Method for manufacturing magnetic adsorption materials and use thereof

Abstract

This invention provides a method for producing an improved magnetic biocarbon adsorption material and its use. [Solution] The adsorbent material is manufactured using three types of biomass—urban sludge, straw, and antimony ore slag—as biochar sources, and further supported with magnetic nano-γ-Fe2O3 particles. In the above process, by controlling the mass of the three materials—urban sludge, straw, and antimony ore slag—the composition and performance of the biochar base material in the adsorbent material can be controlled, and the abundant active sites in the sludge and straw can be fully utilized to achieve support for magnetic nano-γ-Fe2O3 particles. The microfibril structure in the straw and the highly active mesoporous support in the antimony ore slag can not only improve the support rate of magnetic nano-γ-Fe2O3 particles to some extent, but are also advantageous for the diffusion and capture of heavy metal ions during use, and can improve the overall adsorption rate of the material to heavy metal ions.

Description

[Technical Field]

[0001] The present invention relates to the technical field of biochar adsorption materials, and more particularly to a method for producing magnetic biochar adsorption materials and the use thereof. [Background technology]

[0002] Antimony (Sb) and its associated heavy metals (Pb(II), Cd(II)) are globally controlled environmental pollutants. Due to the complex rainfall characteristics and deposit site features of antimony mining areas, as well as the geological and hydrological conditions, the complex chemical composition of antimony ore slag (waste residue) and the release of heavy metals under filtration by rainfall at deposit sites result in complex antimony-containing heavy metal wastewater. This leads to a reduction in the volume and resource utilization of slag rock, which is cooperatively converted from multi-source fixed waste in antimony mining areas, and there is little research on antimony-containing heavy metal wastewater treatment technologies at deposit sites. Adsorption composite materials are considered an effective and economical method for treating heavy metal wastewater both domestically and internationally due to their advantages such as ease of operation, high adsorption capacity, and sustainability. In the material selection process, magnetic iron oxide exhibits significant advantages due to its excellent stability and superior metal adsorption capacity, making it an ideal magnetic base material. γ-Fe2O3, in heavy metal contamination treatment, particularly in the adsorption process of Sb, shows broad applicability due to its stable structure and high adsorption efficiency. In the selection process of carbon-based materials, biochar is a porous solid material formed by high-temperature decomposition and carbonization of organic matter in anaerobic or hypoxic environments, possessing a high specific surface area and carbon content. In recent years, biochar has been widely used to remove heavy metals, organic pollutants, and nutrients from water due to its excellent adsorption performance. Scholars both domestically and internationally have succeeded in developing mineral-based and magnetically modified mineral-based nanoadsorbents that are economically efficient, highly selective, recyclable, and have large adsorption capacity. While these exhibit remarkable efficacy in treating single heavy metal wastewater, treating multiple types of heavy metal wastewater remains difficult. Furthermore, the adsorbent material is prone to leakage, making separation and recycling relatively challenging. There is room for improvement in developing composite materials using multi-component waste from the mineral domain, which has a wide range of uses and is inexpensive.

[0003] To solve the above problems, it is necessary to design a manufacturing method and use for an improved magnetic biocarbon adsorption material. [Overview of the Initiative]

[0004] The present invention aims to provide a method for producing a magnetic biocarbon adsorption material and a method for using the same.

[0005] To achieve the objectives of the above invention, the present invention provides a method for producing a magnetic biocarbon adsorption material, comprising the following steps. S1: A biomass mixture is mixed with an aqueous solution of carboxymethylcellulose and dried to produce a biochar precursor, the biomass mixture consisting of urban sludge, straw, and antimony ore slag. S2: After mixing the biochar precursor obtained in step S1 with the magnetic γ-Fe2O3 precursor solution, a hydrothermal reaction is carried out at 160-180°C for 15-17 hours. The product obtained from the reaction is then subjected to stepwise thermal decomposition to obtain a magnetic biochar adsorbent material. Preferably, in step S1, the mass ratio of urban sludge, straw, and antimony ore slag is (3-5):(2-4):(1-3).

[0006] Preferably, in step S2, the magnetic γ-Fe2O3 precursor solution is obtained by dissolving FeCl3·6H2O and urea in a molar ratio of 1:(1-3) in 40-60 mL of ethylene glycol.

[0007] Preferably, in step S2, the stepwise thermal decomposition treatment is carried out by maintaining the temperature at 100-200°C for 30 minutes in a nitrogen atmosphere, then maintaining the temperature at 200-300°C for 30 minutes, and finally maintaining the temperature at 300-400°C for 60 minutes.

[0008] Preferably, in step S1, the urban sludge needs to be pretreated, and the pretreatment is carried out by adding FeSO4·7H2O and H2O2 to the urban sludge to be treated, with the amount of FeSO4·7H2O added being 0.15 mol / kg and the amount of H2O2 added being 0.75 mol / kg, the pH of the solution after the addition of H2O2 being 3.0, and after the reaction for 1 hour, Ca(OH)2 is added until the pH of the solution becomes 7.0, and the obtained precipitate is dried to obtain the pretreated urban sludge.

[0009] Preferably, in step S1, the antimony ore slag needs to be pretreated, which involves crushing the antimony ore slag to be treated into particulate matter with a particle size of less than 0.5 cm, further pickling the particulate matter with an acid rinse solution of 1 M HCl, a flow rate of 2 BV / h, a liquid-to-solid ratio of 10:1, and pickling performed 3 times, followed by ball mill activation of the particulate matter after pickling using zirconium oxide balls as mill balls, with a ball / material ratio of 10:1, a rotation speed of 300 rpm, and a ball mill time of 2 hours, after which the ball mill is completed and dried at 80°C for 12 hours to obtain the pretreated antimony ore slag.

[0010] Preferably, in step S1, the mass ratio of urban sludge, straw, and antimony ore slag is 4:3:2.

[0011] Preferably, in step S2, the stepwise thermal decomposition treatment is carried out by maintaining the temperature at 100°C for 30 minutes in a nitrogen atmosphere, then maintaining the temperature at 200°C for 30 minutes, and finally maintaining the temperature at 300°C for 60 minutes.

[0012] The magnetic biocarbon adsorption material produced by the manufacturing method of the present invention is It contains biochar as a base material and magnetic nano-γ-Fe2O3 particles. The magnetic nano-γ-Fe2O3 particles are distributed within the channel structure and on the surface of the biochar, with a particle size of 200-500 nm, and the specific surface area of ​​the magnetic biochar adsorbent material is 20-80 m². 2The value is / g. The magnetic biochar adsorption material can be applied to the adsorption of Sb(V), Pb(II), and Cd(II) in wastewater.

[0013] The beneficial effects of this invention are as follows: The present invention provides a method for producing magnetic biochar adsorption materials, using three types of biomass—urban sludge, straw, and antimony ore slag—as biochar sources, and further supporting magnetic nano-γ-Fe2O3 particles. By fully utilizing the structural and compositional characteristics of these three materials, the support of magnetic nano-γ-Fe2O3 particles can be achieved. In the above process, by controlling the mass of the three materials—urban sludge, straw, and antimony ore slag—the composition and performance of the biochar substrate in the adsorption material can be adjusted, and the abundant active sites in the sludge and straw can be fully utilized to achieve loading of magnetic nano-γ-Fe2O3 particles. The microfibril structure in straw and the highly active mesoporous support in antimony ore slag can not only improve the loading rate of magnetic nano-γ-Fe2O3 particles to some extent, but are also advantageous for the diffusion and capture of heavy metal ions in the application process, and can improve the overall adsorption rate of the material to heavy metal ions.

[0014] The manufacturing method provided in the present invention enables the support of magnetic nano-γ-Fe2O3 particles on a biochar precursor by hydrothermal treatment and stepwise thermal decomposition. This avoids aggregation of nanoparticles, effectively improves the bonding strength between the γ-Fe2O3 precursor and the biochar precursor, facilitates support, ensures effective bonding between the supported particles and the biochar precursor, improves the overall stability of the material, and prevents nanoparticle detachment during application, thus avoiding material instability. [Brief explanation of the drawing]

[0015] [Figure 1] This is a process flowchart of the method for producing a magnetic biochar adsorption material according to the present invention. [Figure 2] This is an XRD diagram of the magnetic biocarbon adsorption material produced in Example 1 of the present invention. [Figure 3]FTIR diagram of the magnetic biochar adsorption material manufactured in Example 1 of the present invention. [Figure 4] BET result diagram of the magnetic biochar adsorption material manufactured in Example 1 of the present invention. [Figure 5] VSM characteristic diagram of the magnetic biochar adsorption material manufactured in Example 1 of the present invention. [Figure 6] SEM diagram of the magnetic biochar adsorption material manufactured in Example 1 of the present invention. [Figure 7] Local enlarged view of FIG. 6. [Figure 8] Results of the cyclic adsorption experiment of the magnetic biochar adsorption material manufactured in Example 1 of the present invention for Sb(V), Pb(II) and Cd(II). [Figure 9] Adsorption results for Sb(V) of the magnetic biochar adsorption material manufactured in Example 1 of the present invention in the presence of interfering ions. [Figure 10] Adsorption results for Pb(II) of the magnetic biochar adsorption material manufactured in Example 1 of the present invention in the presence of interfering ions. [Figure 11] Adsorption results for Cd(II) of the magnetic biochar adsorption material manufactured in Example 1 of the present invention in the presence of interfering ions.

Mode for Carrying Out the Invention

[0016] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the drawings and specific embodiments.

[0017] Here, it is necessary to explain that only the structures and / or processing steps closely related to the technical solution of the present invention are shown in the drawings in order to avoid obscuring the present invention with unnecessary details, and other details that are not closely related to the present invention are omitted.

[0018] Furthermore, it should be noted that the terms “include,” “incorporate,” or any other variation thereof are intended to cover non-exclusive inclusion, thereby including not only those elements but also other elements not explicitly listed, or elements specific to such process, method, article, or device.

[0019] The present invention provides a magnetic biochar adsorption material comprising a biochar base material and magnetic nano-γ-Fe2O3 particles. Magnetic nano-γ-Fe2O3 particles are distributed within and on the channel structure of the biochar, with a particle size of 200-500 nm, and the specific surface area of ​​the magnetic biochar adsorbent material is 20-80 m². 2 It is / g.

[0020] As shown in Figure 1, the present invention provides a method for producing a magnetic biochar adsorption material, comprising the following steps. S1: After pretreatment, the urban sludge, straw, and antimony ore slag are mixed, then mixed with an aqueous solution of carboxymethylcellulose, and dried to produce a biochar precursor. S2: After mixing the biochar precursor obtained in step S1 with the magnetic γ-Fe2O3 precursor solution, a hydrothermal reaction is carried out at 160-180°C for 15-17 hours. The product obtained from the reaction is then subjected to stepwise thermal decomposition to obtain a magnetic biochar adsorbent material.

[0021] In the above proposed technology, a γ-Fe2O3 precursor (iron hydroxide and related products) is synthesized by a hydrothermal reaction between FeCl3·6H2O (as a magnetic component) and urea (as an alkaline reactant), uniformly supported on a biochar precursor, and then converted into magnetic nano-γ-Fe2O3 by thermal decomposition treatment, thereby effectively ensuring uniformity and stability of the support. This method avoids aggregation of nanoparticles by directly supporting the γ-Fe2O3 precursor within the biochar precursor and then converting the precursor into magnetic nanoions. Compared to the method of directly supporting the nano-γ-Fe2O3 precursor on the biochar, the binding force between the γ-Fe2O3 precursor and the biochar precursor is stronger, making support easier to achieve, ensuring effective bonding between the supported particles and the biochar precursor, improving the overall stability of the material, and preventing nanoparticle detachment during use, which can lead to unstable material performance.

[0022] The manufacturing mechanism and applications of the magnetic biocarbon adsorption material provided in this invention are as follows. After the sludge is carbonized, activated oxygen-containing functional groups such as -COOH and -OH are exposed on the surface. This not only provides binding sites for the γ-Fe2O3 loading process, but also provides complex formation sites and electrostatic adsorption sites for the metal ions adsorbed during subsequent use. After the straw is carbonized, a microfibril channel structure develops inside, significantly improving the specific surface area and mass transfer performance. This is advantageous for the precursor solution to penetrate into the carbon precursor during the γ-Fe2O3 loading process in the manufacturing stage, and it exerts a certain concentration effect on the treated solution during use, improving the adsorption effect of the target metal ions. On the other hand, after the antimony ore slag is carbonized, a mineral skeleton containing a large amount of SiO2, Al2O3, etc. is formed inside, providing a stable support structure and mineral-based adsorption sites for the entire adsorbent material. The three types of carbon source precursors cooperate to impart a good pore structure, chemical stability, and interfacial reaction activity to the adsorbent material. During use, the three types of metal ions are adsorbed by different mechanisms. Sb(V), in anionic form, preferentially binds to the Fe-OH moiety through electrostatic adsorption and surface coordination to form an Fe-O-Sb complex structure. This structure further adjusts the surface charge and functional group arrangement, promoting the subsequent complexation and precipitation adsorption of Pb(II) and Cd(II). This achieves synergistic concentration and mutual promotion effects among the three components, ultimately significantly improving the metal ion removal rate and material usability.

[0023] In some examples, in step S1, the pretreatment of urban sludge is carried out as follows: FeSO4·7H2O and H2O2 at a mass percentage of 30% are added to the urban sludge to be treated, with a molar ratio of 1:5, the amount of FeSO4·7H2O added being 0.15 mol / kg, and the amount of H2O2 added being 0.75 mol / kg, that is, the amount of FeSO4·7H2O added per 1 kg of dry-base urban sludge is 0.15 mol, the amount of H2O2 added per 1 kg of dry-base urban sludge is 0.75 mol, the pH of the solution in the initial stage of treatment is 3.0, the reaction proceeds for 1 hour, and Fe 2+The Fenton reaction with H2O2 generates hydroxyl radicals (·OH). These strongly oxidizing ·OH disrupt the organic structure in the sludge, improving dewatering performance and decomposing toxic and harmful substances. Subsequently, Ca(OH)2 is added until the pH reaches 7.0, and the mixture is left to stand for 30 minutes to remove residual Fe 3+ The material is allowed to settle, dewatered by pressure filtration, and the moisture content of the filtration residue is kept below 65%. The filtration residue is then crushed to a particle size of 100 mesh and dried at 60°C until the moisture content is below 10% to obtain pre-treated urban sludge. Here, the conditions for the pressure filtration process are a pressure of 0.8 MPa and a time of 30 min.

[0024] Furthermore, the straw is pre-treated as follows: a combined alkaline treatment-mechanical crushing process is employed. The specific treatment steps involve placing the straw to be treated into a 1% NaOH solution, immersing it at room temperature for 12 hours in a liquid-to-solid ratio of 10:1 to remove some of the lignin and expanded fiber structure in the straw. The straw is turned over once every 3 hours during the treatment process to ensure thorough treatment. After immersion, the straw is thoroughly rinsed with deionized water until the pH of the filtrate approaches neutral (6.5-7.0), then dried and stored. After drying, the straw is cut into 5-10 cm segments to reduce energy consumption in subsequent processing. After crushing, the segments are rinsed with deionized water to avoid affecting the conductivity of the material. Next, the segments are treated until the D90 is less than 2 mm, and then vacuum-dried until the moisture content of the straw is less than 10%.

[0025] The pretreatment of antimony ore slag is carried out as follows: First, the slag is crushed into granules with a particle size of less than 0.5 cm, then the granules are pickled using a percolation column with a 1 M HCl rinse solution, a flow rate of 2 BV / h, a liquid-to-solid ratio of 10:1, and 3 pickling cycles. Next, zirconia balls with a diameter of 5 mm are used as mill balls to activate the pickled granules with a ball / material ratio of 10:1, a rotation speed of 300 rpm, and a ball milling time of 2 hours. The rotation direction is changed every 10 minutes to ensure sufficient ball milling treatment during the ball milling process. After the ball milling is complete, the granules are washed with an alkaline solution to remove the adsorbed acidic solution from the surface, and finally dried at 80°C for 12 hours to obtain the pretreated antimony ore slag. The percolation column has an inner diameter of 10 cm and a height of 50 cm, and a slag bed layer with a height of 30 cm is packed inside it.

[0026] Antimony ore slag can be selected as a source of carbon precursors to provide active mineral components and construct a functional framework. This is because antimony ore slag is rich in mineral components such as SiO2, Al2O3, and Fe2O3, which can be converted into a silica-alumina-based neutral framework with strong stability and surface reaction activity during the thermal decomposition and activation process, contributing to improved structural strength and channel stability of the material. Furthermore, trace amounts of Sb or Sb oxide species may remain in the antimony ore slag, which can participate in doping or surface coordination during the composite material construction process, adjusting the electron distribution and surface charge of the material. This enhances the electron affinity between the adsorbent and the metal ions to be removed (especially Sb(V)), improving the selective recognition ability for the target metal. Furthermore, some metal oxides in antimony ore slag, such as Fe-O, Al-O, and Sb-O, have the potential for synergistic complex formation or coprecipitation, contributing to the formation of a stable surface coordination structure during the adsorption process and enhancing the synergistic concentration and selective adsorption effects on coexisting heavy metal ions such as Sb(V), Pb(II), Cd(II), and Cd(II).

[0027] In the above proposed technology, pretreatment of urban sludge by the Fenton method exposes active sites (-COOH, -OH, etc.) in the sludge, providing more active sites for the adsorption of heavy metal ions, and improving the surface chemical properties and hydrophilicity of the material. By treating straw with an alkaline treatment method, its microfibril structure can be exposed. This structure's surface is rich in active hydroxy-OH, providing a template for supporting magnetic nanoparticles. By ball milling and pickling antimony ore slag, the iron-manganese minerals within it can be converted into a highly active mesoporous support, which is advantageous for supporting magnetic nanoparticles. When subsequently used for the adsorption of heavy metal ions, the presence of the mesoporous structure is advantageous for the diffusion and capture of heavy metal ions, improving the material's adsorption capacity to heavy metal ions.

[0028] In some embodiments, in step S1, the mass ratio of the three components—urban sludge, straw, and antimony slag—is (3-5):(2-4):(1-3). An aqueous carboxymethylcellulose solution is used as a binder, and its mass percentage in the total raw materials is 2 wt%, meaning that the ratio of the mass of the aqueous carboxymethylcellulose solution to the sum of the masses of the four components—urban sludge, straw, antimony slag, and aqueous carboxymethylcellulose solution—is 2%. The straw consists of the stems and leaves of crops such as rice, corn, and wheat.

[0029] In the above proposed technology, by adjusting the masses of urban sludge, straw, and antimony ore slag, the composition and performance of the biochar substrate in the adsorption material can be adjusted, and the abundant active sites in the sludge and straw can be fully utilized to achieve the loading of magnetic nano-γ-Fe2O3 particles. The microfibril structure in the straw and the highly active mesoporous support in the antimony ore slag can not only improve the loading of magnetic nano-γ-Fe2O3 particles to some extent, but are also advantageous for the diffusion and capture of heavy metal ions during use, and can improve the overall adsorption rate of the material to heavy metal ions.

[0030] In some embodiments, in step S2, the magnetic γ-Fe2O3 precursor solution is obtained by dissolving FeCl3·6H2O and urea in 40-60 mL of ethylene glycol in a molar ratio of 1:(1-3).

[0031] In some embodiments, the stepwise pyrolysis treatment in step S2 has the following steps: namely, the material is heated in a nitrogen gas environment at 100-200°C for 30 minutes, then at 200-300°C for 30 minutes, and finally at 300-400°C for 60 minutes.

[0032] In the above proposed technology, under conditions of 100-200°C, hemicellulose in straw can be decomposed to create a pore structure, and protein-based functional groups in sludge can be retained. Under conditions of 200-300°C, carbonization of the biochar precursor can be promoted to form a mesoporous network, and a mineral skeleton can be constructed using the silica-alumina component in the slag. Under conditions of 300-400°C, it is advantageous for the formation of an adsorption structure. By controlling the temperature and atmosphere in stages, this process can optimize the pore structure, surface chemical properties, and magnetic nanoparticle support of the biochar, thereby imparting excellent adsorption properties to the material.

[0033] The method for producing the magnetic biocarbon adsorption material according to the present invention and its use will be further described below with reference to specific examples.

[0034] Example 1 This embodiment provides a method for producing a magnetic biocarbon adsorption material, and the production method includes the following steps.

[0035] S1: Municipal sludge is mixed with FeSO4·7H2O and H2O2 at a mass percentage of 30%, with an amount of FeSO4·7H2O added of 0.15 mol / kg and an amount of H2O2 added of 0.75 mol / kg. That is, in 1 kg of dry-base municipal sludge, the amount of FeSO4·7H2O added is 0.15 mol, and in 1 kg of dry-base municipal sludge, the amount of H2O2 added is 0.75 mol. The pH of the pre-treatment solution is 3.0, Fe 2+A Fenton reaction between the iron and H2O2 generated hydroxyl radicals (·OH). These strongly oxidizing ·OH disrupted the organic structure in the sludge, improving dewatering performance and decomposing toxic substances. Subsequently, Ca(OH)2 was added to a pH of 7.0, and the remaining Fe 3+ The material was allowed to settle, dewatered by pressure filtration, and the moisture content of the filtration residue was kept below 65%. The filtration residue was crushed to a particle size of 100 mesh and dried at 60°C until the moisture content was below 10% to obtain pre-treated urban sludge. Here, the conditions for the pressure filtration process were a pressure of 0.8 MPa and a time of 30 min. The urban sludge was obtained from the wastewater treatment of the Baodaxing mining area of ​​the Hunan Tin Mine. place It originated from dewatered sludge, with total solids (TS) accounting for 35.6% and volatile solids (VS) for 52.7%.

[0036] The process employs a combined alkaline treatment-mechanical crushing process, including coarse crushing, washing, fine crushing, and drying. In the coarse crushing stage, the rice straw is cut into 5-10 cm segments to reduce energy consumption in subsequent processing. After coarse crushing, the segmented straw is washed with deionized water to avoid affecting the material's conductivity. Next, the segmented straw is processed until the D90 is less than 2 mm, and then vacuum-dried until the straw moisture content is less than 10%. The pre-treated rice straw is obtained from rice straw collected from the area surrounding the mining site, and its cellulose content was 35%, hemicellulose content was 25%, and lignin content was 20%.

[0037] First, the antimony ore slag was crushed into granules with a particle size of less than 0.5 cm, and then the granules were pickled using a percolation column. The pickling rinse solution was 1 M HCl, the flow rate was 2 BV / h, the liquid-to-solid ratio was 10:1, and the number of pickling cycles was 3. Next, zirconia balls with a diameter of 5 mm were used as milling balls to activate the pickled granules with a ball / material ratio of 10:1, the rotation speed was 300 rpm, and the ball milling time was 2 hours. To ensure sufficient ball milling treatment during the ball milling process, the rotation direction was changed every 10 minutes. After the ball milling was completed, the granules were washed with an alkaline solution to remove the acidic solution adsorbed on the surface. Finally, the granules were dried at 80°C for 12 hours to obtain the pre-treated antimony ore slag. Here, the percolation column had an inner diameter of 10 cm and a height of 50 cm, and was filled with a slag bed layer with a height of 30 cm. The antimonite slag was weathered slag from the surface of the slag yard in the Baodaxing section of the Hunan Tin Mine, with a particle size of 1-5 cm, and its main minerals were 45% quartz, 30% calcite, 15% limonite, and the remainder being impurities.

[0038] After pretreatment, urban sludge, rice straw, and antimony ore slag were mixed in a mass ratio of 4:3:2. This mixture was then mixed with 1.8 mL of carboxymethylcellulose aqueous solution. The resulting mixture was kneaded in a kneader for 30 minutes to form a plastic material. A cylindrical body measuring Φ20 × 10 mm was then produced by pressing it at a pressure of 20 MPa using a hydraulic press. The material was cured at room temperature for 12 hours to dry and produce a biochar precursor. The mass percentage of the carboxymethylcellulose aqueous solution in the mixture was 2 wt%.

[0039] S2: After mixing the biochar precursor obtained in step S1 with the magnetic γ-Fe₂O₃ precursor solution, a hydrothermal reaction is carried out at 170 °C for 16 h. The product obtained by the reaction is collected, washed 3 - 5 times each with ethanol and deionized water, dried in an environment of 60 °C, and then the sample is placed in a three-stage tubular furnace, kept warm at T1 = 100 °C for 30 min, further kept warm at T2 = 200 °C for 30 min, and then continuously kept warm at T3 = 300 °C for 60 min. By performing a stepwise pyrolysis treatment on the sample, a magnetic biochar adsorbent material is manufactured. The whole process of the pyrolysis treatment is carried out in a nitrogen gas environment, and the gas flow rate is 200 mL / min. Here, the magnetic γ-Fe₂O₃ precursor solution is obtained by adding FeCl₃·6H₂O and urea to 50 mL of ethylene glycol (analytical purity), and the molar ratio of FeCl₃·6H₂O to urea is 1:2.

[0040] As shown in Figure 2, when comparing the XRD pattern of the magnetic biochar adsorbent material with the XRD standard card of γ-Fe₂O₃, it can be seen that the diffraction peaks of the adsorbent material mainly include the characteristic peaks of γ-Fe₂O₃ (2θ = 35.7°, 57.3°, 62.9°, etc.) and the broad peaks of biochar, indicating that γ-Fe₂O₃ is supported on the biochar. Regarding the FTIR pattern of the adsorbent, as shown in Figure 3, in the figure, at 3385.54 cm -1 and 1150.83 cm -1 the characteristic absorption peaks of the hydroxyl group (-OH) and carboxyl group (-COOH) derived from biochar appear respectively. Regarding the BET result diagram of the adsorbent material, as shown in Figure 4, as a result, the adsorbent material has a multi-stage structure of micropore - mesopore - macropore, and mainly consists of mesopores (pore diameter 2 - 10 nm). The calculated result shows that the specific surface area of the adsorbent material is 60.808 m 2The value was / g. As shown in Figure 5, the VSM characterization diagram of the adsorbent material shows that the adsorbent material exhibits typical superparamagnetism, can aggregate when approached by a magnetic material, and has excellent magnetic recovery performance. A SEM diagram of the adsorbent material is shown in Figure 6. A local magnified view of the area circled in red in Figure 6 is shown in Figure 7. As can be seen from Figure 7, some wrinkles are formed on the surface of the material, and a high specific surface area support region is formed between two adjacent wrinkles, and nano-sized spherical γ-Fe2O3 particles are supported in this region.

[0041] Furthermore, this embodiment further investigated the use of magnetic biochar adsorbent material in heavy metal adsorption. The specific test method involved adjusting the pH of a 50 mL Sb(V), Pb(II), and Cd(II) composite contamination solution with an initial concentration of 20 mg / L to pH 5. 200 mg of magnetic biochar adsorbent material was added to the solution, and the mixture was shaken at 150 rpm for 240 mins at 25°C. 10 mL samples were taken every 30 mins, filtered using a 0.45 μm filtration membrane, and the residual concentrations of Sb(V), Pb(II), and Cd(II) in the solution were measured. Calculations showed that under the above conditions, the adsorption rates of the adsorbent material for Sb(V), Pb(II), and Cd(II) were 91.25%, 82.76%, and 85.63%, respectively. The XRD and FTIR diagrams of the adsorbent material after adsorption saturation are shown in Figures 2 and 3, respectively. Comparing the XRD diagrams of the adsorbent material before and after adsorption in Figure 2, the characteristic diffraction peak positions of both materials are almost identical, and there is no clear change in the peaks, indicating that the adsorbent material has excellent stability. Comparing the FTIR diagrams of the adsorbent material before and after adsorption in Figure 3, after adsorption, at 1200-1500 cm⁻¹ -1 The characteristic peaks of the material were relatively flattened by tensile vibration. This is because the C=C and C=O double bonds are broken, Fe can coordinate via oxygen bonds, forming Fe-O and Fe-O-Cl active sites, which can better bind to biochar and act on target metal ions, and are related to the formation of complexes of Sb(V), Pb(II), and Cd(II).

[0042] After the adsorption saturates, the adsorbent material is removed, eluted with a 0.1 mol / L NaOH solution, washed by repeated centrifugation until the supernatant becomes neutral, dried at 60°C, and reused. Figure 8 shows the results of the cyclic adsorption experiment on Sb(V), Pb(II), and Cd(II) of the adsorbent material. As a result, in the fifth cyclic experiment, the adsorption rate of the adsorbent material for Sb(V), Pb(II), and Cd(II) still exceeded 65%, indicating that the adsorbent material produced in this example has excellent adsorption capacity for Sb(V), Pb(II), and Cd(II).

[0043] In particular, this embodiment further investigated the adsorption capacity of adsorbents for target ions in complex aqueous solutions containing various interfering ions. During the test, the adsorbents were used to adsorb Na + Ca 2+ Mg 2+ Cl - CO 2- , PO 3- Figure 9 shows the adsorption results for Sb(V), Pb(II), and Cd(II) in a heavy metal wastewater solution containing PO4, Figure 10 shows the adsorption results for Pb(II), and Figure 11 shows the adsorption results for Cd(II). As a result, PO4 3- Although the influence on the adsorption process is greatest, in the presence of high concentrations of interfering ions, the adsorption rates of the adsorbent material for Sb(V), Pb(II), and Cd(II) are all maintained at 70% or higher, indicating that the adsorbent material possesses excellent anti-interference capabilities and synergistic adsorption capabilities for Sb(V), Pb(II), and Cd(II).

[0044] Examples 2-5 Examples 2-5 are the same as Example 1 except that the mass ratio of urban sludge, rice straw, and antimony ore slag in the biochar precursor in step S1 is different from Example 1, so their explanation is omitted here.

[0045] Table 1 shows the mass ratios of urban sludge, straw, and antimony ore slag in the biochar precursors of Examples 1-5, and the adsorption performance of the adsorbent materials produced under the corresponding conditions. As can be seen from the analysis of the data in the table, the adsorption capacity of the adsorbent materials for Sb(V), Pb(II), and Cd(II) is related to the ratio of the three carbon sources in the biochar precursor. This is because the three carbon sources exert different effects during the adsorption process, and the surface of the sludge after carbonization is rich in oxygen-containing functional groups such as -COOH and -OH, which can provide abundant complex formation and electrostatic adsorption sites for metal ions. The unique wrinkled structure formed after straw carbonization significantly improves the mass transfer rate of metal ions, which is advantageous for promoting the metal ion adsorption process. After carbonization of antimony ore slag, Fe / Mn adsorption auxiliary sites in the skeleton are exposed, not only providing a stable support for γ-Fe2O3 nanoparticles but also having a selective complex formation effect for Sb(V). If the proportions of the three carbon sources are too high or too low, the synergistic effect between the three cannot be maximized, and the adsorption rate decreases. In other words, efficient synergistic adsorption performance for the three metal ions can only be achieved simultaneously when the three carbon sources are mixed in specific proportions.

[0046] Table 1: Mass ratios of urban sludge, straw, and antimony ore slag in biochar precursors of Examples 1-5 and adsorption performance of adsorbent materials produced under corresponding conditions [Table 1]

[0047] Examples 6-7 Examples 6-7 are the same as Example 1 in all other experimental parameters, except that the molar ratio of FeCl3·6H2O to urea in the magnetic γ-Fe2O3 precursor solution in step S2 is different from that of Example 1. Therefore, a detailed explanation is omitted here.

[0048] Table 2 shows the molar ratio of FeCl3·6H2O to urea and the adsorption performance of the adsorbent material produced under the corresponding conditions in Examples 1 and 6-7. As can be seen from the results, the adsorption capacity of the adsorbent material gradually improves with increasing molar ratio of FeCl3·6H2O to urea, but if the loading amount is too high, the improvement in adsorption efficiency tends to slow down. This is because, in the hydrothermal reaction, FeCl3·6H2O undergoes hydrolysis to form Fe(OH)3, which is then further oxidized to produce a γ-Fe2O3 precursor, and the reaction equation for the reaction process is as follows. FeCl3+3NH3·H2O→Fe(OH)3↓+3NH4Cl 2Fe(OH)3 → γ-Fe2O3 precursor + 3H2O In the subsequent thermal decomposition process, magnetic nano-γ-Fe2O3 particles are formed, and the specific reaction equation is γ-Fe2O3 precursor → magnetic nano-γ-Fe2O3. The molar ratio of FeCl3·6H2O to urea directly affects the number, size, and distribution of the final γ-Fe2O3 precursors, and if the urea concentration is too low, Fe 3+ Insufficient hydrolysis of ions may result in incomplete or large particle formation of the γ-Fe2O3 precursor, which is unfavorable for the adsorption reaction. If the concentration is too high, it is likely to cause aggregation of nanoparticles, which may further affect the performance of magnetic nano-γ-Fe2O3 adsorption.

[0049] Table 2: Molar ratio of FeCl3·6H2O to urea in Examples 1 and 6 to 7 and adsorption performance of adsorbent materials produced under the corresponding conditions [Table 2]

[0050] Examples 8-10 Examples 8-10 are the same as Example 1 except for the temperature settings for the three stages during the stepwise pyrolysis process in step S2; therefore, their explanation is omitted here.

[0051] Table 3 shows the temperature settings for the stepwise pyrolysis treatment in Examples 1 and 8-10, and the adsorption performance of the adsorbent materials produced under the corresponding conditions. As can be seen from the analysis of the data in the table, the adsorption performance of the adsorbent material produced under the conditions of Example 1 is optimal. This is because pyrolysis treatment at a specific temperature allows for the formation of a unique pore structure (multi-stage structure of micropores-mesopores-macropores) in the material. Pore structures of different scales provide abundant adsorption sites and ensure smooth flow of ion transport channels, resulting in the highest adsorption efficiency. If the temperature of the pyrolysis treatment process is too high and the span is too large, carbon precursors are prone to collapse or fusion, making it impossible to form a pore structure and adsorption area favorable for metal ion adsorption.

[0052] Table 3: Temperature settings for stepwise pyrolysis treatment in Examples 1 and 8-10 and adsorption performance of adsorbent materials produced under corresponding conditions [Table 3]

[0053] Comparative Example 1 Comparative Example 1 differs in the carbon source composition of the biochar precursor in step S1. Specifically, the biochar precursor is produced using pre-treated urban sludge and rice straw, with a mass ratio of sludge to straw of 4.74:3.19. The sum of the masses of the two is the same as the sum of the masses of urban sludge, rice straw, and antimony ore slag in Example 1. Other experimental parameters are the same as in Example 1, so a detailed explanation is omitted here.

[0054] Comparative Example 2 Comparative Example 2 differs in the carbon source composition of the biochar precursor in step S1. Specifically, the biochar precursor is produced using pre-treated urban sludge and antimony ore slag, with a mass ratio of 3.19:2.24 between urban sludge and antimony ore slag. The sum of the masses of the two is the same as the sum of the masses of urban sludge, rice straw, and antimony ore slag in Example 1. Other experimental parameters are the same as in Example 1, so a detailed explanation is omitted here.

[0055] Table 4 shows the adsorption effects of the adsorbents produced in Example 1 and Comparative Examples 1-2. As a result, the adsorption effect of Example 1 is far higher than that of Comparative Examples 1-2. This is because, although the adsorbent produced using sludge and straw in Comparative Example 1 has a certain adsorption capacity, its surface activity is low and its pore structure is not sufficiently optimized, resulting in a relatively weak removal effect on heavy metal ions.

[0056] The main reason why the adsorption effect of Example 1 is significantly superior to that of Comparative Examples 1 and 2 is that the material obtained after optimizing the blending ratio of its composite carbon source has a richer pore structure and a larger specific surface area. Specifically, in Example 1, the carbon-based precursor constructed by the cooperation of urban sludge, rice straw, and antimony ore slag forms an excellent porous structure during the thermal decomposition process, resulting in many wrinkles on the material surface, a uniform pore distribution, a higher specific surface area, and more complex three-dimensional adsorption channels. This allows heavy metal ions to obtain more active sites when they come into contact with the material surface, enabling rapid and efficient concentration. In contrast, in Comparative Example 1, the mineral template effect of antimony ore slag is poor, resulting in a single pore structure, a relatively flat surface, and limited ion adsorption channels and diffusion efficiency. In Comparative Example 2, the microfibril structure of the straw is not introduced, resulting in a dense overall material structure, reduced wrinkles, and a low specific surface area, which is unfavorable for the entry and sufficient adsorption of metal ions. Therefore, the material produced in Example 1 exhibits more wrinkles, a higher specific surface area, and a superior channel system in its microstructure, which is considered to be the reason why its adsorption performance is clearly superior to that of Comparative Examples 1 and 2.

[0057] Table 4: Adsorption effect of adsorbent materials obtained in Example 1 and Comparative Examples 1-2 [Table 4]

[0058] The above embodiments are merely for illustrative purposes and not limiting purposes. While the invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the proposed invention without departing from the spirit and scope of the proposed invention.

Claims

1. A method for producing a magnetic biocarbon adsorption material, comprising the following steps S1 and S2, S1: A biomass mixture is mixed with an aqueous solution of carboxymethylcellulose and dried to produce a biochar precursor. The biomass mixture consists of dewatered sludge from a wastewater treatment plant, straw, and antimony ore slag, and the mass ratio of the three is 4:3:

2. S2: The biochar precursor obtained in step S1 and magnetic γ-Fe ２ O ３ After mixing with the precursor solution, a hydrothermal reaction is carried out at 160-180°C for 15-17 hours. The product obtained from the reaction is then subjected to stepwise thermal decomposition to obtain a magnetic biocarbon adsorbent material. The magnetic γ-Fe ２ O ３ The precursor solution is FeCl ３ 6H ２ The product is obtained by dissolving oxygen and urea in a molar ratio of 1:(1-3) in 40-60 mL of ethylene glycol, and the manufacturing method is characterized in that the stepwise thermal decomposition treatment is carried out in a nitrogen gas environment by maintaining the temperature at 100°C for 30 min, then at 200°C for 30 min, and finally at 300°C for 60 min.

2. In step S1, it is necessary to pretreat the dewatered sludge, and the pretreatment is to add FeSO ４ ·7H ２ O and H ２ O ２ to the dewatered sludge to be treated. The addition amount of FeSO ４ ·7H ２ O is 0.15 mol / kg, and the addition amount of H ２ O ２ is 0.75 mol / kg. The pH of the solution after adding H ２ O ２ is 3.

0. After reacting for 1 h, Ca(OH) ２ is added until the pH of the solution reaches 7.

0. After drying the obtained precipitate, the pretreated dewatered sludge is obtained. The manufacturing method according to claim 1 is characterized in that it is carried out in this way.

3. The manufacturing method according to claim 1, characterized in that in step S1, the antimony ore slag needs to be pretreated, the pretreatment is performed by crushing the antimony ore slag to be treated into particulate matter with a particle size of less than 0.5 cm, further pickling the particulate matter with an acid rinse solution of 1 M HCl, a flow rate of 2 BV / h, a liquid-to-solid ratio of 10:1, and pickling three times, then ball milling the particulate matter after pickling using zirconium oxide balls as mill balls, with a ball / material ratio of 10:1, a rotation speed of 300 rpm, a ball milling time of 2 hours, and after the completion of ball milling, drying at 80°C for 12 hours to obtain the pretreated antimony ore slag.

4. Use of a magnetic biocarbon adsorbent material produced by the manufacturing method described in any one of claims 1 to 3 for the adsorption of Sb(V), Pb(II), and Cd(II) in wastewater.

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