Carbon phosphorus specific flocculation adsorption magnetic carbon-based material and preparation method thereof

Abstract

The application discloses a preparation method of a carbon-phosphorus specific flocculation adsorption magnetic carbon-based material and application thereof, and belongs to the field of sewage treatment materials. A certain proportion of biochar, iron salt and iron powder are uniformly mixed under certain conditions (pH, stirring speed and stirring time) to obtain a first mixed solution, the first mixed solution is dried, broken, and then placed in a muffle furnace for anaerobic pyrolysis to obtain a magnetic biochar adsorbent. The magnetic biochar adsorbent is acid-modified by using hydrochloric acid with a certain concentration to obtain a second mixed solution. The second mixed solution is dried and cooled, and the product is sieved to obtain the carbon-phosphorus specific flocculation adsorption magnetic carbon-based material. The carbon-phosphorus specific flocculation adsorption magnetic carbon-based material has low cost, integrates the functions of flocculation, adsorption and magnetic response, and is suitable for sewage treatment.

Description

Technical Field

[0001] The invention belongs to the field of sewage treatment materials, and in particular relates to a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material and a preparation method thereof. Background Art

[0002] With the development of urbanization, the amount of recalcitrant organic matter in various industrial wastewaters and urban sewage has increased, and sewage treatment plant discharge standards have been tightened. Currently, treatment technologies, such as coagulation and sedimentation processes, are gradually shifting from removing suspended solids to capturing and recycling them. Coagulation and sedimentation combined with simultaneous adsorption using porous materials has great potential in wastewater treatment.

[0003] Magnetic coagulation and sedimentation is an enhanced sedimentation process that adds magnetic powder to the conventional coagulation and sedimentation process. This allows the magnetic powder to further bind with the flocs produced by the coagulant, thereby increasing the density of the flocs, accelerating the floc settling rate, increasing the surface hydraulic load, and reducing the equipment footprint. Magnetic coagulation and sedimentation also has a good removal effect on both phosphorus and suspended solids.

[0004] However, the magnetic coagulation precipitation technology with a single addition of magnetic powder has problems such as easy generation of rust in water, narrow applicable pH range, and generation of large amounts of iron-containing sludge after the reaction. Due to the above problems, the magnetic coagulation precipitation technology with a single addition of magnetic powder is not conducive to its large-scale promotion and application. Therefore, researchers' research on magnetically loaded coagulation adsorption materials mainly focuses on two aspects: (1) finding or preparing suitable low-cost carriers so that the active components of the metal can be evenly and firmly loaded on the carrier to improve the performance of the flocculant and its solid-liquid separation ability; (2) selecting and optimizing material components, and regulating the metal in the active component by optimizing the preparation conditions to prepare efficient and stable magnetically loaded coagulation adsorption materials with higher efficiency, better adaptability, and a wider pH range of use.

[0005] Powdered adsorbents prepared using biochar as a carrier have high carbon and phosphorus removal efficiency, but are easily lost during water treatment reactions. Therefore, the material can be given magnetic properties by adding magnetic iron powder during the preparation process, and acid modification can further enrich the active sites on the material's surface, allowing it to be used for coagulation and adsorption of target pollutants in wastewater. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies in the prior art and prepare a low-cost magnetic carbon-based material that integrates carbon-phosphorus synergistic capture and magnetic responsiveness functions, and specifically provide a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material and a preparation method thereof.

[0007] The specific technical solutions adopted in the present invention are as follows:

[0008] In a first aspect, the present invention provides a method for preparing a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material, the specific steps of which are as follows:

[0009] S1: Disperse biochar powder evenly in water to obtain a biochar dispersion. Add iron salt to the biochar dispersion and stir evenly to obtain a biochar mixture.

[0010] S2: After iron powder is added to the biochar mixed solution for mixing reaction, sodium hydroxide solution is added dropwise to adjust the pH value to a range of 10 to 11 to obtain a first mixed solution.

[0011] S3: drying the first mixed solution under anoxic conditions to obtain a first product, performing anoxic pyrolysis on the first product, and then grinding the first product to obtain a powdered magnetic biochar adsorbent.

[0012] S4: The magnetic biochar adsorbent is acid-modified with hydrochloric acid to obtain a second mixed solution, wherein the mass concentration of the hydrochloric acid is 5% to 70%. The second mixed solution is dried and cooled to obtain a second product, and the second product is sieved to obtain a carbon-phosphorus specific flocculation adsorption magnetic carbon-based material.

[0013] Preferably, the biochar dispersion is prepared by adding biochar through a 200-mesh sieve to water and dispersing the biochar by microwaves, wherein the microwave dispersion frequency is 40 to 60 Hz and the microwave dispersion time is 15 to 30 minutes.

[0014] Preferably, the iron salts are ferrous sulfate heptahydrate and ferric sulfate. The mass ratio of ferrous sulfate heptahydrate and ferric sulfate to biochar in the biochar mixture is 20:7:100.

[0015] Preferably, the biochar mixture in S1 is stirred at a coagulation stirring rate of 250 r / min for 30 min using a coagulation test mixer. The mixing reaction process in S2 is carried out using a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min.

[0016] Preferably, the particle size of the iron powder is less than 300 mesh. The mass ratio of biochar to iron powder in the first mixed solution is 100:(20-60).

[0017] Preferably, the first product is placed in a covered crucible and subjected to an oxygen-deficient pyrolysis process in a muffle furnace. The pyrolysis temperature in the muffle furnace is 350°C, the pyrolysis time is 2 hours, and the heating program is set as follows: heating to 350°C at a heating rate of 5°C / min, and holding time is 2 hours.

[0018] Preferably, the mass concentration of the hydrochloric acid is 50% to 70%. The hydrochloric acid and the magnetic biochar adsorbent are mixed in a ratio of 1 mL:1 g.

[0019] Preferably, the particle size of the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material is less than 200 meshes.

[0020] In a second aspect, the present invention provides a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material prepared by the preparation method described in the first aspect.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] Compared with existing technologies,

[0023] (1) The carbon-phosphorus specific flocculation adsorption magnetic carbon-based material prepared by the present invention has a honeycomb-like porous structure on the surface, with a large number of pores visible inside, the pore sizes are different, the specific surface area is large, and the adsorption and removal effect of pollutants is good;

[0024] (2) The carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material prepared by the present invention is acid-modified, and has a large number of oxygen-containing functional groups on its surface as reactive sites. Compared with traditional coagulants, it can better bind to target pollutants through electrical neutralization, adsorption bridging, and sweeping flocculation, undergoing hydroxyl complexation to produce multi-nuclear hydroxyl complexes, which aggregate into colloids and precipitate more quickly. This material is used as a flocculant in sewage treatment, with a fast reaction speed and high treatment efficiency.

[0025] (3) The carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material prepared by the present invention has a high proportion of iron, and the magnetic responsiveness of elemental iron itself can be used to give the biochar coagulation catalyst magnetism, which is convenient for separation or recycling after recovery by magnetic separation equipment;

[0026] (4) The preparation method provided by the present invention is an overall technical solution, in which each step and condition parameter are closely linked and work together, and has the advantages of simple process route, low production cost, and mild production conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flow chart for preparing the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material provided by the present invention;

[0028] Figure 2 The SEM images of the unmodified biochar BC and the carbon-phosphorus specific flocculation adsorption magnetic carbon-based material of Example 1;

[0029] Figure 3 XRD patterns of different materials;

[0030] Figure 4 Comparison of carbon and phosphorus removal effects of different materials, where (a) is COD removal and (b) is phosphorus removal;

[0031] Figure 5 This is the VSM diagram of the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material of Example 1;

[0032] Figure 6 This is a comparison chart of the carbon and phosphorus removal effects of the carbon-phosphorus specific flocculation adsorption magnetic carbon-based materials obtained by modifying the magnetic biochar adsorbent with hydrochloric acid of different mass concentrations, where (a) is COD removal and (b) is phosphorus removal. DETAILED DESCRIPTION

[0033] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention may be combined accordingly, provided that there is no conflict between them.

[0034] The preparation process of a carbon-phosphorus specific flocculation adsorption magnetic carbon-based material provided by the present invention is as follows: Figure 1 As shown in the figure, a certain proportion of biochar, iron salt, and iron powder are mixed under specific conditions (pH, stirring rate, and stirring time) to produce a first mixed solution. The first mixed solution is dried, crushed, and placed in a muffle furnace for anoxic pyrolysis to produce a magnetic biochar adsorbent (M-BC). The magnetic biochar adsorbent (M-BC) is acid-modified with a certain concentration of hydrochloric acid to produce a second mixed solution. The dried, cooled, and sieved product of the second mixed solution is used to prepare a carbon-phosphorus-specific flocculating magnetic carbon-based material (A / M-BC).

[0035] Example 1

[0036] This embodiment provides a method for preparing a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material modified with hydrochloric acid having a mass concentration of 50%. The specific steps are as follows:

[0037] (1) Biochar powder passed through a 200-mesh sieve was uniformly dispersed in water using microwave dispersion. The microwave dispersion frequency was 45 Hz and the duration was 20 min, ultimately obtaining a biochar dispersion with a moisture content of 80%. Iron salt was added to the biochar dispersion in a mass ratio of ferrous sulfate heptahydrate: ferric sulfate: biochar of 20:7:100, and the mixture was stirred in a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min to obtain a biochar mixture.

[0038] (2) Iron powder with a particle size of less than 300 mesh was added to the above biochar mixture at a mass ratio of biochar to iron powder of 100:25, and the mixture was stirred at a coagulation stirring rate of 250 r / min for 30 min in a coagulation test mixer, and sodium hydroxide solution was added dropwise to adjust the pH to 11 to obtain a first mixed solution.

[0039] (3) The first mixed solution was placed in a covered crucible to form an oxygen-deficient condition, placed in an oven at 105°C for 24 hours, and dried to obtain the first product. After the first product was ground and crushed, it was placed in a 50 mL crucible and sealed with a cover, and then placed in a muffle furnace for anoxic pyrolysis. The pyrolysis temperature in the muffle furnace was 350°C, the pyrolysis time was 2 hours, and the heating program was set as follows: heating to 350°C at a heating rate of 5°C / min, and the residence time was 2 hours. After the pyrolysis was completed, the black powder in the crucible was taken out after the muffle furnace was cooled to below 100°C, and after grinding and passing through a 200 mesh sieve, a powdered magnetic biochar adsorbent (M-BC) was obtained.

[0040] (4) The magnetic biochar adsorbent (M-BC) was acid-modified using hydrochloric acid at a mass concentration of 50%. The mixture was uniformly mixed in a ratio of hydrochloric acid: M-BC = 1 mL: 1 g to obtain a second mixed solution. The second mixed solution was placed in an oven and dried at 105°C for 24 hours. After grinding and passing through a 200-mesh sieve, a carbon-phosphorus-specific flocculating adsorption magnetic carbon-based material (A / M-BC) was obtained.

[0041] In order to characterize the surface morphology and elemental composition of the carbon-phosphorus specific flocculation adsorption magnetic carbon-based material (A / M-BC) prepared in this example, the samples were characterized and analyzed by SEM and XRD. The results are as follows: Figure 2 and Figure 3 As shown. Figure 2 (a) and Figure 2 (b) are scanning electron micrographs of the original biochar (unmodified biochar BC) and the carbon-phosphorus specific flocculation adsorption magnetic carbon-based material (A / M-BC) prepared in Example 1. It can be seen that the A / M-BC prepared in Example 1 has a honeycomb-like porous structure on the surface, with a large number of pores visible inside, with different pore sizes and a large specific surface area. Figure 3 Analysis of the XRD results shows that the A / M-BC prepared in Example 1 has a high carbon content and contains various iron oxides. The XRD pattern shows the corresponding generation of FeOOH, which easily produces hydroxyl radicals, capable of oxidizing most organic matter and promoting the harmlessness of organic pollutants.

[0042] Figure 5 This is the VSM diagram of the carbon-phosphorus specific flocculation adsorption magnetic carbon-based material (A / M-BC) prepared in Example 1. The results show that the material has paramagnetism. Figure 3 Comparing the XRD results with the standard spectrum, it was found that magnetic powder and magnetite-like magnetic substances were effectively attached to the material, so it was suitable for magnetic separation after flocculation, which was consistent with the VSM results.

[0043] In order to verify the effect of the above-mentioned A / M-BC material on the removal of carbon and phosphorus in sewage, 1L of biochemical effluent from a sewage treatment plant was taken. The raw water COD was 194mg / L and TP was 2.1686mg / L. The above-mentioned A / M-BC material was added to the raw water at a mass concentration of 400mg / L. The mixture was stirred at 300r / min for 3min and then at 200r / min for 30min on a coagulation test mixer. After standing for 0.5h, the supernatant was taken to determine the COD and TP.

[0044] After treatment, the COD was 69 mg / L, the TP was 0.1376 mg / L, the COD removal rate was 64.43%, and the TP removal rate was 93.65%.

[0045] Example 2

[0046] This embodiment provides a method for preparing a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material modified with hydrochloric acid having a mass concentration of 70%. The specific steps are as follows:

[0047] (1) Biochar powder passed through a 200-mesh sieve was uniformly dispersed in water using microwave dispersion. The microwave dispersion frequency was 45 Hz and the duration was 20 min, ultimately obtaining a biochar dispersion with a moisture content of 80%. Iron salt was added to the biochar dispersion in a mass ratio of ferrous sulfate heptahydrate: ferric sulfate: biochar of 20:7:100, and the mixture was stirred in a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min to obtain a biochar mixture.

[0048] (2) Iron powder with a particle size of less than 300 mesh was added to the above biochar mixture at a mass ratio of biochar to iron powder of 100:25, and the mixture was stirred at a coagulation stirring rate of 250 r / min for 30 min in a coagulation test mixer, and sodium hydroxide solution was added dropwise to adjust the pH to 11 to obtain a first mixed solution.

[0049] (3) The first mixed solution was placed in a covered crucible to form an oxygen-deficient condition, placed in an oven at 105°C for 24 hours, and dried to obtain the first product. After the first product was ground and crushed, it was placed in a 50 mL crucible and sealed with a cover, and then placed in a muffle furnace for anoxic pyrolysis. The pyrolysis temperature in the muffle furnace was 350°C, the pyrolysis time was 2 hours, and the heating program was set as follows: heating to 350°C at a heating rate of 5°C / min, and the residence time was 2 hours. After the pyrolysis was completed, the black powder in the crucible was taken out after the muffle furnace was cooled to below 100°C, and after grinding and passing through a 200 mesh sieve, a powdered magnetic biochar adsorbent (M-BC) was obtained.

[0050] (4) The magnetic biochar adsorbent (M-BC) was acid-modified using hydrochloric acid at a mass concentration of 70%. The mixture was evenly mixed in a ratio of hydrochloric acid: M-BC = 1 mL: 1 g to obtain a second mixed solution. The second mixed solution was placed in an oven and dried at 105°C for 24 hours. After grinding and passing through a 200-mesh sieve, a carbon-phosphorus-specific flocculating adsorption magnetic carbon-based material (A / M-BC) was obtained.

[0051] In order to verify the effect of the above-mentioned A / M-BC material on the removal of carbon and phosphorus in sewage, 1L of biochemical effluent from a sewage treatment plant was taken. The raw water COD was 270mg / L and TP was 4.1290mg / L. The above-mentioned A / M-BC material was added to the raw water at a mass concentration of 400mg / L. The mixture was stirred at 300r / min for 3min and then at 200r / min for 30min on a coagulation test mixer. After standing for 0.5h, the supernatant was taken to determine the COD and TP.

[0052] After treatment, the COD was 66 mg / L, the TP was 0.2838 mg / L, the COD removal rate was 75.74%, and the TP removal rate was 93.13%.

[0053] Example 3

[0054] This embodiment provides a method for preparing a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material modified with hydrochloric acid having a mass concentration of 60%. The specific steps are as follows:

[0055] (1) Biochar powder passed through a 200-mesh sieve was uniformly dispersed in water using microwave dispersion. The microwave dispersion frequency was 45 Hz and the duration was 20 min, ultimately obtaining a biochar dispersion with a moisture content of 80%. Iron salt was added to the biochar dispersion in a mass ratio of ferrous sulfate heptahydrate: ferric sulfate: biochar of 20:7:100, and the mixture was stirred in a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min to obtain a biochar mixture.

[0056] (2) Iron powder with a particle size of less than 300 mesh was added to the above biochar mixture at a mass ratio of biochar to iron powder of 100:25, and the mixture was stirred at a coagulation stirring rate of 250 r / min for 30 min in a coagulation test mixer, and sodium hydroxide solution was added dropwise to adjust the pH to 11 to obtain a first mixed solution.

[0057] (3) The first mixed solution was placed in a covered crucible to form an oxygen-deficient condition, placed in an oven at 105°C for 24 hours, and dried to obtain the first product. After the first product was ground and crushed, it was placed in a 50 mL crucible and sealed with a cover, and then placed in a muffle furnace for anoxic pyrolysis. The pyrolysis temperature in the muffle furnace was 350°C, the pyrolysis time was 2 hours, and the heating program was set as follows: heating to 350°C at a heating rate of 5°C / min, and the residence time was 2 hours. After the pyrolysis was completed, the black powder in the crucible was taken out after the muffle furnace was cooled to below 100°C, and after grinding and passing through a 200 mesh sieve, a powdered magnetic biochar adsorbent (M-BC) was obtained.

[0058] (4) The magnetic biochar adsorbent (M-BC) was acid-modified using hydrochloric acid with a mass concentration of 60%. The mixture was evenly mixed in a ratio of hydrochloric acid: M-BC = 1 mL: 1 g to obtain a second mixed solution. The second mixed solution was placed in an oven and dried at a temperature of 105°C for 24 hours. After grinding and passing through a 200-mesh sieve, a carbon-phosphorus-specific flocculating adsorption magnetic carbon-based material (A / M-BC) was obtained.

[0059] In order to verify the effect of the above-mentioned A / M-BC material on the removal of carbon and phosphorus in sewage, 1L of biochemical effluent from a sewage treatment plant was taken. The raw water COD was 270mg / L and TP was 4.1290mg / L. The above-mentioned A / M-BC material was added to the raw water at a mass concentration of 400mg / L. The mixture was stirred at 300r / min for 3min and then at 200r / min for 30min on a coagulation test mixer. After standing for 0.5h, the supernatant was taken to determine the COD and TP.

[0060] After treatment, the COD was 73 mg / L, the TP was 0.3018 mg / L, the COD removal rate was 72.96%, and the TP removal rate was 92.69%.

[0061] Example 4

[0062] This embodiment provides a method for preparing a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material modified with hydrochloric acid having a mass concentration of 50%. The specific steps are as follows:

[0063] (1) Biochar powder passed through a 200-mesh sieve was uniformly dispersed in water using microwave dispersion. The microwave dispersion frequency was 45 Hz and the duration was 20 min, ultimately obtaining a biochar dispersion with a moisture content of 80%. Iron salt was added to the biochar dispersion in a mass ratio of ferrous sulfate heptahydrate: ferric sulfate: biochar of 20:7:100, and the mixture was stirred in a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min to obtain a biochar mixture.

[0064] (2) Iron powder with a particle size of less than 300 mesh was added to the above biochar mixture at a mass ratio of biochar to iron powder of 100:40, and the mixture was stirred at a coagulation stirring rate of 250 r / min for 30 min in a coagulation test mixer, and sodium hydroxide solution was added dropwise to adjust the pH to 11 to obtain a first mixed solution.

[0065] (3) The first mixed solution was placed in a covered crucible to form an oxygen-deficient condition, placed in an oven at 105°C for 24 hours, and dried to obtain the first product. After the first product was ground and crushed, it was placed in a 50 mL crucible and sealed with a cover, and then placed in a muffle furnace for anoxic pyrolysis. The pyrolysis temperature in the muffle furnace was 350°C, the pyrolysis time was 2 hours, and the heating program was set as follows: heating to 350°C at a heating rate of 5°C / min, and the residence time was 2 hours. After the pyrolysis was completed, the black powder in the crucible was taken out after the muffle furnace was cooled to below 100°C, and after grinding and passing through a 200 mesh sieve, a powdered magnetic biochar adsorbent (M-BC) was obtained.

[0066] (4) The magnetic biochar adsorbent (M-BC) was acid-modified using hydrochloric acid at a mass concentration of 50%. The mixture was uniformly mixed in a ratio of hydrochloric acid: M-BC = 1 mL: 1 g to obtain a second mixed solution. The second mixed solution was placed in an oven and dried at 105°C for 24 hours. After grinding and passing through a 200-mesh sieve, a carbon-phosphorus-specific flocculating adsorption magnetic carbon-based material (A / M-BC) was obtained.

[0067] To verify the effectiveness of the A / M-BC material in removing carbon and phosphorus from wastewater, 1L of biochemical effluent from a sewage treatment plant with a COD of 214 mg / L and a TP of 3.9380 mg / L was added to the water at a concentration of 400 mg / L. The mixture was stirred in a coagulation test mixer at 300 rpm for 3 minutes, then at 200 rpm for 30 minutes. After standing for 0.5 hours, the supernatant was collected and measured for COD and TP. After treatment, the COD and TP values ​​were 61 mg / L and 0.3729 mg / L, respectively, resulting in COD removal rates of 71.50% and TP removal rates of 90.53%.

[0068] Comparative Example 1

[0069] Compared with Example 4, this comparative example provides a method for preparing a magnetic biochar adsorbent (M-BC) without hydrochloric acid modification, and the specific steps are as follows:

[0070] (1) Biochar powder passed through a 200-mesh sieve was uniformly dispersed in water using microwave dispersion. The microwave dispersion frequency was 45 Hz and the duration was 20 min, ultimately obtaining a biochar dispersion with a moisture content of 80%. Iron salt was added to the biochar dispersion in a mass ratio of ferrous sulfate heptahydrate: ferric sulfate: biochar of 20:7:100, and the mixture was stirred in a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min to obtain a biochar mixture.

[0071] (2) Iron powder with a particle size of less than 300 mesh was added to the above biochar mixture at a mass ratio of biochar to iron powder of 100:40, and the mixture was stirred at a coagulation stirring rate of 250 r / min for 30 min in a coagulation test mixer, and sodium hydroxide solution was added dropwise to adjust the pH to 11 to obtain a first mixed solution.

[0072] (3) The first mixed solution was placed in a covered crucible to form an oxygen-deficient condition, placed in an oven at 105°C for 24 hours, and dried to obtain the first product. After the first product was ground and crushed, it was placed in a 50 mL crucible and sealed with a cover, and then placed in a muffle furnace for anoxic pyrolysis. The pyrolysis temperature in the muffle furnace was 350°C, the pyrolysis time was 2 hours, and the heating program was set as follows: heating to 350°C at a heating rate of 5°C / min, and the residence time was 2 hours. After the pyrolysis was completed, the black powder in the crucible was taken out after the muffle furnace was cooled to below 100°C, and after grinding and passing through a 200 mesh sieve, a powdered magnetic biochar adsorbent (M-BC) was obtained.

[0073] To verify the effectiveness of the M-BC material in removing carbon and phosphorus from wastewater, 1L of biochemical effluent from a sewage treatment plant with a COD of 286mg / L and a TP of 4.2350mg / L was added to the water at a concentration of 400mg / L. The mixture was stirred in a coagulation test mixer at 300r / min for 3 minutes, then at 200r / min for 30 minutes. After standing for 0.5h, the supernatant was collected and measured for COD and TP. After treatment, the COD was 144mg / L and the TP was 3.3406mg / L, resulting in COD removal rates of 49.62% and TP removal rates of 21.12%.

[0074] Comparative Example 2

[0075] This comparative example provides a method for preparing a magnetic biochar adsorbent (M-BC) without hydrochloric acid modification, and the specific steps are as follows:

[0076] (1) Biochar powder passed through a 200-mesh sieve was uniformly dispersed in water using microwave dispersion. The microwave dispersion frequency was 45 Hz and the duration was 20 min, ultimately obtaining a biochar dispersion with a moisture content of 80%. Iron salt was added to the biochar dispersion in a mass ratio of ferrous sulfate heptahydrate: ferric sulfate: biochar of 20:7:100, and the mixture was stirred in a coagulation test mixer at a coagulation stirring rate of 250 r / min for 30 min to obtain a biochar mixture.

[0077] (2) Iron powder with a particle size of less than 300 mesh was added to the above biochar mixture at a mass ratio of biochar to iron powder of 100:20, and the mixture was stirred at a coagulation stirring rate of 250 r / min for 30 min in a coagulation test mixer, and sodium hydroxide solution was added dropwise to adjust the pH to 11 to obtain a first mixed solution.

[0078] (3) The first mixed solution was placed in a covered crucible to form an oxygen-deficient condition, placed in an oven at 105°C for 24 hours, and dried to obtain the first product. After the first product was ground and crushed, it was placed in a 50 mL crucible and sealed with a cover, and then placed in a muffle furnace for anoxic pyrolysis. The pyrolysis temperature in the muffle furnace was 350°C, the pyrolysis time was 2 hours, and the heating program was set as follows: heating to 350°C at a heating rate of 5°C / min, and the residence time was 2 hours. After the pyrolysis was completed, the black powder in the crucible was taken out after the muffle furnace was cooled to below 100°C, and after grinding and passing through a 200 mesh sieve, a powdered magnetic biochar adsorbent (M-BC) was obtained.

[0079] To verify the effectiveness of the M-BC material in removing carbon and phosphorus from wastewater, 1L of biochemical effluent from a sewage treatment plant with a COD of 286mg / L and a TP of 4.235mg / L was added to the water at a concentration of 400mg / L. The mixture was stirred in a coagulation test mixer at 300r / min for 3 minutes, then at 200r / min for 30 minutes. After standing for 0.5h, the supernatant was collected and measured for COD and TP. After treatment, the COD was 161mg / L and the TP was 3.2169mg / L, resulting in COD removal rates of 43.77% and TP removal rates of 24.04%.

[0080] Figure 4The carbon and phosphorus removal effects of the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material of Example 1 and several other unmodified or incompletely modified carbon materials are shown. It can be seen that the COD content of the wastewater actually increases after the addition of the unmodified biochar BC, because the carbon powder cannot remove the pollutant particles well, and the small molecular pollutants aggregate with the carbon powder into larger particles, but the overall sedimentation performance is poor, and they are suspended in the water body, causing an increase in tCOD. In contrast, the M-BC modified with magnetic powder alone and the A / M-BC modified with magnetic powder and acid improve the carbon removal and phosphorus removal capabilities, among which the strengthening effect of M-BC is weaker, with a TCOD removal rate of 45.55% and a TP removal rate of 17.06%. The carbon and phosphorus removal capabilities of A / M-BC are obvious, with a TCOD removal rate of 70.42% and a TP removal rate of 93.91%.

[0081] Figure 4 Figure 1 shows the carbon-phosphorus removal performance of the carbon-phosphorus-specific flocculating magnetic carbon-based material of Example 1 and several other unmodified or partially modified carbon materials. pCOD (particle COD) represents particulate COD, sCOD (soluble COD) represents dissolved COD, and their sum is tCOD (total COD), also known as total COD. DP (dissolved phosphorus) represents dissolved phosphorus, and PP (particle phosphorus) represents particulate phosphorus. Their sum is TP (total phosphorus), also known as total phosphorus.

[0082] It can be seen that the COD content of the wastewater actually increased after the addition of unmodified biochar (BC). This is because biochar alone cannot effectively remove pollutant particles, and small molecular pollutants aggregate with biochar to form larger particles with poor overall settling performance, remaining suspended in the water, causing an increase in tCOD. In contrast, M-BC modified with iron powder alone and A / M-BC modified with iron powder and acid improved carbon and phosphorus removal capabilities. Among them, M-BC had a weaker enhancement effect, with a tCOD removal rate of 45.55% and a TP removal rate of 17.06%. A / M-BC had significant carbon and phosphorus removal capabilities, with a tCOD removal rate of 70.42% and a TP removal rate of 93.91%.

[0083] This is because the iron powder loading allows the carbon particles to act as magnetic nuclei, forming flocculation centers. This not only strengthens the adsorption of dissolved pollutants but also enhances the aggregation of particulate and colloidal pollutants. The iron powder also imparts magnetic properties to the flocs, enhancing their capture in an external magnetic field and achieving rapid sedimentation. Furthermore, acid modification increases the number of active sites on the material's surface, improving the removal of phosphorus-containing pollutants such as phosphate from water through electrostatic attraction.

[0084] Figure 6This is a comparison chart of the carbon-phosphorus removal effects of the carbon-phosphorus specific flocculation adsorption magnetic carbon-based material (A / M-BC) obtained after modification with hydrochloric acid of different mass concentrations. As can be seen from the figure, when the concentration of modified hydrochloric acid is 5% to 50%, the carbon-phosphorus removal effect of the A / M-BC material gradually improves. When the hydrochloric acid concentration is 50% to 70%, the increase in the removal rate slows down, and the ideal removal effect can be achieved (REtCOD≈70%, RETP≈95%). During the experiment, it was found that there was obvious mutual conversion between COD in different states, and the removal rate had obvious differences, and pCOD was easier to remove. The phosphorus-containing pollutants in different states are relatively stable, and the removal rates of DP and PP are relatively consistent, but the former is slightly higher. The reason for this is that the surface of the material after acid / magnetic modification is easy to react with DP (such as PO4 - ) The active sites for binding are increased, and removal is enhanced.

[0085] The A / M-BC prepared by the present invention has a honeycomb-like porous structure on its surface and a large specific surface area. The ferromagnetic powder and heavy metals loaded in the biochar have a certain catalytic effect and have a strong magnetic responsiveness in a magnetic field. It is used as a coagulation catalyst for sewage treatment and has the advantages of high efficiency, small footprint, easy operation and low cost. It can be used in the fields of sewage treatment plant influent pretreatment, biochemical effluent deep treatment and so on.

[0086] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material, characterized in that: The specific steps are as follows: S1: evenly dispersing biochar powder in water to obtain a biochar dispersion; adding iron salt to the biochar dispersion and stirring evenly to obtain a biochar mixture; S2: adding iron powder to the biochar mixture for mixing reaction, and then adding sodium hydroxide solution to adjust the pH value to a range of 10 to 11 to obtain a first mixed solution; the particle size of the iron powder is less than 300 mesh; S3: drying the first mixed solution under anoxic conditions to obtain a first product; The first product is subjected to anoxic pyrolysis and then ground to obtain a powdered magnetic biochar adsorbent; S4: acid-modifying the magnetic biochar adsorbent with hydrochloric acid to obtain a second mixed solution; the mass concentration of the hydrochloric acid is 5% to 70%; drying and cooling the second mixed solution to obtain a second product, and sieving the second product to obtain a carbon-phosphorus specific flocculation adsorption magnetic carbon-based material; The biochar dispersion is prepared by adding biochar through a 200-mesh sieve to water and dispersing it through microwaves; the microwave dispersion frequency is 40 to 60 Hz, and the microwave dispersion time is 15 to 30 minutes; The iron salts are ferrous sulfate heptahydrate and ferric sulfate; the mass ratio of ferrous sulfate heptahydrate and ferric sulfate to biochar in the biochar mixture is 20:7:100; The first product is placed in a covered crucible and subjected to an oxygen-deficient pyrolysis process in a muffle furnace; the pyrolysis temperature in the muffle furnace is 350° C., the pyrolysis time is 2 h, and the heating program is set as follows: heating to 350° C. at a heating rate of 5° C. / min, and the residence time is 2 h; The mass concentration of the hydrochloric acid is 50% to 70%; the hydrochloric acid and the magnetic biochar adsorbent are mixed in a ratio of 1 mL:1 g.

2. The method for preparing carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material according to claim 1, characterized in that: The biochar mixture in S1 was stirred at a coagulation stirring rate of 250 r / min for 30 min using a coagulation test mixer; the mixing reaction process in S2 was stirred at a coagulation stirring rate of 250 r / min for 30 min using a coagulation test mixer.

3. The method for preparing the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material according to claim 1, characterized in that: The mass ratio of biochar to iron powder in the first mixed solution is 100:(20-60).

4. The method for preparing the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material according to claim 1, characterized in that: The particle size of the carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material is less than 200 meshes.

5. A carbon-phosphorus specific flocculation and adsorption magnetic carbon-based material prepared by the preparation method according to any one of claims 1 to 4.

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