Magnetic composite soil pollution repairing agent and preparation method thereof

Abstract

The invention belongs to the technical field of soil treatment, and discloses a magnetic composite soil pollution repairing agent and a preparation method thereof, and the repairing agent comprises the following raw materials by weight: 10-40 parts of manganite, 20-60 parts of red mud, 1-20 parts of glucose, 0.01-2 parts of a surfactant, and 10-40 parts of water. According to the invention, industrial solid waste red mud and manganite are selected and subjected to a hydrothermal reaction with glucose to prepare the magnetic composite soil pollution repairing agent which can be used for adsorbing and enriching heavy metals in soil and degrading organic pollutants. According to the prepared magnetic composite soil pollution repairing agent, the red mud is used for treating pollution with waste, the utilization rate of industrial solid waste is increased, the purposes of resource recycling, cost reduction and multi-directional pollution treatment are achieved, and the green sustainable development concept is met.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, specifically a magnetic composite soil pollution remediation agent and its preparation method. Background Technology

[0002] In recent years, with rapid economic development and urbanization, the number of enterprises engaged in mining, electroplating, chemical, printing and dyeing, and machinery industries has surged. Simultaneously, the excessive application of chemical fertilizers and pesticides to increase agricultural output has led to severe heavy metal and organic pollution of the soil. Heavy metals and pesticide residues are difficult to decompose in the soil, have a long-term cumulative effect, and can enter the human body through bioaccumulation in plants and animals, posing a significant threat. Therefore, soil pollution remediation is urgently needed.

[0003] Currently, common soil pollution remediation technologies mainly fall into three categories: physical, chemical, and biological remediation. Physical remediation primarily utilizes soil replacement, vitrification, electrokinetic remediation, and thermal desorption; chemical remediation mainly employs solidification / stabilization technologies and soil leaching; and biological remediation is represented by phytoremediation and microbial remediation. Given the complexity of soil pollution, single remediation methods are often insufficient, leading to the development of combined remediation technologies.

[0004] Existing technologies still have some unresolved problems. For example, patent CN118389157A discloses a method and product for preparing a heavy metal contaminated soil remediation agent using red mud. However, the sulfur residue in this remediation agent contains elemental sulfur and residual heavy metals. In the soil, the sulfur is oxidized into sulfuric acid by microbial catalysis, triggering local acidification and activating some heavy metals, thus introducing new sources of pollution. The organic matter in the fermentation broth is unstable and easily degrades, and long-term use will consume soil oxygen and produce anaerobic toxins. This technology has many problems and cannot be widely used.

[0005] In summary, while the preparation of heavy metal removal soil remediation agents using red mud via hydrothermal reaction has applications in soil remediation technology, it suffers from drawbacks such as targeting only a single pollution source, introducing new heavy metal pollution sources, depleting soil's effective components, and damaging soil structure. Therefore, there is an urgent need to develop a magnetic composite soil remediation agent to achieve synergistic and efficient remediation of multiple pollutants. Summary of the Invention

[0006] The purpose of this invention is to provide a magnetic composite soil remediation agent. In this soil remediation agent, manganese ore and red mud undergo a self-dissimilatory reaction and recrystallization, and a hydrothermal reaction with glucose, enhancing reactivity. The product structure and properties are regulated by surfactants, promoting the adsorption and enrichment of heavy metals, forming a highly efficient "oxidative degradation-adsorption fixation-magnetic separation" process to adsorb heavy metals and remove organic pollutants from the soil, avoiding diffusion and waste.

[0007] Another objective of this invention is to provide a method for preparing the aforementioned magnetic composite soil pollution remediation agent. The method involves a hydrothermal reaction of manganese ore and red mud, followed by reduction modification with glucose and the addition of a surfactant to enhance dispersion stability. This process not only generates amphoteric oxide α-MnO2, improving the removal of heavy metals, but also forms a TiO2 / MnO2 / Fe3O4 composite material, achieving both magnetic separation and photocatalytic functions.

[0008] The objective of this invention is achieved through the following solution: A magnetic composite soil pollution remediation agent comprises the following components in parts by weight: 10-40 parts of manganese ore, 20-60 parts of red mud, 1-20 parts of glucose, 0.01-2 parts of surfactant, and 10-40 parts of water; wherein the surfactant is a combination of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0009] The CaO and Na₂O contained in red mud react with water to produce Ca(OH)₂ and NaOH, forming a strongly alkaline environment that promotes the self-disproportionation reaction of manganese hydroxide (MnOOH): some Mn 3+ Oxidized to Mn 4+ Meanwhile, another part was reduced to Mn 2+ Dissolved oxygen and oxygen environment will affect Mn 2+ Oxidized to Mn 4+ Ultimately driving Mn 4+ The lattice is reconstructed into a tunnel structure α-MnO2 with strong oxidizing properties. High-temperature, high-pressure water molecules violently erode the mineral surface, leading to a significant increase in surface hydroxyl density. This, in turn, induces lattice distortion through a localized dissolution-recrystallization process, generating defects such as oxygen and cation vacancies. Surface hydroxyl groups act as proton transfer mediators, enhancing adsorption capacity. The vacancy defects optimize electron transfer efficiency, trapping electrons to form active centers, thus strengthening the redox ability of α-MnO2 and improving its surface reactivity and catalytic performance.

[0010] Glucose selectively reduces Fe2O3 to Fe3O4, which then reacts with TiO2 and α-MnO2 in red mud to form a TiO2 / MnO2 / Fe3O4 composite material, achieving magnetic separation and photocatalytic functions.

[0011] Surfactant molecules regulate the structure and properties of the product, influencing the particle size and size distribution of Fe3O4 by modulating the nucleation-growth kinetics. Polyvinylpyrrolidone (PVP) encapsulates the particle surface through steric hindrance, inhibiting particle aggregation and enhancing dispersion stability, thus yielding uniformly dispersed Fe3O4 nanoparticles. Hexadecyltrimethylammonium bromide (CTAB) preferentially adsorbs onto the {100} facet, where the iron atoms are tightly packed and generate a strong electrostatic interaction with the Br⁻ of CTAB, inhibiting {100} facet growth and promoting preferential growth along the {111} direction.

[0012] Preferably, the magnetic composite soil pollution remediation agent comprises the following components in parts by weight: 17.7-32.5 parts of manganese ore, 35.4-53.6 parts of red mud, 1.32-4.84 parts of glucose, 0.01-0.5 parts of surfactant, and 15.6-35.2 parts of water.

[0013] More preferably, the magnetic composite soil pollution remediation agent comprises the following components in parts by weight: 19.1-25.6 parts of manganese ore, 39.8-50.6 parts of red mud, 2.4-4.1 parts of glucose, 0.01-0.05 parts of surfactant, and 20.3-30.2 parts of water.

[0014] Manganese ore is eventually converted into amphoteric oxide α-MnO2, which improves the removal efficiency of heavy metals. Red mud provides strong alkalinity for the hydrothermal reaction of manganese ore. At the same time, Fe2O3 in red mud is hydrothermally converted into Fe3O4. Fe3O4, α-MnO2, and TiO2 react to form a TiO2 / MnO2 / Fe3O4 composite material. Fe3O4 can provide magnetism. Glucose reduces Fe2O3 to Fe3O4, and quantitative proportioning avoids complete reduction to FeO.

[0015] Preferably, the water manganese ore has the composition of MnO(OH), a total manganese content of 20-60%, an effective manganese (IV) ratio of 50-90%, and a pH of 5-9.

[0016] More preferably, the total manganese content of the manganese ore is 30-50%, the effective manganese (IV) ratio is 60-80%, and the pH is 6-8.

[0017] Mn in manganese ore 3+ In an intermediate valence state, it is prone to redox cycles (Mn 3+ ↔Mn 4+ Manganese minerals can maintain their catalytic activity in alkaline environments, while most manganese minerals are easily deactivated under alkaline conditions. The layered structure of manganese ore contains hydroxyl groups (-OH), which can adsorb heavy metals through ion exchange and at the same time provide protons to participate in the reaction.

[0018] Preferably, the red mud composition includes 24-38% Fe2O3, 15-25% Al2O3, 5-10% SiO2, 5-10% TiO2, 15-25% CaO, and 2-9% Na2O.

[0019] Red mud has a high pH of 10-13, which neutralizes acidic soil and promotes the precipitation of heavy metals. It also contains natural catalytic components; Al₂O₃ and Fe₂O₃ can react with Mn. 3+ A multi-metal synergistic catalytic system is formed, which broadens the activation range; red mud is a waste residue from the aluminum industry, and using it as a raw material can achieve "pollution control with waste", improve utilization rate and reduce cost.

[0020] A method for preparing the above-mentioned magnetic composite soil pollution remediation agent comprises the following steps: S1: Place manganese ore and red mud into a planetary ball mill for ball milling. After grinding, add them, surfactant and water into a high-pressure hydrothermal reactor, introduce oxygen intermittently, and stir to react. S2: Add glucose to the reactor and stir at 100-200 rpm for 6-8 hours at 160-200℃; S3: Allow the autoclave to cool naturally to below 85°C, then wash and dry to obtain the product.

[0021] Preferably, in step S1, the planetary ball mill rotates at 400-800 rpm, the milling time is 5-10 h, the oxygen ventilation interval is 2 h, the stirring speed is 100-200 rpm, the reaction temperature is 160-200℃, and the reaction time is 20-28 h.

[0022] Pulverized manganese ore (γ-MnOOH) and red mud (mainly containing Fe2O3, Al2O3, TiO2, etc.) into nano- or submicron particles significantly increases specific surface area and reactivity. A high-temperature, high-pressure environment provides the necessary thermodynamic conditions for crystal transformation and new phase formation. Under strongly alkaline conditions, manganese ore undergoes a disproportionation reaction of MnOOH to generate MnO2 and Mn(OH)2. During this reaction, oxygen is introduced to further oxidize low-valence manganese, ensuring product purity. Dynamic control of oxygen introduction and discontinuation is crucial. When oxygen is introduced, O2 fills oxygen vacancies, forming an oxide layer. When oxygen is stopped, at 160-200℃, oxygen inserted into the crystal lattice migrates to the surface, generating internal oxygen vacancies, thus circulating and enhancing surface reactivity.

[0023] Preferably, the glucose in step S2 is obtained from the cellulose extraction of sugarcane bagasse.

[0024] Sugarcane bagasse is a byproduct of the sugar industry. It is widely available and has almost zero cost, avoiding competition from grain raw materials. Sugarcane bagasse contains 40-50% cellulose and has a low lignin content, making pretreatment easier. In addition, the cellulose in sugarcane bagasse has low crystallinity, making it more accessible to cellulase and resulting in a high hydrolysis conversion rate. The sucrose remaining in sugarcane bagasse can be converted into glucose simultaneously, increasing the glucose yield.

[0025] Preferably, the glucose extraction method in step S2 is as follows: sugarcane bagasse is dried and pulverized, acid-soaked for 30-40 minutes, neutralized and washed, then cellulase is added, and hydrolyzed at 40-50℃ and pH 4-5 for 24-48 hours, and the supernatant is obtained by centrifugation.

[0026] Acid leaching pretreatment breaks down stubborn structures, disrupts complex barriers, and improves subsequent enzymatic hydrolysis efficiency; 40-50℃ can maintain cellulose activity, and pH 4-5 matches the activity peak of acidic cellulase, avoiding enzyme inactivation caused by neutrality; the lower limit of 24h completes the rapid saccharification of accessible cellulose, and the upper limit of 48h can completely hydrolyze the crystalline region of cellulose.

[0027] This invention also discloses the application of the above-mentioned magnetic composite soil pollution remediation agent, which is used for the adsorption and enrichment of heavy metals in soil, photochemical degradation of organic matter in soil, maintenance of soil structure, improvement of soil microbial ecological environment, and collection of soil pollution remediation agent to avoid secondary pollution.

[0028] The beneficial effects of this invention are as follows: the remediation agent can adsorb and enrich heavy metals while photodegrading organic matter, thereby improving remediation efficiency and effectively treating soil pollution; the use of red mud to "treat pollution with waste" improves the utilization rate of industrial solid waste, achieves resource recycling, and reduces costs; it treats pollution in multiple directions and simultaneously restores soil structure and microbial ecological environment, which is in line with the concept of green and sustainable development. Detailed Implementation

[0029] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0030] Example 1: A magnetic composite soil pollution remediation agent, prepared through the following process steps: This embodiment provides a magnetic composite soil pollution remediation agent, the components of which include manganese hydrate, red mud, surfactant, water, and glucose. The surfactant is one or both of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0031] In this embodiment, the mass fractions of each component are 23.0 parts of manganese ore, 47.0 parts of red mud, 0.03 parts of surfactant, 27.0 parts of water, and 3.0 parts of glucose.

[0032] S1: 23.0 parts of manganese ore and 47.0 parts of red mud were respectively placed in a planetary ball mill and ball-milled at 800 rpm for 8 hours. The samples were then removed for later use. The pretreated manganese ore, red mud, 0.03 parts of surfactant, and 27.0 parts of water were added to a high-pressure hydrothermal reactor and reacted at 180℃ and 100 rpm for 24 hours. S2: After reacting for 24 hours, open the high-pressure hydrothermal reactor and add 3.0 parts of glucose into the reactor. React for 8 hours at a reaction temperature of 180℃ and a stirring speed of 100 rpm. S3: After the hydrothermal reaction is completed, place the autoclave in the air to cool naturally to below 85°C, perform solid-liquid separation on the mixture, wash it 5 times with deionized water and ethanol, and dry it at 60°C.

[0033] Example 2: A magnetic composite soil pollution remediation agent, prepared through the following process steps: This embodiment provides a magnetic composite soil remediation agent, the components of which include manganese hydrate, montmorillonite, surfactant, water, and glucose. The surfactant is one or both of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0034] In this embodiment, the mass fractions of each component are 23.0 parts of manganese ore, 47.0 parts of montmorillonite, 0.03 parts of surfactant, 27.0 parts of water, and 3.0 parts of glucose.

[0035] S1: 23.0 parts of manganese ore and 47.0 parts of montmorillonite were placed in a planetary ball mill and ball-milled at 800 rpm for 8 hours. The samples were then removed for later use. Under an atmosphere where oxygen was introduced every 2 hours, the pretreated manganese ore, red mud, 0.03 parts of surfactant, and 27.0 parts of water were added to a high-pressure hydrothermal reactor. The reaction was carried out at 180℃ and a stirring speed of 100 rpm for 24 hours. S2: After reacting for 24 hours, open the high-pressure hydrothermal reactor and add 3.0 parts of glucose into the reactor. React for 8 hours under the conditions of oxygen being introduced every 2 hours, reaction temperature of 180℃, and stirring speed of 100 rpm. S3: After the hydrothermal reaction is completed, place the autoclave in the air to cool naturally to below 85°C, perform solid-liquid separation on the mixture, wash it 5 times with deionized water and ethanol, and dry it at 60°C.

[0036] Example 3: A magnetic composite soil pollution remediation agent, prepared through the following process steps: This embodiment provides a magnetic composite soil pollution remediation agent, the components of which include manganese hydrate, kaolin, surfactant, water, and glucose. The surfactant is one or both of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0037] In this embodiment, the mass fractions of each component are 23.0 parts of manganese ore, 47.0 parts of kaolin, 0.03 parts of surfactant, 27.0 parts of water, and 3.0 parts of glucose.

[0038] S1: 23.0 parts of manganese ore and 47.0 parts of kaolin were placed in a planetary ball mill and ball-milled at 800 rpm for 8 hours. The samples were then removed for later use. Under an atmosphere where oxygen was introduced every 2 hours, the pretreated manganese ore, kaolin, 0.03 parts of surfactant, and 27.0 parts of water were added to a high-pressure hydrothermal reactor and reacted at 180℃ and 100 rpm for 24 hours. S2: After reacting for 24 hours, open the high-pressure hydrothermal reactor and add 3.0 parts of glucose into the reactor. React for 8 hours under the conditions of oxygen being introduced every 2 hours, reaction temperature of 180℃, and stirring speed of 100 rpm. S3: After the hydrothermal reaction is completed, place the autoclave in the air to cool naturally to below 85°C, perform solid-liquid separation on the mixture, wash it 5 times with deionized water and ethanol, and dry it at 60°C.

[0039] Example 4: A magnetic composite soil pollution remediation agent, prepared through the following process steps: This embodiment provides a magnetic composite soil pollution remediation agent, the components of which include manganese hydrate, red mud, surfactant, water, and glucose. The surfactant is one or both of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0040] In this embodiment, the mass fractions of each component are 23.0 parts of manganese ore, 47.0 parts of red mud, 0.03 parts of surfactant, 27.0 parts of water, and 3.0 parts of glucose.

[0041] S1: 23.0 parts of manganese ore and 47.0 parts of red mud were placed in a planetary ball mill and ball-milled at 800 rpm for 8 hours. The samples were then removed for later use. Under an atmosphere where oxygen was introduced every 2 hours, the pretreated manganese ore, red mud, 0.03 parts of surfactant, and 27.0 parts of water were added to a high-pressure hydrothermal reactor and reacted at 180℃ and 100 rpm for 24 hours. S2: After reacting for 24 hours, open the high-pressure hydrothermal reactor and add 3.0 parts of glucose into the reactor. React for 8 hours under the conditions of oxygen being introduced every 2 hours, reaction temperature of 160℃, and stirring speed of 100 rpm. S3: After the hydrothermal reaction is completed, place the autoclave in the air to cool naturally to below 85°C, perform solid-liquid separation on the mixture, wash it 5 times with deionized water and ethanol, and dry it at 60°C.

[0042] Example 5: A magnetic composite soil pollution remediation agent, prepared through the following process steps: This embodiment provides a magnetic composite soil pollution remediation agent, the components of which include manganese hydrate, red mud, surfactant, water, and glucose. The surfactant is one or both of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0043] In this embodiment, the mass fractions of each component are as follows: 23.0 parts of manganese ore, 47.0 parts of red mud, 0.03 parts of surfactant, 27.0 parts of water, and 3.0 parts of glucose.

[0044] S1: 23.0 parts of manganese ore and 47.0 parts of red mud were placed in a planetary ball mill and ball-milled at 800 rpm for 8 hours. The samples were then removed for later use. Under an atmosphere where oxygen was introduced every 2 hours, the pretreated manganese ore, red mud, 0.03 parts of surfactant, and 27.0 parts of water were added to a high-pressure hydrothermal reactor and reacted at 180℃ and 100 rpm for 24 hours. S2: After reacting for 24 hours, open the high-pressure hydrothermal reactor and add 3.0 parts of glucose into the reactor. React for 8 hours under the conditions of oxygen being introduced every 2 hours, reaction temperature of 180℃, and stirring speed of 100 rpm. S3: After the hydrothermal reaction is completed, place the autoclave in the air to cool naturally to below 85°C, perform solid-liquid separation on the mixture, wash it 5 times with deionized water and ethanol, and dry it at 60°C.

[0045] Example 6: A magnetic composite soil pollution remediation agent, prepared through the following process steps: This embodiment provides a magnetic composite soil pollution remediation agent, the components of which include manganese hydrate, red mud, surfactant, water, and glucose. The surfactant is one or both of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

[0046] In this embodiment, the mass fractions of each component are as follows: 23.0 parts of manganese ore, 47.0 parts of red mud, 0.03 parts of surfactant, 27.0 parts of water, and 3.0 parts of glucose.

[0047] S1: 23.0 parts of manganese ore and 47.0 parts of red mud were placed in a planetary ball mill and ball-milled at 800 rpm for 8 hours. The samples were then removed for later use. Under an atmosphere where oxygen was introduced every 2 hours, the pretreated manganese ore, red mud, 0.03 parts of surfactant, and 27.0 parts of water were added to a high-pressure hydrothermal reactor and reacted at 180℃ and 100 rpm for 24 hours. S2: After reacting for 24 hours, open the high-pressure hydrothermal reactor and add 3.0 parts of glucose into the reactor. React for 8 hours under the conditions of oxygen being introduced every 2 hours, reaction temperature of 200℃, and stirring speed of 100 rpm. S3: After the hydrothermal reaction is completed, place the autoclave in the air to cool naturally to below 85°C, perform solid-liquid separation on the mixture, wash it 5 times with deionized water and ethanol, and dry it at 60°C.

[0048] Experimental Example 1: This experimental example is the test of heavy metal and organic matter content in contaminated soil in Examples 1-6. S1 Sample Pretreatment: The total amount of contaminated soil is 2kg. Spread the sample in a sterile tray and air dry naturally in a cool and ventilated place indoors (avoid direct sunlight). After removing stones and plant debris, pass the sample through a 100-mesh nylon sieve (0.15mm). Use the "quartering method" to take 500g of representative sample, which will be used for heavy metal and Rhodamine B detection respectively. S2 Heavy Metal Detection: Weigh 0.5000g of sieved soil sample into a 50ml digestion vessel, add 10ml of freshly prepared aqua regia (HNO3:HCl=1:3), cover and let stand overnight. The next day, place in a graphite digester, pre-digest at 120℃ for 1.5h, then raise the temperature to 180℃ for 8h. After cooling, dilute to a 50ml volumetric flask, filter through a 0.50μm filter membrane, and determine Pb using graphite furnace atomic absorption spectrometry (GFAAS). 2+ Cd 2+ The content of As was determined by hydride generation-atomic fluorescence spectrometry (HG-AFS). 3+ Content. For each batch of samples, a blank control and a spiked recovery test should be performed (spiking amount ≈ 0.5-2 times the sample concentration). The recovery rate should be 80-120%, verified using soil standard materials (such as GSS-4), with a deviation ≤15%. Content (mg / kg) = (C−C0)×V×D / (W*10) -3 ) C: Sample concentration (μg / L), C0: Blank concentration V: Volume to be adjusted (ml), D: Dilution factor W: Dry weight of soil sample (g) S3 Rhodamine B Detection: Detection was performed using ultrasonic-assisted extraction-high performance liquid chromatography-fluorescence (HPLC-FLD) (operation under complete darkness). Weigh 5.00 g of soil sample into a 50 ml centrifuge tube, add 20 ml of methanol-water mixture (volume ratio 8:2), ultrasonically extract for 30 min, then centrifuge, collect the supernatant, repeat extraction, combine the supernatants, evaporate to near dryness at 45℃, redissolve with 1 ml of methanol, and filter through a 0.22 μm filter membrane. Wash the column with mobile phase for ≥30 min until baseline stable. Inject standard solutions of 0.01-5.0 mg / L sequentially from low to high concentrations, record peak areas, and inject 20 μL of the test solution into the HPLC. Each sample was injected twice, with simultaneous processing of soil-free reagent blanks and uncontaminated matrix blanks. Rhodamine B content (mg / kg) = C × V / W C: Sample concentration (mg / L) calculated from the standard curve V: Final volume (ml), here V = 1.0 ml W: Soil dry weight (g) S4 Pollution Remediation: Weigh 500g of contaminated soil and add 25g of this product at 5% of the soil mass. Mix manually for ten minutes until there are no lumps. Spray deionized water into the mixture until the soil moisture content reaches 40%. Seal the mixture with plastic film and make holes. Store at a constant temperature of 25℃ in the dark. Open the bottle and stir three times a day. Replace the bottle cap film after 72 hours. Turn on a 300W xenon lamp (30cm away from the bottle opening, light intensity 100mW / cm²) for the light-illuminated experimental group. Keep the dark reaction group in the dark throughout the process. After 48 hours, spread the soil evenly on a sterile tray and let it air dry naturally. Take samples using the quartering method and test them as described above.

[0049] Table 1. Test results of contaminated soil remediation experiments in Examples 1-6 Project Name <![CDATA[Pb 2+ (mg / kg)]]> <![CDATA[Cd 2+ (mg / kg)]]> <![CDATA[As 3+ (mg / kg)]]> Rhodamine (mg / kg) Contaminated soil samples 124.45 26.33 56.34 128.57 Implementation Case 1 18.67 6.58 9.01 48.86 Implementation Case 2 32.36 9.22 14.09 70.71 Implementation Case 3 31.11 10.53 16.90 77.14 Implementation Case 4 14.93 4.48 4.51 27.00 Implementation Case 5 9.96 3.16 2.82 23.14 Implementation Case 6 13.69 3.95 3.94 25.71 Analysis of the experimental data from the six soil remediation implementation cases in Table 1 shows that Case 5, with its components of 23.0 parts manganese ore, 47.0 parts red mud, 0.03 parts surfactant, 27.0 parts water, and 3.0 parts glucose, and a hydrothermal reaction temperature of 180℃, exhibited the best performance in the simultaneous remediation of heavy metals and organic pollutants, with its Pb... 2+ Cd 2+ As 3+ The residual concentrations of Rhodamine B were reduced to 9.96, 3.16, 2.82 and 23.14 mg / kg, respectively, with corresponding removal rates of 92%, 88%, 95% and 82%, all of which were better than other cases.

[0050] Comparing data from contaminated soil samples, Case 1 (which lacked an oxygen-rich environment), and Case 5, significant differences in remediation effectiveness were observed. After treatment and recovery with soil remediation agents, the Pb concentration in Case 1 was significantly lower. 2+ Content 18.67 mg / kg, Cd 2+ The content was 6.58 mg / kg and the Rhodamine B content was 48.86 mg / kg, which was twice that of Implementation Case 5. 3+ The content of 9.01 mg / kg was four times that of Case 5, due to the effect of oxygen. The introduction of oxygen provided an oxidizing environment for the self-diversion reaction of manganese ore, significantly increasing the Mn content. 3+ To Mn 4+ Conversion efficiency. The oxidizing environment, in conjunction with the hydrothermal reaction, places the manganese in the manganese ore at a higher valence state, making it more susceptible to disproportionation. This allows for a more thorough and rapid conversion to high-purity α-MnO2 in the subsequent alkaline hydrothermal environment. In Case 1, where the oxidizing environment was not provided, Mn...3+ The transformation may be incomplete or insufficient, resulting in lower crystal form, purity, or activity of the generated MnO2. This is directly reflected in Case 5 for all pollutants (especially strongly oxidizing As). 3+ The removal rate of (and rhodamine) significantly exceeded that of Case 1.

[0051] Comparing the data from contaminated soil samples in Case 2 (where red mud was replaced with montmorillonite), Case 3 (where red mud was replaced with kaolin), and Case 5, the Pb content in Case 2... 2+ The content of 32.36 mg / kg is 4 times that of Case 5, Cd 2+ The content of 9.22 mg / kg is twice that of Implementation Case 5. 3+ The content of Pb in Case 3 was 14.09 mg / kg, which was 7 times that of Case 5; the content of Rhodamine B was 70.71 mg / kg, which was 3.5 times that of Case 5; and the content of Pb in Case 3 was... 2+ The content of 31.11 mg / kg was 3.5 times that of Implementation Case 5, Cd 2+ The content of 10.53 mg / kg is three times that of Implementation Case 5. As 3+ The content of Pb was 16.90 mg / kg, which was 8 times that of Case 5, and the content of Rhodamine B was 77.14 mg / kg, which was 4 times that of Case 5. The absence of red mud in Case 2 (montmorillonite) and Case 3 (kaolin) led to the breakage of the core reaction chain. The tunnel structure of α-MnO2 can capture Pb. 2+ / Cd 2+ While the layered structure of montmorillonite / kaolinite has some adsorption capacity (such as montmorillonite cation exchange), the As in cases 2 and 3... 3+ The residual amounts (14.09-16.90 mg / kg) were significantly higher than in Case 5 (2.82 mg / kg), demonstrating that manganese oxide tunnel adsorption is superior to clay mineral ion exchange. Rhodamine degradation requires strong oxidants (such as α-MnO2) or photocatalytic activity. The residual amounts of rhodamine in Cases 2 and 3 (70.71-77.14 mg / kg) were more than three times higher than in Case 5 (23.14 mg / kg). After the red mud was replaced, it was impossible to form a TiO2 / MnO2 / Fe3O4 structure. α-MnO2 lacked the energy level matching of TiO2 and could not effectively degrade rhodamine, proving that the function of red mud is irreplaceable. The failures of Cases 2 and 3 indicate that even with the retention of manganese ore, the absence of the environment provided by red mud will still lead to zero oxidation capacity, collapse of the composite material structure, and ultimately, a remediation efficiency less than 50% of that in Case 5.

[0052] Comparing the data from contaminated soil samples, Case 4 (hydrothermal reaction temperature 160℃), Case 5 (hydrothermal reaction temperature 180℃), and Case 6 (hydrothermal reaction temperature 200℃), it can be concluded that while Cases 4 and 6 are similar to Case 5 in some indicators, they are less effective against highly toxic Cd.2+ And As 3+ The fixation capacity was slightly weaker; in cases 1, 2, and 3, due to insufficient degradation of organic pollutants, the removal rate of Rhodamine B was only 40-62%, and the removal efficiency of heavy metals was also low, resulting in poor overall remediation effects. As at 160℃ 3+ →As 5+ The oxidation efficiency of As decreases. 3+ The residue (4.51 mg / kg) was significantly higher than that in Case 5 (2.82 mg / kg), Cd 2+ The residual concentration (4.48 mg / kg) was higher than that at 180℃ (3.16 mg / kg), indicating incomplete degradation of rhodamine. Due to the slow reaction rate at 160℃, α-MnO2 crystals were incomplete, resulting in poor stability of the active sites and Mn... 4 Insufficient conversion rate, reduced residual Mn³⁺ oxidation capacity, weak hydrothermal erosion intensity, low surface hydroxyl (-OH) density, reduced heavy metal complexation sites, and insufficient oxygen vacancy concentration all negatively impact Cd oxidation. 2+ Weak adsorption; at 200℃, Pb 2+ The residue (13.69 mg / kg) was higher than that in Implementation Case 5 (9.96 mg / kg), As 3+ The residual concentration (3.94 mg / kg) was higher than that in Case 5 (2.82 mg / kg), and the residual concentration of rhodamine (25.71 mg / kg) was higher than that in Case 5 (23.14 mg / kg). α-MnO2 partially transformed into the more thermodynamically stable β-MnO2, thus failing to effectively capture Pb with a large ionic radius. 2+ Furthermore, excessive water erosion leads to over-dissolution and recrystallization of particles, resulting in a decrease in specific surface area. Overheating causes dehydration and condensation of surface hydroxyl groups, reducing adsorption sites. α-MnO2 lattice migration repairs some oxygen vacancies, decreasing reactivity. Excessive growth or oxidation of Fe3O4 to γ-Fe2O3 weakens magnetism and reduces Fe... 2 + The decrease in content inhibits the reaction; 180℃ is the optimal temperature for hydrothermal reaction, which can completely trigger the complete disproportionation reaction, generate highly active α-MnO2, induce high-density defects on the crystal surface without destroying the crystal structure, and achieve the optimal function of Fe3O4 / TiO2 / MnO2 composite material.

[0053] In summary, the success of Example 5 verifies the feasibility of using a multi-mechanism combination of "adsorption-oxidation-catalysis". The remediation agent may achieve efficient remediation of complex contaminated soil by precisely controlling the ratio of iron and manganese active sites, the loading of oxidant and the pore structure of the carrier.

[0054] This magnetic composite soil remediation agent achieves integrated remediation of "oxidative degradation-heavy metal enrichment and stabilization" through multi-component synergistic design: Manganese ore lattice reconstruction transforms into a highly oxidizing tunnel structure α-MnO2, which adsorbs and enriches heavy metal ions; red mud provides a strongly alkaline environment, solidifying heavy metals through precipitation and adsorption, and neutralizing acidic byproducts; manganese ore and red mud construct a bifunctional catalytic carrier, enhancing the surface reactivity and catalytic performance of the soil remediation agent, efficiently degrading organic pollutants; selective glucose reduction transforms manganese ore and red mud into a TiO2 / MnO2 / Fe3O4 composite material, which, as a carbon source, is biocompatible, regulating the microbial environment, synergistically degrading small-molecule organic pollutants, neutralizing the alkalinity of red mud, and preventing soil alkalization; surfactants influence the particle size and distribution of Fe3O4 by regulating the "nucleation-growth" kinetics, inhibiting particle aggregation and enhancing dispersion stability. The synergistic effect of organic and inorganic components enhances environmental resistance, achieving long-term stabilization of heavy metals, ultimately realizing integrated soil remediation of "oxidative degradation-heavy metal enrichment and stabilization."

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A magnetic composite soil pollution remediation agent, characterized in that, It comprises the following components in parts by weight: 10-40 parts of manganese ore, 20-60 parts of red mud, 1-20 parts of glucose, 0.01-2 parts of surfactant, and 10-40 parts of water; wherein the surfactant is a combination of polyvinylpyrrolidone and hexadecyltrimethylammonium bromide.

2. The magnetic composite soil pollution remediation agent according to claim 1, characterized in that, It includes the following components in parts by weight: 17.7-32.5 parts of manganese ore, 35.4-53.6 parts of red mud, 1.32-4.84 parts of glucose, 0.01-0.5 parts of surfactant, and 15.6-35.2 parts of water.

3. The magnetic composite soil pollution remediation agent according to claim 1, characterized in that, It includes the following components in parts by weight: 19.1-25.6 parts of manganese ore, 39.8-50.6 parts of red mud, 2.4-4.1 parts of glucose, 0.01-0.05 parts of surfactant, and 20.3-30.2 parts of water.

4. A magnetic composite soil pollution remediation agent according to claim 1 or 2, characterized in that, The water manganese ore has the composition of MnO(OH), a total manganese content of 20-60%, an effective manganese (IV) ratio of 50-90%, and a pH of 5-9.

5. The magnetic composite soil pollution remediation agent according to claim 4, characterized in that, The specific total manganese content of the water manganese ore is 30-50%, the effective manganese (IV) ratio is 60-80%, and the pH is 6-8.

6. A magnetic composite soil pollution remediation agent according to claim 1 or 2, characterized in that, The red mud composition includes 24-38% Fe2O3, 15-25% Al2O3, 5-10% SiO2, 5-10% TiO2, 15-25% CaO, and 2-9% Na2O.

7. A method for preparing a magnetic composite soil pollution remediation agent according to any one of claims 1-6, characterized in that, The specific steps are as follows: S1: Place manganese ore and red mud into a planetary ball mill for ball milling. After grinding, add them, surfactant and water into a high-pressure hydrothermal reactor, introduce oxygen intermittently, and stir to react. S2: Add glucose to the reactor and stir at 100-200 rpm for 6-8 hours at 160-200℃; S3: Allow the autoclave to cool naturally to below 85°C, then wash and dry to obtain the product.

8. The preparation method of a magnetic composite soil pollution remediation agent according to claim 7, characterized in that, In step S1, the planetary ball mill rotates at 400-800 rpm, the milling time is 5-10 h, the oxygen supply interval is 2 h, the stirring speed is 100-200 rpm, the reaction temperature is 160-200℃, and the reaction time is 20-28 h.

9. The preparation method of a magnetic composite soil pollution remediation agent according to claim 7, characterized in that, In step S2, glucose is obtained by extracting cellulose from sugarcane bagasse.

10. The preparation method of the magnetic composite soil pollution remediation agent according to claim 7 or 9, characterized in that, The glucose extraction method in step S2 is as follows: sugarcane bagasse is dried and crushed, acid-soaked for 30-40 minutes, neutralized and washed, then cellulase is added, and hydrolyzed at 40-50℃ and pH 4-5 for 24-48 hours. The supernatant is then obtained by centrifugation.