A biochar packing material for wastewater treatment, its preparation method and application

Abstract

This invention belongs to the field of wastewater treatment technology, and relates to a biochar packing material for wastewater treatment, its preparation method, and its application. The biochar packing material for wastewater treatment comprises iron-based biochar and a CaO2 layer supported on the outer layer of the iron-based biochar. The iron-based biochar is biochar containing α-Fe2O3 / Fe3O4 heterojunctions. In application, wetland plants are arranged according to water depth gradients. After the biochar packing material is applied to the polluted wetland, the oxygen secretion from the plant roots drives the Fe content in the biochar packing material. 3+ / Fe 2+ In this cycle, acidic substances secreted by plant roots trigger the decomposition of the CaO2 layer, releasing H2O2. The released H2O2 is activated by α-Fe2O3 / Fe3O4 heterojunctions to generate hydroxyl radicals. The synergistic effect of biochar filler and plant roots achieves pollutant degradation. This solves the problem that existing wetland organic pollution remediation technologies cannot simultaneously meet the requirements of natural wetland adaptability and targeted pollutant degradation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a biochar packing material for wastewater treatment, its preparation method, and its application. Background Technology

[0002] As riparian runoff catchment areas and river water conveyance zones, the pollution status and environmental geochemical behavior of recalcitrant organic pollutants in riparian wetlands have become a significant environmental issue of great concern. Therefore, developing ecological restoration technologies for riparian natural wetlands to alleviate organic pollutant pollution is urgently needed. Currently, the remediation of organic pollution in riparian natural wetlands mainly relies on the following three types of technologies, which have the following shortcomings:

[0003] (1) Phytoremediation technology: pollutants are absorbed by wetland plants (such as cattails and reeds) or degraded by root microorganisms. However, the oxygen utilization rate of plants is extremely low and there is a lack of catalytic active sites, resulting in a removal rate of less than 50% for recalcitrant organic matter. In addition, the reaction between root exudates and pollutants is random and cannot target and activate oxidation reactions.

[0004] (2) Iron-loaded biochar remediation: Iron oxides were loaded onto the surface of biochar using an impregnation method, but the iron dispersion was poor, the loading was small, and it was prone to agglomeration and deactivation. More importantly, without the addition of an external oxidant, the ·OH yield was <1μM, which is far below the requirements of the Fenton-like reaction.

[0005] (3) Chemical enhancement remediation: Adding H2O2 or persulfate to activate Fenton-like reactions, but the agents will cause pH fluctuations, aquatic organism death, and damage the ecological balance of wetlands. Continuous drug application is difficult to implement in natural wetlands.

[0006] In summary, none of the above three types of technologies can simultaneously meet the requirements of natural wetland adaptability (zero chemical addition / no external energy supply) and pollutant targeted degradation efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a biochar packing material for wastewater treatment, its preparation method, and its application, which solves the problem that existing wetland organic pollution remediation technologies cannot simultaneously meet the requirements of natural wetland adaptability and pollutant targeted degradation efficiency.

[0008] This invention is achieved through the following technical solution:

[0009] This invention discloses a method for preparing biochar packing material for wastewater treatment, comprising the following steps:

[0010] Step 1: After crushing the straw, add it to the phosphoric acid solution, stir thoroughly, carry out the hydrothermal reaction, wash until neutral, and dry to obtain the phosphate esterified carbon carrier;

[0011] Phosphate-esterified carbon support is carbonized under oxygen-limited conditions of 450-550 ℃ to form micro / mesoporous hierarchical porous biochar.

[0012] Step 2: The micro / mesoporous graded porous biochar is impregnated in a soluble ferric salt solution, subjected to ultrasonic-assisted loading, and then dried; subsequently, it is calcined at 450-550 °C to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0013] Step 3: Impregnate the biochar loaded with α-Fe2O3 nanoparticles with ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination is carried out at 300-350 °C to generate α-Fe2O3 / Fe3O4 heterojunction in situ, thus obtaining iron-based biochar.

[0014] Step 4: Add the iron-based biochar to a mixed solution of Ca(OH)2 and H2O2 to react, and generate a CaO2 layer in situ on the surface of the iron-based biochar to obtain a biochar packing material for wastewater treatment.

[0015] Furthermore, in step one, the oxygen-limiting condition is pyrolysis under a nitrogen atmosphere.

[0016] Furthermore, in step two, the soluble ferric salt solution is either a ferric nitrate solution or a ferric chloride solution.

[0017] Furthermore, in step two, the concentration of the soluble ferric salt solution is 0.5-1.0 M;

[0018] During impregnation, the solid-liquid ratio of the micro / mesoporous graded porous biochar to the soluble ferric salt solution is 1g:10-20mL.

[0019] Furthermore, in step two, the power of the ultrasonic-assisted load is 30-60 kHz, and the duration is 20-50 min.

[0020] Furthermore, in step three, the ascorbic acid-Fe 2+ In the complex solution, ascorbic acid and Fe 2+ The molar ratio is 1.5-2.5:1.

[0021] Furthermore, in step three, the vacuum permeation process is as follows: the impregnated material is placed in a vacuum environment, the vacuum degree is maintained at -0.08 MPa for 20-60 minutes, and then the pressure is restored to normal.

[0022] Furthermore, in step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1-1.5:1.

[0023] The present invention also discloses a biochar packing material for wastewater treatment prepared by the above preparation method. The biochar packing material for wastewater treatment includes iron-based biochar and a CaO2 layer supported on the outer layer of the iron-based biochar. The iron-based biochar is biochar containing α-Fe2O3 / Fe3O4 heterojunctions.

[0024] This invention also discloses the application of the aforementioned biochar filler for sewage treatment as a pollutant treatment agent in the field of ecological restoration of riparian natural wetlands. Wetland plants are configured according to water depth gradients, and the biochar filler for sewage treatment is applied to the polluted wetland to degrade pollutants.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] This invention discloses a method for preparing biochar packing material for wastewater treatment. First, a combination of phosphate esterification pretreatment and oxygen-limited carbonization is used to induce esterification and cross-linking reactions between phosphoric acid and straw components. In the subsequent oxygen-limited carbonization, phosphoric acid plays an in-situ chemical activation role rather than physical mixing. The pores etched by phosphoric acid and its decomposition products extend from micropores to mesopores, forming a micro / mesoporous hierarchical porous structure. This provides a huge specific surface area and abundant anchoring points for the subsequent loading of active components. The hierarchical pores are like an efficient transportation network. Micropores use their high specific surface area to adsorb and enrich pollutants, while mesopores act as fast channels to promote mass transfer and provide a space for large-sized active nanoparticles (such as heterojunctions and CaO2), thus avoiding pore blockage. Then, after in-situ preparation of α-Fe2O3 / Fe3O4 heterojunctions using a stepwise calcination method, a built-in electric field is formed at the interface, which can greatly promote the directional migration of electrons from Fe3O4 to α-Fe2O3 and significantly improve the electron-hole pair separation efficiency. This allows the filler to generate more and more persistent strong oxidizing free radicals (such as ·OH or SO4·) when activating hydrogen peroxide or persulfate. - The catalytic activity is far higher than that of single iron oxides. Finally, an in-situ precipitation reaction is carried out between iron-based biochar and a Ca(OH)2 / H2O2 mixture to generate a uniform and robust CaO2 layer on the surface of the heterojunction. In summary, this invention, through a four-step continuous and precise chemical design, transforms biochar (adsorption and enrichment), iron heterojunction (highly efficient catalysis), and CaO2 layer (slow-release supply and pH adjustment) from a simple physical mixture into a tightly coupled, functionally synergistic organic whole. Ultimately, this results in the packing material exhibiting outstanding advantages such as high catalytic activity, good stability, wide applicability, and long service life.

[0027] This invention also discloses a biochar packing material for wastewater treatment. The biochar packing material comprises iron-based biochar and a CaO2 layer supported on the outer layer of the iron-based biochar. The iron-based biochar is biochar containing α-Fe2O3 / Fe3O4 heterojunctions. When the biochar packing material is applied to polluted wetlands, it achieves intelligent synergy of three major functions: the CaO2 layer slowly decomposes upon contact with water, continuously providing H2O2, overcoming the shortcomings of easily ineffective decomposition and low utilization rate of added H2O2; the decomposition process simultaneously releases OH-. - It can maintain a stable and suitable weakly alkaline environment for heterojunction catalytic reactions, avoiding the problem of narrow pH range in traditional Fenton reactions; the core heterojunction instantly activates the CaO2 layer to release H2O2, forming a highly efficient internal cycle of "on-demand production and use", which greatly improves the utilization rate of oxidant and the degradation rate of pollutants.

[0028] This invention also discloses the application of biochar filler for wastewater treatment as a pollutant treatment agent in the ecological restoration of riparian wetlands. Wetland plants are configured according to water depth gradients. After the biochar filler is applied to the polluted wetland, combined with plant gradient oxygen release technology, shallow roots secrete oxalic acid to activate CaO2 and target the release of H2O2; middle-layer root exudates maintain pH 4.5-6; and deep roots synergistically drive continuous Fe production through high oxygen release. 3+ / Fe 2+ ·OH is generated in a cycle. The plant roots, configured according to the water depth gradient, can secrete oxalic acid, dissolving iron oxides in the biochar filler and generating Fe in situ. 2+ At the same time, the roots release H2O2, forming a plant-driven Fenton-like reaction that can efficiently degrade organic pollutants without the need for external chemical reagents. Attached Figure Description

[0029] Figure 1 This is a pore size distribution diagram of the micro / mesoporous graded porous biochar formed in Examples 1 to 3 of the present invention;

[0030] Figure 2 The image shows the XRD pattern of biochar loaded with α-Fe2O3 nanoparticles generated in Example 1 of this invention.

[0031] Figure 3 This is a SEM image of biochar loaded with α-Fe2O3 nanoparticles generated in Example 3 of this invention;

[0032] Figure 4 The XRD pattern of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 4 is shown in the present invention.

[0033] Figure 5 This is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in this invention;

[0034] Figure a is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 1 of the present invention.

[0035] Figure b is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 2 of the present invention;

[0036] Figure c is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 4 of the present invention;

[0037] Figure d is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 5 of the present invention;

[0038] Figure e is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 6 of the present invention;

[0039] Figure 6 The relationship between the Fe(II) concentration in the reaction system and time when using the biochar packing material for wastewater treatment prepared in Examples 1 to 8 of this invention for wastewater treatment;

[0040] Figure 7 The relationship between the H2O2 concentration in the reaction system and time when using the biochar packing material for wastewater treatment prepared in Examples 1 to 8 of this invention for wastewater treatment;

[0041] Figure 8 The amount of •OH generated was measured when the biochar packing material for wastewater treatment prepared in Examples 1 to 8 of this invention and the plant oxygen release control technology were used for wastewater treatment.

[0042] Figure 9 The pollutant removal rate obtained when using the biochar packing material for wastewater treatment prepared in Examples 1 to 8 of this invention and the plant oxygen release control technology for wastewater treatment;

[0043] Figure 10 This is to reduce the cost of using the biochar packing material and plant oxygen release control technology prepared in Examples 1 to 8 of the present invention for wastewater treatment. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0045] The detailed description of the embodiments of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the figures and embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0046] This invention discloses a method for preparing biochar packing material for wastewater treatment, comprising the following steps:

[0047] Step 1: After crushing the straw, add it to the phosphoric acid solution, stir thoroughly, carry out the hydrothermal reaction, wash until neutral, and dry to obtain the phosphate esterified carbon carrier;

[0048] Phosphate-esterified carbon support is carbonized under oxygen-limited conditions of 450-550 ℃ to form micro / mesoporous hierarchical porous biochar.

[0049] Step 2: The micro / mesoporous graded porous biochar is impregnated in a soluble ferric salt solution, subjected to ultrasonic-assisted loading, and then dried; subsequently, it is calcined at 450-550 °C to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0050] Step 3: Impregnate the biochar loaded with α-Fe2O3 nanoparticles with ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination is carried out at 300-350 °C to generate α-Fe2O3 / Fe3O4 heterojunction in situ, thus obtaining iron-based biochar.

[0051] Step 4: Add the iron-based biochar to a mixed solution of Ca(OH)2 and H2O2 to react, and generate a CaO2 layer in situ on the surface of the iron-based biochar to obtain a biochar packing material for wastewater treatment.

[0052] The biochar packing material used for wastewater treatment includes iron-based biochar and a CaO2 layer supported on the outer layer of the iron-based biochar. The iron-based biochar is biochar containing α-Fe2O3 / Fe3O4 heterojunctions.

[0053] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0054] Example 1

[0055] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0056] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphate esterified carbon carrier.

[0057] Phosphate-esterified carbon support was activated at 450℃ under limited oxygen conditions (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0058] Step 2: The micro / mesoporous graded porous biochar was impregnated in 0.5 M Fe(NO3)3 solution, ultrasonically loaded, and dried at 60℃. Subsequently, it was calcined in a calcination furnace at 450℃ for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0059] In this case, the solid-liquid ratio of the micro / mesoporous graded porous biochar to the Fe(NO3)3 solution was 1 g: 20 mL. The solid-liquid ratios in Examples 2 and 3 were the same.

[0060] The ultrasonic-assisted load has a power of 40 kHz and a duration of 30 min.

[0061] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0062] Among them, ascorbic acid-Fe 2+ The complex solution was prepared from ascorbic acid and ferrous sulfate heptahydrate (FeSO4·7H2O). The ascorbic acid-Fe... in the following examples... 2+ The preparation of complex solutions is the same.

[0063] The molar ratio of ascorbic acid to FeSO4·7H2O is 2:1.

[0064] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 20 minutes, and then restore normal pressure.

[0065] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a filler material with an α-Fe2O3 / Fe3O4 heterojunction coated with a CaO2 layer, which is the biochar filler material used for wastewater treatment.

[0066] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1:1.

[0067] The biochar filler material prepared in this embodiment for wastewater treatment was applied to an artificially polluted wetland simulating tetracycline pollution. The initial tetracycline concentration was 105 mg / L, and the weight of the biochar filler material added was 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to the water depth gradient, with water celery planted in the shallow layer (0-10 cm) at 20 plants / m². 2 Iris plants are planted in the middle layer (10-30 cm), 15 plants / m². 2 Plant cattails at a depth of >30 cm, 8 plants / m² 2 After operating for 14 days under natural light and without external power supply, samples were taken from the effluent outlet to determine the tetracycline concentration, which was found to be 1.89 mg / L. Based on this, the tetracycline removal rate reached 98.2%, proving that the biochar packing material used for wastewater treatment can efficiently drive the generation of ·OH in wetlands, achieving efficient degradation of organic pollutants.

[0068] Example 2

[0069] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0070] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphate esterified carbon carrier.

[0071] Phosphate-esterified carbon support was activated at 500℃ under limited oxygen conditions (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0072] Step 2: The micro / mesoporous graded porous biochar was impregnated in 0.5 M Fe(NO3)3 solution, ultrasonically loaded, and dried at 60 °C. Subsequently, it was calcined in a calcination furnace at 450 °C for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0073] The ultrasonic-assisted load has a power of 40 kHz and a duration of 30 min.

[0074] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0075] The molar ratio of ascorbic acid to FeSO4·7H2O is 2:1.

[0076] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 20 minutes, and then restore normal pressure.

[0077] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0078] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1.2:1.

[0079] The biochar packing material prepared in this embodiment for wastewater treatment was applied to an artificially polluted wetland simulating benzo[a]pyrene contamination. The initial concentration of benzo[a]pyrene was 50 mg / L, and the weight of the biochar packing material added was 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to the water depth gradient, with water celery planted in the shallow layer (0-10 cm) at 25 plants / m². 2 Plant irises in the middle layer (10-30 cm), 15 plants / m² 2 Plant cattails at a depth of >30 cm, 8 plants / m² 2 Operating under natural light and room temperature (25±2℃), it requires no external power supply or chemical reagents. After 21 days of operation, samples were taken from the effluent to determine the concentration of benzo[a]pyrene. The test results showed that the effluent benzo[a]pyrene concentration decreased to 1.75 mg / L, and the calculated removal rate reached 96.5%. This result demonstrates that the biochar packing material of this invention for wastewater treatment also has excellent and efficient degradation capabilities for recalcitrant polycyclic aromatic hydrocarbons (PAHs).

[0080] Example 3

[0081] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0082] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphate esterified carbon carrier.

[0083] Phosphate-esterified carbon support was activated at 550℃ with limited oxygen (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0084] Step 2: The micro / mesoporous graded porous biochar was impregnated in 0.5 M Fe(NO3)3 solution, ultrasonically loaded, and dried at 60℃. Subsequently, it was calcined in a calcination furnace at 450℃ for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0085] The ultrasonic-assisted load has a power of 40 kHz and a duration of 30 min.

[0086] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0087] The molar ratio of ascorbic acid to FeSO4·7H2O is 2.5:1.

[0088] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 20 minutes, and then restore normal pressure.

[0089] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0090] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1:1.

[0091] The biochar filler material prepared in this embodiment for wastewater treatment was applied to an artificially polluted wetland simulating combined pollution. The initial concentration of chemical oxygen demand (COD) was 395 mg / L, the initial concentration of tetracycline was 105 mg / L, and the weight of the biochar filler material added was 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to the water depth gradient, with water celery planted in the shallow layer (0-10 cm) at 25 plants / m². 2 Plant irises and loosestrife in the middle layer (10-30 cm), 15 plants each per m². 2 Plant cattails at a depth of >30 cm, 8 plants / m² 2The system operates under natural light and room temperature (25±2℃) conditions, requiring no external power supply or chemical reagents. After 21 days of operation, samples were taken from the effluent outlet. COD concentration was determined using the dichromate method, and tetracycline concentration was determined using high-performance liquid chromatography (HPLC). Test results showed that the effluent COD concentration decreased to 8.3 mg / L, corresponding to a removal rate of 97.9%; the effluent tetracycline concentration decreased to 2.1 mg / L, corresponding to a removal rate of 98.0%.

[0092] The results demonstrate that even under harsh conditions of high loads of complex pollutants, the biochar packing material for wastewater treatment of the present invention can still achieve a self-driven Fenton-like reaction within the system through synergistic effects with diverse plant communities, enabling simultaneous and efficient degradation of multiple types of organic pollutants.

[0093] Example 4

[0094] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0095] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphate esterified carbon carrier.

[0096] Phosphate-esterified carbon support was activated at 500℃ under limited oxygen (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0097] Step 2: The micro / mesoporous graded porous biochar was impregnated in 0.8 M Fe(NO3)3 solution, ultrasonically loaded, and then dried at 60℃. Subsequently, it was calcined in a calcination furnace at 450℃ for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0098] The solid-liquid ratio of the micro / mesoporous graded porous biochar to the Fe(NO3)3 solution was 1g:15mL.

[0099] The ultrasonic-assisted load has a power of 40 kHz and a duration of 30 min.

[0100] Step 3: Then immerse it in 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0101] The molar ratio of ascorbic acid to FeSO4·7H2O is 2:1.

[0102] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 40 minutes, and then restore normal pressure.

[0103] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0104] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1.5:1.

[0105] The biochar packing material prepared in this embodiment for wastewater treatment was applied to an artificially polluted wetland simulating sulfamethoxazole pollution. The initial concentration of sulfamethoxazole was 80 mg / L, and the weight of the biochar packing material added was 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to the water depth gradient, with water celery planted in the shallow layer (0-10 cm) at 20 plants / m². 2 Plant calamus and alisma in the middle layer (10-30 cm), 15 plants / m². 2 and 10 plants / m 2 Plant cattails at a depth of >30 cm, 8 plants / m² 2 The system operates under natural light and room temperature (25±2℃) conditions, requiring no external power supply or chemical reagents. After 21 days of operation, samples were taken from the effluent outlet, filtered through a 0.45 μm filter membrane, and the sulfamethoxazole concentration was measured. The test results showed that the effluent sulfamethoxazole concentration decreased to 3.44 mg / L, with a calculated removal rate of 95.7%. This result demonstrates that even with adjustments to the reactant ratio for CaO2 generation in step four, the biochar packing material of this invention exhibits excellent and stable degradation performance for sulfonamide antibiotics, further confirming the reliability of the preparation method and the versatility of the packing material product.

[0106] Example 5

[0107] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0108] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphoric acid esterified carbon carrier.

[0109] Phosphate-esterified carbon support was activated at 500℃ under limited oxygen (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0110] Step 2: The micro / mesoporous graded porous biochar was impregnated in 1 M Fe(NO3)3 solution, ultrasonically loaded, and dried at 60℃; then, it was calcined in a calcining furnace at 450℃ for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0111] The solid-liquid ratio of porous biochar to Fe(NO3)3 solution was 1g:15mL.

[0112] The ultrasonic-assisted load has a power of 40 kHz and a duration of 30 min.

[0113] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 300 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0114] The molar ratio of ascorbic acid to FeSO4·7H2O is 2:1.

[0115] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 20 minutes, and then restore normal pressure.

[0116] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0117] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1:1.

[0118] The biochar packing material for wastewater treatment prepared in this embodiment is applied to simulated petroleum hydrocarbons (C). 10 -C 30 The artificially polluted wetland had an initial petroleum hydrocarbon concentration of 500 mg / kg, and the biochar filler was added at 2% of the dry weight of the artificially polluted wetland substrate. Wetland vegetation was configured according to water depth gradients, with water celery planted in the shallow layer (0-10 cm) at 20 plants / m². 2 Plant irises in the middle layer (10-30cm), 15 plants / m² 2 Plant water onions and wild rice in the deep layer (>30 cm), 8 plants / m² 2 and 4 plants / m 2The system operates under natural light and room temperature (25±2℃) conditions, requiring no external power supply or chemical reagents. After 21 days of operation, water and soil samples were collected from the wetland, and the concentration of petroleum hydrocarbons was measured. The test results showed that the concentration of petroleum hydrocarbons in the water decreased to 28.5 mg / kg, and the calculated removal rate reached 94.3%. This result demonstrates that even with a lower proportion of filler added and mild reducing calcination conditions (450℃, 2h), the biochar filler prepared in this invention for wastewater treatment exhibits excellent degradation ability for high concentrations of hydrophobic petroleum hydrocarbon pollutants, further expanding the application boundaries of this invention and confirming the breadth and effectiveness of the heterojunction formation conditions.

[0119] Example 6

[0120] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0121] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphoric acid esterified carbon carrier.

[0122] Phosphate-esterified carbon support was activated at 500℃ under limited oxygen (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0123] Step 2: The micro / mesoporous graded porous biochar was impregnated in 0.6 M Fe(NO3)3 solution, ultrasonically loaded, and dried at 60℃; then, it was calcined in a calcining furnace at 450℃ for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0124] The solid-liquid ratio of the micro / mesoporous graded porous biochar to the Fe(NO3)3 solution was 1g:20mL.

[0125] The ultrasonic-assisted load has a power of 40 kHz and a duration of 20 min.

[0126] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0127] The molar ratio of ascorbic acid to FeSO4·7H2O is 1.5:1.

[0128] In step three, the conditions for the vacuum permeation treatment are: maintain a vacuum of -0.08 MPa for 60 minutes, and then restore normal pressure.

[0129] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0130] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1:1.

[0131] The biochar filler material prepared in this embodiment for wastewater treatment was applied to an artificially polluted wetland simulating tetracycline pollution, with a water temperature of 10℃±1℃ (to simulate a low-temperature environment). The initial tetracycline concentration was 105 mg / L, and the weight of the biochar filler material added was 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to the water depth gradient, with water celery planted in the shallow layer (0-10 cm) at 20 plants / m². 2 Plant irises in the middle layer (10-30 cm), 15 plants / m² 2 Plant reeds at a depth of >30 cm, 8 plants / m² 2 Operating under natural light and low temperature conditions, it requires no external power supply or chemical reagents. After 21 days of operation, samples were taken from the effluent to determine the tetracycline concentration. The test results showed that the tetracycline concentration in the effluent decreased to 10.9 mg / L, and the calculated removal rate reached 89.6%. This result demonstrates that even in a low-temperature environment (10℃) unfavorable to chemical reactions, the biochar packing material prepared in this invention for wastewater treatment can still maintain high catalytic degradation activity through synergistic effects with wetland plants, showcasing its practical application potential and stability under a wide range of climatic conditions.

[0132] Example 7

[0133] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0134] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphoric acid esterified carbon carrier.

[0135] Phosphate-esterified carbon support was activated at 500℃ under limited oxygen (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0136] Step 2: The micro / mesoporous graded porous biochar was impregnated in a 0.6 M Fe(NO3)3 solution, ultrasonically loaded, and then dried at 60 °C. Subsequently, it was calcined in a calcining furnace at 500 °C for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0137] The solid-liquid ratio of the micro / mesoporous graded porous biochar to the Fe(NO3)3 solution was 1g:15mL.

[0138] The ultrasonic-assisted load has a power of 30 kHz and a duration of 50 min.

[0139] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination was carried out at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0140] The molar ratio of ascorbic acid to FeSO4·7H2O is 2:1.

[0141] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 20 minutes, and then restore normal pressure.

[0142] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0143] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1:1.

[0144] The biochar packing material for wastewater treatment prepared in this embodiment was applied to a simulated hydraulic load of 0.8 m. 3 / m 2 .d. An artificially polluted wetland contaminated with benzo[a]pyrene, with an initial benzo[a]pyrene concentration of 50 mg / L. The biochar filler was added at 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to water depth gradients, with water lilies and water snowflakes planted in the shallow layer (0-10 cm) at 40 plants / m². 2 and 80 plants / m 2 Plant irises in the middle layer (10-30 cm), 15 plants / m² 2 Plant cattails at a depth of >30 cm, 8 plants / m² 2The system operates under natural light and room temperature (25±2℃) conditions, requiring no external power supply or chemical reagents. After 21 days of operation, samples were taken from the effluent to determine the concentration of benzo[a]pyrene. The test results showed that the effluent benzo[a]pyrene concentration decreased to 3.45 mg / L, and the calculated removal rate reached 93.1%. This result demonstrates that even under high hydraulic loading conditions, the biochar packing material prepared in this invention for wastewater treatment can maintain efficient and stable pollutant degradation performance through synergistic effects with specific wetland plant communities, exhibiting good adaptability to hydraulic fluctuations.

[0145] Example 8

[0146] This embodiment discloses a method for preparing biochar packing material for wastewater treatment, including the following steps:

[0147] Step 1: After crushing the straw, add it to a 1.2 M phosphoric acid solution, stir thoroughly, react at 80℃ for 24 h, wash with deionized water until neutral, and dry at 105℃ to obtain a phosphoric acid esterified carbon carrier.

[0148] Phosphate-esterified carbon support was activated at 500℃ under limited oxygen (N2 flow rate of 50 mL / min) for 1 h to form micro / mesoporous hierarchical porous biochar.

[0149] Step 2: The micro / mesoporous graded porous biochar was impregnated in 0.6 M Fe(NO3)3 solution, ultrasonically loaded, and dried at 60℃; then, it was calcined in a calcining furnace at 550℃ for 1 h to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles.

[0150] The solid-liquid ratio of the micro / mesoporous graded porous biochar to the Fe(NO3)3 solution was 1g:10mL.

[0151] The ultrasonic-assisted load has a power of 60 kHz and a duration of 20 min.

[0152] Step 3: Then, the biochar loaded with α-Fe2O3 nanoparticles is impregnated with 0.3 M ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, the mixture was reduced and calcined at 350 °C for 2 h to generate α-Fe2O3 / Fe3O4 heterojunctions in situ, thus obtaining iron-based biochar.

[0153] The molar ratio of ascorbic acid to FeSO4·7H2O is 2:1.

[0154] In step three, the conditions for the vacuum permeation treatment are as follows: maintain a vacuum of -0.08 MPa for 20 minutes, and then restore normal pressure.

[0155] Step 4: Add iron-based biochar to a mixed solution of Ca(OH)2 and H2O2, and react for 30 min to generate a CaO2 layer, thus obtaining a packing material coated with a CaO2 layer and α-Fe2O3 / Fe3O4 heterojunction, which is the biochar packing material used for wastewater treatment.

[0156] In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1:1.

[0157] The biochar filler prepared in this embodiment for wastewater treatment was applied to an artificially polluted wetland simulating tetracycline and petroleum hydrocarbon combined pollution. The initial concentration of tetracycline was 80 mg / L, and the initial concentration of petroleum hydrocarbon was 500 mg / kg. The weight of the biochar filler added was 5% of the dry weight of the artificially polluted wetland substrate. Wetland plants were arranged according to the water depth gradient, with water celery planted in the shallow layer (0-10 cm) at 20 plants / m². 2 Plant irises and loosestrife in the middle layer (10-30 cm), 15 plants each per m². 2 Plant cattails at a depth of >30 cm, 8 plants / m² 2 The system operates under natural light and room temperature (25±2℃) conditions, requiring no external power supply or chemical reagents. To simulate long-term operation, 5% fresh packing material was added every 30 days after startup (primarily to shallow water areas with higher pollutant concentrations), continuing operation for 60 days. After operation, water and soil samples were collected to determine the concentrations of tetracycline and petroleum hydrocarbons. Test results showed that the tetracycline concentration in the effluent decreased to 6.88 mg / L, corresponding to a removal rate of 91.4%; the petroleum hydrocarbon concentration in the soil decreased to 46.0 mg / kg, corresponding to a removal rate of 90.8%. These results demonstrate that by periodically and intermittently replenishing the packing material, this invention can maintain efficient and stable degradation performance against complex pollutants during long-term operation, providing a reliable technical solution for addressing the long-term effectiveness of packing materials in practical wetland remediation projects.

[0158] The specific surface area, pore volume, and pore size of the micro / mesoporous hierarchical porous biochar formed in step one of Examples 1 to 3 of this invention were analyzed using the N2 adsorption / desorption method. The results are as follows: Figure 1 As shown, the successful preparation of porous biochar has been confirmed.

[0159] Diffraction analysis was performed on the α-Fe2O3 nanoparticles generated in step two of Example 1 of this invention, and the results were as follows: Figure 2 The XRD pattern shown confirms the successful preparation of biochar loaded with α-Fe2O3 nanoparticles.

[0160] Electron microscopy was performed on the α-Fe2O3 nanoparticles generated in step two of Example 3 of the present invention to obtain the following results: Figure 3 The SEM image shown.

[0161] To perform diffraction analysis on the α-Fe2O3 / Fe3O4 heterojunction generated in step three of Example 4 of the present invention, the following results were obtained: Figure 4 The XRD pattern shown confirms the successful loading of the α-Fe2O3 / Fe3O4 heterojunction.

[0162] like Figure 5 As shown, Figure 5 Figure a in the figure is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 1 of the present invention; Figure 5 Figure b in the figure is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 2 of the present invention; Figure 5 Figure c in the figure is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 4 of the present invention; Figure 5 Figure d in the figure is a SEM image of the α-Fe2O3 / Fe3O4 heterojunction of iron-based biochar in Example 5 of the present invention; Figure 5 Figure e in the image is a SEM image of the α-Fe₂O₃ / Fe₃O₄ heterojunction of iron-based biochar in Example 6 of this invention. From... Figure 5 Figures a through e show that the fillers prepared in each embodiment have a micron-sized (~2 μm) network pore structure, and the microporosity of Example 2 (with increased hydrothermal phosphoric acid concentration) is significantly improved compared to Example 1; the increased CaO2 coating in Example 4 results in more particles being loaded into the filler pores; and in Example 5, ascorbic acid-Fe 2+ A distinct heterojunction structure can be observed after the concentration of the complex is increased.

[0163] Figure 6 This paper examines the change in Fe(II) concentration over time in the reaction system when using the biochar packing materials prepared in Examples 1 to 8 of this invention for wastewater treatment. It can be seen that the Fe2O3 / Fe3O4 heterojunction in the biochar packing material continuously releases Fe(II). Fe(II) is continuously released in all examples, with maximum release concentrations of 9.52 mg / L, 10.62 mg / L, 10.71 mg / L, 8.90 mg / L, 8.43 mg / L, 7.48 mg / L, 9.23 mg / L, and 8.47 mg / L over 6 hours, respectively. This indicates that by controlling the composition of the packing material and the plant species, efficient and controllable release of Fe(II) can be achieved, providing a sufficient source of reduced iron for the subsequent self-Fenton reaction. The release rate and sustainability are significantly better than those of single iron materials.

[0164] Figure 7This study examines the change in H2O2 concentration over time in the reaction system when using the biochar packing materials prepared in Examples 1-8 of this invention for wastewater treatment. It shows that, under the regulation of plant root exudates, calcium peroxide is slowly released to produce H2O2. The H2O2 concentration in each example continuously increases, reaching a maximum of 9.86 mg / L, 10.24 mg / L, 11.49 mg / L, 8.20 mg / L, 7.81 mg / L, 6.72 mg / L, 7.54 mg / L, and 7.85 mg / L within 6 hours, respectively. These results confirm the effectiveness of the plant-packing material synergistic controlled release of H2O2 technology, demonstrating its ability to form a good match with the synchronously released Fe(II), thereby driving a highly efficient and continuous self-Fenton oxidation process. The amount and stability of H2O2 generated far exceed those of existing technologies that directly add exogenous H2O2.

[0165] Figure 8 When using the biochar packing material and plant oxygen release control technology prepared in Examples 1 to 8 of this invention for wastewater treatment, the amount of •OH generated was measured. It can be seen that the amount of •OH generated varies significantly with different plant configurations, and is 4.1 μM, 4.3 μM, 4.5 μM, 3.9 μM, 4.0 μM, 2.8 μM, 3.5 μM and 3.2 μM, respectively, all of which are higher than those of the prior art.

[0166] Figure 9 The pollutant removal rates obtained when using the biochar packing material for wastewater treatment prepared in Examples 1 to 8 of this invention and the plant oxygen release control technology for wastewater treatment are shown to be 98.2%, 96.5%, 97.9%, 95.7%, 94.3%, 89.6%, 93.1% and 91.4%, respectively, all of which are higher than the prior art.

[0167] Figure 10 The cost of using the biochar packing material and plant oxygen release control technology prepared in Examples 1 to 8 of this invention for wastewater treatment is shown to be 3.38 yuan / ton of water, 3.42 yuan / ton of water, 3.15 yuan / ton of water, 3.51 yuan / ton of water, 3.28 yuan / ton of water, 3.87 yuan / ton of water, 3.33 yuan / ton of water and 2.95 yuan / ton of water, respectively. Among them, Example 8 underwent a simulation experiment for 180 days, indicating that the system has long-term stability.

[0168] This invention achieves precise control of the material structure from macroscopic pores to microscopic interfaces through a progressive design: preparation of porous biochar, preparation of biochar loaded with α-Fe2O3 nanoparticles, in-situ generation of heterojunctions, and coating with a calcium peroxide (CaO2) layer. This not only greatly enhances catalytic activity but also achieves long-term stable pH regulation by leveraging the slow-release properties of CaO2. This results in a significant synergistic effect among adsorption, catalysis, and pH regulation, ultimately yielding a composite filler with high activity, strong stability, and long service life. This effectively overcomes the technical bottlenecks of existing technologies, such as single-function active components, uneven mixing, and easy deactivation.

[0169] This invention presents a three-tiered technology system based on phosphoric acid-activated directional pore formation, stepwise heterostructure preparation, and controlled oxygen release from plants. This system not only eliminates the need for external chemical reagents but also allows for plant selection based on water depth gradients. The plant roots secrete oxalic acid, dissolving soil iron oxides and generating Fe in situ. 2+ Simultaneously, the roots release H2O2, forming a plant-driven Fenton-like reaction. The periodic alternation of wet and dry conditions can drive continuous Fe production through redox oscillations. 3+ / Fe 2+ The process involves cycling to generate ·OH, which promotes the efficient degradation of organic pollutants. It is not a simple superposition of multiple steps, but a progressive and synergistic organic whole. Through precise design of chemical reaction pathways, a novel filler with a unique core-shell structure and multiple synergistic effects has been controllably prepared at the molecular and nanoscale.

[0170] In wetland systems, vegetation is a crucial driver of reactive oxygen species production. The cumulative concentration of hydroxyl radicals (•OH) varies significantly in soils planted with different types of vegetation, primarily due to bio-induced generation mediated by the Fenton system. Addressing the three major technical bottlenecks in the remediation of organic pollution in riparian wetlands—low iron cycling efficiency, low H2O2 supply rate, and poor material-plant synergy—this invention innovatively designs the following:

[0171] By constructing a tightly coupled α-Fe₂O₃ / Fe₃O₄ heterojunction structure on the surface of functionalized biochar, the Fe content in the matrix material is increased. 2+ Regeneration rate and in-situ H2O2 generation efficiency.

[0172] By placing biochar packing material in wetlands, the acidic substances secreted by plant roots trigger the dissolution of the CaO2 layer and release H2O2. At the same time, the root exudates help maintain the pH of the rhizosphere microenvironment between 4.5 and 6.0, thereby optimizing the iron cycling efficiency.

[0173] By constructing a hierarchical pore structure of micropores and mesopores to promote root penetration and introducing phosphate esterification groups to enhance hydrophilicity and avoid root avoidance effects, the phosphoric acid pretreatment step in the preparation process is equivalent to acid washing and ash removal, effectively removing ash and plant growth inhibitors such as phenols from the biomass raw materials, thereby promoting root colonization and increasing plant biomass. Through a three-level synergistic approach of accelerating iron cycling with heterojunction electron bridges, controlling the release of root exudates at thresholds, and designing an ecologically adapted carrier, the project overcomes the contradictions of "mass transfer-reaction-ecology" in natural wetlands, achieving the goal of efficiently degrading antibiotic pollutants within 14 days.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing biochar packing material for wastewater treatment, characterized in that, Includes the following steps: Step 1: After crushing the straw, add it to the phosphoric acid solution, stir thoroughly, carry out the hydrothermal reaction, wash until neutral, and dry to obtain the phosphate esterified carbon carrier; Phosphate-esterified carbon support is carbonized under oxygen-limited conditions of 450-550 ℃ to form micro / mesoporous hierarchical porous biochar. Step 2: The micro / mesoporous graded porous biochar is impregnated in a soluble ferric salt solution, subjected to ultrasonic-assisted loading, and then dried; subsequently, it is calcined at 450-550 °C to generate α-Fe2O3 nanoparticles, thus obtaining biochar loaded with α-Fe2O3 nanoparticles. Step 3: Impregnate the biochar loaded with α-Fe2O3 nanoparticles with ascorbic acid-Fe 2+ After vacuum permeation treatment in the complex solution, reduction calcination is carried out at 300-350 °C to generate α-Fe2O3 / Fe3O4 heterojunction in situ, thus obtaining iron-based biochar. Step 4: Add the iron-based biochar to a mixed solution of Ca(OH)2 and H2O2 to react, and generate a CaO2 layer in situ on the surface of the iron-based biochar to obtain a biochar packing material for wastewater treatment.

2. The method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step one, the oxygen-limiting condition is pyrolysis under a nitrogen atmosphere.

3. The method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step two, the soluble ferric salt solution is either ferric nitrate solution or ferric chloride solution.

4. A method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step two, the concentration of the soluble ferric salt solution is 0.5-1.0 M; During impregnation, the solid-liquid ratio of the micro / mesoporous graded porous biochar to the soluble ferric salt solution is 1g:10-20mL.

5. A method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step two, the power of the ultrasonic-assisted load is 30-60 kHz, and the duration is 20-50 min.

6. The method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step three, the ascorbic acid-Fe 2+ In the complex solution, ascorbic acid and Fe 2+ The molar ratio is 1.5-2.5:

1.

7. A method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step three, the vacuum permeation process is as follows: the impregnated material is placed in a vacuum environment, the vacuum degree is maintained at -0.08 MPa for 20-60 minutes, and then the pressure is restored to normal.

8. The method for preparing biochar packing material for wastewater treatment according to claim 1, characterized in that, In step four, the molar ratio of Ca(OH)2 to H2O2 in the mixed solution of Ca(OH)2 and H2O2 is 1-1.5:

1.

9. A biochar packing material for wastewater treatment prepared by the preparation method according to any one of claims 1-8, characterized in that, The biochar packing material used for wastewater treatment includes iron-based biochar and a CaO2 layer supported on the outer layer of the iron-based biochar. The iron-based biochar is biochar containing α-Fe2O3 / Fe3O4 heterojunctions.

10. The application of the biochar packing material for sewage treatment as described in claim 9 as a pollutant treatment agent in the field of riparian natural wetland ecological restoration, characterized in that... Wetland plants are configured according to water depth gradients, and the biochar filler used for sewage treatment is applied to the polluted wetland to degrade pollutants.

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