Atomically dispersed metal supported on millimeter carbon sphere catalyst, preparation method thereof, and water treatment method and use thereof

Abstract

The present application relates to a kind of atomically dispersed metal loaded millimeter carbon ball catalyst, its preparation method and water treatment method and use.The present application uses single atom or double atom site as catalytic group, using the easy forming characteristics of alginic acid salt polymer, atomically dispersed metal loaded millimeter carbon ball is prepared.The catalyst of the present application has high catalytic activity and strong mechanical strength simultaneously and is easy to separate and recycle, is conducive to being widely used in water treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic materials and water treatment, in particular to a kind of atom dispersion metal loaded millimeter carbon ball catalyst and its preparation method and water treatment method induced by non-radical path from this catalyst and the use of this catalyst for organic matter degradation. BACKGROUND

[0002] Catalytic oxidation is a kind of efficient wastewater treatment technology, which can effectively remove refractory organic pollutants in water. In recent years, single-atom catalysts have attracted widespread attention in the field of catalytic oxidation due to their maximum metal atom utilization efficiency and excellent catalytic reaction activity. Double-atom catalytic sites have higher metal loading, more flexible metal active centers and synergistic effects between metal atoms, which have unique advantages in regulating reactant adsorption and reaction.

[0003] Patent document 1 (CN116826085A) discloses an iron-cobalt double-atom catalyst for redox reaction, which utilizes the structural characteristics of ZIF to encapsulate the nitrogen-rich molecular cobalt triethylenediamine complex in situ into the ZIF cage, introduces Fe into the ZIF framework, and obtains the iron-cobalt double-atom catalyst through high-temperature carbonization; the catalyst shows excellent catalytic activity in oxygen reduction activity test. Patent document 2 (CN117920299A) discloses a Fe-Ni / CN bimetallic single-atom catalyst based on nitrogen-doped carbon, which uses imidazole-based metal organic framework as carbon-based precursor carrier to anchor Fe-Ni species and nitrogen coordination. First, metal organic framework ZIF-8 is used as carbon precursor, and metal zinc is sublimated at high temperature through high-temperature calcination, forming a nitrogen-doped carbon CN substrate with vacancies. Nickel nitrate and iron nitrate are used as metal precursors and mixed with CN at high temperature to form a Fe-Ni-N6 coordinated bimetallic site single-atom catalyst with adjacent iron and nickel sites. The iron-nickel bimetallic site single-atom catalyst is used as a heterogeneous Fenton-like catalyst to activate peroxymonosulfate for the degradation of p-nitrophenol.

[0004] However, current single-atom or double-atom ozone catalysts are mostly in the form of nanometer or sub-micron scale, in the form of powder. Although powder catalysts have excellent mass transfer and reaction characteristics, their separation and recovery is a big problem. To promote the application of single-atom or double-atom catalysts in the field of environmental catalysis, macro-forming technology of single-atom or double-atom catalysts should be actively developed. SUMMARY

[0005] Problems to be solved by the application

[0006] In view of the above, it is necessary to provide a method that can macroscopically form single-atom or double-atom catalysts, thereby facilitating the separation and recovery of the catalyst and improving the mechanical strength of the catalyst.

[0007] Solutions for solving the problem

[0008] In the present application, single / diatomic (i.e. single atom or diatomic) powder catalyst or catalyst precursor is used as atomic dispersed metal site, polymer alginate is used as crosslinking agent, and the characteristics of good flowability and easy molding of alginate polymer are used to realize macro-molding of diatomic catalytic site, and diatomic-based millimeter carbon sphere catalyst with high catalytic activity and strong mechanical strength and easy separation and recovery is prepared. The catalyst catalyzes ozone process to efficiently and deeply treat landfill leachate, pharmaceutical wastewater, coal chemical wastewater and other various refractory organic wastewater.

[0009] Specifically, the present application provides an atomic dispersed metal loaded millimeter carbon sphere catalyst, wherein the catalyst takes carbon sphere as substrate, and single metal atom or double metal atom is loaded on the carbon sphere,

[0010] The loading amount of the single metal atom or double metal atom is 0.2wt%-2.0wt%.

[0011] According to the above-mentioned catalyst, the single metal atom or double metal atom is selected from one or two of Fe, Co, Mn, Cu and Ni; preferably, the double metal atom is Fe and Co.

[0012] When the catalyst is diatomic-based millimeter carbon sphere catalyst, the ratio of the loading amount of the two metal atoms is 1:2-2:1, preferably 1:1.

[0013] According to the above-mentioned catalyst, the compressive strength of the catalyst is 30N-70N.

[0014] The average particle size of the catalyst is 1mm-10mm.

[0015] The present application also provides a preparation method of the above-mentioned atomic dispersed metal loaded millimeter carbon sphere catalyst, which comprises the following steps:

[0016] Step S1: preparing single / diatomic-ZIF precursor;

[0017] Step S2: mixing the single / diatomic-ZIF precursor with alginate aqueous solution, so as to obtain a mixed solution;

[0018] Step S3: dropping the mixed solution obtained in step S2 into divalent or trivalent metal salt aqueous solution, and standing and washing, so as to obtain single / diatomic-ZIF@alginate hydrogel;

[0019] Step S4: drying and pyrolyzing the single / diatomic-ZIF@alginate hydrogel, so as to obtain atomic dispersed metal loaded millimeter carbon sphere catalyst.

[0020] According to the preparation method described above, wherein step S1 comprises: dissolving a mono / diatomic metal salt and a zinc salt in an alcohol solvent to obtain solution A, dissolving 2-methylimidazole in an alcohol solvent to obtain solution B, pouring solution A into solution B, and stirring, standing, separating, and drying to obtain a mono / diatomic-ZIF precursor;

[0021] In step S1, the molar ratio of the mono / diatomic metal salt to the zinc salt is (0.002-0.6):1, the molar ratio of the zinc salt to 2-methylimidazole is 1:(2-10), and the addition amount of the alcohol solvent relative to the zinc salt is (5-50) mL / mmol;

[0022] In step S2, the mass ratio of the mono / diatomic-ZIF precursor to the alginate is 1:1-15:1;

[0023] In step S3, the divalent or trivalent metal salt is selected from an organic metal salt and an inorganic metal salt;

[0024] The organic metal salt is selected from one or more of acetylacetone salt, acetate salt, cyclopentadiene salt, and citrate salt, and the inorganic metal salt is selected from one or more of nitrate, chloride, and sulfate;

[0025] When the divalent or trivalent metal salt is an organic metal salt, the mass ratio of the mono / diatomic-ZIF precursor to the organic metal salt is 1:10-1:1;

[0026] When the divalent or trivalent metal salt is an inorganic metal salt, the mass ratio of the mono / diatomic-ZIF precursor to the inorganic metal salt is 1:100-1:20;

[0027] In step S4, the pyrolysis temperature is 800-1200°C, and the time is 2-5 h.

[0028] The application further provides a method for water treatment using the atomic-level dispersed metal loaded millimeter carbon sphere catalyst described above or using the atomic-level dispersed metal loaded millimeter carbon sphere catalyst obtained by the preparation method described above,

[0029] The method utilizes the atomic-level dispersed metal loaded millimeter carbon sphere catalyst to decompose ozone to produce reactive oxygen species to degrade organic matter in water.

[0030] According to the method described above, wherein the dosage of the atomic-level dispersed metal loaded millimeter carbon sphere catalyst is 0.02-5 g / L, the concentration of the ozone is 2-20 mg / L, and the flow rate of the ozone is 0.1-2 L / min.

[0031] According to the method, the water comprises drinking water, municipal sewage, and organic wastewater, the treatment of the drinking water and the municipal sewage comprises deep reduction of organic matter and inactivation of pathogenic microorganisms.

[0032] According to the method, the organic wastewater comprises one or more of pharmaceutical wastewater, coal gasification wastewater, coal-to-olefin wastewater, landfill leachate, petrochemical wastewater, dyeing wastewater, and papermaking wastewater.

[0033] The application further provides a use of the atomically dispersed metal supported millimeter carbon sphere catalyst or the atomically dispersed metal supported millimeter carbon sphere catalyst obtained by the preparation method for degradation of organic matter,

[0034] wherein the atomically dispersed metal supported millimeter carbon sphere catalyst is used to decompose ozone to generate active oxygen species for degradation of organic matter.

[0035] Effects of the application

[0036] The above technical solution of the application has the following beneficial effects:

[0037] (1) The atomically dispersed metal supported carbon sphere catalyst of the application is millimeter-sized, macroscopically realizes powder catalyst, and the millimeter-sized catalyst has high catalytic activity, strong mechanical strength, and is convenient to separate and recover.

[0038] (2) The preparation method of the atomically dispersed metal supported millimeter carbon sphere catalyst is simple, safe, and low in cost, and is conducive to practical application.

[0039] (3) The atomically dispersed metal supported millimeter carbon sphere catalyst has excellent reaction activity in treatment of p-hydroxybenzoic acid, landfill leachate, pharmaceutical wastewater, coal gasification wastewater, and coal-to-olefin wastewater, and exhibits good deep treatment performance. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a schematic diagram showing that alginate polymer helps FeCo-ZIF to be formed.

[0041] Figure 2 is a diagram showing scanning electron microscope (SEM) photos of each precursor and each catalyst prepared in Examples 1 to 3 and Comparative Example 1.

[0042] Figure 3 is a diagram showing X-ray powder diffraction patterns of each precursor and each catalyst prepared in Examples 1 to 3 and Comparative Example 1, and a Raman spectrum of the catalyst.

[0043] Figure 4is a particle size distribution chart of FeCo diatomic-based millimeter carbon spheres.

[0044] Figure 5 is a chart showing the comparison of the compressive strength of FeCo millimeter carbon sphere precursors and FeCo millimeter carbon sphere catalysts in Example 3 with commercially available alumina.

[0045] Figure 6 is a chart showing the transmission electron microscopy (TEM) results of Co-NC catalysts.

[0046] Figure 7 is a high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) chart of Co-NC catalysts.

[0047] Figure 8 is a chart showing the transmission electron microscopy (TEM) results of FeCo-NC catalysts.

[0048] Figure 9 is a high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) chart of FeCo-NC catalysts.

[0049] Figure 10 is a chart showing the results of the catalytic ozonation of p-hydroxybenzoic acid by each catalyst prepared in Examples 1-3 and Comparative Example 1.

[0050] Figure 11 is a chart showing the results of the catalytic ozonation of landfill leachate by FeCo millimeter carbon sphere catalysts: (a) chemical oxygen demand (COD) change curve; (b) total organic carbon (TOC) removal effect; (c) reuse experiment.

[0051] Figure 12 is a chart showing the results of the catalytic ozonation of pharmaceutical wastewater by FeCo millimeter carbon sphere catalysts: (a) COD change curve; (b) TOC removal effect; (c) reuse experiment.

[0052] Figure 13 is a chart showing the results of the catalytic ozonation of coal gasification wastewater by FeCo millimeter carbon sphere catalysts: (a) COD change curve; (b) TOC removal effect.

[0053] Figure 14 is a chart showing the results of the catalytic ozonation of coal-to-olefin wastewater by FeCo millimeter carbon sphere catalysts: (a) COD change curve; (b) TOC removal effect; (c) reuse experiment. DETAILED DESCRIPTION

[0054] Embodiments of the present application will be described below, but the present application is not limited thereto. The present application is not limited to each configuration described below, and various changes can be made within the scope of the present application, and embodiments obtained by appropriately combining the technical means disclosed in each of the different embodiments and examples are also included in the technical scope of the present application. In addition, the documents cited in the present specification are all cited as reference documents in the present specification.

[0055] Unless otherwise defined, all technical and scientific terms used in the present specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0056] In the context of the present specification, and particularly in the context of the appended claims, the terms "a," "an," and "the" and similar referents are to be construed to cover both the singular and plural unless otherwise indicated by context or the contrary is clearly intended by the context. Thus, the terms "a" (or "an"), as well as the terms "the" and "said," can be construed to cover both singular and plural situations unless the context clearly indicates otherwise.

[0057] In the present specification, a numerical range indicated by "numerical value A to numerical value B" or "numerical value A - numerical value B" means a range including the end point values A, B.

[0058] In the present specification, the meaning indicated by "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process. In the present specification, "optional" or "optionally" means that the event or circumstance described next can occur or not occur, and the description includes the case where the event occurs and the case where the event does not occur.

[0059] In the present specification, the phrases "some specific / preferred embodiments," "other specific / preferred embodiments," "some specific / preferred technical solutions," "other specific / preferred technical solutions," and the like mean that the specific elements (for example, features, structures, properties, and / or characteristics) described in relation to the embodiments are included in at least one of the embodiments described herein, and can or can not be present in other embodiments. In addition, it should be understood that the described elements can be combined in various embodiments in any suitable manner.

[0060] The term "comprising" and its variants, such as "comprise" and "comprises," as used in the specification and claims of this application, are intended to mean "including but not limited to." For example, a process, method, or system, product, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements, but can optionally include additional steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0061] First aspect

[0062] The first aspect of the present application provides an atomic dispersed metal loaded millimeter carbon sphere catalyst. The catalyst of the present application takes carbon sphere as substrate, and has single metal atom or double metal atom loaded on the carbon sphere. The single metal atom or double metal atom can be selected from one or two of Fe, Co, Mn, Cu and Ni. In the atomic dispersed metal loaded millimeter carbon sphere catalyst of the present application, the loading amount of single atom or double atom is 0.2wt% to 1.0wt%.

[0063] Compared with single atom catalytic site, double atom catalytic site has higher metal loading amount, more flexible metal active center and synergistic effect between metal atoms, and has unique advantages in adjusting adsorption of reactants and reaction. Therefore, from the perspective of catalytic activity, double atom based millimeter carbon sphere catalyst is preferred. Among them, the double atom is preferably Fe and Co. In the double atom based millimeter carbon sphere catalyst, the ratio of the loading amount of the two metal atoms is not particularly limited, for example, can be 1:2 to 2:1, preferably 1:1.

[0064] The catalyst of the present application is millimeter level, and the average particle size is 1mm to 10mm, for example, can be 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 6mm, 7mm, 8mm, 9mm, etc. The average pore size of the catalyst can be 3nm to 5nm, for example, can be 3.5nm, 4.0nm, 4.5nm, etc.; the specific surface area can be 200m 2 / g to 400m 2 / g, for example, can be 250m 2 / g, 300m 2 / g, 350m 2 / g, etc.

[0065] In the packed bed reactor, the mechanical strength of the catalyst is crucial. The compressive strength of the atomic dispersed metal loaded millimeter carbon sphere catalyst of the present application can be 30N to 70N, for example, can be 35N, 40N, 45N, 50N, 55N, 60N, 65N, etc.

[0066] Second aspect

[0067] The second aspect of the present application relates to a preparation method of the catalyst. The preparation method of the atomic dispersed metal loaded millimeter carbon sphere catalyst of the present application comprises the following steps:

[0068] Step S1: preparing single / double atom-ZIF precursor;

[0069] Step S2: mixing the single / double atom-ZIF precursor with alginate aqueous solution, so as to obtain a mixed solution;

[0070] Step S3: drop the mixed solution obtained in step S2 into an aqueous solution of a divalent or trivalent metal salt, and perform standing and washing, thereby obtaining mono / diatomic-ZIF@alginate hydrogel;

[0071] Step S4: dry and pyrolyze the mono / diatomic-ZIF@alginate hydrogel, thereby obtaining an atomic-dispersed metal loaded millimeter carbon sphere catalyst.

[0072] The following will be described in detail.

[0073] Step S1

[0074] In step S1, first, mono / diatomic metal salt and zinc salt are dissolved in an alcohol solvent to obtain solution A, 2-methyl imidazole is dissolved in an alcohol solvent to obtain solution B, then solution A is quickly poured into solution B at normal temperature and pressure, and stirring, standing, separation and drying are performed, thereby obtaining mono / diatomic-ZIF precursor.

[0075] The mono / diatomic metal salt can be nitrate, chloride, acetylacetone salt, etc. For example, when the mono / diatomic atom contains iron, acetylacetone iron can be used; when the mono / diatomic atom contains cobalt, cobalt nitrate can be used; when the mono / diatomic atom contains nickel, nickel nitrate can be used.

[0076] The above-mentioned zinc salt can be zinc nitrate, zinc chloride, etc. The above-mentioned alcohol solvent can be methanol, ethanol, propanol, etc. The alcohol solvent used for solution A and solution B can be the same or different, preferably the same.

[0077] In the present application, the molar ratio of mono / diatomic metal salt to zinc salt can be (0.002-0.6):1, and further preferably (0.02-0.5):1. If the amount of zinc salt is too large, it will not be able to disperse the transition metal well, and the transition metal particles in the catalyst will have a tendency to agglomerate. The molar ratio of zinc salt to 2-methyl imidazole is 1:(2-10), and further preferably 1:(5-9); the amount of solvent added relative to the zinc salt is (5-50)mL / mmol, and further preferably (10-30)mL / mmol. When the amount of solvent is too low, it is difficult to synthesize porous crystals, and when the amount of solvent is too large, the synthesized catalyst has a tendency to agglomerate.

[0078] After solution A is poured into solution B, the stirring time can be 0.5-2h, and the standing time can be 12-36h. After standing, the precipitate can be recovered by centrifugal separation, then washed with an alcohol solvent 3 times, and dried in an oven at 50-70℃ for 10-15h, thereby obtaining a powder-like mono / diatomic-ZIF precursor.

[0079] Step S2

[0080] In step S2, first, an aqueous alginate solution is prepared, then the mono / diatomic-ZIF precursor obtained in step S1 is added to the solution, and then stirring is performed for 12-36 h to allow the precursor to be sufficiently dispersed to form a uniform mixture.

[0081] The alginate used in the present application can be sodium alginate, potassium alginate, etc. The concentration of the aqueous alginate solution is not particularly limited, and can be, for example, 1-5 wt%. In the present application, the mass ratio of the mono / diatomic-ZIF precursor to the alginate can be 5:1-15:1, and can be, for example, 8:1, 10:1, 12:1, etc.

[0082] Step S3

[0083] In step S3, first, an aqueous divalent or trivalent metal salt solution is prepared, then the mixed solution obtained in step S2 is added dropwise to the aqueous divalent or trivalent metal salt solution by means of a peristaltic pump, and left to stand for 12-36 h to allow the alginate to be sufficiently crosslinked with the metal ions. Then, the product is washed with deionized water several times to obtain a mono / diatomic-ZIF@alginate hydrogel.

[0084] The divalent or trivalent metal salt used in step S3 can be selected from one or more of organic metal salts and inorganic metal salts. The organic metal salt can be selected from one or more of acetylacetone salts, acetate salts, cyclopentadienyl salts, citrate salts, and the inorganic metal salt can be selected from one or more of nitrate salts, chloride salts, sulfate salts. For example, when the divalent or trivalent metal salt is a zinc salt, zinc acetate, zinc nitrate, zinc chloride, etc. can be used, which can be the same as or different from the zinc salt used in step S1, and is preferably the same. The concentration of the aqueous divalent or trivalent metal salt solution is not particularly limited, and can be, for example, 1-5 wt%.

[0085] When the divalent or trivalent metal salt is an organic metal salt, the mass ratio of the mono / diatomic-ZIF precursor to the organic metal salt can be 1:10-1:1, and can be, for example, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, etc. When the divalent or trivalent metal salt is an inorganic metal salt, the mass ratio of the mono / diatomic-ZIF precursor to the inorganic metal salt can be 1:100-1:20, and can be, for example, 1:90, 1:80, 1:70, 1:60, 1:50, 1:40, 1:30, etc.

[0086] Sodium alginate is a natural high molecular polysaccharide, and the basic structural unit is β-D-mannuronic acid (M) and α-L-guluronic acid (G), which are C5 epimers. The basic unit is connected into alginate polymer through 1-4 bond. The alginate contains rich hydroxyl and carboxyl groups, which can be chelated with divalent or multivalent metal ions to form millimeter alginate hydrogel. The powder catalyst or catalyst precursor is mixed with the alginate solution, and the powder catalyst can be macroscopically realized by cross-linking. In the application, the good flowability and easy molding characteristics of alginate polymer are utilized to realize the macro-molding of monoatomic / diatomic-ZIF precursor.

[0087] Figure 1 The schematic diagram of alginate polymer assisting FeCo-ZIF molding is shown in FIG. 1. From the figure, it can be seen that the alginate solution containing FeCo-ZIF is dropped into the Zn Figure 1 solution, and the alginate is cross-linked with zinc ions to form a hydrogel. 2+

[0088] Step S4

[0089] In step S4, the monoatomic / diatomic-ZIF@alginate hydrogel is dried to obtain the precursor of monoatomic / diatomic millimeter carbon sphere; and the monoatomic / diatomic millimeter carbon sphere catalyst can be obtained after pyrolysis of the monoatomic / diatomic millimeter carbon sphere precursor. The pyrolysis temperature can be 800℃-1200℃, and the time can be 2-5h. For example, the pyrolysis temperature can be 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, etc.

[0090] The above drying can be vacuum freeze drying or oven drying. When vacuum freeze drying is used, the drying temperature can be-70℃--40℃; when oven drying is used, the drying temperature can be 50℃-100℃. The drying time can be 12-24h.

[0091] Third aspect

[0092] The third aspect of the application provides a method for water treatment using the atomic-level dispersed metal loaded millimeter carbon sphere catalyst in the first aspect or using the atomic-level dispersed metal loaded millimeter carbon sphere catalyst obtained by the preparation method in the second aspect, which utilizes the atomic-level dispersed metal loaded millimeter carbon sphere catalyst to decompose ozone to produce reactive oxygen species to degrade organic matter in water.

[0093] ​Ozone (O3) as a strong oxidant, can effectively remove phenol, cyanide, sulfide, pesticides, oil and other pollutants in wastewater. Usually ozone catalytic oxidation technology is through the catalyst to activate the decomposition of ozone to produce hydroxyl radicals, using hydroxyl radicals to remove refractory organic matter. In the present application, the atomic dispersion metal supported carbon sphere catalyst can decompose ozone to produce reactive oxygen species, such as surface adsorption atomic oxygen and singlet oxygen, which can effectively degrade refractory organic matter.

[0094] In some embodiments of the present application, the atomic dispersion metal supported carbon sphere catalyst of the present application is used to decompose ozone to produce surface adsorption atomic oxygen and / or singlet oxygen, rather than hydroxyl radicals, in different environments. Compared with the traditional hydroxyl radical reaction process, the non-radical process dominated by surface adsorption atomic oxygen and singlet oxygen shows strong anti-interference performance to impurities in water, such as anions, and has potential advantages for the treatment of actual complex wastewater.

[0095] In the case of monatomic-based carbon sphere catalyst, molecular dynamics analysis shows that ozone is decomposed at the metal atom-N4 active site on the surface of the monatomic catalyst. One end of the oxygen atom in ozone is combined with the metal atom of the metal atom-N4 group, and then the near-surface oxygen-oxygen bond in ozone is elongated and broken, producing surface adsorption atomic oxygen *O ad and superoxide anion radical O2 ·- , and the superoxide anion radical is further disproportionated into singlet oxygen 1 O2.

[0096] In the case of diatomic-based carbon sphere catalyst, molecular dynamics analysis shows that in addition to the metal atom-N4 monatomic coordination structure, there is also a diatomic coordination structure of double metal atom-N6. In the first step of catalyzing ozone reaction at the diatomic atom-N6 site, surface adsorption atomic oxygen *O ad is produced, and in the second step, active oxygen species singlet oxygen 1 O2 is directly produced. The product of the second step of catalyzing ozone is obviously different from that of the monatomic catalyst. As described above, in the monatomic catalyst ozone system, the product of decomposing ozone is mainly superoxide anion radical O2 ·- , and the disproportionation process of O2 ·- is the main way to produce 1 O2, while in the diatomic site, due to the synergistic effect of the diatomic center, the surface electron transfer ability is greatly improved, and O2 1 can be directly produced by surface single electron transfer process. Although O2 ·- is not detected in the theoretical simulation reaction path of the diatomic site catalyzing ozone, O2 ·-The signal of the double-atom catalyst is obviously higher than that of the single-atom catalytic ozone system, indicating that the single-atom sites on the surface of the double-atom catalyst also play an important role in the generation of active oxygen species and the degradation of organic pollutants.

[0097] In addition, it is proved by the calculation of adsorption energy that the sites with double-atom coordination structure have obvious advantages over the sites with single-atom coordination structure in terms of small molecule substances such as ozone and pollutants. Ozone adsorption is the first step of the ozone catalytic oxidation chain reaction, and the sites with double-atom coordination structure have stronger adsorption capacity for ozone molecules and pollutants. Stronger adsorption can strengthen the mass transfer process of pollutants, thus being beneficial to the degradation of pollutants on the catalyst surface / interface.

[0098] In a specific embodiment of the water treatment method, the atomically dispersed metal supported carbon sphere catalyst is filled into a reactor, ozone and water to be treated are introduced, and the organic matter in the water is degraded. In order to take into account the degradation effect and cost, the dosage of the atomically dispersed metal supported carbon sphere catalyst is preferably 0.02-5 g / L, further preferably 0.04-2 g / L, and more further 0.05-0.5 g / L, the concentration of ozone is 2-20 mg / L, further 3-20 mg / L, and the flow rate of ozone is 0.1-2 L / min, further 0.2-1 L / min.

[0099] The water to be treated of the present application includes domestic or industrial organic wastewater or drinking water, and more further, the organic wastewater includes one or more of pharmaceutical wastewater, coal gasification wastewater, coal olefin wastewater, landfill leachate, petroleum chemical wastewater, printing and dyeing wastewater, and papermaking wastewater. The present application can effectively degrade and remove the refractory organic matter in the water to be treated at normal temperature and pressure, i.e. without additional heating and pressurization of the reactor, a high organic matter removal efficiency can be achieved, and the present application has potential advantages in the advanced treatment of complex actual wastewater.

[0100] Fourth aspect

[0101] The fourth aspect of the present application provides the use of the atomically dispersed metal supported millimeter carbon sphere catalyst described above or the atomically dispersed metal supported millimeter carbon sphere catalyst obtained by the preparation method described above for organic matter degradation, wherein the atomically dispersed metal supported millimeter carbon sphere catalyst is used to decompose ozone to generate active oxygen species for degrading organic matter.

[0102] In some preferred embodiments of the present application, the active oxygen species are selected from one or both of surface adsorbed atomic oxygen and singlet oxygen.

[0103] The organic matter herein mainly refers to refractory organic matter, which generally includes polycyclic aromatic compounds, heterocyclic compounds, chlorinated aromatic compounds, organic cyanides, drugs, pesticides, etc.

[0104] In some preferred embodiments of the present application, the removal rate of organic matter by the atomically dispersed metal loaded millimeter carbon sphere catalyst ozone system of the present application is more than twice that of the ozone system alone for actual wastewater advanced treatment. Therefore, the atomically dispersed metal loaded millimeter carbon sphere catalyst of the present application has superior reaction activity in the ozone catalytic oxidation advanced water purification process.

[0105] Examples

[0106] The embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. If no specific conditions are indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagents or instruments used is indicated, it is a conventional product that can be obtained by purchase on the market.

[0107] Example 1

[0108] Take 2.96 g of zinc nitrate hexahydrate and 4 mmol of iron acetylacetonate, dissolve them in 100 mL of methanol to obtain solution A. Take 6.56 g of 2-methylimidazole, dissolve it in 100 mL of methanol by room temperature stirring to obtain solution B. Under normal temperature and pressure, quickly pour solution A into solution B, continue stirring for 1 h, and then stand for 24 h. Centrifugally recover the precipitate, and wash it with methanol for 3 times, and then air dry for 12 h to obtain the Fe-ZIF-8 precursor.

[0109] Place the Fe-ZIF-8 precursor in a tube furnace, heat it to 1000℃ at a rate of 5℃ / min under the protection of argon atmosphere, and keep the temperature for 3 h of calcination, during which the metal zinc species evaporates; take it out after natural cooling to room temperature to obtain the Fe-NC catalyst.

[0110] Take 1 g of sodium alginate and add it to 50 mL of water to prepare a 2wt% sodium alginate aqueous solution. The sodium alginate (Macklin) used has an AR grade purity and a M to G unit ratio of 1:1. Add 10 g of Fe-ZIF precursor to the sodium alginate aqueous solution and stir for 24 h to form a uniform mixture. Drop the sodium alginate solution containing the Fe-ZIF precursor into a 2wt% zinc chloride aqueous solution at a pump rate of 5 mL / min by using a peristaltic pump, and stand for 24 h to allow the alginate to crosslink with the zinc ions. Then wash it with deionized water for multiple times to obtain the Fe-ZIF@alginate hydrogel. Dry the Fe-ZIF@alginate hydrogel in an oven at 60℃ for 24 h to obtain the precursor of Fe millimeter carbon spheres, and then pyrolyze it at 1000℃ for 3 h to obtain the Fe atom-based millimeter carbon sphere catalyst.

[0111] Example 2

[0112] Take 2.96 g of zinc nitrate hexahydrate and 0.1 mmol of cobalt nitrate hexahydrate, dissolve them in 100 mL of methanol to obtain solution A. Take 6.56 g of 2-methylimidazole, dissolve it in 100 mL of methanol by room temperature stirring to obtain solution B. Under normal temperature and pressure, quickly pour solution A into solution B, continue stirring for 1 h, then stand for 24 h. Centrifugal recovery of the precipitate, and washed with methanol 3 times, natural air dry 12 h to obtain Co-ZIF-8 precursor.

[0113] Put the Co-ZIF-8 precursor into a tube furnace, under the protection of argon atmosphere, heat to 1000℃ at 5℃ / min, keep the temperature for 3h, the metal zinc species evaporates in the pyrolysis process; take it out after natural cooling to room temperature, obtain Co-NC catalyst.

[0114] Take 1 g of sodium alginate and add it to 50 mL of water to prepare a 2wt% sodium alginate aqueous solution. The sodium alginate (Macklin) used has a purity of AR grade and a M to G unit ratio of 1:1. Add 10 g of Co-ZIF precursor to the sodium alginate aqueous solution and stir for 24 h to form a uniform mixture. Use a peristaltic pump to drop the sodium alginate solution containing the Co-ZIF precursor into a 2wt% zinc chloride aqueous solution at a pump rate of 5 mL / min. Allow the sodium alginate and zinc ions to crosslink fully by standing for 24 h, then wash with deionized water several times to obtain a Co-ZIF@alginate hydrogel. Dry the Co-ZIF@alginate hydrogel in an oven at 60℃ for 24 h to obtain the precursor of Co-millimeter carbon spheres, which can be obtained by pyrolysis at 1000℃ for 3 h.

[0115] Example 3

[0116] Take 2.96 g of zinc nitrate hexahydrate, 4 mmol of iron acetylacetone, and 0.1 mmol of cobalt nitrate hexahydrate, dissolve them in 100 mL of methanol to obtain solution A. Take 6.56 g of 2-methylimidazole, dissolve it in 100 mL of methanol by room temperature stirring to obtain solution B. Under normal temperature and pressure, quickly pour solution A into solution B, continue stirring for 1 h, then stand for 24 h. Centrifugal recovery of the precipitate, and washed with methanol 3 times, natural air dry 12 h to obtain FeCo-ZIF-8 precursor.

[0117] Put the FeCo-ZIF-8 precursor into a tube furnace, under the protection of argon atmosphere, heat to 1000℃ at 5℃ / min, keep the temperature for 3h, the metal zinc species evaporates in the pyrolysis process; take it out after natural cooling to room temperature, obtain FeCo-NC catalyst.

[0118] Take 1 g of sodium alginate and add it to 50 mL of water to prepare a 2 wt% sodium alginate solution. The sodium alginate used (Macklin) has a purity of AR grade and a M to G unit ratio of 1:1. Add 10 g of FeCo-ZIF precursor to the sodium alginate solution and stir for 24 h to allow the precursor to disperse evenly and form a uniform mixture. Use a peristaltic pump to drop the sodium alginate solution containing the FeCo-ZIF precursor into a 2 wt% zinc chloride solution at a pump rate of 5 mL / min. Allow the alginate and zinc ions to crosslink fully by standing for 24 h, then wash with deionized water several times to obtain the FeCo-ZIF@alginate hydrogel. Dry the FeCo-ZIF@alginate hydrogel in an oven at 60°C for 24 h to obtain the precursor of the FeCo millimeter carbon sphere, and then pyrolyze at 1000°C for 3 h to obtain the FeCo bimetallic millimeter carbon sphere catalyst.

[0119] Comparative Example 1

[0120] Take 2.96 g of zinc nitrate hexahydrate and dissolve it in 100 mL of methanol to obtain solution A. Take 6.56 g of 2-methylimidazole and dissolve it in 100 mL of methanol by stirring at room temperature to obtain solution B. Pour solution A into solution B quickly under normal temperature and pressure, continue stirring for 1 h, then stand for 24 h. Centrifuge to recover the precipitate and wash it with methanol 3 times, then air dry for 12 h to obtain the ZIF-8 precursor.

[0121] Place the ZIF-8 precursor in a tube furnace and heat it to 1000°C at a rate of 5°C / min under an argon atmosphere, and maintain the temperature for 3 h of calcination. During pyrolysis, the zinc metal species evaporates. After natural cooling to room temperature, remove the sample to obtain the NC catalyst.

[0122] Catalyst characterisation

[0123] Surface morphology: SEM (Zessi Gemini SEM 500) was used to take SEM images of the catalyst. TEM (JEOL-2010F) equipped with an energy dispersive spectrometer (EDS, INCA-IET 200) was used to take TEM images, high-resolution TEM (HRTEM) images, and EDS images. FEI Titan 80-300 instrument was used to take high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images.

[0124] Physicochemical properties: The crystal structure of the catalyst was analyzed by X-ray diffractometer (XRD, Rigaku D / max-2500 / PC). The degree of graphitization of carbon in the catalyst was analyzed by Raman spectrometer (HR800). The specific surface area and pore size of the catalyst were analyzed by nitrogen adsorption-desorption instrument (Quantachrome). The surface elements and valence states of the catalyst were analyzed by X-ray photoelectron spectrometer (XPS, ThermoFisher 250XI). The Zeta potential of the catalyst at different pH was recorded by Zeta potential instrument (Delsa Nano C, Beckman Coulter), and the isoelectric point of the catalyst was calculated. The loading amount of metal in the catalyst was analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES, Thermo Fisher iCAP7400). The electrochemical characterization of the catalyst was determined by electrochemical workstation (Autolab PGSTAT-128N), in which the rotating disc electrode (RDE) was the working electrode, the Ag / AgCl electrode was the reference electrode, the platinum wire was the counter electrode, and the electrolyte was 0.05M sodium sulfate solution.

[0125] The SEM photos of the Fe-ZIF-8 precursor, the Co-ZIF-8 precursor, the FeCo-ZIF-8 precursor obtained in Examples 1-3 and the ZIF-8 precursor in Comparative Example 1 are shown in Figure 2 (a)-(d). The ZIF-8 nanoparticles without FeCo doping are small and have a tendency to agglomerate. When the iron source is introduced, the Fe-ZIF-8 precursor particles become significantly larger, have better dispersibility, and have a regular rhombohedron dodecahedron shape. The Co-ZIF-8 particles are still small, which may be related to the small amount of cobalt source added during preparation, which has less effect on the growth of ZIF-8 crystals. When the iron source and the cobalt source are present at the same time, the FeCo-ZIF-8 precursor also has good dispersibility and a regular rhombohedron dodecahedron morphology.

[0126] Figure 3 The XRD characterization results of the precursors are shown in Table 1. As shown in Figure 3 (a), the Fe-ZIF-8 precursor, the Co-ZIF-8 precursor, the FeCo-ZIF-8 precursor and the ZIF-8 precursor all have good crystal structures, which are basically consistent with the simulated ZIF-8 diffraction peaks.

[0127] The SEM photos of the catalysts obtained after pyrolysis are shown in Figure 2(e)-(f). After pyrolysis, NC and Co-NC obviously agglomerated, while Fe-NC and FeCo-NC still maintained the morphology of rhombic dodecahedron with good dispersibility, but the surface became rough. Meanwhile, in the XRD spectra of all catalysts, only two broad diffraction peaks at 24° and 44° corresponding to the (002) and (100) crystal planes of the graphite carbon skeleton (JCPDS #75-1621) were detected, and no diffraction peaks of any iron species or cobalt species were detected (see Figure 3 (b)). Due to the catalytic graphitization of transition metals, the Raman characterization results (see Figure 3 (c)) showed that the degree of graphitization of the carbon skeleton in FeCo-NC was improved after the introduction of iron and cobalt sources. In the Raman spectra, D and G band scattering peaks were detected in all catalysts, which were peaks of the carbon skeleton, and the peak intensity ratio of D and G bands was negatively correlated with the degree of graphitization of the carbon skeleton. The results showed that the D and G band intensity ratios of NC, Fe-NC, Co-NC and FeCo-NC catalysts were 1.11, 1.07, 1.09 and 1.06, respectively, and FeCo-NC had a lower peak intensity ratio, and the degree of graphitization of the carbon skeleton was higher.

[0128] The particle size distribution of the FeCo biatomic-based millimeter carbon spheres obtained in Example 3 can be seen in Figure 4 . As shown in Figure 4 , the average particle size of the FeCo biatomic-based millimeter carbon spheres was about 2.4 mm. In addition, nitrogen adsorption-desorption experiments were performed on the FeCo biatomic-based millimeter carbon spheres, and the results showed that the pore structure was mainly microporous, the average pore size was about 4.5 nm, and the specific surface area was 235 m 2 / g.

[0129] In addition, in the present application, alumina pellets with a particle size similar to that of the FeCo biatomic-based millimeter carbon spheres were selected as controls to evaluate the compressive strength of the FeCo millimeter carbon spheres and their precursors obtained in Example 3, and the results are shown in Figure 5 . As shown in Figure 5 , the compressive strength of the alumina pellets of about 3 mm was about 70 N; the compressive strength of the FeCo millimeter carbon sphere precursor obtained after drying the FeCo-ZIF@alginate hydrogel was about 56 N; and the compressive strength of the FeCo millimeter carbon catalyst prepared after pyrolysis was about 53 N.

[0130] The TEM characterization results of the Co-NC catalyst obtained in Example 2 are shown in Figure 6 . As shown in the left graph in Figure 6 , the Co-NC catalyst agglomerated, and the particle size was about 300 nm. As shown in Figure 6TEM dark field image and EDS mapping results show that Co and N are dispersed on the surface of carbon skeleton, as shown in the right image of FIG. 1. Further, the FeCo-NC catalyst was photographed by using spherical aberration electron microscopy (HAADF-STEM) to characterize the existing form of cobalt species. The HAADF-STEM image (FIG. 2) confirms that the cobalt species in the FeCo-NC catalyst is in the form of single atom. Figure 7

[0131] The TEM characterization results of the FeCo-NC catalyst of Example 3 are shown in FIG. 3. As shown in FIG. 3(a), the FeCo-NC catalyst is well dispersed, and the size of a single particle is about 300 nm or so. As shown in FIG. 3(b) and the right image, the TEM dark field image and EDS mapping results show that Fe, Co and N are uniformly dispersed on the surface of the carbon skeleton, and no nanoparticles are observed on the carbon substrate. Therefore, it is speculated that the iron species and the cobalt species in the FeCo-NC catalyst may be in an atomic dispersion state. Further, the FeCo-NC catalyst was photographed by using spherical aberration electron microscopy (HAADF-STEM) to characterize the existing form of iron species and cobalt species. The HAADF-STEM image (FIG. 3) confirms that the iron species and the cobalt species in the FeCo-NC catalyst are in the form of single atom (highlighted by a red circle) or double atom (highlighted by a yellow frame). Figure 8 Figure 8 Figure 8 Figure 9 (Instruments and Experimental Methods)

[0132] Performance testing Chemical oxygen demand (COD): detected by using a water quality multi-parameter measuring instrument (Lianhua 5B-3BV8), and the measurement method is potassium dichromate rapid digestion spectrophotometry.

[0133] p-hydroxybenzoic acid: detected by using a high-performance liquid chromatograph (Agilent 1200) in combination with a chromatographic column (C18 reversed-phase chromatographic column). The mobile phase A is pure methanol, the mobile phase B is 1‰ phosphoric acid aqueous solution, the flow rate is 1.0 mL / min. The column temperature is 30°C, a DAD detector is used, and the wavelength is 280 nm.

[0134] TOC removal efficiency (removal rate) = (change value of the concentration of the target substance before and after treatment (C-C0)) / original concentration value of the target substance before treatment (C0) x 100%.

[0135] Deep treatment efficiency = (difference value of COD before and after treatment) / original COD value before treatment x 100%.

[0136] Deep treatment efficiency = (difference value of COD before and after treatment) / original COD value before treatment x 100%.

[0137] Deep treatment efficiency = (difference value of COD before and after treatment) / original COD value before treatment x 100%.

[0138] ​​​The ozone catalytic reaction was carried out in a powder fluidized bed reactor in a sequencing batch or semi-sequencing batch mode. A certain amount of monatomic catalyst was added to the wastewater in the cylindrical reactor, and an ozone generator (Longevity EXT120) was used to generate ozone with pure oxygen as the source. The generated ozone was introduced into the reaction solution through the aeration head after being detected by an ozone concentration detector (Tonglin 3S-J5000). The catalytic reaction was started, and the wastewater was sampled and filtered at regular intervals to measure the organic matter in the wastewater.

[0139] The performance of the catalyst was evaluated using p-hydroxybenzoic acid simulated wastewater. The concentration of the p-hydroxybenzoic acid simulated wastewater was 50 mg / L, and the pH was not adjusted. The initial pH was about 4.3. The target wastewater volume for single treatment was 250 mL, the ozone concentration was 3 mg / L, the gas flow rate was 0.2 L / min, and the reaction time was 60 min.

[0140] Degradation of the model pollutant p-hydroxybenzoic acid

[0141] As shown in Figure 10 , the degradation effect of the typical phenolic pollutant p-hydroxybenzoic acid showed that the catalytic ozone removal of p-hydroxybenzoic acid by FeCo-NC was the best. As shown in Figure 10 , the adsorption experiment of the catalyst on p-hydroxybenzoic acid showed that the adsorption efficiency of NC on p-hydroxybenzoic acid after 60 min was only 6% due to the agglomeration of nanoparticles during the pyrolysis process. Co-NC also agglomerated during the pyrolysis process, and its adsorption efficiency on p-hydroxybenzoic acid after 60 min was 10%. Fe-NC, which had better dispersion, had an adsorption efficiency of 27%. FeCo-NC, which contained FeCo double atoms, had a higher adsorption efficiency of about 59%. The higher the adsorption efficiency of the catalyst on the pollutant, the more conducive to the diffusion and mass transfer of the pollutant to the surface of the catalyst, so that it can be oxidized by the active oxygen species generated. After the introduction of ozone, the FeCo-NC catalytic ozone system also showed the best and fastest p-hydroxybenzoic acid removal performance. The pseudo-first-order kinetic model was used to fit the removal process of p-hydroxybenzoic acid in different systems. As shown in Figure 10 (d), ozone itself is an oxidant that can attack electron-rich organic matter, and its reaction rate constant with p-hydroxybenzoic acid is calculated to be 0.058 min -1 . The catalytic ozone oxidation process can further promote the removal of p-hydroxybenzoic acid. The kinetic constants for the degradation of p-hydroxybenzoic acid in the NC / O3, Fe-NC / O3, Co-NC / O3, and FeCo-NC / O3 systems are 0.063, 0.090, 0.073, and 0.146 min -1 ( Figure 10 (d)), respectively. The rate constant for the degradation of p-hydroxybenzoic acid in the FeCo-NC catalytic ozone system is about 2.5 times that of the ozone system alone Figure 10(d)). The results show that the FeCo-NC catalyst containing FeCo diatoms has superior reactivity in the ozone catalytic oxidation deep water purification process.

[0142] (Performance in advanced treatment of landfill leachate)

[0143] Landfill leachate is a type of high-concentration, recalcitrant organic wastewater that still retains a high concentration of COD even after biological treatment. The COD value of the biochemically treated effluent from the landfill leachate used in this invention is approximately 110 mg / L. For example... Figure 11 As shown in (a), after 60 minutes of reaction in the ozone system alone, the effluent COD decreased to 73 mg / L. Without ozone, the FeCo millimeter carbon sphere packed column in Example 3 showed weak adsorption performance for organic matter in landfill leachate, with an effluent COD of approximately 94 mg / L in the adsorption experiment. When ozone was introduced, the FeCo millimeter carbon sphere catalytic ozone process effectively removed organic matter from the landfill leachate, reducing the effluent COD to 39 mg / L, achieving a removal rate of 64.5%. Figure 11 As shown in (b), the TOC value of the influent to the landfill leachate deep treatment project was approximately 36.8 mg / L. The TOC removal efficiency first increased and then stabilized with reaction time, with the effluent TOC removal efficiency being approximately 56.8%. Figure 11 As shown in (c), five reuse experiments were conducted using FeCo millimeter carbon sphere packed columns. The COD of the effluent from all five reuse experiments was below 50 mg / L, and the COD removal rate was above 62%, indicating that the FeCo millimeter carbon spheres have good stability. The experimental results show that the FeCo millimeter carbon sphere catalytic ozone system of Example 3 exhibits good reactivity in the deep treatment of landfill leachate.

[0144] (Performance in advanced treatment of pharmaceutical wastewater)

[0145] The rise of the pharmaceutical industry has led to the generation of large amounts of pharmaceutical wastewater, characterized by high pollutant content, complex composition, high toxicity, and recalcitrant degradation. To promote the recycling of pharmaceutical wastewater, the removal of recalcitrant organic pollutants has become a major challenge. This invention applies the FeCo millimeter-sized carbon sphere catalytic ozone process from Example 3 to the advanced treatment of pharmaceutical wastewater, and evaluates its treatment performance. Figure 12 As shown in (a), the COD of the biochemically treated pharmaceutical wastewater was approximately 74 mg / L. Ozone oxidation alone could reduce its COD to 57 mg / L. After adsorption by FeCo millimeter carbon spheres, the effluent COD decreased to 66 mg / L. However, after passing through a FeCo millimeter carbon sphere catalytic ozone packed column reactor, the effluent COD could be reduced to 33 mg / L, achieving a deep treatment efficiency of 55.4%. Figure 12 As shown in (b), after advanced treatment, the TOC value of the pharmaceutical wastewater decreased from 22.5 mg / L to 11.4 mg / L, with a TOC removal rate of 49.3%.Figure 12 As shown in (c), the COD of the effluent from the five repeated reuse experiments were 36, 31, 37, 39, and 40 mg / L, respectively, all consistently below 50 mg / L, indicating that the FeCo millimeter carbon spheres also exhibit good stability in the advanced treatment of pharmaceutical wastewater. The results demonstrate that the FeCo diatomic millimeter carbon sphere catalytic ozone system of Example 3 also possesses excellent advanced treatment performance for pharmaceutical wastewater.

[0146] (Performance of advanced treatment of coal gasification wastewater)

[0147] Coal gasification wastewater is a typical type of recalcitrant organic industrial wastewater, and even after biological treatment, it still has a high COD value. The COD value of the biochemically treated effluent from the coal gasification wastewater used in this invention is approximately 130 mg / L, and the pH value is approximately 8.0. Figure 13 As shown in (a), using a standalone ozone oxidation system as a control, the COD value gradually decreased as the reaction proceeded. After 60 minutes of reaction, the effluent COD value was 89 mg / L, with a removal efficiency of only 31.5%. Under conditions without ozone introduction, the adsorption efficiency of the FeCo millimeter carbon sphere packed column in Example 3 for organic matter in coal gasification wastewater was investigated. The effluent COD value after adsorption was 117 mg / L, with an adsorption efficiency of 10%, indicating that adsorption contributed little to the removal of organic matter. Figure 13 As shown in (b), the FeCo millimeter-sized carbon sphere ozone catalytic oxidation packed column exhibits superior advanced treatment performance for coal gasification wastewater, reducing the effluent COD value to 48 mg / L with a degradation efficiency of 63%. Figure 13 As shown in (c), five catalyst reuse experiments were conducted. The influent COD was approximately 130 mg / L in all five experiments. After deep treatment, the effluent COD was reduced to below 50 mg / L. The COD and TOC degradation effects indicate that the FeCo diatomic-based millimeter carbon spheres of Example 3 can efficiently catalyze ozone, achieving deep reduction of recalcitrant organic pollutants in coal gasification wastewater.

[0148] (Performance of advanced treatment of coal-to-olefins wastewater)

[0149] The coal-to-olefins wastewater used in this invention is the effluent from the advanced treatment stage fiber filter. After treatment in the biochemical stage and filtration in the fiber filter, the COD of the coal-to-olefins wastewater is approximately 76 mg / L. Figure 14 As shown in (a), the ozone oxidation process alone can remove some organic matter, reducing the COD value to 57 mg / L; FeCo millimeter carbon spheres have almost no adsorption capacity for organic matter in coal-to-olefins wastewater, with the COD only decreasing to 73 mg / L after 60 min of adsorption; however, after the advanced treatment of coal-to-olefins wastewater by FeCo millimeter carbon sphere catalytic ozone oxidation in Example 3, the effluent COD decreased to 38 mg / L, with a removal efficiency of approximately 48%. Furthermore, the advanced treatment performance of the FeCo millimeter carbon sphere catalytic ozone oxidation process for coal-to-olefins wastewater was evaluated by TOC determination.Figure 14 (b) shows that as the reaction proceeds, the TOC value of coal-to-olefin wastewater is continuously reduced, and after 60 min, the TOC is reduced from 15.5 mg / L to 10.2 mg / L, and the removal efficiency is about 34%. Five experiments of deep treatment of coal-to-olefin wastewater by catalytic ozone oxidation using FeCo millimeter carbon ball packed column were carried out, as shown in Figure 14 (c) shows that the results show that the COD value after deep treatment can be effectively reduced to about 40 mg / L. Therefore, the FeCo millimeter carbon ball catalytic ozone system of Example 3 also has effective and stable deep reduction performance for the refractory organic pollutants in coal-to-olefin wastewater.

[0150] Industrial applicability

[0151] In the present application, a single atom or double atom site is used as a catalytic group, and the easy forming property of alginate polymer is used to prepare an atomic dispersion metal loaded millimeter carbon ball catalyst. The catalyst of the present application has high catalytic activity and strong mechanical strength and is easy to separate and recover, and therefore is conducive to being widely used in water treatment.

Claims

1. An application of water treatment using atomic dispersed metal supported millimeter carbon sphere catalyst, characterized in that, Utilize the atomic dispersed metal loaded millimeter carbon sphere catalyst to decompose ozone to produce active oxygen species to degrade organic matter in water, The catalyst is based on carbon spheres, and double metal atoms are loaded on the carbon spheres, The loading amount of the double metal atoms is 0.2 wt%-2.0 wt%, The double metal atoms are Fe and Co, The preparation method of the atomic dispersed metal loaded millimeter carbon sphere catalyst comprises the following steps: Step S1: preparing a double atom-ZIF precursor; Step S2: mixing the double atom-ZIF precursor with an alginate aqueous solution to obtain a mixed solution; Step S3: dropping the mixed solution obtained in step S2 into a divalent or trivalent metal salt aqueous solution, and performing standing and washing to obtain a double atom-ZIF@alginate hydrogel; Step S4: drying and pyrolyzing the double atom-ZIF@alginate hydrogel to obtain an atomic dispersed metal loaded millimeter carbon sphere catalyst.

2. The use according to claim 1, wherein the loading amount ratio of the two metal atoms is 1:2-2:

1.

3. The use according to claim 1 or 2, wherein the average particle size of the catalyst is 1 mm-10 mm.

4. Use according to claim 1 or 2, wherein step S1 comprises: The double atom metal salt and zinc salt are dissolved in an alcohol solvent to obtain solution A, 2-methyl imidazole is dissolved in an alcohol solvent to obtain solution B, solution A is poured into solution B, and stirring, standing, separation and drying are performed to obtain a double atom-ZIF precursor; In step S1, the molar ratio of the double atom metal salt to the zinc salt is (0.002-0.6):1, and the molar ratio of the zinc salt to 2-methyl imidazole is 1:(2-10), and the addition amount of the alcohol solvent relative to the zinc salt is 5-50 mL / mmol; In step S2, the mass ratio of the double atom-ZIF precursor to alginate is 1:1-15:1; In step S3, the divalent or trivalent metal salt is selected from organic metal salt and inorganic metal salt; The organic metal salt is selected from one or more of acetylacetone salt, acetate salt, ferrocene salt, citrate salt, and the inorganic metal salt is selected from one or more of nitrate, chloride, sulfate; When the divalent or trivalent metal salt is an organic metal salt, the mass ratio of the double atom-ZIF precursor to the organic metal salt is 1:10-1:1; When the divalent or trivalent metal salt is an inorganic metal salt, the mass ratio of the double atom-ZIF precursor to the inorganic metal salt is 1:100-1:20; In step S4, the pyrolysis temperature is 800°C-1200°C, and the time is 2-5 h.

5. The use according to claim 1 or 2, wherein the addition amount of the atomic dispersed metal loaded millimeter carbon sphere catalyst is 0.02-5 g / L, the concentration of ozone is 2-20 mg / L, and the flow rate of ozone is 0.1-2 L / min.

6. The use according to claim 1 or 2, wherein the water includes drinking water, municipal sewage, and organic wastewater, and the treatment of the drinking water and municipal sewage includes deep reduction of organic matter and inactivation of pathogenic microorganisms.

7. The use according to claim 6, wherein the organic wastewater comprises one or more of pharmaceutical wastewater, coal gasification wastewater, coal to olefin wastewater, landfill leachate, petrochemical wastewater, dyeing wastewater, and papermaking wastewater.

8. A use of an atomic dispersion metal loaded millimeter carbon sphere catalyst for degrading organic matter, characterized in that, active oxygen species are generated by decomposing ozone with the atomic dispersion metal loaded millimeter carbon sphere catalyst to degrade organic matter, the catalyst is based on carbon spheres, and double metal atoms are loaded on the carbon spheres, wherein the loading amount of the double metal atoms is 0.2 wt% to 2.0 wt%, and the double metal atoms are Fe and Co.

9. A preparation method of the atomic dispersion metal loaded millimeter carbon sphere catalyst, comprising the following steps: Step S1: preparing a double atom-ZIF precursor; Step S2: mixing the double atom-ZIF precursor with an alginate aqueous solution to obtain a mixed solution; Step S3: dropping the mixed solution obtained in Step S2 into a divalent or trivalent metal salt aqueous solution, and performing standing and washing to obtain a double atom-ZIF@alginate hydrogel; Step S4: drying and pyrolyzing the double atom-ZIF@alginate hydrogel to obtain the atomic dispersion metal loaded millimeter carbon sphere catalyst. ​ ​ ​ ​

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