Preparation method of photocatalytic cement and application of photocatalytic cement in water purification and green ammonia preparation

Abstract

The application belongs to the field of building materials, and particularly relates to a preparation method of photocatalytic cement and application of the photocatalytic cement in water purification and green ammonia preparation. The preparation method comprises PMMA etching, photocatalytic fine aggregate preparation and photocatalytic cement preparation. The photocatalytic fine aggregate is lifted to the surface layer of the material by using the high light transmission and low density characteristics of PMMA and combining with aluminum powder gas production, so that the light utilization rate and mass transfer efficiency are greatly improved. The photocatalytic cement can efficiently purify water pollutants, reduce nitrate in situ to prepare green ammonia, and can be used for preparing floating infrastructure or small equipment devices with water purification and in-situ ammonia preparation functions. The process is simple, the cost is controllable, the microstructure and cleaning function are highly customizable, and the process is easy to scale up for engineering applications.

Description

Technical Field

[0001] This invention belongs to the field of building materials, specifically relating to a method for preparing photocatalytic cement and its application in water purification and green ammonia preparation. Background Technology

[0002] In dense urban concrete buildings, airflow is obstructed, and wastewater from urban canals and sewers is difficult to clean in a timely manner, significantly impacting building durability, aesthetics, and residents' health. Therefore, there is an urgent need to develop efficient and scalable new environmental purification technologies to improve environmental pollution.

[0003] Introducing photocatalysis technology into cement-based materials to prepare photocatalytic cement-based composites is a rapidly scalable, low-cost, effective, and practical environmental improvement solution. Photocatalytic cement-based composites can replace ordinary cement, performing not only basic load-bearing functions but also, under light exposure, removing pollutants, self-cleaning surfaces, and reducing the probability of steel reinforcement corrosion, achieving a unified "structure-function" integration.

[0004] First, these materials have advantages in large-area concrete structures such as bridges, roads, ditches, and building facades: their long-term exposure to sunlight and direct contact with air and water pollutants provides ideal conditions for photocatalytic environmental purification. Moreover, cement is the second most used material in human history after water. Leveraging cement's high strength-to-price ratio, excellent durability, and simple production process, photocatalytic cement-based composite materials have become a superior approach for the large-scale production and industrialization of nano-photocatalysts.

[0005] The existing technologies mainly include the following technical solutions:

[0006] First, photocatalyst nanoparticles are directly incorporated into cement to prepare photocatalytic cement-based composite materials. However, due to the complex amorphous porous structure and opaque nature of hydrated calcium silicate gel, light cannot penetrate deeply into the material. Only the exposed nanoparticles on the outer layer can effectively function. Therefore, this method has low photocatalytic efficiency, low mass transfer efficiency in the high-density porous structure, and requires a large amount of photocatalyst, which is not conducive to cost control.

[0007] Secondly, photocatalytic coatings can be applied to existing concrete / cement mortar structures. These coatings are composites of photocatalysts and organic matrices such as epoxy resins and acrylates. However, the coating preparation process is complex, has low durability in real-world environments (easily aging or corroding), and has high solvent costs.

[0008] Third, current mainstream approaches to the large-scale production of photocatalysts mainly include support-supported methods (such as immobilizing photocatalysts on metal, ceramic, or polymer substrates) and the construction of various photocatalytic reactors. However, these methods still have significant limitations in terms of cost control, structural durability, long-term operational stability, process simplicity, and scalability, making it difficult to meet the needs of engineering applications.

[0009] Fourth, existing photocatalytic building materials generally only have the function of degrading a single pollutant, and most of them only achieve the harmless removal of pollutants. Very few can simultaneously achieve pollutant treatment and resource recycling, which is difficult to meet the environmental governance development needs of "treating waste with waste and recycling resources". The added value and application scenarios of the materials are greatly limited.

[0010] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0011] To address the problems existing in the prior art, the present invention provides a method for preparing photocatalytic cement, the method comprising the following steps: (I) Etching of polymethyl methacrylate (PMMA) (I-1) The polymethyl methacrylate particles were washed and dried to obtain dried polymethyl methacrylate particles; (I-2) Immerse the dried polymethyl methacrylate particles in an etching solution, clean and dry them after etching to obtain etched polymethyl methacrylate particles. (II) Preparation of photocatalytic fine aggregate (II-1) The photocatalyst, the etched polymethyl methacrylate particles, trihydroxyaminomethane, and dopamine hydrochloride were added to water in sequence and stirred to obtain a mixed solution; (II-2) The mixed solution is heated and evaporated to dryness to obtain solid particles; (II-3) The solid particles are sequentially impregnated and dried to obtain polymethyl methacrylate particles loaded with photocatalyst, which are photocatalytic fine aggregates; the pH of the hydrochloric acid dopamine system can be adjusted to be weakly alkaline, and polydopamine is formed under oxygen-containing conditions, thereby adhering the nano-photocatalyst to the surface of the etched PMMA particles, and successfully preparing photocatalytic fine aggregates. (III) Preparation of photocatalytic cement (III-1) Mix cement, standard sand, and activated carbon, then add water and stir to obtain cementitious material; (III-2) The photocatalytic fine aggregate and aluminum powder are added to the cement base in sequence and stirred. The stirred mixture is then shaped to obtain the photocatalytic cement.

[0012] The photocatalyst is a nanopowder type photocatalyst, including but not limited to one of P25 type TiO2, g-C3N4 or AgCu-CN; the cement is ordinary silicate cement conforming to national standard GB175-2023; and the standard sand is standard sand conforming to national standard GB / T17671-2021.

[0013] To facilitate understanding of this invention, the working principle of this invention is explained as follows: (1) The photocatalytic cement of the present invention relies on the photocatalyst supported on the etched PMMA particles to carry out photocatalytic action to remove pollutants in water and reduce nitrate in water to ammonia.

[0014] (2) PMMA particles have the characteristics of high light transmittance and low density. During the 24 hours before demolding, they can be automatically lifted to the upper layer of the material by the hydrogen gas generated by the reaction of aluminum powder reducing water. This principle allows the photocatalytic fine aggregate to be close to the surface of the material, increasing the amount of photocatalytic fine aggregate directly exposed to sunlight, thereby improving the absorption efficiency of photocatalytic cement to sunlight.

[0015] (3) PMMA particles dispersed in cement matrix, with their high light transmittance and combined with the porous properties of cement matrix, can improve the penetration depth of light in the material volume, thereby improving the light absorption efficiency of nano-photocatalyst in cement matrix.

[0016] (4) Porous cement matrix can promote the mass transfer efficiency of pore solution, thereby improving the efficiency of photocatalytic pollutant cleaning and material conversion.

[0017] Preferably, in step (I-1), polymethyl methacrylate particles are added to deionized water, ultrasonically cleaned at 40-45°C for 1-2 hours and then dried; then the dried polymethyl methacrylate particles are added to methanol, ultrasonically cleaned at 40-45°C for 1-2 hours and then dried to obtain dried polymethyl methacrylate particles.

[0018] The PMMA particles are cleaned by ultrasonic cleaning with deionized water and methanol to remove dust, oil, and residual additives from the production process. Drying removes residual solvents from the particle surface and pores to ensure that the etching solution is in full contact with the PMMA substrate during the subsequent etching process.

[0019] Preferably, in step (I-2), the dried polymethyl methacrylate particles are immersed in piranha washing solution and etched at 15-25℃ (room temperature) for 30-60 seconds. After etching, they are washed with deionized water and dried to obtain etched polymethyl methacrylate particles.

[0020] The piranha solution is a mixture of concentrated sulfuric acid and 30% hydrogen peroxide solution in a volume ratio of 7:3. The strong oxidizing properties of the piranha solution are used to micro-etch the surface of PMMA particles, creating abundant micro-nano rough structures and active groups on the particle surface. This enhances the loading strength and amount of subsequent photocatalysts on the particle surface. The short etching time avoids damage to the overall structure of the PMMA particles, preserving their core characteristics of low density and high light transmittance.

[0021] Preferably, in step (II-1), the photocatalyst is added to deionized water and stirred at 15-25°C for 30-40 min; then the etched polymethyl methacrylate particles are added and stirred at 15-25°C for 30-40 min; then trihydroxyaminomethane is added and stirred at 15-25°C for 1-3 min; then dopamine hydrochloride is added and stirred at 15-25°C for 30-40 min to obtain a mixed solution. The mass ratio of the photocatalyst, the etched polymethyl methacrylate particles, the trihydroxyaminomethane, and the dopamine hydrochloride is 0.3:0.5-20:1-3:0.1-1.

[0022] The stepwise feeding and stirring process ensures uniform dispersion of all raw materials. Dispersing the photocatalyst first prevents nanoparticle agglomeration and ensures its uniform distribution in the solution. Adding etched PMMA particles followed by stirring allows the photocatalyst to fully contact the particle surface. Trihydroxyaminomethane acts as a buffer, rapidly adjusting the pH of the system to a weakly alkaline state, providing a suitable reaction environment for the self-polymerization of dopamine hydrochloride. Dopamine hydrochloride self-polymerizes into polydopamine in a weakly alkaline and oxygen-containing environment, providing strong adhesion between the photocatalyst and PMMA particles and preventing the photocatalyst from falling off.

[0023] Preferably, in step (II-2), the mixed solution is heated to 50-60°C and maintained for 12-16 hours until the water evaporates to obtain solid particles.

[0024] Among these methods, heating at a low temperature of 50-60℃ can slowly evaporate moisture, avoiding rapid drying which would lead to uneven distribution of the photocatalyst on the particle surface. In addition, the PMMA particles need to be disturbed and turned over at regular intervals during the operation to ensure that the photocatalyst is uniformly loaded on each surface of the PMMA particles, avoiding insufficient loading at the bottom of the particles. During heating, the supernatant can also be aspirated in stages to reduce the heating time, improve the preparation efficiency, and at the same time prevent the photocatalyst on the particle surface from being lost with the supernatant.

[0025] Preferably, in step (II-3), the solid particles are immersed in deionized water at 15-25°C for 1-2 hours. After completion, they are taken out and dried at 60-65°C for 2-6 hours to obtain polymethyl methacrylate particles loaded with photocatalyst, which is photocatalytic fine aggregate.

[0026] Among them, deionized water wetting can wash away the free photocatalyst and residual reaction aids that are not firmly loaded on the particle surface, so as to avoid the free photocatalyst being wrapped by cement hydration products and unable to play a catalytic role after the cement base material is added later; low temperature drying can remove the moisture in the particle pores, while avoiding the aging and decomposition of the polydopamine layer caused by high temperature, thus ensuring the loading strength of the photocatalyst.

[0027] Preferably, in step (III-1), cement, standard sand, and activated carbon are mixed for 30-40 seconds and then added to deionized water and stirred for 30-40 seconds to obtain cementitious material; The mass ratio of the cement, the standard sand, and the activated carbon is 8:1-24:0.1-2.

[0028] The process of first dry-mixing cement, standard sand, and activated carbon ensures uniform mixing of solid powders. Activated carbon is dispersed in the cement matrix in advance, providing adsorption sites for subsequent water pollutants. After adding water and stirring, the cement undergoes a preliminary hydration reaction, forming a cement paste with a certain fluidity, which provides a matrix for the subsequent dispersion of aggregates and aluminum powder.

[0029] Preferably, in step (III-2), the photocatalytic fine aggregate is added to the cementitious base and stirred for 60-90 seconds, then aluminum powder is added and stirred for 120-150 seconds, and finally the stirred mixture is placed in a mold and cured for 24-36 hours under the national standard GB / T17671-2021 to obtain the photocatalytic cement.

[0030] The process involves first adding photocatalytic fine aggregate and stirring to ensure that the aggregate is evenly dispersed in the cementitious matrix; then adding aluminum powder and stirring to prevent the aluminum powder from reacting with water prematurely and generating gas, thus ensuring that the aluminum powder is evenly dispersed in the slurry; the aluminum powder reacts with the alkaline solution produced by cement hydration to generate hydrogen gas, forming tiny bubbles in the slurry, while simultaneously lifting the low-density photocatalytic fine aggregate to the upper layer of the slurry, making the aggregate closer to the material surface and improving light utilization; and curing under standard conditions for 24 hours ensures that the cementitious matrix is ​​fully hydrated and formed.

[0031] Based on the same technical concept, another aspect of the present invention is to provide a photocatalytic cement obtained by the above preparation method, which comprises the following raw materials in parts by weight: 8 parts cement, 1-24 parts standard sand, 0.1-2 parts activated carbon, and 2-24 parts photocatalytic fine aggregate.

[0032] Based on the same technical concept, another aspect of the present invention provides the application of the aforementioned photocatalytic cement in the preparation of floating or non-floating water purification and in-situ ammonia production infrastructure or small-scale equipment. The photocatalytic cement can float on the water surface or be fixed in place to purify polluted water, while simultaneously producing ammonia with high production and application value in situ. Specifically, the infrastructure or small-scale equipment includes, but is not limited to: (a) Floating infrastructure: (1) Floating revetment / slope protection components for river ecological restoration; (2) Infrastructure for floating ecological boardwalks / access platforms in landscape water bodies and wetland parks; (3) Floating intercepting and purification dam for municipal drainage pipe network sewage outlets into rivers; (4) Floating ecological purification pond structure components for decentralized rural sewage treatment; (5) Floating circulating purification dam and isolation dike for aquaculture wastewater treatment; (6) Floating seepage-proof purification tank structure for wastewater treatment in mines / industrial parks; (7) Floating ecological buffer zone infrastructure for watershed non-point source pollution control in sponge city projects; (8) Floating ecological enclosure and purification dam for improving water quality in reservoirs / lakes.

[0033] (ii) Non-floating infrastructure (1) Fixed underwater lining / slope protection components for river ecological restoration; (2) Foundation lining structural components for underwater boardwalks / waterfront platforms in landscape water bodies and wetland parks; (3) Inspection wells and sewage outlets of municipal drainage networks, fixed intercepting and purification linings and retaining wall components; (4) Fixed tank lining purification structure for rural decentralized sewage treatment biochemical ponds; (5) Fixed bottom water purification and denitrification structure for aquaculture ponds; (6) Fixed seepage-proof lining and purification wall components for wastewater treatment ponds in mines / industrial parks; (7) Sponge city regulating tanks and rain garden fixed filter bed purification lining structural components; (8) Fixed underwater ecological dam and enclosure purification components for water quality improvement of reservoirs / lakes.

[0034] (III) Floating Small Equipment and Components (1) Household landscape fish pond / aquarium floating water purification and ammonia generation integrated module; (2) Modular floating water purification unit devices that can be spliced ​​together for small rivers / ditches; (3) Core components of a laboratory-scale photocatalytic water purification and nitrate reduction ammonia production reactor; (4) Floating initial rainwater purification and storage module for rain gardens / sponge cities; (5) Floating modular photocatalytic purification package for emergency water pollution treatment; (6) Floating water quality precision control and purification device for aquaculture seedling ponds; (7) Floating self-cleaning purification and circulation module for urban landscape fountains; (8) Floating photocatalytic denitrification purification unit device for pretreatment of livestock and poultry breeding wastewater.

[0035] (iv) Non-floating small equipment and components (1) Household fish tank / aquarium fixed built-in water purification and ammonia generation integrated module; (2) Small-scale fixed wall-mounted water purification unit for rivers / ditches; (3) Core component of the fixed built-in reaction tank liner of the laboratory photocatalytic reaction device; (4) Fixed infiltration and purification modules for rain gardens / sponge cities; (5) Emergency water pollution treatment stationary submersible photocatalytic purification unit device; (6) Fixed bottom water quality precision control and purification device for aquaculture seedling ponds; (7) Fixed pool bottom self-cleaning purification and circulation module for urban landscape fountains; (8) Fixed built-in photocatalytic denitrification and purification unit device for livestock and poultry breeding wastewater pretreatment pond.

[0036] The beneficial effects of this invention are as follows: 1. Solving the core pain point of low light utilization rate of traditional materials: This invention uses polymethyl methacrylate (PMMA) to support photocatalysts by etching, and combines aluminum powder hydration gas generation to lift low-density, high-transmittance photocatalytic fine aggregates to the surface of the material, which greatly improves the light absorption efficiency of the photocatalyst; at the same time, the high light transmittance of PMMA can increase the penetration depth of light into the cement matrix, solving the problem that the photocatalysts of the traditional internal doping method are blocked by the cement matrix and only have a small amount of effect on the surface.

[0037] 2. Enhanced mass transfer efficiency and improved catalytic performance: The porous cement matrix of this invention, combined with the adsorption effect of activated carbon, can enrich water pollutants, promote the mass transfer of pollutants to photocatalytic active sites, and simultaneously realize the adsorption and enrichment of pollutants and photocatalytic degradation, thereby significantly improving the efficiency of water purification and nitrate reduction to ammonia production.

[0038] 3. Strong process adaptability and easy to scale up application: The preparation process of this invention is simple, requires no complex equipment, and the raw materials used are all industrially available products. It can be directly adapted to the existing production and construction process of cement-based materials without additional production line modification, and has excellent potential for engineering promotion.

[0039] 4. High functional integration and wide range of applications: The material of this invention combines the structural load-bearing performance of cement-based materials with photocatalytic purification and in-situ ammonia production functions. It can float directly on the water surface, realizing the integration of "structure and function". It is suitable for in-situ water purification and resource recycling in multiple scenarios such as rivers, landscape water bodies, and municipal ditches.

[0040] 5. Strong load and excellent long-term stability: This invention uses the strong adhesion of polydopamine to firmly load the photocatalyst onto the surface of PMMA particles, avoiding the problems of easy peeling and aging of traditional coating methods; the cement matrix provides the material with excellent structural stability and environmental tolerance, and can operate stably in the natural environment for a long time. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a SEM-BSE image of the etched PMMA particle surface.

[0043] Figure 2 This is an EDX image of the etched PMMA particle surface.

[0044] Figure 3 This is a SEM-BSE image of PMMA particles loaded with the photocatalyst g-C3N4.

[0045] Figure 4 This is an EDX image of PMMA particles loaded with the photocatalyst g-C3N4.

[0046] Figure 5 This is a photograph of the photocatalytic cement prepared in Example 1 (front view, a cylinder with a diameter of 50 mm and a height of 25 mm).

[0047] Figure 6 This is a photograph of the photocatalytic cement prepared in Example 1 (top view, a cylinder with a diameter of 50 mm and a height of 25 mm).

[0048] Figure 7This is a TEM image of the high-performance photocatalyst AgCu-CN.

[0049] Figure 8 This is the XRD pattern of the high-performance photocatalyst AgCu-CN.

[0050] Figure 9 It is nitrate ions (NO3) - A statistical chart of 14-day removal rates for nitrogen (N-N).

[0051] Figure 10 This is a statistical chart of 14-day concentration data for ammonia monohydrate (NH3•H2O-N, calculated as nitrogen).

[0052] Figure 11 This is a statistical chart of the 14-day removal rate of Rhodamine B.

[0053] Figure 12 It is nitrate ions (NO3) - A statistical chart of 28-day removal rates for nitrogen (N-N).

[0054] Figure 13 This is a statistical chart of the 28-day concentration data of ammonia monohydrate (NH3•H2O-N, calculated as nitrogen).

[0055] Figure 14 This is a statistical chart of the 28-day removal rate of Rhodamine B. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] Example 1 This embodiment provides a method for preparing photocatalytic cement, the method comprising the following steps: (I) Preparation of photocatalyst g-C3N4 (I-1) Place 5g of dicyandiamine powder in an agate mortar and grind it evenly; grind the blocky dicyandiamine raw material into a uniform powder to increase the heat contact area of ​​the raw material, ensure that the reaction is uniform and sufficient in the subsequent calcination process, and avoid the occurrence of local unreacted raw material blocks; (I-2) The ground powder is placed in a covered crucible and heated to 600°C in a muffle furnace at a heating rate of 5°C / min under air atmosphere and held for 3 hours; the dicyandiamine undergoes a thermal polymerization reaction at high temperature through programmed temperature control to generate graphite-like carbon nitride (g-C3N4) nanosheets with visible light response; the covered crucible can prevent the raw material powder from being blown away by the hot air flow and ensure the product yield; (I-3) After the crucible is cooled to room temperature, the obtained beige powder is collected and ground evenly to obtain g-C3N4 nanosheets, which are photocatalysts. Natural cooling to room temperature can avoid oxidation of the high-temperature powder when it comes into contact with air. Grinding again can break up the agglomerated product after calcination and obtain nano-photocatalysts with uniform particle size, ensuring good dispersibility in the subsequent loading process. (II) Etching of polymethyl methacrylate (II-1) PMMA particles were added to deionized water, ultrasonically cleaned at 40°C for 1 hour and dried; then the dried PMMA particles were added to methanol, ultrasonically cleaned at 40°C for 1 hour and dried to obtain dried PMMA particles. (II-2) The dried PMMA particles were immersed in piranha washing solution and etched at 15°C for 30 seconds. After etching, they were washed with deionized water and dried to obtain etched PMMA particles. (III) Preparation of photocatalytic fine aggregate (III-1) Add 0.3g of photocatalyst g-C3N4 to 0.2L of deionized water and stir magnetically at 15°C for 30min; then add 6g of the etched PMMA particles and stir magnetically at 15°C for 30min; then add 1.5g of trihydroxyaminomethane and stir magnetically at 15°C for 1min; then add 0.3g of dopamine hydrochloride and stir magnetically at 15°C for 30min to obtain a mixed solution; (III-2) The mixed solution is heated to 50°C and maintained for 12 hours. During this period, the solution is slightly disturbed every hour, and the etched PMMA particles are turned over. During heating, the upper liquid is drawn off in several batches until the liquid level is slightly higher than the etched PMMA particles. The solution is heated at 50°C until the water evaporates to obtain solid particles. (III-3) The solid particles are immersed in deionized water at 15°C for 1 hour. After completion, they are taken out and dried at 60°C for 2 hours to obtain PMMA particles loaded with photocatalyst, which are photocatalytic fine aggregates. (IV) Preparation of photocatalytic cement (IV-1) Mix 8g of cement, 3g of standard sand and 0.5g of activated carbon for 30s, then add 5g of deionized water and continue stirring for 30s to obtain cement base material; (IV-2) Add 6g of the photocatalytic fine aggregate to the cement base and stir for 60s, then add 0.1g of aluminum powder and stir for 120s. Finally, put the stirred mixture into a mold, cure it for 24h under the national standard GB / T17671-2021, and then remove the mold to obtain the photocatalytic cement.

[0058] Example 2 This embodiment provides a method for preparing photocatalytic cement, the method comprising the following steps: (I) Preparation of photocatalyst g-C3N4 (I-1) Place 5g of dicyandiamine powder in an agate mortar and grind it evenly; (I-2) Place the ground powder in a covered crucible and heat it to 600°C in an air atmosphere at a heating rate of 5°C / min, and hold for 3 hours; (I-3) After the crucible is cooled to room temperature, the obtained beige powder is collected and ground evenly to obtain g-C3N4 nanosheets, which are photocatalysts; (II) Etching of polymethyl methacrylate (II-1) PMMA particles were added to deionized water, ultrasonically cleaned at 40°C for 1 hour and dried; then the dried PMMA particles were added to methanol, ultrasonically cleaned at 40°C for 1 hour and dried to obtain dried PMMA particles. (II-2) The dried PMMA particles were immersed in piranha washing solution and etched at 15°C for 30 seconds. After etching, they were washed with deionized water and dried to obtain etched PMMA particles. (III) Preparation of photocatalytic fine aggregate (III-1) Add 0.3g of photocatalyst g-C3N4 to 0.2L of deionized water and stir magnetically at 15°C for 30min; then add 6g of the etched PMMA particles and stir magnetically at 15°C for 30min; then add 1.5g of trihydroxyaminomethane and stir magnetically at 15°C for 1min; then add 0.3g of dopamine hydrochloride and stir magnetically at 15°C for 30min to obtain a mixed solution; (III-2) The mixed solution is heated to 50°C and maintained for 12 hours. During this period, the solution is slightly disturbed every hour, and the etched PMMA particles are turned over. During heating, the upper liquid is drawn off in several batches until the liquid level is slightly higher than the etched PMMA particles. The solution is heated at 50°C until the water evaporates to obtain solid particles. (III-3) The solid particles are immersed in deionized water at 15°C for 1 hour. After completion, they are taken out and dried at 60°C for 2 hours to obtain PMMA particles loaded with photocatalyst, which are photocatalytic fine aggregates.

[0059] (IV) Preparation of photocatalytic cement (IV-1) Mix 8g of cement, 3g of standard sand and 0.5g of activated carbon for 30s, then add 5g of deionized water and continue stirring for 30s to obtain cement base material; (IV-2) Add 2g of the photocatalytic fine aggregate to the cement base and stir for 60s, then add 0.1g of aluminum powder and stir for 120s. Finally, put the stirred mixture into a mold, cure for 24h under the national standard GB / T17671-2021, and then remove the mold to obtain the photocatalytic cement.

[0060] Example 3 This embodiment provides a method for preparing photocatalytic cement, the method comprising the following steps: (I) Preparation of photocatalyst In this embodiment, the photocatalyst is the commercially available mainstream photocatalyst P25 TiO2, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd. (II) Etching of polymethyl methacrylate (II-1) PMMA particles were added to deionized water, ultrasonically cleaned at 40°C for 1 hour and dried; then the dried PMMA particles were added to methanol, ultrasonically cleaned at 40°C for 1 hour and dried to obtain dried PMMA particles. (II-2) The dried PMMA particles were immersed in piranha washing solution and etched at 15°C for 30 seconds. After etching, they were washed with deionized water and dried to obtain etched PMMA particles. (III) Preparation of photocatalytic fine aggregate (III-1) Add 0.3g of P25 type TiO2 photocatalyst to 0.2L of deionized water and stir magnetically at 15℃ for 30min; then add 6g of the etched PMMA particles and stir magnetically at 15℃ for 30min; then add 1.5g of trihydroxyaminomethane and stir magnetically at 15℃ for 1min; then add 0.3g of dopamine hydrochloride and stir magnetically at 15℃ for 30min to obtain a mixed solution; (III-2) The mixed solution is heated to 50°C and maintained for 12 hours. During this period, the solution is slightly disturbed every hour, and the etched PMMA particles are turned over. During heating, the upper liquid is drawn off in several batches until the liquid level is slightly higher than the etched PMMA particles. The solution is heated at 50°C until the water evaporates to obtain solid particles. (III-3) The solid particles are immersed in deionized water at 15°C for 1 hour. After completion, they are taken out and dried at 60°C for 2 hours to obtain PMMA particles loaded with photocatalyst, which are photocatalytic fine aggregates. (IV) Preparation of photocatalytic cement (IV-1) Mix 8g of cement, 3g of standard sand and 0.5g of activated carbon for 30s, then add 5g of deionized water and continue stirring for 30s to obtain cement base material; (IV-2) Add 6g of the photocatalytic fine aggregate to the cement base and stir for 60s, then add 0.1g of aluminum powder and stir for 120s. Finally, put the stirred mixture into a mold, cure it for 24h under the national standard GB / T17671-2021, and then remove the mold to obtain the photocatalytic cement.

[0061] Example 4 This embodiment provides a method for preparing photocatalytic cement, the method comprising the following steps: (I) Preparation of high-performance photocatalyst AgCu-CN (I-1) Dissolve 10 mmol of melamine and 9.5 mmol of cyanuric acid in 40 mL of deionized water to obtain melamine solution and cyanuric acid solution, respectively. (I-2) Dissolve a mixture of 1 mmol citric acid, 0.25 mmol AgNO3 and 0.25 mmol Cu(NO3)2·3H2O in 10 mL of deionized water to obtain a preliminary mixture; (I-3) Add the initial mixture to the cyanuric acid solution and stir for 10 minutes, then add the melamine solution and stir at room temperature for 4 hours to obtain the mixture; (I-4) Centrifuge the mixture, and the product obtained is purified once with deionized water and once with anhydrous ethanol. Centrifuge to collect the purified product, and dry the product at 60°C under vacuum for 12 hours. Grind the dried sample into fine powder. (I-5) The fine powder is heated to 600°C in a tube furnace at a heating rate of 5°C / min and calcined for 4 hours under nitrogen protection. The resulting yellow powder is AgCu-CN photocatalyst. (II) Etching of polymethyl methacrylate (II-1) PMMA particles were added to deionized water, ultrasonically cleaned at 40°C for 1 hour and dried; then the dried PMMA particles were added to methanol, ultrasonically cleaned at 40°C for 1 hour and dried to obtain dried PMMA particles. (II-2) The dried PMMA particles were immersed in piranha washing solution and etched at 15°C for 30 seconds. After etching, they were washed with deionized water and dried to obtain etched PMMA particles. (III) Preparation of photocatalytic fine aggregate (III-1) Add 0.3g of high-performance photocatalyst AgCu-CN to 0.2L of deionized water and stir magnetically at 15℃ for 30min; then add 6g of the etched PMMA particles and stir magnetically at 15℃ for 30min; then add 1.5g of trihydroxyaminomethane and stir magnetically at 15℃ for 1min; then add 0.3g of dopamine hydrochloride and stir magnetically at 15℃ for 30min to obtain a mixed solution; (III-2) The mixed solution is heated to 50°C and maintained for 12 hours. During this period, the solution is slightly disturbed every hour, and the etched PMMA particles are turned over. During heating, the upper liquid is drawn off in several batches until the liquid level is slightly higher than the etched PMMA particles. The solution is heated at 50°C until the water evaporates to obtain solid particles. (III-3) The solid particles are immersed in deionized water at 15°C for 1 hour. After completion, they are taken out and dried at 60°C for 2 hours to obtain PMMA particles loaded with photocatalyst, which are photocatalytic fine aggregates.

[0062] (IV) Preparation of photocatalytic cement (IV-1) Mix 8g of cement, 3g of standard sand and 0.5g of activated carbon for 30s, then add 5g of deionized water and continue stirring for 30s to obtain cement base material; (IV-2) Add 6g of the photocatalytic fine aggregate to the cement base and stir for 60s, then add 0.1g of aluminum powder and stir for 120s. Finally, put the stirred mixture into a mold, cure it for 24h under the national standard GB / T17671-2021, and then remove the mold to obtain the photocatalytic cement.

[0063] Application Performance Test 1: Cleaning Water Pollutants Nitrate and In-situ Ammonia Production 1. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 1 was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate (i.e., curing, cleaning, and ammonia production were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days of age, the nitrate ion concentration (NO3) in the curing water was measured. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 15.4%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.27 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was... - The removal rate of nitrate (NH3•H2O-N, as nitrogen) was 26.4%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.35 mmol / L. These results demonstrate the successful loading of the photocatalyst and the successful application of photocatalytic cement in cleaning water pollutants such as nitrate and producing ammonia in situ.

[0064] Lighting period: February 11, 2026 to March 11, 2026.

[0065] Geographic coordinates: 121.546491°E, 31.29897°N (Yangpu District, Shanghai).

[0066] Daily average radiation 14.43 MJ / m 2 .

[0067] Data source: China Meteorological Administration: https: / / www.nmc.cn / publish / forecast / ASH / shanghai.html (hereinafter the same).

[0068] 2. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 2 was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate (i.e., curing, cleaning, and ammonia production were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days of age, the nitrate ion concentration (NO3) in the curing water was measured. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 10%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.12 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was measured. - The removal rate of nitrate (NH3•H2O-N, as nitrogen) was 23.5%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.18 mmol / L. Compared with Example 1, this demonstrates that when the amount of photocatalytic fine aggregate is reduced, the performance of photocatalytic cement in cleaning water pollutants such as nitrate and generating ammonia in situ decreases.

[0069] 3. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 3 was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate (i.e., curing, cleaning, and ammonia production were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days of age, the nitrate ion concentration (NO3) in the curing water was measured. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 14.6%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.24 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was... -The removal rate of nitrate (NH3•H2O-N, as nitrogen) was 27.9%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.19 mmol / L. These results demonstrate the successful loading of the photocatalyst and the successful application of photocatalytic cement in cleaning nitrate pollutants in water and generating ammonia in situ. Compared to Example 1, this example demonstrates that P25-type TiO2, due to its narrower photoresponse range and more positive conduction band potential (i.e., weaker reducing power) compared to g-C3N4, performs slightly worse in cleaning nitrate pollutants in water and generating ammonia in situ.

[0070] 4. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 4 was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate (i.e., curing, cleaning, and ammonia production were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days of age, the nitrate ion concentration (NO3) in the curing water was measured. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 17%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 1.1 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was measured. - The removal rate of nitrate (NH3•H2O-N, as nitrogen) was 44.8%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 1.8 mmol / L. These results demonstrate the successful loading of the photocatalyst and the successful application of photocatalytic cement in cleaning nitrate pollutants in water and generating ammonia in situ. Compared to Example 1, this example demonstrates that AgCu-CN performs better than g-C3N4 in cleaning nitrate pollutants in water and generating ammonia in situ.

[0071] Application Performance Test 2: Rhodamine B Dye for Cleaning Water Pollutants 1. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 1 was immediately placed in a 10 ppm Rhodamine B solution (i.e., curing and cleaning were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days, the removal rate of Rhodamine B in the curing water was measured to be 37.8%. At 28 days, the removal rate of Rhodamine B in the curing water was measured to be 62.5%. These test results demonstrate the successful loading of the photocatalyst and also prove the successful application and good performance of the photocatalytic cement in cleaning water pollutants, specifically Rhodamine B dye.

[0072] 2. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 3 was immediately placed in a 10 ppm Rhodamine B solution (i.e., curing and cleaning were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days, the removal rate of Rhodamine B in the curing water was measured to be 39.7%. At 28 days, the removal rate of Rhodamine B in the curing water was measured to be 64.5%. These test results demonstrate the successful loading of the photocatalyst and the successful application and good performance of the photocatalytic cement in cleaning Rhodamine B dye pollutants in water. Compared with the other two photocatalysts exemplified in this patent, P25 TiO2 showed the best cleaning effect on Rhodamine B dye pollutants in water.

[0073] 3. To simulate actual working conditions, the photocatalytic cement obtained after demolding in Example 4 was immediately placed in a 10 ppm Rhodamine B solution (i.e., curing and cleaning were carried out simultaneously) under the conditions of room temperature, sealing, and natural light. At 14 days, the removal rate of Rhodamine B in the curing water was measured to be 36.3%. At 28 days, the removal rate of Rhodamine B in the curing water was measured to be 65.4%. These test results demonstrate the successful loading of the photocatalyst and also prove the successful application and good performance of the photocatalytic cement in cleaning water pollutants, specifically Rhodamine B dye.

[0074] Comparative Example 1 (Application Performance) This comparative example is used to test the cleaning performance of national standard cement mortar against water pollutants, serving as a blank group.

[0075] Standard cement mortar was prepared according to the steps and proportions of the national standard GB / T17671-2021, i.e., the mass ratio of water:cement:standard sand was 0.5:1:3. The curing conditions and molding form before demolding after 24 hours were the same as those in the above embodiment.

[0076] To simulate actual working conditions, the molded standard cement mortar obtained after demolding was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate under the same conditions of room temperature, sealed environment, and natural light (as described above). At 14 days of curing, the nitrate ion concentration (NO3) in the curing water was measured. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 4.63%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was measured. - The removal rate of nitrate (NH3•H2O-N, as nitrogen) was 5.85%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0 mmol / L. These results demonstrate that standard cement mortar possesses a certain adsorption capacity for nitrate, thus removing some nitrate from water, but it does not have the ability to photocatalytically remove nitrate or photocatalytically reduce nitrate to produce ammonia.

[0077] Comparative Example 2 (Application Performance) This comparative example is used to test the cleaning performance of standard cement mortar composite material with activated carbon on water pollutants, serving as the first control group.

[0078] Standard cement mortar was prepared according to the steps and proportions of the national standard GB / T17671-2021. Activated carbon was added to the freshly mixed mortar, and after continuous stirring for 2 minutes, it was poured into a mold for molding. The mass ratio of water:cement:standard sand:activated carbon was 0.5:1:3:0.025. The curing conditions and molding method before demolding after 24 hours were the same as in the above embodiment.

[0079] To simulate actual working conditions, the standard cement mortar composite material with activated carbon added obtained after demolding was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate under the same conditions of room temperature, sealed environment, and natural light (as described above). Nitrate ions (NO3) in the curing water were measured at 14 days. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 9.25%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was measured. - The removal rate of nitrate (NH3•H2O-N, as nitrogen) was 10.9%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0 mmol / L. These results demonstrate that the activated carbon-doped standard cement mortar composite material possesses certain adsorption properties for nitrate, thus removing some nitrate from the water, but it does not have the ability to photocatalytically remove nitrate or photocatalytically reduce nitrate to ammonia.

[0080] Comparative Example 3 (Application Performance) This comparative example is a test of the cleaning performance of photocatalytic cement, which is commonly used to directly dopant photocatalyst powder, on water pollutants, and serves as a second control group.

[0081] The preparation method is as follows: (1) Mix 8g of cement, 3g of standard sand and 0.5g of activated carbon and stir for 30 seconds.

[0082] (2) Add 5g of deionized water to the mixture in step one and stir for 30 seconds.

[0083] (3) Add 0.3g of nano-photocatalyst (g-C3N4 powder) to the mixture in step two and stir for 1 minute.

[0084] (4) Add 0.1g of aluminum powder to the mixture in step three and stir for 2 minutes.

[0085] (5) Place the mixture from step four into a mold and shape it. After curing for 24 hours under the national standard GB / T17671-2021, remove the mold to obtain photocatalytic cement directly doped with g-C3N4.

[0086] To simulate actual working conditions, the photocatalytic cement directly doped with g-C3N4 obtained after demolding was immediately placed in a mixed solution of 1 mol / L potassium hydroxide and 0.2 mol / L potassium nitrate under the same conditions of room temperature, sealed environment, and natural light (as described above). At 14 days of curing, the nitrate ion concentration (NO3) in the curing water was measured. - The removal rate of nitrate ions (NO3-N, as nitrogen) in the culture water was 7.71%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.19 mmol / L. At 28 days of age, the concentration of nitrate ions (NO3-N, as nitrogen) in the culture water was measured. - The removal rate of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 12.7%, and the concentration of ammonia monohydrate (NH3•H2O-N, as nitrogen) was 0.22 mmol / L. These results demonstrate that the photocatalytic cement proposed in this invention, compared to commonly used photocatalytic cement directly doped with g-C3N4, possesses enhanced water pollutant removal capabilities and enhanced in-situ ammonia production capabilities, thanks to the improved light utilization and mass transfer efficiency of the photocatalytic cement proposed in this invention.

[0087] In summary, compared with the application performance comparison test examples 1-3, the photocatalytic cement proposed in this invention (Examples 1-4) has significant effects on cleaning pollutants in water bodies and producing ammonia in situ.

[0088] Characterization example 1. The etched PMMA particles (without photocatalyst) prepared in step (II) of Example 1 were characterized, such as... Figure 1 , Figure 2 As shown. Figure 1 SEM-BSE image of the etched PMMA particle surface; Figure 2 The EDX image of the PMMA particle surface was etched, and the data results are shown in Table 1. The trace nitrogen element comes from dopamine hydrochloride and trihydroxyaminomethane.

[0089] Table 1

[0090] 2. The PMMA particles with supported photocatalysts prepared in step (III) of Example 1 were characterized, and the results are as follows: Figure 3 , Figure 4 As shown. Figure 3 SEM-BSE image of PMMA particles loaded with photocatalyst; Figure 4The EDX image of the PMMA particles loaded with the photocatalyst is shown in Table 2. The data results show that the significant increase in carbon and nitrogen content proves the successful loading of the photocatalyst g-C3N4.

[0091] Table 2

[0092] 3. Figure 5 , Figure 6 The image shows a photograph of the photocatalytic cement finally prepared in Example 1. As can be seen from the image, the photocatalytic cement has a porous structure and can float on water. It can be used as a floating water purification and in-situ ammonia production infrastructure or small equipment.

[0093] 4. The high-performance photocatalyst AgCu-CN prepared in step (I) of Example 4 was characterized, and the results are as follows: Figure 7 , Figure 8 As shown. Figure 7 TEM image of the high-performance photocatalyst AgCu-CN; Figure 8 The XRD pattern of the high-performance photocatalyst AgCu-CN is shown in the figure. As can be seen from the figure, g-C3N4 has characteristic peaks at 13.3º (100 plane) and 27.5º (002 plane). The doping of Ag and Cu causes the characteristic peaks of AgCu-CN at these two locations to shift significantly to the left. In addition, the ICP composition data of the high-performance photocatalyst AgCu-CN are shown in Table 3.

[0094] Table 3

[0095] 5. Nitrate ions (NO3) on a 14-day-old plant. - The removal rate data of -N (as nitrogen) are summarized, such as Figure 9 As shown, by Figure 9 It can be seen that the nitrate ion removal rates of Examples 1-4 of the present invention are significantly higher than those of the comparative examples. Among them, Example 4 has the highest nitrate ion removal rate, reaching 17%, while the removal rates of Examples 1 and 3 are 15.4% and 14.6%, respectively, which are all much higher than those of Comparative Example 1 (blank cement mortar, 4.63%), Comparative Example 2 (cement mortar with activated carbon, 9.25%), and Comparative Example 3 (cement material directly doped with photocatalyst, 7.71%). This indicates that the preparation method of the present invention can significantly improve the removal capacity of infrastructure itself for nitrate pollutants in water. At the same time, it verifies that activated carbon can only remove a small amount of nitrate ions through adsorption, and the removal effect of directly doping with photocatalyst is limited due to low light utilization. However, the present invention effectively improves the efficiency of photocatalytic removal of nitrate ions through the design of supported photocatalytic fine aggregate.

[0096] The concentration data of ammonia monohydrate (NH3•H2O-N, calculated as nitrogen) at 14 days of age were summarized, such as... Figure 10 As shown, by Figure 10 It can be seen that the ammonia concentration in Comparative Examples 1 and 2 was 0 mmol / L, indicating that the blank cement mortar and the activated carbon-added cement mortar did not have the ability to reduce nitrate to ammonia. The ammonia concentration in Comparative Example 3 was only 0.19 mmol / L, while the ammonia concentration in Examples 1-4 of the present invention was significantly improved. Among them, the ammonia concentration in Example 4 was the highest, reaching 1.1 mmol / L, which is more than 4 times that of Example 1 (0.27 mmol / L) and Example 3 (0.24 mmol / L), respectively. This shows that the material of the present invention can efficiently realize the photocatalytic reduction of nitrate to ammonia, and by optimizing the type of photocatalyst (such as AgCu-CN), the performance of in-situ ammonia production can be further significantly improved.

[0097] The removal rate data of Rhodamine B at 14 days of maintenance were summarized, such as... Figure 11 As shown, by Figure 11 It can be seen that the removal rate of Rhodamine B in Examples 1, 3, and 4 of this invention all exceeded 35%, with Example 3 showing the highest removal rate at 39.7%. The removal rates in Examples 1 and 4 were 37.8% and 36.3%, respectively, indicating that the photocatalytic cement prepared by this invention has excellent purification effects on organic dye pollutants in water. At the same time, different photocatalysts have different compatibility. P25 TiO2 has a better degradation effect on Rhodamine B, while g-C3N4 and AgCu-CN are more suitable for the scenario of nitrate reduction to produce ammonia. The corresponding photocatalyst can be selected according to the actual application requirements.

[0098] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing photocatalytic cement, characterized in that, The preparation method includes the following steps: (I) Etching of polymethyl methacrylate (I-1) The polymethyl methacrylate particles were washed and dried to obtain dried polymethyl methacrylate particles; (I-2) Immerse the dried polymethyl methacrylate particles in an etching solution, clean and dry them after etching to obtain etched polymethyl methacrylate particles. (II) Preparation of photocatalytic fine aggregate (II-1) The photocatalyst, the etched polymethyl methacrylate particles, trihydroxyaminomethane, and dopamine hydrochloride were added to water in sequence and stirred to obtain a mixed solution; (II-2) The mixed solution is heated and evaporated to dryness to obtain solid particles; (II-3) The solid particles are sequentially impregnated and dried to obtain polymethyl methacrylate particles loaded with photocatalyst, which are photocatalytic fine aggregates; (III) Preparation of photocatalytic cement (III-1) Mix cement, standard sand, and activated carbon, then add water and stir to obtain cementitious material; (III-2) The photocatalytic fine aggregate and aluminum powder are added to the cement base in sequence and stirred. The stirred mixture is then shaped to obtain the photocatalytic cement.

2. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (I-1), polymethyl methacrylate particles are added to deionized water, ultrasonically cleaned at 40-45℃ for 1-2 hours and then dried; then the dried polymethyl methacrylate particles are added to methanol, ultrasonically cleaned at 40-45℃ for 1-2 hours and then dried to obtain dried polymethyl methacrylate particles.

3. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (I-2), the dried polymethyl methacrylate particles are immersed in piranha washing solution and etched at 15-25°C for 30-60 seconds. After etching, they are washed with deionized water and dried to obtain etched polymethyl methacrylate particles.

4. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (II-1), the photocatalyst is added to deionized water and stirred at 15-25°C for 30-40 min; then the etched polymethyl methacrylate particles are added and stirred at 15-25°C for 30-40 min; then trihydroxyaminomethane is added and stirred at 15-25°C for 1-3 min; then dopamine hydrochloride is added and stirred at 15-25°C for 30-40 min to obtain a mixed solution. The mass ratio of the photocatalyst, the etched polymethyl methacrylate particles, the trihydroxyaminomethane, and the dopamine hydrochloride is 0.3:0.5-20:1-3:0.1-1. The preparation method of the photocatalyst includes the following steps: (i) Melamine and cyanuric acid are dissolved in deionized water to obtain melamine solution and cyanuric acid solution, respectively; (ii) Dissolve the mixture of citric acid, AgNO3 and Cu(NO3)2·3H2O in deionized water to obtain a preliminary mixture; (iii) Add the initial mixture to the cyanuric acid solution and stir, then add the melamine solution and continue stirring to obtain a mixed solution; (iv) Centrifuge the mixture, collect the purified product, dry the purified product and grind it into fine powder; (v) The fine powder is heated and calcined to obtain the photocatalyst AgCu-CN.

5. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (II-2), the mixed solution is heated to 50-60°C and maintained for 12-16 hours until the water evaporates to obtain solid particles.

6. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (II-3), the solid particles are immersed in deionized water at 15-25°C for 1-2 hours. After completion, they are taken out and dried at 60-65°C for 2-6 hours to obtain polymethyl methacrylate particles loaded with photocatalyst, which are photocatalytic fine aggregates.

7. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (III-1), cement, standard sand, and activated carbon are mixed for 30-40 seconds and then added to deionized water and stirred for 30-40 seconds to obtain cement base material; The mass ratio of the cement, the standard sand, and the activated carbon is 8:1-24:0.1-2.

8. The method for preparing photocatalytic cement according to claim 1, characterized in that, In step (III-2), the photocatalytic fine aggregate is added to the cement base and stirred for 60-90 seconds, then aluminum powder is added and stirred for 120-150 seconds. Finally, the stirred mixture is placed in a mold and cured for 24-36 hours under the national standard GB / T17671-2021 to obtain the photocatalytic cement.

9. The photocatalytic cement obtained by the preparation method according to any one of claims 1-8, characterized in that, The preparation materials include the following parts by weight: 8 parts cement, 1-24 parts standard sand, 0.1-2 parts activated carbon, and 2-24 parts photocatalytic fine aggregate.

10. The application of the photocatalytic cement of claim 9 in the preparation of floating or non-floating water purification and in-situ green ammonia preparation infrastructure or small equipment devices.

Images