Monatomic catalyst for high-selectivity generation of superoxide radicals as well as preparation method and application of monatomic catalyst

Abstract

The invention discloses a monatomic catalyst for high-selectivity generation of superoxide radicals as well as a preparation method and application of the monatomic catalyst. The catalyst comprises a nitrogen-doped Ti3C2Tx nanosheet and a transition metal monatomic targeted on the nitrogen-doped Ti3C2Tx nanosheet in an asymmetric coordination structure. The preparation method comprises the following steps: mixing the Ti3C2Tx nanosheet, a nitrogen precursor and soluble transition metal salt, self-assembling, centrifuging, freeze-drying and pyrolyzing. The monatomic catalyst provided by the invention can realize high-selectivity generation of superoxide radicals, and is a novel catalyst which can directionally generate superoxide radicals, is efficient and low-consumption, and can be recycled; when being used as a catalyst for activating peroxymonosulfate and treating wastewater, the PMS composite material can quickly and thoroughly remove organic pollutants in a water body under the condition of low catalyst dosage, can effectively purify organic wastewater, can overcome the defects of large catalyst dosage, low PMS activation efficiency and the like in a heterogeneous catalysis process, and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the field of new environmental materials and relates to a single-atom catalyst for highly selectively generating superoxide free radicals and a preparation method and application thereof. Background Art

[0002] With the continuous increase of trace organic pollutants in water bodies, water pollution poses an increasingly serious threat to ecosystems, public health and economic development. In recent years, advanced oxidation processes, as a promising green decontamination technology, can use in-situ generated strong oxidizing active substances to remediate water pollutants. Among them, the Fenton-like technology based on permonosulfate (PMS) has received widespread attention in organic wastewater treatment due to its advantages such as high efficiency and economy.

[0003] Under natural conditions, PMS alone exhibits only limited oxidizing properties. Currently, many single-atom catalysts have been developed, which show structure-dependent induction of colorful PMS activation pathways, and these catalysts mainly involve directional regulation of PMS molecules to directly crack and generate HO· or SO4· - , or non-free radicals obtained by indirect cleavage (such as 1 O2, high-valent iron oxide species and electron transfer). However, so far, no studies have been reported on the directional and highly selective generation of O2 - Therefore, the development of a single-atom catalyst for the highly selective generation of superoxide radicals is of great significance for promoting the widespread application of permonosulfate (PMS)-based Fenton-like technology in the treatment of organic wastewater and achieving efficient purification of organic wastewater. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a single-atom catalyst for highly selectively generating superoxide free radicals and a preparation method and application thereof.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A single-atom catalyst for highly selective generation of superoxide radicals, comprising nitrogen-doped Ti3C2T x Nanosheets and transition metal single atoms, wherein the transition metal single atoms are anchored in the nitrogen-doped Ti3C2T x On nanosheets.

[0007] The above-mentioned single-atom catalyst is further improved in that the mass percentage of transition metal single atoms in the single-atom catalyst is 0.8% to 1.3%.

[0008] The above-mentioned single-atom catalyst is further improved in that the mass percentage of transition metal single atoms in the single-atom catalyst is 0.9% to 1.2%.

[0009] The above-mentioned single-atom catalyst is further improved, wherein the transition metal single atom is one of a cobalt atom, a manganese atom, an iron atom, and a copper atom.

[0010] As a general technical concept, the present invention also provides a method for preparing the above-mentioned single-atom catalyst for highly selectively generating superoxide radicals, comprising the following steps:

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

[0012] S2. Pyrolyzing the catalyst precursor to obtain a single atom catalyst for highly selectively generating superoxide radicals.

[0013] The above preparation method is 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; the soluble transition metal salt is one of a soluble cobalt salt, a soluble manganese salt, a soluble iron salt and a soluble copper salt.

[0014] The above preparation method is further improved, in step S1, the centrifugal speed is 4000r / min to 6000r / min; the centrifugal time is 8min to 15min; the freeze-drying time is 24h to 48h.

[0015] The above preparation method is further improved, in step S2, the pyrolysis is carried out under a nitrogen atmosphere; the heating rate during the pyrolysis process is 3°C / min to 8°C / min; the pyrolysis temperature is 500°C to 550°C; and the pyrolysis time is 1h to 4h.

[0016] The above preparation method is further improved, and further comprises the following treatment after the pyrolysis is completed: washing the pyrolysis product with water and ethanol in sequence, and drying the washed pyrolysis product under vacuum conditions.

[0017] As a general technical concept, the present invention also provides the use of the above-mentioned single-atom catalyst or the single-atom catalyst prepared by the above-mentioned preparation method as a catalyst for permonosulfate in treating organic wastewater.

[0018] The above application is further improved and includes the following steps: mixing the single-atom catalyst, permonosulfate and organic wastewater to carry out a catalytic reaction to remove organic matter in the wastewater.

[0019] The above application is further improved in that the added amount of the single atom catalyst is 0.05 g to 0.15 g per liter of organic wastewater.

[0020] The above application is further improved in that the concentration of permonosulfate in the organic wastewater is 0.3mM to 0.9mM.

[0021] The above application is further improved in that the concentration of the organic wastewater is 20 μM to 40 μM.

[0022] The above application is further improved in that the organic matter in the organic wastewater is acetaminophenol.

[0023] The above application is further improved in that the pH value of the organic wastewater is 3-11.

[0024] The above application is further improved in that the catalytic reaction is carried out under stirring conditions; the stirring speed is 300r / min to 600r / min; and the catalytic reaction time is 3min to 5min.

[0025] In the present invention, the Ti3C2T x The preparation method of the nanosheets comprises the following steps: adding LiF to an HCl solution and stirring evenly, then slowly adding Ti3AlC2, continuing stirring at 35°C to 45°C for 24 to 36 hours, washing with ultrapure water until the pH value of the supernatant is 5.5 to 6.5, ultrasonicating the remaining precipitate, centrifuging, obtaining an upper dark green solution, freeze-drying the solution, and obtaining a few-layer Ti3C2Tx nanosheets. The ratio of LiF to the HCl solution is 1 g to 2 g: 20 mL to 40 mL; and the mass ratio of LiF to Ti3AlC2 is 1 to 2: 1 to 2.

[0026] In the present invention, the protonated melamine used is positively charged protonated melamine, and its preparation method comprises the following steps: adding melamine to anhydrous ethanol and stirring for 60 minutes, adding HCl solution and continuing stirring for 60 minutes, drying, washing with ultrapure water and ethanol alternately, and drying, and the obtained powder is protonated melamine. The ratio of melamine to anhydrous ethanol is 1g-2g: 15mL-30mL; the ratio of melamine to HCl solution is 2g-4g: 3mL-6mL.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] (1) The present invention provides a single-atom catalyst for highly selectively generating superoxide radicals, comprising nitrogen-doped Ti3C2T x Nanosheets and transition metal atoms, where the transition metal atoms are anchored to the nitrogen-doped Ti3C2T3 with an asymmetric coordination structure. x In the present invention, nitrogen-doped Ti3C2T x The active sites formed by the joint action of nanosheets and transition metal single atoms have an electronic structure and chemical environment co-regulated by nitrogen and oxygen. When the single-atom catalyst formed in this way is used to activate oxidants, it achieves the first highly selective generation of superoxide free radicals, which is conducive to the efficient removal of organic pollutants in wastewater. It is a new type of catalyst that can generate superoxide free radicals in a targeted manner, is highly efficient, low-consumption, and recyclable, with high use value and good application prospects.

[0029] (2) The present invention also provides a method for preparing a single-atom catalyst for highly selectively generating superoxide radicals. First, Ti3C2T x The nanosheets, nitrogen precursors and soluble transition metal salt solutions were mixed for self-assembly reaction and freeze-dried. The nitrogen precursors and transition metal ions were uniformly adsorbed on the Ti3C2T4 matrix by electrostatic adsorption. x Nanosheets, and then by pyrolyzing the catalyst precursor, nitrogen and Ti3C2T x The oxygen coupling on the nanosheet regulates the transition metal atom coordination microenvironment, forming an asymmetrically coordinated transition metal single atom catalyst, which can achieve highly selective generation of superoxide radicals. At the same time, the prepared single atom catalyst presents a highly wrinkled state, which is conducive to the exposure of metal active sites, thereby enhancing the effective contact between organic pollutants and oxidants in wastewater and the surface of the single atom catalyst, thereby improving the efficiency and selectivity of the reaction. More importantly, the prepared single atom catalyst has excellent structural stability, is easy to separate, can be recycled and reused, and has good cycle performance and broad application prospects. In addition, the preparation method of the present invention also has the advantages of simple steps and low cost, is suitable for large-scale preparation, and is easy to realize the industrial application of single atom catalysts.

[0030] (3) The present invention also provides an application of a single-atom catalyst as a catalyst for permonosulfate in the treatment of organic wastewater, wherein the single-atom catalyst is used to activate permonosulfate and form a large amount of superoxide free radicals with strong oxidizing properties, and then these superoxide free radicals are used to achieve efficient degradation of organic pollutants. The present invention has the advantages of simple process, small catalyst dosage, low cost, high treatment efficiency, good removal effect, etc., and can achieve rapid and thorough removal of organic pollutants in water under low catalyst dosage conditions, and can achieve effective purification of organic wastewater, and can overcome the defects of large catalyst dosage and low PMS activation efficiency in heterogeneous catalysis, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] Figure 1 The single-atom catalyst (Co SA -N-Ti3C2T x ) of the scanning electron microscope.

[0033] Figure 2 The single-atom catalyst (Co SA -N-Ti3C2T x )'s element distribution diagram.

[0034] Figure 3 The single-atom catalyst (Co SA -N-Ti3C2T x )、Ti3C2T x Nanosheets (Ti3C2T x ), N-Ti3C2T prepared in Comparative Example 2 x Catalyst (N-Ti3C2T x )’s XRD pattern.

[0035] Figure 4 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 ) is a comparison chart of the removal effect of acetaminophen when used to activate PMS.

[0036] Figure 5 is Co under different quenchers in Example 3 of the present invention SA -N-Ti3C2T x Comparison chart of the removal effect of / PMS system on acetaminophen.

[0037] Figure 6is the Co at different PMS concentrations in Example 4 of the present invention SA -N-Ti3C2T x Comparison chart of the removal effect of / PMS system on acetaminophen.

[0038] Figure 7 is Co at different pH in Example 5 of the present invention SA -N-Ti3C2T x Comparison chart of the removal effect of / PMS system on acetaminophen.

[0039] Figure 8 The single atom catalyst (Co SA -N-Ti3C2T x )Comparison chart of repeated removal effects on acetaminophen. DETAILED DESCRIPTION

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

[0041] In the following examples of the present invention, 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] Example 1

[0043] A single-atom catalyst for highly selective generation of superoxide radicals, comprising nitrogen-doped Ti3C2T x Nanosheets and transition metal atoms, where the transition metal atoms are anchored on nitrogen-doped Ti3C2T in an asymmetric coordination structure (N-Ti3C2Tx). x On nanosheets.

[0044] In this embodiment, the mass percentage of transition metal single atoms in the single atom catalyst is 1.0%.

[0045] In this embodiment, the transition metal single atom is a cobalt atom.

[0046] A method for preparing a single-atom catalyst for highly selectively generating superoxide radicals in the above-mentioned embodiment comprises the following steps:

[0047] a. 75 mg Ti3C2T x Nanosheets (Ti3C2T x ), 300 mg of protonated melamine and a solution containing 3.6 mg of CoCl2.6H2O were slowly mixed to carry out a self-assembly reaction to obtain a precursor.

[0048] b. The precursor obtained in step a was centrifuged at 5000 r / min for 10 min in a high-speed centrifuge, and the precipitated product was collected and dried in a freeze dryer for 36 h.

[0049] c. The solid obtained in step b was pyrolyzed at 550°C for 3 h at a heating rate of 5°C / min under the protection of high-purity nitrogen, washed thoroughly with water and ethanol, and dried in a vacuum drying oven at 40°C. The resulting powder was a single-atom catalyst for highly selective generation of superoxide radicals, denoted as Co SA -N-Ti3C2T x .

[0050] In the present invention, the Ti3C2T x The preparation method of the nanosheets includes the following steps: adding 1g LiF to 20mL HCl solution, stirring evenly, slowly adding 1g Ti3AlC2, stirring at 40°C for 24 hours, washing with ultrapure water until the pH value of the effluent is 6, ultrasonicating, centrifuging to obtain an upper dark green solution, and freeze-drying the upper dark green solution to obtain a few-layer Ti3C2Tx nanosheets.

[0051] In the present invention, the protonated melamine used is positively charged protonated melamine, and its preparation method comprises the following steps: 2g of melamine is added into 30mL of anhydrous ethanol and stirred for 60min, 3mL of HCl solution is added and stirred for 60min, drying, washing with ultrapure water and ethanol alternately, drying, and the obtained powder is protonated melamine.

[0052] Figure 1 The single-atom catalyst (Co SA -N-Ti3C2T x ). Figure 1 It can be seen that the single atom catalyst (Co SA -N-Ti3C2T x ) is highly wrinkled.

[0053] Figure 2 The single-atom catalyst (Co SA -N-Ti3C2T x ) element distribution diagram. Figure 2 It can be seen that the single atom catalyst (Co SA -N-Ti3C2T x ) contains, in addition to a single cobalt atom, Ti, C, O and N.

[0054] Comparative Example 1

[0055] A Ti3C2T x-anneal catalyst preparation method, and the single atom catalyst (Co SA -N-Ti3C2T x ) are basically the same, except that in Comparative Example 1, no CoCl2.6H2O and protonated melamine are added.

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

[0057] Comparative Example 2

[0058] A N-Ti3C2T x The preparation method of the catalyst is the same as that of the single atom catalyst (Co SA -N-Ti3C2T x ) are basically the same, the only difference is 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 SA -N-Ti3C2T x ) are basically the same, except that: in Comparative Example 3, no protonated melamine is added, and 3M HCl is slowly stirred for 3 h 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 SA -N-Ti3C2T x )、Ti3C2T x Nanosheets (Ti3C2T x ), N-Ti3C2T prepared in Comparative Example 2 x Catalyst (N-Ti3C2T x ) is XRD pattern. Figure 3 It can be seen that N-Ti3C2T x and Co SA-N-Ti3C2T x The XRD patterns of the catalysts are similar and have no significant peaks characteristic of the crystalline phase associated with cobalt particles.

[0064] Example 2

[0065] A single atom catalyst for highly selectively generating superoxide radicals in treating organic wastewater, specifically: the single atom catalyst (Co SA -N-Ti3C2T x ) as catalyst and permonosulfate (PMS) as oxidant to construct Co SA -N-Ti3C2T x The / PMS system treats acetaminophen wastewater, comprising the following steps:

[0066] Weigh 5 mg of the single atom catalyst (Co SA -N-Ti3C2T x ), added to 100 mL of 20 μM acetaminophenol solution, mixed evenly, added permonosulfate (PMS) to make the concentration of PMS in the solution 0.7 mM, and carried out catalytic reaction under magnetic stirring at a speed of 500 r / min for 5 minutes to complete the removal of acetaminophenol in the wastewater.

[0067] Control group: Ti3C2T x Nanosheets (Ti3C2T x ), Ti3C2T prepared in Comparative Examples 1-3 x -anneal catalyst (Ti3C2T x -anneal)、N-Ti3C2T x Catalyst (N-Ti3C2T x )、Co-Ti3C2T x Catalyst (Co-Ti3C2T x ), replacing the single atom catalyst (Co SA -N-Ti3C2T x ), construct systems with different catalysts and PMS, and keep other conditions the same.

[0068] During the magnetic stirring process, 1 mL of sample was taken every 1 min, and the sample was filtered using a 0.22 μm filter head. The filtrate was measured by high performance liquid chromatography to determine the remaining acetaminophenol concentration, thereby obtaining the removal effect of acetaminophenol by different catalyst / PMS systems. The results are as follows: Figure 4 shown.

[0069] Figure 4 The single atom catalyst (CoSA -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 ) is used to activate PMS to remove acetaminophen. Figure 4 It can be seen that 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 ) after 5 min of catalytic reaction, the removal rates of acetaminophen were 100%, 2.02%, 1.63%, 19.02% and 4.94% respectively, which shows that the single atom catalyst (Co SA -N-Ti3C2T x ) can efficiently activate PMS and achieve efficient removal of acetaminophen in wastewater, while other catalysts do not have such performance.

[0070] Example 3

[0071] Co prepared in Example 1 SA -N-Ti3C2T x as catalyst, permonosulfate (PMS) as oxidant, and acetaminophen as organic pollutant to explore the SA -N-Ti3C2T x The main active species in the / PMS system are as follows:

[0072] Methanol, tert-butyl alcohol, furfuryl alcohol and p-benzoquinone were selected as active substance probes, and added to the acetaminophenol solution (the volume of the solution was 100 mL and the concentration was 20 μM) at concentrations of 200 mM, 200 mM, 1.5 mM and 1.5 mM, respectively. 5 mg of Co prepared in Example 1 was added SA -N-Ti3C2T x As catalyst and PMS, the concentration of PMS in the wastewater is made to be 0.7mM, and the catalytic reaction is carried out for 5 minutes under magnetic stirring at a speed of 500r / min.

[0073] During the magnetic stirring process, 1 mL of sample was taken every 1 min, and the sample was filtered using a 0.22 μm filter head. The filtrate was measured by high performance liquid chromatography to determine the remaining acetaminophenol concentration, thereby obtaining the Co SA -N-Ti3C2T x The removal effect of acetaminophen by the / PMS system is shown in the following figure. Figure 5 shown.

[0074] Figure 5 is Co under different quenchers in Example 3 of the present invention SA -N-Ti3C2T x Comparison chart of the removal effect of acetaminophen by the / PMS system. Figure 5 It can be seen that the degradation of acetaminophen was not significantly inhibited by the addition of methanol (200 mM), tert-butyl alcohol (200 mM) and furfuryl alcohol (1.5 mM), indicating that the common HO·, SO4· - and 1 However, in the presence of 1.5 mM p-benzoquinone, the removal of acetaminophen was severely inhibited, which can be judged as Co SA -N-Ti3C2T x During the activation of PMS, O2 - Plays a key role and is highly selectively produced.

[0075] Example 4

[0076] Co prepared in Example 1 SA -N-Ti3C2T x The results showed that the catalytic activity of Co was 0.0447 W·m-1·K-1 and the oxidative activity of PMS was 0.0447 W·m-1. SA -N-Ti3C2T x The removal effect of acetaminophen by the / PMS system is as follows:

[0077] Weigh 5 mg of Co prepared in Example 1 SA -N-Ti3C2Tx As a catalyst, it was added into the acetaminophenol solution (the volume of the solution was 100 mL and the concentration was 20 μM) and mixed evenly, and then PMS was added respectively 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, and the catalytic reaction was carried out for 5 min under magnetic stirring at a speed of 500 r / min.

[0078] During the magnetic stirring process, 1 mL of sample was taken every 1 min, and the sample was filtered using a 0.22 μm filter head. The filtrate was measured by high performance liquid chromatography to determine the remaining acetaminophen concentration, thereby obtaining the Co SA -N-Ti3C2T x The removal effect of acetaminophen by the / PMS system is shown in the following figure. Figure 6 shown.

[0079] Figure 6 is the Co at different PMS concentrations in Example 4 of the present invention SA -N-Ti3C2T x Comparison chart of the removal effect of acetaminophen by the / PMS system. Figure 6 It can be seen that when 0.3mM-0.9mM PMS was added, the removal rate of acetaminophenol reached 100% within 5 minutes, and there was little difference in the removal rate of acetaminophenol when 0.7mM and 0.9mM PMS were added.

[0080] Example 5

[0081] Co prepared in Example 1 SA -N-Ti3C2T x The effects of Co on the degradation of the organic pollutant were investigated by using permonosulfate (PMS) as the catalyst and acetaminophen as the oxidant. SA -N-Ti3C2T x The removal effect of acetaminophen by the / PMS system is as follows:

[0082] Weigh 5 mg of Co prepared in Example 1 SA -N-Ti3C2T x As a catalyst, each portion was added to the acetaminophenol solution (the volume of the solution was 100 mL and the concentration was 20 μM) and mixed evenly, and then the pH values ​​were adjusted to 3.01, 4.99, 6.86, 7.02, 8.99, and 11.01 by sodium hydroxide solution and hydrochloric acid solution, respectively, and PMS was added respectively to make the concentration of PMS in each solution 0.7 mM, and the catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min for 5 min.

[0083] During the magnetic stirring process, 1 mL of sample was taken every 1 min, and the sample was filtered using a 0.22 μm filter head. The filtrate was measured by high performance liquid chromatography to determine the remaining acetaminophen concentration, thereby obtaining the Co SA -N-Ti3C2T x The removal effect of acetaminophen by the / PMS system is shown in the following figure. Figure 7 shown.

[0084] Figure 7 is Co at different pH in Example 5 of the present invention SA -N-Ti3C2T x Comparison chart of the removal effect of acetaminophen by the / PMS system. Figure 7 It can be seen that the wide initial pH value (3.01-11.01) has little effect on the removal efficiency of acetaminophen, indicating that Co SA -N-Ti3C2T x Activated PMS has a wide pH tolerance.

[0085] Embodiment 6:

[0086] According to the method in Example 2, the Co prepared in Example 1 was investigated. SA -N-Ti3C2T x The recyclability of the catalyst is as follows:

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

[0088] Figure 8 The single atom catalyst (Co SA -N-Ti3C2T x ) Comparison chart of repeated removal effects on acetaminophen. Figure 8 It can be seen that after four cycles, the single atom catalyst (Co SA -N-Ti3C2T x ) can still reach 100% degradation efficiency within 5 min, which shows that CoSA-N-Ti3C2T x It has very excellent stability and good reusability.

[0089] From the above results, it can be seen that the single-atom catalyst of the present invention can achieve highly selective generation of superoxide free radicals, and is a new type of catalyst that can directionally generate superoxide free radicals, is highly efficient, has low consumption, and can be recycled and reused. When used as a catalyst to activate permonosulfate and treat wastewater, these superoxide free radicals can be used to achieve efficient degradation of organic pollutants, and can achieve rapid and thorough removal of organic pollutants in water bodies under low catalyst dosage conditions, can achieve effective purification of organic wastewater, and can overcome the defects of large catalyst dosage and low PMS activation efficiency in heterogeneous catalysis, and has good application prospects.

[0090] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

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, wherein the transition metal single atoms are anchored in the nitrogen-doped Ti3C2T x On nanosheets.

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. The single atom catalyst according to claim 1 or 2, characterized in that The transition metal single atom is one of a cobalt atom, a manganese atom, an iron atom and a copper atom.

4. A method for preparing a single atom catalyst for highly selectively generating superoxide radicals as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Ti3C2T x The nanosheets, the nitrogen precursor and the soluble transition metal salt solution are mixed for self-assembly reaction, centrifuged and freeze-dried to obtain a catalyst precursor; S2. Pyrolyzing the catalyst precursor to obtain a single atom catalyst for highly selectively generating superoxide radicals.

5. The preparation method according to claim 4, characterized in that: 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; the soluble transition metal salt is one of a soluble cobalt salt, a soluble manganese salt, a soluble iron salt and a soluble copper salt.

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

7. Use of the single-atom catalyst according to any one of claims 1 to 3 or the single-atom catalyst prepared by the preparation method according to any one of claims 4 to 6 as a catalyst for permonosulfate in treating organic wastewater.

8. The use according to claim 7, characterized in that: The method comprises the following steps: mixing a single-atom catalyst, permonosulfate and organic wastewater to carry out a catalytic reaction, thereby completing the removal of organic matter in the wastewater.

9. The use according to claim 8, characterized in that: The addition amount of the single-atom catalyst is 0.05g to 0.15g per liter of organic wastewater; the concentration of permonosulfate 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 acetaminophenol; the pH value of the organic wastewater is 3 to 11.

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

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