Modified calcium hydroxide-based piezocatalytic material, and preparation method and application thereof

Abstract

This invention discloses a modified calcium hydroxide-based piezoelectric catalytic material, its preparation method, and its applications, belonging to the field of inorganic non-metallic material preparation technology. The material is prepared by introducing a sulfur-containing surfactant during the synthesis of calcium hydroxide. The sulfur element in the material exists in the form of -SO3 groups and possesses piezoelectric catalytic activity. This method is mild and simple to operate, enabling intrinsically piezoelectric non-pyroelectric Ca(OH)2 to acquire highly efficient piezoelectric catalytic activity. This enriches the types of piezoelectric catalytic materials, fills the research gap in calcium-based piezoelectric catalytic materials, and has significant theoretical and applied value. The prepared material has multiple advantages, including high activity, good stability, strong environmental adaptability, low raw material cost, and environmentally friendly sources, showing broad application prospects in environmental catalysis fields such as wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic materials technology, specifically relating to a modified calcium hydroxide-based piezoelectric catalytic material, its preparation method, and its application. Background Technology

[0002] With the continuous advancement of industrialization, energy shortages and environmental pollution have become increasingly prominent issues, posing significant bottlenecks to global sustainable development. Developing efficient, green, and low-cost catalytic technologies and materials has become a research hotspot and urgent need in the fields of materials science and environmental engineering. Piezoelectric catalysis, as a novel mechanochemical catalysis method, can directly convert mechanical energy, such as that widely present in the environment including mechanical vibration, ultrasonic action, and fluid impact, into chemical energy to drive redox reactions. It shows promising application prospects in environmental remediation, clean energy conversion, and organic synthesis, providing a new path to overcome the limitations of traditional catalytic technologies that rely on external energy sources such as light and electricity (Science in China: Chemistry, 2023, 53, 1336–1354).

[0003] Currently reported piezoelectric catalytic materials mainly include piezoelectric ceramics (such as lead zirconate titanate and barium titanate), piezoelectric semiconductors (such as zinc oxide and bismuth ferrite), and piezoelectric polymers (such as polyvinylidene fluoride). However, these materials generally have significant shortcomings: traditional lead-based piezoelectric ceramics are highly toxic, easily causing secondary pollution, which does not meet the requirements of green environmental protection, and the preparation process is complex and costly; piezoelectric semiconductors such as zinc oxide have low piezoelectric coefficients and limited catalytic efficiency; piezoelectric polymers have problems such as unstable piezoelectric properties and poor high-temperature resistance, which seriously restrict the practical application and industrialization of piezoelectric catalysis technology (Angew. Chem. Int. Ed., 2023, 62, e202213927; Chemical Industry Progress, 2024, 43, 5723–5733).

[0004] Therefore, there is an urgent need in this field to develop novel, efficient, environmentally friendly, and low-cost lead-free piezoelectric catalytic materials. Calcium-based compounds, due to their environmental friendliness, wide availability of raw materials, low cost, and good biocompatibility, have become the most ideal lead-free piezoelectric materials. Calcium hydroxide (Ca(OH)2), as a typical calcium-based inorganic compound, has outstanding application potential in the field of piezoelectric catalysis: on the one hand, it has excellent environmental friendliness, with no risk of leaching of heavy metals such as lead, and can be gradually converted into calcium carbonate in a carbon dioxide-containing natural environment, without persistent pollution problems; on the other hand, calcium hydroxide raw materials are readily available, production costs are low, and it is a major component of industrial solid waste carbide slag, with a huge annual output. Using it in the preparation of high-performance piezoelectric catalysts can realize the resource utilization and high-value utilization of solid waste, achieving both economic and environmental benefits. However, from a crystal structure perspective, calcium hydroxide is hexagonal with a centrosymmetric crystal point group, theoretically lacking intrinsic piezoelectric activity, making it difficult to directly use in efficient piezoelectric catalytic reactions. How to enable the intrinsically piezoelectric-free Ca(OH)2 to obtain excellent piezoelectric catalytic performance has become a key technical problem restricting its application in the field of piezoelectric catalysis.

[0005] A search of existing technologies at home and abroad revealed no literature reports on Ca(OH)2 as a piezoelectric catalytic material. Its piezoelectric catalytic performance, preparation methods, and related applications are all currently unexplored. Summary of the Invention

[0006] Given the various shortcomings of existing piezoelectric catalytic materials, the first objective of this invention is to provide a highly efficient, environmentally friendly, and low-cost modified calcium hydroxide-based piezoelectric catalytic material to overcome the problems of low catalytic efficiency, high toxicity, and high cost of existing piezoelectric catalytic materials.

[0007] To achieve the above-mentioned technical objectives, the inventors conducted extensive experimental research and unremitting exploration, and finally broke the intrinsic crystal symmetry of calcium hydroxide by molecular modification with a specific surfactant, thereby endowing it with piezoelectric catalytic activity, and obtained the following technical solution: a modified calcium hydroxide-based piezoelectric catalytic material, which is prepared by introducing a sulfur-containing surfactant during the synthesis of calcium hydroxide, wherein the sulfur element in the material exists in the form of -SO3 group and has piezoelectric catalytic activity.

[0008] It should be noted that by introducing the -SO3 group and successfully grafting or modifying it onto the Ca(OH)2 molecule, the present invention disrupts the original centrosymmetry of the Ca(OH)2 structure, causing local polarization of its crystal structure, thereby obtaining piezoelectric properties that are not intrinsically present.

[0009] More preferably, in the modified calcium hydroxide-based piezoelectric catalytic material as described above, the sulfur-containing surfactant is sodium dodecylbenzenesulfonate; and / or, the atomic ratio of S / Ca in the material is (0.06-0.09):1; and / or, the material has a mesoporous structure.

[0010] This invention creatively transforms inexpensive and environmentally friendly calcium hydroxide into a high-performance piezoelectric catalytic material. Through a sophisticated and parameter-controlled synthesis method, it solves the problems of high toxicity, high cost, or insufficient performance of traditional piezoelectric materials. Therefore, a second objective of this invention is to provide a method for preparing the modified calcium hydroxide-based piezoelectric catalytic material described above, comprising the following steps:

[0011] (1) Under the protection of an inert gas, sodium hydroxide and sulfur-containing surfactant are dissolved in an acidic aqueous solution with a pH of 3 to 5 and mixed evenly to obtain the main reaction solution;

[0012] (2) Under inert gas protection and stirring conditions, calcium salt solution is added dropwise to the main reaction solution, and the reaction is carried out at 50-60°C first, and then the temperature is raised to 75-85°C to continue the reaction for 2-3 hours to obtain precipitate;

[0013] (3) The precipitate is separated, washed and dried to obtain the modified calcium hydroxide-based piezoelectric catalytic material.

[0014] More preferably, in step (1), the sulfur-containing surfactant is sodium dodecylbenzenesulfonate, and its concentration in the main reaction solution is 1.2 to 2 g / L; and / or, the concentration of sodium hydroxide in the main reaction solution is 0.1 to 0.6 mol / L.

[0015] More preferably, in steps (1) and (2), the inert gas is nitrogen or argon, and its flow rate is 2 to 5 mL / min.

[0016] More preferably, in step (2), the calcium salt is calcium chloride, calcium nitrate or calcium acetate; the concentration of the calcium salt solution is 0.1 to 0.45 mol / L, and the dropping rate is 2 to 5 mL / min.

[0017] More preferably, in step (3), the drying is vacuum drying at 50-70°C.

[0018] To verify the piezoelectric catalytic activity of the material of this invention, the inventors selected organic dyes and antibiotics as typical target pollutants. Through a simulated wastewater system, they systematically studied the catalytic degradation performance of the mesoporous calcium hydroxide-based piezoelectric catalytic material prepared by the above method on organic pollutants. The results showed that the modified calcium hydroxide-based piezoelectric catalytic material prepared in this invention exhibited excellent piezoelectric catalytic degradation effects on various organic pollutants in wastewater, while also demonstrating strong resistance to interference from coexisting components such as inorganic ions and natural organic matter in the aquatic environment. Furthermore, the modified calcium hydroxide-based piezoelectric catalytic material maintained good catalytic activity over a wide pH range and showed strong adaptability to the acidity and alkalinity of organic wastewater.

[0019] Therefore, a third objective of this invention is to utilize the modified calcium hydroxide-based piezoelectric catalytic material as a piezoelectric catalyst for the removal of organic pollutants. Specifically, this invention provides an application of the modified calcium hydroxide-based piezoelectric catalytic material as described above, wherein the modified calcium hydroxide-based piezoelectric catalytic material is used as a piezoelectric catalyst for the degradation of organic pollutants in water.

[0020] More preferably, the organic pollutant includes at least one of methyl orange, methylene blue, rhodamine B, neutral red, Congo red, and tetracycline; the application is carried out in an aqueous solution with a pH of 3 to 13, and the piezoelectric catalytic reaction is driven by providing mechanical energy through ultrasound.

[0021] More preferably, the inorganic ions include sodium ions, potassium ions, calcium ions, magnesium ions, carbonate ions, nitrate ions, chloride ions, sulfate ions, and bicarbonate ions; the natural organic matter is humic acid.

[0022] Compared with existing technologies, the modified calcium hydroxide-based piezoelectric catalytic material and its preparation method provided by this invention have the following advantages and advancements:

[0023] (1) Imparting piezoelectric activity to intrinsically non-piezoelectric materials. The core innovation of this invention lies in the introduction of a specific sulfur-containing surfactant (sodium dodecylbenzenesulfonate) during the synthesis process and precise process control, enabling Ca(OH)2 to acquire piezoelectric properties that it does not possess. The control experiment of Comparative Example 1 (without the addition of this surfactant) clearly confirms that the generated pure Ca(OH)2 does not possess piezoelectric current response and catalytic activity, while the material of this invention exhibits a clear piezoelectric hysteresis loop and high piezoelectric current density.

[0024] (2) A novel high-performance, green, lead-free calcium-based piezoelectric catalytic material has been developed. Existing high-efficiency piezoelectric materials (such as lead zirconate titanate) often contain lead, which has the problems of high toxicity and easy secondary pollution. This invention is the first to successfully modify intrinsically non-piezoelectric calcium hydroxide into a material with excellent piezoelectric catalytic activity. Its raw materials are environmentally friendly and biocompatible, thus avoiding the risk of heavy metal pollution from the source.

[0025] (3) The preparation process is simple and low-cost, and it realizes the potential for high-value utilization of solid waste. The raw material calcium hydroxide used in this invention has extremely low cost and is the main component of industrial solid waste carbide slag. Developing it into a high-performance catalyst provides a new approach for the resource utilization and high-value utilization of carbide slag, with significant economic and environmental benefits. In addition, the preparation method mainly involves solution reaction and conventional heat treatment, which is simple, safe and controllable, and uses conventional instruments and equipment, making it suitable for large-scale production.

[0026] (4) The prepared material exhibits excellent piezoelectric catalytic performance and wide applicability. Example data shows that, under ultrasonic driving, the material of this invention achieves a degradation rate of over 93% for the model pollutant Rhodamine B within 20 minutes, and also shows significant degradation effects on methylene blue, tetracycline, Congo red, etc., indicating high catalytic activity and strong universality. Furthermore, the material also possesses wide pH adaptability and strong anti-interference ability. Example data shows that the material maintains good catalytic activity within a wide pH range of 3-13, solving the problem of many catalysts being sensitive to the acidity or alkalinity of the reaction system. Simultaneously, it can withstand various common inorganic ions (Na+, Na ... + K + Ca 2+ Mg 2+ Cl - SO4 2- CO3²⁻, HCO3 - NO3 - In water bodies containing natural organic matter (humic acid), its catalytic performance is not significantly affected, demonstrating strong environmental adaptability and practicality.

[0027] (5) Precise control of material structure and properties was achieved through a specific synthesis process. Comparative Examples 2-5 systematically verified the necessity and non-obviousness of key process parameters. Specifically, Comparative Example 2 indicated that if the solution is not adjusted to acidity (pH 3-5), a large amount of CaCO3 impurities will be generated, severely inhibiting catalytic performance (degradation rate drops to 56%). Comparative Example 3 indicated that if the reaction process is not continuously protected by inert gas (N2 / Ar), CaCO3 will also be generated, leading to a decrease in performance (degradation rate 64%). Comparative Example 4 indicated that if the two-step method of "reacting at low temperature (50-60℃) first, then heating (75-85℃)" is not adopted, but instead a direct high-temperature reaction is carried out, the performance of the obtained material will be significantly degraded (degradation rate is only 38.7%). Comparative Example 5 indicated that if other sulfur-containing compounds (sodium dodecyl sulfate, sodium thiosulfate) are used to replace sodium dodecylbenzenesulfonate, it is completely impossible to obtain materials with piezoelectric catalytic activity. These comparative experiments collectively demonstrate that the success of this invention is not simply a matter of replacing raw materials or a conventional combination of processes, but rather relies on a synergistic and indispensable specific technical solution of "acidic environment + inert gas protection + specific sulfur-containing surfactant + stepwise heating reaction". This solution ensures that sulfur successfully modifies Ca(OH)2 in the form of -SO3 groups and forms the desired mesoporous structure, thereby endowing it with excellent piezoelectric catalytic performance. Attached Figure Description

[0028] Figure 1 The images show the XRD patterns of S-Ca(OH)2 and Ca(OH)2 materials in Example 1 and Comparative Example 1 of this invention.

[0029] Figure 2 The infrared spectrum of the S-Ca(OH)2 material in Example 1 of this invention;

[0030] Figure 3 This is a fine XPS spectrum of S2p in the S-Ca(OH)2 material in Example 1 of the present invention;

[0031] Figure 4 This is a TEM image of the S-Ca(OH)2 material in Example 1 of the present invention;

[0032] Figure 5 This is a nitrogen adsorption diagram of the S-Ca(OH)2 material in Example 1 of the present invention;

[0033] Figure 6 The amplitude / phase-voltage curve of the S-Ca(OH)2 material in Example 1 of this invention; the catalytic cycle life of the Cu@C composite material for the degradation of methyl orange;

[0034] Figure 7 Transient piezoelectric current diagrams of S-Ca(OH)2 and Ca(OH)2 materials in Example 1 and Comparative Example 1 of this invention;

[0035] Figure 8 This is a performance diagram of the piezoelectric catalytic degradation of RhB by the S-Ca(OH)2 material in Example 1 of this invention;

[0036] Figure 9 The graph shows the performance of the S-Ca(OH)2 material in Example 1 of this invention in piezoelectric catalytic degradation of methyl orange, methylene blue, tetracycline, Congo red and neutral red.

[0037] Figure 10 This is a graph showing the effect of inorganic ions on the piezoelectric catalytic degradation of RhB by S-Ca(OH)2 in Example 1 of the present invention;

[0038] Figure 11 This is a graph showing the effect of the initial solution pH on the piezoelectric catalytic degradation of RhB by S-Ca(OH)2 in Example 1 of this invention.

[0039] Figure 12 This is a graph showing the effect of water on the piezoelectric catalytic degradation of RhB by S-Ca(OH)2 in Example 1 of this invention;

[0040] Figure 13 The image shows the XRD pattern of the material obtained in Comparative Example 2 of this invention.

[0041] Figure 14 This is the XRD pattern of the material obtained in Comparative Example 3 of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of protection of the present invention. Furthermore, unless specific technical operation steps or conditions are specified in the embodiments, they are all performed according to the general techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0043] Example 1

[0044] Measure 80 mL of deionized water into a clean container, adjust the pH to 3.2 using a precision pH meter, and purge with nitrogen at a rate of 5 mL / min for protection. While continuously stirring under nitrogen purging, add solid NaOH to dissolve, preparing a 0.92 mol / L NaOH solution. Then add 50 mL of 4.0 g / L sodium dodecylbenzenesulfonate solution, stir for 5 min until homogeneous, and transfer the entire solution to a 500 mL round-bottom flask. Seal the flask and maintain nitrogen purging; this is the main reaction solution. Place the round-bottom flask containing the main reaction solution in a water bath and heat to 55 °C under nitrogen protection. Take 80 mL of 0.45 mol / L calcium chloride solution, place it in a constant-pressure dropping funnel, and add it dropwise to the main reaction solution at a rate of 5 mL / min. After the addition is complete, rapidly raise the temperature to 80 °C and maintain the reaction at this temperature for 3 h under nitrogen purging throughout, until a white precipitate forms. After the reaction was completed, the system was cooled to room temperature and nitrogen flow was stopped. A white precipitate was obtained by repeated filtration and washing, and then dried in a vacuum drying oven at 60 °C to finally obtain the mesoporous S-Ca(OH)2 piezoelectric catalyst.

[0045] The composition, microstructure and properties of the S-Ca(OH)2 material prepared in Example 1 were analyzed and characterized by XRD, infrared, XPS, TEM, EDS, electrochemistry and PFM.

[0046] (1) Phase composition, microstructure and piezoelectric properties analysis

[0047] Figure 1 The X-ray powder diffraction pattern of the S-Ca(OH)2 material prepared in Example 1 of this invention shows that the obtained S-Ca(OH)2 sample exhibited eight diffraction peaks at 2θ = 28.7°, 47.2°, 50.8°, 54.4°, 62.7°, 64.3°, and 71.8°, which are consistent with the characteristic diffraction peaks of Ca(OH)2. EDS analysis revealed that the S / Ca atomic ratio in the sample was 0.087. The infrared spectrum of the S-Ca(OH)2 material (…) Figure 2 It can be seen that at 873 cm -1 The infrared absorption peaks at 1013 and 1134 cm⁻¹ correspond to the Ca-O stretching vibration. -1 The infrared absorption peaks at 1042 and 1181 cm⁻¹ are attributed to the symmetric tensile vibration of -SO₃H. -1 The infrared absorption peak at that point corresponds to the asymmetric tensile vibration of O=S=O.

[0048] like Figure 3 The figure shows the fine XPS peak of S 2p in the S-Ca(OH)2 material. The fitted peak of S 2p at 168.56 eV corresponds to the SO binding energy in the -SO3 group, which indicates that -SO3 has been successfully modified to Ca(OH)2.

[0049] like Figure 4 The image shown is a TEM image of S-Ca(OH)2 material. The image shows a clear mesoporous channel structure, where the black shadows represent the pore walls and the white areas represent the channels.

[0050] like Figure 5 The figure shows the nitrogen adsorption diagram of S-Ca(OH)2 material, with a specific surface area of ​​55.56 cm². 2 / g. The figure shows that there is a significant hysteresis loop between P / P0 and 0.4, indicating the formation of a mesoporous structure.

[0051] Figure 6 The amplitude / phase-voltage curve of the S-Ca(OH)2 material prepared in Example 1 of this invention is shown. The sample exhibits a representative 180° ferroelectric phase transition hysteresis loop and amplitude-voltage butterfly curve, which clearly confirms its inherent piezoelectric properties.

[0052] Figure 7 The transient piezoelectric current density of S-Ca(OH)₂ under ultrasonic irradiation was demonstrated. Clearly, S-Ca(OH)₂ exhibits a high transient piezoelectric current density under ultrasonic driving, along with excellent repeatability and stability. These results confirm that S-Ca(OH)₂ is a high-performance piezoelectric catalyst, exhibiting superior charge separation efficiency and significant electron mobility.

[0053] In summary, this invention successfully prepared S-Ca(OH)2 piezoelectric catalytic material.

[0054] (2) Piezoelectric catalysis experiment

[0055] Prepare 50 mL of a 10 mg / L Rhodamine B solution. Add 20 mg of the S-Ca(OH)₂ piezoelectric material prepared by the above method to the Rhodamine B solution. Figure 8 As shown, the reaction was stirred at room temperature (25℃) until adsorption equilibrium was reached. Under ultrasonic drive, after 20 min of reaction, the degradation rate of Rhodamine B by the S-Ca(OH)2 material reached over 93%. The S-Ca(OH)2 material obtained in this invention exhibits excellent piezoelectric catalytic performance. The S-Ca(OH)2 sample has strong universal applicability to organic wastewater. After 20 min of piezoelectric catalytic reaction, the degradation rates of methylene blue, tetracycline, Congo red, methyl orange, and neutral red were 89.6%, 75.6%, 82.4%, 15.4%, and 69%, respectively. Figure 9It also exhibits strong resistance to interference from coexisting components such as inorganic ions and natural organic matter in the aquatic environment. In the presence of inorganic ions such as sodium ions, potassium ions, calcium ions, magnesium ions, carbonate ions, nitrate ions, chloride ions, sulfate ions, and bicarbonate ions, as well as natural organic matter in the form of humic acid, the degradation rate of Rhodamine B remains above 93%. Figure 10 Furthermore, this catalyst exhibits good pH adaptability, maintaining good catalytic activity within a pH range of 3–13 without significant impact. Figure 11 Furthermore, it showed good adaptability to different water bodies: deionized water, tap water, and Weihe River water, with the degradation rate of Rhodamine B remaining above 83%. Figure 12 ).

[0056] Example 2

[0057] Measure 50 mL of deionized water into a clean container, adjust the pH to 4.0 using a precision pH meter, and purge with nitrogen at a rate of 3 mL / min for protection. While stirring continuously under nitrogen purging, add solid NaOH to dissolve and prepare a 0.8 mol / L NaOH solution. Then add 50 mL of 2.8 g / L sodium dodecylbenzenesulfonate solution, stir for 5 min until homogeneous, and transfer the entire solution to a 500 mL round-bottom flask. Seal the flask and maintain nitrogen purging; this is the main reaction solution. Place the round-bottom flask containing the main reaction solution in a water bath and heat to 60 °C under nitrogen protection. Take 50 mL of 0.38 mol / L calcium chloride solution, place it in a constant-pressure dropping funnel, and add it dropwise to the main reaction solution at a rate of 4 mL / min. After the addition is complete, rapidly raise the temperature to 75 °C and maintain the reaction temperature for 2.5 h under nitrogen purging throughout, until a white precipitate forms. After the reaction was completed, the system was cooled to room temperature and nitrogen flow was stopped. A white precipitate was obtained by repeated filtration and washing, and then dried in a vacuum drying oven at 60 °C to finally obtain the mesoporous S-Ca(OH)2 piezoelectric catalyst.

[0058] The product was characterized by XRD, infrared, XPS, TEM, EDS, electrochemical and PFM analysis, which showed that S-Ca(OH)2 piezoelectric catalyst with an S / Ca atomic ratio of 0.065 was successfully prepared.

[0059] Prepare 50 mL of a 10 mg / L Rhodamine B solution. Add 20 mg of the S-Ca(OH)2 piezoelectric material prepared in the above method to the Rhodamine B solution. Stir the reaction at room temperature (25℃) until adsorption equilibrium is reached. Under ultrasonic drive, after 20 min of reaction, the degradation rate of Rhodamine B by the S-Ca(OH)2 material reaches more than 93%.

[0060] Example 3

[0061] Measure 65 mL of deionized water into a clean container, adjust the pH to 4.0 using a precision pH meter, and purge with nitrogen at a rate of 3 mL / min for protection. While stirring continuously under nitrogen purging, add solid NaOH to dissolve, preparing a 0.4 mol / L NaOH solution. Then add 50 mL of 3.5 g / L sodium dodecylbenzenesulfonate solution, stir for 5 min until homogeneous, and transfer the entire solution to a 500 mL round-bottom flask. Seal the flask and maintain nitrogen purging; this is the main reaction solution. Place the round-bottom flask containing the main reaction solution in a water bath and heat to 50 °C under nitrogen protection. Take 65 mL of 0.18 mol / L calcium chloride solution, place it in a constant-pressure dropping funnel, and add it dropwise to the main reaction solution at a rate of 2 mL / min. After the addition is complete, rapidly raise the temperature to 85 °C and maintain the reaction temperature for 2.0 h under nitrogen purging throughout, resulting in the formation of a white precipitate. After the reaction was completed, the system was cooled to room temperature and nitrogen flow was stopped. A white precipitate was obtained by repeated filtration and washing, and then dried in a vacuum drying oven at 60 °C to finally obtain the mesoporous Ca(OH)2 piezoelectric catalyst.

[0062] The product was characterized by XRD, infrared, XPS, TEM, EDS, electrochemical and PFM analysis, which showed that S-Ca(OH)2 piezoelectric catalyst with an S / Ca atomic ratio of 0.076 was successfully prepared.

[0063] Prepare 50 mL of a 10 mg / L Rhodamine B solution. Add 20 mg of the S-Ca(OH)2 piezoelectric material prepared in the above method to the Rhodamine B solution. Stir the reaction at room temperature (25℃) until adsorption equilibrium is reached. Under ultrasonic drive, after 20 min of reaction, the degradation rate of Rhodamine B by the S-Ca(OH)2 material reaches more than 93%.

[0064] Comparative Example 1

[0065] The processing procedure and parameters are the same as in Example 1 of this invention, except that sodium dodecylbenzenesulfonate is not added, resulting in a white product with an S / Ca atomic ratio of 0, which is analyzed by XRD ( Figure 1 As can be seen, Ca(OH)2 was formed. Figure 7 The transient piezoelectric current density of Ca(OH)₂ material under ultrasonic irradiation was shown. Ca(OH)₂ did not exhibit a transient piezoelectric current density under ultrasonic driving, indicating that Ca(OH)₂ is not a piezoelectric catalyst. Furthermore, after 20 min of reaction, the degradation rate of Rhodamine B by Ca(OH)₂ material was almost zero.

[0066] Comparative Example 2

[0067] The processing procedure and parameters are the same as in Example 1 of this invention, except that the pH of the deionized water was not adjusted to acidity, resulting in a white product with an S / Ca atomic ratio of 0.0865, which was analyzed by XRD ( Figure 13 It can be seen that the obtained sample is a mixture of CaCO3 and S-Ca(OH)2. After 20 min of ultrasonic reaction, the degradation rate of Rhodamine B by the mixture of CaCO3 and S-Ca(OH)2 is only 56%, indicating that CaCO3 significantly inhibits the piezoelectric catalytic performance of S-Ca(OH)2.

[0068] Comparative Example 3

[0069] The processing procedure and parameters are the same as in Example 1 of this invention, except that continuous nitrogen protection was not performed, resulting in a white product with an S / Ca atomic ratio of 0.0873, which was analyzed by XRD ( Figure 14 It can be seen that the obtained sample is a mixture of CaCO3 and S-Ca(OH)2. After 20 minutes of ultrasonic reaction, the degradation rate of Rhodamine B by the mixture of CaCO3 and S-Ca(OH)2 is only 64%, indicating that CaCO3 significantly inhibits the piezoelectric catalytic performance of S-Ca(OH)2.

[0070] Comparative Example 4

[0071] The processing procedure and parameters were the same as in Example 1 of this invention. The difference was that the round-bottom flask containing the main reaction solution was placed in a water bath and heated directly to 80 °C under nitrogen protection. Finally, a white product S-Ca(OH)2 with an S / Ca atomic ratio of 0.024 was obtained. After 20 min of ultrasonic reaction, the degradation rate of Rhodamine B by S-Ca(OH)2 was only 38.7%, indicating that the piezoelectric catalytic performance of S-Ca(OH)2 obtained by directly heating to 80 °C was significantly reduced.

[0072] Comparative Example 5

[0073] The processing procedure and parameters are the same as in Example 1 of this invention, except that sodium dodecyl sulfate or sodium thiosulfate is used instead of sodium dodecylbenzenesulfonate. The final product is white and has no piezoelectric catalytic performance.

Claims

1. A modified calcium hydroxide-based piezoelectric catalytic material, characterized in that, This material is prepared by introducing a sulfur-containing surfactant during the synthesis of calcium hydroxide. The sulfur element in the material exists in the form of -SO3 groups and has piezoelectric catalytic activity.

2. The modified calcium hydroxide-based piezoelectric catalytic material according to claim 1, characterized in that, The sulfur-containing surfactant is sodium dodecylbenzenesulfonate; and / or, the atomic ratio of S / Ca in the material is (0.06-0.09):1; and / or, the material has a mesoporous structure.

3. A method for preparing a modified calcium hydroxide-based piezoelectric catalytic material as described in claim 1 or 2, characterized in that, The method includes the following steps: (1) Under the protection of an inert gas, sodium hydroxide and sulfur-containing surfactant are dissolved in an acidic aqueous solution with a pH of 3 to 5 and mixed evenly to obtain the main reaction solution; (2) Under inert gas protection and stirring conditions, calcium salt solution is added dropwise to the main reaction solution, and the reaction is carried out at 50-60°C first, and then the temperature is raised to 75-85°C to continue the reaction for 2-3 hours to obtain precipitate; (3) The precipitate is separated, washed and dried to obtain the modified calcium hydroxide-based piezoelectric catalytic material.

4. The preparation method according to claim 3, characterized in that, In step (1), the sulfur-containing surfactant is sodium dodecylbenzenesulfonate, and its concentration in the main reaction solution is 1.2 to 2 g / L.

5. The preparation method according to claim 3, characterized in that, In step (1), the concentration of sodium hydroxide in the main reaction solution is 0.1 to 0.6 mol / L.

6. The preparation method according to claim 3, characterized in that, In steps (1) and (2), the inert gas is nitrogen or argon, and its flow rate is 2 to 5 mL / min.

7. The preparation method according to claim 3, characterized in that, In step (2), the calcium salt is calcium chloride, calcium nitrate or calcium acetate; the concentration of the calcium salt solution is 0.1 to 0.45 mol / L and the dropping rate is 2 to 5 mL / min.

8. The preparation method according to claim 3, characterized in that, In step (3), the drying is performed under vacuum at 50–70°C.

9. The application of a modified calcium hydroxide-based piezoelectric catalytic material as described in claim 1 or 2 as a piezoelectric catalyst for the degradation of organic pollutants in water.

10. The application according to claim 9, characterized in that, The organic pollutant includes at least one of methyl orange, methylene blue, rhodamine B, neutral red, Congo red, and tetracycline; the application is carried out in an aqueous solution with a pH of 3 to 13, and the piezoelectric catalytic reaction is driven by providing mechanical energy through ultrasound.

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