Method for preparing photocatalytic material through illumination-induced kaolinite structure reconstruction
By inducing the structural transformation of kaolinite under alkaline conditions using ultraviolet light, a multiphase coexisting photocatalytic material was prepared, which solved the problems of complex traditional kaolinite modification methods and low efficiency of traditional photocatalysts, and achieved efficient treatment of organic dye wastewater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENYANG JIANZHU UNIVERSITY
- Filing Date
- 2026-01-22
- Publication Date
- 2026-04-21
AI Technical Summary
Existing methods for modifying kaolinite are complex, energy-intensive, and have limited modification effects. Traditional photocatalysts have narrow photoresponse ranges and low quantum efficiency, making it difficult to meet the needs of organic dye wastewater treatment.
By inducing structural transformation of kaolinite under alkaline conditions using ultraviolet light, and through the synergistic effect of light and alkaline environment, multiphase coexisting photocatalytic materials, including montmorillonite and pyrophyllite, were prepared, thereby improving the separation efficiency of electron-hole pairs and the generation of reactive oxygen species.
It significantly enhances the material's adsorption and catalytic degradation capabilities for organic pollutants, improves the treatment efficiency of organic dye wastewater, and has promising application prospects.
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Figure CN121892115A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction. Background Technology
[0002] Currently, the academic community generally believes that the evolution of surface clay minerals is closely related to weathering. Weathering is the process by which Earth's surface rocks gradually decompose and transform under the combined influence of physical, chemical, and biological factors. During long-term weathering, sunlight is a continuous and relatively stable environmental factor. The influence of sunlight involves energy transfer, material transformation, and the interaction of environmental factors. Therefore, the interaction between sunlight, clay minerals, and the environment plays a crucial role in the geochemical cycle of elements and the weathering and evolution of clay minerals.
[0003] Inorganic minerals can convert solar energy, forming mineral photoelectron energy. Under certain conditions, solar radiation can even lead to changes or decomposition of mineral structures. Traditionally, non-semiconductor clay minerals such as kaolinite were considered inert to light, but recent studies have found that their surface hydroxyl groups or structural defects may cause weak photothermal / photochemical effects. For example, Yu et al. reported for the first time in a *Science* article that the Na₂O-Al₂O₃-SiO₂-H₂O system can generate •OH under ultraviolet light irradiation, effectively accelerating the crystallization process of silicate minerals. Liu et al. found that under γ-ray irradiation, the montmorillonite aqueous system generates free radicals, promoting the breaking of Si-O and Al-O bonds in its structure. Other studies have shown that under light conditions, kaolinite and aerogel droplets can generate •OH through synergistic action at the gas-liquid-solid three-phase interface, thereby accelerating the transformation of aerogels.
[0004] With rapid industrial development, the discharge of dye-containing wastewater is increasing daily. Organic dyes such as Rhodamine B (RhB) are highly toxic and difficult to degrade, posing a serious threat to the ecological environment and human health if directly discharged. Currently, methods for treating organic dye wastewater mainly include physical adsorption, chemical oxidation, biodegradation, and photocatalytic degradation. Among these, photocatalytic degradation has become a research hotspot in the field of wastewater treatment due to its advantages of high efficiency, environmental friendliness, and lack of secondary pollution.
[0005] The core of photocatalysis technology lies in the performance of the photocatalyst. Traditional photocatalysts, such as titanium dioxide and zinc oxide, while possessing certain photocatalytic activity, suffer from problems such as narrow light response range, low quantum efficiency, and difficulty in recycling, limiting their large-scale practical application. Therefore, developing novel, efficient, stable, and easily recyclable photocatalysts has become an important research direction in the field of photocatalysis.
[0006] Kaolinite is an abundant and inexpensive natural layered silicate mineral with good chemical stability, thermal stability, and adsorption properties. Most studies use kaolinite as a catalyst support. In recent years, some researchers have discovered that modifying kaolinite can endow it with photocatalytic properties, making it a potential photocatalytic material. Currently, the main methods for modifying kaolinite include ion exchange, intercalation composites, and high-temperature calcination. However, these methods mostly suffer from complex processes, high energy consumption, and limited modification effects. Furthermore, the improvement in photocatalytic activity after modification is relatively small, making it difficult to meet the needs of practical wastewater treatment.
[0007] In summary, developing a simple, low-energy-consumption, and efficient method for modifying kaolinite, utilizing ultraviolet light to induce structural transformation in kaolinite, and preparing high-performance photocatalytic materials for application in the treatment of organic dye wastewater is of great significance for promoting the practical application of photocatalytic technology and the high-value utilization of kaolinite. Summary of the Invention
[0008] To address the shortcomings of the existing technologies, one of the objectives of this invention is to provide a method for preparing photocatalytic materials by inducing structural reconstruction of kaolinite under light. This invention utilizes ultraviolet light to induce structural transformation in kaolinite under alkaline conditions to prepare high-performance photocatalytic materials.
[0009] The above-mentioned objective of this invention is achieved through the following technical solution:
[0010] A method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction includes the following steps:
[0011] Kaolinite was dispersed in deionized water to obtain a slurry. The pH value was adjusted to 8-13, and then stirred under ultraviolet light irradiation for 24-72 hours. After centrifugation, washing, drying, and grinding, the photocatalytic material was obtained.
[0012] Structural defects in kaolinite (such as lattice distortions and lattice vacancies resulting from isomorphic substitution) can act as electron or hole trapping centers under alkaline environments and ultraviolet irradiation, promoting electron-hole pair separation, increasing oxygen vacancies, and thus enhancing the generation efficiency of reactive oxygen species. The core of photoradiation is its ability to induce the formation of catalytically active substances on the surface of clay minerals. These active substances drive the directional transformation of kaolinite's topological structure by regulating reaction pathways, lowering the energy barrier of structural transformation, or accelerating ion migration. Structural characterization results show that the phase composition of the photoreaction products exhibits diverse characteristics: in addition to montmorillonite, it also includes incompletely transformed kaolinite and pyrophyllite. This multiphase coexistence structure, due to the increased interface effect and defect density, significantly enhances the material's adsorption and catalytic degradation capabilities for organic pollutants, making the prepared photocatalytic material a promising candidate for wastewater treatment.
[0013] This invention promotes the structural transformation of kaolinite through the synergistic effect of ultraviolet light irradiation and alkaline environment. The duration of ultraviolet light irradiation plays a decisive role. If the ultraviolet light irradiation time is too short, the kaolinite reaction is incomplete, the oxygen vacancy content does not change significantly, and the photocatalytic effect is not significantly improved.
[0014] Preferably, the concentration of kaolinite in the slurry is 5~15 g / L.
[0015] Preferably, water cooling is performed during ultraviolet irradiation to control the system temperature at 20~30℃. To avoid interference from the heat generated by the ultraviolet portion of the simulated sunlight irradiation, circulating cooling water is introduced into the quartz water-cooled cold trap during the reaction process.
[0016] Preferably, the specific conditions for ultraviolet light are: a wavelength of 365 nm and an irradiance of 2~18 mW / cm². 2 .
[0017] Preferably, the ultraviolet light irradiation time is 48~72h.
[0018] Preferably, the drying conditions are drying at 60~70℃ for 10~20h.
[0019] Preferably, the material is ground and then passed through a 200-mesh sieve.
[0020] Another object of the present invention is to provide a photocatalytic material prepared by the method, wherein the structure of the photocatalytic material includes kaolinite, montmorillonite and pyrophyllite.
[0021] Another object of the present invention is to provide the application of the photocatalytic material prepared by the method in the removal of organic dyes, wherein the application method is as follows: the photocatalytic material is added to wastewater containing organic dyes, mixed, and subjected to catalytic degradation reaction under ultraviolet light.
[0022] Preferably, the concentration of the photocatalytic material in the wastewater is 0.5~2g / L.
[0023] Compared with the prior art, the advantages of the present invention are:
[0024] This invention promotes the structural transformation of kaolinite through the synergistic effect of ultraviolet light and alkaline environment, generating photocatalytic reaction products comprising montmorillonite, kaolinite, and pyrophyllite. This multiphase coexistence structure system significantly enhances the adsorption and catalytic degradation capabilities of organic pollutants such as Rhodamine B due to the improved interface effect and defect density, making the prepared photocatalytic material a promising candidate for wastewater treatment. Attached Figure Description
[0025] Figure 1 XRD patterns of raw kaolinite ore, the photocatalytic material obtained in Example 1, and the material obtained in Comparative Example 1;
[0026] Figure 2 TEM images of raw kaolinite ore and the photocatalytic material obtained in Example 1;
[0027] Figure 3 The removal rates of the photocatalytic material obtained in Example 1 at different RhB solution concentrations are shown.
[0028] Figure 4 The removal rate of RhB by the photocatalytic material obtained in Example 1 at different times;
[0029] Figure 5 The removal rate of RhB by the photocatalytic material obtained in Example 1 at different pH values is shown. Detailed Implementation
[0030] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction of the present invention includes the following steps:
[0032] Kaolinite was dispersed in deionized water to obtain a slurry. The pH value was adjusted to 8-13, and then stirred under ultraviolet light irradiation for 24-72 hours. After centrifugation, washing, drying, and grinding, the photocatalytic material was obtained.
[0033] In some embodiments, the concentration of kaolinite in the slurry is 5 g / L; in other embodiments, the concentration of kaolinite in the slurry is 15 g / L; and in some preferred embodiments, the concentration of kaolinite in the slurry is 10 g / L.
[0034] In some embodiments, the wavelength of the ultraviolet light is 365 nm and the irradiance is 2 mW / cm². 2 In other embodiments, the wavelength of the ultraviolet light is 365 nm, and the irradiance is 18 mW / cm². 2 In some preferred embodiments, the wavelength of the ultraviolet light is 365 nm, and the irradiance is 10 mW / cm². 2 .
[0035] In some embodiments, the ultraviolet light irradiation time is 24 hours; in other embodiments, the ultraviolet light irradiation time is 72 hours; and in some preferred embodiments, the ultraviolet light irradiation time is 48 hours.
[0036] In some embodiments, the material is ground and then passed through a 200-mesh sieve.
[0037] The kaolinite (Al2Si2O5(OH)4) used in this embodiment of the invention was purchased from China Kaolin Co., Ltd., and sodium hydroxide (NaOH) and ethanol were purchased from Sinopharm Chemical Reagent Shenyang Co., Ltd. All chemical reagents used were of analytical grade and required no further purification.
[0038] The instruments used in this embodiment of the invention are as follows: a 300 W xenon lamp, a quartz water-cooled cold trap, a stirrer, and several sealable quartz tubes (height: 10 cm, volume: 200 mL).
[0039] Example 1
[0040] This embodiment provides a method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction, including the following steps:
[0041] S1. Raw material pretreatment: Disperse 2g of purified kaolinite powder in 200mL of deionized water in a 500mL beaker, then adjust the pH of the dispersion to 10 with NaOH, stir for 30min to fully disperse and form a stable and uniform slurry;
[0042] S2. Photoinduced reaction: After pouring the slurry into the quartz tube, place the quartz tube on the stirrer of the quartz cold trap, then turn on the xenon lamp, controlling the distance between the quartz tube and the light source to be 10 cm, the wavelength of the ultraviolet light to be 365 nm, and the irradiance to be 10 mW / cm². 2To avoid the heat generated by the ultraviolet light portion of the simulated sunlight from interfering with the experiment, circulating cooling water was introduced into the quartz water-cooled cold trap during the reaction process to maintain the system temperature at 25℃ and the reaction time was 48h. The synergistic effect of light and alkaline environment caused the kaolinite to undergo structural transformation.
[0043] S3. Post-processing steps: After the reaction is completed, the slurry is centrifuged with deionized water and ethanol to collect the precipitate; then it is repeatedly washed with deionized water until neutral to remove residual impurities; the washed product is placed in an oven and dried at 65°C to constant weight; after grinding, it is passed through a 200-mesh sieve to obtain a photocatalytic material product with uniform particle size.
[0044] Example 2
[0045] This embodiment provides a method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction, including the following steps:
[0046] S1. Raw material pretreatment: Disperse 2g of purified kaolinite powder in 200mL of deionized water in a 500mL beaker, then adjust the pH of the dispersion to 9 with NaOH, stir for 30min to fully disperse and form a stable and uniform slurry;
[0047] S2. Photoinduced reaction: After pouring the slurry into the quartz tube, place the quartz tube on the stirrer of the quartz cold trap, then turn on the xenon lamp, controlling the distance between the quartz tube and the light source to be 10 cm, the wavelength of the ultraviolet light to be 365 nm, and the irradiance to be 3 mW / cm². 2 To avoid interference from the heat generated by the ultraviolet light portion of the simulated sunlight, circulating cooling water was introduced into the quartz water-cooled cold trap during the reaction process to maintain the system temperature at 25℃. The reaction time was 72h. The synergistic effect of light and alkaline environment caused the kaolinite to undergo structural transformation.
[0048] S3. Post-processing steps: After the reaction is completed, the slurry is centrifuged with deionized water and ethanol to collect the precipitate; then it is repeatedly washed with deionized water until neutral to remove residual impurities; the washed product is placed in an oven and dried at 60°C to constant weight; after grinding, it is passed through a 200-mesh sieve to obtain a photocatalytic material product with uniform particle size.
[0049] Example 3
[0050] This embodiment provides a method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction, including the following steps:
[0051] S1. Raw material pretreatment: Disperse 2g of purified kaolinite powder in 200mL of deionized water in a 500mL beaker, then adjust the pH of the dispersion to 10 with NaOH, stir for 30min to fully disperse and form a stable and uniform slurry.
[0052] S2. Photoinduced reaction: After pouring the slurry into the quartz tube, place the quartz tube on the stirrer of the quartz cold trap, then turn on the xenon lamp, controlling the distance between the quartz tube and the light source to be 10 cm, the wavelength of the ultraviolet light to be 365 nm, and the irradiance to be 18 mW / cm². 2 To avoid the heat generated by the ultraviolet light portion of the simulated sunlight from interfering with the experiment, circulating cooling water was introduced into the quartz water-cooled cold trap during the reaction process to maintain the system temperature at 25℃ and the reaction time was 24h. The synergistic effect of light and alkaline environment caused the kaolinite to undergo structural transformation.
[0053] S3. Post-processing steps: After the reaction is completed, the slurry is centrifuged with deionized water and ethanol to collect the precipitate; then it is repeatedly washed with deionized water until neutral to remove residual impurities; the washed product is placed in an oven and dried at 70°C to constant weight; after grinding, it is passed through a 200-mesh sieve to obtain a photocatalytic material product with uniform particle size.
[0054] Comparative Example 1
[0055] The preparation method of the photocatalytic material in this comparative example is basically the same as that in Example 1, except that step S2 is as follows:
[0056] Dark reaction: After pouring the slurry into the quartz tube, place the quartz tube on the stirrer of the quartz cold trap, and stir for 48 hours at 25°C in the dark without turning on the xenon lamp.
[0057] Comparative Example 2
[0058] The preparation method of the photocatalytic material in this comparative example is basically the same as that in Example 1, except that step S1 is as follows:
[0059] Raw material pretreatment: Disperse 2g of purified kaolinite powder in 200mL of deionized water in a 500mL beaker until fully dispersed to form a stable and uniform slurry.
[0060] Comparative Example 3
[0061] The preparation method of the comparative photocatalytic material is basically the same as that of Example 1, except that the reaction time in step S2 is 10h.
[0062] The XRD patterns of kaolinite ore, the photocatalytic material obtained in Example 1, and the material obtained in Comparative Example 1 are shown below. Figure 1As shown in the XRD results, the selected kaolinite ore has high purity and good crystallinity, exhibiting typical characteristic diffraction peaks at d(001) and d(002). After the same reaction time, the XRD spectrum of the product obtained in Comparative Example 1 under dark reaction conditions is basically unchanged from that of kaolinite, indicating that the reaction product is still kaolinite. The XRD spectrum of the reaction product obtained under simulated sunlight irradiation conditions in Example 1 shows that the intensity of the diffraction peaks of kaolinite is significantly weakened or even disappears, especially the typical characteristic peak at d(001) position, which basically disappears, and the characteristic diffraction peak at d(002) is also significantly weakened. At the same time, the characteristic diffraction peaks of montmorillonite begin to appear, with its d(001) characteristic peak (2θ=5.7º) becoming the strongest peak in the spectrum. In addition to montmorillonite, the phase composition of the product from the light-irradiated reaction also includes incompletely transformed kaolinite and pyrophyllite.
[0063] TEM images of raw kaolinite ore and the photocatalytic material obtained in Example 1 are shown below. Figure 2 As shown, Figure a is a TEM image of raw kaolinite ore, and Figure b is a TEM image of the photocatalytic material of Example 1. It can be seen from the figures that the raw ore exhibits the typical single-crystal pseudo-hexagonal lamellar structure of kaolinite. Figure 2 a); and the morphology of the product changed significantly after being exposed to light ( Figure 2 (b) The original pseudo-hexagonal platy morphology blurred and disappeared, and a distinct folded platy structure appeared around the aggregate, which is consistent with the typical microscopic morphological characteristics of montmorillonite. This indicates that kaolinite partially transformed into montmorillonite after ultraviolet light irradiation.
[0064] Application examples
[0065] 0.1 g of the photocatalytic material prepared in each example and comparative example was added to 100 mL of Rhodamine B aqueous solution, sonicated for 5 min, and then placed in a photochemical reactor. The reaction was stirred under room temperature and sunlight conditions. At the specified time, 2 mL of the reaction solution was pipetted into an equal volume of methanol and filtered through a 0.22 μm filter membrane. The absorbance of the sample was immediately measured using a UV-Vis spectrophotometer, and the degradation capacity of the photocatalytic material for Rhodamine B was calculated.
[0066] (1) In the experiment with RhB solution concentration as the variable group, the photocatalytic degradation results of 0.1g of the photocatalytic material of Example 1 (kaolinite after structural transformation) and 0.1g of raw kaolinite ore on 100mL of RhB solution were compared as follows: Figure 3The RhB solution concentrations were 50, 100, 250, 500, 750, 1000, and 1400 mg / L. The results showed that the photocatalytic material in Example 1 exhibited a significantly higher removal rate for higher concentrations of RhB solution than the raw kaolinite ore. In a solution with an RhB concentration of 750 mg / L, the photocatalytic material in Example 1 achieved a removal rate of 78.57 mg / g, while the removal rate of the raw kaolinite ore was only 66.07 mg / g, representing an increase of 18.92%. With increasing concentration, the photocatalytic efficiency decreased. In a 1400 mg / L RhB solution, the photocatalytic material in Example 1 achieved a removal rate of 85 mg / g, while the removal rate of the raw kaolinite ore was only 75 mg / g.
[0067] (2) In the experiment with photocatalytic reaction time as the variable group, the comparison results of photocatalytic degradation of 100 mL of 750 mg / L RhB solution by 0.1 g of the photocatalytic material of Example 1 and 0.1 g of raw kaolinite are as follows: Figure 4 The photocatalytic reaction times were 10, 30, 60, 120, 240, and 300 min. The results showed that the removal rate of RhB solution by the photocatalytic material of Example 1 was significantly higher than that of raw kaolinite at different reaction times. When the reaction time was 120 min, the removal rate of the photocatalytic material of Example 1 reached 83.93 mg / g, while the removal rate of raw kaolinite was only 77.68 mg / g, an increase of 8.05%. With increasing reaction time, the photocatalytic efficiency decreased. After 300 min of reaction, the removal rate of the photocatalytic material of Example 1 reached 104.46 mg / g, while the removal rate of raw kaolinite was only 89.29 mg / g.
[0068] (3) In the experiment with solution pH as the variable group, the photocatalytic degradation results of 0.1g of the photocatalytic material of Example 1 and 0.1g of raw kaolinite in 100mL of 750mg / L RhB solution for 120min were compared as follows: Figure 5 The pH values were 2, 4, 6, 7, 8, 10, and 12. The results showed that under acidic, alkaline, and neutral conditions, the photocatalytic effect of the photocatalytic material in Example 1 on RhB solution was significantly better than that of raw kaolinite, and the difference became more pronounced with increasing acidity and alkalinity. At pH 2, the removal rate of the photocatalytic material in Example 1 reached 133.93 mg / g, while the removal rate of raw kaolinite was only 100.89 mg / g, an increase of 32.75%. At pH 12, the removal rate of the photocatalytic material in Example 1 reached 121.43 mg / g, while the removal rate of raw kaolinite was only 96.43 mg / g, an increase of 25.93%.
[0069] (4) The photocatalytic degradation results of 0.1g of each example and comparative example photocatalyst material reacted in 100mL of 750mg / L RhB solution for 120min at pH 2 are shown in Table 1.
[0070] Table 1. Removal rate of RhB by photocatalytic materials in each embodiment and comparative example.
[0071]
[0072] As shown in Table 1, the photocatalytic materials obtained in Examples 1-3 of this invention exhibit excellent catalytic degradation ability for Rhodamine B. A comparison of Example 1 and Comparative Examples 1-2 reveals that, compared to either an alkaline environment or UV irradiation alone, this invention, by simultaneously inducing structural transformation of kaolinite under an alkaline environment using UV light, can enhance the catalytic degradation ability of the material for Rhodamine B. A comparison of Example 1 and Comparative Example 3 shows that if the UV irradiation time is too short, the kaolinite reaction is incomplete, the oxygen vacancy content does not change significantly, and the improvement in photocatalytic effect is not obvious.
[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction, characterized in that, Includes the following steps: Kaolinite was dispersed in deionized water to obtain a slurry. The pH value was adjusted to 8-13, and then stirred under ultraviolet light irradiation for 24-72 hours. After centrifugation, washing, drying, and grinding, the photocatalytic material was obtained.
2. The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction according to claim 1, characterized in that, The concentration of kaolinite in the slurry is 5~15g / L.
3. The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction according to claim 1, characterized in that, Water cooling was performed during ultraviolet irradiation, and the system temperature was controlled at 20~30℃.
4. The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction according to claim 1, characterized in that, The specific conditions for ultraviolet light are: wavelength of 365 nm and irradiance of 2~18 mW / cm². 2 .
5. The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction according to claim 1, characterized in that, The duration of ultraviolet light irradiation is 48-72 hours.
6. The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction according to claim 1, characterized in that, The drying conditions are 60-70℃ for 10-20 hours.
7. The method for preparing photocatalytic materials by light-induced kaolinite structural reconstruction according to claim 1, characterized in that, After grinding, it is passed through a 200-mesh sieve.
8. A photocatalytic material, characterized in that, The photocatalytic material is prepared by the method according to any one of claims 1 to 7, and the structure of the photocatalytic material includes kaolinite, montmorillonite and pyrophyllite.
9. The application of the photocatalytic material prepared by the method according to any one of claims 1 to 7 in the removal of organic dyes, characterized in that, The application method is as follows: the photocatalytic material is added to wastewater containing organic dyes, mixed, and subjected to catalytic degradation reaction under ultraviolet light.
10. The application according to claim 9, characterized in that, The concentration of the photocatalytic material in the wastewater is 0.5~2g / L.