A sulfur-manganese-iron co-doped porous carbon composite material and application thereof

Abstract

The application belongs to the technical field of environmental pollution remediation, and relates to a sulfur-manganese-iron co-doped porous carbon composite material and application thereof. The sulfur-manganese-iron co-doped porous carbon composite material is prepared according to the following steps: after biomass is immersed and treated by a potassium permanganate aqueous solution, pyrolysis is performed to obtain activated biological porous carbon; the activated biological porous carbon is mixed with a soluble iron salt to obtain a magnetic porous carbon material; a metal sulfide is loaded on the magnetic porous carbon material to obtain a sulfur-manganese-iron co-doped porous carbon composite material with a porous core-shell structure. The composite material can significantly reduce the cadmium and lead content in water bodies and soil, has the advantages of excellent remediation effect, high environmental adaptability, low cost and recyclability, and has great potential in the remediation application of cadmium and lead contaminated water bodies and soil.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution remediation technology, and relates to a sulfur-manganese-iron co-doped porous carbon composite material and its application. Background Technology

[0002] Cadmium and lead are common environmental pollutants. Industrial activities involving the mining, beneficiation, and smelting of cadmium and lead-containing metal ores, as well as industrial activities using cadmium and lead compounds as raw materials and catalysts in electroplating, chemical, electronics, and nuclear industries, and the combustion of gasoline, all generate large amounts of cadmium- and lead-containing waste gas, wastewater, and waste residue. These pollutants enter the ecosystem through atmospheric / wet deposition, surface runoff, and leaching. Furthermore, cadmium and lead pollution can migrate and transform among the atmosphere, water bodies, and soil, making the pollution situation increasingly complex. Therefore, the remediation of cadmium- and lead-contaminated water bodies and soil is urgently needed.

[0003] Currently, the main technologies for remediating cadmium and lead contaminated water and soil include bioremediation, physical remediation, and chemical remediation. Bioremediation includes animal, plant, and microbial remediation techniques. Bioremediation is low-cost and environmentally friendly, but it requires specific water and soil conditions for biological growth. Generally, it can only absorb specific types of cadmium or lead. Furthermore, this technology has a long remediation cycle, unstable remediation efficiency, and poor operability, thus limiting its applicability. Physical remediation technologies for cadmium and lead contaminated water include water dilution, sediment dredging, membrane separation, flotation, and adsorption. However, water dilution is only suitable for emergency treatment and may alter the aquatic ecosystem; sediment dredging is too costly and carries the risk of secondary pollution; membrane separation requires unique equipment and is complex to operate; flotation suffers from equipment malfunctions, unstable remediation effects, and energy waste. Physical remediation technologies for cadmium- and lead-contaminated soil mainly include soil replacement, vitrification, and magnetic separation. However, soil replacement is costly and may cause secondary pollution; vitrification requires high temperature and pressure, resulting in large-scale and costly engineering; and magnetic separation requires high-gradient magnetic fields and unique electromagnetic devices, with high processing costs. Chemical remediation technologies for cadmium- and lead-contaminated water mainly include chemical precipitation and electrochemical treatment. However, chemical precipitation requires the addition of large amounts of chemical reagents, easily generating sludge and posing a risk of secondary pollution; electrochemical treatment is energy-intensive, requires specialized equipment and materials, and has low remediation efficiency when dealing with high-concentration cadmium- and lead-contaminated wastewater. Chemical remediation technologies for cadmium- and lead-contaminated soil include chemical leaching and in-situ solidification stabilization. Chemical leaching may damage soil structure and easily cause secondary pollution when used in water treatment in areas with secondary contamination; while in-situ solidification stabilization can inhibit the bioavailability of cadmium and lead in the short term, they may be released and regain activity later.

[0004] In contrast, the adsorbent addition method stands out among various treatment technologies due to its advantages such as simple operation, low engineering cost, and recyclability, and has received widespread attention in the remediation of cadmium and lead contaminated water and soil. However, the key to this technology is the preparation of efficient and low-cost adsorbents. Waste biomass materials such as wood waste, straw, fruit shells, plant roots and stems, animal manure and bones, waste paper, and edible oils are produced in huge quantities, making the efficient and high-value-added utilization of these waste biomass materials crucial for green and sustainable development. In recent years, numerous research and engineering cases have documented the application of these waste biomass materials in the remediation of cadmium and lead contaminated water and soil through high-temperature anaerobic pyrolysis to transform them into valuable bioporous carbon remediation materials. However, due to the different types of raw materials and pyrolysis temperatures of bioporous carbon, as well as the different physicochemical properties of the two heavy metals, the remediation efficiency of raw bioporous carbon for complex cadmium and lead pollution is not satisfactory. Especially when facing high concentrations of cadmium and lead contaminated water and soil, the removal efficiency of raw bioporous carbon materials for cadmium and lead is unsatisfactory. Meanwhile, cadmium and lead in the environmental medium are only transferred to biochar, but the binding force between cadmium and lead and bioporous carbon may be affected by environmental conditions. Over time, cadmium and lead may be released from bioporous carbon again, which will still harm the ecological environment and human health. This has become an urgent problem to be solved in the application of bioporous carbon materials in the remediation of cadmium and lead polluted water and soil.

[0005] Therefore, many scholars have proposed grafting functional modifiers onto pristine bioporous carbon. These modifiers use bioporous carbon as a carrier, resulting in a composite material with extremely high affinity for cadmium and lead. Cadmium and lead in water and soil are transferred to the adsorbent material through adsorption (such as electrostatic attraction, complexation reaction, ion exchange, co-precipitation, and biochar π-cadmium / lead reaction), thereby achieving the clean remediation of water and soil. Modifiers involve chemical modification methods such as acids / bases / oxidants, metals / metal oxides / metal sulfides, organic compounds, and carbonaceous structures. Among these, potassium permanganate (KMnO4), as a strong oxidant, may increase the oxygen-containing functional groups on the surface of bioporous carbon after activation treatment. It may then undergo a complexation reaction with cadmium and lead, potentially leading to the adsorption and enrichment of pollutants on the surface of bioporous carbon. However, KMnO4 also disrupts the nanoporous structure of bioporous carbon materials, reducing their specific surface area and porosity, thus inhibiting the pore adsorption reaction of cadmium and lead on the porous carbon. Iron(III) oxide (Fe3O4) is commonly used to achieve the reuse and separation of bioporous carbon materials in aquatic and soil environments. Fe3O4 endows bioporous carbon composite materials with magnetic properties, allowing them to be easily separated from environmental media by an external magnetic field. This solves the problem of the large engineering costs associated with the use of ordinary filter paper / membrane for bioporous carbon materials. Most importantly, it achieves the complete removal of cadmium and lead pollutants from aquatic and soil environments. However, magnetic porous carbon materials also have the following three drawbacks: (1) Fe3O4 particles are prone to agglomeration in liquid environmental media systems (water and soil solutions), resulting in low adsorption efficiency; (2) Fe3O4-modified magnetic porous carbon materials do not have outstanding adsorption efficiency for cadmium and lead in environmental media. The adsorption process is lengthy and can only work within a very narrow range of environmental pH; (3) Because Fe3O4 particles are mostly exposed on the surface of magnetic porous carbon materials, iron is easily released into the environmental media by external influences, which may cause iron pollution and reduce adsorption performance. These factors greatly limit the application of magnetic porous carbon materials in the remediation of cadmium and lead pollution. Furthermore, metal sulfides, especially ferrous sulfide (FeS), in which the sulfur (S)-ligand acts as a Lewis base, can coordinate with Lewis acids Cd(II) / Pb(II) to form complexes. Simultaneously, the S provided by the metal sulfide... 2- It readily co-precipitates with Cd(II) and Pb(II) to form stable, insoluble CdS and PbS (Ksp(CdS) = 8 × 10⁻⁶). -27 Ksp(PbS) = 8 × 10 -28 However, FeS particles tend to aggregate in solution, and the distribution of FeS particles on FeS-modified porous carbon materials may be uneven. Furthermore, there is currently very little research on the remediation of cadmium and lead in environmental media using FeS-modified porous carbon materials.

[0006] Therefore, the present invention aims to provide a sulfur-manganese-iron co-doped highly active magnetic porous carbon composite material, in order to efficiently and stably treat cadmium and lead in polluted environments. Summary of the Invention

[0007] The purpose of this invention is to provide a sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material. This material aims to offer a novel, staged modified bioporous carbon through activation-magnetization-sulfidation, addressing the problems of low removal efficiency, strong antagonistic effects during adsorption in cadmium-lead contaminated water and soil remediation methods, and difficulty in separating the adsorbent from the polluted medium. This composite material can significantly reduce the cadmium and lead content in water and soil, exhibiting advantages such as excellent remediation effect, high environmental adaptability, low cost, and recyclability. It has great potential for application in the remediation of cadmium-lead contaminated water and soil.

[0008] The specific technical solution provided by this invention is as follows:

[0009] In a first aspect, the present invention provides a manganese-iron co-doped porous carbon composite material, which is prepared according to the following steps:

[0010] Biomass was treated by soaking in an aqueous solution of potassium permanganate and then pyrolyzed to obtain activated bioporous carbon.

[0011] The activated bioporous carbon was mixed with a soluble iron salt to obtain a magnetic porous carbon material.

[0012] Metal sulfides are loaded onto the magnetic porous carbon material to obtain a porous core-shell structure of sulfur-manganese-iron co-doped porous carbon composite material.

[0013] Preferably, the concentration of the potassium permanganate aqueous solution is 0.05-0.2 mol / L, and the solid-liquid ratio of biomass to potassium permanganate aqueous solution is 1 g: 5-25 mL.

[0014] Preferably, the impregnation treatment involves mixing the biomass with an aqueous solution of potassium permanganate and stirring for 2–8 hours.

[0015] Preferably, the pyrolysis involves separating the impregnated biomass and then heating it to 500-600°C at a rate of 5-10°C / min under inert protection for 0.5-2 hours.

[0016] Preferably, the activated bioporous carbon is mixed and stirred with an aqueous solution of soluble iron salt for 12–24 hours, the pH is adjusted to 10–12 to generate ferric hydroxide precipitate, and then aged for 12–48 hours. The solid material is then separated, which is the magnetic porous carbon material. The pH can be adjusted using a 10–20 mol / L sodium hydroxide solution or potassium hydroxide solution. The aging process involves placing the material under sealed conditions for 24–48 hours, then separating the ferric hydroxide precipitate from the solution using an external magnetic field, and finally drying it to obtain the magnetic porous carbon material. The aging process makes the generated precipitate more stable.

[0017] Preferably, the soluble iron salt is a mixture of ferric salt and ferrous salt in a molar ratio of 2:1, wherein the ferric salt is one of ferric chloride, ferric nitrate, and ferric sulfate, and the ferrous salt is one of ferrous chloride, ferrous nitrate, and ferrous sulfate.

[0018] The mixing ratio of the activated bioporous carbon to the aqueous solution of soluble iron salt is 1g:40-100mL, and the total amount of iron ions added to the aqueous solution of soluble iron salt is 10-30% of the total mass of the activated bioporous carbon.

[0019] Preferably, the specific operation process for loading metal sulfides onto the magnetic porous carbon material is as follows: After dispersing the magnetic porous carbon material, a reducing environment is created using an inert gas, and soluble ferrous salts and water-soluble sulfides are added. The mixture is then sealed and allowed to stand to generate ferrous sulfide and manganese sulfide. The solid material is then separated, which is the sulfur-manganese-iron co-doped porous carbon composite material. The sealing and standing time is 24–48 hours. Then, the solid material is separated from the solution using an external magnetic field, and the mixture is vacuum freeze-dried to obtain the sulfur-manganese-iron co-doped porous carbon composite material.

[0020] The dispersion of magnetic porous carbon materials can be achieved using inorganic or organic dispersants, such as starch or gelatin. Organic dispersants are preferred, including triethylhexylphosphate, sodium dodecyl sulfate, methylpentanol, and cellulose derivatives. Sodium carboxymethyl cellulose is further preferred as a dispersant because it is a natural polymer compound with high dispersibility, stability, and safety, and its use in food has been approved by the FAO and WHO. However, those skilled in the art should understand that this is not a specific limitation on the dispersant.

[0021] Preferably, the concentration of the sodium carboxymethyl cellulose solution is 0.02–0.04 mmol / L, and the mixing ratio of the magnetic bioporous carbon material to the sodium carboxymethyl cellulose solution is 1 g: 40–100 mL.

[0022] Preferably, the water-soluble sulfide is a soluble metal sulfide or ammonium sulfide, and the soluble divalent ferrous salt is ferrous sulfate, ferrous nitrate, or ferrous halide.

[0023] More preferably, the readily soluble metal sulfide is selected from alkali metal sulfides.

[0024] Considering the stability, toxicity, and price of readily soluble metal sulfides, as well as the adsorption performance of the final manganese-iron co-doped porous carbon composite material, sodium sulfide is further preferred as the readily soluble metal sulfide. However, those skilled in the art should understand that this is not a specific limitation on the readily soluble metal sulfide.

[0025] More preferably, the molar ratio of the alkali metal sulfide to ferrous sulfate is 2:0.5-2. When the alkali metal sulfide is sodium sulfide, the amount of both the aqueous solution of sodium sulfide and the aqueous solution of ferrous sulfate added is 10-20 mL, and the concentrations of both the aqueous solutions of sodium sulfide and ferrous sulfate are 0.5-2 mol / L.

[0026] In the aforementioned sulfidation reaction, metal sulfides are generated on the surface of the magnetic porous carbon material, specifically a mixture of manganese sulfide and ferrous sulfide. The water-soluble sulfides provide sulfide ions, which react with ferrous ions in ferrous sulfate to form ferrous sulfide. Sulfide ions can also combine with manganese ions on the magnetically active porous carbon to form manganese sulfide. Ferrous sulfide and manganese sulfide serve as functional substances for adsorbing heavy metals. Furthermore, sulfate ions can react with cadmium and lead to form lead cadmium sulfate precipitate, which is beneficial for improving adsorption performance.

[0027] In a second aspect, the present invention provides the use of the sulfur-manganese-iron co-doped porous carbon composite material in the removal of cadmium- and lead-containing contaminants.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention proposes for the first time a stepwise method for modifying porous carbon through activation-magnetization-sulfidation. First, the surface of the original porous carbon is modified by KMnO4 erosion to generate activated porous carbon, further reconstructing the mesopore and macropore structure of the porous carbon material to promote the anchoring of metal sulfide minerals in the later stage. Then, magnetic Fe3O4 particles are uniformly coated on the surface of the activated porous carbon to achieve effective separation of the magnetic adsorbent from the environmental medium after cadmium and lead pollution is remediated. Finally, a dispersant such as sodium carboxymethyl cellulose is used to uniformly disperse the generated FeS and MnS sulfide particles on the outer surface of the magnetic porous carbon. At the same time, the sulfide shell formed can protect the internal magnetic particles, reduce the risk of Fe leaching, and facilitate the remediation of cadmium and lead pollution in the environmental medium.

[0030] 2. This invention prepares a ferrous sulfide / manganese fine particle magnetic highly active porous carbon composite material by loading it onto a magnetic highly active porous carbon material using directional doping technology. This solves the problems of ferrous sulfide / manganese fine particle aggregation and low adsorption efficiency in liquid systems. It not only improves the dispersion of ferrous sulfide / manganese and magnetic iron tetroxide on highly active porous carbon materials, but also promotes the adsorption reaction between cadmium and lead pollutants in the environmental medium and the functional groups and metal minerals on the final adsorbent. This allows the adsorbent composite material to exhibit good stability, easy recycling, recyclability, and high remediation efficiency for pollutants.

[0031] 3. The biomass raw material used in this invention can be wood waste, which has an annual urban output of approximately 90 million tons in my country. However, due to the lack of mandatory regulations and policy support for the recycling of waste wood in my country, the process of recycling and industrialization of waste wood is very slow, with most of it ultimately used as industrial fuel, resulting in huge resource waste. This invention uses these wood wastes as biomass raw materials, which are widely available, abundant, and inexpensive, making it an important measure to achieve the sustainable utilization of waste wood resources.

[0032] 4. The reagents used in this invention, such as potassium permanganate, ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, sodium hydroxide, potassium hydroxide, sodium carboxymethyl cellulose, and sodium sulfide, are inexpensive, green, and pollution-free.

[0033] 5. This invention has the advantages of being able to efficiently remove cadmium and lead pollutants from water and soil simultaneously, having low cost, good effect, strong operability, not causing secondary pollution, beautifying the environment, being easy to separate and collect, and being recyclable multiple times. It has potential engineering application value and can be widely promoted and applied.

[0034] 6. The sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material prepared by this invention has the characteristics of being green and pollution-free. When the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material is used to remove cadmium and lead pollutants from environmental media, if the performance of the material does not meet the requirements after repeated use, it indicates that the material has failed and can be directly incinerated. The obtained solid residue contains iron, manganese, cadmium, lead, etc., which can be used as mineral raw materials for the recovery of elements such as iron, manganese, cadmium, and lead, or sent to a hazardous waste treatment center for treatment, without causing secondary pollution to the environment. Attached Figure Description

[0035] Figure 1 This is a hysteresis loop (VSM) diagram of the magnetically highly active porous carbon (M-KAC) and sulfur-manganese-iron co-doped magnetically highly active porous carbon composite material (SM-KAC) provided in Embodiment 1 of the present invention.

[0036] Figure 2These are scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) images of the highly active porous carbon (KAC) (a,b,c,d), the magnetic highly active porous carbon (M-KAC) (e,f,g,h), and the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) (i,j,k,l) ​​provided in Example 1 of this invention.

[0037] Figure 3 This is the X-ray crystal diffraction (XRD) pattern of the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) provided in Example 1 of the present invention;

[0038] Figure 4 The isothermal adsorption fitting curves of cadmium (a) and lead (b) in water by the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) provided in Example 1 of this invention, and the kinetic adsorption fitting curves of cadmium (c) and lead (d) by the three adsorption materials.

[0039] Figure 5 The effect of solution pH of the present invention on the adsorption of cadmium (a) and lead (b) by the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC) and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) provided in Example 1, and the amount of iron precipitated after adsorption by M-KAC and SM-KAC (c).

[0040] Figure 6 The adsorption efficiencies (a, b, c) of the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) provided in Example 1 of this invention in a composite pollution system with cadmium as the main component and lead as the guest component, and the adsorption efficiencies (d, e, f) of the three materials in a composite pollution system with lead as the main component and cadmium as the guest component.

[0041] Figure 7 The effects of sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) provided in Examples 1 and 5 of the present invention on the cadmium and lead content in Chinese cabbage (a), wheat (b), and soil (d, c) under pollution stress.

[0042] Figure 8 The effects of the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) provided in Examples 1 and 5 of this invention on the cadmium (a) and lead (b) content in leachate from solid waste landfills are described. Detailed Implementation

[0043] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0046] S101. The collected wood waste is gradually rinsed with tap water and deionized water to remove the impurities attached to it. It is dried at 105℃, crushed, and then 1g of dried wood waste biomass is weighed and mixed with 5mL of 0.05mol / L potassium permanganate solution and stirred for 2h. The solid material is separated under centrifugal force of 5000rpm, loaded into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature is raised to 500℃ at a rate of 5℃ / min and pyrolyzed for 0.5h. After cooling, activated bioporous carbon is obtained and labeled as highly active porous carbon (KAC).

[0047] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 40mL of FeCl3 / FeCl2 mixed solution and stir for 12h. In the FeCl3 / FeCl2 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 10 with 10mol / L sodium hydroxide solution, then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0048] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 40mL of sodium carboxymethyl cellulose solution with a concentration of 0.02mol / L. Under inert protection, first add 10mL of 0.5mol / L sodium sulfide solution and stir for 0.5h. Then add 10mL of 0.5mol / L ferrous sulfate solution and continue stirring for 2h to form a homogeneous suspension. Then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0049] Example 2

[0050] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0051] S101. The collected wood waste was gradually rinsed with tap water and deionized water to remove the impurities attached to it. It was dried at 105℃, crushed, and then 1g of dried wood waste biomass was weighed and mixed with 10mL of 0.1mol / L potassium permanganate solution and stirred for 4h. The solid material was separated under centrifugal force of 5000rpm, packed into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature was raised to 550℃ at a rate of 10℃ / min and pyrolyzed for 1h. After cooling, activated bioporous carbon was obtained and labeled as highly active porous carbon (KAC).

[0052] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 60mL of Fe(NO3)3 / Fe(NO3)2 mixed solution and stir for 24h. In the Fe(NO3)3 / Fe(NO3)2 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 11 with 10mol / L potassium hydroxide solution, and then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0053] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 60mL of sodium carboxymethyl cellulose solution with a concentration of 0.03mol / L. Under inert protection, first add 20mL of 1mol / L sodium sulfide solution and stir for 0.5h. Then add 10mL of 0.5mol / L ferrous sulfate solution and continue stirring for 2h to form a homogeneous suspension. Then seal and place for 48h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain the sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0054] Example 3

[0055] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0056] S101. The collected wood waste is gradually rinsed with tap water and deionized water to remove the impurities attached to it. It is dried at 105℃, crushed, and then 1g of dried wood waste biomass is weighed and mixed with 15mL of 0.15mol / L potassium permanganate solution and stirred for 6h. The solid material is separated under centrifugal force of 5000rpm, loaded into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature is raised to 600℃ at a rate of 10℃ / min and pyrolyzed for 1.5h. After cooling, activated bioporous carbon is obtained and labeled as highly active porous carbon (KAC).

[0057] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 80mL of Fe2(SO4)3 / FeSO4 mixed solution and stir for 12h. In the Fe2(SO4)3 / FeSO4 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 12 with 20mol / L sodium hydroxide solution, and then seal and place for 48h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0058] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 80mL of sodium carboxymethyl cellulose solution with a concentration of 0.04mol / L. Under inert protection, first add 10mL of 2mol / L sodium sulfide solution and stir for 0.5h. Then add 20mL of 0.5mol / L ferrous chloride solution and continue stirring for 2h to form a homogeneous suspension. Then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0059] Example 4

[0060] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0061] S101. The collected wood waste was gradually rinsed with tap water and deionized water to remove the impurities attached to it. It was dried at 105℃, crushed, and then 1g of dried wood waste biomass was weighed and mixed with 20mL of 0.2mol / L potassium permanganate solution and stirred for 8h. The solid material was separated under centrifugal force of 5000rpm, packed into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature was raised to 500℃ at a rate of 5℃ / min and pyrolyzed for 1h. After cooling, activated bioporous carbon material was obtained and labeled as highly active porous carbon (KAC).

[0062] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 100mL of Fe(NO3)3 / Fe(NO3)2 mixed solution and stir for 12h. In the Fe(NO3)3 / Fe(NO3)2 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 10 with 20mol / L sodium hydroxide solution, and then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0063] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 60mL of sodium carboxymethyl cellulose solution with a concentration of 0.02mol / L. Under inert protection, first add 20mL of 1mol / L sodium sulfide solution and stir for 0.5h. Then add 10mL of 2mol / L ferrous sulfate solution and continue stirring for 2h to form a homogeneous suspension. Then seal and place for 48h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain the sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0064] Example 5

[0065] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0066] S101. The collected wood waste was gradually rinsed with tap water and deionized water to remove the impurities attached to it. It was dried at 105℃, crushed, and then 1g of dried wood waste biomass was weighed and mixed with 25mL of 0.2mol / L potassium permanganate solution and stirred for 8h. The solid material was separated under centrifugal force of 5000rpm, packed into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature was raised to 600℃ at a rate of 10℃ / min and pyrolyzed for 2h. After cooling, activated bioporous carbon material was obtained and labeled as highly active porous carbon (KAC).

[0067] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 100mL of FeCl3 / FeSO4 mixed solution and stir for 24h. In the FeCl3 / FeSO4 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 12 with 20mol / L potassium hydroxide solution, and then seal and place for 48h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0068] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 100mL of sodium carboxymethyl cellulose solution with a concentration of 0.04mol / L. Under inert protection, first add 20mL of 2mol / L sodium sulfide solution and stir for 0.5h. Then add 20mL of 2mol / L ferrous sulfate solution and continue stirring for 2h to form a homogeneous suspension. Then seal and place for 48h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0069] Example 6

[0070] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0071] S101. The collected wood waste is gradually rinsed with tap water and deionized water to remove the impurities attached to it. It is dried at 105℃, crushed, and then 1g of dried wood waste biomass is weighed and mixed with 5mL of 0.05mol / L potassium permanganate solution and stirred for 2h. The solid material is separated under centrifugal force of 5000rpm, loaded into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature is raised to 500℃ at a rate of 5℃ / min and pyrolyzed for 0.5h. After cooling, activated bioporous carbon material is obtained and labeled as highly active porous carbon (KAC).

[0072] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 40mL of FeCl3 / FeCl2 mixed solution and stir for 12h. In the FeCl3 / FeCl2 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 10 with 10mol / L sodium hydroxide solution, then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0073] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 40mL of a 0.02mol / L triethylhexyl phosphoric acid solution. Under inert protection, first add 10mL of 0.5mol / L ammonium sulfide solution and stir for 0.5h. Then add 10mL of 0.5mol / L ferrous sulfate solution and continue stirring for 2h to form a homogeneous suspension. Then seal and place for 24h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain the sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0074] Example 7

[0075] A sulfur-manganese-iron co-doped magnetically active porous carbon composite material is prepared according to the following steps:

[0076] S101. The collected wood waste was gradually rinsed with tap water and deionized water to remove the impurities attached to it. It was dried at 105℃, crushed, and then 1g of dried wood waste biomass was weighed and mixed with 25mL of 0.2mol / L potassium permanganate solution and stirred for 8h. The solid material was separated under centrifugal force of 5000rpm, packed into a porcelain crucible and compacted, and transferred into a temperature-controlled muffle furnace. Under inert protection, the temperature was raised to 600℃ at a rate of 10℃ / min and pyrolyzed for 2h. After cooling, activated bioporous carbon material was obtained and labeled as highly active porous carbon (KAC).

[0077] S102. Mix 1g of the above-mentioned activated bioporous carbon material with 100mL of FeCl3 / FeSO4 mixed solution and stir for 24h. In the FeCl3 / FeSO4 mixed solution, the molar ratio of ferric iron to ferrous iron is 2:1. Adjust the pH to 12 with 20mol / L potassium hydroxide solution, and then seal and place for 48h. Separate the solid material from the solution by applying an external magnetic field and dry at 60℃ to obtain magnetically highly active porous carbon material (M-KAC).

[0078] S103. Disperse 1g of the above-mentioned magnetically active porous carbon material in 100mL of starch solution with a concentration of 0.04mol / L. Under inert protection, first add 20mL of 2mol / L potassium sulfide solution and stir for 0.5h. Then add 20mL of 2mol / L ferrous sulfate solution and continue stirring for 2h to form a homogeneous suspension. Then seal and let stand for 48h. Separate the solid material from the solution by applying an external magnetic field and freeze-dry under vacuum at -50℃ to obtain sulfur-manganese-iron co-doped magnetically active porous carbon composite material (SM-KAC).

[0079] Since the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite materials (SM-KAC) prepared in Examples 1 to 7 have basically the same properties, the following description will only take the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material prepared in Example 1 as an example.

[0080] Magnetic strength analysis of the magnetically highly active porous carbon (M-KAC) and the sulfur-manganese-iron co-doped magnetically highly active porous carbon composite material (SM-KAC) obtained in Example 1 revealed that ( Figure 1 Both have extremely strong magnetic strength.

[0081] The highly active porous carbon (KAC), magnetically highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetically highly active porous carbon composite material (SM-KAC) obtained in Example 1 were analyzed by scanning electron microscopy (SEM-EDS, e.g.) Figure 2 ) and X-ray crystallography (XRD, such as Figure 3 It was found that manganese sulfide, ferrous sulfide, and iron oxide particles were uniformly dispersed on the surface and in the pores of the bioporous carbon. Mn, Fe, and S elements were most uniformly distributed on SM-KAC. The final prepared sulfur-manganese-iron co-doped magnetic high-activity porous carbon composite material is a porous core-shell structured carbon composite material.

[0082] Since the adsorption properties of the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) prepared in Examples 1, 2, 3, 4, 5, 6, and 7 are basically the same, the following will only take the three adsorbent materials prepared in Example 1 as examples to illustrate their removal effect on cadmium and lead pollutants.

[0083] (I) To investigate the effects of initial concentration, reaction time and solution pH on the adsorption of cadmium and lead by highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC) and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC).

[0084] Investigating the effect of initial concentration: In the adsorption system of a single pollutant, 0.5 g of the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) prepared in Example 1 were added to 200 mL of a single pollutant solution (solid-liquid ratio of 2.5 g / L). The initial concentration of Cd(II) or Pb(II) pollutant solution was 0.5–1000 mg / L. After reacting in a constant temperature shaker at 25 °C and 180 rpm for 6 h, adsorption equilibrium was reached, and the contents of Cd(II) and Pb(II) in the solution were measured.

[0085] When the adsorption reaction reaches equilibrium, the adsorption process better conforms to the Langmuir isotherm model, such as... Figure 4 As shown in a and b, the adsorption capacities of the three adsorbents for Cd(II) and Pb(II) gradually increased to saturation with increasing initial concentrations. The saturated adsorption capacities of highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) for Cd(II) were 33.56, 38.33, and 137.12 mg·g⁻¹, respectively. -1 The saturated adsorption capacities for Pb(II) were 69.60, 138.91, and 293.45 mg·g, respectively. -1 The prepared sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) exhibited the highest adsorption capacity for Cd(II) and Pb(II). SM-KAC could remove more than 90% of cadmium / lead pollutants from water bodies when the initial concentration of Cd(II) was 0.5–300 mg / L or the initial concentration of Pb(II) was 0.5–800 mg / L.

[0086] Investigating the effect of reaction time: In the adsorption system of a single pollutant, 0.5 g of the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) prepared in Example 1 were added to 200 mL of a single pollutant solution (solid-liquid ratio of 2.5 g / L). The initial concentrations of Cd(II) and Pb(II) pollutants were set at 300 mg / L. The adsorption reaction was carried out in a constant temperature shaker at 25 °C and 180 rpm. Samples were taken at reaction times of 5, 10, 15, 20, 30, 45, 60, 120, 240, 480, 720, and 1440 minutes, and the contents of Cd(II) and Pb(II) in the solutions sampled at different times were measured.

[0087] When the adsorption reaction reaches equilibrium, the adsorption process conforms more closely to the Pseudo-second-order kinetic model, such as... Figure 4 As shown in c and d, the adsorption of Cd(II) by KAC, M-KAC, and SM-KAC reached more than 90% of the maximum adsorption capacity at 120, 120, and 20 min, respectively, while the adsorption of Pb(II) by KAC, M-KAC, and SM-KAC exceeded 90% of the equilibrium adsorption capacity at 60, 45, and 45 min, respectively. The prepared sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) showed a shorter removal time for Cd(II) and Pb(II) compared to the other two.

[0088] The effect of solution pH was investigated: In the adsorption system of a single pollutant, the solid-liquid ratio of the three adsorbents to the pollutant solution was 2.5 g / L, and the initial concentrations of Cd(II) and Pb(II) pollutants in the solution were 300 mg / L. The adsorption reaction was carried out in a constant temperature shaker at 25℃ and 180 rpm / min. The initial pH of the pollutant solution was set to 1-6. The contents of Cd(II) and Pb(II) in the solution, as well as the amount of Fe precipitated, were measured.

[0089] like Figure 5As shown, the adsorption capacity gradually increases with increasing solution pH. The adsorption capacity of highly active porous carbon (KAC) and magnetic highly active porous carbon (M-KAC) under acidic conditions is unsatisfactory. At pH 1, the adsorption capacities of KAC and M-KAC are 26.76% and 31.09% of their saturated adsorption capacities, respectively; at pH 2, the adsorption capacities are 65.14% and 54.71% of their saturated adsorption capacities, respectively. However, the adsorption capacities of SM-KAC at pH 1 and 2 are 86.03% and 89.62% of their saturated adsorption capacities, respectively. In contrast, the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) maintains high adsorption capacity over a wider range of environmental pH. Furthermore, the Fe precipitation of M-KAC in solutions with lower pH is 0.7–1.2%, while the iron precipitation of SM-KAC is significantly reduced to less than 0.1%, thus lowering the risk of iron pollution in water bodies.

[0090] In the adsorption system for cadmium-lead combined pollution, the mass ratio of the highly active porous carbon (KAC), magnetic highly active porous carbon (M-KAC), and sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) prepared in Example 1 to the volume of the combined pollution solution remained at 2.5 g / L. In the combined solution with cadmium (lead) as the main component and lead (cadmium) as the guest component (i.e., coexisting substances), the initial concentration of Cd(II) / Pb(II) pollution solution was 0.5–1000 mg / L, and the concentrations of guest Pb(II) / Cd(II) were set to 1, 5, 10, 25, 50, and 100 mg / L, respectively. After reacting for 6 hours in a constant-temperature shaker at 25°C and 180 rpm / min, adsorption equilibrium was reached, and the content of Cd(II) or Pb(II) in the solution was measured. The adsorption removal rate in the combined pollution system is shown in [the figure]. Figure 6 .

[0091] The results showed that the removal rates of Cd by highly active porous carbon (KAC) and magnetic highly active porous carbon (M-KAC) were significantly affected by the presence of coexisting Pb. The removal rates were highest when the bulk Cd concentration ranged from 0.5 to 400 mg·L⁻¹. -1 The coexisting Pb concentration was 100 mg·L⁻¹. -1 At the specified concentrations, KAC, M-KAC, and SM-KAC exhibited Cd removal rates of 2.1–79.3%, 4.1–82.3%, and 61.0–100%, respectively. This was achieved when the main Pb concentration ranged from 0.5 to 1000 mg·L⁻¹. -1 The coexisting Cd concentration was 100 mg·L⁻¹ -1At that time, the removal rates of Cd by KAC, M-KAC and SM-KAC were 5.8–83.2%, 11.4–89.2%, and 99.8–100%, respectively. Therefore, it can be concluded that the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) can exhibit good adsorption capacity for both pollutants in the cadmium-lead composite pollution system.

[0092] In summary, compared with highly active porous carbon (KAC) and magnetic highly active porous carbon (M-KAC), the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) shows the best performance in terms of adsorption efficiency, reaction time, adaptability to environmental pH, risk of Fe precipitation, and adsorption capacity in complex pollution systems. Therefore, in the following cadmium and lead pollution remediation applications, only the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material (SM-KAC) prepared in Examples 1 and 5 will be used as examples to illustrate its removal effect on cadmium and lead pollutants.

[0093] (II) Application of the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite materials prepared in Examples 1 and 5 in the treatment of cadmium-lead co-polluted water bodies

[0094] The actual adsorption performance of the prepared sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material was verified by conducting adsorption tests on water samples containing cadmium and lead (including leachate from tailings / hazardous waste landfills, leachate from municipal solid waste landfills, and surface water from a river outside a tailings landfill). When removing cadmium and lead pollutants from polluted water, 0.5 g of the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material was added to 1 L of polluted wastewater. After stirring thoroughly for 6–12 h and allowing to stand for 10 min, the porous carbon material was magnetically separated and recovered from the solution using a magnet. The treated water was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-MS) according to the Environmental Protection Standards of the People's Republic of China. The results are shown in Tables 1 and 2.

[0095] Table 1. Removal effect of sulfur-manganese-iron co-doped magnetic highly active porous carbon composite materials prepared in Examples 1 and 5 on cadmium in polluted water.

[0096]

[0097] Table 2. Removal effect of sulfur-manganese-iron co-doped magnetic highly active porous carbon composite materials prepared in Examples 1 and 5 on lead in polluted water.

[0098]

[0099]

[0100] The heavy metal content in the treated tailings / hazardous solid waste landfill leachate is lower than the cadmium limit of 0.1 mg / L and the lead limit of 1.0 mg / L specified in the "Integrated Wastewater Discharge Standard". The heavy metal content in the treated municipal solid waste landfill leachate is lower than the cadmium limit of 0.01 mg / L and the lead limit of 0.1 mg / L specified in the "Pollution Control Standard for Municipal Solid Waste Landfills" (GB16889-2008). The heavy metal content in the treated surface water is lower than the cadmium limit of 0.001 mg / L and the lead limit of 0.01 mg / L specified in the "Environmental Quality Standard for Surface Water" (GB3838-2002) for Class I surface water.

[0101] (III) Application of the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite materials prepared in Examples 1 and 5 in the remediation of cadmium-lead co-contaminated soil and safe production of agricultural products

[0102] The soil used in the experiment was collected from vegetable fields in Feng County, Baoji City, Shaanxi Province, which were contaminated with cadmium and lead (cadmium and lead contents were 1.96 mg / kg and 452.27 mg / kg, respectively, and pH value was 7.04). The soil was mixed with the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material prepared in Examples 1 and 5 at a mass ratio of 2%. The control group was soil without the addition of remediation material. Each plot was 20 square meters, and each treatment was replicated three times. After the pakchoi matured and was harvested, the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material was magnetically separated from the soil using an external magnetic field (such as a magnet). The changes in cadmium and lead content in the aboveground parts (edible parts) of the pakchoi were analyzed.

[0103] The specific results are attached. Figure 7 As shown, after applying the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material to cadmium- and lead-contaminated soil, the cadmium and lead content in the aboveground parts of pakchoi was significantly reduced compared to the control. After treating the contaminated soil with remediation materials prepared in Examples 1 and 5 at a concentration of 2%, the cadmium content in the aboveground parts of pakchoi decreased by 67.31% and 71.35%, respectively, and the lead content decreased by 63.64% and 72.73%, respectively. Before remediation, the cadmium content in the aboveground parts of pakchoi was 0.52 mg / kg and the lead content was 0.77 mg / kg, which was higher than the national food safety standard levels (cadmium 0.2 mg / kg, lead 0.3 mg / kg) (GB2762-2022). After remediation, the cadmium content in the aboveground parts of pakchoi was 0.17 and 0.15 mg / kg, and the lead content was 0.28 and 0.21 mg / kg, respectively, meeting the standards for safe consumption.

[0104] (IV) Application of the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite materials prepared in Examples 1 and 5 in the remediation of cadmium-lead co-contaminated soil and safe production of agricultural products

[0105] The soil used in the experiment was collected from wheat soil contaminated with cadmium and lead in Tongguan County, Weinan City, Shaanxi Province (total cadmium and lead contents were 0.83 mg / kg and 186.45 mg / kg, respectively, pH value 7.28). The soil was mixed with the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material prepared in Examples 1 and 5 at a mass ratio of 2%. The control group was soil without added remediation material. Each plot was 16 square meters, and each treatment was replicated three times. After the wheat matured and was harvested, the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material was magnetically separated from the soil using an external magnetic field (such as a magnet). The changes in cadmium and lead content in the soil and wheat grains were analyzed.

[0106] The specific results are attached. Figure 7 As shown, after applying the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material to cadmium- and lead-contaminated soil, the heavy metal content in the soil and wheat grains was significantly reduced compared to the control. After treating contaminated soil with the remediation materials prepared in Examples 1 and 5 at an addition ratio of 2%, the total cadmium content in the soil decreased by 30.12% and 34.94%, respectively, and the total lead content decreased by 9.78% and 13.02%, respectively; the cadmium content in wheat grains decreased by 52.63% and 63.16%, respectively, and the lead content decreased by 41.94% and 48.39%, respectively. Before remediation, wheat grains contained 0.19 mg / kg of cadmium and 0.31 mg / kg of lead, exceeding the national food safety standards (0.1 mg / kg for cadmium and 0.2 mg / kg for lead) (GB2762-2022). Soil contained 0.83 mg / kg of cadmium and 186.45 mg / kg of lead, exceeding the screening values ​​in the "Soil Pollution Risk Control Standard for Agricultural Land" (GB15618-2018) (0.6 mg / kg for cadmium and 170 mg / kg for lead). However, after remediation, wheat grains contained 0.09 and 0.07 mg / kg of cadmium and 0.18 and 0.16 mg / kg of lead, meeting safe consumption standards. Soil samples after remediation contained 0.58 and 0.54 mg / kg of cadmium and 168.22 and 162.17 mg / kg of lead, posing a low risk to agricultural product quality and safety, crop growth, and the soil ecological environment, and are generally negligible.

[0107] (V) Indoor simulation application of the sulfur-manganese-iron co-doped magnetic high-activity porous carbon composite material prepared in Example 5 in the safe treatment of leachate from slag landfills.

[0108] The tailings were collected from a gold mine tailings pond in Anle Town, Tongguan County, Shaanxi Province, containing 9.02 mg / kg of cadmium and 2292.4 mg / kg of lead. In this study, a column-type semi-dynamic leaching test was used to simulate the leachate leaching process of tailings in a landfill. The sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material prepared in Example 5 was used as the adsorbent layer to investigate the removal capacity of the adsorbent material for cadmium and lead in the leachate. The cylindrical model used was made of acrylic material, 600 mm high, with an inner diameter of 50 mm, and no bottom. The inner wall of the column was sanded, and the bottom had evenly distributed pores with a diameter of 1.0 mm for uniform flow. Approximately 1000 g of dried and pulverized tailings sample was loaded into the column and then appropriately compressed to a height of 420 mm to achieve a filling density of 1.2 g / cm³. 3 The bulk density was close to that of tailings from the mine in the study area, and was designated as the control group (CK). In addition, before filling the slag sample, an adsorption layer with a thickness of 42 mm or 210 mm was placed on the bottom quartz sand layer. The adsorption layer was filled with the sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material prepared in Example 5, maintaining the filling density of the adsorption material consistent with the slag. The column treatments with the 42 mm and 210 mm adsorption layers were designated as T1 and T2, respectively. Washed fine-grained quartz sand was filled at both ends of the cylinder, and filter paper was placed before sealing to prevent slag particles from migrating out of the column. The filled column was moistened with a small amount of deionized water for 24 hours to saturate the compressed slag. Simultaneously, 100 mL of deionized water was supplied daily from the top of the cylinder using a peristaltic pump. The leaching test was conducted for 60 days, and the cadmium and lead concentrations in the leachate were measured daily.

[0109] The leaching release curves of cadmium and lead in slag are as follows: Figure 8 As shown, with the extension of leaching time, the concentration of cadmium in the leachate under all three treatments showed an overall slow decreasing trend, while lead showed a phenomenon of first increasing for a short period and then slowly decreasing. In the control treatment (CK) without remediation material as an adsorption layer, the cadmium and lead concentrations in the leachate were higher than the cadmium limit of 0.1 mg / L and the lead limit of 1.0 mg / L specified in the "Integrated Wastewater Discharge Standard" for the first 25 days and the first 10 days, respectively. On day 60, the cadmium and lead concentrations in the leachate were still higher than the cadmium limit of 0.01 mg / L and the lead limit of 0.1 mg / L specified in Class V surface water of the "Surface Water Environmental Quality Standard" (GB3838-2002). However, in the treatments (T1 and T2) with sulfur-manganese-iron co-doped magnetic highly active porous carbon composite material as an adsorption layer, the cadmium and lead concentrations in the leachate were lower than the limits specified in the "Integrated Wastewater Discharge Standard" throughout the 60-day leaching period. On day 60, the cadmium and lead concentrations in the leachate were lower than the limits of 0.001 mg / L for cadmium and 0.01 mg / L for lead in Class I surface water as specified in the "Environmental Quality Standard for Surface Water" (GB3838-2002).

[0110] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All technical solutions that fall within the scope of the present invention are protected by the present invention.

Claims

1. A sulfur-manganese-iron co-doped porous carbon composite material, characterized in that, It is prepared according to the following steps: Biomass was treated by soaking in an aqueous solution of potassium permanganate and then pyrolyzed to obtain activated bioporous carbon. The activated bioporous carbon was mixed with a soluble iron salt to obtain a magnetic porous carbon material. By loading metal sulfides onto the magnetic porous carbon material, a porous core-shell structure of sulfur-manganese-iron co-doped porous carbon composite material is obtained. The specific operation process of loading metal sulfides onto the magnetic porous carbon material is as follows: after dispersing the magnetic porous carbon material in a solution containing a dispersant, soluble divalent iron salt and water-soluble sulfides are added under inert conditions, the mixture is sealed and allowed to stand, and the solid material is separated, which is the sulfur-manganese-iron co-doped porous carbon composite material.

2. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 1, characterized in that, The concentration of the potassium permanganate aqueous solution is 0.05~0.2mol / L, and the solid-liquid ratio of biomass to potassium permanganate aqueous solution is 1g:5~25mL.

3. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 1, characterized in that, The activated bioporous carbon is mixed with an aqueous solution of soluble iron salt and stirred for 12-24 h, the pH is adjusted to 10-12, aged for 12-48 h, and the solid material is separated to obtain the magnetic porous carbon material.

4. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 3, characterized in that, The soluble iron salt is a mixture of ferric salt and ferrous salt in a molar ratio of 2:1, wherein the ferric salt is one of ferric chloride, ferric nitrate, and ferric sulfate, and the ferrous salt is one of ferrous chloride, ferrous nitrate, and ferrous sulfate. The total amount of iron ions added to the aqueous solution of the soluble iron salt is 10-30% of the total mass of the activated bioporous carbon.

5. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 1, characterized in that, The water-soluble sulfide is a soluble metal sulfide or ammonium sulfide, and the soluble divalent ferrous salt is ferrous sulfate, ferrous nitrate or ferrous halide.

6. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 5, characterized in that, Easily soluble metal sulfides are selected from alkali metal sulfides.

7. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 1, characterized in that, The dispersion is achieved by dispersing the magnetic porous carbon material in a solution of any one of sodium hexametaphosphate, triethylhexylphosphate, sodium dodecyl sulfate, methylpentanol, cellulose derivatives, polyacrylamide, starch, or gelatin.

8. The sulfur-manganese-iron co-doped porous carbon composite material according to claim 7, characterized in that, The magnetic porous carbon material is dispersed using sodium carboxymethyl cellulose. The concentration of the sodium carboxymethyl cellulose solution is 0.02~0.04 mmol / L, and the mixing ratio of the magnetic bioporous carbon material to the sodium carboxymethyl cellulose solution is 1g:40~100mL.

9. The use of the sulfur-manganese-iron co-doped porous carbon composite material according to any one of claims 1 to 8 in the removal of cadmium- and lead-containing pollutants.

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