A method for preparing multi-dimensional layer adsorption material for wastewater treatment

Abstract

The present invention relates to the field of adsorption materials and provides a method for preparing a multi-dimensional layer adsorption material for wastewater treatment. First, a titanium-containing precursor solution is prepared by an ice template method to form a directional porous titanium dioxide precursor skeleton. Subsequently, the precursor is subjected to high-temperature calcination to obtain a columnar porous titanium dioxide adsorption material. Then, iron-containing metal organic framework (MOF) nanowires are in situ grown within the pores of the titanium dioxide adsorption material. The directional growth of the nanowires is achieved by controlling the metal salt concentration, solvent system, and magnetic field induction. Finally, multi-stage purification and structural stabilization treatment are used to improve the mechanical stability and adsorption performance of the material. By optimizing the pore structure and MOF loading, the present invention improves the material's adsorption capacity and degradation efficiency for pollutants, overcomes the problems of insufficient mechanical strength and poor stability of traditional materials, and is suitable for high-efficiency wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the field of adsorption materials, and in particular to a method for preparing a multi-dimensional layer adsorption material for wastewater treatment. Background Art

[0002] In the process of modern industrialization, wastewater treatment has become a crucial component of environmental protection and sustainable development. This is particularly true in industries such as chemical, metallurgy, pharmaceuticals, and printing and dyeing. These processes generate large amounts of wastewater containing heavy metal ions, organic pollutants, and recalcitrant compounds. These pollutants not only cause severe damage to the ecological environment but can also accumulate through the food chain, posing a threat to human health. Therefore, developing efficient, stable adsorbent materials suitable for complex wastewater environments is crucial for improving wastewater purification efficiency. Ideal adsorbent materials for wastewater treatment should possess excellent mechanical strength to prevent breakage and structural collapse during long-term use, as well as a high specific surface area and a rich pore structure to enhance their adsorption capacity for pollutants. Furthermore, to enhance treatment effectiveness, these materials should exhibit excellent catalytic degradation properties, accelerating the decomposition of pollutants under specific conditions and thus reducing secondary pollution. Taken together, mechanical strength, adsorption capacity, and degradation performance are key indicators that determine the long-term stability of adsorbent materials in wastewater treatment applications, reduce maintenance costs, and improve overall treatment efficiency. Therefore, optimizing material design around these core properties can not only improve the actual effect of wastewater treatment, but also broaden the application scope of adsorption materials and promote the development of water treatment technology in the direction of high efficiency, low cost and sustainability.

[0003] Currently, a variety of adsorbent materials have been used in wastewater treatment, including activated carbon, zeolites, metal-organic frameworks (MOFs), and titanium dioxide. However, these materials still have numerous limitations. For example, Chinese Patent Publication No. CN118580510A discloses MOF adsorbent materials, their preparation methods, and applications. While their large surface area and high adsorption capacity are beneficial, the inherent brittleness of MOF structures makes them susceptible to structural collapse during long-term water treatment, resulting in insufficient mechanical strength and limiting their industrial application. Furthermore, while traditional titanium dioxide adsorbents are widely used in wastewater treatment, their adsorption capacity primarily relies on the action of surface hydroxyl groups, making them difficult to efficiently remove complex pollutants. This is particularly true in weakly acidic or alkaline environments, where adsorption saturation is a common symptom, reducing treatment efficiency. Furthermore, some studies have attempted to incorporate catalytic degradation functions, such as loading precious metal catalysts or constructing multifunctional composite materials. However, these approaches often increase the complexity and cost of material synthesis, making them difficult to implement in large-scale industrial applications. Therefore, how to improve the mechanical strength of adsorbent materials while optimizing their adsorption and degradation capabilities, while also balancing the feasibility and cost-effectiveness of their synthesis, remains an urgent challenge in wastewater treatment material research. Summary of the Invention

[0004] (1) Technical problems solved

[0005] The purpose of the present invention is to provide a method for preparing a multi-dimensional layer adsorption material for wastewater treatment, so as to solve the problem that the current multi-dimensional layer adsorption material has insufficient mechanical strength, adsorption and degradation performance.

[0006] (2) Technical solution

[0007] A method for preparing a multi-dimensional layer adsorption material for wastewater treatment comprises the following steps:

[0008] S1. Prepare a titanium-containing precursor solution and obtain a directional porous titanium dioxide precursor skeleton by ice template method;

[0009] S2. A columnar porous titanium dioxide adsorption material is obtained by high temperature calcination;

[0010] S3. In situ growth of iron-containing metal organic framework nanowires within the pores of the titanium dioxide adsorbent material;

[0011] S4. A multi-dimensional layer adsorption material is obtained through multi-stage purification and structural stabilization treatment.

[0012] Furthermore, the step S1 specifically includes: mixing tetrabutoxytitanium, anhydrous ethanol and 0.1-0.5 mol / L hydrochloric acid solution in a volume ratio of 1:(10~15):(0.5~1.5), mechanically stirring at 300~500 rpm for 10~30 min under nitrogen protection to form a sol; adding 2~5 wt% polyvinyl pyrrolidone as a pore template agent, and circulating the temperature at 25~40°C at a heating and cooling rate of 0.5~1.0°C / min for 3~5 times to obtain a gradient viscosity sol; injecting fluorosilane to modify the mold, and directionally freezing at -40~-80°C with an axial cooling rate of 5~10°C / min and a radial temperature difference of ≤2°C / cm for 4~8 h, and freeze-drying in two stages, first at a temperature of -80~-70°C and a temperature of 10~20 Primary drying is performed under vacuum conditions of 30 Pa to remove free water, and then the temperature is adjusted to -30~-20℃ and the vacuum degree is 30~50Pa to complete secondary drying to remove bound water, and finally a directional porous titanium dioxide precursor skeleton is obtained.

[0013] Furthermore, step S2 specifically includes: treating the oriented porous titanium dioxide precursor skeleton with a step-by-step temperature program: heating to 200~220°C at 0.5~1.0°C / min and keeping warm for 30~60 min to remove adsorbed water, then heating to 350~360°C at 1~2°C / min and keeping warm for 30~60 min to decompose the template, and then heating to 450~600°C at 3~5°C / min and keeping warm for 30~60 min to achieve crystal transformation, thereby obtaining a porous titanium dioxide adsorption material.

[0014] This invention utilizes an ice-templating method combined with high-temperature calcination and metal-organic framework (MOF) functionalization to enhance the mechanical strength, pore structure stability, adsorption performance, and catalytic degradation capabilities of the adsorbent material. First, a uniform sol is formed under nitrogen protection by controlling the ratio of tetrabutoxytitanium, anhydrous ethanol, and hydrochloric acid solution. Polyvinylpyrrolidone is introduced as a pore template to control the sol's viscosity and pore-forming properties. Subsequently, under strictly controlled cyclic heating and cooling conditions, the sol is brought to a gradient viscosity state, thereby enhancing the controllability of the pore structure during the subsequent freezing process. Under low-temperature conditions, a fluorosilane-modified mold is used, combined with axial cooling and radial temperature differential control, to achieve directional freeze-forming, resulting in a highly ordered pore structure within the material. A two-stage freeze-drying process sequentially removes free and bound water, ensuring a stable pore structure during the curing process and providing a strong skeletal foundation for subsequent calcination. The oriented porous titanium dioxide precursor framework is then calcined using a step-by-step temperature ramp. Adsorbed water is first removed at a low temperature to prevent structural shrinkage and pore collapse. The template is then decomposed at a moderate temperature to ensure pore integrity. Finally, a high-temperature calcination process is performed, transforming the titanium dioxide from an amorphous state to a stable crystalline form, thereby enhancing the material's chemical stability and photocatalytic activity. Subsequently, iron-containing metal-organic framework (MOF) nanowires are in situ grown within the titanium dioxide pores via an impregnation-growth method. An axial static magnetic field is then applied to induce vertical alignment, resulting in a highly synergistic composite structure between the MOF and titanium dioxide, further enhancing the material's adsorption capacity and catalytic degradation performance. This synergistic effect allows the titanium dioxide to provide a stable porous framework and photocatalytically active sites, while the MOF possesses excellent metal coordination and complex pollutant enrichment, enabling efficient pollutant capture and catalytic degradation. Furthermore, the oriented alignment of the MOF nanowires optimizes electron transport pathways, reduces the recombination of photogenerated electron-hole pairs, and improves photocatalytic degradation efficiency. Throughout the entire process, the various components work synergistically, the sol viscosity is regulated to ensure uniform pore formation, freeze-drying maintains pore stability, and the calcination process optimizes the crystal form and mechanical strength. The introduction of MOF and magnetic field-induced growth further enhance the adsorption and degradation properties of the material, thereby obtaining a multi-dimensional layered adsorption material with high adsorption capacity, excellent stability, and efficient catalytic degradation performance.

[0015] Furthermore, the step S3 specifically includes: dissolving ferric nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a molar ratio of metal ions to organic ligands of 1:(2~4), controlling the metal salt concentration to be 0.05~0.2 mol / L, adding polyvinyl pyrrolidone with a mass concentration of 0.5~2.0% as a morphology regulator, and then at a temperature of 40~60°C, assisted by an ultrasonic frequency of 20~40 kHz and a power density of 50~100 W / L for 30~60 min to form a homogeneous growth solution; after vertically immersing the porous titanium dioxide adsorption material in the growth solution, first heating the temperature to 120~130°C at a rate of 2~4°C / min and keeping the temperature for 30~45 min to complete the crystal nucleation, and then continuing to heat the temperature to 120~180°C at a rate of 1~2°C / min and maintaining the temperature for 6~12 h completes the nanowire growth, and at the same time applies an axial static magnetic field to induce the metal organic framework nanowire to grow perpendicular to the direction of the titanium dioxide pores to obtain iron-containing metal organic framework nanowires.

[0016] Furthermore, the magnitude of the axial static magnetic field is 10-50 mT.

[0017] The present invention adopts the design of in-situ growth of iron-containing metal organic framework nanowires and axial static magnetic field induction, which is mainly used to enhance the pollutant removal ability, structural stability and mechanical strength of the adsorbent material. First, the metal salt concentration is controlled by a reasonable ratio of iron nitrate nonahydrate and terephthalic acid, and polyvinyl pyrrolidone is added to the N,N-dimethylformamide solvent system as a morphology regulator to improve the nanowire morphology and improve the dispersibility. Under ultrasonic assistance conditions, the precursor is ensured to be uniformly dispersed to form a stable homogeneous growth liquid, thereby providing a good reaction environment for the subsequent directional growth of nanowires. Subsequently, the porous titanium dioxide adsorbent material is vertically immersed in the growth liquid, and the nucleation and growth process is controlled by step-by-step temperature increase to complete the formation of crystal nuclei and the expansion of nanowires within a suitable temperature range. At the same time, an axial static magnetic field is applied to induce the metal organic framework nanowires to grow directional along the direction of the titanium dioxide pores, so that a stable load structure is formed inside the pores, thereby improving the overall structural stability of the adsorbent material. The grown material needs to undergo multiple stages of purification and structural stabilization. First, it is rinsed with N,N-dimethylformamide solvent to remove loose attachments. Then, anhydrous ethanol is used as the cleaning medium, and unreacted precursors are removed through multiple centrifugal washings to ensure that the resulting nanowire structure is complete and evenly distributed. Finally, the material is vacuum-dried in stages to remove solvent residues under appropriate temperature and vacuum conditions, and the structural stability of the material is further enhanced through an activation process. Throughout the entire process, the synergistic effect of each component is crucial. Reasonable control of the metal salt concentration and the ratio of organic ligands ensures the stable growth of MOF nanowires, ultrasonic-assisted dispersion improves uniformity, and static magnetic field induction enhances the directional arrangement of nanowires and improves structural stability. Purification and drying treatments further optimize the mechanical strength and long-term performance of the material, thereby obtaining a multi-dimensional layer adsorption material with high adsorption capacity, excellent stability and good mechanical strength.

[0018] Furthermore, the step S4 specifically includes: first, using N,N-dimethylformamide to continuously flush at a flow rate of 2~5 mL / min for 10~20 minutes to remove loose attachments on the surface of the product of step S3, and then using anhydrous ethanol as a cleaning medium and performing three centrifugal washings under a centrifugal force of 800~1200g, each centrifugation time is 10~15 minutes to remove unreacted precursors; placing the washed product in a vacuum drying oven and treating it in two stages, the first stage is drying at a temperature of 60~80°C and a vacuum degree of 1~5 kPa for 2~4 hours to remove residual solvent, and the second stage is heating to 100~120°C and activating at a vacuum degree of 0.1~0.5 kPa for 2~4 hours to enhance the structural stability of the material.

[0019] Furthermore, the thixotropic index of the gradient viscosity sol in step S2 is 1.2-1.8; the porosity of the oriented porous titanium dioxide precursor skeleton after freeze-drying is 85-95%, and the pore size distribution is 40-100 μm.

[0020] Furthermore, in step S2, the average width of the columnar pores is 38-94 μm.

[0021] Furthermore, in step S3, the average diameter of the iron-containing metal organic framework nanowires is 50-200 nm, and the length is 40-100 μm.

[0022] Furthermore, in step S4, the multi-dimensional layer adsorption material includes a porous titanium dioxide adsorption material and iron-containing metal organic framework nanowires supported on the pore surface of the porous titanium dioxide adsorption material;

[0023] Furthermore, the nanoscale iron-containing metal organic framework nanowires fill and connect the pores inside the micrometer-scale porous titanium dioxide adsorption material to form a highly interconnected adsorption structure;

[0024] Furthermore, the mass ratio of the porous titanium dioxide adsorption material to the iron-containing metal organic framework nanowires is (95.0-98.0): (2.0-5.0).

[0025] In the present invention, nanometer-scale iron-containing metal organic framework nanowires fill and connect the pores within the micron-scale porous titanium dioxide adsorption material, forming a highly interconnected adsorption structure, thereby improving the material's mechanical strength, pore structure stability, adsorption capacity, and catalytic degradation performance. The present invention adopts an ice-templating method combined with high-temperature calcination and in-situ growth of iron-containing metal organic framework nanowires to prepare a multi-dimensional layer adsorption material with high adsorption capacity, excellent structural stability, and efficient catalytic degradation performance. First, the pore formation process is precisely controlled by the ice-templating method, so that the micron-scale titanium dioxide adsorption material forms a highly ordered porous structure under directional freezing conditions, thereby optimizing the pore distribution and enhancing mass transfer efficiency. At the same time, the rheological properties of the sol are precisely controlled to ensure the formation of a stable gradient viscosity state, providing a good structural foundation for subsequent molding. Subsequently, high-temperature calcination is used to promote the crystal transformation of the precursor skeleton, transforming the titanium dioxide from an amorphous structure to a stable crystalline phase, and removing the template to enhance the chemical stability and mechanical strength of the material, enabling it to maintain structural integrity for a long time in complex wastewater environments. Based on this, nanoscale iron-containing metal-organic framework (MOF) nanowires were in situ grown within the pores of a titanium dioxide adsorbent material via an impregnation-growth method. Using an axial static magnetic field, they were induced to align vertically, forming a highly synergistic composite structure with the titanium dioxide. This design not only enhances the material's adsorption capacity but also optimizes electron transport pathways, reducing the recombination of photogenerated electron-hole pairs, thereby improving photocatalytic degradation efficiency. Titanium dioxide provides a stable porous framework and photocatalytically active sites, while the MOF nanowires enhance pollutant accumulation through metal coordination and synergistically accelerate pollutant degradation. Finally, multi-stage purification and structural stabilization treatments remove unreacted precursors and surface deposits. Precisely controlled drying and activation conditions further enhance the material's structural stability and long-term performance. Throughout the entire process, the components work synergistically. Ice templating ensures pore order, high-temperature calcination optimizes the crystal form and mechanical strength, and the oriented growth of the MOF nanowires enhances adsorption and catalytic degradation capabilities. The purification and stabilization steps further optimize the material's durability and practical application. In summary, this design optimizes the multi-dimensional layer structure to form an efficient composite system of titanium dioxide adsorption material and MOF nanowires, achieving high adsorption, high stability and high catalytic degradation ability, providing high-quality material solutions for pollutant removal and wastewater treatment.

[0026] (3) Beneficial technical effects

[0027] 1. This invention constructs a highly interconnected adsorption structure by filling and connecting the internal pores of micron-scale porous titanium dioxide adsorbent materials with nanoscale iron-containing metal-organic framework nanowires, significantly improving mechanical strength, pore structure stability, adsorption performance, and catalytic degradation efficiency. Ice-templating ensures pore order, while high-temperature calcination optimizes crystal form and durability. The directional growth of the MOF nanowires enhances pollutant accumulation and electron transport. The overall synergistic effect reduces photogenerated electron-hole recombination, improving photocatalytic efficiency and making it suitable for efficient wastewater treatment.

[0028] 2. This invention achieves a synergistic improvement in pollutant removal capacity, structural stability, and mechanical strength through the in situ growth of iron-containing metal-organic framework nanowires and the induction of an axial static magnetic field. Compared with existing technologies, the material has excellent dispersibility, a stable pore-loaded structure, and high adsorption and degradation efficiency, overcoming the shortcomings of traditional adsorption materials such as low mechanical strength and poor long-term effectiveness. It is suitable for high-difficulty wastewater treatment, promotes the development of high-performance adsorption materials, and has broad industrial application prospects.

[0029] 3. The present invention constructs a directional porous titanium dioxide skeleton through an ice-templating method, combines high-temperature calcination to optimize the crystal structure, and utilizes the in-situ growth of iron-containing metal organic framework nanowires and static magnetic field induction to achieve efficient synergy between adsorption and catalytic degradation. Compared with existing technologies, the material has higher pore order, better mass transfer efficiency, and stronger structural stability, overcoming the shortcomings of traditional adsorption materials such as low mechanical strength and insufficient degradation ability. It is suitable for high-difficulty wastewater treatment, promotes the development of high-performance adsorption catalytic materials, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the microstructure morphology of the columnar porous titanium dioxide adsorption material prepared in Example 1 of the present invention.

[0031] Figure 2 This is the XRD phase analysis spectrum of the columnar porous titanium dioxide adsorption material prepared in Example 1 of the present invention.

[0032] Figure 3 This is the microstructural morphology of the multi-dimensional layer adsorption material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] Example 1

[0035] A method for preparing a multi-dimensional layer adsorption material for wastewater treatment comprises the following steps:

[0036] S1. Prepare a titanium-containing precursor solution and obtain a directional porous titanium dioxide precursor skeleton by an ice template method; specifically, the following steps are performed: tetrabutoxytitanium, anhydrous ethanol and 0.1 mol / L hydrochloric acid solution are mixed in a volume ratio of 1:10:0.5, and mechanically stirred at 300 rpm for 10 min under nitrogen protection to form a sol; 2 wt% polyvinyl pyrrolidone is added as a pore template agent, and the solution is subjected to a cyclic treatment at 25°C with a heating and cooling rate of 0.5°C / min for 3 times to obtain a gradient viscosity sol; after injecting a fluorosilane-modified mold, the solution is directionally frozen at -40°C with an axial cooling rate of 5°C / min and a radial temperature difference of ≤2°C / cm for 4 h, and subjected to two-stage freeze drying. First, primary drying is performed at -80°C and a vacuum degree of 10 Pa to remove free water, and then the temperature is adjusted to -30°C and a vacuum degree of 30 Pa to complete secondary drying to remove bound water, thereby finally obtaining a directional porous titanium dioxide precursor skeleton. The thixotropic index of the gradient viscosity sol is 1.2; the porosity of the oriented porous titanium dioxide precursor skeleton after freeze-drying is 85%, and the pore size distribution is 40 μm.

[0037] S2. Producing a columnar porous titanium dioxide adsorption material by high-temperature calcination; specifically, the process comprises: heating the oriented porous titanium dioxide precursor skeleton to 200°C for 30 minutes at a rate of 0.5°C / min to remove adsorbed water, then heating to 350°C for 30 minutes at a rate of 1°C / min to decompose the template, and then heating to 450°C for 30 minutes at a rate of 3°C / min to achieve crystal transformation, thereby obtaining the porous titanium dioxide adsorption material. The columnar pores have an average width of 38 μm.

[0038] S3. In situ growth of iron-containing metal-organic framework nanowires within the pores of a titanium dioxide adsorbent. Specifically, the method involves dissolving ferric nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a metal ion to organic ligand molar ratio of 1:2, controlling the metal salt concentration to 0.05 mol / L. Polyvinylpyrrolidone (PVP) at a mass concentration of 0.5% is added as a morphology modifier. Subsequently, a homogeneous growth solution is formed at 40°C with ultrasonic dispersion at a frequency of 20 kHz and a power density of 50 W / L for 30 minutes. The porous titanium dioxide adsorbent is vertically immersed in the growth solution. The temperature is first increased at a rate of 2°C / min to 120°C and maintained at this temperature for 30 minutes to complete nucleation. The temperature is then increased at a rate of 1°C / min to 120°C and maintained at this temperature for 6 hours to complete nanowire growth. Simultaneously, an axial static magnetic field of 10 mT is applied to induce oriented growth of the metal-organic framework nanowires perpendicular to the titanium dioxide pores, yielding the iron-containing metal-organic framework nanowires. The average diameter of the iron-containing metal-organic framework nanowires is 50 nm and the length is 40 μm.

[0039] S4. A multi-dimensional layered adsorption material was obtained through multi-stage purification and structural stabilization. First, loose surface deposits on the product from step S3 were removed by continuous washing with N,N-dimethylformamide at a flow rate of 2 mL / min for 10 minutes. Subsequently, the product was centrifuged three times with anhydrous ethanol as the cleaning medium at 800 g for 10 minutes each to remove unreacted precursors. The washed product was then placed in a vacuum drying oven and treated in two stages: the first stage was drying at 60°C and 1 kPa vacuum for 2 hours to remove residual solvent, and the second stage was heating to 100°C and activating at 0.1 kPa vacuum for 2 hours to enhance the structural stability of the material.

[0040] The multidimensional layer adsorption material of this embodiment includes a porous titanium dioxide adsorption material and iron-containing metal organic framework nanowires loaded on the pore surface of the porous titanium dioxide adsorption material; the nanoscale iron-containing metal organic framework nanowires fill and connect the pores inside the micron-scale porous titanium dioxide adsorption material to form a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorption material and the iron-containing metal organic framework nanowires is 98.0:2.0.

[0041] Figure 1 The microstructure morphology of the columnar porous titanium dioxide adsorption material prepared in Example 1 of the present invention is shown, which clearly proves that the material presents a columnar porous structure with good pore directionality, which helps to improve the adsorption performance. Figure 2 This is the XRD phase analysis spectrum of the material. The results show that the prepared titanium dioxide has a clear crystal form, which further verifies that the calcination process successfully achieved crystal phase transformation and ensured the structural stability and functionality of the material. Figure 3 The microstructural morphology of the multidimensional layer adsorption material prepared in this example is demonstrated, confirming that the material is composed of a porous titanium dioxide adsorption skeleton and iron-containing metal organic framework nanowires loaded on the surface of its pores. The nanoscale MOF nanowires effectively fill and connect the internal pores of the micron-scale porous titanium dioxide to form a highly interconnected adsorption structure. This multi-scale composite structure helps to improve the adsorption capacity of pollutants and the efficiency of photocatalytic degradation.

[0042] Example 2

[0043] A method for preparing a multi-dimensional layer adsorption material for wastewater treatment comprises the following steps:

[0044] S1. Prepare a titanium-containing precursor solution and obtain a directional porous titanium dioxide precursor skeleton by an ice template method; specifically, the following steps are: tetrabutoxytitanium, anhydrous ethanol and 0.2 mol / L hydrochloric acid solution are mixed in a volume ratio of 1:12:0.8, and mechanically stirred at 360 rpm for 16 min under nitrogen protection to form a sol; 3 wt% polyvinyl pyrrolidone is added as a pore template agent, and the solution is subjected to a 4-cycle treatment at 30°C with a heating and cooling rate of 0.7°C / min to obtain a gradient viscosity sol; after injecting a fluorosilane-modified mold, the solution is directionally frozen at -52°C with an axial cooling rate of 7°C / min and a radial temperature difference of ≤2°C / cm for 5 h, and subjected to two-stage freeze drying. First, primary drying is performed at -77°C and a vacuum degree of 13 Pa to remove free water, and then the temperature is adjusted to -27°C and a vacuum degree of 36 Pa to complete secondary drying to remove bound water, thereby finally obtaining a directional porous titanium dioxide precursor skeleton. The thixotropic index of the gradient viscosity sol is 1.4; the porosity of the oriented porous titanium dioxide precursor skeleton after freeze-drying is 88%, and the pore size distribution is 58 μm.

[0045] S2. Producing a columnar porous titanium dioxide adsorption material by high-temperature calcination; specifically, the process comprises: heating the oriented porous titanium dioxide precursor skeleton to 206°C at 0.7°C / min and holding for 39 minutes to remove adsorbed water; then heating to 353°C at 1°C / min and holding for 39 minutes to decompose the template; and then heating to 495°C at 4°C / min and holding for 39 minutes to achieve crystal transformation, thereby obtaining the porous titanium dioxide adsorption material. The average width of the columnar pores is 55 μm.

[0046] S3. In situ growth of iron-containing metal-organic framework nanowires within the pores of a titanium dioxide adsorbent. Specifically, the method involves dissolving ferric nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a metal ion to organic ligand molar ratio of 1:3, controlling the metal salt concentration to 0.1 mol / L. Polyvinylpyrrolidone (PVP) at a mass concentration of 1.0% is added as a morphology modifier. Subsequently, a homogeneous growth solution is formed at 46°C using ultrasonic dispersion at a frequency of 26 kHz and a power density of 65 W / L for 39 minutes. The porous titanium dioxide adsorbent is vertically immersed in the growth solution and then heated to 123°C at a rate of 3°C / min for 35 minutes to complete nucleation. The temperature is then continuously increased to 138°C at a rate of 1°C / min and maintained for 8 hours to complete nanowire growth. Simultaneously, an axial static magnetic field of 22 mT is applied to induce oriented growth of the metal-organic framework nanowires perpendicular to the titanium dioxide pores, yielding the iron-containing metal-organic framework nanowires. The average diameter of the iron-containing metal-organic framework nanowires is 95 nm and the length is 58 μm.

[0047] S4. A multi-dimensional layered adsorption material was obtained through multi-stage purification and structural stabilization. First, the product from step S3 was rinsed with N,N-dimethylformamide at a flow rate of 3 mL / min for 13 minutes to remove loose attachments from the surface. Subsequently, the product was centrifuged three times with anhydrous ethanol at a centrifugal force of 920 g for 12 minutes each to remove unreacted precursors. The washed product was then placed in a vacuum drying oven and treated in two stages: the first stage was drying at 66°C and a vacuum of 2 kPa for 3 hours to remove residual solvent. The second stage was heating to 106°C and activating at a vacuum of 0.2 kPa for 3 hours to enhance the structural stability of the material.

[0048] The multidimensional layer adsorption material of this embodiment includes a porous titanium dioxide adsorption material and iron-containing metal organic framework nanowires loaded on the pore surface of the porous titanium dioxide adsorption material; the nanoscale iron-containing metal organic framework nanowires fill and connect the pores inside the micron-scale porous titanium dioxide adsorption material to form a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorption material and the iron-containing metal organic framework nanowires is 97.0:3.0.

[0049] Example 3

[0050] A method for preparing a multi-dimensional layer adsorption material for wastewater treatment comprises the following steps:

[0051] S1. Prepare a titanium-containing precursor solution and obtain a directional porous titanium dioxide precursor skeleton by an ice template method; specifically, the following steps are: tetrabutoxytitanium, anhydrous ethanol and 0.3 mol / L hydrochloric acid solution are mixed in a volume ratio of 1:13:1.1, and mechanically stirred at 420 rpm for 22 min under nitrogen protection to form a sol; 4 wt% polyvinyl pyrrolidone is added as a pore template agent, and the solution is subjected to a 4-cycle treatment at 34°C with a heating and cooling rate of 0.8°C / min to obtain a gradient viscosity sol; after injecting a fluorosilane-modified mold, the solution is directionally frozen at -64°C with an axial cooling rate of 8°C / min and a radial temperature difference of ≤2°C / cm for 6 h, and subjected to two-stage freeze drying. First, primary drying is performed at -74°C and a vacuum degree of 16 Pa to remove free water, and then the temperature is adjusted to -24°C and a vacuum degree of 42 Pa to complete secondary drying to remove bound water, thereby finally obtaining a directional porous titanium dioxide precursor skeleton. The thixotropic index of the gradient viscosity sol is 1.6; the porosity of the oriented porous titanium dioxide precursor skeleton after freeze-drying is 91%, and the pore size distribution is 76 μm.

[0052] S2. Producing a columnar porous titanium dioxide adsorption material by high-temperature calcination; specifically, the process comprises: heating the oriented porous titanium dioxide precursor skeleton to 212°C at 0.8°C / min and holding for 48 minutes to remove adsorbed water; then heating to 356°C at 2°C / min and holding for 48 minutes to decompose the template; and then heating to 540°C at 4°C / min and holding for 48 minutes to achieve crystal transformation, thereby obtaining the porous titanium dioxide adsorption material. The columnar pores have an average width of 72 μm.

[0053] S3. In situ growth of iron-containing metal-organic framework nanowires within the pores of a titanium dioxide adsorbent. Specifically, the method involves dissolving ferric nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a metal ion to organic ligand molar ratio of 1:3, controlling the metal salt concentration to 0.1 mol / L. Polyvinylpyrrolidone (PVP) at a mass concentration of 1.4% is added as a morphology modifier. Subsequently, a homogeneous growth solution is formed at 52°C using ultrasonic assisted dispersion at a frequency of 32 kHz and a power density of 80 W / L for 48 minutes. The porous titanium dioxide adsorbent is vertically immersed in the growth solution and then heated to 126°C at a rate of 3°C / min for 39 minutes to complete nucleation. The temperature is then continuously increased to 156°C at a rate of 2°C / min and maintained for 10 hours to complete nanowire growth. Simultaneously, an axial static magnetic field of 34 mT is applied to induce oriented growth of the metal-organic framework nanowires perpendicular to the titanium dioxide pores, yielding the iron-containing metal-organic framework nanowires. The average diameter of the iron-containing metal-organic framework nanowires is 140 nm and the length is 76 μm.

[0054] S4. A multi-dimensional layered adsorption material was obtained through multi-stage purification and structural stabilization. First, the product from step S3 was rinsed with N,N-dimethylformamide at a flow rate of 4 mL / min for 16 minutes to remove loose surface deposits. Subsequently, the product was centrifuged three times with anhydrous ethanol at a centrifugal force of 1040 g for 13 minutes each to remove unreacted precursors. The washed product was then placed in a vacuum drying oven and treated in two stages: the first stage was drying at 72°C and a vacuum of 3 kPa for 3 hours to remove residual solvent. The second stage was heating to 112°C and activating at a vacuum of 0.3 kPa for 3 hours to enhance the structural stability of the material.

[0055] The multidimensional layer adsorption material of this embodiment includes a porous titanium dioxide adsorption material and an iron-containing metal organic framework nanowire loaded on the pore surface of the porous titanium dioxide adsorption material; the nanoscale iron-containing metal organic framework nanowire fills and connects the pores inside the micron-scale porous titanium dioxide adsorption material to form a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorption material and the iron-containing metal organic framework nanowire is 95.0:5.0.

[0056] Example 4

[0057] A method for preparing a multi-dimensional layer adsorption material for wastewater treatment comprises the following steps:

[0058] S1. Prepare a titanium-containing precursor solution and obtain a directional porous titanium dioxide precursor skeleton by an ice template method; specifically, the following steps are: tetrabutoxytitanium, anhydrous ethanol and 0.5 mol / L hydrochloric acid solution are mixed in a volume ratio of 1:15:1.5, and mechanically stirred at 500 rpm for 30 min under nitrogen protection to form a sol; 5 wt% polyvinyl pyrrolidone is added as a pore template agent, and the solution is subjected to a cyclic treatment at 40°C with a heating and cooling rate of 1.0°C / min for 5 times to obtain a gradient viscosity sol; after injecting a fluorosilane-modified mold, the solution is directionally frozen at -80°C with an axial cooling rate of 10°C / min and a radial temperature difference of ≤2°C / cm for 8 h, and subjected to two-stage freeze drying. First, primary drying is performed at -70°C and a vacuum degree of 20 Pa to remove free water, and then the temperature is adjusted to -20°C and a vacuum degree of 50 Pa to complete secondary drying to remove bound water, thereby finally obtaining a directional porous titanium dioxide precursor skeleton. The thixotropic index of the gradient viscosity sol is 1.8; the porosity of the oriented porous titanium dioxide precursor skeleton after freeze-drying is 95%, and the pore size distribution is 100 μm.

[0059] S2. Producing a columnar porous titanium dioxide adsorption material by high-temperature calcination; specifically, the process comprises: heating the oriented porous titanium dioxide precursor skeleton to 220°C (1.0°C / min) and holding for 60 minutes to remove adsorbed water; then heating to 360°C (2°C / min) and holding for 60 minutes to decompose the template; and finally heating to 600°C (5°C / min) and holding for 60 minutes to achieve crystal transformation, thereby obtaining the porous titanium dioxide adsorption material. The columnar porous structure has an average width of 94 μm.

[0060] S3. In situ growth of iron-containing metal-organic framework nanowires within the pores of a titanium dioxide adsorbent. Specifically, the method involves dissolving ferric nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a metal ion to organic ligand molar ratio of 1:4, controlling the metal salt concentration to 0.2 mol / L. Adding 2.0% polyvinyl pyrrolidone as a morphology modifier, the solution is then dispersed at 60°C with an ultrasonic frequency of 40 kHz and a power density of 100 W / L for 60 minutes to form a homogeneous growth solution. The porous titanium dioxide adsorbent is vertically immersed in the growth solution and then heated to 130°C at a rate of 4°C / min for 45 minutes to complete nucleation. The solution is then heated to 180°C at a rate of 2°C / min and maintained for 12 hours to complete nanowire growth. Simultaneously, an axial static magnetic field of 50 mT is applied to induce oriented growth of the metal-organic framework nanowires perpendicular to the titanium dioxide pores, yielding the iron-containing metal-organic framework nanowires. The average diameter of the iron-containing metal-organic framework nanowires is 200 nm and the length is 100 μm.

[0061] S4. A multi-dimensional layered adsorption material was obtained through multi-stage purification and structural stabilization. First, loose surface deposits on the product from step S3 were removed by continuous washing with N,N-dimethylformamide at a flow rate of 5 mL / min for 20 minutes. Subsequently, the product was centrifuged three times with anhydrous ethanol at a centrifugal force of 1200 g for 15 minutes each to remove unreacted precursors. The washed product was then placed in a vacuum drying oven and treated in two stages: the first stage was drying at 80°C and a vacuum of 5 kPa for 4 hours to remove residual solvent, and the second stage was heating to 120°C and activating at a vacuum of 0.5 kPa for 4 hours to enhance the structural stability of the material.

[0062] The multidimensional layer adsorption material of this embodiment includes a porous titanium dioxide adsorption material and iron-containing metal organic framework nanowires loaded on the pore surface of the porous titanium dioxide adsorption material; the nanoscale iron-containing metal organic framework nanowires fill and connect the pores inside the micron-scale porous titanium dioxide adsorption material to form a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorption material and the iron-containing metal organic framework nanowires is 95.8:4.2.

[0063] Comparative Example 1

[0064] It is basically the same as Example 1, except that the ice template method is not used for directional freezing, but direct drying and molding is performed, which results in disordered pore structure of the titanium dioxide precursor skeleton, decreased pore connectivity, and reduced adsorption performance.

[0065] Comparative Example 2

[0066] It is basically the same as Example 1, except that polyvinyl pyrrolidone is not added as a pore template when preparing the titanium-containing precursor solution. The pore size distribution of the obtained titanium dioxide precursor skeleton is uneven, the pore structure collapse rate increases, and the adsorption efficiency is affected.

[0067] Comparative Example 3

[0068] It is basically the same as Example 1, except that the directional freezing temperature is -20°C, which does not reach the range of -40~-80°C, resulting in uneven pore formation, reduced porosity, and decreased specific surface area and mass transfer efficiency of the material.

[0069] Comparative Example 4

[0070] The method is basically the same as Example 1, except that the primary drying temperature during the freeze-drying process is -50°C, which is higher than -80~-70°C, resulting in insufficient removal of some solvents, severe shrinkage of the precursor skeleton, and damage to the pore structure.

[0071] Comparative Example 5

[0072] The method is basically the same as Example 1, except that the maximum calcination temperature is adjusted to 400°C, which is lower than the range of 450-600°C, resulting in the failure of titanium dioxide to form a stable crystal phase, the collapse of the pore structure, and the decrease in adsorption capacity.

[0073] Comparative Example 6

[0074] The results are basically the same as Example 1, except that the metal salt concentration is set to 0.01 mol / L, which is lower than the range of 0.05-0.2 mol / L, resulting in insufficient growth of Fe-MOF nanowires, uneven filling, and decreased adsorption performance.

[0075] Comparative Example 7

[0076] The method is basically the same as Example 1, except that the nanowire growth temperature is set to 90°C, which is lower than 120-180°C, resulting in insufficient crystallinity of the MOF nanowires, reduced electron transport capacity, and decreased photocatalytic efficiency.

[0077] Comparative Example 8

[0078] The method is basically the same as Example 1, except that no axial static magnetic field is applied, the MOF nanowires fail to grow in a directional manner, the filling efficiency is reduced, the pore connectivity is reduced, and the pollutant enrichment ability is reduced.

[0079] Performance testing:

[0080] Mechanical Strength Testing (Compression Testing): A universal material testing machine was used to perform compression testing on the adsorbent material, measuring its compressive strength and Young's modulus to assess its structural stability in wastewater treatment environments. The test rate was set at 1 mm / min, and the ultimate stress and strain were recorded. This method was based on ASTM D695.

[0081] Adsorption performance testing (dynamic adsorption experiments): Ultraviolet-visible (UV-Vis) spectrophotometry is used to monitor the removal rate of pollutants (such as rhodamine B or methyl orange) from aqueous solutions to assess adsorption kinetics and saturation capacity. A defined mass of material is placed in the pollutant-containing solution, and samples are taken at different time intervals. The absorbance is measured and the adsorption capacity is calculated. This method is suitable for adsorption isotherm and kinetic studies.

[0082] Photocatalytic degradation experiments (degradation of organic pollutants): In a photocatalytic reactor, a 300W xenon lamp (simulating sunlight) is used to irradiate an aqueous solution containing pollutants (such as tetracycline or phenol). Samples are taken regularly and the degradation products analyzed using high-performance liquid chromatography (HPLC). Concentration changes at different catalytic times are compared, and the degradation rate constant is calculated to evaluate the material's photocatalytic degradation ability.

[0083] The properties of the adsorption materials of Examples 1 to 4 and Comparative Examples 1 to 8 are summarized in Table 1.

[0084] Table 1 Performance summary of adsorption materials of Examples 1 to 4 and Comparative Examples 1 to 8

[0085]

[0086] The mechanical strength, adsorption capacity and photocatalytic degradation efficiency of the material are affected by many factors. The directional freezing process is crucial for pore order. When it is missing, the pore structure is disordered, resulting in a significant decrease in mechanical strength. At the same time, the pore connectivity is reduced, and the adsorption capacity and photocatalytic efficiency are impaired. The addition of a pore template optimizes the pore size distribution and improves the adsorption capacity. However, when it is not used, the pore collapse rate increases and the adsorption performance decreases. The freezing temperature affects the porosity. Lower temperatures help form more uniform pores and improve adsorption efficiency, while higher temperatures reduce the porosity and weaken the mass transfer capacity. Improper control of freeze-drying conditions will affect the stability of the precursor skeleton, causing the material structure to shrink, affecting the adsorption and catalytic performance. The calcination temperature determines the crystal transformation of titanium dioxide. Too low a temperature will cause the pore structure to collapse, reducing the adsorption capacity and catalytic activity. The growth concentration and temperature of MOF nanowires affect their filling uniformity and crystallinity. Under low concentration or low temperature conditions, the MOF structure is incomplete, the electron transport capacity is reduced, and the photocatalytic efficiency is reduced. Magnetic field-induced growth optimizes the orientation of MOF nanowires, improving electron transfer efficiency and, consequently, photocatalytic degradation performance. Without a magnetic field, the MOFs are disordered, and while adsorption capacity remains high, photocatalytic efficiency decreases. Overall, Example 3 achieves the highest mechanical strength, adsorption capacity, and photocatalytic degradation efficiency by optimizing various parameters, demonstrating the synergistic enhancement effect of pore structure optimization, oriented MOF nanowire growth, and titanium dioxide crystal stability.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that any equivalent structural transformations made within the scope of the present invention using the contents of the present invention's description and drawings should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a multi-dimensional layer adsorption material for wastewater treatment, characterized in that: The following steps are involved: S1. Prepare a titanium-containing precursor solution and obtain a directional porous titanium dioxide precursor skeleton by ice template method; S2. A columnar porous titanium dioxide adsorption material is obtained by high temperature calcination; S3. In situ growth of iron-containing metal organic framework nanowires within the pores of the titanium dioxide adsorbent material; S4. Obtaining a multi-dimensional layer adsorption material through multi-stage purification and structural stabilization treatment; The step S1 specifically comprises: mixing tetrabutoxytitanium, anhydrous ethanol and 0.1-0.5 mol / L hydrochloric acid solution in a volume ratio of 1:(10-15):(0.5-1.5), mechanically stirring at 300-500 rpm for 10-30 min under nitrogen protection to form a sol; adding 2-5 wt% polyvinyl pyrrolidone as a pore template agent, and performing a cyclic treatment at 25-40°C with a heating and cooling rate of 0.5-1.0°C / min for 3-5 times to obtain a gradient viscosity solution; glue; after injecting fluorosilane to modify the mold, directionally freeze at -40~-80℃ with an axial cooling rate of 5~10℃ / min and a radial temperature difference of ≤2℃ / cm for 4~8h, and then freeze-dry in two stages. First, primary drying is performed at a temperature of -80~-70℃ and a vacuum degree of 10~20Pa to remove free water, and then the temperature is adjusted to -30~-20℃ and a vacuum degree of 30~50Pa to complete secondary drying to remove bound water, finally obtaining a directional porous titanium dioxide precursor skeleton; The step S3 specifically comprises: dissolving ferric nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a metal ion to organic ligand molar ratio of 1:(2-4), controlling the metal salt concentration to be 0.05-0.2 mol / L, adding polyvinyl pyrrolidone with a mass concentration of 0.5-2.0% as a morphology control agent, and then dispersing the mixture at a temperature of 40-60°C with an ultrasonic frequency of 20-40 kHz and a power density of 50-100 W / L for 30-60 minutes to form a homogeneous growth solution; vertically immersing the porous titanium dioxide adsorbent material in the growth solution, first heating the mixture to 120-130°C at a rate of 2-4°C / min and maintaining the temperature for 30-45 minutes to complete crystal nucleation, and then continuing to heat the mixture to 120-180°C at a rate of 1-2°C / min and maintaining the temperature for 6-12 minutes. h completes the nanowire growth, and at the same time applies an axial static magnetic field to induce the metal organic framework nanowire to grow perpendicular to the direction of the titanium dioxide pores to obtain iron-containing metal organic framework nanowires.

2. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, characterized in that: The step S2 specifically includes: treating the oriented porous titanium dioxide precursor skeleton with a step-by-step temperature program: heating to 200-220°C at 0.5-1.0°C / min and keeping warm for 30-60 min to remove adsorbed water, then heating to 350-360°C at 1-2°C / min and keeping warm for 30-60 min to decompose the template, and then heating to 450-600°C at 3-5°C / min and keeping warm for 30-60 min to achieve crystal transformation, thereby obtaining a porous titanium dioxide adsorption material.

3. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, wherein: The magnitude of the axial static magnetic field is 10-50 mT.

4. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, wherein: The step S4 specifically includes: first, using N,N-dimethylformamide to continuously rinse at a flow rate of 2-5 mL / min for 10-20 minutes to remove loose attachments on the surface of the product of step S3, and then using anhydrous ethanol as a cleaning medium and performing three centrifugal washings under a centrifugal force of 800-1200 g, each centrifugation time is 10-15 minutes to remove unreacted precursors; placing the washed product in a vacuum drying oven and treating it in two stages, the first stage is drying at a temperature of 60-80° C. and a vacuum degree of 1-5 kPa for 2-4 hours to remove residual solvent, and the second stage is heating to 100-120° C. and activating at a vacuum degree of 0.1-0.5 kPa for 2-4 hours to enhance the structural stability of the material.

5. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, wherein: The thixotropic index of the gradient viscosity sol in step S1 is 1.2-1.8; the porosity of the oriented porous titanium dioxide precursor skeleton after freeze-drying is 85-95%, and the pore size distribution is 40-100 μm.

6. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, wherein: In step S2, the average width of the columnar pores is 38-94 μm.

7. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, wherein: In step S3, the average diameter of the iron-containing metal organic framework nanowires is 50-200 nm and the length is 40-100 μm.

8. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, wherein: The multi-dimensional layer adsorption material in step S4 includes a porous titanium dioxide adsorption material and an iron-containing metal organic framework nanowire supported on the pore surface of the porous titanium dioxide adsorption material; The iron-containing metal organic framework nanowires fill and connect the pores inside the micron-sized porous titanium dioxide adsorption material to form a highly interconnected adsorption structure; The mass ratio of the porous titanium dioxide adsorption material to the iron-containing metal organic framework nanowire is (95.0-98.0): (2.0-5.0).

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