Magnesium-doped zero-valent iron biochar composites, their preparation methods, and their application in degrading organic pollutants in wastewater.

Abstract

This invention relates to the field of water treatment, and discloses a magnesium-doped zero-valent iron biochar composite material, its preparation method, and its application in degrading organic pollutants in wastewater. The magnesium-doped zero-valent iron biochar composite material comprises porous biochar as a carrier and Fe uniformly loaded in the porous biochar. 0 @MgFe2O4 / MgO particles; where: Fe 0 @MgFe2O4 / MgO particles have a core-shell structure, consisting of Fe particles coated with spinel-type MgFe2O4 and MgO. 0 Particles; the spinel-type MgFe2O4 and MgO in Fe 0 An active interface structure with oxygen vacancy defects is formed on the particle surface. The magnesium-doped zero-valent iron biochar composite material of this invention exhibits excellent activation activity for H2O2, and can efficiently, stably, and selectively activate H2O2 generation. 1 O2; In addition, the composite material has the advantages of wide pH adaptability, low iron sludge production and magnetic recovery. Therefore, the composite material is suitable as a catalyst to work with hydrogen peroxide to degrade organic pollutants in wastewater.

Description

Technical Field

[0001] This invention relates to the field of water treatment, and more particularly to a magnesium-doped zero-valent iron biochar composite material, its preparation method, and its application in the degradation of organic pollutants in wastewater. Background Technology

[0002] The discharge of industrial wastewater and domestic sewage, as well as agricultural non-point source pollution, leads to the entry of large amounts of toxic organic pollutants (such as pesticides and antibiotics) into aquatic environments. These pollutants are persistent, bioaccumulative, and resistant to biochemical degradation, posing a serious threat to ecosystems and human health.

[0003] Currently, the main methods for removing organic pollutants include biochemical methods, physicochemical methods, and advanced oxidation technologies (AOPs). Biochemical methods are limited by the toxicity and inhibitory effects of organic pollutants on microorganisms, making deep removal difficult. Physicochemical methods, such as adsorption and membrane separation, only achieve pollutant transfer and are costly. AOPs include the Fenton reaction and ozone oxidation, among which the Fenton reaction has attracted much attention due to its fast reaction rate and efficient degradation of organic pollutants; however, the traditional Fenton reaction involves Fe... 2+ The / H2O2 system suffers from problems such as the generation of large amounts of iron sludge, the need for acidic conditions, and the easy quenching of ·OH by coexisting substances, which seriously affect its actual treatment efficiency and increase operating costs.

[0004] In recent years, Fe 0 The / H2O2-type Fenton system is due to its sustainable iron cycle (Fe) 0 Fe reduction 3+ Regenerated Fe 2+ It has attracted attention due to the production of less iron sludge. For example, Chinese patent CN112645427A discloses a method based on Fe... 0 -Fe 2+ A catalytic Fenton oxidation method for wastewater treatment exists, but this method requires the addition of acid-base adjusters to control precipitate formation, increasing operational complexity. Chinese patent CN104229973A discloses a method utilizing nano-Fe... 0 A Fenton-like technique is used to remove diclofenac from wastewater, but it still requires a pH ≤ 4 during treatment, and it also involves nano-Fe. 0 Problems such as easy aggregation and surface oxidation passivation layer hindering electron transfer lead to the failure of active sites.

[0005] Furthermore, existing technologies still primarily utilize non-selective ·OH radicals, which have short lifetimes and are easily affected by water quality fluctuations. Singlet oxygen ( 1 O2, due to its mild reactivity and long lifespan, has become an excellent candidate for selective detergency. 1O2 possesses high electrophilicity and a specific affinity for electron-rich substrates, which helps to minimize the adverse effects of the formation of toxic halide byproducts. However, the activation of such iron-based catalysts selectively generates… 1 O2 is not very efficient. Therefore, it is necessary to develop a method for efficiently, stably, and selectively activating H2O2 generation. 1 O2 containing Fe 0 Catalysts are of positive significance for the deep reduction of organic pollutants in water. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a magnesium-doped zero-valent iron biochar composite material, its preparation method, and its application in the degradation of organic pollutants in wastewater. The magnesium-doped zero-valent iron biochar composite material of this invention exhibits excellent activation activity for H2O2, efficiently, stably, and selectively activating H2O2 to form... 1 O2; In addition, the composite material has the advantages of wide pH adaptability, low iron sludge production and magnetic recovery. Therefore, the composite material is suitable as a catalyst to work with hydrogen peroxide to degrade organic pollutants in wastewater.

[0007] The specific technical solution of this invention is as follows: First, a magnesium-doped zero-valent iron biochar composite material (i.e., MgFe) 0 @BC), which includes porous biochar (BC) as a carrier and Fe uniformly loaded in the porous biochar. 0 @MgFe2O4 / MgO particles.

[0008] Wherein, the Fe 0 @MgFe2O4 / MgO particles have a core-shell structure, consisting of Fe particles coated with spinel-type MgFe2O4 and MgO. 0 Particles; the spinel-type MgFe2O4 and MgO in Fe 0 An active interface structure with oxygen vacancy defects is formed on the particle surface.

[0009] In the magnesium-doped zero-valent iron biochar composite material of the present invention, biochar serves as a carrier for dispersing Fe. 0 Particles, and through Mg doping in Fe 0 A MgFe₂O₄ / MgO composite phase forms on the particle surface. The MgFe₂O₄ / MgO composite phase coats the Fe particles. 0 On the particle surface, an active interface structure with oxygen vacancy defects is formed. This unique core-shell structure (Fe) 0 @MgFe2O4 / MgO) can not only protect Fe 0 The core is not easily oxidized or passivated, and its abundant oxygen vacancies on the surface become key sites for electron transport and reactive oxygen species (ROS) conversion.

[0010] When this composite material is used to activate H2O2, MgO hydrolysis generates surface hydroxyl groups that adsorb and activate H2O2, producing ·OH groups that can be adsorbed onto its surface via a Fenton-like reaction; oxygen vacancies (OVs) in the MgFe2O4 lattice promote electron conduction and activation, enabling the highly selective conversion of adsorbed ·OH groups into H2O2. 1 O2; generated 1 The specific reactions of O2 are as follows: ; ; ; ; ; .

[0011] Preferably, the Fe 0 In @MgFe2O4 / MgO, the mass ratio of Fe to Mg is 1:0.089-0.23.

[0012] If the ratio of Fe to Mg is too high, it will be impossible to [achieve the desired effect] in Fe [elements]. 0 The surface of @BC generates sufficient oxygen vacancies and hydroxyl groups, and ·OH is converted to 1 O2 efficiency decreases; if the proportion is too low, excessive MgO tends to form on the material surface, reducing the material's conductivity and thus reducing Fe. 0 Electron conduction in the core is impeded.

[0013] Preferably, the specific surface area of ​​the magnesium-doped zero-valent iron biochar composite material is 300-400 m². 2 / g; the average pore size of the magnesium-doped zero-valent iron biochar composite material is 5-10 nm; the O of the magnesium-doped zero-valent iron biochar composite material A / O L The ratio is 4.5-5.5.

[0014] Compared with pure biochar (BC) or zero-valent iron biochar (Fe) 0 Compared to @BC), the magnesium-doped zero-valent iron biochar composite material (MgFe) of the present invention 0 The physicochemical properties of the modified material (@BC) underwent a series of changes. The modified material surface exhibited more uniformly dispersed fine particles, a significantly increased surface roughness, a substantial increase in specific surface area, and a marked decrease in average pore size, indicating that the generated particles at least partially filled the original pore spaces of the biochar matrix. More importantly, the material's O... A / O LThe ratio (an important indicator for measuring OV concentration) was also significantly improved, indicating that the introduction of Mg effectively increased the OV density in the material. This suggests that the incorporation of Mg promotes the formation of a more oxidizing structure in the material and can induce the generation of more oxygen defect sites.

[0015] Secondly, a method for preparing a magnesium-doped zero-valent iron biochar composite material includes the following steps: 1) Mix the iron-containing solution with the biomass powder evenly to obtain a mixture.

[0016] 2) Add alkaline liquid to the mixture to maintain the pH at neutral, centrifuge, take the precipitate and dry it to obtain iron-loaded biomass powder.

[0017] In step 2), since the Fe-containing solution is acidic, Fe ions cannot adhere to the biomass in large quantities. By dripping in an alkaline liquid, Fe hydroxide deposition can be increased, so that the Fe in the solution can adhere to the biomass to the greatest extent.

[0018] 3) Iron-loaded biomass powder is mixed with magnesium-containing materials (the mass ratio of iron-loaded biomass powder to Mg is 10:0.25-0.63), and pyrolyzed under an inert atmosphere. After cooling, magnesium-doped zero-valent iron biochar composite material (MgFe) is obtained. 0 @BC).

[0019] In-situ synthesis of MgFe can be achieved during the pyrolysis process in step 3). 0 @BC, its formation mechanism includes two core steps: (1) Under pyrolysis conditions of 700 ℃~750 ℃, the reducing gas (CO / H2) produced by biomass decomposition will reduce Fe 3+ Gradually reduced to Fe 0 Particles, and uniformly dispersed in biochar; (2) With the increase of pyrolysis temperature (from room temperature to target pyrolysis temperature), MgO generated by the decomposition of magnesium-containing substances (e.g., MgCl2) and some iron oxides (in the process of pyrolysis, high-valent iron is gradually reduced to zero-valent iron, but there are still some iron oxides that have not been reduced to zero-valent iron) react with MgO to form spinel-type MgFe2O4. This type of composite oxide and the residual MgO together coat the Fe 0 On the particle surface, an active interface structure with oxygen vacancy defects is formed. This unique core-shell structure (Fe) 0 @MgFe2O4 / MgO) can not only protect Fe 0 The core is not easily oxidized or passivated, and its abundant oxygen vacancies on the surface become key sites for electron transport and reactive oxygen species (ROS) conversion.

[0020] Preferably, in step 1), the mass ratio of iron element to biomass powder in the iron-containing solution is 0.2-0.5:1.

[0021] If the Fe content is too low, there will be too little Fe adhering to the surface of biomass. 0 Insufficient active ingredients in the particles lead to Fe 0 The catalytic performance of @BC is limited; conversely, if the Fe content is too high, it can easily lead to excessive Fe adhering to the biomass, which will produce Fe after pyrolysis. 0 Aggregates into larger particles, making Fe 0 Its activity is greatly affected.

[0022] Preferably, in step 1), the iron-containing solution is an aqueous solution containing one or more inorganic salts such as Fe2(SO4)3 and FeCl3.

[0023] Preferably, in step 1), the concentration of iron in the iron-containing solution is 10-25 g / L; most preferably, it is 20 g / L.

[0024] Preferably, in step 1), the biomass powder is selected from one or more agricultural and forestry wastes such as walnut shell powder, straw powder, branch powder, and fruit peel powder.

[0025] Preferably, in step 1), the biomass powder is passed through a 100-mesh sieve.

[0026] Preferably, in step 1), the biomass powder is pre-washed, dried to a constant weight, and then pulverized.

[0027] Preferably, in step 2), the centrifugation speed is 3000-5000 rpm.

[0028] Preferably, in step 2), the alkaline solution is an aqueous solution of one or more alkaline substances such as NaOH, KOH, and NH4HCO3.

[0029] Preferably, in step 3), the magnesium-containing substance is one or more inorganic salts such as MgCl2 and Mg3(SO4)2.

[0030] Preferably, in step 3), the pyrolysis is carried out under nitrogen protection at a rate of 4-6 °C / min, with the temperature increased to 700-750 °C and held for 20-40 min.

[0031] During pyrolysis, if the heating rate is too fast or the temperature is too low, the entire reaction process will be too short, failing to allow the biomass to decompose effectively and produce enough reducing CO and H2 to convert high-valence Fe to Fe. 0 The efficiency is too low. Furthermore, if the temperature is too high, the high-valence Fe will completely convert to Fe. 0MgO cannot form enough MgFe2O4 with Fe oxides, resulting in insufficient oxygen vacancies. If the heating rate is too low, it will hinder the preparation of MgFe... 0 @BC's costs are too high.

[0032] Finally, the application of magnesium-doped zero-valent iron biochar composite material as a catalyst in the degradation of organic pollutants in wastewater includes: adding the magnesium-doped zero-valent iron biochar composite material to wastewater containing organic pollutants for pre-adsorption, followed by the addition of hydrogen peroxide; the H2O2 in the hydrogen peroxide is converted into organic matter under the activation effect of the magnesium-doped zero-valent iron biochar composite material. 1 O2, thereby achieving the degradation of organic pollutants.

[0033] When the magnesium-doped zero-valent iron biochar composite material of the present invention is used as a catalyst in conjunction with hydrogen peroxide to degrade organic pollutants in wastewater, the composite material can activate H2O2. Specifically, MgO hydrolysis generates surface hydroxyl groups that adsorb and activate H2O2, producing ·OH that can be adsorbed on its surface through a Fenton-like reaction; oxygen vacancies (OV) in the MgFe2O4 lattice can promote electron conduction and activation, enabling the highly selective conversion of adsorbed ·OH into 1 O2.

[0034] Preferably, the amount of magnesium-doped zero-valent iron biochar composite material added is 0.2-0.6 wt% of the wastewater.

[0035] Preferably, the concentration of the hydrogen peroxide is 25-35 wt%, and the concentration in the wastewater after addition is 8-12 mM.

[0036] Preferably, the organic pollutant is ciprofloxacin hydrochloride.

[0037] Preferably, the pH of the wastewater is 3.0-9.0, and more preferably 3.0-7.0.

[0038] Compared with the prior art, the beneficial effects of the present invention are: (1) The magnesium-doped zero-valent iron biochar composite material of the present invention has excellent activation effect on H2O2, and can efficiently, stably and selectively activate H2O2 to generate 1 O2. MgO hydrolysis generates surface hydroxyl groups that adsorb and activate H2O2, producing ·OH groups that can adsorb onto its surface via a Fenton-like reaction; oxygen vacancies (OVs) in the MgFe2O4 lattice promote electron conduction and activation, converting the adsorbed ·OH groups into… 1 O2.

[0039] (2) The magnesium-doped zero-valent iron biochar composite material of the present invention has the advantages of wide pH adaptability, less iron sludge production, and magnetic recovery. The degradation rate of ciprofloxacin hydrochloride can reach 90.09% within 45 min, which is higher than that of traditional Fe0 Zero-valent iron biochar composite material (Fe 0 @BC) increased by 1.6 times. Attached Figure Description

[0040] Figure 1 For example 1, pure biochar (BC) and four different iron loadings of Fe were tested. 0 Comparison of the removal performance of ciprofloxacin hydrochloride by @BC; Figure 2 For Fe in test example 2 0 @BC and 4 types of MgFe 0 Comparison of the removal performance of ciprofloxacin hydrochloride by @BC; Figure 3 For test example 3, BC and Fe 0 @BC (best group in test case 1) and MgFe 0 XRD (X-ray diffraction) pattern of @BC (best group in test example 2); Figure 4 For test example 3, BC and Fe 0 @BC (best group in test case 1) and MgFe 0 Scanning electron microscope (SEM) image of @BC (best group in test case 2); Figure 5 For Fe in test example 3 0 @BC (best group in test case 1) and MgFe 0 Transmission electron microscopy (TEM) energy dispersive spectroscopy (EDS) of @BC (best group in test example 2); Figure 6 For test example 3, BC and Fe 0 @BC (best group in test case 1) and MgFe 0 N2 adsorption / desorption curves of @BC (best group in test example 2); Figure 7 For Fe in test example 3 0 @BC (best group in test case 1) and MgFe 0 High-resolution O 1s spectrum (a) and electron paramagnetic resonance (EPR) spectrum (b) of @BC (best group in test example 2); Figure 8 For Fe in test example 4 0 @BC (optimal group) and MgFe 0 Data graph of adsorption of ciprofloxacin hydrochloride in water by @BC (optimal group); Figure 9 For test example 5, BC and Fe 0 @BC (optimal group) and MgFe 0 Data graph of adsorption of ciprofloxacin hydrochloride in water by @BC (optimal group); Figure 10 To test the quenching results of reactive oxygen species in Example 6 and the electron paramagnetic resonance spectrum; Figure 11 To test the effect of different initial pH values ​​on MgFe in Example 7 0 The effect of ciprofloxacin hydrochloride removal efficiency in the BC / H2O2 system; Figure 12 To test the effects of common background components in the water body in Example 7 on MgFe 0 The effect of the BC / H2O2 system on the efficiency of ciprofloxacin hydrochloride removal. Detailed Implementation

[0041] To more clearly illustrate the purpose and advantages of this invention, the following examples further explain the invention. Many specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may also be implemented in other ways different from those described herein.

[0042] In the following case, the pecan shell powder was obtained from a pecan processing plant in Lin'an District, Hangzhou City, Zhejiang Province; the chemical reagents, including FeCl3 hexahydrate, anhydrous MgCl2, NH4HCO3, HCl, and NaOH, were purchased from Yonghua Chemical Co., Ltd.; and ciprofloxacin hydrochloride was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0043] The drying method described in this invention is not particularly limited, as long as a product with constant weight can be obtained.

[0044] The pulverization method described in this invention is not particularly limited, as long as the product with the desired particle size can be obtained.

[0045] In this invention, ciprofloxacin hydrochloride, a third-generation fluoroquinolone antibiotic, is used as a representative organic pollutant.

[0046] The method for determining the removal efficiency / removal amount of ciprofloxacin in various materials in this invention is as follows: 0.04 g of catalyst is added to 50 mL of 20 mg / L ciprofloxacin hydrochloride solution (initial pH=5), and the solution is continuously shaken at 25.0±0.5 ℃ for 20 min (180 rpm). 30% hydrogen peroxide is added to make the concentration reach 10 mM. The supernatant is taken out at different time points and the concentration of residual ciprofloxacin is measured. The removal efficiency / removal amount at each time point is calculated accordingly.

[0047] Test Example 1 After washing the pecan shells with ultrapure water, they were dried in an oven (80 ℃) to constant weight, then pulverized and passed through a 100-mesh sieve to obtain pecan shell powder. 10 g of the pecan shell powder was added to 200 mL of a FeCl3 solution containing 10 g / L, 15 g / L, 20 g / L, and 25 g / L of Fe. The mixture was stirred with a magnetic stirrer for 12 h. Then, 100 g / L NH4HCO3 was added to the mixture to bring the pH to 7. The mixture was then centrifuged at 4000 rpm, and the bottom precipitate was collected and dried to obtain iron-loaded pecan shell powder.

[0048] Pure biochar (BC) and Fe 0 The preparation steps of @BC are as follows: Weigh 5g of pecan shell powder or iron-loaded pecan shell powder, place it directly into a tube furnace, heat to 720℃ at a constant nitrogen flow rate of 400 mL / min and a heating rate of 5℃ / min and hold for 30 min, then naturally cool to room temperature under nitrogen protection to obtain BC and Fe respectively. 0 @BC.

[0049] BC and 4 kinds of Fe 0 @BC was used to catalyze the generation of reactive oxygen species from H2O2 to degrade ciprofloxacin hydrochloride in water. The aim was to compare and evaluate the removal performance of the iron-modified composite material for ciprofloxacin hydrochloride. Figure 1 (Degradation time: 45 min) It was found that as the Fe concentration in the Fe-containing solution increased from 0 to 20 g / L, the removal efficiency of ciprofloxacin hydrochloride increased from 15.25% to 59.77%. When the Fe concentration in the Fe-containing solution further increased to 25 g / L, the removal rate of ciprofloxacin hydrochloride decreased slightly to 58.34%. Based on economic considerations and the treatment efficiency of ciprofloxacin hydrochloride, an Fe content of 20 g / L in the Fe-containing solution is optimal.

[0050] Test Example 2 According to the mass ratios of pecan shell powder loaded with iron to magnesium (10:0.25, 10:0.38, 10:0.51, and 10:0.63), the pecan shell powder loaded with iron (20 g / L) with the optimal Fe loading obtained in Test Example 1 (before pyrolysis) was mixed with anhydrous MgCl2. This mixture was placed in a tube furnace and pyrolyzed under the same conditions as in Test Example 1. Subsequently, it was naturally cooled to room temperature under nitrogen protection. The resulting solid powder was MgFe. 0 @BC.

[0051] Fe 0 @BC and the four MgFe obtained from Test Example 2 0@BC was used to catalyze the generation of reactive oxygen species from H2O2 to degrade ciprofloxacin hydrochloride in water, aiming to compare and evaluate the effects of Mg-modified Fe. 0 @BC's removal performance of ciprofloxacin hydrochloride. (Through...) Figure 2 It was found that when the mass ratio of magnesium to iron-loaded pecan shell powder increased from 0:10 to 0.51:10, the removal rate of ciprofloxacin hydrochloride increased from 58.34% to 90.09%. Further increasing the amount of MgCl2 added did not significantly improve the pollutant removal efficiency. Therefore, the optimal mass ratio of iron-loaded pecan shell powder to magnesium is 10:0.51.

[0052] Test Example 3 To compare BC and Fe 0 @BC (best group in test case 1) and MgFe 0 The changes in the physicochemical properties of @BC (the best group in Test Example 2) were characterized by XRD (X-ray diffraction), scanning electron microscopy (SEM), transmission electron microscopy (TEM) N2 adsorption / desorption curves, and electron paramagnetic resonance (EPR).

[0053] The crystal structures of the three materials are as follows Figure 3 As shown, BC exhibits a distinct diffraction peak at 26.5°, indicating a highly graphitized carbon structure. In Fe... 0 In the XRD pattern of @BC, three distinct diffraction peaks appeared at 44.6°, 65.0°, and 82.3°, which can be attributed to zero-valent iron (Fe). 0 The (110), (200), and (211) crystal planes of Fe confirm that Fe 0 It has been successfully loaded onto the surface structure of biochar. In MgFe... 0 In sample BC, Fe 0 The diffraction peak intensity is higher than that of Fe 0 The decrease in @BC indicates that the introduction of Mg may have altered the Fe... 0 The crystallinity or particle size. New diffraction peaks appeared at 42.6°, 61.9°, 65.1°, 74.2° and 78.1°, which were attributed to MgO and spinel-type MgFe2O4, respectively.

[0054] BC, Fe 0 @BC and MgFe 0 SEM images of the surface morphology of @BC are shown below. Figure 4 As shown, the modified material surface exhibits more uniformly dispersed fine particles and a significantly increased surface roughness, proving that Fe and Mg-related substances have been successfully loaded onto the biochar surface. TEM-elemental distribution map (attached) Figure 5The results showed a significant spatial correlation among the Fe, Mg, and O signals, indicating that zero-valent iron (Fe) 0 The surface of the particles is coated with MgO and / or MgFe2O4.

[0055] Brunauer–Emmett–Teller (BET) surface area analysis results ( Figure 6 Table 1 shows that the specific surface area of ​​the material has been significantly improved: the specific surface area of ​​BC is 25.25 m². 2 / g, while Fe 0 @BC and MgFe 0 @BC increased to 280.17 m respectively. 2 / g and 311.89 m 2 / g. In contrast, the average pore size decreased significantly, from 33.67 nm in BC to Fe 0 @BC at 7.21 nm and MgFe 0 The 7.29 nm of @BC indicates that the generated particles at least partially filled the original pore space of the biochar matrix.

[0056] Table 1: Specific surface area, pore volume, and pore diameter From Fe 0 @BC and MgFe 0 High-resolution O 1s spectrum obtained by @BC ( Figure 7 As shown in a), the deconvolution results in three distinct peaks: lattice oxygen (O) at 530.2 eV. L ), adsorbed oxygen species at 531.6 eV (O A , such as O 2- (O⁻, etc.) and the –OH group located at 532.7 eV. Among them, O A / O L The ratio is an important indicator for measuring OV concentration; this ratio is derived from Fe. 0 @BC significantly increased from 1.85 to MgFe 0 The increase of 2.7 times from 5.01 for @BC indicates that the introduction of Mg effectively improved the OV density in the material. (EPR results) Figure 7 b) This further corroborates the conclusion: the EPR signal intensity at g=2.003 (the characteristic signal of oxygen vacancies) in MgFe 0 @BC is significantly higher than Fe 0 @BC. The XPS and EPR analyses show a high degree of consistency, indicating that Mg incorporation promotes the formation of a more oxidizing structure in the material, and that Fe... 0 @BC induces the generation of more oxygen defect sites.

[0057] Test Example 4 The Fe obtained in test example 1-2 0 @BC (optimal group) and MgFe 0 @BC (optimal group) was used to adsorb ciprofloxacin hydrochloride (20 mg / L) in water. Kinetic results showed that rapid adsorption occurred within 1 minute and adsorption equilibrium was reached at 15 minutes (see [link to study]). Figure 8 After 45 min, MgFe 0 The adsorption capacity of @BC (64.57%) is higher than that of Fe. 0 @BC (46.30%) indicates that adsorption alone cannot completely remove pollutants; catalytic oxidation is necessary for effective removal. Therefore, all catalytic experiments were conducted after a 20-minute pre-adsorption step to establish adsorption-desorption equilibrium.

[0058] Test Example 5 The results of Test Example 4 show that simple adsorption cannot completely remove ciprofloxacin hydrochloride contaminants from water. The BC and Fe values ​​obtained in Test Examples 1-2 were also effective. 0 @BC (optimal group) and MgFe 0 @BC (optimal group): After a 20-minute pre-adsorption step, 30% H2O2 was added to bring its concentration in the reaction system to 10 mM, thereby initiating the catalytic reaction. The H2O2 was derived from 30% hydrogen peroxide by mass. Figure 9 As shown in figure a, the degradation of ciprofloxacin hydrochloride by the system with only H2O2 addition is negligible, confirming the necessity of a catalyst in the catalytic oxidation process. Similarly, BC alone did not exhibit Fenton-like activity, indicating that Fe-based active sites are crucial for H2O2 activation. Accordingly, Fe... 0 The BC / H2O2 system achieved a 57.67% removal rate of ciprofloxacin hydrochloride within 45 min (Figure 9b). Meanwhile, MgFe... 0 @BC exhibited significant H2O2 activation performance under the same experimental conditions, achieving a removal rate of 90.09%, compared to Fe. 0 @BC increased by 56.21%, demonstrating the effect of Mg doping on Fe 0 The synergistic enhancement effect of @BC. Pseudo-first-order kinetic model analysis results show that MgFe... 0 The apparent rate constant of @BC ( k obs The value was 0.039 min. -1 Approximately Fe 0 @BC k obs = 0.0053 min -1The reaction rate was 7.4 times that of MgFe, indicating a significant acceleration, further demonstrating that MgFe 0 @BC exhibits superior catalytic activity.

[0059] Test Example 6 To determine the Fe during the degradation of ciprofloxacin hydrochloride 0 @BC / H2O2 and MgFe 0 Quenching experiments were conducted on reactive oxygen species that play a dominant role in the BC / H2O2 system, using a variety of specific quenchers: tert-butanol (TBA) for quenching hydroxyl radicals (•OH), and superoxide dismutase (SOD) for quenching superoxide anion radicals (O2). •⁻ ), and furfuryl alcohol (FFA) is used to quench singlet oxygen ( 1 O2). In Fe 0 In the @BC / H2O2 system, the addition of TBA significantly inhibited the removal of ciprofloxacin hydrochloride, reducing the removal efficiency from 87.79% to 62.58%, while the apparent rate constant ( k obs The value also dropped to its lowest level of 0.029 min. -1 ( Figure 10 a). In the same system, the addition of SOD or FFA had minimal impact on degradation performance, indicating that •OH is the main ROS in this system. However, in MgFe... 0 In the BC / H2O2 system, the addition of TBA and SOD had no significant effect on the degradation efficiency; conversely, the addition of FFA significantly reduced the removal rate from 92.64% to 64.34%. k obs It dropped to its lowest value of 0.031 min. -1 ,illustrate 1 O2 is the main ROS in this system. Dissolved oxygen can be used as... 1 O2 is a potential precursor, but the introduction of nitrogen (N2) has a slight impact on the degradation effect, indicating that the activation of molecular oxygen is not... 1 An important pathway for O2 generation. Therefore, 1 O2 most likely originates directly from MgFe 0 @BC directly converts H2O2 through activation.

[0060] In addition, Fe was also treated using EPR technology. 0 BC / H2O2 and MgFe 0 The ROS generated in the BC / H2O2 system was verified. Figure 10 (b, c). DMPO is used as a spin trapping agent for the detection of •OH and O2. •⁻ TEMP is used to capture 1 O2. In Fe0 In the BC / H2O2 system, only •OH and O2 were observed. •⁻ and 1 The weak characteristic signal of O2. The low intensity of the OH signal may be due to its rapid and preferential consumption before it can be effectively captured. In contrast, MgFe... 0 In the BC / H2O2 system, •OH and O2 •⁻ The significantly enhanced EPR signal indicates an improved ROS generation efficiency within the system. In particular, a strong TEMP- was detected. 1 The O2 adduct signal indicates that H2O2 is present in MgFe 0 @BC catalysis transforms into a specific reaction pathway to 1 O2 provides strong evidence.

[0061] Test Example 7 The effect of initial pH on MgFe was studied. 0 The effect of ciprofloxacin hydrochloride removal on the BC / H2O2 system was as follows: Figure 11 As shown, the removal efficiency of ciprofloxacin hydrochloride decreased significantly from 98.03% to 38.49% when the pH increased from 3.0 to 9.0, indicating that the reaction is significantly pH-dependent, mainly due to the high pH conditions. 0 Surface passivation inhibited its reactivity. Furthermore, at an initial pH of 9.0, the CO / C ratio after 45 min of reaction... t The ratio increased significantly compared to 0 minutes, which may be due to the weakened electrostatic attraction between ciprofloxacin hydrochloride and the catalyst surface, thereby inhibiting the subsequent degradation process.

[0062] Test Example 8 The impact of common background components in water bodies on the removal efficiency of ciprofloxacin hydrochloride was evaluated. For example... Figure 11 As shown, humic acid and chloride ions (Cl⁻) had no significant effect on the removal of ciprofloxacin hydrochloride, consistent with reports of Fenton-like reaction systems. Sulfate ions (SO₄²⁻) 2- ) and bicarbonate (HCO3) - The presence of SO4 significantly inhibited the removal of ciprofloxacin hydrochloride. 2- Subsequently, the removal efficiency decreased from 90.10% to 66.43%, due to SO42-. 2- It forms strong complexes with iron ions, interfering with the redox cycle of iron species on the active surface. Meanwhile, HCO3... - The inhibitory effect was more significant, almost completely eliminating MgFe. 0 The removal effect of the @BC / H2O2 system on ciprofloxacin hydrochloride. This phenomenon is mainly due to HCO3. - With surface Fe2+ The reaction produces insoluble FeCO3 and inert hydroxylated species, which cover and passivate the active sites, thereby greatly reducing the ability to generate ROS.

Claims

1. A magnesium-doped zero-valent iron biochar composite material, characterized in that: This includes porous biochar as a carrier and Fe uniformly loaded in porous biochar. 0 @MgFe2O4 / MgO particles; The Fe 0 @MgFe2O4 / MgO particles have a core-shell structure, consisting of Fe particles coated with spinel-type MgFe2O4 and MgO. 0 Particles; the spinel-type MgFe2O4 and MgO in Fe 0 An active interface structure with oxygen vacancy defects is formed on the particle surface; The Fe 0 In @MgFe2O4 / MgO, the mass ratio of Fe to Mg is 1:0.089-0.

23.

2. The magnesium-doped zero-valent iron biochar composite material as described in claim 1, characterized in that: The specific surface area of ​​the magnesium-doped zero-valent iron biochar composite material is 300-400 m². 2 / g; The average pore size of the magnesium-doped zero-valent iron biochar composite material is 5-10 nm. The magnesium-doped zero-valent iron biochar composite material O A / O L The ratio is 4.5-5.

5.

3. A method for preparing a magnesium-doped zero-valent iron biochar composite material as described in claim 1 or 2, characterized in that... Includes the following steps: 1) Mix the iron-containing solution with the biomass powder until homogeneous to obtain a mixture; The mass ratio of iron to biomass powder in the iron-containing solution is 0.2-0.5:1; 2) Add alkaline liquid to the mixture to maintain the pH at neutral, centrifuge, take the precipitate and dry it to obtain iron-loaded biomass powder; 3) Iron-loaded biomass powder is mixed with magnesium-containing material and pyrolyzed under an inert atmosphere. After cooling, magnesium-doped zero-valent iron biochar composite material is obtained. The mass ratio of magnesium in the iron-loaded biomass powder to magnesium-containing material is 10: 0.25-0.

63.

4. The preparation method according to claim 3, characterized in that: In step 1), The iron-containing solution is an aqueous solution containing one or more of Fe2(SO4)3 and FeCl3; The concentration of iron in the iron-containing solution is 10-25 g / L; The biomass powder is selected from one or more of the following: pecan shell powder, straw powder, branch powder, and fruit peel powder; The biomass powder is passed through a 100-mesh sieve.

5. The preparation method according to claim 3, characterized in that: In step 2), The centrifuge speed is 3000-5000 rpm; The alkaline solution is an aqueous solution of one or more of NaOH, KOH, and NH4HCO3.

6. The preparation method according to claim 3, characterized in that: In step 3), the magnesium-containing substance is one or more of MgCl2 and Mg3(SO4)2.

7. The preparation method according to claim 3, characterized in that: In step 3), the pyrolysis is carried out under nitrogen protection at a rate of 4-6 °C / min, with the temperature increased to 700-750 °C and held for 20-40 min.

8. The application of the magnesium-doped zero-valent iron biochar composite material as described in claim 1 or 2, or the magnesium-doped zero-valent iron biochar composite material obtained by the preparation method described in any one of claims 3-7, as a catalyst in the degradation of organic pollutants in wastewater, characterized in that: Magnesium-doped zero-valent iron biochar composite material was added to wastewater containing organic pollutants for pre-adsorption, followed by the addition of hydrogen peroxide. The H2O2 in the hydrogen peroxide was activated by the magnesium-doped zero-valent iron biochar composite material to generate... 1 O2, thereby achieving the degradation of organic pollutants.

9. The application as described in claim 8, characterized in that: The amount of the magnesium-doped zero-valent iron biochar composite material added is 0.2-0.6 wt% of the wastewater. The concentration of the hydrogen peroxide is 25-35 wt%, and the concentration in the wastewater after addition is 8-12 mM.

10. The application as described in claim 8, characterized in that: The organic pollutant is ciprofloxacin hydrochloride; The pH of the wastewater is 3.0-9.0.

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