Preparation method of multi-dimensional layer adsorption material for wastewater treatment

Abstract

The invention relates to the field of adsorption materials, and provides a preparation method of a multi-dimensional layer adsorption material for wastewater treatment. Firstly, a titanium-containing precursor solution is prepared through an ice template method, and an oriented porous titanium dioxide precursor framework is formed; and then, carrying out high-temperature calcination to obtain the columnar porous titanium dioxide adsorption material. Then, in-situ growth of an iron-containing metal organic framework (MOF) nanowire is carried out in the pore channel of the titanium dioxide adsorption material, and directional growth of the nanowire is realized by controlling the concentration of metal salt, a solvent system and magnetic field induction. And finally, multi-stage purification and structure stabilization treatment are adopted, so that the mechanical stability and the adsorption performance of the material are improved. By optimizing the pore structure and MOF loading, the adsorption capacity and degradation efficiency of the material to pollutants are improved, the problems that a traditional material is insufficient in mechanical strength and poor in stability are solved, and the material is suitable for efficient wastewater treatment.

Description

Technical Field

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

[0002] In the process of modern industrialization, wastewater treatment has become an important part of environmental protection and sustainable development. Especially in industries such as chemical engineering, metallurgy, pharmaceuticals, and printing and dyeing, a large amount of wastewater containing heavy metal ions, organic pollutants, and refractory compounds is generated during the production process. These pollutants not only cause serious damage to the ecological environment but may also accumulate through the food chain, posing a threat to human health. Therefore, developing efficient, stable, and adsorption materials suitable for complex wastewater environments is the key to improving the efficiency of wastewater purification. An ideal wastewater treatment adsorption material should have excellent mechanical strength to ensure that it is not easily broken or structurally collapsed during long-term use, and at the same time have a high specific surface area and a rich pore structure to enhance the adsorption capacity for pollutants. In addition, to improve the treatment effect, the material should also have excellent catalytic degradation performance, capable of accelerating the decomposition of pollutants in a specific environment, thereby reducing secondary pollution. Generally speaking, mechanical strength, adsorption capacity, and degradation performance are the key indicators determining whether the adsorption material can operate stably in wastewater treatment applications for a long time, reduce maintenance costs, and improve the overall treatment efficiency. Therefore, optimizing the 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, promoting the development of water treatment technology towards high efficiency, low cost, and sustainability.

[0003] Currently, various adsorption materials have been used in the field of wastewater treatment, such as activated carbon, zeolite, metal-organic frameworks (MOF), and titanium dioxide, etc., but there are still many limitations. For example, the Chinese patent with the publication number CN118580510A discloses a MOF adsorption material and its preparation method and application. Although it has a relatively large specific surface area and can provide a high adsorption capacity, due to the brittleness of the MOF structure itself, it is prone to structural collapse during long-term water treatment, resulting in insufficient mechanical strength and limiting its industrial application. In addition, traditional titanium dioxide adsorption materials are widely used in wastewater treatment, but their adsorption capacity mainly depends on the action of surface hydroxyl groups, making it difficult to achieve efficient removal of complex pollutants. Especially in a weak acid or weak base environment, it is prone to adsorption saturation, reducing the treatment efficiency. On the other hand, some studies have tried to introduce catalytic degradation functions, such as loading noble metal catalysts or constructing multifunctional composite materials. However, these methods often increase the synthesis complexity and cost of the materials and are difficult to be popularized in large-scale industrial applications. Therefore, how to improve the mechanical strength of adsorption materials while optimizing their adsorption and degradation capabilities and taking into account the feasibility and economy of synthesis is still an urgent problem to be solved in the current research on wastewater treatment materials. Summary of the Invention

[0004] (1) Technical Problem to be Solved The object of the present invention is to provide a preparation method of a multi-dimensional layer adsorption material for wastewater treatment, so as to solve the problems of insufficient mechanical strength, adsorption and degradation performance of the current multi-dimensional layer adsorption materials.

[0005] (2) Technical Solution A preparation method of a multi-dimensional layer adsorption material for wastewater treatment includes the following steps: S1. Prepare a titanium-containing precursor solution and obtain an oriented porous titanium dioxide precursor framework through the ice template method; S2. Obtain a columnar porous titanium dioxide adsorption material through high-temperature calcination; S3. In-situ grow iron-containing metal-organic framework nanowires in the pores of the titanium dioxide adsorption material; S4. Obtain a multi-dimensional layer adsorption material through multi-stage purification and structure stabilization treatment.

[0006] Further, the step S1 specifically includes: mixing tetrabutyl titanate, absolute ethanol and 0.1 - 0.5 mol / L hydrochloric acid solution according to 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% polyvinylpyrrolidone as a pore template agent, performing cyclic treatment at a temperature rise and fall rate of 0.5 - 1.0 °C / min at 25 - 40 °C for 3 - 5 times to obtain a gradient viscosity sol; injecting the fluorosilane-modified mold, and performing directional freezing at -40 - 80 °C at an axial cooling rate of 5 - 10 °C / min and a radial temperature difference ≤ 2 °C / cm for 4 - 8 h, and performing two-stage freeze-drying. First, perform primary drying to remove free water at a temperature of -80 - 70 °C and a vacuum degree of 10 - 20 Pa, and then adjust to a temperature of -30 - 20 °C and a vacuum degree of 30 - 50 Pa to complete secondary drying to remove bound water, and finally obtain an oriented porous titanium dioxide precursor framework.

[0007] Further, the step S2 specifically includes: treating the oriented porous titanium dioxide precursor framework with a stepped heating program: heating at 0.5 - 1.0 °C / min to 200 - 220 °C and holding for 30 - 60 min to remove adsorbed water, then heating at 1 - 2 °C / min to 350 - 360 °C and holding for 30 - 60 min to decompose the template agent, and then heating at 3 - 5 °C / min to 450 - 600 °C and holding for 30 - 60 min to achieve crystal form transformation to obtain a porous titanium dioxide adsorption material.

[0008] The present invention adopts a design combining ice-templating method with high-temperature calcination and metal-organic framework (MOF) functionalization, mainly used to enhance the mechanical strength, pore structure stability, adsorption performance and catalytic degradation ability of adsorption materials. First, by controlling the ratio of tetrabutyl titanate, absolute ethanol and hydrochloric acid solution, a uniform sol is formed under nitrogen protection, and polyvinylpyrrolidone is introduced as a pore template agent to regulate the viscosity and pore-forming characteristics of the sol. Subsequently, under strictly controlled cyclic heating and cooling conditions, the sol reaches a gradient viscosity state, thereby improving the controllability of the pore structure during the subsequent freezing process. In a low-temperature environment, the mold is modified with fluorosilane, combined with axial cooling and radial temperature difference control, to achieve directional freeze-forming, so that a highly ordered pore structure is formed inside the material. After two-stage freeze-drying, free water and bound water are removed in turn to ensure that the material maintains a stable pore structure during solidification, providing a solid skeleton basis for subsequent calcination. Then, the directional porous titanium dioxide precursor skeleton is calcined through a stepped heating program. First, adsorbed water is removed at a lower temperature to avoid pore collapse caused by structural shrinkage, and then the template agent is decomposed in the medium-temperature stage to ensure the integrity of the pores. Finally, crystal form transformation is achieved under high-temperature conditions, and titanium dioxide is transformed from an amorphous state to a stable crystal form, thereby improving the chemical stability and photocatalytic activity of the material. Subsequently, iron-containing metal-organic framework (MOF) nanowires are in-situ grown in the pores of titanium dioxide by the impregnation-growth method, and an axial static magnetic field is applied to induce their vertical alignment, so that MOF and titanium dioxide form a highly synergistic composite structure, further enhancing the adsorption capacity and catalytic degradation performance of the material. Under this synergistic effect, titanium dioxide provides a stable porous skeleton and photocatalytic active sites, while MOF has excellent metal coordination ability and complex pollutant enrichment effect, enabling pollutants to be efficiently captured and catalytically degraded. At the same time, the aligned arrangement of MOF nanowires optimizes the electron transport path, reduces the recombination of photo-generated electron-hole pairs, and improves the photocatalytic degradation efficiency. During the whole process, each component acts synergistically. The sol viscosity regulation ensures pore uniformity, freeze-drying maintains pore stability, the calcination process optimizes the crystal form and mechanical strength, and the introduction of MOF and magnetic field-induced growth further improve the adsorption and degradation performance of the material, thereby obtaining a multi-dimensional layer adsorption material with high adsorption capacity, excellent stability and high catalytic degradation performance.

[0009] Further, 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 polyvinylpyrrolidone with a mass concentration of 0.5 - 2.0% as a morphology regulator, then under the temperature condition of 40 - 60 °C, assisted by ultrasonic waves with a frequency of 20 - 40 kHz and a power density of 50 - 100 W / L for dispersion for 30 - 60 min to form a homogeneous growth solution; vertically immersing the porous titanium dioxide adsorbent material into this growth solution, first heating it at a heating rate of 2 - 4 °C / min to 120 - 130 °C and holding for 30 - 45 min to complete crystal nucleus formation, and then continuing to heat it at a heating rate of 1 - 2 °C / min to 120 - 180 °C and maintaining for 6 - 12 h to complete the growth of nanowires, while applying an axial static magnetic field to induce the metal-organic framework nanowires to grow perpendicularly to the direction of the titanium dioxide pore channels to obtain iron-containing metal-organic framework nanowires.

[0010] Further, the magnitude of the axial static magnetic field is 10 - 50 mT.

[0011] 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 adsorption materials. First, through the reasonable ratio of iron(III) nitrate nonahydrate and terephthalic acid, the metal salt concentration is controlled, and polyvinylpyrrolidone is added as a morphology regulator in the N,N-dimethylformamide solvent system to improve the nanowire morphology and dispersion. Under ultrasonic assistance, the precursors are ensured to be uniformly dispersed to form a stable homogeneous growth solution, thus providing a good reaction environment for the subsequent directional growth of nanowires. Subsequently, the porous titanium dioxide adsorption material is vertically immersed in the growth solution, and the nucleation and growth processes are controlled by stepwise heating. The formation of crystal nuclei and the expansion of nanowires are completed within a suitable temperature range. At the same time, an axial static magnetic field is applied to induce the directional growth of metal-organic framework nanowires along the pore channels of titanium dioxide, so as to form a stable loading structure inside the pore channels, thereby enhancing the overall structural stability of the adsorption material. The grown material needs to undergo multi-stage purification and structure stabilization treatment. First, it is rinsed with N,N-dimethylformamide solvent at a flow rate of 2-5 mL / min for 10-20 min to remove loose attachments. Subsequently, anhydrous ethanol is used as the cleaning medium, and three centrifugal washes are carried out at a centrifugal force of 800-1200 g, with each centrifugation time of 10-15 minutes to remove unreacted precursors, ensuring that the obtained nanowire structure is complete and evenly distributed. Finally, the material is treated by vacuum drying in stages. The solvent residues are removed at a suitable temperature and vacuum degree, and the structural stability of the material is further enhanced through the activation process. Throughout the process, the synergistic effect of each component is crucial. Reasonably controlling the metal salt concentration and the proportion of organic ligands ensures the stable growth of MOF nanowires. Ultrasonic-assisted dispersion improves the uniformity. Static magnetic field induction enhances the directional arrangement of nanowires and improves the structural stability. Purification and drying treatments further optimize the mechanical strength and long-term use performance of the material, thereby obtaining a multi-dimensional layer adsorption material with high adsorption capacity, excellent stability and good mechanical strength.

[0012] Further, the step S4 specifically includes: first, N,N-dimethylformamide is used to continuously rinse the surface of the product in step S3 at a flow rate of 2-5 mL / min for 10-20 min to remove loose attachments, and then anhydrous ethanol is used as the cleaning medium, and three centrifugal washes are carried out under the condition of a centrifugal force of 800-1200 g, with each centrifugation time of 10-15 minutes to remove unreacted precursors; the washed product is placed in a vacuum drying oven and treated in two stages. In the first stage, it is dried at a temperature of 60-80 °C and a vacuum degree of 1-5 kPa for 2-4 h to remove residual solvents, and in the second stage, the temperature is raised to 100-120 °C and activated at a vacuum degree of 0.1-0.5 kPa for 2-4 h to enhance the structural stability of the material.

[0013] Further, the thixotropic index of the gradient viscosity sol in the step S2 is 1.2-1.8; the porosity of the oriented porous titanium dioxide precursor framework after freeze-drying is 85-95%, and the pore size distribution is 40-100 μm.

[0014] Further, the average width of the columnar pores in step S2 is 38-94 μm.

[0015] Further, 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.

[0016] Further, in step S4, the multi-dimensional layer adsorption material includes a porous titanium dioxide adsorption material and iron-containing metal-organic framework nanowires loaded on the pore surfaces of the porous titanium dioxide adsorption material; Further, the iron-containing metal-organic framework nanowires at the nanoscale fill and connect the pores inside the porous titanium dioxide adsorption material at the microscale to form a highly interconnected adsorption structure; Further, 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).

[0017] In the present invention, iron-containing metal-organic framework nanowires at the nanoscale fill and connect the pores inside the micron-scale porous titanium dioxide adsorbent material, forming a highly interconnected adsorption structure, thereby enhancing the mechanical strength, pore structure stability, adsorption capacity, and catalytic degradation performance of the material. The present invention adopts a design combining an ice-templating method, high-temperature calcination, and in-situ growth of iron-containing metal-organic framework nanowires, aiming to prepare a multi-dimensional layer adsorbent material with high adsorption capacity, excellent structural stability, and high catalytic degradation performance. First, the pore-forming process is precisely controlled by the ice-templating method, enabling the micron-scale titanium dioxide adsorbent material to form a highly ordered porous structure under directional freezing conditions, thereby optimizing the pore distribution and enhancing the mass transfer efficiency. At the same time, the rheological properties of the sol are precisely regulated to ensure the formation of a stable gradient viscosity state, providing a good structural basis for subsequent shaping. Subsequently, high-temperature calcination promotes the crystal phase transformation of the precursor framework, converting titanium dioxide from an amorphous structure to a stable crystal phase and removing the template agent to enhance the chemical stability and mechanical strength of the material, enabling it to maintain structural integrity in a complex wastewater environment for a long time. On this basis, iron-containing metal-organic framework nanowires at the nanoscale are in-situ generated in the pores of the titanium dioxide adsorbent material by an impregnation-growth method, and their vertical orientation is induced by an axial static magnetic field, forming a highly synergistic composite structure with titanium dioxide. This design not only enhances the adsorption capacity of the material but also optimizes the electron transport path, reducing the recombination of photo-generated electron-hole pairs and thus improving the photocatalytic degradation efficiency. Among them, titanium dioxide provides a stable porous skeleton and photocatalytic active sites, while MOF nanowires enhance the enrichment ability of pollutants through metal coordination and accelerate the degradation of pollutants through synergistic catalysis. Finally, after multi-stage purification and structure stabilization treatment, unreacted precursors and surface attachments are removed, and by precisely controlling the drying and activation conditions, the structural stability and long-term use performance of the material are further improved. Throughout the process, each component acts synergistically. The ice-templating method ensures the orderliness of the pores, high-temperature calcination optimizes the crystal form and mechanical strength, the directional growth of MOF nanowires enhances the adsorption and catalytic degradation capabilities, and the purification and stabilization process further optimizes the durability and practical application effect of the material. In summary, through the optimization of the multi-dimensional layer structure, this design enables the titanium dioxide adsorbent material and MOF nanowires to form an efficient composite system, achieving high adsorption, high stability, and high catalytic degradation capabilities, providing an excellent material solution for pollutant removal and wastewater treatment.

[0018] (3) Beneficial technical effects 1. The present invention fills and connects the internal pores of a micron-scale porous titanium dioxide adsorbent material with iron-containing metal-organic framework nanowires at the nanoscale to construct a highly interconnected adsorption structure, significantly enhancing the mechanical strength, pore structure stability, adsorption performance, and catalytic degradation efficiency. The ice-templating method ensures the orderliness of the pores, high-temperature calcination optimizes the crystal form and durability, and the directional growth of MOF nanowires enhances pollutant enrichment and electron transport. The overall synergistic effect reduces the recombination of photo-generated electrons and holes, improving the photocatalytic efficiency, and is applicable to high-efficiency wastewater treatment.

[0019] 2. The present invention realizes the synergistic improvement of pollutant removal ability, structural stability, and mechanical strength through the in-situ growth of iron-containing metal-organic framework nanowires and axial static magnetic field induction. Compared with the prior art, the material has excellent dispersibility, a stable pore loading structure, and high adsorption and degradation efficiency, overcoming the defects of low mechanical strength and poor long-term effectiveness of traditional adsorption materials. It is applicable to the treatment of high-difficulty wastewater, promotes the development of high-performance adsorption materials, and has broad industrial application prospects.

[0020] 3. The present invention constructs an oriented porous titanium dioxide framework through the ice-templating method, optimizes the crystal structure by high-temperature calcination, and uses the in-situ growth and static magnetic field induction of iron-containing metal-organic framework nanowires to achieve efficient synergy between adsorption and catalytic degradation. Compared with the prior art, the material has higher pore orderliness, better mass transfer efficiency, and stronger structural stability, overcoming the defects of low mechanical strength and insufficient degradation ability of traditional adsorption materials. It is applicable to the treatment of high-difficulty wastewater, promotes the development of high-performance adsorption and catalytic materials, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the microstructure morphology of the columnar porous titanium dioxide adsorbent material prepared in Example 1 of the present invention.

[0022] Figure 2 It is the XRD phase analysis pattern of the columnar porous titanium dioxide adsorbent material prepared in Example 1 of the present invention.

[0023] Figure 3 It is the microstructure morphology of the multi-dimensional layer adsorption material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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.

[0025] Example 1 A preparation method of a multi-dimensional layer adsorption material for wastewater treatment, comprising the following steps: S1. Prepare a titanium precursor solution and obtain an oriented porous titanium dioxide precursor framework through the ice-templating method. Specifically, it includes: mixing tetrabutyl titanate, absolute ethanol, and 0.1 mol / L hydrochloric acid solution in a volume ratio of 1:10:0.5, and mechanically stirring at 300 rpm for 10 min under nitrogen protection to form a sol; adding 2 wt% polyvinylpyrrolidone as a pore template agent, cycling the temperature at a rate of 0.5 °C / min for 3 times at 25 °C to obtain a gradient viscosity sol; injecting the sol into a fluorosilane-modified mold, and then directionally freezing at -40 °C with an axial cooling rate of 5 °C / min and a radial temperature difference ≤ 2 °C / cm for 4 h. After two-stage freeze-drying, first perform primary drying to remove free water at -80 °C and a vacuum of 10 Pa, and then adjust to -30 °C and a vacuum of 30 Pa to complete secondary drying to remove bound water, finally obtaining an oriented porous titanium dioxide precursor framework. The thixotropic index of the gradient viscosity sol is 1.2; the porosity of the oriented porous titanium dioxide precursor framework after freeze-drying is 85%, and the pore size distribution is 40 μm.

[0026] S2. Obtain a columnar porous titanium dioxide adsorbent material through high-temperature calcination. Specifically, it includes: treating the oriented porous titanium dioxide precursor framework with a stepwise heating program: heating to 200 °C at 0.5 °C / min and holding for 30 min to remove adsorbed water, then heating to 350 °C at 1 °C / min and holding for 30 min to decompose the template agent, and then heating to 450 °C at 3 °C / min and holding for 30 min to achieve crystal form transformation, obtaining a porous titanium dioxide adsorbent material. The average width of the columnar pores is 38 μm.

[0027] S3. In-situ grow iron-containing metal-organic framework nanowires in the pores of the titanium dioxide adsorbent material. Specifically, it includes: dissolving iron(III) nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a molar ratio of metal ions to organic ligands of 1:2, controlling the metal salt concentration to be 0.05 mol / L, adding 0.5% (by mass) polyvinylpyrrolidone as a morphology regulator, and then under a temperature condition of 40 °C, assisting in dispersion for 30 min at an ultrasonic frequency of 20 kHz and a power density of 50 W / L to form a homogeneous growth solution; vertically immersing the porous titanium dioxide adsorbent material into the growth solution, first heating to 120 °C at a heating rate of 2 °C / min and holding for 30 min to complete nucleation, and then continuing to heat to 120 °C at a heating rate of 1 °C / min and maintaining for 6 h to complete the growth of nanowires. At the same time, apply an axial static magnetic field to induce the metal-organic framework nanowires to grow directionally perpendicular to the direction of the titanium dioxide pores, obtaining iron-containing metal-organic framework nanowires. The magnitude of the axial static magnetic field is 10 mT. The average diameter of the iron-containing metal-organic framework nanowires is 50 nm, and the length is 40 μm.

[0028] S4. A multi-dimensional layer adsorption material is obtained through multi-stage purification and structure stabilization treatment. First, N,N-dimethylformamide is used to continuously rinse the surface of the product in step S3 at a flow rate of 2 mL / min for 10 min to remove loose attachments, and then three centrifugal washings are carried out with absolute ethanol as the cleaning medium under a centrifugal force of 800 g, with each centrifugation time being 10 minutes to remove unreacted precursors; the washed product is placed in a vacuum drying oven and treated in two stages. In the first stage, it is dried at 60 °C and a vacuum of 1 kPa for 2 h to remove residual solvents, and in the second stage, the temperature is raised to 100 °C and activated at a vacuum of 0.1 kPa for 2 h to enhance the structural stability of the material.

[0029] The multi-dimensional layer adsorption material of this example includes a porous titanium dioxide adsorption material and iron-containing metal-organic framework nanowires loaded on the pore surfaces 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 to the iron-containing metal-organic framework nanowires is 98.0:2.0.

[0030] Figure 1 The microstructure morphology of the columnar porous titanium dioxide adsorption material prepared in Example 1 of the present invention is shown, clearly demonstrating 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 pattern of the material, and the results show that the prepared titanium dioxide has a definite crystal form, further verifying that the calcination process has successfully achieved crystal phase transformation, ensuring the structural stability and functionality of the material. Figure 3 The microstructure morphology of the multi-dimensional layer adsorption material prepared in this example is shown, confirming that the material is composed of a porous titanium dioxide adsorption framework and iron-containing metal-organic framework nanowires loaded on the pore surfaces thereof. 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 photocatalytic degradation efficiency.

[0031] Example 2 A preparation method of a multi-dimensional layer adsorption material for wastewater treatment, comprising the following steps: S1. Prepare a titanium precursor solution and obtain an oriented porous titanium dioxide precursor framework through the ice-templating method. Specifically, it includes: mixing tetrabutyl titanate, absolute ethanol, and 0.2 mol / L hydrochloric acid solution in a volume ratio of 1:12:0.8, and mechanically stirring at 360 rpm for 16 min under nitrogen protection to form a sol; adding 3 wt% polyvinylpyrrolidone as a pore template agent, and cyclically treating at 30°C with a temperature rising and falling rate of 0.7°C / min for 4 times to obtain a gradient viscosity sol; injecting the sol into a fluorosilane-modified mold, and then directionally freezing at -52°C with an axial cooling rate of 7°C / min and a radial temperature difference ≤ 2°C / cm for 5 h. After two-stage freeze-drying, first perform primary drying to remove free water at a temperature of -77°C and a vacuum degree of 13 Pa, and then adjust to a temperature of -27°C and a vacuum degree of 36 Pa to complete secondary drying to remove bound water, finally obtaining an oriented porous titanium dioxide precursor framework. The thixotropic index of the gradient viscosity sol is 1.4; the porosity of the oriented porous titanium dioxide precursor framework after freeze-drying is 88%, and the pore size distribution is 58 μm.

[0032] S2. Obtain a columnar porous titanium dioxide adsorbent material through high-temperature calcination. Specifically, it includes: treating the oriented porous titanium dioxide precursor framework with a stepped heating program: heating to 206°C at 0.7°C / min and holding for 39 min to remove adsorbed water, then heating to 353°C at 1°C / min and holding for 39 min to decompose the template agent, and then heating to 495°C at 4°C / min and holding for 39 min to achieve crystal form transformation, obtaining a porous titanium dioxide adsorbent material. The average width of the columnar pores is 55 μm.

[0033] S3. In-situ grow iron-containing metal-organic framework nanowires in the pores of the titanium dioxide adsorbent material. Specifically, it includes: dissolving iron(III) nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent at a molar ratio of metal ions to organic ligands of 1:3, controlling the metal salt concentration to be 0.1 mol / L, adding 1.0% (by mass) polyvinylpyrrolidone as a morphology regulator, and then under a temperature condition of 46°C, assisted by ultrasonic waves at a frequency of 26 kHz and a power density of 65 W / L for 39 min to form a homogeneous growth solution; vertically immersing the porous titanium dioxide adsorbent material into the growth solution, first heating to 123°C at a heating rate of 3°C / min and holding for 35 min to complete crystal nucleation, and then continuing to heat to 138°C at a heating rate of 1°C / min and maintaining for 8 h to complete the growth of nanowires. At the same time, apply an axial static magnetic field to induce the metal-organic framework nanowires to grow directionally perpendicular to the direction of the titanium dioxide pores, obtaining iron-containing metal-organic framework nanowires. The magnitude of the axial static magnetic field is 22 mT. The average diameter of the iron-containing metal-organic framework nanowires is 95 nm, and the length is 58 μm.

[0034] S4. A multi-dimensional layer adsorption material is obtained through multi-stage purification and structure stabilization treatment. First, N,N-dimethylformamide is used to continuously rinse the surface of the product in step S3 at a flow rate of 3 mL / min for 13 min to remove loose attachments, and then three centrifugal washings are carried out with absolute ethanol as the cleaning medium under a centrifugal force of 920 g, with each centrifugation time being 12 minutes to remove unreacted precursors; the washed product is placed in a vacuum drying oven and treated in two stages. In the first stage, it is dried at a temperature of 66 °C and a vacuum of 2 kPa for 3 h to remove residual solvents, and in the second stage, the temperature is raised to 106 °C and activated at a vacuum of 0.2 kPa for 3 h to enhance the structural stability of the material.

[0035] The multi-dimensional layer adsorption material of this example 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 iron-containing metal-organic framework nanowires at the nanoscale fill and connect the pores inside the porous titanium dioxide adsorption material at the microscale to form a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorption material to the iron-containing metal-organic framework nanowires is 97.0:3.0.

[0036] Example 3 A preparation method of a multi-dimensional layer adsorption material for wastewater treatment includes the following steps: S1. Prepare a titanium precursor solution and obtain an oriented porous titanium dioxide precursor framework through the ice template method; specifically include: mixing tetrabutyl titanate, absolute ethanol, and 0.3 mol / L hydrochloric acid solution in a volume ratio of 1:13:1.1, mechanically stirring at 420 rpm for 22 min under nitrogen protection to form a sol; adding 4 wt% polyvinylpyrrolidone as a pore template agent, cycling at a temperature rise and fall rate of 0.8 °C / min at 34 °C for 4 times to obtain a gradient viscosity sol; injecting the sol into a fluorosilane-modified mold, and then performing directional freezing at -64 °C at an axial cooling rate of 8 °C / min and a radial temperature difference ≤ 2 °C / cm for 6 h, followed by two-stage freeze-drying. First, primary drying is carried out at a temperature of -74 °C and a vacuum of 16 Pa to remove free water, and then the temperature is adjusted to -24 °C and a vacuum of 42 Pa to complete secondary drying to remove bound water, and finally an oriented porous titanium dioxide precursor framework is obtained. The thixotropic index of the gradient viscosity sol is 1.6; the porosity of the oriented porous titanium dioxide precursor framework after freeze-drying is 91%, and the pore size distribution is 76 μm.

[0037] S2. Obtain a columnar porous titanium dioxide adsorbent material through high-temperature calcination; specifically including: treating the oriented porous titanium dioxide precursor framework with a stepwise heating program: heating at 0.8 °C / min to 212 °C and holding for 48 min to remove adsorbed water, then heating at 2 °C / min to 356 °C and holding for 48 min to decompose the template agent, and then heating at 4 °C / min to 540 °C and holding for 48 min to achieve crystal form transformation, obtaining a porous titanium dioxide adsorbent material. The average width of the columnar pores is 72 μm.

[0038] S3. In-situ grow iron-containing metal-organic framework nanowires inside the pores of the titanium dioxide adsorbent material; specifically including: dissolving iron(III) nitrate nonahydrate and terephthalic acid in an N,N-dimethylformamide solvent according to a molar ratio of metal ions to organic ligands of 1:3, controlling the metal salt concentration to be 0.1 mol / L, adding polyvinylpyrrolidone with a mass concentration of 1.4% as a morphology regulator, and then under the temperature condition of 52 °C, assisted by ultrasonic waves with a frequency of 32 kHz and a power density of 80 W / L for dispersion for 48 min to form a homogeneous growth solution; vertically immersing the porous titanium dioxide adsorbent material into this growth solution, first heating at a heating rate of 3 °C / min to 126 °C and holding for 39 min to complete crystal nucleation, and then continuing to heat at a heating rate of 2 °C / min to 156 °C and maintaining for 10 h to complete the growth of nanowires. At the same time, apply an axial static magnetic field to induce the metal-organic framework nanowires to grow directionally perpendicular to the direction of the titanium dioxide pores, obtaining iron-containing metal-organic framework nanowires. The magnitude of the axial static magnetic field is 34 mT. The average diameter of the iron-containing metal-organic framework nanowires is 140 nm, and the length is 76 μm.

[0039] S4. Obtain a multi-dimensional layer adsorbent material through multi-stage purification and structure stabilization treatment. First, continuously rinse with N,N-dimethylformamide at a flow rate of 4 mL / min for 16 min to remove loose attachments on the surface of the product in step S3. Subsequently, use absolute ethanol as the cleaning medium and perform three centrifugal washings under a centrifugal force of 1040 g, with each centrifugation time being 13 minutes to remove unreacted precursors; place the cleaned product in a vacuum drying oven and process it in two stages. In the first stage, dry at a temperature of 72 °C and a vacuum of 3 kPa for 3 h to remove residual solvents, and in the second stage, raise the temperature to 112 °C and activate at a vacuum of 0.3 kPa for 3 h to enhance the structural stability of the material.

[0040] The multi-dimensional layer adsorbent material of this embodiment includes a porous titanium dioxide adsorbent material and iron-containing metal-organic framework nanowires loaded on the pore surfaces of the porous titanium dioxide adsorbent material; the iron-containing metal-organic framework nanowires at the nanoscale fill and connect the pores inside the porous titanium dioxide adsorbent material at the micron scale, forming a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorbent material to the iron-containing metal-organic framework nanowires is 95.0:5.0.

[0041] Example 4 A preparation method of a multi-dimensional layer adsorption material for wastewater treatment, comprising the following steps: S1. Prepare a titanium-containing precursor solution and obtain an oriented porous titanium dioxide precursor framework by the ice-templating method; specifically, include: mixing tetrabutyl titanate, absolute ethanol and 0.5 mol / L hydrochloric acid solution in a volume ratio of 1:15:1.5, and mechanically stirring at 500 rpm for 30 min under nitrogen protection to form a sol; adding 5 wt% polyvinylpyrrolidone as a pore template agent, and cyclically treating at 40 °C with a heating and cooling rate of 1.0 °C / min for 5 times to obtain a gradient viscosity sol; injecting the fluorosilane-modified mold, and then directionally freezing at -80 °C with an axial cooling rate of 10 °C / min and a radial temperature difference ≤ 2 °C / cm for 8 h, followed by two-stage freeze-drying. First, primary drying is carried out at -70 °C and a vacuum degree of 20 Pa to remove free water, and then adjusted to -20 °C and a vacuum degree of 50 Pa to complete secondary drying to remove bound water, and finally an oriented porous titanium dioxide precursor framework is obtained. The thixotropic index of the gradient viscosity sol is 1.8; the porosity of the oriented porous titanium dioxide precursor framework after freeze-drying is 95%, and the pore size distribution is 100 μm.

[0042] S2. Obtain a columnar porous titanium dioxide adsorption material by high-temperature calcination; specifically, include: treating the oriented porous titanium dioxide precursor framework with a stepwise heating program: heating to 220 °C at 1.0 °C / min and holding for 60 min to remove adsorbed water, then heating to 360 °C at 2 °C / min and holding for 60 min to decompose the template agent, and then heating to 600 °C at 5 °C / min and holding for 60 min to achieve crystal form transformation to obtain a porous titanium dioxide adsorption material. The average width of the columnar pores is 94 μm.

[0043] S3. In-situ grow iron-containing metal-organic framework nanowires inside the pores of the titanium dioxide adsorbent material; specifically, it includes: dissolving iron(III) nitrate nonahydrate and terephthalic acid in N,N-dimethylformamide solvent at a molar ratio of metal ions to organic ligands of 1:4, controlling the metal salt concentration to be 0.2 mol / L, adding polyvinylpyrrolidone with a mass concentration of 2.0% as a morphology regulator, then under the temperature condition of 60 °C, assisted by ultrasonic waves with a frequency of 40 kHz and a power density of 100 W / L for 60 min to form a homogeneous growth solution; vertically immerse the porous titanium dioxide adsorbent material into this growth solution, first heat it to 130 °C at a heating rate of 4 °C / min and keep it warm for 45 min to complete the formation of crystal nuclei, and then continue to heat it to 180 °C at a heating rate of 2 °C / min and maintain it for 12 h to complete the growth of nanowires. At the same time, apply an axial static magnetic field to induce the metal-organic framework nanowires to grow perpendicular to the direction of the titanium dioxide pores to obtain iron-containing metal-organic framework nanowires. The magnitude of the axial static magnetic field is 50 mT. The average diameter of the iron-containing metal-organic framework nanowires is 200 nm, and the length is 100 μm.

[0044] S4. Obtain a multi-dimensional layer adsorbent material through multi-stage purification and structure stabilization treatment. First, continuously wash the product of step S3 with N,N-dimethylformamide at a flow rate of 5 mL / min for 20 min to remove the loose attachments on the surface, and then use absolute ethanol as the cleaning medium and perform three centrifugal washings under the condition of a centrifugal force of 1200 g, with each centrifugation time being 15 minutes to remove the unreacted precursors; place the washed product in a vacuum drying oven and process it in two stages. In the first stage, dry it at a temperature of 80 °C and a vacuum degree of 5 kPa for 4 h to remove the residual solvent, and in the second stage, raise the temperature to 120 °C and activate it at a vacuum degree of 0.5 kPa for 4 h to enhance the structural stability of the material.

[0045] The multi-dimensional layer adsorbent material of this example includes a porous titanium dioxide adsorbent material and iron-containing metal-organic framework nanowires loaded on the pore surfaces of the porous titanium dioxide adsorbent material; the iron-containing metal-organic framework nanowires at the nanoscale fill and connect the pores inside the porous titanium dioxide adsorbent material at the microscale to form a highly interconnected adsorption structure; the mass ratio of the porous titanium dioxide adsorbent material to the iron-containing metal-organic framework nanowires is 95.8:4.2.

[0046] Comparative Example 1 It is basically the same as Example 1, the difference is that the directional freezing is not carried out by the ice template method, but directly dried and formed, resulting in the disordered pore structure of the titanium dioxide precursor framework, the decrease of pore connectivity, and the reduction of adsorption performance.

[0047] Comparative Example 2 Basically the same as Example 1, except that polyvinylpyrrolidone was not added as a pore template agent when preparing the titanium-containing precursor solution, resulting in uneven pore size distribution of the obtained titanium dioxide precursor framework, increased pore structure collapse rate, and affecting the adsorption efficiency.

[0048] Comparative Example 3 Basically the same as Example 1, except that the directional freezing temperature was -20°C, not reaching 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.

[0049] Comparative Example 4 Basically the same as Example 1, except that the primary drying temperature during freeze-drying was -50°C, higher than -80~-70°C, resulting in incomplete removal of some solvents, severe shrinkage of the precursor framework, and damage to the pore structure.

[0050] Comparative Example 5 Basically the same as Example 1, except that the maximum calcination temperature was adjusted to 400°C, lower than the range of 450~600°C, resulting in the failure of titanium dioxide to form a stable crystal phase, pore structure collapse, and decreased adsorption capacity.

[0051] Comparative Example 6 Basically the same as Example 1, except that the metal salt concentration was set to 0.01 mol / L, lower than the range of 0.05~0.2 mol / L, resulting in insufficient growth of iron-containing metal-organic framework nanowires, uneven filling, and decreased adsorption performance.

[0052] Comparative Example 7 Basically the same as Example 1, except that the nanowire growth temperature was set to 90°C, lower than 120~180°C, resulting in insufficient crystallinity of MOF nanowires, reduced electron transport ability, and decreased photocatalytic efficiency.

[0053] Comparative Example 8 Basically the same as Example 1, except that no axial static magnetic field was applied, and the MOF nanowires failed to grow directionally, resulting in reduced filling efficiency, decreased pore connectivity, and decreased pollutant enrichment ability.

[0054] Performance test: Mechanical strength test (compression test): The adsorption material was subjected to a compression test using a universal material testing machine to measure its compressive strength and Young's modulus to evaluate the structural stability of the material in the wastewater treatment environment. The test rate was set at 1 mm / min, and the ultimate stress and strain were recorded. This method refers to the ASTM D695 standard.

[0055] Adsorption performance test (dynamic adsorption experiment): An ultraviolet-visible spectrophotometer (UV-Vis) was used to monitor the removal rate of pollutants (such as Rhodamine B or methyl orange) in aqueous solution to evaluate the adsorption kinetics and saturated adsorption capacity. A certain mass of the material was placed in a solution containing pollutants, samples were taken at different time intervals, the absorbance was measured, and the adsorption capacity was calculated. This method is applicable to the study of adsorption isotherms and kinetics.

[0056] Photocatalytic degradation experiment (degrading organic pollutants): In a photocatalytic reactor, a 300W xenon lamp (simulating sunlight) was used to irradiate an aqueous solution containing pollutants (such as tetracycline or phenol), samples were taken at regular intervals, and the degradation products were analyzed by high performance liquid chromatography (HPLC). By comparing the concentration changes at different catalytic times, the degradation rate constant was calculated to evaluate the photocatalytic degradation ability of the material.

[0057] The performance of the adsorption materials in Examples 1-4 and Comparative Examples 1-8 was summarized in Table 1.

[0058] Table 1 Summary of the performance of the adsorption materials in Examples 1-4 and Comparative Examples 1-8 The mechanical strength, adsorption capacity, and photocatalytic degradation efficiency of the material are affected by various factors. The directional freezing process is crucial for the pore orderliness. In the absence of it, the pore structure is disordered, resulting in a significant decrease in mechanical strength. At the same time, the pore connectivity decreases, and the adsorption capacity and photocatalytic efficiency are impaired. The addition of a pore template agent optimizes the pore size distribution and improves the adsorption ability. When not used, the pore collapse rate increases, and the adsorption performance deteriorates. The freezing temperature affects the porosity. A lower temperature helps to form more uniform pores and improve the adsorption efficiency, while a higher temperature reduces the porosity and weakens the mass transfer ability. Improper control of the freeze-drying conditions will affect the stability of the precursor skeleton, leading to the shrinkage of the material structure and affecting the adsorption and catalytic performance. The calcination temperature determines the crystal form transformation of titanium dioxide. Too low a temperature will cause the pore structure to collapse, reducing the adsorption ability 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 ability decreases, and the photocatalytic efficiency is reduced. Magnetic field-induced growth optimizes the orientation of MOF nanowires, improves the electron transport efficiency, and thus enhances the photocatalytic degradation performance. When the magnetic field is not applied, the MOF is disorderly arranged. Although the adsorption ability is still high, the photocatalytic efficiency decreases. Generally speaking, Example 3 achieved the highest mechanical strength, adsorption capacity, and photocatalytic degradation efficiency by optimizing various parameters, verifying the synergistic enhancement effect of pore structure optimization, directional growth of MOF nanowires, and crystal form stability of titanium dioxide.

[0059] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that any equivalent structural transformation made under the concept of the present invention using the content of the specification and drawings of the present invention should be covered within the scope 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. preparing a titanium-containing precursor solution and obtaining a directional porous titanium dioxide precursor skeleton by an 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 in the pores of the titanium dioxide adsorbent material; S4. A multi-dimensional layer adsorption material is obtained through multi-stage purification and structure stabilization treatment.

2. The method for preparing a multi-dimensional layer adsorbent material for wastewater treatment according to claim 1, characterized in that: 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), and 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, it is directionally frozen at -40~-80℃ with an axial cooling rate of 5~10℃ / min and a radial temperature difference of ≤2℃ / cm for 4~8h. After two-stage freeze-drying, first, primary drying is carried out at -80~-70℃ and a vacuum degree of 10~20Pa 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.

3. The method for preparing a multi-dimensional layer adsorbent 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 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.

4. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, characterized in that: The step S3 specifically comprises: dissolving ferric nitrate nonahydrate and terephthalic acid in 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 dispersing for 30-60 min at a temperature of 40-60°C with an ultrasonic frequency of 20-40 kHz and a power density of 50-100 W / L to form a homogeneous growth solution; vertically immersing the porous titanium dioxide adsorbent 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 formation of crystal nuclei, 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 min. 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 directional ly perpendicular to the titanium dioxide pore direction, thereby obtaining iron-containing metal organic framework nanowires.

5. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 4, characterized in that: The magnitude of the axial static magnetic field is 10-50 mT.

6. The method for preparing a multi-dimensional layer adsorbent material for wastewater treatment according to claim 1, characterized in that: The step S4 specifically includes: firstly, using N,N-dimethylformamide to continuously wash at a flow rate of 2-5 mL / min for 10-20 min 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 at 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 h 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 h to enhance the structural stability of the material.

7. The method for preparing a multi-dimensional layer adsorbent material for wastewater treatment according to claim 2, characterized in that: 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.

8. The method for preparing a multi-dimensional layer adsorbent material for wastewater treatment according to claim 2, characterized in that: The average width of the columnar pores in step S2 is 38-94 μm.

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

10. The method for preparing a multi-dimensional layer adsorption material for wastewater treatment according to claim 1, characterized in that: 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 nanometer-scale 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; 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).

Images