A membrane-free tilted asymmetric electrode electrochemical water softening reactor

Abstract

This invention discloses a membrane-free inclined asymmetric electrode electrochemical water softening reactor, relating to the field of water treatment technology. It includes a reaction tank for electrolysis, with an asymmetric mesh anode and an asymmetric mesh stainless steel cathode arranged at a certain inclined angle. An anode overflow outlet and a cathode overflow outlet are respectively provided on both sides of the reaction tank. This invention, by employing a mesh cathode and selecting appropriate mesh size and mesh count, reduces the resistance of wastewater passing through the cathode surface, increases the contact area between hardness ions in the wastewater and the electrode plate, and improves the hardness ion crystallization efficiency. Simultaneously, under the action of water flow and bubbles, crystals on the cathode surface are carried away from the cathode surface. Furthermore, the back of the cathode is coated with a conductive and hydrophobic material, further effectively inhibiting scaling on the cathode surface.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically a membrane-free inclined asymmetric electrode electrochemical water softening reactor. Background Technology

[0002] The adhesion and deposition of mineral hardness compounds can cause scaling, which is usually caused by the supersaturation precipitation of CaCO3 or Mg(OH)2. Scaling has attracted considerable attention in various aspects of industrial processes and household facilities due to its ability to shorten equipment lifespan and cause economic losses. Methods such as adding scale inhibitors, chemical precipitation, ion exchange, and reverse osmosis have been used to prevent scaling. However, these technologies have inherent drawbacks. Electrochemical softening technology has received increasing attention in the water softening field due to its environmental friendliness, lack of need for additional reagents, and ability to simultaneously produce chlorine for disinfection.

[0003] Electrochemical deposition is a common hardness removal technology. Due to the mass transfer resistance of the liquid film, OH- generated by the electrolysis of water at the cathode will accumulate in the liquid film on the cathode surface, forming a local strong alkaline atmosphere, which drives the hardness ions in the liquid film to undergo a crystallization reaction, thereby removing the hardness ions. In this process, scale is continuously deposited on the cathode surface, increasing the electrode resistance and weakening the efficiency of OH- generation by the electrolysis of water.

[0004] Furthermore, due to the resistance to ion diffusion to the cathode surface, continuously increasing the current density cannot achieve a linear increase in descaling efficiency. In addition, in conventional electrochemical reactors, the anode and cathode are generally placed in parallel, and the electrolysis reaction mainly occurs directly opposite the anode and cathode. This causes the H+ and OH- generated by electrolysis to migrate in opposite directions and undergo a neutralization reaction in the bulk solution, further reducing the efficiency of electrochemical hardening removal.

[0005] The key to improving the efficiency of electrochemical hardening removal is to avoid the neutralization reaction between OH- and H+ generated during electrolysis. By embedding a separator between the anode and cathode, the acid-base neutralization reaction can be effectively suppressed, allowing most OH- to enter the bulk solution and maintain a high concentration. This drives the hardness ions to undergo a homogeneous crystallization reaction in the alkaline solution, thereby achieving highly efficient electrochemical hardening removal. However, during use, scale can deposit on the separator surface, leading to membrane fouling and other problems, increasing the risk of subsequent treatment. Furthermore, separators (e.g., ion exchange membranes) are costly. Therefore, designing a separatorless electrochemical reactor with acid-base separation capabilities and no cathode scaling is of great significance for the industrial-scale promotion of electrochemical softening technology. Summary of the Invention

[0006] The purpose of this invention is to provide a diaphragm-free inclined asymmetric electrode electrochemical water softening reactor to solve the problems of scale formation on the cathode surface, insufficient utilization of acid and alkali, and poor hardening effect in the process of diaphragm-free electrochemical hardening.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a membrane-free inclined asymmetric electrode electrochemical water softening reactor, comprising a reaction tank for performing an electrolysis reaction, wherein an asymmetric mesh anode and an asymmetric mesh stainless steel cathode are disposed inside the reaction tank, and the asymmetric mesh anode and the asymmetric mesh stainless steel cathode are disposed at a certain inclined angle.

[0008] The reaction tank is provided with an anode overflow outlet and a cathode overflow outlet on both sides respectively. The cathode overflow outlet is connected to a crystallization chamber through a pipe. The crystallization chamber is used for cathode alkaline effluent to enhance the precipitation of CaCO3.

[0009] The bottom of the reaction tank is provided with a water inlet, which is connected to a peristaltic pump via a pipe. The input end of the peristaltic pump is connected to a water inlet pool, and the peristaltic pump is used to draw water from the bottom of the reaction tank.

[0010] As a further embodiment of the present invention: the asymmetric mesh anode uses different coatings on its front and back sides, with an insulating material coated on the front side and a DSA, BDD, Sb-SnO2, PbO2, and Ti4O7 catalyst coated on the back side.

[0011] As a further aspect of the present invention: the asymmetric mesh stainless steel cathode uses different coatings on its front and back sides, with an insulating material on the front side and a superhydrophobic conductive material on the back side.

[0012] As a further aspect of the present invention: the asymmetric mesh stainless steel cathode is made of stainless steel materials of type 304, 304L, 304N, 316, 316L, or 321.

[0013] As a further embodiment of the present invention: the asymmetric mesh anode is connected to the positive terminal of the power supply via a wire, the asymmetric mesh stainless steel cathode is connected to the negative terminal of the power supply via a wire, and the angle between the asymmetric mesh anode and the asymmetric mesh stainless steel cathode is 0-20°.

[0014] As a further aspect of the present invention: the reaction time of the wastewater to be treated in the reaction tank is determined by the inlet and outlet flow rates of the water pump, and the residence time of the wastewater in the reaction tank is controlled to be 1-30 minutes.

[0015] As a further aspect of the present invention: the current density used for the reaction in the reaction tank is 1-30 mA / cm². 2 between.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] (1) The traditional electrode placement method has been changed, and the electrodes are placed at a certain tilt angle. This design can promote the unimpeded upward floating of bubbles and suppress their cross-movement process on H. + and OH - The convective migration promotes acid-base separation.

[0018] (2) By using “asymmetric electrodes”, different coatings are applied to the front and back sides of the anode and cathode respectively, and an insulating coating is applied to the front side of the electrode. The electrolysis reaction is mainly on the back side of the electrode. The H+ and OH- generated on the back side of the asymmetric electrode are separated from the back side of the mesh electrode under the action of water flow, bubbles, etc., which effectively inhibits the occurrence of neutralization reaction between H+ and OH-.

[0019] (3) By adopting a mesh cathode and selecting a reasonable mesh size and mesh number, the resistance of wastewater passing through the cathode surface is reduced, the contact area between hardness ions in the wastewater and the electrode plate is increased, and the crystallization efficiency of hardness ions is improved. At the same time, under the action of water flow and bubbles, the crystals on the cathode surface will be carried away from the cathode surface. In addition, the back of the cathode is coated with a conductive hydrophobic material, which further effectively inhibits the scaling on the cathode surface. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the system flow of the electrochemical softening method of the membrane-free asymmetric electrode of the present invention;

[0021] Figure 2 The figure shows the experimental results of the effect of symmetrical electrode angle and asymmetrical electrode angle on the acid-base separation effect in an embodiment of the present invention.

[0022] Figure 3 The effect of current density on the acid-base separation effect of the asymmetric electrode is illustrated in the embodiments of the present invention.

[0023] Figure 4 This invention illustrates the effect of symmetrical electrode angles and asymmetrical electrode angles on calcium hardening removal efficiency in embodiments of the present invention.

[0024] Figure 5 The effect of current density on calcium hardening removal efficiency when using symmetrical and asymmetrical electrodes in embodiments of the present invention.

[0025] In the diagram: 1. Reaction tank; 2. Asymmetric mesh anode; 3. Asymmetric mesh stainless steel cathode; 4. Anode overflow outlet; 5. Cathode overflow outlet; 6. Crystallization chamber; 7. Inlet; 8. Peristaltic pump; 9. Inlet pool; 10. Power supply. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The following describes embodiments of the invention based on its overall structure.

[0028] Please see Figures 1 to 5 In this embodiment of the invention, a membrane-free inclined asymmetric electrode electrochemical water softening reactor includes a reaction tank 1 for electrolysis. The reaction tank 1 is provided with an asymmetric mesh anode 2 and an asymmetric mesh stainless steel cathode 3. The asymmetric mesh anode 2 and the asymmetric mesh stainless steel cathode 3 are arranged at a certain inclined angle.

[0029] The reaction tank 1 is provided with an anode overflow outlet 4 and a cathode overflow outlet 5 on both sides. The cathode overflow outlet 5 is connected to a crystallization chamber 6 through a pipe. The crystallization chamber 6 is used for the cathode alkaline water output to enhance the precipitation of CaCO3.

[0030] The bottom of the reaction tank 1 is provided with a water inlet 7, and the water inlet 7 is connected to a peristaltic pump 8 through a pipe. The input end of the peristaltic pump 8 is connected to a water inlet pool 9. The peristaltic pump 8 is used to introduce water from the bottom of the reaction tank 1.

[0031] The asymmetric mesh anode 2 uses different coatings on its front and back sides. The front side is coated with an insulating material, and the back side is coated with DSA, BDD, Sb-SnO2, PbO2, and Ti4O7 catalyst.

[0032] The asymmetric mesh stainless steel cathode 3 uses different coatings on its front and back sides. The front side is coated with an insulating material, and the back side is coated with a superhydrophobic and conductive material.

[0033] The asymmetric mesh stainless steel cathode 3 is made of stainless steel materials of the following grades: 304, 304L, 304N, 316, 316L, and 321.

[0034] The asymmetric mesh anode 2 is connected to the positive terminal of the power supply 10 via a wire, and the asymmetric mesh stainless steel cathode 3 is connected to the negative terminal of the power supply 10 via a wire. The angle between the asymmetric mesh anode 2 and the asymmetric mesh stainless steel cathode 3 is 0-20°.

[0035] The reaction time of the wastewater to be treated in reaction tank 1 is determined by the inlet and outlet flow rates of the water pump, and the residence time of the wastewater in reaction tank 1 is controlled to be 1-30 min;

[0036] The current density used in the reaction in reaction tank 1 is 1-30 mA / cm². 2 between.

[0037] In this embodiment, it should be noted that the insulating materials used on the front of the anode and cathode include water-based metallic fluorocarbon paint, Teflon coating, nano-silica coating, acetal, polyesterimide, polyimide electrical insulating paint, etc.; the superhydrophobic conductive materials used on the back are fluorinated electronic nano-coating agent X25, Dow Corning 184 (polydimethylsiloxane), stearic acid, myristic acid, etc.

[0038] Without using a diaphragm, acid-base separation and cathode surface scale inhibition are achieved by modifying the electrode coating and altering the electrode placement (forming a certain angle between the electrodes). Using an "asymmetric" electrode ensures that the electrolysis reaction primarily occurs on the outer surface of the asymmetric electrode, making it easier for lattice ions in the solution to enter the electrode / solution interface. The substances at the interface (H... + OH-) diffuses more easily into the bulk solution. The flowing water, the porous "asymmetric" electrode, and the tilted electrode placement help reduce the accumulation of bubbles on the electrode and promote H+ diffusion. + With OH - The separation of the electrodes, and the presence of superhydrophobic conductive material on the back of the electrodes, effectively inhibits scaling on the electrode surface. The chemical (ionic) equation for the reaction is:

[0039] O2 + 2H2O + 4e - →4OH -

[0040] 2H2O+2e - →H2+2OH -

[0041] 2H2O+2e - →O2+4H+

[0042] OH - +HCO3 - →CO3 2- +H2O

[0043] Ca 2+ +CO3 2- →CaCO3↓

[0044] Mg 2+ +2OH - →2Mg(OH)2↓

[0045] The specific experimental procedure is as follows:

[0046] Example 1:

[0047] An electrolyte solution with a conductivity of 3.0 mS / cm and an initial pH of 6.92 was prepared using anhydrous sodium sulfate. The electrochemical electrolysis unit employed both asymmetric and symmetric DSA meshes as anodes (electrolysis with electrodes facing each other and placed parallel to each other), and asymmetric and symmetric stainless steel meshes as cathodes. The angles between the anode and cathode were 0°, 5°, 10°, 15°, and 20°, respectively. Insulating baffles separated the anode and cathode. The influent flow rate was 240 mL / min, and the current density was 15 mA / cm². 2 The experiment was conducted under the specified conditions, and the results were as follows: Figure 2 As shown.

[0048] Example 2:

[0049] An electrolyte solution with a conductivity of 3.0 mS / cm and an initial pH of 6.92 was prepared using anhydrous sodium sulfate. The electrochemical electrolysis unit employed an asymmetric DSA mesh as the anode and an asymmetric stainless steel mesh as the cathode, with a 5° angle between the anode and cathode. An insulating baffle separated the anode and cathode. The influent flow rate was 240 mL / min, and the current density was 3 mA / cm². 2 5mA / cm 2 10mA / cm 2 15mA / cm 2 20mA / cm 2 The experiment was conducted under the specified conditions, and the results were as follows: Figure 3 As shown.

[0050] Example 3:

[0051] A solution containing 400 mg / L calcium hardness (calculated as CaCO3), 100 mg / L magnesium hardness, and 400 mg / L total alkalinity was prepared using anhydrous calcium chloride, magnesium sulfate, sodium bicarbonate, and anhydrous sodium sulfate. 2+ With HCO3 -A simulated feed solution with a molar ratio of 1:2 and a conductivity of 3.2 mS / cm was used. The electrochemical electrolysis unit employed asymmetric and symmetric DSA meshes as anodes, and asymmetric and symmetric stainless steel meshes as cathodes, with included angles of 0°, 5°, 10°, 15°, and 20° between the anodes and cathodes, respectively. Insulating baffles separated the anodes and cathodes, and the current density was 15 mA / cm². 2 The experiment was conducted under the condition that the influent and effluent flow rates were 240 mL / min, and the results are as follows: Figure 4 As shown.

[0052] Example 4:

[0053] A solution containing 400 mg / L calcium hardness (calculated as CaCO3), 100 mg / L magnesium hardness, and 400 mg / L total alkalinity was prepared using anhydrous calcium chloride, magnesium sulfate, sodium bicarbonate, and anhydrous sodium sulfate. 2+ With HCO3 - The simulated feed solution had a molar ratio of 1:2 and a conductivity of 3.2 mS / cm. The electrochemical electrolysis unit used an asymmetric DSA mesh as the anode and an asymmetric stainless steel mesh as the cathode, with a 5° angle between the anode and cathode. An insulating baffle separated the anode and cathode, and the current density was 3 mA / cm². 2 5mA / cm 2 10mA / cm 2 15mA / cm 2 20mA / cm 2 The experiment was conducted under the condition that the influent flow rate was 240 mL / min, and the treatment results are as follows: Figure 5 As shown.

[0054] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A membrane-free inclined asymmetric electrode electrochemical water softening reactor, comprising a reaction tank (1) for carrying out electrolysis, characterized in that, The reaction tank (1) is equipped with an asymmetric mesh anode (2) and an asymmetric mesh stainless steel cathode (3), with the asymmetric mesh anode (2) and the asymmetric mesh stainless steel cathode (3) set at an angle of 0-20º. The asymmetric mesh anode (2) uses different coatings on its front and back sides. The front side is coated with an insulating material, and the back side is coated with a DSA, BDD, Sb-SnO2, PbO2, Ti4O7 catalytic coating. The asymmetric mesh stainless steel cathode (3) uses different coatings on its front and back sides. The front side is coated with an insulating material, and the back side is coated with a superhydrophobic conductive material. The reaction tank (1) is provided with an anode overflow outlet (4) and a cathode overflow outlet (5) on both sides respectively. The cathode overflow outlet (5) is connected to a crystallization chamber (6) through a pipe. The crystallization chamber (6) is used for cathode alkaline water discharge to enhance the precipitation of CaCO3. The bottom of the reaction tank (1) is provided with a water inlet (7), and the water inlet (7) is connected to a peristaltic pump (8) through a pipe. The input end of the peristaltic pump (8) is connected to a water inlet pool (9), and the peristaltic pump (8) is used to draw water from the bottom of the reaction tank (1).

2. The membrane-free inclined asymmetric electrode electrochemical water softening reactor according to claim 1, characterized in that, The asymmetric mesh stainless steel cathode (3) is made of stainless steel of type 304, 304L, 304N, 316, 316L, or 321.

3. The membrane-free inclined asymmetric electrode electrochemical water softening reactor according to claim 1, characterized in that, The asymmetric mesh anode (2) is connected to the positive terminal of the power supply (10) via a wire, and the asymmetric mesh stainless steel cathode (3) is connected to the negative terminal of the power supply (10) via a wire.

4. The membrane-free inclined asymmetric electrode electrochemical water softening reactor according to claim 1, characterized in that, The reaction time of the wastewater to be treated in the reaction tank (1) is determined by the inlet and outlet flow rates of the water pump, and the residence time of the wastewater in the reaction tank (1) is controlled to be 1-30 min.

5. The membrane-free inclined asymmetric electrode electrochemical water softening reactor according to claim 1, characterized in that, The current density used in the reaction tank (1) is 1-30 mA / cm². 2 between.

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