Electrochemical method and system for fully / polyhalogenated organic matters in mineralized water

Abstract

The invention discloses an electrochemical method and system for fully / polyhalogenated organic matters in mineralized water, and the method comprises the following steps: adding electrolyte and hydrogen peroxide into wastewater containing fully / polyhalogenated organic matters, and uniformly mixing to obtain a mixed solution A; introducing the mixed solution A and ozone into a mixer, and uniformly mixing to obtain a mixed solution B; and introducing the mixed solution B into a penetration type reactor, and carrying out sufficient electrolysis by taking an inert electrode as an anode and a porous electrode as a cathode so as to realize mineralization of the fully / polyhalogenated organic matters in the wastewater. The method is simple and convenient to operate, metal ions do not need to be added, expensive electrode materials do not need to be used, and the form and distribution of the alkaline diffusion layer can be regulated and controlled by regulating the current density and the overflowing hydraulic state in the reaction, so that the generation of oxidizing and reducing species is regulated and controlled, efficient mineralization of full / polyhalogenated organic matters is realized, and the method is suitable for industrial production. And the method has good practical application value, so that the treatment of all / polyhalogenated organic matters is more economical and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of advanced oxidation water treatment, and in particular relates to an electrochemical method and system for mineralizing full / polyhalogenated organic matter in water. Background Art

[0002] As a special type of pollutant, the halogens in the molecular structure of fully / polyhalogenated organic matter have strong negative electronegativity, which makes it difficult to remove such organic matter by simple oxidation. Typical fully / polyhalogenated organic matter include perfluorooctanoic acid / sulfonic acid (PFOA / PFOS), polychlorinated phenols and polybrominated diphenyl ethers, which pose a serious threat to the environment and human health.

[0003] As a mature ozone advanced oxidation water treatment technology, ozone-hydrogen peroxide technology can produce a variety of active species including strong oxidizing and reducing species to degrade fully / polyhalogenated organic matter. However, in actual application, the direct reaction rate between hydrogen peroxide molecules and ozone is extremely low, which limits the treatment efficiency of ozone-hydrogen peroxide technology. The ionization product of hydrogen peroxide, HO2 - It can produce chain reaction with ozone molecules, and then generate OH and Therefore, the ionization of hydrogen peroxide is the key step in its chain reaction with ozone. However, the pKa of hydrogen peroxide is 11.8. Under neutral or weakly alkaline conditions, the degree of ionization of hydrogen peroxide is low, which has become a major bottleneck limiting the application of ozone-hydrogen peroxide technology.

[0004] Although there have been reports on advanced oxidation methods for electrocatalytic ozone-hydrogen peroxide processes, such as CN114716001A, which discloses a device and method for in-situ electrogenerated hydrogen peroxide in combination with ozone to treat refractory organic matter. However, the device for in-situ electrogenerated hydrogen peroxide requires a high power input, so the cost is high; at the same time, the electrode material has high requirements, so the electrode stability is poor; and due to the limitation of oxygen mass transfer, the concentration of hydrogen peroxide produced will be low, which is difficult to meet the reducing conditions required for the dehalogenation of fully / polyhalogenated organic matter. Therefore, how to solve the problem of extremely low direct reaction rate between hydrogen peroxide molecules and ozone, so as to improve the organic matter treatment efficiency of ozone-hydrogen peroxide, and thus achieve efficient mineralization of fully / polyhalogenated organic matter has become an urgent problem to be solved. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an electrochemical method for mineralizing full / polyhalogenated organic matter in water, which solves the problem of extremely low direct reaction rate of hydrogen peroxide molecules and ozone in the prior art, and simultaneously generates oxidizing and reducing species to efficiently mineralize full / polyhalogenated organic matter.

[0006] Furthermore, the present invention also provides an electrochemical system for implementing the above method.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] An electrochemical method for mineralizing fully / polyhalogenated organic matter in water comprises the following steps:

[0009] (1) adding electrolyte and hydrogen peroxide to wastewater containing fully / polyhalogenated organic matter and mixing them evenly to obtain a mixed solution A;

[0010] (2) introducing the mixed solution A and ozone into a mixer and mixing them evenly to obtain a mixed solution B;

[0011] (3) The mixed solution B is introduced into an electrochemical reactor, with an inert electrode as an anode and a porous electrode as a cathode, and sufficient electrolysis is performed to achieve the mineralization of the full / poly-halogenated organic matter in the wastewater; the anode and the cathode are arranged vertically from top to bottom, and the mixed solution B is introduced into the electrochemical reactor, first flowing through the anode, and then flowing from the anode to the cathode.

[0012] Furthermore, in step (1), the concentration of hydrogen peroxide in the mixed solution A is 10 to 100 mmol / L. A concentration of hydrogen peroxide higher than this range will result in a decrease in the oxidizing capacity during the treatment process, because hydrogen peroxide itself reacts with ·OH, thereby consuming oxidizing species; while a concentration of hydrogen peroxide lower than this range will result in the inability of ozone to be effectively activated to produce active species, resulting in a waste of ozone in the treatment process and a decrease in the treatment effect.

[0013] Furthermore, in step (1), the concentration of the electrolyte in the mixed solution A is 1 to 100 mmol / L. If the electrolyte concentration is lower than this range, an electric circuit cannot be formed in the electrochemical reactor, resulting in the inability to carry out the electrochemical reaction and a decrease in the treatment effect; if the electrolyte concentration is higher than this range, salt precipitation occurs and there is a risk of clogging the reactor, so the electrolyte concentration of the reaction solution should be 1 to 100 mmol / L.

[0014] Furthermore, in step (2), the concentration of ozone introduced into the mixer is 10-100 mg / L, and the gas flow rate is 0.1-0.5 L / min. If the ozone concentration is lower than this range, the efficiency of ozone dissolving in water will be reduced, because the dissolution of ozone in water obeys Henry's law and is proportional to its partial pressure in the gas phase. Low concentration will cause it to be unable to effectively dissolve in water to participate in the reaction; if the concentration is higher than this range, it will also cause ozone to overflow before being used in time, resulting in reduced efficiency, high energy consumption, and poor economy. If the gas flow rate is lower than this range, the ozone gas and the aqueous solution cannot be fully mixed, resulting in a decrease in the treatment effect; if it is higher than this range, the proportion of gas in the reactor will be too large, occupying the reaction area and causing a decrease in treatment efficiency.

[0015] Furthermore, in step (3), the mixed solution B is introduced into the electrochemical reactor at a pressure of 0.01 to 0.3 MPa.

[0016] Furthermore, in step (3), the current density of electrolysis is 1 to 10 mA / cm 2 .

[0017] Furthermore, in step (3), the inert electrode includes titanium-plated platinum or ruthenium-iridium electrode; the porous electrode includes a metal electrode, a metal oxide electrode or a carbon-based electrode.

[0018] Furthermore, the electrolyte includes one or more electrolytes selected from the group consisting of sulfate, chloride, and carbonate.

[0019] Furthermore, the carbon-based electrode includes graphite, activated carbon fiber, carbon nanotube or graphene.

[0020] An electrochemical system for mineralizing full / polyhalogenated organic matter in water, comprising a wastewater pool, an ozone generator, a water ejector and a penetrating reactor, wherein the liquid outlet of the wastewater pool and the gas outlet of the ozone generator are connected to the feed port of the water ejector through a liquid outlet pipe and a gas outlet pipe respectively, the discharge port of the water ejector is connected to the liquid inlet pipe of the penetrating reactor through a pipe, and the gas inlet of the ozone generator is connected to an oxygen cylinder through a pipe; a water pump, a pressure reducing valve and a pressure gauge are sequentially arranged on the liquid outlet pipe along the direction of liquid flow; an ozone detector and a gas flow meter are sequentially arranged on the gas outlet pipe along the direction of gas flow;

[0021] The penetration reactor comprises an upper cover and a lower cover, and a cylindrical cavity is formed when the upper cover and the lower cover are closed. A titanium mesh support layer, a porous cathode and a hollow titanium foil are arranged in sequence from bottom to top in the lower cover; an inert anode is installed at the top of the upper cover, and a sealing rubber gasket is arranged between the upper cover and the lower cover, so that the penetration reactor can form a good seal after the upper cover and the lower cover are closed; a liquid inlet pipe is arranged on one side wall of the upper cover, and a lower chamber liquid outlet pipe is arranged on the side wall of the lower cover; the penetration reactor also includes a power supply, the positive electrode of the power supply is connected to the inert anode through an anode terminal, and the negative electrode of the power supply is connected to the hollow titanium foil through a wire.

[0022] Furthermore, an upper chamber liquid outlet pipe is arranged on the other side wall of the upper cover, and the liquid outlet is connected to the liquid inlet of the wastewater tank through a pipeline.

[0023] Furthermore, a hydrogen peroxide dosing device is arranged above the wastewater pool.

[0024] Working principle: The electrochemical method for mineralizing full / polyhalogenated organic matter in water adopts a penetrating reactor for electrolysis. When the porous cathode is energized, an alkaline diffusion layer can be formed between the cathode and the surrounding area, providing a local strong alkaline environment. The alkaline diffusion layer near the cathode can promote the ionization of hydrogen peroxide, thereby enhancing the ozone-hydrogen peroxide process and generating oxidative (·OH) and reductive ( · H. ) species, and quickly mineralize fully / polyhalogenated organic matter. In this process, the present invention regulates the pH and distribution of the alkaline diffusion layer by adjusting the hydraulic state and current density, thereby regulating the generation of oxidizing and reducing species. By adjusting the wastewater inflow pressure, the hydraulic conditions when the water flows through the porous cathode can be adjusted, thereby optimizing the activation efficiency of ozone in the cathode alkaline diffusion layer and regulating the generation of oxidizing and reducing active species; at the same time, the electric field strength in the reactor can be regulated by adjusting the current density of the DC power supply, thereby regulating the pH on the electrode surface, so as to achieve the regulation of ozone in the cathode alkaline diffusion layer to produce oxidizing and reducing species and the degradation and mineralization of fully / polyhalogenated organic matter.

[0025] Hydrogen peroxide ionizes in a strong alkaline environment to produce , and the generated It reacts quickly with ozone to generate oxidizing and reducing active species through chain reactions to degrade fully / polyhalogenated organic matter.

[0026] The main pathways for the generation of active species are:

[0027] (1) Generation of reducing active species:

[0028]

[0029] e - +H + → · H

[0030]

[0031] (2) Generation of oxidative active species:

[0032]

[0033]

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The electrochemical method for mineralizing all / polyhalogenated organic matter in water of the present invention, on the one hand, realizes the efficient removal of all / polyhalogenated organic matter in mineralized water by combining ozone oxidation and electrochemical treatment technology; on the other hand, by accurately controlling the current density and the overcurrent pressure, the fine regulation of the morphology and distribution of the alkaline diffusion layer is realized. This regulation strategy not only optimizes the generation of oxidizing and reducing active species in the ozone-hydrogen peroxide process, but also realizes the efficient mineralization of all / polyhalogenated organic matter with lower energy input. The present invention is easy to operate, does not require the addition of metal ions, and does not require the use of expensive electrode materials. It has good practical value and makes the treatment of all / polyhalogenated organic matter more economical and environmentally friendly. Compared with traditional treatment methods, the method of the present invention reduces the operating cost and environmental impact while ensuring a high mineralization rate (up to 90% or more), and provides a new efficient and environmentally friendly way to treat wastewater containing all / polyhalogenated organic matter.

[0036] 2. The electrochemical system for mineralizing all / polyhalogenated organic matter in water of the present invention effectively enriches all / polyhalogenated organic matter through the porous cathode in the penetration reactor, and efficiently degrades it by using the oxidizing and reducing active species generated by ozone and hydrogen peroxide; wherein the huge specific surface area and abundant pores of the porous cathode not only promote the local enrichment of pollutants, but also create a strong alkaline environment, accelerate the ionization of hydrogen peroxide and the reaction with ozone, thereby significantly improving the degradation efficiency of all / polyhalogenated organic matter. This design makes the electrochemical process more efficient and reduces processing time and energy consumption.

[0037] 3. The electrochemical system for mineralizing all / polyhalogenated organic matter in water of the present invention has a unique design of the penetration reactor, which uses a porous cathode to enrich pollutants and create a local strong alkaline environment, promotes the rapid reaction of hydrogen peroxide ionization and ozone, generates a large number of oxidizing and reducing active species, and significantly enhances the degradation efficiency of organic matter. At the same time, by adjusting the overflow pressure and current intensity, the strength and distribution of the alkaline diffusion layer, as well as the alkalinity range and strength of the porous cathode surface can be flexibly regulated, thereby optimizing the treatment process and reducing energy input. In addition, the setting of the circulation treatment system further improves the treatment effect of wastewater and ensures the effluent water quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a time-removal rate diagram of PFOA in wastewater after electrochemical treatment in Example 1, Comparative Examples 1 and 2.

[0039] Figure 2 This is a graph showing the TOC removal rate of PFOA in wastewater after electrochemical treatment in Example 1, Comparative Examples 1 and 2.

[0040] Figure 3 This is a time-removal rate diagram of PFOA in wastewater after electrochemical treatment in Examples 1, 2, and 3.

[0041] Figure 4 This is a graph showing the TOC removal rate of PFOA in wastewater after electrochemical treatment in Examples 1, 2, and 3.

[0042] Figure 5 This is a graph showing the removal rates of various types of fully / polyhalogenated organic matter in wastewater after electrochemical treatment in Examples 4 to 7.

[0043] Figure 6 This is a time-removal rate diagram of PFOA in wastewater after electrochemical treatment in Examples 1, 8, and 9.

[0044] Figure 7 This is a graph showing the TOC removal rate of PFOA in wastewater after electrochemical treatment in Examples 1, 8, and 9.

[0045] Figure 8 is the pH value of the wastewater after electrochemical treatment in Example 8.

[0046] Fig. 9 It is a schematic diagram of the structure of the electrochemical system for mineralizing full / polyhalogenated organic matter in water according to the present invention.

[0047] Fig. 9 Among them, 1. hydrogen peroxide dosing device; 2. wastewater tank; 3. water pump; 4. pressure reducing valve; 5. pressure gauge; 6. water ejector; 7. DC power supply; 8. liquid inlet pipe; 9. anode terminal; 10. upper cover; 11. inert anode; 12. upper chamber liquid outlet pipe; 13. sealing rubber pad; 14. hollow titanium foil; 15. porous cathode; 16. lower chamber liquid outlet pipe; 17. titanium mesh support layer; 18. lower cover; 19. gas flow meter; 20. ozone detector; 21. ozone generator; 22. oxygen cylinder; 23. penetration reactor. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0049] The fully / polyhalogenated organic compounds described in the present invention are organic compounds in which the hydrogen atoms in the compounds are replaced by one or more halogens (fluorine, chlorine, bromine, iodine), mainly including: perfluorinated or partially fluorinated compounds (PFCs), chlorinated organic compounds (COCs) and brominated organic compounds (BOCs).

[0050] 1. Implementation

[0051] Example 1

[0052] This embodiment provides an electrochemical method for mineralizing fully / polyhalogenated organic matter in water to treat wastewater containing PFOA; the method comprises the following steps:

[0053] (1) Prepare 10 mg / L PFOA solution before the experiment;

[0054] (2) adding anhydrous sodium sulfate and hydrogen peroxide to the PFOA solution and mixing them evenly to obtain a mixed solution A; the concentration of anhydrous sodium sulfate in the mixed solution A is 1 mmol / L, and the concentration of hydrogen peroxide is 20 mmol / L;

[0055] (3) Mixing the mixed solution A and ozone into a water injector and mixing them evenly to obtain a mixed solution B; the concentration of ozone introduced into the water injector is 80 mg / L, and the gas flow rate is 0.2 L / min;

[0056] (4) The mixed solution B was introduced into an electrochemical reactor at a pressure of 0.1 MPa, with a titanium-plated platinum electrode as the anode and activated carbon fiber as the cathode. The current density was 10 mA / cm 2 The mineralization of the full / polyhalogenated organic matter in the wastewater can be achieved by fully electrolyzing under the conditions; the anode and the cathode in the electrochemical reactor are arranged vertically from top to bottom, and the mixed solution B is introduced into the electrochemical reactor, first flowing through the anode, and then flowing from the anode to the cathode.

[0057] Example 2

[0058] This embodiment provides an electrochemical method for mineralizing fully / polyhalogenated organic matter in water. The main steps are the same as those in Example 1, except that the current density during electrolysis is 5 mA / cm 2 .

[0059] Example 3

[0060] This embodiment provides an electrochemical method for mineralizing fully / polyhalogenated organic matter in water. The main steps are the same as those in Example 1, except that the current density during electrolysis is 1 mA / cm 2 .

[0061] Example 4

[0062] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water to treat wastewater containing diclofenac; the method comprises the following steps:

[0063] (1) Prepare 20 μmol / L diclofenac solution before the experiment;

[0064] (2) adding anhydrous sodium sulfate and hydrogen peroxide to the PFOA solution and mixing them evenly to obtain a mixed solution A; the concentration of anhydrous sodium sulfate in the mixed solution A is 1 mmol / L, and the concentration of hydrogen peroxide is 10 mmol / L;

[0065] (3) Mixing the mixed solution A and ozone into a water injector and mixing them evenly to obtain a mixed solution B; the concentration of ozone introduced into the water injector is 50 mg / L, and the gas flow rate is 0.2 L / min;

[0066] (4) The mixed solution B was introduced into an electrochemical reactor at a pressure of 0.1 MPa, with a titanium-plated platinum electrode as the anode and activated carbon fiber as the cathode. The current density was 5 mA / cm 2 The mineralization of the full / polyhalogenated organic matter in the wastewater can be achieved by fully electrolyzing under the conditions; the anode and the cathode in the electrochemical reactor are arranged vertically from top to bottom, and the mixed solution B is introduced into the electrochemical reactor, first flowing through the anode, and then flowing from the anode to the cathode.

[0067] Example 5

[0068] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water. The main steps are the same as those in Example 4, except that diclofenac is replaced by p-chlorobenzoic acid.

[0069] Example 6

[0070] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water. The main steps are the same as those in Example 4, except that diclofenac is replaced by ibuprofen.

[0071] Example 7

[0072] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water. The main steps are the same as those in Example 4, except that diclofenac is replaced by 2,4-dichlorophenoxyacetic acid.

[0073] Example 8

[0074] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water. The main steps are the same as those in Embodiment 1, except that the pressure is adjusted to 0.2 MPa.

[0075] Example 9

[0076] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water. The main steps are the same as those in Embodiment 1, except that the pressure is adjusted to 0.3 MPa.

[0077] Example 10

[0078] This embodiment provides an electrochemical method for mineralizing full / polyhalogenated organic matter in water. The main steps are the same as those in Embodiment 1, except that the following device of the present invention is used for treatment.

[0079] In the penetration reactor of this embodiment, the pH of the inlet water, the outlet water of the upper chamber and the outlet water of the lower chamber are as follows: Figure 8 As shown by Figure 8 It can be seen that the inlet pH is 5.2, the outlet pH of the upper chamber is 2.9, and the outlet pH of the lower chamber is 12.1. The results show that the penetrating reactor can provide an alkaline environment for the generation of oxidative and reductive active species and promote the degradation of fully / polyhalogenated organic matter.

[0080] Comparative Example 1

[0081] This comparative example provides a method for mineralizing full / polyhalogenated organic matter in water, and its main steps are the same as those of Example 1, except that no electricity is applied for electrolysis.

[0082] Comparative Example 2

[0083] This comparative example provides a method for mineralizing full / polyhalogenated organic matter in water, and its main steps are the same as those of Example 1, except that hydrogen peroxide is not added to the wastewater.

[0084] 2. Data Analysis

[0085] 1. Effects of power supply conditions and hydrogen peroxide on organic matter degradation

[0086] The time-removal rate of PFOA in the wastewater after electrochemical treatment in Example 1 of the present invention and Comparative Examples 1 and 2 is as follows Figure 1 As shown by Figure 1 It can be seen that after 60 minutes of treatment, the PFOA removal rate of the ozone-hydrogen peroxide process enhanced by the alkaline diffusion layer in Example 1 of the present invention is 99.0%, while the PFOA removal rate of the ozone-hydrogen peroxide process in Comparative Example 1 is 25.6%, and the PFOA removal rate of the electro-ozone process in Comparative Example 2 is 47.5%.

[0087] Further, the TOC removal rate of PFOA in the wastewater after electrochemical treatment in Example 1 of the present invention and Comparative Examples 1 and 2 is shown in FIG. Figure 2 As shown by Figure 2 It can be seen that after 60 minutes of treatment, the TOC removal rate of PFOA by the ozone-hydrogen peroxide process enhanced by the alkaline diffusion layer in Example 1 of the present invention is 92.6%, the TOC removal rate of PFOA by the ozone-hydrogen peroxide process in Comparative Example 1 is 10.6%, and the TOC removal rate of PFOA by the electro-ozone process in Comparative Example 2 is 23.8%.

[0088] It can be seen that compared with the situation where no power is applied and no hydrogen peroxide is added, the addition of the alkaline diffusion layer of the present invention can greatly improve the efficiency of activating ozone, degrade PFOA in water, and effectively improve the TOC removal rate.

[0089] 2. Influence of current density

[0090] The time-removal rate of PFOA in the wastewater after electrochemical treatment in Examples 1, 2 and 3 of the present invention is as follows: Figure 3 As shown by Figure 3 It can be seen that after 60 minutes of reaction, the current density of Example 1 is 10 mA / cm 2 When the current density of Example 2 is 5 mA / cm 2 When the current density of Example 3 is 1 mA / cm 2 When , the removal rate of PFOA was 65.5%;

[0091] Further, the TOC removal rate of PFOA in the wastewater after electrochemical treatment in Examples 1, 2, and 3 of the present invention is shown in FIG. Figure 4 As shown by Figure 4 It can be seen that after 60 minutes of reaction, the current density of Example 1 is 10 mA / cm 2 When the TOC removal rate of PFOA is 92.6%, the current density of Example 2 is 5 mA / cm 2 When the current density of Example 3 is 1 mA / cm 2 The TOC removal rate of PFOA was 19.4%.

[0092] It can be seen that when the current density is 1~10mA / cm 2 When the current density is 1mA / cm 2 The degradation effect of organic matter is not good when the current density is 5-10 mA / cm 2 .

[0093] 3. Influence of organic matter types

[0094] The removal rates of various types of fully / polyhalogenated organic matter in wastewater after electrochemical treatment in Examples 4 to 7 of the present invention are shown in the figure below. Figure 5 As shown by Figure 5 It can be seen that the TOC removal rates of diclofenac, p-chlorobenzoic acid, ibuprofen and 2,4-dichlorophenoxyacetic acid by the alkaline diffusion layer enhanced ozone-hydrogen peroxide process are 98.2%, 90.3%, 95.6% and 92.6%, respectively. It can be seen that the electrochemical method of the present invention is suitable for the efficient degradation of various fully / polyhalogenated organic matter.

[0095] 4. Influence of overcurrent pressure

[0096] The time-removal rate of PFOA in the wastewater after electrochemical treatment in Examples 1, 8 and 9 of the present invention is as follows: Figure 6 As shown by Figure 6It can be seen that after 60 minutes of reaction, when the overflow pressure of Example 1 was 0.1MPa, the removal rate of PFOA was 99.0%; when the current density of Example 8 was 0.2MPa, the removal rate of PFOA was 88.5%; when the current density of Example 9 was 0.3MPa, the removal rate of PFOA was 72.1%;

[0097] Further, the TOC removal rate of PFOA in the wastewater after electrochemical treatment in Examples 1, 8 and 9 of the present invention is shown in FIG. Figure 7 As shown by Figure 7 It can be seen that after 60 minutes of reaction, when the overflow pressure of Example 1 was 0.1 MPa, the TOC removal rate of PFOA was 92.6%; when the overflow pressure of Example 8 was 0.2 MPa, the TOC removal rate of PFOA was 69.9%; when the overflow pressure of Example 9 was 0.3 MPa, the TOC removal rate of PFOA was 42.8%.

[0098] It can be seen that when the current density is 0.1-0.3 MPa, the degradation of PFOA and the removal of TOC can be achieved, but when the overflow pressure is greater than 0.1 MPa, the degradation effect of organic matter is not good. The preferred overflow pressure is 0.1 MPa.

[0099] 3. The present invention also provides a system for realizing the electrochemical method for mineralizing the full / polyhalogenated organic matter in water.

[0100] like Fig. 9 As shown, an electrochemical system for mineralizing full / polyhalogenated organic matter in water comprises a wastewater pool 2, an ozone generator 21, a water ejector 6 and a penetration reactor 23, wherein the liquid outlet of the wastewater pool 2 and the gas outlet of the ozone generator 21 are connected to the feed port of the water ejector 6 through a liquid outlet pipe and a gas outlet pipe respectively, the discharge port of the water ejector 6 is connected to the liquid inlet pipe 8 of the penetration reactor 23 through a pipe, a hydrogen peroxide dosing device 1 is arranged above the wastewater pool 2, and the gas inlet of the ozone generator 21 is connected to an oxygen cylinder 22 through a pipe; a water pump 3, a pressure reducing valve 4 and a pressure gauge 5 are arranged in sequence on the liquid outlet pipe along the direction of liquid flow; an ozone detector 20 and a gas flow meter 19 are arranged in sequence on the gas outlet pipe along the direction of gas flow;

[0101] The penetration reactor 23 includes an upper cover 10 and a lower cover 18, and the upper cover 10 and the lower cover 18 form a cylindrical cavity when they are closed. In the lower cover 18, a titanium mesh support layer 17, a porous cathode 15, and a hollow titanium foil 14 are stacked in sequence from bottom to top; an inert anode 11 is installed on the top of the upper cover 10, and a sealing rubber gasket 13 is arranged between the upper cover 10 and the lower cover 18, so that the penetration reactor 23 can form a good seal when the upper cover 10 and the lower cover 18 are closed; a liquid inlet pipe 8 is arranged on a side wall of the upper cover 10, and a lower chamber liquid outlet pipe 16 is arranged on the side wall of the lower cover 18; the penetration reactor 23 also includes a DC power supply 7, the positive electrode of the DC power supply 7 is connected to the inert anode 11 through the anode terminal 9, and the negative electrode of the DC power supply 7 is connected to the hollow titanium foil 14 through a wire.

[0102] In a specific implementation, an upper chamber liquid outlet pipe 12 is disposed on the other side wall of the upper cover 10 .

[0103] During specific implementation, the liquid outlet of the upper chamber liquid outlet pipe 12 is connected to the liquid inlet of the wastewater pool 2 through a pipeline.

[0104] In specific implementation, the distance between the inert anode 11 and the porous cathode 15 is 1 cm, and the hydraulic retention time of the electrolyte in the reactor is 0.1 to 1 min. Too short a hydraulic retention time will result in the reaction solution being unable to fully react in the reactor, and a longer hydraulic retention time will allow the reaction solution to fully react, and the treatment efficiency is very high, but it will greatly increase energy consumption and have poor economic efficiency, so a moderate hydraulic retention time is appropriate.

[0105] Working principle:

[0106] (1) Wastewater pretreatment and ozone generation:

[0107] The wastewater is first collected in the wastewater pool 2. The hydrogen peroxide dosing device 1 arranged above the wastewater pool 2 can add hydrogen peroxide to the wastewater as needed to enhance the subsequent treatment effect. The oxygen provided by the oxygen cylinder 22 is input into the ozone generator 21 through a pipeline to provide pressure for the pipeline. At the same time, the ozone generator 21 converts oxygen into ozone using high voltage or ultraviolet rays.

[0108] (2) Mixing of wastewater and ozone:

[0109] Wastewater is pumped out from the liquid outlet of the wastewater tank 2 by a water pump 3 and flows along the liquid outlet pipe. On the pipe, a pressure reducing valve 4 is sequentially arranged to adjust the water pressure and thus adjust the hydraulic state in the penetration reactor 23, and a pressure gauge 5 is used to monitor the water pressure in the pipe. At the same time, the ozone generated by the ozone generator 21 is output through the gas outlet pipe. An ozone detector 20 is arranged on the pipe to monitor the ozone concentration, and a gas flow meter 19 is used to detect and adjust the flow rate of ozone. Wastewater and ozone meet and mix at the water ejector 6. The water ejector 6 uses the negative pressure generated by the high-speed water flow to absorb ozone and fully mix it with the wastewater to form an ozone-containing wastewater solution.

[0110] (3) Electrochemical treatment:

[0111] The ozone-containing wastewater solution enters the penetration reactor 23 through a pipeline. The penetration reactor 23 is composed of a cylindrical cavity formed by closing the upper cover 10 and the lower cover 18, and a titanium mesh support layer 17, a porous cathode 15 and a hollow titanium foil 14 are stacked in sequence inside. An inert anode 11 is installed on the top of the upper cover 10 and is connected to the positive electrode of the DC power supply 7. The hollow titanium foil 14 is connected to the negative electrode of the DC power supply 7 through a wire to form an electrolysis circuit. Under the action of pressure and gravity, the ozone-containing wastewater solution flows downward in the penetration reactor 23, flushing the porous cathode 15, and the fully / polyhalogenated organic matter is adsorbed on the surface of the porous cathode 15 to achieve enrichment. Under the action of the electric field, the rich pores of the porous cathode 15 have a local strong alkaline environment, and hydrogen peroxide is more easily ionized when flowing through the porous cathode 15, and its ionization product It can react quickly with ozone to generate oxidizing and reducing active species at the same time, and quickly degrade the electrolyte and the fully / polyhalogenated organic matter adsorbed on the surface of the porous cathode 15. In the whole system, the hydraulic state in the penetration reactor 23 can be adjusted by adjusting the pipeline pressure, and then the flow rate on the surface of the porous cathode 15 can be adjusted to adjust the strength and distribution of the alkaline diffusion layer. At the same time, the current intensity can also be adjusted to change the alkalinity range and strength on the surface of the porous cathode 15, thereby promoting the ionization of hydrogen peroxide, breaking the rate-limiting step of the ozone-hydrogen peroxide process, and greatly enhancing the ozone-hydrogen peroxide process with a small energy input to simultaneously generate oxidizing and reducing active species to degrade fully / polyhalogenated organic matter.

[0112] (4) Recycling of treated wastewater:

[0113] The treated wastewater is discharged from the lower chamber outlet pipe 16 under the action of pressure.

[0114] During specific implementation, an upper chamber liquid outlet pipe 12 is also provided on the other side wall of the upper cover 10, so that water can also flow out from the upper chamber liquid outlet pipe 12 under the action of water pressure, and form a cross flow with the lower chamber liquid outlet pipe 16, thereby avoiding blockage of the liquid outlet pipe. At the same time, the liquid outlet of the upper chamber liquid outlet pipe 12 is connected to the liquid inlet of the wastewater tank 2 through a pipeline to form a circulation treatment system. In this way, the treated wastewater can re-enter the wastewater tank 2 for further treatment, or be discharged or recycled according to the treatment effect. It can be seen that the present invention effectively removes the full / polyhalogenated organic matter in the mineralized water through the combination of ozone oxidation and electrochemical treatment, thereby improving the treatment efficiency and effect of the wastewater.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrochemical method for mineralizing fully / polyhalogenated organic matter in water, characterized in that: The following steps are involved: (1) adding electrolyte and hydrogen peroxide to wastewater containing fully / polyhalogenated organic matter and mixing them evenly to obtain a mixed solution A; (2) introducing the mixed solution A and ozone into a mixer and mixing them evenly to obtain a mixed solution B; (3) The mixed solution B is introduced into an electrochemical reactor, with an inert electrode as an anode and a porous electrode as a cathode, and sufficient electrolysis is performed to achieve the mineralization of the full / poly-halogenated organic matter in the wastewater; the anode and the cathode are arranged vertically from top to bottom, and the mixed solution B is introduced into the electrochemical reactor, first flowing through the anode, and then flowing from the anode to the cathode.

2. The electrochemical method for mineralizing full / polyhalogenated organic matter in water according to claim 1, characterized in that: In the step (1), the concentration of hydrogen peroxide in the mixed solution A is 10 to 100 mmol / L.

3. The electrochemical method for mineralizing full / polyhalogenated organic matter in water according to claim 1, characterized in that: In the step (1), the concentration of the electrolyte in the mixed solution A is 1 to 100 mmol / L.

4. The electrochemical method for mineralizing full / polyhalogenated organic matter in water according to claim 1, characterized in that: In the step (2), the concentration of ozone introduced into the mixer is 10 to 100 mg / L, and the gas flow rate is 0.1 to 0.5 L / min.

5. The electrochemical method for mineralizing full / polyhalogenated organic matter in water according to claim 1, characterized in that: In the step (3), the mixed solution B is introduced into the electrochemical reactor at a pressure of 0.01 to 0.3 MPa.

6. The electrochemical method for mineralizing full / polyhalogenated organic matter in water according to claim 1, characterized in that: In the step (3), the current density of electrolysis is 1-10 mA / cm 2 .

7. The electrochemical method for mineralizing full / polyhalogenated organic matter in water according to claim 1, characterized in that: In the step (3), the inert electrode includes a titanium-plated platinum or ruthenium-iridium electrode; the porous electrode includes a metal electrode, a metal oxide electrode or a carbon-based electrode.

8. An electrochemical system for mineralizing fully / polyhalogenated organic matter in water, characterized in that: It includes a wastewater pool, an ozone generator, a water ejector and a penetrating reactor. The liquid outlet of the wastewater pool and the gas outlet of the ozone generator are connected to the feed port of the water ejector through a liquid outlet pipe and a gas outlet pipe respectively. The discharge port of the water ejector is connected to the liquid inlet pipe of the penetrating reactor through a pipe, and the gas inlet of the ozone generator is connected to the oxygen cylinder through a pipe. A water pump, a pressure reducing valve and a pressure gauge are sequentially arranged on the liquid outlet pipe along the direction of liquid flow; an ozone detector and a gas flow meter are sequentially arranged on the gas outlet pipe along the direction of gas flow. The penetration reactor comprises an upper cover and a lower cover, and a cylindrical cavity is formed when the upper cover and the lower cover are closed. A titanium mesh support layer, a porous cathode and a hollow titanium foil are arranged in sequence from bottom to top in the lower cover; an inert anode is installed at the top of the upper cover, and a sealing rubber gasket is arranged between the upper cover and the lower cover, so that the penetration reactor can form a good seal after the upper cover and the lower cover are closed; a liquid inlet pipe is arranged on one side wall of the upper cover, and a lower chamber liquid outlet pipe is arranged on the side wall of the lower cover; the penetration reactor also includes a power supply, the positive electrode of the power supply is connected to the inert anode through an anode terminal, and the negative electrode of the power supply is connected to the hollow titanium foil through a wire.

9. The electrochemical system for mineralizing full / polyhalogenated organic matter in water according to claim 8, characterized in that: An upper chamber liquid outlet pipe is arranged on the other side wall of the upper cover, and the liquid outlet is connected to the liquid inlet of the wastewater tank through a pipeline.

10. The electrochemical system for mineralizing full / polyhalogenated organic matter in water according to claim 9, characterized in that: A hydrogen peroxide dosing device is arranged above the wastewater pool.

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