Non-metallic catalyst, method for preparing the same, and catalytic system

Abstract

The application discloses a non-metallic catalyst and a preparation method and a catalytic system thereof, and the preparation method comprises the following steps: S1: dissolving cyanuric acid and xanthine in pure water to prepare a first solution; dissolving melamine in pure water to prepare a second solution; S2: stirring and mixing the first solution and the second solution under water bath conditions, and then performing centrifugation and drying to obtain a first product; S3: adding the first product into polytetrafluoroethylene dispersion liquid and pure water, and performing ultrasonic dispersion to obtain a third solution; S4: performing calcination on the third solution in a protective atmosphere, and performing grinding after cooling to obtain a second product; and S5: performing calcination on the second product in a protective atmosphere, and performing grinding after cooling to obtain the non-metallic catalyst. The non-metallic catalyst, the preparation method and the catalytic system thereof have the advantages of high performance, high stability, environmental friendliness and the like, and can realize carrier recycling and regeneration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and particularly relates to a non-metallic catalyst, a preparation method thereof and a catalytic system. BACKGROUND

[0002] With the acceleration of global urbanization and industrialization, water resource shortage and water pollution have become the core environmental problems restricting the sustainable development of society. The "new pollutants" containing pharmaceuticals, personal care products, endocrine disruptors and persistent organic pollutants, etc. have the characteristics of persistence, non-degradability and "three hazards" (mutagenicity, teratogenicity and carcinogenicity), which can cause irreversible damage to aquatic ecosystems and human health even at concentrations of nanograms to micrograms. In 2022, China issued the "New Pollutant Control Action Plan", which clearly requires deepening the research and development of end-of-pipe treatment technologies, and proposes urgent needs for technological innovation for efficient treatment of new pollutants.

[0003] The advanced oxidation process (PMS-AOP) based on persulfate (PMS) has become one of the mainstream technologies for degrading refractory organic matter, because it can generate highly active free radicals (such as SO4 - However, PMS-AOP has inherent limitations: the active species have a short lifetime (only microsecond to millisecond level), the mass transfer efficiency is low, and the nano-sized metal catalysts have leaching toxicity and are easy to be lost, resulting in rapid decay of catalytic efficiency; more importantly, once the metal catalysts supported on the porous carrier are deactivated (such as carbon deposition coverage, valence change or particle sintering), it is difficult to completely remove the nano-sized particles from the pores of the carrier, and high-temperature calcination can easily lead to further sintering of the metal particles, and acid washing can easily corrode the carrier structure, ultimately causing the porous carrier and the deactivated catalyst to be scrapped together, causing serious resource waste, and making it difficult for the entire catalytic system to operate stably for a long time.

[0004] To solve the defects of metal catalysts, non-metallic catalysts represented by graphite phase carbon nitride (g-C3N4) have attracted attention due to their environmental friendliness and natural advantages of no heavy metal dissolution. However, the existing non-metallic catalyst system has not broken through the performance bottleneck, and mainly has the following defects: first, the layered crystal structure forms a dense accumulation due to strong π-π stacking, and the specific surface area is limited. A large number of catalytically active sites (such as pyridine nitrogen and graphite nitrogen) are wrapped in the interlayer and cannot effectively contact the pollutants; second, the imbalance between surface hydrophobicity and acidity weakens the adsorption and capture ability of polar organic pollutants, which violates the basic principle of limited catalysis of "reactant enrichment-active site efficient collision"; third, it mainly relies on surface defect sites to initiate PMS activation reaction, and low defect density leads to low generation efficiency and short life of active species, and the catalytic activity is 2-3 orders of magnitude lower than that of Co, Fe and other metal catalysts; fourth, there is no targeted structure regulation method to improve the catalytic performance through functional group modification and defect engineering; fifth, the existing non-metallic catalysts lack effective methods for loading on porous carriers, and lack of supporting simple carrier regeneration process, further increasing the long-term operation cost of the catalytic system, restricting the sustainability of its industrialization promotion.

[0005] In summary, it is urgent to develop a non-metallic catalyst with high activity through precise structure regulation to break through the technical bottleneck of the existing technology and promote the industrial application of new pollution control technology.

[0006] The disclosure of the above background art content is only used to assist in understanding the concept and technical solutions of the present application, and it does not necessarily belong to the prior art of the present patent application. In the absence of explicit evidence that the above content has been disclosed before the filing date of the present patent application, the above background art should not be used to evaluate the novelty and inventiveness of the present application. SUMMARY

[0007] To solve the above technical problems, the present application provides a non-metallic catalyst, its preparation method and catalytic system, which has high performance, high stability, environmental friendliness and can realize carrier recycling and regeneration.

[0008] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application discloses a preparation method of a non-metallic catalyst, comprising the following steps:

[0010] S1: Dissolve cyanuric acid and xanthine in pure water to prepare a first solution; dissolve melamine in pure water to prepare a second solution;

[0011] S2: Stir and mix the first solution and the second solution under water bath condition, then centrifuge and dry to obtain a first product;

[0012] S3: adding the first product into a polytetrafluoroethylene dispersion liquid and pure water, and obtaining a third solution after ultrasonic dispersion;

[0013] S4: calcining the third solution in a protective atmosphere, and grinding after cooling to obtain a second product;

[0014] S5: calcining the second product in a protective atmosphere, and grinding after cooling to obtain a non-metallic catalyst.

[0015] Preferably, the molar ratio of cyanuric acid, xanthine and melamine in step S1 is (1-10):(1-5):(5-20).

[0016] Preferably, the step S2 of stirring and mixing the first solution and the second solution under water bath conditions specifically includes: ultrasonic treatment of the first solution and the second solution respectively, then adding the second solution into the first solution, and stirring in a constant temperature water bath at 25-60°C for 2-6h.

[0017] Preferably, the step S2 of centrifugation and drying specifically includes: transferring the mixed solution of stirring and mixing the first solution and the second solution under water bath conditions to a centrifuge tube, centrifuging at a speed of 5000-12000 rpm for 2-10 min to collect the bottom precipitate; then washing with pure water for 1-5 times and with anhydrous ethanol for 1-5 times, centrifuging at a speed of 5000-12000 rpm for 1-10 min after each washing, and finally drying the obtained precipitate in an oven at 45-70°C for more than 12h.

[0018] Preferably, step S3 specifically includes: adding (1-5)a g of the first product into (1-5)a mL of 40wt%-60wt% polytetrafluoroethylene dispersion liquid and (2-5)a mL of pure water, and obtaining a third solution after ultrasonic dispersion for 1-5h, wherein a is a scaling factor or a reference amount.

[0019] Preferably, step S4 specifically includes: placing the third solution in a heating device, heating from room temperature to 450-650°C at a rate of 5-15°C / min in a protective atmosphere, keeping for 1-5h, then naturally cooling to room temperature and grinding to obtain a second product.

[0020] Preferably, step S5 specifically includes: placing the second product in a heating device, heating from room temperature to 650-750°C at a rate of 5-15°C / min in a protective atmosphere, keeping for 1-5h, then naturally cooling to room temperature and grinding to obtain the non-metallic catalyst.

[0021] Preferably, the temperature rising from room temperature to 650-750℃ at a rate of 5-15℃ / min in the protection atmosphere in step S5 specifically comprises: filling the protection atmosphere into the heating device, controlling the flow of the protection atmosphere to be 50-100 mL / min, and then rising the temperature from room temperature to 450-650℃ at a rate of 5-15℃ / min after the air in the heating device is completely removed; closing the protection atmosphere inlet valve, and then continuing to rise the temperature to 650-750℃ at a rate of 5-15℃ / min.

[0022] Preferably, the protection atmosphere is nitrogen, argon or a mixture of ammonia and hydrogen.

[0023] In the second aspect, the application discloses a non-metallic catalyst prepared by the preparation method of the non-metallic catalyst.

[0024] In the third aspect, the application discloses a catalytic system formed by loading the non-metallic catalyst in the second aspect on a porous carrier.

[0025] Compared with the prior art, the application has the beneficial effects that: the preparation method of the non-metallic catalyst disclosed by the application successfully prepares a high-performance non-metallic catalyst with a unique ultra-thin nanosheet structure, multiple active sites (pyrrole nitrogen + nitrogen vacancy + F doping) and a non-free radical (singlet oxygen 1 O2) dominant reaction path through the synergy of "F doping and imidazole structure modification" and the process innovation of "two-step calcination", and the non-metallic characteristics of the non-metallic catalyst enable the deactivated catalyst to be completely removed from the carrier by simple high-temperature incineration, thereby realizing a revolutionary improvement in catalytic activity, stability and life cycle economy.

[0026] Further, the preparation method of the non-metallic catalyst of the application can prepare a high-activity non-metallic catalyst with the following effects:

[0027] (1) Rich and efficient active sites: through the synergy of F doping and imidazole structure modification, F atoms enhance the electronegativity and surface acidity of the material, the imidazole structure regulates the type of nitrogen atoms (increases the proportion of pyrrole nitrogen), and the secondary calcination process introduces a large number of nitrogen vacancy defects, which significantly improves the PMS activation efficiency, and achieves a removal rate of 96.7% of sulfisoxazole (SFX) in 30 s;

[0028] (2) Excellent adsorption-catalysis synergy: the catalyst is in the form of an ultra-thin nanosheet (thickness <50 nm), the sheet layers are staggered to form 20-100 nm nanopores, the specific surface area is significantly improved, and the surface acidity is optimized to enhance the adsorption capacity of polar pollutants, realizing efficient synergy of "adsorption-activation-degradation";

[0029] (3) Environmentally friendly and stable: the entire process uses non-metal raw materials, with no risk of heavy metal leaching;

[0030] (4) Strong controllability of preparation process: supramolecular self-assembly ensures uniformity of the precursor, two-step calcination process precisely regulates doping efficiency and defect density, and the heating device can control the atmosphere to avoid oxidation failure, facilitating large-scale production;

[0031] (5) Convenient carrier regeneration and high resource utilization rate: the catalyst can be conveniently loaded on a porous carrier (such as alumina-based ceramic), and when the catalyst is deactivated after long-term operation, only a simple high-temperature air calcination process is needed to completely remove the deactivated catalyst and pollutant residues on the surface and pores of the carrier. The carrier can be completely restored to its initial clean state and stable loading performance and can be recycled, avoiding the resource waste problem of "life binding" of the carrier and deactivated catalyst in traditional metal catalyst loading systems, significantly reducing long-term operation costs and improving the sustainability of technology industrialization.

[0032] Other benefits of the embodiments of the present application will be further described below. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a flow chart of the preparation method of the non-metallic catalyst disclosed in the preferred embodiments of the present application;

[0034] Figure 2 is an electron microscope image of the non-metallic catalyst prepared in the specific embodiments of the present application;

[0035] Figure 3 is a comparison chart of the effect of the non-metallic catalyst prepared in the specific embodiments of the present application and the non-metallic catalyst prepared in each comparative example on the degradation of sulfisoxazole;

[0036] Figure 4a is a schematic diagram of the detection of hydroxyl radicals in the PMS system activated by the non-metallic catalyst prepared in the specific embodiments of the present application;

[0037] Figure 4b is a schematic diagram of the detection of superoxide radicals in the PMS system activated by the non-metallic catalyst prepared in the specific embodiments of the present application;

[0038] Figure 4c is a schematic diagram of the detection of singlet oxygen in the PMS system activated by the non-metallic catalyst prepared in the specific embodiments of the present application;

[0039] Figure 5a is a schematic diagram of the pollutant removal rate of the non-metallic catalyst prepared in the specific embodiments of the present application and the control group;

[0040] Figure 5bis a schematic diagram of the results of the DPBF probe experiment of the PMS system activated by the non-metallic catalyst prepared by the specific embodiment of the present application;

[0041] Figure 6 is a schematic diagram of the regeneration feasibility of the porous structure carrier under the MPX system prepared by the specific embodiment of the present application. DETAILED DESCRIPTION

[0042] The embodiments of the present application are described in detail below. It should be emphasized that the following description is only exemplary, and is not intended to limit the scope of the present application and its applications.

[0043] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, the connection can be for fixing or for circuit / signal communication.

[0044] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0045] In addition, the terms "first", "second", "third", etc. are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0046] As shown in Figure 1 The preferred embodiment of the present application discloses a preparation method of a non-metallic catalyst, taking "F-doped + imidazole structure modified" graphite phase carbon nitride (g-C3N4) as the core, preparing a high-activity non-metallic catalyst through a supramolecular self-assembly-pyrolysis process, including the following steps:

[0047] S1: Dissolve cyanuric acid and xanthine in pure water to prepare a first solution; dissolve melamine in pure water to prepare a second solution;

[0048] The molar ratio of the cyanuric acid, the xanthine, and the melamine is (1-10):(1-5):(5-20).

[0049] S2: The first solution and the second solution are mixed under stirring in a water bath, and then centrifuged and dried to obtain a first product.

[0050] The step S2 specifically includes:

[0051] S21: The first solution and the second solution are respectively subjected to ultrasonic treatment, and then the second solution is added to the first solution, which is stirred in a constant-temperature water bath at 25-60°C for 2-6h.

[0052] S22: The mixture of the first solution and the second solution is transferred to a centrifuge tube, and centrifuged at a speed of 5000-12000rpm for 2-10min to collect the bottom precipitate.

[0053] S23: The bottom precipitate in the step S22 is washed with pure water for 1-5 times and with anhydrous ethanol for 1-5 times, and after each washing, it is centrifuged at a speed of 5000-12000rpm for 1-10min, and finally the obtained precipitate is dried in an oven at 45-70°C for 12h or more.

[0054] S3: The first product is added to a polytetrafluoroethylene dispersion liquid and pure water, and after ultrasonic dispersion, a third solution is obtained.

[0055] The (1-5)a g first product is added to (1-5)a mL 40wt%-60wt% polytetrafluoroethylene dispersion liquid and (2-5)a mL pure water, and after ultrasonic dispersion for 1-5h, the third solution is obtained, wherein a is a scaling factor or a reference amount, which only represents the proportion relationship between the first product, the polytetrafluoroethylene, and the pure water in this step.

[0056] S4: The third solution is calcined in a protective atmosphere, and after cooling, it is ground to obtain a second product.

[0057] The third solution is transferred to an alumina crucible, sealed, and placed in a tube furnace, and heated from room temperature to 450-650°C at a rate of 5-15°C / min in a protective atmosphere, and then naturally cooled to room temperature and ground to obtain the second product. The protective atmosphere is nitrogen, argon, or a mixture of ammonia and hydrogen.

[0058] S5: The second product is calcined in a protective atmosphere, and after cooling, it is ground to obtain a non-metallic catalyst.

[0059] The second product is transferred to an alumina crucible and placed in a tube furnace, and is heated at 5℃ / min~15℃ / min from room temperature to 650℃~750℃ in a protective atmosphere, and is kept for 1h~5h, and then is ground after natural cooling to room temperature to obtain a non-metallic catalyst. Further, heating at 5℃ / min~15℃ / min from room temperature to 650℃~750℃ in a protective atmosphere specifically includes: filling the tube furnace with a protective atmosphere, and controlling the flow of the protective atmosphere to be 50mL / min~100mL / min, and after completely removing the air in the tube furnace, heating at 5℃ / min~15℃ / min from room temperature to 450℃~650℃, closing the protective atmosphere inlet valve, and then continuing to heat at 5℃ / min~15℃ / min to 650℃~750℃. The protective atmosphere is nitrogen, argon, or a mixture of ammonia and hydrogen.

[0060] Another preferred embodiment of the present application discloses a non-metallic catalyst prepared by the above preparation method.

[0061] A preferred embodiment of the present application discloses a catalytic system formed by loading the above non-metallic catalyst on a porous carrier.

[0062] The non-metallic catalyst and the preparation method thereof have the following advantages:

[0063] (1) The dual regulation strategy of "F element doping + imidazole structure modification" is adopted to form a synergistic effect: (a) F doping takes PTFE as a precursor to generate HF in situ by pyrolysis to realize lattice doping, significantly enhancing the negative electrification and surface acidity of the material and regulating the electron transfer path; (b) the imidazole structure is introduced by xanthine to directionally increase the proportion of pyrrole nitrogen and optimize the active site type; (c) the synergistic effect of dual regulation makes the catalyst form a multi-activity site system of "pyridine nitrogen-pyrrole nitrogen-nitrogen vacancy", solving the bottleneck of single active site and low efficiency of traditional g-C3N4.

[0064] (2) Supramolecular self-assembly-two-step calcination process innovation, precise controllable structure regulation ability is obtained through process innovation: (a) Supramolecular precursor preparation link, using the hydrogen bond interaction of cyanuric acid and melamine, combined with the molecular guiding effect of xanthine, forming a uniform dispersion of precursor aggregates, laying the foundation for the uniformity of subsequent doping and modification; (b) The first calcination realizes the "F doping and g-C3N4 condensation at the same time", the in-situ reaction of HF generated by PTFE pyrolysis and supramolecular precursors avoids the uneven distribution problem caused by traditional post-doping; (c) The second calcination "self-pyrolysis atmosphere regulation" technology, by closing the protective atmosphere inlet valve (such as closing the nitrogen valve) and using CO, CH4, etc. generated by the pyrolysis of residual organic matter to form a local reducing-inert environment, directional generation of nitrogen vacancy, this process does not need to additional reduce gas, is the key innovation of defect regulation, need to clear the protection range of process parameters (heating rate, holding time, atmosphere switching node).

[0065] (3) Structure-performance coordinated morphology and active site innovation: (a) Morphology characteristics: ultrathin nanosheet structure (thickness <50 nm) and 20 nm~100 nm nanometer pore formation mechanism between the layers, this structure is realized by the coordination of F doping weakening interlayer van der Waals force and imidazole structure steric hindrance, significantly improving the specific surface area (3~5 times higher than traditional g-C3N4), further forming the unique structure of non-metallic catalyst to realize high performance; (b) Active site system: clear "pyrrole nitrogen + nitrogen vacancy + F doping site" ternary active site composition, among which pyrrole nitrogen improves electron transfer efficiency, nitrogen vacancy enhances PMS adsorption and activation ability, F doping site regulates surface acidity, and the three synergistically realize efficient connection of "adsorption-activation-degradation"; (c) Performance index: 96.7% removal rate of sulfonamidoxazole within 30 s.

[0066] (4) Carrier-catalyst separation and regeneration technology innovation: (a) Regeneration principle innovation: based on the non-metallic material characteristics of the catalyst, after deactivation, it can be completely decomposed into CO2, N2, etc. by high-temperature air calcination (600℃~650℃), without solid residue or lattice attachment, completely escaping from the pores of the porous carrier, solving the core pain point of "lifetime binding" of traditional metal catalyst and carrier; (b) Regeneration process innovation: the regeneration process does not need complex reagents (such as acid washing, alkali washing), only needs single high-temperature air atmosphere treatment, the process is simple and controllable, and does not corrode the carrier structure and destroy the porosity of the carrier; (c) Adaptability protection: the catalyst can be conveniently loaded on alumina-based ceramics, molecular sieves and other porous carriers, and the regeneration process is universal for various carriers.

[0067] The following further details the preparation method of the non-metallic catalyst disclosed in the preferred embodiments of the present application with specific examples.

[0068] A high-activity non-metallic catalyst is prepared by a supramolecular self-assembly-pyrolysis process with graphite phase carbon nitride (g-C3N4) doped with "F" and modified with an imidazole structure as a core. The specific steps and parameters for preparing the non-metallic catalyst (MPX) are as follows:

[0069] A1: Tricyanic acid (1 mmol~10 mmol), xanthine (1 mmol~5 mmol), and melamine (5 mmol~20 mmol) are selected as carbon and nitrogen sources, and 40wt%~60wt% polytetrafluoroethylene (PTFE) dispersion is used as the F source; ultrapure water is used as the solvent. Tricyanic acid and xanthine are dissolved in 50 mL~100 mL ultrapure water, and magnetic stirring is performed for 20 min~60 min until complete dissolution to obtain a first solution; melamine is dissolved in 50 mL~100 mL ultrapure water, and stirring is performed for 20 min~60 min to obtain a second solution.

[0070] A2: The first solution and the second solution are respectively subjected to ultrasonic treatment (power 1000~2000 W) for 20 min~60 min to ensure sufficient dispersion of the precursors; the second solution is slowly poured into the first solution, and vigorous stirring (rotational speed 800 rpm) is performed at 25℃~60℃ in a constant-temperature water bath for 2 h~6 h to form stable supramolecular aggregates by hydrogen bonding between tricyanic acid and melamine; the mixed solution is transferred to a centrifuge tube, and centrifugation is performed at a rotational speed of 5000 rpm~12000 rpm for 2 min~10 min to collect the precipitate at the bottom; the cycle of "ultrapure water cleaning 1~5 times + anhydrous ethanol cleaning 1~5 times" is adopted, and centrifugation (10000 rpm, 1 min~10 min) is performed after each cleaning; finally, the precipitate is placed in a 60℃ oven for drying for 12 h to obtain a first sample.

[0071] A3: 1g~5g of the first sample is taken, 2 mL~5 mL of ultrapure water and 1 mL~5 mL of 40wt%~60wt% PTFE solution are added, and ultrasonic dispersion (power 1000W~2000 W) is performed for 1h~5 h to obtain a third solution; the third solution is transferred to an alumina crucible, sealed with aluminum foil, and placed in a tube furnace, and pure nitrogen gas with a purity of 99.99% is used as a protective atmosphere, the temperature is increased from room temperature to 450℃~650℃ at a rate of 5℃ / min~15℃ / min, and the temperature is maintained for 1h~5 h (at this temperature, PTFE pyrolysis produces HF to realize in-situ doping of F, and xanthine promotes the conversion of pyridine nitrogen to pyrrole nitrogen; meanwhile, the supramolecular precursor is polycondensed into g-C3N4); after natural cooling to room temperature, grinding is performed to obtain a second sample.

[0072] A4: Take the ground second sample, transfer it to an alumina crucible, place it in a tube furnace, use 99.99% pure nitrogen as a protective atmosphere, control the nitrogen flow rate to 50 mL / min~100 mL / min, and after completely purging the air in the furnace, raise the temperature from room temperature to 450℃~750℃ at a rate of 5℃ / min~15℃ / min; when the temperature reaches 450℃~650℃, close the nitrogen inlet valve, and use the self-heating decomposition gas (mainly CO, CH4, N2, etc.) generated by the pyrolysis of the second sample to form a local reducing-inert atmosphere. Through the interaction between the self-heating decomposition gas and the catalyst lattice, promote the desorption and recombination of N atoms in g-C3N4, and directionally generate more nitrogen vacancies, edge unsaturated sites and other active defect structures; after reaching 650℃~750℃, hold for 1h~5h, then naturally cool to room temperature, and grind to obtain the final high-performance MPX. In MPX, M refers to melamine and cyanuric acid, P refers to polytetrafluoroethylene (PTFE), and X refers to xanthine. In this invention, MPX refers to a non-metallic catalyst prepared by the method of this invention.

[0073] The following provides further explanation of the performance testing of the non-metallic catalyst (MPX) prepared according to specific embodiments of the present invention.

[0074] (1) Description of the obtained electron microscope images

[0075] The morphology of the MPX prepared in the specific embodiments of this invention was characterized using a SU8010 scanning electron microscope (accelerating voltage 5.0 kV, magnification 50.0 k, scale bar 1.00 μm), as shown below. Figure 2 As shown, from Figure 2 It can be seen that the non-metallic catalyst exhibits an ultrathin, multi-level, loosely stacked nanosheet structure with a sheet thickness of <50 nm. The sheets are aggregated in a curled and interlaced dispersed state, without dense block agglomeration, and nanoscale pores of 20 nm to 100 nm are naturally formed between the sheets. This morphology is formed by the synergistic regulation of "F element doping + imidazole structure modification": the strong electronegativity of F atoms weakens the interlayer van der Waals forces of the graphitic carbon nitride matrix, while the steric hindrance of the imidazole structure further hinders the dense stacking of the sheets, ultimately leading to the characteristic structure of thin sheet-like loose aggregation. This structure provides the core support for the catalyst's high efficiency performance: on the one hand, it significantly increases the specific surface area, reserving sufficient sites for pollutant adsorption; on the other hand, the nanopores between the sheets construct an efficient mass transfer channel between "reactants and active sites," while the thin sheet structure can expose more surface defects and active groups, directly enhancing its PMS activation efficiency and pollutant degradation ability.

[0076] (2) The influence of the non-metallic catalyst on the degradation of sulfisoxazole (SFX) is explained

[0077] To explore the influence of the non-metallic catalyst prepared by the preparation method of the non-metallic catalyst provided in the specific embodiments of the present application on the degradation of sulfisoxazole (SFX), the present application also simultaneously provides the following examples and comparative examples for comparison:

[0078] Example 1: Preparation of MPX (melamine + cyanuric acid + PTFE + xanthine, tube furnace + nitrogen atmosphere + 650 DEG C + secondary calcination)

[0079] In this embodiment, the MPX is prepared by the steps of A1 to A4, wherein the first calcination in step A3 is performed by using a tube furnace to heat to 550 DEG C in a nitrogen atmosphere for heat preservation, and the second calcination in step A4 is performed by using a tube furnace to heat to 650 DEG C in a nitrogen atmosphere for heat preservation.

[0080] Comparative Example 1: Preparation of MX (melamine + cyanuric acid + xanthine, tube furnace + nitrogen atmosphere + 650 DEG C + secondary calcination)

[0081] The difference between the present comparative example 1 and the example 1 is that: in the present comparative example, no PTFE is added, and in step A3, the first sample is directly added into ultrapure water to prepare a third solution, and then the subsequent steps are performed, and the other steps are the same, which will not be repeated here.

[0082] Comparative Example 2: Preparation of MP (melamine + cyanuric acid + PTFE, tube furnace + nitrogen atmosphere + 650 DEG C + secondary calcination)

[0083] The difference between the present comparative example 2 and the example 1 is that: in the present comparative example, no xanthine is added, and in step A1, the cyanuric acid is directly dissolved in ultrapure water to obtain a first solution, and then the subsequent steps are performed, and the other steps are the same, which will not be repeated here.

[0084] Comparative Example 3: Preparation of MPX 550 / T (the same doping as example 1, tube furnace + nitrogen atmosphere + 550 DEG C + primary calcination)

[0085] The difference between the present comparative example 3 and the example 1 is that: the present comparative example does not include the second calcination step of step A4, and the second sample prepared after the first calcination (using a tube furnace to heat to 550 DEG C in a nitrogen atmosphere for heat preservation) of step A3 is directly used as the final non-metallic catalyst product.

[0086] Comparative Example 4: Preparation of MPX 550 / M (the same doping as example 1, muffle furnace + air atmosphere + 550 DEG C + primary calcination)

[0087] The difference between the present comparative example 4 and example 1 is that the present comparative example does not include the second calcination step of step A4, and directly takes the second sample prepared after the first calcination (using a muffle furnace to heat to 550°C in an air atmosphere for heat preservation) of step A3 as the final non-metallic catalyst product.

[0088] Comparative example 5: preparation of MPX 650 / M (same doping as example 1, muffle + air atmosphere + 650°C + secondary calcination)

[0089] The difference between the present comparative example 5 and example 1 is that the first calcination in step A3 of the present comparative example uses a muffle furnace to heat to 550°C in an air atmosphere for heat preservation, and the second calcination in step A4 uses a muffle furnace to heat to 650°C in an air atmosphere for heat preservation.

[0090] Under the condition of magnetic stirring (500 rpm), the effects of the above six catalysts, including example 1 and comparative examples 1 to 5, on the degradation performance of sulfisoxazole (SFX) were compared in a 50 mL reaction system (containing 5 mg / L SFX and 0.5 mM PMS). The experimental results show that, as shown in Figure 3 , the catalyst performance is jointly affected by element doping and preparation process. The performance of the MPX series catalysts containing both PTFE and xanthine is significantly better than that of MX and MP lacking any component, confirming the synergistic effect of the two in constructing active sites and surface structure. Under the same doping conditions, the MPX prepared by tube furnace + nitrogen atmosphere + 650°C + secondary calcination shows the best degradation efficiency, achieving a 96.7% removal rate of SFX in 30 s, which is significantly better than that of MPX 550 / T prepared by tube furnace + nitrogen atmosphere + 550°C + primary calcination and the corresponding sample prepared by muffle furnace, indicating that secondary calcination and controllable protective atmosphere are also crucial for forming a large number of active sites. The final formula of this embodiment is melamine-cyanuric acid-PTFE-xanthine, and the optimal process route is tube furnace + nitrogen atmosphere + 650°C + secondary calcination.

[0091] (3) EPR detection of active species based on quenching agent and correlation analysis

[0092] Electron paramagnetic resonance (EPR) technology can be used to detect the active species of the MPX activated PMS system combined with different trapping agents: hydroxyl radicals (•OH) use 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the trapping agent, superoxide radicals (O2• - ) use a combination of DMPO and dimethyl sulfoxide (DMSO) as the trapping agent, and singlet oxygen ( 1O2) with 2,2,6,6-tetramethylpiperidine (TEMP) as the trapping agent; 200 μL of the reaction solution (0.5 mM PMS + 0.1 g / L non-metallic catalyst) was taken and 10 μL of the trapping agent was added thereto, and the detection results were as shown in Figures 4a to 4c Figure; wherein, as shown in Figure 4a Figure, the MPX system in the •OH detection only showed weak characteristic fluctuation signals after being captured by DMPO, and the blank PMS system had almost no signal; as shown in Figure 4b Figure, the O2• - Figure, no characteristic signal peaks appeared in the MPX system in the O2• Figure 4c Figure, and 1 Figure, the MPX system in the O2 detection showed very strong characteristic triplet signals after being captured by TEMP, and the signal intensity was much higher than that of MP (preparation method as described in Comparative Example 2) and MX (preparation method as described in Comparative Example 1); thus, it can be determined that the dominant active species of the activated PMS of MPX is 1 O2, and only a small amount of hydroxyl radicals and almost no superoxide radicals are generated, which not only embodies the directional regulation effect of the “F doping + imidazole structure modification” double regulation on the PMS activation path, but also explains the core reason why MPX has the ability to rapidly degrade pollutants — compared with radicals that are easily quenched by water matrix, 1 O2 is more stable.

[0093] (4) Verification of the dominant active species

[0094] The dominant active species was verified by quenching experiments and 1,3-diphenylisobenzofuran (DPBF) probe experiments with “0.5 mM PMS + 0.1 g / L MPX + 5 ppm SFX” as the reaction system: in the quenching experiments, 100 mM methanol (quenching •OH), 100 mM chloroform (quenching O2• - ), and 20 mM furfuryl alcohol (FFA, quenching 1 O2) were added, respectively, and the pollutant removal rate was detected after 1 min, and the results were as shown in Figure 5a Figure, wherein the removal rate of the control group (without quenching agent) was close to 100%, the removal rates of the methanol (MeOH) and chloroform (CHCl3) groups did not decrease significantly, and the removal rate of the FFA group decreased sharply to about 30%, indicating that hydroxyl radicals and superoxide radicals were not the dominant active species of the system, and singlet oxygen ( 1O2) is the core driving force of degradation; the results of the DPBF probe experiment (system of MPX + 0.5 mM PMS) conducted simultaneously are as follows: Figure 5b As shown, the DPBF removal rate was monitored to increase rapidly over time, reaching nearly 100% in about 1.5 minutes, proving that a large amount of DPBF was continuously generated during the MPX activation of PMS. 1 O2; the quenching experiment and DPBF probe experiment in this embodiment, combined with the EPR detection results mentioned above, mutually corroborate each other, clarifying that the dominant active species for MPX activation of PMS is O2. 1 O2 further supports the technical logic that "the non-radical-dominated pathway is the core mechanism for the efficient degradation of MPX".

[0095] (5) Feasibility of regeneration of porous structure carriers in MPX system

[0096] Using an alumina crucible (a ceramic support) as the subject, the feasibility of regenerating porous supports in the MPX system was verified. During the experiment, the initial state was a clean white alumina crucible (…). Figure 6 The upper part of the crucible is used in the calcination preparation process of MPX (carrying the supramolecular precursor to complete the primary and secondary calcination pyrolysis reactions); after the reaction, the surface of the crucible is loaded with carbon-based residues generated during the catalyst preparation process, which appear dark black. Figure 6 (Middle); Subsequently, the black crucible was regenerated by placing it in a muffle furnace and heating it to 650°C at a rate of 10°C / min in air atmosphere, holding it at that temperature for 1 hour, thus achieving one-step regeneration of the ceramic carrier. After treatment, the crucible was restored to its initial clean white state. Figure 6 (below).

[0097] The results of this experiment show that MPX can be conveniently loaded onto the surface and pores of porous ceramic supports (such as alumina-based ceramics). The supported catalytic system constructed in this way can be stably applied to long-term, continuous pollutant degradation. When the MPX loaded on the support becomes deactivated, a simple high-temperature air calcination process can efficiently regenerate the support, restoring it to its initial clean state and stable carrying capacity. This characteristic reduces the cost of porous support materials and provides process support for the large-scale loading of MPX on various porous structures (such as ceramics and molecular sieves) and the recycling of supports, significantly improving the industrial economics and sustainability of the technology.

[0098] The background section of this invention may include background information about the problems or circumstances surrounding the invention, rather than a description of prior art by others. Therefore, the content included in the background section is not an admission of prior art by the applicant.

[0099] The above description is further to the present application in conjunction with specific / preferred embodiments, and cannot be deemed as limiting the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, they can make several substitutions or variations to the described embodiments, and these substitutions or variations shall be deemed as falling within the protection scope of the present application. In the description of the present application, the description of the terms "an embodiment", "some embodiments", "a preferred embodiment", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Furthermore, the skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction. Although the embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope defined by the appended claims.

Claims

1. A method for preparing a non-metallic catalyst, characterized by, The method comprises the following steps: S1: Dissolving cyanuric acid and xanthine in pure water to form a first solution; dissolving melamine in pure water to form a second solution, wherein the molar ratio of cyanuric acid, xanthine and melamine is (1-10):(1-5):(5-20); S2: Stirring and mixing the first solution and the second solution under water bath conditions, then centrifuging, drying to obtain a first product; S3: Adding the first product into polytetrafluoroethylene dispersion liquid and pure water, ultrasonic dispersion to obtain a third solution; S4: Calcining the third solution in a protective atmosphere, and after cooling, grinding to obtain a second product; Step S4 specifically comprises: placing the third solution in a heating device, heating from room temperature to 450-650°C at a rate of 5-15°C / min in a protective atmosphere, keeping for 1-5 hours, then naturally cooling to room temperature and grinding to obtain the second product; S5: Calcining the second product in a protective atmosphere, and after cooling, grinding to obtain the non-metallic catalyst; Step S5 specifically comprises: placing the second product in a heating device, heating from room temperature to 650-750°C at a rate of 5-15°C / min in a protective atmosphere, keeping for 1-5 hours, then naturally cooling to room temperature and grinding to obtain the non-metallic catalyst; Wherein, heating from room temperature to 650-750°C at a rate of 5-15°C / min in a protective atmosphere specifically comprises: filling the heating device with a protective atmosphere, controlling the flow of the protective atmosphere to be 50-100 mL / min, completely removing the air in the heating device, and then heating from room temperature to 450-650°C at a rate of 5-15°C / min, closing the protective atmosphere inlet valve, using the self-decomposition gas generated by the pyrolysis of the second product to form a local reduction-inert atmosphere, and generating nitrogen vacancies in a targeted manner, and then continuing to heat to 650-750°C at a rate of 5-15°C / min.

2. The method of claim 1, wherein the non-metallic catalyst is prepared by a process comprising: In step S2, stirring and mixing the first solution and the second solution under water bath conditions specifically comprises: ultrasonic treatment of the first solution and the second solution respectively, then adding the second solution into the first solution, and stirring in a constant temperature water bath at 25-60°C for 2-6 hours.

3. The method of claim 1, wherein the non-metallic catalyst is prepared by a process comprising: In step S2, centrifuging and drying specifically comprises: transferring the mixed solution of the first solution and the second solution stirred and mixed under water bath conditions to a centrifuge tube, centrifuging at a speed of 5000-12000 rpm for 2-10 minutes to collect the bottom precipitate; then washing the bottom precipitate with pure water 1-5 times and anhydrous ethanol 1-5 times, centrifuging at a speed of 5000-12000 rpm for 1-10 minutes after each washing, and finally drying the obtained precipitate in an oven at 45-70°C for more than 12 hours.

4. The method of preparing a non-metallic catalyst according to claim 1, characterized in that, The step S3 specifically comprises: adding (1~5)×a g of the first product into (1~5)×a mL of 40wt%-60wt% polytetrafluoroethylene dispersion liquid and (2~5)×a mL of pure water, and obtaining a third solution after ultrasonic dispersion for 1h-5h, wherein a is a scaling factor or a reference amount.

5. A non-metallic catalyst characterized by, The non-metallic catalyst is prepared by the method of any one of claims 1-4.

6. A catalyst characterized by, The non-metallic catalyst is formed by loading the non-metallic catalyst of claim 5 on a porous carrier.

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