Electrocatalysis and electroflocculation coupled wastewater treatment system and method

Abstract

The application provides an electro-catalysis and electro-flocculation coupled wastewater treatment system and method. The system comprises a water inlet tank, a middle water tank, a water outlet tank, A and B electrode groups, and A and B diode switches. The A and B electrode groups each comprise one or more than two electrodes in series, and the electrodes use a tubular electrode plate with a coaxial middle axis and a detachable columnar electrode plate as cathode and anode plates. The water inlet tank is connected to the middle water tank through the channels between the cathode and anode of each electrode of the A electrode group. The middle water tank is connected to the water outlet tank through the channels between the cathode and anode of each electrode of the B electrode group. The circuit currents of the A and B electrode groups are reversely connected in parallel, and the A and B diode switches are arranged at the anode interfaces of the two electrode groups. The ratio of the product of the total water resistance of the A electrode group and the maximum anode area to the product of the total water resistance of the B electrode group and the minimum anode area is not more than 1:5. The electro-catalysis and electro-flocculation are coupled to treat wastewater under the same alternating current power supply.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an electrocatalytic and electrocoagulation coupled wastewater treatment system and a method for electrocatalytic and electrocoagulation coupled wastewater treatment. Background Technology

[0002] Electrocoagulation is a technology that utilizes the principle of electrolysis to release flocculants through anodic oxidation. With the increasing complexity of wastewater types and the growing demand for integrated wastewater treatment equipment, it is now widely used in the treatment of wastewater from heavy metals, printing and dyeing, papermaking, and leather tanning, as well as in water treatment processes such as drinking water defluorination and rainwater purification. However, electrocoagulation technology faces several technical challenges that hinder its large-scale application. These challenges primarily stem from two aspects related to the properties of current conduction: one is the obstruction caused by anodic passivation. Anodic passivation refers to the accumulation of metal ions generated at the metal anode under the polarization of an electric field, which react with other substances to form metal oxides or salts, adhering to the surface of the anode plate to form a dense passivation film. The presence of this passivation film prevents the dissolution of the metal plate and electron transfer, limiting flocculant production and significantly hindering the normal reaction. The other obstacle is the obstruction caused by cathodic adsorption passivation. Wastewater contains cations such as calcium and magnesium, which move to the vicinity of the cathode under the influence of an electric field, reacting with free OH groups around the cathode. - The reaction produces hydroxide precipitates. Anodic passivation is a reaction between the anolyte and the ionization products of water, forming passivation products with chemical bonds that cannot be removed by mechanical or physical methods. Cathode adsorption passivation products are unrelated to the composition of the cathode material; they are a type of physical adsorption scale that can be removed by mechanical or physical methods. Both anodic and cathodic passivation are positively correlated with current density, preventing electrocoagulation from operating at high current densities. This limits the ability of electrocoagulation to treat wastewater with high organic content, leading to the development of electrocatalysis technology.

[0003] Electrocatalysis is an advanced oxidation technology that utilizes high current densities. Its principle involves using the oxidation of organic pollutants in water by hydroxyl radicals (·OH) generated on the surface of an inert metal anode. This process mineralizes the organic matter into CO2 and H2O, or converts it into low-toxicity, easily biodegradable small-molecule organic compounds. However, electrocatalysis cannot sacrifice the anode to produce flocculants, thus its ability to remove impurities other than COD is relatively weak. It also faces the challenge of cathode adsorption passivation.

[0004] The electrocoagulation process has undergone a certain development process. In electrocoagulation, electrode connection methods are divided into unipolar and bipolar types. The characteristic of the unipolar type is that the two outermost plates are directly connected to an external power source, and each face of the middle plate has a completely opposite electrical polarity to its adjacent plates; the same plate exhibits two electrical polarities. In a unipolar electrode, the current always flows from one anode to the adjacent cathode, without bypassing the middle plate to flow to other cathodes. In a bipolar type, each plate is connected to an external power source, and the polarity of the plate electrode is the same as the power source polarity; the current flow is opposite to that of the unipolar type. Electrodes are the carriers of the electrocoagulation process, and plates are the most common electrode shape in electrocoagulation. Currently, electrode shapes are diverse, gradually evolving from plate-like shapes to spherical, rod-like, mesh-like, and tubular shapes, as well as three-stage electrodes composed of anodes, cathodes, and a third-dimensional electrode. The most commonly used power source in electrocoagulation is DC power. However, DC power is susceptible to electrode passivation during operation. Therefore, some researchers have attempted to replace traditional DC power with newer power sources such as AC and pulsed power, which are beneficial for reaction diffusion and reduce electrode passivation. Compared with DC electrocoagulation, pulsed electrocoagulation reduces energy consumption. AC electrocoagulation, through the periodic transformation of the electric field, prevents charged particles from moving in a specific direction, thus slowing down the formation of passivation films. Experiments show that periodic transformation can solve the electrode passivation problem to some extent while reducing energy consumption. Although existing electrocoagulation processes have made technical improvements in electrode shape and conduction methods, playing a role in delaying electrode passivation, most of these improvements are based on concentration polarization considerations, neglecting the polarization effect of the electrostatic field (conservative force field) on the hydroelectric medium, resulting in poor performance. In particular, the current mainstream electrode conduction method, while able to delay the decay of anodic current to some extent, causes passivation products to coexist on both electrodes, which is detrimental to subsequent processing.

[0005] Unlike electrocoagulation, electrocatalysis primarily employs a bipolar connection. The electrodes are the common electrode shapes used in electrocatalysis. The anode material mainly uses inert metals or metal oxides with high corrosion potential, while the cathode has no special requirements and primarily uses carbon-based or metallic materials. Electrocatalysis involves a higher current density, generally more than five times that of electrocoagulation, and it is prone to adsorption passivation at the cathode, limiting its ability to treat hard wastewater. Currently, it is mainly used for treating organic wastewater. Furthermore, electrocatalytic treatment of organic matter produces low-toxicity, easily biodegradable secondary small-molecule organic byproducts, thus requiring further treatment of the wastewater treated by electrocatalysis.

[0006] Currently, no technical solution has been proposed that can achieve the coupling of electrocatalysis and electrocoagulation, let alone a technical solution that can achieve the coupling of electrocatalysis and electrocoagulation and solve the problems of anode and cathode passivation in electrocoagulation and cathode passivation in electrocatalysis. Summary of the Invention

[0007] The purpose of this invention is to provide a technical solution that enables the coupling of electrocatalysis and electrocoagulation.

[0008] To achieve the above objectives, the present invention provides the following two technical solutions.

[0009] In a first aspect, the present invention provides an electrocatalytic and electrocoagulation coupled wastewater treatment system, wherein the system comprises: an inlet tank, an intermediate tank, an outlet tank, one or more parallel (in the circuit) A electrode groups, one or more parallel (in the circuit) B electrode groups, an A diode switch, and a B diode switch.

[0010] Each A electrode group includes one or more A electrodes connected in series (meaning connected in series in the circuit), and each B electrode group includes one or more B electrodes connected in series (meaning connected in series in the circuit); the A and B electrodes use a tubular electrode plate and a detachable cylindrical electrode plate fitted inside the tubular electrode plate as the anode and cathode respectively (the tubular electrode plate can be used as the cathode and the cylindrical electrode plate as the anode, or the tubular electrode plate can be used as the anode and the cylindrical electrode plate as the cathode), the central axes of the tubular electrode plate and the cylindrical electrode plate coincide, and the inner wall of the tubular electrode plate and the outer wall of the cylindrical electrode plate are spaced apart to form a channel;

[0011] The inlet tank is connected to the intermediate water tank through the channels formed between the cathodes and anodes of each A electrode (i.e., the water channels formed between the cathodes and anodes of each A electrode between the inlet tank and the intermediate water tank are connected in parallel); the intermediate water tank is connected to the outlet tank through the channels formed between the anodes and cathodes of each B electrode (i.e., the water channels formed between the cathodes and anodes of each B electrode between the intermediate water tank and the outlet water tank are connected in parallel); that is, the water flows of the A electrode group and the B electrode group are connected in the same direction in series.

[0012] One phase of the three-phase AC power supply is connected to the anode interface of each A electrode group and the cathode interface of each B electrode group, respectively. The A diode switch is set on the connection line between the anode interface of each A electrode group and the three-phase AC power supply. The cathode interface of each A electrode group and the anode interface of each B electrode group are connected to the neutral point of the three-phase AC power supply, and the B diode switch is set on the connection line between the anode interface of each B electrode group and the three-phase AC power supply. That is, the current direction of the A electrode group and the B electrode group is reversed and connected in parallel.

[0013] The ratio of the product of the total water resistance of each A electrode group and the maximum anode area of ​​the A electrode in that A electrode group to the product of the total water resistance of each B electrode group and the minimum anode area of ​​the B electrode in that B electrode group (i.e., The ratio shall not exceed 1:5; where, the total water resistance of the electrode group refers to the sum of the water resistance in the channel formed between the cathode and anode of each electrode in the electrode group (i.e., the total water resistance of an A electrode group refers to the sum of the water resistance of each A electrode in the A electrode group, the total water resistance of a B electrode group refers to the sum of the water resistance of each B electrode in the B electrode group, and the water resistance of an electrode refers to the water resistance in the channel formed between the cathode and anode; the maximum anode area of ​​an A electrode group refers to the anode area of ​​the largest anode among the A electrodes in the A electrode group, and the minimum anode area of ​​a B electrode group refers to the anode area of ​​the smallest anode among the B electrodes in the B electrode group, where the anode area refers to the surface area of ​​the anode in the channel formed between the cathode and anode.

[0014] The electrocatalytic and electrocoagulation coupled wastewater treatment system provided by this invention achieves different current densities for electrocatalysis and electrocoagulation using the same AC power supply through phase-coupled rectification settings, thereby realizing the coupled electrocatalysis and electrocoagulation for wastewater treatment and simplifying the process flow of electro-treated wastewater.

[0015] According to a preferred embodiment of the first aspect, electrode B includes a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The columnar cathode of electrode B is cylindrical, and the cross-section of the tubular anode of electrode B is annular. The columnar cathode of electrode B is made of a non-reactive metal, and the tubular anode of electrode B is made of iron. The ratio of the inner radius of the tubular anode to the outer radius of the columnar cathode of electrode B is 2-4, and the difference between the inner radius of the tubular anode and the outer radius of the columnar cathode of electrode B is 1-2.5 cm. The ratio of the product of the total water resistance of each electrode group A and the maximum anode area of ​​the electrode A in that electrode group to the product of the total water resistance of each electrode group B and the minimum anode area of ​​the electrode B in that electrode group (i.e., ...) is... The ratio shall not exceed 2:15; at least one of the inlet tank and the intermediate tank shall be equipped with a first pH adjustment device to adjust the pH value of the water entering the channel formed between the cathode and anode of the B electrode to 4-5.

[0016] This preferred technical solution establishes a novel electrode structure, laying the foundation for achieving appropriate electrode polarization and reverse bias. Combined with acid-assisted dissolution, it can effectively solve the anode passivation problem and help increase the cathode's ability to treat hard wastewater. In addition, the detachable cylindrical cathode, which is fitted inside the tubular anode, is easy to disassemble and remove cathode passivation scale, which helps to control the cathode's adsorption passivation.

[0017] More preferably, electrode A includes a tubular cathode and a detachable columnar anode housed inside the tubular anode. The columnar anode of electrode A is cylindrical, and the cross-section of the tubular cathode of electrode A is annular. The columnar anode of electrode A is made of platinum or a platinum-plated metal that does not react with water, and the tubular cathode of electrode A is made of a metal that does not react with water. The ratio of the inner radius of the tubular cathode of electrode A to the outer radius of the columnar anode of electrode A is 1.2-1.5. The difference in outer radius is 0.5-1cm; the ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each A electrode in each A electrode group to the total cross-sectional area of ​​the channel formed between the cathode and anode of each B electrode in each B electrode group is 1:4-10; more preferably, the number of A electrode groups is the same as the number of B electrode groups, the ratio of the number of A electrodes in each A electrode group to the number of B electrodes in each B electrode group is 1:2-1:5, and the ratio of the water resistance of the B electrode to the water resistance of the A electrode is 4-10:1.

[0018] This preferred technical solution, supplemented by a special electrode setup for electrocatalysis, enhances the catalytic intensity of the anode while creating different current densities and different water flow rates at the same power source for both the electrocatalytic and electrocoagulation ends. This lays the foundation for high-speed water flow within the channel formed between the tubular cathode and columnar anode of resistor A, thereby inhibiting cathode adsorption scaling during electrocatalysis. In a further preferred technical solution, by limiting the ratio of the number of electrodes A to B and the water resistance ratio, different current intensities and different water flow rates are created at the same power source for both the electrocatalytic and electrocoagulation ends (see...). Figure 5 This allows for better coupling of electrocatalysis and electrocoagulation.

[0019] More preferably, the length of the portion of the cylindrical cathode and tubular anode of electrode B that is fitted together is 5-20 times the inner radius of the tubular anode.

[0020] More preferably, the inner radius of the tubular anode of electrode B is 2-5 cm.

[0021] More preferably, the length of the portion of the cylindrical anode and the tubular cathode of electrode A that are fitted together is 5-20 times the inner radius of the tubular cathode.

[0022] More preferably, the inner radius of the tubular cathode of electrode B is 2-5 cm.

[0023] More preferably, the columnar anode of electrode A is made of stainless steel with a platinum-plated surface, and the tubular cathode of electrode A is made of stainless steel.

[0024] More preferably, the columnar cathode of electrode B is made of stainless steel.

[0025] More preferably, each A electrode group is identical, and each A electrode group contains identical A electrodes.

[0026] More preferably, each B electrode group is identical, and each B electrode contained in the B electrode group is identical.

[0027] According to a preferred embodiment of the first aspect, the inlet tank and the intermediate tank are provided with sleeves for fixing the A electrode to secure the cylindrical and tubular plates of the A electrode. Specifically, the inlet tank is provided with a sleeve for fixing the cylindrical plates of the A electrode that penetrates two opposite sides of the inlet tank along the direction of the A electrode, and the intermediate tank is provided with a corresponding sleeve for fixing the cylindrical plates of the A electrode that penetrates two opposite sides of the intermediate tank along the direction of the A electrode. Each cylindrical plate of the A electrode is respectively inserted through one sleeve for fixing the cylindrical plates of the A electrode in the inlet tank and one sleeve for fixing the cylindrical plates of the A electrode in the intermediate tank to secure the cylindrical plates of the A electrode. At least one end of the cylindrical plate of the A electrode protrudes from the sleeve for fixing the cylindrical plates of the A electrode to facilitate insertion and removal of the cylindrical plates. At least one of the inlet tank and the intermediate tank is provided with a sleeve for fixing the tubular plates of the A electrode to secure the tubular plates of the A electrode.

[0028] According to a preferred embodiment of the first aspect, the intermediate water tank and the outlet water tank are provided with B-electrode fixing sleeves to fix the columnar electrode plate and tubular electrode plate of the B-electrode. Specifically, the intermediate water tank is provided with a B-electrode columnar electrode plate fixing sleeve penetrating two opposite sides of the intermediate water tank along the B-electrode setting direction, and the outlet water tank is correspondingly provided with a B-electrode columnar electrode plate fixing sleeve penetrating two opposite sides of the outlet water tank along the B-electrode setting direction. The columnar electrode plate of each B-electrode is respectively inserted through one B-electrode columnar electrode plate fixing sleeve in the intermediate water tank and one B-electrode columnar electrode plate fixing sleeve in the outlet water tank to fix the columnar electrode plate, and at least one end of the columnar electrode plate of the B-electrode extends out of the B-electrode columnar electrode plate fixing sleeve to facilitate the insertion and removal of the columnar electrode plate; at least one of the intermediate water tank and the outlet water tank is provided with a B-electrode tubular electrode plate fixing sleeve to fix the tubular electrode plate of the B-electrode.

[0029] According to a preferred embodiment of the first aspect, the water inlet tank is connected to the intermediate water tank through a channel formed between the cathode and anode of each A electrode in the following manner:

[0030] The inlet tank, each A electrode group, and the intermediate water tank are arranged from bottom to top;

[0031] The top surface of the water inlet tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each A electrode in each A electrode group, and the fluid channel opening is provided with a sleeve for fixing the tubular electrode plate of the A electrode. The water inlet tank is provided with a sleeve for fixing the tubular electrode plate of the A electrode that matches the size of the tubular electrode plate of each A electrode in each A electrode group, which penetrates the top and bottom surfaces of the water inlet tank, and the sleeve for fixing the tubular electrode plate of the A electrode is fixed to the bottom surface of the water inlet tank.

[0032] The bottom surface of the intermediate water tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each A electrode in each A electrode group, and the fluid channel opening is provided with a sleeve for fixing the columnar electrode plate of the A electrode. The outlet water tank is provided with a sleeve for fixing the columnar electrode plate of the A electrode that matches the size of the tubular electrode plate of each A electrode in each A electrode group, penetrating the top and bottom surfaces of the intermediate water tank, and the sleeve for fixing the columnar electrode plate of the A electrode is fixed to the top surface of the intermediate water tank.

[0033] Each A electrode's tubular plate is fixed between the inlet and intermediate water tanks via a sleeve for fixing the tubular plate of the A electrode in the inlet tank and a sleeve for fixing the columnar plate of the A electrode in the intermediate water tank. The sleeves for fixing the tubular plate of the A electrode in the inlet tank and the sleeves for fixing the columnar plate of the A electrode in the outlet tank can achieve a seal at the interface between the tubular plate of each A electrode and the inlet and intermediate water tanks, preventing water from overflowing from the interface.

[0034] Each columnar electrode plate of A electrode is respectively inserted into a tubular electrode plate fixing sleeve of A electrode in the inlet tank and a columnar electrode plate fixing sleeve of A electrode in the outlet tank to fix the columnar electrode plate, and at least one end of the columnar electrode plate extends out of the electrode fixing sleeve to facilitate the insertion and removal of the columnar electrode plate.

[0035] Water in the inlet tank flows through the fluid channels on the top surface of the inlet tank to the channels formed between the tubular and cylindrical plates of each A electrode, and then flows into the intermediate water tank through the fluid channels on the bottom surface of the intermediate water tank.

[0036] According to the preferred embodiment of the first aspect, the outlet tank is connected to the outlet tank through a channel formed between the anode and cathode of each B electrode in the following manner:

[0037] The intermediate water tank, each B electrode group, and the outlet water tank are arranged from bottom to top;

[0038] The top surface of the intermediate water tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each B electrode in each B electrode group, and the fluid channel opening is provided with a sleeve for fixing the tubular electrode plate of the B electrode. The intermediate water tank is provided with a sleeve for fixing the tubular electrode plate of the B electrode that matches the size of the tubular electrode plate of each B electrode in each B electrode group, which runs through the top and bottom surfaces of the intermediate water tank, and the sleeve for fixing the tubular electrode plate of the B electrode is fixed to the bottom surface of the intermediate water tank.

[0039] The bottom surface of the water outlet tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each B electrode in each B electrode group, and the fluid channel opening is provided with a sleeve for fixing the columnar electrode plate of the B electrode. The water outlet tank is provided with a sleeve for fixing the columnar electrode plate of the B electrode that matches the size of the tubular electrode plate of each B electrode in each B electrode group, which penetrates the top and bottom surfaces of the water outlet tank, and the sleeve for fixing the columnar electrode plate of the B electrode is fixed to the top surface of the water outlet tank.

[0040] Each B electrode's tubular plate is fixed between the intermediate water tank and the outlet water tank via a B electrode tubular plate fixing sleeve in the intermediate water tank and a B electrode columnar plate fixing sleeve in the outlet water tank. The B electrode tubular plate fixing sleeve in the intermediate water tank and the B electrode columnar plate fixing sleeve in the outlet water tank can achieve a seal at the interface between each B electrode's tubular plate and the intermediate water tank and the outlet water tank, preventing water from overflowing from the interface.

[0041] Each B electrode's cylindrical plate is respectively inserted into a B electrode tubular plate fixing sleeve in the intermediate water tank and a B electrode cylindrical plate fixing sleeve in the outlet water tank to fix the cylindrical plate, and at least one end of the cylindrical plate extends out of the electrode fixing sleeve to facilitate the insertion and removal of the cylindrical plate.

[0042] Water in the intermediate water tank flows through the fluid channels on the top surface of the intermediate water tank to the channels formed between the tubular and cylindrical plates of each B electrode, and then flows into the outlet water tank through the fluid channels on the bottom surface of the outlet water tank.

[0043] According to the preferred embodiment of the first aspect, the inlet tank, intermediate tank, and outlet tank are insulated tanks.

[0044] According to the preferred embodiment of the first aspect, both the sleeve for fixing the tubular electrode plate and the sleeve for fixing the cylindrical electrode plate are made of insulating sleeve.

[0045] According to a preferred embodiment of the first aspect, a second pH adjustment device is provided at the outlet of the water tank to maintain the pH value of the water discharged from the water tank at 8-9 by adding alkaline substances.

[0046] According to a preferred embodiment of the first aspect, a turbulence impeller is provided at the inlet of the channel formed between the tubular electrode plate and the cylindrical electrode plate of electrode A (i.e., the inlet near the water inlet tank). The turbulence impeller helps to form a high-speed rotating water flow, which creates high-speed scouring and lateral shearing on the cathode plate surface of electrode A, preventing adsorption passivation of electrode A cathode.

[0047] According to a preferred embodiment of the first aspect, a turbulence impeller is provided at the inlet of the channel formed between the tubular electrode plate and the cylindrical electrode plate of electrode B (i.e., the inlet near the end of the intermediate water tank). The turbulence impeller helps to reduce the effect of concentration polarization. Specifically, the turbulence blades make the water flow more uniform and generate lateral shear force, reducing the scaling and adhesion of suspended pollutants to the electrode plate and increasing the flocculation efficiency.

[0048] In a second aspect, the present invention provides a method for treating wastewater using a coupled electrocatalysis and electrocoagulation system, wherein the method is performed using the coupled electrocatalysis and electrocoagulation wastewater treatment system provided in the first aspect of the present invention, and the method includes:

[0049] The wastewater to be treated is fed into the inlet tank;

[0050] The wastewater to be treated in the inlet tank enters the channel formed between the anode and cathode of each A electrode in each A electrode group. Alternating current is used to electrocatalyze the wastewater to be treated in the channel formed between the anode and cathode of each A electrode in each A electrode group to obtain electrocatalyzed water.

[0051] The water treated by electrocatalysis enters the intermediate water tank;

[0052] The water treated by electrocatalysis in the intermediate water tank enters the channel formed between the anode and cathode of each B electrode in each B electrode group. Alternating current is used to electrocoagulate the water treated by electrocatalysis in the channel formed between the anode and cathode of each B electrode in each B electrode group to obtain water treated by electrocoagulation.

[0053] The water treated by electrocoagulation enters the outlet tank;

[0054] Among them, the ratio of the effective current density of the anode of electrode A during the electrocatalysis process (referring to the current density of the anode during the conduction period of electrode A) to the effective current density of the anode of electrode B during the electrocoagulation process (referring to the current density of the anode during the conduction period of electrode B) shall not be less than 5:1.

[0055] The invention provides a wastewater treatment method that combines electrocatalysis and electrocoagulation. It utilizes the same AC power source to sequentially perform electrocatalysis and electrocoagulation on the wastewater to be treated. By setting the rectification through phase coupling, it achieves wastewater treatment through the coupling of electrocatalysis and electrocoagulation, thus simplifying the process flow for electro-treated wastewater.

[0056] According to a preferred embodiment of the second aspect, the method further includes adjusting the pH of the wastewater to be treated in the inlet tank or the water after electrocatalytic treatment in the intermediate tank to 4-5; and during the electrocoagulation process, the B electrode used includes a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The columnar cathode of the B electrode is cylindrical, the cross-section of the tubular anode of the B electrode is annular, the columnar cathode of the B electrode is made of a non-reactive metal, the tubular anode of the B electrode is made of iron, the ratio of the inner radius of the tubular anode of the B electrode to the outer radius of the columnar cathode of the B electrode is 2-4, the difference between the inner radius of the tubular anode of the B electrode and the outer radius of the columnar cathode of the B electrode is 1-2.5 cm, and the ratio of the product of the total water resistance of each A electrode group and the maximum anode area of ​​the A electrode in that A electrode group to the product of the total water resistance of each B electrode group and the minimum anode area of ​​the B electrode in that B electrode group does not exceed 2:15; and during the electrocoagulation process, the effective current density of the anode of the B electrode does not exceed 2.0 mA / cm². 2 ;

[0057] This preferred technical solution achieves polarization deflection through a special B electrode setting combined with an appropriate effective anode current density, which in turn effectively solves the anode passivation problem with acid-assisted dissolution. At the same time, the polarization deflection increases the cathode's ability to treat hard wastewater, and the pluggable design of the cathode makes it easy to clean the passivation film, thus effectively solving the cathode passivation problem.

[0058] More preferably, during the electrocoagulation process, the effective current density at the anode of electrode B is 1.0-2.0 mA / cm². 2 .

[0059] More preferably, pH adjustment to 4-5 is achieved by adding sulfuric acid.

[0060] More preferably, the method further includes: after the water treated by electrocoagulation enters the outlet tank, the pH value is adjusted to 8-9 before being discharged; adjusting the pH value of the water treated by electrocoagulation to 8-9 can achieve the removal of Fe 2+ The conversion to Fe(OH)2 further enhances flocculation; more preferably, the pH value is adjusted to 8-9 by adding sodium hydroxide and / or potassium hydroxide.

[0061] More preferably, the method further includes: monitoring the effective current of electrode B during electrocoagulation, and cleaning the cathode of electrode B after the decline of the effective current reaches the current decline threshold; more preferably, the current decline threshold is 10%-15% of the effective current during normal operation (i.e., when there is no scale on the cathode and anode); although polarization deflection prevents the formation of the anode passivation film, it cannot solve the cathode adsorption passivation problem. When the calcium and magnesium hardness in the wastewater is high, calcium and magnesium scale will inevitably be adsorbed at the cathode. Using the current decline as a trigger condition to treat the scale on the cathode can solve the cathode passivation problem more scientifically and reasonably.

[0062] According to a preferred embodiment of the second aspect, in the electrocatalysis process, the A electrode used includes a tubular cathode and a detachable columnar anode fitted inside the tubular anode. The columnar anode of the A electrode is cylindrical, and the cross-section of the tubular cathode of the A electrode is annular. The columnar anode of the A electrode is made of platinum or a platinum-plated metal that does not react with water, and the tubular cathode of the A electrode is made of a metal that does not react with water. The ratio of the inner radius of the tubular cathode of the A electrode to the outer radius of the columnar anode of the A electrode is 1.2-1.5, the difference between the inner radius of the tubular cathode of the A electrode and the outer radius of the columnar anode of the A electrode is 0.5-1 cm, and the ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each A electrode in each A electrode group to the total cross-sectional area of ​​the channel formed between the cathode and anode of each B electrode in each B electrode group is 1:4-10. Furthermore, in the electrocatalysis process, the effective current density of the anode of the A electrode is not less than 15 mA / cm². 2 Furthermore, the water flow velocity in the channel formed between the anode and cathode of electrode A is not less than 0.4 m / s;

[0063] This preferred technical solution enhances the catalytic intensity of the anode while suppressing cathode adsorption scaling during electrocatalysis through the high-speed flow of water in the channel formed between the tubular cathode and columnar anode of resistor A.

[0064] More preferably, during the electrocatalytic process, the effective current density at the anode of electrode A is 15-50 mA / cm². 2 ;

[0065] More preferably, the water flow velocity in the channel formed between the anode and cathode of electrode A is 0.4-0.6 m / s.

[0066] According to a preferred embodiment of the second aspect, the water flow velocity in the channel formed between the anode and cathode of electrode B does not exceed 0.1 m / s; more preferably, the water flow velocity in the channel formed between the anode and cathode of electrode B is 0.04-0.1 m / s.

[0067] According to a preferred embodiment of the second aspect, the ratio of the current intensity of electrode A during electrocatalysis to the current intensity of electrode B during electrocoagulation is (10-30):1.

[0068] According to a preferred embodiment of the second aspect, the water flow velocity in the channel formed between the anode and cathode of electrode A is (4-10) times the water flow velocity in the channel formed between the anode and cathode of electrode B.

[0069] According to the preferred embodiment of the second aspect, the frequency of the alternating current is 30-100 Hz.

[0070] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0071] 1. By using phase-coupled rectification settings, different current densities for electrocatalysis and electrocoagulation are achieved under the same AC power supply, thereby enabling the coupled electrocatalysis and electrocoagulation for wastewater treatment and simplifying the process flow for electro-treated wastewater.

[0072] 2. In the preferred technical solution, at the electrocoagulation end, polarization deflection is achieved through a special electrode setup combined with an appropriate anolyte current density. This polarization deflection increases the cathode's ability to treat hard wastewater. Furthermore, the cylindrical pluggable cathode is easy to handle, effectively controlling cathode adsorption passivation and solving the energy loss problem caused by cathode passivation. Additionally, chemical cleaning is unnecessary, significantly increasing the operating cycle and avoiding the problem of localized corrosion and damage to the iron anode caused by chemical cleaning.

[0073] 3. In the preferred technical solution, at the electrocatalytic end, the high-speed rotating water flow controls the generation of cathode adsorption passivation, thus solving the energy loss problem of cathode passivation formation.

[0074] 4. By not using a conductive electrode, the problem of cathode passivation products existing simultaneously at both electrodes due to the conductive electrode is avoided.

[0075] 5. It has no strict requirements on wastewater indicators and has a wide range of applications. It is specifically designed for treating mixed wastewater containing high molecular weight organic compounds and high hardness. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of the structure of an electrocatalytic and electrocoagulation coupled wastewater treatment system provided in an embodiment of the present invention.

[0077] Figure 2 This is a schematic diagram illustrating the principle of electrocatalysis and electrocoagulation polarization deflection.

[0078] Figure 3 This is a phase sampling diagram of the AC power supply.

[0079] Figure 4 This is a schematic diagram illustrating the electrode current after rectification.

[0080] Figure 5 This diagram illustrates the changes in the ratio of the number of electrodes, the resistance formed between the electrodes, and the water flow rate.

[0081] Figure 6 This is a schematic diagram of the electrocatalytic and electrocoagulation coupled wastewater treatment system provided in Example 1.

[0082] Figure 7 This is a schematic diagram illustrating the process of electrode A being turned on and electrode B being turned off.

[0083] Figure 8 This is a schematic diagram of the process where electrode B is turned on and electrode A is turned off.

[0084] Figure 9 This is a schematic diagram of a traditional plate-type DC electrocoagulation system.

[0085] Figure 10 This is a schematic diagram of a traditional plate-type AC flocculation system. Detailed Implementation

[0086] 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.

[0087] See Figure 1 A specific embodiment of the present invention provides an electrocatalytic and electrocoagulation coupled wastewater treatment system, wherein the electrocatalytic and electrocoagulation coupled wastewater treatment system includes:

[0088] 21. Inlet tank; 22. Intermediate tank; 23. One or more parallel (parallel in circuit) A electrode group; 24. One or more parallel (parallel in circuit) B electrode group; 25. A diode switch and B diode switch; 26. Outlet tank;

[0089] Each A electrode group 23 includes one or more A electrodes connected in series (meaning connected in series in the circuit). The A electrode includes a tubular cathode and a detachable columnar anode fitted inside the tubular electrode, or a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The central axis of the A electrode anode coincides with the central axis of the cathode. Each B electrode group 24 includes one or more B electrodes connected in series (meaning connected in series in the circuit). The B electrode includes a tubular cathode and a detachable columnar anode fitted inside the tubular electrode, or a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The central axis of the B electrode anode coincides with the central axis of the cathode.

[0090] The inlet tank 21 is connected to the intermediate tank 22 through the channels formed between the cathodes and anodes of each A electrode in each A electrode group 23 (i.e., the water channels formed between the cathodes and anodes of each A electrode in the inlet tank 21 and the intermediate tank 22 are connected in parallel); the intermediate tank 22 is connected to the outlet tank 27 through the channels formed between the anodes and cathodes of each B electrode in each B electrode group 24 (i.e., the water channels formed between the cathodes and anodes of each B electrode in the intermediate tank 22 and the outlet tank 27 are connected in parallel); that is, the water flows of the A electrode group and the B electrode group are connected in the same direction in series.

[0091] One phase of the three-phase AC power supply is connected to the anode interface of each A electrode group 23 and the cathode interface of each B electrode group 24, respectively. A diode switch 25 is set on the connection line between the anode interface of each A electrode group 23 and the three-phase AC power supply. The cathode interface of each A electrode group 23 and the anode interface of each B electrode group 24 are connected to the neutral point of the three-phase AC power supply. B diode switch 26 is set on the connection line between the anode interface of each B electrode group 24 and the three-phase AC power supply. That is, the current direction of A electrode group 23 and B electrode group 24 is reversed and connected in parallel.

[0092] The ratio of the product of the total water resistance of each A electrode group 23 and the maximum anode area of ​​the A electrode of that A electrode group 23 to the product of the total water resistance of each B electrode group 23 and the minimum anode area of ​​the B electrode of that B electrode group 24 (i.e., The ratio shall not exceed 1:5; where, the total water resistance of the electrode group refers to the sum of the water resistance in the channel formed between the cathode and anode of each electrode in the electrode group (i.e., the total water resistance of an A electrode group 23 refers to the sum of the water resistance of each A electrode in the A electrode group 23, the total water resistance of a B electrode group 24 refers to the sum of the water resistance of each B electrode in the B electrode group 24, and the water resistance of the electrode refers to the water resistance in the channel formed between the cathode and anode; the maximum anode area of ​​an A electrode group 23 refers to the anode area value of the largest anode area among the A electrodes in the A electrode group 23, and the minimum anode area of ​​a B electrode group 24 refers to the anode area value of the smallest anode area among the B electrodes in the B electrode group 24, where the anode area refers to the surface area of ​​the anode in the channel formed between the cathode and anode).

[0093] The aforementioned electrocatalysis and electrocoagulation coupled wastewater treatment system achieves different current densities for electrocatalysis and electrocoagulation using the same AC power supply through phase-coupled rectification settings, thereby realizing the coupled electrocatalysis and electrocoagulation for wastewater treatment and simplifying the process flow for electro-treated wastewater.

[0094] The passivation of anode and cathode during electrocoagulation and the passivation of cathode during electrocatalysis restrict the efficient implementation of electrocoagulation and electrocatalysis. Therefore, this invention proposes a further preferred technical solution.

[0095] Further, electrode B includes a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The columnar cathode of electrode B is cylindrical, and the cross-section of the tubular anode of electrode B is annular. The columnar cathode of electrode B is made of a non-reactive metal, and the tubular anode of electrode B is made of iron. The ratio of the inner radius of the tubular anode to the outer radius of the columnar cathode of electrode B is 2-4, and the difference between the inner radius of the tubular anode and the outer radius of the columnar cathode of electrode B is 1-2.5 cm. The ratio of the total water resistance of each electrode group 23 to the product of the maximum anode area of ​​the A electrode of electrode group 23 and the product of the total water resistance of each electrode group 23 to the minimum anode area of ​​the B electrode of electrode group 24 (i.e., ...) is... The ratio shall not exceed 2:15; at least one of the inlet tank 21 and the intermediate tank 22 shall be provided with a first pH adjustment device to adjust the pH value of the water entering the channel formed between the cathode and anode of the B electrode to 4-5.

[0096] This preferred technical solution sets the ratio of the inner radius of the tubular anode (with a circular cross-section made of iron) to the outer radius of the cylindrical cathode to be 2-4, achieving a cathode interface field strength that is 2-4 times that of the anode interface field strength. This lays the foundation for achieving appropriate electrode polarization and reverse bias. Combined with acid-assisted dissolution, it can effectively solve the anode passivation problem and help increase the cathode's ability to treat hard wastewater. In addition, the detachable cylindrical cathode, which is fitted inside the tubular anode, is easy to disassemble and facilitates the removal of cathode passivation scale, which helps to control the adsorption passivation of the cathode.

[0097] While existing electrocoagulation processes have made technical improvements in electrode shape and conduction methods, playing a role in delaying electrode passivation, most are based on concentration polarization considerations, neglecting the polarization effect of the electrostatic field (conservative force field) on the water-electrolyte. Water molecules and hydroxide ions are dipoles. After the initial ionization of water molecules to form hydroxide ions, under the influence of an external electric field, an increase in the external electric field strength will lead to an increase in the polarization of OH groups in the Stern layer. - Atomic polarization. OH - The positively charged center of mass H moves in the direction of the electric field, while the negatively charged center of mass oxygen moves in the opposite direction, increasing the distance between the shared electron pairs and hydrogen atoms, thus causing OH... - The Coulomb force between the hydrogen atom and the shared electron pair weakens, while the Coulomb force between the oxygen atom and the shared electron pair strengthens. This change in the Coulomb force enhances the positive charge of the hydrogen atom and the negative charge of the oxygen atom. OH - The bonding mechanism between hydrogen and oxygen atoms changed from primarily Coulomb forces between shared electron pairs to primarily Coulomb forces between positive and negative ions. OH - The polar covalent bonds undergo heterolytic cleavage, reducing the Fe... 2+With O 2- In OH - The potential energy barrier for the reaction. Because Fe 2+ and O 2- The Gibbs free energy of the reaction is much greater than that of H. + and O 2- The Gibbs free energy of the reaction, and the fact that matter always transforms into a more stable state, therefore, the Fe reaction occurs. 2+ Replace H + The reaction in Fe 2+ and O 2- A bond forms between them, creating a new surface film product, FeO. It is impossible to completely solve the problem of iron anode passivation without considering the electric field strength. There is a fundamental difference between cathode passivation and anode passivation. Anode passivation is a reaction between the anode bulk material and the ionization products of water. The anode bulk combines with oxygen and hydroxide ions to form passivation products with chemical bonds, which cannot be removed by mechanical or physical methods. Furthermore, the passivation product FeO is a p-type semiconductor material without a corresponding n-type semiconductor contact, thus hindering current conduction on the anode surface and increasing the risk of Fe2+ degradation. 2+ The difficulty in releasing the flocculant limits its production, and the electric field strength has a positive correlation with the passivation of the iron anode. The cathode adsorbent passivation products are unrelated to the cathode's bulk composition; they are produced by cathode byproduct reactions. These passivation products are a type of physical adsorption scale, which can be removed using mechanical methods, thereby eliminating the obstruction to current conduction.

[0098] Based on this, the present invention improves the electrocoagulation process based on the principle of alternating current conduction and establishes a brand-new electrode structure as described above, so that the polarization of the cathode and anode is uniformly deflected, realizing weak polarization of the anode and strong polarization of the cathode; and in terms of the setting of the cathode structure, the cathode polarization products can be easily mechanically or manually processed, thereby solving the problem that the passivation of the cathode and anode hinders the conduction of ferroelectric coagulation current.

[0099] Furthermore, electrode A includes a tubular cathode and a detachable columnar anode housed inside the tubular anode. The columnar anode of electrode A is cylindrical, and the cross-section of the tubular cathode of electrode A is annular. The columnar anode of electrode A is made of platinum or a platinum-plated metal that does not react with water, and the tubular cathode of electrode A is made of a metal that does not react with water. The ratio of the inner radius of the tubular cathode of electrode A to the outer radius of the columnar anode of electrode A is 1.2-1.5, and the difference between the inner radius of the tubular cathode of electrode A and the outer radius of the columnar anode of electrode A is... The cross-sectional area is 0.5-1cm; the ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each A electrode in each A electrode group 23 to the total cross-sectional area of ​​the channel formed between the cathode and anode of each B electrode in each B electrode group 24 is 1:4-10; furthermore, the number of A electrode groups 23 is the same as the number of B electrode groups 24, the ratio of the number of A electrodes in each A electrode group 23 to the number of B electrodes in each B electrode group 24 is 1:2-1:3, and the ratio of the water resistance of the B electrode to the water resistance of the A electrode is 4-10:1.

[0100] This preferred technical solution sets the ratio of the inner radius of the tubular cathode (made of platinum or platinum-plated material with a circular cross-section) to the outer radius of the cylindrical anode to be 1.2-1.5; the ratio of the inner radius of the tubular anode (made of iron with a circular cross-section) to the outer radius of the cylindrical cathode to be 2-4; the ratio of the product of the total water resistance of each A electrode group 23 and the maximum anode area of ​​the A electrode of that A electrode group 23 to the product of the total water resistance of each B electrode group 23 and the minimum anode area of ​​the B electrode of that B electrode group 24 to be no more than 2:15; and the ratio of the cathode and anode of each A electrode in each A electrode group 23 to the outer radius of the cylindrical anode to be 1.2-1.5. The ratio of the total cross-sectional area of ​​the channels formed between the electrodes to the total cross-sectional area of ​​the channels formed between the cathodes and anodes of each B electrode group 24 is 1:4-10. This achieves an anode interface field strength at the electrocatalytic end that is 1.2-1.5 times that of the cathode interface, enhancing the catalytic intensity of the anode. Simultaneously, it creates different current densities and different water flow velocities at the same power source for the electrocatalytic and electrocoagulation ends. This lays the foundation for high-speed water flow within the channels formed between the tubular cathode and columnar anode of resistor A, thereby inhibiting cathode adsorption scaling during electrocatalysis. In a further optimized technical solution, by limiting the ratio of the number of A electrodes to B electrodes and the water resistance ratio, different current intensities are created at the same power source for the electrocatalytic and electrocoagulation ends, allowing for better coupling of electrocatalysis and electrocoagulation.

[0101] Furthermore, the length of the portion of electrode B where the cylindrical cathode and tubular anode are fitted together is 5-20 times the inner radius of the tubular anode.

[0102] Furthermore, the inner radius of the tubular anode of electrode B is 2-5 cm.

[0103] Furthermore, the length of the portion of electrode A where the cylindrical anode and tubular cathode are fitted together is 5-20 times the inner radius of the tubular cathode.

[0104] Furthermore, the inner radius of the tubular cathode of electrode B is 2-5 cm.

[0105] Furthermore, the columnar anode of electrode A is made of stainless steel with a platinum-plated surface, and the tubular cathode of electrode A is made of stainless steel.

[0106] Furthermore, the columnar cathode of electrode B is made of stainless steel.

[0107] Furthermore, each A electrode group 23 is identical, and each A electrode contained in the A electrode group 23 is identical.

[0108] Furthermore, each B electrode group 24 is identical, and each B electrode contained in the B electrode group 24 is identical.

[0109] Furthermore, the number of electrode group A 23 is 1, and the number of electrode group B 24 is 1.

[0110] In the aforementioned wastewater treatment system coupled with electrocatalysis and electrocoagulation, the use of the special electrocatalytic electrode A causes the electric field strength to decrease from the inside out, while the use of the special electrocoagulation electrode B causes the electric field strength to increase from the outside in. For example... Figure 2 As shown, electric field lines originate from positive charges and terminate at negative charges. According to Gauss's law, the formula for the electric field strength at any equipotential surface P around the cylindrical plate is: in, Let ∑q be the charge density per unit length of the columnar electrode, ∑q be the charge on the columnar electrode formed by the current intensity, l be the length of the portion of the columnar electrode and the tubular electrode that are fitted together, i.e., the effective length of the conductive surface of the columnar electrode in contact with water, R be the distance from the equipotential surface surrounding the columnar electrode to the center point of the columnar electrode, d be the inner radius of the tubular electrode, r be the outer radius of the columnar electrode, and ε0 be the dielectric constant. The electric field strength is minimum when R = d (point Q) and maximum when R = r (point O). In the above electrocatalysis and electrocoagulation coupled wastewater treatment system, setting d / r = 1.2-1.5 for electrode A ensures that the electric field strength at the anode interface is 1.2-1.5 times that at the cathode interface, thus enhancing the catalytic intensity of the anode. Setting d1 / r1 = 2-4 for electrode B ensures that the electric field strength at the cathode interface is 2-4 times that at the anode interface, laying the foundation for achieving appropriate polarization and reverse bias of the electrodes.

[0111] The aforementioned electrocatalytic and electrocoagulation coupled wastewater treatment system forms a closed loop with any one phase and the neutral point of a three-phase AC power supply (see [link]). Figure 3The design employs electrode group A (23) and electrode group B (24) connected to the two poles of the power supply. Diode switches are installed at the input terminals of electrode groups A (23) and B (24), forming an electrolytic circuit where the electrocatalytic and electrocoagulation processes are connected in series in the same direction of water flow and in parallel in the opposite direction of current flow. Under alternating current, the anode of electrode A in electrode group A (23) and the anode of electrode B in electrode group B (24) are always at a high potential, achieving π-periodic cyclic conduction of electrode groups A (23) and B (24) with different current intensities. Figure 4 As shown. See also Figure 5 The water flow rate at electrode A in electrode group 23 is 4-10 times that at electrode B in electrode group 24, ensuring smooth water flow and laying the foundation for high-speed water flow within the channel formed between the tubular cathode and columnar anode of resistor A. Furthermore, the number of resistors in electrode groups 23 and 24 can be determined based on the wastewater treatment volume.

[0112] Under alternating current, a peak field strength will inevitably be generated at the wave crest, promoting the formation of a small amount of FeO. At the same time, dissolved oxygen in the water will also cause non-dense oxidation of the iron matrix. By installing a pH adjustment device in at least one of the inlet tank 21 and the intermediate tank 22, the pH value of the water used for electrocoagulation is maintained at 4-5. When the stack is turned off, FeO dissolves to form Fe. 2+ H2O and other substances prevent the FeO passivation film from accumulating and thickening.

[0113] The aforementioned electrocatalysis and electrocoagulation coupled wastewater treatment system utilizes a special electrocoagulation electrode setup to achieve appropriate polarization deflection, which, combined with acid-assisted dissolution, effectively solves the anode passivation problem. Simultaneously, the polarization deflection increases the cathode's ability to treat hard wastewater, and the pluggable cathode design facilitates easy cleaning of the passivation film, effectively resolving the cathode passivation issue. Furthermore, the special electrocatalysis electrode setup enhances the catalytic intensity of the anode while laying the foundation for high-speed water flow within the channel formed between the tubular cathode and columnar anode of the A resistor, thus inhibiting adsorbent scaling on the cathode during the electrocatalytic process.

[0114] Furthermore, the inlet tank 21 and the intermediate tank 22 are provided with A-electrode fixing sleeves to fix the columnar electrode plate and tubular electrode plate of the A-electrode. Specifically, the inlet tank 21 is provided with an A-electrode columnar electrode plate fixing sleeve penetrating two opposite sides of the inlet tank 21 along the A-electrode setting direction, and the intermediate tank 22 is correspondingly provided with an A-electrode columnar electrode plate fixing sleeve penetrating two opposite sides of the intermediate tank 22 along the A-electrode setting direction. The columnar electrode plate of each A-electrode is respectively inserted through one A-electrode columnar electrode plate fixing sleeve in the inlet tank 21 and one A-electrode columnar electrode plate fixing sleeve in the intermediate tank 22 to fix the columnar electrode plate, and at least one end of the columnar electrode plate of the A-electrode extends out of the A-electrode columnar electrode plate fixing sleeve to facilitate the insertion and removal of the columnar electrode plate; at least one of the inlet tank 21 and the intermediate tank 22 is provided with an A-electrode tubular electrode plate fixing sleeve to fix the A-electrode tubular electrode plate.

[0115] Furthermore, the intermediate water tank 22 and the outlet water tank 27 are provided with B electrode fixing sleeves to fix the columnar electrode plate and the tubular electrode plate of the B electrode. Specifically, the intermediate water tank 22 is provided with a B electrode columnar electrode plate fixing sleeve penetrating two opposite sides of the intermediate water tank 22 along the B electrode setting direction, and the outlet water tank 27 is correspondingly provided with a B electrode columnar electrode plate fixing sleeve penetrating two opposite sides of the outlet water tank 27 along the B electrode setting direction. The columnar electrode plate of each B electrode is respectively inserted through one B electrode columnar electrode plate fixing sleeve in the intermediate water tank 22 and one B electrode columnar electrode plate fixing sleeve in the outlet water tank 27 to fix the columnar electrode plate, and at least one end of the columnar electrode plate of the B electrode protrudes from the B electrode columnar electrode plate fixing sleeve to facilitate the insertion and removal of the columnar electrode plate; at least one of the intermediate water tank 22 and the outlet water tank 27 is provided with a B electrode tubular electrode plate fixing sleeve to fix the B electrode tubular electrode plate.

[0116] Furthermore, the inlet tank 21 is connected to the intermediate tank 22 through the channels formed between the cathodes and anodes of each A electrode in each A electrode group 23 in the following manner:

[0117] The inlet tank 21, each A electrode group 23, and the intermediate water tank 22 are arranged from bottom to top;

[0118] The top surface of the water inlet tank 21 is provided with a fluid channel opening that matches the size of the tubular electrode plate of each A electrode in each A electrode group 23, and the fluid channel opening is provided with a sleeve for fixing the tubular electrode plate of the A electrode. The water inlet tank 21 is provided with a sleeve for fixing the tubular electrode plate of the A electrode that matches the size of the tubular electrode plate of each A electrode in each A electrode group 23, which penetrates the top and bottom surfaces of the water inlet tank 21, and the sleeve for fixing the tubular electrode plate of the A electrode is fixed to the bottom surface of the water inlet tank 21.

[0119] The bottom surface of the intermediate water tank 22 is provided with a fluid channel opening that matches the size of the tubular electrode plate of each A electrode in each A electrode group 23, and the fluid channel opening is provided with a sleeve for fixing the columnar electrode plate of the A electrode. The outlet water tank 27 is provided with a sleeve for fixing the columnar electrode plate of the A electrode that matches the size of the tubular electrode plate of each A electrode in each A electrode group 23, which penetrates the top and bottom surfaces of the intermediate water tank 22, and the sleeve for fixing the columnar electrode plate of the A electrode is fixed to the top surface of the intermediate water tank 22.

[0120] In each A electrode group 23, the tubular electrode plate of each A electrode is fixed between the inlet tank 21 and the intermediate water tank 22 by a sleeve for fixing the tubular electrode plate of the A electrode in the inlet tank 21 and a sleeve for fixing the columnar electrode plate of the A electrode in the intermediate water tank 22. The sleeve for fixing the tubular electrode plate of the A electrode in the inlet tank 21 and the sleeve for fixing the columnar electrode plate of the A electrode in the outlet tank 27 can achieve the sealing of the interface between the tubular electrode plate of each A electrode in each A electrode group 23 and the inlet tank 21 and the intermediate water tank 22 to prevent water from overflowing from the interface.

[0121] In each A electrode group 23, the columnar electrode plate of each A electrode is respectively inserted into a tubular electrode plate fixing sleeve of the A electrode in the water inlet tank 21 and a columnar electrode plate fixing sleeve of the A electrode in the water outlet tank 27 to fix the columnar electrode plate, and at least one end of the columnar electrode plate extends out of the electrode fixing sleeve to facilitate the insertion and removal of the columnar electrode plate.

[0122] Water in the inlet tank 21 flows through the fluid channels on the top surface of the inlet tank 21 to the channels formed between the tubular and columnar plates of each A electrode in each A electrode group 23, and then flows into the intermediate water tank 22 through the fluid channels on the bottom surface of the intermediate water tank 22.

[0123] Furthermore, the outlet tank 27 is connected to the outlet tank 27 through the channel formed between the anode and cathode of each B electrode in each B electrode group 24 in the following manner:

[0124] The intermediate water tank 22, each B electrode group 24, and the outlet water tank 27 are arranged from bottom to top;

[0125] The top surface of the intermediate water tank 22 is provided with a fluid channel opening that matches the size of the tubular electrode plate of each B electrode in each B electrode group 24, and the fluid channel opening is provided with a sleeve for fixing the tubular electrode plate of the B electrode. The intermediate water tank 22 is provided with a sleeve for fixing the tubular electrode plate of the B electrode that matches the size of the tubular electrode plate of each B electrode in each B electrode group 24, which runs through the top and bottom surfaces of the intermediate water tank 22, and the sleeve for fixing the tubular electrode plate of the B electrode is fixed to the bottom surface of the intermediate water tank 22.

[0126] The bottom surface of the water outlet tank 27 is provided with a fluid channel opening that matches the size of the tubular electrode plate of each B electrode in each B electrode group 24, and the fluid channel opening is provided with a sleeve for fixing the columnar electrode plate of the B electrode. The water outlet tank 27 is provided with a sleeve for fixing the columnar electrode plate of the B electrode that matches the size of the tubular electrode plate of each B electrode in each B electrode group 24, which penetrates the top and bottom surfaces of the water outlet tank 27, and the sleeve for fixing the columnar electrode plate of the B electrode is fixed to the top surface of the water outlet tank 27.

[0127] The tubular electrode plate of each B electrode in each B electrode group 24 is fixed between the intermediate water tank 22 and the outlet water tank 27 by a B electrode tubular electrode plate fixing sleeve in the intermediate water tank 22 and a B electrode columnar electrode plate fixing sleeve in the outlet water tank 27. The B electrode tubular electrode plate fixing sleeve in the intermediate water tank 22 and the B electrode columnar electrode plate fixing sleeve in the outlet water tank 27 can achieve the sealing of the interface between the tubular electrode plate of each B electrode in each B electrode group 24 and the intermediate water tank 22 and the outlet water tank 27 to prevent water from overflowing from the interface.

[0128] In each B electrode group 24, the columnar electrode plate of each B electrode is respectively inserted into a B electrode tubular electrode plate fixing sleeve in the intermediate water tank 22 and a B electrode columnar electrode plate fixing sleeve in the outlet water tank 27 to fix the columnar electrode plate, and at least one end of the columnar electrode plate extends out of the electrode fixing sleeve to facilitate the insertion and removal of the columnar electrode plate.

[0129] Water in the intermediate water tank 22 flows through the fluid channels on the top surface of the intermediate water tank 22 to the channels formed between the tubular and columnar plates of each B electrode in each B electrode group 24, and then flows into the outlet water tank 27 through the fluid channels on the bottom surface of the outlet water tank 27.

[0130] Furthermore, insulated water tanks are selected for inlet tank 21, intermediate water tank 22, and outlet tank 27.

[0131] Furthermore, insulating sleeves are selected for both the tubular electrode plate fixing sleeve and the columnar electrode plate fixing sleeve.

[0132] Furthermore, a second pH adjustment device is installed at the outlet of the water tank 27 to maintain the pH value of the water discharged from the water tank 27 at 8-9 by adding alkaline substances.

[0133] Furthermore, a turbulence impeller is installed at the inlet of the channel formed between the tubular and cylindrical plates of electrode A (i.e., the inlet near the water inlet tank). The turbulence impeller helps to create a high-speed rotating water flow, which forms a high-speed scouring and lateral shearing effect on the cathode plate surface of electrode A, preventing adsorption passivation of electrode A cathode.

[0134] Furthermore, a turbulence impeller is installed at the inlet of the channel formed between the tubular and cylindrical plates of electrode B (i.e., the inlet near the middle water tank). The turbulence impeller helps to reduce the effect of concentration polarization. Specifically, the turbulence blades make the water flow more uniform and generate lateral shear force, reducing the scaling and adhesion of suspended pollutants to the plates and increasing flocculation efficiency.

[0135] A specific embodiment of the present invention provides a method for treating wastewater using a coupling of electrocatalysis and electrocoagulation, wherein the method is performed using the electrocatalysis and electrocoagulation coupled wastewater treatment system provided in the above embodiments of the present invention, and the method includes:

[0136] The wastewater to be treated is fed into the inlet tank 21;

[0137] The wastewater to be treated in the inlet tank 21 enters the channel formed between the anode and cathode of each A electrode in each A electrode group 23. Alternating current is used to electrocatalyze the wastewater to be treated in the channel formed between the anode and cathode of each A electrode in each A electrode group 23 to obtain electrocatalyzed water.

[0138] The water after electrocatalytic treatment enters the intermediate water tank 22;

[0139] The water treated by electrocatalysis in the intermediate water tank 22 enters the channel formed between the anode and cathode of each B electrode in each B electrode group 24. Alternating current is used to electrocoagulate the water treated by electrocatalysis in the channel formed between the anode and cathode of each B electrode in each B electrode group 24 to obtain water treated by electrocoagulation.

[0140] The water treated by electrocoagulation enters the outlet tank 27;

[0141] Among them, the ratio of the effective current density of the anode of electrode A during the electrocatalysis process (referring to the current density of the anode during the conduction period of electrode A) to the effective current density of the anode of electrode B during the electrocoagulation process (referring to the current density of the anode during the conduction period of electrode B) shall not be less than 5:1.

[0142] The above-mentioned wastewater treatment method that couples electrocatalysis and electrocoagulation utilizes the same AC power source to sequentially perform electrocatalysis and electrocoagulation on the wastewater to be treated. By setting the phase coupling rectification, the wastewater treatment is achieved through the coupling of electrocatalysis and electrocoagulation, which simplifies the process flow of electro-treated wastewater.

[0143] Furthermore, the method also includes adjusting the pH of the water in the inlet tank 21 or the water in the intermediate tank 22 to 4-5; and during the electrocoagulation process, the B electrode used includes a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The columnar cathode of the B electrode is cylindrical, and the cross-section of the tubular anode of the B electrode is annular. The columnar cathode of the B electrode is made of a non-reactive metal, and the tubular anode of the B electrode is made of iron. The ratio of the inner radius of the tubular anode to the outer radius of the columnar cathode of the B electrode is 2-4, and the difference between the inner radius of the tubular anode and the outer radius of the columnar cathode of the B electrode is 1-2.5 cm. The ratio of the product of the total water resistance of each A electrode group and the maximum anode area of ​​the A electrode in that A electrode group to the product of the total water resistance of each B electrode group and the minimum anode area of ​​the B electrode in that B electrode group does not exceed 2:15; and during the electrocoagulation process, the effective current density of the anode of the B electrode does not exceed 2.0 mA / cm². 2 ;

[0144] This preferred technical solution achieves polarization deflection through a special B electrode setting combined with an appropriate effective anode current density, which in turn effectively solves the anode passivation problem with acid-assisted dissolution. At the same time, the polarization deflection increases the cathode's ability to treat hard wastewater, and the pluggable design of the cathode makes it easy to clean the passivation film, thus effectively solving the cathode passivation problem.

[0145] Furthermore, during the electrocoagulation process, the effective current density at the anode of electrode B is 1.0-2.0 mA / cm². 2 ;

[0146] Furthermore, the pH value can be adjusted to 4-5 by adding sulfuric acid;

[0147] Furthermore, the method also includes: adjusting the pH of the water after electrocoagulation treatment in the outlet tank 27 to 8-9 before discharging it; adjusting the pH of the flocculated water to 8-9 can achieve the removal of Fe 2+ The flocculation is further enhanced by converting it to Fe(OH)2; and then, the pH value is adjusted to 8-9 by adding sodium hydroxide and / or potassium hydroxide.

[0148] Furthermore, the method also includes: monitoring the effective current of electrode B during electrocoagulation, and cleaning the cathode of electrode B after the decline of the effective current reaches the current decline threshold; furthermore, the current decline threshold is 10%-15% of the effective current during normal operation (i.e., when there is no scale on the cathode and anode); although polarization deflection prevents the formation of the anode passivation film, it cannot solve the cathode adsorption passivation problem. When the calcium and magnesium hardness in the wastewater is high, calcium and magnesium scale will inevitably be adsorbed at the cathode. Using the current decline as a trigger condition to treat the scale on the cathode can solve the cathode passivation problem more scientifically and reasonably.

[0149] Furthermore, in the electrocatalytic process, the A electrode used includes a tubular cathode and a detachable columnar anode fitted inside the tubular anode. The columnar anode of the A electrode is cylindrical, and the cross-section of the tubular cathode of the A electrode is annular. The columnar anode of the A electrode is made of platinum or a platinum-plated metal that does not react with water, and the tubular cathode of the A electrode is also made of a metal that does not react with water. The ratio of the inner radius of the tubular cathode of the A electrode to the outer radius of the columnar anode of the A electrode is 1.2-1.5, and the difference between the inner radius of the tubular cathode and the outer radius of the columnar anode of the A electrode is 0.5-1 cm. Furthermore, during the electrocatalytic process, the effective current density of the anode of the A electrode is not less than 15 mA / cm². 2 The ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each A electrode in each A electrode group to the total cross-sectional area of ​​the channel formed between the cathode and anode of each B electrode in each B electrode group is 1:4-10; and the water flow velocity in the channel formed between the anode and cathode of the A electrode is not less than 0.4 m / s.

[0150] This preferred technical solution enhances the catalytic strength of the anode while suppressing cathode adsorption scaling during electrocatalysis through the high-speed flow of water in the channel formed between the tubular cathode and columnar anode of resistor A.

[0151] Furthermore, during the electrocatalytic process, the effective current density at the anode of electrode A is 15-50 mA / cm². 2 ;

[0152] Furthermore, the water flow velocity in the channel formed between the anode and cathode of electrode A is 0.4-0.6 m / s.

[0153] Furthermore, the water flow velocity in the channel formed between the anode and cathode of electrode B does not exceed 0.1 m / s; even further, the water flow velocity in the channel formed between the anode and cathode of electrode B is 0.04-0.1 m / s.

[0154] Furthermore, the ratio of the current intensity of electrode A during electrocatalysis to the current intensity of electrode B during electrocoagulation is (10-30):1.

[0155] Furthermore, the water flow velocity in the channel formed between the anode and cathode of electrode A is 4-10 times that in the channel formed between the anode and cathode of electrode B.

[0156] Furthermore, the frequency of alternating current is 30-100 Hz.

[0157] Example 1

[0158] This embodiment provides a wastewater treatment system that couples electrocatalysis and electrocoagulation.

[0159] like Figure 6 As shown, the system includes an inlet tank, an intermediate tank, an outlet tank, an A electrode group, a B electrode group, an A diode switch, and a B diode switch.

[0160] Electrode group A consists of one electrode A, and electrode group B consists of two identical electrodes connected in series.

[0161] Electrode A includes a tubular cathode with a circular cross-section and a detachable cylindrical anode fitted inside the tubular cathode. The central axis of the cylindrical anode coincides with the central axis of the tubular cathode. The cylindrical anode is made of 316 stainless steel with a platinum-plated surface, and the tubular cathode is also made of 316 stainless steel. The inner radius d of the tubular cathode is 3 cm, the outer radius r of the cylindrical anode is 2.5 cm, the length l of the tubular cathode is 20 cm, and the cylindrical anode is longer than the tubular cathode. The length of the portion of the cylindrical anode fitted inside the tubular cathode is 20 cm.

[0162] Electrode B includes a tubular anode with a circular cross-section and a detachable cylindrical cathode fitted inside the tubular anode. The central axis of the cylindrical cathode coincides with the central axis of the tubular anode. The cylindrical cathode is made of 316 stainless steel, and the tubular anode is made of iron. The inner radius d1 of the tubular anode is 3cm, the outer radius r1 of the cylindrical cathode is 1cm, and the length l1 of the tubular anode is 20cm. The cylindrical cathode is longer than the tubular anode, and the length of the portion of the cylindrical cathode fitted inside the tubular anode is 20cm.

[0163] The inlet tank, A electrode assembly, and intermediate water tank are arranged from bottom to top. The top surface of the inlet tank has a fluid channel opening matching the size of the tubular electrode plate of the A electrode in the A electrode assembly, and a sleeve for fixing the tubular electrode plate is installed at the fluid channel opening. The inlet tank also has a sleeve for fixing the tubular electrode plate, matching the size of the A electrode, that penetrates both the top and bottom surfaces of the inlet tank and is fixed to the bottom surface of the inlet tank. The bottom surface of the intermediate water tank has a fluid channel opening matching the size of the tubular electrode plate of the A electrode, and a sleeve for fixing the columnar electrode plate of the A electrode is installed at the fluid channel opening. The outlet tank has a sleeve for fixing the columnar electrode plate, matching the size of the tubular electrode plate of the A electrode, that penetrates both the top and bottom surfaces of the intermediate water tank and is fixed to the top surface of the intermediate water tank. The tubular electrode plate of electrode A is fixed between the inlet and intermediate water tanks via a fixing sleeve for the tubular electrode plate of electrode A in the inlet tank and a fixing sleeve for the cylindrical electrode plate of electrode A in the intermediate water tank. These sleeves ensure a seal at the interface between the tubular electrode plate of electrode A and the inlet and intermediate water tanks, preventing water leakage. The cylindrical electrode plate of electrode A is fixed by passing through the fixing sleeves for the tubular electrode plate of electrode A in the inlet and outlet tanks, with both ends extending from the fixing sleeves for easy insertion and removal. Water in the inlet tank flows through fluid channels on the top surface of the inlet tank into the channels formed between the tubular and cylindrical electrode plates of electrode A, and then flows into the intermediate water tank through fluid channels on the bottom surface of the intermediate water tank.

[0164] The intermediate water tank, B-electrode group, and outlet water tank are arranged from bottom to top. The top surface of the intermediate water tank has two fluid channel openings matching the dimensions of the tubular plates of each B-electrode in the B-electrode group, and each fluid channel opening is equipped with a sleeve for fixing the tubular plates of the B-electrode. The intermediate water tank also has two sleeves, each matching the dimensions of the tubular plates of each B-electrode, penetrating both the top and bottom surfaces of the intermediate water tank, and these sleeves are fixed to the bottom surface of the intermediate water tank. The bottom surface of the outlet water tank has two fluid channel openings matching the dimensions of the tubular plates of each B-electrode, and each fluid channel opening is equipped with a sleeve for fixing the columnar plates of the B-electrode. The outlet water tank also has two sleeves, each matching the dimensions of the tubular plates of each B-electrode, penetrating both the top and bottom surfaces of the outlet water tank, and these sleeves are fixed to the top surface of the outlet water tank. Each B electrode's tubular plate is fixed between the intermediate water tank and the outlet water tank via a B electrode tubular plate fixing sleeve in the intermediate water tank and a B electrode cylindrical plate fixing sleeve in the outlet water tank. These sleeves ensure a seal at the interface between the tubular plate of each B electrode and the intermediate and outlet water tanks, preventing water leakage. Each B electrode's cylindrical plate is secured by passing through one of the B electrode tubular plate fixing sleeves in the intermediate water tank and another in the outlet water tank, with both ends of the cylindrical plate extending from the electrode fixing sleeve for easy insertion and removal. Water in the intermediate water tank flows through fluid channels on the top surface of the intermediate water tank into the channels formed between the tubular and cylindrical plates of each B electrode in the B electrode assembly, and then flows into the outlet water tank through fluid channels on the bottom surface of the outlet water tank.

[0165] One phase of the three-phase AC power supply is connected to the anode interface of electrode group A and the cathode interface of electrode group B, respectively, and diode switch A is set on the connection line between the anode interface of electrode group A and the three-phase AC power supply; the cathode interface of electrode group A and the anode interface of electrode group B are both connected to the neutral point of the three-phase AC power supply, and diode switch B is set on the connection line between the cathode interface of electrode group A and the three-phase AC power supply; that is, the current direction of electrode group A and electrode group B 24 is reversed and connected in parallel.

[0166] The inlet tank is equipped with a first pH adjustment device to adjust the pH of the water entering the channel formed between the cathode and anode of the B electrode to 4-5. The outlet tank is equipped with a second pH adjustment device to maintain the pH of the water discharged from the outlet tank at 8-9 by adding alkaline substances.

[0167] A turbulence impeller is installed at the entrance of the channel formed between the tubular anode and the cylindrical cathode of each B electrode (i.e., the entrance near the end of the intermediate water tank). A turbulence impeller is also installed at the entrance of the channel formed between the tubular cathode and the cylindrical anode of the A electrode (i.e., the entrance near the end of the inlet tank).

[0168] Insulated water tanks are selected for the inlet tank, intermediate water tank, and outlet tank. Insulated sleeves are also selected for the tubular electrode plate fixing sleeve and the columnar electrode plate fixing sleeve.

[0169] Two ammeters L are set up to measure the current intensity of electrode B and electrode A, respectively.

[0170] The water resistance is directly proportional to the electrode spacing and is constrained by the side with the smaller electrode area. That is, the area of ​​the cylindrical electrode and the distance between the anode and cathode determine the water resistance. The water resistance of electrode B is approximately 10 times that of electrode A. The number of electrodes B in electrode group B is twice the number of electrodes A in electrode group A. The total water resistance of electrode group B is 10 × 2 = 20 times that of electrode group A. The ratio of the anode area of ​​electrode A to the anode area of ​​electrode B is r / d1 = 5 / 6. Therefore, the ratio of the product of the total water resistance of electrode group A and the largest anode area to the product of the total water resistance of electrode group B and the smallest anode area is 1 / 20 × 5 / 6 = 1 / 24, not exceeding 2:15. The ratio of the sum of the cross-sectional areas of the channels formed between the cathodes and anodes of each electrode A in electrode group A to the sum of the cross-sectional areas of the channels formed between the cathodes and anodes of each electrode B in electrode group B is...

[0171] Example 2

[0172] This embodiment provides a wastewater treatment method that couples electrocatalysis and electrocoagulation.

[0173] This method uses the electrocatalytic and electrocoagulation coupled wastewater treatment system provided in Example 1, and the method includes:

[0174] 1) The wastewater to be treated (domestic sewage from a converter station) is fed into the inlet tank and the pH value is adjusted to 4-5 by adding sulfuric acid to obtain the wastewater to be electrocatalyzed;

[0175] 2) The wastewater to be electrocatalyzed in the inlet tank enters the channel formed between the tubular cathode and the cylindrical anode of electrode A. Alternating current is used to electrocatalyze the wastewater to be treated in the channel formed between the anode and cathode of each electrode A in each electrode group, so as to obtain water after electrocatalytic treatment.

[0176] 3) The water treated by electrocatalysis enters the intermediate water tank;

[0177] 4) The electrocatalytically treated water in the intermediate water tank enters the channel formed between the anode and cathode of each B electrode in the B electrode group. Alternating current is used to electrocoagulate the electrocatalytically treated water in the channel formed between the anode and cathode of each B electrode in the B electrode group to obtain electrocoagulated water. During the process, the effective current of the electrocatalytically treated water entering the channel formed between the tubular anode and cylindrical cathode of each B electrode is monitored.

[0178] The total water flow velocity is 1.8m. 3 The water flow rate in electrode A is 1.8 m / h. 3 / h (meaning the water flow velocity in electrode A is 0.58 m / s), and the water flow velocity in each electrode B is 0.9 m / s. 3 / h (meaning the water flow rate in electrode B is 0.1 m / s);

[0179] The effective current density of electrode B during normal operation is 2 mA / cm². 2 The effective current density of the anode during normal operation, excluding the cutoff π-angle A electrode, is 48 mA / cm². 2 The frequency of alternating current is 50 Hz.

[0180] Among them, when the effective current decay of electrode B reaches the current decay threshold (15% of the effective current during normal operation), the cylindrical cathodes of each electrode B are cleaned.

[0181] 5) After electrocoagulation treatment, the water enters the outlet tank, where sodium hydroxide is added to adjust the pH to 9 before being discharged.

[0182] In the electrocatalytic and electrocoagulation coupled wastewater treatment method provided in this embodiment, the effective current density at the π conduction angle (excluding the cutoff π angle) formed when the anode of electrode B at the electrocoagulation end is working normally is σ. e =2mA / cm 2 The effective current density formed at the cathode of electrode B is 2 × 3 = 6 mA / cm². 2 The effective current intensity of electrode B is I = 2πdσ e ·l=2×3.14×3×2×20=753.6mA, the effective monitoring current formed by the 2π cycle (including the cutoff π angle) is 753.6÷2=376.8mA, and the current decay threshold is approximately 376.8mA×15%=56.5mA.

[0183] The water resistance of electrode group A at the electrocatalytic end is 1 / 20 of that of electrode group B at the electrocoagulation end. The effective monitoring current formed by the 2π cycle at the electrocatalytic end is 20 × 376.8 ≈ 7536 mA. The effective current intensity of electrode A is I = 7536 × 2 = 15072 mA. The effective current density formed by the anode within the π conduction angle is σ. e =48mA / cm 2 .

[0184] In the electrocatalytic and electrocoagulation coupled wastewater treatment method provided in this embodiment, the ratio of the flow area of ​​the water flow formed by the electrocoagulation end and the electrocatalytic end (i.e., the ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each B electrode in the B electrode group to the cross-sectional area of ​​the channel formed between the cathode and anode of the A electrode in the A electrode group) is: Therefore, the water flow velocity in the channel formed between the electrode A and the anode of the electrocatalytic reactor is 5.82 times that in the channel formed between the electrode B and the anode of the electrocoagulation reactor. The rotating impeller is passively rotated under hydraulic pressure, causing the longitudinal water flow to spiral upwards. This achieves different water flow velocities at the same flow rate; the high flow velocity effectively inhibits the passivation of the cathode adsorption at the electrocatalytic end, while the low flow velocity facilitates the flocculation process at the electrocoagulation end.

[0185] In the wastewater treatment method coupled with electrocatalysis and electrocoagulation provided in this embodiment, see [link to relevant documentation]. Figure 7 The electrocatalytic end (electrode A) is conducting, while the electrocoagulation end (electrode B) is cut off. When the voltage on the power supply side is greater than the turn-on voltage of diode A, electrode A conducts. The reverse potential of diode B is always greater than the forward potential, therefore electrode B is cut off. Within one 2π cycle, the AC power supply forms a positive conduction angle of π. The cylindrical anode of electrode A is at a high potential, and the tubular cathode is at a low potential.

[0186] See Figure 8 The electrocoagulation end (electrode B) is on, while the electrocatalytic end (electrode A) is off. When the voltage on the power supply side is greater than the turn-on voltage of diode B, electrode B conducts, and the reverse potential of diode A is always greater than the forward potential, so electrode A is off. Within one 2π cycle, the AC power supply achieves a negative conduction angle of π. The tubular anode is at a high potential, generating flocculated iron ions, while the cylindrical cathode is at a low potential, corresponding to the loss of electrons at the anode, and hydrogen ions gain electrons to produce hydrogen gas.

[0187] In summary, high-potential conduction of both the cylindrical electrode at the electrocatalytic end and the tubular electrode at the electrocoagulation end was achieved within a 2π cycle, and this cycle was repeated in 2π cycles, as described in the following diagram. Figure 4 ,accomplish

[0188] In the electrocatalytic and electrocoagulation coupled wastewater treatment method provided in this embodiment, electrocatalytic secondary organic small molecule products and fine cathode scaling particles formed by hydraulic shearing are hydraulically propelled into the electrocoagulation stack. The change in the water channel area causes a decrease in water flow velocity, which is beneficial for the flocculant to function. At the same time, the fine particles adsorb impurities and small molecule organic matter in the water through flocculant bridging, forming larger colloidal clusters. Furthermore, the colloidal clusters and Fe(OH)2 generated under pH adjustment at the total outlet flow into the coagulation and clarification device, achieving enhanced flocculation and solid-liquid separation. Water samples after solid-liquid separation are taken for analysis, and the treatment results are shown in Table 1.

[0189] Table 1

[0190] Laboratory items Before processing After processing Removal rate <![CDATA[Hardness (mg·L -1 )]]> 532 83 84.4 Turbidity / degree 132.0 13.3 89.92 <![CDATA[COD / (mg·L -1 )]]> 897.7 13.2 98.53 <![CDATA[Suspended solids / (mg·L -1 )]]> 193.9 2.4 98.76 Bacterial count 5715 20 99.65

[0191] During the water treatment process, the device operated for approximately 121 hours before the effective current at electrode B reached the current decay threshold, necessitating a shutdown to treat cathode scaling, replace the cathode column, and revert to standby after treatment. During the shutdown for cathode scaling treatment, passivation was assessed on the anode of electrode B and the cathode of electrode A. No passivation was detected on the anode of electrode B, nor was significant passivation detected on the cathode of electrode A.

[0192] Experimental Example 1

[0193] In this experiment, methods 1, 2, 3, and 4 were used to perform electrocatalytic and electrocoagulation treatments on a saturated sodium sulfate solution with zero hardness.

[0194] Method 1: The electrocatalytic and electrocoagulation coupled wastewater treatment system provided in Example 1 is used. The only difference between this method and the electrocatalytic and electrocoagulation coupled wastewater treatment system provided in Example 1 is that the inner radius d1 of the tubular anode and the outer radius r1 of the cylindrical cathode of electrode B in electrode group B are different.

[0195] The specific steps are as follows:

[0196] 1) The wastewater to be treated (saturated sodium sulfate solution with zero hardness) is input into the inlet tank, and the pH value is adjusted to 4-5 by adding sulfuric acid to obtain the wastewater to be electrocatalyzed;

[0197] 2) The wastewater to be electrocatalyzed in the inlet tank enters the channel formed between the tubular cathode and the cylindrical anode of electrode A. Alternating current is used to electrocatalyze the wastewater in the channel formed between the anode and cathode of electrode A to obtain electrocatalyzed water.

[0198] 3) The water treated by electrocatalysis enters the intermediate water tank;

[0199] 4) The electrocatalytically treated water in the intermediate water tank enters the channel formed between the anode and cathode of each B electrode in the B electrode group. Alternating current is used to electrocoagulate the electrocatalytically treated water in the channel formed between the anode and cathode of each B electrode in the B electrode group to obtain electrocoagulated water. During the process, the effective current of the wastewater to be flocculated enters the channel formed between the tubular anode and cylindrical cathode of each B electrode and is used for electrocoagulation with alternating current. The time taken for the effective current to decline to reach 25% of the effective current when the electrode is working normally is recorded, and the passivation of the cathode and anode is detected when the current decline reaches 25% of the effective current when the electrode is working normally.

[0200] The total water flow rate is 1.8m. 3 The water flow rate in electrode A is 1.8 m³ / h. 3 / h (meaning the water flow rate in electrode A is 0.58 m / s);

[0201] The effective current density of the anode during normal operation, excluding the cutoff π-angle A electrode, is 48 mA / cm². 2 ;

[0202] The frequency of the alternating current is 50 Hz;

[0203] Specifically, the outer radius r1 of the cylindrical cathode in electrode group B was changed, and the effective current density of the anode of electrode B during normal operation was controlled to be 8.07 mA / cm². 2 (That is, the effective current during the 2π cycle when electrode B is working normally is 3042.4 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 2 cm), 4.11 mA / cm 2 (That is, when electrode B is working normally, the effective current within the 2π cycle is 1549.5 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 1.5 cm), 2.05 mA / cm 2 (That is, the effective current during the 2π cycle when electrode B is working normally is 772.9 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 1 cm), 0.81 mA / cm 2 (That is, when electrode B is working normally, the effective current within the 2π cycle is 301.6mA, at which time the inner radius d1 of the tubular anode is 3cm and the outer radius r1 of the cylindrical cathode is 0.5cm).

[0204] 5) After electrocoagulation treatment, the water enters the outlet tank, where sodium hydroxide is added to adjust the pH value to 9 before it is discharged.

[0205] Method 2: The only difference between this method and Method 1 is that the pH value of the wastewater to be treated is not adjusted when it enters the inlet tank, and the pH value of the water after flocculation treatment is not adjusted when it enters the outlet tank.

[0206] Method 3: First, use the A electrode assembly used in Method 1 to perform electrocatalytic treatment on the wastewater. Then, use a traditional plate-type DC electrocoagulation system for electrocoagulation treatment. The traditional plate-type DC electrocoagulation system is as follows: Figure 9 As shown, the specific steps are as follows:

[0207] 1) The wastewater to be treated enters the channel formed between the tubular cathode and the cylindrical anode of electrode A, where electrocatalysis is performed using alternating current to obtain electrocatalytically treated water; wherein, the water flow velocity in electrode A is 1.8 m / s. 3 / h (i.e., the water flow velocity in electrode A is 0.58 m / s), and the effective current density of the anode of electrode A during normal operation, excluding the cutoff π angle, is 48 mA / cm². 2 The frequency of the alternating current is 50 Hz;

[0208] 2) The water after electrocatalytic treatment enters the iron anode plate (the area of ​​the iron anode plate is 377 cm²). 2 Electrocoagulation was performed between the iron anode plate and the 316 stainless steel cathode plate to obtain flocculated water. During the process, the effective current of the wastewater entering the electrocoagulation process between the iron anode plate and the 316 stainless steel cathode plate was monitored. The time taken for the effective current to decay to reach 25% of the effective current when the electrode was working normally was recorded, and the passivation of the electrode was detected when the current decay reached 25% of the effective current when the electrode was working normally. The total water flow rate was 0.1 m / s.

[0209] Electrocoagulation was performed using direct current, with the effective current density controlled at 8.07 mA / cm² during normal anode operation. 2 (i.e., effective current of 3042.4mA during normal operation), 4.11mA / cm 2 (i.e., effective current of 1549.5mA during normal operation), 2.05mA / cm 2 (i.e., effective current of 772.9mA during normal operation), 0.81mA / cm 2 (That is, the effective current during normal operation is 301.6mA).

[0210] Method 4: First, use the A electrode assembly used in Method 1 to perform electrocatalytic treatment on the wastewater. Then, use a traditional plate-type AC electrocoagulation system. The traditional plate-type AC electrocoagulation system is as follows: Figure 10 As shown, the specific steps are as follows:

[0211] 1) The wastewater to be treated enters the channel formed between the tubular cathode and cylindrical anode of electrode A, where electrocatalysis is performed using alternating current to obtain electrocatalytically treated water; the water flow rate in electrode A is 1.8 m³ / min. 3 / h (i.e., the water flow velocity in electrode A is 0.58 m / s), and the effective current density of the anode of electrode A during normal operation, excluding the cutoff π angle, is 48 mA / cm². 2 The frequency of the alternating current is 50 Hz;

[0212] 2) The water after electrocatalytic treatment enters the iron anode plate (the area of ​​the iron anode plate is 377 cm²). 2 ) and iron cathode plate (the area of ​​the iron cathode plate is 377cm²) 2 Electrocoagulation was performed between the two iron plates to obtain flocculated water. During the process, the effective current between the two iron plates was monitored, the time taken for the effective current to decline to reach 25% of the effective current when the electrode was working normally was recorded, and the passivation of the electrode was detected when the current decline reached 25% of the effective current when the electrode was working normally. The total water flow rate was 0.1 m / s.

[0213] Electrocoagulation was performed using alternating current, with the effective current density controlled at 8.07 mA / cm² during normal anode operation. 2 (i.e., effective current of 3042.4mA during normal operation), 4.11mA / cm 2 (i.e., effective current of 1549.5mA during normal operation), 2.05mA / cm 2 (i.e., effective current of 772.9mA during normal operation), 0.81mA / cm 2 (i.e., the effective current during normal operation is 301.6mA); the frequency of the AC power is 50Hz.

[0214] The results are shown in Table 2. Under several methods, the monitoring current declined to varying degrees with increasing current density. In this experimental example, the hardness of the wastewater to be treated was zero, and there was almost no anion adsorption passivation during electrocoagulation. The decline in the monitoring current was due to anodic passivation. Method 3 showed the fastest decline, while Method 1 showed the slowest. This indicates that Method 3, with the iron anode, is the fastest way to grow the passivation film. Although Method 4 delayed the current decline time, it resulted in passivation on both electrodes, making the effect less than ideal. Method 2 significantly delayed the current decline time, but could not prevent the accumulation of passivation, making it inferior to Method 1 from an operational cycle perspective.

[0215] Table 2

[0216]

[0217] Experiment Example 2

[0218] In this experiment, electrocoagulation treatment was performed on a saturated sodium sulfate solution with a hardness of 200 mg / L using methods one, two, three, and four as described in Experiment Example 1.

[0219] In Method 1 and Method 2, the outer radius r1 of the cylindrical cathode in Electrode Group B is changed, and the effective current density of the anode of Electrode B during normal operation is controlled to be 8.11 mA / cm². 2 (That is, the effective current during the 2π cycle when electrode B is working normally is 3057.5 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 2 cm), 4.13 mA / cm 2 (That is, when electrode B is working normally, the effective current within a 2π cycle is 1557mA, at which time the inner radius d1 of the tubular anode is 3cm and the outer radius r1 of the cylindrical cathode is 1.5cm), 2.15mA / cm 2 (That is, the effective current during the 2π cycle when electrode B is working normally is 810.5 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 1 cm), 1.37 mA / cm 2 (That is, when electrode B is working normally, the effective current within the 2π cycle is 516.5 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 0.75 cm), 1.05 mA / cm 2 (That is, when electrode B is working normally, the effective current within the 2π cycle is 395.8 mA, at which time the inner radius d1 of the tubular anode is 3 cm and the outer radius r1 of the cylindrical cathode is 0.6 cm), 0.81 mA / cm 2 (That is, when electrode B is working normally, the effective current within the 2π cycle is 305.4mA, at which time the inner radius d1 of the tubular anode is 3cm and the outer radius r1 of the cylindrical cathode is 0.5cm), and the frequency of the alternating current is 50HZ.

[0220] The results are shown in Table 3.

[0221] Table 3

[0222]

[0223] Comparing the data from Experiment 1 and Experiment 2, it can be seen that the scaling time is shortened when treating hard water compared to treating non-hard water, especially in Method 1 and Method 2. This is because the polarization deflection leads to stronger adsorption passivation of the columnar cathode, which hinders current conduction.

[0224] For methods one and two, when d1 / r1 < 2, due to the high anode current density and short mass transfer distance, a strong redox reaction occurs at the anode, resulting in significant anode passivation. The anode passivation resistance is the main obstacle to current conduction. When d1 / r1 > 4, the current declines rapidly, and cathode passivation is significant. This is because the small cathode area causes an exponential amplification effect in the adsorption passivation resistance; furthermore, a small cathode area is detrimental to hardness removal in water. d1 / r1 = 2-4 effectively avoids anode passivation, controls the degree of cathode passivation, and is beneficial for hardness removal. On the other hand, regarding the current decline caused by hardness, for the same anode and cathode area, the current decline caused by adsorption passivation is less than that caused by anode passivation. This is because adsorption passivation is less dense than oxidative passivation.

[0225] Experimental Example 3

[0226] This experimental example uses a saturated sodium sulfate solution with a hardness of 200 mg / L to verify the effect of flow rate on the adsorption passivation of the electrocatalytic cathode.

[0227] The electrocatalytic and electrocoagulation coupled wastewater treatment system provided in Example 1 was used, and the specific steps are as follows:

[0228] 1) Input the wastewater to be treated into the inlet tank, and adjust the pH value to 4-5 by adding sulfuric acid to obtain the wastewater to be electrocatalyzed;

[0229] 2) The wastewater to be electrocatalyzed in the inlet tank enters the channel formed between the tubular cathode and cylindrical anode of electrode A. Alternating current is used to electrocatalyze the wastewater in the channel to obtain electrocatalyzed water. During the process, the effective current during electrocoagulation in the channel is monitored, and the effective current decay rate over 3000 minutes is recorded.

[0230] The water flow velocity in electrode A was controlled at 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.4 m / s, 0.5 m / s, and 0.6 m / s, respectively; the effective current density of the cathode of electrode A during normal operation was controlled at 20 mA / cm², respectively. 2 30mA / cm 2 40mA / cm 2 50mA / cm 2 ;

[0231] 3) The water treated by electrocatalysis enters the intermediate water tank;

[0232] 4) The water treated by electrocatalysis in the intermediate water tank enters the channel formed between the anode and cathode of each B electrode in the B electrode group. Alternating current is used to electrocoagulate the water treated by electrocatalysis in the channel formed between the anode and cathode of each B electrode in the B electrode group to obtain water treated by electrocoagulation.

[0233] 5) After electrocoagulation treatment, the water enters the outlet tank, where sodium hydroxide is added to adjust the pH to 9 before being discharged.

[0234] The results are shown in Table 4.

[0235] Table 4

[0236]

[0237] As can be seen from Table 4, during the electrocatalytic treatment process, the increase in water flow rate in the electrode helps to suppress the occurrence of cathode adsorption passivation.

[0238] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A wastewater treatment system coupled with electrocatalysis and electrocoagulation, characterized in that, The electrocatalytic and electrocoagulation coupled wastewater treatment system includes: an inlet tank, an intermediate tank, an outlet tank, one or more parallel A electrode groups, one or more parallel B electrode groups, an A diode switch, and a B diode switch. Each A electrode group includes one or more A electrodes connected in series, and each B electrode group includes one or more B electrodes connected in series; the A electrode and the B electrode each use a tubular electrode plate and a detachable cylindrical electrode plate fitted inside the tubular electrode plate as the anode and cathode, respectively. The central axes of the tubular electrode plate and the cylindrical electrode plate coincide, and the inner wall of the tubular electrode plate and the outer wall of the cylindrical electrode plate are spaced apart to form a channel. The inlet tank is connected to the intermediate water tank through the channel formed between the cathode and anode of each A electrode; the intermediate water tank is connected to the outlet tank through the channel formed between the anode and cathode of each B electrode. One phase of the three-phase AC power supply is connected to the anode interface of each A electrode group and the cathode interface of each B electrode group, and the A diode switch is set on the connection line between the anode interface of each A electrode group and the three-phase AC power supply; the cathode interface of each A electrode group and the anode interface of each B electrode group are connected to the neutral point of the three-phase AC power supply, and the B diode switch is set on the connection line between the anode interface of each B electrode group and the three-phase AC power supply. The ratio of the product of the total water resistance of each A electrode group and the maximum anode area of ​​the A electrode in that A electrode group to the product of the total water resistance of each B electrode group and the minimum anode area of ​​the B electrode in that B electrode group shall not exceed 1:

5. In this process, the wastewater to be treated in the inlet tank enters the channel formed between the anode and cathode of each A electrode in each A electrode group, and the wastewater to be treated in the channel formed between the anode and cathode of each A electrode in each A electrode group is electrocatalyzed using alternating current. In this process, the water treated by electrocatalysis in the intermediate water tank enters the channel formed between the anode and cathode of each B electrode in each B electrode group, and the water treated by electrocatalysis in the channel formed between the anode and cathode of each B electrode in each B electrode group is electrocoagulated using alternating current.

2. The system according to claim 1, characterized in that, Electrode B includes a tubular anode and a detachable cylindrical cathode housed inside the tubular anode. The cylindrical cathode of electrode B is cylindrical, and the cross-section of the tubular anode of electrode B is annular. The cylindrical cathode of electrode B is made of a non-reactive metal, and the tubular anode of electrode B is made of iron. The ratio of the inner radius of the tubular anode to the outer radius of the cylindrical cathode of electrode B is 2-4, and the difference between the inner radius of the tubular anode and the outer radius of the cylindrical cathode of electrode B is 1-2.5 cm. The ratio of the product of the total water resistance of each electrode group A and the maximum anode area of ​​electrode A in that electrode group to the product of the total water resistance of each electrode group B and the minimum anode area of ​​electrode B in that electrode group does not exceed 2:

15. At least one of the inlet tank and the intermediate tank is equipped with a first pH adjustment device to adjust the pH value of the water entering the channel formed between the cathode and anode of electrode B to 4-5.

3. The system according to claim 2, characterized in that, Electrode A includes a tubular cathode and a detachable columnar anode housed inside the tubular anode. The columnar anode of electrode A is cylindrical, and the cross-section of the tubular cathode of electrode A is annular. The columnar anode of electrode A is made of platinum or a platinum-plated metal that does not react with water. The tubular cathode of electrode A is made of a metal that does not react with water. The ratio of the inner radius of the tubular cathode of electrode A to the outer radius of the columnar anode is 1.2-1.5, and the difference between the inner radius of the tubular cathode of electrode A and the outer radius of the columnar anode is 0.5-1 cm. The ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each electrode in each electrode A group to the total cross-sectional area of ​​the channel formed between the cathode and anode of each electrode B group is 1:4-10.

4. The system according to claim 3, characterized in that, The number of electrode groups A is the same as the number of electrode groups B. The ratio of the number of electrodes A in each electrode group A to the number of electrodes B in each electrode group B is 1:2 to 1:

5. The ratio of the water resistance of electrode B to the water resistance of electrode A is 4 to 10:

1.

5. The system according to claim 2, characterized in that, The length of the portion of the cylindrical cathode and tubular anode of electrode B that is fitted together is 5-20 times the inner radius of the tubular anode; The inner radius of the tubular anode of electrode B is 2-5 cm.

6. The system according to claim 3, characterized in that, The length of the portion of electrode A where the cylindrical anode and tubular cathode are fitted together is 5-20 times the inner radius of the tubular cathode. The inner radius of the tubular cathode of electrode A is 2-5 cm.

7. The system according to claim 1 or 3, characterized in that, The water inlet tank is connected to the intermediate water tank through the channels formed between the cathodes and anodes of each A electrode in the following manner: The inlet tank, each A electrode group, and the intermediate water tank are arranged from bottom to top; The top surface of the water inlet tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each A electrode in each A electrode group, and the fluid channel opening is provided with a sleeve for fixing the tubular electrode plate of the A electrode. The water inlet tank is provided with a sleeve for fixing the tubular electrode plate of the A electrode that matches the size of the tubular electrode plate of each A electrode in each A electrode group, which penetrates the top and bottom surfaces of the water inlet tank, and the sleeve for fixing the tubular electrode plate of the A electrode is fixed to the bottom surface of the water inlet tank. The bottom surface of the intermediate water tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each A electrode in each A electrode group, and the fluid channel opening is provided with a sleeve for fixing the columnar electrode plate of the A electrode. The intermediate water tank is provided with a sleeve for fixing the columnar electrode plate of the A electrode that matches the size of the tubular electrode plate of each A electrode in each A electrode group, penetrating the top and bottom surfaces of the intermediate water tank, and the sleeve for fixing the columnar electrode plate of the A electrode is fixed to the top surface of the intermediate water tank. Each A electrode's tubular plate is fixed between the inlet tank and the intermediate tank via a sleeve for fixing the tubular plate of the A electrode in the inlet tank and a sleeve for fixing the columnar plate of the A electrode in the intermediate tank. The sleeves for fixing the tubular plate of the A electrode in the inlet tank and the sleeves for fixing the columnar plate of the A electrode in the intermediate tank can achieve a seal at the interface between the tubular plate of each A electrode and the inlet tank and the intermediate tank, preventing water from overflowing from the interface. Each columnar electrode plate of A electrode is respectively inserted into a tubular electrode plate fixing sleeve of A electrode in the water inlet tank and a columnar electrode plate fixing sleeve of A electrode in the intermediate water tank to fix the columnar electrode plate, and at least one end of the columnar electrode plate extends out of the electrode fixing sleeve to facilitate the insertion and removal of the columnar electrode plate. Water in the inlet tank flows through the fluid channels on the top surface of the inlet tank to the channels formed between the tubular and cylindrical plates of each A electrode, and then flows into the intermediate water tank through the fluid channels on the bottom surface of the intermediate water tank.

8. The system according to claim 1 or 2, characterized in that, The outlet tank is connected to the outlet tank through the channel formed between the anode and cathode of each B electrode in the following manner: The intermediate water tank, each B electrode group, and the outlet water tank are arranged from bottom to top; The top surface of the intermediate water tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each B electrode in each B electrode group, and the fluid channel opening is provided with a sleeve for fixing the tubular electrode plate of the B electrode. The intermediate water tank is provided with a sleeve for fixing the tubular electrode plate of the B electrode that matches the size of the tubular electrode plate of each B electrode in each B electrode group, which runs through the top and bottom surfaces of the intermediate water tank, and the sleeve for fixing the tubular electrode plate of the B electrode is fixed to the bottom surface of the intermediate water tank. The bottom surface of the water outlet tank is provided with a fluid channel opening that matches the size of the tubular electrode plate of each B electrode in each B electrode group, and the fluid channel opening is provided with a sleeve for fixing the columnar electrode plate of the B electrode. The water outlet tank is provided with a sleeve for fixing the columnar electrode plate of the B electrode that matches the size of the tubular electrode plate of each B electrode in each B electrode group, which penetrates the top and bottom surfaces of the water outlet tank, and the sleeve for fixing the columnar electrode plate of the B electrode is fixed to the top surface of the water outlet tank. Each B electrode's tubular plate is fixed between the intermediate water tank and the outlet water tank via a B electrode tubular plate fixing sleeve in the intermediate water tank and a B electrode columnar plate fixing sleeve in the outlet water tank. The B electrode tubular plate fixing sleeve in the intermediate water tank and the B electrode columnar plate fixing sleeve in the outlet water tank can achieve a seal at the interface between each B electrode's tubular plate and the intermediate water tank and the outlet water tank, preventing water from overflowing from the interface. Each B electrode's cylindrical plate is respectively inserted into a B electrode tubular plate fixing sleeve in the intermediate water tank and a B electrode cylindrical plate fixing sleeve in the outlet water tank to fix the cylindrical plate, and at least one end of the cylindrical plate extends out of the electrode fixing sleeve to facilitate the insertion and removal of the cylindrical plate. Water in the intermediate water tank flows through the fluid channels on the top surface of the intermediate water tank to the channels formed between the tubular and cylindrical plates of each B electrode, and then flows into the outlet water tank through the fluid channels on the bottom surface of the outlet water tank.

9. The system according to claim 2, characterized in that, A second pH adjustment device is installed at the outlet of the water tank to maintain the pH value of the water discharged from the water tank at 8-9 by adding alkaline substances.

10. The system according to claim 1 or 3, characterized in that, A turbulence impeller is installed at the entrance of the channel formed between the tubular electrode plate and the cylindrical electrode plate of electrode A.

11. The system according to claim 1 or 2, characterized in that, A turbulence impeller is installed at the entrance of the channel formed between the tubular electrode plate and the cylindrical electrode plate of electrode B.

12. A wastewater treatment method coupled with electrocatalysis and electrocoagulation, characterized in that, This method is carried out using the electrocatalytic and electrocoagulation coupled wastewater treatment system according to any one of claims 1-11, and the method includes: The wastewater to be treated is fed into the inlet tank; The wastewater to be treated in the inlet tank enters the channel formed between the anode and cathode of each A electrode in each A electrode group. Alternating current is used to electrocatalyze the wastewater to be treated in the channel formed between the anode and cathode of each A electrode in each A electrode group to obtain electrocatalyzed water. The water treated by electrocatalysis enters the intermediate water tank; The water treated by electrocatalysis in the intermediate water tank enters the channel formed between the anode and cathode of each B electrode in each B electrode group. Alternating current is used to electrocoagulate the water treated by electrocatalysis in the channel formed between the anode and cathode of each B electrode in each B electrode group to obtain water treated by electrocoagulation. The water treated by electrocoagulation enters the outlet tank; Among them, the ratio of the effective current density of electrode A in the electrocatalysis process to the effective current density of electrode B in the electrocoagulation process is not less than 7.5:

1.

13. The method according to claim 12, characterized in that, The method also includes adjusting the pH of the wastewater to be treated in the inlet tank or the electrocatalytically treated water in the intermediate tank to 4-5; and during the electrocoagulation process, the B electrode used includes a tubular anode and a detachable columnar cathode fitted inside the tubular anode. The columnar cathode of the B electrode is cylindrical, and the cross-section of the tubular anode of the B electrode is annular. The columnar cathode of the B electrode is made of a non-reactive metal, and the tubular anode of the B electrode is made of iron. The ratio of the inner radius of the tubular anode to the outer radius of the columnar cathode of the B electrode is 2-4, and the difference between the inner radius of the tubular anode and the outer radius of the columnar cathode of the B electrode is 1-2.5 cm. The ratio of the product of the total water resistance of each A electrode group and the maximum anode area of ​​the A electrode in that A electrode group to the product of the total water resistance of each B electrode group and the minimum anode area of ​​the B electrode in that B electrode group does not exceed 2:15; and during the electrocoagulation process, the effective current density of the anode of the B electrode does not exceed 2.0 mA / cm². 2 .

14. The method according to claim 13, characterized in that, The method also includes: after the water treated by electrocoagulation enters the outlet tank, the pH value is adjusted to 8-9 before being discharged.

15. The method according to claim 13, characterized in that, The method also includes: monitoring the effective current of electrode B during electrocoagulation, and cleaning the cathode of electrode B after the amount of decline of the effective current reaches the current decline threshold.

16. The method according to claim 13, characterized in that, In the electrocatalytic process, the A electrode used includes a tubular cathode and a detachable columnar anode fitted inside the tubular anode. The columnar anode of the A electrode is cylindrical, and the cross-section of the tubular cathode of the A electrode is annular. The columnar anode of the A electrode is made of platinum or a platinum-plated metal that does not react with water. The tubular cathode of the A electrode is also made of a metal that does not react with water. The ratio of the inner radius of the tubular cathode to the outer radius of the columnar anode of the A electrode is 1.2-1.5, and the difference between the inner radius of the tubular cathode and the outer radius of the columnar anode is 0.5-1 cm. The ratio of the total cross-sectional area of ​​the channel formed between the cathode and anode of each A electrode in each A electrode group to the total cross-sectional area of ​​the channel formed between the cathode and anode of each B electrode in each B electrode group is 1:4-10. Furthermore, during the electrocatalytic process, the effective current density of the anode of the A electrode is not less than 15 mA / cm². 2 Furthermore, the water flow velocity in the channel formed between the anode and cathode of electrode A is not less than 0.4 m / s.

17. The method according to any one of claims 12-16, characterized in that, The water flow velocity in the channel formed between the anode and cathode of electrode B does not exceed 0.1 m / s.

18. The method according to any one of claims 12-16, characterized in that, The ratio of the current intensity of electrode A during electrocatalysis to that of electrode B during electrocoagulation is 10-30:

1.

19. The method according to any one of claims 12-16, characterized in that, The water flow velocity in the channel formed between the anode and cathode of electrode A is 4-10 times that in the channel formed between the anode and cathode of electrode B.

20. The method according to any one of claims 12-16, characterized in that, The frequency of alternating current is 30-100 Hz.

Images