A method for treating water by oxidation transfer based on separate synergistic catalysis and a galvanic cell device

Abstract

The present invention provides an oxidation transfer water treatment method and a primary cell device based on separate synergistic catalysis. The separate synergistic catalytic primary cell device includes a positive electrode chamber, in which a carbon nanotube-loaded electrode is provided; a negative electrode chamber, in which a metal oxide-loaded electrode is provided; a diaphragm; the diaphragm separates the positive electrode chamber from the negative electrode chamber; and a wire connecting the metal oxide-loaded electrode and the carbon nanotube-loaded electrode. The device greatly improves the reaction efficiency through the synergistic catalytic effect of the positive and negative electrodes, and has the potential for further optimization of space and practical application. The device can physically separate pollutants and oxidants, and can avoid toxic side reactions between non-target species in sewage and oxidants and competitive consumption of oxidants from the source, and avoid the introduction of sulfate ions into the wastewater by the addition of oxidants; pollutants are removed through non-decomposition transfer, do not rely on degradation and mineralization pathways, use a small amount of oxidant, and can achieve simultaneous removal of pollutants and TOC.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and in particular relates to an oxidation transfer water treatment method based on separate collaborative catalysis and a primary cell device. Background Art

[0002] Persulfate-based advanced oxidation processes (AOPs) have attracted widespread attention in the field of water pollution control due to their strong oxidative capacity. However, traditional AOPs, which remove organic pollutants through degradation and mineralization, often suffer from issues such as incomplete removal, the generation of secondary pollutant intermediates, high oxidant dosages, and large amounts of residual sulfate.

[0003] The direct oxidative transfer process (DOTP) offers a new paradigm for wastewater treatment: Under the combined action of a catalyst and an oxidant, pollutants undergo non-degradative oxidative transfer on the catalyst surface. This process requires minimal oxidant consumption, enabling the simultaneous removal of pollutants and TOC, effectively alleviating the challenges inherent in traditional advanced oxidation processes. However, due to the direct contact between pollutants and the oxidant, toxic side effects between non-target species in the wastewater and the oxidant, competitive consumption of the oxidant, and residual sulfate from the addition of persulfate remain unavoidable. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an oxidation transfer water treatment method based on separate cooperative catalysis, which uses a dual-chamber galvanic cell device to separate the oxidant and pollutants in the positive and negative electrode chambers, avoiding direct contact between the pollutants and the oxidant; innovatively introduces a positive and negative electrode separation cooperative catalytic strategy, and achieves a significant improvement in pollutant removal efficiency by loading catalysts that are conducive to activating the corresponding substrates on the positive and negative electrode plates respectively; through a direct oxidation transfer process, the non-decomposition removal of pollutants on the catalyst surface is achieved. This technology avoids many problems in traditional AOP technology, combines DOTP technology with the advantages of galvanic cell devices, and develops a separate cooperative catalytic strategy, which has broad development space and application potential.

[0005] The present invention provides a separated cooperative catalytic galvanic cell device, comprising a positive electrode chamber, wherein a carbon nanotube (CNT) loaded electrode is provided in the positive electrode chamber;

[0006] A negative electrode chamber, wherein a metal oxide loaded electrode is provided in the negative electrode chamber;

[0007] The separator separates the positive electrode chamber and the negative electrode chamber;

[0008] A wire is connected between the metal oxide loaded electrode and the carbon nanotube loaded electrode.

[0009] The separated cooperative catalytic primary cell device is an H-shaped cell containing a double electrode chamber, wherein the positive and negative electrode chambers are separated by a cation exchange membrane, the positive electrode chamber contains an oxidant solution, the negative electrode chamber contains a pollutant solution, and both the positive and negative electrode chamber solutions contain electrolytes. The catalyst loaded on the positive electrode plate is a carbon nanotube, and the catalyst loaded on the negative electrode plate is a metal oxide. The positive and negative electrode plates are connected by a wire, and magnetic stirring is used to accelerate mass transfer during the reaction process.

[0010] In the present invention, the metal oxide is selected from copper oxide or cobalt oxide;

[0011] The substrate of the metal oxide loaded electrode is carbon paper;

[0012] The substrate of the carbon nanotube-loaded electrode is carbon paper.

[0013] In the present invention, the membrane is a cation exchange membrane.

[0014] The present invention provides an oxidation transfer water treatment method based on the device described in the above technical solution, comprising the following steps:

[0015] With a metal oxide-loaded electrode as the negative electrode and a carbon nanotube-loaded electrode as the positive electrode, in the presence of an oxidant and an electrolyte, phenol pollutants are enriched on the negative electrode surface through oxidative coupling and polymerization reactions.

[0016] In the present invention, the oxidant is peroxymonosulfate and / or peroxydisulfate; in a specific embodiment, the oxidant is potassium peroxydisulfate (PDS).

[0017] The electrolyte is selected from one or more of sodium sulfate, sodium nitrate, sodium chloride, sodium bromide, sodium bicarbonate, sodium carbonate, potassium sulfate, ammonium sulfate and magnesium sulfate.

[0018] In the present invention, the molar ratio of the phenolic pollutant to the oxidant is 1:2 to 1:1000, preferably 1:20 to 300, and more preferably 1:40 to 100. In specific embodiments, the molar ratio of the phenolic pollutant to the oxidant is 1:5 to 1:60. During the reaction, the ratio of the oxidant consumption to the pollutant removal is measured to be 2 to 5.

[0019] The concentration of the electrolyte is 1 to 1000 mmol / L, preferably 10 to 300 mmol / L, more preferably 15 to 150 mmol / L. In a specific embodiment, the concentration of the electrolyte is 20 mmol / L.

[0020] The temperature of the oxidative coupling and polymerization reactions in the present invention is 10 to 65°C, and the pH value is 4.0 to 10.0. The present invention preferably uses borate buffer to adjust the pH value. In a specific embodiment, the pH value is preferably 7.5. The phenolic pollutants are transferred to the surface of the negative electrode catalyst via oxidative coupling and polymerization pathways to achieve the simultaneous removal of the pollutants and their corresponding total organic carbon. For example, if the phenolic pollutants include 2,6-M-PhOH, the reaction products are eluted with ethanol and toluene, respectively, and analyzed using liquid chromatography-mass spectrometry (LC-MS), gel permeation chromatography (GPC), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), respectively (such as Figure 8 ), the results showed that the ethanol elution product was diphenoquinone compound, and the toluene elution product was 2,6-dimethyl polyphenylene ether. It can be inferred that the main product in the PhOH system is polyphenylene ether, and the reaction occurs through cross-linking polymerization.

[0021] In the present invention, the phenolic pollutants include one or more of phenol, 4-chlorophenol, bisphenol A, 2,6-dimethylphenol and guaiacol.

[0022] The electrodes used in the process of the present invention can be reused for more than 8 times without significant decrease in reaction activity.

[0023] The DOTP ratio defined in the present invention = TOC removal rate in the solution / removal rate of the target pollutant. Since the oxidant consumption is extremely low, the pollutants cannot be removed by mineralization.

[0024] The present invention provides a separated synergistic catalytic primary cell device, comprising a positive electrode chamber, in which a carbon nanotube-loaded electrode is disposed; a negative electrode chamber, in which a metal oxide-loaded electrode is disposed; a diaphragm; the diaphragm separates the positive electrode chamber from the negative electrode chamber; and a wire connecting the metal oxide-loaded electrode and the carbon nanotube-loaded electrode. The device significantly improves reaction efficiency through the synergistic catalytic effect of the positive and negative electrodes, and has the potential for further optimization of space and practical application. The device can physically separate pollutants and oxidants, avoiding toxic side reactions between non-target species in sewage and oxidants and competitive consumption of oxidants at the source, and avoiding the introduction of sulfate ions into the wastewater by the addition of oxidants; pollutants are removed through non-decomposition transfer, independent of degradation and mineralization pathways, with low oxidant usage (reduced by 2 to 3 orders of magnitude compared to traditional Fenton advanced oxidation systems), and can achieve simultaneous removal of pollutants and TOC. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a diagram of a separate cooperative catalytic galvanic cell device. The main body of the device is an H-shaped cell containing two electrode chambers, with the positive and negative electrodes connected by wires;

[0026] Figure 2Performance of the galvanic cell reaction for the removal of pollutant phenol (PhOH) using four different electrode combinations (positive CNT-negative CuO, positive CuO-negative CuO, positive CNT-negative CNT, positive CuO-negative CNT) and a blank control group (positive carbon paper-negative carbon paper): (a) reaction kinetics curve; (b) PhOH removal rate after 120 min of reaction; (c) pseudo-first-order reaction kinetics fitting curve; (d) pseudo-first-order reaction rate constant;

[0027] Figure 3 Results of the original battery cycle stability test: (a) PhOH removal curve; (b) PDS consumption curve;

[0028] Figure 4 (a) DOTP ratio; (b) PhOH removal / PDS consumption for four primary cell combinations (positive electrode CNT-negative electrode CuO, positive electrode CuO-negative electrode CuO, positive electrode CNT-negative electrode CNT, positive electrode CuO-negative electrode CNT);

[0029] Figure 5 Transmission electron microscopy (TEM) characterization results of the negative electrode CuO catalyst before and after the positive electrode CNT-negative electrode CuO combination reaction: (a) TEM image of CuO before reaction; (b) TEM image of CuO after reaction; (cg) high-angle annular dark field (HAADF) image and energy dispersive spectroscopy (EDS) elemental analysis of CuO after reaction;

[0030] Figure 6 (a) Infrared spectrum of the negative electrode CuO catalyst before and after the positive electrode CNT-negative electrode CuO combination reaction; (b) XPS spectrum;

[0031] Figure 7 (a) Relative concentrations of PhOH and TOC in the negative electrode solution before and after the positive electrode CNT-negative electrode CuO combination reaction; (b) Thermogravimetric analysis results of the negative electrode CuO catalyst;

[0032] Figure 8 Product identification results of the negative electrode CuO catalyst after ethanol elution and toluene elution after the positive electrode CNT-negative electrode CuO combination reaction using 2,6-dimethylphenol (2,6-M-PhOH) as the substrate: (ab) Liquid chromatography-mass spectrometry (LC-MS) test results of the ethanol elution product; (c) Schematic diagram of the coupling reaction pathway; (de) LC-MS test results of the toluene elution product; (f) Schematic diagram of the polymerization reaction pathway. DETAILED DESCRIPTION

[0033] In order to further illustrate the present invention, the following detailed description of an oxidation transfer water treatment method and device based on a separate cooperative catalytic primary cell device provided by the present invention is given in combination with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0034] Example 1 Preparation of catalyst-loaded electrode

[0035] (1) Preparation of CuO-loaded electrode: 12.5 mg of CuO was dispersed in 1 mL of H2O and 0.25 mL of isopropanol solution to prepare a catalyst dispersion. The dispersion was then ultrasonically treated for 20 min to uniformly disperse the solution. Carbon paper was cut into small pieces of 2 cm × 2.5 cm. The catalyst dispersion was evenly coated on the surface of the carbon paper and dried. The carbon paper was then calcined in a muffle furnace at 200°C for 2 h at a heating rate of 3°C / min.

[0036] (2) Preparation of CNT-loaded electrode: 5 mg of CNT was dispersed in 1 mL of H2O, 0.25 mL of isopropanol, and 0.03 mL of Nafion (perfluorosulfonic acid polymer) solution to prepare a catalyst dispersion. The dispersion was then ultrasonically treated for 20 min to uniformly disperse the CNT. The carbon paper was cut into small pieces of 2 cm × 2.5 cm. The catalyst dispersion was evenly coated on the surface of the carbon paper and dried.

[0037] Example 2 Performance of the Separate Co-catalytic Cell Device

[0038] (1) PhOH removal performance test: An H-shaped reaction cell with a cation exchange membrane separating the positive and negative electrode chambers was prepared. 18.5 mL of an aqueous solution containing 10 mg / LPhOH, 20 mM sodium sulfate, and 20 mM boric acid buffer was added to the negative electrode chamber, and the solution pH was 7.5. 18.5 mL of an aqueous solution containing 20 mM sodium sulfate and 20 mM boric acid buffer was added to the positive electrode chamber, and the solution pH was 7.5. The H-shaped cell was placed on a magnetic stirrer and stirred evenly.

[0039] The CuO and CNT loaded carbon paper electrodes were fixed on the electrode clips and placed in the negative and positive chambers respectively (for comparison, four control groups were set up, namely: positive electrode CuO-negative electrode CuO, positive electrode CNT-negative electrode CNT, positive electrode CuO-negative electrode CNT, positive electrode carbon paper-negative electrode carbon paper) to allow them to pre-adsorb for 1 hour. After that, 2.5 mg of potassium persulfate (PDS) was added to the positive chamber, stirred and dissolved, and then a wire was connected between the positive and negative electrodes to start the reaction. Before the start of the reaction and during the whole process of the reaction, 0.2 mL of sample solution was taken from the negative chamber, filtered through a 0.22 μm filter membrane, and the concentration of PhOH was detected using ultra-performance liquid chromatography (UPLC). Samples were taken at 0 min and 120 min to determine the TOC in the solution, and samples were taken at 0 min and 120 min to determine the PDS concentration in the positive chamber solution (color developed by the reaction of potassium iodide and PDS, and tested using a UV-visible spectrophotometer). The reaction device is as follows: Figure 1 shown.

[0040] The performance of four different electrode combinations in removing PhOH was compared, and their pseudo-first-order reaction kinetic constants k (min -1 ) and the order of PhOH removal rate within 120 min is positive electrode CNT-negative electrode CuO>positive electrode CuO-negative electrode CuO>positive electrode CNT-negative electrode CNT>positive electrode CuO-negative electrode CNT (such as Figure 2 ). This result shows that in the core experimental group of positive electrode CNT-negative electrode CuO, there is a synergistic effect between the positive and negative electrode catalysts. The positive electrode catalyst CNT is more conducive to activating the positive electrode substrate PDS, and the negative electrode catalyst CuO is more conducive to activating the negative electrode substrate PhOH.

[0041] (2) Cyclic stability test of primary cell removal of PhOH: An H-shaped reaction cell was used to separate the positive and negative electrode compartments using a cation exchange membrane. 18.5 mL of an aqueous solution containing 10 mg / L PhOH, 20 mM sodium sulfate, and 20 mM borate buffer was added to the negative electrode compartment, with a pH of 7.5. 18.5 mL of an aqueous solution containing 20 mM sodium sulfate and 20 mM borate buffer was added to the positive electrode compartment, with a pH of 7.5. The H-shaped cell was placed on a magnetic stirrer and stirred evenly. CuO- and CNT-loaded carbon paper electrodes were fixed to electrode holders and placed in the negative and positive electrode compartments, respectively, for pre-adsorption for 1 h. Afterwards, 30 mg of PDS was added to the positive electrode compartment, stirred and dissolved, and then a wire was connected between the positive and negative electrodes to initiate the reaction. Before the start of the reaction and during the entire reaction process, 0.2 mL of sample solution was taken from the negative electrode chamber, filtered through a 0.22 μm filter membrane, and the PhOH concentration was detected using UPLC. Samples were taken at 0 min and 120 min of each cycle to determine the PDS concentration in the positive electrode solution. After the reaction was carried out for 120 min, PhOH, borate buffer, and sodium sulfate were added to the negative electrode chamber to make the concentrations of each substance reach the initial state. After stirring evenly, the wires were reconnected to start the reaction. This was repeated for 8 rounds. The results of the cyclic stability experiment are shown in Figure 2. Figure 3 As shown in the figure, the reaction activity of the system did not decrease significantly in 8 cycles, and PDS was steadily consumed.

[0042] (3) Identification of surface oxidation transfer pathways: Based on the PhOH removal rates in the above four electrode combination comparison experiments and the TOC test data of the negative electrode chamber solution before and after the reaction, the DOTP ratios of the four electrode combination galvanic cell reactions were calculated (DOTP ratio = TOC removal rate in solution / PhOH removal rate). Figure 4 As shown, the DOTP ratios of the four electrode combinations are all above 76%, indicating that the system is dominated by the DOTP process. Compared with the other three control groups, the positive electrode CNT-negative electrode CuO combination has the highest DOTP ratio, further demonstrating the advantages of this electrode combination. By measuring the PDS consumption in the reactions of the four electrode combinations, the calculated ratio of PDS consumption to PhOH removal is less than 2.5, further indicating that the process is a DOTP process rather than a degradation mineralization process in traditional advanced oxidation.

[0043] Afterwards, the negative electrode catalyst after the positive electrode CNT-negative electrode CuO combination reaction was ultrasonically stripped and the collected catalyst was characterized and analyzed. TEM results showed that a thick coating layer appeared around the catalyst particles after the reaction. EDS-mapping results showed that the C element was widely distributed in the sample area, but the distribution state was not completely consistent with that of O and Cu, indicating that the coating of the polymerization product on the catalyst was uneven (such as Figure 5). IR and XPS results show that compared with the original CuO, the sample after reaction has new peaks corresponding to CO and COC, indicating that the reaction may generate polyphenylene ether attached to the catalyst (such as Figure 6 ). Compared with the sample before the reaction, the XPS signals of Cu and O elements became weaker after the reaction (excluding new peaks), while the signal of C element became stronger. Since XPS is a surface analysis method, combined with the TEM characterization results, it can be seen that the polymer generated by the reaction is wrapped on the CuO surface. Thermogravimetric analysis results show that the catalyst after the reaction loses weight significantly in a narrow temperature range of 300°C, which is the characteristic of a composite polymer. Thereafter, the products transferred to the catalyst surface during the reaction were quantitatively analyzed by TOC removal combined with thermogravimetric analysis (such as Figure 7 ), calculated by TOC removal, 60% of the pollutants removed from the solution were transferred to the catalyst surface, and the theoretical mass of the product transferred to the surface was 8.73 mg. The actual mass of the polymer on the catalyst surface was calculated by thermogravimetric analysis to be 8.29 mg, indicating that 95% of the pollutants transferred to the catalyst surface were polymers.

[0044] Since the product after the PhOH reaction was difficult to elute, the substrate was replaced with 2,6-M-PhOH, and the reaction products were eluted with ethanol and toluene, respectively, and analyzed by liquid chromatography-mass spectrometry (LC-MS), gel permeation chromatography (GPC), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), respectively (e.g. Figure 8 ), the results showed that the ethanol elution product was diphenoquinone compound, and the toluene elution product was 2,6-dimethyl polyphenylene ether. It can be inferred that the main product in the PhOH system is polyphenylene ether, and the reaction occurs through cross-linking polymerization.

[0045] Product elution method: The catalyst obtained by ultrasonic stripping after the reaction was placed in a centrifuge tube, 10 mL of ethanol was added, and the mixture was centrifuged at 10,000 rpm. The supernatant was collected for LC-MS testing; the catalyst after ethanol elution was placed in a centrifuge tube, 10 mL of toluene was added, and the mixture was centrifuged at 10,000 rpm. The supernatant was collected and the solution was dried in an oven at 80°C. The product was a gel-like brown solid, which was tested by GPC and MALDI-TOF.

[0046] As can be seen from the above examples, the present invention achieves green and efficient water treatment by placing pollutants and oxidants in the negative and positive electrode chambers of a dual-chamber galvanic cell device, respectively, and loading catalysts that are conducive to activating the corresponding substrates on the plates of the two chambers. This allows pollutants in water to be enriched on the catalyst surface through an oxidation transfer pathway, and avoids the introduction of chemical agents into the wastewater. The pollutants and oxidants are phenolic organic compounds and persulfate, respectively, and the negative and positive electrode catalysts are metal oxides and carbon nanotubes, respectively. This process physically separates pollutant-containing wastewater from the oxidant, avoiding toxic side reactions and competitive consumption of the oxidant caused by direct contact between complex components in the water and the oxidant, has strong anti-interference ability, and avoids the introduction of sulfate ions into the wastewater due to the use of persulfate. The oxidant consumption in this process is only 2 to 3 times the initial concentration of the pollutants, which can significantly reduce treatment costs. The process selects catalysts that are conducive to the activation of the substrates in the positive and negative electrode chambers, respectively, and effectively improves treatment efficiency through the synergistic effect of positive and negative electrode catalysis. Therefore, the water treatment process provided by the present invention is highly innovative and has broad application prospects.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A separate cooperative catalytic galvanic cell device comprising a cathode chamber, wherein a carbon nanotube-loaded electrode is disposed in the cathode chamber; A negative electrode chamber, wherein a metal oxide loaded electrode is provided in the negative electrode chamber; The separator separates the positive electrode chamber and the negative electrode chamber; A wire is connected between the metal oxide loaded electrode and the carbon nanotube loaded electrode; The peroxymonosulfate and / or peroxydisulfate oxidants are placed in the positive electrode chamber; and the phenolic pollutants are placed in the negative electrode chamber.

2. The device according to claim 1, characterized in that The metal oxide is selected from copper oxide or cobalt oxide.

3. The device according to claim 1, characterized in that The substrate of the metal oxide loaded electrode is carbon paper; The substrate of the carbon nanotube-loaded electrode is carbon paper.

4. The device according to claim 1, characterized in that The diaphragm is a cation exchange membrane.

5. A method for treating oxidative transfer water based on the device according to claim 1, comprising the following steps: With a metal oxide-loaded electrode as the negative electrode and a carbon nanotube-loaded electrode as the positive electrode, in the presence of an oxidant and an electrolyte, phenolic pollutants are enriched on the negative electrode surface through oxidative coupling and polymerization reactions. The peroxymonosulfate and / or peroxydisulfate oxidants are placed in the positive electrode chamber; and the phenolic pollutants are placed in the negative electrode chamber.

6. The oxidation transfer water treatment method according to claim 5, characterized in that: The electrolyte is selected from one or more of sodium sulfate, sodium nitrate, sodium chloride, sodium bromide, sodium bicarbonate, sodium carbonate, potassium sulfate, ammonium sulfate and magnesium sulfate.

7. The oxidation transfer water treatment method according to claim 5, characterized in that: The molar ratio of the phenolic pollutant to the oxidant is 1:2 to 1:1000; The concentration of the electrolyte is 1 to 1000 mmol / L.

8. The oxidation transfer water treatment method according to claim 5, characterized in that: The temperature of the oxidative coupling and polymerization reaction is 10-65° C., and the pH value is 4.0-10.

0.

9. The oxidation transfer water treatment method according to claim 5, characterized in that: The phenolic pollutants include one or more of phenol, 4-chlorophenol, bisphenol A, 2,6-dimethylphenol and guaiacol.

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