Method for green and efficient removal of hydrophobic VOCs (Volatile Organic Compounds) through electrocatalysis-induced oxidation-absorption coupling

Abstract

The invention discloses a method for green and efficient removal of hydrophobic VOCs (Volatile Organic Compounds) through electro-catalysis-induced oxidation-absorption coupling, and belongs to the field of VOCs treatment. The method comprises the following steps: constructing an iodine-based electrooxidation self-circulation system for removing hydrophobic VOCs by taking a high oxygen evolution overpotential electrode as an anode, a material capable of realizing efficient reduction of IO3 <-> as a cathode and an alkaline iodine salt solution as an electrolyte; under the condition of electrification, the high-oxygen-evolution over-potential electrode electrically oxidizes the iodized salt solution under the alkaline condition, and generates IO3. And. OH free radicals through electro-catalysis; iO3. And. OH free radicals in the electrolyte quickly oxidize the liquid-phase VOCs by utilizing the strong oxidizing property of the free radicals, so that the mass transfer process of the gas-liquid-phase VOCs is promoted, and the quick degradation of the gas-phase hydrophobic VOCs is realized; after VOCs are oxidized, IO3 <-> in the solution is reduced into a low-valence iodine salt solution, and self-circulation of iodine in the system is achieved. The method has the characteristics of high efficiency, greenness and sustainability.

Description

Technical Field

[0001] The present invention belongs to the field of VOCs treatment, and particularly relates to a green and efficient method for removing hydrophobic VOCs by electrocatalytically initiated oxidation-absorption coupling. Background Art

[0002] For the removal of VOCs, currently in industry, various processes such as absorption method and catalytic combustion method are mainly adopted. Among them, the absorption method based on aqueous solution has been widely used in VOCs treatment due to its simple operation and low cost. However, the treatment effect of the absorption method highly depends on the gas-liquid mass transfer efficiency. For hydrophobic VOCs, due to their poor solubility, the mass transfer process is limited, and it is difficult to improve the treatment effect, which becomes a major difficulty in VOCs treatment. Therefore, for hydrophobic VOCs, the chemical absorption-oxidation method is commonly used in industry. This method adds strong oxidants (such as potassium permanganate, sodium hypochlorite, etc.) to the absorption liquid, and uses the strong oxidizing property of the absorption liquid to oxidize VOCs into easily soluble organic substances and dissolve them into the absorption liquid. However, this method usually relies on the continuous replenishment of a large amount of strong oxidants, not only with high operating costs, but also may cause secondary pollution problems, and it is difficult to achieve the goal of green and low-consumption treatment. In addition, these oxidants are difficult to completely oxidize VOCs, so the absorption liquid is extremely likely to become waste liquid and needs further treatment.

[0003] As a green technology driven only by electric energy, electrochemically oxidation is more green and efficient than ozone oxidation, Fenton oxidation, etc., providing a new idea for VOCs treatment. Compared with the chemical absorption-oxidation method, the chemical absorption-electrochemical oxidation method can continuously generate oxidants through a stable power supply, significantly reducing the operating costs, and at the same time avoiding secondary pollution caused by the replenishment of oxidants. Currently, some researchers have used the electrochemical oxidation method to synthesize ferrate and permanganate, but these methods face a common problem, that is, insoluble precipitates such as iron and manganese dioxide will be generated during the electrolysis process, resulting in the system unable to operate stably for a long time, thus limiting its further application. Summary of the Invention

[0004] To solve the problems in the prior art, the present invention provides a green and efficient method for removing hydrophobic VOCs by electrocatalytically initiated oxidation-absorption coupling.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention discloses a green and efficient method for removing hydrophobic VOCs by electrocatalytically initiated oxidation-absorption coupling, comprising the following steps:

[0007] Using a high oxygen evolution overpotential electrode as the anode, and being able to achieve IO3 -A material with high reduction efficiency is used as the cathode, and an alkaline iodine salt solution is used as the electrolyte to construct an iodine-based electro-oxidation self-circulation system for removing hydrophobic VOCs;

[0008] Under the condition of power-on, the iodine salt solution is electro-oxidized under alkaline conditions by a high oxygen evolution overpotential electrode. Without external addition of an oxidant, only driven by electric energy, periodate is continuously and stably generated. Periodate will in-situ electrocatalytically generate IO3 · and ·OH radicals on the electrode; after the gaseous hydrophobic VOCs are introduced into the electrolyte, IO3 · and ·OH radicals use their strong oxidizing properties to rapidly oxidize the soluble-phase VOCs, avoiding the mass transfer limitation between the gas-liquid phases, thereby realizing the rapid degradation of gaseous hydrophobic VOCs; after oxidizing the VOCs, the IO3 - in the solution is reduced to a low-valence iodine salt solution at the cathode, and finally the self-circulation of iodine in the system is realized.

[0009] Furthermore, the above-mentioned high oxygen evolution overpotential electrode has a high adsorption selectivity for low-valence iodine and a low oxidation energy barrier. Therefore, it maintains a high selectivity electro-oxidation of low-valence iodine during long-term operation and stably generates periodate with strong oxidizing properties; at the same time, the electrode has a high oxygen evolution reaction energy barrier, which can effectively inhibit the occurrence of oxygen evolution side reactions on the electrode surface; the electrode material of the high oxygen evolution overpotential electrode is a titanium plate, BDD (boron-doped diamond), SbO2, SnO2, PbO2 or M-Sb / SnO2 electrode; wherein, M is a metal element other than Sb and Sn, and the electrode has a pair of I - and IO3 - suitable adsorption free energy to ensure the high priority of the iodine oxidation reaction;

[0010] The cathode can efficiently reduce IO3 - to I - , and the materials that can be used as the cathode to achieve the efficient reduction of IO3 - are nickel mesh, copper mesh, platinum sheet or DSA.

[0011] Furthermore, the pH range of the alkaline iodine salt solution is 8-14, the concentration of the iodine salt in the alkaline iodine salt solution is 0.1-30 wt%, and the iodine salt is one or more of potassium iodide, sodium iodide, potassium iodate or sodium iodate.

[0012] Furthermore, the preparation method of the M-Sb / SnO2 electrode includes: dissolving a tin salt, an antimony salt and a metal salt M in deionized water to obtain a mixed solution, immersing a substrate in the mixed solution, and then taking it out for drying and calcination to obtain a substrate loaded with a catalyst; repeating the operations of immersing, drying and calcining the substrate until the catalyst loading on the substrate reaches 1-5 mg / cm 2, finally, the substrate of the supported catalyst is calcined to achieve the atomic-level dispersion of Mn and Sb in SnO2, and the catalyst grows firmly on the substrate, thus obtaining the Mn-Sb / SnO2 electrode.

[0013] Compared with the prior art, the present invention has the following remarkable beneficial effects:

[0014] 1) High efficiency and low cost: The present invention adopts an electro-synthesis method to achieve the continuous generation of periodate, with mild operating conditions and low operating costs;

[0015] 2) Strong stability: No insoluble substances are generated during the operation of the system, enabling long-term continuous and stable operation; specifically, the chemical properties of iodine make only iodine insoluble in water during the electrolysis process, and in an alkaline environment, iodine can undergo a disproportionation reaction to generate iodide ions and iodate ions, thereby avoiding the generation of insoluble precipitates in the system. This provides the possibility for the continuous and stable operation of the system, and avoids the problem in the prior art that the removal of hydrophobic VOCs relies on the continuous replenishment of a large amount of strong oxidants, and does not cause secondary pollution problems, achieving the goal of green and low-consumption treatment; at the same time, the present invention also avoids the problem in the prior art that insoluble precipitates such as iron and manganese dioxide are generated during the electrolysis process, resulting in the inability of the system to operate stably for a long time.

[0016] 3) High Faraday efficiency: The Faraday efficiency of the electro-synthesis of periodate is significantly improved, with more excellent iodine oxidation reaction performance;

[0017] 4) Excellent oxidation performance: The IO3 · and ·OH radicals generated by the activation of the synthesized periodate on the anode have extremely strong oxidizing properties, can rapidly oxidize liquid-phase VOCs, and promote the efficient mass transfer of gas-liquid phase VOCs, thereby achieving the complete degradation of gas-phase hydrophobic VOCs;

[0018] 5) Superior electrode performance: The M-Sb / SnO2 electrode is adopted, which exhibits excellent iodine oxidation activation performance, has a low electro-oxidation voltage, and maintains good stability. Description of the Drawings

[0019] Figure 1 is the synthesis schematic diagram of the Mn-Sb / SnO2 electrode and the relevant characterization test diagrams of SEM and TEM.

[0020] Figure 2 is the LSV curve and Faraday efficiency diagram of the electro-oxidation of iodate on the Mn-Sb / SnO2 electrode.

[0021] Figure 3 is the LSV curve and Faraday efficiency diagram of the electro-oxidation of iodate on the industrial BDD electrode.

[0022] Figure 4 are the XRD curves of different electrodes.

[0023] Figure 5 are the partially enlarged XRD curves of different electrodes.

[0024] Figure 6 is the Sn 3d XPS curve of different electrodes.

[0025] Figure 7 is the Sn 3d XPS curve of different electrodes 3 / 2 diagram.

[0026] Figure 8 is the O1s XPS curve of different electrodes.

[0027] Figure 9 is the LSV curve of iodate electrooxidation of different electrodes.

[0028] Figure 10 is the Faraday efficiency diagram of iodate electrooxidation of different electrodes.

[0029] Figure 11 is the diagram of relevant parameters of different electrodes.

[0030] Figure 12 is the stability test curve diagram of the Mn-Sb / SnO2 electrode.

[0031] Figure 13 is the free energy change diagram of I - and IO3 - before and after adsorption on the Sb / SnO2 electrode and the Mn-Sb / SnO2 electrode.

[0032] Figure 14 is the free energy change diagram of the reaction intermediates of the OER (Oxygen Evolution Reaction) on the Sb / SnO2 electrode and the Mn-Sb / SnO2 electrode.

[0033] Figure 15 is the free energy change diagram of the reaction intermediates of the iodide oxidation reaction on the Sb / SnO2 electrode and the Mn-Sb / SnO2 electrode.

[0034] Figure 16 is the flow chart of the experimental device.

[0035] Figure 17 is the toluene removal rate diagram under long-term stable operation.

[0036] Figure 18 is the numerical diagram of the chemical oxygen demand (COD) and toluene mineralization rate of the electrolyte.

[0037] Figure 19It is the Faraday efficiency diagram of the electrolysis system for generating periodate at different current densities.

[0038] Figure 20 It is the toluene removal rate diagram of the system after adding different radical scavengers.

[0039] Figure 21 It is the mechanism diagram of electro-oxidation-absorption coupling for treating hydrophobic VOCs. Specific Embodiments

[0040] The present invention will be further described and explained below in conjunction with specific embodiments. The described embodiments are only illustrative of the present disclosure and do not delimit the scope of limitation. The technical features of each embodiment of the present invention can be combined accordingly without conflict.

[0041] Compared with the existing electrolysis system, the iodine-based electrolysis system shows great potential. The chemical properties of iodine make only iodine insoluble in water during the electrolysis process, while iodate and periodate have better stability under alkaline conditions. In an alkaline environment, iodine can undergo a disproportionation reaction to generate iodide and iodate, thus avoiding the formation of insoluble precipitates in the system, which provides the possibility for the continuous and stable operation of the system.

[0042] However, during the electro-oxidation synthesis of periodate, the potential required for the oxidation of iodate to periodate is relatively high (1.6 V), far exceeding the potential of the oxygen evolution reaction (1.23 V). Therefore, the oxygen evolution reaction will preferentially occur on a conventional electrode, affecting the formation of periodate. To solve this problem, electrode materials with low oxygen evolution activity, such as titanium (Ti) and tin (Sn), etc., are needed, which can increase the overpotential of the oxygen evolution reaction, thereby promoting the efficient synthesis of periodate.

[0043] For this reason, the present invention proposes a green and efficient method for removing hydrophobic VOCs by electrocatalytically initiated oxidation-absorption coupling for the removal of hydrophobic VOCs. This method electro-oxidizes an iodide solution through an electrode with a high oxygen evolution overpotential to continuously generate periodate, and at the same time, periodate will be in-situ activated on the electrode with a high oxygen evolution overpotential to generate IO3 · and ·OH radicals. Finally, combined with an efficient absorption technology, the efficient removal of different hydrophobic VOCs can be completed only by electric energy drive. Compared with traditional methods, the present invention does not require additional oxidant supplementation, has low operating costs, a stable system, no risk of secondary pollution, and at the same time has the characteristics of environmental protection and high efficiency and stability, providing a new solution for the treatment of hydrophobic VOCs.

[0044] The green and efficient method for removing hydrophobic VOCs by electrocatalytically initiated oxidation-absorption coupling of the present invention includes the following steps:

[0045] Using a high oxygen evolution overpotential electrode as the anode, a material capable of achieving efficient reduction of IO3 - as the cathode, and an alkaline iodine salt solution as the electrolyte, an iodine-based electrooxidation self-circulation system for removing hydrophobic VOCs is constructed;

[0046] Under the condition of power-on, the iodine salt solution is electrooxidized by the high oxygen evolution overpotential electrode under alkaline conditions. Without external addition of oxidant, periodate can be continuously and stably generated only by relying on electric energy drive. Periodate will in-situ electrocatalytically generate IO3 · and ·OH radicals on the electrode; after the gaseous hydrophobic VOCs are introduced into the electrolyte, IO3 · and ·OH radicals rapidly oxidize the soluble-phase VOCs by using their strong oxidizing properties, avoiding the mass transfer limitation problem between gas-liquid phases, thereby achieving the rapid degradation of gaseous hydrophobic VOCs; after oxidizing the VOCs, the IO3 - in the solution is reduced to a low-valent iodine salt solution at the cathode, and finally the self-circulation of iodine in the system is realized.

[0047] The high oxygen evolution overpotential electrode used in the present invention has a high adsorption selectivity for low-valent iodine and a low oxidation energy barrier. Therefore, it can maintain a high selectivity electrooxidation of low-valent iodine during long-term operation and stably generate periodate with strong oxidizing properties; at the same time, the electrode has a high oxygen evolution reaction energy barrier, which can effectively inhibit the occurrence of oxygen evolution side reactions on the electrode surface. Therefore, the applicable electrode materials include but are not limited to titanium plates, BDD (boron-doped diamond), SbO2, SnO2, PbO2, and electrodes formed by doping or surface modification of the above electrode materials, that is, M-Sb / SnO2 electrodes, where M is a metal element other than Sb and Sn, and the electrode should have suitable adsorption free energies for I - and IO3 - to ensure the high priority of the iodine oxidation reaction. The cathode is used to efficiently reduce IO3 - to I - , specifically, the material capable of achieving efficient reduction of IO3 - used as the cathode is nickel mesh, copper mesh, platinum sheet or DSA.

[0048] In the present invention, the method for preparing the M-Sb / SnO2 electrode capable of obtaining better iodate oxidation electrochemical performance includes:

[0049] Dissolve tin salt, antimony salt and metal salt M in deionized water to obtain a mixed solution. Immerse the substrate in the mixed solution, then take it out for drying and calcination to obtain the substrate loaded with the catalyst; repeat the operations of immersion, drying and calcination on the substrate until the catalyst loading on the substrate reaches 1-5 mg / cm 2, finally, the substrate loaded with the catalyst is calcined to achieve the atomic-level dispersion of Mn and Sb in SnO₂, and the firm growth of the catalyst on the substrate, thus obtaining the Mn-Sb / SnO₂ electrode.

[0050] In an embodiment of preparing the M-Sb / SnO₂ electrode, the metal salt M is one or more of nickel salt, copper salt, cobalt salt, iron salt or manganese salt, and the concentration ratio should satisfy the formation of a solid solution metal oxide; the concentration of the tin salt in the mixed solution is 200 - 500 mmol / L, the concentration of the antimony salt is 5 - 50 mmol / L, and the concentration of the metal salt M is 1 - 50 mmol / L.

[0051] To solve the problem that the oxygen evolution reaction will preferentially occur on the conventional electrode, affecting the formation of periodate, the present invention needs to use electrode materials with lower oxygen evolution activity, such as titanium (Ti) and tin (Sn), etc., which can increase the overpotential of the oxygen evolution reaction, thereby promoting the efficient synthesis of periodate. Therefore, the material of the substrate is titanium, lead, tin, ruthenium or zirconium. The synthesized electrode of the present invention raises the oxygen evolution potential to 1.9 - 2.2 V, which is higher than the standard potential (1.6 V) for the oxidation of iodate to periodate. Therefore, when the synthesized electrode is used as the anode, the iodate oxidation reaction will occur instead of the oxygen evolution reaction.

[0052] In a specific embodiment of the present invention, before immersing the substrate in the mixed solution, it further includes a step of pretreating the substrate, and the pretreatment includes: first, grinding the substrate to remove the surface oxide; then preparing a 5 - 10 wt% sodium carbonate solution, immersing the ground substrate into the sodium carbonate solution and ultrasonically cleaning for 1 - 2 hours; then preparing a 10 - 20 wt% hydrochloric acid solution and heating it to 50 - 100 °C, immersing the ultrasonically cleaned substrate into the hydrochloric acid solution for etching for 1 - 2 hours; finally, rinsing the etched substrate with clean water to complete the pretreatment.

[0053] In a preferred embodiment of the present invention, the impregnation time is 1 - 5 min, the drying temperature is room temperature, the calcination temperature is 500 - 1000 °C, and the calcination time is 10 - 30 min.

[0054] In an alternative embodiment of the present invention, the M-Sb / SnO₂ electrode can effectively inhibit the oxygen evolution side reaction and maintain a high selectivity for the electrooxidation of low-valent iodine during long-term operation, stably generating strongly oxidizing periodate. At the same time, the pH range of the alkaline iodide solution is 8 - 14, the concentration of the iodide in the alkaline iodide solution is 0.1 - 30 wt%, and the iodide is one or more of potassium iodide, sodium iodide, potassium iodate or sodium iodate.

[0055] Example 1 Preparation of Mn-Sb / SnO₂ Electrode

[0056] As Figure 1As shown, a titanium plate with a usable area of 2 cm 2 is used as the substrate. Before use, it is polished with sandpaper and then ultrasonically cleaned in a 5 wt% sodium carbonate solution for 60 minutes. Subsequently, the titanium plate is etched in a 20 wt% hydrochloric acid solution at 80 °C for 2 hours. Finally, the etched titanium plate is rinsed with clean water, and the pretreatment step ends here.

[0057] Dissolve soluble tin salt, antimony salt, and manganese salt in deionized water to prepare a mixed solution with concentrations of 360 mmol / L, 15 mmol / L, and 4 mmol / L respectively. Immerse the pretreated titanium plate in the mixed solution for 1 minute, take it out and dry it at room temperature, and then calcine it at 600 °C for 10 minutes. Repeat the above operation until the catalyst loading on the titanium plate reaches 1.3 mg / cm 2 , and finally calcine it at 600 °C for 1.5 hours to obtain the Mn-Sb / SnO2 electrode.

[0058] Figure 1 (a) in Figure 1 shows the synthesis schematic diagram of the Mn-Sb / SnO2 electrode, Figure 1 (b) in Figure 1 shows the SEM image of the surface of the Mn-Sb / SnO2 electrode. It can be seen that the surface of the Mn-Sb / SnO2 electrode presents a cracked state.

[0059] As shown in Figure 2 and Figure 3 , Figure 2 shows the LSV curve and Faraday efficiency of the iodine oxidation reaction of the Mn-Sb / SnO2 electrode, Figure 3 shows the LSV curve and Faraday efficiency of the industrial BDD electrode; it can be seen that compared with the industrial BDD electrode (Boron-Doped Diamond Electrode), the Mn-Sb / SnO2 electrode has a lower oxidation voltage and a higher Faraday efficiency, so it has more excellent iodine oxidation reaction performance.

[0060] In addition, by using heavy metal salts such as nickel salts, copper salts, cobalt salts, and iron salts to replace the manganese salts used above, the corresponding Ni-Sb / SnO2, Cu-Sb / SnO2, Co-Sb / SnO2, and Fe-Sb / SnO2 electrodes can be obtained. XPS, XRD, and iodate oxidation electrochemical performance tests were respectively carried out on Ni-Sb / SnO2, Cu-Sb / SnO2, Co-Sb / SnO2, Fe-Sb / SnO2, Mn-Sb / SnO2, and Sb / SnO2. Figure 4 shows the total XRD spectra of different electrodes, Figure 5 shows the enlarged view of the local area of the XRD spectra of different electrodes, Figure 6 shows the Sn 3d spectra of different electrodes; Figure 7 shows the Sn 3d 3 / 2 spectra, Figure 8 shows the O 1s spectra of different electrodes. As Figures 4 - 8 shown, the peak shifts of XRD and XPS indicate the successful doping of different metal elements. At the same time, the Mn-Sb / SnO2 electrode exhibits the highest oxygen vacancy concentration and the best iodate oxidation electrochemical performance.

[0061] In addition, Figure 9 shows the LSV curves of iodate electrooxidation of different electrodes, Figure 10 shows the Faraday efficiency of the iodate electrooxidation reaction of different electrodes, Figure 11 shows the relevant performance parameters of different electrodes, Figure 12 shows the test results of the iodide oxidation reaction stability of the Mn-Sb / SnO2 electrode at different current densities. As can be seen from Figures 9 - 12 it, the Mn-Sb / SnO2 electrode shows a lower iodide oxidation overpotential, a higher iodide oxidation Faraday efficiency, better electrocatalytic performance parameters, and excellent iodide oxidation reaction stability compared with the electrodes doped with other metal elements. These data all prove the excellent electrocatalytic performance of the Mn-Sb / SnO2 electrode in the iodide oxidation reaction.

[0062] At the same time, Figure 13 the free energy changes of I - and IO3 - before and after adsorption on the Mn-Sb / SnO2 and Sb / SnO2 electrodes were calculated, and it was found that I - and IO3 - are more likely to be adsorbed on the surface of Mn-Sb / SnO2. Figure 14 The free energy changes of the reaction intermediates in the OER process on the Mn-Sb / SnO2 and Sb / SnO2 electrodes were calculated. It can be seen from this that the OER side reaction is less likely to occur on the surface of the Mn-Sb / SnO2 electrode. Figure 15The free energy changes of reaction intermediates during the iodine oxidation process on the Mn-Sb / SnO2 and Sb / SnO2 electrodes were calculated. It can be seen from this that the iodine oxidation reaction is more likely to occur on the surface of the Mn-Sb / SnO2 electrode. In summary, the results of density functional theory calculations (DFT) show that Mn-Sb / SnO2 exhibits more excellent iodine oxidation reaction performance than Sb / SnO2.

[0063] Example 2

[0064] As Figure 16 shown, it is an electrolysis system that uses the Mn-Sb / SnO2 electrode as the anode to absorb toluene gas. 200 mL of electrolyte with pH = 13 and potassium iodate concentration of 2 wt% was prepared. The Mn-Sb / SnO2 electrode was used as the anode and the platinum sheet electrode was used as the cathode. Electrolysis was carried out under the conditions of a current density of 0.1 A / cm 2 , and a current of 0.2 A. The toluene concentration in the treated gas was 100 ppm and the gas velocity was 300 mL / min. During the reaction process, the gas released by the electrolysis system was also detected using a gas chromatography analysis system.

[0065] As Figure 17 and Figure 18 shown, after the electrolysis system operated stably for a long time for 30 days, it still maintained a 100% toluene removal rate, and the mineralization rate of toluene and the COD (Chemical Oxygen Demand) value of the electrolyte also remained constant. At the same time, under different current density conditions, the average Faraday efficiency of the electrolysis system for generating periodate was 85%, as Figure 19 shown.

[0066] As Figure 20 shown, Figure 20 (a) in is the toluene removal rate in the electrolysis system after adding 0.2 mM phenol to the electrolyte, that is, adding an IO3 · radical quencher; Figure 20 (b) in is the toluene removal rate in the electrolysis system after adding 1 mM p-benzoquinone to the electrolyte, that is, adding an O2 -· radical quencher; Figure 20 (c) in is the toluene removal rate in the electrolysis system after adding 10 mM sodium azide to the electrolyte, that is, adding 1 an O2 radical quencher; Figure 20 (d) in is the toluene removal rate in the electrolysis system after adding 10 mM tert-butanol to the electrolyte, that is, a ·OH radical quencher. After adding different radical quenchers, the change in the toluene removal efficiency in the electrolysis system proves that the electrolysis system generates IO3 · and ·OH radicals.

[0067] Example 3

[0068] Adjust the pH of the electrolyte in Example 2 to 7 with sulfuric acid. Keep the anode and cathode materials of the electrolysis system unchanged, and continue to maintain the electrolysis under the conditions of a current density of 0.1 A / cm 2 , and a current of 0.2 A. After electrolysis for 5 h, collect the solid precipitate (iodine) deposited on the cathode surface, and dry the precipitate to recover iodine in the electrolyte.

[0069] As Figure 21 shown, the mechanism of electro-oxidation-absorption coupling method for treating hydrophobic VOCs is presented in a graphical form. Specifically, in this schematic diagram, the Mn-Sb / SnO2 electrode is used as the anode, the Pt is used as the cathode, and the KI / KOH solution is used as the electrolyte. When the electro-chemical reaction system is powered on, at the anode, the iodide ion I - in the electrolyte is oxidized to iodate IO3 - , and then the iodate is oxidized to periodate IO4 - at the anode. The periodate is then electro-activated to IO3 · and ·OH radicals at the anode. IO3 · and ·OH radicals combine with IO4 - to react with toluene dissolved in the electrolyte, mineralize it into CO2, and then be reduced to IO3 - itself, thus completing the removal of hydrophobic VOCs. At this time, the cathode reduces iodate to iodide ion, and then the iodide ion is oxidized at the anode to complete the iodide cycle, thereby realizing the whole process of highly efficient removal of different hydrophobic VOCs only driven by electric energy. Compared with traditional methods, the present invention does not require additional supplement of oxidants, has low operating costs, a stable system, no risk of secondary pollution, and at the same time has the characteristics of environmental friendliness and high efficiency and stability, providing a new solution for the treatment of hydrophobic VOCs.

[0070] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A green and efficient method for removing hydrophobic VOCs by electrocatalytically induced oxidation-absorption coupling, characterized in that: The following steps are involved: Using a high oxygen evolution overpotential electrode as the anode to achieve IO3 - The highly efficient reducing material is used as the cathode, and the alkaline iodized salt solution is used as the electrolyte to construct an iodine-based electro-oxidation self-circulating system for removing hydrophobic VOCs. When powered on, the iodine salt solution is electro-oxidized under alkaline conditions by a high oxygen evolution overpotential electrode. No external oxidant is required. Periodate is continuously and stably produced by electric energy alone. The periodate ions will electrocatalyze IO3 in situ on the electrode. · and ·OH free radicals; after gas-phase hydrophobic VOCs are introduced into the electrolyte, IO3 · The ·OH free radicals use their strong oxidizing properties to rapidly oxidize the VOCs in the soluble phase, avoiding the mass transfer limitation between the gas and liquid phases, thereby achieving rapid degradation of hydrophobic VOCs in the gas phase. After oxidizing the VOCs, the IO3 - It is reduced to a low-valent iodine salt solution at the cathode, ultimately achieving self-circulation of iodine in the system.

2. The green and efficient method for removing hydrophobic VOCs according to claim 1, characterized in that: The high oxygen evolution overpotential electrode has high adsorption selectivity and low oxidation energy barrier for low-valent iodine, so it can maintain high selectivity for electro-oxidation of low-valent iodine during long-term operation, and stably generate periodate with strong oxidizing property; at the same time, the electrode has a high oxygen evolution reaction energy barrier, which can effectively inhibit the occurrence of oxygen evolution side reaction on the electrode surface; The electrode material of the high oxygen evolution overpotential electrode includes but is not limited to titanium plate, BDD, SbO2, SnO2, PbO2 or M-Sb / SnO2 electrode; wherein M is a metal element other than Sb and Sn, and the electrode has a - and io3 - Appropriate adsorption free energy ensures high priority of iodine oxidation reaction; The cathode can convert IO3 - Efficient reduction to I - , used as cathode to achieve IO3 - The materials for efficient reduction are nickel mesh, copper mesh, platinum sheet or DSA.

3. The green and efficient method for removing hydrophobic VOCs according to claim 1, characterized in that: The pH range of the alkaline iodized salt solution is 8-14, the concentration of iodized salt in the alkaline iodized salt solution is 0.1-30wt%, and the iodized salt is one or more of potassium iodide, sodium iodide, potassium iodate or sodium iodate.

4. The green and efficient method for removing hydrophobic VOCs according to claim 1, characterized in that: The electrode material of the high oxygen evolution overpotential electrode is preferably M-Sb / SnO2 electrode.

5. The green and efficient method for removing hydrophobic VOCs according to claim 4, characterized in that: The preparation method of the M-Sb / SnO2 electrode comprises: Tin salt, antimony salt and metal salt M are dissolved in deionized water to obtain a mixed solution, a substrate is immersed in the mixed solution, and then taken out for drying and calcination to obtain a catalyst-loaded substrate; the substrate is repeatedly immersed, dried and calcined until the catalyst loading on the substrate reaches 1-5 mg / cm 2 Finally, the catalyst-loaded substrate is calcined to achieve atomic-level dispersion of Mn and Sb in SnO2, and the catalyst layer is firmly grown on the substrate to obtain a Mn-Sb / SnO2 electrode.

6. The green and efficient method for removing hydrophobic VOCs according to claim 5, characterized in that: The metal salt M is one or more of nickel salt, copper salt, cobalt salt, iron salt or manganese salt, and the concentration ratio satisfies the formation of solid solution metal oxide; The concentration of the tin salt in the mixed solution is 200-500 mmol / L, the concentration of the antimony salt is 5-50 mmol / L, and the concentration of the metal salt M is 1-50 mmol / L.

7. The green and efficient method for removing hydrophobic VOCs according to claim 5, characterized in that: The material of the substrate is titanium, lead, tin, ruthenium or zirconium.

8. The green and efficient method for removing hydrophobic VOCs according to claim 5, characterized in that: Before the substrate is immersed in the mixed solution, the substrate is pretreated to construct an interface suitable for the growth of Mn-Sb / SnO2. The pretreatment includes: First, the substrate is polished to remove the oxide on the surface; then, a 5-10wt% sodium carbonate solution is prepared, and the polished substrate is immersed in the sodium carbonate solution and ultrasonically cleaned for 1-2 hours; then, a 10-20wt% hydrochloric acid solution is prepared and heated to 50-100°C, and the ultrasonically cleaned substrate is immersed in the hydrochloric acid solution for etching for 1-2 hours; finally, the etched substrate is rinsed with clean water to complete the pretreatment.

9. The green and efficient method for removing hydrophobic VOCs according to claim 5, characterized in that: The impregnation time is 1-5 minutes, the drying temperature is room temperature, the calcination temperature is 500-1000° C., and the calcination time is 10-30 minutes.

10. The green and efficient method for removing hydrophobic VOCs according to claim 1, characterized in that: After the removal of hydrophobic VOCs, the pH range of the electrolyte is adjusted to 8-5 with acid, and the electrochemical reaction system continues to be powered. At this time, the iodine element will precipitate on the anode and cathode surfaces in the form of precipitation, ultimately achieving the recovery of iodine in the alkaline iodized salt solution.

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