A single atom catalyst mediated contaminant polymerization shift water treatment process

Abstract

The present application provides a single-atom catalyst-mediated pollutant polymerization transfer water treatment process, which adds a trace amount of oxidant and catalyst to water containing organic pollutants, so as to realize the polymerization phase transfer of the pollutants in the water to the surface of the catalyst, thereby completing the efficient and safe removal of the pollutants. The water treatment process provided by the present application involves a non-radical mechanism occurring on the surface of the catalyst, does not involve the mineralization degradation of the pollutants, and therefore does not produce secondary pollution intermediates, and has strong resistance to actual environmental interference; since the active sites are dispersed in the form of single atoms, the atom utilization rate is high, the reaction activity is strong, and the rapid polymerization transfer of the pollutants can be realized in minutes; since the oxidant addition amount is small, and the post-treatment of by-products (such as Fe mud and sulfate) is not required, the water treatment cost is greatly reduced while the treatment effect is ensured; in addition, the value-added chemicals polymerized on the surface of the catalyst can be easily washed and enriched by an organic solvent, and the catalyst can be regenerated.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution control, and in particular to a pollutant polymerization transfer water treatment process mediated by a single atom catalyst. Background Art

[0002] Advanced oxidation processes (AOPs) are currently one of the most effective water treatment technologies for removing persistent organic pollutants. Among them, Fenton-like technologies, represented by peroxymonosulfate (PMS), have garnered widespread attention from academia and industry due to their strong oxidizing power and wide pH range (2-10). However, whether using free radical or non-radical pathways, Fenton-like technologies suffer from incomplete pollutant removal, are prone to secondary pollution, and even generate highly toxic dicarbonyl intermediates, posing a serious threat to aquatic ecosystems.

[0003] The emergence of polymerization transfer (PT) technology has made sustainable wastewater treatment possible. This technology removes pollutants and converts them into valuable new substances through oxidative polymerization and phase transfer to a catalyst surface. PT, with its advantages of low oxidant usage (1-2 times the amount of pollutant), high electron utilization efficiency (close to theoretical values), strong anti-interference capabilities, and the absence of secondary pollutants, has effectively promoted the practical application of Fenton-like technologies.

[0004] Current research on PT technology mainly focuses on nanomaterials, especially metal oxides (CuO, Co3O4, NiO, MnxOy). However, due to the uneven distribution of their active sites, their atomic utilization is low (less than 20%), resulting in a slow reaction rate. At the same time, there is also a lack of in-depth understanding of the types of active species that trigger PT and their regulatory mechanisms. As a result, the PT catalytic system always faces a trade-off between efficiency and selectivity, limiting its application prospects as an advanced water treatment process. Summary of the Invention

[0005] In light of this, the present invention provides a single-atom catalyst-mediated pollutant polymerization and transfer water treatment process. This process enables highly selective polymerization and transfer of pollutants into value-added chemicals at single-atom sites, avoiding the secondary pollution problems associated with pollutant mineralization in traditional water treatment technologies. It also utilizes minimal oxidant consumption, offers high reaction efficiency, and exhibits strong anti-interference capabilities.

[0006] The present invention provides a single-atom catalyst-mediated pollutant polymerization transfer water treatment process, comprising:

[0007] Adding single-atom catalysts and oxidants to sewage to carry out oxidative polymerization reaction, thereby purifying the water;

[0008] in,

[0009] The oxidant is persulfate;

[0010] The single-atom catalyst includes a carrier and a single atom supported on the carrier; wherein the carrier is a carbon-based material; and the single atom is at least one of Cu, Fe, Ni and Co.

[0011] Preferably, the carrier is selected from at least one of carbon nitride, carbon black, carbon nanotubes and metal-organic framework materials.

[0012] Preferably, the oxidant is peroxymonosulfate and / or peroxydisulfate.

[0013] Preferably, the organic pollutants in the sewage include aromatic compounds containing electron-rich groups.

[0014] Preferably, the electron-rich group is a hydroxyl group and / or an amino group.

[0015] Preferably, the aromatic compound includes at least one of phenol, 2,6-dimethylphenol and aniline.

[0016] Preferably, the temperature of the oxidative polymerization reaction is room temperature, and the time is ≤30 min.

[0017] Preferably, the pH value of the oxidative polymerization reaction is 2.0 to 10.0.

[0018] Preferably, the molar ratio of the oxidant to the organic pollutants in the sewage is (1-2):1.

[0019] Preferably, the amount of the catalyst used in sewage is 0.1 to 2.0 g / L.

[0020] The present invention provides a single-atom catalyst-mediated pollutant polymerization transfer water treatment process, in which a single-atom catalyst and a low-dose PMS are added to the polluted water body to carry out a highly selective oxidative polymerization reaction. The treated water achieves the simultaneous removal of emerging pollutants and TOC; the generated value-added polymerization products can be eluted and enriched by a simple organic solvent, and the catalyst is regenerated at the same time. The present invention provides an important reference for the types of metal atoms and the regulation rules for realizing the PT process at the level of a single atom of the catalyst, realizes the spontaneous polymerization of pollutants at the single-atom active site, avoids the generation of more toxic and difficult-to-remove intermediates, and has a strong anti-interference ability (does not undergo the mineralization degradation path of the traditional AOP mechanism, and does not rely on · OH or SO4 ·-It has high electron utilization efficiency (small amount of oxidant, only 1 to 2 times of the pollutant, which is 2 to 3 orders of magnitude lower than the traditional H2O2-based AOP technology), high removal efficiency (minute level), and improved recovery methods of polymerization products, making it a water treatment process with application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0022] Figure 1 XRD patterns of the carbon substrate and the series of single-atom catalysts supported by carbon nitride in Example 1;

[0023] Figure 2 This is a spherical aberration electron microscope image of a series of single-atom catalysts supported by carbon nitride in Example 1; wherein, Figure 2 (a) to (d) are spherical aberration electron microscopy images of single-atom catalysts Cu-SACs, Fe-SACs, Ni-SACs, and Co-SACs, respectively;

[0024] Figure 3 This is a test effect diagram of the sewage treatment capacity in Example 2; wherein, Figure 3 (a) to (e) are the test results of single-atom catalysts Cu-SACs, Fe-SACs, Ni-SACs, Co-SACs and carbon substrates respectively;

[0025] Figure 4 The effect diagram of elution of the Co-SACs / PMS / PhOH system in Example 2 and identification of the elution of the polymerization product is shown in Figure 2 using different organic solvents (THMs, CAN, THF);

[0026] Figure 5 This is a diagram showing the effect of using the organic solvent THF to elute the TM-SACs / PMS / 2,6-M-PhOH system in Example 2 and identify the eluted polymer product;

[0027] Figure 6 is the NMR spectrum of the eluted polymer in Example 3;

[0028] Figure 7 is the partial wave density of states (PDOS) change diagram of the metal center during the reaction of different single atom catalysts; Figure 7(a) and (b) respectively represent the PDOS diagram of the adsorption of TM-SACs on PMS and the further reaction of the pollutants on the surface to polymerize. DETAILED DESCRIPTION

[0029] The application provides a single-atom catalyst-mediated pollutant polymerization transfer water treatment process, comprising:

[0030] The single-atom catalyst and the oxidant are added to the sewage to perform an oxidative polymerization reaction, so as to purify the water body.

[0031] In the application,

[0032] The oxidant is a persulfate salt.

[0033] The single-atom catalyst comprises a carrier and single atoms loaded on the carrier; the carrier is a carbon-based material; and the single atoms are at least one of Cu, Fe, Ni and Co.

[0034] The water treatment process of the application needs to ensure suitable system oxidation capacity to guarantee high selectivity of the reaction, and therefore, the concentration of pollutants in the sewage needs to be determined first before the oxidant and the catalyst are added. In the application, the organic pollutants in the sewage (i.e. the polluted water body) mainly include one or more of the biologically refractory emerging pollutants from medical chemicals and daily life. In the application, the organic pollutants include aromatic compounds containing electron-rich groups. The electron-rich groups are preferably hydroxyl groups and / or amino groups. In the application, more preferably, the aromatic compounds include at least one of phenol (PhOH), 2,6-dimethylphenol (2,6-M-PhOH) and aniline (AN).

[0035] The water treatment process of the application needs to guarantee high selectivity of the pollutants to react and polymerize on the single-atom sites, and therefore, the type and dosage of the oxidant need to be further determined. In the application, the oxidant is a persulfate salt, preferably a persulfate salt (PMS) and / or a perdisulfate salt (PDS), and more preferably a persulfate salt (PMS). In the application, the molar ratio of the oxidant to the organic pollutants in the sewage is preferably (1-2):1. Specifically, after the concentration of the organic pollutants in the sewage is measured, the above-mentioned ratio of the oxidant can be added. The application controls the dosage of the oxidant to be less than 2 times the concentration of the pollutants, which belongs to a low-dosage oxidant, improves the electron utilization efficiency, and effectively reduces the usage amount of the oxidant.

[0036] After determining the ratio of pollutants to oxidants, the present invention selects a suitable single-atom catalyst. In the present invention, the single-atom catalyst comprises a support and single atoms supported on the support; wherein the support is a carbon-based material, preferably at least one of carbon nitride (C3N4), carbon black, carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). The single atoms are preferably at least one of Cu, Fe, Ni, and Co. The present invention places no particular restrictions on the source of the single-atom catalyst, which can be a commercially available product or prepared according to conventional preparation methods in the art.

[0037] In some embodiments of the present invention, the single-atom catalyst used has a carrier of carbon nitride and a single atom of at least one of Cu, Fe, Ni, and Co. In the present invention, the single-atom catalyst can be prepared by the following preparation method:

[0038] S1, dissolving cyanuric acid and xanthine in water to obtain a mixed solution 1;

[0039] S2, dissolving melamine in water to obtain a mixed solution 2;

[0040] S3, mixing the mixed solution 1 with the mixed solution 2 to obtain a mixed solution 3;

[0041] S4, mixing the metal salt solution with the mixed solution 3 to obtain a metal precursor solution;

[0042] S5, centrifuging, washing, and drying the metal precursor solution, and then calcining to obtain a single-atom catalyst;

[0043] There is no order restriction for step S1 and step S2.

[0044] Regarding step S1: The molar ratio of cyanuric acid to xanthine is preferably 9.6:2.4. The water is preferably DI water (i.e., deionized water). The amount ratio of cyanuric acid to water is preferably 9.6 mmol:80 mL. After adding cyanuric acid and xanthine to water, ultrasonic dispersion is preferably performed to fully dissolve and mix the materials, thereby obtaining a mixed solution 1.

[0045] Regarding step S2: the water is preferably DI water (i.e., deionized water). The ratio of melamine to water is preferably 1.2 mmol:80 mL. After adding melamine to water, ultrasonic dispersion is preferably performed to fully dissolve and mix the materials, thereby obtaining a mixed solution 2.

[0046] Regarding step S3: Mixed solution 1 and mixed solution 2 are rapidly mixed to form a suspension, and then subjected to ultrasonic treatment and magnetic stirring in sequence. The ultrasonic treatment duration is preferably 10 to 30 minutes, more preferably 20 minutes. The magnetic stirring duration is preferably 2 to 6 hours, more preferably 4 hours. The magnetic stirring is preferably carried out at room temperature. After the above treatments, mixed solution 3 is obtained.

[0047] Regarding step S4: the metal salt solution is a solution of a metal salt dissolved in water. Wherein, the metal salt refers to the metal salt of the above-mentioned single-atom metal, preferably nitrate and / or sulfate. The water is preferably DI water (i.e., deionized water). The amount ratio of the metal salt to water is preferably 9.6mmol:40mL. The molar ratio of melamine in step S1 to the metal salt in step S4 is preferably 1:1. The method of mixing the metal salt solution with the mixed solution 3 in the present invention is preferably stirring and mixing. The stirring and mixing time is preferably 0.5 to 2h, more preferably 1h. During the stirring process, the self-assembly of the metal-carbon polymer is achieved to obtain a metal precursor solution.

[0048] Regarding step S5: The washing is preferably done with pure water. The drying is preferably done in vacuum. The drying temperature is preferably 50-80°C, more preferably 60°C. The drying time is preferably 5-24h, more preferably 10h. After the drying, grinding is preferably performed, and then calcination is performed. The calcination atmosphere is preferably a protective atmosphere. The present invention has no special restrictions on the type of gas providing the protective atmosphere, and it can be any conventional protective gas in the art, such as nitrogen or argon. The heating rate of the calcination is preferably 2-10°C / min, specifically 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, more preferably 5°C / min. The calcination temperature is preferably 500-600°C, specifically 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, and more preferably 550°C. The calcination time is preferably 1-3 hours, specifically 1 hour, 2 hours, 3 hours, and more preferably 2 hours. After the above calcination, a single-atom catalyst is obtained, specifically a single-atom catalyst supported by carbon nitride (C3N4), denoted as TM-SACs (wherein TM = at least one of Cu, Fe, Ni and Co).

[0049] In the present invention, the dosage of the catalyst in sewage is preferably 0.1 to 2.0 g / L. Adjusting the dosage within the above range can increase the active sites and polymerization transfer interfaces, thereby further improving the reaction efficiency.

[0050] In the actual implementation process of the present invention, after determining the concentration of pollutants in the sewage, 1 to 2 times the oxidant and an appropriate amount of catalyst can be directly added, and a highly selective oxidative polymerization reaction occurs in the sewage. Specifically, the polymerized phase of the pollutants in the sewage is transferred to the surface of the catalyst, thereby completing the efficient and safe removal of the pollutants. The treated water achieves the simultaneous removal of emerging pollutants and TOC (total organic carbon).

[0051] In the present invention, the temperature for carrying out the oxidative polymerization reaction is room temperature, specifically 25±10°C. In the present invention, the pH value of the oxidative polymerization reaction (i.e., the pH value of the sewage) is preferably 2.0-10.0, specifically 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, and more preferably 7.0. It can be seen that the water treatment process of the present invention has strong environmental adaptability and can be carried out spontaneously and efficiently under the conditions of room temperature (25±10°C) and a wide pH value (2.0-10.0). In the present invention, the time of the oxidative polymerization reaction is in the minute level (≤60min), preferably ≤30min, that is, the oxidative polymerization reaction and water purification are completed within 30min.

[0052] In the present invention, the water treatment process preferably comprises: adding an oxidizing agent to the wastewater, then adjusting the pH of the system using a pH regulator, and then adding a catalyst to carry out an oxidative polymerization reaction, thereby purifying the water. The pH regulator is preferably an H2SO4 solution and / or a NaOH solution.

[0053] In the present invention, after the water treatment process, the catalyst can be regenerated and recycled. Specifically, after the water treatment process, the generated value-added polymer is eluted and enriched using a simple organic solvent, thereby recovering the value-added chemicals polymerized on the catalyst surface and simultaneously completing catalyst regeneration. The organic solvent is preferably at least one of ethanol (EtOH), acetonitrile (ACN), chloroform (THMs), toluene (MB), and tetrahydrofuran (THF), with tetrahydrofuran (THF) being most preferred.

[0054] The pollutant polymerization transfer water treatment process mediated by the single atom catalyst provided by the present invention, adds a trace amount of oxidant and catalyst to the water with organic pollutants, that is, the polymerization phase of the pollutants in the water can be transferred to the catalyst surface, thereby completing the efficient and safe removal of pollutants. The water treatment process provided by the present invention relates to a non-radical mechanism occurring on the surface of the catalyst, does not involve the mineralization degradation of pollutants, and therefore does not produce secondary pollution intermediates, and has strong resistance to actual environmental interference; because the active sites are dispersed in the form of single atoms, the atomic utilization rate is high, the reaction activity is strong, and the rapid polymerization transfer of pollutants can be achieved at the minute level; and because the oxidant dosage is small, and there is no need for post-processing of by-products (such as Fe mud, sulfate), the water treatment cost is greatly reduced while ensuring the treatment effect; finally, the value-added chemicals polymerized on the catalyst surface can be easily eluted and enriched by organic solvents, and catalyst regeneration is completed. Therefore, the pollutant polymerization transfer water treatment process mediated by the single atom catalyst provided by the present invention has important practical application value and broad development prospects.

[0055] Compared with the existing technology, the present invention provides a single-atom catalyst-mediated pollutant polymerization transfer water treatment process, in which single-atom catalysts and low-dose PMS are added to the polluted water body to carry out a highly selective oxidative polymerization reaction. The treated water achieves the simultaneous removal of emerging pollutants and TOC; the generated value-added polymerization products can be eluted and enriched by simple organic solvents, and the catalyst is regenerated at the same time. The present invention provides an important reference for the types of metal atoms and the regulation rules for realizing the PT process at the level of a single atom of the catalyst, realizes the spontaneous polymerization of pollutants at single-atom active sites, avoids the generation of more toxic and difficult-to-remove intermediates, and has strong anti-interference ability (does not undergo the mineralization degradation path of the traditional AOP mechanism, and does not rely on · OH or SO4 ·- It has high electron utilization efficiency (small amount of oxidant, only 1 to 2 times of the pollutant, which is 2 to 3 orders of magnitude lower than the traditional H2O2-based AOP technology), high removal efficiency (minute level), and improved recovery methods of polymerization products, making it a water treatment process with application prospects.

[0056] In this invention, the PT ratio is defined as TOC removal rate in the solution / removal rate of the target pollutant. Due to the extremely low oxidant dosage, the pollutants cannot be removed through mineralization. This invention provides a water treatment process involving a novel non-radical polymerization mechanism for pollutant removal, which has strong anti-interference capabilities and practical application potential.

[0057] The present invention provides a new water treatment process with advanced technology, clear mechanism, low cost, and simplicity. Among them, the advanced technology is reflected in the following: the current deep treatment technology for water treatment still relies on the traditional Fenton technology, and the current persulfate-based advanced oxidation technology is limited by the high operating costs caused by secondary pollution and expensive oxidants, and generally remains in the laboratory pilot stage. The new process proposed by the present invention takes a different approach and realizes the polymerization value-added removal of pollutants within minutes (<30min), replacing the traditional mineralization approach, which is of great significance for energy conservation, emission reduction and carbon neutrality in sewage treatment plants. The clear mechanism is reflected in the following: the present invention makes full use of the research platform of single-atom catalysts, and provides an in-depth understanding of the types of active species and their regulatory mechanisms in inducing PT of different single-atom catalysts from the in-depth perspective of atomic properties (that is, SACs with d-band centers far away from the Fermi level can efficiently realize the PT process), providing a reliable theoretical reference for actual working condition operation and maintenance. The low cost is reflected in the fact that the extremely low amount of oxidant used in the present invention balances the problem of the high cost of PMS that limits its application. Although the price of PMS is 1.5 times that of H2O2, the amount used is 2 to 3 orders of magnitude lower than the H2O2 used in the traditional Fenton system, which is expected to greatly reduce the cost of water treatment. The simplicity and ease of use are reflected in the fact that the persulfate / single-atom catalyst combination used in the present invention does not need to treat the hazardous waste Fe mud produced by traditional Fenton technology, and a small amount of persulfate will not produce secondary sulfate pollution. The carbon-based single-atom catalyst used has low environmental toxicity. Therefore, it is only necessary to add the catalyst and oxidant to the water to achieve efficient disposal of sewage without the need for other equipment and post-treatment. The catalyst can be loaded and fixed in the form of a packed column, a fluidized bed, etc. Therefore, from the perspective of cost, rate, benefit and other aspects, this process has huge potential for environmental application.

[0058] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0059] Example 1: Preparation of single-atom catalysts TM-SACs (where TM = Cu, Fe, Ni, or Co)

[0060] 1. Preparation of single-atom catalysts TM-SACs

[0061] S1. Dissolve cyanuric acid (9.6 mmol) and xanthine (2.4 mmol) in DI water (80 mL) and disperse by ultrasonication to obtain a mixed solution 1.

[0062] S2. Melamine (1.2 mmol) was dissolved in DI water (80 mL) and dispersed by ultrasonication to obtain a mixed solution 2.

[0063] S3. Mixed solution 2 and mixed solution 1 were quickly mixed to form a suspension, ultrasonically dispersed for 20 minutes, and then magnetically stirred at room temperature for 4 hours to obtain mixed solution 3.

[0064] S4. Dissolve 9.6 mmol of the corresponding monoatomic metal salt (nitrate or sulfate) in 40 mL of DI water to obtain a metal salt solution. Add the metal salt solution to the mixed solution 3 and stir for 1 hour to obtain a metal precursor solution.

[0065] S5. After centrifuging and washing with pure water, the metal precursor solution was vacuum dried at 60°C for 10 h. The dried sample was then ground in a mortar. After that, the temperature was raised to 550°C at a rate of 5°C / min and calcined for 2 h in a N2 atmosphere to obtain single-atom catalysts Cu-SACs, Fe-SACs, Ni-SACs, and Co-SACs, respectively.

[0066] 2. Preparation of carbon substrate

[0067] The above preparation process is followed, except that no metal salt solution is introduced, and a blank carbon substrate (i.e., carbon nitride C3N4) without single-atom loading is finally obtained.

[0068] 3. Characterization and testing:

[0069] (1) XRD test

[0070] X-ray diffraction (XRD) tests were performed on a series of single-atom catalysts on carbon substrates and carbon nitride support, and the results are as follows: Figure 1 As shown in Figure 2, it can be seen that the metal doping does not change the structure of the carbon substrate itself, and there are no metal oxides or metal nanoparticles.

[0071] (2) Spherical aberration electron microscopy characterization

[0072] Spherical aberration electron microscopy images of a series of single-atom catalysts supported by carbon nitride are shown in Figure 2. Figure 2 As shown, the bright spots in the figure indicate that the metal is uniformly dispersed as single atoms in the carbon substrate and the surface single atom catalyst is successfully prepared.

[0073] (3) Inductively coupled atomic emission spectroscopy (ICP AES) test

[0074] The carbon substrate and single-atom catalysts Cu-SACs, Fe-SACs, Ni-SACs, and Co-SACs were thoroughly dissolved in nitric acid and then tested by inductively coupled atomic emission spectroscopy (ICP AES). The results showed that the contents of Cu, Fe, Ni, and Co were as high as 9.46wt.%, 7.32wt.%, 7.02wt.%, and 7.71wt.%, respectively. The materials obtained by a single synthesis are at the gram level, showing good application potential.

[0075] Example 2: Single-atom catalyst treatment of pollutants

[0076] 1. Phenol system water treatment

[0077] Prepare simulated sewage: dissolve the organic pollutant phenol (PhOH) in water to obtain simulated sewage (sewage volume 20 mL, PhOH dosage 0.5 mmol).

[0078] Water treatment process: The oxidant PMS (1.0 mmol) was added to simulated wastewater. The pH of the system was adjusted to 7.0 using H2SO4 solution / NaOH solution. The catalyst (1.0 g / L based on wastewater) was then added to initiate the reaction. During the reaction, 1 mL of sample solution was added to a 0.2 mL aqueous NaSO4 solution (200 mM) for quenching. After filtration through a 0.22 μm filter membrane, the PhOH concentration in the filtrate was determined by ultra-performance liquid chromatography (UPLC). Separate samples were taken at 0 and 30 minutes for determination of TOC.

[0079] The above tests were carried out using the carbon substrate and the series of single atoms supported by carbon nitride in Example 1 as catalysts (corresponding to the carbon substrate / PMS / PhOH system, Co-SACs / PMS / PhOH system, Fe-SACs / PMS / PhOH system, Ni-SACs / PMS / PhOH system, and Cu-SACs / PMS / PhOH system, respectively). The test results are shown in Figure 2. Figure 3 As shown ( Figure 3 The Fenton-like catalytic performance, TOC changes and calculated PT ratio are shown). Among them, PT ratio = TOC removal rate in solution / removal rate of target pollutants, and the PT effect is used to evaluate whether pollutants and TOC can be removed simultaneously. It can be seen that single-atom catalysts Cu-SACs, Fe-SACs, Ni-SACs, and Co-SACs can achieve the simultaneous removal of PhOH and TOC, with PT ratios of 99.3%, 44.9%, 98.0%, and 100.8%, respectively. Among them, the PT ratios of Co, Cu, and Ni systems are close to 100%, indicating that it is the same mechanism and is in line with the metal screening of PT technology, while the PT ratio of Fe system is only 44.9%, which means that Fe-SACs have other degradation pathways in addition to the PT pathway. From the perspective of degradation efficiency (see Figure 3 In the line graph, the lower the line within 30 min, the better the degradation efficiency), Co-SACs>Fe-SACs>Ni-SACs>Cu-SACs. Overall, the Co-SACs / PMS / PhOH system is most likely to be applied in practice. If the actual environmental toxicity is taken into consideration, the performance of Ni and Cu-SACs has room for improvement.

[0080] 2. Analysis of catalytic reaction pathways

[0081] Methanol and tert-butanol were added to the water treatment process described in Example 2 as free radical inhibitors, but they failed to inhibit the degradation of PhOH. Electron paramagnetic resonance (EPR) spectroscopy further eliminated the contribution of free radicals and singlet oxygen. Raman spectroscopy, probe analysis, and electrochemical methods also demonstrated that the system achieved the PT process via a non-free radical mechanism.

[0082] 3. Water treatment of 2,6-dimethylphenol system

[0083] The experiment was carried out in the same manner as in the first experiment above, except that the substrate phenol (PhOH) was replaced with 2,6-dimethylphenol (2,6-M-PhOH). These correspond to the Co-SACs / PMS / 2,6-M-PhOH system, the Ni-SACs / PMS / 2,6-M-PhOH system, the Fe-SACs / PMS / 2,6-M-PhOH system, and the Cu-SACs / PMS / 2,6-M-PhOH system, respectively.

[0084] Example 3: Collection and identification of polymerization products on the catalyst surface

[0085] 1. Elution and identification of Co-SACs / PMS / PhOH system

[0086] The PT process of the water treatment process in Example 2 achieves phase transfer of the pollutants, that is, the polymer is transferred from the dissolved state in the solution to the solid state and then to the catalyst surface. After the process of Example 2 is completed, an organic solvent is used to complete the elution of the polymer product and catalyst regeneration. The specific elution method is as follows: the catalyst after the reaction is filtered and dried, 10 mg is placed in a 5 mL centrifuge tube, 4 mL of organic solvent is added, and after sonication for 30 minutes, the solution is centrifuged at 15,000 rpm and the solution is collected. The solution now appears bright yellow. After repeating this operation several times, an organic solution of the polymer is obtained and directly measured by MALDI-TOF-MS. Alternatively, the polymer solid can be directly collected by drying the solvent.

[0087] According to the above method, different organic solvents (THMs, CAN, THF) were used to elute the Co-SACs / PMS / PhOH system in Example 2 and identify the polymerized product. The results are as follows: Figure 4 As shown in the figure, it can be seen that the elution effect of the phenol system wastewater using the organic solvent THF is the best, and the cross-linked polymerization product of PhOH (chain trimer) is observed. This is because PhOH has more active H.

[0088] 2. Elution and identification of TM-SACs / PMS / 2,6-M-PhOH system

[0089] The TM-SACs / PMS / 2,6-M-PhOH system (where TM = Cu, Fe, Ni, Co) in Example 2 was eluted using the organic solvent THF and the polymer product was identified. Figure 5 As shown in the figure, after the substrate was replaced with 2,6-M-PhOH (few active H atoms, tending to chain polymerization), polymer signals with a repeating unit close to 120 were observed in the eluted products in the TM-SACs system, indicating that the 2,6-M-PhOH (molecular weight of 122.1644, missing 2 H atoms during chain polymerization) in the solution was polymerized and transferred to the catalyst surface.

[0090] 3. Nuclear magnetic resonance (NMR) identification of eluted polymer

[0091] The solid polymers collected from each system in the above experiment 2 were subjected to nuclear magnetic resonance (NMR) tests with standard polyphenylene ether (PPO). The results are as follows: Figure 6 As shown, it can be seen that the peak signal of the collected solid is completely consistent with that of the standard, indicating that 2,6-M-PhOH in the sewage system is polymerized into PPO and transferred to the catalyst surface to achieve pollutant removal. PPO is one of the world's top five engineering plastics and has a wide range of application scenarios. The present invention can not only remove pollutants but also obtain valuable resources.

[0092] Example 4: Selection of metal species that induce PT process

[0093] In Example 2, it can be seen that the PT of the Fe system accounts for less than 50%. Figure 7 As a reference and basis for the selection of different single atoms, the changes in the partial density of states (PDOS) of the metal center during the reaction are shown. Figure 7 (a) shows the adsorption of PMS by TM-SACs. Figure 7 (b) shows that further reaction makes pollutants aggregate on the surface. Figure 7 As shown in the figure, after verification by theoretical calculations, we believe that metals with higher d-band centers (not close to the Fermi level, such as Cu, Ni, and Co) have suitable adsorption capabilities and are more likely to induce the PT process, while Fe has a lower d-band center and has a strong adsorption effect on O, especially on PMS. Raman analysis has shown that a PMS* complex is formed, which destroys the highly selective polymerization path brought about by the moderate oxidizing ability of the system and results in a low proportion of PT.

[0094] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that are not substantially different from the literal description of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A pollutant polymerization transfer water treatment process mediated by a single atom catalyst, characterized in that: include: Adding single-atom catalysts and oxidants to sewage to carry out oxidative polymerization reaction, thereby purifying the water; in, The oxidant is peroxymonosulfate and / or peroxydisulfate; The single-atom catalyst comprises a carrier and a single atom supported on the carrier; wherein the carrier is carbon nitride; the single atom is at least one of Cu, Fe, Ni and Co; The organic pollutants in the sewage include aromatic compounds containing electron-rich groups; The molar ratio of the oxidant to the organic pollutants in the sewage is (1-2):

1.

2. The water treatment process according to claim 1, characterized in that The electron-rich group is a hydroxyl group and / or an amino group.

3. The water treatment process according to claim 1 or 2, characterized in that: The aromatic compound includes at least one of phenol, 2,6-dimethylphenol and aniline.

4. The water treatment process according to claim 1, characterized in that: The temperature of the oxidative polymerization reaction is room temperature, and the time is ≤30 min.

5. The water treatment process according to claim 1, characterized in that: The pH value of the oxidative polymerization reaction is 2.0-10.

0.

6. The water treatment process according to claim 1, characterized in that: The dosage of the catalyst in sewage is 0.1-2.0 g / L.

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