Three-dimensional electro-catalytic oxidation device and method for treating electronic waste water

Abstract

The application discloses a three-dimensional electro-catalytic oxidation device, which comprises a three-dimensional electro-catalytic reactor and a power supply; the three-dimensional electro-catalytic reactor is internally provided with an anode plate, a cathode plate and a particle electrode between the anode plate and the cathode plate; the particle electrode is modified scale graphite loaded with La2O3-Al2O3-TiO2; the anode plate and the cathode plate are respectively connected with the power supply through wires; the power supply comprises a linearly increasing power supply mode and an exponentially decaying power supply mode; the time of the two power supply modes is the same; in the first half of the reactor reaction time, the power supply is powered in the linearly increasing power supply mode, and at this time, the current density is linearly increased; in the second half of the reactor reaction time, the power supply is powered in the exponentially decaying power supply mode. The application further discloses a method for treating electronic waste water by using the three-dimensional electro-catalytic oxidation device.

Description

TECHNICAL FIELD

[0001] The present application relates to a three-dimensional electro-catalytic oxidation device, and a method for treating electronic wastewater by using the three-dimensional electro-catalytic oxidation device. BACKGROUND

[0002] Electronic wastewater has complex components and contains many toxic and harmful substances. Moreover, the pollutants are mostly organic substances that are difficult to biodegrade. In particular, the tail water after biochemical treatment has a very low B / C ratio and poor biodegradability, so it is difficult to effectively treat by using a biological method. For such organic wastewater that is difficult to biodegrade, the commonly used treatment process is advanced oxidation.

[0003] Among many advanced oxidation processes, electro-catalytic oxidation technology has attracted widespread attention in the field of wastewater treatment due to its good treatment effect, no need for additional chemical reagents, and no secondary pollution. However, the existing electro-catalytic oxidation process mainly has the following shortcomings: (1) The electrode area of the traditional two-dimensional electrochemical oxidation method is small, and the effective contact area of the organic matter in the water body is small, so the mass and energy transfer efficiency is poor, which often leads to poor treatment efficiency and high energy consumption. (2) The three-dimensional electro-catalytic oxidation technology developed rapidly in recent years greatly promotes the mass transfer efficiency by adding a third electrode. However, it is difficult to simultaneously achieve excellent catalytic performance and electrical energy efficiency during the catalytic oxidation process. Often, the electrical energy efficiency is sacrificed to achieve excellent catalytic performance, which seriously hinders the industrial development of three-dimensional electro-catalytic oxidation technology. For example, in patent CN113184960A, coal columnar activated carbon, coated coal columnar activated carbon, etc. are selected as particle electrodes. However, the poor electrical conductivity of activated carbon (electrical conductivity <0.9Ω -1 ·cm -1 ) easily leads to high operating voltage and high electrical energy loss. Although the removal rate of wastewater TOC is effectively improved, the service life of the filler is short, which leads to high maintenance frequency, i.e., the filler in the reactor needs to be frequently replaced, and the long-term treatment capacity is poor. SUMMARY

[0004] The present application aims to provide a three-dimensional electro-catalytic oxidation device that can achieve efficient use of electrical energy while ensuring catalytic effect. Another purpose of the present application is to provide a method for treating electronic wastewater by using the three-dimensional electro-catalytic oxidation device.

[0005] The technical scheme of the three-dimensional electro-catalytic oxidation device comprises a three-dimensional electro-catalytic reactor and a power supply; the three-dimensional electro-catalytic reactor is internally provided with an anode plate, a cathode plate and a particle electrode between the anode plate and the cathode plate, the particle electrode is modified flaky graphite loaded with La2O3-Al2O3-TiO2; the anode plate and the cathode plate are respectively connected with the power supply through wires; the power supply comprises a linearly increasing power supply mode and an exponentially decaying power supply mode; the time of the two power supply modes is the same; in the first half of the reactor reaction time, the power supply is powered in the linearly increasing power supply mode, at this time, the current density is linearly increased; in the second half of the reactor reaction time, the power supply is powered in the exponentially decaying power supply mode, at this time, with the reaction, the current density is exponentially decaying with a decay coefficient n, and the current density corresponding to each moment in the reaction process in the exponentially decaying power supply mode is shown in the following formula:

[0006] I t =I1*exp(-n*(t-t0))

[0007] In the formula, I t is the input current density of the reactor at t moment, unit: mA / cm 2 ; I1 is the current density corresponding to the end of the linearly increasing power supply mode, unit: mA / cm 2 ; n is the decay coefficient, unit: s -1 , the value range is 0.001-0.002; t is the reaction time, unit: s, which is calculated from the time when the reactor starts; t0 is the time corresponding to the end of the linearly increasing power supply mode, unit: s, which is calculated from the time when the reactor starts.

[0008] The modified flaky graphite loaded with La2O3-Al2O3-TiO2 is prepared by the following method, and the specific steps are as follows:

[0009] (1) The water contact angle of the original state of flaky graphite is measured by using an electrode surface hydrophilicity contact angle measuring instrument (OCA20);

[0010] (2) Isopropyl alcohol and tetrabutyl titanate are used as raw materials, anhydrous ethanol is used as a solvent, and isopropyl alcohol aluminum ethanol solution with a concentration of 1 mol / L and tetrabutyl titanate ethanol solution with a concentration of 1 mol / L are prepared respectively; the isopropyl alcohol aluminum ethanol solution, the tetrabutyl titanate ethanol solution and distilled water (volume ratio of 1:1:2) are mixed, 1 mol / L HCl is added thereto, the pH is adjusted to 5, and magnetic stirring is carried out for 1 h until the solution is clear, to obtain an Al2O3-TiO2 sol;

[0011] (3) add the flake graphite into the Al2O3-TiO2 sol and stir thoroughly, so that the surface of the graphite particles is in full contact with the sol, slowly and uniformly drop 25wt% sodium carbonate solution into it to make it gel, and filter the product;

[0012] (4) dry the particles obtained by filtration in an oven at 165℃ for 2h, then place them in a muffle furnace and calcine them at 600℃ for 4h to obtain Al2O3-TiO2 coated flake graphite particles;

[0013] (5) use lanthanum nitrate hexahydrate as raw material and anhydrous ethanol as solvent to prepare a 2mol / L lanthanum nitrate ethanol solution; mix the lanthanum nitrate ethanol solution, Al2O3-TiO2 sol and distilled water (volume ratio 2:1:2) to obtain a mixed solution, stir for 1h, then slowly add 10% of the mixed solution by volume of 68wt% concentrated nitric acid, continue to magnetically stir the mixed solution for 5h to obtain La2O3-Al2O3-TiO2 sol;

[0014] (6) add the Al2O3-TiO2 coated flake graphite particles obtained in step (4) to the La2O3-Al2O3-TiO2 sol, stir thoroughly, so that the surface of the graphite particles is in full contact with the solution, slowly and uniformly drop 25wt% sodium carbonate solution into it to make it gel, and filter the product; wherein the Al2O3-TiO2 coated flake graphite particles and the La2O3-Al2O3-TiO2 sol are mixed in a mass ratio of 1:2;

[0015] (7) dry the particles obtained by filtration in step (6) at 100℃ for 48h, then place them in a muffle furnace and calcine them at 700℃ for 4h to obtain modified flake graphite loaded with La2O3-Al2O3-TiO2, and measure its water contact angle with a CA instrument.

[0016] In the modification process, firstly, alumina and titanium dioxide are loaded on the surface of flake graphite by sol-gel method, the Al-O bond in Al2O3 interacts with the Ti-O bond in TiO2, and a stable Al-O-Ti bond is formed on the surface of flake graphite. The formation of Al-O-Ti bond further improves the hydrophilicity of the interface and the stability of the coating, and enhances the band bending of the charge region on the surface of graphite, adding a fast transfer channel for the charge, thereby improving the electron transfer rate and enhancing the catalytic efficiency; on the basis of using metal oxide Al2O3 for coating, a hydrophilic heterogeneous coating is constructed by TiO2 modification, the addition of TiO2 not only can further improve the hydrophilicity of graphite and improve the catalytic efficiency, but also can provide support for the Al2O3 layer, enhance the stability of the coating layer and the adhesion with graphite, and greatly reduce the risk of coating falling off during the reaction process;

[0017]

[0018] In the process of electrocatalytic reaction, strong oxidizing substances such as hydroxyl radicals generated at the anode diffuse into the particle electrode, which is easy to cause electrochemical corrosion of flake graphite, thereby causing serious loss of particle electrode, greatly reducing the service life of the material and the catalytic efficiency. In order to prolong the service life of the particle electrode and improve its stability, the flake graphite is passivated by doping with rare earth oxides, so as to reduce the electrochemical corrosion process and improve the corrosion resistance of the particle electrode. Lanthanum element has a special 4f electron structure, can produce multi-electron configuration, and is easy to deform, can enter the metal oxide lattice in the form of substitution, form a new more stable chemical bond, and make the coating more compact. In the modification process, the La-O bond in La2O3 can interact with the Al-O-Ti bond to form an Al-O-Ti-O-La bond at the interface, and the doping of lanthanum element can reduce the recombination probability of electron-hole pairs, effectively hinder the transfer of active oxygen to the particle electrode, and improve the stability and corrosion resistance of the particle electrode;

[0019]

[0020] The modified flake graphite has a mesh number of 30-50 meshes, and the filling ratio of the modified flake graphite is 50% of the volume of the reactor.

[0021] The three-dimensional electrocatalytic oxidation device further comprises a water inlet adjusting tank and a water outlet tank; the water inlet of the three-dimensional electrocatalytic reactor is connected with the water inlet adjusting tank through a water inlet pipe, and the water outlet is connected with the water outlet tank through a water outlet pipe; the water inlet and outlet of the three-dimensional electrocatalytic reactor is up-in and down-out.

[0022] The three-dimensional electro-catalytic oxidation device further comprises a water quality on-line monitoring device and a dosing device, the water quality on-line monitoring device is arranged outside the effluent tank, the dosing device is connected with the influent adjusting tank through a dosing pipeline, and a pH sensor is arranged in the influent adjusting tank; the influent adjusting tank is connected with the dosing device, so that the pH of the influent in the influent adjusting tank is neutralized.

[0023] The three-dimensional electro-catalytic oxidation device further comprises a water quality on-line monitoring device and a dosing device, the water quality on-line monitoring device is arranged outside the effluent tank, the dosing device is connected with the influent adjusting tank through a dosing pipeline, and a pH sensor is arranged in the influent adjusting tank; the influent adjusting tank is connected with the dosing device, so that the pH of the influent in the influent adjusting tank is neutralized.

[0024] The three-dimensional electro-catalytic oxidation device further comprises a water quality on-line monitoring device and a dosing device, the water quality on-line monitoring device is arranged outside the effluent tank, the dosing device is connected with the influent adjusting tank through a dosing pipeline, and a pH sensor is arranged in the influent adjusting tank; the influent adjusting tank is connected with the dosing device, so that the pH of the influent in the influent adjusting tank is neutralized.

[0025] The cathode plate is a plate-type graphite electrode, a stainless steel electrode or a nickel-plated iron electrode; and the anode plate is a plate-type graphite electrode, a glassy carbon electrode, a metal oxide electrode or a BDD electrode.

[0026] The method for treating electronic wastewater based on the three-dimensional electro-catalytic oxidation device comprises the following steps:

[0027] (1) The electronic wastewater enters the three-dimensional electro-catalytic reactor for catalytic oxidation, the cathode plate in the reactor is a graphite electrode, the anode plate is a ruthenium-iridium-titanium electrode, the hydraulic retention time is not higher than 1 h, and the modified flake graphite is filled between the cathode plate and the anode plate, and the filling ratio of the modified flake graphite is 50-55% of the volume of the reactor.

[0028] (2) The initial current density of the power supply is not lower than 20 mA / cm 2 , the current density is increased at a speed with a slope of 0.3-0.6 mA / (cm 2 ·min), the operation time of the linearly increased power supply mode is 25-30 min, the current density is exponentially attenuated with a decay coefficient n as the reaction proceeds, and the operation time of the exponential attenuation power supply mode is 25-30 min.

[0029] In the exponential attenuation power supply mode, the current density corresponding to each moment of the reaction process is shown in the following formula:

[0030] I t =I1*exp(-n*(t-t0))

[0031] In the formula, I t is the input current density of the reactor at t moment, unit: mA / cm 2 ; I1 is the current density corresponding to the end of the linearly increased power supply mode, unit: mA / cm 2 ; and n is the decay coefficient, unit: s -1, the value range is 0.001~0.002;t is reaction time, unit: s, from the time of starting reactor;t0 is the time corresponding to the end of linear increase power supply mode, unit: s, from the time of starting reactor;

[0032] (3) the reactor effluent enters the effluent pool;Through the on-line monitoring device of water quality, the COD index in the effluent pool is monitored in real time, when the COD removal rate is more than 90%, the effluent is discharged through the effluent pipe;When the COD removal rate is less than 90%, the reflux pipe switch under the effluent pool is opened, and refluxed to the influent adjusting pool for secondary catalytic oxidation treatment.

[0033] Beneficial effects: compared with the prior art, the present application has the following effects: (1) the device of the present application uses modified flake graphite as particle electrode, which can solve the problems of poor adsorption of hydrophilic substances in wastewater, poor resistance to electrochemical corrosion and low oxidation resistance of graphite as the third electrode derived electrode in the existing three-dimensional electro-catalytic system, the present application modifies the flake graphite by loading La2O3-Al2O3-TiO2, which can form a protective barrier outside the flake graphite, thereby effectively improving its resistance to electrochemical corrosion and oxidation resistance, and also improving the adsorption capacity of flake graphite for hydrophilic substances in wastewater;The reaction efficiency, catalytic efficiency and long-term treatment capacity of the whole reaction system are improved;(2) the method of the present application uses modified flake graphite as particle electrode, and simultaneously cooperates with a specific power supply mode, which realizes excellent catalytic performance and power efficiency in the process of catalytic oxidation, that is, realizes high efficient use of electric energy while realizing good catalytic effect. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the three-dimensional electro-catalytic reactor of the present application;

[0035] Figure 2 It is a curve diagram of the power supply mode (linear increase-exponential decay) of the three-dimensional electro-catalytic oxidation device of the present application;

[0036] Figure 3 It is a structural schematic diagram of the three-dimensional electro-catalytic oxidation device of the present application;

[0037] Figure 4 It is a water contact angle change diagram before and after modification of flake graphite;

[0038] Figure 5 It is a COD treatment result diagram in the effluent pool in example 1;

[0039] Figure 6 It is a COD treatment result diagram in the effluent pool in example 2;

[0040] Figure 7This is a diagram showing the COD treatment results in the effluent tank of Comparative Example 1.

[0041] Figure 8 This is a graph showing the COD treatment results in the effluent tank of Comparative Example 2.

[0042] Figure 9 This is a graph showing the COD treatment results in the effluent tank of Comparative Example 3.

[0043] Figure 10 This is a diagram showing the COD treatment results in the effluent tank of Comparative Example 4.

[0044] Figure 11 This is a graph showing the COD treatment results in the effluent tank of Comparative Example 5.

[0045] Figure 12 This is a diagram showing the COD treatment results in the effluent tank of Comparative Example 6.

[0046] Figure 13 This is a diagram showing the COD treatment results in the effluent tank of Comparative Example 7.

[0047] Figure 14 This is a diagram showing the COD treatment results in the effluent tank of Comparative Example 8. Detailed Implementation

[0048] like Figure 1 As shown, the three-dimensional electrocatalytic oxidation device of the present invention includes a three-dimensional electrocatalytic reactor 3 and a power supply 9. The three-dimensional electrocatalytic reactor 3 is equipped with an anode plate 4, a cathode plate 5, and a particle electrode located between the anode and cathode plates. The particle electrode is modified flake graphite loaded with La2O3-Al2O3-TiO2 (the loading material is La2O3-Al2O3-TiO2 metal oxide). The anode plate 4 and cathode plate 5 are respectively connected to the power supply 9 via wires. The three-dimensional electrocatalytic reactor 3 is a trough reactor with a rectangular cross-section. The cathode plate 5 and anode plate 4 are located on the two side walls of the reactor 3, and the particle electrode-modified flake graphite is located between the anode and cathode plates.

[0049] The cathode material in reactor 3 can be selected from plate graphite electrode, stainless steel electrode, nickel-plated iron electrode, etc., and the anode material can be selected from plate graphite electrode, glassy carbon electrode, metal oxide electrode (PbO2, DSA, etc.), metal electrode (ruthenium-iridium-titanium electrode, Pb / Sn / Pt electrode, etc.), BDD electrode, etc.

[0050] The modified flake graphite supported on La2O3-Al2O3-TiO2 of this invention is prepared by the following method, specifically including the following steps:

[0051] (1) Take 204.24 g of aluminum isopropoxide and dissolve it in 1 L of anhydrous ethanol to obtain a 1 mol / L aluminum isopropoxide ethanol solution; take 340.32 g of tetrabutyl titanate and dissolve it in 1 L of anhydrous ethanol to obtain a 1 mol / L tetrabutyl titanate ethanol solution; mix the aluminum isopropoxide ethanol solution, the tetrabutyl titanate ethanol solution, and distilled water in a volume ratio of 1:1:2, and add 1 mol / L HCl to adjust the pH to 5; place the obtained solution on a magnetic stirrer and stir magnetically for 1 h until the solution is clear to prepare an Al2O3-TiO2 sol;

[0052] (2) Add 500 g of flake graphite to the Al2O3-TiO2 sol prepared in step (1) and stir thoroughly (the mass ratio of flake graphite to Al2O3-TiO2 sol is 1:2) to obtain a mixed solution I, the surface of the graphite particles is in full contact with the sol, and slowly and uniformly drop 10% of the volume of the mixed solution I into a 25 wt% sodium carbonate solution to make it gel;

[0053] (3) Filter the gel obtained in step (2), and place the filtered microparticles in a high-temperature oven for drying treatment at 165°C for 2 h; place the dried particles in a muffle furnace for calcination treatment at 600°C for 4 h to obtain Al2O3-TiO2 loaded flake graphite particles;

[0054] (4) Take 866 g of lanthanum nitrate hexahydrate and dissolve it in 1 L of anhydrous ethanol to prepare a 2 mol / L lanthanum nitrate ethanol solution; mix the lanthanum nitrate ethanol solution, the Al2O3-TiO2 solution, and distilled water in a volume ratio of 2:1:2, and after stirring for 1 h, obtain a mixed solution II, slowly add 10% of the volume of the mixed solution II into a 68 wt% concentrated nitric acid, and continue to magnetically stir the mixed solution for 5 h to prepare a La2O3-Al2O3-TiO2 sol;

[0055] (5) Add the Al2O3-TiO2 loaded flake graphite particles (Al2O3-TiO2 coated flake graphite particles mixed with the La2O3-Al2O3-TiO2 sol in a mass ratio of 1:2) prepared in step (3) to the La2O3-Al2O3-TiO2 sol of step (4) and stir thoroughly to obtain a mixed solution III, the surface of the graphite particles is in full contact with the solution, and slowly and uniformly drop 10% of the volume of the mixed solution III into a 25 wt% sodium carbonate solution to make it gel, and perform a filtering treatment;

[0056] (6) Dry the particles obtained by filtering in step (5) at 100°C for 48 h, and then place them in a muffle furnace and calcine at 700°C for 4 h to obtain La2O3-Al2O3-TiO2 loaded modified flake graphite.

[0057] As Figure 2As shown, the power supply of the three-dimensional electrocatalytic oxidation device of the present invention includes a linearly increasing power supply mode and an exponentially decreasing power supply mode; the two power supply modes are for the same duration; during the first half of the reactor reaction, the power supply operates in the linearly increasing power supply mode, at which time the current density increases linearly; during the second half of the reactor reaction, the power supply operates in the exponentially decreasing power supply mode, at which time the current density decreases exponentially with the decay coefficient n as the reaction proceeds. Under the exponentially decreasing power supply mode, the current density at each moment of the reaction process is shown in the following formula:

[0058] I t =I1*exp(-n*(t-t0))

[0059] In the formula, I t The input current density of the reactor at time t, in mA / cm². 2 I1 represents the current density at the end of the linearly increasing power supply mode, in mA / cm². 2 ; n is the attenuation coefficient, unit: s -1 The value ranges from 0.001 to 0.002; t is the reaction time, in seconds, calculated from the start time of the reactor; t0 is the time corresponding to the end of the linearly increasing power supply mode, in seconds, calculated from the start time of the reactor.

[0060] During the reaction, the COD concentration of the wastewater is measured in real time. When the COD value is in the initial stage of the reaction, which is gradually increasing, the power supply mode is linearly increasing, and the initial current density is 20 mA / cm³. 2 The current density increases linearly with a slope of 0.3–0.6 mA / (cm²·min). When the COD value begins to gradually decrease, the power supply mode becomes an exponential decay mode, with the current density decreasing exponentially with a decay coefficient n until it drops to 5 mA / cm². 2 This maximizes current efficiency.

[0061] like Figure 3 As shown, the three-dimensional electrocatalytic oxidation device of the present invention further includes an inlet regulating tank 1 and an outlet tank 2; the inlet of the three-dimensional electrocatalytic reactor 3 is connected to the inlet regulating tank 1 through an inlet pipe 6, and the outlet is connected to the outlet tank 2 through an outlet pipe 7. The three-dimensional electrocatalytic oxidation device also includes an online water quality monitoring device 11 and a dosing device 10. The online water quality monitoring device 11 is used to detect the COD and ammonia nitrogen levels in the water in the outlet tank 2; the dosing device 10 is connected to the inlet regulating tank 1 through a dosing pipe, and a pH sensor is installed in the inlet regulating tank; the pH of the inlet water in the inlet regulating tank is brought to neutral through the dosing device. A return pipe 8 is also provided between the inlet regulating tank 1 and the outlet tank 2. When the COD and ammonia nitrogen levels in the water in the outlet tank 2 exceed the standards, the effluent is returned to the inlet regulating tank through the return pipe for secondary treatment.

[0062] The corrosion resistance of unmodified flake graphite, Al2O3-TiO2-loaded modified flake graphite, and La2O3-Al2O3-TiO2-loaded modified flake graphite was characterized by mass change method, as follows:

[0063] (1) 20 g each of unmodified flake graphite, Al2O3-TiO2-loaded flake graphite, and La2O3-Al2O3-TiO2-loaded flake graphite were immersed in a NaCl solution with a mass concentration of 3.5% for 24 h;

[0064] (2) After immersion, the samples were filtered, washed twice with deionized water, and dried in an oven at 105°C for 2 h to obtain the mass of the samples after the corrosion reaction;

[0065] (3) The corrosion rate V was calculated as follows:

[0066] V = (ΔW x 24 x 10 3 ) / t, ΔW = (W0-W) / S

[0067] where V is the corrosion rate (mg / (cm 2 ·d)), W0 is the mass of the material before the experiment (g), W is the mass of the material after the experiment (g), S is the total area of the material (cm 2 ), and t is the immersion time (h).

[0068] The corrosion rates of the three materials are shown in Table 1. Compared with unmodified flake graphite, the corrosion rate of Al2O3-TiO2-modified flake graphite decreased from 0.123 mg·cm -2 ·d -1 to 0.094 mg·cm -2 ·d -1 , and the corrosion rate of La2O3-Al2O3-TiO2-modified flake graphite decreased from 0.123 mg·cm -2 ·d -1 to 0.042 mg·cm -2 ·d -1 , indicating that the doping of La2O3 greatly improved the corrosion resistance of flake graphite.

[0069] Table 1

[0070]

[0071] The particle electrode stability of unmodified flake graphite, Al2O3-TiO2-loaded flake graphite, and La2O3-Al2O3-TiO2-loaded flake graphite was determined, as follows:

[0072] (1) each of unmodified flake graphite, Al2O3-TiO2 loaded flake graphite and La2O3-Al2O3-TiO2 loaded flake graphite with a filling ratio of 50% (50% of the reactor volume) is added into a three-dimensional electro-catalytic reactor, wherein a ruthenium iridium titanium electrode is used as an anode and a graphite electrode is used as a cathode, a constant voltage of 10V is applied, and a semiconductor factory tail water (initial COD is 180mg / L) is used as the wastewater to be treated;

[0073] (2) the power supply is turned on, the reaction time is set to 60min, and the COD concentration of the effluent is measured after the reaction is completed;

[0074] (3) after each reaction is completed, the particle electrode is recovered and taken out, washed with deionized water for 2 times, and dried in a 105℃ oven for 2h;

[0075] (4) the particle electrode after washing and drying is reused, and steps (2)-(3) are repeated for 5 times, the COD removal effect of the three particle electrodes after being reused for 5 times is evaluated, and the specific data are shown in Table 2. After being reused for 5 times, the COD removal rate of the unmodified flake graphite decreases from 38% to 14%, after being modified by Al2O3-TiO2, the COD removal rate decreases from 78% to 65%, and after being passivated by the rare earth oxide La2O3, the stability of the particle electrode is greatly improved, and the COD removal rate is basically stable, which indicates that the doping of La2O3 greatly improves the stability of the flake graphite particle electrode.

[0076] Table 2

[0077]

[0078] By Figure 4 It can be known that, before modification, the water contact angle of the flake graphite is 56°, and the water contact angle of the flake graphite modified by loading La2O3-Al2O3-TiO2 is 131°.

[0079] Example 1

[0080] The particle electrode filled in the three-dimensional electro-catalytic reactor of the three-dimensional electro-catalytic oxidation device of the application is a modified graphite particle loaded with La2O3-Al2O3-TiO2, and the filling amount of the particle electrode is 50% of the reactor volume; the power supply adopts a linear increase-exponential decay power supply mode, and the method for treating electronic wastewater based on the three-dimensional electro-catalytic oxidation device of the application comprises the following steps:

[0081] (1) the raw water quality information is shown in the following table:

[0082]

[0083]

[0084] (2) The electronic tail water enters the three-dimensional electro-catalytic reactor for catalytic oxidation, the cathode plate in the reactor is a graphite electrode, the anode plate is a ruthenium iridium titanium electrode, and the hydraulic retention time is 1 h;

[0085] (3) The initial current density is set to 20 mA / cm 2 , and the slope is linearly increased at a rate of 0.5 mA / (cm 2 / min) in the linear increase power supply mode; the power supply is continued for 30 min, and then the power supply mode is adjusted to an exponential decay power supply mode, that is, I t =35*exp(-0.0012*(t-1800)) continues for 30 min, wherein I t is the input current density at t (unit: mA / cm 2 ), and t is the reaction time (unit: s) from the start of the reactor;

[0086] (4) The COD index in the effluent tank is monitored in real time through a water quality online monitoring device, and the water quality data in the reaction process are shown in Table 1. Figure 5 After 1 h, the COD decreases from 185 mg / L to 15 mg / L.

[0087] The energy consumption is about 63.67 kWh / kg COD, the energy consumption per ton of water is 10.83 kWh / m 3 , and the cost per ton of water is 7.58 yuan / m 3 .

[0088] Embodiment 2

[0089] The particle electrode filled in the three-dimensional electro-catalytic reactor of the three-dimensional electro-catalytic oxidation device is a modified graphite particle loaded with La2O3 / Al2O3 / TiO2, and the filling amount of the particle electrode is 50% of the volume of the reactor; the power supply source adopts a linear increase-exponential decay power supply mode, and the method for treating electronic waste water based on the three-dimensional electro-catalytic oxidation device includes the following steps:

[0090] (1) The raw water quality information is shown in the following table:

[0091] Source COD (mg / L) pH Water quantity Tail water of a semiconductor factory in Wuxi 120 7.2 100 L / h

[0092] (2) The electronic tail water enters the three-dimensional electro-catalytic reactor for catalytic oxidation, the cathode plate in the reactor is a graphite electrode, the anode plate is a ruthenium iridium titanium electrode, and the hydraulic retention time is 1 h;

[0093] (3) The initial current density is set to 20 mA / cm 2 , and the slope is linearly increased at a rate of 0.5 mA / (cm 2The power supply increases linearly for 30 minutes, then switches to an exponentially decaying power supply mode, as shown in the formula: I t =35*exp(-0.0012*(t-1800)) continue to supply power for 30 minutes, where I t Input current density at time t (unit: mA / cm²) 2 ), where t is the reaction time (unit: s), calculated from the start time of the reactor;

[0094] (4) The COD index in the effluent pool is monitored in real time using an online water quality monitoring device. Water quality data during the reaction process is as follows: Figure 6 As shown, COD decreased from 120 mg / L to 28 mg / L after 1 hour.

[0095] Meanwhile, the energy consumption is calculated to be approximately 96.48 kWh / kg COD, and the energy consumption per ton of water is 8.88 kWh / m³. 3 The cost per ton of water is 6.21 yuan / m³. 3 .

[0096] Comparative Example 1

[0097] Comparative Example 1 uses a three-dimensional electrocatalytic oxidation device. The device in Comparative Example 1 is basically the same as the device in Example 1, except that the particle electrode filled in the three-dimensional electrocatalytic reactor of Comparative Example 1 is unmodified flake graphite (30-50 mesh), and the filling amount of the particle electrode is 50% of the reactor volume.

[0098] (1) The raw water quality information is shown in the table below:

[0099] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0100] (2) The electronic wastewater enters a three-dimensional electrocatalytic reactor for catalytic oxidation. The cathode plate in the reactor is a graphite electrode, the anode plate is a ruthenium-iridium-titanium electrode, and the hydraulic residence time is 1 hour.

[0101] (3) Set the initial current density to 20 mA / cm². 2 When the power supply is increased linearly, the slope is 0.5 mA / (cm). 2 The power supply increases linearly for 30 minutes, then switches to an exponentially decaying power supply mode, as shown in the formula: I t =35*exp(-0.0012*(t-1800)) continue to supply power for 30 minutes, where I t The current density input to the reactor at time t (unit: mA / cm²) 2 ), where t is the reaction time (unit: s), calculated from the start time of the reactor;

[0102] (4) COD index in the effluent tank was monitored in real time by the water quality online monitoring device, and the water quality data during the reaction process were as shown in Table 4, and the COD decreased from 120 mg / L to 76 mg / L after 1 h. Figure 7

[0103] The energy consumption was about 119.27 kWh / kg COD, the energy consumption per ton of water was 13 kWh / m 3 , and the cost per ton of water was 9.10 yuan / m 3 .

[0104] It can be seen from the comparison between Comparative Example 1 and Example 1 that the COD removal rate can be increased by more than 30% by using the modified graphite particle loaded with La2O3 / Al2O3 / TiO2 as the particle electrode, and energy saving and consumption reduction of about 45% can be realized.

[0105] Comparative Example 2

[0106] Comparative Example 2

[0107] (1) The raw water quality information is shown in the following table:

[0108] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0109] (2) The electronic tail water enters the three-dimensional electro-catalytic reactor for catalytic oxidation, the cathode plate in the reactor is a graphite electrode, the anode plate is a ruthenium-iridium-titanium electrode, and the hydraulic retention time is 1 h.

[0110] (3) The reactor is powered by a constant direct current, and the direct current source current density is 20 mA / cm 2 .

[0111] (4) COD index in the effluent tank was monitored in real time by the water quality online monitoring device, and the water quality data during the reaction process were as shown in Table 4, and the COD decreased from 120 mg / L to 76 mg / L after 1 h. Figure 8

[0112] The energy consumption was about 119.27 kWh / kg COD, the energy consumption per ton of water was 13 kWh / m 3 , and the cost per ton of water was 9.10 yuan / m 3 .

[0113] ​​By comparing Example 1 with Comparative Example 2, it can be seen that the COD removal rate can be increased by more than 60% and energy saving and consumption reduction can be achieved by about 75% by using the modified graphite particles loaded with La2O3 / Al2O3 / TiO2 as the particle electrode and by using the linear increase-exponential decay mode as the power supply mode.

[0114] Comparative Example 3

[0115] Comparative Example 3 uses a two-dimensional electro-catalytic oxidation device, and the device structure in Comparative Example 3 is basically the same as that in Example 1, and the only difference is that no particle electrode is filled between the cathode and the anode in the two-dimensional electro-catalytic reactor in Comparative Example 3.

[0116] (1) The raw water quality information is shown in the following table:

[0117] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0118] (2) The electronic tail water enters the two-dimensional electro-catalytic reactor for catalytic oxidation, the cathode plate in the reactor is a graphite electrode, and the anode plate is a ruthenium-iridium-titanium electrode, and the hydraulic retention time is 1 h.

[0119] (3) The initial current density is set to 20 mA / cm 2 , and in the linear increase power supply mode, the slope is linearly increased by 0.5 mA / (cm 2 ·min), and the power supply is continued for 30 min, and then adjusted to the exponential decay power supply mode, and the formula is: I t =35*exp(-0.0012*(t-1800)), which is continued for 30 min, wherein I t is the input current density at time t (unit: mA / cm 2 ), t is the reaction time (unit: s), and the time is counted from the start of the reactor.

[0120] (4) The COD index in the effluent tank is monitored in real time by the water quality online monitoring device, and the water quality data during the reaction process is shown in Table 1, and the COD is reduced from 185 mg / L to 105 mg / L after 1 h. Figure 9

[0121] At the same time, the energy consumption is about 278.7 kWh / kg COD, the energy consumption per ton of water is 22.3 kWh / m 3 , and the cost per ton of water is 15.61 yuan / m 3 .

[0122] ​By comparing Example 1 with Comparative Example 3, it can be seen that, when the modified graphite particles loaded with La2O3 / Al2O3 / TiO2 are used as particle electrodes to construct a three-dimensional electro-catalytic oxidation system, the COD removal rate can be increased by more than 50% compared with a two-dimensional electro-catalytic oxidation system, and energy saving and consumption reduction of about 77% can be realized. By comparing Comparative Example 3 with Comparative Example 1, it can be seen that, when unmodified flake graphite is used as particle electrodes to construct a three-dimensional electro-catalytic oxidation system, the COD removal rate can be increased by more than 26% compared with a two-dimensional electro-catalytic oxidation system, and energy saving and consumption reduction of about 57% can be realized.

[0123] Comparative Example 4

[0124] Comparative Example 4 uses a three-dimensional electro-catalytic oxidation device. The device in Comparative Example 4 is basically the same as that in Example 1, and the only difference is that the device in Comparative Example 4 is powered by a constant direct current power supply.

[0125] (1) The raw water quality information is shown in the following table:

[0126] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0127] (2) The electronic tail water enters a two-dimensional electro-catalytic reactor for catalytic oxidation. The cathode plate in the reactor is a graphite electrode, and the anode plate is a ruthenium-iridium-titanium electrode. The hydraulic retention time is 1 h.

[0128] (3) The reactor is powered by a constant direct current. The current density of the direct current power supply is 20 mA / cm 2 .

[0129] (4) The COD index in the effluent tank is monitored in real time by a water quality online monitoring device. The water quality data during the reaction process are shown in the following table. After 1 h, the COD decreases from 185 mg / L to 97 mg / L. Figure 10

[0130] The energy consumption is about 161.4 kWh / kg COD, the energy consumption per ton of water is 14.2 kWh / m 3 , and the cost per ton of water is 9.94 yuan / m 3 . By comparing Comparative Example 4 with Example 1, it can be seen that, by using the linear increase-exponential decay power supply mode, the catalytic performance can be effectively improved, the current efficiency can be maximized, the COD removal rate can be increased by more than 48%, and energy saving and consumption reduction of 60.5% can be realized.

[0131] Comparative Example 5

[0132] ​Comparative Example 5 Method A three-dimensional electro-catalytic oxidation device was used in Comparative Example 5. The device in Comparative Example 5 was substantially the same as the device in Example 1, except that the particle electrode filled in the three-dimensional electro-catalytic reactor in Comparative Example 5 was Al2O3-TiO2-loaded flaky graphite (30-50 mesh), and the filling amount of the particle electrode was 50% of the volume of the reactor.

[0133] (1) The raw water quality information is shown in the following table:

[0134] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0135] (2) The electronic tail water entered the three-dimensional electro-catalytic reactor for catalytic oxidation. The cathode plate in the reactor was a graphite electrode, and the anode plate was a ruthenium-iridium-titanium electrode. The hydraulic retention time was 1 h.

[0136] (3) The initial current density was set to 20 mA / cm 2 , and the slope was linearly increased at a rate of 0.5 mA / (cm 2 ·min) in the linear power supply mode. The power supply was continued for 30 min, and then the power supply mode was adjusted to an exponential decay mode, with the formula being I t = 35*exp(-0.0012*(t-1800)). The power supply was continued for another 30 min. In the formula, I t is the current density input into the reactor at time t (unit: mA / cm 2 ), and t is the reaction time (unit: s), which is counted from the start of the reactor.

[0137] (4) The COD index in the effluent tank was monitored in real time by the water quality online monitoring device. The water quality data during the reaction process are shown in Table 1. After 1 h, the COD decreased from 185 mg / L to 45 mg / L. The data also showed that the COD removal rate did not continue to rise after 30 min. Figure 11

[0138] The energy consumption was about 83.5 kWh / kg COD, the energy consumption per ton of water was 11.69 kWh / m 3 , and the cost per ton of water was 8.18 yuan / m 3 .

[0139] Comparative Example 5 and Example 1 were compared. When Al2O3-TiO2-loaded flaky graphite was used as the particle electrode, the COD removal rate decreased by 17.6%, and the energy consumption increased by 23.7%. This indicated that further loading of lanthanum on flaky graphite could effectively improve the catalytic oxidation performance of the reactor and reduce energy consumption.

[0140] Comparative Example 6

[0141] ​Comparative Example 6 Method A three-dimensional electro-catalytic oxidation device was used in Comparative Example 6. The device in Comparative Example 6 was substantially the same as the device in Example 1, except that the particle electrodes filled in the three-dimensional electro-catalytic reactor in Comparative Example 6 were calcined at 400°C in a muffle furnace for 4h in the preparation step (6), and the filling amount of the particle electrodes was 50% of the volume of the reactor.

[0142] (1) The raw water quality information is shown in the following table:

[0143] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0144] (2) The electronic tail water entered the three-dimensional electro-catalytic reactor for catalytic oxidation. The cathode plate in the reactor was a graphite electrode, and the anode plate was a ruthenium-iridium-titanium electrode. The hydraulic retention time was 1h;

[0145] (3) The initial current density was set to 20mA / cm 2 , and the slope was linearly increased at a rate of 0.5mA / (cm 2 ·min) in the linear power supply mode. The power supply was continued for 30min, and then adjusted to an exponential decay power supply mode, with the formula being I t = 35*exp(-0.0012*(t-1800)) for a continuous power supply of 30min. In the formula, I t is the current density input into the reactor at time t (unit: mA / cm 2 ), and t is the reaction time (unit: s), counted from the start of the reactor;

[0146] (4) The COD index in the effluent tank was monitored in real time by the water quality online monitoring device. The water quality data during the reaction process are shown in Table 1. The COD decreased from 185mg / L to 33mg / L after 1h. Figure 12

[0147] The energy consumption was about 74.07kWh / kg COD, the energy consumption per ton of water was 11.26kWh / m 3 , and the cost per ton of water was 7.88 yuan / m 3 .

[0148] Comparative Example 6 and Example 1 show that when the modified flaky graphite particles loaded with La2O3-Al2O3-TiO2 are prepared, reducing the calcination temperature in the preparation step reduces the COD removal rate by 10.6% and increases the energy consumption by 14%, indicating that a suitable calcination temperature during the preparation of the particle electrodes can effectively improve the catalytic oxidation performance of the reactor and reduce the energy consumption.

[0149] Comparative Example 7

[0150] ​Comparative Example 7 Method A three-dimensional electro-catalytic oxidation device was used in Comparative Example 7. The device in Comparative Example 7 was substantially the same as the device in Example 1, except that the mass ratio of flake graphite to Al2O3-TiO2 sol in the preparation step (2) of the particle electrode filled in the three-dimensional electro-catalytic reactor in Comparative Example 7 was 1:1, and the filling amount of the particle electrode was 50% of the volume of the reactor.

[0151] (1) The raw water quality information is shown in the following table:

[0152] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0153] (2) The electronic tail water entered the three-dimensional electro-catalytic reactor for catalytic oxidation. The cathode plate in the reactor was a graphite electrode, and the anode plate was a ruthenium-iridium-titanium electrode. The hydraulic retention time was 1 h.

[0154] (3) The initial current density was set to 20 mA / cm 2 . When the power supply mode was linearly increased, the slope was linearly increased at a rate of 0.5 mA / (cm 2 ·min). The power supply was continued for 30 min, and then the power supply mode was adjusted to an exponential decay mode, with the formula being I t = 35*exp(-0.0012*(t-1800)). The power supply was continued for another 30 min. In the formula, I t is the current density input into the reactor at time t (unit: mA / cm 2 ), and t is the reaction time (unit: s), which is counted from the start of the reactor.

[0155] (4) The COD index in the effluent tank was monitored in real time by the water quality online monitoring device. The water quality data during the reaction process are shown in Table 2. After 1 h, the COD decreased from 185 mg / L to 40 mg / L. Figure 13

[0156] At the same time, the energy consumption was about 79.13 kWh / kg COD, the energy consumption per ton of water was 11.47 kWh / m 3 , and the cost per ton of water was 8.03 yuan / m 3 .

[0157] By comparing Comparative Example 7 with Example 1, it can be seen that when the modified flake graphite particles loaded with La2O3-Al2O3-TiO2 are prepared, the mass ratio of flake graphite to Al2O3-TiO2 sol is changed from 1:2 to 1:1. The COD removal rate decreases by 14.7%, and the energy consumption increases by 19.5%. This indicates that when the particle electrode is prepared, reducing the mass ratio of flake graphite to Al2O3-TiO2 sol can effectively improve the catalytic oxidation performance of the reactor and reduce the energy consumption.

[0158] Comparative Example 8

[0159] ​Comparative Example 8 Method A three-dimensional electro-catalytic oxidation device was used in Comparative Example 8. The device in Comparative Example 8 was substantially the same as the device in Example 1, except that the order of preparation of the particle electrode filled in the three-dimensional electro-catalytic reactor in Comparative Example 8 was changed. In this comparative example, the unmodified flake graphite was first mixed with the La2O3-Al2O3-TiO2sol to obtain flake graphite loaded with La2O3-Al2O3-TiO2, and then mixed with the Al2O3-TiO2sol to obtain the modified flake graphite used in this comparative example, i.e., the preparation steps were changed to (1) - (4) - (5) - (6) - (2) - (3), and the filling amount of the particle electrode was 50% of the volume of the reactor.

[0160] (1) The raw water quality information is shown in the following table:

[0161] Source COD (mg / L) pH Water quantity Tail water of a panel factory in Kunshan 185 7.5 100 L / h

[0162] (2) The electronic tail water was introduced into the three-dimensional electro-catalytic reactor for catalytic oxidation. The cathode plate in the reactor was a graphite electrode, and the anode plate was a ruthenium-iridium-titanium electrode. The hydraulic retention time was 1 h.

[0163] (3) The initial current density was set to 20 mA / cm 2 , and the slope was linearly increased at a rate of 0.5 mA / (cm 2 ·min). The power supply was maintained for 30 min, and then adjusted to an exponential decay power supply mode, with the formula being I t =35*exp(-0.0012*(t-1800)) continuing for 30 min. In the formula, I t is the current density input into the reactor at time t (unit: mA / cm 2 ), and t is the reaction time (unit: s), counted from the start of the reactor.

[0164] (4) The COD index in the effluent tank was monitored in real time by the water quality online monitoring device. The water quality data during the reaction process are shown in Figure 14 . After 1 h, the COD decreased from 185 mg / L to 43 mg / L.

[0165] The energy consumption was about 81.76 kWh / kg COD, the energy consumption per ton of water was 11.61 kWh / m 3 , and the cost per ton of water was 8.13 yuan / m 3 .

[0166] By comparing the Example 1 with the Comparative Example 8, it can be seen that when the modified flaky graphite particles loaded with La2O3-Al2O3-TiO2 are prepared, the order of loading steps is reversed, the COD removal rate is reduced by 16.5%, and the energy consumption is increased by 22%, which indicates that when the particle electrode is prepared, Al2O3-TiO2 is loaded first, La2O3 is loaded second, and the catalytic oxidation performance of the modified flaky graphite obtained thereafter is better, and meanwhile the energy consumption is reduced.

Claims

1. A three-dimensional electro-catalytic oxidation device, characterized in that: The application relates to a three-dimensional electro-catalytic reactor (3) and a power supply (9); the three-dimensional electro-catalytic reactor (3) is internally provided with an anode plate (4), a cathode plate (5) and a particle electrode between the anode plate and the cathode plate; the particle electrode is modified scale graphite loaded with La2O3-Al2O3-TiO2; the anode plate (4) and the cathode plate (5) are respectively connected with the power supply (9) through wires; the power supply (9) comprises a linearly-increasing power supply mode and an exponentially-decaying power supply mode; the time of the two power supply modes is the same; in the first half of the reaction time of the reactor (3), the power supply (9) is powered in the linearly-increasing power supply mode, and the current density is linearly increased at this time; in the second half of the reaction time of the reactor (3), the power supply (9) is powered in the exponentially-decaying power supply mode, and the current density is decayed with a decay coefficient n. Under the exponentially-decaying power supply mode, the current density corresponding to each time in the reaction process is shown in the following formula: I t = I1*exp(-n*(t-t0)) In the formula, I t is the input current density at time t, in units of mA / cm 2 ; I1 is the current density corresponding to the end of the linear increase power supply mode, unit: mA / cm 2 ; n is the attenuation coefficient, unit: s -1 , the value range is 0.001~0.002; t is the reaction time, unit: s, from the beginning of the reactor. t0 is the time corresponding to the end of the linearly-increasing power supply mode, and the unit is s, which is calculated from the time when the reactor starts.

2. The three-dimensional electro-catalytic oxidation device according to claim 1, characterized in that: The modified scale graphite loaded with La2O3-Al2O3-TiO2 is prepared by the following method, and the specific steps are as follows: (1) taking aluminum isopropoxide and tetrabutyl titanate as raw materials and anhydrous ethanol as a solvent, an aluminum isopropoxide ethanol solution and a tetrabutyl titanate ethanol solution are respectively obtained; the aluminum isopropoxide ethanol solution, the tetrabutyl titanate ethanol solution and distilled water are mixed, the pH value is adjusted to be not higher than 5, and an Al2O3-TiO2 sol is obtained after stirring; (2) scale graphite is added into the Al2O3-TiO2 sol and fully stirred to make the surface of the graphite particles fully contact with the sol, then sodium carbonate solution is slowly and uniformly dropped into the mixture to make it gelatinize, and the mixture is filtered; (3) the obtained particles are dried in an oven at 165-170 DEG C, and then calcined at 600-650 DEG C to obtain scale graphite particles coated with Al2O3-TiO2; (4) taking lanthanum nitrate hexahydrate as a raw material and anhydrous ethanol as a solvent, a lanthanum nitrate ethanol solution is obtained; the lanthanum nitrate ethanol solution, the Al2O3-TiO2 sol and distilled water are mixed, and concentrated nitric acid is slowly added into the mixture, and the mixture is continuously stirred to obtain a La2O3-Al2O3-TiO2 sol; (5) the Al2O3-TiO2 coated scale graphite particles obtained in step (3) are added into the La2O3-Al2O3-TiO2 sol, fully stirred to make the surface of the graphite particles fully contact with the sol, then sodium carbonate solution is slowly and uniformly dropped into the mixture to make it gelatinize, and the mixture is filtered; (6) the particles obtained in step (5) are dried at 100-105 DEG C, and then calcined at 700-750 DEG C to obtain the modified scale graphite loaded with La2O3-Al2O3-TiO2.

3. The three-dimensional electro-catalytic oxidation device according to claim 2, characterized in that: In step (1), the concentration of the aluminum isopropoxide ethanol solution is 1-1.5 mol / L, and the concentration of the tetrabutyl titanate ethanol solution is 1-1.5 mol / L; the volume ratio of the aluminum isopropoxide ethanol solution, the tetrabutyl titanate ethanol solution and the distilled water is 1:1:2-3.

4. The three-dimensional electro-catalytic oxidation device according to claim 2, wherein: In step (4), the concentration of the lanthanum nitrate ethanol solution is 2-2.5 mol / L; the volume ratio of the lanthanum nitrate ethanol solution, the Al2O3-TiO2 sol and the distilled water is 2:1:2-3; and the amount of the concentrated nitric acid added is 10-12% of the total volume of the mixture of the lanthanum nitrate ethanol solution, the Al2O3-TiO2 sol and the distilled water.

5. The three-dimensional electro-catalytic oxidation device according to claim 2, wherein: The modified flake graphite has a mesh number of 30-50 meshes, and the filling ratio of the modified flake graphite is 50-55% of the volume of the reactor.

6. The three-dimensional electro-catalytic oxidation device according to claim 1, wherein: The three-dimensional electro-catalytic oxidation device further comprises a water inlet adjusting tank (1) and a water outlet tank (2); the water inlet of the three-dimensional electro-catalytic reactor (3) is connected with the water inlet adjusting tank (1) through a water inlet pipe (6), and the water outlet is connected with the water outlet tank (2) through a water outlet pipe (7).

7. The three-dimensional electro-catalytic oxidation device according to claim 1, wherein: The three-dimensional electro-catalytic oxidation device further comprises a water quality on-line monitoring device (11) and a dosing device (10); the water quality on-line monitoring device (11) is used for detecting the COD and ammonia nitrogen indexes of the water body in the water outlet tank (2); the dosing device (10) is connected with the water inlet adjusting tank (1) through a dosing pipeline, and a pH sensor is arranged in the water inlet adjusting tank; the water inlet adjusting tank is adjusted to neutral by the dosing device.

8. The three-dimensional electro-catalytic oxidation device according to claim 6, wherein: A reflux pipe (8) is further arranged between the water inlet adjusting tank (1) and the water outlet tank (2); when the COD and ammonia nitrogen indexes of the water body in the water outlet tank (2) exceed the standard, the water outlet is refluxed to the water inlet adjusting tank for secondary treatment.

9. The method of treating electronic wastewater with the three-dimensional electrocatalytic oxidation device of claim 1, wherein, Specifically comprising the following steps: (1) The electronic wastewater is subjected to catalytic oxidation in the three-dimensional electro-catalytic reactor; the cathode plate in the reactor is a graphite electrode, the anode plate is a ruthenium-iridium-titanium electrode, and the hydraulic retention time is not higher than 1 h; modified flake graphite is filled between the cathode plate and the anode plate, and the filling ratio of the modified flake graphite is 50-55% of the volume of the reactor; (2) the initial current density of the power supply is not less than 20 mA / cm 2 , and the speed increases at a slope of 0.3-0.6 mA / (cm 2 •min), and the linear increase power supply mode runs for 25-30 min; as the reaction proceeds, the current density exponentially decays with a decay coefficient n, and the exponential decay power supply mode runs for 25-30 min; In the exponential decay power supply mode, the current density corresponding to each time in the reaction process is shown in the following formula: I t = I1*exp(-n*(t-t0)) wherein I is the input current density of the reactor at time t, in mA / cm2 t wherein I is the input current density of the reactor at time t, in mA / cm2 2 ; I1 is the current density corresponding to the end of the linear increase power supply mode, unit: mA / cm 2 ; n is the attenuation coefficient, unit: s -1 , the value range is 0.001~0.002; t is the reaction time, unit: s, from the start time of the reactor t0 is the time corresponding to the end of the linear increase power supply mode, and the unit is s, which is calculated from the start time of the reactor; (3) The reactor water outlet enters the water outlet tank; the COD index in the water outlet tank is monitored in real time by the water quality on-line monitoring device; when the COD removal rate is higher than 90%, the water is discharged through the water outlet pipe; when the COD removal rate is less than 90%, the reflux pipe switch under the water outlet tank is opened, and the water is refluxed to the water inlet adjusting tank for secondary catalytic oxidation treatment.

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