A monatomic catalyst for activating permonosulfate and a preparation method and application thereof

Abstract

The application discloses a monatomic catalyst for activating peroxymonosulfate and a preparation method and application thereof. The catalyst comprises nitrogen-sulfur co-doped Ti3C2T x nanosheets and iron monatomic atoms or cobalt monatomic atoms targeted on the asymmetric coordination structure. The preparation method comprises mixing Ti3C2T x nanosheets, a nitrogen-containing source and a sulfur-containing precursor, and a soluble metal salt, self-assembling, freeze-drying and pyrolyzing. The monatomic catalyst has excellent electrical conductivity and electronic structure, can form a large amount of active oxygen substances in a catalytic degradation system under the premise of low peroxymonosulfate addition amount, has the advantages of high peroxymonosulfate activation efficiency and effective reduction of peroxymonosulfate usage, can activate peroxymonosulfate to realize efficient purification of organic wastewater, can effectively reduce the operation cost of peroxymonosulfate activation technology, and can also significantly reduce the new environmental pollution risk caused by the large use of peroxymonosulfate.

Description

Technical Field

[0001] This invention belongs to the field of new environmental materials, and relates to a single-atom catalyst for activating persulfate, its preparation method, and its application. Background Technology

[0002] Persulfate monosulfate (PMS) activation technology has become a research hotspot in water treatment technology due to its ability to efficiently generate reactive oxygen species such as hydroxyl radicals, sulfate radicals, superoxide radicals, and singlet oxygen, which can effectively remove organic pollutants such as pharmaceuticals, dyes, and industrial chemicals. However, complete degradation of pollutants usually requires high concentrations of PMS, which not only increases operating costs but also exposes the plant to the environmental disadvantages of high sulfate loading. Therefore, optimizing process conditions to minimize PMS dosage while maximizing pollutant removal efficiency remains a key research area.

[0003] Currently, single-atom catalysts have the advantage of high atom utilization, thus effectively reducing the amount of PMS required for activation to some extent. However, when using conventional single-atom catalysts to activate PMS, a relatively large amount of PMS still needs to be added to maximize pollutant removal rates, with the minimum addition amount of PMS still as high as 1mM to 2mM. This is not conducive to effectively reducing the operating cost of persulfate activation technology. Furthermore, the large amount of PMS used also introduces a significant amount of sulfate, leading to secondary pollution, ultimately hindering the widespread practical application of persulfate activation technology. Therefore, obtaining a single-atom catalyst with high PMS activation efficiency and the ability to effectively reduce PMS usage is of great significance for achieving low-cost application of persulfate activation technology and promoting its widespread use 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 shortcomings of the prior art and provide a single-atom catalyst for activating persulfate with high activation efficiency for PMS and effective reduction of PMS usage, as well as its preparation method and application.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A single-atom catalyst for activating persulfate, comprising nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, wherein the metal single atoms are targeted in an asymmetric coordination structure onto 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] In a further improvement of the aforementioned single-atom catalyst, the mass of the metal single atom is 0.1% to 0.5% of the mass of the single-atom catalyst.

[0008] In a further improvement of the aforementioned single-atom catalyst, 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 for activating persulfate, comprising the following steps:

[0010] S1, Ti3C2T x Nanosheets, a precursor containing a nitrogen source and a sulfur source, and a soluble metal salt solution are mixed and subjected to a 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-dry the precursor obtained in step S1;

[0012] S3. Pyrolyze the solid obtained after freeze-drying in step S1 to obtain a single-atom catalyst activated by monosulfate.

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

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

[0015] In a further improvement to the above preparation method, 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 is 9:1; the heating rate during the pyrolysis process is 3℃ / min to 8℃ / min; the pyrolysis temperature is 350℃ to 450℃; the pyrolysis time is 1h to 4h; and 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.

[0016] In a further improvement to the above preparation method, the single-atom catalyst comprises nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, wherein the metal single atoms are targeted in an asymmetric coordination structure onto the nitrogen-sulfur co-doped Ti3C2T xOn the nanosheet; the metal single atom is an iron single atom or a cobalt single atom.

[0017] In a further improvement to the above preparation method, the mass of the metal single atom is 0.1% to 0.5% of the mass of the single-atom catalyst.

[0018] In a further improvement to the above preparation method, 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 application of the above-described single-atom catalyst or the single-atom catalyst prepared by the above-described preparation method as a permonosulfate catalyst in the treatment of organic wastewater.

[0020] Further improvements to the above application include the following steps: mixing a single-atom catalyst, persulfate, and organic wastewater to carry out a catalytic reaction to remove organic pollutants from the wastewater; the concentration of persulfate in the catalytic reaction system is ≤0.9mM.

[0021] In a further improvement to the above application, the amount of the single-atom catalyst added is 0.01g to 0.02g per liter of the organic wastewater.

[0022] In a further improvement to the above application, the concentration of persulfate in the catalytic reaction system is 0.05 mM to 0.6 mM.

[0023] In the above-described application, a further improvement is made, wherein the concentration of the organic wastewater is ≤20μM.

[0024] In a further improvement to the above application, the organic pollutant in the organic wastewater is acetaminophen.

[0025] In a further improvement to the above application, the catalytic reaction is carried out under stirring conditions; the stirring speed is 200 r / min to 500 r / min; the temperature of the system is controlled at 10℃ to 35℃ during the catalytic reaction; and the catalytic reaction time is 3 min to 8 min.

[0026] In this invention, Ti3C2T is used. xThe preparation method of the nanosheets includes the following steps: LiF is added to an HCl solution and stirred until homogeneous. Ti3AlC2 is then slowly added, and the mixture is stirred at 35℃~45℃ for 24 hours~36 hours. The supernatant is washed with ultrapure water until the pH value is 5.5~6.5. The remaining precipitate is sonicated and centrifuged to obtain a dark green upper layer solution. This solution is then freeze-dried to obtain a few layers of Ti3C2Tx nanosheets. The ratio of LiF to HCl solution is 1g~2g : 20mL~40mL; the mass ratio of LiF to Ti3AlC2 is 1~2 : 1~2.

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

[0028] (1) To address the shortcomings of existing single-atom catalysts, such as low activation efficiency and large amount of permonosulfate added, this invention provides a single-atom catalyst for activating permonosulfate, comprising nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, with the metal single atoms targeting nitrogen-sulfur co-doped Ti3C2T in an asymmetric coordination structure. x On the nanosheet, the metal single atoms are either iron or cobalt single atoms. In this invention, iron or cobalt single atoms are targeted in an asymmetric coordination structure onto nitrogen-sulfur co-doped Ti3C2T. x On the nanosheets, on the one hand, the conductivity of the single-atom catalyst can be improved, thereby enhancing the activation efficiency of the single-atom catalyst for permonosulfate by increasing the electron transfer rate. On the other hand, it can construct an asymmetric coordination microenvironment for iron or cobalt single atoms. Its excellent electronic structure allows for the formation of a large amount of reactive oxygen species in the catalytic degradation system with low permonosulfate addition, achieving highly efficient purification of organic wastewater. The single-atom catalyst of this invention has advantages such as high activation efficiency for permonosulfate and effective reduction of permonosulfate usage. It is a novel catalyst that is highly efficient, low-consumption, recyclable, and has high application value and promising prospects.

[0029] (2) The present invention also provides a method for preparing a single-atom catalyst, wherein Ti3C2T x Nanosheets, nitrogen- and sulfur-containing precursors, and soluble metal salt solutions (soluble iron or cobalt salt solutions) undergo a self-assembly reaction. Electrostatic adsorption is utilized to uniformly adsorb the nitrogen- and sulfur-containing precursors and metal ions onto Ti3C2T. x Nanosheets are then freeze-dried to immobilize nitrogen- and sulfur-containing precursors and metal ions on Ti3C2T. xOn the nanosheets, the dried precursor is pyrolyzed. During pyrolysis, nitrogen and sulfur co-doping is achieved through high temperature, and an asymmetric coordination microenvironment is constructed for the metal atoms (iron or cobalt single atoms). This creates asymmetric coordination microregions within the catalyst, ultimately yielding a single-atom catalyst with high activation efficiency for persulfate and effectively reducing the amount of persulfate used. Furthermore, the preparation method of this invention has advantages such as simple steps and low cost, making it suitable for large-scale preparation and facilitating the industrial application of single-atom catalysts.

[0030] (3) This invention also provides an application of a single-atom catalyst as a catalyst for permonosulfate in the treatment of organic wastewater. By using the single-atom catalyst to catalyze the activation of permonosulfate, a large amount of highly oxidizing reactive oxygen species (such as O2) can be formed. - and 1 The degradation system constructed using this method (O2) can achieve rapid and thorough removal of organic pollutants by utilizing the large amount of reactive oxygen species generated in the system, with minimal use of persulfate. Specifically, the system of this invention requires only 0.1 mM of persulfate to achieve rapid and efficient removal of organic pollutants, effectively reducing the operating costs of persulfate activation technology and significantly mitigating the risk of new environmental pollution caused by the large-scale use of persulfate. This invention's application method has advantages such as simple process, low PMS dosage, low cost, high treatment efficiency, and good removal effect. It can be widely used to treat organic wastewater and achieve effective purification of organic wastewater, while overcoming the shortcomings of conventional methods such as large PMS dosage and low PMS activation efficiency, showing excellent application prospects. Attached Figure Description

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0032] Figure 1 The single-atom catalyst (Fe) prepared in Example 1 of this invention SA -NS-Ti3C2T x Scanning electron microscope image of ).

[0033] Figure 2 The single-atom catalyst (Fe) prepared in Example 1 of this invention SA -NS-Ti3C2T x ) element distribution diagram.

[0034] Figure 3 Fe under different PMS concentrations in Example 2 of the present invention SA -NS-Ti3C2T x / PMS system for removing acetaminophen.

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

[0036] Figure 5 The single-atom catalyst (Fe) in Example 4 of this invention SA -NS-Ti3C2T x (Image showing the repeated degradation effect of para-acetaminophen)

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

[0038] Figure 7 The graph shows the removal effect of acetaminophen in the degradation systems constructed with different catalysts in Example 6 of this invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0040] In the following embodiments 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 activating persulfate, comprising nitrogen-sulfur co-doped Ti3C2T x Nanosheets and metal single atoms, with the metal single atoms targeting nitrogen-sulfur co-doped Ti3C2T in an 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 microregions are formed in the single-atom catalyst. Specifically, the metal single atom is targeted at the nitrogen-sulfur co-doped Ti3C2T with an asymmetric coordination structure. x Asymmetric coordination microenvironments are formed on the nanosheets.

[0045] A method for preparing a single-atom catalyst of activated persulfate as described in this embodiment includes the following steps:

[0046] a. Take 150mg Ti3C2T x Nanosheets, 450 mg of thiourea, and FeCl3 solution (containing 4.8 mg of FeCl3) were slowly mixed to undergo a self-assembly reaction, yielding 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 is pyrolyzed at 400°C for 2 hours under a mixed atmosphere of nitrogen and hydrogen (N 2 90% and H 2 10%, i.e., the volume ratio of nitrogen to hydrogen in the mixed atmosphere is 9:1) at a heating rate of 5°C / min. After thorough washing with water and ethanol, it is dried in a vacuum drying oven at 60°C. The resulting powder is a single-atom catalyst for activated persulfate, denoted as Fe. SA -NS-Ti3C2T x In this invention, pyrolysis is performed under a protective atmosphere of nitrogen and hydrogen, and hydrogen can be used to suppress Ti3C2T. x It is oxidized.

[0049] In this invention, Ti3C2T is used. x The preparation method of the nanosheets includes the following steps: 1g LiF is added to 20mL HCl solution and stirred evenly. 1g Ti3AlC2 is slowly added and stirred at 40℃ for 24 hours. The solution is washed with ultrapure water until the pH of the effluent is 6. The solution is sonicated, centrifuged, and the upper dark green solution is freeze-dried to obtain a few layers of Ti3C2Tx nanosheets.

[0050] Figure 1 The single-atom catalyst (Fe) prepared in Example 1 of this invention SA -NS-Ti3C2T x Scanning electron microscope image of ). By Figure 1 It can be seen that the single-atom catalyst (Fe) prepared in Example 1 of this study... SA -NS-Ti3C2T x It exhibits a sheet-like-densely packed structure.

[0051] Figure 2 The single-atom catalyst (Fe) prepared in Example 1 of this invention SA -NS-Ti3C2T x The element distribution diagram of ). Figure 2 It can be seen that the single-atom catalyst (Fe) prepared in Example 1 of this study... SA -NS-Ti3C2T xIn addition to a single iron atom, the presence of Ti, C, O, N and S is also indicated.

[0052] In this embodiment, single-atom catalysts with different metal atoms were also prepared, and their preparation methods were the same as those for the single-atom catalyst (Fe) in Example 1. SA -NS-Ti3C2T x The preparation methods are basically the same, the only difference being that cobalt chloride solution, copper chloride solution, and manganese chloride solution are used in sequence instead of ferric chloride solution in Example 1. The single-atom catalysts prepared using cobalt chloride solution, copper chloride solution, and manganese chloride solution as soluble metal salt solutions are, in sequence, Co. SA -NS-Ti3C2T x Mn SA -NS-Ti3C2T x Cu SA -NS-Ti3C2T x .

[0053] Example 2

[0054] The application of a single-atom catalyst as a permonosulfate catalyst in the treatment of organic wastewater, specifically using Fe prepared in Example 1. SA -NS-Ti3C2T x Using persulfate (PMS) as a catalyst, acetaminophen as an organic pollutant, and para-aminophenol as an oxidant, this study investigated the effects of different PMS concentrations on Fe2+. SA -NS-Ti3C2T x The removal efficiency 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 a catalyst, 10 mg of each sample was added to a 100 mL solution of acetaminophen (20 μM concentration) and mixed thoroughly. Then, different amounts of PMS were added to achieve PMS concentrations of 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 500 r / min. During the catalytic reaction, the temperature of the system was adjusted to 25 °C using a water bath to complete the removal of acetaminophen from the wastewater.

[0056] During magnetic stirring, 1 mL of sample was taken every 1 minute and filtered through a 0.22 μm filter. The filtrate was then analyzed by high-performance liquid chromatography (HPLC) to determine the remaining concentration of acetaminophen, thereby obtaining the Fe concentration at different PMS concentrations. SA -NS-Ti3C2Tx The removal effect of acetaminophen by the PMS system.

[0057] Figure 3 Fe under different PMS concentrations in Example 2 of the present invention SA -NS-Ti3C2T x The removal effect of acetaminophen in the PMS system is shown in the figure. Figure 3 It can be seen that the removal rate of acetaminophen reaches 100% within 6 minutes when 0.1mM-0.6mM PMS is added. However, the removal rate of acetaminophen is not significantly different when more than 0.1mM PMS is added. It is evident that the single-atom catalyst of this invention can achieve rapid and efficient removal of organic pollutants by adding only 0.1mM persulfate in the activated persulfate system. This not only reduces water treatment operating costs but also avoids the environmental disadvantages caused by the high sulfate load.

[0058] Example 3:

[0059] The application of a single-atom catalyst as a permonosulfate catalyst in the treatment of organic wastewater, specifically using Fe prepared in Example 1. SA -NS-Ti3C2T x Using persulfate (PMS) as a catalyst, acetaminophen as an organic pollutant, and para-aminophenol as a catalyst, the study investigated the effects of different temperatures on Fe. SA -NS-Ti3C2T x The removal effect of PMS system on acetaminophen 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 of each sample was added to a 100 mL solution of acetaminophen (20 μM concentration) and mixed thoroughly. The temperature was then adjusted to 10℃, 15℃, 20℃, 25℃, 30℃ and 35℃ in a water bath. 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 500 r / min to complete the removal of acetaminophen from wastewater.

[0061] During magnetic stirring, 1 mL of sample was taken every 1 minute and filtered through a 0.22 μm filter. The filtrate was then analyzed by high-performance liquid chromatography to determine the remaining concentration of acetaminophen, thereby obtaining the Fe concentration at different temperatures. SA -NS-Ti3C2T x The removal effect of acetaminophen by the PMS system.

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

[0063] Example 4:

[0064] The application of a single-atom catalyst as a permonosulfate catalyst in the treatment of organic wastewater, specifically using Fe prepared in Example 1. SA -NS-Ti3C2T x Using persulfate (PMS) as a catalyst, acetaminophen as an organic pollutant, and para-aminophenol as an oxidant, the study investigated the effects of Fe... SA -NS-Ti3C2T x The reusability of the catalyst includes the following steps:

[0065] Weigh out 3 portions (3 parallel groups) of Fe prepared in Example 1 SA -NS-Ti3C2T x As a catalyst, 10 mg of each sample was added to a 100 mL solution of acetaminophen (20 μM concentration) and mixed thoroughly. Then, PMS was added to bring the concentration of PMS in the system to 0.1 mM. The catalytic reaction was carried out under magnetic stirring at 500 r / min. During the catalytic reaction, the temperature of the system was adjusted to 25 °C using a water bath to complete the removal of acetaminophen from the wastewater.

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

[0067] Figure 5 The single-atom catalyst (Fe) in Example 4 of this invention SA -NS-Ti3C2T x (Graph showing the repeated degradation effect of acetaminophen.) Figure 5 It can be seen that after 4 cycles, the single-atom catalyst (Fe) of this invention... SA -NS-Ti3C2T x The degradation efficiency can still reach 91.21% within 8 minutes, which indicates that the Fe of this invention... SA -NS-Ti3C2T xIt exhibits very high stability, can be repeatedly used to treat organic wastewater, and consistently achieves good removal results.

[0068] Example 5:

[0069] Fe prepared in Example 1 SA -NS-Ti3C2T x Using persulfate (PMS) as a catalyst, acetaminophen as an organic pollutant, and para-aminophenol as an oxidant, the study investigated the effects of Fe... SA -NS-Ti3C2T x The main active species in the / PMS system are as follows:

[0070] Methanol (200 mM), tert-butanol (200 mM), furfuryl alcohol (1.5 mM), and ascorbic acid (1.5 mM) were selected as active substance probes and added to an acetaminophen solution (100 mL, 20 μM concentration). 10 mg of Fe2+ prepared in Example 1 was added to each sample. SA -NS-Ti3C2T x Using a catalyst, and with the addition of PMS to achieve a PMS concentration of 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 using a water bath to complete the removal of acetaminophen from wastewater.

[0071] During magnetic stirring, 1 mL of sample was taken every 1 minute and filtered through a 0.22 μm filter. The filtrate was then analyzed by high-performance liquid chromatography to determine the remaining concentration of acetaminophen, thereby obtaining the Fe concentration under different quenchers. SA -NS-Ti3C2T x / PMS system effect diagram for removing acetaminophen.

[0072] Figure 6 Fe under different quenchers in Example 5 of the present invention SA -NS-Ti3C2T x The removal effect of acetaminophen in the PMS system is shown in the figure. Figure 6 It can be seen that the degradation of acetaminophen was not significantly inhibited after the addition of methanol (100 mM) and tert-butanol (100 mM), indicating that the common H2O· and SO4· - The contribution was relatively weak. However, the addition of furfuryl alcohol (1.5 mM) resulted in some inhibition, indicating that... 1 The presence of O2. In the presence of 1.5 mM ascorbic acid, the removal of acetaminophen was severely inhibited, indicating that O2... - The existence of Fe can be determined from this. SA -NS-Ti3C2Tx O2 in the PMS system - and 1 O2 plays a crucial role.

[0073] Example 6

[0074] The application of a single-atom catalyst as a permonosulfate catalyst in the treatment of organic wastewater, specifically using 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 Using nanosheets as a catalyst, persulfate (PMS) as an oxidant, and acetaminophen as an organic pollutant, this study investigated the removal efficiency of different catalyst-constructed degradation systems for acetaminophen, 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 a catalyst, 10 mg of each sample was added to a 100 mL solution of acetaminophen (20 μM concentration) and mixed thoroughly. Then, PMS was added to bring the concentration of PMS in the system to 0.1 mM. The catalytic reaction was carried out under magnetic stirring at 500 r / min. During the catalytic reaction, the temperature of the system was adjusted to 25 °C using a water bath to complete the removal of acetaminophen from the wastewater.

[0076] Control group 1: Ti3C2T x Nanosheets (Ti3C2T for short) x ) instead of Fe SA -NS-Ti3C2T x All other conditions are the same.

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

[0078] In this embodiment, NS-Ti3C2T is used. x Nanosheets (NS-Ti3C2T) x The preparation method of Fe in Example 1 is the same as that in Example 1. SA -NS-Ti3C2T x The preparation methods are basically the same, the only difference being that ferric chloride solution is not added.

[0079] During magnetic stirring, 1 mL of sample was taken every 1 min and filtered using a 0.22 μm filter. The filtrate was then analyzed by high performance liquid chromatography to determine the concentration of acetaminophen, thereby obtaining the removal efficiency of acetaminophen in degradation systems constructed with different catalysts.

[0080] Figure 7 This image shows the removal efficiency of acetaminophen in the degradation systems constructed with different catalysts in Example 6 of this invention. Figure 7 It can be seen that, under the same experimental conditions as in Example 1, Ti3C2T x The nanosheets only achieved a 1.36% removal rate of acetaminophen within 8 minutes. NS-Ti3C2T x The nanosheets removed only 0.98% of acetaminophen within 8 minutes; additionally, such as Figure 7 It can be seen that Mn SA -NS-Ti3C2T x and Cu SA -NS-Ti3C2T x The removal rates of acetaminophen within 8 min were 11.72% and 29.69%, respectively; Fe SA -NS-Ti3C2T x Co SA -NS-Ti3C2T x The removal rate of acetaminophen was 100% within 6 minutes.

[0081] The results above show that, compared with conventional single-atom catalysts, the single-atom catalyst of this invention has advantages such as high activation efficiency for permonosulfate and effective reduction in the amount of permonosulfate used. It is a novel catalyst that is highly efficient, low-consumption, and recyclable. When used as a catalyst to activate permonosulfate, it can rapidly generate a large amount of active oxygen substances (such as O2) with a small amount of permonosulfate used. - and 1The degradation system constructed thereby can achieve rapid and thorough removal of organic pollutants by utilizing the large amount of active oxygen generated in the system with minimal use of persulfate (O2). In particular, in the system of this invention, only 0.1 mM of persulfate needs to be added to achieve rapid and efficient removal of organic pollutants, which can effectively reduce the operating cost of persulfate activation technology and significantly reduce the risk of new environmental pollution caused by the large-scale use of persulfate.

[0082] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. The application of a single-atom catalyst as a permonosulfate catalyst in the treatment of organic wastewater, characterized in that, The method includes the following steps: mixing a single-atom catalyst, persulfate, and organic wastewater to carry out a catalytic reaction to remove organic pollutants from the wastewater; the concentration of persulfate in the catalytic reaction system is 0.05 mM to 0.9 mM; and the concentration of the organic wastewater is ≤20 μM. The preparation method of the single-atom catalyst includes the following steps: S1, Ti3C2T x Nanosheets, a precursor containing a nitrogen source and a sulfur source, and a soluble metal salt solution are mixed and subjected to a 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-dry the precursor obtained in step S1; S3. The solid obtained after freeze-drying in step S2 is pyrolyzed to obtain a single-atom catalyst; the pyrolysis is carried out in a mixed atmosphere of nitrogen and hydrogen; the volume ratio of nitrogen to hydrogen in the mixed atmosphere is 9:1; the temperature of the pyrolysis is 350℃~450℃. The single-atom catalyst includes nitrogen-sulfur co-doped Ti3C2T. x Nanosheets and metal single atoms, wherein the metal single atoms are anchored in an asymmetric coordination structure to 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 application according to claim 1, characterized in that, The amount of the single-atom catalyst added is 0.01g to 0.02g per liter of the organic wastewater; the concentration of persulfate in the catalytic reaction system is 0.05mM to 0.6mM; the organic pollutant in the organic wastewater is acetaminophen; 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 at 10℃ to 35℃ during the catalytic reaction; and the reaction time is 3min to 8min.

3. The application according to claim 1, characterized in that, In step S1, the Ti3C2T x The mass ratio of the nanosheets, the nitrogen- and sulfur-containing precursors, and the soluble metal salt in the soluble metal salt solution is 100:100-600:1.1-6.4; the nitrogen- and sulfur-containing precursor is thiourea.

4. The application according to claim 3, 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 heating rate during the pyrolysis process is 3℃ / min to 8℃ / min; the pyrolysis time is 1h to 4h; after the pyrolysis is completed, the following treatment is also included: the pyrolysis product is washed with water and ethanol in sequence, and the washed pyrolysis product is dried under vacuum conditions.

5. The application according to any one of claims 1, 3, and 4, characterized in that, The mass of the metal single atom is 0.1% to 0.5% of the mass of the single-atom catalyst.

6. The application according to claim 5, characterized in that, The mass of the metal single atom is 0.15% to 0.3% of the mass of the single-atom catalyst.

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