A Nitrogen-doped self-supporting porous calcium sphere ozone oxidation catalyst

Abstract

This invention relates to an N-doped self-supporting porous calcium sphere ozone oxidation catalyst. The catalyst comprises a network of porous carbon spheres and metallic and non-metallic active components dispersed on the network of porous carbon spheres. The network of porous carbon spheres is formed by high-temperature calcination of calcium alginate gel. The metallic active component is a calcium compound, and the non-metallic active components are nitrogen and silicon compounds. This catalyst is based on sodium alginate and Ca... 2+ The catalyst is designed and synthesized based on the principle of instantaneous spheroidization through cross-linking polymerization. Specifically, an auxiliary agent and a nitrogen source are introduced into the sodium alginate solution to further functionalize the catalyst, achieving metal-nonmetal synergistic catalysis. The preparation method of the catalyst described in this invention has a simple process flow; the cross-linking-calcination process enables rapid catalyst preparation. It exhibits good catalytic performance and stability in the deep treatment of saline organic wastewater, making it suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to an N-doped self-supporting porous calcium sphere ozone oxidation catalyst for deep treatment of saline organic wastewater, its preparation method and application. Background Technology

[0002] With the development of human civilization, people's environmental awareness has gradually increased, and countries have become increasingly stringent in their requirements for water pollutant discharge. Advances in production processes and water-saving and energy-efficient technologies mean that wastewater now contains not only organic matter but also chlorides (Cl). - SO4 2- Na + PO4 3- Wastewater contains salts and other saline substances. Dyeing and printing wastewater, coking wastewater, and papermaking wastewater are all saline organic wastewaters, characterized by high salt content, complex composition, and high toxicity, seriously threatening water environment safety. Therefore, their advanced treatment has significant environmental value and social importance.

[0003] The most widely used pretreatment method for saline organic wastewater is biological treatment. While effective in reducing wastewater color and COD, it struggles to effectively remove recalcitrant organic matter in a saline state. Excessive accumulation of intermediates in these recalcitrant organic compounds and the presence of inorganic salts inhibit microbial activity, failing to achieve the desired treatment effect. Therefore, a targeted, effective, and efficient advanced treatment technology for saline organic wastewater is needed. Currently, advanced treatment technologies for saline organic wastewater mainly include membrane treatment, advanced oxidation processes (AOPs), and bioaugmentation. Among these, AOPs are an effective technology for removing recalcitrant organic pollutants from water. Of the various AOPs, heterogeneous catalytic ozonation is a powerful water purification technology that degrades pollutants through the effective oxidation of ozone molecules and reactive oxygen species (ROS) generated by ozone activation.

[0004] The catalysts used in heterogeneous catalytic ozone oxidation technology mainly include metal-based catalysts and non-metallic carbon-based catalysts. Among them, metal-based catalysts are the most widely used due to their advantages such as good catalytic activity and low cost. Chinese patent CN113262787 A discloses a Fe... x O yThe Al2O3 iron-based composite catalyst uses alumina as a support and urea as a self-sacrificing template. Iron oxides are loaded onto the alumina surface, and the presence of urea facilitates the precipitation of Fe on the support. This preparation method significantly improves the dispersibility of Fe. Furthermore, the catalyst disclosed in this patent increases the COD removal rate of coal chemical wastewater from 43±0.5% with pure ozone oxidation to 80±2.5%, demonstrating excellent wastewater treatment performance. For example, Jianlong Wang et al. (HaiChen, Jianlong Wang. MOF-derived Co3O4-C@FeOOH as an efficient catalyst for catalytic ozonation of norfloxacin. Journal of Hazardous Materials, 2021, 403, 123697) designed and synthesized a Co3O4-C@FeOOH composite catalyst. This catalyst promotes the decomposition of O3 to generate more hydroxyl radicals (·OH), increasing the TOC removal rate from 25.6% to 56.7% compared to ozone treatment alone. Although metal-based catalysts have achieved good results in wastewater treatment, problems such as catalyst instability and metal leaching exist during long-term use. Therefore, modification methods such as coating and heteroatom doping are needed to increase the activity and stability of the catalysts. Nitrogen (N) is considered a non-metallic element that can effectively improve the activity and stability of catalysts. It can regulate the coordination environment of metal active sites, forming a metal-nitrogen-carbon (MNC) structure with unique functions. The type of N and the coordination environment of the metal play a crucial role in catalyst performance. The main types of N include pyridine-N, pyrrole-N, graphite-N, and oxide-N. Studies have shown that graphite-N can regulate the surface charge distribution of the catalyst and improve the charge transfer ability between the catalyst and the adsorbate, which is beneficial for promoting the adsorption and activation of O3 molecules.

[0005] Currently, most methods for preparing nitrogen-doped metal-based catalysts are supported methods, requiring the introduction of a nitrogen source onto a support before loading the active metal, a relatively complex process. Furthermore, the active metal components are mostly transition metals or metal oxides; if trace amounts are leached during long-term ozone catalytic oxidation, the accumulated leached elements in the water will cause secondary pollution, posing a threat to the aquatic environment. Therefore, there is an urgent need to design and synthesize a simple, green, efficient, and inexpensive ozone catalyst to replace conventional supported transition metal-based catalysts. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing an N-doped self-supporting porous calcium sphere ozone oxidation catalyst; compared with traditional N-doped modified catalysts, this catalyst exhibits advantages in Ca... 2+Non-metals are introduced during the crosslinking process with sodium alginate, simultaneously achieving non-metal modification and metal loading, forming porous calcium spheres with a self-supporting network structure and active centers for metal-non-metal synergistic catalysis distributed on the porous calcium spheres. This process has advantages such as high catalytic activity, environmental friendliness, and low cost.

[0007] Therefore, the first aspect of the present invention provides an N-doped self-supporting porous calcium sphere ozone oxidation catalyst, which is composed of a network of porous carbon spheres and metal active components and non-metal active components dispersed on the network of porous carbon spheres; wherein the network of porous carbon spheres is formed by high-temperature calcination of calcium alginate gel, the metal active component is a calcium compound, and the non-metal active component is a nitrogen compound and a silicon compound.

[0008] In some embodiments of the present invention, the network-like porous calcium spheres are made of Ca 2+ Ions are cross-linked and polymerized with sodium alginate to form gel microspheres, which are then freeze-dried and calcined at high temperature to form microspheres with a diameter of 2-5 mm. Preferably, the Ca... 2+ The crosslinking process between ions and sodium alginate also includes the addition of auxiliaries and nitrogen sources; more preferably, the auxiliaries include one or more of liquid silica gel, phenolic resin, and starch. The nitrogen sources include one or more of polyimide, urea, melamine, and dopamine.

[0009] Preferably, the specific surface area of ​​the N-doped self-supporting porous calcium sphere ozone oxidation catalyst is 20-200 m². 2 / g, pore size 2-40nm, pore volume 0.02-0.5cm³ 3 / g.

[0010] The second aspect of this invention provides a method for preparing the N-doped self-supporting porous calcium sphere ozone oxidation catalyst described in the first aspect of this invention, comprising:

[0011] Step A: Add the additive and nitrogen source to the sodium alginate aqueous solution and stir thoroughly until the solution is evenly mixed to obtain the sodium alginate-nitrogen source mixture.

[0012] Step B: Add the sodium alginate-N source mixture dropwise to the Ca2+ aqueous solution to crosslink into spheres, filter, wash, and obtain calcium-based gel microspheres;

[0013] Step C: The calcium-based gel microspheres were freeze-dried to obtain the catalyst precursor;

[0014] Step D involves calcining the catalyst precursor to obtain an N-doped self-supporting porous calcium sphere ozone oxidation catalyst.

[0015] According to the method of the present invention, the concentration of the sodium alginate aqueous solution is 0.5wt%-4wt%; and / or, Ca 2+ Ca in aqueous solution2+ The concentration ranges from 0.01 to 5.0 mol / L.

[0016] In some embodiments of the present invention, in step A, the mass ratio of sodium alginate to the additive is 1:(5-30); preferably, the additive includes one or more of liquid silica gel, starch and phenolic resin.

[0017] In some embodiments of the present invention, in step A, the mass ratio of sodium alginate to nitrogen source is 1:(2-50); preferably, the nitrogen source includes one or more of polyimide, urea, melamine and dopamine.

[0018] According to the present invention, in step C, the freeze-drying temperature is -65°C to -40°C, and the freeze-drying time is 3-9 hours.

[0019] According to the present invention, in step D, calcination is carried out in an inert gas atmosphere; preferably, the calcination temperature is 400-1000°C; and / or, the calcination time is 0.5-8h.

[0020] The third aspect of the present invention provides the application of the N-doped self-supporting porous calcium sphere ozone oxidation catalyst as described in the first aspect of the present invention or the N-doped self-supporting porous calcium sphere ozone oxidation catalyst prepared by the preparation method described in the second aspect of the present invention in the deep treatment of saline organic wastewater.

[0021] Preferably, the application includes filling an ozone oxidation catalyst into a wastewater treatment device, introducing wastewater and ozone to treat the wastewater with ozone oxidation, and obtaining oxidized effluent that meets emission standards.

[0022] In some embodiments of the present invention, the reaction conditions for ozone oxidation treatment are as follows: COD of the wastewater: 80-300 mg / L, TDS: 3000-5000 mg / L, pH: 2-11, ozone flow rate: 0.01-0.20 L / min, catalyst loading amount: 50-200 g / L, reaction time: 10-180 min, and ozone dosage ratio: 0.2-6.0.

[0023] The beneficial effects of this invention are mainly in the following two aspects:

[0024] (I) The N-doped self-supporting porous calcium sphere ozone oxidation catalyst proposed in this invention requires no additional support. The porous carbon network formed by high-temperature calcination of sodium alginate provides support for the loading of calcium oxide sites. This porous carbon network has strong hydrophobicity and excellent adsorption capacity for organic pollutants, effectively promoting the oxidative degradation of organic pollutants. Compared with traditional supported metal-based catalysts, this catalyst has advantages such as high catalytic activity, environmental friendliness, and low cost.

[0025] (II) Based on sodium alginate and Ca 2+ A metal-nonmetal dual-site catalyst was synthesized in situ via a crosslinking process. The advantage of this catalyst lies in the simultaneous construction of metal calcium sites and nonmetal nitrogen sites. Nitrogen doping can modulate the electronic structure of the carbon adjacent to nitrogen, activating non-radical pathways and enhancing electron transfer between organic matter, O3, and the catalyst, thereby accelerating the decomposition of organic matter. Simultaneously, the introduction of N sites provides both adsorption / catalytic active sites and metal bonding sites, reducing the loss of active metals. In particular, the introduction of the N source significantly enhances the mechanical strength of the catalyst, which is crucial for improving its stability and lifespan. Attached Figure Description

[0026] The present invention will now be described in further detail with reference to the accompanying drawings:

[0027] Figure 1 COD removal rates of catalysts prepared with different SA:PI:LSR ratios.

[0028] Figure 2 COD removal rates of catalysts prepared for different calcium ion concentrations. Detailed Implementation

[0029] To facilitate understanding of the present invention, it will be described in detail below with reference to the accompanying drawings and embodiments. However, before describing the present invention in detail, it should be understood that the present invention is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for describing specific embodiments only and is not intended to be restrictive.

[0030] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While any methods and materials similar to or equivalent to those described herein may also be used in the practice or testing of this invention, preferred methods and materials are now described.

[0031] I. Terminology

[0032] The term "TDS" (Total Dissolved Solids) used in this invention, also known as total dissolved solids, is measured in milligrams per liter (mg / L). It indicates how many milligrams of dissolved solids are dissolved in one liter of water. A higher TDS value indicates a greater amount of dissolved matter in the water. Total dissolved solids refer to the total amount of all solutes in water, including both inorganic and organic matter. Generally, conductivity values ​​can be used to roughly estimate the salt content of a solution; generally, higher conductivity indicates higher salt content and a higher TDS. Therefore, TDS also reflects the salt level in wastewater.

[0033] In this invention, the term "salt-containing organic wastewater" refers to wastewater that contains not only organic pollutants but also a large amount of inorganic salts, such as Cl. - SO4 2- PO4 3- Plasma.

[0034] The term "deep wastewater treatment" as used in this invention generally refers to further treating residual organic matter in Class II effluent that has undergone biochemical treatment, using advanced oxidation and other technologies.

[0035] Unless otherwise specified or limited, the term "water" as used in this invention refers to deionized water, ultrapure water, or distilled water.

[0036] II. Implementation Plan

[0037] Existing heterogeneous ozone oxidation catalysts have some shortcomings. For example, there is the problem of metal component loss, especially the formation of heavy metal ion pollution, which will bring difficulties to subsequent treatment. At the same time, current ozone oxidation catalysts exhibit selective degradation of some recalcitrant new pollutants or organic compounds containing special functional groups, thus requiring the development of specific catalysts for targeted degradation of certain types of wastewater. Furthermore, the widely used supported metal-based catalysts require support from a carrier, and the requirements for the carrier are relatively high, such as a large specific surface area and abundant pore structure. Complex carrier pretreatment processes, long catalyst preparation cycles, and high operating costs are also problems associated with current supported metal-based catalysts.

[0038] While nitrogen-doped metal-based catalysts are beneficial for promoting the adsorption and activation of O3 molecules, existing methods for preparing them are mostly supported, requiring the introduction of a nitrogen source onto a support before loading the active metal, a relatively complex process. Furthermore, the active metal components are often transition metals or metal oxides; if trace amounts leach out during long-term ozone catalytic oxidation, the accumulated leached elements in the water will cause secondary pollution, posing a threat to the aquatic environment. Therefore, there is an urgent need to design and synthesize a simple, green, efficient, and inexpensive ozone catalyst to replace conventional supported transition metal-based catalysts. In light of this, the inventors have conducted extensive and in-depth research on nitrogen-doped metal-based catalysts and their ozone oxidation technology for the deep treatment of saline organic wastewater.

[0039] The inventors have discovered that, based on sodium alginate and Ca... 2+Ion crosslinking can form a green and efficient metal-nonmetal dual-site N-doped self-supporting porous calcium sphere ozone oxidation catalyst. Unlike traditional supported N-doped catalysts, N and active metal components grow simultaneously within the self-supporting network, avoiding the complex steps of first modifying the support and then loading the metal. This method offers advantages such as simple preparation, environmental friendliness, and high cost-effectiveness, and can be used for the advanced treatment of saline organic wastewater. The catalyst obtained by this method exhibits excellent catalytic performance, high catalytic efficiency, good stability, and can be repeatedly recycled.

[0040] Therefore, the N-doped self-supporting porous calcium sphere ozone oxidation catalyst for deep treatment of saline organic wastewater according to the first aspect of the present invention is composed of network porous carbon spheres and metal active components and non-metal active components supported on the network porous carbon spheres, wherein the network porous carbon spheres are formed by high-temperature calcination of calcium alginate gel, the metal active component is a calcium compound, and the non-metal active component is a nitrogen compound and a silicon compound.

[0041] Based on the above, it is easy to understand that the self-supporting porous calcium sphere catalyst is made of Ca. 2+ Ions crosslink with sodium alginate to form gel microspheres, which are then freeze-dried and calcined at high temperature to form microspheres with a diameter of 2-5 mm; and the Ca... 2+ The cross-linking process between ions and sodium alginate also includes the addition of an N source; preferably, the N source includes one or more of polyimide, urea, melamine and dopamine.

[0042] Preferably, the Ca 2+ The crosslinking process between ions and sodium alginate also includes the addition of an auxiliary agent; more preferably, the auxiliary agent includes one or more of liquid silica gel, phenolic resin and starch.

[0043] The inventors have discovered that N-doped self-supporting metal-based catalysts, such as N-doped porous calcium sphere catalysts, can achieve the simultaneous introduction of the N source and the active metal component without a loading step. The catalyst size is adjustable, the cost is low, and the preparation process is simple, demonstrating good application potential. During pyrolysis, nitrogen atoms and the active metal component grow simultaneously in the self-supporting calcium sphere network, actively forming MO / MN. x The catalyst exhibits a stable structure and allows for the conversion between different types of nitrogen by adjusting the pyrolysis temperature. Specifically, traditional supported nitrogen-doped metal-based catalysts used for the deep treatment of saline organic wastewater typically have particle diameters of 3-5 mm. These catalyst particles are stacked to form a fixed-bed reactor, resulting in partial coverage of active sites on the contacting particles. In contrast, nitrogen-doped self-supporting metal-based catalysts have adjustable sizes, enabling uniform dispersion of catalyst particles in the water body to form a fluidized-bed reactor, significantly improving the mass transfer efficiency of the catalytic ozone oxidation process.

[0044] The research results show that the specific surface area of ​​the self-supporting porous calcium sphere catalyst provided by this invention is 20-200 m². 2 / g, pore size 2-40nm, pore volume 0.02-0.5cm³ 3 / g.

[0045] The preparation method of the self-supporting porous calcium sphere ozone oxidation catalyst as described in the first aspect, as disclosed in the second aspect of this invention, includes the following steps:

[0046] (1) Dissolve sodium alginate powder in ultrapure water and shake in a shaker at 60°C until the sodium alginate is completely dissolved to obtain an aqueous solution of sodium alginate; dissolve calcium chloride in ultrapure water to obtain a solution containing Ca. 2+ Aqueous solution of calcium chloride.

[0047] (2) Add the additive and N source to the sodium alginate aqueous solution and stir thoroughly until the solution is evenly mixed to obtain sodium alginate-N source mixture;

[0048] (3) Place the sodium alginate-N source mixture in a separatory funnel, adjust the stopcock of the separatory funnel, and add the sodium alginate-N source mixture dropwise at a uniform rate through the lower opening of the separatory funnel to the mixture containing Ca. 2+ In an aqueous solution of calcium chloride, cross-linking is performed to form spheres, followed by filtration and washing to obtain calcium-based gel spheres;

[0049] (4) The calcium-based gel microspheres were freeze-dried to obtain the catalyst precursor;

[0050] (5) The catalyst precursor is calcined to obtain N-doped self-supporting porous calcium sphere ozone oxidation catalyst.

[0051] This invention is based on sodium alginate and Ca 2+ Ionic crosslinking forms a green and efficient N-doped self-supporting porous calcium sphere ozone oxidation catalyst; therefore, it is necessary to investigate and determine the optimal preparation conditions.

[0052] The results show that in step (1), the concentration of the sodium alginate aqueous solution is 0.5wt%-4wt%, and the calcium chloride aqueous solution contains Ca... 2+ When the concentration is 0.01-5.0 mol / L, sodium alginate and Ca 2+ The gel microspheres formed by cross-linking polymerization have the best mechanical properties.

[0053] Studies have found that in step (2), adding an N source to the sodium alginate solution can enhance the mechanical strength of the catalyst pellets and introduce N active sites. Preferably, the mass ratio of sodium alginate to N source is 1:(2-50). More preferably, the N source includes one or more of polyimide, urea, melamine and dopamine.

[0054] In some embodiments of the present invention, in step (2), the mass ratio of sodium alginate to the additive is 1:(5-30); preferably, the additive includes one or more of liquid silica gel, starch and phenolic resin.

[0055] In some embodiments of the present invention, in step (4), calcium-based gel microspheres are freeze-dried to create pores, wherein the freeze-drying temperature is -65°C to -40°C and the freeze-drying time is 3-9 hours.

[0056] According to the method of the present invention, in step (5), the catalyst is calcined in an inert gas atmosphere to form metal active sites and non-metal active sites; preferably, the calcination temperature is 400-1000℃; and / or the calcination time is 0.5-8h.

[0057] The results show that the N-doped self-supporting catalyst prepared by the method of this invention differs from traditional supported N-doped catalysts. In this method, N and the active metal component grow simultaneously within the self-supporting network, avoiding the complex steps of first modifying the support and then loading the metal. This represents a novel and simple method for preparing N-doped self-supporting catalysts. Furthermore, this catalyst exhibits a COD removal rate of over 70% for high-salt organic wastewater, demonstrating excellent ability to treat high-salt wastewater.

[0058] The application of the N-doped self-supporting porous calcium sphere ozone oxidation catalyst as described in the first aspect of the present invention or the ozone oxidation catalyst prepared by the preparation method described in the second aspect of the present invention in the deep treatment of saline organic wastewater can be understood as a method for deep treatment of saline organic wastewater using the N-doped self-supporting porous calcium sphere ozone oxidation catalyst as described in the first aspect of the present invention or the N-doped self-supporting porous calcium sphere ozone oxidation catalyst prepared by the preparation method described in the second aspect of the present invention.

[0059] Preferably, the application includes filling an ozone oxidation catalyst into a wastewater treatment device, introducing wastewater and ozone to treat the wastewater with ozone oxidation, and obtaining oxidized effluent that meets emission standards.

[0060] The saline organic wastewater mentioned in this invention includes, but is not limited to, biochemical effluent from chemical industrial parks and / or petrochemical wastewater.

[0061] In some embodiments of the present invention, the reaction conditions for ozone oxidation treatment are as follows: COD: 130-140 mg / L, TDS: 5000-5500 mg / L, pH = 3-10, ozone flow rate: 0.03 L / min, reaction time: 60 min, catalyst loading: 50-200 g / L, reaction time: 10-180 min, and ozone dosage ratio: 0.2-6.0.

[0062] This invention provides an N-doped self-supporting porous calcium sphere ozone oxidation catalyst for the deep treatment of saline organic wastewater and its preparation method. This invention is based on sodium alginate and Ca... 2+ Based on the principle of instantaneous spherical formation through cross-linking polymerization, a self-supporting porous spherical catalyst was designed and synthesized. Specifically, an auxiliary agent and a nitrogen source were introduced into a sodium alginate solution to further functionalize the catalyst, achieving metal-nonmetal synergistic catalysis. The catalyst structure comprises a network of porous carbon spheres and metal and nonmetal sites distributed on the network of porous carbon spheres. The catalyst prepared by this invention has a simple process flow; the cross-linking-calcination process enables rapid catalyst preparation. It exhibits good catalytic performance and stability in the deep treatment of saline organic wastewater, making it suitable for industrial application.

[0063] Example

[0064] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the experimental methods described below are standard laboratory methods. Unless otherwise specified, the experimental materials described below are commercially available.

[0065] In the following examples, COD was determined using Hach COD reagent digested on a Hach DRB200 digester (Hach Instruments, Inc., USA), and then measured using a DR5000 UV spectrophotometer (Hach Instruments, Inc., USA). TDS was determined using a DDSJ-319L conductivity meter (Shanghai Leici Instruments Co., Ltd.). The COD removal rate was calculated using the following formula:

[0066] COD removal rate = (COD removal rate) 原始 -COD 氧化后 COD 原始 ×100%

[0067] Example 1:

[0068] (1) Prepare 50 mL of 2.0 wt% sodium alginate aqueous solution and dissolve calcium chloride in ultrapure water to obtain a calcium chloride (CaCl2) aqueous solution with a concentration of 0.16 mol / L;

[0069] (2) According to the mass ratio of sodium alginate to polyimide of 1:1.5 and the mass ratio of sodium alginate to liquid silica gel of 1:(5-25), sodium alginate is mixed with polyimide (N source) and 30% liquid silica gel (additive), and stirred thoroughly until the solution is uniform to obtain sodium alginate-N source mixture.

[0070] (3) Place the sodium alginate-N source mixture in a separatory funnel and gradually add it dropwise into the CaCl2 aqueous solution to crosslink into spheres. Filter and wash with water to obtain calcium-based gel spheres.

[0071] (4) Place the calcium-based gel microspheres in a freeze dryer at -50℃ for 7 hours to obtain the catalyst precursor;

[0072] (5) The catalyst precursor was placed in an inert gas atmosphere in a tube furnace and calcined at 850°C for 2 hours to obtain N-doped calcium-based porous carbon sphere catalyst.

[0073] Reaction conditions: Biochemical effluent from chemical industrial park wastewater, COD: 130-140 mg / L, TDS: 5000-5500 mg / L, pH=7, ozone flow rate: 0.03 L / min, reaction time: 60 min, ozone concentration: 12 mg / L.

[0074] Experimental results show that the COD removal rate of the prepared N-doped self-supporting porous calcium sphere ozone oxidation catalyst is between 55% and 75%.

[0075] Example 2:

[0076] (1) Prepare 50 mL of 2.0 wt% sodium alginate aqueous solution and dissolve calcium chloride in ultrapure water to obtain a calcium chloride aqueous solution with a concentration of 0.05-0.30 mol / L;

[0077] (2) Sodium alginate and polyimide were mixed according to a mass ratio of 1:1.5 and a mass ratio of 1:20. 30% liquid silica gel was added and the mixture was stirred until the solution was homogeneous to obtain sodium alginate-N source mixture.

[0078] (3) Place the sodium alginate-N source mixture in a separatory funnel and gradually add it dropwise to a 0.05-0.30 mol / L CaCl2 solution to crosslink into spheres. Filter and wash with water to obtain calcium-based gel spheres.

[0079] (4) Place the calcium-based gel microspheres in a freeze dryer at -50℃ for 7 hours to obtain the catalyst precursor;

[0080] (5) The catalyst precursor was placed in an inert gas atmosphere in a tube furnace and calcined at 850°C for 2 hours to obtain N-doped calcium-based porous carbon sphere catalyst.

[0081] Reaction conditions: Biochemical effluent from chemical industrial park wastewater, COD: 130-140 mg / L, TDS: 5000-5500 mg / L, pH=7, ozone flow rate: 0.03 L / min, reaction time: 60 min, ozone concentration: 12 mg / L.

[0082] Experimental results show that the COD removal rate of the prepared N-doped self-supporting porous calcium sphere ozone oxidation catalyst is between 60% and 80%.

[0083] It should be noted that the embodiments described above are merely preferred embodiments of the present invention, used to explain the present invention, and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications having the same function.

Claims

1. An N-doped self-supporting porous calcium sphere ozone oxidation catalyst, comprising a network of porous carbon spheres, and metallic and non-metallic active components dispersed on the network of porous carbon spheres; wherein, The network-like porous carbon spheres are formed by high-temperature calcination of calcium alginate gel, the metallic active component is a calcium compound, and the non-metallic active components are nitrogen compounds and silicon compounds. The N-doped self-supporting porous calcium sphere ozone oxidation catalyst is composed of Ca... 2+ The calcium alginate gel spheres are formed by a cross-linking reaction with sodium alginate, and then freeze-dried and calcined at high temperature to form spheres with a diameter of 2-5 mm; the Ca... 2+ The crosslinking process with sodium alginate also includes the addition of additives and nitrogen sources; the additives include liquid silica gel; the nitrogen sources include one or more of polyimide, urea, melamine and dopamine. The mass ratio of sodium alginate to the additive is 1:(5-30); the mass ratio of sodium alginate to the nitrogen source is 1:1.

5.

2. The N-doped self-supporting porous calcium sphere ozone oxidation catalyst according to claim 1, characterized in that, The specific surface area of ​​the N-doped self-supporting porous calcium sphere ozone oxidation catalyst is 20-200 m². 2 / g, pore size 2-40nm, pore volume 0.02-0.5cm³ 3 / g.

3. The method for preparing the N-doped self-supporting porous calcium sphere ozone oxidation catalyst according to claim 1 or 2, comprising: Step A: Add the additive and nitrogen source to the sodium alginate aqueous solution and stir thoroughly until the solution is evenly mixed to obtain the sodium alginate-nitrogen source mixture. Step B, add the sodium alginate-N source mixture dropwise to Ca 2+ In an aqueous solution, cross-linking is performed to form spheres, followed by filtration and washing to obtain calcium-based gel microspheres; Step C: The calcium-based gel microspheres were freeze-dried to obtain the catalyst precursor; Step D involves calcining the catalyst precursor to obtain an N-doped self-supporting porous calcium sphere ozone oxidation catalyst.

4. The preparation method according to claim 3, characterized in that, The concentration of the sodium alginate aqueous solution is 0.5wt%-4wt%; and / or, Ca 2+ Ca in aqueous solution 2+ The concentration ranges from 0.01 to 5.0 mol / L.

5. The preparation method according to claim 3, characterized in that, In step C, the freeze-drying temperature is -65°C to -40°C, and the freeze-drying time is 3-9 hours.

6. The preparation method according to any one of claims 3-5, characterized in that, In step D, calcination is carried out in an inert gas atmosphere; the calcination temperature is 400-1000℃; and the calcination time is 0.5-8h.

7. The application of the N-doped self-supporting porous calcium sphere ozone oxidation catalyst as described in claim 1 or 2, or the N-doped self-supporting porous calcium sphere ozone oxidation catalyst prepared by any one of the preparation methods described in claims 3-6, in the deep treatment of saline organic wastewater; the application includes filling an ozone oxidation catalyst into a wastewater treatment device, introducing wastewater, and introducing ozone to treat the wastewater by ozone oxidation.

8. The application according to claim 7, characterized in that, The reaction conditions for ozone oxidation treatment are as follows: COD of the wastewater: 80-300 mg / L, TDS: 3000-5000 mg / L, pH: 2-11, ozone flow rate: 0.01-0.20 L / min, catalyst loading: 50-200 g / L, and reaction time: 10-180 min.

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