine is a positively charged protonated melamine, and the preparation method thereof comprises the following steps: 2g of melamine is added into 30mL of anhydrous ethanol and stirred for 60min, 3mL of an HCl solution is added and stirred for 60min, dried, washed with ultrapure water and ethanol alternately, and dried, and the obtained powder is the protonated melamine.

[0052] Figure 1 is the scanning electron microscope image of the monatomic catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 of the present application. Figure 1 It can be seen that the monatomic catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 of the present application presents a highly wrinkled state.

[0053] Figure 2 is the element distribution diagram of the monatomic catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 of the present application. Figure 2 It can be seen that the monatomic catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 of the present application contains Ti, C, O and N in addition to single cobalt atoms.

[0054] Comparative Example 1

[0055] A preparation method of a Ti3C2T x -anneal catalyst, and the monatomic catalyst (Co SA -N-Ti3C2T xThe preparation methods are basically the same, the only difference being that CoCl2.6H2O and protonated melamine are not added in Comparative Example 1.

[0056] Ti3C2T prepared in Comparative Example 1 x -anneal catalyst, denoted as Ti3C2T x -anneal.

[0057] Comparative Example 2

[0058] A type of N-Ti3C2T x The preparation method of the catalyst is the same as that of the single-atom catalyst (Co) in Example 1. SA -N-Ti3C2T x The preparation methods are basically the same, the only difference being that CoCl2.6H2O is not added in Comparative Example 2.

[0059] N-Ti3C2T prepared in Comparative Example 2 x Catalyst, denoted as N-Ti3C2T x .

[0060] Comparative Example 3

[0061] A Co-Ti3C2T x The preparation method of the catalyst is the same as that of the single-atom catalyst (Co) in Example 1. SA -N-Ti3C2T x The preparation methods are basically the same, except that: in Comparative Example 3, protonated melamine is not added, and the mixture is slowly stirred with 3M HCl for 3 hours before washing to remove excess cobalt particles.

[0062] Co-Ti3C2T prepared in Comparative Example 3 x Catalyst, denoted as Co-Ti3C2T x .

[0063] Figure 3 The single-atom catalyst (Co) prepared in Example 1 of this invention SA -N-Ti3C2T x Ti3C2T x Nanosheets (Ti3C2T) x N-Ti3C2T prepared in Comparative Example 2 x Catalyst (N-Ti3C2T) x XRD pattern of ). Figure 3 It can be seen that N-Ti3C2T x and Co SA -N-Ti3C2T x The XRD patterns of the catalysts were similar, and there were no significant characteristic peaks of the crystal phase associated with cobalt particles.

[0064] Example 2

[0065] The application of a single-atom catalyst for high-selectivity generation of superoxide radicals in the treatment of organic wastewater, in particular: the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 is used as a catalyst, persulfate (PMS) is used as an oxidant, and a Co SA -N-Ti3C2T x / PMS system is constructed to treat p-acetamidophenol wastewater, including the following steps:

[0066] 5 mg of the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 is weighed and added to 100 mL of a p-acetamidophenol solution with a concentration of 20 μM, mixed uniformly, and persulfate (PMS) is added to make the concentration of PMS in the solution 0.7 mM, and the catalytic reaction is carried out under magnetic stirring at a speed of 500 r / min for 5 min to complete the removal of p-acetamidophenol in the wastewater.

[0067] The control group: Ti3C2T x nanosheets (Ti3C2T x ), the Ti3C2T x -anneal catalyst (Ti3C2T x -anneal), the N-Ti3C2T x catalyst (N-Ti3C2T x ), and the Co-Ti3C2T x catalyst (Co-Ti3C2T x ) prepared in Comparative Examples 1-3 are used instead of the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in Example 1 to construct different catalyst / PMS systems, and other conditions are the same.

[0068] During the magnetic stirring, 1 mL of sample is taken every 1 min, and the sample is filtered using a filter head with a pore size of 0.22 μm, and the filtrate is determined by high-performance liquid chromatography to determine the concentration of the remaining p-acetamidophenol, thereby obtaining the removal effect of the different catalyst / PMS systems on p-acetamidophenol, and the results are shown in Table 2. Figure 4

[0069] Figure 4 The application of a single-atom catalyst for high-selectivity generation of superoxide radicals in the treatment of organic wastewater, in particular: the single-atom catalyst (Co SA -N-Ti3C2T x ), Ti3C2T x nanosheets (Ti3C2T​x ), Ti3C2T x -anneal catalyst (Ti3C2T x -anneal), N-Ti3C2T x catalyst (N-Ti3C2T x ), Co-Ti3C2T x catalyst (Co-Ti3C2T x ) for activating PMS. It can be known from Figure 4 the control chart of removal effect of p-acetamidophenol that the removal rate of p-acetamidophenol after 5 min of catalytic reaction of the single-atom catalyst (Co SA -N-Ti3C2T x ), Ti3C2T x nanosheet (Ti3C2T x ), Ti3C2T x -anneal catalyst (Ti3C2T x -anneal), N-Ti3C2T x catalyst (N-Ti3C2T x ), Co-Ti3C2T x catalyst (Co-Ti3C2T x ) is 100%, 2.02%, 1.63%, 19.02% and 4.94% respectively, which shows that the single-atom catalyst (Co SA -N-Ti3C2T x ) prepared in the application can efficiently activate PMS and realize efficient removal of p-acetamidophenol in wastewater, and other catalysts do not have such performance.

[0070] Example 3

[0071] Co SA -N-Ti3C2T x prepared in Example 1 is used as a catalyst, persulfate (PMS) is used as an oxidant, and p-acetamidophenol is used as an organic pollutant, and the main active species in the Co SA -N-Ti3C2T x / PMS system is explored, and the specific process is as follows:

[0072] Methanol, tert-butyl alcohol, furfuryl alcohol and p-benzoquinone are respectively selected as active substance probes, and are respectively added to an acetamidophenol solution (the volume of the solution is 100 mL, and the concentration is 20 μM) according to the concentration of 200 mM, 200 mM, 1.5 mM and 1.5 mM, and 5 mg of Co SA -N-Ti3C2T xThe concentration of PMS in the wastewater was 0.7 mM, and the catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min for 5 min.

[0073] During magnetic stirring, 1 mL of sample was taken every 1 min, and the sample was filtered with a filter head of 0.22 μm. The filtrate was determined by high performance liquid chromatography to determine the remaining concentration of p-acetamidophenol, so as to obtain the removal effect of Co SA -N-Ti3C2T x / PMS system on p-acetamidophenol. Figure 5

[0074] Figure 5 The removal effect of Co SA -N-Ti3C2T x / PMS system on p-acetamidophenol was determined. Figure 5 It can be seen that the degradation of p-acetamidophenol is not significantly inhibited after adding methanol (200 mM), tert-butyl alcohol (200 mM) and furfuryl alcohol (1.5 mM), indicating that the contribution of common HO·, SO4· - and 1 O2 is weak. However, in the presence of 1.5 mM p-benzoquinone, the removal process of p-acetamidophenol is severely inhibited, indicating that Co SA -N-Ti3C2T x ·O2 - plays a key role in the activation of PMS and has high selectivity.

[0075] Example 4

[0076] Co SA -N-Ti3C2T x was prepared in Example 1, and persulfate (PMS) was used as an oxidant. P-acetamidophenol was used as an organic pollutant to explore the removal effect of Co SA -N-Ti3C2T x / PMS system on p-acetamidophenol under different PMS concentrations.

[0077] 5 mg of Co SA -N-Ti3C2T x was prepared in Example 1 was weighed and added to a p-acetamidophenol solution (the volume of the solution was 100 mL, and the concentration was 20 μM) and mixed uniformly. Then PMS was added to make the concentration of PMS in the solution 0.1 mM, 0.3 mM, 0.5 mM, 0.7 mM and 0.9 mM, respectively. The catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min for 5 min.​

[0078] During the magnetic stirring process, 1 mL sample was taken every 1 min, and the sample was filtered by using a filter head of 0.22 μm, and the filtrate was determined by using a high performance liquid chromatograph to determine the remaining concentration of p-acetamidophenol, so as to obtain the Co SA -N-Ti3C2T x The removal effect of the p-acetamidophenol by the Co Figure 6

[0079] Figure 6 The removal effect of the p-acetamidophenol by the Co SA -N-Ti3C2T x The removal effect of the p-acetamidophenol by the Co Figure 6 It can be known that, when the PMS is added in the amount of 0.3 mM-0.9 mM, the removal rate of the p-acetamidophenol reaches 100% within 5 min, and the difference in the removal rate of the p-acetamidophenol is not large when the PMS is added in the amount of 0.7 mM and 0.9 mM.

[0080] Example 5

[0081] The Co SA -N-Ti3C2T x was prepared in Example 1, and the peroxymonosulfate (PMS) was used as an oxidant, and the p-acetamidophenol was used as an organic pollutant, and the removal effect of the p-acetamidophenol by the Co SA -N-Ti3C2T x The removal effect of the p-acetamidophenol by the Co

[0082] 5 mg of the Co SA -N-Ti3C2T x was prepared in Example 1 was weighed, and was added into the p-acetamidophenol solution (the volume of the solution was 100 mL, and the concentration was 20 μM) every time, and was uniformly mixed, and then the pH value was adjusted to be 3.01, 4.99, 6.86, 7.02, 8.99 and 11.01 by using sodium hydroxide solution and hydrochloric acid solution respectively, and the PMS was added so that the concentration of the PMS in each solution was 0.7 mM, and the catalytic reaction was carried out under the magnetic stirring at the rotating speed of 500 r / min for 5 min.

[0083] During the magnetic stirring process, 1 mL sample was taken every 1 min, and the sample was filtered by using a filter head of 0.22 μm, and the filtrate was determined by using a high performance liquid chromatograph to determine the remaining concentration of p-acetamidophenol, so as to obtain the Co SA -N-Ti3C2T x The removal effect of the p-acetamidophenol by the Co​Figure 7 As shown.

[0084] Figure 7 CoSA-N-Ti3C2T SA -N-Ti3C2T x The removal effect of the PMS system on p-acetamidophenol is shown in the control chart. From Figure 7 It can be seen that the wide initial pH value (3.01-11.01) has little effect on the removal efficiency of p-acetamidophenol, indicating that CoSA-N-Ti3C2T SA -N-Ti3C2T x The activated PMS has a wide pH tolerance.

[0085] Example 6:

[0086] According to the method in Example 2, the CoSA-N-Ti3C2T SA -N-Ti3C2T x catalyst prepared in Example 1 was explored. The specific performance is as follows:

[0087] 5 mg of CoSA-N-Ti3C2T SA -N-Ti3C2T x catalyst prepared in Example 1 was weighed and added into a p-acetamidophenol solution (the volume of the solution was 100 mL, and the concentration was 20 μM) and mixed uniformly, and then PMS was added to make the concentration of PMS in the solution 0.7 mM, and the catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min for 5 min. After each cycle, the catalyst was washed with deionized water and centrifuged, and then dried in a vacuum drying oven at 40°C for the next cycle test.

[0088] Figure 8 CoSA-N-Ti3C2T SA -N-Ti3C2T x The repeated removal effect of the single-atom catalyst (CoSA-N-Ti3C2T Figure 8 It can be seen that after four cycles, the degradation efficiency of the single-atom catalyst (CoSA-N-Ti3C2T SA -N-Ti3C2T x ) prepared in Example 1 of the application can still reach 100% within 5 min, indicating that CoSA-N-Ti3C2T x has very excellent stability and excellent reusability.

[0089] From the above results, the monatomic catalyst of the present application can realize high selectivity of superoxide radical generation, is a novel catalyst capable of directional generation of superoxide radical, high efficiency, low consumption and recycling, as a catalyst for activating permonosulfate and treating wastewater, can utilize the superoxide radicals to realize efficient degradation of organic pollutants, can realize rapid and complete removal of organic pollutants in water under low catalyst dosage, can realize effective purification of organic wastewater, and can overcome the defects of large catalyst dosage and low PMS activation efficiency in heterogeneous catalytic process, and has good application prospect.

[0090] The above examples are only preferred embodiments of the present application, and the protection scope of the present application is not limited to the above examples. Any technical solution falling within the concept of the present application belongs to the protection scope of the present application. It should be pointed out that improvements and refinements made by ordinary skilled in the art without departing from the principles of the present application should also be considered as the protection scope of the present application.

Claims

1. A single-atom catalyst for highly selectively generating superoxide radicals, characterized in that, Including nitrogen-doped Ti3C2T x Nanosheets and transition metal single atoms, the transition metal single atoms being anchored in an asymmetric coordination structure in nitrogen-doped Ti3C2T x On the nanosheet; the transition metal single atom is one of cobalt, manganese, iron, and copper atoms; the preparation method of the single-atom catalyst for highly selectively generating superoxide radicals includes the following steps: (1) Ti3C2T x Nanosheets, a nitrogen precursor, and a soluble transition metal salt solution were mixed and subjected to a self-assembly reaction. The mixture was then centrifuged and freeze-dried to obtain a catalyst precursor, wherein the nitrogen precursor was protonated melamine. (2) Pyrolysis of the catalyst precursor yields a single-atom catalyst for highly selective superoxide radical generation.

2. The single-atom catalyst according to claim 1, characterized in that, The mass percentage of transition metal single atoms in the single-atom catalyst is 0.8% to 1.3%.

3. A method for preparing a single-atom catalyst for highly selective superoxide radical generation as described in claim 1 or 2, characterized in that, Includes the following steps: S1, Ti3C2T x Nanosheets, a nitrogen precursor, and a soluble transition metal salt solution were mixed and subjected to a self-assembly reaction. The mixture was then centrifuged and freeze-dried to obtain a catalyst precursor, wherein the nitrogen precursor was protonated melamine. S2. Pyrolyze the catalyst precursor to obtain a single-atom catalyst for highly selective superoxide radical generation.

4. The preparation method according to claim 3, characterized in that, In step S1, the Ti3C2T x The mass ratio of the nanosheets, the nitrogen precursor, and the soluble transition metal salt in the soluble transition metal salt solution is 100:100-800:1.2-9.6; the soluble transition metal salt is one of soluble cobalt salt, soluble manganese salt, soluble iron salt, and soluble copper salt.

5. The preparation method according to claim 3 or 4, characterized in that, In step S1, the centrifugation speed is 4000 r / min to 6000 r / min; the centrifugation time is 8 min to 15 min; and the freeze-drying time is 24 h to 48 h. In step S2, the pyrolysis is carried out under a nitrogen atmosphere; the heating rate during the pyrolysis process is 3℃ / min to 8℃ / min; the pyrolysis temperature is 500℃ to 550℃; the pyrolysis time is 1h to 4h; after the pyrolysis is completed, the following treatment is also included: the pyrolysis product is washed sequentially with water and ethanol, and the washed pyrolysis product is dried under vacuum conditions.

6. The application of a single-atom catalyst as described in claim 1 or 2, or a single-atom catalyst prepared by any one of claims 3 to 5, as a permonosulfate catalyst in the treatment of organic wastewater.

7. The application according to claim 6, characterized in that, The process includes the following steps: mixing a single-atom catalyst, persulfate, and organic wastewater to carry out a catalytic reaction, thereby removing organic matter from the wastewater.

8. The application according to claim 7, characterized in that, The amount of the single-atom catalyst added is 0.05g to 0.15g per liter of organic wastewater; the concentration of persulfate in the organic wastewater is 0.3mM to 0.9mM; the concentration of the organic wastewater is 20μM to 40μM; the organic matter in the organic wastewater is acetaminophen; and the pH value of the organic wastewater is 3 to 11.

9. The application according to claim 7 or 8, characterized in that, The catalytic reaction is carried out under stirring conditions; the stirring speed is 300 r / min to 600 r / min; the catalytic reaction time is 3 min to 5 min.

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