A visible light responsive photocatalytic sphere and its preparation method and application

Abstract

The present invention belongs to the field of photocatalysis, and in particular relates to a visible light responsive photocatalytic sphere, a preparation method thereof, and an application thereof. The visible light responsive photocatalytic sphere provided by the present invention is made from a mixture of a nitrogen-rich compound and a gelling material after oxygen-free calcination, ball formation, and carbonization curing. The present invention loads g-C3N4 having a wide spectral absorption range and good photocatalytic performance on the surface of the gelling material through a calcination method, and utilizes the carbon fixation and condensation effect of the gelling material to improve the overall mechanical strength of the product. The visible light responsive photocatalytic sphere provided by the present invention has good mechanical strength and photocatalytic performance, and has good economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysis, and in particular relates to a visible light responsive photocatalytic ball and a preparation method and application thereof. Background Art

[0002] Steel slag is a functional byproduct of the steelmaking process and an inevitable byproduct. With the acceleration of urbanization, steel production and consumption have steadily increased, and the amount of steel slag has also increased rapidly. Large amounts of steel slag storage not only consumes land resources but also poses significant safety risks to the ecological environment. How to better realize the high-quality resource utilization of steel slag is a pressing technical challenge.

[0003] Photocatalysis is a technology that utilizes the redox activity of photocatalysts under the influence of light to purify pollutants, synthesize substances, or decompose them. Currently, the most widely used photocatalyst is TiO2, and the development of new photocatalytic materials is a current research hotspot. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a visible light responsive photocatalytic ball and its preparation method and application. The visible light responsive photocatalytic ball provided by the present invention has good mechanical strength and photocatalytic performance, realizing the resource utilization of steel slag.

[0005] The present invention provides a method for preparing visible light responsive photocatalytic spheres, comprising the following steps:

[0006] calcining a mixture of the nitrogen-rich compound and the gelling material under a protective gas atmosphere to obtain a calcined material;

[0007] preparing the calcined material into spheres;

[0008] The spheres are carbonized and cured to obtain visible light responsive photocatalytic spheres.

[0009] Preferably, the mass ratio of the nitrogen-rich compound to the gelling material is (0.5-1):1.

[0010] Preferably, the nitrogen-rich compound is one or more of dicyandiamide, melamine and urea.

[0011] Preferably, the cementitious material is one or more of steel slag, magnesium slag, furnace slag, dicalcium silicate and tricalcium silicate.

[0012] Preferably, the particle size of the mixture is 60-200 mesh.

[0013] Preferably, the mixture is prepared according to the following steps:

[0014] The nitrogen-rich compound and the gelling material are dry-ground and mixed to obtain a mixture of the nitrogen-rich compound and the gelling material.

[0015] Preferably, the calcination temperature is 480-580° C.; the calcination heating rate is 2-5° C. / min; and the calcination holding time is 5-10 h.

[0016] Preferably, the diameter of the sphere is 0.3 to 0.5 cm.

[0017] Preferably, the calcined material is prepared into spheres in a spheroidizer; the spheroidizer is a cylindrical spheroidizer, a disc spheroidizer or a drum spheroidizer.

[0018] Preferably, the carbon dioxide concentration of the carbonization curing is 60-90%; the temperature of the carbonization curing is 15-35° C.; and the time of the carbonization curing is 6-12 hours.

[0019] The invention provides a visible light responsive photocatalytic ball, which is prepared from a mixture of a nitrogen-rich compound and a gelling material through oxygen-free calcination, ball formation and carbonization curing.

[0020] The present invention provides a photocatalytic method, which performs a photocatalytic reaction in the presence of the visible light responsive photocatalytic balls prepared by the preparation method described in the above technical solution or the visible light responsive photocatalytic balls described in the above technical solution.

[0021] Compared with the prior art, the present invention provides a visible light responsive photocatalytic sphere, a preparation method thereof, and an application thereof. The visible light responsive photocatalytic sphere provided by the present invention is made from a mixture of a nitrogen-rich compound and a gelling material after oxygen-free calcination, ball formation, and carbonization curing. The present invention loads g-C3N4 having a wide spectral absorption range and good photocatalytic performance on the surface of the gelling material through a calcination method, and utilizes the carbon fixation and condensation effect of the gelling material to improve the overall mechanical strength of the product. The visible light responsive photocatalytic sphere provided by the present invention has good mechanical strength and photocatalytic performance, and has good economic and environmental benefits. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0023] In the present invention, the cementitious material is exemplified by steel slag, and the nitrogen-rich compound is exemplified by dicyandiamide.

[0024] The invention provides a visible light responsive photocatalytic ball, which is prepared from a mixture of dicyandiamide and steel slag through oxygen-free calcination, ball formation and carbonization curing.

[0025] In the visible light responsive photocatalytic balls provided by the present invention, the steel slag is slag discharged from steelmaking, which is mainly composed of oxides of calcium, iron, silicon, and magnesium, and also contains a small amount of oxides of aluminum, manganese, phosphorus, etc. In one embodiment of the present invention, the CaO content of the steel slag is preferably 35-45 wt%, specifically 41.591 wt%; the SiO2 content of the steel slag is preferably 10-15 wt%, specifically 13.304 wt%; the Al2O3 content of the steel slag is preferably 2-8 wt%, specifically 4.477 wt%; the Fe2O3 content of the steel slag is preferably 20-30 wt%, specifically 24.186 wt%; the Na2O content of the steel slag is preferably 0.1-0.5 wt%, specifically 0.222 wt%; the MgO content of the steel slag is preferably 2-8 wt%, specifically 5.903 wt%; the MnO content of the steel slag is preferably 1-5 wt%, specifically 3.389 wt%; and the P2O5 content of the steel slag is preferably 0.5-4 wt%, specifically 1.772 wt%. In the present invention, the dicyandiamide is industrial grade dicyandiamide.

[0026] In the visible light responsive photocatalytic balls provided by the present invention, the mass ratio of the dicyandiamide to the steel slag is preferably (0.5-1):1, specifically 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1 or 1:1; the particle size of the mixture is preferably 60-200 mesh, specifically 60 mesh, 70 mesh, 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh or 200 mesh.

[0027] In the visible light responsive photocatalytic ball provided by the present invention, the temperature of the oxygen-free calcination is preferably 480-580°C, specifically 480°C, 485°C, 490°C, 495°C, 500°C, 505°C, 510°C, 515°C, 520°C, 525°C, 530°C, 535°C, 540°C, 545°C, 550°C, 555°C, 560°C, 565°C, 570°C, 575°C or 580°C; the heating rate of the oxygen-free calcination is preferably 2-5°C / min, specifically 2°C / min, 2.3°C / min. n, 2.5 ° C / min, 2.7 ° C / min, 3 ° C / min, 3.2 ° C / min, 3.5 ° C / min, 3.7 ° C / min, 4 ° C / min, 4.2 ° C / min, 4.5 ° C / min, 4.7 ° C / min or 5 ° C / min, the heating rate refers to the heating rate before reaching the set oxygen-free calcination temperature; the holding time of the oxygen-free calcination is preferably 5 to 10 hours, specifically 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours or 10 hours. In the present invention, under the above-mentioned oxygen-free calcination conditions, it is easier to generate g-C3N4 with a high visible light response rate, so that the product has a higher photocatalytic activity.

[0028] In the visible light responsive photocatalytic balls provided by the present invention, the ball formation is preferably carried out in a ball forming machine, and the ball forming machine sprays water while rotating during the ball forming process; the ball forming machine is preferably a cylindrical ball forming machine, a disc ball forming machine or a drum ball forming machine; the diameter of the ball is preferably 0.3 to 0.5 cm, specifically 0.3 cm, 0.31 cm, 0.32 cm, 0.33 cm, 0.34 cm, 0.35 cm, 0.36 cm, 0.37 cm, 0.38 cm, 0.39 cm, 0.4 cm, 0.41 cm, 0.42 cm, 0.43 cm, 0.44 cm, 0.45 cm, 0.46 cm, 0.47 cm, 0.48 cm, 0.49 cm or 0.5 cm.

[0029] In the visible light responsive photocatalytic ball provided by the present invention, the carbon dioxide concentration of the carbonization curing is preferably 60-90%, specifically 60%, 62%, 65%, 67%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 87% or 90%; the carbonization curing temperature is preferably 15-35°C, specifically 15°C, 16°C, 17°C, 18°C, 19°C, 20°C , 21°C, 22°C, 23°C, 24°C, 25°C (room temperature), 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C; the carbonization curing time is preferably 6 to 12 hours, specifically 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours or 12 hours. In the present invention, under the above carbonization curing conditions, the obtained product has higher strength.

[0030] The present invention also provides a method for preparing visible light responsive photocatalytic spheres, comprising the following steps:

[0031] calcining a mixture of dicyandiamide and steel slag under a protective gas atmosphere to obtain a calcined material;

[0032] preparing the calcined material into spheres;

[0033] The spheres are carbonized and cured to obtain visible light responsive photocatalytic spheres.

[0034] In the preparation method provided by the present invention, the steel slag is slag discharged from steelmaking, which is mainly composed of oxides of calcium, iron, silicon, and magnesium, and also contains a small amount of oxides of aluminum, manganese, phosphorus, etc.; the dicyandiamide is industrial-grade dicyandiamide.

[0035] In the preparation method provided by the present invention, the mass ratio of the dicyandiamide to the steel slag is preferably (0.5-1:1), specifically 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1 or 1:1; the particle size of the mixture is preferably 60-200 mesh, specifically 60 mesh, 70 mesh, 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh or 200 mesh.

[0036] In the preparation method provided by the present invention, the mixture is preferably prepared according to the following steps: dry-grinding and mixing dicyandiamide and steel slag to obtain a mixture of dicyandiamide and steel slag. In the present invention, the prepared mixture is preferably sieved.

[0037] In the preparation method provided by the present invention, the protective gas includes but is not limited to nitrogen; the calcination temperature is preferably 480-580°C, specifically 480°C, 485°C, 490°C, 495°C, 500°C, 505°C, 510°C, 515°C, 520°C, 525°C, 530°C, 535°C, 540°C, 545°C, 550°C, 555°C, 560°C, 565°C, 570°C, 575°C or 580°C; the calcination heating rate is preferably 2-5°C / min, specifically 2°C / min, 2. 3℃ / min, 2.5℃ / min, 2.7℃ / min, 3℃ / min, 3.2℃ / min, 3.5℃ / min, 3.7℃ / min, 4℃ / min, 4.2℃ / min, 4.5℃ / min, 4.7℃ / min or 5℃ / min, the heating rate refers to the heating rate before reaching the set calcination temperature; the calcination holding time is preferably 5-10h, specifically 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h.

[0038] In the preparation method provided by the present invention, the calcined material is preferably prepared into spheres in a sphere forming machine, and the sphere forming machine sprays water while rotating during the sphere forming process; the sphere forming machine is preferably a cylindrical sphere forming machine, a disc sphere forming machine or a drum sphere forming machine; the diameter of the sphere is preferably 0.3 to 0.5 cm, specifically 0.3 cm, 0.31 cm, 0.32 cm, 0.33 cm, 0.34 cm, 0.35 cm, 0.36 cm, 0.37 cm, 0.38 cm, 0.39 cm, 0.4 cm, 0.41 cm, 0.42 cm, 0.43 cm, 0.44 cm, 0.45 cm, 0.46 cm, 0.47 cm, 0.48 cm, 0.49 cm or 0.5 cm.

[0039] In the preparation method provided by the present invention, the carbon dioxide concentration of the carbonization curing is preferably 60-90%, specifically 60%, 62%, 65%, 67%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 87% or 90%; the carbonization curing temperature is preferably 15-35°C, specifically 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 2 1°C, 22°C, 23°C, 24°C, 25°C (room temperature), 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C; the carbonization curing time is preferably 6 to 12 hours, specifically 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours or 12 hours.

[0040] The present invention also provides a photocatalytic method, in which a photocatalytic reaction is carried out in the presence of the visible light responsive photocatalytic balls described in the above technical solution or the visible light responsive photocatalytic balls prepared by the preparation method described in the above technical solution.

[0041] The technical solution provided by the present invention uses a calcination method to load g-C3N4, which has a wide spectral absorption range and excellent photocatalytic performance, onto the surface of steel slag. The carbon fixation and condensation effect of the steel slag is then utilized to enhance the overall mechanical strength of the product. The visible light-responsive photocatalytic spheres provided by the present invention have excellent mechanical strength and photocatalytic performance, realizing the resource utilization of steel slag with good economic and environmental benefits. More specifically, the technical solution provided by the present invention has the following technical advantages:

[0042] 1) Loading g-C3N4 on the surface of steel slag by calcination can make rational use of industrial waste slag and save land resources;

[0043] 2) The entire preparation process only requires one calcination treatment, which saves processing resources and energy consumption and simplifies the process flow;

[0044] 3) g-C3N4 is loaded on the surface of steel slag, which solves the problem of easy agglomeration of g-C3N4 and is more conducive to the contact between g-C3N4 and light, thereby improving the photocatalytic performance;

[0045] 4) The carbon fixation and solidification of steel slag produces hard spheres, allowing the visible light-responsive photocatalytic spheres provided by the present invention to be used in the preparation of various building materials and road engineering materials, effectively improving the mechanical properties of the materials;

[0046] 5) The technical solution of the present invention not only realizes the resource utilization of steel slag solid waste, but also plays the role of photocatalytic degradation of pollutants, providing an important solution for achieving the goal.

[0047] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples and comparative examples.

[0048] In the following embodiments and comparative examples of the present invention, the steel slag used has a CaO content of 41.591 wt%, a SiO2 content of 13.304 wt%, an Al2O3 content of 4.477 wt%, a Fe2O3 content of 24.186 wt%, a Na2O content of 0.222 wt%, a MgO content of 5.903 wt%, a MnO content of 3.389 wt%, and a P2O5 content of 1.772 wt%.

[0049] Example 1

[0050] 5 g of dicyandiamide and 5 g of steel slag are dry-ground and evenly mixed as a precursor; the precursor is sieved through a 60-mesh sieve; the precursor passing through the 60-mesh sieve is calcined in a nitrogen atmosphere at a temperature of 580°C, a heating rate of 2°C / min, and a holding time of 5 hours to obtain a calcined material; the calcined material is prepared into spheres with a diameter of about 0.5 cm using a cylindrical sphere-forming machine, and the sphere-forming machine sprays water while rotating during the sphere-forming process; the spheres are carbonized and cured in a 90% carbon dioxide environment at room temperature for 12 hours to obtain visible light responsive photocatalytic spheres.

[0051] Example 2

[0052] 2.5 g of dicyandiamide and 5 g of steel slag were dry-ground and evenly mixed as a precursor; the precursor was sieved through a 60-mesh sieve; the precursor that passed the 60-mesh sieve was calcined under a nitrogen atmosphere at a temperature of 580°C, a heating rate of 2°C / min, and a holding time of 5 hours to obtain a calcined material; the calcined material was prepared into spheres with a diameter of about 0.5 cm using a cylindrical sphere-forming machine, and the sphere-forming machine was sprayed with water while rotating during the sphere-forming process; the spheres were carbonized and cured in a 90% carbon dioxide environment at room temperature for 12 hours to obtain visible light responsive photocatalytic spheres.

[0053] Example 3

[0054] 5 g of dicyandiamide and 5 g of steel slag were dry-ground and evenly mixed as a precursor; the precursor was sieved through a 60-mesh sieve; the precursor that passed the 60-mesh sieve was calcined under a nitrogen atmosphere at a temperature of 580°C, a heating rate of 2°C / min, and a holding time of 10 hours to obtain a calcined material; the calcined material was prepared into spheres with a diameter of about 0.5 cm using a cylindrical sphere-forming machine, and the sphere-forming machine was sprayed with water while rotating during the sphere-forming process; the spheres were carbonized and cured in a 90% carbon dioxide environment at room temperature for 12 hours to obtain visible light responsive photocatalytic spheres.

[0055] Example 4

[0056] 5 g of dicyandiamide and 5 g of steel slag were dry-ground and evenly mixed as a precursor; the precursor was sieved through a 60-mesh sieve; the material passing through the 60-mesh sieve was calcined in a nitrogen atmosphere at a temperature of 480°C, a heating rate of 2°C / min, and a holding time of 5 hours to obtain a calcined material; the calcined material was prepared into spheres with a diameter of about 0.5 cm using a drum pelletizer, and the pelletizer was sprayed with water while rotating during the pelletizing process; the spheres were carbonized and cured in a 90% carbon dioxide environment at room temperature for 12 hours to obtain visible light responsive photocatalytic spheres.

[0057] Comparative Example 1

[0058] 10 g of steel slag was dry-ground and uniformly used as a precursor; the precursor was sieved through a 60-mesh sieve; the precursor that passed the 60-mesh sieve was calcined under a nitrogen atmosphere at a temperature of 580°C, a heating rate of 2°C / min, and a holding time of 5 hours to obtain a calcined material; the calcined material was prepared into spheres with a diameter of about 0.5 cm using a cylindrical sphere forming machine, and the sphere forming machine was sprayed with water while rotating during the sphere forming process; the spheres were carbonized and cured in a 90% carbon dioxide environment at room temperature for 12 hours to obtain spherical particles of the control group.

[0059] Performance testing

[0060] The visible light responsive photocatalytic balls prepared in Examples 1 to 4 and the spherical particles prepared in Comparative Example 1 were subjected to a photocatalytic reaction experiment. The specific experimental steps are as follows: First, a 20 mg / L methyl orange solution was prepared. 200 mL of the methyl orange solution was placed in a 500 mL container. 10 g of the visible light responsive photocatalytic balls or the comparative example spherical particles were added. The container was then placed under a 30 W fluorescent lamp for 24 hours for a comparative degradation experiment. The degradation efficiency was calculated using an ultraviolet spectrophotometer. The experimental results are shown in Table 1:

[0061] Table 1 Degradation comparison test results

[0062]

[0063]

[0064] By comparing the experimental results in Table 1, it can be seen that the present invention uses dicyandiamide and steel slag of specific components as precursors, and performs oxygen-free calcination and carbonization curing on the precursors to prepare visible light responsive photocatalytic spheres with excellent degradation efficiency. Compared with the spherical particles without dicyandiamide in Comparative Example 1, the degradation efficiency of the visible light responsive photocatalytic spheres with dicyandiamide added in Examples 1 to 4 of the present invention is significantly higher than that of the spherical particles without dicyandiamide in Comparative Example 1. Among them, the ratio of dicyandiamide to steel slag is 1:1, the calcination temperature is 580°C, and the calcination time is 10h. The visible light responsive photocatalytic spheres show better degradation efficiency.

[0065] The visible light responsive photocatalytic spheres of the present invention load g-C3N4 on the surface of steel slag by a calcination method, thereby solving the problem of g-C3N4 easily agglomerating, being more conducive to the contact of g-C3N4 with light, and improving the photocatalytic performance. The carbon fixation and condensation function of steel slag is used to make hard spheres, which can be used in the preparation of various building materials and road engineering materials. The doping of metal elements can effectively improve the mechanical properties, anti-skid properties, and wear resistance of the materials. The visible light responsive photocatalytic spheres prepared by the present invention not only realize the resource utilization of solid waste, but also can serve the purpose of photocatalytic degradation of pollutants.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing visible light responsive photocatalytic spheres, characterized in that: The following steps are involved: calcining a mixture of the nitrogen-rich compound and the gelling material under a protective gas atmosphere to obtain a calcined material; The mass ratio of the nitrogen-rich compound to the gelling material is (0.5-1):1, the nitrogen-rich compound is one or more of dicyandiamide, melamine and urea, and the gelling material is one or more of steel slag, magnesium slag, dicalcium silicate and tricalcium silicate; preparing the calcined material into spheres; The spheres are carbonized and cured to obtain visible light responsive photocatalytic spheres with g-C3N4 loaded on the surface of the gelling material; The carbon dioxide concentration of the carbonization curing is 60-90%, the temperature of the carbonization curing is 15-35° C., and the time of the carbonization curing is 6-12 hours.

2. The preparation method according to claim 1, characterized in that The particle size of the mixture is 60-200 meshes.

3. The preparation method according to claim 1, characterized in that The mixed material is prepared according to the following steps: The nitrogen-rich compound and the gelling material are dry-ground and mixed to obtain a mixture of the nitrogen-rich compound and the gelling material.

4. The preparation method according to claim 1, characterized in that The calcination temperature is 480-580° C.; the calcination heating rate is 2-5° C. / min; and the calcination holding time is 5-10 h.

5. The preparation method according to claim 1, characterized in that The diameter of the sphere is 0.3-0.5 cm.

6. The preparation method according to claim 1, characterized in that The calcined material is prepared into spheres in a sphere-forming machine; the sphere-forming machine is a cylindrical sphere-forming machine, a disc sphere-forming machine or a drum sphere-forming machine.

7. A visible light responsive photocatalytic ball, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 6.

8. A photocatalytic method, characterized in that: The photocatalytic reaction is carried out in the presence of the visible light responsive photocatalytic spheres as claimed in claim 7.

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