Supported photocatalytic diatomite-based porous ceramsite as well as preparation method and application thereof

Abstract

The invention relates to supported photocatalytic diatomite-based porous ceramsite, the supported photocatalytic diatomite-based porous ceramsite is prepared from the following raw materials in parts by weight: 40 to 60 parts of diatomite, 10 to 20 parts of g-C3N4, 1 to 3 parts of La2O3, 0.5 to 2.1 parts of Ce2O3, 5 to 10 parts of binder and 3 to 8 parts of pore forming agent, and the porous ceramsite has excellent performance of photocatalytic degradation of organic matters in sewage.

Description

Technical Field

[0001] The invention relates to a loaded photocatalytic diatomaceous earth-based porous ceramsite and a preparation method and application thereof, belonging to the technical field of photocatalytic sewage treatment. Background Art

[0002] Wastewater treatment is a hot topic in industrial production, and the large amount of organic matter in wastewater becomes a difficult problem in the treatment process.

[0003] It has been confirmed that diatomaceous earth has a good adsorption effect on organic matter in sewage due to its rich active micropores, but its diatomaceous earth only has an adsorption effect and does not have the ability to further decompose and treat it. In recent years, g-C3N4 has been shown to have excellent photocatalytic effects and can degrade organic matter in sewage. It has been proven feasible to use diatomaceous earth and g-C3N4 in combination for sewage treatment. For example, patent CN108187610A discloses that g-C3N4 is loaded on diatomaceous earth, which has good photocatalytic efficiency and can play a certain role in sewage treatment. However, the above patent has a low level of degradation rate of organic matter in sewage, which is only below 95%, and cannot meet the increasingly stringent sewage treatment discharge requirements.

[0004] In order to solve the above problems, the present invention provides a loaded photocatalytic diatomaceous earth-based porous ceramsite with a high degradation rate of organic matter in sewage. Summary of the Invention

[0005] The present invention provides a loaded photocatalytic diatomite-based porous ceramsite, its preparation method, and application. The porous ceramsite uses diatomite as the matrix and is combined with a pore-forming agent to produce a porous ceramsite with excellent adsorption properties. Furthermore, g-C3N4 doped with La2O3 / Ce2O3 is loaded onto the porous ceramsite. Under photocatalytic conditions, adsorbed organic matter can be efficiently degraded. The present invention also provides a preparation method for the porous ceramsite, which is ultimately applied to sewage treatment. Testing has shown that the porous ceramsite has a sewage organic matter degradation rate exceeding 98%, demonstrating broad industrial application prospects.

[0006] The present invention aims to provide a loaded photocatalytic diatomite-based porous ceramsite, the raw materials of which include, by weight, 40-60 parts of diatomite, 10-20 parts of g-C3N4, 1-3 parts of La2O3, 0.5-2.1 parts of Ce2O3, 5-10 parts of binder, and 3-8 parts of pore-forming agent.

[0007] The present invention uses diatomaceous earth as a matrix, which is a porous material. After sintering, porous ceramsite can be obtained. By adding an appropriate amount of pore-forming agent to the diatomaceous earth matrix, the porosity of the ceramsite can be further increased, more active micropores can be introduced, the porous structure of the ceramsite can be enriched, and the through channels between pores can be expanded to a greater extent, thereby increasing the adsorption surface area of the porous ceramsite. The g-C3N4 composite doped with La2O3 / Ce2O3 is loaded on the porous ceramsite. Compared with a single g-C3N4, the photocatalytic degradation effect is better and the efficiency is higher. In the sewage treatment process, the organic matter adsorbed on the porous ceramsite can be rapidly and relatively completely degraded.

[0008] As a preferred technical solution, both La2O3 and Ce2O3 are doped with g-C3N4 through mechanical alloying. High-energy ball milling of the mixture of La2O3, Ce2O3, and g-C3N4 allows the La2O3 and Ce2O3 particles to be doped onto the surface of the g-C3N4 particles in the form of interlocking, embedding, or encapsulation. Compared to g-C3N4 particles, the g-C3N4 composite doped with La2O3 / Ce2O3 has more active sites, thereby demonstrating superior photocatalytic degradation of organic matter in wastewater.

[0009] As a preferred technical solution, the sum of the amounts of La2O3 and Ce2O3 is calculated as RE2O3, and the ratio of g-C3N4 to RE2O3 is 1:0.11-0.37. Too little La2O3 and Ce2O3 results in a weak doping effect, presumably due to insufficient increase in active sites, resulting in a lack of significant improvement in photocatalytic degradation. Excessive amounts of La2O3 and Ce2O3 also reduce the doping effect, presumably because the excess La2O3 and Ce2O3 impairs the exposure of g-C3N4 active sites, leading to unsatisfactory photocatalytic degradation results. As a further preferred technical solution, the ratio of La2O3 to Ce2O3 in RE2O3 is 1:0.58-1.45.

[0010] As a non-limiting description, the binder used in the present invention includes but is not limited to a mixture of one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), paraffin, and sodium carboxymethyl cellulose (CMC); the pore-forming agent used in the present invention includes but is not limited to a mixture of one or more of starch and sawdust powder.

[0011] The particle size of each raw material is preferably 50 μm or less.

[0012] The present invention also provides a preparation method of the aforementioned loaded photocatalytic diatomite-based porous ceramsite, comprising the following steps: S1: weighing each raw material in proportion; S2: placing g-C3N4, La2O3, and Ce2O3 into a high-energy ball mill for mechanical alloying; S3: mixing La2O3 / Ce2O3-doped g-C3N4, diatomite, a binder, and a pore-forming agent obtained by high-energy ball milling, and adding water and stirring evenly to form a mud material; S4: extruding the mud material to obtain a green body, and drying the green body; S5: sintering the dried green body, and cooling to obtain the loaded photocatalytic diatomite-based porous ceramsite.

[0013] As a preferred technical solution, the mechanical alloying process is performed at a ball milling speed of 200-400 rpm for 1-3 hours. Through mechanical alloying, La2O3 and Ce2O3 particles are doped onto the surface of the g-C3N4 particles in a manner such as intercalation, embedding, or encapsulation, thereby providing more active sites during the subsequent photocatalytic degradation process.

[0014] As a preferred technical solution, the sintering process is divided into two stages. The first stage involves heating to 450-550°C at a rate of no more than 3°C / min, holding at that temperature for 0.5-1.5 hours, then heating to 800-1350°C at a rate of 5-10°C / min, holding at that temperature for 2-4 hours, and then naturally cooling. During this first stage, moisture and binder removal and the decomposition of the pore-forming agent occur. In the second stage, as the temperature rises, sintering necks gradually form between the particles. During the holding period, a certain bonding strength is achieved, leading to final formation.

[0015] During the slurry preparation process, water should be added in an amount of 35%-50% of the total weight of the raw materials. Too little or too much water will result in poor slurry forming properties. During the drying process, the green body is preferably dried at 80-120°C for 12-24 hours.

[0016] The present invention also provides the use of the aforementioned supported photocatalytic diatomite-based porous ceramsite, or the supported photocatalytic diatomite-based porous ceramsite obtained by the aforementioned method for preparing the supported photocatalytic diatomite-based porous ceramsite, in sewage treatment. The supported photocatalytic diatomite-based porous ceramsite of the present invention has a well-developed pore structure, a large specific surface area, and excellent adsorption properties. Furthermore, the supported photocatalytic diatomite-based porous ceramsite utilizes La2O3 / Ce2O3 composite-doped g-C3N4 as a photocatalytic degradation material, which has numerous active sites and a good catalytic degradation effect, achieving a catalytic degradation rate of over 98% for organic matter in sewage.

[0017] The present invention adds a pore-forming agent on the basis of a diatomite matrix. In the sintering process of preparing ceramsite, it is conducive to increasing the porosity of the ceramsite, introducing more active micropores, enriching the porous structure of the ceramsite, expanding the through-channels between the pores, and increasing the adsorption surface area of the porous ceramsite; g-C3N4 and La2O3 / Ce2O3 are doped, and the g-C3N4 compositely doped with La2O3 / Ce2O3 is loaded on the porous ceramsite. Compared with a single g-C3N4, its photocatalytic degradation effect is better and more efficient. The ceramsite of the present invention coordinates the adsorption of diatomite and the photocatalytic effect of g-C3N4, so that in the process of sewage treatment, organic matter adsorbed on the porous ceramsite can be rapidly and relatively completely degraded. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to fully understand the technical solutions and beneficial effects of the present invention, further explanation is given below in conjunction with specific test examples.

[0019] Prepare the ceramsite raw materials according to Table 1, with a particle size of 35-45 μm for each raw material. Mechanically alloy g-C3N4 with La2O3 and / or Ce2O3 in a high-energy ball mill (for groups without La2O3 and Ce2O3, high-energy ball mill g-C3N4 alone) at 300 rpm for 1.2 h. La2O3 and / or Ce2O3 doped g-C3N4 (the group without La2O3 and Ce2O3 added is g-C3N4) obtained by high-energy ball milling, diatomaceous earth, a binder, and a pore-forming agent (the group without pore-forming agent added is mixed without pore-forming agent), and 40% of the total weight of water of the raw materials is added and stirred evenly to form a mud; the mud is extruded to obtain a number of cylindrical green bodies with a diameter of 5 mm and a length of 1 cm, and the green bodies are dried at 105°C for 18 hours; the dried green bodies are sintered in a muffle furnace, and the sintering is divided into two stages, first, the temperature is increased to 500°C at a heating rate of 1.5°C / min and kept warm for 1 hour, then, the temperature is increased to 1080°C at a heating rate of 8°C / min and kept warm for 2.5 hours, and then naturally cooled to room temperature in the furnace to obtain loaded photocatalytic diatomaceous earth-based porous ceramsite.

[0020] In Table 1, RE2O3 represents the sum of the added amounts of La2O3 and Ce2O3.

[0021] Table 1: Raw materials of various ceramsite (unit: g).

[0022]

[0023] Industrial wastewater was measured to have a COD value of 3156.75 mg / L. Seventeen 5L portions of this industrial wastewater were measured, corresponding to ceramsite test numbers 1-17. 150g of ceramsite from test numbers 1-17 was added to each portion of the industrial wastewater. The industrial wastewater was then irradiated at 20,000 lux for 2 hours at room temperature. The COD value in each wastewater was then measured again, and the COD removal rate was used as the organic matter degradation rate. The measurement and calculation results are recorded in Table 2.

[0024] Table 2: COD values and organic matter degradation rates of various wastewaters after photocatalytic degradation treatment.

[0025]

[0026] It can be seen from the above experiments that the raw materials for preparing ceramsite of test numbers 1-5 meet the requirements of the present invention, and ultimately they demonstrate good efficiency in photocatalytic degradation of organic matter, with degradation rates reaching more than 98%.

[0027] When neither Ce2O3 nor La2O3 was added, that is, when g-C3N4 was doped with only La2O3 or Ce2O3 (as in Experiments 6 and 7), the photocatalytic degradation efficiency of the ceramsite decreased. When neither Ce2O3 nor La2O3 was added, that is, when g-C3N4 was not doped (as in Experiment 8), the photocatalytic degradation efficiency of the ceramsite for organic matter in wastewater decreased even more significantly.

[0028] Even if the sum of the added amounts of La2O3 and Ce2O3 is replaced by an equal amount of La2O3 or Ce2O3 (such as test numbers 9 and 10 relative to test numbers 4 and 5), the photocatalytic degradation effect of the ceramsite finally obtained still cannot reach a high level, indicating that the composite doping of La2O3 / Ce2O3 has a better photocatalytic degradation effect of organic matter than the single doping of La2O3 or Ce2O3, and the composite doping of La2O3 / Ce2O3 on g-C3N4 has a synergistic effect.

[0029] In addition, for ceramsite without pore-forming agent (such as test numbers 11 and 12), the level of photocatalytic degradation of organic matter in wastewater is not satisfactory, probably because its microporous structure is not well developed and cannot effectively and fully adsorb organic matter in wastewater.

[0030] Although, as mentioned above, the composite doping of La2O3 / Ce2O3 on g-C3N4 can improve the photocatalytic degradation ability of ceramsite, but too high or too low La2O3 or Ce2O3 addition will lead to the deterioration of the photocatalytic degradation ability of ceramsite (such as test numbers 13, 14, 15, and 16). It is speculated that when the La2O3 or Ce2O3 addition amount is too high, it will affect the exposure of the active sites of g-C3N4, resulting in unsatisfactory effects during photocatalytic degradation; and when the La2O3 or Ce2O3 addition amount is too low, the doping effect is not prominent, and due to insufficient increase in active sites, the photocatalytic degradation effect is not significantly improved.

[0031] Therefore, not only do La2O3 and Ce2O3 need to be added at the same time, but the addition amounts of La2O3 and Ce2O3 also need to be controlled at corresponding levels in order to obtain the best doping effect on g-C3N4 and to obtain the optimal ability to photocatalytically degrade organic matter.

[0032] When neither La2O3, Ce2O3, nor a pore-forming agent was added (as in Experiment 17), the ceramsite's ability to photocatalytically degrade organic matter decreased significantly. This suggests that the degradation of organic matter in wastewater by ceramsite relies both on the adsorption and capture of organic matter by the matrix and on the photocatalytic degradation of adsorbed organic matter by g-C3N4. By increasing the porosity through the introduction of a pore-forming agent and co-doping g-C3N4 with La2O3 / Ce2O3, the combination of these two factors yields excellent photocatalytic degradation of organic matter.

[0033] Furthermore, when both g-C3N4:RE2O3 and La2O3:Ce2O3 met the further requirements of the present invention (Tests 1 and 2), they demonstrated even greater photocatalytic degradation efficiency for organic matter, reaching degradation rates exceeding 99.5%. Therefore, further optimization of g-C3N4:RE2O3 and La2O3:Ce2O3 can achieve even greater photocatalytic degradation efficiency for organic matter.

[0034] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A supported photocatalytic diatomite-based porous ceramsite, characterized in that: The raw materials of the loaded photocatalytic diatomite-based porous ceramsite include, by weight, 40-60 parts of diatomite, 10-20 parts of g-C3N4, 1-3 parts of La2O3, 0.5-2.1 parts of Ce2O3, 5-10 parts of binder, and 3-8 parts of pore-forming agent.

2. The supported photocatalytic diatomite-based porous ceramsite according to claim 1, characterized in that: The La2O3 and Ce2O3 are both doped with g-C3N4 by mechanical alloying.

3. The supported photocatalytic diatomite-based porous ceramsite according to any one of claims 1 to 2, characterized in that: The sum of La2O3 and Ce2O3 is calculated as RE2O3, and the ratio of g-C3N4 to RE2O3 is 1:0.11-0.

37.

4. The supported photocatalytic diatomite-based porous ceramsite according to any one of claims 1 to 3, characterized in that: The usage ratio of La2O3 and Ce2O3 in the RE2O3 is 1:0.58-1.

45.

5. The supported photocatalytic diatomite-based porous ceramsite according to any one of claims 1 to 4, characterized in that: The binder is a mixture of one or more of polyvinyl alcohol, polyethylene glycol, paraffin, and sodium carboxymethyl cellulose; and the pore-forming agent is a mixture of one or more of starch and sawdust powder.

6. The method for preparing the supported photocatalytic diatomite-based porous ceramsite according to any one of claims 1 to 5, comprising the following steps: S1: Weigh each raw material in proportion; S2: g-C3N4, La2O3 and Ce2O3 are placed in a high-energy ball mill for mechanical alloying; S3: Mix the La2O3 / Ce2O3-doped g-C3N4 obtained by high-energy ball milling, diatomaceous earth, a binder, and a pore-forming agent, and add water and stir evenly to form a slurry; S4: Extruding the clay to obtain a green body, and drying the green body; S5: Sintering the dried green body, and obtaining the loaded photocatalytic diatomite-based porous ceramsite after cooling.

7. The method for preparing the supported photocatalytic diatomite-based porous ceramsite according to claim 6, characterized in that: The ball milling speed of the mechanical alloying is 200-400 rpm, and the ball milling time is 1-3 hours.

8. The method for preparing the supported photocatalytic diatomite-based porous ceramsite according to any one of claims 6 to 7, characterized in that: The sintering is divided into two stages. In the first stage, the temperature is raised to 450-550°C at a heating rate of no more than 3°C / min, kept at this temperature for 0.5-1.5 hours, then raised to 800-1350°C at a heating rate of 5-10°C / min, kept at this temperature for 2-4 hours, and cooled naturally.

9. The method for preparing the supported photocatalytic diatomite-based porous ceramsite according to any one of claims 6 to 8, characterized in that: The amount of water added is 35%-50% of the total weight of the raw materials.

10. Use of the supported photocatalytic diatomite-based porous ceramsite according to claims 1 to 9 in sewage treatment.

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