Monatomic catalyst for activating peroxymonosulfate as well as preparation method and application of monatomic catalyst

Abstract

The invention discloses a monatomic catalyst for activating peroxymonosulfate as well as a preparation method and application of the monatomic catalyst. The catalyst comprises a nitrogen and sulfur co-doped Ti3C2Tx nanosheet and an iron monatomic or cobalt monatomic targeted on the nanosheet in an asymmetric coordination structure. The preparation method comprises the following steps: mixing the Ti3C2Tx nanosheet, a precursor containing a nitrogen source and a sulfur source, and soluble metal salt, self-assembling, freeze-drying and pyrolyzing. The monatomic catalyst provided by the invention has excellent conductivity and electronic structure, can form a large amount of reactive oxygen species in a catalytic degradation system on the premise of low addition amount of peroxymonosulfate, and has the advantages of high activation efficiency on peroxymonosulfate, capability of effectively reducing the usage amount of peroxymonosulfate and the like; the peroxymonosulfate can be activated to achieve efficient purification of organic wastewater, the operation cost of the peroxymonosulfate activation technology can be effectively reduced, and meanwhile, the new environmental pollution risk caused by the fact that a large amount of peroxymonosulfate is used can be remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the field of new environmental materials and relates to a single-atom catalyst for activating permonosulfate and a preparation method and application thereof. Background Art

[0002] Permonosulfate (PMS) activation technology has become a research hotspot in current water treatment technology because it can efficiently produce reactive oxygen species such as hydroxyl radicals, sulfate radicals, superoxide radicals and singlet oxygen, and can efficiently remove organic pollutants such as drugs, dyes and industrial chemicals. However, complete degradation of pollutants usually requires high concentrations of PMS, which not only increases operating costs but also requires the environmental disadvantages of high sulfate loads. Therefore, optimizing process conditions to minimize the amount of PMS added while maximizing pollutant removal efficiency remains a key research area.

[0003] At present, single-atom catalysts have the advantage of high atomic utilization, so when they are used to activate PMS, the amount of PMS added can be effectively reduced to a certain extent. However, when conventional single-atom catalysts are used to activate PMS, in order to maximize the removal rate of pollutants, more PMS still needs to be added, and the minimum amount of PMS added is still as high as 1mM to 2mM, which is not conducive to effectively reducing the operating cost of permonosulfate activation technology. At the same time, a large amount of PMS used will also introduce a large amount of sulfate, which will cause secondary pollution, and ultimately make it difficult for permonosulfate activation technology to be widely used in practice. Therefore, obtaining a single-atom catalyst with high PMS activation efficiency and the ability to effectively reduce the amount of PMS used is of great significance for realizing the low-cost application of permonosulfate activation technology and promoting its widespread application in the treatment 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 activating permonosulfate with high PMS activation efficiency and capable of effectively reducing the amount of PMS used, as well as 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 the activation of permonosulfate, including nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, wherein the metal single atoms are anchored in the nitrogen-sulfur co-doped Ti3C2T x On the nanosheet; the metal single atom is an iron single atom or a cobalt single atom.

[0007] The above-mentioned single atom catalyst is further improved, and the mass of the metal single atom is 0.1% to 0.5% of the mass of the single atom catalyst.

[0008] The above-mentioned single atom catalyst is further improved, and the mass of the metal single atom is 0.15% to 0.3% of the mass of the single atom catalyst.

[0009] As a general technical concept, the present invention also provides a method for preparing a single-atom catalyst of activated permonosulfate, comprising the following steps:

[0010] S1. Ti3C2T x The nanosheets, a precursor containing a nitrogen source and a sulfur source, and a soluble metal salt solution are mixed for self-assembly reaction to obtain a precursor; the soluble metal salt solution is a soluble iron salt solution or a soluble cobalt salt solution;

[0011] S2, freeze-drying the precursor obtained in step S1;

[0012] S3, pyrolyzing the solid obtained after freeze-drying in step S1 to obtain a single-atom catalyst of activated permonosulfate.

[0013] The above preparation method is further improved, in step S1, the Ti3C2T x The mass ratio of the nanosheet, the precursor containing nitrogen source and sulfur source, and the soluble metal salt in the soluble metal salt solution is 100:100-600:1.1-6.4; the precursor containing nitrogen source and sulfur source is thiourea.

[0014] The above preparation method is further improved in that in step S2, the freeze drying is carried out in a freeze dryer; the freeze drying time is 24h to 48h.

[0015] The above preparation method is further improved, in step S3, the pyrolysis is carried out in a mixed atmosphere of nitrogen and hydrogen; the volume ratio of nitrogen to hydrogen in the mixed atmosphere of nitrogen and hydrogen is 9:1; the heating rate during the pyrolysis process is 3°C / min~8°C / min; the pyrolysis temperature is 350°C~450°C; the pyrolysis time is 1h~4h; 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.

[0016] The above preparation method is further improved, wherein the single atom catalyst comprises nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, wherein the metal single atoms are anchored in the nitrogen-sulfur co-doped Ti3C2T xOn the nanosheet; the metal single atom is an iron single atom or a cobalt single atom.

[0017] The above preparation method is further improved in that the mass of the metal single atom is 0.1% to 0.5% of the mass of the single atom catalyst.

[0018] The above preparation method is further improved in that the mass of the metal single atom is 0.15% to 0.3% of the mass of the single atom catalyst.

[0019] 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.

[0020] The above application is further improved and includes the following steps: mixing the single-atom catalyst, permonosulfate and organic wastewater for catalytic reaction to remove organic pollutants in the wastewater; the concentration of permonosulfate in the catalytic reaction system is ≤0.9mM.

[0021] The above application is further improved in that the added amount of the single atom catalyst is 0.01 g to 0.02 g per liter of the organic wastewater.

[0022] The above application is further improved in that the concentration of permonosulfate in the catalytic reaction system is 0.05mM to 0.6mM.

[0023] The above application is further improved in that the concentration of the organic wastewater is ≤20 μM.

[0024] The above application is further improved in that the organic pollutant in the organic wastewater is acetaminophenol.

[0025] The above application is further improved, wherein the catalytic reaction is carried out under stirring conditions; the stirring speed is 200r / min to 500r / min; the temperature of the system is controlled to be 10°C to 35°C during the catalytic reaction; and the time of the catalytic reaction is 3min to 8min.

[0026] In the present invention, the Ti3C2T xThe 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.

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

[0028] (1) In view of the defects of existing single-atom catalysts such as low activation efficiency and large amount of permonosulfate added, the present invention provides a single-atom catalyst for activating permonosulfate, including nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal atoms, metal atoms are targeted on nitrogen-sulfur co-doped Ti3C2T with asymmetric coordination structure x The metal single atom is an iron single atom or a cobalt single atom. In the present invention, the iron single atom or the cobalt single atom is fixed to the nitrogen-sulfur co-doped Ti3C2T x On the nanosheet, on the one hand, the conductivity of the single-atom catalyst can be improved, and by increasing the electron transfer rate, the activation efficiency of the single-atom catalyst for permonosulfate can be promoted. On the other hand, an asymmetric coordinated microenvironment can be constructed for the iron single atom or the cobalt single atom. Its excellent electronic structure can form a large amount of active oxygen species in the catalytic degradation system under the premise of low permonosulfate addition, and can achieve efficient purification of organic wastewater. The single-atom catalyst of the present invention has the advantages of high activation efficiency for permonosulfate and can effectively reduce the use of permonosulfate. It is a new type of catalyst that is efficient, low-consumption, recyclable and reusable, with high use value and good application prospects.

[0029] (2) The present invention also provides a method for preparing a single-atom catalyst, firstly x The nanosheets, the precursor containing nitrogen and sulfur sources, and the soluble metal salt solution (soluble iron salt solution or soluble cobalt salt solution) are mixed for self-assembly reaction, and the precursor containing nitrogen and sulfur sources and the metal ions are uniformly adsorbed on the Ti3C2T x The nanosheets are then freeze-dried to fix the precursors containing nitrogen and sulfur sources and metal ions on the Ti3C2T xOn the nanosheet, the dried precursor is finally pyrolyzed, and nitrogen and sulfur co-doping is achieved through high temperature during the pyrolysis process, and an asymmetric coordination microenvironment is constructed for the metal atom (iron single atom or cobalt single atom), so that an asymmetric coordination microregion is formed in the catalyst, and finally a single atom catalyst with high activation efficiency for permonosulfate and capable of effectively reducing the amount of permonosulfate used is obtained. At the same time, the preparation method of the present invention also has the advantages of simple steps, low cost, etc., is suitable for large-scale preparation, and is convenient for realizing 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 treating organic wastewater. The single-atom catalyst is used to catalyze and activate permonosulfate to form a large amount of active oxygen species (such as O2 - and 1 O2), the degradation system thus constructed can use the active oxygen species generated in the system in large quantities to achieve rapid and thorough removal of organic pollutants under the premise of a small amount of permonosulfate used. In particular, in the system of the present invention, only 0.1mM of permonosulfate needs to be added to achieve rapid and efficient removal of organic pollutants, which can effectively reduce the operating cost of permonosulfate activation technology and significantly reduce the risk of new environmental pollution caused by the large-scale use of permonosulfate. The application method of the present invention has the advantages of simple process, small amount of PMS used, low cost, high treatment efficiency, good removal effect, etc., can be widely used in treating organic wastewater and can achieve effective purification of organic wastewater, while overcoming the defects of large PMS dosage and low PMS activation efficiency in conventional methods, and has very 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 (Fe SA -NS-Ti3C2T x ) of the scanning electron microscope.

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

[0034] Figure 3 The Fe SA -NS-Ti3C2T x / PMS system acetaminophen removal effect diagram.

[0035] Figure 4 is Fe at different temperatures in Example 3 of the present invention SA -NS-Ti3C2T x / PMS system acetaminophen removal effect diagram.

[0036] Figure 5 The single atom catalyst (Fe SA -NS-Ti3C2T x ) Schematic diagram of the repeated degradation effect of acetaminophen.

[0037] Figure 6 is Fe under different quenchers in Example 5 of the present invention SA -NS-Ti3C2T x / PMS system acetaminophen removal effect diagram.

[0038] Figure 7 This is a diagram showing the removal effect of acetaminophen in the degradation system constructed with different catalysts in Example 6 of the present invention. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] Example 1

[0042] A single-atom catalyst for the activation of permonosulfate, including nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal atoms, metal atoms are targeted on nitrogen-sulfur co-doped Ti3C2T with asymmetric coordination structure x On the nanosheet, the metal single atom is an iron single atom.

[0043] In this embodiment, the mass of the metal single atom is 0.2% of the mass of the single atom catalyst.

[0044] In this embodiment, asymmetric coordination micro-regions are formed in the single-atom catalyst. Specifically, the metal single atom is fixed on the nitrogen-sulfur co-doped Ti3C2T x An asymmetric coordinated microenvironment is formed on the nanosheet.

[0045] A method for preparing the single-atom catalyst for activating permonosulfate in the present embodiment comprises the following steps:

[0046] a. 150mg Ti3C2T x The nanosheets, 450 mg of thiourea and a FeCl 3 solution (the content of FeCl 3 in the solution is 4.8 mg) are slowly mixed to perform a self-assembly reaction to obtain a precursor.

[0047] b. Dry the precursor obtained in step a in a freeze dryer for 36 hours.

[0048] c. The solid obtained in step b was pyrolyzed at 400° C. for 2 h at a heating rate of 5° C. / min under the protection of a mixed atmosphere of nitrogen and hydrogen (N2 90% and H2 10% in the mixed atmosphere, i.e., the volume ratio of nitrogen to hydrogen in the mixed atmosphere was 9:1), and then washed thoroughly with water and ethanol, and dried in a vacuum drying oven at 60° C. The resulting powder was a single-atom catalyst of activated permonosulfate, denoted as Fe SA -NS-Ti3C2T x In the present invention, pyrolysis is performed under the protection of a mixed atmosphere of nitrogen and hydrogen, and hydrogen can be used to inhibit the Ti3C2T x Oxidized.

[0049] In the present invention, the Ti3C2T x The preparation method of the nanosheets includes the following steps: adding 1 g of LiF to 20 mL of HCl solution, stirring evenly, slowly adding 1 g of Ti3AlC2, stirring at 40°C for 24 hours, washing with ultrapure water until the pH value of the effluent is 6, ultrasonicating, centrifuging, and freeze-drying the upper dark green solution to obtain a few-layer Ti3C2Tx nanosheet.

[0050] Figure 1 The single-atom catalyst (Fe SA -NS-Ti3C2T x ). Figure 1 It can be seen that the single atom catalyst (Fe SA -NS-Ti3C2T x ) presents a flake-close-packed structure.

[0051] Figure 2 The single-atom catalyst (Fe SA -NS-Ti3C2T x ) element distribution diagram. Figure 2 It can be seen that the single atom catalyst (Fe SA -NS-Ti3C2T x) shows the presence of Ti, C, O, N and S in addition to a single iron atom.

[0052] In this example, single-atom catalysts of different metal atoms were also prepared. Their preparation methods were similar to those of the single-atom catalyst (Fe SA -NS-Ti3C2T x ) are basically the same, except that: cobalt chloride solution, copper chloride solution and manganese chloride solution are used in sequence to replace the ferric chloride solution in Example 1, wherein the single-atom catalyst prepared by using cobalt chloride solution, copper chloride solution and manganese chloride solution as soluble metal salt solutions is Co SA -NS-Ti3C2T x , Mn SA -NS-Ti3C2T x , Cu SA -NS-Ti3C2T x .

[0053] Example 2

[0054] Application of a single-atom catalyst as a catalyst for permonosulfate in treating organic wastewater, specifically Fe prepared in Example 1 SA -NS-Ti3C2T x The results showed that Fe SA -NS-Ti3C2T x The removal effect of acetaminophen by the PMS system includes the following:

[0055] Weigh 21 portions (3 parallel groups) of Fe prepared in Example 1 SA -NS-Ti3C2T x As catalyst, 10 mg each was added into acetaminophenol solution (the volume of the solution was 100 mL and the concentration was 20 μM) and mixed evenly. Then different amounts of PMS were added to make the concentration of PMS in the system 0.05 mM, 0.1 mM, 0.2 mM, 0.3 mM, 0.4 mM, 0.5 mM and 0.6 mM respectively. The catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min. During the catalytic reaction, the temperature of the system was adjusted to 25°C by a water bath to complete the removal of acetaminophenol in the wastewater.

[0056] During the magnetic stirring process, 1 mL of sample was taken every 1 min and filtered using a 0.22 μm filter. The filtrate was measured by high performance liquid chromatography to determine the remaining acetaminophen concentration, thereby obtaining the Fe SA -NS-Ti3C2Tx / PMS system for the removal of acetaminophen.

[0057] Figure 3 The Fe SA -NS-Ti3C2T x The removal effect of acetaminophen in the / PMS system. Figure 3 It can be seen that when 0.1mM-0.6mM PMS is added, the removal rate of acetaminophenol reaches 100% within 6 minutes, but the addition of more than 0.1mM PMS has little difference in the removal rate of acetaminophenol. It can be seen that the single-atom catalyst of the present invention only needs to add 0.1mM permonosulfate in the system of activating permonosulfate to achieve rapid and efficient removal of organic pollutants, which not only reduces the operating cost of water treatment, but also avoids the environmental disadvantages brought about by the high load of sulfate.

[0058] Embodiment 3:

[0059] Application of a single-atom catalyst as a catalyst for permonosulfate in treating organic wastewater, specifically Fe prepared in Example 1 SA -NS-Ti3C2T x The results showed that Fe SA -NS-Ti3C2T x The removal effect of acetaminophen by the PMS system includes the following steps:

[0060] Weigh 18 portions (3 parallel groups) of Fe prepared in Example 1 SA -NS-Ti3C2T x As a catalyst, 10 mg each 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 the temperature was adjusted to 10°C, 15°C, 20°C, 25°C, 30°C and 35°C in a water bath, and finally PMS was added to make the concentration of PMS in the system 0.1 mM. The catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min to complete the removal of acetaminophenol in the wastewater.

[0061] During the magnetic stirring process, 1 mL of sample was taken every 1 min and filtered using a 0.22 μm filter. The filtrate was measured by high performance liquid chromatography to determine the remaining acetaminophen concentration, thereby obtaining the Fe SA -NS-Ti3C2T x / PMS system for the removal of acetaminophen.

[0062] Figure 4 is Fe at different temperatures in Example 3 of the present invention SA -NS-Ti3C2T x The removal effect of acetaminophen in the / PMS system. Figure 4 It can be seen that at a temperature of 20°C-35°C, the Fe SA -NS-Ti3C2T x / PMS systems can quickly remove acetaminophen. In particular, the higher the temperature, the faster the removal efficiency.

[0063] Embodiment 4:

[0064] Application of a single-atom catalyst as a catalyst for permonosulfate in treating organic wastewater, specifically Fe prepared in Example 1 SA -NS-Ti3C2T x As catalyst, permonosulfate (PMS) as oxidant, and acetaminophen as organic pollutant, the Fe SA -NS-Ti3C2T x The recyclable performance of the catalyst comprises the following steps:

[0065] Weigh 3 portions (3 parallel groups) of Fe prepared in Example 1 SA -NS-Ti3C2T x As catalyst, 10 mg each was added into acetaminophenol 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 concentration of PMS in the system 0.1 mM. The catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min. During the catalytic reaction, the temperature of the system was adjusted to 25°C in a water bath to complete the removal of acetaminophenol in the wastewater.

[0066] After each cycle, the catalyst was fully washed with deionized water and centrifuged, and then dried in a vacuum drying oven at 60°C for the next cycle test.

[0067] Figure 5 The single atom catalyst (Fe SA -NS-Ti3C2T x ) The repeated degradation effect diagram of acetaminophen. Figure 5 It can be seen that after 4 cycles, the single-atom catalyst (Fe SA -NS-Ti3C2T x ) can still reach 91.21% in 8 min, which shows that the degradation efficiency of Fe SA -NS-Ti3C2T xIt has very high stability and can be repeatedly used to treat organic wastewater, and can achieve good removal effects.

[0068] Embodiment 5:

[0069] The Fe prepared in Example 1 SA -NS-Ti3C2T x As catalyst, permonosulfate (PMS) as oxidant, and acetaminophen as organic pollutant, the Fe SA -NS-Ti3C2T x The main active species in the / PMS system are as follows:

[0070] Methanol (200 mM), tert-butyl alcohol (200 mM), furfuryl alcohol (1.5 mM) and ascorbic acid (1.5 mM) were selected as active substance probes and added to the acetaminophen solution (the solution volume was 100 mL and the concentration was 20 μM), and 10 mg of Fe prepared in Example 1 was added to each portion. SA -NS-Ti3C2T x As a catalyst, PMS was added to make the concentration of PMS in the system 0.1mM, and the catalytic reaction was carried out under magnetic stirring at a rotation speed of 500r / min. During the catalytic reaction, the temperature of the system was adjusted to 25°C in a water bath to complete the removal of acetaminophenol in the wastewater.

[0071] 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 Fe SA -NS-Ti3C2T x / PMS system to remove acetaminophen.

[0072] Figure 6 is Fe under different quenchers in Example 5 of the present invention SA -NS-Ti3C2T x The removal effect of acetaminophen in the / PMS system. Figure 6 It can be seen that the degradation of acetaminophen was not significantly inhibited by the addition of methanol (100 mM) and tert-butyl alcohol (100 mM), indicating that the common HO· and SO4· - However, after adding furfuryl alcohol (1.5 mM), it was inhibited to some extent, indicating that 1 In the presence of 1.5 mM ascorbic acid, the removal of acetaminophen was severely inhibited, indicating that O2 - From this, we can judge that Fe SA -NS-Ti3C2Tx / PMS system·O2 - and 1 O2 plays a key role.

[0073] Example 6

[0074] Application of a single-atom catalyst as a catalyst for permonosulfate in treating organic wastewater, specifically Fe prepared in Example 1 SA -NS-Ti3C2T x 、Co SA -NS-Ti3C2T x , Mn SA -NS-Ti3C2T x , Cu SA -NS-Ti3C2T x 、Ti3C2T x Nanosheets, NS-Ti3C2T x Nanosheets were used as catalysts, permonosulfate (PMS) as oxidant, and acetaminophenol as organic pollutant to explore the removal effect of acetaminophenol by degradation systems constructed with different catalysts, including the following:

[0075] Weigh 12 portions (3 parallel groups) of Fe prepared in Example 1 SA -NS-Ti3C2T x 、Co SA -NS-Ti3C2T x , Mn SA -NS-Ti3C2T x , Cu SA -NS-Ti3C2T x As catalyst, 10 mg each was added into acetaminophenol 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 concentration of PMS in the system 0.1 mM. The catalytic reaction was carried out under magnetic stirring at a speed of 500 r / min. During the catalytic reaction, the temperature of the system was adjusted to 25°C in a water bath to complete the removal of acetaminophenol in the wastewater.

[0076] Control group 1: Ti3C2T x Nanosheets (Ti3C2T x ) instead of Fe SA -NS-Ti3C2T x , other conditions being the same.

[0077] Control group 2: NS-Ti3C2T x Nanosheets replace Fe SA -NS-Ti3C2T x, other conditions being the same.

[0078] In this embodiment, the NS-Ti3C2T x Nanosheets (NS-Ti3C2T x ) is prepared in the same manner as Fe in Example 1 SA -NS-Ti3C2T x The preparation method is basically the same, the only difference is that no ferric chloride solution is added.

[0079] During the magnetic stirring process, 1 mL of sample was taken every 1 min and 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 in the degradation system constructed with different catalysts.

[0080] Figure 7 This is a diagram showing the removal effect of acetaminophen in the degradation system constructed with different catalysts in Example 6 of the present invention. Figure 7 It can be seen that under the same experimental conditions as in Example 1, Ti3C2T x The removal rate of acetaminophen by nanosheets was only 1.36% within 8 min, while that of NS-Ti3C2T x The removal rate of acetaminophen by the nanosheets was only 0.98% within 8 min; Figure 7 It can be seen that Mn SA -NS-Ti3C2T x and Cu SA -NS-Ti3C2T x The removal rates of acetaminophen were 11.72% and 29.69% within 8 min; Fe SA -NS-Ti3C2T x 、Co SA -NS-Ti3C2T x The removal rate of acetaminophen was 100% within 6 min.

[0081] It can be seen from the above results that, compared with conventional single-atom catalysts, the single-atom catalyst of the present invention has the advantages of high activation efficiency for permonosulfate and can effectively reduce the amount of permonosulfate used, and is a new type of catalyst with high efficiency, low consumption, and recyclable. When it is used as a catalyst for activating permonosulfate, it can quickly generate a large amount of active oxygen species (such as O2 - and 1O2), the degradation system thus constructed can use the active oxygen species generated in large quantities in the system to achieve rapid and thorough removal of organic pollutants under the premise of using a small amount of permonosulfate. In particular, in the system of the present invention, only 0.1 mM of permonosulfate needs to be added to achieve rapid and efficient removal of organic pollutants, which can effectively reduce the operating cost of the permonosulfate activation technology and significantly reduce the risk of new environmental pollution caused by the large-scale use of permonosulfate.

[0082] 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 activating permonosulfate, characterized in that: Including nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, wherein the metal single atoms are anchored in the nitrogen-sulfur co-doped Ti3C2T x On the nanosheet; the metal single atom is an iron single atom or a cobalt single atom.

2. The single atom catalyst according to claim 1, characterized in that The mass of the metal single atom is 0.1% to 0.5% of the mass of the single atom catalyst.

3. The single atom catalyst according to claim 1 or 2, characterized in that The mass of the metal single atom is 0.15% to 0.3% of the mass of the single atom catalyst.

4. A method for preparing a single-atom catalyst for activated permonosulfate, characterized in that: The following steps are involved: S1. Ti3C2T x The nanosheets, a precursor containing a nitrogen source and a sulfur source, and a soluble metal salt solution are mixed for self-assembly reaction to obtain a precursor; the soluble metal salt solution is a soluble iron salt solution or a soluble cobalt salt solution; S2, freeze-drying the precursor obtained in step S1; S3, pyrolyzing the solid obtained after freeze-drying in step S1 to obtain a single-atom catalyst of activated permonosulfate.

5. The preparation method according to claim 4, characterized in that: In step S1, the Ti3C2T x The mass ratio of the nanosheet, the precursor containing nitrogen source and sulfur source, and the soluble metal salt in the soluble metal salt solution is 100:100-600:1.1-6.4; the precursor containing nitrogen source and sulfur source is thiourea.

6. The preparation method according to claim 5, characterized in that: In step S2, the freeze drying is carried out in a freeze dryer; the freeze drying time is 24h to 48h; In step S3, the pyrolysis is carried out in a mixed atmosphere of nitrogen and hydrogen; the volume ratio of nitrogen to hydrogen in the mixed atmosphere of nitrogen and hydrogen is 9:1; the heating rate during the pyrolysis process is 3°C / min to 8°C / min; the pyrolysis temperature is 350°C to 450°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. The preparation method according to any one of claims 4 to 6, characterized in that The single-atom catalyst includes nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, wherein the metal single atoms are anchored in the nitrogen-sulfur co-doped Ti3C2T x On the nanosheet; the metal single atom is an iron single atom or a cobalt single atom; the mass of the metal single atom is 0.1% to 0.5% of the mass of the single atom catalyst.

8. 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 7 as a catalyst for permonosulfate in treating organic wastewater.

9. The use according to claim 8, characterized in that: The method comprises the following steps: mixing a single-atom catalyst, permonosulfate and organic wastewater for catalytic reaction to remove organic pollutants in the wastewater; and the concentration of permonosulfate in the catalytic reaction system is ≤0.9 mM.

10. The use according to claim 9, characterized in that: The addition amount of the single-atom catalyst is 0.01g~0.02g per liter of the organic wastewater; the concentration of permonosulfate in the catalytic reaction system is 0.05mM~0.6mM; the concentration of the organic wastewater is ≤20μM; the organic pollutant in the organic wastewater is acetaminophenol; the catalytic reaction is carried out under stirring conditions; the stirring speed is 200r / min~500r / min; the temperature of the system is controlled at 10℃~35℃ during the catalytic reaction; the time of the catalytic reaction is 3min~8min.

Images