Zero-oxidant-addition transition metal monatomic catalyst preparation method based on electron transfer pollutant degradation
By preparing N-doped carbon@transition metal single-atom catalysts, the electron transfer mechanism is used to reduce pollutants under zero oxidant conditions, the problem of limited catalytic activity in the traditional Fenton system in a low-oxygen environment is solved, and efficient and low-cost sewage treatment effect is achieved.
Patent Information
- Application Number
- CN202510636660.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-17
- Publication Date
- 2025-08-22
AI Technical Summary
The traditional Fenton system has limited catalytic activity in a low-oxygen environment, the degradation effect of electron-containing pollutants is not ideal, and the oxidant consumption is large and the long-term operation cost is high, making it difficult to achieve green and sustainable development.
The N-doped carbon@transition metal single-atom catalyst was prepared, and the electron transfer mechanism was used to reduce the pollutants under zero oxidant conditions. The catalyst was prepared by calcining by using ZIF-8 and g-C3N4 of doped metals.
Efficiently degrade a variety of pollutants under zero oxidant conditions, it has anti-environmental interference and reusable performance, reduces operating costs, and is suitable for sewage treatment in low-oxygen environments.
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Figure CN120515464A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of pollutant degradation and sewage purification, and relates to a method for preparing an N-doped C@transition metal single-atom catalyst that can degrade pollutants based on electron transfer without the need for an oxidant. Background Art
[0002] Fenton and Fenton-like reactions, as effective oxidation technologies for pollutant degradation, typically rely on oxidants such as H₂O₂, persulfate, periodate, and peracetic acid. However, traditional Fenton systems suffer from high oxidant consumption and long-term operating costs, making them difficult to achieve green and sustainable development. Therefore, finding ways to efficiently degrade pollutants using low-energy, low-oxidant, or even zero-oxidant conditions is an important research direction.
[0003] The surfaces of the reported dual-reaction-center catalysts contain both electron-rich and defective regions. During pollutant degradation, electron-donating pollutants transfer electrons to the electron-deficient regions. These electrons then migrate along the metal-oxygen-carbon bridges on the catalyst surface to the electron-rich regions, activating dissolved oxygen to form reactive oxygen species that oxidize the pollutants, achieving degradation. This mechanism effectively overcomes the rate limitations of traditional Fenton systems. However, catalytic activity is limited in low-oxygen environments, making degradation less effective for pollutants containing electron acceptors.
[0004] Based on this, the present invention prepares a new type of N-doped carbon@transition metal single-atom catalyst, which realizes the degradation of pollutants by relying on electron transfer mechanism under zero oxidant conditions by constructing electron-deficient centers. It has universal applicability, is suitable for low-oxygen environments, is resistant to environmental interference, and can degrade pollutants for a long time and repeatedly. Summary of the Invention
[0005] The purpose of the present invention is to achieve efficient degradation of multiple pollutants under zero-oxidant conditions. A preparation method for an N-doped carbon@transition metal single-atom catalyst rich in electron-deficient centers is proposed. The catalyst is prepared by calcination using ZIF-8 and metal-doped g-C3N4, and the reaction conditions are simple.
[0006] The technical solution of the present invention is:
[0007] A method for preparing a transition metal single-atom catalyst for pollutant degradation based on electron transfer without adding an oxidant, comprising the following steps:
[0008] (1) Zn(NO3)2·6H2O and 2-methylimidazole in a molar ratio of 1:(4-6) were dissolved in methanol, respectively, and the metal@g-C3N4 powder was dispersed in the Zn salt solution. The 2-methylimidazole solution and the Zn salt solution were mixed and then transferred to a high-pressure reactor and kept at 110-150°C for 1-4 hours. After the reaction was completed, the reaction was centrifuged, washed, and dried to obtain a ZIF-8 / g-C3N4 precursor;
[0009] (2) The prepared ZIF-8 / g-C3N4 precursor was reacted at 600-900°C for 2-4h in an inert gas atmosphere to obtain a N-doped C@transition metal single atom catalyst;
[0010] Furthermore, in step (1), the amount of metal@g-C3N4 added is 1-20 mg.
[0011] Furthermore, in step (1), the metal@thiourea complex and a nitrogen-containing precursor are calcined in a muffle furnace to produce metal@g-C3N4. The nitrogen-containing precursor includes but is not limited to urea, melamine, thiourea, or cyanamide. The calcination temperature is 400-650°C for 2-5 hours.
[0012] Furthermore, in step (1), the metal in metal@g-C3N4 includes but is not limited to Fe, Mn, Co, and Cu.
[0013] Furthermore, in the step (1), the metal loading amount in metal@g-C3N4 is 0.5% to 3%.
[0014] Furthermore, the metal@thiourea complex in step (1) is synthesized as follows: a metal salt is dissolved in a near-boiling isopropanol solution, thiourea is added, the resulting mixture is kept constant at 90°C for 1 hour, the precipitate is cooled to a temperature, centrifuged, and then recrystallized from a hot acetone solution to finally obtain the metal@thiourea complex. The molar ratio of the metal ion to the thiourea is 1:(3-5).
[0015] Furthermore, the N-doped C@transition metal catalyst is directly dispersed into the pollutant solution or loaded into the polyurethane foam without adding an oxidant to carry out the degradation reaction.
[0016] Beneficial effects of the present invention:
[0017] The present invention synthesizes an N-doped C@transition metal single-atom catalyst. For the first time, the catalyst uses only its electron-deficient structure to efficiently degrade and mineralize electron-donating pollutants such as ciprofloxacin, levofloxacin, tetracycline, sulfamethoxazole, bisphenol A, p-chlorophenol, and phenol, and electron-accepting pollutants such as p-nitrophenol, metronidazole, and p-nitrobenzoic acid, by electron transfer without adding an oxidant, requiring no illumination or electricity, and without resorting to dissolved oxygen. The catalyst has strong resistance to interference from coexisting ions in water, excellent reusability, and can be applied to actual sewage treatment, thereby reducing operating costs and achieving truly green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 Scanning and transmission electron microscopy images of N-doped C@Mn;
[0019] Figure 2 This is the removal rate diagram of different types of pollutants degraded by N-doped C@Mn without adding oxidant;
[0020] Figure 3 This is the pollutant removal rate diagram of N-doped C@Mn degradation under N2 saturation conditions;
[0021] Figure 4 The open circuit voltage change curve of glassy carbon electrode coated with N-doped C@Mn after adding different pollutants;
[0022] Figure 5 This is the scanning electron microscopy image of N-doped C@Mn loaded into polyurethane foam;
[0023] Figure 6 The removal rate of ciprofloxacin degradation by N-doped C@Mn loaded on polyurethane foam without adding oxidant through flow reactor;
[0024] Figure 7 Figure 3. Degradation of (a) bisphenol A and (b) p-nitrophenol removal rates of recycled polyurethane foam loaded with N-doped C@Mn by flow reactor.
[0025] Figure 8 This is the removal rate diagram of different types of pollutants degraded by N-doped C@Fe without adding oxidant; DETAILED DESCRIPTION
[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0027] In order to further understand the present invention, the present invention will be further described with reference to the accompanying drawings and embodiments.
[0028] Example 1
[0029] This embodiment provides a method for preparing a N transition metal single atom catalyst for pollutant degradation based on electron transfer without adding an oxidant, and the steps are as follows:
[0030] (1) Preparation of Mn@thiourea complex: Heat 25 mL of isopropanol to 90°C, add 6.2 g of manganese nitrate tetrahydrate, dissolve it, then add 7.61 g of thiourea and stir for 1 hour. After the reaction is complete, filter the mixture and dissolve the collected powder in acetone at 70°C and stir for 2 hours. After the reaction is complete, filter the mixture and obtain the Mn@thiourea complex.
[0031] Preparation of Mn@g-C3N4: 33.0 mg of Mn@thiourea complex and 6.0 g of urea were mixed evenly, placed in a crucible, and calcined at 550 °C in a muffle furnace for 4 h to obtain Mn@g-C3N4.
[0032] Preparation of ZIF-8 / Mn@g-C3N4: 7.5mmol C4H6N2 was dissolved in 15mL methanol, recorded as solution A; 1.5mmol Zn(NO3)2·6H2O was dissolved in 30mL methanol, and then 5mg Mn@g-C3N4 was added. Ultrasonication was performed for 10min, recorded as solution B. Solution A was poured into solution B, stirred for 10min, and then transferred to a reactor. After the reaction, centrifugation, washing, and drying were performed to obtain the ZIF-8 / g-C3N4 precursor.
[0033] The ZIF-8 / g-C3N4 was placed in a porcelain boat and calcined in a tube furnace under N2 atmosphere at 800℃ for 2h to obtain the N-doped C@Mn catalyst.
[0034] The prepared NC@Mn was analyzed by scanning and transmission electron microscopy. Figure 1 It can be seen from the figure that the prepared NC@Mn has a polyhedral morphology with pores on the surface.
[0035] (2) Degradation experiment: 4.5 mg of N-C@Mn was weighed and dispersed into 45 mL of a 10 ppm pollutant solution. Approximately 3.0 mL of the supernatant was collected at regular intervals and centrifuged. The residual pollutant concentration in the supernatant was measured using a UV-visible spectrophotometer or high-performance liquid chromatography.
[0036] Depend on Figure 2 Yes, the prepared NC@Mn can quickly degrade a variety of pollutants containing electron-donating and electron-withdrawing groups; Figure 3 It can be seen that after the N2 was passed to remove the dissolved oxygen in the solution, the pollutant degradation performance of NC@Mn remained basically unchanged, eliminating the effect of dissolved oxygen. Figure 4The open circuit voltage curve shows that after the addition of pollutants, the potential of the glassy carbon electrode covered with NC@Mn decreases to varying degrees, indicating that there is electron transfer between the pollutants and NC@Mn.
[0037] (3) Online flow reactor for pollutant degradation: 100 mg of NC@Mn was dispersed in water, then immersed in 12 pieces of polyurethane (PU) foam and dried. Figure 5 It can be seen that the catalyst is densely loaded on the PU. During online degradation, the pollutant solution flows from bottom to top through the PU at a flow rate of 120 mL / h. The degradation solution is taken from the upper layer at regular intervals to measure the residual pollutant concentration.
[0038] Depend on Figure 6 Yes, 100mg of NC@Mn@PU successfully degraded a 10ppm ciprofloxacin solution, achieving a ciprofloxacin removal rate of over 90%. After 10 hours, the catalyst-loaded PU was rinsed with ethanol to remove degradation intermediates adsorbed on the surface. After drying, the ciprofloxacin degradation performance was restored.
[0039] Furthermore, the NC@Mn@PU after degradation of ciprofloxacin was recovered, washed with ethanol, and dried. Figure 7 a Yes, the NC@Mn@PU system has excellent bisphenol A degradation performance. After the second recovery and washing, the NC@Mn@PU system degrades 4-nitrophenol. Figure 7 b Yes, it has excellent 4-nitrophenol degradation performance, indicating that NC@Mn can be used for a long time and repeatedly.
[0040] Example 2
[0041] This embodiment provides a method for preparing a N transition metal single atom catalyst for pollutant degradation based on electron transfer without adding an oxidant, and the steps are as follows:
[0042] (1) The preparation method of Fe@thiourea complex is shown in Example 1, and the Fe source is ferric nitrate 9 hydrate.
[0043] The preparation method of Fe@g-C3N4 is shown in Example 1: 20 mg of Fe@thiourea complex and 6.0 g of urea are mixed and calcined.
[0044] Preparation of ZIF-8 / Fe@g-C3N4: Dissolve 7.5 mmol of dimethylimidazole in 15 mL of methanol, labeled Solution A; dissolve 1.5 mmol of Zn(NO3)2·6H2O in 30 mL of methanol, labeled Solution B. Add 10 mg of Fe@g-C3N4, pour Solution A into Solution B, stir for 10 minutes, and transfer to a reactor incubated at 120°C for 4 hours. After the reaction, centrifuge, wash, and dry to obtain the ZIF-8 / Fe@g-C3N4 precursor. Place the ZIF-8 / Fe@g-C3N4 in a porcelain boat and calcine in a tube furnace at 800°C for 2.5 hours under a nitrogen atmosphere to obtain the N-doped C@Fe catalyst.
[0045] (2) Degradation experiment: 4.5 mg of NC@Fe was weighed and dispersed into 45 mL of a 10 ppm pollutant solution. Approximately 3.0 mL of the supernatant was collected at regular intervals and centrifuged. The residual pollutant concentration in the supernatant was measured using a UV-visible spectrophotometer or high-performance liquid chromatography.
[0046] Depend on Figure 8 Yes, the prepared NC@Fe can quickly degrade a variety of pollutants without adding oxidants, turning on lights, or applying electricity;
[0047] Example 3
[0048] This embodiment provides a method for preparing a N transition metal single atom catalyst for pollutant degradation based on electron transfer without adding an oxidant, and the steps are as follows:
[0049] (1) The preparation method of Co@thiourea complex is shown in Example 1, and the Co source is hexahydrated cobalt nitrate.
[0050] The preparation method of Co@g-C3N4 is shown in Example 1: 20 mg of Co@thiourea complex and 6.0 g of urea are mixed and calcined.
[0051] Preparation of ZIF-8 / Co@g-C3N4: Dissolve 5 mmol of dimethylimidazole in 15 mL of methanol, labeled Solution A; dissolve 1.0 mmol of Zn(NO3)2·6H2O in 30 mL of methanol, labeled Solution B. Add 30 mg of Co@g-C3N4 and sonicate for 10 minutes. Pour Solution A into Solution B, stir for 10 minutes, and transfer to a reactor incubated at 120°C for 4 hours. After the reaction, centrifuge, wash, and dry to obtain the ZIF-8 / Co@g-C3N4 precursor. Place the ZIF-8 / Co@g-C3N4 in a porcelain boat and calcine in a tube furnace at 800°C for 2 hours in a N2 atmosphere to obtain the N-doped C@Co catalyst.
[0052] (2) Degradation experiment: 4.5 mg of NC@Co was weighed and dispersed into 45 mL of 10 ppm pollutant solution. Approximately 3.0 mL of the supernatant was collected at regular intervals and centrifuged. The residual pollutant concentration in the supernatant was measured using a UV-visible spectrophotometer or high-performance liquid chromatography.
[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, and modifications made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.
Claims
1. A method for preparing a transition metal single-atom catalyst for pollutant degradation based on electron transfer without adding an oxidant, characterized in that: The following steps are involved: (1) Zn(NO3)2·6H2O and 2-methylimidazole in a molar ratio of 1:(4-6) were dissolved in methanol, and the metal@g-C3N4 powder was dispersed in the Zn salt solution. The C4H4N2 solution and the Zn salt solution were mixed and transferred to a reactor. The mixture was kept at 110-150°C for 1-4 hours. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain a ZIF-8 / g-C3N4 precursor. (2) The prepared ZIF-8 / g-C3N4 precursor was reacted in an inert gas atmosphere at 600-900°C for 2-4h to obtain N-doped C@transition metal single atom catalyst.
2. The method for preparing an N-doped C@transition metal single-atom catalyst for degrading pollutants based on electron transfer without an oxidant according to claim 1, characterized in that: The amount of metal@g-C3N4 required is 1-20 mg.
3. The method for preparing an N-doped C@transition metal single-atom catalyst for pollutant degradation based on electron transfer without the need for an oxidant according to claim 1, characterized in that: Metal@g-C3N4 is prepared by calcining a metal@thiourea complex with urea, melamine, thiourea, or cyanamide in a muffle furnace at a temperature of 400-650°C for 2-5 hours.
4. The method for preparing an N-doped C@transition metal single-atom catalyst for degrading pollutants based on electron transfer without an oxidant according to claim 1, characterized in that: The metals in metal@g-C3N4 are Fe, Mn, Co, Cu, etc., and the loading amount is 0.5% to 3.0%.
5. The method for preparing an N-doped C@transition metal single-atom catalyst for degrading pollutants based on electron transfer without the need for an oxidant according to claim 1, characterized in that: The metal@thiourea complex is prepared by dissolving a metal salt in near-boiling isopropanol, adding thiourea, and heating the resulting mixture at 90°C for 1 hour. The precipitate is cooled, centrifuged, and then recrystallized from hot acetone to obtain the metal@thiourea complex. The molar ratio of the metal ion to thiourea is 1:(3-5).
6. The method for preparing an N-doped C@transition metal single-atom catalyst for degrading pollutants based on electron transfer without the need for an oxidant according to claim 1, characterized in that: In the present invention, when N-doped C@transition metal single atoms degrade pollutants, no oxidants such as persulfate, H2O2, PAA, etc. are added, no light is required, and no external power supply is required. Pollutants can be efficiently degraded by relying on electron transfer.
7. The method for preparing an N-doped C@transition metal single-atom catalyst for degrading pollutants based on electron transfer without the need for an oxidant according to claim 1, characterized in that: The prepared N-doped C@transition metal catalyst is dispersed into a pollutant solution or loaded into polyurethane foam for degradation reaction. The catalyst has good reusability, resistance to environmental interference and long-term pollutant degradation performance.
8. The method for preparing an N-doped C@transition metal single-atom catalyst for degrading pollutants based on electron transfer without the need for an oxidant according to claim 1, characterized in that: It has good degradation performance for both electron-donating and electron-withdrawing pollutants.