Device and method for efficient electrochemical degradation of organic wastewater

Abstract

The application belongs to the technical field of wastewater treatment, and provides a device and method for efficiently electrochemically degrading organic wastewater. The device comprises an electrochemical degradation reactor and a water flow circulation structure matched with the reactor. A hollow rotating shaft is arranged in the electrochemical degradation reactor, a cylindrical anode is sleeved on the outer wall of the hollow rotating shaft, a cylindrical cathode is arranged on the inner wall of the reactor shell, and a micro-scale annular gap is formed between the anode and the cathode. The method of the application is based on the device, and wastewater is treated under the condition that the hollow rotating shaft is rotated to drive the anode to rotate and the water flow is circulated. The method can solve the problem of bubble adhesion on the electrode surface, strengthen the mass transfer in the electrochemical degradation device, and improve the degradation efficiency of organic wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to an apparatus and method for the efficient electrochemical degradation of organic wastewater. Background Technology

[0002] Organic wastewater contains various toxic and harmful substances. Direct discharge can cause irreversible damage to aquatic organisms and ecosystems, posing a serious threat to the environment and human health. Therefore, the harmless treatment of organic wastewater is crucial. Currently, commonly used methods for treating organic wastewater include biodegradation, physicochemical methods, and chemical treatment. However, these methods suffer from drawbacks such as low treatment efficiency or high costs. In contrast, electrochemical methods have unique advantages and great potential in treating organic wastewater. Electrochemical methods utilize electric current and electrode catalysts to promote the oxidation or reduction reactions of organic pollutants in organic wastewater, thereby converting them into harmless substances. Electrochemical methods are characterized by simple operation, low energy consumption, and relatively high treatment efficiency. Electrochemical methods can also achieve highly efficient degradation of specific organic pollutants without the need for additional chemical agents, which helps reduce the use of chemical reagents and the risk of secondary pollution. Therefore, electrochemical methods are considered one of the important methods for green, environmentally friendly, and efficient degradation of organic wastewater.

[0003] Current technologies primarily utilize trough-type equipment for the degradation of organic wastewater. In this equipment, the electrodes are fixed, requiring agitation to enhance the electrolysis process. During electrolysis, bubbles are generated at the anode and adhere to the electrode surface. This bubble adhesion reduces the number of electrolytically active sites, leading to a decrease in current density and weakening the wastewater degradation effect and efficiency. Once the current density decreases due to bubble adhesion, more energy is required to maintain a normal current density, resulting in high energy consumption and increased wastewater treatment costs. Furthermore, the relatively weak turbulence within the trough-type equipment leads to insufficient mixing of the wastewater, resulting in better degradation near the electrodes and poorer degradation further away. Additionally, the long migration time of pollutants from a distance to the vicinity of the electrodes further weakens the wastewater degradation effect and reduces efficiency.

[0004] CN107840416A discloses a rotating electrode tubular electrochemical reactor, comprising at least one electrochemical reactor shell, a rotating anode, a stationary cathode, a rotating shaft, a motor, a conductive slip ring, and bearings; the electrochemical reactor shell is a vertical tubular or cylindrical body with an insulated inner wall, and has an inlet and an outlet; the rotating shaft is longitudinally arranged inside the electrochemical reactor shell; the rotating anode is fixed on the rotating shaft, and the stationary cathode is fixed on the inner wall of the electrochemical reactor shell, with the rotating anode and stationary cathode alternately arranged; the conductive slip ring provided on the top surface of the electrochemical reactor shell is used to connect the rotating anode and the positive terminal of a DC regulated power supply. The electrochemical reactor drives the rotation of the rotating anode through the rotating shaft, which can accelerate the removal of bubbles on the electrode surface and avoid the problem of reduced effective electrode area caused by bubbles adhering to the electrode surface to a certain extent. However, the following problems still need to be solved: (1) The rotating anode is circular and fixed vertically on the rotating shaft. During the rotation of the rotating anode, the bubbles at the outer edge of the rotating anode will fall off first under the action of high shear force, while the bubbles near the rotating shaft are subjected to less centrifugal force or shear force and are not easy to fall off, especially under the condition that the rotation speed of the rotating anode is only 30 to 500 rpm. That is to say, the distribution of bubbles on the entire rotating anode is uneven, which will lead to uneven electrolysis effect on pollutants, more serious backmixing, and reduced electrolysis efficiency. (2) The flow direction of the electrolyte is perpendicular to the direction of the rotating anode and the stationary cathode. This means that the electrolyte will continuously impact the electrode plate during the flow process, which will cause the catalyst layer loaded on the electrode plate surface to fall off, thereby shortening the service life of the electrode. (3) The vertical distance between adjacent rotating anodes and stationary cathodes is relatively large (15-40 mm), resulting in a long transmission distance and time required for transmission. This is detrimental to improving degradation efficiency and effectiveness. Therefore, there is an urgent need to develop more effective electrochemical degradation devices and methods to enhance the degradation of organic wastewater. Summary of the Invention

[0005] To address the problems of low degradation efficiency and poor degradation effect of organic wastewater caused by the adhesion of bubbles on the electrode surface and low mass transfer efficiency within the device in existing electrochemical degradation equipment, this invention provides a device and method for high-efficiency electrochemical degradation of organic wastewater. This method enhances mass transfer within the electrochemical degradation device by solving the problem of bubble adhesion on the electrode surface, thereby improving the degradation efficiency and effect of organic wastewater.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] An efficient electrochemical degradation device for organic wastewater includes an electrochemical degradation reactor, a regulated power supply, a delivery pump, and a storage tank.

[0008] The electrochemical degradation reactor includes a drive unit, a transmission shaft, a conductive slip ring, a reactor shell, a cathode, an anode, and a hollow rotating shaft. The reactor shell is a cylinder closed at both ends, with its axis perpendicular to the horizontal plane. The upper part of the reactor shell has an outlet, and the lower part has an inlet. The hollow rotating shaft is also a cylinder closed at both ends, located inside the reactor shell. The axis of the hollow rotating shaft coincides with the axis of the reactor shell. One end of the hollow rotating shaft is connected to the drive unit via the transmission shaft, and the other end is connected to a bushing located inside the reactor shell via a connecting shaft. The reactor shell and the hollow rotating shaft are non-conductive. Both the cathode and anode are cylindrical. The anode is sleeved on the outer wall of the hollow rotating shaft, and the cathode surrounds the anode and is fixed to the inner wall of the reactor shell. An annular gap with a width of 1.5–30 mm is formed between the anode and the cathode. The conductive slip ring is fixed to the transmission shaft. The anode is connected to the positive terminal of a regulated power supply via a wire located inside the hollow rotating shaft and the conductive slip ring. The cathode is connected to the negative terminal of the regulated power supply via a wire.

[0009] The outlet is connected to the inlet via a delivery pipe, a delivery pump, and a storage tank.

[0010] In the above-mentioned technical solution of the device for efficient electrochemical degradation of organic wastewater, the cathode, anode and hollow rotating shaft are at the same height, and the cathode and anode are installed at the same height position.

[0011] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the height of the hollow rotating shaft is preferably 60% to 90% of the height of the reactor shell, and the hollow rotating shaft is installed in the middle of the reactor shell.

[0012] In the aforementioned technical solution for the highly efficient electrochemical degradation of organic wastewater, the diameters of the drive shaft above the hollow rotating shaft and the connecting shaft below the hollow rotating shaft are both smaller than the diameter of the hollow rotating shaft. Typically, the diameter of the hollow rotating shaft is 2 to 5 times the diameter of the drive shaft and the connecting shaft. This structural design can reduce the disturbance to the influent and effluent caused by the swirling flow field formed by the rotation of the anode driven by the hollow rotating shaft, making the influent and effluent more stable.

[0013] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the preferred ratio of the height to the diameter of the hollow rotating shaft is (5-25):1.

[0014] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the height of the reactor shell and the hollow rotating shaft can be determined according to the actual application requirements. Typically, the height of the hollow rotating shaft can be 15 to 150 cm.

[0015] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the width of the annular gap formed between the anode and the cathode is preferably 1.5 to 10 mm.

[0016] In the above-mentioned technical solution for the highly efficient electrochemical degradation of organic wastewater, the anode is a screen anode or a plate anode, and the cathode is a screen cathode or a plate cathode. Further, the porosity of the screen anode is 20%–60%, and the porosity of the screen cathode is 20%–60%.

[0017] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the anode is made of iron, iron-based oxide coating, titanium, titanium-based oxide coating, nickel, or nickel-based oxide coating; the iron-based oxide coating, titanium-based oxide coating, and nickel-based oxide coating refer to those formed by plating metal oxide coatings on iron-based, titanium-based, and nickel-based materials; the cathode is made of stainless steel.

[0018] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the reactor shell and hollow rotating shaft are made of non-conductive materials, or a non-conductive material layer formed of non-conductive materials is provided on the reactor shell and hollow rotating shaft. The non-conductive materials can be polytetrafluoroethylene, plexiglass, polycarbonate, etc.

[0019] In the above-mentioned technical solution for the device for efficient electrochemical degradation of organic wastewater, the driving device can be a drive motor.

[0020] This invention also provides a method for the efficient electrochemical degradation of organic wastewater, which uses the aforementioned apparatus for the efficient electrochemical degradation of organic wastewater and includes the following steps:

[0021] Turn on the transfer pump to introduce the organic wastewater in the storage tank into the annular gap inside the reactor shell through the inlet, and make the wastewater circulate between the storage tank and the annular gap. After the circulation is stable, turn on the drive device to drive the transmission shaft to rotate the hollow shaft at a speed of 1000-5000 rpm. Turn on the regulated power supply connected to the anode and cathode. Under the condition that the hollow shaft drives the anode to rotate and the wastewater circulates, the wastewater is electrolyzed. Control the speed of the wastewater circulation to be no less than 0.7 m / s. After the wastewater treatment is completed, discharge the wastewater from the storage tank.

[0022] During the electrolytic treatment of wastewater, bubbles are generated on the anode surface and adhere to the anode, reducing the number of activation sites and increasing the ohmic drop. This increases electrolytic energy consumption and reduces degradation efficiency. In the aforementioned high-efficiency electrochemical degradation method for organic wastewater, a hollow rotating shaft drives the anode to rotate at an appropriate speed. This allows the bubbles adhering to the anode surface to receive appropriate centrifugal force and quickly detach from the anode surface. This helps maintain the anode activity at its maximum and effectively reduces the adverse effects of bubble adhesion on pollutant degradation. However, after the bubbles detach from the anode surface and enter the wastewater, the increased number of bubbles in the wastewater leads to an increase in the ohmic drop between the anode and cathode, which in turn increases electrolytic energy consumption and reduces degradation efficiency. In the aforementioned high-efficiency electrochemical degradation method for organic wastewater, a transfer pump controls the rapid circulation between the wastewater storage tank and the confined space of the annular gap. This allows the bubbles that have detached from the anode surface and entered the wastewater to be quickly removed from the electrochemical degradation reactor, thereby reducing the ohmic drop between the anode and cathode, thus reducing electrolytic energy consumption and improving degradation efficiency. Furthermore, the electrolytic treatment process of wastewater is affected by mass transfer, especially the mass transfer distance and material turbulence, which significantly impact degradation efficiency. In the aforementioned high-efficiency electrochemical degradation method for organic wastewater, a hollow rotating shaft drives the anode to rotate at an appropriate speed, introducing a swirling flow field of suitable intensity within the confined space of the annular gap. On the one hand, the microscale confined space significantly shortens the mass transfer distance; on the other hand, the introduction of the swirling flow field enhances turbulence and interface renewal, effectively improving mass transfer efficiency and thus degradation efficiency.

[0023] In the above-mentioned technical solution of the efficient electrochemical degradation method for organic wastewater, the wastewater is treated intermittently. After one batch of wastewater is treated, the wastewater in the storage tank is discharged and replaced with the next batch of wastewater for treatment.

[0024] In the above-mentioned technical solution for the efficient electrochemical degradation of organic wastewater, the preferred current density is controlled at 20–500 A / m. 2 When applying it, the specific current density level can be determined based on the actual water quality of the organic wastewater.

[0025] In the above-mentioned technical solution of the method for efficient electrochemical degradation of organic wastewater, the wastewater circulates between the storage tank and the annular gap, which means that the wastewater circulates in the following direction: the wastewater in the storage tank enters the annular gap inside the reactor shell through the inlet, is discharged through the outlet and then enters the storage tank, and then enters the annular gap inside the reactor shell from the storage tank.

[0026] In the above-mentioned technical solution for the efficient electrochemical degradation of organic wastewater, the wastewater circulation speed refers to the flow speed of the wastewater at the outlet. To ensure effective removal of air bubbles in the wastewater through rapid circulation, and considering the energy consumption of wastewater treatment, it is best to control the wastewater circulation speed to 0.7–10 m / s.

[0027] In the above-mentioned technical solution of the method for efficient electrochemical degradation of organic wastewater, the organic wastewater refers to wastewater containing organic pollutants, including but not limited to phenolic substances, amine substances, phosphorus-containing organic matter, nitrogen-containing organic matter, etc.

[0028] Generally, organic wastewater can be treated by electrolysis. In the above-mentioned method for efficient electrochemical degradation of organic wastewater, in order to ensure that the electrolysis process proceeds more smoothly, depending on the quality of the organic wastewater, an electrolyte can be added to the organic wastewater. For example, an electrolyte can be added to the organic wastewater so that the concentration of the electrolyte in the wastewater is less than 50 mmol / L. A feasible electrolyte is sodium sulfate.

[0029] The principle of the technical solution described in this invention is mainly as follows:

[0030] During the electrolytic treatment of organic wastewater, bubbles are generated on the anode surface and adhere to it. This reduces the number of active sites on the anode, leading to an increase in ohmic drop, which in turn increases electrolytic energy consumption and reduces degradation efficiency. The technical solution of this invention utilizes a hollow rotating shaft at an appropriate speed, which allows the bubbles attached to the anode surface to receive sufficient centrifugal force and quickly detach from the anode surface. This facilitates the full exposure of the active sites on the anode, maintaining the anode's activity at its maximum at all times, and effectively reducing the adverse effects of bubble adhesion on the electrochemical degradation of pollutants. However, after detaching from the anode surface, the bubbles enter the wastewater, increasing the number of bubbles in the wastewater. This increase in bubbles in the wastewater leads to an increase in the ohmic drop between the anode and cathode, which in turn increases electrolytic energy consumption and reduces degradation efficiency. The technical solution of this invention controls the rapid circulation of wastewater within the confined space of the storage tank and the annular gap using a delivery pump. This effectively reduces the residence time of air bubbles in the electrochemical degradation reactor. When wastewater containing a large number of air bubbles enters the storage tank outside the electrochemical degradation reactor, the air bubbles easily escape rapidly from the liquid phase due to the density difference between the gas and liquid phases. This achieves the rapid removal of air bubbles that have detached from the anode surface and entered the wastewater from the electrochemical degradation reactor, thereby reducing the ohmic drop between the anode and cathode, thus reducing electrolysis energy consumption and improving degradation efficiency. Furthermore, mass transfer distance and material turbulence significantly affect the degradation efficiency of pollutants in wastewater. The technical solution of this invention controls the hollow shaft to rotate the anode at an appropriate speed, introducing a swirling flow field of appropriate intensity within the confined space of the annular gap. On the one hand, the microscale confined space significantly shortens the mass transfer distance; on the other hand, the introduction of the swirling flow field enhances turbulence and interface renewal, effectively improving mass transfer efficiency and thus degradation efficiency.

[0031] The technical solution of this invention organically combines the following techniques: using a hollow rotating shaft to drive the anode to rotate and apply a swirling flow field; setting up a water circulation structure and using a delivery pump to make the wastewater circulate rapidly between the storage tank and the annular gap; and setting up a micro-scale annular gap. This combination effectively avoids the adverse effects of bubbles generated at the anode on the electrolytic treatment process of wastewater, effectively enhances mass transfer, and ultimately improves the degradation efficiency and degradation effect of organic wastewater.

[0032] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0033] 1. The present invention provides a device for efficiently electrochemically degrading organic wastewater. The device includes an electrochemical degradation reactor and a water flow circulation structure supporting the reactor. A hollow rotating shaft is provided in the electrochemical degradation reactor, and a cylindrical anode is sleeved on the outer wall of the hollow rotating shaft, and a cylindrical cathode is sleeved on the inner wall of the reactor housing. Meanwhile, a micro-scale annular gap is formed between the anode and the cathode. On the one hand, by rotating the anode driven by the hollow rotating shaft in the present invention, the bubbles generated on the anode and attached thereto during the electrolysis process can be quickly detached from the anode surface, which is conducive to the full exposure of the activation sites of the anode, keeping the activity of the anode at the maximum value at all times, and effectively reducing the adverse effects of the attachment of bubbles on the anode surface on the electrolytic treatment of pollutants. On the other hand, through the water flow circulation structure and an appropriate water flow velocity in the present invention, the bubbles detached from the anode and entering the wastewater can be quickly removed in the storage tank, avoiding the problem of increased ohmic drop caused by the presence of bubbles in the wastewater in the reactor. On the third hand, by introducing a swirling flow field in the micro-scale annular gap through the rotation of the hollow rotating shaft in the present invention, the turbulence and interface renewal can be enhanced and the mass transfer distance can be shortened. Through the mutual cooperation of the above aspects in the present invention, the problems of reduced electrode activation sites and increased ohmic drop caused by the bubbles generated during the electrolytic treatment process can be effectively avoided, the energy consumption of wastewater treatment can be reduced, and the degradation efficiency can be improved.

[0034] 2. Based on the above device for efficiently electrochemically degrading organic wastewater, the present invention also provides a method for electrochemically degrading organic wastewater. The method feeds the organic wastewater in the storage tank into the annular gap in the reactor housing through a delivery pump, and makes the wastewater circulate between the storage tank and the annular gap, and conducts electrolytic treatment of the wastewater under the conditions that the anode is rotated by the hollow rotating shaft and the wastewater circulates. The operation of this method is simple. By controlling the speed of the wastewater circulation, the rotation speed of the hollow rotating shaft, and the current density at appropriate levels, the problems of reduced electrode activation sites and increased ohmic drop caused by the attachment of the bubbles generated during the electrolysis process to the anode and the entry of the bubbles into the wastewater, which further lead to low wastewater treatment efficiency and high energy consumption, can be effectively avoided. Compared with the existing wastewater electrolysis technology, the method of the present invention can improve the wastewater degradation efficiency on the basis of reducing energy consumption, which is conducive to popularization and application in engineering practice. Description of the Drawings

[0035] Figure 1 is a schematic structural view of the device for efficiently electrochemically degrading organic wastewater according to the present invention.

[0036] Figure 2 is a schematic view of the electrochemical degradation reactor.

[0037] In the figure, 1-drive motor, 2-drive shaft, 3-conductive slip ring, 4-reactor shell, 5-outlet, 6-cathode, 7-anode, 8-hollow rotating shaft, 9-shaft sleeve, 10-inlet, 11-connecting shaft, 12-stabilized power supply, 13-wire, 14-transfer pump, 15-transfer pipe, 16-storage tank. Detailed Implementation

[0038] The following examples further illustrate the apparatus and method for the efficient electrochemical degradation of organic wastewater provided by the present invention. It should be noted that the following examples are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0039] Example 1

[0040] In this embodiment, an apparatus for the efficient electrochemical degradation of organic wastewater is provided.

[0041] A schematic diagram of a device for the efficient electrochemical degradation of organic wastewater is shown below. Figure 1 As shown, it includes an electrochemical degradation reactor, a regulated power supply 12, a wire 13, a delivery pump 14, a delivery pipe 15, and a storage tank 16.

[0042] A schematic diagram of the electrochemical degradation reactor is shown below. Figure 2 As shown, it includes a drive unit 1, a transmission shaft 2, a conductive slip ring 3, a reactor shell 4, a cathode 6, an anode 7, and a hollow rotating shaft 8. The reactor shell 4 is a closed cylinder at both ends, with its axis perpendicular to the horizontal plane. An outlet 5 is located at the top of the side wall of the reactor shell 4, and an inlet 10 is located at the bottom of the side wall. The hollow rotating shaft 8 is also a closed cylinder at both ends, located inside the reactor shell 4. The axis of the hollow rotating shaft 8 coincides with the axis of the reactor shell 4. One end of the hollow rotating shaft 8 is connected to the drive device 1 via a transmission shaft 2, and the other end is connected to a bushing 9 located inside the reactor shell 4 via a connecting shaft 11. The cathode 6 and anode 7 are both cylindrical. The anode 7 is fitted onto the outer wall of the hollow rotating shaft 8, and the cathode 6 surrounds the anode 7 and is fixed to the inner wall of the reactor shell. A 3mm wide annular gap is formed between the anode 7 and the cathode 6. A conductive slip ring 3 is fixed to the transmission shaft 2. The anode 6 is connected to the positive terminal of the regulated power supply 12 via a wire 13 located inside the hollow rotating shaft 8 and the conductive slip ring 3. The cathode 7 is connected to the negative terminal of the regulated power supply 12 via a wire 13.

[0043] Specifically, the cathode 6, anode 7, and hollow rotating shaft 8 are all 50cm high, with the cathode 6 and anode 7 installed at the same height. The height of the hollow rotating shaft 8 is 80% of the height of the reactor shell 4, and it is installed in the middle of the reactor shell 4. The height-to-diameter ratio of the hollow rotating shaft 8 is 5:1, and the diameter of the hollow rotating shaft 8 is 5 times the diameter of the drive shaft 2 and connecting shaft 11. The anode 7 is a screen-type anode with a porosity of 60%, and the anode material is a titanium-based oxide compound, i.e., a titanium-based IrO2-Ta2O5 coated anode. The cathode 6 is a screen-type cathode with a porosity of 60%, and the cathode material is stainless steel. Both the reactor shell 4 and the hollow rotating shaft 8 are made of polytetrafluoroethylene (PTFE). The drive device 1 is a drive motor, which drives the drive shaft 2 to rotate the hollow rotating shaft 8.

[0044] The outlet 5 is connected to the inlet 10 via the delivery pipe 15, delivery pump 14, and storage tank 16.

[0045] Example 2

[0046] In this embodiment, the device for high-efficiency electrochemical degradation of organic wastewater has a basically the same structure as the device in Example 1, with the only difference being:

[0047] Both the reactor shell 4 and the hollow rotating shaft 8 are made of polycarbonate. A 10mm wide annular gap is formed between the anode 7 and the cathode 6. The cathode 6, anode 7, and hollow rotating shaft 8 have the same height of 100cm. The height of the hollow rotating shaft 8 is 70% of the height of the reactor shell 4, and the height-to-diameter ratio of the hollow rotating shaft 8 is 25:1. The diameter of the hollow rotating shaft 8 is twice the diameter of the drive shaft 2 and the connecting shaft 11. The anode 7 is a screen-type anode with a porosity of 50%. The anode 7 is made of an iron-based oxide compound, i.e., the anode is an iron-based Co-doped Fe3O4 anode. The cathode 6 is a screen-type cathode with a porosity of 50%.

[0048] Example 3

[0049] In this embodiment, the device for high-efficiency electrochemical degradation of organic wastewater has a basically the same structure as the device in Example 1, with the only difference being:

[0050] A 15mm wide annular gap is formed between the anode 7 and the cathode 6. The cathode 6, anode 7, and hollow rotating shaft 8 have the same height, all 90cm. The height of the hollow rotating shaft 8 is 90% of the height of the reactor shell 4, and the height-to-diameter ratio of the hollow rotating shaft 8 is 10:1. The diameter of the hollow rotating shaft 8 is three times the diameter of the drive shaft 2 and the connecting shaft 11. The anode 7 is a screen-type anode with a porosity of 20%. The anode 7 is made of a nickel-based oxide compound, i.e., the anode is a nickel-based NiCr2O4 anode. The cathode 6 is a screen-type cathode with a porosity of 20%.

[0051] Example 4

[0052] In this embodiment, the device for high-efficiency electrochemical degradation of organic wastewater has a basically the same structure as the device in Example 1, with the only difference being:

[0053] A 30mm wide annular gap is formed between the anode 7 and the cathode 6. The cathode 6, anode 7, and hollow rotating shaft 8 are all 120cm high. The height of the hollow rotating shaft 8 is 80% of the height of the reactor shell 4, and the height-to-diameter ratio of the hollow rotating shaft 8 is 12:1. The diameter of the hollow rotating shaft 8 is four times the diameter of the drive shaft 2 and the connecting shaft 11. The anode 7 is a plate anode made of iron, and the cathode 6 is a plate cathode.

[0054] Example 5

[0055] In this embodiment, the device for high-efficiency electrochemical degradation of organic wastewater has a basically the same structure as the device in Example 1, with the only difference being:

[0056] A 1.5mm wide annular gap is formed between the anode 7 and the cathode 6. The cathode 6, anode 7, and hollow rotating shaft 8 are all 80cm high. The height of the hollow rotating shaft 8 is 80% of the height of the reactor shell 4, and the height-to-diameter ratio of the hollow rotating shaft 8 is 8:1. The diameter of the hollow rotating shaft 8 is 2.5 times the diameter of the drive shaft 2 and the connecting shaft 11. The anode 7 is a plate anode made of titanium, and the cathode 6 is a plate cathode.

[0057] Example 6

[0058] In this embodiment, the device for high-efficiency electrochemical degradation of organic wastewater has a basically the same structure as the device in Example 1, with the only difference being:

[0059] A 4mm wide annular gap is formed between the anode 7 and the cathode 6. The cathode 6, anode 7, and hollow rotating shaft 8 are all 60cm high. The height of the hollow rotating shaft 8 is 60% of the height of the reactor shell 4, and the height-to-diameter ratio of the hollow rotating shaft 8 is 12:1. The diameter of the hollow rotating shaft 8 is twice the diameter of the drive shaft 2 and the connecting shaft 11. The anode 7 is a plate anode made of nickel, and the cathode 6 is a plate cathode.

[0060] Example 7

[0061] In this embodiment, a phenol solution with a concentration of 1000 ppm is used as the wastewater to be treated. The wastewater is treated using the high-efficiency electrochemical degradation device for organic wastewater described in Example 1, and the operation is as follows:

[0062] Add 40L of wastewater to be treated to the storage tank. Turn on the transfer pump to introduce the wastewater from the storage tank into the annular gap inside the reactor shell through the inlet. After the wastewater fills the annular gap, it flows out through the outlet back into the storage tank. The wastewater in the storage tank is then pumped back to the annular gap through the inlet by the transfer pump, ultimately creating a circulation flow between the storage tank and the annular gap. Control the circulation flow speed of the wastewater (specifically, the flow speed of the wastewater at the outlet) at 0.7m / s. After the circulation flow stabilizes, turn on the drive device to drive the transmission shaft to rotate the hollow shaft at a speed of 2000rpm, thereby rotating the anode. Turn on the regulated power supply connected to the anode and cathode and adjust the current density to 200A / m. 2 The wastewater is electrolyzed under the conditions of a hollow rotating shaft driving the anode to rotate and wastewater circulating. The treatment is completed after 60 minutes, and the wastewater in the storage tank is discharged.

[0063] After wastewater treatment, samples were taken and the phenol content was determined by high-performance liquid chromatography (HPLC). The phenol removal efficiency was calculated as follows: phenol removal efficiency = (initial phenol concentration - final phenol concentration) / initial phenol concentration × 100%. The results showed that in this embodiment, the phenol content in the treated wastewater was 10 ppm, and the phenol removal efficiency was 99%.

[0064] Comparative Example 1

[0065] The operation of this comparative example is basically the same as that of Example 7, using a phenol solution with a concentration of 1000 ppm as the wastewater to be treated. The only difference is that the drive device is not turned on; that is, the hollow shaft rotates and the anode remains stationary during wastewater treatment. After 60 minutes of wastewater treatment, a sample is taken and the phenol content is determined by high-performance liquid chromatography (HPLC). The phenol removal efficiency is calculated as: phenol removal efficiency = (initial phenol concentration - final phenol concentration) / initial phenol concentration × 100%. The results show that in this example, the phenol content in the treated wastewater is 660 ppm, and the phenol removal efficiency is only 34%.

[0066] As can be seen from Example 7 and Comparative Example 1, even when using the same high-efficiency electrochemical degradation device for organic wastewater as in Example 1, and treating wastewater with the same phenol concentration at the same current density, the removal efficiency of phenol is very low when the hollow shaft and anode are not rotating, even if the wastewater is circulated.

[0067] Comparative Example 2

[0068] The operation of this comparative example is basically the same as that of Example 3, using a phenol solution with a concentration of 1000 ppm as the wastewater to be treated. The only difference is that the wastewater circulation flow rate is controlled at 0.35 m / s. After 60 minutes of wastewater treatment, samples are taken and the phenol content is determined by high-performance liquid chromatography (HPLC). The phenol removal efficiency is calculated as: phenol removal efficiency = (initial phenol concentration - final phenol concentration) / initial phenol concentration × 100%. The results show that in this example, the phenol content in the treated wastewater is 500 ppm, and the phenol removal efficiency is 50%.

[0069] As can be seen from Example 7 and Comparative Example 2, even when using the same high-efficiency electrochemical degradation device for organic wastewater as in Example 1, and treating wastewater with the same phenol concentration at the same current density, the phenol removal efficiency cannot be effectively improved when the circulation velocity of the wastewater between the storage tank and the annular gap is too low, even if the hollow rotating shaft is in a rotating state. This indicates that for the method of the present invention, controlling the hollow rotating shaft to drive the anode to rotate at an appropriate speed and controlling the wastewater circulation velocity between the storage tank and the annular gap are both essential for improving the removal efficiency of organic pollutants.

[0070] Comparative Example 3

[0071] In this comparative example, a conventional tank-type electrochemical degradation device (electrolytic cell) was used for wastewater treatment.

[0072] The electrolytic cell used in this comparative example has a rectangular cross-section and longitudinal section. The anode in the electrolytic cell is a titanium-based IrO2-Ta2O5 coated anode with a porosity of 60%, and the cathode is a stainless steel cathode with a porosity of 60%. The distance between the anode and the cathode is 5 cm.

[0073] Using a phenol solution with a concentration of 1000 ppm as the wastewater to be treated, 40 L of the wastewater was added to the electrolytic cell. The regulated power supply connected to the anode and cathode was turned on, and the current density was adjusted to 200 A / m. 2Wastewater was treated, and after 60 minutes of treatment, samples were taken from the electrolytic cell and the phenol content was determined by high-performance liquid chromatography (HPLC). The phenol removal efficiency was calculated as follows: phenol removal efficiency = (initial phenol concentration - final phenol concentration) / initial phenol concentration × 100%. The results showed that in this embodiment, the phenol content in the treated wastewater was 770 ppm, and the phenol removal efficiency was 23%.

[0074] As can be seen from Example 7 and Comparative Example 3, compared with the conventional method of wastewater treatment using a tank-type electrochemical degradation device (electrolytic cell), the device and method for treating organic wastewater using the present invention can significantly improve the removal efficiency of organic pollutants.

[0075] Example 8

[0076] In this embodiment, a phenol solution with a concentration of 1000 ppm is used as the wastewater to be treated. The wastewater is treated using the high-efficiency electrochemical degradation device for organic wastewater described in Example 1, and the operation is as follows:

[0077] Add 40L of wastewater to be treated to the storage tank. Turn on the transfer pump to introduce the wastewater from the storage tank into the annular gap inside the reactor shell through the inlet. After the wastewater fills the annular gap, it flows out through the outlet back into the storage tank. The wastewater in the storage tank is then pumped back to the annular gap through the inlet by the transfer pump, ultimately creating a circulation flow between the storage tank and the annular gap. Control the circulation flow speed of the wastewater (specifically, the flow speed of the wastewater at the outlet) at 0.7m / s. After the circulation flow stabilizes, turn on the drive device to drive the transmission shaft to rotate the hollow shaft at a speed of 5000rpm, thereby rotating the anode. Turn on the regulated power supply connected to the anode and cathode and adjust the current density to 200A / m. 2 The wastewater is electrolyzed under the conditions of a hollow rotating shaft driving the anode to rotate and wastewater circulating. The treatment is completed after 30 minutes, and the wastewater in the storage tank is discharged.

[0078] After wastewater treatment, samples were taken and the phenol content was determined by high-performance liquid chromatography (HPLC). The phenol removal efficiency was calculated as follows: phenol removal efficiency = (initial phenol concentration - final phenol concentration) / initial phenol concentration × 100%. The results showed that in this embodiment, the phenol content in the treated wastewater was 10 ppm, and the phenol removal efficiency was 99%.

[0079] Example 9

[0080] In this embodiment, a phenol solution with a concentration of 1000 ppm is used as the wastewater to be treated. The wastewater is treated using the high-efficiency electrochemical degradation device for organic wastewater described in Example 1, and the operation is as follows:

[0081] Add 40L of wastewater to be treated to the storage tank. Turn on the transfer pump to introduce the wastewater from the storage tank into the annular gap inside the reactor shell through the inlet. After the wastewater fills the annular gap, it flows out through the outlet back into the storage tank. The wastewater in the storage tank is then pumped back to the annular gap through the inlet by the transfer pump, ultimately creating a circulation flow between the storage tank and the annular gap. Control the circulation flow speed of the wastewater (specifically, the flow speed of the wastewater at the outlet) at 10m / s. After the circulation flow stabilizes, turn on the drive device to drive the drive shaft to rotate the hollow shaft at a speed of 1000rpm, thereby rotating the anode. Turn on the regulated power supply connected to the anode and cathode and adjust the current density to 500A / m. 2 The wastewater is electrolyzed under the conditions of a hollow rotating shaft driving the anode to rotate and wastewater circulating. The treatment is completed after 60 minutes, and the wastewater in the storage tank is discharged.

[0082] After wastewater treatment, samples were taken and the phenol content was determined by high-performance liquid chromatography (HPLC). The phenol removal efficiency was calculated as follows: phenol removal efficiency = (initial phenol concentration - final phenol concentration) / initial phenol concentration × 100%. The results showed that in this embodiment, the phenol content in the treated wastewater was 10 ppm, and the phenol removal efficiency was 99%.

Claims

1. A method for efficient electrochemical degradation of organic wastewater, characterized in that, Organic wastewater is treated using a device with the following structure: the device includes an electrochemical degradation reactor, a regulated power supply (12), a transfer pump (14), and a storage tank (16); the electrochemical degradation reactor includes a drive device (1), a transmission shaft (2), a conductive slip ring (3), a reactor shell (4), a cathode (6), an anode (7), and a hollow rotating shaft (8); the reactor shell (4) is a cylinder closed at both ends, and the reactor shell (4) is in a state where its axis is perpendicular to the horizontal plane, with an outlet (5) at the top and an inlet (10) at the bottom; the hollow rotating shaft (8) is a cylinder closed at both ends, and the hollow rotating shaft (8) is a cylinder closed at both ends. The hollow shaft (8) is located inside the reactor shell (4), and its axis coincides with the axis of the reactor shell (4). One end of the hollow shaft (8) is connected to the drive device (1) through the transmission shaft (2), and the other end is connected to the bushing (9) set inside the reactor shell (4) through the connecting shaft (11). The reactor shell (4) and the hollow shaft (8) are non-conductive. The cathode (6) and the anode (7) are both cylindrical. The anode (7) is sleeved on the outer wall of the hollow shaft (8), and the cathode (6) is arranged around the anode (7) and fixed on the inner wall of the reactor shell (4). A gap of 1.5~10 cm is formed between the anode (7) and the cathode (6). The annular gap is mm; the conductive slip ring (3) is fixed on the transmission shaft (2), the anode (7) is connected to the positive terminal of the regulated power supply (12) through the conductive slip ring (3) via the wire (13) located in the hollow rotating shaft (8), and the cathode (6) is connected to the negative terminal of the regulated power supply (12) through the wire (13); the outlet (5) is connected to the inlet (10) through the delivery pipe (15) via the delivery pump (14) and the storage tank (16); The method includes the following steps: Turn on the delivery pump (15) to introduce the organic wastewater in the storage tank (16) into the annular gap in the reactor shell (4) through the inlet (10), and make the wastewater circulate between the storage tank (16) and the annular gap. After the circulation is stable, turn on the drive device (1) to drive the transmission shaft (2) to drive the hollow rotating shaft (8) to rotate at a speed of 1000~5000 rpm. Turn on the regulated power supply (12) connected to the anode (7) and cathode (6). Under the condition that the hollow rotating shaft (8) drives the anode to rotate and the wastewater circulates, the wastewater is electrolyzed. The speed of the wastewater circulation is controlled to be 0.7~10 m / s. After the wastewater treatment is completed, the wastewater in the storage tank (16) is discharged.

2. The method for efficient electrochemical degradation of organic wastewater according to claim 1, characterized in that, The cathode (6), anode (7) and hollow rotating shaft (8) are at the same height, and the cathode (6) and anode (7) are installed at the same height position.

3. The method for efficient electrochemical degradation of organic wastewater according to claim 1, characterized in that, The height of the hollow shaft (8) is 60% to 90% of the height of the reactor shell (4), and the hollow shaft (8) is installed in the middle of the reactor shell (4).

4. The method for efficient electrochemical degradation of organic wastewater according to claim 1, characterized in that, The ratio of the height to the diameter of the hollow rotating shaft (8) is (5~25):

1.

5. The method for efficient electrochemical degradation of organic wastewater according to any one of claims 1 to 4, characterized in that, The anode (7) is a screen anode or a plate anode, and the cathode (6) is a screen cathode or a plate cathode.

6. The method for efficient electrochemical degradation of organic wastewater according to claim 5, characterized in that, The porosity of the screen anode is 20%~60%, and the porosity of the screen cathode is 20%~60%.

7. The method for efficient electrochemical degradation of organic wastewater according to any one of claims 1 to 4, characterized in that, The anode (7) is made of iron, iron-based oxide, titanium, titanium-based oxide, nickel, or nickel-based oxide; the cathode (6) is made of stainless steel.

8. The method for efficient electrochemical degradation of organic wastewater according to claim 1, characterized in that, Control current density is 20~500 A / m 2 .

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