A multi-polar electrochemical treatment method suitable for high-salt organic wastewater

Abstract

A kind of multi-pole electrochemical treatment method suitable for high salt organic wastewater, in electrochemical reactor, with the order of first metal iron electrode, titanium-based metal oxide coating electrode, second metal iron electrode, boron-doped diamond electrode, each electrode is arranged in parallel;Wherein, first metal iron electrode and boron-doped diamond electrode are cathode and anode respectively, titanium-based metal oxide coating electrode and second metal iron electrode are both anode on the side close to first metal iron electrode, and the other side is cathode;High salt organic wastewater is introduced into electrochemical reactor, OH ‑ Is generated on the cathode side;Chloride ion in high salt organic wastewater is converted into active chlorine on the anode side of titanium-based metal oxide coating electrode;Fe (OH) 3 is generated on the anode side of second metal iron electrode;Boron-doped diamond electrode converts sulfate ion in high salt organic wastewater into sulfate radical;Active chlorine oxidation, sulfate radical oxidation and coagulation effect jointly strengthen the removal of organic matter in high salt organic wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, relates to sewage and wastewater treatment technology, and particularly relates to a multi-electrode electrochemical treatment method suitable for high-salt organic wastewater. Background Art

[0002] Wastewater from the energy and chemical industry is diverse, complex, and challenging to treat. High-salinity organic wastewater, containing large amounts of inorganic salt ions and organic pollutants, is particularly challenging to treat. Commonly used wastewater treatment technologies include advanced oxidation processes (ADTs). These processes remove organic matter by generating oxidatively active species, such as hydroxyl radicals. However, the presence of large amounts of inorganic anions quenches these reactive oxygen species, limiting their effectiveness in treating high-salinity organic wastewater. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a multipolar electrochemical treatment method suitable for high-salt organic wastewater. By arranging multiple electrodes in parallel, one side of the electrodes other than the extreme electrodes is an anode and the other side is a cathode, and the anions in the high-salt organic wastewater are converted in situ into various types of oxidative active species, which are oxidized to remove organic matter through free radical and non-free radical pathways, and at the same time, hardness ions are removed through cathode precipitation.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A multi-electrode electrochemical treatment method for high-salt organic wastewater, wherein in an electrochemical reactor, the electrodes are arranged in parallel in the order of a first metallic iron electrode, a titanium-based metal oxide-coated electrode, a second metallic iron electrode, and a boron-doped diamond electrode; wherein the first metallic iron electrode and the boron-doped diamond electrode serve as a cathode and an anode, respectively, and the titanium-based metal oxide-coated electrode and the second metallic iron electrode each serve as an anode on one side thereof close to the first metallic iron electrode and as a cathode on the other side thereof;

[0006] The high-salt organic wastewater is introduced into the electrochemical reactor, and the cathode side of the first metal iron electrode, the cathode side of the titanium-based metal oxide coating electrode and the cathode side of the second metal iron electrode generate OH - The hardness ions in high-salt organic wastewater are precipitated and removed; the anode side of the titanium-based metal oxide coated electrode converts the chloride ions in the high-salt organic wastewater into active chlorine; the anode side of the metal iron electrode produces Fe(OH)3 to enhance the coagulation effect in the treatment of high-salt organic wastewater; the boron-doped diamond electrode converts sulfate ions in the high-salt organic wastewater into sulfate radicals; active chlorine oxidation, sulfate radical oxidation and coagulation jointly enhance the removal of organic matter in the high-salt organic wastewater, and multiple cathodes enhance the removal of hardness ions.

[0007] In one embodiment, the organic matter content of the high-salt organic wastewater in terms of total hardness, chloride ion, sulfate ion and COD ranges from 600 to 1000 mg / L, 1000 to 20000 mg / L, 1000 to 10000 mg / L and 150 to 300 mg / L, respectively.

[0008] In one embodiment, the first metal iron electrode and the boron-doped diamond electrode are both extreme electrodes, connected to the negative electrode and the positive electrode of the power supply respectively, and the titanium-based metal oxide coating electrode and the second metal iron electrode are both non-extreme electrodes, not connected to the power supply output; the current density of the extreme electrodes is 10-17 mA / cm 2 .

[0009] In one embodiment, each electrode is in the shape of a flat plate, the distance between adjacent electrodes is 50 to 60 mm, and the reaction time is 60 to 80 minutes.

[0010] In one embodiment, the cathode of the first metal iron electrode, the titanium-based metal oxide coating electrode, and the cathode side of the second metal iron electrode undergo hydrogen evolution reaction to generate OH - , and remove hardness ions by precipitation.

[0011] In one embodiment, the boron-doped diamond electrode converts sulfate ions into sulfate radicals to participate in the removal of organic matter, and then the sulfate radicals are converted into peroxydisulfate, which is reduced to sulfate radicals near the second metal iron electrode and continues to participate in the oxidative removal of organic matter.

[0012] In one embodiment, when the chloride ion content in the high-salt organic wastewater is greater than 20,000 mg / L, the chloride ions are first removed by precipitation to reduce the content to below 20,000 mg / L, and then the electrodes are energized to avoid affecting the generation of sulfate radicals.

[0013] In one embodiment, the anode side of the second metal iron electrode produces Fe(OH)3 to participate in the coagulation removal of organic matter, and at the same time co-precipitates with the hardness ions on the cathode side of the titanium-based metal oxide coated electrode, thereby enhancing the coagulation and precipitation removal of organic matter and hardness ions.

[0014] In one embodiment, the anode side of the titanium-based metal oxide coated electrode converts chloride ions into active chlorine, enhancing the oxidative removal of organic matter.

[0015] In one embodiment, the process of oxidative removal of organic matter based on sulfate radicals is a free radical pathway, and the process of oxidative removal of organic matter by active chlorine is a non-free radical pathway.

[0016] Compared with the existing technology, the present invention uses a multi-electrode arrangement to make one side of the non-extreme electrode an anode and the other side a cathode, fully utilizing the role of each electrode, and converting the anions in high-salt organic wastewater into oxidative active species in situ for the oxidative removal of organic matter. The final removal of organic matter includes both free radical and non-free radical pathways, alleviating the impact of inorganic quenching anions on the treatment effect, and can remove hardness ions through coagulation and coprecipitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the mechanism of the present invention.

[0018] Figure 2 Schematic diagram of the effect of an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0020] High-salt organic wastewater, as referred to in this article, is wastewater rich in hardness ions, chloride ions, sulfate ions, and organic matter, including coal chemical wastewater, printing and dyeing wastewater, and smelting wastewater. In terms of parameters, the total hardness, chloride ion, sulfate ion, and organic matter (COD) contents in high-salt organic wastewater range from 600 to 1,000 mg / L, 1,000 to 20,000 mg / L, 1,000 to 10,000 mg / L, and 150 to 300 mg / L, respectively.

[0021] Existing high-salinity organic wastewater treatment mostly uses advanced oxidation technologies that rely on free radicals. However, its active oxygen species are easily quenched by a large number of inorganic anions, seriously affecting the treatment effect. To this end, the present invention adopts a structure with multiple electrodes arranged in parallel, so that one side of the electrodes other than the extreme electrodes is the anode and the other side is the cathode, giving full play to the role of each electrode, and converting the anions in the high-salinity organic wastewater into oxidative active species in situ. The removal of organic matter in the multipolar electrochemical reactor includes a free radical pathway centered on sulfate radical oxidation and a non-free radical pathway centered on active chlorine oxidation and coagulation. In addition, the coagulation and coprecipitation processes can also effectively remove hardness ions in high-salinity organic wastewater.

[0022] Specifically, if Figure 1 As shown, the present invention is applicable to a multi-electrode electrochemical treatment method for high-salt organic wastewater, and its steps and principles include:

[0023] In an electrochemical reactor, the electrodes are arranged in parallel in the order of a first metallic iron electrode 1, a titanium-based metal oxide-coated electrode 2, a second metallic iron electrode 3, and a boron-doped diamond electrode 4. The first metallic iron electrode 1 and the boron-doped diamond electrode 4 serve as the cathode and anode, respectively. The titanium-based metal oxide-coated electrode 2 and the second metallic iron electrode 3 each serve as an anode on the side closest to the first metallic iron electrode 1, and as a cathode on the other side. Specifically, the first metallic iron electrode 1 is connected to the negative pole of a power supply and serves as the cathode. The titanium-based metal oxide-coated electrode 2 serves as the anode on the side opposite the first metallic iron electrode 1, and as a cathode on the other side. The boron-doped diamond electrode 4 is connected to the positive pole of a power supply and serves as the anode. The second metallic iron electrode 3 serves as the cathode on the side opposite the boron-doped diamond electrode 4, and as an anode on the other side. The electrodes are arranged in this order and connected to a power supply.

[0024] In the present invention, the first metallic iron electrode 1 and the boron-doped diamond electrode 4 are both extreme electrodes, and the titanium-based metal oxide-coated electrode 2 and the second metallic iron electrode 3 are both non-extreme electrodes. The extreme electrodes refer to the electrodes located on both sides and connected to the power supply, while the non-extreme electrodes refer to the electrodes arranged in the middle and not connected to the power supply. In the present invention, the first metallic iron electrode 1 and the boron-doped diamond electrode 4 are connected to the negative and positive poles of the power supply, respectively, while the titanium-based metal oxide-coated electrode 2 and the second metallic iron electrode 3 are not connected to the power supply output.

[0025] In the present invention, the current range of the extreme electrode is determined by the effective area of ​​the electrode plate and the current density, and is preferably limited to 10-17 mA / cm 2 In practical applications, the current parameters can be determined based on the effective area of ​​the existing electrode plates and the current density range provided in this patent. Furthermore, the electrodes of the present invention are all flat, with the spacing between adjacent electrodes preferably being 50-60 mm, and the reaction time preferably being 60-80 minutes.

[0026] The titanium-based metal oxide coated electrode 2 of the present invention has a titanium substrate and the metal oxide can be ruthenium dioxide, iridium dioxide, manganese dioxide, etc. There is no requirement for the coating thickness, and any commercial titanium-based metal oxide coated electrode can be used.

[0027] The boron-doped diamond electrode 4 of the present invention can be any commercial boron-doped diamond electrode available on the market, and there is no requirement on the amount of boron doped.

[0028] When high-salt organic wastewater is passed into the electrochemical reactor, the following synergistic removal effects are produced during the reaction process:

[0029] The first metal iron electrode 1, the cathode side of the titanium-based metal oxide coating electrode 2 and the cathode side of the second metal iron electrode 3 undergo hydrogen evolution reaction to produce OH - , remove hardness ions in high-salt organic wastewater by precipitation.

[0030] The anode side of the titanium-based metal oxide coating electrode 2 converts chloride ions in the high-salt organic wastewater into active chlorine, thereby strengthening the non-radical oxidation removal process of organic matter.

[0031] The anode side of the second metal iron electrode 3 produces Fe(OH)3 which participates in the coagulation and removal of organic matter, thereby enhancing the coagulation effect in the treatment of high-salt organic wastewater. At the same time, it can co-precipitate with the hardness ions on the cathode side of the titanium-based metal oxide coated electrode 2, further enhancing the coagulation and precipitation removal of organic matter and hardness ions.

[0032] The boron-doped diamond electrode 4 converts sulfate ions in the high-salt organic wastewater into sulfate radicals to participate in the removal of organic matter, and then the sulfate radicals are converted into peroxydisulfate. The peroxydisulfate is reduced to sulfate radicals near the second metal iron electrode 3 and continues to participate in the oxidation removal of organic matter, thereby strengthening the free radical oxidation removal process of organic matter.

[0033] For example, when the chloride ion content in the high-salt organic wastewater is greater than 20,000 mg / L, the chloride ions are first removed by precipitation to reduce the content to below 20,000 mg / L, and then the electrodes are energized to avoid affecting the generation of sulfate radicals.

[0034] In a specific embodiment, the treatment object is secondary reverse osmosis concentrated water from the coal chemical industry, in which the total hardness, chloride ion, sulfate ion and organic matter (COD) contents are 622 mg / L, 7045 mg / L, 7111 mg / L and 272 mg / L respectively. The extreme electrode current density is 10 mA / cm 2 The distance between adjacent electrodes is 50mm. The processing structure can be referred to Figure 2 As shown in the figure, with the increase of treatment time, the hardness and organic matter removal rates increased significantly, especially at 60 to 80 minutes, and reached the maximum treatment rate at 80 minutes, at which time the organic matter removal rate was greater than 40% and the hardness removal rate could reach 80%.

[0035] In the present invention, during the reaction, the first metal iron electrode 1 and the second metal iron electrode 3 may be covered with sediments, corroded, etc., and should be replaced in time to ensure the treatment effect.

[0036] In practical applications, the present invention can improve the treatment effect of high-salt organic wastewater by adjusting the current density, operating time and plate spacing conditions.

[0037] In summary, the present invention, through the parallel arrangement of multiple electrodes, achieves the conversion of anions in high-salinity organic wastewater into oxidatively active species. This promotes the removal of organic matter by enhancing free radical and non-radical oxidation pathways, while coagulation and coprecipitation effectively remove hardness ions. Active chlorine oxidation, sulfate radical oxidation, and coagulation jointly enhance the removal of organic matter in high-salinity organic wastewater, while multiple cathodes simultaneously enhance the removal of hardness ions, enriching the removal pathways for hardness ions and organic matter during high-salinity organic wastewater treatment.

[0038] At the same time, the control means for the entire electrochemical method of the present invention in operation are only current density, operation time, and plate spacing. Each electrode with a cathode surface has different precipitation effects due to its own different characteristics, and no additional control is required.

Claims

1. A multi-electrode electrochemical treatment method for high-salt organic wastewater, characterized by: In an electrochemical reactor, the electrodes are arranged in parallel in the order of a first metal iron electrode (1), a titanium-based metal oxide coating electrode (2), a second metal iron electrode (3), and a boron-doped diamond electrode (4); wherein the first metal iron electrode (1) and the boron-doped diamond electrode (4) are respectively a cathode and an anode, and the titanium-based metal oxide coating electrode (2) and the second metal iron electrode (3) are both anodes on one side close to the first metal iron electrode (1) and cathodes on the other side; High-salt organic wastewater is introduced into the electrochemical reactor, and OH is generated on the cathode side of the first metal iron electrode (1), the titanium-based metal oxide coating electrode (2), and the cathode side of the second metal iron electrode (3). - The hardness ions in the high-salt organic wastewater are precipitated and removed; the anode side of the titanium-based metal oxide coating electrode (2) converts the chloride ions in the high-salt organic wastewater into active chlorine; the anode side of the second metal iron electrode (3) generates Fe(OH)3 to enhance the coagulation effect in the treatment of the high-salt organic wastewater; the boron-doped diamond electrode (4) converts the sulfate ions in the high-salt organic wastewater into sulfate free radicals; the active chlorine oxidation, sulfate free radical oxidation and coagulation jointly enhance the removal of organic matter in the high-salt organic wastewater, and the multiple cathodes enhance the removal of hardness ions.

2. A multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The high-salt organic wastewater has organic matter contents in terms of total hardness, chloride ions, sulfate ions and COD ranging from 600 to 1000 mg / L, 1000 to 20000 mg / L, 1000 to 10000 mg / L and 150 to 300 mg / L, respectively.

3. A multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The first metal iron electrode (1) and the boron-doped diamond electrode (4) are both extreme electrodes, connected to the negative electrode and the positive electrode of the power supply respectively; the titanium-based metal oxide coating electrode (2) and the second metal iron electrode (3) are both non-extreme electrodes, not connected to the power supply output; the current density of the extreme electrodes is 10~17mA / cm 2 .

4. A multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1 or 3, characterized in that: Each electrode is flat, the distance between adjacent electrodes is 50~60mm, and the reaction time is 60~80min.

5. The multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The first metal iron electrode (1), the cathode of the titanium-based metal oxide coating electrode (2), and the cathode side of the second metal iron electrode (3) undergo hydrogen evolution reaction to generate OH - , and remove hardness ions by precipitation.

6. A multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The boron-doped diamond electrode (4) converts sulfate ions into sulfate radicals to participate in the removal of organic matter, and then the sulfate radicals are converted into peroxydisulfate. The peroxydisulfate is reduced to sulfate radicals near the second metal iron electrode (3) and continues to participate in the oxidation and removal of organic matter.

7. A multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1 or 6, characterized in that: When the chloride ion content in the high-salt organic wastewater is greater than 20,000 mg / L, the chloride ions are first removed by precipitation to reduce the content to below 20,000 mg / L, and then the electrodes are energized to avoid affecting the generation of sulfate radicals.

8. The multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The anode side of the second metal iron electrode (3) produces Fe(OH)3 which participates in the coagulation and removal of organic matter, and simultaneously co-precipitates with the hardness ions on the cathode side of the titanium-based metal oxide coating electrode (2), thereby strengthening the coagulation and precipitation removal of organic matter and hardness ions.

9. The multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The anode side of the titanium-based metal oxide coating electrode (2) converts chloride ions into active chlorine, thereby enhancing the oxidation and removal of organic matter.

10. The multi-electrode electrochemical treatment method for high-salt organic wastewater according to claim 1, characterized in that: The oxidation and removal process of organic matter based on sulfate radicals is a free radical pathway, and the oxidation and removal process of organic matter by active chlorine is a non-free radical pathway.

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