Proton coupling electron transfer method for resource removal of organic pollutants

Abstract

The invention provides a proton coupling electron transfer method for resource removal of organic pollutants. The method comprises the following steps: S1, generating high-valence metal oxygen species with selective oxidation characteristics in situ; s2, determining optimal generation conditions of high-valence metal oxygen species; s3, determining an optimal condition for initiating a proton coupling electron transfer reaction by the high-valence metal oxygen species; s4, determining a key intermediate of a proton coupled electron transfer reaction initiated by the high-valence metal oxygen species; and S5, removing the organic pollutants in a recycling manner based on a proton coupling electron transfer method. By utilizing the method, the conversion of an organic pollutant water treatment mode from pollution control to resource recovery can be realized, a sustainable path is provided for resource recovery of organic pollutants, and low-carbon water purification can be realized.

Description

Technical Field

[0001] The present invention relates to the fields of environmental protection and sewage treatment, and in particular to a proton-coupled electron transfer method for resource-based removal of organic pollutants. Background Art

[0002] Increasingly severe water pollution and water scarcity pose a global threat to the sustainable development of economies, societies, and ecosystems, driving innovation in water purification and reuse solutions. Since the early twentieth century, chemical oxidation has been a paradigm shift in eliminating waterborne diseases and water pollution. The development of chemical oxidation processes has focused on improving degradation efficiency to eliminate pollutants and meet stringent wastewater discharge standards. However, the vast resources contained in wastewater contrast sharply with the large amount of energy required for treatment, driving a shift in water treatment from pollution control to resource recovery and carbon footprint reduction, and posing a significant challenge to traditional, energy-intensive oxidation processes. Therefore, a new chemical oxidation model is urgently needed to shift the carbon evolution pathway from molecular fragmentation to resource recovery while controlling pollution. In a typical chemical oxidation process, the chemical bonds of the pollutants are broken down with the help of external energy to produce smaller molecules and / or carbon dioxide, which is a mineralization process. It is conceivable that a potential strategy for resource recovery of dissolved organic pollutants is to convert them into high molecular weight polymers, which usually have low solubility and can be separated from water by adsorption, filtration or flotation for potential chemical refining and power generation. The ideal polymerization reaction does not require the decomposition of the carbon skeleton of the pollutant, which not only reduces the chemical or energy input, but also retains the contained chemical energy. For example, in a traditional oxidation system, the conversion of aniline into carbon dioxide requires the consumption of at least 7.75 equivalents of oxygen and the release of about 3390 kJmol into the water. -1 The internal energy is about 3390kJmol -1 The polymerization of aniline to tetramers theoretically requires only one equivalent of oxygen. Although the polymerization potential of various oxidative systems has been re-examined recently, the success has been very limited, which has prompted more efforts to explore how to divert the oxidative pathway from degradation to polymerization. Here, we focused our research on the proton-coupled electron transfer method, thus filling the above-mentioned knowledge gap and proving that the removal pathway of pollutants is achieved through the polymerization of organic pollutants. The proton-coupled electron transfer method can not only achieve the transformation of the water treatment mode of organic pollutants from pollution control to resource recovery, but also help environmental engineers understand the inherent mechanism characteristics of the water treatment mode transformation, and thus better regulate the carbon evolution pathway to achieve resource recovery and sustainable water purification. At present, the methods for achieving resource recovery of organic pollutants still cannot meet the requirements, which limits the development and application of new and lower-cost wastewater resource treatment technologies. In addition, compared with phenol pollutants, the difficulty in removing aniline and thiophene pollutants stems from the stability of their chemical structure and the complexity of their by-products, requiring strong oxidation conditions and targeted design of treatment processes. Summary of the Invention

[0003] Technical problem to be solved: The present invention provides a proton-coupled electron transfer method for resource-based removal of organic pollutants. This method can achieve the transformation of the organic pollutant water treatment mode from pollution control to resource recovery, providing a sustainable path for the resource recovery of organic matter.

[0004] Technical solution: A proton-coupled electron transfer method for resource-based removal of organic pollutants comprises the following steps: S1. In situ generation of high-valent metal oxygen species with selective oxidation properties; S2. Determine the optimal conditions for the formation of high-valent metal oxygen species; S3. Determine the optimal conditions for proton-coupled electron transfer reactions initiated by high-valent metal oxygen species; S4. Identify the key intermediates in proton-coupled electron transfer reactions initiated by high-valent metal oxygen species; S5. Resource-based removal of organic pollutants based on proton-coupled electron transfer method. Preferably, the in-situ generation of high-valent metal oxygen species with selective oxidation properties in S1 comprises the following steps: S11. Determining that the transition metal oxide catalyst is any one of a nickel-based oxide, a copper-based oxide, or a cobalt-based oxide; S12. Determine either monopersulfate or peroxydisulfate for the generation of high-valent metal oxygen species. Preferably, the optimal generation conditions for the high-valent metal oxygen species in S2 include the following conditions: Condition 1. Catalyst concentration in the reaction system; Condition 2. Oxidant concentration in the reaction system; Condition 3. Target pollutant concentration in the reaction system; Condition 4. Buffer concentration in the reaction system and kinetic apparent rate constant. Preferably, the optimal conditions for the high-valent metal oxygen species in S3 to induce the proton-coupled electron transfer reaction include the following conditions: Condition 1. Active H + concentration; Condition 2. Kinetic apparent rate constant k; Condition 3. The logarithm of the apparent kinetic rate constant k, i.e. lgk; Condition 4. Fit the logarithmic apparent rate constant lgk to obtain a fitting curve, and then generate different fitting curves according to different proton activities: when the proton activity is low, the logarithmic apparent rate constant increases linearly; when the proton activity is high, the logarithmic apparent rate constant decreases linearly; Condition 5. Based on the fitting curve obtained in Condition 4, the optimal rate of the pollutant under a specific proton activity condition is obtained. Preferably, determining the key intermediate of the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species in S4 comprises the following steps: S41. Determine the removal rate of organic pollutants by spectrophotometry; S42. Determine the proportion of organic pollutants removed through cross-linking and polymerization pathways using total chemical oxygen demand; S43. Determine the ratio of polymerization products by matrix-assisted laser desorption ionization time-of-flight mass spectrometry; S44. Determine the ratio of cross-linked products by liquid chromatography-mass spectrometry; S45. The key intermediate in the proton-coupled electron transfer reaction was identified as phenoxy radical. Preferably, the high-valent metal oxygen species with selective oxidation characteristics in S5 is determined by S1, the optimal generation conditions of the high-valent metal oxygen species are determined by S2, the optimal conditions for the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species are determined by S3, and the key intermediates of the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species are determined by S4. Preferably, the nickel-based oxide in S11 is NiO, the copper-based oxide is CuO, and the cobalt-based oxide is Co3O4. Preferably, the monopersulfate in S12 is potassium hydrogen persulfate, and the peroxydisulfate is potassium persulfate. Beneficial effects: The present invention has the following advantages: 1. The method provided in this invention can achieve a shift in the water treatment model for organic pollutants from pollution control to resource recovery, changing the carbon evolution pathway of organic pollutants from degradation and mineralization (producing carbon dioxide and water) to oxidative polymerization (producing polymers). Oxidative polymerization-driven pollutant removal provides a sustainable path for the resource recovery of aniline and thiophene pollutants, contributing to low-carbon water purification. 2. The method provided in the present invention can be widely used in the resource treatment of organic wastewater, including low-cost treatment of soil leachate contaminated by organic matter, and low-cost treatment of organic wastewater generated by coking plants, gas generation stations, pharmaceutical plants and synthetic fiber plants. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a cross-linked product (cross-linked polyaniline) obtained by proton-coupled electron transfer method; Figure 2 It is a cross-linked product (cross-linked polythiophene) obtained by a proton-coupled electron transfer method; Figure 3 It is a polymer product (polyaniline) obtained by a proton-coupled electron transfer method; Figure 4 It is a polymer product (polythiophene) obtained by a proton-coupled electron transfer method; Figure 5 This is the matrix-assisted laser desorption / ionization time-of-flight mass spectrum of the polymerization product (polyaniline); Figure 6 This is the matrix-assisted laser desorption / ionization time-of-flight mass spectrum of the polymerization product (polythiophene); Figure 7 is the liquid chromatography-mass spectrum of the cross-linked product (cross-linked polyaniline); Figure 8 This is the liquid chromatography-mass spectrum of the cross-linked product (cross-linked polythiophene). DETAILED DESCRIPTION The present invention will be further described below in conjunction with examples, which are provided to explain the present invention and are not limited to the following examples: In an embodiment, a proton-coupled electron transfer method for resource-based removal of organic pollutants includes the following five steps: S1. in situ generation of high-valent metal oxygen species with selective oxidation properties; S2. Determine the optimal conditions for the formation of high-valent metal oxygen species; S3. Determine the optimal conditions for proton-coupled electron transfer reactions initiated by high-valent metal oxygen species; S4. Identify the key intermediates in proton-coupled electron transfer reactions initiated by high-valent metal oxygen species; S5. Resource-based removal of organic pollutants based on proton-coupled electron transfer method. The in-situ generation of high-valent metal oxygen species with selective oxidation properties in S1 comprises the following steps: 1) Synthesis of NiO: 0.5 mol of NiCl2·6H2O was dissolved in 100 mL of deionized water. The pH was then adjusted to 9.0 by adding ammonia solution (25.0–28.0%), and the solution was heated to 90°C for 30 minutes. Subsequently, 220 mL of 0.50 M NaOH solution was slowly added continuously with stirring. The resulting mixture was then stirred at 90°C for 2.0 hours and centrifuged to obtain a β-Ni(OH)2 precursor. The precursor was then washed three times with ethanol and deionized water and then freeze-dried. The β-Ni(OH)2 precursor was then calcined at 450°C for 5.0 hours in N2 at a heating rate of 3.0°C / min. 2) Synthesis of CuO: 0.1 mol CuCl2 was dissolved in 100 mL of deionized water, and an ammonia solution (25.0–28.0%) was added to adjust the pH to 9.0. Then, 200 mL of 0.1 M NaOH solution (0.1 M) was slowly added. The mixture was stirred for 2 hours to form a blue precipitate of Cu(OH)2. Subsequently, the Cu(OH)2 precipitate was centrifuged, washed three times with deionized water, freeze-dried, and ground. The dried Cu(OH)2 was further calcined in air at 180°C for 2 hours to obtain CuO. 3) Co3O4 was purchased from Shanghai Maijin Biotechnology Co., Ltd. Table 1. In situ generation of high-valent metal oxygen species with selective oxidation properties name symbol High-valent nickel Ni(IV)=O High-valent copper Cu(III) High-valent cobalt Co(IV)=O The optimal generation conditions for high-valent metal oxide species in S2 include the following conditions: Condition 1. Catalyst concentration in the reaction system; Condition 2. Oxidant concentration; Condition 3. Target pollutant concentration; Condition 4. Buffer concentration; Condition 5. Kinetic apparent rate constant (k). The optimal generation conditions for the above-mentioned high-valent metal oxide species can be determined through the following experimental steps: CuIII is inherently unstable and prone to decomposition in aqueous solutions. However, it can form a stable CuIII-periodate complex by coordinating with periodate (IO4-). This complex has a characteristic absorption peak at 420nm. Experiments have shown that the introduction of periodate into the CuO / PMS system significantly enhances the absorbance at 420nm, which continues to rise over time, confirming that CuIII is the key active species. After kinetic experiments, it was verified that the optimal conditions for the generation of high-valent metal oxygen species were a catalyst (CuO, NiO, Co3O4) concentration of 0.2 g / L, an oxidant (potassium persulfate, potassium hydrogen persulfate) concentration of 0.3 mmol / L, a target pollutant concentration of 0.15 mmol / L, and a buffer (borate) concentration of 0.1 mol / L, as shown in Tables 2 and 3. Table 2. Specific reaction parameters of high-valent metal oxygen species Table 3. Optimal conditions for the generation of high-valent metal oxide species Before fitting, first select any kinetic experimental data and determine the correlation coefficient R21 (first order: -ln(C / C0) = R 2 1t), C0 / C and time (min) were fitted to determine the correlation coefficient R 2 2(Secondary: C0 / C=R 2 2t), select the correlation coefficient close to 1. The apparent kinetic rate constant (k) was determined by first-order fitting or second-order fitting. In order to determine the kinetic model that best fits the kinetic data, a linear correlation coefficient (R 2 ): For pseudo-first-order kinetics, the rate constant was determined by fitting a linear regression between ln(C / C0) and time (min) using the following formula: lnC=lnC0-kt; For second-order kinetics, the rate constant was determined by fitting a linear regression between C0 / C and time (min) using the following formula: Where C0 is the initial concentration of the experimental pollutant, unit is mol / L, C t is the concentration of the experimental pollutant at time t that changes with time, in mol / L, and k is the experimental kinetic apparent rate constant. For CuO, the pseudo-first-order kinetic model was determined to be the most suitable for the kinetic fitting. For NiO and Co3O4, the second-order kinetic model was determined to be the most suitable for kinetic fitting. Wherein, determining the optimal conditions for the proton-coupled electron transfer reaction induced by the high-valent metal oxygen species in S3 comprises the following steps: S31. Determine proton activity: Determine the active H in the system through acid-base titration experiments +concentration. Before the titration experiment began, the pH electrode was calibrated at three points using standard buffer solutions with pH values of 4.00, 6.86, and 9.18 to ensure measurement accuracy. 30 mg of metal oxide samples (CuO, NiO, Co3O4) were dispersed in 10 mL of 0.1 M KNO3 solution for titration, and 0.5 mL of hydrochloric acid (0.025 M) solution was added at the initial stage of the titration. Subsequently, a linear titration mode was adopted to add KOH solution (0.025 M) in increments of 0.05 mL / time, with an interval of 60 seconds between each addition until the pH value of the system reached 11.5. During the titration process, the proton concentration in the solution can be accurately determined by the pH meter, and the amount of alkali solution added recorded by the system can accurately reflect the changes in the total amount of protons in the system. The difference between the above two parameters is the net excess or deficiency of surface protons. This difference directly reflects the dynamic changes in the density of hydroxyl groups on the surface of the metal oxide; S32. Determine the apparent kinetic rate constant (k): This can be obtained using the first-order or second-order kinetic formula. S33. Determine the logarithmic apparent rate constant (k), i.e., lgk; S34. Fit the logarithm of the apparent kinetic rate constant, lgk, using lgk as the y-value and the target proton activity as the x-value. Use Origin to obtain the fitted curve. S35. Different proton activities correspond to different fitting curves: when the proton activity is low, the logarithmic value of the apparent kinetic rate constant increases linearly; when the proton activity is high, the logarithmic value of the apparent kinetic rate constant decreases linearly; S36. Based on the fitting curve obtained in S35, the optimal rate of the pollutant under a specific proton activity condition is obtained. Wherein, determining the key intermediate of the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species in S4 comprises the following steps: S41. Determine the removal rate of organic pollutants by spectrophotometry (0.15 mM before removal, removal rate 100%); S42. Determine the proportion of organic pollutants removed by cross-linking and polymerization pathways by total chemical oxygen demand: Mix the sample with a COD reagent consisting of 2.25 mL of Ag2SO4 solution (10 g L -1 , dissolved in concentrated H2SO4), 0.75mL K2Cr2O7 solution (0.5M, dissolved in 10% v / v H2SO4 / H2O) and 0.2mL HgSO4 solution (240g L -1 , dissolved in 10% v / v H2SO4 / H2O). The mixture was heated for 20 minutes and then allowed to cool naturally. The resulting clear solution was analyzed by UV-visible spectrophotometry at a wavelength of 610 nm for detection; S43. Determine the ratio of polymerization products by matrix-assisted laser desorption ionization time-of-flight mass spectrometry: Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS): The coupling and polymerization products on the catalyst surface can be eluted with ethanol and toluene, respectively, wherein the coupling product is eluted with ethanol and the polymerization product is eluted with toluene. After the reaction is completed, the catalyst is collected and washed with toluene and ethanol, respectively. Subsequently, the product dissolved in toluene is evaporated to eliminate the solvent, thereby producing a soft solid for further characterization. The accumulated soft polymer solid is dissolved in tetrahydrofuran and characterized by matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF-MS); S44. Determination of the proportion of cross-linked products by liquid chromatography-mass spectrometry: The ethanol-dissolved product (i.e., the cross-linked product) was analyzed by liquid chromatography-mass spectrometry (LC-MS) using a heated electrospray ionization source and a UHPLC system. LC-MS analysis was performed using a Waters Xevo G2QTOF mass spectrometer. The target compounds were separated using a C18 column (ACQUITY BEH C18, 100 mm × 2.1 mm ID, 1.7 μm, Waters Co., USA) in positive ionization mode. Mobile phase A consisted of acetonitrile, and mobile phase B consisted of deionized water containing 0.1% formic acid. The mobile phase gradient separation program was as follows: 0–1.0 min, 5% A; 1–4.0 min, 5%–30% A; 4.0–6.0 min, 30% A–70% A; 6.0–10.0 min, 70% A–80% A; 10.0–13.0 min, 100% A; 13.0–15.0 min, 5% A. The flow rate was set at 0.4 mL min –1 , the column temperature was maintained at 40 °C, and the injection volume was 1 μL; S45. The key intermediate in the proton-coupled electron transfer reaction was identified as phenoxy radical. In summary, using copper-based oxides as an example in S1, the oxidant and catalyst generate high-valent metal oxygen species through electron transfer. These high-valent metal oxygen species oxidize and degrade pollutants, causing them to lose electrons and protons to generate organic free radicals. Simultaneously, the high-valent metal gains electrons and protons and is reduced. The organic free radicals undergo transient resonance transfer on the catalyst surface, forming positively charged centers on the ortho- and para-carbons of the organic free radicals, inducing the stable organic free radicals to spontaneously polymerize to form crosslinked products and polymerized products. Table 4 Removal efficiency of 4-tert-butyl-2,6-dimethyl-aniline using NiO Table 53, Removal efficiency of 4-dimethylthiophene using NiO Table 6 Removal efficiency of 4-tert-butyl-2,6-dimethyl-aniline using Co3O4 Table 73, Removal efficiency of 4-dimethylthiophene using Co3O4 As shown in Tables 4-7, the systems demonstrated near-simultaneous removal of organic pollutants and COD, suggesting that the system's mechanism of action is triggered by high-valent metal oxygen species. COD and kinetic experimental results revealed that the NiO / PMS system demonstrated 100% organic pollutant removal from the bulk solution, accompanied by 90.36%-97.56% COD accumulation on the solid surface; the Co3O4 / PMS system demonstrated 100% organic pollutant removal, accompanied by 90.22%-93.67% COD accumulation on the solid surface. These results demonstrate that organic pollutant and COD removal occurred nearly simultaneously in both systems, with oxidation products accumulating on the catalyst surface in the form of polymers, indicating that the system's mechanism of action is triggered by high-valent metal oxygen species. Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A proton-coupled electron transfer method for resource-based removal of organic pollutants, characterized by: The following steps are involved: S1. In situ generation of high-valent metal oxygen species with selective oxidation properties; S2. Determine the optimal conditions for the formation of high-valent metal oxygen species; S3. Determine the optimal conditions for proton-coupled electron transfer reactions initiated by high-valent metal oxygen species; S4. Identify the key intermediates in proton-coupled electron transfer reactions initiated by high-valent metal oxygen species; S5. Resource-based removal of aniline or thiophene pollutants based on proton-coupled electron transfer method.

2. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 1, characterized in that: The in-situ generation of high-valent metal oxygen species with selective oxidation properties in S1 comprises the following steps: S11. Determining that the transition metal oxide catalyst is any one of a nickel-based oxide, a copper-based oxide, or a cobalt-based oxide; S12. Determine that the oxidant used to generate high-valent metal oxygen species is either monopersulfate or peroxydisulfate.

3. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 1, characterized in that: The optimal generation conditions for high-valent metal oxygen species in S2 include the following conditions: Condition 1. Catalyst concentration in the reaction system; Condition 2. Oxidant concentration in the reaction system; Condition 3. Target pollutant concentration in the reaction system; Condition 4. Buffer concentration in the reaction system and kinetic apparent rate constant.

4. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 1, characterized in that: The optimal conditions for the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species in S3 include the following conditions: Condition 1. Active H + concentration; Condition 2. Kinetic apparent rate constant k; Condition 3. The logarithm of the apparent kinetic rate constant k, i.e. lgk; Condition 4. Fit the logarithmic apparent rate constant lgk to obtain a fitting curve, and then generate different fitting curves according to different proton activities: when the proton activity is low, the logarithmic apparent rate constant increases linearly; when the proton activity is high, the logarithmic apparent rate constant decreases linearly; Condition 5. Based on the fitting curve obtained in Condition 4, the optimal rate of the pollutant under a specific proton activity condition is obtained.

5. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 1, characterized in that: Determining the key intermediates of the proton-coupled electron transfer reaction initiated by high-valent metal oxygen species in S4 comprises the following steps: S41. Determine the removal rate of organic pollutants by spectrophotometry; S42. Determine the proportion of organic pollutants removed through cross-linking and polymerization pathways using total chemical oxygen demand; S43. Determine the ratio of polymerization products by matrix-assisted laser desorption ionization time-of-flight mass spectrometry; S44. Determine the ratio of cross-linked products by liquid chromatography-mass spectrometry; S45. The key intermediate in the proton-coupled electron transfer reaction was identified as phenoxy radical.

6. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 1, characterized in that: The high-valent metal oxygen species with selective oxidation properties in S5 is determined by S1, the optimal generation conditions of the high-valent metal oxygen species are determined by S2, the optimal conditions for the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species are determined by S3, and the key intermediates of the proton-coupled electron transfer reaction initiated by the high-valent metal oxygen species are determined by S4.

7. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 2, characterized in that: The nickel-based oxide in the S11 is NiO, the copper-based oxide is CuO, and the cobalt-based oxide is Co3O4.

8. The proton-coupled electron transfer method for resource-based removal of organic pollutants according to claim 2, characterized in that: In the S12, the monopersulfate is potassium hydrogen persulfate, and the peroxydisulfate is potassium persulfate.

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