A salt-templated confined nitrogen-doped carbon film, its preparation method and application

Abstract

This invention belongs to the field of water treatment technology and provides a salt-templated confined nitrogen-doped carbon film, its preparation method, and its application. The method includes the following steps: mixing and precipitating an imidazole suspension and a potassium salt solution, followed by mixing with a hydrochloric acid solution to obtain a photocatalytic material; salt-sealing and carbonizing a melamine sponge as a substrate; then sequentially coating a polyvinyl alcohol solution and a photocatalytic material dispersion onto the surface of the carbonized salt-sealed melamine sponge to obtain the salt-templated confined nitrogen-doped carbon film. The salt-templated confined nitrogen-doped carbon film of this invention solves the problems of traditional powdered photocatalysts being difficult to recover and prone to secondary pollution. It exhibits stable properties and a phenol degradation rate of 0.071 min. ‑1 Under sufficient oxygen supply, the degradation rate of phenol in groundwater can reach over 99.3% within 30 minutes, and the degradation rate of phenol in rainwater can reach over 97%, achieving 100% mineralization.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a salt-templated confined nitrogen-doped carbon film, its preparation method, and its application. Background Technology

[0002] Among water pollutants, various organic pollutants, represented by antibiotics and volatile organic compounds (VOCs), have become a current research hotspot. To address these issues, phosphoric acid molybdenum (PMS), as a novel catalytic material, is expected to become an important direction for future water treatment due to its ability to broaden the pathways for active species generation and enhance pollutant removal. Although PMS achieves high catalytic degradation rates, it is usually accompanied by low mineralization (typically 15-25%). To solve this problem, various PMS activation methods have been employed, including heteroatom doping (such as N and S), ultraviolet activation, microwave activation, thermal activation, and photoactivation. Among these, photo-induced PMS activation has significant advantages, effectively enhancing electron transfer and suppressing photogenerated carrier recombination. However, how to guide reactive oxygen species (ROS) towards deep oxidation, thereby solving the problems of limited mineralization and slow degradation, poses a significant challenge to the precise design of catalysts and the construction of catalytic systems, and has both scientific significance and application value. Summary of the Invention

[0003] The purpose of this invention is to provide a salt template-confined nitrogen-doped carbon film, its preparation method and application, overcoming the defects existing in the prior art.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a nitrogen-doped carbon film confined to a salt template, comprising the following steps:

[0006] (1) Under vacuum conditions, the imidazole suspension and potassium salt solution were mixed to obtain a precipitate;

[0007] (2) The precipitate and hydrochloric acid solution were mixed and dried to obtain the photocatalytic material;

[0008] (3) After mixing melamine sponge, ethanol and sodium chloride solution, recrystallize and carbonize in sequence to obtain carbonized salt-sealed melamine sponge;

[0009] (4) A polyvinyl alcohol solution and a photocatalytic material dispersion are sequentially coated on the surface of the carbonized salt-sealed melamine sponge to obtain the salt template-confined nitrogen-doped carbon film.

[0010] Preferably, the imidazole suspension in step (1) comprises imidazole, chitosan, 3,4,9,10-perylenetetracarboxylic dianhydride, ethanol and hydrochloric acid solution;

[0011] The mass-to-volume ratio of the imidazole, chitosan, 3,4,9,10-perylenetetracarboxylic dianhydride, ethanol, and hydrochloric acid solution is 15-25g: 1-2g: 1-3g: 150-250mL: 50-150mL;

[0012] The concentration of the hydrochloric acid solution is 9–12 mol / L;

[0013] Preferably, the potassium salt solution in step (1) contains KOH, KCl and water;

[0014] The mass-to-volume ratio of KOH, KCl and water is 55-65g: 43-55g: 550-650mL;

[0015] The mass ratio of imidazole to KOH is 15-25:55-65.

[0016] Preferably, the hydrochloric acid solution in step (2) has a mass fraction of 5-15%;

[0017] In step (2), the volume-to-mass ratio of hydrochloric acid solution to imidazole is 150-250 mL: 15-25 g;

[0018] In step (2), the vacuum degree of drying is 0.03 to 0.07 MPa, the drying temperature is -40 to -60°C, and the drying time is 3 to 7 days.

[0019] Preferably, in step (3), the volume ratio of melamine sponge to ethanol is 0.8–2.0 cm³. 3 14-20 mL.

[0020] Preferably, the recrystallization time in step (3) is 3 to 7 minutes;

[0021] The carbonization temperature is 350–400°C, the carbonization heating time is 25–35 min, and the carbonization holding time is 15–25 min.

[0022] Preferably, the mass fraction of the polyvinyl alcohol solution in step (4) is 5-15%;

[0023] The photocatalytic material dispersion in step (4) contains ethanol, water, and the photocatalytic material from step (2);

[0024] The volume-to-mass ratio of the ethanol, water, and photocatalyst material in step (2) is 0.2–1 mL: 0.2–1 mL: 3–7 mg.

[0025] Preferably, in step (4), the volume-to-area ratio of the photocatalytic material dispersion to the carbide-sealed melamine sponge is 0.5–1.5 mL: 3–5 cm². 2.

[0026] The present invention provides a nitrogen-doped carbon film confined to a salt template obtained by the preparation method described above.

[0027] The present invention also provides the application of the salt template-confined nitrogen-doped carbon membrane in the treatment of organic pollutants in wastewater.

[0028] The present invention has the following beneficial effects:

[0029] (1) In this invention, an imidazole suspension is mixed with a potassium salt solution to precipitate and then mixed with a hydrochloric acid solution to obtain a photocatalytic material. A polyvinyl alcohol solution and a photocatalytic material dispersion are coated on the surface of a melamine sponge sealed with carbide. Since the substrate is soaked with a crosslinking agent before use, the photocatalytic material (PDI@CTS) is easily and uniformly dispersed on the N-rich support through HC=N-. The large amount of nitrogen anchored on the membrane makes the prepared composite membrane stable and recyclable.

[0030] (2) The salt-templated nitrogen-doped carbon film of the present invention uses melamine sponge as a substrate, which solves the problem that traditional powdered photocatalysts are difficult to recycle and are prone to secondary pollution.

[0031] (3) The hydrophilic catalyst layer of the salt template confined nitrogen-doped carbon film of the present invention is formed by the hybridization between PMS and photocatalytic material (PDI@CTS), which can accelerate the activation of PMS and achieve 100% mineralization. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the shape of the nitrogen-doped carbon film confined by the salt template in Example 1;

[0033] Figure 2 This is a SEM image of the nitrogen-doped carbon film confined to a salt template in Example 1;

[0034] Figure 3 The image shows the degradation effect of phenol on the nitrogen-doped carbon film confined to a salt template in Example 1.

[0035] Figure 4 The graph shows the degradation rate of phenol by the nitrogen-doped carbon film confined to a salt template in Example 1.

[0036] Figure 5 The graph shows the degradation effect of phenol on the nitrogen-doped carbon film confined to a salt template in Example 1 after 5 cycles.

[0037] Figure 6 This is a graph showing the change in TOC of the nitrogen-doped carbon film confined to a salt template in Example 1;

[0038] Figure 7 The image shows the degradation effect of the salt template-confined nitrogen-doped carbon film of Example 1 on phenol in groundwater and rainwater. Detailed Implementation

[0039] This invention provides a method for preparing a nitrogen-doped carbon film confined to a salt template, comprising the following steps:

[0040] (1) Under vacuum conditions, the imidazole suspension and potassium salt solution were mixed to obtain a precipitate;

[0041] (2) The precipitate and hydrochloric acid solution were mixed and dried to obtain the photocatalytic material;

[0042] (3) After mixing melamine sponge, ethanol and sodium chloride solution, recrystallize and carbonize in sequence to obtain carbonized salt-sealed melamine sponge;

[0043] (4) A polyvinyl alcohol solution and a photocatalytic material dispersion are sequentially coated on the surface of the carbonized salt-sealed melamine sponge to obtain the salt template-confined nitrogen-doped carbon film.

[0044] In this invention, the imidazole suspension in step (1) preferably comprises imidazole, chitosan, 3,4,9,10-perylenetetracarboxylic dianhydride, ethanol and hydrochloric acid solution.

[0045] In this invention, the preferred mass-to-volume ratio of imidazole, chitosan, 3,4,9,10-perylenetetracarboxylic dianhydride, ethanol, and hydrochloric acid solution is 15-25g:1-2g:1-3g:150-250mL:50-150mL, more preferably 17-23g:1.1-1.9g:1.3-2.7g:170-230mL:65-135mL, and even more preferably 19-21g:1.2-1.8g:1.6-2.4g:190-210mL:80-110mL.

[0046] In this invention, the concentration of the hydrochloric acid solution is preferably 9-12 mol / L, more preferably 9.5-11.5 mol / L, and even more preferably 10-11 mol / L.

[0047] In this invention, imidazole, chitosan, and 3,4,9,10-perylenetetracarboxylic dianhydride are mixed and then added to a mixture of ethanol and hydrochloric acid solution, and stirred to obtain an imidazole suspension.

[0048] In this invention, the mixing temperature is preferably 120–160°C, more preferably 125–155°C, and even more preferably 130–150°C; the mixing time is preferably 44–52 h, more preferably 45–51 h, and even more preferably 46–50 h; the mixing stirring rate is preferably 250–350 r / min, more preferably 265–335 r / min, and even more preferably 280–320 r / min.

[0049] In this invention, the mixture is cooled after mixing, and then a mixture of ethanol and hydrochloric acid solution is added.

[0050] In this invention, the stirring time is preferably 20-28h, more preferably 21-27h, and even more preferably 22-26h; the stirring rate is preferably 250-350r / min, more preferably 265-335r / min, and even more preferably 280-320r / min.

[0051] In this invention, the potassium salt solution in step (1) preferably contains KOH, KCl and water.

[0052] In this invention, the preferred mass-to-volume ratio of KOH, KCl and water is 55-65g:43-55g:550-650mL, more preferably 57-63g:45-53g:570-630mL, and even more preferably 59-61g:47-51g:590-610mL.

[0053] In this invention, the mass ratio of imidazole to KOH is preferably 15-25:55-65, more preferably 17-23:57-63, and even more preferably 19-21:59-61.

[0054] In this invention, an organic filter membrane is used to vacuum the imidazole suspension, and then a potassium salt solution is added and mixed to obtain a precipitate.

[0055] In this invention, the vacuum degree is preferably 0.05-0.11 MPa, more preferably 0.06-0.10 MPa, and even more preferably 0.07-0.09 MPa.

[0056] In this invention, the pore size of the organic filter membrane is preferably 0.40-0.50 μm, more preferably 0.42-0.58 μm, and even more preferably 0.44-0.56 μm.

[0057] In this invention, the potassium salt solution is used to wash the imidazole suspension, and the precipitate is obtained after washing and precipitation.

[0058] In this invention, the number of times the washing and sedimentation is performed is preferably 1 to 6 times, more preferably 2 to 5 times, and even more preferably 3 to 4 times.

[0059] In this invention, after washing, the precipitate is allowed to drain naturally before proceeding to the next reaction step.

[0060] In this invention, the mass fraction of the hydrochloric acid solution in step (2) is preferably 5-15%, more preferably 7-13%, and even more preferably 9-11%.

[0061] In this invention, the volume-to-mass ratio of hydrochloric acid solution to imidazole in step (2) is preferably 150-250 mL: 15-25 g, more preferably 170-230 mL: 17-23 g, and even more preferably 190-210 mL: 19-21 g.

[0062] In this invention, hydrochloric acid solution is added to the drained precipitate and stirred. The clear liquid at the top is neutralized by centrifugation and washing, and then dried to finally obtain a brown powder product, which is the photocatalytic material.

[0063] In this invention, the stirring time is preferably 20-28h, more preferably 21-27h, and even more preferably 22-26h; the stirring rate is preferably 250-350r / min, more preferably 265-335r / min, and even more preferably 280-320r / min.

[0064] In this invention, the centrifugation parameters are preferably 6500-7500 r / min, more preferably 6700-7300 r / min, and even more preferably 6900-7100 r / min.

[0065] In this invention, the vacuum degree of drying in step (2) is preferably 0.03 to 0.07 MPa, more preferably 0.035 to 0.065 MPa, and even more preferably 0.04 to 0.06 MPa; the drying temperature is preferably -40 to -60°C, more preferably -44 to -56°C, and even more preferably -48 to -52°C; the drying time is preferably 3 to 7 days, more preferably 3.5 to 6.5 days, and even more preferably 4 to 6 days.

[0066] In this invention, the volume of melamine sponge and ethanol in step (3) is preferably 0.8–2.0 cm³. 3 14–20 mL, more preferably 0.9–1.9 cm 3 15–19 mL, more preferably 1.0–1.8 cm 3 16-18 mL.

[0067] In this invention, melamine sponge is dissolved in a first portion of ethanol, then mixed with a saturated sodium chloride solution, and the remaining ethanol is added after mixing for recrystallization.

[0068] In this invention, the volume ratio of the first portion of ethanol to the remaining ethanol is preferably 3-7:10-14, more preferably 3.5-6.5:10.5-13.5, and even more preferably 4-6:11-13.

[0069] In this invention, the mixing is preferably performed sequentially by ultrasonic treatment and stirring.

[0070] In this invention, the frequency of the ultrasonic treatment is preferably 20-30 kHz, more preferably 22-28 kHz, and even more preferably 24-26 kHz; the duration of the ultrasonic treatment is preferably 25-35 min, more preferably 27-33 min, and even more preferably 29-31 min.

[0071] In this invention, the stirring rate is preferably 250-350 r / min, more preferably 265-335 r / min, and even more preferably 280-320 r / min, and the stirring time is preferably 25-35 min, more preferably 27-33 min, and even more preferably 29-31 min.

[0072] In this invention, the recrystallization time in step (3) is preferably 3 to 7 minutes, more preferably 3.5 to 6.5 minutes, and even more preferably 4 to 6 minutes.

[0073] The recrystallized melamine sponge was dried to obtain salt-sealed carbonized sponge.

[0074] In this invention, the drying temperature is preferably 70-90°C, more preferably 74-86°C, and even more preferably 78-82°C; the drying time is preferably 1-3 hours, more preferably 1.4-2.6 hours, and even more preferably 1.8-2.2 hours.

[0075] After drying, the melamine sponge is carbonized to obtain carbonized salt-sealed melamine sponge.

[0076] In this invention, the carbonization temperature in step (3) is preferably 350-400°C, more preferably 360-390°C, and even more preferably 370-380°C; the carbonization heating time is preferably 25-35 min, more preferably 27-33 min, and even more preferably 29-31 min; the carbonization holding time is preferably 15-25 min, more preferably 17-23 min, and even more preferably 19-21 min.

[0077] In this invention, carbonized salt-sealed melamine sponge is obtained by naturally cooling after carbonization.

[0078] In this invention, the mass fraction of the polyvinyl alcohol solution in step (4) is preferably 5-15%, more preferably 7-13%, and even more preferably 9-11%.

[0079] In this invention, the preferred method of coating with polyvinyl alcohol solution is to immerse the salt-sealed carbonized melamine sponge in the polyvinyl alcohol solution.

[0080] In this invention, the soaking time of the melamine sponge is preferably 6 to 12 hours, more preferably 7 to 11 hours, and even more preferably 8 to 10 hours.

[0081] In this invention, the photocatalytic material dispersion in step (4) preferably contains ethanol, water and the photocatalytic material in step (2).

[0082] In this invention, the volume-to-mass ratio of ethanol, water and photocatalytic material in step (2) is preferably 0.2-1 mL: 0.2-1 mL: 3-7 mg, more preferably 0.3-0.9 mL: 0.3-0.9 mL: 3.5-6.5 mg, and even more preferably 0.4-0.8 mL: 0.4-0.8 mL: 4-6 mg.

[0083] In this invention, photocatalytic materials are weighed and dissolved in ethanol and water, and ultrasonically dissolved to obtain a dispersion of photocatalytic materials.

[0084] In this invention, the frequency of the ultrasound is preferably 20-30 kHz, more preferably 22-28 kHz, and even more preferably 24-26 kHz; the duration of the ultrasound is preferably 10-20 min, more preferably 12-18 min, and even more preferably 14-16 min.

[0085] A photocatalytic material dispersion was coated onto a salt-sealed carbonized melamine sponge substrate that had been soaked in a polyvinyl alcohol solution, and then vacuum dried to obtain a nitrogen-doped carbon film confined to a salt template.

[0086] In this invention, the preferred volume-to-area ratio of the photocatalytic material dispersion and the carbide-sealed melamine sponge in step (4) is 0.5–1.5 mL: 3–5 cm². 2 More preferably, the concentration is 0.7–1.3 mL: 3.4–4.6 cm. 2 More preferably, the concentration is 0.9–1.1 mL; 3.8–4.2 cm. 2 .

[0087] In this invention, the vacuum degree of the vacuum drying is preferably 0.03-0.07 MPa, more preferably 0.035-0.065 MPa, and even more preferably 0.04-0.06 MPa; the vacuum drying temperature is preferably 42-50°C, more preferably 43-49°C, and even more preferably 44-48°C; the vacuum drying to constant weight yields a salt template-confined nitrogen-doped carbon film.

[0088] The present invention also provides a nitrogen-doped carbon film confined to a salt template obtained by the preparation method.

[0089] The present invention also provides the application of the salt template-confined nitrogen-doped carbon membrane in the treatment of organic pollutants in wastewater.

[0090] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0091] Example 1

[0092] 20 g imidazole, 1.64 g chitosan, and 2 g 3,4,9,10-perylenetetracarboxylic dianhydride were heated at 140 °C and stirred at 300 r / min for 48 h. After the system cooled, a mixture prepared from 200 mL ethanol and 100 mL 12 mol / L hydrochloric acid solution was added, and the mixture was stirred at 300 r / min for 24 h to obtain an imidazole suspension.

[0093] The imidazole suspension was evacuated to 0.08 MPa using a 0.45 μm organic filter membrane. The precipitated imidazole suspension was washed three times with a pre-prepared potassium salt solution (60 g KOH and 48 g KCl were weighed and mixed with 600 mL of water) to obtain the precipitate.

[0094] After all the precipitate was naturally drained, 200 mL of 10% hydrochloric acid solution was added and stirred at 300 r / min for 24 h. The clear liquid at the top was neutralized by centrifugation at 7000 r / min. Then, it was dried at a vacuum of 0.05 MPa and -51 °C for 5 days to obtain a brown powder product, which is the photocatalytic material.

[0095] The volume is 1.2cm 3 The melamine sponge was dissolved in 5 mL of ethanol, then poured into a saturated sodium chloride solution, and sonicated at a frequency of 25 kHz for 30 min. After that, it was stirred at a rate of 300 r / min for 30 min. After stirring, 12 mL of ethanol was slowly added dropwise. At this time, the solution underwent a recrystallization process, and a white precipitate was obtained after 5 min.

[0096] The white precipitate was placed in an oven and dried at 80°C for 2 hours to obtain salt-sealed carbonized sponge.

[0097] The dried melamine sponge was placed in a tube furnace and heated to 375°C for 30 minutes, then carbonized for 20 minutes and allowed to cool naturally to obtain carbonized melamine sponge.

[0098] Weigh 5 mg of photocatalytic material and dissolve it in 0.5 mL of ethanol and 0.5 mL of water. Sonicate the solution at 25 kHz for 15 min to obtain a dispersion of the photocatalytic material.

[0099] The carbonized melamine sponge was immersed in a 10% (w / w) polyvinyl alcohol solution for 9 hours. Then, the photocatalytic material dispersion was coated onto the carbonized melamine sponge substrate that had been immersed in the polyvinyl alcohol solution (the volume area of ​​the photocatalytic material dispersion to the melamine sponge substrate was 1 mL: 4 cm²). 2 The nitrogen-doped carbon film confined to a salt template was obtained by vacuum drying at 46°C and 0.05 MPa to constant weight (coating in proportion to the coating ratio).

[0100] The shape of the salt template-confined nitrogen-doped carbon film prepared in this embodiment is as follows: Figure 1 As shown.

[0101] from Figure 1 It can be seen that the nitrogen-doped carbon film confined to the salt template has the advantages of flexibility and scalability, which allows it to be customized according to actual water remediation requirements, and its geometry remains stable and does not deform during long-term immersion.

[0102] The nitrogen-doped carbon film confined to a salt template prepared in this embodiment was observed using a scanning electron microscope, as shown below. Figure 2 As shown.

[0103] from Figure 2 The SEM images of the salt-templated confined nitrogen-doped carbon film show the morphology of the upper and lower surfaces, clearly displaying the catalytic layer (upper layer) covering the catalyst and the typical carbonized structure of the gas attraction and transport layer (lower layer). The salt-templated confined nitrogen-doped carbon film is essentially a hydrophobic structure, which gives it the potential adsorption capacity for gases.

[0104] The salt-templated confined nitrogen-doped carbon film prepared in this embodiment was used in 10 mL of a 1 mg / L phenol solution, and the optical power was 1 kWm. -2 Photocatalytic experiments were conducted under a xenon lamp to determine the degradation effect on phenol. Figure 3 As shown, the degradation rate of phenol is as follows: Figure 4 As shown. (Sponge is melamine sponge; NCM is nitrogen-doped carbon film; C-NCM is nitrogen-doped carbon film confined to a salt template without photocatalytic material; PDI@CTS is photocatalytic material; Sponge-PDI@CTS is photocatalytic material supported by melamine sponge; NCM-PDI@CTS is photocatalytic material supported by nitrogen-doped carbon film; c-NCM-PDI@CTS is nitrogen-doped carbon film confined to a salt template)

[0105] With the assistance of PMS, the melamine sponge-supported photocatalytic material completely degraded phenol within 140 min, achieving a degradation rate of 0.028 min. -1This is 47 times faster than conventional two-phase photocatalysis. To facilitate catalyst recycling, a porous membrane was used as the catalyst support. The phenol degradation rate in the three-phase interface degradation system with a nitrogen-doped carbon film confined to a salt template was increased to 0.030 min. -1 Under these conditions, the catalytic system of the salt-templated confined nitrogen-doped carbon film (c-NCM-PDI@CTS) achieved a degradation rate of 0.071 min within 80 minutes. -1 Compared with the directly carbonized NCM and two-phase degradation systems, the C-NCM system showed significantly improved catalytic performance, with phenol degradation rates increasing by 2.4 times and 2.5 times, respectively. The hydrophilic catalyst layer, due to the contact between PDI@CTS and PMS, led to the generation of hydroxyl and sulfate radicals in PMS, accelerating phenol degradation.

[0106] The salt-templated confined nitrogen-doped carbon film prepared in this embodiment was placed on top of (i.e., the upper surface) a 10 mL solution of 1 mg / L phenol, and then subjected to an optical power of 1 kWm. -2 Photocatalysis experiments were conducted under a xenon lamp.

[0107] With the aid of PMS, five consecutive cycles of experiments were conducted to test and observe its stability and changes in phenol degradation rate, such as... Figure 5 As shown in the figure, the results indicate that the degradation rate of phenol in the salt-templated nitrogen-doped carbon film remained at 89% in the fifth cycle during continuous degradation, demonstrating that the salt-templated nitrogen-doped carbon film prepared in this invention possesses high activity and ultra-stability. This superior stability is one of the key factors for practical applications.

[0108] The salt-templated confined nitrogen-doped carbon film prepared in this embodiment was placed on top of (i.e., the upper surface) a 10 mL solution of 1 mg / L phenol. Photocatalytic experiments were then conducted under xenon lamps of varying power, and the changes in TOC were observed as follows: Figure 6 As shown.

[0109] from Figure 6 The changes in TOC of the nitrogen-doped carbon film confined by the salt template can be seen. With the assistance of PMS, at 1kW m -2 Under certain conditions, the mineralization efficiency of nitrogen-doped carbon films confined to salt templates reached 91.2% at 2kWm. -2 and 3kWm -2 Under high light intensity, the mineralization efficiency can be further improved to 96.0% and 100%. The mineralization degree of the nitrogen-doped carbon film confined by the salt template is significantly higher than that of the photocatalytic material alone and the nitrogen-rich carbon film. The key to achieving high mineralization degree is the excellent catalyst material and the improved hole performance caused by the rapid generation and transfer of electrons.

[0110] The salt-templated confined nitrogen-doped carbon film prepared in this embodiment was placed in different water bodies for experiments, and the degradation effect on phenol was as follows: Figure 7 As shown.

[0111] from Figure 7 The results show that the salt-tempered nitrogen-doped carbon membrane exhibits excellent degradation effects on phenol in both groundwater and rainwater. With the assistance of PMS, the degradation performance of phenol in groundwater samples decreased slightly compared to ultrapure water. Under sufficient oxygen supply, the degradation rate of groundwater was 99.3% and that of rainwater was 97% after 30 minutes. These results demonstrate that the salt-tempered nitrogen-doped carbon membrane still exhibits excellent catalytic and mineralization efficiency for phenol in complex real-world water conditions, indicating its significant practical application potential for all aromatic organic pollutants containing benzene rings.

[0112] Example 2

[0113] 15g imidazole, 1g chitosan, and 1g 3,4,9,10-perylenetetracarboxylic dianhydride were heated at 120℃ and stirred at 250r / min for 44h. After the system cooled, a mixture of 150mL ethanol and 50mL 9mol / L hydrochloric acid solution was added, and the mixture was stirred at 250r / min for 20h to obtain an imidazole suspension.

[0114] The imidazole suspension was evacuated to 0.05 MPa using a 0.40 μm organic filter membrane. The precipitated imidazole suspension was washed once with a pre-prepared potassium salt solution (55 g KOH and 43 g KCl were weighed and mixed with 550 mL of water) to obtain the precipitate.

[0115] After all the precipitate was naturally drained, 150 mL of 5% hydrochloric acid solution was added and stirred at 250 r / min for 20 h. The clear liquid at the top was neutralized by centrifugation at 6500 r / min, and then dried at a vacuum of 0.03 MPa and -40 °C for 3 days to obtain a brown powder product, i.e., photocatalytic material.

[0116] The volume is 0.8cm 3 The melamine sponge was dissolved in 3 mL of ethanol, then poured into a saturated sodium chloride solution, and sonicated at a frequency of 20 kHz for 25 min. After stirring at a rate of 250 r / min for 25 min, 11 mL of ethanol was slowly added dropwise. At this time, the solution underwent recrystallization, and a white precipitate was obtained after 3 min.

[0117] The white precipitate was placed in an oven and dried at 70°C for 1 hour to obtain salt-sealed carbonized sponge.

[0118] The dried melamine sponge was placed in a tube furnace and heated to 350°C for 25 minutes. After carbonization for 15 minutes, it was allowed to cool naturally to obtain carbonized melamine sponge.

[0119] Weigh 3 mg of photocatalytic material and dissolve it in 0.2 mL of ethanol and 0.2 mL of water. Sonicate the solution at 20 kHz for 10 min to obtain a dispersion of the photocatalytic material.

[0120] The carbonized melamine sponge was immersed in a 5% (w / w) polyvinyl alcohol solution for 6 hours. Then, the photocatalytic material dispersion was coated onto the carbonized melamine sponge substrate that had been immersed in the polyvinyl alcohol solution (the volume ratio of the photocatalytic material dispersion to the melamine sponge substrate was 0.5 mL: 3 cm²). 2 The nitrogen-doped carbon film confined to a salt template was obtained by vacuum drying at 42°C and 0.03 MPa to constant weight (coating in proportion to the coating ratio).

[0121] The salt template-confined nitrogen-doped film prepared in this embodiment was subjected to photocatalytic experiments according to the method and conditions of Example 1.

[0122] The results showed that the degradation rate of the nitrogen-doped carbon film catalytic system confined by the salt template could reach 0.068 min within 80 minutes. -1 During the continuous degradation process, the degradation rate of phenol remained at 85% in the fifth cycle.

[0123] The effect of salt-templated confined nitrogen-doped carbon film on TOC was tested with the aid of PMS at a temperature of 1 kWm. -2 Under high light intensity, the mineralization efficiency of nitrogen-doped carbon films confined in salt templates can reach 90.5% at 2kWm. -2 and 3kWm -2 Under high light intensity, mineralization efficiency can be further increased to 95.0% and 99.4%.

[0124] The degradation effect of nitrogen-doped carbon film confined in salt template on phenol in groundwater and rainwater was tested. With the assistance of PMS and sufficient oxygen supply, the degradation rate of groundwater was 97.5% and the degradation rate of rainwater was 95.3% after 30 minutes.

[0125] Example 3

[0126] 25g imidazole, 2g chitosan, and 3g 3,4,9,10-perylenetetracarboxylic dianhydride were heated at 160℃ and stirred at 350r / min for 52h. After the system cooled, a mixture prepared from 250mL ethanol and 150mL hydrochloric acid solution with a concentration of 12mol / L was added, and the mixture was stirred at 350r / min for 28h to obtain an imidazole suspension.

[0127] The imidazole suspension was evacuated to 0.11 MPa using a 0.50 μm organic filter membrane. The precipitated imidazole suspension was washed six times with a pre-prepared potassium salt solution (65 g KOH and 55 g KCl were weighed and mixed with 650 mL of water) to obtain the precipitate.

[0128] After all the precipitate was naturally drained, 250 mL of 15% hydrochloric acid solution was added and stirred at 350 r / min for 28 h. The clear liquid at the top was neutralized by centrifugation at 7500 r / min, and then dried at a vacuum of 0.07 MPa and -60 °C for 7 days to obtain a brown powder product, i.e., photocatalytic material.

[0129] The volume is 2.0 cm 3 The melamine sponge was dissolved in 7 mL of ethanol, then poured into a saturated sodium chloride solution, and sonicated at a frequency of 30 kHz for 25 min. After stirring at a rate of 350 r / min for 35 min, 13 mL of ethanol was slowly added dropwise. At this time, the solution underwent recrystallization, and a white precipitate was obtained after 7 min.

[0130] The white precipitate was placed in an oven and dried at 90°C for 3 hours to obtain salt-sealed carbonized sponge.

[0131] The dried melamine sponge was placed in a tube furnace and heated to 400°C for 35 minutes, then carbonized for 25 minutes and allowed to cool naturally to obtain carbonized melamine sponge.

[0132] Weigh 7 mg of photocatalytic material and dissolve it in 1 mL of ethanol and 1 mL of water. Sonicate the solution at 30 kHz for 20 min to obtain a dispersion of the photocatalytic material.

[0133] The carbonized melamine sponge was immersed in a 15% (w / w) polyvinyl alcohol solution for 12 hours. Then, the photocatalytic material dispersion was coated onto the carbonized melamine sponge substrate that had been immersed in the polyvinyl alcohol solution (the volume ratio of the photocatalytic material dispersion to the melamine sponge substrate was 1.5 mL: 5 cm²). 2 The nitrogen-doped carbon film confined to a salt template was obtained by vacuum drying at 50°C and 0.07 MPa to constant weight (coating in proportion to the coating ratio).

[0134] The salt template-confined nitrogen-doped film prepared in this embodiment was subjected to photocatalytic experiments according to the method and conditions of Example 1.

[0135] The results showed that the degradation rate of the nitrogen-doped carbon film catalytic system confined by the salt template could reach 0.069 min within 80 minutes. -1 During the continuous degradation process, the degradation rate of phenol remained at 86.9% in the fifth cycle.

[0136] The effect of salt-templated confined nitrogen-doped carbon film on TOC was tested with the aid of PMS at a temperature of 1 kWm. -2 Under high light intensity, the mineralization efficiency of nitrogen-doped carbon films confined in salt templates can reach 90.8% at 2kWm. -2 and 3kWm -2 Under high light intensity, mineralization efficiency can be further increased to 95.3% and 100%.

[0137] The degradation effect of nitrogen-doped carbon film confined in salt template on phenol in groundwater and rainwater was tested. With the assistance of PMS and sufficient oxygen supply, the degradation rate of groundwater was 98.3% and that of rainwater was 96.6% after 30 minutes.

[0138] As can be seen from the above embodiments, the present invention provides a method for preparing a salt-templated confined nitrogen-doped carbon film, comprising the following steps: mixing an imidazole suspension with a potassium salt solution to precipitate the film, and then mixing it with a hydrochloric acid solution to obtain a photocatalytic material; coating a polyvinyl alcohol solution and a photocatalytic material dispersion onto the surface of a carbonized salt-sealed melamine sponge; since the substrate is soaked with a crosslinking agent before use, the photocatalytic material is easily and uniformly dispersed on the nitrogen-rich support via HC=N-; the large amount of nitrogen anchored on the film makes the prepared composite film stable and recyclable; the hydrophilic catalyst layer of the salt-templated confined nitrogen-doped carbon film of the present invention is a hybrid formed between PMS and the photocatalytic material (PDI@CTS), which can accelerate the activation of PMS and achieve 100% mineralization; as can be seen from the test results of the embodiments, the salt-templated confined nitrogen-doped carbon film provided by the present invention can achieve a degradation rate of phenol of 0.071 min within 80 minutes. -1 The above indicates that during continuous degradation, the degradation rate of phenol remained above 89% even in the fifth cycle; at a light power of 3kWm -2 Under xenon lamp intensity, the mineralization efficiency reaches 100%; under sufficient oxygen supply, the degradation rate of phenol in groundwater can reach over 99.3% within 30 minutes, and the degradation rate of phenol in rainwater can reach over 97%. The salt-tempered confined nitrogen-doped carbon membrane exhibits excellent catalytic and mineralization efficiency for phenol in water, indicating that the salt-tempered confined nitrogen-doped carbon membrane has outstanding practical application potential for all aromatic organic pollutants containing benzene rings.

[0139] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon film confined to a salt template, characterized in that, Includes the following steps: (1) Under vacuum conditions, the imidazole suspension and potassium salt solution were mixed to obtain a precipitate; The imidazole suspension comprises imidazole, chitosan, 3,4,9,10-perylenetetracarboxylic dianhydride, ethanol, and hydrochloric acid solution; the mass-to-volume ratio of imidazole, chitosan, 3,4,9,10-perylenetetracarboxylic dianhydride, ethanol, and hydrochloric acid solution is 15-25 g: 1-2 g: 1-3 g: 150-250 mL: 50-150 mL; the concentration of the hydrochloric acid solution is 9-12 mol / L; the imidazole, chitosan, and 3,4,9,10-perylenetetracarboxylic dianhydride are mixed and then added to a mixture of ethanol and hydrochloric acid solution, and stirred to obtain the imidazole suspension, wherein the mixing temperature is 120-160℃ and the mixing time is 44-52 h; The imidazole suspension was vacuum-sealed using an organic filter membrane, and then mixed with a potassium salt solution to obtain a precipitate. The potassium salt solution contained KOH, KCl, and water. The mass-to-volume ratio of KOH, KCl, and water was 55-65 g: 43-55 g: 550-650 mL. The mass ratio of imidazole to KOH was 15-25: 55-65. (2) The precipitate and hydrochloric acid solution were mixed and dried to obtain the photocatalytic material; The hydrochloric acid solution has a mass fraction of 5-15%; the volume-to-mass ratio of the hydrochloric acid solution to imidazole is 150-250 mL: 15-25 g. (3) After mixing melamine sponge, ethanol and sodium chloride solution, recrystallize and carbonize in sequence to obtain carbonized salt-sealed melamine sponge; (4) A polyvinyl alcohol solution and a photocatalytic material dispersion are sequentially coated on the surface of the carbonized salt-sealed melamine sponge to obtain the salt template-confined nitrogen-doped carbon film.

2. The preparation method according to claim 1, characterized in that, In step (2), the vacuum degree of drying is 0.03 to 0.07 MPa, the drying temperature is -40 to -60°C, and the drying time is 3 to 7 days.

3. The preparation method according to claim 1, characterized in that, In step (3), the volume ratio of melamine sponge to ethanol is 0.8~2.0 cm³. 3 14~20mL.

4. The preparation method according to claim 1, characterized in that, The recrystallization time in step (3) is 3-7 minutes; The carbonization temperature is 350~400℃, the carbonization heating time is 25~35min, and the carbonization holding time is 15~25min.

5. The preparation method according to claim 1, characterized in that, The mass fraction of the polyvinyl alcohol solution in step (4) is 5-15%; The photocatalytic material dispersion in step (4) contains ethanol, water, and the photocatalytic material from step (2); The volume-to-mass ratio of the ethanol, water, and photocatalyst material in step (2) is 0.2~1mL:0.2~1mL:3~7mg.

6. The preparation method according to claim 5, characterized in that, In step (4), the volume-to-area ratio of the photocatalytic material dispersion to the carbide-sealed melamine sponge is 0.5~1.5mL:3~5cm². 2 .

7. The salt-template-confined nitrogen-doped carbon film obtained by the preparation method according to any one of claims 1 to 6.

8. The application of the salt template-confined nitrogen-doped carbon membrane according to claim 7 in the treatment of organic pollutants in wastewater.

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