Iron-manganese loaded nitrogen-doped modified biochar, and preparation method and application thereof

Abstract

The application discloses iron-manganese loaded nitrogen-doped modified biochar as well as a preparation method and application thereof, and belongs to the field of functional materials and environmental cross technology. The iron-manganese loaded nitrogen-doped modified biochar is rich in a large number of oxygen-containing functional groups and oxygen vacancies on the surface, and iron and manganese are uniformly loaded on the surface of the biochar matrix in the form of bimetallic composite. The preparation method comprises the following steps: limiting oxygen pyrolysis of chestnut shell to obtain biochar, mixing the biochar with potassium ferricyanide, manganese acetate and melamine, and secondarily pyrolyzing under a nitrogen atmosphere to obtain the iron-manganese loaded nitrogen-doped modified biochar. The iron-manganese loaded nitrogen-doped modified biochar can efficiently activate peroxyacetic acid to generate various active oxygen species, and the removal rate of sulfamethoxazole in water with a concentration of 10 mg / L can reach more than 99%. The application can realize resource utilization of chestnut shell waste, efficiently and deeply degrade organic pollutants in water, realize synergistic effect of waste pollution control, solid waste resource utilization and water environment treatment, and is suitable for sulfamethoxazole wastewater purification treatment.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of functional materials and environmental technologies, specifically relating to a modified biochar supported on iron and manganese and doped with nitrogen, its preparation method, and its application. Background Technology

[0002] With the continuous advancement of industrial and agricultural modernization and the large-scale production and use of various chemical and pharmaceutical products, sulfamethoxazole (SMX) antibiotic pollutants are constantly entering the natural ecosystem through various channels such as industrial wastewater, domestic sewage, and agricultural and livestock farming. Sulfamethoxazole possesses three major characteristics: stable chemical structure, difficulty in natural degradation, and easy bioaccumulation along the food chain, posing a significant potential threat to the ecological environment and human health. Existing treatment technologies suffer from drawbacks such as high treatment costs, complex processes, and limited practical application scenarios. Therefore, developing efficient, economical, and environmentally friendly sulfamethoxazole pollution control technologies has become an urgent technical challenge in the field of environmental governance.

[0003] Advanced oxidation processes (AOPs) based on peracetic acid (PAA, chemical formula: CH3CO3H) generate reactive oxygen species (ROS) by breaking oxygen-oxygen bonds, achieving efficient degradation of sulfamethoxazole. Peracetic acid has low oxygen-oxygen bond energies, making it easily catalytically activated. During activation, various free radicals and non-free radical active components are simultaneously generated, including alkyl radicals, hydroxyl radicals, superoxide radicals, singlet oxygen, and high-valence metal oxides. Through the synergistic effect of multiple oxidation pathways, the degradation and transformation of sulfamethoxazole are significantly promoted. Peracetic acid alone has limited ability to degrade pollutants, requiring additional activation methods. Biochar, with its porous structure and oxygen-containing functional groups on its surface, possesses certain potential for activating peracetic acid. However, raw biochar suffers from limited active sites and low electron transfer efficiency, resulting in insufficient activation performance and cycle stability. Therefore, enhancing the activation capacity of biochar for peracetic acid through modification is crucial for constructing efficient advanced oxidation process systems and achieving deep removal of sulfamethoxazole.

[0004] Loading with iron-manganese bimetal is a cost-effective modification method for optimizing the adsorption and catalytic performance of biochar. Iron possesses excellent redox properties, effectively reshaping the pore structure of the biochar, expanding adsorption active sites, and exhibiting good complexation and fixation effects on pollutants. Furthermore, it is abundant, inexpensive, and ecologically safe. Manganese has multiple valence states and outstanding catalytic activity, accelerating interfacial electron migration, broadening the pathways of pollutant action, and effectively enhancing the material's treatment capacity. While single-metal loading has performance limitations, loading with iron-manganese bimetal can create a synergistic effect. The interaction between the two further increases the specific surface area of ​​the material, enriches surface functional groups, and balances both adsorption enrichment and catalytic degradation. Compared to other metal-loaded systems, this combined modification effect is more comprehensive, the material structure is more stable, and the overall treatment efficiency is significantly better than that of single-metal-loaded biochar.

[0005] Nitrogen doping introduces nitrogen atoms into biochar, significantly increasing the nitrogen and oxygen-containing functional groups on the surface, enhancing the material's polarity and hydrophilicity. Simultaneously, it optimizes the pore structure, increases active sites and oxygen vacancies, and the post-doped nitrogen can form a carbon-nitrogen encapsulation structure, effectively inhibiting metal agglomeration by encapsulating iron-manganese bimetallic particles. Combining this with an impregnation-pyrolysis method allows for simultaneous enhancement of nitrogen doping and iron-manganese loading, giving the material both high-efficiency adsorption and catalytic degradation capabilities. The process is simple, environmentally friendly, and significantly improves the removal efficiency of sulfamethoxam wastewater.

[0006] Chinese invention patent CN 120155189A discloses a method for preparing sludge biochar / iron-manganese layered bimetallic oxide composite material and its application. The modified layered bimetallic oxide prepared by the method solves the problems of easy agglomeration and high cost of single iron-manganese layered bimetallic oxide, realizes the resource utilization of sludge, and efficiently degrades bisphenol A in water. The material has both wide pH adaptability and recyclability.

[0007] Chinese invention patent CN 121060551A discloses an iron-manganese composite oxide modified biochar, its preparation method, and its application. The iron-manganese composite oxide modified biochar prepared by the method solves the problems of insufficient catalytic activity and low persulfate activation efficiency of the original biochar, achieving the effect of highly efficient activation of persulfate and enhanced removal of recalcitrant organic pollutants, realizing the resource utilization of sludge solid waste, and also has the advantages of stable catalytic performance and mild reaction conditions.

[0008] Chinese invention patent CN 121945097A discloses a composite catalyst for peracetic acid activation system, its preparation method and application. The cobalt-manganese composite metal oxide catalyst prepared by the method solves the problems of low activation efficiency and poor stability of peracetic acid by single metal catalysts. It achieves the effect of significantly improving the rate of peracetic acid free radical generation and efficient degradation of organic pollutant sulfamethoxazole in water, while also having good structural stability and recyclability. Summary of the Invention

[0009] To address the shortcomings of existing treatment technologies, this invention aims to provide an iron-manganese-loaded nitrogen-doped modified biochar and its preparation method, and to apply it to the treatment of sulfamethoxazole wastewater. This invention uses chestnut shells, agricultural and forestry waste, as raw material to prepare modified biochar, achieving not only the resource recovery and reuse of chestnut shell waste, but also enabling the activated peracetic acid by the modified biochar to efficiently remove sulfamethoxazole from water, effectively improving wastewater treatment efficiency, and ultimately achieving the dual benefits of combining waste-to-waste treatment, solid waste utilization, and water pollution control.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, the present invention provides an iron-manganese-supported nitrogen-doped modified biochar, which is prepared from chestnut shell waste. The modified biochar is characterized in that its surface is rich in a large number of oxygen-containing functional groups and oxygen vacancies, and iron and manganese are uniformly loaded on the surface of the biochar matrix in a bimetallic composite form.

[0011] According to a second aspect of the present invention, a method for preparing iron-manganese supported nitrogen-doped modified biochar is provided, characterized by the following specific steps: (1) The chestnut shell buckets were washed, dried and ground, and then placed in a muffle furnace for high-temperature pyrolysis under limited oxygen conditions to obtain chestnut shell bucket biochar. (2) The above chestnut shell biochar, potassium ferricyanide and manganese acetate were added to deionized water and mixed. After stirring continuously in a beaker, the mixture was transferred to an oven for drying. The dried material was then mixed with melamine and placed in a tube furnace for high-temperature pyrolysis under a nitrogen atmosphere to finally obtain iron-manganese loaded nitrogen-doped modified biochar.

[0012] Preferably, the chestnut shells used in step (1) are agricultural and forestry waste, collected in Yixing City, Jiangsu Province.

[0013] Preferably, the high-temperature pyrolysis process parameters in step (1) are: heating rate of 5℃ / min, heating to 450℃ and then pyrolyzing at a constant temperature for 2 h.

[0014] Preferably, in step (2), the amounts of chestnut shell biochar, potassium ferricyanide, and manganese acetate used are 1 g, 3.95 g, and 0.98 g, respectively, and the amount of deionized water used is 50 mL.

[0015] Preferably, the stirring time in step (2) is 12 h; the high-temperature pyrolysis conditions are to heat to 800°C at a heating rate of 5°C / min and continue pyrolysis for 2 h; the drying temperature is 60°C and the drying time is 12 h.

[0016] According to a third aspect of the present invention, the application of the above-described iron-manganese-supported nitrogen-doped modified biochar is further provided. The biochar is prepared by the preparation method described above and is mainly used for the purification treatment of wastewater containing sulfamethoxazole.

[0017] In one embodiment, the iron-manganese-loaded nitrogen-doped modified biochar is mixed with sulfamethoxazole-containing water, peracetic acid is added, and the mixture is stirred continuously at room temperature for 60 min. After the reaction has continued for 2, 5, 10, 15, 30, and 60 min, the mixture is filtered to obtain a solution after sulfamethoxazole removal.

[0018] Preferably, the initial concentration of sulfamethoxazole in the water to be treated is 10 mg / L, the initial concentration of peracetic acid is 0.3 mmol / L, and the dosage of iron-manganese-loaded nitrogen-doped modified biochar is 0.3 g / L.

[0019] Compared with the prior art, the present invention has the following advantages: (1) This invention uses chestnut shell waste as raw material to prepare iron-manganese-loaded nitrogen-doped modified biochar. Currently, chestnut shells are mostly used only as fertilizer or fuel, and the resource utilization method is singular. Applying this modified biochar to the treatment of wastewater containing sulfamethoxazole not only realizes the high-value resource utilization of agricultural and forestry waste, but also efficiently removes sulfamethoxazole pollutants from water bodies, achieving the comprehensive benefits of treating pollution with waste.

[0020] (2) The iron-manganese-supported nitrogen-doped modified biochar prepared by this invention has good structural stability and its surface is rich in oxygen-containing functional groups and oxygen vacancies. For sulfamethoxazole-containing water with an initial concentration of 10 mg / L, its pollutant removal rate can reach more than 99%, making it a high-quality environmental functional remediation material suitable for the treatment of sulfamethoxazole-containing wastewater. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a further detailed description will be provided below in conjunction with the accompanying drawings. The drawings illustrate several embodiments of this disclosure by way of example and not limitation, wherein: Figure 1 This is a scanning electron microscope image of the iron-manganese-supported nitrogen-doped modified biochar in Example 2 of the present invention; Figure 2 The Fourier transform infrared spectrum of the iron-manganese-supported nitrogen-doped modified biochar in Example 2 of this invention; Figure 3 This is the X-ray diffraction pattern of the iron-manganese-loaded nitrogen-doped modified biochar in Example 2 of the present invention; Figure 4 The electron spin resonance spectrum of the iron-manganese-supported nitrogen-doped modified biochar in Example 2 of this invention; Figure 5 The removal rate of sulfamethoxazole in water by iron-manganese-loaded nitrogen-doped modified biochar in Example 3 of the present invention at different reaction times; Figure 6 The removal rate of sulfamethoxazole in water by iron-manganese-supported nitrogen-doped modified biochar in Example 4 of the present invention under different pH conditions; Figure 7 The figure shows the removal rate of sulfamethoxazole in water by iron-manganese-supported nitrogen-doped modified biochar in Example 5 of this invention at different reaction temperatures. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments. The described embodiments are only for explaining the present invention, and those skilled in the art should understand that process parameters can be adaptively adjusted to address different application scenarios. It is specifically noted that any parameter improvements or process changes made based on the technical solution of the present invention do not depart from the protection scope of the present invention. Specific implementation examples are as follows:

[0023] Example 1 This embodiment describes the preparation of iron-manganese-loaded nitrogen-doped modified biochar.

[0024] Specifically, the following steps are included: A certain amount of chestnut shell granules was weighed, washed, dried, and ground, and passed through a 20-mesh sieve to obtain chestnut shell granules. These granules were placed in a crucible and pyrolyzed in a muffle furnace at 450℃ for 2 h to obtain chestnut shell biochar. The biochar was then removed and cooled to room temperature. Next, 1 g of chestnut shell biochar, 0.98 g of manganese acetate, and 3.95 g of potassium ferricyanide were mixed into 100 mL of deionized water and magnetically stirred at 300 rpm for 12 h. The resulting mixture was then filtered and washed in a vacuum filter. The filtered solid was dried in an oven at 60℃ for 12 h. This solid was then mixed with 1 g of melamine and placed in a quartz boat, where it was pyrolyzed in a tube furnace under a nitrogen atmosphere at 800℃ for 2 h.

[0025] Example 2 This embodiment characterizes the iron-manganese-supported nitrogen-doped modified biochar prepared in Example 1.

[0026] An appropriate amount of iron-manganese-supported nitrogen-doped modified biochar was analyzed by scanning electron microscopy to observe its morphology. The results are as follows: Figure 1 As shown, the surface of iron-manganese-loaded nitrogen-doped modified biochar is rough and the pores are destroyed. This is because during pyrolysis, the surface of the biochar is affected by the activation effect of iron-manganese metal and nitrogen doping, forming a mixed form of nanoparticles and nanosheets.

[0027] An appropriate amount of iron-manganese-supported nitrogen-doped modified biochar was subjected to Fourier transform infrared spectroscopy to qualitatively analyze its functional groups. The results are as follows: Figure 2 As shown. Iron-manganese supported nitrogen-doped modified biochar at 3200-3600 cm⁻¹ -1 and 2933 cm -1 and 1627cm -1 The peaks on the left and right sides are attributed to the stretching vibrations of -OH, -CH, and C=C / C=N; at 1400 cm⁻¹ -1 1007 cm -1 and 832 cm -1 The peaks on the left and right sides are attributed to the stretching vibrations of -COOH, -CO, and -CH; at 2167 cm⁻¹ -1 702 cm -1 and 663 cm -1 The presence of -C≡N, Mn-O, and Fe-O peaks at the respective locations indicates that the surface of the iron-manganese-supported nitrogen-doped modified biochar contains abundant nitrogen-containing functional groups, oxygen-containing functional groups, and metal oxides.

[0028] An appropriate amount of iron-manganese-supported nitrogen-doped modified biochar was subjected to X-ray diffraction to analyze its crystal structure. The results are as follows: Figure 3 As shown, iron-manganese supported nitrogen-doped modified biochar exhibits C (2θ = 26.61°), FeMnO3 (2θ = 32.98°), and Fe... 2.7 Mn 0.3 The characteristic diffraction peaks of C (2θ = 37.76°, 39.2°, 43.10°, 43.94°, 44.74°, 46.05°) indicate that iron, manganese and nitrogen were successfully loaded and doped onto chestnut shell biochar.

[0029] An appropriate amount of iron-manganese-supported nitrogen-doped modified biochar was subjected to electron spin resonance testing to analyze the surface vacancy situation. The results are as follows: Figure 4 As shown, the iron-manganese-supported nitrogen-doped modified biochar exhibits a symmetrical absorption peak at a g=2.003. The signal at this position typically originates from unpaired electrons trapped by oxygen vacancies on the oxide material surface. This demonstrates that the material surface contains a high concentration of oxygen vacancies, and that these vacancies possess a distinct g=2.003 fingerprint characteristic.

[0030] Example 3 This embodiment investigates the removal rate of sulfamethoxazole in water by iron-manganese-loaded nitrogen-doped biochar-activated peracetic acid at different reaction times.

[0031] In this embodiment, the sulfamethoxazole-containing wastewater was prepared using sulfamethoxazole at an initial concentration of 10 mg / L. The peracetic acid-containing aqueous solution was prepared by mixing acetic acid and hydrogen peroxide in a 1:1 (v:v) ratio, and diluted 10 times with deionized water to an initial concentration of 0.05 M. 50 mL of the above sulfamethoxazole solution was placed in a 100 mL beaker, and 15 mg of iron-manganese-supported nitrogen-doped modified biochar was added. Timing began from the addition of 0.3 mL of the above peracetic acid solution. Under room temperature conditions, the mixed solution was collected at 2, 5, 10, 15, 30, and 60 min, filtered, and the concentration of sulfamethoxazole in the filtrate was determined using high-performance liquid chromatography (HPLC).

[0032] Results analysis: Figure 5 The removal rate of sulfamethoxazole in water by iron-manganese-supported nitrogen-doped modified biochar activated with peracetic acid at different reaction times was investigated. The removal rate of sulfamethoxazole in water by iron-manganese-supported nitrogen-doped modified biochar reached 98.6% after 30 min.

[0033] Example 4 This embodiment investigates the removal rate of sulfamethoxazole in water by iron-manganese-supported nitrogen-doped biochar-activated peracetic acid under different initial pH conditions.

[0034] In this embodiment, the sulfamethoxazole-containing wastewater was prepared using sulfamethoxazole at an initial concentration of 10 mg / L. The peracetic acid-containing aqueous solution was prepared by mixing acetic acid and hydrogen peroxide in a 1:1 (v:v) ratio, and diluted 10 times with deionized water to an initial concentration of 0.05 M. 50 mL of the above sulfamethoxazole solution was placed in a 100 mL beaker, and the initial pH of the solution was adjusted to 3.0, 5.0, 7.0, 9.0, and 11.0 using 1 M hydrochloric acid or 1 M sodium hydroxide. 15 mg of iron-manganese-supported nitrogen-doped modified biochar was added. Timing began from the addition of 0.3 mL of the above peracetic acid solution. Under room temperature conditions, the mixed solution was collected at 2, 5, 10, 15, 30, and 60 min after the reaction had proceeded. The solution was filtered, and the concentration of sulfamethoxazole in the filtrate was determined using high-performance liquid chromatography (HPLC).

[0035] Results analysis: Figure 6 The figure represents the removal rate of sulfamethoxazole from water under different initial pH conditions by iron-manganese-loaded nitrogen-doped modified biochar. When the initial pH of the sulfamethoxazole solution is 11, the removal effect of iron-manganese-loaded nitrogen-doped modified biochar on cadmium in the water is the worst, with a removal rate of 35.2%.

[0036] Example 5 This embodiment investigates the removal rate of sulfamethoxazole in water by iron-manganese-loaded nitrogen-doped modified biochar at different reaction temperatures.

[0037] In this embodiment, the sulfamethoxazole-containing wastewater was prepared using sulfamethoxazole at an initial concentration of 10 mg / L. The peracetic acid-containing aqueous solution was prepared by mixing acetic acid and hydrogen peroxide in a 1:1 (v:v) ratio and diluting it 10 times with deionized water to an initial concentration of 0.05 M. 50 ml of the above sulfamethoxazole solution was placed in a 100 ml beaker, and 15 mg of iron-manganese-supported nitrogen-doped modified biochar was added. Timing was started from the addition of 0.3 mL of the above peracetic acid solution. The mixed solution was collected at 25, 35, and 45°C after 2, 5, 10, 15, 30, and 60 min of reaction time, filtered, and the concentration of sulfamethoxazole in the filtrate was determined using high-performance liquid chromatography (HPLC).

[0038] Results analysis: Figure 7 The removal rate of sulfamethoxazole from water by iron-manganese-supported nitrogen-doped modified biochar at different reaction temperatures was shown. The highest removal rate of sulfamethoxazole from water was observed at a reaction temperature of 45℃.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the implementation of the present invention. Any changes, modifications, substitutions, combinations, or simplifications made within the scope of the present invention without departing from its spirit and principle are considered equivalent substitutions and should be covered within the protection scope of the present invention.

Claims

1. A type of iron-manganese-supported nitrogen-doped modified biochar based on chestnut shell waste, characterized in that: The modified biochar has abundant oxygen-containing functional groups and oxygen vacancy structures, with iron and manganese supported on the biochar in a bimetallic form.

2. A method for preparing the iron-manganese-supported nitrogen-doped modified biochar of claim 1, characterized in that, The preparation steps include the following: (1) The chestnut shell buckets were washed, dried and ground, and placed in a muffle furnace for high-temperature pyrolysis under limited oxygen conditions to obtain chestnut shell bucket biochar. (2) The chestnut shell biochar, potassium ferricyanide and manganese acetate obtained in step (1) are mixed in deionized water, stirred continuously in a beaker and dried in an oven. After being mixed with melamine, the mixture is placed in a tube furnace and subjected to high-temperature pyrolysis under nitrogen conditions to obtain iron-manganese loaded nitrogen-doped modified biochar.

3. The method for preparing iron-manganese supported nitrogen-doped modified biochar according to claim 2, characterized in that, The raw material used in step (1) is chestnut shells, which are agricultural and forestry waste. The raw material is sourced from Yixing City, Jiangsu Province.

4. The method for preparing iron-manganese supported nitrogen-doped modified biochar according to claim 2, characterized in that, In step (1), the heating rate is 5℃ / min, and the temperature is kept constant for 2 hours after reaching 450℃.

5. The method for preparing iron-manganese supported nitrogen-doped modified biochar according to claim 2, characterized in that, Step (2) Raw material usage: 1 g of chestnut shell biochar, 3.95 g of potassium ferricyanide, 0.98 g of manganese acetate, and 50 ml of deionized water.

6. The method for preparing iron-manganese supported nitrogen-doped modified biochar according to claim 2, characterized in that, The stirring time in step (2) is 12 h; the heating rate of high temperature pyrolysis is 5℃ / min, and the temperature is kept constant for 2 h after heating to 800℃; the drying temperature is 60℃ and the drying time is 12 h.

7. A type of iron-manganese supported nitrogen-doped modified biochar, characterized in that, The biochar is prepared by the preparation method according to any one of claims 1 to 6.

8. An application of iron-manganese supported nitrogen-doped modified biochar, characterized in that: The biochar is prepared by the preparation method according to any one of claims 1 to 6, and the biochar is used for the treatment of wastewater containing sulfamethoxazole.

9. The application of the iron-manganese supported nitrogen-doped modified biochar according to claim 8, characterized in that, The process includes the following steps: mixing the iron-manganese-loaded nitrogen-doped modified biochar with sulfamethoxazole-treated water, adding peracetic acid, stirring continuously at room temperature for 60 min, and filtering after the reaction has continued for 2, 5, 10, 15, 30, and 60 min to obtain a solution after sulfamethoxazole removal.

10. The application of the iron-manganese supported nitrogen-doped modified biochar according to claim 9, characterized in that, The initial concentration of sulfamethoxazole in the water to be treated was set at 10 mg / L, the dosage of iron-manganese-loaded nitrogen-doped modified biochar was 0.3 g / L, and the dosage of peracetic acid was 0.3 mmol / L.

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