Scale inhibition electrochemical reactor and application thereof

Abstract

The invention relates to a scale inhibition electrochemical reactor and application thereof.The scale inhibition electrochemical reactor mainly comprises an electrode set and a cathode chamber and an anode chamber which are separated by the electrode set, the electrode set mainly comprises a cathode, an anode and a porous aeration assembly arranged between the cathode and the anode, the porous aeration assembly is of a net structure formed by interweaving a plurality of aeration pipes, and the aeration pipes are communicated with the cathode chamber and the anode chamber. One side facing the cathode chamber is provided with an aeration port, and the rest part is sealed. The reactor provided by the invention can realize isolation of the cathode chamber and the anode chamber and rapid diffusion of an alkaline region, has excellent removal performance when being applied to removal of metal ions in wastewater, and can avoid electrode scaling and improve the use performance of the electrode.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a scale inhibition electrochemical reactor and application thereof. Background Art

[0002] Electrochemical technology is favored by more and more researchers due to its advantages such as environmental friendliness, easy operation and no secondary pollution. It can be widely used in pollutant removal by utilizing the redox characteristics of the anode and cathode, including common electrochemical degradation of organic matter, electrochemical reduction removal of nitrates, electrochemical descaling, etc. In addition, it is also widely used in electrochemical enhanced biochemical processes, electrochemical production of hydrogen peroxide, electrochemical production of acids and alkalis, etc.

[0003] Patent CN106277369A discloses an electrochemical scale inhibition method, including: 1) dividing the electrolytic cell into an anode chamber and a cathode chamber through a diaphragm, and placing the anode and cathode in the anode chamber and the cathode chamber respectively; 2) allowing the water to be treated to flow through the anode chamber through the anode chamber inlet: after power is turned on, the anode chamber becomes an acidic area; using the acidity generated by the anode to reduce or remove the alkalinity in the water flowing through the anode chamber, and then flowing out from the anode chamber outlet, and in the cathode chamber, using a conductive liquid for circulation. This invention is aimed at treating the alkalinity in the water to be treated. During the treatment process, no scale is precipitated in the anode chamber. Therefore, unlike traditional electrochemical descaling technology, it is not necessary to design a large number of components or devices to complete the scraping and discharge of scale on the anode. However, the diaphragm used is an expensive anion exchange membrane, cation exchange membrane or bipolar membrane, which has a high cost; and the electrode spacing is far, and the energy consumption is large.

[0004] CN108083455A discloses a plug-flow electrochemical water softening method and device. Alternately arranged positive and negative electrodes are vertically installed in the electrochemical reactor in sequence, and the positive and negative electrodes are staggered up and down to form multiple electrode chambers. Water passages are left at the bottom of all cathodes or anodes to connect with the adjacent electrode chambers at the bottom, and water passages are left at the top of all anodes or cathodes to connect with the adjacent electrode chambers at the top, and the bottom water passages and the top water passages are arranged alternately. The method is a two-step process, namely, a water softening stage and a cathode descaling stage, wherein in the water softening stage: hard water passes through the electrochemical reactor, and direct current is used to promote water electrolysis, and CaCO3 and Mg(OH)2 are generated and deposited on the cathode surface, and the hardness ions in the water are removed; in the cathode descaling stage: air is introduced into the electrochemical reactor, and the cathode is descaled by the shear force generated by the bursting of bubbles, and the removed precipitate is discharged from the mud discharge port. The invention has the phenomenon of electrode scaling, which will lead to increased energy consumption and reduced descaling efficiency during the electrochemical descaling process. The later descaling process will require shutdown and production stoppage, and the descaling process will cause irreversible damage to the electrode, seriously affecting the service life of the electrode.

[0005] Wenda Kang (Water Research 232 (2023) 119694) et al. used nylon mesh to isolate the anode and cathode in the electrochemical system, divided the electrochemical reactor into anode and cathode zones, and achieved homogeneous nucleation of calcium and magnesium ions by controlling the convection state and utilizing the alkalinity generated in the cathode zone. The removal efficiency and energy consumption were significantly better than those of traditional electrochemical hardness removal methods. However, the diffusion rate in the alkaline area achieved by electrode regulation and flow state control is slow, which will lead to low initial water inlet descaling efficiency, and when the cathode zone expands and the water inlet flow rate increases, the time it takes for the alkaline zone to fill the cathode zone will be significantly extended. In addition, the reactor has a single cathode chamber, and the alkali production efficiency is limited.

[0006] Therefore, it is of great significance to construct an electrochemical reactor or reaction system with low cost, low energy consumption and anti-scaling performance. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a scale-inhibiting electrochemical reactor and its application. The reactor provided by the present invention can achieve the isolation of the anode and cathode chambers and the rapid diffusion of the alkaline region, has excellent removal performance when applied to the removal of metal ions in wastewater, and can avoid electrode scaling and improve electrode performance.

[0008] The present invention provides a scale inhibition electrochemical reactor, which mainly comprises an electrode group and a cathode chamber and an anode chamber separated by the electrode group. The electrode group mainly comprises a cathode, an anode and a porous aeration component arranged between the cathode and the anode. The porous aeration component is a mesh structure formed by interweaving a plurality of aeration tubes, an aeration port is arranged on one side facing the cathode chamber, and the rest of the parts are sealed.

[0009] In the present invention, the electrode group divides the reactor into an anode chamber and a cathode chamber, wherein the anode chamber is close to the anode and the cathode chamber is close to the cathode, wherein the volume ratio of the cathode chamber to the anode chamber is 3:1-10:1.

[0010] In the present invention, in the electrode group, the cathode, the porous aeration assembly and the anode are arranged closely, and the electrode spacing is 1.0-10.0 mm.

[0011] In the present invention, the porous aeration component can be in any structural form such as ring, sheet, column, etc., with a thickness of 1.0-10.0 mm, preferably 2.0-8.0 mm, and further preferably the same shape as the cathode and the anode. The mesh of the mesh structure can be in any one of diamond, square, circle, etc., with a mesh size of 10 to 800 meshes.

[0012] In the present invention, the diameter of the aeration tube is 1.0-10.0 mm, and a plurality of aeration ports are evenly distributed on one side, that is, toward the cathode chamber, with a pore size of 1-100 microns. The aeration tube is made of any one of ceramic, rubber, nylon, PVC, etc.

[0013] In the present invention, the anode is any one of the shape-stable anodes such as titanium-based ruthenium-iridium electrode, ruthenium-tantalum electrode, iridium-tantalum electrode, ruthenium-iridium-tantalum electrode, ruthenium-iridium-tin electrode, etc., with a mesh size of 10-800 meshes, and can be any structural form such as ring, sheet or column.

[0014] In the present invention, the cathode is any of palladium, titanium, zinc, bismuth, tin, iron, cobalt, aluminum, nickel, platinum single electrode or their alloy electrodes, with a mesh size of 10-800 meshes, and can be in any structural form such as ring, sheet or column.

[0015] In the present invention, the electrochemical reaction system can be in the shape of a cuboid, a cylinder, etc. Multiple electrode groups and anode and cathode chambers can be set according to needs, and the number of electrode groups is an even number, preferably 2-8, for example, when two parallel electrode groups are set, there is one cathode chamber and two anode chambers, and when four parallel electrode groups are set, there are two cathode chambers and three anode chambers. A water inlet is provided at the bottom of each cathode chamber, a drain outlet is provided at the top, and a slag outlet is provided at the bottom; a drain outlet is provided at the top of each anode chamber.

[0016] In the present invention, when used for removing metal ions, a solid separation device is provided under the cathode chamber, and the generated solid can be added to the cathode chamber as a seed, or the solid separation device is provided with a reflux system to return to the cathode chamber.

[0017] The present invention also provides an application of the scale inhibition electrochemical reactor in electrochemical removal of metal ions in wastewater.

[0018] In the application of the present invention, wastewater enters the reactor from the water inlet at the bottom of the cathode chamber, the porous aeration component is started and gas aeration is introduced to generate OH - It is used to remove metal ions from wastewater. The wastewater with metal ions removed is discharged from the upper part of the cathode chamber, and the generated acidic solution is discharged from the upper part of the anode chamber.

[0019] In the application of the present invention, the metal ion is at least one of calcium ion, magnesium ion, manganese ion, lead ion, copper ion, etc., and the concentration of the metal ion in the wastewater is not higher than 3000 mg / L.

[0020] In the application of the present invention, the gas introduced into the porous aeration component can be any one or more of air, nitrogen, carbon dioxide, etc., preferably carbon dioxide.

[0021] In the application of the present invention, the current density is 5-20 mA / cm 2, the residence time is 30-60min.

[0022] In the application of the present invention, the pH value of the cathode chamber is greater than 10, preferably 11-12.

[0023] In the application of the present invention, 5%-30% of the acidic water can be taken out of the anode chamber regularly, and the remaining acidic water is mixed with the outlet water of the cathode chamber to maintain the outlet water pH.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention places the anode, porous aeration assembly and cathode in close proximity to form an electrode group, wherein the porous aeration assembly aerates toward the cathode chamber, which not only achieves isolation between the anode and cathode chambers and fully utilizes the cathode to produce alkali to achieve efficient and rapid removal of metal ions; it also allows the alkaline area produced on the electrode surface to diffuse rapidly, thereby avoiding electrode scaling.

[0026] (2) The present invention avoids the use of expensive ion membranes and the like, and has a relatively low cost; it also effectively prevents electrode scaling and does not affect the use of the electrodes.

[0027] (3) The present invention realizes material recycling. The generated acid can be used to clean the electrode group, and the generated scale can be added to the reaction system as a seed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the composition of the two-anode-one-cathode chamber reaction system of the present invention;

[0029] Figure 2 It is a schematic diagram of the composition of the three-anode and two-cathode chamber reaction system of the present invention;

[0030] Figure 3 This is a schematic diagram of the location and structure of the porous aeration component. DETAILED DESCRIPTION

[0031] The technical solution of the present invention and its effects are further described in detail below through examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0032] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0033] In the embodiment, the metal ions in the water body are measured by ICP-MASS. Metal ion removal rate = (influent metal ion concentration - effluent metal ion concentration) / influent metal ion concentration × 100%.

[0034] Example 1

[0035] The electrochemical reaction system uses Figure 1 The structure shown is a rectangular reactor, including two electrode groups and a cathode chamber and two anode chambers separated by the electrode groups. The volume ratio of the cathode chamber to the anode chamber is 3:1. A nickel electrode is selected as the cathode and a titanium-based ruthenium-iridium electrode is selected as the anode. The mesh number is 100 meshes, the thickness is 4.0 mm, and the structure is a mesh sheet. The cathode, porous aeration assembly and anode are closely arranged, and the electrode spacing is 10 mm. A water inlet is provided at the bottom of the cathode chamber, a drain outlet is provided at the top, and a slag outlet is provided at the bottom; a drain outlet is provided at the top of each anode chamber.

[0036] The porous aeration component is a ceramic mesh interwoven by several aeration tubes, with a thickness of 4.0 mm and the same shape as the cathode and anode. The mesh of the ceramic mesh is diamond-shaped and the mesh number is 100. The diameter of the aeration tube is 4.0 mm, and an aeration port is provided on the side facing the cathode chamber. The aperture of the aeration port is 50 microns, and the rest is sealed.

[0037] The treated wastewater contains copper ion concentration of 1000 mg / L.

[0038] The treatment method includes: wastewater enters from the bottom of the cathode chamber and exits from the top of the cathode chamber, and carbon dioxide is introduced into the porous aeration component for aeration, and the cathode chamber between the two cathodes can quickly form an alkaline area, which is quickly diffused for metal ion removal and scale is avoided. The control conditions are as follows: the current density is 10mA / cm 2 , the residence time is 60min, and the pH value of the cathode chamber is regulated to about 11.5.

[0039] After the reaction is completed, the removal rate of copper ions can reach 93.9%.

[0040] Example 2

[0041] The electrochemical reaction system uses Figure 1 In the structure shown, the volume ratio of the cathode chamber to the anode chamber is 3:1, the iron electrode is selected as the cathode, and the ruthenium tantalum electrode is selected as the anode. The mesh number is 10 meshes, the thickness is 10.0 mm, and both are mesh sheet structures. The cathode, porous aeration assembly and anode are closely arranged, and the electrode spacing is 1.0 mm. A water inlet is provided at the bottom of the cathode chamber, a drain outlet is provided at the top, and a slag outlet is provided at the bottom; a drain outlet is provided at the top of each anode chamber.

[0042] The porous aeration component is a ceramic mesh interwoven by several aeration tubes, with a thickness of 1.0 mm and the same shape as the cathode and anode. The mesh of the ceramic mesh is diamond-shaped and the mesh number is 800. The diameter of the aeration tube is 1.0 mm, and an aeration port is provided on the side facing the cathode chamber. The aperture of the aeration port is 10 microns, and the rest is sealed.

[0043] The treatment method includes: the treated wastewater is the same as in Example 1, entering from the bottom of the cathode chamber and exiting from the top of the cathode chamber, and at the same time, carbon dioxide is introduced into the porous aeration assembly for aeration, and the cathode chamber between the two cathodes can quickly form an alkaline area, and quickly diffuse for metal ion removal, while avoiding scaling. The control conditions are as follows: the current density is 20mA / cm 2 , the residence time is 30 minutes, and the pH value of the anode chamber is adjusted to about 11.2.

[0044] After the reaction is completed, the removal rate of copper ions can reach 92.0%.

[0045] Example 3

[0046] The electrochemical reaction system uses Figure 1 In the structure shown, the volume ratio of the cathode chamber to the anode chamber is 10:1. A titanium electrode is selected as the cathode and an iridium-tantalum electrode is selected as the anode. The mesh number is 800 meshes, the thickness is 1.0 mm, and both are mesh sheet structures. The cathode, porous aeration assembly and anode are closely arranged, and the electrode spacing is 10.0 mm. A water inlet is provided at the bottom of the cathode chamber, a drain outlet is provided at the top, and a slag outlet is provided at the bottom; a drain outlet is provided at the top of each anode chamber.

[0047] The porous aeration component is a ceramic mesh interwoven by several aeration tubes, with a thickness of 10.0 mm and the same shape as the cathode and anode. The mesh of the ceramic mesh is diamond-shaped and the mesh number is 10. The diameter of the aeration tube is 10 mm, and an aeration port is provided on the side facing the cathode chamber. The aperture of the aeration port is 100 microns, and the rest is sealed.

[0048] The treatment method includes: the treated wastewater is the same as in Example 1, entering from the bottom of the cathode chamber and exiting from the top of the cathode chamber, and carbon dioxide is introduced into the porous aeration assembly for aeration, and the cathode chamber between the two cathodes can quickly form an alkaline area, which can quickly diffuse for metal ion removal and avoid scaling. The control conditions are as follows: the current density is 5mA / cm 2 , the residence time is 60min, and the pH value of the anode chamber is regulated to about 11.0.

[0049] After the reaction is completed, the removal rate of copper ions can reach 90.3%.

[0050] Example 4

[0051] Same as Example 1, except that: Figure 2The device shown is in the form of three anode and two cathode chambers. Part of the acid solution in the anode chamber can be taken out regularly. After the reaction is completed, the solutions in the two chambers are mixed to maintain the pH of the solution. The porous aeration component is the same as that in Example 1, and the water treatment capacity is twice that of Example 1.

[0052] The treatment method includes: the treated wastewater is the same as that in Example 1, the wastewater enters from the bottom of the cathode chamber and exits from the top of the cathode chamber, and carbon dioxide is introduced into the porous aeration assembly for aeration, and the cathode chamber between the two cathodes can quickly form an alkaline area, and quickly diffuse for metal ion removal, while avoiding scaling. The control conditions are as follows: the current density is 10mA / cm 2 , the residence time is 60min, and the pH value of the anode chamber is regulated to about 11.5.

[0053] After the reaction is completed, the removal rate of copper ions can reach 93.4%.

[0054] Example 5

[0055] Similar to Example 1, the treatment method includes: wastewater enters from the bottom of the cathode chamber and exits from the top of the cathode chamber, and air is introduced into the porous aeration assembly, and the cathode chamber between the two cathodes can quickly form an alkaline area, and quickly diffuse for metal ion removal, while avoiding scaling. The control conditions are as follows: the current density is 10mA / cm 2 , the residence time is 60min, and the pH value of the cathode chamber is regulated to about 11.5.

[0056] After the reaction is completed, the removal rate of copper ions can reach 85.2%.

[0057] Example 6

[0058] The same as Example 1, except that in the treated wastewater, the calcium ion concentration is 1000 mg / L, and the bicarbonate concentration is 1000 mg / L.

[0059] After the reaction is completed, the removal rate of calcium ions can reach 90.4%.

[0060] Comparative Example 1

[0061] Same as Example 1, except that the porous aeration assembly was replaced with a common PVC screen and no aeration was performed. After the reaction was completed, the removal rate of calcium ions was 52.4%, which was due to the OH generated by electrolysis. - The diffusion rate is slow, and it cannot replenish carbon dioxide and provide sufficient carbonate ions, resulting in a decrease in the removal effect.

[0062] Comparative Example 2

[0063] Same as Example 1, except that the porous aeration assembly was replaced with an ion membrane and aeration was not possible. After the reaction was completed, the calcium ion removal rate was 56.7%. The reason for this was that the diffusion rate of OH- generated by electrolysis was slow, and carbon dioxide could not be supplemented to provide sufficient carbonate ions, resulting in a decrease in the removal effect.

[0064] Comparative Example 3

[0065] The same as Example 1, except that the porous aeration assembly is bidirectionally aerated. After the reaction is completed, the removal rate of calcium ions is 87.2%. It can be seen that aerating the cathode chamber and the anode chamber at the same time cannot improve the removal rate of calcium ions.

[0066] Comparative Example 4

[0067] The same as Example 1, except that no porous aeration assembly was provided. After the reaction was completed, the removal rate of calcium ions was 43.2%. The reason was that no porous aeration assembly was provided, and the H generated at the anode was too small due to the small electrode spacing. + and OH- react with each other, and most of the scale is formed on the cathode surface.

Claims

1. A scale inhibition electrochemical reactor, characterized in that It mainly includes an electrode group and a cathode chamber and an anode chamber separated by the electrode group. The electrode group mainly includes a cathode, an anode and a porous aeration component arranged between the cathode and the anode. The porous aeration component is a mesh structure formed by interweaving a plurality of aeration tubes, an aeration port is arranged on the side facing the cathode chamber, and the rest of the parts are sealed.

2. The system according to claim 1, characterized in that: The electrode group divides the reactor into an anode chamber and a cathode chamber, wherein the anode chamber is close to the anode, and the cathode chamber is close to the cathode, and the volume ratio of the cathode chamber to the anode chamber is 3:1-10:

1.

3. The system according to claim 1, characterized in that: In the electrode group, the cathode, the porous aeration assembly and the anode are arranged closely, and the electrode spacing is 1.0-10.0 mm.

4. The system according to claim 1, characterized in that: The porous aeration component is in any of the structural forms of annular, sheet-like or columnar, with a thickness of 1.0-10.0 mm, preferably 2.0-8.0 mm, and is further preferably in the same shape as the cathode and the anode.

5. The system according to claim 1, characterized in that: The meshes of the mesh structure are any one of diamond, square and circle, and the mesh number is 10 to 800.

6. The system according to claim 1, characterized in that: The diameter of the aeration pipe is 1.0-10.0 mm, and a plurality of aeration ports are evenly distributed on one side, ie, toward the cathode chamber, with a pore size of 1-100 microns; the material of the aeration pipe is any one of ceramic, rubber, nylon, and PVC.

7. The system according to claim 1, characterized in that: The anode is any one of a titanium-based ruthenium-iridium electrode, a ruthenium-tantalum electrode, an iridium-tantalum electrode, a ruthenium-iridium-tantalum electrode, and a ruthenium-iridium-tin electrode, with a mesh size of 10-800 meshes and any ring, sheet or columnar structural form.

8. The system according to claim 1, characterized in that: The cathode is any one of palladium, titanium, zinc, bismuth, tin, iron, cobalt, aluminum, nickel, platinum single-element electrodes or alloy electrodes thereof, with a mesh size of 10-800 meshes and any ring, sheet or columnar structural form.

9. The system according to claim 1, characterized in that: The electrochemical reaction system is in the shape of a cuboid or a cylinder; multiple electrode groups and anode and cathode chambers are arranged according to needs, and the number is an even number, preferably 2-8.

10. The system according to claim 1, characterized in that: A water inlet is arranged at the lower part of each cathode chamber, a water outlet is arranged at the upper part, and a slag outlet is arranged at the bottom; and a water outlet is arranged at the upper part of each anode chamber.

11. The system according to claim 1, characterized in that: When used for metal ion removal, a solid separation device is provided under the cathode chamber, and the generated solid is added to the cathode chamber as a seed, or a reflux system is provided in the solid separation device to return to the cathode chamber.

12. Use of the scale-inhibiting electrochemical reactor according to any one of claims 1 to 11 in electrochemical removal of metal ions from wastewater.

13. The use according to claim 11, characterized in that: Wastewater enters the reactor from the water inlet at the bottom of the cathode chamber, the porous aeration component is started and gas aeration is introduced to generate OH - It is used to remove metal ions from wastewater. The wastewater with metal ions removed is discharged from the upper part of the cathode chamber, and the generated acidic solution is discharged from the upper part of the anode chamber.

14. The use according to claim 11 or 12, characterized in that: The metal ion is at least one of calcium ion, magnesium ion, manganese ion, lead ion and copper ion, and the concentration of the metal ion in the wastewater is not higher than 3000 mg / L.

15. The use according to claim 11 or 12, characterized in that: The gas introduced into the porous aeration component is any one or more of air, nitrogen and carbon dioxide, preferably carbon dioxide.

16. The use according to claim 11 or 12, characterized in that: The current density is 5-20mA / cm 2 , the residence time is 30-60min.

17. The use according to claim 11 or 12, characterized in that: The pH value of the cathode chamber is greater than 10, preferably 11-12.

18. The use according to claim 11 or 12, characterized in that: 5%-30% of the acidic water is taken out from the anode chamber regularly, and the remaining acidic water is mixed with the effluent from the cathode chamber to maintain the effluent pH.

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