Method for preparing nitrogen-doped bone black catalyst and method for treating coking wastewater

Abstract

The invention relates to the technical field of carbon material preparation and industrial wastewater treatment, in particular to preparation of a nitrogen-doped bone black catalyst and a method for treating coking wastewater. The preparation process of the nitrogen-doped bone black catalyst comprises the following steps: S1, preparing bone meal slurry; s2, preparing bone black precursor powder; s3, bone pre-carbonization; and S4, preparing the nitrogen-doped bone black catalyst. The nitrogen-doped bone black material is wide in source, does not contain metal components, and is free of secondary pollution; the coking wastewater is economically and efficiently treated by activating peracetic acid with nitrogen-doped bone black, so that the problem that refractory organic matters are difficult to treat in an existing coking wastewater treatment process is solved; the nitrogen-doped bone black catalyst is combined with the membrane, peracetic acid generated in situ can be activated, COD in the coking wastewater is further degraded, the safety problem caused by direct putting of peracetic acid and the effluent acidification problem are avoided, and meanwhile recycling of nitrogen-doped bone black is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon material preparation and industrial wastewater treatment, and in particular to a method for preparing a nitrogen-doped bone char catalyst and treating coking wastewater. Background Art

[0002] Coke, as a representative product of the traditional coal chemical industry, plays an important role in the steel industry. However, as a highly polluting and water-intensive industry, each stage of coal coking produces a large amount of wastewater. Moreover, coking wastewater is produced in large quantities, has high pollutant concentrations, and is difficult to treat. It is recognized as a difficult-to-treat industrial wastewater. The composition of coking wastewater is complex, and its organic components are mainly phenolic compounds, nitrogen-containing heterocyclic compounds, and polycyclic aromatic hydrocarbons. In addition, coking wastewater also contains inorganic pollutants such as ammonia, cyanide, and thiocyanate, as well as heavy metals. Coking wastewater treated with conventional biological treatment methods is difficult to meet emission standards. Pollutants that are difficult to biodegrade, such as polycyclic aromatic hydrocarbons, alkylphenols, and amines, still remain in the biochemical effluent. Therefore, deep treatment of the biochemical wastewater is required. At present, it is very necessary to develop an efficient, green, universal, and low-cost deep treatment technology for coking wastewater.

[0003] Advanced oxidation processes (AOPs) are effective methods for degrading organic micropollutants by generating active species that can degrade and mineralize organic matter in situ. Oxidants used include hydrogen peroxide (H2O2), peroxydisulfate (PDDS), and peroxymonosulfate (PMS). In recent years, peracetic acid (PAA), as a highly efficient and economical oxidant, has found application in wastewater purification using advanced oxidation processes. PAA has a relatively high redox potential (1.06–1.96 eV). It shares a similar OO bond with persulfate and hydrogen peroxide, but its cleavage energy is lower than that of other oxidants. Consequently, it can generate a variety of free radicals, including hydroxyl radicals and organic free radicals, with lower toxicity and higher selectivity. This has led to the establishment of a new advanced oxidation system with great development potential based on peracetic acid.

[0004] PAA-based advanced oxidation technology not only degrades organic pollutants but also has a high ability to simultaneously disinfect them. PAA has certain application advantages in the treatment of medical wastewater. The activation pathways of PAA reported in the current public literature mainly include activation through external energy input (for example, thermal activation, ultraviolet activation, and photocatalysis, etc.), and activation through homogeneous / heterogeneous catalysts. Due to the high cost of activation methods using high energy inputs such as ultraviolet light, PAA advanced oxidation technology using catalyst activation is relatively more economical. The heterogeneous metal-based catalysts used have attracted widespread attention due to their high catalytic activity, convenient recycling, and little impact from water quality.

[0005] Although peracetic acid is a promising oxidant, its application is limited by its strong odor, volatility, and explosive potential at low temperatures and at concentrations exceeding 45%. Furthermore, it is unstable and difficult to transport, and requires constant titration to determine its concentration. A new activation method is urgently needed to address this issue. Using a solid oxygen-based activator and peroxide to generate peracetic acid in situ, followed by activation with a catalyst to achieve pollutant degradation, not only avoids the risks of direct peracetic acid addition but also offers advantages such as safe and convenient operation, higher peracetic acid utilization efficiency, strong stability, a wide pH range, and the avoidance of effluent acidification, thus possessing great potential for application.

[0006] Chinese patent application CN117776371A discloses a method for treating medical wastewater using iron-nitrogen co-doped biochar to activate peracetic acid. Using water-soluble ferrous iron as the iron source and urea and melamine as nitrogen sources, the iron-carbon co-doped biochar is hydrothermally calcined to activate persulfate, which is then used to treat medical wastewater. The iron-nitrogen co-doped biochar produced is a green, efficient, and low-cost material for activating peracetic acid. However, the material synthesis process is complex, requiring the addition of an additional reducing agent and the direct addition of peracetic acid to complete the reaction.

[0007] Chinese patent application CN117619365A discloses "An iron-loaded biochar, its preparation method, and application." Using straw as the biochar raw material and hydrates of ferric chloride, ferric sulfate, and ferric nitrate as the iron source, the iron-loaded biochar is produced through a single high-temperature calcination step. This method can effectively improve the treatment efficiency of sulfonamide antibiotic wastewater and has potential application in treating antibiotic wastewater. However, this method requires the direct addition of peracetic acid to complete the reaction, and the catalyst contains iron, posing a risk of secondary pollution.

[0008] The Chinese patent application with the publication number CN117244580A discloses "A preparation and application method of an activated peracetic acid catalyst for the oxidation and degradation of antibiotic wastewater." Using ferric chloride / boron nitride quantum dots / melamine as precursors, a carbon nitride-based peracetic acid activation catalyst is obtained by high-temperature calcination and used to degrade antibiotic wastewater. The prepared material has high stability, and although it carries iron ions, the iron ion leaching concentration is low. However, in this solution, the catalyst body is carbon nitride, and the precursor cost is relatively high. Furthermore, peracetic acid needs to be directly added to react.

[0009] Chinese patent application CN105419809A discloses a method for preparing a biomass remediation agent for heavy metal-contaminated soil. Using fresh cattle bones as raw material, the method uses a single-step calcination process to produce charcoal powder. This charcoal is then combined with earthworm-derived biomass sludge, flour, and egg white to create a biomass remediation agent for heavy metal-contaminated soil. While this method avoids secondary pollution, it has high material costs, complex synthesis, and differs from the application areas of the present invention. Summary of the Invention

[0010] The present invention provides a method for preparing a nitrogen-doped bone char catalyst and treating coking wastewater. The nitrogen-doped bone char material is widely available, does not contain metal components, and has no secondary pollution problem. The nitrogen-doped bone char is used to activate peracetic acid to treat the coking wastewater economically and efficiently, solving the problem of difficult-to-degrade organic matter in the existing coking wastewater treatment process. The nitrogen-doped bone char catalyst is combined with a membrane to activate peracetic acid generated in situ and thus degrade COD in the coking wastewater, avoiding the safety problem of directly adding peracetic acid and the problem of effluent acidification, and is conducive to the recovery of the nitrogen-doped bone char.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for preparing a nitrogen-doped bone char catalyst, wherein the nitrogen-doped bone char catalyst is bone char doped with nitrogen; the preparation process comprises the following steps:

[0013] S1. Preparing bone powder slurry: subjecting animal bones to high-temperature treatment, draining, crushing, and grinding to obtain bone powder; mixing the bone powder with ethanol, stirring, and ultrasonically mixing to obtain bone powder slurry;

[0014] S2. Preparing bone char precursor powder: adding a nitrogen-containing compound to the bone powder slurry obtained in step S1, evaporating to dryness under constant temperature stirring, and grinding to obtain bone char precursor powder;

[0015] S3, bone pre-carbonization: subjecting the bone char precursor powder obtained in step S2 to a high-temperature pre-reaction to obtain pre-carbonized bone char;

[0016] S4, preparing nitrogen-doped bone char catalyst: grinding the pre-carbonized bone char obtained in step S3, calcining under an inert gas atmosphere, and then grinding, acid washing, alcohol washing, and drying to obtain a nitrogen-doped bone char catalyst.

[0017] In step S1, the mass content of amorphous carbon in the animal bones is 9% to 13%, and the mass content of phosphorus is 18% to 26%; the high-temperature treatment is to boil the animal bones in boiling water at a high temperature for 1 to 3 hours; the grinding is ball milling, and the ball milling conditions are: a ball milling speed of 600 to 800 r / min, a ball milling time of 120 to 240 min, and a ball-to-material mass ratio of 50 to 100:1; the particle size of the bone powder is 0.5 to 2.5 mm; the mixing ratio of bone powder to ethanol is 3 to 5 g of bone powder: 50 to 100 mL of ethanol; the stirring paddle speed during stirring is 600 to 800 r / min, and the stirring time is 60 to 90 min; and the ultrasonic mixing time is 20 to 30 min.

[0018] In step S2, the nitrogen-containing compound is ammonium nitrate, hexamethylenetetramine or aminoguanidine; the mixing ratio of the nitrogen-containing compound to the bone powder slurry is 0.25g to 1.2g of the nitrogen-containing compound: 50 to 100mL of the bone powder slurry; the parameters for constant temperature stirring and evaporation are: temperature 60 to 70°C, stirring paddle speed 1000 to 1200 r / min; and grinding time 10 to 30 minutes.

[0019] In step S3, the high-temperature pre-reaction is calcined in a muffle furnace, and the calcination parameters are: temperature 300-500° C., heating rate 2-5° C. / min, and calcination time 90-150 min.

[0020] In step S4, the grinding time of the pre-carbonized bone char is 20 to 40 minutes; the calcination under an inert gas atmosphere is carried out in a tubular furnace, and the inert gas is nitrogen, argon or helium; the inert gas flow rate is 0.3 to 0.5 L / min, the calcination temperature is 450 to 800° C., the heating rate is 5 to 10° C. / min, and the calcination time is 2 to 4 hours; the pickling solution is glacial acetic acid, hydrochloric acid or sulfuric acid; the drying temperature is 60 to 80° C., and the drying time is 12 to 20 hours.

[0021] A method for treating coking wastewater specifically comprises the following steps:

[0022] T1. Preparation of nitrogen-doped bone char filter membrane: dissolving the nitrogen-doped bone char catalyst in an organic solvent and ultrasonically dispersing the resulting nitrogen-doped bone char dispersion, vacuum filtering the resulting nitrogen-doped bone char dispersion onto a polypropylene filter membrane, washing with alcohol, and drying to obtain the nitrogen-doped bone char filter membrane;

[0023] T2. Degradation reaction of coking wastewater: The nitrogen-doped bone char filter membrane is fixed to the membrane assembly, and the coking wastewater with added oxygen-based active agents and peroxides is used as the feed liquid to carry out a cyclic catalytic degradation reaction.

[0024] In step T1, the organic solvent is one of dimethylformamide, N,N-dimethylacetamide, and glycerol.

[0025] In the step T1, the ultrasonic dispersion time is 30 to 60 minutes, the drying temperature is 60 to 80° C., and the drying time is 12 to 20 hours.

[0026] In step T2, the cyclic catalytic degradation reaction is specifically: using a circulating pump to drive the coking wastewater to circulate at a pressure of 0.05 to 0.1 bar, the feed liquid enters the reaction container from top to bottom, and the reaction time is 3 to 6 hours.

[0027] In step T2, the oxygen-based active agent is tetraacetylethylenediamine with a concentration of 5 to 10 mM; the peroxide is sodium percarbonate with a concentration of 5 to 10 mM.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The nitrogen-doped bone char catalyst of the present invention has a large specific surface area and numerous pores, allowing it to adsorb new pollutants. The surface of the nitrogen-doped bone char catalyst of the present invention has abundant electron transfer channels, enabling it to continuously and efficiently deliver a large number of surface phosphorus-nitrogen sites generated by activated peracetic acid into water. The nitrogen-doped bone char with multidentate coordination containing phosphorus-nitrogen bonds has specific degradation properties for refractory cyclic aliphatic organic matter in coking wastewater, overcoming the drawbacks of conventional biochar materials that have unsatisfactory effects on degrading organic pollutants when activated with persulfate or peracetic acid in wastewater treatment processes.

[0030] 2) Compared with conventional carbon materials, the nitrogen-doped bone char material of the present invention has a wide range of sources, does not contain metal components, and has no secondary pollution problem.

[0031] 3) The nitrogen-doped bone char catalyst of the present invention is combined with a membrane to activate the in-situ generated peracetic acid to degrade COD in the coking wastewater, avoiding the safety issues and effluent acidification problems of directly adding peracetic acid, and is conducive to the recovery of nitrogen-doped bone char. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process curve diagram of degrading coking wastewater by activating peracetic acid with nitrogen-doped bone char in Examples 4 to 6 of the present invention. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing a nitrogen-doped bone char catalyst, wherein the nitrogen-doped bone char catalyst is bone char doped with nitrogen. The preparation process comprises the following steps:

[0034] S1. Preparing bone powder slurry: subjecting animal bones to high-temperature treatment, draining, crushing, and grinding to obtain bone powder; mixing the bone powder with ethanol, stirring, and ultrasonically mixing to obtain bone powder slurry;

[0035] S2. Preparing bone char precursor powder: adding a nitrogen-containing compound to the bone powder slurry obtained in step S1, evaporating to dryness under constant temperature stirring, and grinding to obtain bone char precursor powder;

[0036] S3, bone pre-carbonization: subjecting the bone char precursor powder obtained in step S2 to a high-temperature pre-reaction to obtain pre-carbonized bone char;

[0037] S4, preparing nitrogen-doped bone char catalyst: grinding the pre-carbonized bone char obtained in step S3, calcining under an inert gas atmosphere, and then grinding, acid washing, alcohol washing, and drying to obtain a nitrogen-doped bone char catalyst.

[0038] In step S1, the mass content of amorphous carbon in the animal bones is 9% to 13%, and the mass content of phosphorus is 18% to 26%; the high-temperature treatment is to boil the animal bones in boiling water at a high temperature for 1 to 3 hours; the grinding is ball milling, and the ball milling conditions are: a ball milling speed of 600 to 800 r / min, a ball milling time of 120 to 240 min, and a ball-to-material mass ratio of 50 to 100:1; the particle size of the bone powder is 0.5 to 2.5 mm; the mixing ratio of bone powder to ethanol is 3 to 5 g of bone powder: 50 to 100 mL of ethanol; the stirring paddle speed during stirring is 600 to 800 r / min, and the stirring time is 60 to 90 min; and the ultrasonic mixing time is 20 to 30 min.

[0039] In step S2, the nitrogen-containing compound is ammonium nitrate, hexamethylenetetramine or aminoguanidine; the mixing ratio of the nitrogen-containing compound to the bone powder slurry is 0.25g to 1.2g of the nitrogen-containing compound: 50 to 100mL of the bone powder slurry; the parameters for constant temperature stirring and evaporation are: temperature 60 to 70°C, stirring paddle speed 1000 to 1200 r / min; and grinding time 10 to 30 minutes.

[0040] In step S3, the high-temperature pre-reaction is calcined in a muffle furnace, and the calcination parameters are: temperature 300-500° C., heating rate 2-5° C. / min, and calcination time 90-150 min.

[0041] In step S4, the grinding time of the pre-carbonized bone char is 20 to 40 minutes; the calcination under an inert gas atmosphere is carried out in a tubular furnace, and the inert gas is nitrogen, argon or helium; the inert gas flow rate is 0.3 to 0.5 L / min, the calcination temperature is 450 to 800° C., the heating rate is 5 to 10° C. / min, and the calcination time is 2 to 4 hours; the pickling solution is glacial acetic acid, hydrochloric acid or sulfuric acid; the drying temperature is 60 to 80° C., and the drying time is 12 to 20 hours.

[0042] The method for treating coking wastewater of the present invention specifically comprises the following steps:

[0043] T1. Preparation of nitrogen-doped bone char filter membrane: dissolving the nitrogen-doped bone char catalyst in an organic solvent and ultrasonically dispersing the resulting nitrogen-doped bone char dispersion, vacuum filtering the resulting nitrogen-doped bone char dispersion onto a polypropylene filter membrane, washing with alcohol, and drying to obtain the nitrogen-doped bone char filter membrane;

[0044] T2. Degradation reaction of coking wastewater: The nitrogen-doped bone char filter membrane is fixed to the membrane assembly, and the coking wastewater with added oxygen-based active agents and peroxides is used as the feed liquid to carry out a cyclic catalytic degradation reaction.

[0045] In step T1, the organic solvent is one of dimethylformamide, N,N-dimethylacetamide, and glycerol.

[0046] In the step T1, the ultrasonic dispersion time is 30 to 60 minutes, the drying temperature is 60 to 80° C., and the drying time is 12 to 20 hours.

[0047] In step T2, the cyclic catalytic degradation reaction is specifically: using a circulating pump to drive the coking wastewater to circulate at a pressure of 0.05 to 0.1 bar, the feed liquid enters the reaction container from top to bottom, and the reaction time is 3 to 6 hours.

[0048] In step T2, the oxygen-based active agent is tetraacetylethylenediamine with a concentration of 5 to 10 mM; the peroxide is sodium percarbonate with a concentration of 5 to 10 mM.

[0049] In order to more intuitively embody the present invention, the embodiments of the present invention are further described in conjunction with examples. The following examples are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solution that can be obviously obtained by a person skilled in the art within the technical scope disclosed in the present invention, including simple changes or equivalent replacements, is within the scope of protection of the present invention.

[0050] The materials and instruments used in the following examples are all commercially available, and the raw materials are of analytical grade. In the following examples, unless otherwise specified, the data obtained are the average values of more than three repeated experiments.

[0051] [Example 1]

[0052] In this embodiment, the preparation process of the nitrogen-doped bone char catalyst is as follows:

[0053] S1. Animal bones with an amorphous carbon content of 9.34% by mass and a phosphorus content of 18.97% by mass were boiled in boiling water for 1 hour, naturally air-dried, and crushed. The bones were placed in a ball mill and ball-milled for 120 minutes at a ball-to-material mass ratio of 50:1 and a rotation speed of 600 r / min to obtain bone powder with a particle size of 2.5 mm; 3 g of the obtained bone powder was mixed with 50 mL of ethanol, stirred continuously at a rotation speed of 600 r / min for 60 minutes, and then ultrasonically treated for 25 minutes to obtain a bone powder slurry.

[0054] S2. Add 0.25 g of ammonium nitrate to the bone powder slurry obtained in step S1, evaporate to dryness with constant stirring at 60° C. and 1200 rpm, and grind the obtained material for 10 min to obtain bone char precursor powder.

[0055] S3. The bone char precursor powder obtained in step S2 is transferred into a crucible and placed in a muffle furnace. The crucible is heated to 300° C. at a heating rate of 2° C. / min and calcined at 300° C. for 150 min to obtain pre-carbonized bone char.

[0056] S4. Grind the pre-carbonized bone char obtained in step S3 for 20 minutes, transfer it to a crucible and place it in a tube furnace. In a nitrogen atmosphere with a gas flow rate of 0.5 L / min, heat it to 450°C at a heating rate of 5°C / min, and calcine it at 450°C for 4 hours. After cooling, grind it, pickle it with glacial acetic acid and alcohol, and dry it at 60°C for 20 hours to obtain a nitrogen-doped bone char catalyst, marked as N / BBC450.

[0057] [Example 2]

[0058] In this embodiment, the preparation process of the nitrogen-doped bone char catalyst is as follows:

[0059] S1. Animal bones with an amorphous carbon content of 11.21% by mass and a phosphorus content of 21.39% by mass were placed in boiling water and boiled for 2 hours. The bones were naturally air-dried and then ground into powder. The bones were placed in a ball mill and ball-milled for 180 minutes at a ball-to-material mass ratio of 75:1 and a rotation speed of 700 r / min to obtain bone powder with a particle size of 1.5 mm. 4 g of the obtained bone powder was mixed with 75 mL of ethanol, and the mixture was stirred continuously at a rotation speed of 700 r / min for 75 minutes, followed by ultrasonic treatment for 25 minutes to obtain a bone powder slurry.

[0060] S2. Add 0.75 g of hexamethylenetetramine to the bone powder slurry obtained in step S1, evaporate to dryness under constant temperature stirring at 65° C. and 1100 rpm, and grind the obtained material for 20 min to obtain bone char precursor powder.

[0061] S3. The bone char precursor powder obtained in step S2 is transferred into a crucible and placed in a muffle furnace. The crucible is heated to 450° C. at a heating rate of 5° C. / min and calcined at 450° C. for 120 min to obtain pre-carbonized bone char.

[0062] S4. Grind the pre-carbonized bone char obtained in step S3 for 30 minutes, transfer it to a crucible and place it in a tube furnace. In an argon atmosphere with a gas flow rate of 0.4 L / min, heat it to 700°C at a heating rate of 5°C / min, and calcine it at 700°C for 3 hours. After cooling, grind it, pickle it with hydrochloric acid and wash it with alcohol, and then dry it at 70°C for 16 hours to obtain a nitrogen-doped bone char catalyst, marked as N / BBC700.

[0063] [Example 3]

[0064] In this embodiment, the preparation process of the nitrogen-doped bone char catalyst is as follows:

[0065] S1. Animal bones with an amorphous carbon content of 12.44% by mass and a phosphorus content of 25.28% by mass were boiled in boiling water for 3 hours, naturally air-dried, and crushed. The bones were placed in a ball mill and ball-milled for 240 minutes at a ball-to-material mass ratio of 100:1 and a rotation speed of 800 r / min to obtain bone powder with a particle size of 0.5 mm; 5 g of the obtained bone powder was mixed with 100 mL of ethanol, stirred continuously at a rotation speed of 800 r / min for 90 minutes, and then ultrasonically treated for 30 minutes to obtain a bone powder slurry.

[0066] S2. Add 1.25 g of aminoguanidine to the bone powder slurry obtained in step S1, evaporate to dryness under constant temperature stirring at 70° C. and 1000 rpm, and grind the obtained material for 30 minutes to obtain bone char precursor powder.

[0067] S3. The bone char precursor powder obtained in step S2 is transferred into a crucible and placed in a muffle furnace. The crucible is heated to 500° C. at a heating rate of 5° C. / min and calcined at 500° C. for 90 min to obtain pre-carbonized bone char.

[0068] S4. Grind the pre-carbonized bone char obtained in step S3 for 40 minutes, transfer it to a crucible and place it in a tube furnace. In a nitrogen atmosphere with a gas flow rate of 0.3 L / min, heat it to 800°C at a heating rate of 10°C / min, and calcine it at 800°C for 2 hours. After cooling, grind it, pickle it with sulfuric acid and wash it with alcohol, and then dry it at 80°C for 12 hours to obtain a nitrogen-doped bone char catalyst, which is marked as N / BBC800.

[0069] [Example 4]

[0070] In this embodiment, the process of treating coking wastewater using nitrogen-doped bone char catalyst to activate in-situ synthesized peracetic acid is as follows:

[0071] T1. Dissolve the N / BBC450 nitrogen-doped bone char catalyst prepared in Example 1 in dimethylformamide and sonicate for 30 minutes. Vacuum filter the evenly dispersed N / BBC450 nitrogen-doped bone char solution onto a polypropylene filter membrane, wash with alcohol, and dry at 80°C for 12 hours to obtain a nitrogen-doped bone char filter membrane.

[0072] T2. Fix the nitrogen-doped bone char filter membrane to the membrane assembly, use coking wastewater containing tetraacetylethylenediamine and sodium percarbonate as the feed liquid, the concentration of tetraacetylethylenediamine in the feed liquid is 5mM, and the concentration of sodium percarbonate is 5mM. Use a circulating pump with a hydraulic driving force of 0.05bar to carry out a cyclic catalytic degradation reaction from top to bottom. Take the filtrate after the filter membrane at regular intervals for COD concentration testing. The data are shown in the attached figure. Figure 1 shown.

[0073] The same method was used to measure the N / BBC700 nitrogen-doped bone char catalyst and the N / BBC800 nitrogen-doped bone char catalyst. The data are shown in the attached figure. Figure 1 shown.

[0074] [Example 5]

[0075] In this embodiment, the process of treating coking wastewater using nitrogen-doped bone char catalyst to activate in-situ synthesized peracetic acid is as follows:

[0076] T1. Dissolve the N / BBC450 nitrogen-doped bone char catalyst prepared in Example 1 in N,N-dimethylacetamide and sonicate for 45 minutes. Vacuum filter the evenly dispersed N / BBC450 nitrogen-doped bone char solution onto a polypropylene filter membrane, wash with alcohol, and dry at 70°C for 16 hours to obtain a nitrogen-doped bone char filter membrane.

[0077] T2. Fix the nitrogen-doped bone char filter membrane to the membrane assembly, use coking wastewater containing tetraacetylethylenediamine and sodium percarbonate as the feed liquid, the concentration of tetraacetylethylenediamine in the feed liquid is 7.5mM, and the concentration of sodium percarbonate is 7.5mM. Use a circulating pump with a hydraulic driving force of 0.1bar to carry out a cyclic catalytic degradation reaction from top to bottom. Take the filtrate after the filter membrane at regular intervals for COD concentration testing. The data are shown in the attached figure. Figure 1 shown.

[0078] The same method was used to measure the N / BBC700 nitrogen-doped bone char catalyst and the N / BBC800 nitrogen-doped bone char catalyst. The data are shown in the attached figure. Figure 1 shown.

[0079] [Example 6]

[0080] In this embodiment, the process of treating coking wastewater using nitrogen-doped bone char catalyst to activate in-situ synthesized peracetic acid is as follows:

[0081] T1. Dissolve the N / BBC450 nitrogen-doped bone char catalyst prepared in Example 1 in glycerol and sonicate for 60 minutes. Vacuum filter the evenly dispersed N / BBC450 nitrogen-doped bone char solution onto a polypropylene filter membrane. After washing with alcohol, dry it at 60°C for 20 hours to obtain a nitrogen-doped bone char filter membrane.

[0082] T2. Fix the nitrogen-doped bone char filter membrane to the membrane assembly, use coking wastewater containing tetraacetylethylenediamine and sodium percarbonate as the feed liquid, the concentration of tetraacetylethylenediamine in the feed liquid is 10mM, and the concentration of sodium percarbonate is 10mM. Use a circulating pump with a hydraulic driving force of 0.1bar to carry out a cyclic catalytic degradation reaction from top to bottom. Take the filtrate after the filter membrane at regular intervals for COD concentration testing. The data are shown in the attached figure. Figure 1 shown.

[0083] The same method was used to measure the N / BBC700 nitrogen-doped bone char catalyst and the N / BBC800 nitrogen-doped bone char catalyst. The data are shown in the attached figure. Figure 1 shown.

[0084] Compare with Figure 1 According to the data of Examples 4-6, N / BBC700 nitrogen-doped bone char catalyst has a better effect of activating peracetic acid to degrade COD in coking wastewater than N / BBC800 nitrogen-doped bone char catalyst and N / BBC450 nitrogen-doped bone char catalyst, which proves that increasing the concentration of oxygen-based active agents and peroxides is beneficial to the degradation of pollutants in coking wastewater.

[0085] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-doped bone char catalyst, characterized in that: The nitrogen-doped bone char catalyst is bone char doped with nitrogen; the preparation process comprises the following steps: S1. Preparing bone powder slurry: subjecting animal bones to high-temperature treatment, draining, crushing, and grinding to obtain bone powder; mixing the bone powder with ethanol, stirring, and ultrasonically mixing to obtain bone powder slurry; S2. Preparing bone char precursor powder: adding a nitrogen-containing compound to the bone powder slurry obtained in step S1, evaporating to dryness under constant temperature stirring, and grinding to obtain bone char precursor powder; S3, bone pre-carbonization: subjecting the bone char precursor powder obtained in step S2 to a high-temperature pre-reaction to obtain pre-carbonized bone char; S4, preparing nitrogen-doped bone char catalyst: grinding the pre-carbonized bone char obtained in step S3, calcining under an inert gas atmosphere, and then grinding, acid washing, alcohol washing, and drying to obtain a nitrogen-doped bone char catalyst.

2. The method for preparing a nitrogen-doped bone char catalyst according to claim 1, characterized in that: In step S1, the mass content of amorphous carbon in the animal bones is 9% to 13%, and the mass content of phosphorus is 18% to 26%; the high-temperature treatment is to boil the animal bones in boiling water at a high temperature for 1 to 3 hours; the grinding is ball milling, and the ball milling conditions are: a ball milling speed of 600 to 800 r / min, a ball milling time of 120 to 240 min, and a ball-to-material mass ratio of 50 to 100:1; the particle size of the bone powder is 0.5 to 2.5 mm; the mixing ratio of bone powder to ethanol is 3 to 5 g of bone powder: 50 to 100 mL of ethanol; the stirring paddle speed during stirring is 600 to 800 r / min, and the stirring time is 60 to 90 min; and the ultrasonic mixing time is 20 to 30 min.

3. The method for preparing a nitrogen-doped bone char catalyst according to claim 1, characterized in that: In step S2, the nitrogen-containing compound is ammonium nitrate, hexamethylenetetramine or aminoguanidine; the mixing ratio of the nitrogen-containing compound to the bone powder slurry is 0.25g to 1.2g of the nitrogen-containing compound: 50 to 100mL of the bone powder slurry; the parameters for constant temperature stirring and evaporation are: temperature 60 to 70°C, stirring paddle speed 1000 to 1200 r / min; and grinding time 10 to 30 minutes.

4. The method for preparing a nitrogen-doped bone char catalyst according to claim 1, characterized in that: In step S3, the high-temperature pre-reaction is calcined in a muffle furnace, and the calcination parameters are: temperature 300-500° C., heating rate 2-5° C. / min, and calcination time 90-150 min.

5. The method for preparing a nitrogen-doped bone char catalyst according to claim 1, characterized in that: In step S4, the grinding time of the pre-carbonized bone char is 20 to 40 minutes; the calcination under an inert gas atmosphere is carried out in a tubular furnace, and the inert gas is nitrogen, argon or helium; the inert gas flow rate is 0.3 to 0.5 L / min, the calcination temperature is 450 to 800° C., the heating rate is 5 to 10° C. / min, and the calcination time is 2 to 4 hours; the pickling solution is glacial acetic acid, hydrochloric acid or sulfuric acid; the drying temperature is 60 to 80° C., and the drying time is 12 to 20 hours.

6. A method for treating coking wastewater, using the nitrogen-doped bone char catalyst according to any one of claims 1 to 5, characterized in that: The specific steps include: T1. Preparation of nitrogen-doped bone char filter membrane: dissolving the nitrogen-doped bone char catalyst in an organic solvent and ultrasonically dispersing the resulting nitrogen-doped bone char dispersion, vacuum filtering the resulting nitrogen-doped bone char dispersion onto a polypropylene filter membrane, washing with alcohol, and drying to obtain the nitrogen-doped bone char filter membrane; T2. Degradation reaction of coking wastewater: The nitrogen-doped bone char filter membrane is fixed to the membrane assembly, and the coking wastewater with added oxygen-based active agents and peroxides is used as the feed liquid to carry out a cyclic catalytic degradation reaction.

7. A method for treating coking wastewater according to claim 6, characterized in that: In step T1, the organic solvent is one of dimethylformamide, N,N-dimethylacetamide, and glycerol.

8. The method for treating coking wastewater according to claim 6, characterized in that: In the step T1, the ultrasonic dispersion time is 30 to 60 minutes, the drying temperature is 60 to 80° C., and the drying time is 12 to 20 hours.

9. The method for treating coking wastewater according to claim 6, characterized in that: In step T2, the cyclic catalytic degradation reaction is specifically: using a circulating pump to drive the coking wastewater to circulate at a pressure of 0.05 to 0.1 bar, the feed liquid enters the reaction container from top to bottom, and the reaction time is 3 to 6 hours.

10. The method for treating coking wastewater according to claim 6, characterized in that: In step T2, the oxygen-based active agent is tetraacetylethylenediamine with a concentration of 5 to 10 mM; the peroxide is sodium percarbonate with a concentration of 5 to 10 mM.

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