Enteromorpha-based high-dispersed iron atom modified carbon-based nanomaterial, and preparation method and application thereof

Abstract

The application discloses a Enteromorpha-based high-dispersed iron atom modified carbon-based nanomaterial and a preparation method and application thereof, and belongs to the field of biological comprehensive utilization and marine environmental pollution treatment. The Enteromorpha biomass is high-temperature calcined in an inert atmosphere at >700 DEG C, the obtained material is mixed with graphite-type carbon nitride, the mixed material is uniformly mixed, and the Enteromorpha-based high-dispersed iron atom modified carbon-based nanomaterial is obtained by heat treatment at 300-500 DEG C for 1-3 hours. The preparation method is simple and efficient, saves time and effort, is environment-friendly and energy-saving, solves the problems of low utilization rate of Enteromorpha and environmental pollution, greatly expands the application range of the graphite-type carbon nitride material g-C3N4, improves the degradation efficiency of herbicides, and for atrazine, the degradation efficiency can reach nearly 80% in 10 minutes, and the degradation rate is 0.13112 min ‑1 , which is 4.39 times of the degradation rate of g-C3N4.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of organisms and marine environmental pollution control, specifically relating to a highly dispersed iron atom modified carbon-based nanomaterial based on *Ulva prolifera*, its preparation method and application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Long-residual herbicides pose significant environmental and non-target biosafety risks due to their residues in the environment. Current pesticide degradation methods are hampered by high operating costs and low efficiency, thus necessitating the development of efficient, environmentally friendly, and widely applicable pesticide residue degradation technologies.

[0004] The inventors discovered that visible light catalytic degradation of various pesticides can be achieved based on graphitic carbon nitride materials (g-C3N4), but the material has poor adsorption for the target pesticides and low removal efficiency, which limits its practical environmental application.

[0005] *Enteromorpha prolifera* is a type of green algae rich in nitrogenous compounds, widely distributed, abundant in sources, and exhibiting strong growth. In recent years, due to climate change and eutrophication, *Enteromorpha prolifera* has frequently experienced explosive proliferation in coastal areas of China during spring and summer, causing green tides and adversely affecting the aquatic environment and organisms. The situation is particularly severe in the waters near Qingdao, where, since its first outbreak in 2007, hundreds of thousands of tons have been harvested annually, impacting shipping lanes, disrupting the balance of aquatic ecosystems, and negatively affecting aquaculture and tourism. Currently, the development and utilization of *Enteromorpha prolifera* mainly focuses on food, feed, active substance extraction, and biomass energy. Research on its use in the preparation of high-efficiency catalysts is limited, resulting in low utilization rates and an inability to quickly solve environmental pollution problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera*, its preparation method, and its application. This invention utilizes waste *Ulva prolifera* to prepare a highly dispersed iron-modified carbon nitride material, which is then used for the catalytic degradation of high-risk herbicides. The nanomaterial prepared by this invention exhibits very high visible-light photocatalytic degradation efficiency for herbicides such as atrazine and simazine.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera*, comprising the following steps:

[0009] The biomass of *Ulva prolifera* is calcined at >700℃ in an inert atmosphere. The resulting material is mixed with graphite-type carbon nitride, and the mixture is thoroughly mixed and then heat-treated at 300-500℃ for 1-3 hours to obtain the final product.

[0010] In a second aspect, the present invention provides a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera* obtained by the above preparation method.

[0011] The *Ulva prolifera*-based highly dispersed iron-modified carbon-based nanomaterials of the present invention exhibit photocatalytic degradation of herbicides and can be used as catalysts. Therefore, a third aspect of the present invention provides the application of the aforementioned *Ulva prolifera*-based highly dispersed iron-modified carbon-based nanomaterials in a catalyst, wherein the catalyst exhibits photocatalytic degradation of herbicides.

[0012] The beneficial effects of this invention are as follows:

[0013] The present invention discloses a method for preparing highly dispersed iron atom modified carbon-based nanomaterials based on Ulva prolifera. The raw material Ulva prolifera is inexpensive and widely available. The biomass carbon-based material with high specific surface area is prepared by one-step high-temperature pyrolysis. After mixing with g-C3N4 and heat treatment, the material is obtained. The preparation method is simple, efficient, time-saving, labor-saving, environmentally friendly and energy-saving. Moreover, the simple preparation method has the potential for large-scale production and is conducive to promotion and application.

[0014] This invention successfully prepared highly dispersed iron-modified carbon-based nanomaterials based on *Ulva prolifera* and g-C3N4, which have the advantages of large specific surface area and high efficiency in degrading herbicides. For the herbicide atrazine, the degradation efficiency can reach nearly 80% in 10 minutes, with a degradation rate of 0.13112 min. -1 It has a degradation rate 4.39 times that of g-C3N4; for herbicides such as atrazine and cypermethrin, the degradation efficiency can reach more than 90% in 10 minutes, which successfully solves the problems of low utilization rate and environmental pollution of seaweed, while greatly expanding the application range of graphite-type carbon nitride material g-C3N4, achieving two goals at once. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 SA Fe-CN, the material prepared in Example 1 of this invention 20 TEM photographs;

[0017] Figure 2 SA Fe-CN, the material prepared in Example 2 of this invention 10 TEM photographs;

[0018] Figure 3 SA Fe-CN, the material prepared in Example 1 of this invention 20 HAADF-STEM image;

[0019] Figure 4 SA Fe-CN, the material prepared in Example 2 of this invention 10 HAADF-STEM image;

[0020] Figure 5 HAADF-STEM image of NP Fe-CN5, the material prepared in Example 3 of this invention;

[0021] Figure 6 The material SA Fe-CN prepared for the embodiments of the present invention 10 SA Fe-CN 20 And XANES plots of the control sample on the Fe K-side;

[0022] Figure 7 The material SA Fe-CN prepared for the embodiments of the present invention 10 SA Fe-CN 20 and the FT k of the control sample 3 Weighted XANES plot;

[0023] Figure 8 This is a comparison chart of the materials prepared in the embodiments and comparative examples of the present invention and the degradation rate of atrazine herbicide by g-C3N4;

[0024] Figure 9 This is a comparison chart of the materials prepared in the embodiments and comparative examples of the present invention and the degradation rate of atrazine herbicide by g-C3N4;

[0025] Figure 10 SEM images of biomass-based carbon materials obtained from *Ulva prolifera* biomass at different calcination temperatures are shown. Among them, A is the SEM image of the material obtained by high-temperature calcination of *Ulva prolifera* biomass at 400℃ and under nitrogen protection for 2 hours, B is the SEM image of the material obtained by high-temperature calcination of *Ulva prolifera* biomass at 600℃ and under nitrogen protection for 2 hours, and C is the SEM image of the material obtained by high-temperature calcination of *Ulva prolifera* biomass at 800℃ and under nitrogen protection for 2 hours.

[0026] Figure 11 SA Fe-CN, the material prepared in Example 2 of this invention 10 Comparison of degradation rates of atrazine, simazine, cypermethrin, terbufos, and atrazine herbicides. Detailed Implementation

[0027] Given the limitations of existing g-C3N4 due to its poor adsorption and low herbicide removal rate, as well as the low utilization rate of Ulva prolifera, this invention proposes a Ulva prolifera-based highly dispersed iron atom modified carbon-based nanomaterial, its preparation method, and its application.

[0028] A typical embodiment of the present invention provides a method for preparing a highly dispersed iron atom-modified carbon-based nanomaterial based on *Ulva prolifera*, comprising the following steps:

[0029] The biomass of *Ulva prolifera* is calcined at >700℃ in an inert atmosphere. The resulting material is mixed with graphite-type carbon nitride, and the mixture is thoroughly mixed and then heat-treated at 300-500℃ for 1-3 hours to obtain the final product.

[0030] The inventive principle of this invention is as follows:

[0031] This invention significantly improves the photocatalytic performance of g-C3N4 by adjusting its band structure and increasing its specific surface area. Specifically, this invention obtains a biomass-based carbon material with a large specific surface area and a distinct porous structure through high-temperature calcination of *Ulva prolifera* biomass. This material is then combined with graphitic carbon nitride (g-C3N4), greatly increasing the specific surface area of ​​g-C3N4 and providing more active sites for degradation reactions, thus enhancing its adsorption performance and consequently improving photocatalytic performance. Simultaneously, *Ulva prolifera* contains a high Fe content (0.2–0.5 wt%). When the biomass-based carbon material is mixed with g-C3N4, Fe readily forms coordinate bonds with the N atoms in the g-C3N4 structure, promoting the delocalization of π electrons in g-C3N4 and further enhancing photocatalytic activity. In other words, iron (Fe) doping modulates the band structure of g-C3N4, significantly improving its photocatalytic performance. Furthermore, compared with other metal dopants, the material obtained from iron-doped g-C3N4 exhibits better environmental friendliness.

[0032] In some embodiments of this implementation, the high-temperature calcination temperature is 800°C. After calcination at temperatures above 700°C, the specific surface area of ​​the resulting biomass-based carbon material increases significantly, and it exhibits a distinct porous structure, thus improving its adsorption performance. Considering both production costs and calcination effects, a calcination temperature of 800°C was determined.

[0033] In some embodiments of this implementation, the high-temperature calcination time is 1-3 hours, preferably 2 hours.

[0034] In some embodiments of this implementation, the mass ratio of the obtained material to graphitic carbon nitride is 1:5-20, preferably 1:8-20, and more preferably 1:10. Within the mass ratio of 1:5-20, the higher the proportion of the obtained material, the better the catalytic degradation performance of the herbicide by the obtained nanomaterial. When the content of biomass-based carbon material is too low, the iron content in the obtained nanomaterial is low, affecting the catalytic performance of the nanomaterial. When the mass ratio of biomass-based carbon material to graphitic carbon nitride is greater than 1:5, the iron content in the obtained nanomaterial is high, and clusters appear, which are not entirely single atoms, also affecting the catalytic performance of the nanomaterial. Therefore, the mass ratio of biomass-based carbon material to graphitic carbon nitride should not exceed 1:5.

[0035] In some embodiments of this implementation, the present invention does not limit the specific method of mixing; as long as the material obtained after calcining *Ulva prolifera* is thoroughly mixed with graphite-type carbon nitride, it is acceptable. Thorough mixing facilitates the coordination and bonding of iron and nitrogen atoms during heat treatment. Preferably, the mixing process involves: placing the mixed material in an aqueous solution, ultrasonicating, stirring, centrifuging to remove the supernatant, drying to obtain a solid material, and then grinding the solid material into powder.

[0036] In some embodiments of this implementation, the ultrasound duration is 0.5-1.0 h, preferably 0.5 h.

[0037] In some embodiments of this implementation, the stirring time is 0.5-1.5 hours, preferably 1 hour.

[0038] In some embodiments of this implementation, the drying process involves a drying temperature of 30-50°C and a drying time of 10-14 hours; preferably, drying at 40°C for 12 hours.

[0039] In some embodiments of this implementation, the heat treatment is: heat treatment at 400°C for 2 hours.

[0040] In a second aspect, the present invention provides a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera* obtained by the above preparation method.

[0041] In some embodiments of this implementation, the Ulva-based highly dispersed iron atom modified carbon-based nanomaterial includes single-atom iron and a carbon nitride substrate, wherein the single-atom iron is coordinated with nitrogen atoms in the carbon nitride substrate.

[0042] In some embodiments of this implementation, in the Ulva-based highly dispersed iron atom modified carbon-based nanomaterials, the iron atoms and nitrogen atoms are 5-coordinated or 6-coordinated.

[0043] In some embodiments of this implementation, the valence state of iron atoms in the *Ulva prolifera*-based highly dispersed iron atom-modified carbon-based nanomaterials is Fe. δ+All are between +2 and +3.

[0044] A third aspect of the present invention provides the application of the above-mentioned Ulva-based highly dispersed iron atom modified carbon-based nanomaterials in a catalyst, wherein the catalyst has the function of photocatalytic degradation of herbicides.

[0045] In some embodiments of this implementation, the herbicide is a high-risk herbicide; more preferably, the high-risk herbicide includes, but is not limited to, atrazine, simazine, cypermethrin, terbufos, and atrazine.

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0047] Example 1

[0048] A method for preparing a highly dispersed iron atom-modified carbon-based nanomaterial based on *Ulva prolifera* includes the following steps:

[0049] The biomass of *Ulva prolifera* was calcined at 800℃ under nitrogen protection for 2 hours. The resulting material was mixed with graphitic carbon nitride at a mass ratio of 1:20, then added to water and sonicated for half an hour. The mixture was then stirred at room temperature for 1 hour, centrifuged to remove the supernatant, and dried at 40℃ for 12 hours. The resulting solid was ground into powder and then heat-treated at 400℃ for 2 hours to obtain the final product. The obtained material was labeled SAFe-CN. 20 .

[0050] Example 2

[0051] A method for preparing a highly dispersed iron atom-modified carbon-based nanomaterial based on *Ulva prolifera* includes the following steps:

[0052] The biomass of *Ulva prolifera* was calcined at 800℃ under nitrogen protection for 2 hours. The resulting material was mixed with graphitic carbon nitride at a mass ratio of 1:10, then added to water and sonicated for half an hour. The mixture was then stirred at room temperature for 1 hour, centrifuged to remove the supernatant, and dried at 40℃ for 12 hours. The resulting solid was ground into powder and then heat-treated at 400℃ for 2 hours to obtain the final product. The obtained material is labeled SAFe-CN. 10 .

[0053] Example 3

[0054] A method for preparing a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera* differs from Example 1 in that the mass ratio of the obtained material to graphitic carbon nitride is 1:5. The obtained material is labeled as NP Fe-CN5.

[0055] Comparative Example 1

[0056] A method for preparing a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera* differs from Example 1 in that the mass ratio of the obtained material to graphitic carbon nitride is 1:2. The obtained material is labeled as NP Fe-CN2.

[0057] Comparative Example 2

[0058] A method for preparing a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera* differs from Example 1 in that the mass ratio of the obtained material to graphitic carbon nitride is 1:1. The obtained material is labeled as NP Fe-CN1.

[0059] Performance testing

[0060] 1. Microscopic morphology and structure

[0061] The microstructure and structure of the materials prepared in Examples 1, 2, and 3, as well as Comparative Examples 1 and 2, were characterized by TEM.

[0062] from Figure 1 It can be seen that SA Fe-CN 20 No obvious *Ulva prolifera*-based biochar material was observed on the surface due to the low doping concentration. However, when the doping concentration was doubled, the prepared SA Fe-CN... 10 The material surface is loaded with biomass-based carbon materials.

[0063] The morphology of Fe atoms was confirmed using spherical aberration electron microscopy.

[0064] from Figure 3 and Figure 4 It can be seen that in SA Fe-CN 20 SA Fe-CN 10 In both materials, Fe is distributed as single atoms, without clusters or particles.

[0065] from Figure 5 It can be seen that in NP Fe-CN5 material, Fe is not distributed as single atoms, but rather Fe clusters appear. When the content of biomass-based carbon material is higher, i.e. NP Fe-CN2 and NP Fe-CN1 materials, the Fe clusters increase, and the performance of the herbicide catalytically degrading carbon-based nanomaterials modified with highly dispersed iron atoms based on Ulva lactuca is reduced.

[0066] Figure 10 SEM images of biomass-based carbon materials obtained from *Ulva prolifera* biomass at different calcination temperatures are shown. Image A shows the SEM image of the material obtained by calcining *Ulva prolifera* biomass at 400℃ for 2 hours under nitrogen protection; image B shows the SEM image of the material obtained by calcining *Ulva prolifera* biomass at 600℃ for 2 hours under nitrogen protection; and image C shows the SEM image of the material obtained by calcining *Ulva prolifera* biomass at 800℃ for 2 hours under nitrogen protection. The specific surface area of ​​the materials obtained at calcination temperatures of 400, 600, and 800℃ was measured to be 5.1658 m².2 / g, 5.3862m 2 / g and 61.3309m 2 / g. Through Figure 10 It can be seen that when the temperature is above 700℃, the specific surface area of ​​biomass-based carbon materials increases significantly and they have obvious porous structures.

[0067] 2. Chemical valence state and bonding mode of Fe atoms in Ulva prolifera-based highly dispersed iron atom modified carbon-based nanomaterials

[0068] Synchrotron radiation analysis was used to determine the chemical valence state and bonding mode of Fe atoms in the material.

[0069] from Figure 6 It can be seen that Fe in both materials δ+ All are between +2 and +3.

[0070] EXAFS fitting was used to analyze the bonding mode of Fe atoms in *Ulva prolifera*-based highly dispersed iron-modified carbon nanomaterials. The EXAFS fitting parameters are as follows: The obtained XAFS data were processed in Athena (version 0.9.26) for background, leading edge, and trailing edge calibration. Then, Fourier transform fitting was performed in Artemis (version 0.9.26). k... 3 Weighted, k ranges from The range of R is use range of k and The R range was used to fit the sample. Four parameters, coordination number, bond length, Debye-Waller factor, and E0 shift (CN, R, ΔE0), were fitted without any parameters being fixed, and σ was set. 2 The obtained EXAFS fitting results are shown in Table 1.

[0071] Table 1 EXAFS Fitting Results

[0072]

[0073]

[0074] from Figure 7 It can be seen that in SA Fe-CN 10 SA Fe-CN 20 Neither of the two materials contains Fe-Fe bonds, and The peak at that location corresponds to an Fe-N bond, further confirming the presence of a single Fe atom, which forms a coordinate bond with the N atom in the carbon nitride material.

[0075] Based on the fitted data (Table 1), SA Fe-CN 20In the material, Fe-N is 5-coordinated, SA Fe-CN 10 The Fe-N group in the material is 6-coordinated.

[0076] Application Example 1

[0077] The materials obtained in Examples 1, 2, and 3, as well as Comparative Examples 1 and 2, and graphitic carbon nitride g-C3N4 were used for the visible light catalytic degradation of the herbicide atrazine.

[0078] The illumination wavelengths used were all visible light (λ>400nm). The photoreaction was carried out in a 150mL jacketed beaker equipped with circulating cooling water. A certain amount (30mg) of catalyst was added to 100mL of atrazine aqueous solution of a certain concentration (0.5ppm), and stirred in the dark to allow the catalyst and the target degradation product to reach adsorption-desorption equilibrium. After illumination, 0.5mL of the reaction solution was taken out at specific intervals, filtered through a membrane, and ready for sample injection and analysis. The elimination rate was determined based on the change in atrazine concentration during the illumination process. t C0 represents the initial concentration of the target analyte at the time of sampling.

[0079] Test results as follows Figure 8 , Figure 9 As shown. For the visible light catalytic degradation of the herbicide atrazine, SA Fe-CN 10 It exhibits the highest activity, achieving a degradation efficiency of nearly 80% within 10 minutes, with a degradation rate of 0.13112 min. -1 The degradation rate was 4.39 times that of g-C3N4. The visible light photocatalytic degradation activities of the materials obtained in Examples 1, 2, and 3, and Comparative Examples 1 and 2, compared to g-C3N4, for the herbicide atrazine, from highest to lowest, were: SA Fe-CN 10 >NP Fe-CN5>SA Fe-CN 20 >g-C3N4>NP Fe-CN2>NP Fe-CN1.

[0080] Application Example 2

[0081] The material obtained in Example 2 was used for the visible light catalytic degradation of the herbicides simazine, cypermethrin, terbutaline, or atrazine.

[0082] The difference between the detection method and application example 1 is that atrazine is replaced with simazine, cimetidine, terbutaline, or atrazine.

[0083] Test results as follows Figure 11 As shown, for the visible light catalytic degradation of herbicides atrazine and cypermethrin, SA Fe-CN 10 It exhibits higher activity, with a degradation efficiency of over 90% within 10 minutes.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a highly dispersed iron-modified carbon-based nanomaterial based on *Ulva prolifera*, characterized in that, The preparation method steps are as follows: The biomass of *Ulva prolifera* was calcined at >700℃ in an inert atmosphere. The resulting material was mixed with graphite-type carbon nitride. The mixture was then thoroughly mixed and heat-treated at 300-500℃ for 1-3 hours to obtain the final product. In the step of mixing the obtained material with graphite-type carbon nitride, the mass ratio of the material to graphite-type carbon nitride is 1:5-20; The *Ulva prolifera*-based highly dispersed iron atom modified carbon-based nanomaterial comprises single-atom iron and a carbon nitride substrate, wherein the single-atom iron is coordinated with nitrogen atoms in the carbon nitride substrate.

2. The preparation method according to claim 1, characterized in that, The high-temperature calcination temperature is 800℃.

3. The preparation method according to claim 1, characterized in that, The high-temperature calcination time is 1-3 hours.

4. The preparation method according to claim 3, characterized in that, The high-temperature calcination time is 2 hours.

5. The preparation method according to claim 1, characterized in that, In the step of mixing the material with graphite-type carbon nitride, the mass ratio of the material to graphite-type carbon nitride is 1:

10.

6. The preparation method according to claim 1, characterized in that, The mixing process specifically involves: placing the mixed material in an aqueous solution, ultrasonicating, stirring, centrifuging to remove the supernatant, drying to obtain a solid material, and then grinding the solid material into powder.

7. The preparation method according to claim 6, characterized in that, The ultrasound duration is 0.5-1.0 h.

8. The preparation method according to claim 7, characterized in that, The ultrasound duration is 0.5 h.

9. The preparation method according to claim 6, characterized in that, The stirring time is 0.5-1.5 h.

10. The preparation method according to claim 9, characterized in that, The stirring time is 1 hour.

11. The preparation method according to claim 6, characterized in that, The drying temperature is 30-50℃, and the drying time is 10-14 h.

12. The preparation method according to claim 11, characterized in that, The drying process involves drying at 40°C for 12 hours.

13. The preparation method according to claim 1, characterized in that, The heat treatment was performed at 400°C for 2 hours.

14. The *Ulva prolifera*-based highly dispersed iron atom modified carbon-based nanomaterials obtained by any of the preparation methods described in claims 1-13.

15. The *Ulva prolifera*-based highly dispersed iron-atom modified carbon-based nanomaterial as described in claim 14, characterized in that, The monatomic iron atom and nitrogen atom are either 5- or 6-coordinated.

16. The application of the Ulva prolifera-based highly dispersed iron atom modified carbon-based nanomaterials of claim 14 in the photocatalytic degradation of herbicides.

17. The application as described in claim 16, characterized in that, The herbicide in question is a high-risk herbicide.

18. The application as described in claim 17, characterized in that, The high-risk herbicides include atrazine, simazine, cypermethrin, terbufos, and atrazine.

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