Iron-manganese oxide modified biochar, preparation method thereof and application of iron-manganese oxide modified biochar in degradation of sulfonamide metformin

Abstract

The present application relates to the field of environmental governance, and discloses a kind of iron manganese oxide modified biochar and its preparation method and application in degrading sulfonamides metformin.The iron manganese oxide modified biochar includes biochar and iron manganese oxide particles loaded on the surface and pore surface of biochar;The iron manganese oxide modified biochar is obtained by calcining after impregnating adsorbing the solution of manganese precursor and iron precursor by biomass carbon source.The iron manganese oxide modified biochar of the present application can efficiently degrade sulfonamides metformin in soil in the absence of oxidant system, and due to the abundance of iron and manganese in natural environment, it has higher environmental safety when applied to soil environment, and does not cause secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation, and in particular to an iron-manganese oxide modified biochar, its preparation method, and its application in the degradation of sulfamethoxypyrimidine. Background Technology

[0002] Antibiotics are not completely absorbed and metabolized in livestock and poultry; almost all are excreted in feces, except for a small amount remaining in tissues. Livestock and poultry manure, whether untreated or after composting, is widely used as fertilizer in farmland, leading to residual antibiotics entering the soil. It is estimated that 58% of antibiotics are excreted, with 54% of that entering the soil. Antibiotics entering the soil environment migrate and transform, affecting the growth, development, and reproduction of plants, soil animals, and microorganisms to varying degrees. They can also induce an increase in the abundance of resistant bacteria and resistance genes, posing a potential threat to human health. Therefore, developing technologies for controlling antibiotics in soil is a current research hotspot in the field of environmental science.

[0003] Currently, most antibiotic degradation and removal technologies are used in wastewater treatment. Non-biological methods, including adsorption, photodegradation, and electrochemical oxidation, are effective in wastewater treatment, demonstrating high efficiency and speed. However, due to high costs and the risk of secondary pollution, they are largely unsuitable for in-situ remediation of antibiotic residues in soil and aquatic environments. Healthy soil possesses natural functions of filtering, buffering, and even detoxifying potential pollutants. Key pathways of antibiotic degradation in the environment, including hydrolysis, photodegradation, and biodegradation, can aid in antibiotic detoxification. However, sulfonamide antibiotics are not easily hydrolyzed in the natural environment, unlike tetracycline antibiotics (TCs) and macrolide antibiotics (MLs). For the removal of sulfonamide antibiotics from soil, biodegradation is likely the primary pathway. Therefore, improving the soil's capacity for antibiotic degradation and detoxification is a more ecological, lower-cost, multifunctional, and effective method for remediating antibiotic-contaminated soils.

[0004] Biochar is a porous, highly aromatic, and insoluble solid material formed by the thermal decomposition and carbonization of biomass under anaerobic or partially anaerobic and high-temperature conditions. Due to its broad potential in many agricultural and environmental applications, it has received widespread attention in recent years. The main applications of biochar include soil amendment, pollutant adsorption / stabilization, carbon sequestration, and energy production. As a promising soil amendment, biochar can reduce soil bulk density, regulate soil porosity, increase soil organic matter, and promote plant growth when applied in farmland. Furthermore, biochar can be used as an adsorbent for antibiotic removal. Existing technologies have also reported on modifying biochar for antibiotic adsorption; for example, modifying biochar through acid-base oxidation, organic loading, or inorganic loading can improve its antibiotic adsorption capacity.

[0005] However, physical adsorption cannot completely reduce antibiotic levels at the source; degradation is the best way to detoxify organic pollutants and avoid their reactivation. In existing technologies, biochar has been reported as a catalyst in advanced oxidation processes (AOPs) for degrading organic pollutants. Oxidants such as hydrogen peroxide, persulfate, and peroxymonosulfate (PMS) are commonly used to generate highly reactive substances such as sulfate radicals and hydroxyl radicals, which can oxidize and degrade organic pollutants in AOPs into harmless substances. However, the addition of oxidants increases the complexity of the system and can easily cause secondary pollution; it also increases costs. Currently, there are no research reports on using modified biochar as a catalyst to degrade antibiotics (especially sulfonamides) in oxidant-free systems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an iron-manganese oxide-modified biochar, its preparation method, and its application in the degradation of sulfamethoxypyrimidine. The iron-manganese oxide-modified biochar of this invention can efficiently degrade sulfamethoxypyrimidine in soil in an oxidant-free system. Furthermore, due to the abundance of iron and manganese in the natural environment, its application in soil environments offers higher environmental safety and avoids secondary pollution.

[0007] The specific technical solution of this invention is as follows:

[0008] In a first aspect, the present invention provides an iron-manganese oxide modified biochar, comprising biochar and iron-manganese oxide particles loaded on the surface and pore surface of the biochar; the iron-manganese oxide modified biochar is obtained by impregnating a solution of manganese precursor and iron precursor with a biomass carbon source and then calcining it.

[0009] Unlike existing technologies that use biochar as a physical adsorbent or degrade organic matter in systems with oxidants, this invention discovers that by attaching iron-manganese oxide particles to the surface of biochar, sulfamethoxypyrimidine (SMM) in soil can be efficiently degraded in a system without oxidants. Iron-manganese oxide-modified biochar can act as a catalyst to promote the biodegradation and non-biodegradation (free radical-mediated degradation) of SMM, with soil biomolecules and •OH playing important roles in the SMM degradation process. Furthermore, due to the abundance of iron and manganese in the natural environment, its application to soil environments offers higher environmental safety and will not cause secondary pollution.

[0010] Preferably, the iron-manganese oxide is MnFe2O4.

[0011] Secondly, the present invention provides a method for preparing iron-manganese oxide modified biochar, comprising the following steps: first, immersing a biomass carbon source in a manganese precursor solution, adsorbing and then filtering; immersing the obtained filter residue in an iron precursor solution, adsorbing and then filtering; mixing the obtained filter residue with a sodium hydroxide solution evenly, allowing it to stand and filter; washing and drying the obtained filter residue, calcining it in an oxygen-free atmosphere, grinding it, and sieving it to obtain iron-manganese oxide modified biochar.

[0012] The invention team discovered that the iron-manganese oxide modified biochar prepared by adsorbing a manganese precursor solution onto a biomass carbon source and then calcining it in an anaerobic environment is more effective in degrading sulfamethoxypyrimidine. If the traditional process of first calcining to prepare biochar and then loading iron-manganese oxide and calcining it is used, it is easy to cause the biochar and iron-manganese oxide to be poorly bonded, resulting in poor stability of the composite material and poor interaction between different substances in the material, thus leading to poor degradation effect.

[0013] Preferably, the mass ratio of the biomass carbon source, manganese precursor, iron precursor and sodium hydroxide is 10:(4-6):(3-5):(3-4).

[0014] Our team discovered that controlling the ratio of biomass carbon source, manganese precursor, iron precursor, and sodium hydroxide within the above-mentioned range results in better degradation of sulfamethoxypyrimidine.

[0015] Preferably, the concentration of the manganese precursor solution is 45-55 g / L; the concentration of the iron precursor solution is 35-45 g / L; and the concentration of the sodium hydroxide solution is 6-8 wt%.

[0016] Preferably, the biomass carbon source is rice husk; the manganese precursor is potassium permanganate; and the iron precursor is ferrous chloride.

[0017] Preferably, the adsorption time of the biomass carbon source in the manganese precursor solution is 40-50 h; the adsorption time of the biomass carbon source in the iron precursor solution is 40-50 h; and the standing time of the biomass carbon source in the sodium hydroxide solution is 4-8 h.

[0018] Preferably, the drying temperature is 60-70℃ and the time is 10-15h;

[0019] Preferably, the calcination temperature is 450-550℃ and the time is 2.5-3.5h.

[0020] Preferably, the sieving is performed through a 100-mesh sieve.

[0021] Thirdly, the present invention provides the application of the above-mentioned iron-manganese oxide modified biochar as a catalyst in the degradation of sulfamethoxypyrimidine in an oxidant-free system.

[0022] Preferably, the sulfamethoxypyrimidine is sulfamethoxypyrimidine found in soil.

[0023] Compared with the prior art, the beneficial effects of the present invention are: the iron-manganese oxide modified biochar of the present invention can efficiently degrade sulfamethoxypyrimidine in soil in an oxidant-free system, and because the natural environment is rich in iron and manganese, it has higher environmental safety when applied to the soil environment and will not cause secondary pollution. Attached Figure Description

[0024] Figure 1 SEM image of rice husk biochar in Comparative Example 1;

[0025] Figure 2 This is a scanning electron microscope image of iron-manganese modified biochar from Example 1;

[0026] Figure 3 EDS analysis chromatogram of iron-manganese modified biochar in Example 1;

[0027] Figure 4 The XRD patterns (a) and infrared spectra (b) of iron-manganese modified biochar in Example 1 and rice husk biochar in Comparative Example 1 are shown.

[0028] Figure 5 Raman spectra of iron-manganese modified biochar in Example 1 and rice husk biochar in Comparative Example 1;

[0029] Figure 6 The nitrogen adsorption-desorption isotherms of iron-manganese modified biochar in Example 1 and rice husk biochar in Comparative Example 1 are shown.

[0030] Figure 7 The pore size distribution diagrams are for iron-manganese modified biochar in Example 1 and rice husk biochar in Comparative Example 1. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments.

[0032] General Implementation Examples

[0033] A modified biochar with iron and manganese oxides includes biochar and iron and manganese oxide (MnFe2O4) particles loaded on the surface and pore surface of the biochar. The preparation method includes the following steps: the biomass carbon source is first immersed in a manganese precursor solution, and after adsorption for 40-50 hours, it is filtered. The resulting filter residue is immersed in an iron precursor solution, and after adsorption for 40-50 hours, it is filtered. The resulting filter residue is mixed evenly with sodium hydroxide solution, allowed to stand for 4-8 hours, and then filtered. The resulting filter residue is washed, dried (60-70℃, 10-15 hours), calcined in an oxygen-free atmosphere (450-550℃, 2.5-3.5 hours), ground, and passed through a 100-mesh sieve to obtain the modified biochar with iron and manganese oxides.

[0034] As a preferred embodiment, the mass ratio of biomass carbon source, manganese precursor, iron precursor and sodium hydroxide is 10:(4-6):(3-5):(3-4); the concentration of manganese precursor solution is 45-55 g / L; the concentration of iron precursor solution is 35-45 g / L; the concentration of sodium hydroxide solution is 6-8 wt%; the biomass carbon source is rice husk; the manganese precursor is potassium permanganate; the iron precursor is ferrous chloride.

[0035] The aforementioned iron-manganese oxide modified biochar can be used as a catalyst in an oxidant-free system for the degradation of sulfamethoxypyrimidine in soil.

[0036] Example 1

[0037] Preparation of iron-manganese oxide modified biochar: Take 10 g of rice husk powder and put it into a 500 mL beaker, add 100 mL of 50 g·L⁻¹ biochar. -1 Add potassium permanganate solution, stir for 10 min, cover with a glass watch glass, soak for 48 h, then filter; return the filter residue to a 500 mL beaker, and add 40 g·L⁻¹ potassium permanganate solution while stirring rapidly. -1 100 mL of ferrous chloride solution was stirred for 10 min, and after soaking for 48 h, it was filtered. The filtered residue was put back into a 500 mL beaker, and 50 mL of sodium hydroxide solution with a mass fraction of 7 wt% was added. The mixture was stirred, soaked for 6 h, and then filtered. The residue was then washed thoroughly with ultrapure water. The residue was placed on a disk and dried at 65 ℃ for 12 h. It was then placed in a crucible and calcined at 500 ℃ in an oxygen-free environment for 3 h. After cooling to room temperature, it was dried at 70 ℃ and ground through a 100-mesh sieve to obtain iron-manganese oxide modified biochar.

[0038] Comparative Example 1

[0039] Preparation of rice husk biochar: Agricultural waste rice husks were dried to constant weight at 105℃. An oxygen-limited temperature-controlled carbonization method was used, placing the waste rice husks in a programmable tube furnace and heating at 500℃ for 3 hours in the absence of oxygen. After pyrolysis was completed and the samples were naturally cooled to room temperature, the samples were removed. The carbonized products were dried in an oven, ground, and sieved through a 100-mesh sieve, then transferred to sealed plastic bags for storage.

[0040] Performance testing

[0041] (1) Scanning electron microscopy and elemental analysis

[0042] Figure 1 and Figure 2 The images show scanning electron microscope (SEM) images of rice husk biochar (Comparative Example 1) and iron-manganese modified biochar (Example 1), respectively. As can be seen from the images, compared to rice husk biochar, the iron-manganese modified biochar has a rougher surface and more developed pores. Furthermore, the surface of the iron-manganese modified biochar is loaded with many small particles. Figure 3 EDS analysis showed that the small particles contained Fe and Mn elements, therefore it is speculated that the small particles are iron-manganese oxide particles.

[0043] (2) XRD and infrared analysis

[0044] from Figure 4 The XRD diffraction pattern of rice husk biochar (RS, Comparative Example 1) shows a broad peak near 2θ = 22°, a characteristic peak of carbon. Additionally, a peak near 26° represents a small amount of silicate present in the rice husk biochar. The XRD pattern of iron / manganese modified biochar (Fe / Mn-RS, Example 1) is significantly different from that of rice husk biochar. It exhibits characteristic peaks at 35.5° and 42.9°, characteristic peaks of magnetic MnFe₂O₄. Combined with the EDS results, it can be concluded that a MnFe₂O₄-biochar composite material was synthesized. Figure 4 As shown in b, both types of biochar contain abundant surface functional groups. In rice husk biochar (RS, Comparative Example 1), at 1585 cm⁻¹... -1 The absorption peak at 1423 cm⁻¹ corresponds to the stretching vibrations of C=C and C=O in the aromatic ring, as well as the antisymmetric stretching vibration of -COO-. -1 The absorption peak of CO3 at the point 2− Or – stretching vibration of COO. 1069,798,458 cm -1 The absorption peak at 568 cm⁻¹ is a vibrational peak of Si-O-Si, which is consistent with the XRD and EDS results. Compared with rice husk biochar, iron-manganese modified biochar (Fe / Mn-RS, Example 1) shows a higher absorption peak at 568 cm⁻¹. -1 A new vibration peak was observed, which can be attributed to the Fe-O vibration. This is consistent with the XRD results.

[0045] (3) Raman analysis

[0046] Raman spectroscopy is also widely used to analyze the degree of graphitization and defect status of carbon-containing materials. D and I G The ratio typically reflects the degree of defects and disorder in carbon materials. Figure 5 The images show the Raman spectra of rice husk biochar (RS, Comparative Example 1) and iron / manganese modified biochar (Fe / Mn-RS, Example 1). From the figures, we can see that the I... D / I G The values ​​were 0.834 and 0.852, respectively. Therefore, iron-manganese modification can significantly improve the defect structure of rice husk biochar, and a higher defect structure can improve the catalytic performance of rice husk biochar.

[0047] (4) Specific surface area analysis

[0048] Figure 6 and Figure 7 The nitrogen adsorption-desorption isotherms and pore size distribution diagrams for rice husk biochar (RS, Comparative Example 1) and iron / manganese modified biochar (Fe / Mn-RS, Example 1) are shown. The specific surface areas of rice husk biochar and iron / manganese modified biochar are 5.26 m² and 5.26 m², respectively. 2 / g, 91.70 m 2 / g. The specific surface area of ​​iron-manganese modified biochar is greater than that of rice husk biochar. The pore volumes of rice husk biochar and iron-manganese modified biochar are 0.018 cm³. 3 / g, 0.20 cm 3 / g.

[0049] Examples 2-9

[0050] The differences between Examples 2-4 and Example 1 are shown in the table below:

[0051]

[0052] Comparative Example 2 (using a process of first preparing biochar and then loading it with iron and manganese)

[0053] Agricultural waste rice husks were dried to constant weight at 105℃. An oxygen-limited temperature-controlled carbonization method was used, where the waste rice husks were placed in a programmable tube furnace and heated at 500℃ in the absence of oxygen for 3 hours. After pyrolysis was completed and the samples were naturally cooled to room temperature, they were removed. The carbonized products were dried in an oven, ground, and sieved through a 100-mesh sieve to obtain rice husk biochar.

[0054] Place 6 g of rice husk biochar into a 500 mL beaker, and add 100 mL of a 50 g·L⁻¹ solution. -1Add potassium permanganate solution, stir for 10 min, cover with a glass watch glass, soak for 48 h, then filter; return the filter residue to a 500 mL beaker, and add 40 g·L⁻¹ potassium permanganate solution while stirring rapidly. -1 100 mL of ferrous chloride solution was stirred for 10 min, and after soaking for 48 h, it was filtered. The filtered residue was put back into a 500 mL beaker, and 50 mL of sodium hydroxide solution with a mass fraction of 7 wt% was added. The mixture was stirred, soaked for 6 h, and then filtered. The residue was then washed thoroughly with ultrapure water. The residue was placed on a disk and dried at 65 ℃ for 12 h. It was then placed in a crucible and calcined at 500 ℃ in an oxygen-free environment for 3 h. After cooling to room temperature, it was dried at 70 ℃ and passed through a 100-mesh sieve to obtain modified biochar.

[0055] (5) Sulfamethoxypyrimidine (SMM) removal test

[0056] Preparation of soil extract: Air-dried soil was mixed with sterile water at a ratio of 1:5, and extracted by shaking at 180 rpm for 2 hours. The extract was then filtered through ordinary filter paper to obtain the soil extract. 5 mL of the soil extract was used to determine the number of soil bacteria using the plate count method (approximately 1 × 10⁻⁶ viable bacteria). 5 (CFU / mL).

[0057] 0.3 g of each product from Examples 1-9 and Comparative Examples 1-2 were dispersed in 30 mL of soil extract containing 1 ppm or 100 ppm SMM and 1 mL LB medium. The mixture was then shaken at 150 rpm at 25°C. A control group without biochar was performed under the same conditions. Shaking was used to avoid precipitation, ensure system homogeneity, and allow sufficient contact between the biochar, microorganisms, and SMM. Samples were analyzed periodically and filtered through a 0.22 μm membrane. To ensure the stability of the experimental results, all experiments were performed three times, and the average value with standard deviation is given. The results are shown in Table 1.

[0058] Table 1

[0059]

[0060] The data comparison in the table above shows that the addition of biochar in each case contributes to the removal of SMM, and the promoting effect of biochar on the removal of low-concentration SMM is better than that on high-concentration SMM. Overall, the effect is that of iron-manganese modified biochar (Examples 1-9, Comparative Example 2) > rice husk biochar (Comparative Example 1), indicating that the removal capacity of iron-manganese modified biochar for SMM is significantly enhanced in an oxidant-free system.

[0061] Furthermore, by comparing the data from Examples 1-9 and Comparative Example 2, it can be found that the cases where biochar preparation and iron-manganese modification were carried out simultaneously (Examples 1-9) were more effective than Comparative Example 2, which prepared biochar first and then modified iron-manganese. This may be because the latter tends to result in a less tight bond between biochar and iron-manganese oxides, leading to poor composite material stability and weaker interactions between different substances in the material, thus resulting in poor removal efficiency.

[0062] Furthermore, a comparison of the data from Examples 1-9 reveals that the iron-manganese modified biochar prepared in Examples 1, 3-4, and 7-8 is superior to that in Examples 2, 5, 6, and 9. This is because the iron and manganese ratios in the latter examples were not within the optimal range during preparation, resulting in a lack of strong interaction. This demonstrates that only iron-manganese modified biochar within a reasonable iron / manganese ratio range can achieve optimal removal of SMM in an oxidant-free system.

[0063] Table 2: Calculation of the contributions of degradation and adsorption during SMM removal

[0064]

[0065] As can be seen from the data comparison in Table 2, degradation is the main mechanism by which iron-manganese oxide modified biochar removes SMM.

[0066] (6) SMM degradation experiment under sterile and non-sterilized conditions: The SMM degradation experiment was carried out in 50 mL centrifuge tubes containing 30 mL of sterile or non-sterilized soil extract, with 0.3 g of modified biochar added to each tube (Example 1). Before the experiment, the concentration of microorganisms was determined by plate counting, and the results are shown in Table 3.

[0067] Table 3

[0068]

[0069] The comparison of SMM degradation data between sterilized and non-sterilized treatments in Table 3 shows that removing biological factors from the soil leachate led to a decrease in the SMM degradation rate. This indicates that the addition of modified biochar has both biotic and abiotic effects on the degradation of SMM in the soil leachate. Modified biochar effectively stimulated both biotic and abiotic degradation of SMM. The promoting effect of modified biochar on abiotic degradation tended to stabilize within 24 hours, but its promoting effect on biotic degradation continuously increased with prolonged incubation time. Therefore, the SMM degradation activated by modified biochar is closely related to biological factors such as soil microorganisms and enzymes.

[0070] Soil biofactors and •OH played important roles in the degradation of soil microorganisms (SMM) induced by modified biochar, indicating that biodegradation and •OH-mediated degradation are crucial for the degradation of SMM catalyzed by modified biochar in soil suspension. Modified biochar established a Fenton-like bioreaction with live microorganisms and enzymes in soil leachate to generate •OH. Fe(III) and Mn(III) / Mn(IV) in the modified biochar served as active sites in the degradation of SMM.

[0071] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. The application of iron-manganese oxide-modified biochar as a catalyst for the degradation of sulfamethoxypyrimidine in soil in a system without added oxidants, characterized in that: Iron-manganese oxide modified biochar includes biochar and iron-manganese oxide particles loaded on the surface and pore surface of biochar. The preparation of the iron-manganese oxide modified biochar includes the following steps: first, rice husks are soaked in a manganese precursor solution, and after adsorption, they are filtered; the resulting filter residue is soaked in an iron precursor solution, and after adsorption, it is filtered; the resulting filter residue is mixed evenly with sodium hydroxide solution, allowed to stand and filtered; the resulting filter residue is washed, dried, calcined in an oxygen-free atmosphere, ground, and sieved. The mass ratio of rice husk, manganese precursor, and iron precursor is 10:5:4; the iron-manganese oxide is MnFe2O4. Iron-manganese oxides enhance the catalytic performance of biochar by improving its defect structure; iron-manganese oxide-modified biochar exhibits improved Ig... D / I G The value is 0.852, and the specific surface area is 91.70 m². 2 / g, pore volume is 0.20 cm³ 3 / g; Iron-manganese oxide modified biochar achieves the degradation of sulfamethoxypyrimidine through both non-biodegradation and biodegradation promotion.

2. The application as described in claim 1, characterized in that: The mass ratio of rice husk, manganese precursor, iron precursor and sodium hydroxide is 10:5:4:(3-4). The concentration of the manganese precursor solution is 50 g / L; The concentration of the iron precursor solution is 40 g / L; The concentration of the sodium hydroxide solution is 6-8 wt%.

3. The application as described in claim 1 or 2, characterized in that: The manganese precursor is potassium permanganate.

4. The application as described in claim 1 or 2, characterized in that: The iron precursor is ferrous chloride.

5. The application as described in claim 1 or 2, characterized in that: The adsorption time of the rice husk in the manganese precursor solution is 40-50 hours.

6. The application as described in claim 1 or 2, characterized in that: The adsorption time of the rice husk in the iron precursor solution is 40-50 hours.

7. The application as described in claim 1 or 2, characterized in that: The rice husks were left to stand in the sodium hydroxide solution for 4-8 hours.

8. The application as described in claim 1 or 2, characterized in that: The calcination temperature is 450-550℃, and the time is 2.5-3.5h.

9. The application as described in claim 1 or 2, characterized in that: The sieving process is a 100-mesh sieve.

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