Method for driving photocatalytic activation of pms degradation rhb by synthesizing p-doped tubular carbon nitride

Abstract

The present application relates to the technical field of water pollution, and more particularly to a method for degrading RhB by synthesizing P-doped tubular carbon nitride to drive photocatalytic activation of PMS. The steps are as follows: S1: preparing P-doped tubular carbon nitride; S2: applying the P-doped tubular carbon nitride obtained in step S1 to photocatalytic activation of PMS; and S3: using the photocatalytic activation of PMS to degrade RhB. The method for degrading RhB by synthesizing P-doped tubular carbon nitride to drive photocatalytic activation of PMS provided by the present application uses phosphoric acid and melamine as raw materials, and prepares P-doped carbon nitride (5P-TCN) with a tubular structure by a method of precursor self-assembly, and evaluates the PMS-photocatalytic effect of the 5P-TCN on a typical organic pollutant, Rhodamine B (RhB), under the action of visible light through batch experiments.

Description

Technical Field

[0001] This invention relates to the field of water pollution technology, and in particular to a method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS. Background Technology

[0002] With the continuous development of industrialization, wastewater discharge has increased year by year, and water pollution has become one of the obstacles to sustainable human development. Rhodamine B (RhB) is a typical industrial dye molecule, widely used in textile, pigment, and cosmetic manufacturing industries. It has certain toxicity and carcinogenicity, and may cause various diseases such as respiratory infections, skin and gastrointestinal irritation. It also has high water solubility and stability, making it difficult to remove through biodegradation. Therefore, finding an efficient and green method to remove RhB from wastewater is of great significance to our lives. Compared with traditional wastewater treatment methods such as adsorption, membrane filtration, and centrifugation, advanced processes such as photocatalysis, persulfate activation, and electrochemical oxidation are more efficient in degrading organic pollutants. Among many wastewater treatment technologies, photocatalysis, as an advanced oxidation technology (AOP), is a sustainable solar energy collection and environmentally friendly photo-oxidation technology with advantages such as low cost, simple operation, and environmental friendliness. It is an important strategy for alleviating the energy crisis and increasingly serious environmental problems. However, large-scale application of photocatalysis still has some limitations. First, the weak light absorption capacity, narrow light response range, and wide band gap limit the application of photocatalytic materials. Second, the currently mainly used metal-based photocatalysts require consideration of heavy metal elution in practical applications, which can cause secondary pollution to the environment. Therefore, the preparation of efficient and environmentally friendly photocatalytic materials for removing organic dyes has become a key issue in global wastewater treatment.

[0003] Graphitic carbon nitride (g-C3N4) is a stable, pollution-free carbon-based non-metallic organic semiconductor with a band gap of approximately 2.7 eV. Due to its suitable band gap, stable physicochemical properties, and high visible light utilization, it has proven to be a promising photocatalyst, widely used in solar energy conversion and wastewater purification. However, the narrow visible light absorption range, limited surface active sites, and rapid recombination of photogenerated carriers in bulk g-C3N4 obtained through simple calcination restrict its practical applications. Therefore, to improve the photocatalytic performance of g-C3N4, various strategies have been actively explored to mitigate these shortcomings, such as heterojunction construction, elemental doping, morphology manipulation, and defect engineering. Among these strategies, elemental doping and morphology manipulation are considered very direct and effective methods to improve the photocatalytic performance of g-C3N4. For example, doping g-C3N4 with non-metallic elements C, O, S, and P has been shown to improve photocatalytic performance. Morphology control in photocatalysis is generally achieved by improving particle size and pore size, or by transforming bulk catalysts into sheet-like or porous forms. This increases the number of active sites on the catalyst, modulates its photoelectric properties, and reduces carrier recombination rates to enhance catalytic performance. Recent studies have shown that supramolecular precursor self-assembly synthesis of modified g-C3N4 has become a mature method for morphology control. However, most molecular self-assembly methods have limitations. They typically require organic solvents or template agents during synthesis, which is environmentally unfriendly, and also necessitates additional post-processing steps. Therefore, finding a simple and green self-assembly method for morphology control of g-C3N4 is particularly important.

[0004] While catalyst modification can improve the photocatalytic performance of g-C3N4 to some extent, its inherent band structure and light absorption range limit its ability to efficiently degrade organic pollutants. Photocatalytic coupling processes have proven to be an effective way to address these issues, such as mature photo-Fenton processes, photoelectrocatalysis, and enzyme-photocoupled catalysis. Furthermore, advanced oxidation technologies based on peroxymonosulfate (PMS) to assist photocatalysis are increasingly proving to be an ideal choice for improving catalytic performance, as light can continuously induce PMS activation. However, most currently highly efficient PMS activation catalysts are metal-based, which cannot avoid the problems of increased color and leaching of toxic metal ions in wastewater, thus limiting their practical application. However, the non-metallic catalyst g-C3N4 contains two coordinated triazine groups and three coordinated nitrogen atoms at its electron-rich N-sites. These sites act as electron donors and, under the influence of light, can promote the breaking of the OO bonds in the PMS molecule. Secondly, during photocatalysis, g-C3N4 generates electron-hole pairs under light excitation. PMS captures electrons in the conduction band to generate sulfate radicals, which inhibits the recombination of electron-hole pairs.

[0005] Therefore, PMS-assisted photocatalysis is considered a very effective method to improve the degradation of organic pollutants in wastewater. It not only has excellent oxidation capacity, but also improves energy utilization, and has huge economic and environmental advantages. Summary of the Invention

[0006] Therefore, it is necessary to provide a method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS, in order to solve the technical problems mentioned in the background.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS to degrade RhB is described below:

[0009] S1: Preparation of P-doped tubular carbon nitride;

[0010] S2: Apply the P-doped tubular carbon nitride obtained in step S1 to photocatalytically activate PMS;

[0011] S3: Photocatalytically activated PMS is used to degrade RhB.

[0012] In a preferred embodiment of the method for RhB degradation by photocatalytic activation of PMS driven by synthesized P-doped tubular carbon nitride provided by the present invention, step S1 involves the preparation of P-doped tubular carbon nitride as follows:

[0013] S11: Dissolve 2g of melamine in 50mL of deionized water, sonicate for 5min, and add 5mL of phosphoric acid to the melamine solution;

[0014] S12: The product obtained in S11 was stirred in an 80℃ water bath for 30 min. After complete mixing, it was transferred to a 100 mL high-pressure reactor with a polytetrafluoroethylene liner and placed in a constant temperature drying oven at 180℃ for 10 h. After cooling to room temperature, the product was washed three times with ultrapure water and ethanol, centrifuged, and dried in a vacuum drying oven at 60℃ for 6 h to obtain a self-assembled complex of melamine and phosphoric acid, which was 5PMHP.

[0015] S13: The complex obtained in S12 was placed in a 10 mL capped corundum boat and heated to 500 °C in a tube furnace at a rate of 2.5 °C / min. After holding at this temperature for 4 h, it was cooled to room temperature.

[0016] In a preferred embodiment of the method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS provided by the present invention, in step S2, the P-doped tubular carbon nitride obtained in step S1 is applied to photocatalytically activate PMS, and the steps are as follows:

[0017] S21: Add a certain amount of photocatalytic material to wastewater containing different pollutants, and sonicate the catalyst suspension for 5 minutes to make the sample evenly dispersed;

[0018] S22: Stir continuously for 30 minutes in the dark to reach adsorption-desorption equilibrium;

[0019] S23: A xenon lamp and a cutoff filter are used as the light source. The distance between the light source and the reactor is maintained at 10 cm. All reaction temperatures are maintained at 25°C for photocatalysis.

[0020] In a preferred embodiment of the method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS provided by the present invention, in step S23, after turning on the xenon lamp, a certain amount of PMS is added, and 2 mL of catalyst suspension is extracted every 3 min, and the photocatalyst is removed through a 0.22 μm filter head.

[0021] In a preferred embodiment of the method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytically activated PMS provided by the present invention, step S3 involves using photocatalytically activated PMS to degrade RhB, as follows:

[0022] RhB was degraded using PMS of different capacities.

[0023] As a preferred embodiment of the method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS provided by the present invention, in the PMS-assisted photocatalytic system, ·SO4 - h + O2 - , 1 Both O2 and ·OH participate in the degradation of RhB. - Plays a major role, and 1 O2, ·OH, h + and SO4 - Plays a secondary role;

[0024] With the addition of PMS, free radicals exhibit a higher EPR signal, generating more ROSs and improving the efficiency of photocatalytic degradation of RhB.

[0025] It is clear without a doubt that the technical solution described above in this application can solve the technical problem that this application aims to address.

[0026] Meanwhile, through the above technical solutions, the present invention has at least the following beneficial effects:

[0027] The present invention provides a method for synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS to degrade RhB. Using phosphoric acid and melamine as raw materials, P-doped carbon nitride (5P-TCN) with tubular structure is prepared by precursor self-assembly. The PMS-photocatalytic effect of this method on the typical organic pollutant Rhodamine B (RhB) under visible light is evaluated through batch experiments.

[0028] With the synergistic effect of PMS, the degradation efficiency of 5P-TCN for RhB was significantly improved, with a degradation rate constant 111.8 times that of the original. This provides a green approach for developing low-cost photocatalysts, and the combination with PMS further demonstrates its superior efficiency in photocatalytic synergistic activation of PMS for RhB degradation.

[0029] Compared to the original g-C3N4, P-TCN, synthesized via calcination of a self-assembled precursor without the use of templates and organic solvents, significantly accelerates the photocatalytic degradation rate of RhB under the synergistic effect of PMS. More notably, this catalyst is metal-free, offering significant economic advantages and eliminating secondary environmental pollution. Furthermore, it requires no template removal after synthesis, simplifying the operation and demonstrating potential for large-scale production. The method of directly preparing P-doped tubular carbon nitride using phosphoric acid and rapidly photocatalytically degrading organic pollutants in wastewater under the synergistic effect of PMS may provide insights into finding efficient and environmentally friendly methods for degrading organic pollutants, and holds broad industrial potential. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram illustrating the preparation principle of the photocatalyst of the present invention;

[0032] Figure 2 This is a schematic diagram of the microstructure of the catalyst of the present invention;

[0033] Figure 3 This is a schematic diagram of the analysis of BCN, HCN and xP-TCN in this invention;

[0034] Figure 4 XPS schematic diagram of BCN and 5P-TCN of the present invention;

[0035] Figure 5 This is a schematic diagram illustrating the photocatalytic efficiency of different catalysts in this invention;

[0036] Figure 6This is a schematic diagram illustrating the influencing factors of the PMS-assisted photocatalytic degradation of RhB by 5P-TCN of the present invention;

[0037] Figure 7 This is a schematic diagram of BCN, HCN, and 5P-TCN of the present invention;

[0038] Figure 8 This is a schematic diagram illustrating the synergistic reaction of different reactive oxygen species (ROSs) in PMS and photocatalysis according to the present invention;

[0039] Figure 9 This is a schematic diagram illustrating the possible degradation pathways of RhB in the 5P-TCN / vis / PMS system according to the present invention;

[0040] Figure 10 This is a schematic diagram illustrating the possible degradation mechanism of RhB in the 5P-TCN / vis / PMS system according to the present invention;

[0041] Figure 11 This is a schematic diagram illustrating the generation of the 5P-TCN of the present invention;

[0042] Figure 12 This is the elemental distribution diagram of the 5PHMP of the present invention;

[0043] Figure 13 This is a schematic diagram of the 5P-TCN element content of the present invention;

[0044] Figure 14 This is a schematic diagram of the adsorption curve of 5P-TCN for RhB according to the present invention.

[0045] Figure 15 This is a schematic diagram illustrating the degradation of RhB in different solutions at natural pH according to the present invention;

[0046] Figure 16 This is a schematic diagram of the degradation kinetics curve in the free radical quenching experiment of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0049] It should be noted that, unless otherwise specified, the embodiments and features and technical solutions in the present invention can be combined with each other.

[0050] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0051] Example 1

[0052] Reference Figures 1-16 A method for the degradation of RhB by photocatalytic activation of PMS driven by the synthesis of P-doped tubular carbon nitride.

[0053] 1. Experimental Section

[0054] 1.1 Chemical products

[0055] Melamine, phosphoric acid (H3PO4), RhB, methylene blue (MB), malachite green (MG), methyl orange (MO), methanol (MeOH), tert-butanol (TBA), p-benzoquinone (P-BQ), furfuryl alcohol (FFA), disodium EDTA-2Na, PMS (KHSO5·0.5KHSO4·0.5K2SO4), NaCl, NaHCO3, Na2SO4, NaNO3, Na2HPO4, EtOH. All commercially purchased chemicals were analytical grade, with no additional purification steps. The pH of the reaction system was adjusted with 1 mM NaOH and HCl, and the required solutions were prepared with deionized water to eliminate ion interference.

[0056] 1.2 Synthesis Process

[0057] P-doped tubular carbon nitride was prepared using a hydrothermal self-assembly method, such as... Figure 1 As shown. In simple terms, 2g of melamine was dissolved in 50mL of deionized water and sonicated for 5min. A certain amount (3mL, 4mL, 5mL, 6mL) of phosphoric acid was added to the melamine solution. The resulting product was stirred in an 80℃ water bath for 30min. After complete mixing, it was transferred to a 100mL high-pressure reactor with a polytetrafluoroethylene liner and heated at 180℃ for 10h in a constant-temperature drying oven. After cooling to room temperature, the product was washed three times with ultrapure water and ethanol, centrifuged, and dried in a vacuum drying oven at 60℃ for 6h to obtain a self-assembled complex of melamine and phosphoric acid, named 5PMHP (a hydrothermal product of phosphoric acid and melamine, x = 3, 4, 5, 6). Finally, the complex was placed in a 10mL covered corundum boat and heated to 500℃ in a tube furnace (under N2 atmosphere) at a rate of 2.5℃ / min, held for 4h, and then cooled to room temperature. Depending on the amount of phosphoric acid added, the resulting product is named xP-TCN (x = 3, 4, 5, 6). This preparation method does not require the use of organic solvents and template agents, making it safer and more environmentally friendly.

[0058] The bulk carbon nitride obtained by directly calcining melamine in a tube furnace under the same conditions is denoted as BCN. The carbon nitride obtained by hydrothermally treating melamine without adding phosphoric acid and then calcining it in a tube furnace under the same conditions is denoted as HCN.

[0059] 1.3 Performance test of photocatalytic oxidation system on organic pollutants

[0060] The photocatalytic oxidation (PO) system consists of a photocatalyst and visible light. A certain amount of photocatalyst material was added to wastewater containing different pollutants. The catalyst suspension was ultrasonically treated for 5 minutes to ensure uniform dispersion, and then continuously stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Subsequently, a 350W xenon lamp and a 420nm cutoff filter were used as the light source, maintaining a 10cm distance between the light source and the reactor. All reaction temperatures were maintained at 25℃ for the photocatalytic experiment. After turning on the xenon lamp, a certain amount of PMS was added, and 2mL of the catalyst suspension was extracted every 3 minutes. The photocatalyst was removed through a 0.22μm filter, and the absorbance of the solution at the maximum wavelength was measured using a UV spectrophotometer.

[0061] 2. Results and Discussion

[0062] 2.1 Structure and Chemical Composition of Catalysts

[0063] SEM images show the microstructure and morphology of BCN, HCN, 5PMHP, and 5P-TCN. Example 2 and... Figure 11 Analysis revealed the growth mechanisms of 5PMHP and 5P-TCN.

[0064] refer to Figure 2 Among them, (a) SEM images of BCN, (b) HCN, (c) 5PMHP and (d) 5P-TCN; (e) TEM images of BCN, (f) HCN, (g) 5PMHP and (h) 5P-TCN; (i) elemental distribution map of 5P-TCN. Figure 2 a shows the structure of BCN, which consists of blocky particles and a smooth surface, a typical morphological feature of blocky carbon nitride. Figure 2 b shows the structure of HCN, where the bulk particles are smaller than those of BCN, but there are no other significant changes. Figure 2 c represents the self-assembly intermediate 5PMHP. Figure 2 The structure of d is 5P-TCN, and the surface still retains the layered stacked structure, which greatly expands the surface area, adsorption sites, and active centers of carbon nitride. The formation of hollow carbon nitride is due to the uneven density of the hexagonal prism polymer caused by the rapid crystallization of the supramolecular precursor. The higher the density on the surface, the lower the density in the internal region. As a result, the pyrolysis or etching of the precursor during calcination starts from the center of the hexagonal prism and gradually extends outward to form a tubular structure.

[0065] TEM scans of BCN, HCN, 5PMHP, and 5P-TCN also confirmed their internal structures. BCN ( Figure 2 e) and HCN ( Figure 2 f) exhibits a typical massive, dense morphology, but the massive volume of HCN is smaller. 5PMHP exhibits a dense, solid hexagonal prism structure. Figure 2 g), after calcination, it exhibits a tubular structure with a very transparent surface ( Figure 2 h) further confirmed the tubular structure of 5P-TCN, with a very thin surface, which is beneficial for shortening the charge. Simultaneously, energy dispersive spectroscopy and elemental mapping were used to detect and study the elemental distribution and composition of the material, from... Figure 12 As can be seen, phosphorus (P) is attached to the surface of the precursor 5PMHP. Upon further calcination, P reacts with 5PMHP to form 5P-TCN, as shown in the elemental mapping diagram (…). Figure 2 i) The distribution of C, N, O, and P elements is uniform in 5P-TCN. C and N are the main elements in the material, while O mainly comes from externally absorbed O2 and CO2. The P content is 0.43%. (See element content table below.) Figure 13 The results show that P was successfully doped into carbon nitride, and P-doped tubular carbon nitride composite material was successfully prepared.

[0066] refer to Figure 3 Among them, (a) XRD pattern, (b) FT-IR pattern, (c) N2 adsorption-desorption isotherms of BCN and 5P-TCN, and (d) pore size distribution curves of each sample, the crystal structure of the materials was analyzed by XRD. Figure 3 a) Pure carbon nitride has two distinct characteristic peaks, located at the (100) characteristic plane at 12.9° and the (002) characteristic plane at 27.4°, corresponding to the interlayer stacking of triazine ring structural units and aromatic systems on the carbon nitride plane, respectively. HCN also has these two peaks, indicating that the crystal structure did not change after the hydrothermal reaction. However, after the introduction of P, the (100) peak gradually disappeared, suggesting that P affected the growth process of the carbon nitride plane, reducing the plane size. This may be due to the hydrogen bond breaking during the hydrothermal process, which led to the widening of the interlayer spacing of the tri-s-triazine rings in the plane. In addition, as the P content increased, the (002) peak gradually weakened and shifted to a larger diffraction angle, indicating that P was successfully introduced. By reducing the stacking spacing of the carbon nitride monolayer, it promoted the polymerization of the supramolecular precursor and the reconstruction of the lattice, affecting the interlayer structure of g-C3N4. In summary, P doping did not significantly change the crystal structure of g-C3N4, nor did it produce other crystal impurities. The structure of the synthesized sample was characterized using infrared spectroscopy. Figure 3 (b) The FTIR spectra of all samples showed several typical absorption bands corresponding to the characteristic structure of g-C3N4 (3000-3500 cm⁻¹).-1 The broadband range is generally associated with the tensile vibrational modes of residual amino groups (NH4) and absorbed water (OH) in g-C3N4. At 1623 and 1555 cm⁻¹... -1 The peak observed at 1408, 1320, and 1236 cm⁻¹ corresponds to the stretching vibration of the C=N bond within the heptaazine unit, while the peaks at 1408, 1320, and 1236 cm⁻¹ correspond to the stretching vibration of the C=N bond within the heptaazine unit. -1 The peaks at these locations correspond to the intrinsic CN tensile vibrations of the heptaazine unit. They are located at 1456 and 1203 cm⁻¹. -1 The peaks correspond to the CN stretching of the C-NHx group, while the peaks at 887 and 808 cm⁻¹ correspond to the CN stretching of the C-NHx group. -1 The peak is caused by the vibration of the triazine ring condensation into a tri-s-triazine ring, which confirms that the addition of P does not change the basic chemical structure of g-C3N4, but only affects the crystal structure, causing the (100) peak in the XRD results to disappear. The results show that P doping has no effect on the chemical structure of g-C3N4.

[0067] The pore size, specific surface area, and pore size distribution of the catalyst were analyzed using N2 adsorption-desorption isotherms and the BJH method, respectively.

[0068] The pore size, specific surface area, and pore size distribution of the catalysts were analyzed using N2 adsorption-desorption isotherms and the BJH method, respectively. Table 1 shows the calculated S values ​​for the BCN and 5P-TCN catalysts. BET Pore ​​volume and pore size distribution. From Figure 3 As can be seen from c, the isotherms of both BCN and 5P-TCN exhibit type IV adsorption curves and type H3 hysteresis loops, indicating that the materials possess mesoporous characteristics. Furthermore, the pore size distributions of the BCN and 5P-TCN catalysts ( Figure 3 d) It can be seen that the tubular structure greatly increases the pore volume of carbon nitride with a pore size of approximately 2-20 nm, resulting in 5P-TCN having a larger specific surface area (31.092 m²). 2 .g -1 ), is BCN(5.918m 2 .g -1 It is 5.25 times larger than that of 5P-TCN. The larger specific surface area can provide more active reaction sites, which will help improve the catalytic degradation performance of pollutants by 5P-TCN.

[0069] Table S1 Pore size distribution of BCN and 5P-TCN

[0070]

[0071] refer to Figure 4 Among them, (a) the total spectrum, (b) the C1s high-resolution spectrum, (c) the N1s high-resolution spectrum, and (d) the P2p high-resolution spectrum of 5P-TCN.

[0072] XPS analysis was used to further investigate the molecular structure and atomic valence states of BCN and 5p-TCN. XPS investigation spectra ( Figure 4 a) The results show that BCN material contains C, N, and O elements, while 5P-TCN contains C, N, O, and P elements, consistent with the EDS results. Note that the peaks are not prominent due to the instrument's low detection limit and the P content being less than 1%. Figure 4 b shows the high-resolution C1s spectra of the two samples. Fitting yields four peaks with binding energies of approximately 284.8 eV, 286.5 eV, 288.1 eV, and 293.5 eV, corresponding to graphitic carbon (CC / C=C), uncompensated amino groups (C-NHx), and the tris-S-triazine unit sp, respectively. 2 Carbon (NC=N) and π-electron delocalization. Figure 4 c represents the N1s high-resolution spectra of the two samples. Fitting the spectra yields four peaks. The three peaks with binding energies of approximately 398.6 eV, 400.0 eV, and 401.0 eV correspond to the bridging nitrogen atom (CN=C), tertiary nitrogen atom (N-C3), and amino nitrogen atom (C-Nx) of the tris-s-triazine unit, respectively. The peak at the binding energy of 404.2 eV is attributed to π-excitation. The high-resolution spectrum of 5P-TCN at 133.4 eV (…) Figure 4 d) The corresponding PN coordination bond indicates that P may replace C to form a PN bond on the triazine ring. Furthermore, the weakening of the NC=N peak intensity (peak area) in the C1s of 5P-TCN also confirms this.

[0073] 2.2 Photocatalytic oxidation system for RhB degradation

[0074] refer to Figure 5 The table shows: (a) the effect of different catalysts on RhB degradation, (b) the corresponding first-order kinetic model, (c) the k constant, (d) the RhB degradation effect in different systems, (e) the corresponding first-order kinetic model, and (f) the k constant.

[0075] The photocatalytic efficiency of different catalysts was evaluated, and the effects of different catalysts on the degradation performance of RhB were studied under simulated visible light (greater than 420 nm) irradiation (unless otherwise specified, under the original pH conditions, the original pH is approximately 4.3). Figure 5 This study shows the degradation performance of different catalysts (400 mg / L) on RhB (10 mg / L). Within 15 min, BCN showed a degradation rate of only 3.9% for RhB under visible light. To investigate the synergistic effect of PMS activation and photocatalysis on improving the RhB degradation rate, PMS (400 mg / L) was introduced into the reaction system. The addition of PMS significantly improved the degradation rate of RhB by BCN, reaching 61.9% within 15 min. This improvement was further supported by a pseudo-first-order kinetic model of BCN degradation on RhB. Figure 5 b) The obtained degradation kinetic constant k is 0.0641 min. -1 ( Figure 5 c) The degradation rate of RhB by HCN obtained through hydrothermal treatment followed by calcination was 25.6 times that without PMS. The degradation rate of RhB by HCN was only slightly improved compared to BCN because HCN only had a slightly smaller volume without any other changes. In stark contrast, the formation of the tubular structure significantly improved the degradation rate of RhB by this system. Furthermore, different amounts of phosphorus introduced caused the degradation rate of RhB by the catalyst to show a trend of first increasing and then decreasing, with 5P-TCN exhibiting the best degradation performance, achieving a 98.1% degradation rate of RhB within 15 minutes, which was 4.4 times that of BCN. This indicates that elemental doping does not necessarily improve degradation performance with more dopant. When the concentration of dopant is too high: on the one hand, it will cause the destruction of the tris-s-triazine structure in g-C3N4; on the other hand, the dopant will turn the isolated energy levels into recombination centers for photogenerated electron-hole pairs, reducing the yield of photogenerated carriers. In summary, the degradation rate constant (k) of RhB by the 5P-TCN / vis / PMS system is 111.8 times that of the BCN photocatalytic system, indicating that a certain amount of P-doped tubular carbon nitride can effectively improve the performance of photocatalysis.

[0076] To further explore the catalytic performance of different systems, the effects of different catalytic systems on the degradation performance of RhB were studied. For example... Figure 5 It is evident that in the dark, light-only, PMS-only, 5P-TCN-only, and PMS / vis systems, RhB solution showed almost no degradation within 15 min. In the 5P-TCN / PMS and 5P-TCN / vis systems, the degradation rates of RhB within 15 min were only 19.5% and 88.8%, respectively, which, combined with the pseudo-first-order kinetic model (…),… Figure 5 e) and the obtained degradation kinetic constant k value are only 0.0129 min. -1 and 0.1424min -1 ( Figure 5 f). In the 5P-TCN / vis / PMS system, the degradation performance was significantly better than all other systems, with a degradation rate reaching 98.1% within 15 minutes. More importantly, the degradation rate constant (k) reached 0.2796 min. -1The degradation performance of 5P-TCN under PMS-only and light-only conditions was 21.7 times and 2.0 times that of PMS-only, respectively. This indicates a synergistic effect between photocatalysis and PMS. Due to differences in experimental systems and conditions, direct numerical comparisons with other studies are not possible. However, the degradation performance of the 5P-TCN / vis / PMS system prepared in this study is at the forefront of non-metallic carbon nitride-based photocatalytic materials, even outperforming many metal-based photocatalysts (Table S2).

[0077] Table S2 shows previous reports on the degradation of RhB using g-C3N4-based catalysts.

[0078]

[0079] refer to Figure 6 (a) Catalyst concentration, (b) RhB concentration, (c) PMS concentration, (d) Initial pH, (e) Coexisting ions (unless otherwise specified, C) RhB =10mg / L,C cat =400mg / L,C PMS =400 mg / L, pH was not adjusted, approximately 4.4), (f) actual water sample. (g) universality test. (h) three-cycle test, and (i) XRD patterns of raw and recovered 5P-TCN.

[0080] Using the 5P-TCN / vis / PMS system as an example, the effects of catalyst dosage, pollutant concentration, and PMS dosage on RhB degradation performance were investigated. Under different dosages, the adsorption of RhB by the 5P-TCN catalyst was negligible. Figure 13 and Figure 14 As shown, during a 30-minute dark adsorption process involving a 400 mg / L 5P-TCN solution and a 10 mg / L RhB solution with thorough stirring, the catalyst adsorbed only 6.6% of the RhB, and adsorption-desorption equilibrium was reached within 30 minutes. Figure 6 a and Figure 15 As can be seen, at the natural pH, with an initial RhB solution concentration of 10 mg / L and a PMS concentration of 400 mg / L, the RhB degradation rate consistently reached approximately 98% as the catalyst concentration increased from 200 mg / L to 500 mg / L. However, the degradation rate constant (k) showed a trend of first increasing and then decreasing, reaching its maximum value at a catalyst concentration of 400 mg / L. The study indicates that a higher catalyst concentration can improve reaction efficiency because it increases the number of active reaction sites and generates more free radicals. However, using excessive catalyst can actually reduce the catalytic effect. This is because excessive catalyst reduces the transparency of the solution, hindering light penetration and reducing light utilization.

[0081] In real wastewater, the initial concentration of pollutants may vary; therefore, studying the effect of concentration on degradation rate is of great significance. For example... Figure 6 b and Figure 15 b. The degradation performance of RhB at different initial concentrations (5, 10, 15, and 20 mg / L) was investigated under natural pH conditions with catalyst and PMS concentrations of 400 mg / L. As the concentration increased, the degradation rate of RhB gradually decreased; when the initial RhB concentration was 20 mg / L, the degradation rate was only 89.2% within 15 minutes.

[0082] It can be concluded that high concentrations of RhB are detrimental to photocatalytic elimination. This is because increased pollutant concentrations reduce visible light transmittance, and more importantly, due to the competitive consumption by oxide species, higher RhB concentrations require more time to achieve the same degradation rate. However, in actual wastewater, pollutant concentrations do not reach such high levels, while low concentrations still result in high degradation rates, demonstrating the practical applicability of this system.

[0083] Next, the relationship between PMS dosage (100, 200, 400, and 800 mg / L) and RhB degradation performance was investigated (e.g., Figure 6 c and Figure 15 c) With increasing PMS dosage, RhB was almost completely degraded within 15 minutes, but the degradation rate initially increased and then decreased. This is because the amount of PMS used is related to the degradation process of RhB and SO42-. - The amount of PMS is related to the quantity of free radicals generated; the higher the amount of PMS, the more free radicals are produced. Therefore, higher PMS concentrations are expected to generate more free radicals, but with a fixed amount of catalyst, the number of photogenerated carriers generated may not be sufficient to activate all PMS. Furthermore, excess PMS can cause SO42- to become volatile organic compounds (VOCs). - Quenching generates SO5, which has lower oxidizing power. - .

[0084] Considering the presence of various inorganic salts and other impurities in actual wastewater, the pH and the presence of multiple coexisting ions (HPO4) in the reaction system were investigated under the conditions of a catalyst dosage of 400 mg / L, a PMS dosage of 400 mg / L, and an RhB concentration of 10 mg / L. 2- HCO3 - SO4 2- NO3 - Cl - The effects of different water sources (5 mM) on degradation performance were investigated. pH plays a crucial role in water treatment; therefore, the RhB solution was adjusted to a wide pH range from strongly acidic to strongly alkaline environments. Figure 6 d and Figure 15 d) To investigate the effect of pH on the system.

[0085] The stronger the acidity of the solution, the better the degradation effect on RhB. When the pH value increased from 3 to 9, the degradation rate of RhB remained above 92% within 15 minutes, indicating that the 5P-TCN / vis / PMS system has strong pH tolerance over a wide pH range. However, under strongly alkaline conditions (pH=11), RhB degradation was unfavorable, with the degradation rate dropping sharply to 42.7% within 15 minutes, and the k value decreasing to 0.0352 min. -1 This is most likely because under alkaline conditions, SO42- - / ·OH and OH - The reaction generates ·OH, whose low oxidation potential and short lifetime weaken the degradation of RhB in this system. In coexisting ion experiments ( Figure 6 e and Figure 15 e) also confirms the above conclusion.

[0086] In HPO4 2- and HCO3 - In the presence of anions, the degradation rates of RhB were 42.7% and 60.9%, respectively. NO3... - Cl - Its presence slightly promotes the degradation of RhB. The stronger the acidity of the coexisting ion, the larger the k value, which further confirms the effect of pH on the degradation of RhB in this system. Furthermore, Cl... - It exhibits an extremely high degradation rate when coexisting (k = 0.3076 min). -1 ( ) to degrade RhB, which is due to Cl - With HSO5 - The reaction generates Cl2 and HClO (Equations 1-7), which promote the degradation of RhB. These results indicate that the 5P-TCN / vis / PMS system has good pH adaptability and can effectively degrade RhB over a wide pH range.

[0087] Cl - +HSO5 - →SO4 2- +HClO (1)

[0088] SO4 - +Cl - →SO4 2- +·Cl (2)

[0089] ·Cl+Cl - →·Cl2 - (3)

[0090] ·Cl2 - +·Cl2 - →Cl₂ + 2Cl -(4)

[0091] SO4 - +HCO3 - →·HCO3 - +SO4 2- (5)

[0092] ·OH+HCO3 - →CO3 2- +H2O (6)

[0093] ·OH+HPO4 2- →·HPO4 - +OH - (7)

[0094] To further evaluate the practicality of the 5P-TCN / vis / PMS system in actual water bodies, tap water and lake water were used to prepare RhB solutions to simulate wastewater. Figure 6 f and Figure 15 f) The degradation of RhB in the system was inhibited to some extent, with k values ​​of 0.1148 and 0.1313 min, respectively. -1 This is because the actual water composition is complex, including soluble natural organic matter, various ions, and other impurities. However, overall, the 5P-TCN / vis / PMS system has strong adaptability to both lake water and tap water, maintaining a removal rate of over 80%.

[0095] A generalization test was conducted on the catalyst. Figure 6 g) In the same system, three organic dyes, MB, MG, and MO, were degraded, with over 92% degradation achieved within 15 minutes. Therefore, this demonstrates that the catalytic effect of the 5P-TCN / vis / PMS system is broad-spectrum and has potential for practical application. Recovery experiments were conducted to evaluate the recyclability and stability of 5P-TCN. Figure 6 As can be seen from h, after three cycles, the degradation rate hardly decreased, and more than 98% of RhB can still be degraded within 15 minutes, which shows very strong stability and is expected to enable the recycling of the material.

[0096] The specific experimental method for the cycle is described in Example 2. Furthermore, the crystal phase of 5P-TCN after the initial and repeated reactions was analyzed by XRD (e.g., Figure 6 i) The characteristic properties of the catalyst are well preserved, further demonstrating its good stability and its potential for large-scale application.

[0097] 2.3 Study on photocatalytic mechanism

[0098] refer to Figure 7Among them, (a) UV-vis DRS plot, (b) Tauc plot, (c) VB-XPS spectrum, (d) schematic diagram of band gap structure, and (e) PL spectrum.

[0099] The optical absorption characteristics and band structure of the catalyst were revealed through UV-Vis diffuse reflectance analysis. For example... Figure 7 Compared to the original g-C3N4, both HCN and 5P-TCN exhibit significant redshifts, resulting in wider light absorption ranges and improved light absorption. Using UV-vis DRS data, the band gap energy was converted to its corresponding value using αhν = A(hν - Eg)exp(n / 2) (where Eg is the band gap energy, An is the proportionality constant, h is Planck's constant, α is the absorption coefficient, ν is the vibrational frequency, and n = 4). Figure 7 In the Tauc plot of b, the estimated Eg values ​​for BCN, HCN, and 5P-TCN are 2.81, 2.71, and 2.70 eV, respectively. Band-edge potentials were analyzed using valence band XPS, such as... Figure 6 As shown in c, the valence band (VB) values ​​of each catalyst are determined by E. VB-NHE =φ+E VB-XPS -4.44 Calculation (E VB-NHE The potential of the hydrogen electrode in a neutral state is represented by φ, which is the work function of the device, with a value of 4.2. The E values ​​for BCN, TCN, and 5P-TCN are... VB-XPS The values ​​are 2.13, 2.03, and 1.98 eV, respectively. Therefore, the E values ​​for BCN, TCN, and 5P-TCN are... VB-NHE The values ​​are 2.81, 2.71, and 2.70 eV, respectively.

[0100] Based on the Eg and EVB-NHE obtained above, further use E CB-NHE =E VB-NHE -Eg(E CB-NHE The conduction band (CB) value was determined by measuring the potential of a normal hydrogen electrode in a neutral state, and the ECB-NHE values ​​for BCN, HCN, and 5P-TCN were -0.68, -0.68, and -0.72 eV, respectively.

[0101] In summary, the band structure diagrams of BCN, HCN, and 5P-TCN are shown below. Figure 7 As shown in d, hydrothermal treatment of carbon nitride primarily lowers the band gap energy, while the doping of P and further morphological changes shift the VB value upwards, making it easier for O2 to convert to ·O2. - While a decrease in band gap energy can promote the excitation of photoelectrons, it may also hinder the dissociation of excitons.

[0102] To further evaluate the separation and transfer efficiency of photogenerated charges, the steady-state PL spectra of BCN, HCN, and 5P-TCN were measured. Figure 7e) The strongest fluorescence intensity of BCN indicates that its recombination rate of photogenerated electrons and holes is relatively high, while the fluorescence intensity of HCN after hydrothermal treatment is not significantly reduced, possibly because hydrothermal treatment does not change anything other than reducing the volume of carbon nitride. The fluorescence intensity of 5P-TCN is significantly reduced, indicating that the formation of P-doped tubular carbon nitride increases the charge transfer rate, thereby inhibiting the recombination of photogenerated electrons and holes.

[0103] refer to Figure 8 (a) Effect of different quenchers on the degradation of RhB. (b) ESR spectra of the 5P-TCN / vis and 5P-TCN / vis / PMS systems (using DMPO to capture ·O2). - (c) EIS plots and (d) photocurrent response curves of BCN and 5P-TCN were used to investigate the contribution of different reactive oxygen species (ROSs) in the synergistic reaction process of PMS and photocatalysis. Free radical quenching experiments were conducted in different systems.

[0104] O2 was quenched using p-BQ (1 mM), TBA (1 mM), FFA (1 mM), MeOH (1 mM), and EDTA-2Na (1 mM), respectively. - ·OH 1 O2, SO4 - / ·OH and h + The RhB degradation curve and k value were obtained as follows: Figure 8 a and Figure 16 As shown, the addition of all quenchers led to varying degrees of reduction in RhB degradation efficiency. Among them, the addition of p-BQ significantly inhibited RhB degradation, indicating that O2... - It is the main active substance for RhB degradation. The contributions of other free radicals to the photodegradation efficiency of RhB are, in descending order: ·OH > 1 O2 > SO4 - / ·OH>h + It is also easy to see from the band structure that in the 5P-TCN / vis / PMS system, OH - Direct oxidation to ·OH is thermodynamically very favorable. EPR analysis further confirmed that ·OH is the main active substance in the 5P-TCN / vis / PMS system. 1 O2, SO4 - / ·OH、·O2 - The formation (such as) Figure 8 bd), no ·OH was observed in the dark. 1 O2, SO4 - / ·OH、·O2 - The signal, typically ·OH, in the 5P-TCN / vis system 1 O2, SO4- / ·OH、·O2 - The generation of surface ROSs is related to the photoinduced excitation of carriers in 5P-TCN, consistent with the previous discussion. Under illumination, after the addition of PMS, ·OH, 1 O2, SO4 - / ·OH、·O2 - The signal intensity was significantly higher than that of the 5P-TCN / vis system, demonstrating that the synergistic activation effect of PMS in photocatalysis enhanced ROS formation, thereby improving the degradation performance of RhB. To further compare the differences in the electrochemical performance of the catalysts and the changes in photocurrent response under different systems, a series of control experiments were conducted using an electrochemical workstation.

[0105] Among them, the electrochemical impedance spectroscopy (EIS) Nyquist plot reveals the charge transfer capability of the catalyst and the electrode ion diffusion process. Figure 8 e) The 5P-TCN curve has a smaller slope than the BCN curve, indicating less resistance to electron transfer and thus more effectively promoting electron separation and migration, reducing electron-hole recombination. Furthermore, Figure 8 f shows a comparison of the photocurrent responses of the samples. The photocurrent response intensity of 5P-TCN is significantly higher than that of BCN, further confirming that 5P-TCN promotes the photodegradation of RhB. In summary, the substitution of N atoms on carbon nitride by P atoms and the resulting morphological changes enhance the light absorption of carbon nitride, making the separation of electrons and holes more efficient, thereby accelerating charge transfer and improving photocatalytic efficiency.

[0106] refer to Figure 9 LC-MS analysis revealed the formation of some intermediates during the catalytic degradation of RhB in the 5P-TCN / vis / PMS system, as shown in Table S1. Based on reported studies and LC-MS analysis results, a possible pathway for RhB degradation in the 5P-TCN / vis / PMS system is proposed. Figure 9In the 5P-TCN / vis / PMS system, RhB molecules typically adsorb onto the catalyst surface and undergo a series of degradation reactions, including N-deethylation, deamination, dealkylation, decarboxylation, chromophore cleavage, cyclocracking, and mineralization. Initially, the methyl group in the RhB molecule (m / z = 443) is attacked by ROSs and detached, leading to deethylation and gradual removal of the ethyl group, forming intermediates (m / z = 429, 415, 387, 359, 331). Then, compound (m / z = 331) undergoes deamination to generate compounds (m / z = 318, 316), and undergoes decarboxylation to generate compound (m / z = 274), as well as compounds induced by decarboxylation (m / z = 278, 222, 182). A ring-opening reaction then occurs, forming some low-molecular-weight organic acids or amides (m / z = 166, 160, 150, 138, 122, 102, 94, 74). Finally, the low-molecular-weight organic acids or amides are further mineralized, eventually decomposing into CO2, H2O, and some small molecules such as alcohols and amines.

[0107] First, under visible light excitation, photogenerated carriers on the 5P-TCN surface separate into electrons (ep). - ) and holes (h + O2 then migrates to the catalyst surface and undergoes a series of reactions (Equation 8). O2 reacts with electrons to generate ·O2. - (Equation 9), h + It can directly oxidize and degrade RhB or remove OH - Oxidation to ·OH (Equations 10 and 11). With the addition of PMS, HSO5 - Capture photogenerated e- and reduce it to SO4. - (Formula 12),·SO4 - With H2O or OH - The reaction produces ·OH (Equation 12) (13 and 14). HSO5 - Capture h + SO5 generation - (Equation 15). For 1 O2 can be formed through the oxidation of pores. - and SO5 - Generate (Equations 16 and 17).

[0108] 5P-TCN+hv→h + +e - (8)

[0109] O2+e - →·O2 - (9)

[0110] h ++RhB→H2O+CO2+other products (10)

[0111] OH - +h + →·OH (11)

[0112] HSO5 - +e - →SO4 - +OH - (12)

[0113] SO4 - +H₂O→SO₄ 2- +·OH+H + (13)

[0114] SO4 - +OH - →SO4 2- +·OH (14)

[0115] HSO5 - +h + →SO5 - +H + (15)

[0116] h + +·O2 - → 1 O2 (16)

[0117] 2·SO5 - →2·SO4 - + 1 O2 (17)

[0118] Based on the above experimental data, it can be seen that in the PMS-assisted photocatalytic system, ·SO4 - h + O2 - , 1 Both O2 and ·OH participate in the degradation of RhB. - Plays a major role, and 1 O2, ·OH, h + and SO4 - It plays a secondary role. With the addition of PMS, the free radicals exhibit a higher EPR signal, indicating the generation of more ROSs, thereby improving the efficiency of photocatalytic degradation of RhB.

[0119] 3. Conclusion

[0120] refer to Figure 10To address the shortcomings of traditional photocatalysts in water treatment, such as metal ion dissolution, narrow light absorption range, and poor stability, this invention employs a precursor self-assembly method to prepare a p-doped tubular carbon nitride (p-TCN) photocatalyst. The carefully regulated 5P-TCN exhibits a larger specific surface area (31.092 m²). 2 ·g -1 The kinetic constant k of the 5P-TCN / vis / PMS system for RhB degradation is 111.8 times that of the BCN / vis system due to its wider light response range (460 nm). The electron circulation system, composed of photogenerated electrons and holes provided by excited 5P-TCN, enhances ROS generation under the synergistic effect of PMS, enabling 5P-TCN to effectively drive the metal-free PMS-photocatalytic reaction over a wider pH range. The degradation rate of RhB reaches over 98% within 15 minutes, solving the problem of poor degradation of aromatic proteins and tryptophan-like proteins in photocatalytic oxidation systems. This invention provides a very promising metal-free catalyst that solves many problems existing in traditional photocatalytic oxidation and PMS oxidation processes in wastewater treatment, and has important theoretical research and practical application significance in environmental wastewater treatment.

[0121] Example 2

[0122] The present invention is based on the above-described Embodiment 1.

[0123] Catalyst growth mechanism

[0124] When H3PO4 is added to a melamine suspension, it partially hydrolyzes into cyanuric acid. Melamine and cyanuric acid bond through supramolecular self-assembly and are vertically stacked through PP interactions, gradually growing into a solid hexagonal prism hydrothermal intermediate 5PMHP with a diameter of approximately 3μm. P is attached to the surface of the intermediate. Figure 12 Through calcination and reaction with melamine, carbon nitride enters the g-C3N4 framework, generating P-doped hollow tubular carbon nitride.

[0125] Cyclic experimental method

[0126] In the cyclic experiment, 20 mg of catalyst was added to 50 mL of RhB (10 mg / L) solution. The catalyst suspension was sonicated for 5 min to ensure uniform dispersion, and then continuously stirred in the dark for 30 min to reach adsorption-desorption equilibrium. Subsequently, photocatalytic experiments were conducted under visible light from a 350 W xenon lamp with a 420 nm cutoff filter. Throughout the experiment, approximately 2.0 mL of the catalyst suspension was extracted every 3 minutes using a syringe, and the photocatalytic material was removed through a 0.22 μm filter.

[0127] The RhB was irradiated with visible light for 15 minutes, and then the absorbance was measured at a wavelength of 554 nm using a UV-2600 ultraviolet spectrophotometer. Finally, the remaining photocatalytic suspension in the photoreactor was obtained by filtration, washed several times with ethanol and ultrapure water, and dried at 60°C for 2 hours.

[0128] To obtain the catalyst needed for the first cycle experiment, the experiment was conducted multiple times, and the resulting catalyst powder was used as the catalyst for the first cycle experiment. The procedure for the first cycle experiment was the same as before. The catalyst powder obtained from the first recovery experiment was used as the catalyst for the second recovery experiment. The procedure for the second cycle experiment was the same as the previous one. The catalyst powder obtained from the second recovery experiment was used as the catalyst for the third recovery experiment. The procedure for the third cycle experiment was the same as the previous one.

[0129] Table S3 shows possible intermediates for RhB degradation in the 5P-TCN\vis\PMS system.

[0130]

[0131]

[0132]

[0133] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS, characterized in that, The steps are as follows: S1: Preparation of P-doped tubular carbon nitride; S2: Apply the P-doped tubular carbon nitride obtained in step S1 to photocatalytically activate PMS; S3: Photocatalytically activated PMS is used to degrade RhB; In PMS-assisted photocatalytic systems, •SO4 - h + •O2 - , 1 Both O2 and •OH participate in the degradation of RhB, •O2 - Plays a major role, and 1 O2, •OH, h + and SO4 - Plays a secondary role; With the addition of PMS, free radicals exhibit a higher EPR signal, generate more ROSs, and improve the efficiency of photocatalytic degradation of RhB; In step S1, p-doped tubular carbon nitride is prepared as follows: S11: Dissolve 2g of melamine in 50mL of deionized water, sonicate for 5min, and add 5mL of phosphoric acid to the melamine solution; S12: The product obtained in S11 was stirred in an 80℃ water bath for 30 min. After complete mixing, it was transferred to a 100 mL high-pressure reactor with a polytetrafluoroethylene liner and placed in a constant temperature drying oven at 180℃ for 10 h. After cooling to room temperature, the product was washed three times with ultrapure water and ethanol, centrifuged, and dried in a vacuum drying oven at 60℃ for 6 h to obtain a self-assembled complex of melamine and phosphoric acid. S13: The complex obtained in S12 was placed in a 10 mL capped corundum boat and heated to 500 °C in a tube furnace at a rate of 2.5 °C / min. After holding at this temperature for 4 h, it was cooled to room temperature.

2. The method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS according to claim 1, characterized in that, In step S2, the P-doped tubular carbon nitride obtained in step S1 is used for photocatalytic activation of PMS, as follows: S21: Add a certain amount of photocatalytic material to wastewater containing different pollutants, and sonicate the catalyst suspension for 5 minutes to make the sample evenly dispersed; S22: Stir continuously for 30 minutes in the dark to reach adsorption-desorption equilibrium; S23: A xenon lamp and a cutoff filter are used as the light source. The distance between the light source and the reactor is maintained at 10 cm. All reaction temperatures are maintained at 25°C for photocatalysis.

3. The method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS according to claim 2, characterized in that, In step S23, after turning on the xenon lamp, a certain amount of PMS is added, and 2 mL of catalyst suspension is extracted every 3 minutes, and the photocatalyst is removed through a 0.22 μm filter.

4. The method for degrading RhB by synthesizing P-doped tubular carbon nitride-driven photocatalytic activation of PMS according to claim 1, characterized in that, In step S3, photocatalytically activated PMS is used to degrade RhB, as follows: RhB was degraded using PMS of different capacities.

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