Gasification slag-based composite phase multi-level porous photocatalytic materials, their preparation methods and applications

Abstract

This invention discloses a gasification slag-based composite phase multi-level porous photocatalytic material, its preparation method, and its applications. It belongs to the technical field of coal-based solid waste resource utilization and environmental pollution control. The preparation method of the gasification slag-based composite phase multi-level porous photocatalytic material includes: calcining a mixture of urea and melamine to obtain graphitic carbon nitride; mixing sodium hydroxide, water glass, and water, and aging the mixture to obtain an alkaline activation liquid; uniformly mixing gasification slag, graphitic carbon nitride, and the alkaline activation liquid to form a slurry; adding a foam stabilizer and a foaming agent to the slurry, and stirring to obtain a foamed slurry; casting the foamed slurry into a mold, curing, and then demolding to obtain a green body with a porous structure; placing the green body in an alkaline mother liquor for a hydrothermal reaction, followed by washing and drying to finally obtain the gasification slag-based composite phase multi-level porous photocatalytic material. The photocatalytic material prepared by this invention has good strength, is easy to separate and recover, and exhibits excellent adsorption and photocatalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of coal-based solid waste resource utilization and environmental pollution control technology, specifically relating to a gasification slag-based composite phase multi-level porous photocatalytic material, its preparation method, and its application. Background Technology

[0002] Gasification slag is an industrial solid waste rich in silicon and aluminum, generated during coal gasification. Its annual production is considerable, and its storage and disposal not only consumes land resources but also poses potential risks of heavy metal leaching and dust dispersion, threatening the surrounding soil and aquatic ecosystems. With the advancement of "zero-waste city" construction and "solid waste resource utilization" policies, developing economical and efficient gasification slag resource utilization technologies has become an urgent need for the sustainable development of the industry. Photocatalysis technology is an effective method for treating recalcitrant organic dye wastewater. Graphite-phase carbon nitride (g-C3N4), as a non-metallic semiconductor photocatalytic material, has attracted widespread attention due to its unique electronic band structure, visible light response characteristics, and good physicochemical stability. However, its inherent limitation—its powder morphology making it prone to agglomeration and difficult sedimentation in liquid-phase reaction systems—severely hinders its practical engineering applications.

[0003] Existing technology (CN202411522305.9) improves catalytic activity by high-temperature calcination of pretreated acid-treated g-C3N4 and gasification slag, but it still fails to solve the problem of catalyst separation and recovery, and the raw material is limited to a small proportion of gasification slag. Another existing technology (CN202411520422.1) uses a hydrothermal method to convert gasification slag into zeolite material for activating persulfate. This preparation process is relatively complex and requires the addition of an oxidant, resulting in high operating costs. Therefore, there is an urgent need for a new technology that can simultaneously achieve the following objectives: 1) using bulk gasification slag (not limited to fine slag) as the main raw material; 2) preparing a tangible catalyst with good strength and easy separation and recovery; 3) possessing both excellent adsorption and photocatalytic performance without the need for additional oxidant; and 4) having a simple process and low cost. Summary of the Invention

[0004] Based on the technical problems existing in the prior art, the present invention provides a gasification slag-based composite phase multi-level porous photocatalytic material, its preparation method and application, which solves the problems of the difficulty in applying or the high cost of existing graphite phase carbon nitride powder. It can prepare a multi-level porous material composed of geopolymer phase and zeolite-like phase, which significantly improves the pollutant enrichment capacity and the separation efficiency of graphite phase carbon nitride photogenerated carriers, and effectively improves the pollutant adsorption capacity and photocatalytic interface reaction efficiency.

[0005] According to the first aspect of the present invention, the present invention provides a method for preparing a gasification slag-based composite phase multi-level porous photocatalytic material, comprising the following steps:

[0006] Step S1: Mix urea and melamine and calcine to obtain graphitic carbon nitride;

[0007] Step S2: Sodium hydroxide, water glass and water are mixed and aged to obtain an alkaline activating solution;

[0008] Step S3: Mix the gasification slag, the graphite phase carbon nitride obtained in step S1, and the alkaline activation liquid obtained in step S2 evenly to form a slurry.

[0009] Step S4: Add foam stabilizer and foaming agent to the slurry obtained in step S3, and stir to obtain foamed slurry;

[0010] Step S5: The foamed slurry obtained in step S4 is poured into a mold, cured and molded, and then demolded to obtain a blank with a porous structure.

[0011] Step S6: Place the green body obtained in step S5 in an alkaline mother liquor for hydrothermal reaction. After the reaction, wash and dry to finally obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0012] In some embodiments, in step S1, the mass ratio of urea to melamine is 3:1; calcination is carried out by heating to 550°C to 600°C at a rate of 4°C / min to 6°C / min and holding at that temperature for 2h to 2.5h.

[0013] In some embodiments, in step S2, the mass ratio of sodium hydroxide, water glass, and water is 17:125:51, the modulus of the alkaline activating solution is 1.4, and the aging time is 24 hours.

[0014] In some embodiments, in step S3, the mass ratio of gasification slag, graphite phase carbon nitride, and alkaline activating liquid is 100: (2.0~2.5): (25~30), the particle size of the gasification slag passes through a 200-mesh sieve, the stirring speed is not less than 1500 r / min, and the stirring time is 1 min~3 min.

[0015] In some embodiments, in step S4, the foam stabilizer is plant protein and sodium dodecylbenzenesulfonate, the foaming agent is hydrogen peroxide solution, and the amounts of plant protein, sodium dodecylbenzenesulfonate, and hydrogen peroxide solution are 8.0%–10.0%, 1.5%, and 2.0% of the mass of gasification slag, respectively. The mass concentration of hydrogen peroxide solution is 30%, the stirring speed is 1200 r / min–1400 r / min, and the stirring time is 20–40 s.

[0016] In some implementations, in step S5, curing is performed at 50℃~70℃ for 12 hours.

[0017] In some embodiments, in step S6, the alkaline mother liquor is a sodium hydroxide solution with a concentration of 1 mol / L to 2 mol / L, the hydrothermal reaction temperature is 120°C to 150°C, and the hydrothermal reaction time is 6 h to 8 h.

[0018] According to the second aspect of the present invention, the present invention provides a gasification slag-based composite phase multi-level porous photocatalytic material prepared by the preparation method of the gasification slag-based composite phase multi-level porous photocatalytic material described in the present invention.

[0019] According to the third aspect of the present invention, the present invention provides an application of the gasification slag-based composite phase multi-level porous photocatalytic material described in the present invention in the degradation of organic dyes.

[0020] In some implementations, the application method is as follows: the gasification slag-based composite phase multi-level porous photocatalytic material is added to the target water body containing organic dyes, and the mixture is first stirred in a dark environment to reach adsorption equilibrium, and then the photocatalytic degradation process is carried out under light.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] 1. This invention develops a novel integrated preparation strategy of "geopolymerization-foaming-hydrothermal crystallization". By precisely controlling the hydrothermal conditions, partial and selective in-situ crystallization of the amorphous gel phase in the porous geopolymer preform is achieved, constructing a unique composite structure in which the geopolymer continuous network and the zeolite-like dispersed phase interpenetrate each other.

[0023] 2. The composite structure of this invention spontaneously forms a synergistic multi-level porous system. The geopolymer phase provides a robust macroscopic framework and large-pore channels, ensuring the mechanical strength and stability of the material. The in-situ derived zeolite-like phase introduces abundant micropores and mesopores, greatly enhancing the specific surface area and adsorption and enrichment capacity of the material for pollutants. The confinement effect of the limited space extends the carrier lifetime of the graphitic carbon nitride phase and enhances catalytic activity through interfacial electron transfer. This integrated design of "robust framework-enrichment sites-catalysis" achieves spatial coupling between adsorption and photocatalysis, significantly improving the degradation effect.

[0024] 3. This invention uses gasification slag as the main raw material and successfully prepares high-performance photocatalytic materials at a temperature significantly lower than that of traditional zeolite synthesis, with a green and economical process. Simultaneously, it overcomes the technical bottlenecks of easy deactivation and difficult recovery of nanocatalysts, as well as the low strength and limited mass transfer of traditional porous materials. It also achieves the goals of "treating waste with waste" and "turning waste into treasure," demonstrating significant environmental and economic benefits. Attached Figure Description

[0025] Figure 1These are XRD diagrams of Embodiment 1, Comparative Embodiment 1, and Comparative Embodiment 2 of the present invention.

[0026] Figure 2 These are the fluorescence spectra of Embodiment 1, Comparative Embodiment 1, and Comparative Embodiment 2 of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] It should also be noted that, for ease of description, only the parts relevant to the inventive point are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0029] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0030] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0031] This invention belongs to the interdisciplinary field of coal-based solid waste resource utilization and environmental pollution control, specifically involving a gasification slag-based composite phase multi-level porous photocatalytic material, its preparation method, and its application. Using gasification slag as the core raw material, this invention mixes it with an alkaline excitation liquid and graphitic carbon nitride (g-C3N4), forming a porous preform through the action of a composite foam stabilizer and foaming. Then, by controlling the low-temperature hydrothermal reaction conditions, a partial phase transformation of the amorphous silica-alumina gel in the preform is induced, ultimately yielding a multi-level porous material composed of a geopolymer phase and a zeolite-like phase. This product, with its unique two-phase structure and multi-level pores, significantly improves the pollutant enrichment capacity and g-C3N4 photogenerated carrier separation efficiency, effectively increasing the pollutant adsorption capacity and photocatalytic interface reaction efficiency, achieving highly efficient degradation of dyeing and printing wastewater (RhB). This invention expands a new pathway for the resource utilization of gasification slag, possessing both environmental and economic benefits.

[0032] This invention provides a method for preparing a gasification slag-based composite phase multi-level porous photocatalytic material, comprising the following steps:

[0033] Step S1: Mix urea and melamine and calcine to obtain graphitic carbon nitride (g-C3N4).

[0034] Step S2: Sodium hydroxide, water glass and water are mixed and aged to obtain an alkaline activating solution;

[0035] Step S3: Mix the gasification slag, the graphite phase carbon nitride obtained in step S1, and the alkaline activation liquid obtained in step S2 evenly to form a slurry.

[0036] Step S4: Add (preferably in sequence) foam stabilizer and foaming agent to the slurry obtained in step S3, and stir to obtain foamed slurry;

[0037] Step S5: The foamed slurry obtained in step S4 is poured into a mold, cured and molded, and then demolded to obtain a blank with a porous structure.

[0038] Step S6: Place the green body obtained in step S5 in an alkaline mother liquor for hydrothermal reaction. After the reaction, wash and dry to finally obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0039] Preferably, in step S1, the mass ratio of urea to melamine is 3:1, which can achieve a better reaction rate and product purity.

[0040] Preferably, in step S1, the calcination is carried out by heating to 550°C to 600°C at a rate of 4°C / min to 6°C / min, and holding at that temperature for 2 hours to 2.5 hours. The relatively slow heating rate ensures overall temperature uniformity; the selection of calcination temperature and holding time ensures complete reaction and avoids decomposition of the desired material.

[0041] In step S2, during the preparation of the alkaline activating solution, sodium hydroxide and water glass undergo hydrolysis and condensation reactions when mixed with water, forming a more stable aluminosilicate activator system. Appropriate water volume ensures the homogeneity and suitable viscosity of the system, preventing uneven mixing and excessively high local concentrations due to insufficient water, or dilution of the active ingredients due to excessive water, which directly affects the efficiency of subsequent polymerization reactions and the structure of the final product.

[0042] Preferably, in step S2, the mass ratio of sodium hydroxide, water glass, and water is 17:125:51. This specific ratio aims to regulate the modulus (SiO2 / Na2O molar ratio) of the alkaline activating solution to approximately 1.4, thereby providing the system with suitable alkalinity and silicate ion concentration. This environment effectively disrupts the glassy structure of the gasification slag to release active silica-alumina species, facilitates the subsequent formation of a stable three-dimensional geopolymer network structure, and creates ideal conditions for the directional crystallization of the zeolite-like phase in the hydrothermal step. Deviations from this ratio may lead to modulus imbalance in the alkaline activating solution, which in turn adversely affects the strength of the geopolymer framework and the conversion efficiency of the zeolite-like phase.

[0043] Preferably, in step S2, the modulus of the alkaline activating liquid is 1.4. This preferred modulus is crucial for achieving synergistic effects between the geopolymerization reaction and subsequent in-situ zeolite crystallization. A modulus that is too low (i.e., excessively alkaline) will over-accelerate the geopolymerization reaction, leading to a rapid increase in slurry viscosity, which is detrimental to the uniform distribution and stability of bubbles during foaming. Conversely, a modulus that is too high will result in insufficient reaction driving force, making it difficult to form a sufficiently strong geopolymer framework and inhibiting the formation of aluminosilicate gels as zeolite-like phase precursors.

[0044] Preferably, in step S2, the aging time is 24 hours. During the aging process, sodium hydroxide and water glass react and diffuse fully, allowing the silicate species in the system to reach depolymerization-polymerization equilibrium, forming a homogeneous and stable oligomeric silicate solution. This not only ensures the uniformity of the chemical properties of the activating solution and avoids localized and violent reactions when subsequently mixed with solid raw materials, but also eliminates the thermal effects generated by mixing, ensuring the stability of the activating solution's performance, thereby guaranteeing good controllability and reproducibility of the polymerization reaction process.

[0045] Preferably, in step S3, the mass ratio of gasification slag, graphite-phase carbon nitride, and alkaline activating liquid is 100 : (2.0-2.5) : (25-30). This preferred ratio ensures that polymerization and condensation reactions occur fully under the action of the alkaline activator to form geopolymers; suitable graphite-phase carbon nitride ensures high dispersibility and active sites while avoiding agglomeration.

[0046] Preferably, in step S3, the gasification slag is sieved through a 200-mesh sieve to ensure a large specific surface area and promote its full interaction with the activator. The stirring speed is preferably not less than 1500 r / min, and the stirring time is, for example, 1 min to 3 min, to ensure the high homogenization of the slurry and lay the foundation for the uniform formation of a multi-level porous structure.

[0047] Preferably, in step S4, the foam stabilizer is plant protein and sodium dodecylbenzenesulfonate, and the foaming agent is hydrogen peroxide solution. The amounts of plant protein, sodium dodecylbenzenesulfonate, and hydrogen peroxide solution are 8.0%–10.0%, 1.5%, and 2.0% of the mass of the gasification slag, respectively, and the mass concentration of the hydrogen peroxide solution is 30%. In this scheme, the specific ratio of the foam stabilizer and the foaming agent constitutes a highly efficient foaming system, which imparts a high specific surface area porous structure to the material while also taking into account its necessary mechanical strength.

[0048] Preferably, in step S4, the stirring speed is 1200 r / min to 1400 r / min, and the stirring time is 20 to 40 s, to ensure uniform mixing, sufficient reaction, and thorough foaming with uniform and fine texture.

[0049] Preferably, in step S5, the curing is carried out at 50℃~70℃ for 12 hours.

[0050] Preferably, in step S6, the alkaline mother liquor is a sodium hydroxide solution with a concentration of 1 mol / L to 2 mol / L, the hydrothermal reaction temperature is 120℃ to 150℃, and the hydrothermal reaction time is 6h to 8h.

[0051] The gasification slag-based composite phase multi-level porous photocatalytic material prepared by the preparation method of the present invention can form a structure in which graphite phase carbon nitride is distributed and fixed in a porous carrier. "Composite phase" refers to a composite structure in which geopolymer continuous network and zeolite-like dispersed phase (zeolite-like phase includes zeolite phase) are interpenetrated. "Multi-level pores" include macroscopic framework and macroporous channels formed by geopolymer phase, as well as micropores and mesopores introduced by in-situ derived zeolite-like phase. Therefore, the photocatalytic material of the present invention has good strength, is easy to separate and recover, and has excellent adsorption and photocatalytic performance.

[0052] More specifically, the gasification slag-based composite phase multi-level porous photocatalytic material of the present invention forms a multi-level porous structure with macropores, mesopores, and micropores. The diameter of the macropores ranges, for example, in the millimeter range (e.g., 0.5 mm to 2.0 mm), the diameter of the mesopores ranges, for example, in the micrometer range (10 μm to 300 μm), and the diameter of the micropores ranges, for example, in the nanometer range (5 nm to 50 nm). The macropores are mainly generated by the foaming agent under the action of the foam stabilizer, and are approximately spherical or ellipsoidal in shape, forming a macroscopic framework throughout the material. The mesopores (channels) are mainly distributed within the walls of the macropores, formed by the interstitial spaces of unreacted solid particles, the shrinkage of the geopolymer gel, and the erosion caused by the hydrothermal reaction; these channels act as "bridges" connecting the macropores. The micropores (zeolite pores) are inherent to the zeolite-like phase generated in situ through hydrothermal reaction within the geopolymer framework, greatly increasing the specific surface area and interfacial area of ​​the material. The key to the precise construction of the above-mentioned complex multi-level structure lies in the uniqueness of the raw materials and the synergistic design of the process: (1) Using a specific silicon-aluminum source, the chemical composition and glass structure of the amorphous geopolymer gel formed under the action of a specific alkali activator with a preferred modulus of 1.4 have chemical homogeneity and reactivity, which provides an ideal and uniformly distributed precursor for the uniform and in-situ nucleation of the subsequent zeolite-like phase; (2) In the subsequent hydrothermal process, the precursor undergoes directional dissolution-recrystallization in an alkaline solution of a specific concentration (such as 1 mol / L to 2 mol / L NaOH), and the zeolite-like phase crystal preferentially grows in situ inside the gel phase and on the walls of the micron-level pores, and its inherent nano-level micropores (zeolite pores) are thus precisely introduced and fixed; (3) At the same time, the moderate erosion of the geopolymer gel by the hydrothermal reaction "reconstructs" and "expands" the original micron-level pores without destroying the millimeter-level macropore skeleton, thereby actively forming a mesoscopic channel connecting the macropores and the nano-level micropores.

[0053] The gasification slag-based composite phase hierarchical porous photocatalytic material of the present invention is particularly suitable for application in the degradation of organic dyes. The application method is as follows: the gasification slag-based composite phase hierarchical porous photocatalytic material is added to a target water body containing organic dyes; first, it is stirred in a dark environment to reach adsorption equilibrium; then, the photocatalytic degradation process is carried out under light. Organic dyes, for example, are methylene blue or rhodamine B (RhB). More specifically, for example, the photocatalytic material of the present invention is mixed with water containing the target pollutant (such as an RhB solution), stirred in a dark environment to reach adsorption-desorption equilibrium, and then stirred under xenon lamp irradiation to carry out a photocatalytic reaction. The initial concentration of RhB in the water containing the target pollutant is 10 mg / L to 50 mg / L, and the dosage of the photocatalytic material is 5 g / L to 8 g / L. The stirring rate in the dark environment is 800 r / min to 1000 r / min, and the time is 30 min to 40 min. The light source is a xenon lamp with a power of 350 W, and the irradiation time is 30 min to 40 min.

[0054] The present invention will be further described below with reference to specific embodiments.

[0055] Example 1

[0056] The preparation method of gasification slag-based composite phase multi-level porous photocatalytic material includes the following steps:

[0057] (1) Mix urea and melamine evenly at a mass ratio of 3:1, place them in a high-temperature sintering furnace, heat them to 600°C at a rate of 5°C / min, keep them at the temperature for 2 hours, and cool them for later use.

[0058] (2) Sodium hydroxide, water glass and water are mixed in a mass ratio of 17:125:51 and stirred until the mixture is homogeneous and clear. Then, it is aged for 24 hours to prepare an alkaline activating solution.

[0059] (3) Mix 100g of gasification slag, 2.5g of g-C3N4 obtained in step (1), and 30g of alkaline activating liquid obtained in step (2), and stir at 1500r / min for 3min to make a slurry;

[0060] (4) Add 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (mass concentration 30%) to the slurry obtained in step (3) in sequence, and stir at a speed of 1300r / min for 30s to form a uniform foamed slurry;

[0061] (5) The foaming slurry is poured into the mold, vibration is applied to remove residual air bubbles, and it is placed in a constant temperature curing box at 60℃ for 12 hours to obtain a porous blank.

[0062] (6) The porous preform is placed in an alkaline mother liquor with a concentration of 2 mol / L and subjected to a hydrothermal reaction at 120°C for 8 hours. After the reaction is completed and cooled, the product is washed and dried to obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0063] Example 2

[0064] The preparation method of gasification slag-based composite phase multi-level porous photocatalytic material includes the following steps:

[0065] (1) Mix urea and melamine evenly at a mass ratio of 3:1, place them in a high-temperature sintering furnace, heat them to 600°C at a rate of 5°C / min, keep them at the temperature for 2 hours, and cool them for later use.

[0066] (2) Sodium hydroxide, water glass and water are mixed in a mass ratio of 17:125:51 and stirred until the mixture is homogeneous and clear. Then, it is aged for 24 hours to prepare an alkaline activating solution.

[0067] (3) Mix 100g of gasification slag, 2.0g of g-C3N4 obtained in step (1), and 30g of alkaline activating liquid obtained in step (2), and stir at 1500r / min for 3min to make a slurry;

[0068] (4) Add 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (mass concentration 30%) to the slurry obtained in step (3) in sequence, and stir at a speed of 1300r / min for 30s to form a uniform foamed slurry;

[0069] (5) The foaming slurry is poured into the mold, vibration is applied to remove residual air bubbles, and it is placed in a constant temperature curing box at 60℃ for 12 hours to obtain a porous blank.

[0070] (6) The porous preform is placed in an alkaline mother liquor with a concentration of 2 mol / L and subjected to a hydrothermal reaction at 150°C for 8 hours. After the reaction is completed and cooled, the product is washed and dried to obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0071] Example 3

[0072] The preparation method of gasification slag-based composite phase multi-level porous photocatalytic material includes the following steps:

[0073] (1) Mix urea and melamine evenly at a mass ratio of 3:1, place them in a high-temperature sintering furnace, heat them to 600°C at a rate of 5°C / min, keep them at the temperature for 2 hours, and cool them for later use.

[0074] (2) Sodium hydroxide, water glass and water are mixed in a mass ratio of 17:125:51 and stirred until the mixture is homogeneous and clear. Then, it is aged for 24 hours to prepare an alkaline activating solution.

[0075] (3) Mix 100g of gasification slag, 2.5g of g-C3N4 obtained in step (1), and 30g of alkaline activating liquid obtained in step (2), and stir at 1500r / min for 3min to make a slurry;

[0076] (4) Add 8.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (mass concentration 30%) to the slurry obtained in step (3) in sequence, and stir at a speed of 1300r / min for 30s to form a uniform foamed slurry;

[0077] (5) The foaming slurry is poured into the mold, vibration is applied to remove residual air bubbles, and it is placed in a constant temperature curing box at 60℃ for 12 hours to obtain a porous blank.

[0078] (6) The porous preform is placed in an alkaline mother liquor with a concentration of 2 mol / L and subjected to a hydrothermal reaction at 150°C for 8 hours. After the reaction is completed and cooled, the product is washed and dried to obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0079] Example 4

[0080] The preparation method of gasification slag-based composite phase multi-level porous photocatalytic material includes the following steps:

[0081] (1) Mix urea and melamine evenly at a mass ratio of 3:1, place them in a high-temperature sintering furnace, heat them to 600°C at a rate of 5°C / min, keep them at the temperature for 2 hours, and cool them for later use.

[0082] (2) Sodium hydroxide, water glass and water are mixed in a mass ratio of 17:125:51 and stirred until the mixture is homogeneous and clear. Then, it is aged for 24 hours to prepare an alkaline activating solution.

[0083] (3) Mix 100g of gasification slag, 2.5g of g-C3N4 obtained in step (1), and 30g of alkaline activating liquid obtained in step (2), and stir at 1500r / min for 3min to make a slurry;

[0084] (4) Add 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (mass concentration 30%) to the slurry obtained in step (3) in sequence, and stir at a speed of 1300r / min for 30s to form a uniform foamed slurry;

[0085] (5) The foaming slurry is poured into the mold, vibration is applied to remove residual air bubbles, and it is placed in a constant temperature curing box at 60℃ for 12 hours to obtain a porous blank.

[0086] (6) The porous preform is placed in an alkaline mother liquor with a concentration of 1 mol / L and subjected to a hydrothermal reaction at 150°C for 8 hours. After the reaction is completed and cooled, the product is washed and dried to obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0087] Example 5

[0088] The preparation method of gasification slag-based composite phase multi-level porous photocatalytic material includes the following steps:

[0089] (1) Mix urea and melamine evenly at a mass ratio of 3:1, place them in a high-temperature sintering furnace, heat them to 600°C at a rate of 5°C / min, keep them at the temperature for 2 hours, and cool them for later use.

[0090] (2) Sodium hydroxide, water glass and water are mixed in a mass ratio of 17:125:51 and stirred until the mixture is homogeneous and clear. Then, it is aged for 24 hours to prepare an alkaline activating solution.

[0091] (3) Mix 100g of gasification slag, 2.5g of g-C3N4 obtained in step (1), and 30g of alkaline activating liquid obtained in step (2), and stir at 1500r / min for 3min to make a slurry;

[0092] (4) Add 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (mass concentration 30%) to the slurry obtained in step (3) in sequence, and stir at a speed of 1300r / min for 30s to form a uniform foamed slurry;

[0093] (5) The foaming slurry is poured into the mold, vibration is applied to remove residual air bubbles, and it is placed in a constant temperature curing box at 60℃ for 12 hours to obtain a porous blank.

[0094] (6) The porous preform is placed in an alkaline mother liquor with a concentration of 2 mol / L and subjected to a hydrothermal reaction at 150°C for 6 hours. After the reaction is completed and cooled, the product is washed and dried to obtain the gasification slag-based composite phase multi-level porous photocatalytic material.

[0095] Comparative Example 1

[0096] A method for preparing a gasification slag-based photocatalytic material, the steps of which are as in Example 1, except that Comparative Example 1 does not have step (6), and the remaining steps are the same as in Example 1.

[0097] Comparative Example 2

[0098] A method for preparing a gasification slag-based photocatalytic material, the steps of which are as in Example 1, except that Comparative Example 2 does not have step (1); in step (3), 100 g of gasification slag and 30 g of alkaline activation liquid obtained in step (2) are mixed and stirred at a speed of 1500 r / min for 3 min to make a slurry; the remaining steps are the same as in Example 1.

[0099] Comparative Example 3

[0100] A method for preparing a gasification slag-based photocatalytic material, the steps of which are as in Example 1, except that in Comparative Example 3, the temperature is raised to 850°C in step (1), and the remaining steps are the same as in Example 1.

[0101] Comparative Example 4

[0102] A method for preparing a gasification slag-based photocatalytic material, the steps are as in Example 1, except that plant protein and sodium dodecylbenzenesulfonate were not added in step (4) of Comparative Example 4, and the remaining steps are the same as in Example 1.

[0103] Comparative Example 5

[0104] A method for preparing a gasification slag-based photocatalytic material, the steps of which are the same as in Example 1, except that there is no alkaline mother liquor in step (7) of Comparative Example 5, and the remaining steps are the same as in Example 1.

[0105] The performance of the gasification slag-based composite phase multi-level porous photocatalytic materials prepared in Examples 1-5 and Comparative Examples 1-5 was tested, and the results are shown in Table 1:

[0106] Table 1. Property parameters of gasification slag-based composite phase hierarchical porous photocatalytic materials

[0107]

[0108] Application Experiment Example 1

[0109] Photocatalytic experiments were conducted using Examples 1-5 and Comparative Examples 1-5, and the specific methods were as follows:

[0110] Weigh 0.25 g of the obtained material and add it to 0.05 L of a 20 mg / L RhB solution. Stir at 1000 rpm for 30 min in the dark to allow it to reach adsorption-desorption equilibrium. Then, stir under a 350 W xenon lamp for 40 min to carry out the photo-reaction. Samples were taken every 10 min, centrifuged, and the supernatant was collected. The concentration change of RhB was measured at 554 nm using a UV-Vis spectrophotometer.

[0111] The results of RhB removal in the examples are shown in Table 2.

[0112] Table 2. Removal results of RhB in the examples

[0113]

[0114] Application Experiment Example 2

[0115] Photocatalytic experiments were conducted using Examples 1-5 and Comparative Examples 1-5, and the specific methods were as follows:

[0116] Weigh 0.30 g of the obtained material and add it to 0.05 L of a 50 mg / L RhB solution. Stir at 1000 rpm for 40 min in the dark to allow it to reach adsorption-desorption equilibrium. Then, stir under a 350 W xenon lamp for 40 min to carry out the photo-reaction. Samples were taken every 10 min, centrifuged, and the supernatant was collected. The concentration change of RhB was measured at 554 nm using a UV-Vis spectrophotometer.

[0117] The results of RhB removal in the comparative examples are shown in Table 3.

[0118] Table 3. RhB Removal Results of Comparative Examples

[0119]

[0120] Figure 1 The XRD patterns of Embodiment 1 and Comparative Embodiments 1 and 2 of the present invention are shown below. Figure 1 It can be seen that the two diffraction peaks at 2θ=27.5° and 13.1° in Example 1 are typical diffraction peaks of g-C3N4. The diffraction peak at 2θ=27.5° belongs to a layered stacked structure similar to graphite, and the diffraction peak at 2θ=13° represents the in-plane repeating unit of triazine heterocyclic atoms, which proves that g-C3N4 was successfully loaded into the material. In addition, the formation of Na-P type zeolite (zeolite P,(na)) and analcime was also observed. Compared with Example 1, there is a clear bulging peak between 2θ=20° and 35° (the bulging peak refers to the "bulge" corresponding to the amorphous polymer gel phase (NASH), that is, a broad and large diffuse peak), which is a typical diffraction peak of NASH. Compared with Example 1, the bulging peak at 2θ=20° to 35° in Example 2 disappears and a zeolite phase appears, which proves that the hydrothermal reaction effectively promotes the transformation of the amorphous polymer gel phase (NASH) into zeolite.

[0121] Figure 2The fluorescence spectra of Example 1 and Comparative Examples 1 and 2 are shown below. Compared to Comparative Examples 1 and 2, the fluorescence intensity of Example 1 is significantly reduced. This indicates that the hierarchical porous geopolymer support provides electron transport channels, significantly reducing the recombination rate of electron-hole pairs, promoting carrier separation, and improving photocatalytic efficiency. Meanwhile, the fluorescence emission peaks of Comparative Examples 1 and 2 are at 475 nm and 450 nm, respectively, while the fluorescence emission peak of Example 1 shifts to 500 nm towards longer wavelengths, indicating that the band gap of Example 1 is increased, resulting in a wider light absorption range. Furthermore, Comparative Example 1 has the largest half-width at half-maximum (HWHM), because its preparation process did not involve a hydrothermal reaction, and amorphous NASH is the main product, which is consistent with the conclusions of the XRD patterns.

[0122] In summary, this invention develops a novel integrated preparation strategy of "geopolymerization-foaming-hydrothermal crystallization". Through precise control of hydrothermal conditions, partial and selective in-situ crystallization of the amorphous gel phase in the porous geopolymer preform is achieved, constructing a unique composite structure in which a continuous geopolymer network and a zeolite-like dispersed phase interpenetrate. This composite structure spontaneously forms a synergistic multi-level porous system. The geopolymer phase provides a robust macroscopic framework and large pore channels, ensuring the material's mechanical strength and stability; the in-situ derived zeolite-like phase introduces abundant micropores and mesopores, greatly enhancing the material's specific surface area and its ability to adsorb and enrich pollutants; the confinement effect of the limited space extends the carrier lifetime of the graphitic carbon nitride phase, improving catalytic activity through interfacial electron transfer. This integrated design of "robust framework-enrichment sites-catalysis" achieves spatial coupling between adsorption and photocatalysis, significantly improving degradation efficiency. Using gasification slag as the main raw material, this invention successfully prepares high-performance photocatalytic materials at temperatures significantly lower than traditional zeolite synthesis temperatures, with a green and economical process. At the same time, it overcomes the technical bottlenecks of easy deactivation and difficult recycling of nanocatalysts, as well as the low strength and limited mass transfer of traditional porous materials, and also achieves the goals of "treating waste with waste" and "turning waste into treasure", with significant environmental and economic benefits.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a gasification slag-based composite phase multi-level pore photocatalytic material, characterized in that, The method comprises the following steps: Step S1, mixing urea and melamine and calcining to prepare graphite-phase carbon nitride; the calcination temperature is 550-600 DEG C; Step S2, mixing sodium hydroxide, water glass and water, and aging to prepare an alkaline activator; the mass ratio of sodium hydroxide, water glass and water is 17:125:51, the modulus of the alkaline activator is 1.4; the aging time is 24 h, so that sodium hydroxide and water glass fully react and diffuse, and silicate species reach depolymerization-polymerization equilibrium, forming a uniform and stable oligomeric silicate solution; Step S3, uniformly mixing gasification slag, graphite-phase carbon nitride prepared in step S1 and the alkaline activator prepared in step S2 to form a slurry; Step S4, adding a foam stabilizer and a foaming agent to the slurry prepared in step S3, and stirring to obtain a foamed slurry; the foaming agent is hydrogen peroxide solution; Step S5, injecting the foamed slurry prepared in step S4 into a mold, demolding after curing and shaping, and preparing a green body with a porous structure; Step S6, placing the green body prepared in step S5 in an alkaline mother liquor, and performing hydrothermal reaction, and finally obtaining the gasification slag-based composite-phase multi-level pore photocatalytic material after washing and drying; the alkaline mother liquor is sodium hydroxide solution with a concentration of 1-2 mol / L, the hydrothermal reaction temperature is 120-150 DEG C, and the hydrothermal reaction time is 6-8 h; the gasification slag-based composite-phase multi-level pore photocatalytic material has a multi-level pore structure with large pores, mesopores and micropores, the diameter of the large pores ranges from 0.5 mm to 2.0 mm, the diameter of the mesopores ranges from 10 μm to 300 μm, and the diameter of the micropores ranges from 5 nm to 50 nm; the large pores serve as a macroscopic framework and are distributed throughout the material, the mesopores are formed by the combined action of unreacted solid particle accumulation gaps, geopolymer gel shrinkage and hydrothermal reaction erosion, and the mesopores are mainly distributed in the wall of the large pores, and the micropores are inherent to the zeolite-like phase generated in situ.

2. The preparation method of the gasification slag-based composite phase multi-level porous photocatalytic material according to claim 1, characterized in that, In step S1, the mass ratio of urea to melamine is 3:1; the calcination is performed at a rate of 4-6 DEG C / min to 550-600 DEG C, and the temperature is kept for 2-2.5 h.

3. The method for preparing the gasification slag-based composite phase multi-level porous photocatalytic material according to claim 1, characterized in that, In step S3, the mass ratio of gasification slag, graphite-phase carbon nitride and alkaline activator is 100:(2.0-2.5):(25-30), the particle size of the gasification slag is over 200 mesh, the stirring speed is not less than 1500 r / min, and the stirring time is 1-3 min.

4. The method of claim 1, wherein the method is characterized by: In step S4, the foam stabilizer is plant protein and sodium dodecyl benzene sulfonate, and the dosages of plant protein, sodium dodecyl benzene sulfonate and hydrogen peroxide solution are 8.0-10.0%, 1.5% and 2.0% of the mass of the gasification slag respectively, the mass concentration of the hydrogen peroxide solution is 30%, the stirring speed is 1200-1400 r / min, and the stirring time is 20-40 s.

5. The method of claim 1, wherein the method further comprises: mixing the slag-based composite phase material with a photocatalytic material to form a mixture; and heating the mixture to form the photocatalytic material. In step S5, the curing is performed at 50-70 DEG C for 12 h.

6. A gasification slag-based composite-phase multi-level pore photocatalytic material prepared by the method according to any one of claims 1-5.

7. The use of the gasification slag-based composite-phase multi-level pore photocatalytic material according to claim 6 in the degradation of organic dyes.

8. Use according to claim 7, characterized in that, The application method is: the gasification slag-based composite-phase multi-level pore photocatalytic material is added to the target water body containing organic dyes, first stirring in the dark environment to reach adsorption equilibrium, and then carrying out the photocatalytic degradation process under light.

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