A magnesium slag tailing composite biochar adsorption material and a preparation method and application thereof

Abstract

The application belongs to the technical field of solid waste resource and water treatment, and particularly relates to a magnesium slag composite biochar adsorption material for treating composite pollution in aquaculture wastewater and a preparation method and application thereof. The adsorption material is composed of the following components: waste leather scrap source biochar and magnesium slag tailings; the material has rich metal groups and porous structure, the pore size distribution is 2-50 nm, and the specific surface area is greater than or equal to 50 m 2 / g. The preparation method comprises the following steps: after WD is impregnated with magnesium-calcium salt, first limited oxygen calcination is performed to obtain MCBC, then MCBC is mixed with IT and ball milling is performed, and second limited oxygen calcination is performed to obtain the magnesium slag composite biochar adsorption material MBMS, which is used for removing Cu 2+ and MB composite pollution in aquaculture wastewater. The target product of the application has high adsorption capacity, good mechanical stability and excellent electron transfer capacity, and can solve the problems of low adsorption capacity and poor selectivity of traditional adsorption materials in composite pollution water body repair.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and water treatment technology, specifically relating to a magnesium slag tailings composite biochar adsorbent material for the treatment of combined pollution of aquaculture wastewater, its preparation method and application. Background Technology

[0002] Recirculating aquaculture systems (RAS) suffer from increasingly severe problems of pollutant accumulation in aquaculture wastewater due to their intensive production model. Heavy metals and organic dyes, commonly used as bactericides and therapeutic agents respectively, form typical compound pollutants in aquaculture water. The synergistic treatment of these compound pollutants has become a critical challenge urgently needing to be addressed in the field of fisheries environmental remediation. Currently, the recovery technology for low-concentration heavy metal-organic compound pollution in seawater mainly relies on adsorption methods, with the core being the development of high-performance adsorption materials. However, traditional adsorption materials such as activated carbon, ion exchange resins, and ordinary biochar generally suffer from problems such as low adsorption capacity, poor selectivity, competitive adsorption of compound pollutants, poor structural stability, and limited electron transfer capacity. Under long-term immersion in water or complex water quality conditions, these materials are prone to structural collapse and active site failure, leading to a decline in adsorption performance.

[0003] Metal oxide loading strategies can partially enhance the active site density and electron transfer capacity of adsorbent materials. Magnesia slag tailings (IT), a solid waste from the magnesium smelting industry, are rich in elements such as Ca, Mg, and Si. After appropriate treatment, its metal oxide components can form covalent bonds (metal-OC) with biochar, enhancing structural stability and promoting electron transfer. However, magnesia slag tailings, when used alone, suffer from low specific surface area and insufficient exposure of active sites. Waste skin (WD) biochar, with its collagen fiber-derived three-dimensional helical structure, can accumulate abundant oxygen- and nitrogen-containing functional groups at relatively low pyrolysis temperatures, exhibiting high adsorption potential. However, WD biochar easily releases SO2 and leaches SO4 during high-temperature treatment. 2- This leads to secondary pollution. Currently, there are no reports of combining magnesium slag tailings with waste biochar through ball milling-pyrolysis to achieve efficient synergistic treatment of composite pollution. Furthermore, existing composite systems mostly simply superimpose adsorption functions without utilizing the electronic structure of the material surface to achieve an integrated mechanism of preferential adsorption, electrostatic control, and synergistic effect, resulting in the treatment efficiency and selectivity of composite pollutants still needing improvement. Therefore, how to construct a highly stable, high-defect-density hierarchical porous network to achieve preferential response and electrostatic control, thereby solving the problems of unstable structure, uneven dispersion of functional components, and easy generation of secondary pollution in traditional adsorption materials, remains a pressing challenge in the industry. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide a magnesium slag tailings composite biochar adsorbent material and its preparation method, which has high adsorption capacity of target products, good mechanical stability, excellent electron transfer ability, and obvious synergistic effect. It can solve the problems of low adsorption capacity, poor selectivity, competitive adsorption and easy structural collapse of traditional adsorbent materials in the remediation of complex polluted water bodies.

[0005] The present invention also provides an application of the above-mentioned magnesium slag composite biochar adsorbent material in the treatment of complex pollution in aquaculture wastewater.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing a magnesium slag tailings composite biochar adsorbent material, comprising the following steps:

[0008] (1) After cleaning and drying the waste leather scraps, place them in a container containing Mg 2+ and Ca 2+ The mixture was impregnated in a mixed salt solution and subjected to a first oxygen-limited calcination to obtain magnesium-calcium modified biochar. In the first oxygen-limited calcination, MgO and CaO nanoparticles were generated in situ, and MgSO4 was generated by the reaction of MgO with SO2 released by the thermal decomposition of waste skin, thus achieving in-situ sulfur fixation.

[0009] (2) The magnesium-calcium modified biochar obtained in step (1) is mixed with magnesium slag tailings, ball milled, and then subjected to a second oxygen-limited calcination to obtain the target product, magnesium slag tailings composite biochar adsorbent material (MBMS). The second oxygen-limited calcination causes the active functional groups on the surface of the magnesium-calcium modified biochar to undergo a dehydration condensation reaction with CaO / MgO in the magnesium slag tailings to form CO-Ca and CO-Mg covalent bonds.

[0010] Furthermore, the obtained magnesium slag tailings composite biochar adsorbent material has a porous structure with metallic groups, a pore size distribution of 2–50 nm, and a specific surface area ≥50 m². 2 / g, total pore volume ≥0.02cm³ 3 / g, Raman spectrum I D / I G The ratio is ≥1.2.

[0011] Further, in step (1), the Mg-containing 2+ and Ca 2+ The mixed salt solution is a 0.5–2 mol / L mixture of MgCl2·6H2O and CaCl2, and the immersion time is 12–24 h; the first or second oxygen-limited calcination conditions are: calcination temperature of 400–600℃, heating rate of 3–10℃ / min, and holding time of 1–4 h.

[0012] Further, in step (2), the mixing mass ratio of the magnesium-calcium modified biochar and magnesium slag tailings is 1:1 to 5; the ball milling time is 2 to 8 hours and the rotation speed is 200 to 600 rpm.

[0013] Furthermore, the waste leather biochar originates from at least one of leather scraps, shaved cowhide shavings, or trimming waste; the main component of the metal oxides in the magnesium slag tailings is calcium oxide.

[0014] Secondly, the present invention also provides a magnesium slag tailings composite biochar adsorbent material prepared by the above-mentioned method for preparing magnesium slag tailings composite biochar adsorbent material.

[0015] Thirdly, the present invention also provides an application of the above-mentioned magnesium slag tailings composite biochar adsorbent material in water treatment, which synergistically treats composite polluted water containing heavy metal ions and organic dyes through the π-π stacking, electrostatic attraction, surface complexation and metal oxide-mediated electron transfer of the adsorbent material.

[0016] Furthermore, the heavy metal ion is Cu. 2+ Cr 6+ Ni 2+ The organic dye is one or more of the following: methylene blue, methyl orange, and Sudan red.

[0017] This invention is the first to introduce magnesium slag tailings (IT) with electron transfer capabilities into a waste leather (WD) biochar system. Through impregnation, calcination, ball milling, and recalcination processes, uniform molecular-level loading and stable interfacial bonding are achieved. The carboxyl and amino groups on the collagen fibers of the waste leather (WD) bind magnesium slag tailings to the Mg2+ through electrostatic attraction and coordination. 2+ and Ca 2+ Uniform anchoring at the molecular level. This lays the foundation for subsequent generation of nano-metal oxides and in-situ sulfur fixation.

[0018] In the first calcination, the impregnated and dried waste skin (WD) was placed in a muffle furnace and heated to 300–600 °C at a rate of 3–10 °C / min, and pyrolyzed for 1–4 hours under oxygen-limited conditions. This process involves two key reactions: collagen carbonization and metal salt thermal decomposition. From a carbonization perspective, the three-dimensional helical structure of collagen fibers undergoes pyrolysis at high temperatures, with carbon atoms reassembling to form an amorphous carbon skeleton. Simultaneously, small molecule gases such as H₂O, CO₂, and NH₃ escape, generating abundant micropores and mesopores in situ. BET results show that the specific surface area of ​​the original BC is only 19.38 m². 2 / g, while the MCBC obtained after Mg / Ca impregnation and calcination has a specific surface area increased to 22.76m². 2 / g, and the pore volume also increased significantly. From the perspective of metal salt thermal decomposition, MgCl2·6H2O and CaCl2 first lose their water of crystallization during pyrolysis, and then undergo thermal decomposition to generate MgO and CaO nanoparticles. These nanoparticles are uniformly loaded on the surface of the biochar framework and the inner walls of the pores. In addition, MgO and CaO can undergo a slight etching reaction with carbon at high temperatures, further increasing porosity and specific surface area. At the same time, these oxide nanoparticles act as nanopillars, preventing excessive shrinkage and collapse of the carbon framework at high temperatures and maintaining the stability of the porous structure. MgO / CaO is strongly alkaline and can react chemically with SO2 released during thermal decomposition (MgO + SO2 + 1 / 2O2 → MgSO4). XPS detected the characteristic peak of MgSO4 in MBMS, confirming the effectiveness of this in-situ sulfur fixation mechanism and fundamentally eliminating the secondary pollution risk of SO2 release during WD pyrolysis.

[0019] In the ball milling stage, the magnesium-calcium modified biochar (MCBC) obtained from the first calcination is mixed with magnesium slag tailings (IT) at a mass ratio of 1:1 to 5 and placed in a planetary ball mill at 200 to 600 rpm for 2 to 8 hours. The ball milling process is a typical method of using mechanical energy to drive chemical reactions, and its effect is far greater than that of simple physical mixing. Specifically, it is manifested in the following aspects: (1) Strong dispersion and homogenization: The shear force and impact force generated by high-energy ball milling enable the two powders, MCBC and IT, to achieve uniform distribution at both the macroscopic and microscopic scales. (2) Surface activation and destruction of inert layer: After the first calcination, an inert and dense carbon layer will form on the surface of MCBC. The mechanical force of ball milling can peel off or thin this inert layer, exposing fresh active sites inside (such as -OH, -COOH, C=C, etc.), while also grinding and refining the large metal oxide particles (CaO, MgO) in IT, thus greatly increasing its specific surface area. (3) Mechanochemical bonding: Under the high-energy impact of ball milling, the active functional groups on the MCBC surface may undergo mechanochemical-induced chemisorption or partial bonding with the metal oxide particles in IT, providing favorable kinetic conditions for the formation of stable covalent bonds (COM) in the subsequent second calcination. (4) Introduction of structural defects: The ball milling process also introduces a large number of structural defects into the carbon skeleton. These defect sites are manifested as a significant increase in the intensity of the D peak in the Raman spectrum. The experimentally measured I of MBMS D / I G The ratio increased further from 1.08 in MCBC to 1.24, which is much higher than the original BC, proving that ball milling significantly increases the defect density of the carbon skeleton. Since defect sites usually have higher reactivity and adsorption affinity, they are key active centers for adsorbing pollutants.

[0020] During the second calcination process, the ball-milled MCBC / IT mixture was placed in a muffle furnace again and heated to 300-600℃ at a rate of 3-10℃ / min, and pyrolyzed for 1-4 hours under oxygen-limited conditions. This is a key step in achieving the final high performance of the material. Its main mechanisms are as follows: (1) Formation of COM covalent bonds. At high temperatures, -OH and -COOH on the surface of the MCBC carbon skeleton undergo dehydration condensation reactions with CaO and MgO in IT to form CO-Ca and CO-Mg covalent bonds. (2) Further defectification of the carbon skeleton. During the second calcination process, the formation of COM bonds will locally extract electrons from the carbon skeleton, resulting in a redistribution of the electron cloud density around the carbon atoms, which is conducive to the formation of more carbon defects (such as five-membered rings, seven-membered rings, edge unsaturated carbon, etc.). At the same time, the catalytic effect of metal oxides will also promote the disordering of carbon, and the I in the Raman spectrum D / I G The further increase in the ratio is a direct manifestation of this process. (3) Redispersion and stable anchoring of metal oxides. During the second calcination process, the agglomerated metal oxide particles that may still exist after ball milling will further melt and recrystallize, and anchor to the defect sites of the carbon skeleton through covalent bonds, achieving atomic-level dispersion stability, effectively avoiding the shedding and leaching of metal oxides during application.

[0021] The application of the magnesium slag tailings composite biochar adsorbent material prepared in this invention includes: directly adding the powdered or granular MBMS obtained by the above method to aquaculture wastewater, and stirring and adsorbing for 30 to 180 minutes under the conditions of pH 4-8, temperature 20-40℃, and dosage 0.2-1.2 g / L. The treated material can be recovered by sedimentation or filtration. Furthermore, during the material preparation process, the mixing ratio of waste scales and magnesium slag tailings, ball milling time, calcination temperature, and holding time should be optimized and adjusted according to the actual wastewater quality characteristics, pollutant concentration, and treatment requirements to ensure that the adsorption performance and economic efficiency of the material reach the ideal state.

[0022] Compared with the prior art, the present invention brings the following beneficial effects:

[0023] (1) The method of the present invention addresses the need for synergistic treatment of complex pollutants in aquaculture wastewater. It integrates three core advantages: porous adsorption, electrostatic regulation, and electron transfer. Through the mechanism of "priority response-electrostatic regulation-synergistic adsorption", it solves the pain points of traditional materials such as "competitive adsorption, poor selectivity, unstable structure, and limited electron transfer". It has significant technical advantages and diverse scenario requirements.

[0024] (2) The technology and materials provided by this invention can achieve efficient synergistic removal of compound pollution. Under optimal conditions, compared with single-component BC and MCBC without IT, MBMS in the binary system increases the removal rate of heavy metals by about 29 percentage points and 7 percentage points, respectively, and the removal rate of organic dyes by about 18 percentage points and 2 percentage points, respectively, which confirms the significant synergistic effect of magnesium slag composite and ball milling-pyrolysis process.

[0025] (3) During the material preparation process, through Mg 2+ / Ca 2+ A pre-impregnation, ball milling-secondary calcination process successfully constructed a high specific surface area (55.79 m²) precipitate. 2 / g), high defect density (I D / I G =1.24) and a hierarchical porous structure. The strong interfacial bonding formed by CO-Mg / CO-Ca covalent bonds gives the material excellent stability. After 6 adsorption-desorption cycles, the removal rates of composite pollutants remained at 92.3% and 89.7%, respectively. The material has good compressive strength, solving the problems of easy pulverization and easy gel collapse of traditional biochar.

[0026] (4) The material provided by this invention has an adsorption capacity of 99.04 mg / g for heavy metals and 340.76 mg / g for organic pollutants, with an adsorption equilibrium time of only 120 min. Its comprehensive performance is superior to many similar adsorption materials recently reported. The preparation process does not require high temperature and high pressure. Ball milling and calcination are mature industrial technologies, which can be mass-produced through continuous equipment. The preparation cost is reduced by 30-40% compared with existing metal oxide modified biochar, providing core support for technology transformation. Attached Figure Description

[0027] Figure 1 These are scanning electron microscope images of the three materials BC, MCBC, and MBMS of this invention.

[0028] Figure 2 This is a pore size distribution diagram of the three materials BC, MCBC, and MBMS of this invention.

[0029] Figure 3 The N2- adsorption-desorption curves of the three materials BC, MCBC, and MBMS of this invention are shown.

[0030] Figure 4 These are Raman images of the three materials BC, MCBC, and MBMS used in this invention.

[0031] Figure 5 The diagram shows the adsorption performance of the three materials BC, MCBC, and MBMS of this invention.

[0032] Figure 6This is a diagram illustrating the recycling performance of the MBMS of this invention.

[0033] Figure 7 This is the fine XPS spectrum of C 1s in the MBMS of this invention.

[0034] Figure 8 Materials for examples and comparative embodiments of the present invention, specifically Cu. 2+ The performance graph for removing MB.

[0035] Figure 9 This is a thermogravimetric-mass spectrometry (TGA) chromatogram of the WD of this invention.

[0036] Figure 10 This is a thermogravimetric-mass spectrometry (TGA) chromatogram of MBMS in this invention. Detailed Implementation

[0037] The present invention will now be described in detail through specific embodiments. These embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended and are interpreted as "comprising but not limited to". The following description is a preferred embodiment for carrying out the invention; however, this description is intended to illustrate the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the invention is determined by the appended claims. Unless otherwise specified, all reagents and materials used in the present invention are commercially available.

[0038] All raw materials used in this invention are designated as conventional in the field, and each designation and abbreviation is clearly defined within its relevant application. Those skilled in the art can obtain them from commercially available sources or prepare them using conventional methods based on the designation, abbreviation, and corresponding application. There are no particular limitations on the purity of any raw materials used in this invention; however, industrial purity or conventional purity used in composite material preparation techniques is preferred. All processes used in this invention are abbreviations commonly used in the field, and each abbreviation is clearly defined within its relevant application. Those skilled in the art can understand the conventional process steps based on the abbreviation. In this invention and its embodiments, the percentages involved in each step and the percentages of each chemical used are based on the mass of the hide or biochar used in the process. The embodiments of this invention are only used to more clearly illustrate the technical solutions of this patent and are therefore only examples, not intended to limit the scope of protection of this patent. It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which this patent pertains. In the process described in this invention, the range of values ​​for each parameter (such as temperature, time, etc.) can be appropriately adjusted according to actual production needs and material types. The adjustment method is a conventional technical means for those skilled in the art.

[0039] This invention relates to a magnesium slag tailings composite biochar adsorbent material, which is synthesized from waste skin (WD) biochar and magnesium slag tailings (IT) through impregnation, calcination, ball milling, and recalcination processes. It achieves highly efficient removal of complex pollutants through the synergistic effects of π-π stacking, electrostatic attraction, and surface complexation. The porous adsorbent material consists of a magnesium-calcium modified biochar framework and magnesium slag tailings-derived metal oxides loaded therein; the composite framework is WD-derived porous biochar, and the functional components are CaO, MgO, and a CO-Mg / CO-Ca covalent bond interface structure. The highly active functional groups derived from the three-dimensional helical structure of WD, the electron transfer channels provided by the metal oxides of IT, and the enhanced structural stability through interfacial covalent bonds achieve highly efficient capture of complex pollutants.

[0040] The preparation method of the magnesium slag tailings composite biochar adsorbent material specifically includes the following steps:

[0041] (1) Preparation of magnesium-calcium modified biochar (MCBC): Waste leather scraps (WD) were cut into small pieces of 2-4 mm, stirred in deionized water at room temperature for 1-4 h, washed until neutral, and dried at 60-80 °C for 8-24 h. 30 g of dried WD was placed in a mixed salt solution of 200 mL of 0.5-2 mol / L MgCl2·6H2O and 100 mL of 0.5-2 mol / L CaCl2, and impregnated at room temperature for 12-24 h, and dried at 80 °C for 12 h. The impregnated WD was placed in a muffle furnace and heated to 400-600 °C at a rate of 3-10 °C / min, and pyrolyzed under oxygen-limited conditions for 1-4 h to obtain MCBC.

[0042] (2) Preparation of magnesium slag composite biochar adsorbent material (MBMS): 1-5g of MCBC was mixed with 5-15g of magnesium slag tailings (IT, mainly containing CaO, MgO, and SiO2) and placed in a planetary ball mill. The mixture was ball-milled at 200-600 rpm for 1-4 hours. The ball-milled mixture was then placed in a muffle furnace and heated to 400-600℃ at 3-10℃ / min. The mixture was then pyrolyzed under oxygen-limited conditions for 1-4 hours to obtain MBMS.

[0043] Example 1:

[0044] A magnesium slag composite biochar adsorbent material (MBMS) and its application in the treatment of complex pollutants includes the following steps:

[0045] (1) Preparation of MCBC: 30g of cut WD (2-4 mm) was stirred in deionized water for 2h, washed and dried, and then immersed in a mixed salt solution of 1mol / L MgCl2·6H2O (200 mL) and CaCl2 (100 mL) for 12h, and dried. The solution was then heated to 500℃ in a muffle furnace at 5℃ / min and subjected to oxygen-limited pyrolysis for 2h to obtain MCBC.

[0046] (2) MBMS preparation: 5g MCBC and 15g IT were mixed and ball-milled at 400rpm for 4h. The mixture after ball milling was then heated to 500℃ at 5℃ / min in a muffle furnace and pyrolyzed under limited oxygen conditions for 2h to obtain MBMS.

[0047] (3) Adsorption application: Preparation of Cu-containing... 2+ Simulated wastewater containing a combination of 10 mg / L HCl and 10 mg / L MB was used. The pH was adjusted to 6.0 with 0.1 mol / L HCl / NaOH, and 0.8 g / L MBMS was added. Adsorption was carried out at 30℃ and 150 rpm for 180 min under constant temperature shaking. The residual concentration was measured after centrifugation and filtration.

[0048] (4) Recycling and resource utilization: The adsorbed MBMS was desorbed with 1 mol / L HNO3 for 1 h, washed with deionized water until neutral, and dried for the next adsorption. The inactivated MBMS after the 6th use was mixed with soil at 2 wt% and used in alfalfa planting experiments.

[0049] Example 2:

[0050] A magnesium slag composite biochar adsorbent material (MBMS) and its application in the treatment of complex pollutants includes the following steps:

[0051] (1) Preparation of MCBC: 30g of cut WD (2-4mm) was stirred in deionized water for 2h, washed and dried, and then immersed in a mixed salt solution of 0.5mol / L MgCl2·6H2O (200mL) and CaCl2 (200mL) for 12h, and dried. The solution was then heated to 500℃ in a muffle furnace at 5℃ / min and subjected to oxygen-limited pyrolysis for 2h to obtain MCBC.

[0052] (2) MBMS preparation: 5g MCBC and 5g IT were mixed and ball-milled at 400rpm for 2h. The mixture after ball milling was then heated to 500℃ at 5℃ / min in a muffle furnace and pyrolyzed under limited oxygen conditions for 2h to obtain MBMS.

[0053] (3) Adsorption application: Preparation of Cu-containing... 2+ Simulated wastewater containing a combination of 10 mg / L HCl and 10 mg / L MB was used. The pH was adjusted to 6.0 with 0.1 mol / L HCl / NaOH, and 0.8 g / L MBMS was added. Adsorption was carried out at 30℃ and 150 rpm for 180 min under constant temperature shaking. The residual concentration was measured after centrifugation and filtration.

[0054] (4) Recycling and resource utilization: The adsorbed MBMS was desorbed with 1 mol / L HNO3 for 1 h, washed with deionized water until neutral, and dried for the next adsorption. The inactivated MBMS after the 6th use was mixed with soil at 2 wt% and used in alfalfa planting experiments.

[0055] Comparative Example 1:

[0056] A magnesium slag composite biochar adsorbent material (MCBC-IT) and its application in the treatment of complex pollutants includes the following steps:

[0057] (1) Preparation of MCBC: 30g of cut WD (2-4mm) was stirred in deionized water for 2h, washed and dried, and then immersed in a mixed salt solution of 0.5mol / L MgCl2·6H2O (200mL) and CaCl2 (200mL) for 12h, and dried. The solution was then heated to 500℃ in a muffle furnace at 5℃ / min and subjected to oxygen-limited pyrolysis for 2h to obtain MCBC.

[0058] (2) Preparation of MCBC-IT: Take 5g of MCBC and 15g of IT and mix them in a simple physical way to form MCBC-IT.

[0059] (3) Adsorption application: Preparation of Cu-containing... 2+ Simulated wastewater containing a combination of 10 mg / L HCl and 10 mg / L MB was used. The pH was adjusted to 6.0 with 0.1 mol / L HCl / NaOH, and 0.8 g / L MCBC-IT was added. Adsorption was carried out at 30℃ and 150 rpm for 180 min under constant temperature shaking. The residual concentration was measured after centrifugation and filtration.

[0060] (4) Recycling and resource utilization: The adsorbed MCBC-IT was desorbed with 1 mol / L HNO3 for 1 h, washed with deionized water until neutral, and dried for the next adsorption. The deactivated MCBC-IT after the 6th use was mixed with soil at 2 wt% and used in alfalfa planting experiments.

[0061] Comparative Example 2:

[0062] A magnesium slag composite biochar adsorbent material (MBM-IT) and its application in the treatment of complex pollutants includes the following steps:

[0063] (1) Preparation of MBM: 30g of cut WD (2-4mm) was stirred in deionized water for 2h, washed and dried, and then immersed in 0.5mol / L MgCl2·6H2O (200mL) salt solution for 12h and dried. The solution was then heated to 500℃ in a muffle furnace at 5℃ / min and pyrolyzed under limited oxygen for 2h to obtain MBM.

[0064] (2) Preparation of MBM-IT: Mix 5g MBM and 15g IT and ball mill at 400rpm for 2h. After ball milling, the mixture is heated to 500℃ at 5℃ / min and pyrolyzed under oxygen-limited conditions for 2h to obtain MBM-IT.

[0065] (3) Adsorption application: Preparation of Cu-containing... 2+ Simulated wastewater containing a combination of 10 mg / L HCl and 10 mg / L MB was used. The pH was adjusted to 6.0 with 0.1 mol / L HCl / NaOH, and 0.8 g / L MBM-IT was added. Adsorption was carried out at 30℃ and 150 rpm for 180 min under constant temperature shaking. The residual concentration was measured after centrifugation and filtration.

[0066] (4) Recycling and resource utilization: The adsorbed MBM-IT was desorbed with 1 mol / L HNO3 for 1 h, washed with deionized water until neutral, and dried for the next adsorption. The inactivated MBM-IT after the 6th use was mixed with soil at 2 wt% and used for alfalfa planting experiments.

[0067] Comparative Example 3:

[0068] A magnesium slag composite biochar adsorbent material (MBC-IT) and its application in the treatment of complex pollutants includes the following steps:

[0069] (1) Preparation of MBC: 30g of cut WD (2-4mm) was stirred in deionized water for 2h, washed and dried, and then immersed in 0.5mol / L CaCl2·6H2O (200mL) salt solution for 12h and dried. The solution was then heated to 500℃ in a muffle furnace at 5℃ / min and subjected to oxygen-limited pyrolysis for 2h to obtain MBC.

[0070] (2) Preparation of MBC-IT: Mix 5g of MBC and 15g of IT and ball mill at 400rpm for 2h. After ball milling, the mixture is heated to 500℃ at 5℃ / min and pyrolyzed under oxygen-limited conditions for 2h to obtain MBC-IT.

[0071] (3) Adsorption application: Preparation of Cu-containing... 2+ Simulated wastewater containing a combination of 10 mg / L MBC-IT and 10 mg / L MB was used. The pH was adjusted to 6.0 with 0.1 mol / L HCl / NaOH, and 0.8 g / L MBC-IT was added. Adsorption was carried out at 30℃ and 150 rpm for 180 min under constant temperature shaking. The residual concentration was measured after centrifugation and filtration.

[0072] (4) Recycling and resource utilization: The adsorbed MBC-IT was desorbed with 1 mol / L HNO3 for 1 h, washed with deionized water until neutral, and dried for the next adsorption. The inactivated MBC-IT after the 6th use was mixed with soil at 2 wt% and used for alfalfa planting experiments.

[0073] Comparative Example 4:

[0074] A magnesium slag composite biochar adsorbent material (MSMB-F) and its application in the treatment of complex pollutants includes the following steps:

[0075] (1) Preparation of WDIT: 5g of cut WD (2-4mm) was mixed with 15g of IT and ball milled at 400rpm for 2h to obtain WDIT.

[0076] (2) WDIT was immersed in a mixed salt solution of 0.5 mol / L MgCl2·6H2O (200 mL) and CaCl2 (200 mL) for 12 h and dried. It was then pyrolyzed in a muffle furnace at 5 °C / min to 500 °C for 2 h under limited oxygen conditions to obtain MSMB-F.

[0077] (3) Adsorption application: Preparation of Cu-containing... 2+Simulated wastewater containing a combination of 10 mg / L MSMB and 10 mg / L MSMB was used. The pH was adjusted to 6.0 with 0.1 mol / L HCl / NaOH, and 0.8 g / L MSMB-F was added. Adsorption was carried out at 30℃ and 150 rpm for 180 min under constant temperature shaking. The residual concentration was measured after centrifugation and filtration.

[0078] (4) Recycling and resource utilization: The adsorbed MSMB-F was desorbed with 1 mol / L HNO3 for 1 h, washed with deionized water until neutral, and dried for the next adsorption. The deactivated MSMB-F after the 6th use was mixed with soil at 2 wt% and used for alfalfa planting experiments.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications and substitutions should all fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a magnesium slag tailings composite biochar adsorbent material, characterized in that, Includes the following steps: (1) After cleaning and drying the waste leather scraps, place them in a container containing Mg 2+ and Ca 2+ The mixture was impregnated in a mixed salt solution and then subjected to a first oxygen-limited calcination to obtain magnesium-calcium modified biochar. In the first oxygen-limited calcination, MgO and CaO nanoparticles are generated in situ, and MgSO4 is generated by the reaction of MgO with SO2 released by the thermal decomposition of waste skin, thus achieving in situ sulfur fixation. (2) The magnesium-calcium modified biochar obtained in step (1) is mixed with magnesium slag tailings, ball-milled, and then subjected to a second oxygen-limited calcination to obtain the target product, magnesium slag tailings composite biochar adsorbent material. The second oxygen-limited calcination causes the active functional groups on the surface of the magnesium-calcium modified biochar to undergo a dehydration condensation reaction with CaO / MgO in the magnesium slag tailings to form CO-Ca and CO-Mg covalent bonds.

2. The preparation method of the magnesium slag tailings composite biochar adsorbent material according to claim 1, characterized in that, The obtained magnesium slag tailings composite biochar adsorbent material has a porous structure with metal groups, a pore size distribution of 2-50 nm, and a specific surface area ≥50 m². 2 / g, total pore volume ≥0.02cm³ 3 / g, Raman spectrum I D / I G The ratio is ≥1.

2.

3. The preparation method of the magnesium slag tailings composite biochar adsorbent material according to claim 1, characterized in that, In step (1), the Mg-containing 2+ and Ca 2+ The mixed salt solution is a 0.5–2 mol / L mixture of MgCl2·6H2O and CaCl2, and the immersion time is 12–24 h; the first or second oxygen-limited calcination conditions are: calcination temperature of 400–600℃, heating rate of 3–10℃ / min, and holding time of 1–4 h.

4. The preparation method of the magnesium slag tailings composite biochar adsorbent material according to claim 3, characterized in that, In step (2), the mixing mass ratio of the magnesium-calcium modified biochar and magnesium slag tailings is 1:1 to 5; the ball milling time is 2 to 8 hours and the rotation speed is 200 to 600 rpm.

5. The method for preparing the magnesium slag tailings composite biochar adsorbent material according to any one of claims 1 to 4, characterized in that, The waste leather biochar is derived from at least one of leather scraps, shaved cowhide shavings, or trimming waste; the main component of the metal oxide in the magnesium slag tailings is calcium oxide.

6. A magnesium slag tailings composite biochar adsorbent material prepared by the preparation method of magnesium slag tailings composite biochar adsorbent material according to any one of claims 1 to 4.

7. The application of the magnesium slag tailings composite biochar adsorbent material as described in claim 6 in water treatment, characterized in that, The adsorbent material synergistically treats water bodies contaminated with heavy metal ions and organic dyes through π-π stacking, electrostatic attraction, surface complexation, and metal oxide-mediated electron transfer.

8. The application of the magnesium slag tailings composite biochar adsorbent material according to claim 7 in water treatment, characterized in that, The heavy metal ion is Cu. 2+ Cr 6+ Ni 2+ The organic dye is one or more of the following: methylene blue, methyl orange, and Sudan red.

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