A magnetic mesoporous silica composite material based on copper smelting slag and a preparation method and application thereof

Abstract

This invention relates to a magnetic mesoporous silica composite material based on copper smelting slag, its preparation method, and its application. The preparation method includes mixing copper smelting slag with an alkaline flux and then heat-treating it to obtain clinker; in a weakly acidic environment, the clinker undergoes a hydrothermal crystallization reaction to obtain a crystallized product, which is then dried to obtain the magnetic mesoporous silica composite material based on copper smelting slag. This invention transforms the linear process of "separation-synthesis" into an integrated process of "activation-assembly," the external mode of "template-based pore formation" into an endogenous mode of "self-template-based pore formation," the composite method of "external magnetization" into a generation method of "in-situ self-magnetization," and the resource view of "silicon as waste" into the high-value utilization of "silicon as a framework."

Description

Technical Field

[0001] This invention relates to the field of composite catalyst preparation technology from copper smelting slag, specifically to a magnetic mesoporous silica composite material based on copper smelting slag, its preparation method, and its application. Background Technology

[0002] Organic dye wastewater is one of the major pollutants discharged from the textile, printing and dyeing industries. It is characterized by high color intensity, strong toxicity, and poor biodegradability, posing a serious threat to aquatic ecosystems and human health. Statistics show that approximately 20% of global water pollution can be attributed to dye wastewater discharge. Therefore, developing efficient and economical dye wastewater treatment technologies has become a research hotspot in the environmental field.

[0003] Advanced oxidation techniques based on Fenton chemistry generate hydroxyl radicals (•OH) and sulfate radicals (SO4). - Reactive oxygen species such as Fe2+ can non-selectively mineralize organic dyes into CO2 and H2O, and are considered an effective method for treating dye wastewater. The classic homogeneous Fenton reaction utilizes Fe2+... 2+ Activation of H2O2 produces •OH, but there is a strict working pH range (pH 2-4), and the reaction produces a large amount of iron-containing sludge, causing secondary pollution, as well as Fe... 3+ / Fe 2+ The slow circulation rate leads to inherent drawbacks such as low catalyst utilization. To overcome these problems, researchers have developed Fenton-like technologies, particularly by using persulfate (PMS) or perdisulfate (PDS) instead of H2O2 as the oxidant, and activating it with a heterogeneous catalyst to produce SO4. - Compared to •OH, SO4 - It features a longer half-life, higher oxidation potential, and a wider pH operating range. In heterogeneous catalytic systems, the catalyst can be separated and recovered from water, avoiding the leaching of metal ions and secondary pollution.

[0004] In recent years, the use of solid waste to prepare environmentally functional materials, achieving "waste-to-waste treatment," has received widespread attention. Copper smelting slag is a major industrial solid waste generated during the copper pyrometallurgical process, producing approximately 2-3 tons of smelting slag for every ton of copper produced, with a global annual production of about 24.6 million tons. The main chemical composition of copper smelting slag is oxides of Fe, Si, and Ca, with Fe content ranging from 35-60% and SiO2 content from 25-40%. Given its high iron content, researchers have attempted to use copper smelting slag directly as a (photo)-Fenton catalyst for pollutant degradation. However, the extremely low specific surface area of ​​raw copper smelting slag leads to insufficient exposure of its active sites and a slow reaction rate, limiting its direct application.

[0005] To enhance the catalytic activity of copper smelting slag, researchers have developed an acid leaching-resynthesis strategy. This involves first leaching active components such as iron from the slag using acid, and then using the leachate as an iron source to synthesize highly active iron-based catalysts. García et al. used citric acid to leach copper smelting slag at room temperature or 40°C. After heat-treating the leachate at 350°C, they prepared a nanocomposite material rich in maghemite (γ-Fe2O3). Through a photo-Fenton process, they achieved a 96.1% degradation rate of 10 ppm indigo carmine dye within 60 minutes (Karen et al., Copper metallurgical slag as a sustainable precursor of iron oxide photocatalysts to remove indigo carmine dye from water using the photo-Fenton process, 2025, https: / / doi.org / 10.1007 / s11356-025-36072-5). Patent CN121198311A discloses a method for preparing an iron-manganese bimetallic catalytic material using copper slag. The method involves reducing and activating the surface of copper slag with ascorbic acid, adding manganese chloride or manganese sulfate, and slowly adding an alkaline solution. After stirring and fully reacting, an iron-manganese precursor complex is obtained. The obtained iron-manganese precursor complex is then calcined at 300℃-700℃ in air for 3-5 hours to obtain the iron-manganese bimetallic catalytic material.

[0006] However, most reported iron oxide catalysts use analytical-grade reagents as precursors, resulting in high preparation costs and limiting their industrial application. Meanwhile, existing acid leaching-resynthesis routes often only utilize the iron component in the slag, while the silicon component, which accounts for 25-40% of the slag mass, is either not effectively utilized or discarded as silicon slag, leading to resource waste. Summary of the Invention

[0007] The purpose of this invention is to use an integrated synergistic transformation mechanism of "alkali fusion activation-hydrothermal crystallization" to simultaneously activate and in-situ assemble the iron and silicon components in copper smelting slag into a mesoporous composite material with magnetic responsiveness.

[0008] To achieve the above-mentioned technical objectives, this invention provides a method for preparing a magnetic mesoporous silica composite material based on copper smelting slag, comprising the following steps: Copper smelting slag is mixed with an alkaline flux and then heat-treated to obtain clinker; In a weakly acidic environment, clinker is subjected to a hydrothermal crystallization reaction. After obtaining the crystallized product, it is dried to obtain a magnetic mesoporous silica composite material based on copper smelting slag.

[0009] Furthermore, the mass ratio of the copper smelting slag to the alkali flux is 1:0.8-1.3.

[0010] Furthermore, the alkali flux includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0011] Furthermore, the heat treatment is carried out at 500-700℃ for 20-50 minutes.

[0012] Furthermore, the pH of the weakly acidic environment is 5-7.

[0013] Furthermore, in the hydrothermal crystallization reaction, water is added at a liquid-to-solid ratio of 4-8:1, and the reaction is carried out at a temperature of 80-100℃ for 3-6 hours.

[0014] Furthermore, the composition of the copper smelting slag, by mass percentage, includes 30wt%-75wt% Fe2O3, 20wt%-40wt% SiO2, 3wt%-20wt% Al2O3, and 2wt%-10wt% CaO.

[0015] The present invention also provides a magnetic mesoporous silica composite material, which is obtained by the above-described preparation method.

[0016] Furthermore, the saturation magnetization of the magnetic mesoporous silica composite material is 10-20 emu / g.

[0017] The present invention also provides the application of the above-mentioned magnetic mesoporous silica composite material in catalytic degradation.

[0018] Compared with the prior art, the beneficial effects of the present invention include: (1) The process flow is short, the equipment requirements are low, and the raw material is industrial solid waste. The existing technology (acid leaching-resynthesis) includes acid leaching → solid-liquid separation → precipitation → washing and drying → calcination → loading magnetic components, while the present invention only requires three steps: alkali melting → hydrothermal → washing and drying, reducing the synthesis preparation steps by more than 40%. (2) Existing technologies often require a variety of reagents such as strong acids (H2SO4, HCl, etc.), precipitants (NaOH), template agents (CTAB, etc.), and magnetic component precursors. The present invention uses fewer reagents, which can significantly reduce reagent costs.

[0019] (3) The material yield (based on slag) of the present invention can reach more than 85%, which is much higher than the utilization rate of iron extraction by existing technology (about 30-40%). The utilization rate of silicon components is increased from "0% (waste)" in the existing technology to "100% (converted into skeleton material)".

[0020] (4) Transform the linear process of “separation-synthesis” into the integrated process of “activation-assembly”, transform the external mode of “template-based hole formation” into the endogenous mode of “self-template-based hole formation”, transform the composite mode of “external magnetization” into the generation mode of “in-situ self-magnetization”, and transform the resource view of “silicon as waste” into the high-value utilization of “silicon as skeleton”. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figures 1(a) and 1(b) show the small-angle and wide-angle XRD patterns of the Fe3O4@mesoporous silica composite material prepared in Example 1, respectively; Figure 2 A scanning electron microscope image of the Fe3O4@mesoporous silica composite material prepared in Example 1 is shown. Figure 3 The X-ray spectral surface scan of the Fe3O4@mesoporous silica composite material prepared in Example 1 is shown. Figure 4 The pore size distribution diagram of the Fe3O4@mesoporous silica composite material prepared in Example 1 is shown. Detailed Implementation

[0023] The existing technologies for the resource utilization of copper smelting slag mainly suffer from the following bottlenecks: (1) Low efficiency of direct utilization of raw slag: The raw copper smelting slag has a small specific surface area and insufficient exposure of active sites, resulting in limited catalytic performance; (2) Complex and costly acid leaching-resynthesis process: Strong acid leaching or high-cost reagents are used, and the process flow is long, only recovering a single component; (3) Ineffective utilization of silicon components: Silicon, which accounts for the main component of slag, is mostly discarded as waste slag, and the high-value conversion of all components has not been achieved; (4) Difficulty in catalyst separation and recovery: Powdered catalysts are easily lost in water, lack magnetic responsiveness, and are difficult to efficiently recover and recycle. Therefore, it is urgent to develop a simple, low-cost composite material preparation method that can achieve the synergistic conversion of iron and silicon components in copper smelting slag and impart magnetic properties to the material for easy recovery.

[0024] In view of this, the present invention transforms the linear process of "separation-synthesis" into an integrated process of "activation-assembly", transforms the external mode of "template-based hole formation" into the endogenous mode of "self-template-based hole formation", transforms the composite method of "external magnetization" into the generation method of "in-situ self-magnetization", and transforms the resource view of "silicon as waste" into the high-value utilization of "silicon as a framework".

[0025] On one hand, the present invention provides a method for preparing a magnetic mesoporous silica composite material based on copper smelting slag, comprising the following steps: Copper smelting slag is mixed with an alkaline flux and then heat-treated to obtain clinker; In a weakly acidic environment, clinker is subjected to a hydrothermal crystallization reaction. After obtaining the crystallized product, it is dried to obtain a magnetic mesoporous silica composite material based on copper smelting slag.

[0026] Heat treatment of copper smelting slag mixed with an alkaline flux can destroy the stable olivine and silicate glass phases in the slag, transforming the silica-alumina components into soluble silicates and aluminates, while simultaneously promoting the oxidation and precipitation of iron components. Iron in copper smelting slag mainly exists as stable silicate minerals such as fir olivine (Fe₂SiO₄). Iron and silicon are firmly bonded by covalent bonds, making them difficult to extract separately using conventional chemical methods. This invention employs high-temperature alkaline fusion treatment, utilizing OH⁻... - The nucleophilic attack on Si-O-Si and Si-O-Fe bonds disrupts the original stable crystal structure in the slag under high-temperature conditions, transforming Fe and Si into soluble silicates and convertible iron oxide / hydroxide precursors, respectively. This process completely breaks the chemical inertness of the components in the slag, achieving "synchronous activation" of the iron and silicon components and laying the foundation for subsequent assembly.

[0027] The key technical points of this step are: ① The amount of solid alkali used must be sufficient to completely destroy the silicate lattice in the slag. If the amount is too low, the activation will be incomplete, and if it is too high, the subsequent hydrothermal system will be too alkaline and the silicon will dissolve too quickly, which is not conducive to the formation of mesoporous structure; ② The reaction temperature must be controlled within a range that can destroy the lattice without causing excessive sintering. If the temperature is too low, the activation effect will be poor, and if the temperature is too high, the product will be over-melted and difficult to disperse after cooling; ③ Using solid alkali for direct mixing and melting, unlike traditional alkali solution leaching, can avoid the presence of water diluting the alkali concentration and reducing the reaction efficiency, thus achieving the high efficiency of "dry activation".

[0028] Preferably, the copper smelting slag is further crushed and ball-milled before use, with a mesh size of 150-300 mesh. The composition of the copper smelting slag, by mass percentage, includes 30wt%-75wt% Fe2O3, 20wt%-40wt% SiO2, 3wt%-20wt% Al2O3, and 2wt%-10wt% CaO.

[0029] Preferably, the mass ratio of the copper smelting slag to the alkali flux is 1:0.8-1.3.

[0030] Preferably, the alkali flux includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0031] Preferably, the heat treatment is carried out at 500-700℃ for 20-50 minutes.

[0032] In a weakly acidic environment, the clinker undergoes a hydrothermal crystallization reaction. During this process, the dissolved silicon species undergo hydrolysis-condensation under weakly acidic to near-neutral conditions. This avoids both excessively rapid condensation leading to disordered precipitation and excessively slow condensation preventing gelation, thus promoting the formation of monodisperse spherical particles. The core purpose of adjusting the pH of the reaction system to 5-7 is to achieve a balance between the hydrolysis and condensation of silicon species, promoting the orderly assembly of silicon species and forming mesoporous silica with high specific surface area, regular pore structure, and good stability.

[0033] Simultaneously, the released iron ions undergo in-situ hydrolysis and nucleation under high temperature and pressure conditions, growing into nanoscale magnetic iron oxide grains (Fe3O4). These grains are then "captured" and "embedded" in-situ by the forming silicon framework, creating a composite structure in which magnetic particles are uniformly embedded in the mesoporous silicon matrix. This "in-situ crystallization-self-assembly" process achieves synergistic regulation of material structure and composition.

[0034] The key technical points of this step are: ① Direct hydrothermal treatment without solid-liquid separation allows dissolved silicon species and released iron ions to coexist in the same reaction system, achieving "in-situ crystallization-self-assembly" and avoiding the problems of component loss and process complexity in the traditional "separation before synthesis" route; ② No template agent (such as surfactant) needs to be added during the hydrothermal process. The mesoporous structure is naturally formed through the self-assembly of silicon species and the "pore-forming" effect of iron oxide nanocrystals, simplifying the process and reducing costs.

[0035] Preferably, the pH of the weakly acidic environment can be controlled by a 1.0-3.0 mol / L sulfuric acid aqueous solution.

[0036] Preferably, in the hydrothermal crystallization reaction, water is added at a liquid-to-solid ratio of 4-8:1, and the reaction is carried out at a temperature of 80-100℃ for 3-6 hours.

[0037] This invention further investigates the catalytic degradation performance of magnetic zeolite composite materials based on copper smelting slag. Results show that the magnetic zeolite composite material can serve as a heterogeneous catalyst for activating peroxy monosulfonate to degrade organic dyes in water. The degradation process includes: adding the magnetic zeolite composite material to wastewater containing organic dyes, adding peroxy monosulfonate, and reacting under shaking or stirring conditions; after the reaction is complete, recovering the catalyst by applying an external magnetic field; the organic dyes include at least one of methylene blue, rhodamine B, or acid orange II; the concentration of peroxy monosulfonate is 1.0-3.0 mmol / L, the concentration of organic dye is 20-50 mg / L, the degradation temperature is 20-35℃, the catalyst dosage is 2.0-5.0 g / L, the pH of the reaction system is 5-14, the reaction time is 45-100 minutes, and the organic dye degradation efficiency is greater than 95%.

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0041] The present invention will be further described in detail below through specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0042] Example 1 A method for preparing a magnetic mesoporous silica composite material based on copper smelting slag includes the following steps: S1. Copper smelting slag was collected from a non-ferrous metal enterprise in Hubei Province. The composition, by mass percentage, included 55.8 wt% Fe2O3, 28.5% SiO2, 6.4 wt% Al2O3, 3.9 wt% CaO, and the remaining components were zinc, copper, sulfur, lead, etc. The copper smelting slag was crushed, ball-milled, and then passed through a 200-mesh sieve.

[0043] S2. Mix the treated copper smelting slag with sodium hydroxide at a mass ratio of 1:1.3, place it in a muffle furnace for high-temperature roasting at 600℃ for 30 minutes, and then let it cool naturally to obtain sintered clinker.

[0044] S3. Grind the sintered clinker, add deionized water at a liquid-to-solid ratio of 5:1 and stir evenly. Adjust the pH of the reaction to 5 using a 2.0 mol / L sulfuric acid aqueous solution. After stirring evenly, carry out a hydrothermal crystallization reaction at a temperature of 100℃ for 4 hours.

[0045] S4. The product after hydrothermal crystallization is filtered and separated, and washed three times alternately with deionized water and anhydrous ethanol. The filter cake is washed until neutral, dried at 90°C for 4 hours, and then ground to obtain a magnetic mesoporous silica composite material based on copper smelting slag, referred to as Fe3O4@mesoporous silica composite material, with a saturation magnetization of 15.56 emu / g.

[0046] Example 2 A method for preparing a magnetic mesoporous silica composite material based on copper smelting slag includes the following steps: S1. Copper smelting slag was collected from a non-ferrous metal enterprise in Hubei Province. The composition, by mass percentage, included 56.8 wt% Fe2O3, 30.7% SiO2, 6.4 wt% Al2O3, 4.9 wt% CaO, and the remaining components were zinc, copper, sulfur, lead, etc. The copper smelting slag was crushed, ball-milled, and then passed through a 200-mesh sieve.

[0047] S2. The treated copper smelting slag and sodium hydroxide are mixed evenly at a mass ratio of 1:1.2 and placed in a muffle furnace for high-temperature roasting at 550℃ for 30 minutes. Then, the mixture is naturally cooled to obtain sintered clinker.

[0048] S3. Grind the sintered clinker, add deionized water at a liquid-to-solid ratio of 6:1 and stir until homogeneous. Adjust the pH of the reaction to 6 using a 2.0 mol / L sulfuric acid aqueous solution. After stirring until homogeneous, carry out a hydrothermal crystallization reaction at a temperature of 90℃ for 4 hours.

[0049] S4. The product after hydrothermal crystallization is filtered and separated, and washed 5 times alternately with deionized water and anhydrous ethanol. The filter cake is washed until neutral, dried at 90°C for 3 hours, and then ground to obtain a magnetic mesoporous silica composite material based on copper smelting slag with a saturation magnetization of 18.12 emu / g.

[0050] Example 3 A method for preparing a magnetic mesoporous silica composite material based on copper smelting slag includes the following steps: S1 is the same as in Example 1, and will not be repeated here.

[0051] S2. Mix the treated copper smelting slag with sodium hydroxide at a mass ratio of 1:1.3, place it in a muffle furnace for high-temperature roasting at 600℃ for 30 minutes, and then let it cool naturally to obtain sintered clinker.

[0052] S3. Grind the sintered clinker, add deionized water at a liquid-to-solid ratio of 6:1 and stir until homogeneous. Adjust the pH of the reaction to 5 using a 2.0 mol / L sulfuric acid aqueous solution. After stirring until homogeneous, carry out a hydrothermal crystallization reaction at a temperature of 90℃ for 4 hours.

[0053] S4. The product after hydrothermal crystallization is filtered and separated, and washed 5 times alternately with deionized water and anhydrous ethanol. The filter cake is washed until neutral, dried at 90°C for 3 hours, and then ground to obtain a magnetic mesoporous silica composite material based on copper smelting slag with a saturation magnetization of 16.65 emu / g.

[0054] Comparative Example 1 A method for preparing a composite material based on copper smelting slag includes the following steps: S1 is the same as in Example 1, and will not be repeated here.

[0055] S2. Add the treated copper smelting slag to deionized water at a liquid-to-solid ratio of 5:1 and stir until homogeneous. Adjust the pH of the reaction to 5 using a 2.0 mol / L sulfuric acid aqueous solution. After stirring until homogeneous, carry out a hydrothermal crystallization reaction at a temperature of 100℃ for 4 hours.

[0056] S3. The product after hydrothermal crystallization is filtered and separated, the filter cake is washed with deionized water until neutral, dried at 90°C for 2 hours and then ground to obtain a composite material based on copper smelting slag with a saturation magnetization of 0.15 emu / g.

[0057] Test case The crystal structure of the Fe3O4@mesoporous silica composite material prepared in Example 1 was characterized by X-ray diffraction, and the results are shown in Figure 1(b). It can be seen that the Fe3O4@mesoporous silica composite material exhibits obvious characteristic Fe3O4 diffraction peaks, and Figure 1(a) shows that it has no (100) characteristic peak at 1-5°, indicating that the mesoporous silica has a long-range disordered mesoporous structure. Scanning electron microscopy analysis results are as follows... Figure 2 As shown, magnetic iron oxide nanocrystals are uniformly embedded or encapsulated within an amorphous or short-range ordered silica matrix, forming a "magnetic core-silicon shell" or "embedded" composite structure, without obvious magnetic particle aggregation. Energy-dispersive X-ray spectroscopy surface scanning ( Figure 3 The uniform distribution of Fe, Si, and O elements indicates a tight bond between Fe3O4 and silicon dioxide. The BJH desorption pore size distribution is shown in the figure. Figure 4 As shown, its average pore size is 18.11 nm, proving that it is a mesoporous structure.

[0058] The leaching toxicity of the Fe3O4@mesoporous silica composite material prepared in Example 1 was tested according to the national environmental protection standard HJ 557-2010 "Leaching Toxicity of Solid Waste - Horizontal Oscillation Method". The results are shown in Table 1.

[0059] Table 1. Leaching toxicity test results of the Fe3O4@mesoporous silica composite material prepared in Example 1

[0060] As can be seen from the results in Table 1, the leaching toxicity of the prepared Fe3O4@mesoporous silica composite material meets the standards and can meet the requirements of practical applications.

[0061] Application examples To investigate the catalytic performance of the composite materials prepared in the examples and comparative examples, these composite materials were used as catalysts to activate peroxymonosulfonate (PMS) for the degradation of methylene blue or acid orange II, and the catalytic degradation performance was evaluated. Specifically, 0.3-0.4 g of catalyst was added to 100 mL of an organic dye solution with a concentration of 20-30 mg / L, and the reaction was carried out with shaking at pH 8.0, PMS concentration of 1.0-3.0 mmol / L, and temperature of 25 °C for 60 min. The degradation rate results of these catalysts are shown in Table 2.

[0062] Table 2 Degradation rate results of the catalyst

[0063] As can be seen from the results in Table 2, the composite materials prepared in Examples 1-3 exhibit good degradation performance for organic dyes, with degradation rates all exceeding 95%. However, compared to Example 1, Comparative Example 1, under the same degradation conditions, showed a degradation rate of only 14.6% for methylene blue.

[0064] The cyclic catalytic degradation performance of the Fe3O4@mesoporous silica composite material prepared in Example 1 was further investigated. The specific steps are as follows: (1) Take 0.3g of Fe3O4@mesoporous silica composite material prepared in Example 1, add it to 100mL of methylene blue solution with a concentration of 20mg / L, add 1.0mmol / L PMS, adjust the pH value to 8.0, shake the reaction at 25℃ for 60min, test the methylene blue concentration after degradation, and calculate the degradation rate; (2) After the reaction is completed, the catalyst is recovered by attracting with a magnet. The Fe3O4@mesoporous silica composite material is washed multiple times with deionized water. The washed Fe3O4@mesoporous silica composite material is dried at 100℃ for 2 hours and cooled to obtain the Fe3O4@mesoporous silica composite material for the second cycle. (3) Cyclic Degradation Experiment: Steps (1) and (2) were repeated for a total of 5 cycles. The concentration of methylene blue was tested after each degradation, and the degradation rate of each degradation process was calculated. The degradation rate data are shown in Table 3. As can be seen from Table 3, after 5 cycles, the degradation rate of methylene blue by the Fe3O4@mesoporous silica composite material of the present invention is still above 90%, which confirms that the Fe3O4@mesoporous silica composite material has good stability and reusability. Fe3O4 endows the material with good magnetic responsiveness. After the reaction is completed, it can be quickly recovered under the action of an external magnetic field. The recovered catalyst can be reused after simple washing, realizing the recycling of the material.

[0065] Table 3. Cyclic catalytic degradation data of methylene blue by Fe3O4@mesoporous silica

[0066] In summary, this invention transforms the linear utilization model of "stepwise extraction-separate synthesis" into an integrated synergistic transformation model of "simultaneous activation-in-situ assembly," which has the following advantages: (1) Existing technologies (including the acid leaching-resynthesis route) follow the traditional metallurgical thinking of "separation first, utilization later": a certain component (usually iron) in the slag is extracted by acid leaching, and then the extract is used as a raw material to synthesize the target material, while the silicon component is discarded as waste or used for other purposes. This approach is essentially a "divide and conquer" of the components in the slag, with a long process flow and low resource utilization. This invention takes the opposite approach and adopts an integrated "alkali fusion activation-hydrothermal crystallization" technology, which does not pursue the separation of components, but rather the synergistic transformation of components. Through high-temperature alkali fusion, the originally chemically bonded Fe and Si in the slag are "simultaneously released" into the reaction system; through hydrothermal crystallization, the released Fe and Si are "assembled in situ" into functional materials with a clear structure. This shift in thinking realizes a leap from "using whatever is extracted from the waste slag" to "transforming the waste slag into its whole form".

[0067] (2) Existing technologies for preparing mesoporous materials typically require the addition of surfactants (such as CTAB and P123) as template agents. These template agents form micelles, and silicon species condense around the micelles to form a mesoscopically ordered structure. Finally, calcination removes the template agent, leaving pores. This "soft template" or "hard template" method suffers from problems such as high template agent costs, waste gas generation during removal, and easy pore collapse. This invention eliminates the need for any external template agent. The formation of the mesoporous structure relies on a "self-templating pore-forming" mechanism: ① Alkali fusion activation completely disintegrates the dense structure of the slag, forming a loose precursor; ② During hydrothermal processing, while silicon species condense to form a framework, in-situ generated iron oxide nanocrystals occupy the space within the framework; ③ These nanocrystals act as "in-situ pore-forming agents," leaving mesoscopic-scale pores during washing and subsequent treatment. This "self-templating" mechanism "embeds" the function of the template agent into the transformation process of the slag itself, achieving a breakthrough in "template-free preparation of mesoporous materials."

[0068] (3) The conventional approach to imparting magnetism to materials using existing technologies is to first synthesize a non-magnetic matrix material, and then load magnetic components (such as adding Fe3O4 nanoparticles) through impregnation, co-precipitation, physical mixing, etc. This approach has problems such as uneven distribution of magnetic components, easy detachment, and multiple preparation steps. In this invention, no additional magnetic components are added; the magnetism originates from the in-situ transformation of the iron components in the copper smelting slag itself. By controlling the alkaline melting and hydrothermal conditions, the iron in the slag is directly transformed into magnetic Fe3O4 nanocrystals during the material formation process, and is "anchored" in situ by the simultaneously formed silicon framework. This "in-situ self-magnetization" mechanism achieves the simultaneous completion of material forming and magnetic endowment, resulting in uniform distribution of magnetic components, strong bonding with the matrix, and stable magnetic properties.

[0069] (4) In existing acid leaching technologies, silicon slag is usually regarded as a worthless waste that needs to be neutralized or stockpiled, which not only increases the processing cost but may also cause secondary pollution. Even some studies that focus on the utilization of silicon mostly extract silicon separately for the preparation of silicon-based materials, which still falls under the category of "step-by-step utilization". This invention redefines the silicon component as the "skeleton material" of the composite material. During the alkaline fusion process, silicon and iron are activated simultaneously; during the hydrothermal process, silicon acts as a precursor of the mesoporous skeleton, constructing a three-dimensional network structure that supports the entire composite material; while iron oxide nanocrystals are embedded in it as functional units.

[0070] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a magnetic mesoporous silica composite material based on copper smelting slag, characterized in that, Includes the following steps: Copper smelting slag is mixed with an alkaline flux and then heat-treated to obtain clinker; In a weakly acidic environment, clinker is subjected to a hydrothermal crystallization reaction. After obtaining the crystallized product, it is dried to obtain a magnetic mesoporous silica composite material based on copper smelting slag.

2. The method for preparing the magnetic mesoporous silica composite material based on copper smelting slag according to claim 1, characterized in that, The mass ratio of copper smelting slag to alkali flux is 1:0.8-1.

3.

3. The method for preparing the magnetic mesoporous silica composite material according to claim 1, characterized in that, The alkaline flux includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

4. The method for preparing the magnetic mesoporous silica composite material according to claim 1, characterized in that, The heat treatment is carried out at 500-700℃ for 20-50 minutes.

5. The method for preparing the magnetic mesoporous silica composite material according to claim 1, characterized in that, The pH of the weakly acidic environment is 5-7.

6. The method for preparing the magnetic mesoporous silica composite material according to claim 1, characterized in that, In the hydrothermal crystallization reaction, water is added at a liquid-to-solid ratio of 4-8:1, and the reaction is carried out at a temperature of 80-100℃ for 3-6 hours.

7. The method for preparing the magnetic mesoporous silica composite material according to claim 1, characterized in that, The copper smelting slag comprises, by mass percentage, 30wt%-75wt% Fe2O3, 20wt%-40wt% SiO2, 3wt%-20wt% Al2O3, and 2wt%-10wt% CaO.

8. A magnetic mesoporous silica composite material, characterized in that, It is obtained by the preparation method according to any one of claims 1-7.

9. The magnetic mesoporous silica composite material according to claim 8, characterized in that, Its saturation magnetization is 10-20 emu / g.

10. The application of a magnetic mesoporous silica composite material as described in claim 8 or 9 in catalytic degradation.

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