Chitosan / poly (N-isopropylacrylamide) / acrylic acid catalytic material as well as preparation method and application thereof
The preparation of chitosan/polyN-isopropylacrylamide/acrylic acid catalytic material by a two-stage crosslinking method solves the problems of insufficient biocompatibility and stability in the existing technology, and achieves the effect of highly efficient catalytic degradation of rhodamine B.
Patent Information
- Application Number
- CN202511049895.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-12-12
AI Technical Summary
In existing technologies, composite materials obtained by grafting chitosan with thermosensitive monomers exhibit reduced biocompatibility, low degradation rates, poor thermosensitive response stability, and insufficient mechanical properties, making it difficult to efficiently catalyze the degradation of organic pollutants such as Rhodamine B.
Chitosan/polyN-isopropylacrylamide/acrylic acid catalytic materials were prepared by a two-stage crosslinking method. First, a crosslinking network of chitosan, acrylic acid, and cellulose was constructed, and then a second crosslinking was carried out in an aqueous solution of N-isopropylacrylamide to form a hierarchical network structure.
It improves the catalytic activity and stability of the catalytic material, enhances the degradation effect on organic pollutants, achieves a degradation rate of 95%, has a stable structure that can be reused, has a wide range of applications, and its temperature-sensitive properties facilitate temperature-controlled separation.
Smart Images
Figure CN121108424A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic materials technology, specifically relating to a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material, its preparation method, and its application. Background Technology
[0002] Colored wastewater mainly originates from industries such as textiles, cosmetics, leather, and papermaking. It contains many toxic pollutants that are difficult to degrade, characterized by complex composition, high concentration, and deep color. Rhodamine B (RhB) is the most representative pollutant in colored wastewater; it is difficult to degrade, easily accumulates, and can cause birth defects and cancer, posing a serious threat to human health and ecosystems. Currently, treatment methods for Rhodamine B-containing wastewater mainly include adsorption, Fenton reaction, ozone oxidation, and electrocatalytic oxidation. However, these methods are difficult to widely apply due to high treatment costs or the potential for secondary pollution. In recent years, photocatalysis technology has developed rapidly, offering advantages such as safety, simplicity, and environmental friendliness, providing an economical, efficient, and sustainable technological approach to solving water pollution. Therefore, developing a high-efficiency, green, and low-cost catalyst has become crucial for the degradation of Rhodamine B wastewater.
[0003] Chitosan, derived from the deacetylation of chitin, is an abundant natural biopolymer on Earth. It possesses a modifiable structure and a wealth of functional groups, such as highly reactive amino and hydroxyl groups, allowing it to react with various substances to create complex network structures. Studies have shown that the three-dimensional network structure formed by the Schiff base reaction of amino and aldehyde groups in chitosan can significantly improve its mechanical properties. Chitosan-based materials can be constructed using various molding techniques to create multi-scale structures, including nanofibers (50-200 nm in diameter), microspheres (0.5-5 μm in particle size), films (10-300 μm in thickness), and 3D-printed scaffolds (porosity >90%). Furthermore, chitosan can be modified through physical, chemical, and biological methods to obtain multifunctional chitosan-based materials. Physical modification does not involve changes in the chemical structure of the molecular chains; performance regulation is mainly achieved through intermolecular forces or physical mixing. Chemical modification, on the other hand, involves preparing corresponding derivatives (such as chemical crosslinking) based on chemical reactions (e.g., esterification, etherification, acylation, degradation, N-alkylation, and graft copolymerization). Chitosan and its derivatives are promising biomaterials due to their unique molecular structure and excellent bioactivity, and have been widely used as biosorbents for removing various metal ions and dyes from wastewater.
[0004] Polymers capable of responding to temperature changes and undergoing physical or chemical transformations are considered thermosensitive materials due to their excellent temperature response mechanisms. These mechanisms typically involve intermolecular hydrogen bonding, hydrophobic interactions, or phase transitions. A typical example is poly(N-isopropylacrylamide) (PNIPAM), with a lower critical solution temperature (LCST) of approximately 32°C. It can achieve a sol-gel transition near body temperature. In recent years, researchers have developed composite materials that possess both temperature responsiveness and bioactivity by grafting thermosensitive monomers (such as NIPAM) onto the chitosan backbone. For instance, chitosan-g-PNIPAM copolymers prepared through atom transfer radical polymerization (ATRP) or free radical polymerization can form self-assembled nanomicelles for drug controlled release and intelligent response systems. However, existing techniques for grafting thermosensitive monomers (such as NIPAM) onto the chitosan backbone have drawbacks, primarily reduced biocompatibility, affected degradation rates, low degradation rates of organic pollutants, poor stability of the temperature-sensitive response, and potential mechanical inadequacy in practical applications.
[0005] Therefore, it is of great significance to provide a catalytic material with high catalytic activity, good degradation effect on organic pollutants, and strong self-stability. Summary of the Invention
[0006] To address the shortcomings of the existing technology, one of the objectives of this invention is to provide a method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material. The prepared chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material exhibits a high catalytic degradation rate for the organic pollutant rhodamine, achieving efficient catalytic degradation of organic pollutants.
[0007] The above-mentioned objective of this invention is achieved through the following technical solution:
[0008] A method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material includes the following steps:
[0009] S1. Chitosan is dissolved in an aqueous acetic acid solution, then heated and stirred. Acrylic acid, crosslinking agent and cellulose are added, and the first crosslinking is carried out under a protective gas atmosphere. After the reaction, the mixture is freeze-dried to obtain the composite material.
[0010] S2. The composite material obtained in step S1 is placed in an aqueous solution of N-isopropylacrylamide and crosslinked for the second time under a protective gas atmosphere. After the reaction, it is freeze-dried to obtain the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst material.
[0011] This invention first constructs a cross-linked network structure using chitosan, acrylic acid, and cellulose to obtain a composite material. Then, the composite material is placed in an aqueous solution of N-isopropylacrylamide for a second cross-linking, forming a hierarchical network structure. Compared to a one-step cross-linking of chitosan, acrylic acid, cellulose, and N-isopropylacrylamide, this invention, through two cross-linking steps, yields a product with a clearer hierarchical and fibrous network structure, a more uniform pore distribution, and more effective dye adsorption, thereby improving the material's degradation efficiency for organic pollutants.
[0012] A novel catalytic material was prepared by the method of the present invention. This catalytic material has high catalytic activity, which greatly improves the degradation effect on organic pollutants. At the same time, the material also has the characteristics of strong stability, high catalytic efficiency and temperature-sensitive properties.
[0013] Preferably, in step S1, the concentration of chitosan in the acetic acid aqueous solution is (0.5~1.5) g / 100 mL.
[0014] Preferably, in step S1, the conditions for the first crosslinking are: reaction at 60-80°C for 6-24 hours under a protective gas atmosphere.
[0015] Preferably, in step S2, the conditions for the second crosslinking are: reaction at 60-80°C for 6-24 hours under a protective gas atmosphere.
[0016] Preferably, the mass of the N-isopropylacrylamide is 15% to 25% of the total mass of chitosan, acrylic acid, crosslinking agent, cellulose and N-isopropylacrylamide.
[0017] Preferably, in step S1, the mass ratio of chitosan, acrylic acid, crosslinking agent, cellulose and N-isopropylacrylamide is 1:(1~3):(0.1~0.5):(0.5~1.5):(0.705~1.175).
[0018] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide.
[0019] Another object of the present invention is to provide a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material prepared by the aforementioned preparation method.
[0020] Another object of the present invention is to provide the application of the chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material prepared by the above preparation method in the catalytic degradation of rhodamine.
[0021] Preferably, the application method of the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst in the catalytic degradation of rhodamine is as follows: the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst is added to the rhodamine solution, mixed, and then potassium persulfate solution is added, and the catalytic degradation reaction is carried out under natural light conditions.
[0022] Compared with the prior art, the advantages of the present invention are:
[0023] (1) The chitosan / polyN-isopropylacrylamide / acrylic acid catalyst prepared by the present invention is a novel catalyst material. This catalyst material can rapidly catalyze the degradation of RhB, shorten the degradation time, improve the degradation efficiency, and achieve a degradation rate of up to 95% for RhB, which greatly improves its degradation effect.
[0024] (2) The catalytic material prepared by the present invention has a stable structure during the degradation process and can be reused multiple times, reducing the cost of use; the material itself is relatively environmentally friendly and has little secondary pollution to the environment; it can maintain good catalytic performance under different pH conditions and has a wide range of applications.
[0025] (3) Compared with the one-step crosslinking of chitosan, acrylic acid, cellulose and N-isopropylacrylamide, the present invention obtains a clearer layered structure and fibrous network structure and a more uniform pore distribution through two crosslinking steps. This allows for more effective adsorption of dyes, thereby improving the material's degradation efficiency for organic pollutants.
[0026] (4) The catalytic material of the present invention has temperature-sensitive properties, which facilitates temperature-controlled separation. After the reaction is completed, the temperature can be increased to precipitate it from the reaction solution, which is easy to recover and reuse. Attached Figure Description
[0027] Figure 1 The XRD patterns of the chitosan / polyN-isopropylacrylamide / acrylic acid catalysts obtained in Examples 1-3 are shown below.
[0028] Figure 2 The infrared spectra of the chitosan / polyN-isopropylacrylamide / acrylic acid catalysts obtained in Examples 1-3 are shown below.
[0029] Figure 3 The image shows the UV absorption spectrum of the chitosan / poly(N-isopropylacrylamide) / acrylic acid catalyst obtained in Example 1 for the degradation of RhB. 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] This invention provides a method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material, comprising the following steps:
[0032] S1. Chitosan is dissolved in an aqueous acetic acid solution, then heated and stirred. Acrylic acid, crosslinking agent and cellulose are added to carry out the first crosslinking. After the reaction, the mixture is freeze-dried to obtain the composite material.
[0033] S2. The composite material obtained in step S1 is placed in an aqueous solution of N-isopropylacrylamide for a second crosslinking. After the reaction, it is freeze-dried to obtain the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst material.
[0034] In some embodiments, the concentration of chitosan in the aqueous acetic acid solution is (0.5~1.5) g / 100 mL. For example, the concentration of chitosan in the aqueous acetic acid solution is 0.5 g / 100 mL, 1.0 g / 100 mL, 1.5 g / 100 mL, etc.
[0035] In some embodiments, in step S1, the conditions for the first crosslinking are: reacting at 60-80°C for 6-24 hours under a protective gas atmosphere.
[0036] In some embodiments, in step S2, the conditions for the second crosslinking are: reacting at 60-80°C for 6-24 hours under a protective gas atmosphere.
[0037] In some embodiments, the mass of the N-isopropylacrylamide is 15% to 25% of the total mass of chitosan, acrylic acid, crosslinking agent, cellulose and N-isopropylacrylamide.
[0038] In some embodiments, in step S1, the mass ratio of chitosan, acrylic acid, crosslinking agent, cellulose and N-isopropylacrylamide is 1:(1~3):(0.1~0.5):(0.5~1.5):(0.705~1.175).
[0039] In the following examples and comparative examples, the degree of deacetylation of chitosan is ≥95%, and the viscosity is 100-200 mpa.s; the volume concentration of the acetic acid solution is 1%~5%.
[0040] Example 1
[0041] This embodiment provides a method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material, including the following steps:
[0042] S1. Weigh 1g of chitosan and dissolve it in 100mL of 2% acetic acid aqueous solution. Then, heat the solution to 70℃ under a nitrogen atmosphere with a condenser and stir for 10 min. Then, add acrylic acid (AA, 2 g), N,N'-methylenebisacrylamide (MBA, 0.1 g) and cellulose (0.6 g) to the solution. Place the system in a nitrogen atmosphere at 70℃ for 8 h to build a cross-linked network structure. Cool the product to room temperature and wash it with a large amount of deionized water to remove unreacted chemicals. After purification, freeze dry to obtain the composite material.
[0043] S2. Weigh 1g of N-isopropylacrylamide (NIPAM) and dissolve it in 5mL of water to obtain an aqueous solution of N-isopropylacrylamide. Then, take out the sample dried in step S1 and place it in the aqueous solution of N-isopropylacrylamide. Crosslink it for the second time in a nitrogen atmosphere at 70℃ to form a hierarchical network structure. After reacting for 12h, freeze dry it. The sample name is recorded as CP-21.
[0044] Example 2
[0045] The preparation method of the chitosan / poly(N-isopropylacrylamide) / acrylic acid catalyst in this embodiment is basically the same as that in Example 1. The only difference is that in step S2, 0.705 g of NIPAM is weighed and dissolved in 5 mL of water to obtain an aqueous solution of N-isopropylacrylamide. Then, the sample dried in step S1 is placed in the aqueous solution of N-isopropylacrylamide and crosslinked for the second time in a nitrogen atmosphere at 70 °C to form a hierarchical network structure. After reacting for 12 h, it is freeze-dried. The sample name is recorded as CP-15.
[0046] Example 3
[0047] The preparation method of the chitosan / poly(N-isopropylacrylamide) / acrylic acid catalyst in this embodiment is basically the same as that in Example 1. The only difference is that in step S2, 1.175g of NIPAM is weighed and dissolved in 5mL of water to obtain an aqueous solution of N-isopropylacrylamide. Then, the sample dried in step S1 is placed in the aqueous solution of N-isopropylacrylamide and crosslinked for the second time in a nitrogen atmosphere at 70°C to form a hierarchical network structure. After reacting for 12h, it is freeze-dried. The sample name is recorded as CP-25.
[0048] Comparative Example 1
[0049] This comparative example provides a method for preparing a chitosan-based material without thermosensitive materials, as detailed below:
[0050] 1 g of chitosan was dissolved in 100 mL of 2% acetic acid aqueous solution. The solution was then heated to 70 °C and stirred for 10 min under a nitrogen atmosphere with a condenser. Acrylic acid (AA, 2 g), N,N'-methylenebisacrylamide (MBA, 0.1 g), and cellulose (0.6 g) were added to the solution. The system was then reacted at 70 °C under a nitrogen atmosphere for 8 h to construct a cross-linked network structure. The product was cooled to room temperature and washed with a large amount of deionized water to remove unreacted chemicals. After purification, the product was freeze-dried to obtain the composite material, which was named CP.
[0051] Figure 1 The XRD patterns of CP-21% obtained in Example 1, CP-15% obtained in Example 2, CP-25% obtained in Example 3, CP obtained in Comparative Example 1, and chitosan (CTS) are shown in the figures. As can be seen from the figures, the XRD patterns show a diffraction peak at 2θ = 19.9 ° for chitosan, while the diffraction patterns of the prepared CP, CP-15%, and other products show a diffraction peak at 2θ = 22.5 °. The change in peak value indicates the formation of a graft copolymer crystal form. The figures show that the diffraction peaks among the products did not change, but the intensities varied. Comparatively, the peak intensity of CP-15% was the strongest, indicating the highest crystallinity.
[0052] Figure 2 The infrared spectra of CP-21% obtained in Example 1, CP-15% obtained in Example 2, CP-25% obtained in Example 3, CP obtained in Comparative Example 1, and chitosan (CTS) are shown in the figures. It can be seen from the figures that at 1454 cm⁻¹... -1 1392 cm -1 1159cm -1 The presence of spectral bands confirmed the success of the grafting crosslinking through the analysis of characteristic peaks of polyacrylic acid and MBA groups. These spectral bands are characteristic bands of CP.
[0053] Comparative Example 2
[0054] This comparative example provides a one-step crosslinking method for preparing temperature-sensitive chitosan-based catalytic materials, as detailed below:
[0055] 1 g of chitosan was dissolved in 100 mL of 2% acetic acid aqueous solution. The solution was then heated to 70 °C and stirred for 10 min under a nitrogen atmosphere with a condenser. Acrylic acid (AA, 2 g), N,N'-methylenebisacrylamide (MBA, 0.1 g), cellulose (0.6 g), and N-isopropylacrylamide (NIPAM, 1 g) were added to the solution. The system was then reacted at 70 °C under a nitrogen atmosphere for 8 h to construct a cross-linked network structure. The product was cooled to room temperature and washed with a large amount of deionized water to remove unreacted chemicals. After purification, the product was freeze-dried to obtain a one-step thermosensitive chitosan-based catalytic material.
[0056] Comparative Example 3
[0057] The preparation method of the catalytic material in this comparative example is basically the same as that in Example 1, except that acrylic acid is not added in step S1.
[0058] Comparative Example 4
[0059] The preparation method of the catalytic material in this comparative example is as follows:
[0060] S1. Add acrylic acid (AA, 2 g), N,N'-methylenebisacrylamide (MBA, 0.1 g), cellulose (0.6 g), N-isopropylacrylamide (NIPAM, 0.705 g) and 100 mL of water to a reaction flask. Place the system in a nitrogen atmosphere at 70 °C and react for 8 h. Cool the product to room temperature and wash it with a large amount of deionized water to remove unreacted chemicals. After purification, freeze dry to obtain the sample.
[0061] S2. Weigh 1g of chitosan and dissolve it in 10mL of 2% acetic acid aqueous solution to obtain chitosan solution. Take out the sample dried in step S1 and dissolve it in chitosan solution. Then carry out a second crosslinking at 70℃ under nitrogen atmosphere. After reacting for 12h, freeze dry to obtain catalytic material.
[0062] Application Example 1
[0063] The catalytic materials prepared in the above embodiments and comparative examples were applied to the catalytic degradation of Rhodamine B. The specific steps are as follows:
[0064] Prepare a 10 mg / L Rhodamine B solution (made from 0.0100 g Rhodamine B and 1 L distilled water). Weigh 10 mg of the above catalyst and add it to 30 mL of Rhodamine B solution and mix. Add potassium persulfate solution to make the concentration of potassium persulfate in the reaction solution 0.2 mmol / L. Shake well and stir magnetically. Under natural light, take out 1 mL of sample at intervals and filter the reaction through a 0.22 μm membrane. Add 100 µL of anhydrous ethanol to terminate the reaction. After reacting for 2.5 h, take out the sample and centrifuge at 4000 r for 10 min, and collect the supernatant.
[0065] The degradation rate of 10 mg / L rhodamine was measured using a UV-Vis spectrophotometer across the entire wavelength range of 300 nm to 600 nm. The optimal detection wavelength (approximately 464 nm) was selected, and the absorbance of the supernatant was measured at this wavelength to calculate the degradation rate. The results are shown in Table 1 below.
[0066] Table 1. Catalytic degradation effect of catalyst materials on rhodamine
[0067]
[0068] As shown in Table 1, the chitosan / poly(N-isopropylacrylamide) / acrylic acid catalytic material prepared in this invention exhibits a degradation rate of over 95% for the organic dye Rhodamine B, demonstrating excellent catalytic performance. Comparison of Examples 1-3 and Comparative Example 1 reveals that the amount of N-isopropylacrylamide affects the degradation effect of the catalytic material on RhB, with the CP-21% material prepared in Example 1 showing the best degradation effect on RhB.
[0069] Compared with Example 1, Comparative Example 1 did not use N-isopropylacrylamide. The degradation rate of RhB by the CP material without temperature-sensitive material decreased from 95.61% to 80.19%, indicating that the addition of temperature-sensitive material is conducive to the formation of a layered structure, which is more conducive to the adsorption of dye and improves the degradation efficiency.
[0070] Compared with Example 1, the degradation rate of RhB by the temperature-sensitive chitosan-based catalytic material prepared by one-step crosslinking in Comparative Example 2 decreased from 95.61% to 76.28%, indicating that the present invention can improve the degradation rate of RhB by two crosslinking steps compared with one-step crosslinking. The possible reason is that, compared with one-step crosslinking, the product obtained by the present invention through two crosslinking steps has a clearer layered structure and fibrous network structure, a more uniform pore distribution, and can more effectively adsorb dyes, thereby improving the degradation efficiency of the material for organic pollutants.
[0071] Compared with Example 1, Comparative Example 3 did not add acrylic acid, and the degradation rate of RhB by the prepared catalyst material decreased from 95.61% to 70.81%.
[0072] Compared with Example 2, Comparative Example 4 first prepared a temperature-sensitive material and then crosslinked it with chitosan. The degradation rate of RhB by the prepared catalytic material decreased from 87.68% to 65.15%, indicating that the method of the present invention can improve the degradation effect of the material on RhB.
[0073] Figure 3 The image shows the UV absorption spectrum of the chitosan / poly(N-isopropylacrylamide) / acrylic acid catalyst obtained in Example 1 for the degradation of RhB. As can be seen from the figure, the degradation rate of RhB gradually increases with time, reaching its maximum at 150 min. Furthermore, the addition of NIPAM has a certain promoting effect on RhB degradation.
[0074] 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 a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material, characterized in that, Includes the following steps: S1. Chitosan is dissolved in an aqueous acetic acid solution, then heated and stirred. Acrylic acid, crosslinking agent and cellulose are added, and the first crosslinking is carried out under a protective gas atmosphere. After the reaction, the mixture is freeze-dried to obtain the composite material. S2. The composite material obtained in step S1 is placed in an aqueous solution of N-isopropylacrylamide and crosslinked for the second time under a protective gas atmosphere. After the reaction, it is freeze-dried to obtain the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst material.
2. The method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material according to claim 1, characterized in that, The concentration of chitosan in the aqueous acetic acid solution is (0.5~1.5) g / 100 mL.
3. The method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material according to claim 1, characterized in that, The conditions for the first crosslinking are: reaction at 60~80℃ for 6~24h.
4. The method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material according to claim 1, characterized in that, The conditions for the second crosslinking are: reaction at 60~80℃ for 6~24h.
5. The method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material according to claim 1, characterized in that, The mass of the N-isopropylacrylamide is 15% to 25% of the total mass of chitosan, acrylic acid, crosslinking agent, cellulose and N-isopropylacrylamide.
6. The method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material according to claim 1, characterized in that, In step S1, the mass ratio of chitosan, acrylic acid, crosslinking agent, cellulose and N-isopropylacrylamide is 1:(1~3):(0.1~0.5):(0.5~1.5):(0.705~1.175).
7. The method for preparing a chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material according to claim 1, characterized in that, The crosslinking agent is N,N'-methylenebisacrylamide.
8. The chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material prepared by the preparation method according to any one of claims 1 to 7.
9. The application of the chitosan / polyN-isopropylacrylamide / acrylic acid catalytic material prepared by the preparation method according to any one of claims 1 to 7 in the catalytic degradation of rhodamine.
10. The application according to claim 9, characterized in that, The application method of the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst in the catalytic degradation of rhodamine is as follows: the chitosan / polyN-isopropylacrylamide / acrylic acid catalyst is added to the rhodamine solution, mixed, and then potassium persulfate solution is added. The catalytic degradation reaction is carried out under natural light conditions.