A porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere based on gasification slag, its preparation method and application

Abstract

This invention discloses a porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere based on gasification slag, its preparation method, and its application. It belongs to the technical field of solid waste resource utilization and wastewater treatment. The preparation method includes: mixing sodium hydroxide, water glass, and water, aging the mixture to obtain an alkaline activator; mixing urea and melamine evenly, calcining the mixture to obtain g-C3N4; mixing gasification slag, the alkaline activator, g-C3N4, and a heterojunction compatible semiconductor to form a slurry; adding a foam stabilizer and a foaming agent to the slurry and stirring to form a foamed slurry; adding the foamed slurry dropwise to hot silicone oil under stirring, allowing the droplets to rapidly solidify and form, then filtering and removing the slurry, followed by curing, filtration, and washing to obtain porous geopolymer-based microspheres; and placing the porous polymer-based microspheres in an alkaline solution for a hydrothermal reaction. This invention solves the problem of recovering powdered catalysts and achieves the dual purpose of solid waste resource utilization and wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and wastewater treatment technology, specifically relating to a gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere, its preparation method, and its application. Background Technology

[0002] Gasification slag is a silicon-aluminum based solid waste generated during coal gasification, with a huge annual output. Its open-air storage not only occupies a large amount of land resources but also easily leads to problems such as heavy metal leaching and dust pollution, seriously threatening soil and groundwater safety. With the deepening of my country's "waste-free city" construction and "solid waste resource utilization" strategy, developing efficient resource utilization technologies for gasification slag has become an urgent need for the sustainable development of the industry. On the other hand, industrial wastewater treatment faces severe challenges. Dyeing and printing wastewater is characterized by large discharge volumes, high organic matter concentrations, and poor biodegradability, belonging to recalcitrant industrial wastewater; antibiotic wastewater comes from the pharmaceutical, medical, and aquaculture industries, and is characterized by strong biotoxicity, recalcitrant degradation, and easy induction of drug resistance, posing a serious threat to aquatic ecosystems and human health. Traditional treatment methods include physical adsorption, biochemical treatment, and conventional oxidation technologies, but these have problems such as limited treatment efficiency, high operating costs, and easy generation of secondary pollution. Photocatalysis technology, as an environmentally friendly advanced oxidation process, shows broad application prospects in the treatment of organic matter degradation. Graphitic carbon nitride (g-C3N4) has been extensively studied due to its excellent visible light response characteristics, high chemical stability, and environmental friendliness. However, single g-C3N4 materials suffer from problems such as high recombination rates of photogenerated electron-hole pairs and limited visible light utilization efficiency, which restricts their practical applications.

[0003] Existing patent technology (CN202411522305.9) discloses a method for preparing a photocatalyst by acid treatment of gasification slag followed by calcination of g-C3N4 at 520–550℃ for 3–5 h. While this method improves the recombination problem of photogenerated carriers in g-C3N4, it still has significant shortcomings: the catalyst is in powder form, prone to agglomeration and poor dispersibility, leading to a reduction in active sites; it has poor resistance to shock loads, making recovery difficult and increasing the economic burden; and it is limited to the utilization of gasification slag, which has a low proportion (20%–40%), making it more suitable for high-value utilization such as co-firing or carbon flotation. Another related patent (CN202411520422.1) reports the preparation of a carbon-zeolite composite material by hydrothermal reaction of gasification slag with alkali, silicon source, and surfactant for the degradation of ammonia nitrogen and phenol in a persulfate system, but the reaction system is complex and the catalyst recovery problem remains unresolved. Therefore, developing a catalyst with broad raw material adaptability (covering gasification coarse slag), high strength, easy recovery, and efficient degradation of various organic substances is of great practical significance for the effective utilization of gasification slag solid waste resources. Summary of the Invention

[0004] Based on the technical problems existing in the prior art, the present invention provides a gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere, its preparation method and application, which solves the problems of easy agglomeration and difficult recovery of existing powdered g-C3N4, as well as the high preparation cost of g-C3N4 composite catalytic materials.

[0005] According to the first aspect of the present invention, the present invention provides a method for preparing gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres, comprising the following steps:

[0006] Step S1: Mix sodium hydroxide, water glass and water, and age to obtain an alkaline activator;

[0007] Step S2: Mix urea and melamine evenly, calcine, and obtain g-C3N4;

[0008] Step S3: Mix the gasification slag, the alkaline activator obtained in step S1, the g-C3N4 obtained in step S2, and the heterojunction adaptor semiconductor to form a slurry;

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

[0010] Step S5: The foaming slurry obtained in step S4 is added drop by drop to hot silicone oil under stirring. After the droplets solidify and form quickly, they are filtered out and then cured, filtered and washed to obtain porous geopolymer-based microspheres.

[0011] Step S6: The porous geopolymer-based microspheres obtained in step S5 are placed in an alkaline solution for hydrothermal reaction. After the reaction is completed, the microspheres are washed and dried to obtain the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0012] In some embodiments, in step S1, the mass ratio of sodium hydroxide, water glass, and water is (15-20):(120-130):(50-55), and the modulus of the alkali activator is 1.3-1.5.

[0013] In some embodiments, in step S2, 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 for 2 hours.

[0014] In some embodiments, in step S3, the particle size of the gasification slag passes through a 200-mesh sieve; the mass ratio of gasification slag, alkali activator, and g-C3N4 is 100:(25-30):(2.0-2.5); the mixing speed is not less than 1500 r / min, and the mixing time is 2 min.

[0015] In some embodiments, in step S3, the heterojunction adapter semiconductor is a type II heterojunction adapter semiconductor, a Z-type heterojunction adapter semiconductor, or an S-type heterojunction adapter semiconductor; the type II heterojunction adapter semiconductor is one or a combination of two or more of BiOI, BiOBr, and TiO2; the Z-type heterojunction adapter semiconductor is one or a combination of two of BiVO4 and α-Fe2O3; the S-type heterojunction adapter semiconductor is CdS; and the molar ratio of g-C3N4 to the heterojunction adapter semiconductor is (1-4):1.

[0016] In some embodiments, in step S4, the foam stabilizer is plant protein and sodium dodecylbenzenesulfonate, and the foaming agent is hydrogen peroxide solution; the mass of plant protein, sodium dodecylbenzenesulfonate, and hydrogen peroxide solution is 8.0% to 10.0%, 1.5%, and 2.0% of the mass of gasification slag, respectively; and the mass concentration of hydrogen peroxide solution is 30%.

[0017] In some embodiments, in step S4, the stirring speed is 1300 r / min and the stirring time is 30 s; in step S5, the hot silicone oil is 70℃~80℃; the curing temperature is 55℃~65℃ and the time is 6 h.

[0018] In some embodiments, in step S6, the alkaline solution is a sodium hydroxide solution with a concentration of 2 mol / L; the hydrothermal reaction temperature is 150℃~180℃, and the time is 8h~10h.

[0019] According to the second aspect of the present invention, the present invention provides a gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere prepared by the preparation method of the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere described in the present invention. The gasification slag-based porous polymer / g-C3N4 heterojunction photocatalytic microsphere has a particle size of 1 mm to 3 mm and a specific surface area of ​​65 m². 2 / g~85m 2 / g, with an average pore size of 20nm~25nm.

[0020] According to the technical solution of the third aspect of the present invention, the present invention provides an application of the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres described in the present invention in the treatment of antibiotic or dye wastewater. The application method includes: adding the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres to wastewater containing antibiotics or dyes, adding persulfate oxidant, stirring under dark conditions to reach adsorption equilibrium, and then carrying out photocatalytic degradation reaction under light source irradiation.

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

[0022] 1. This invention uses solid waste gasification slag as raw material and constructs a matrix material with a three-dimensional network framework through the coupling of geopolymerization reaction and slurry foaming technology. Furthermore, a hydrothermal reaction (e.g., 150℃~180℃) is used to regulate the in-situ transformation of part of the geopolymer gel into a zeolite / zeolite-like phase, forming a hierarchical porous structure. This structure not only significantly improves the specific surface area and active sites of the material but also avoids the high energy consumption and secondary pollution problems caused by traditional high-temperature calcination (>500℃), achieving a balance between energy saving, emission reduction, and green synthesis.

[0023] 2. This invention constructs g-C3N4-based heterojunction composite materials in situ within a hierarchical porous framework. By introducing type II, Z-type, or S-type heterojunction semiconductors, the heterojunction interface effect effectively promotes the separation of photogenerated electron-hole pairs, extending carrier lifetime. The porous geopolymer-zeolite phase support not only provides a good dispersion platform, preventing g-C3N4 aggregation, but its spatial confinement effect further inhibits electron-hole recombination, thereby significantly improving photocatalytic activity compared to single g-C3N4 or geopolymer materials, and greatly enhancing visible light utilization.

[0024] 3. Under light conditions, this invention can not only directly catalyze the degradation of organic dyes, but also activate persulfate to generate sulfate free radicals (SO4). - • and hydroxyl radicals (•OH) and other reactive species. These radicals work synergistically with photogenerated holes to deeply mineralize organic matter through electron transfer, electrophilic addition and other pathways, achieving an advanced oxidation process that combines photocatalysis and persulfate activation. This is far superior to single photocatalysis or chemical oxidation processes, and is especially suitable for the treatment of high-concentration, recalcitrant organic wastewater.

[0025] 4. The photocatalytic microspheres prepared by this invention possess excellent physical strength and water separation properties, solving the industry pain point of difficult recovery of powdered catalysts. The entire process is mild, the raw materials are widely available and inexpensive, and at the same time, it achieves high-value-added utilization of gasification slag through "waste treatment," resulting in significant economic and environmental benefits. Attached Figure Description

[0026] Figure 1a This is a SEM image of Embodiment 1 of the present invention.

[0027] Figure 1b This is a SEM image of Comparative Example 7 of the present invention.

[0028] Figure 2 These are XRD patterns of Embodiment 1 and Comparative Embodiment 7 of the present invention. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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".

[0033] This invention provides a gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microsphere, its preparation method, and its application, solving the problems of easy agglomeration and difficult recovery of existing powdered g-C3N4, as well as the high preparation cost of g-C3N4 composite catalytic materials. The typical preparation method of this invention includes: (1) preparing an alkaline activator; (2) calcining urea and melamine to obtain g-C3N4; (3) mixing gasification slag, alkaline activator, g-C3N4, and heterojunction semiconductor to form a slurry; (4) foaming with a composite foam stabilizer and hydrogen peroxide; (5) curing in hot silicone oil; and (6) obtaining multi-level porous photocatalytic microspheres through an alkaline hydrothermal reaction. This invention employs a three-step method of geopolymerization-foaming-hydrothermal conversion to construct a hierarchical porous structure in a porous geopolymer based on gasification slag and in-situ load g-C3N4 heterostructures. The resulting microsphere material possesses both high photocatalytic activity and easy recyclability, enabling efficient degradation of antibiotic wastewater (such as norfloxacin) and dyeing wastewater (such as methylene blue and RhB). Using gasification slag as raw material, this invention utilizes mild process conditions, solves the problem of recovering powdered catalysts, and achieves the dual objectives of solid waste resource utilization and wastewater treatment.

[0034] The present invention discloses a method for preparing gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres, comprising the following steps:

[0035] Step S1: Mix sodium hydroxide, water glass and water, and age to obtain an alkaline activator;

[0036] Step S2: Mix urea and melamine evenly and calcine to obtain g-C3N4 (graphite phase carbon nitride).

[0037] Step S3: Mix the gasification slag, the alkaline activator obtained in step S1, the g-C3N4 obtained in step S2, and the heterojunction adaptor semiconductor to form a slurry;

[0038] Step S4: Add foam stabilizer and foaming agent to the slurry obtained in step S3, stir, and prepare foamed slurry;

[0039] Step S5: The foaming slurry obtained in step S4 is added drop by drop to hot silicone oil under stirring. After the droplets solidify and form quickly, they are filtered out and then cured, filtered and washed to obtain porous geopolymer-based microspheres.

[0040] Step S6: The porous geopolymer-based microspheres obtained in step S5 are placed in an alkaline solution for hydrothermal reaction. After the reaction is completed, the microspheres are washed and dried to obtain the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0041] More specifically, in step S1, during the preparation of the activator, 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 ingredient due to excessive water, which directly affects the efficiency of subsequent polymerization reactions and the structure of the final product.

[0042] Preferably, in step S1, the mass ratio of sodium hydroxide, water glass, and water is (15-20):(120-130):(50-55), and the modulus of the alkali activator is 1.3-1.5. This preferred ratio aims to prepare a composite alkali activator with a modulus (SiO2 / Na2O molar ratio) of approximately 1.4. This ratio ensures the system has suitable alkalinity, effectively disrupting the glassy structure of the coal gasification slag and releasing active silica-alumina species, while also providing an optimal silicate ion concentration. This provides an ideal thermodynamic and kinetic environment for the subsequent geopolymerization reaction to form a stable three-dimensional network structure and for the directional crystallization of zeolite in the hydrothermal step. Deviating from this preferred ratio may lead to modulus imbalance in the activator, thereby affecting the strength of the geopolymer skeleton and the zeolite conversion efficiency. Optimizing this modulus in this scheme is crucial for achieving synergistic effects between the geopolymerization reaction and subsequent in-situ zeolite crystallization. If the modulus is too low (too alkaline), polymerization will be accelerated excessively, causing the slurry to thicken too quickly, which is not conducive to the uniform distribution and stability of bubbles; if the modulus is too high, the reaction driving force will be insufficient, the strength of the polymer skeleton will be low, and it will not be conducive to the formation of zeolite precursors.

[0043] Preferably, in step S1, the aging time is 24 hours. The aging process is crucial, as it allows sodium hydroxide and water glass to react fully, achieving equilibrium among silicate species within the system and forming a homogeneous and stable oligomeric silicate solution. This not only improves the homogeneity of the activator, preventing fluctuations in subsequent reactions due to excessively high or low local concentrations, but also effectively eliminates the heat generated during mixing, ensuring the stability of the activator's performance and thus guaranteeing the controllability and reproducibility of the polymerization process.

[0044] Preferably, in step S2, the mass ratio of urea to melamine is 3:1, which yields a better reaction rate and product purity. Calcination is performed by heating to 550℃-600℃ at a rate of 4℃ / min to 6℃ / min and holding for 2 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 materials.

[0045] Preferably, in step S3, the gasification slag is passed through a 200-mesh sieve to ensure a large specific surface area and promote its full interaction with the activator.

[0046] Preferably, in step S3, the mass ratio of gasification slag, alkali activator, and g-C3N4 is 100:(25-30):(2.0-2.5). This preferred ratio ensures that polymerization and condensation reactions occur fully under the action of the alkali activator to form geopolymers; the appropriate amount of g-C3N4 ensures high dispersibility and active sites while avoiding agglomeration.

[0047] Preferably, in step S3, the mixing speed is not less than 1500 r / min and the mixing time is 2 min, to ensure the high homogenization of the slurry and lay the foundation for the uniform formation of the multi-level pore structure.

[0048] Preferably, in step S3, the heterojunction adapter semiconductor is a type II heterojunction adapter semiconductor, a Z-type heterojunction adapter semiconductor, or an S-type heterojunction adapter semiconductor. A type II heterojunction adapter semiconductor is, for example, one or a combination of two or more of BiOI, BiOBr, and TiO2. A Z-type heterojunction adapter semiconductor is, for example, one or a combination of two of BiVO4 and α-Fe2O3. An S-type heterojunction adapter semiconductor is, for example, CdS.

[0049] Preferably, in step S3, the molar ratio of g-C3N4 to the heterojunction adapter semiconductor is (1-4):1. The heterojunction adapter semiconductor (such as BiOI, BiVO4, CdS, etc.) and g-C3N4 are precisely band-matched to construct type II, Z-type, or S-type heterojunctions. That is, the built-in electric field induced by the Fermi level difference at the heterojunction interface is used as the main driving force to achieve the directional separation and migration of photogenerated electron-hole pairs. Specifically, the type II heterojunction promotes spatial separation of electron-hole pairs through cross-bandgap; the Z-type heterojunction selectively retains carriers with the strongest redox capabilities; and the S-type heterojunction synergistically utilizes the built-in electric field, band bending, and interface interaction to drive carriers to migrate efficiently along a unique S-shaped path. This heterojunction design, in synergy with the spatial confinement effect of the porous polymer support, significantly suppresses the inherent photogenerated electron-hole pair recombination of g-C3N4 and effectively prolongs the carrier lifetime, thereby synergistically improving the photocatalytic quantum efficiency of the composite material.

[0050] Preferably, in step S4, the foam stabilizer is plant protein and sodium dodecylbenzenesulfonate, and the foaming agent is hydrogen peroxide solution; the mass of plant protein, sodium dodecylbenzenesulfonate, and hydrogen peroxide solution is 8.0%–10.0%, 1.5%, and 2.0% of the mass of gasification slag, respectively; and the mass concentration of hydrogen peroxide solution is 30%.

[0051] Preferably, in step S4, the stirring speed is 1300 r / min and the stirring time is 30 s.

[0052] Preferably, in step S5, the hot silicone oil is heated to 70°C to 80°C.

[0053] Preferably, in step S5, the curing temperature is 55℃~65℃ and the curing time is 6h.

[0054] Preferably, in step S6, the alkaline solution is a sodium hydroxide solution with a concentration of 2 mol / L.

[0055] Preferably, in step S6, the hydrothermal reaction temperature is 150℃~180℃ and the time is 8h~10h.

[0056] The gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres prepared by the method described in this invention preferably have a particle size of 1 mm to 3 mm and a specific surface area of ​​65 m². 2 / g~85m 2With an average pore size of 20nm–25nm, it achieves excellent photocatalytic performance. The process combines geopolymerization and foaming to form a network-like matrix framework with millimeter-scale pores in one step. These millimeter-scale pores are mainly generated by the foaming agent under the action of a foam stabilizer, and are approximately spherical or ellipsoidal in shape, serving as a macroscopic framework throughout the material. Subsequently, a hydrothermal reaction at a certain temperature transforms some of the geopolymers in this matrix framework into zeolite / zeolite-like phases with nanoscale micropores. This results in a multi-level porous structure, significantly increasing the specific surface area and active sites of the material, and preventing g-C3N4 agglomeration. Simultaneously, a heterojunction semiconductor is introduced, utilizing the heterojunction interface effect to effectively promote the separation of photogenerated electron-hole pairs and extend carrier lifetime.

[0057] The gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres of the present invention are particularly suitable for application in the treatment of antibiotic or dye wastewater. The application method includes, for example, adding the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres to wastewater containing antibiotics or dyes, adding a persulfate oxidant, first stirring under dark conditions to reach adsorption equilibrium (e.g., stirring for 30-40 minutes), and then carrying out a photocatalytic degradation reaction under light source irradiation. More specifically, for example, the persulfate oxidant is sodium persulfate or potassium persulfate, the light source is a xenon lamp with a power of 350W, and the irradiation time is 30-60 minutes. For antibiotic wastewater, the antibiotic is norfloxacin (NOR), with an initial concentration of 5 mg / L-20 mg / L, the dosage of the photocatalytic material is 0.8 g / L-2.5 g / L, and the dosage of persulfate is 1.0 mmol / L-1.5 mmol / L. For dye wastewater, the dye is methylene blue or rhodamine (RhB), with an initial concentration of 40 mg / L to 80 mg / L, a photocatalytic material dosage of 4.0 g / L to 8.0 g / L, and a persulfate dosage of 2.0 mmol / L to 3.0 mmol / L.

[0058] The following description, in conjunction with more specific embodiments, provides further details.

[0059] Example 1

[0060] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0061] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0062] Step 3: Weigh 100g of gasification slag, 2.5g of g-C3N4, 30g of alkali activator, and 3.1g of BiOBr and mix them. Stir at 1500r / min for 2min to obtain a slurry.

[0063] Step 4: Weigh 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0064] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0065] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 180℃ for 10 h, wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0066] Example 2

[0067] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0068] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0069] Step 3: Weigh 100g of gasification slag, 2.0g of g-C3N4, 25g of alkali activator, and 3.1g of BiOBr and mix them. Stir at 1500r / min for 2 minutes to obtain a slurry.

[0070] Step 4: Weigh 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0071] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0072] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 180℃ for 10 h, wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0073] Example 3

[0074] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0075] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0076] Step 3: Mix 100g of gasification slag, 2.5g of g-C3N4, 30g of alkali activator, and 3.1g of BiOBr in a stirring device and stir at 1500r / min for 2min to form a slurry;

[0077] Step 4: Weigh 8.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0078] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0079] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 180℃ for 10 h, wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0080] Example 4

[0081] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0082] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0083] Step 3: Mix 100g of gasification slag, 2.5g of g-C3N4, 30g of alkali activator, and 3.1g of BiOBr in a stirring device and stir at 1500r / min for 2min to form a slurry;

[0084] Step 4: Weigh 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0085] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0086] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 150℃ for 10 h, then wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0087] Example 5

[0088] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0089] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0090] Step 3: Mix 100g of gasification slag, 2.5g of g-C3N4, 30g of alkali activator, and 0.8g of TiO2 in a stirring device and stir at 1500r / min for 2min to form a slurry;

[0091] Step 4: Weigh 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0092] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0093] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 180℃ for 10 h, wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0094] Example 6

[0095] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0096] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0097] Step 3: Mix 100 g of gasification slag, 2.5 g of g-C3N4, 30 g of alkali activator, and 2.4 g of BiVO4 in a stirring device and stir at 1500 r / min for 2 min to form a slurry;

[0098] Step 4: Weigh 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0099] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0100] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 180℃ for 10 h, wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0101] Example 7

[0102] Step 1: Weigh 17g sodium hydroxide, 125g water glass and 51g water and mix them evenly. After the solution becomes clear, age it for 24 hours to obtain an alkaline activator with a modulus of 1.4.

[0103] Step 2: Mix urea and melamine at a mass ratio of 3:1 until homogeneous, raise the temperature to 600℃ at a rate of 5℃ / min, and keep it at that temperature for 2 hours to obtain g-C3N4;

[0104] Step 3: Mix 100g of gasification slag, 2.5g of g-C3N4, 30g of alkali activator, and 2.1g of CdS in a stirring device and stir at 1500r / min for 2min to make a slurry;

[0105] Step 4: Weigh 10.0g of plant protein, 1.5g of sodium dodecylbenzenesulfonate and 2.0g of hydrogen peroxide solution (30% mass concentration), add them to the slurry in sequence, and stir at 1300r / min for 30s to prepare foamed slurry;

[0106] Step 5: Add the foaming slurry dropwise into hot silicone oil at 70°C while stirring. After the slurry droplets solidify rapidly during settling, filter and remove them. Cure at 60°C for 6 hours, then wash to obtain porous geopolymer-based microspheres.

[0107] Step 6: Place the porous geopolymer microspheres in an alkaline solution with a mass concentration of 2 mol / L, react at 180℃ for 10 h, wash and dry to prepare gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres.

[0108] Comparative Example 1

[0109] A method for preparing a gasification slag-based photocatalytic material, the steps of which are the same as in Example 1, except that the temperature is raised to 800°C in step 2 of Example 1, while the other steps are the same as in Example 1.

[0110] Comparative Example 2

[0111] A method for preparing a gasification slag-based photocatalytic material, the steps of which are the same as in Example 1, except that in step 4 of Comparative Example 2, plant protein sodium dodecylbenzenesulfonate was not added, while the remaining steps are the same as in Example 1.

[0112] Comparative Example 3

[0113] A method for preparing a gasification slag-based photocatalytic material, the steps of which are the same as in Example 1, except that the heating temperature in step 6 of Comparative Example 3 is 120°C, and the remaining steps are the same as in Example 1.

[0114] Comparative Example 4

[0115] A method for preparing a gasification slag-based photocatalytic material, the steps are as in Example 1, except that Comparative Example 4 does not have step 2, and in step 3, 100g of gasification slag and 30g of alkaline activator are mixed and placed into a stirring device, stirred at 1500r / min for 2min to form a slurry; the remaining steps are the same as in Example 1.

[0116] Comparative Example 5

[0117] A method for preparing a gasification slag-based photocatalytic material, the steps are as in Example 1, the difference being that in Comparative Example 5, in step 3, 100g of gasification slag, 2.5g of g-C3N4 and 30g of alkaline activator are mixed and placed into a stirring device, stirred at 1500r / min for 2min to form a slurry; the remaining steps are the same as in Example 1.

[0118] Comparative Example 6

[0119] A method for preparing a gasification slag-based photocatalytic material, the steps of which are the same as in Example 1, except that Comparative Example 6 does not have step 6, while the remaining steps are the same as in Example 1.

[0120] Comparative Example 7

[0121] A method for preparing a gasification slag-based photocatalytic material, the steps of which are the same as in Example 1, except that in Comparative Example 7, step 3 involves mixing 100g of gasification slag and 30g of alkaline activator in a stirring device and stirring at 1500r / min for 2min to form a slurry; step 6 is omitted, and the remaining steps are the same as in Example 1.

[0122] The performance of the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres prepared in Examples 1-7 and Comparative Examples 1-7 was tested, and the results are shown in Table 1:

[0123] Table 1. Property parameters of gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres

[0124]

[0125] Application Experiment Example 1

[0126] Photocatalytic experiments were conducted using Examples 1-7 and Comparative Examples 1-7, and the specific methods were as follows:

[0127] 0.8 g / L of gasification slag-based photocatalytic material and 1.0 mmol / L of sodium persulfate were added to simulated wastewater containing 5 mg / L NOR and stirred at 1000 r / min in the dark for 30 min to reach adsorption-desorption equilibrium. Then, the mixture was stirred for 60 min under irradiation with a 350 W xenon lamp to carry out the photo-reaction.

[0128] Application Experiment Example 2

[0129] Photocatalytic experiments were conducted using Examples 1-7 and Comparative Examples 1-7, and the specific methods were as follows:

[0130] 2.5 g / L of gasification slag-based photocatalytic material and 1.5 mmol / L of sodium persulfate were added to simulated wastewater containing 20 mg / L NOR and stirred at 1000 r / min in the dark for 40 min to reach adsorption-desorption equilibrium. Then, the mixture was stirred for 60 min under irradiation with a 350 W xenon lamp to carry out the photo-reaction.

[0131] Application Experiment Example 3

[0132] Photocatalytic experiments were conducted using Examples 1-7 and Comparative Examples 1-7, and the specific methods were as follows:

[0133] 4.0 g / L of gasification slag-based photocatalytic material and 2.0 mmol / L of sodium persulfate were added to simulated wastewater containing 40 mg / L RhB. The mixture was stirred at 1000 r / min in the dark for 30 min to reach adsorption-desorption equilibrium. Then, it was stirred for 60 min under a 350 W xenon lamp light source to carry out the photo-reaction.

[0134] Application Experiment Example 4

[0135] Photocatalytic experiments were conducted using Examples 1-7 and Comparative Examples 1-7, and the specific methods were as follows:

[0136] 8.0 g / L of gasification slag-based photocatalytic material and 3.0 mmol / L of sodium persulfate were added to simulated wastewater containing 80 mg / L RhB. The mixture was stirred at 1000 r / min in the dark for 40 min to reach adsorption-desorption equilibrium. Then, it was stirred for 60 min under irradiation with a 350 W xenon lamp to carry out the photo-reaction.

[0137] The removal effects of different gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres on RhB and NOR are shown in Table 2:

[0138] Table 2. Removal results of porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres based on different gasification slags.

[0139]

[0140] Figure 1a , Figure 1b The images show SEM images of Example 1 and Comparative Example 7, respectively. As can be seen from the images, after hydrothermal synthesis control, Example 1 exhibits spherical and flower-like zeolite phases with a rich structure. In contrast, Comparative Example 7 shows a pore structure with larger pore sizes and a simpler pore structure compared to Example 1.

[0141] Figure 2 The XRD patterns of Embodiment 1 and Comparative Embodiment 7 of the present invention are shown below. Figure 2It 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, with the peak at 2θ = 27.5° belonging to a layered stacked structure similar to graphite, and the peak at 2θ = 13° representing an in-plane repeating unit of triazine heterocyclic atoms; the diffraction peaks at 2θ = 27.3°, 34.6°, 46.4°, and 55.9° are characteristic peaks of BiOI; this proves that both g-C3N4 and BiOI were 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 7, there is a distinct bulging peak between 2θ = 20° and 30°, which is a typical diffraction peak of the amorphous polymer gel phase (NASH), proving that the hydrothermal reaction effectively promotes the transformation of (NASH) into zeolite.

[0142] In summary, this invention uses solid waste gasification slag as raw material and constructs a matrix material with a three-dimensional network framework through the coupling of geopolymerization reaction and slurry foaming technology. Furthermore, a hydrothermal reaction (e.g., 150℃~180℃) is used to regulate the in-situ transformation of part of the geopolymer gel into a zeolite / zeolite-like phase, forming a hierarchical porous structure. This structure not only significantly improves the specific surface area and active sites of the material but also avoids the high energy consumption and secondary pollution problems caused by traditional high-temperature calcination (>500℃), achieving a balance between energy saving and green synthesis. This invention in-situ constructs g-C3N4-based heterojunction composite materials within a hierarchical porous framework. By introducing type II, Z-type, or S-type heterojunction semiconductors, the heterojunction interface effect effectively promotes the separation of photogenerated electron-hole pairs, extending carrier lifetime. The porous geopolymer-zeolite phase support not only provides an excellent dispersion platform, preventing g-C3N4 aggregation, but its spatial confinement effect also further inhibits electron-hole recombination, thus significantly improving photocatalytic activity compared to single g-C3N4 or geopolymer materials, and greatly enhancing visible light utilization. Under light irradiation, this invention can not only directly catalyze the degradation of organic dyes, but also activate persulfate to generate sulfate radicals (SO42-). - • and hydroxyl radicals (•OH), among other reactive species. These radicals synergistically interact with photogenerated holes to deeply mineralize organic matter through electron transfer and electrophilic addition, achieving an advanced oxidation process synergistically combining photocatalysis and persulfate activation. This is far superior to single photocatalysis or chemical oxidation processes, and is particularly suitable for treating high-concentration, recalcitrant organic wastewater. The photocatalytic microspheres prepared in this invention possess excellent physical strength and water separation properties, solving the industry pain point of difficult recovery of powdered catalysts. The entire process is mild, with widely available and low-cost raw materials, while simultaneously achieving high-value-added utilization of gasification slag through "waste-to-waste" treatment, resulting in significant economic and environmental benefits.

[0143] 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 porous polymeric / g-C3N4 heterojunction photocatalytic microsphere, characterized in that, The method comprises the following steps: S1, mixing sodium hydroxide, water glass and water, aging to obtain an alkali activator; wherein the aging time is 24 h; the mass ratio of sodium hydroxide, water glass and water is (15-20):(120-130):(50-55), and the modulus of the alkali activator is 1.3-1.5; S2, uniformly mixing urea and melamine, and calcining to obtain g-C3N4; wherein the calcining temperature is 550-600 DEG C; S3, mixing the gasification slag, the alkali activator obtained in S1, the g-C3N4 obtained in S2 and a heterojunction matching semiconductor to prepare a slurry; wherein the heterojunction matching semiconductor is a type II heterojunction matching semiconductor, a type Z heterojunction matching semiconductor or a type S heterojunction matching semiconductor; the type II heterojunction matching semiconductor is one or a combination of two or more of BiOI, BiOBr and TiO2; the type Z heterojunction matching semiconductor is one or a combination of two of BiVO4 and alpha-Fe2O3; the type S heterojunction matching semiconductor is CdS; the molar ratio of g-C3N4 to the heterojunction matching semiconductor is (1-4):1; the particle size of the gasification slag is over 200 mesh; the mass ratio of the gasification slag, the alkali activator and g-C3N4 is 100:(25-30):(2.0-2.5); S4, adding a foam stabilizer and a foaming agent to the slurry obtained in S3, and stirring to prepare a foaming slurry; S5, dropwise adding the foaming slurry obtained in S4 to hot silicon oil under stirring, taking out after the liquid drops are quickly solidified and formed, and obtaining porous geopolymer-based microspheres through curing, filtering and washing; S6, placing the porous geopolymer-based microspheres obtained in S5 in an alkaline solution, and performing hydrothermal reaction, and finally obtaining the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres through washing and drying after the reaction is completed; wherein the alkaline solution is a sodium hydroxide solution with a concentration of 2 mol / L; the hydrothermal reaction temperature is 150-180 DEG C, and the time is 8-10 h.

2. The preparation method of gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres according to claim 1, characterized in that, In S2, the mass ratio of urea to melamine is 3:1; the calcining is performed at a rate of 4-6 DEG C / min to 550-600 DEG C, and the temperature is kept for 2 h.

3. The preparation method of gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres according to claim 1, characterized in that, In S3, the mixing and stirring speed is not less than 1500 r / min, and the stirring time is 2 min.

4. The preparation method of gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres according to claim 1, characterized in that, In S4, the foam stabilizer is plant protein and sodium dodecyl benzene sulfonate, and the foaming agent is hydrogen peroxide solution; the mass of the plant protein, the sodium dodecyl benzene sulfonate and the hydrogen peroxide solution is 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%.

5. The preparation method of gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres according to claim 1, characterized in that, In S4, the stirring speed is 1300 r / min, and the stirring time is 30 s; in S5, the hot silicon oil is at 70-80 DEG C; the curing temperature is 55-65 DEG C, and the time is 6 h.

6. The gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres prepared by the method for preparing the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres according to any one of claims 1 to 5, characterized in that, The gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres have a particle size of 1mm-3mm, a specific surface area of 65m 2 / g-85m 2 / g, and an average pore size of 20nm-25nm.

7. Application of the gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres of claim 6 in the treatment of antibiotic or dye wastewater, characterized by, The application method comprises the following steps: adding gasification slag-based porous geopolymer / g-C3N4 heterojunction photocatalytic microspheres into wastewater containing antibiotics or dyes, adding a persulfate oxidant, stirring in the dark until adsorption equilibrium is reached, and then performing a photocatalytic degradation reaction under light source irradiation.

Images