Three-dimensional electrode filler for electro-catalytic oxidation and preparation method thereof

Abstract

The application discloses a kind of three-dimensional electrode fillings for electrocatalytic oxidation and preparation method thereof, belong to wastewater treatment technical field.The three-dimensional electrode fillings for electrocatalytic oxidation of the application is steel slag particle as carrier, and load ZnO-CoO composite metal oxide with mesoporous structure on steel slag particle.The application fully exploits the surface characteristics and other physical and chemical characteristics of steel slag as three-dimensional electrode filling, under the premise of guaranteeing the catalytic oxidation performance and service life of filling, its raw material cost is lower.At the same time, the application also widens the resource utilization way of waste steel slag, has certain environmental benefits.The application optimizes and improves the manufacturing process of three-dimensional electrode filling, so that three-dimensional electrode filling obtains better surface characteristics, including larger specific surface area, larger specific capacitance and widely distributed mesoporous structure etc., so that three-dimensional electrode filling has higher catalytic oxidation efficiency, better physical and chemical stability and longer service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, and more particularly to a three-dimensional electrode filler for electro-catalytic oxidation. BACKGROUND

[0002] Advanced oxidation technology (AOP S ) has great advantages in treating industrial wastewater containing refractory organic matter, and has the characteristics of high COD removal rate, high mineralization degree, wide adaptability to water quality, good operation stability, good connection with other treatment processes, etc. The essence of using advanced oxidation technology to treat water pollutants is to generate extremely strong ·OH through a series of complex physical and chemical processes, thereby oxidizing and degrading organic pollutants in water. Electro-catalytic oxidation technology is an important branch of advanced oxidation technology, and its principle is to make the anode organic pollutants undergo direct or indirect oxidation reaction through the action of an external direct current power supply. Electro-catalytic oxidation technology has the characteristics of no addition of reagents, no harmful products, mild reaction conditions, and low operation cost, and is more and more applied in industrial water treatment. However, the two-dimensional electrode commonly used in the current industrial electro-catalytic oxidation device, i.e. the cathode plate and the anode plate are both two-dimensional flat plate structures, and the oxidation reaction area is limited by the area of the anode plate. In actual engineering application, multiple longitudinally arranged electrode plate arrays are generally used to increase the area of the electrode plate, which greatly increases the construction cost of the device. At the same time, in order to ensure a large enough current density, the electro-catalytic oxidation device using two-dimensional electrodes has certain requirements for the electrical conductivity of the influent, so it is usually necessary to add electrolyte to the influent to increase the electrical conductivity of the influent, which to some extent increases the operation cost of the device.

[0003] In order to improve the anode plate area of the electro-catalytic oxidation device and increase the oxidation reaction area, researchers have developed a three-dimensional electrode system. One of the forms of the three-dimensional electrode system is an electrode system composed of a two-dimensional electrode plate array and a three-dimensional electrode filler filled in the gap of the two-dimensional electrode plate array. The electro-catalytic oxidation efficiency of the three-dimensional electrode system in this form is closely related to the physical and chemical properties of the three-dimensional electrode filler. In the current research, loading high-catalytic-activity metals and their oxides is one of the main ways to improve the catalytic activity of the three-dimensional electrode filler, such as loading some transition metals and rare earth metals and their oxides. Secondly, the optimization and improvement of the filler preparation process endow the filler with better surface properties, including larger specific surface area, larger specific capacitance, and widely distributed mesoporous structure, etc. The common three-dimensional electrode fillers at present are activated carbon electrode fillers, Al2O3 electrode fillers, TiO2 electrode fillers, etc. The raw materials of these three-dimensional electrode fillers are all finished industrial raw materials, which are relatively high in price. Moreover, due to the immaturity of the manufacturing process, the surface properties and other physical and chemical properties of the fillers often cannot meet the process requirements, and there are generally problems such as low catalytic efficiency of the fillers and large loss of the fillers and significant decline of the catalytic performance of the fillers due to the powdering, passivation, and chemical corrosion of the fillers in engineering applications.

[0004] China's steel production capacity ranks first in the world, and a large amount of steel slag is also produced in the process of steel production. As a kind of waste, if the steel slag cannot be reasonably treated and disposed, it will cause serious harm to the ecological environment. At present, the resource utilization of steel slag is mainly concentrated in the field of building materials, and in the field of water treatment and water environment remediation, steel slag is also commonly used as filter material and artificial wetland filler. The steel slag itself has a micro-porous structure, which makes its specific surface area huge, up to 500 m 2 / kg or more. The steel slag also contains various metal oxides, such as Al2O3, Fe2O3, MgO, MnO, etc., which makes it itself have great potential as a three-dimensional electrode filler. In addition, the compressive strength of the steel slag can generally reach more than 25 MPa, and the steel slag can be used as a carrier of the three-dimensional electrode filler to improve the mechanical strength of the filler and prolong the service life of the filler. SUMMARY

[0005] 1. Technical problems to be solved by the invention

[0006] In order to solve the problems of high cost of raw materials and low catalytic efficiency and short service life caused by immature manufacturing process of the three-dimensional electrode filler for electro-catalytic oxidation, the present invention aims to provide a three-dimensional electrode filler with low price, high catalytic efficiency, good stability, and long service life for the three-dimensional electro-catalytic oxidation device. At the same time, the present invention will also further broaden the resource utilization way of steel slag.

[0007] 2. Technical solutions

[0008] To achieve the above object, the technical scheme provided by the present application is:

[0009] A three-dimensional electrode filler for electro-catalytic oxidation, which takes steel slag particles as carriers and loads ZnO-CoO composite metal oxides with mesoporous structures on the steel slag particles.

[0010] As a further improvement of the present application, the steel slag particle size is 3-5 mm, the compressive strength is greater than 15 MPa, the specific surface area is greater than 0.5 m 2 / g.

[0011] A preparation method of a three-dimensional electrode filler, used for preparing the aforementioned three-dimensional electrode filler for electro-catalytic oxidation, comprising,

[0012] The raw steel slag is first crushed, then screened, autoclaved, washed, dried and screened again to obtain finished steel slag particles as carriers of the three-dimensional electrode filler;

[0013] ZnO-CoO composite metal oxides with mesoporous structures are loaded on the finished steel slag particles through a hydrothermal impregnation and subsequent heat treatment method.

[0014] As a further improvement of the present application, the screening particle size of the first screening is 10-15 mm, and the screening particle size of the second screening is 3-5 mm.

[0015] As a further improvement of the present application, the autoclaving process has a pressure of 2 MPa and a duration of 5-6 h.

[0016] As a further improvement of the present application, the hydrothermal impregnation treatment method specifically comprises,

[0017] S1: configuring a three-phase mixed solvent of ethylenediamine, ethanolamine and ethanol with a volume ratio of 2:3:2;

[0018] S2: dissolving zinc acetate dihydrate and cobalt acetate tetrahydrate in the three-phase mixed solvent configured in step S1 to form a solution with a Zn2+ concentration of 1-1.5 mol / L, the Co 2+ molar concentration in the solution is 1.5 times that of Zn 2+ ;

[0019] S3: heating the finished steel slag particles as carriers and the solution obtained in step S2 to 150 DEG C respectively, then completely immersing the steel slag particles in the solution, keeping the temperature at 150 DEG C, and performing vigorous stirring with a duration of 15-20 s every 5-10 min, the impregnation duration is 2-4 h;

[0020] S4: separating the steel slag particles after the immersion treatment in step S3 from the solution, naturally cooling to room temperature, then immersing and washing 3-4 times with pure water, and then drying with hot air at 80 DEG C to make the water content less than 4%.

[0021] As a further improvement of the application, the heat treatment mode is specifically that the raw material after the hydrothermal immersion treatment is subjected to constant temperature heat treatment at 450-470 DEG C for 5-8 h.

[0022] The heat treatment process further comprises a temperature rising process before the constant temperature heat treatment and a temperature falling process after the constant temperature heat treatment.

[0023] As a further improvement of the application, the temperature rising process before the constant temperature heat treatment is specifically that the temperature is raised to 450-470 DEG C by linear temperature rising for more than 15 min.

[0024] As a further improvement of the application, the temperature falling process after the constant temperature heat treatment is divided into two stages, the first stage is an accelerated temperature falling stage, the temperature is fallen to 330 DEG C, and the temperature falling time is controlled to be 20-25 s; the second stage is a decelerated temperature falling stage, the temperature is fallen to room temperature by linear temperature falling, and the temperature falling time is more than 10 min.

[0025] As a further improvement of the application, the two stages of the temperature falling process are continuous and uniform.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the technical scheme provided by the application has the following beneficial effects:

[0028] (1) The three-dimensional electrode filler provided by the application takes steel slag, which is originally waste, as the carrier, fully excavates the surface characteristics and other physical and chemical characteristics of the steel slag as the three-dimensional electrode filler, compared with the method of taking active carbon, Al2O3 and TiO2 and other finished industrial raw materials as the three-dimensional electrode filler carrier which is generally adopted at present, the method of the application has lower raw material cost under the premise of ensuring the catalytic performance and service life of the filler. Meanwhile, the application also widens the resource utilization way of the waste steel slag, and has certain environmental benefits.

[0029] (2) The application optimizes and improves the manufacturing process of the three-dimensional electrode filler, and the manufacturing process of the finished steel slag particles can obtain a three-dimensional electrode filler carrier with up-to-standard strength and stable physical and chemical properties. The ZnO-CoO composite metal oxide itself and its loading process (hydrothermal immersion + heat treatment) make the three-dimensional electrode filler have better surface characteristics, including larger specific surface area, larger specific capacitance and widely distributed mesoporous structure, etc., so that the three-dimensional electrode filler has higher catalytic efficiency, better physical and chemical stability and longer service life. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Figure 1 is a schematic diagram of the structure of a small-scale experiment device for electro-catalytic oxidation.

[0031] Figure 2 Figure 2 is a schematic diagram of the structure of a small-scale experiment device for electro-catalytic oxidation with three-dimensional electrode fillers added.

[0032] Figure 3 Figure 3 is a graph of the experimental results of the phenol concentration and removal rate of the effluent of a small-scale experiment device for electro-catalytic oxidation.

[0033] Figure 4 Figure 4 is a schematic diagram of the structure of a pilot-scale experiment device for electro-catalytic oxidation.

[0034] Figure 5 Figure 5 is a schematic diagram of the structure of a pilot-scale experiment device for electro-catalytic oxidation with three-dimensional electrode fillers added.

[0035] Figure 6 Figure 6 is a graph of the experimental results of the COD concentration and removal rate of the effluent of a pilot-scale experiment device for electro-catalytic oxidation.

[0036] SCHEMATIC Figure 1 Explanation of the reference numerals in Figures 1 / 2 / 4 / 5:

[0037] 1, direct current power supply; 2, metal mesh; 3, cathode plate unit; 4, anode plate unit; 5, plate unit connection point; 6, jet pipe; 7, backwashing air inlet pipe; 8, backwashing water inlet pipe; 9, water inlet pipe; 10, backwashing water and air distribution pipe; 11, electromagnetic valve 1; 12, electromagnetic valve 2; 13, water outlet pipe; 14, backwashing water distribution pipe; 15, water distribution pipe; 16, three-dimensional electrode filler; 17, overflow weir; 18, three-dimensional electrode filler support layer. DETAILED DESCRIPTION

[0038] In order to further understand the content of the present application, the present application will be described in detail in conjunction with the accompanying drawings and examples.

[0039] The structure, proportion, size, etc. shown in the drawings of the present specification are merely used to cooperate with the content disclosed in the specification, so as to be understood and read by those skilled in the art, and do not have technical substantive significance, and any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope covered by the disclosed technical content. Meanwhile, the terms such as "upper", "lower", "left", "right", "middle" etc. cited in the present specification are merely for the convenience of clear description, and are not used to limit the implementable range, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also considered as the implementable scope of the present application.

[0040] Embodiment 1

[0041] The first embodiment of the present application provides a three-dimensional electrode filler for electro-catalytic oxidation, which takes steel slag particles as carriers and loads ZnO-CoO composite metal oxides on the steel slag particles.

[0042] The steel slag is a waste slag generated in the metallurgical industry, and its generation rate is 8% to 15% of the crude steel output. The chemical composition of the steel slag is very complex, including CaO, Fe2O3, SiO2, Al2O3, MgO, MnO, P2O5, TiO2, SO3 and various components. Al2O3 and TiO2 are also part of the finished industrial raw material components of the three-dimensional electrode filler carrier, and thus the chemical properties of the steel slag itself can also meet the requirements of the three-dimensional electrode filler.

[0043] Further, for the physical properties of the steel slag, the finished steel slag particles as carriers have a particle size of 3 to 5 mm, a compressive strength greater than 15 MPa, and a specific surface area greater than 0.5 m 2 / g. The compressive strength of the steel slag particles determines the mechanical strength and corresponding physical life of the three-dimensional electrode filler. The compressive strength of the steel slag is usually above 25 MPa, and of course there are some poor quality steel slags with a compressive strength below 15 MPa. If used as a carrier of the three-dimensional electrode filler, the final three-dimensional electrode filler is easy to break and pulverize during the operation of the reactor, and thus during the selection of raw materials, qualified steel slag raw materials need to be selected. The specific surface area of the steel slag particles determines the specific surface area of the final three-dimensional electrode filler, and a larger specific surface area of the filler means a larger adsorption and catalytic area, and thus better electro-catalytic oxidation potential.

[0044] In this embodiment, the three-dimensional electrode filler takes the steel slag, which is originally a waste, as a carrier, fully excavates the surface properties and other physical and chemical properties of the steel slag as a three-dimensional electrode filler, and compared with the current common practice of using activated carbon, Al2O3 and TiO2 and other finished industrial raw materials as carriers of the three-dimensional electrode filler, the cost is greatly reduced while the catalytic performance and service life are ensured, and the resource utilization way of the waste steel slag is also widened.

[0045] Embodiment 2

[0046] The second embodiment of the present application is based on the previous embodiment, and the present embodiment provides a preparation method of the steel slag particles.

[0047] Specifically, the raw steel slag is taken, and then is subjected to crushing, primary screening, autoclaving, cleaning, drying and secondary screening to obtain clean, dry and screened steel slag particles with a particle size of 3-5 mm. The primary screening has a screening particle size of 10-15 mm, and the secondary screening has a screening particle size of 3-5 mm. The autoclaving process has a pressure of 2 MPa and a duration of 5-6 h.

[0048] In the production process of the finished steel slag particles, the primary screening, autoclaving and secondary screening are key processes.

[0049] The particle size of the primary screening is determined by experiments and should satisfy that the steel slag particles with a particle size of 3-5 mm account for the maximum proportion after autoclaving. The secondary screening determines the particle size of the finished steel slag. The autoclaving process is used to remove unstable components in the steel slag particles. During the autoclaving process, the steel slag particles are cracked and partially pulverized to release the unstable components, and the particle size of the steel slag particles is reduced due to the cracking and pulverization. The compressive strength of the steel slag particles determines the structural strength and corresponding physical life of the three-dimensional electrode filler.

[0050] In addition, the cleaning process of the steel slag is used to remove the soil and pulverized small particles on the surface and in the pores of the steel slag, so as to avoid that the soil and particles cover the surface of the steel slag or block the pores to cause that the ZnO-CoO composite metal oxide cannot be firmly loaded on the surface and in the pores of the steel slag particles.

[0051] In the steel slag particles produced in the production conditions of the embodiment (the actual autoclaving process has a pressure of 2 MPa and a duration of 6 h), samples are selected for professional detection, the physical and chemical properties are detected, the average of the detection data of the three batches of samples is taken as the performance parameter value of the steel slag particle product, and finally the performance parameters of the finished steel slag particles of the batch are obtained as follows: the steel slag particles have a particle size of 3-5 mm, the soil content of the steel slag particles is 0.27%, the water content is 2.1%, the compressive strength is 21 MPa, and the specific surface area is 0.55 m 2 / g.

[0052] Embodiment 3

[0053] Based on the above embodiment, the third embodiment of the application provides a loading method of ZnO-CoO composite metal oxide with a mesoporous structure, which includes a hydrothermal impregnation and a subsequent heat treatment method.

[0054] The hydrothermal impregnation method specifically includes the following steps.

[0055] S1: configuring a three-phase mixed solvent of ethylenediamine: ethanolamine: ethanol (volume ratio) as 2:3:2;

[0056] S2: dissolving zinc acetate dihydrate and cobalt acetate tetrahydrate in the three-phase mixed solvent configured in S1 to form a Zn-Co mixed solution; S3: placing the Zn-Co mixed solution in a Teflon-lined autoclave, and then adding a certain amount of water to the autoclave to form a mixed solution with a certain volume ratio of the Zn-Co mixed solution to water; S4: placing the autoclave in a water bath, and then heating the autoclave to a temperature of 100-200°C and maintaining the temperature for 1-10 h to obtain a Zn-Co mixed solution with a certain amount of ZnO-CoO composite metal oxide; S5: taking the Zn-Co mixed solution with the ZnO-CoO composite metal oxide out of the autoclave, and then adding a certain amount of water to the Zn-Co mixed solution to form a mixed solution with a certain volume ratio of the Zn-Co mixed solution to water; S6: placing the mixed solution in the Teflon-lined autoclave, and then heating the autoclave to a temperature of 100-200°C and maintaining the temperature for 1-10 h to obtain a Zn-Co mixed solution with a certain amount of ZnO-CoO composite metal oxide; and S7: taking the Zn-Co mixed solution with the ZnO-CoO composite metal oxide out of the autoclave, and then drying the Zn-Co mixed solution to obtain a ZnO-CoO composite metal oxide with a mesoporous structure.2+ concentration of 1-1.5 mol / L, the solution containing Co 2+ concentration of 1-1.5 mol / L, the solution containing Co 2+ concentration of 1-1.5 mol / L, the solution containing Co

[0057] S3: the finished steel slag particles as carriers and the solution in S2 are heated to 150°C respectively, then the steel slag particles are completely immersed in the solution, kept at 150°C, and intense stirring is carried out every 5-10 minutes for 15-20 seconds, and the immersion lasts for 2-4 hours;

[0058] S4: the steel slag particles after the immersion treatment in S3 are separated from the solution, naturally cooled to room temperature, then immersed in pure water for 3-4 times, and then dried with hot air at about 80°C to make the water content less than 4%;

[0059] Further, the subsequent heat treatment mode is specifically as follows: the raw material after the hydrothermal immersion treatment is subjected to heat treatment at a constant temperature of 450-470°C for 5-8 hours. The heat treatment is raised to the predetermined temperature (450-470°C) in a linear heating mode, and the heating time is not less than 15 minutes. The cooling process of the heat treatment is divided into two stages, and the cooling process of the two stages should be continuous and uniform. The first stage is an accelerated cooling stage, and the cooling lasts for 20-25 seconds. The second stage is a decelerated cooling stage, and the cooling is linearly lowered to room temperature, and the cooling time is not less than 10 minutes.

[0060] The hydrothermal method is to load the precursors (zinc acetate and cobalt acetate) of the ZnO-CoO composite metal oxide on the surface and pores of the steel slag particle carrier, and then convert the precursors into the final ZnO-CoO composite metal oxide through heat treatment. The hydrothermal method makes the precursors fully enter the pores of the steel slag particles through a higher immersion temperature and a certain frequency of intense stirring, which is beneficial to increase the active catalytic area of the finally formed three-dimensional electrode filler. The heat treatment process is also a process of forming the binding force between the ZnO-CoO composite metal oxide and the carrier and the mesoporous structure of the ZnO-CoO composite metal oxide. The final heat treatment temperature can convert the precursors into the ZnO-CoO composite metal oxide and form an effective binding force between the carrier and the ZnO-CoO composite metal oxide. The accelerated cooling stage is the key to forming the mesoporous structure of the ZnO-CoO composite metal oxide, and the decelerated cooling stage can avoid the further expansion of the mesoporous structure and the formation of destructive cracks affecting the structural strength. A large number of research results show that the catalyst with mesoporous structure has higher adsorption and catalytic performance. Further, CoO and ZnO both have high theoretical specific capacitance, but poor electrical conductivity. Therefore, in this embodiment, CoO and ZnO are combined to form a composite metal oxide carrier, which greatly improves the electrical conductivity and electrocatalytic oxidation performance of single metal oxide materials.

[0061] Example 4

[0062] The fourth embodiment of the present invention is based on the previous embodiment. In order to verify the characterization parameters of the finally obtained three-dimensional electrode filler, this embodiment selects three parallel samples from a batch of experimentally produced three-dimensional electrode fillers for professional testing.

[0063] The hydrothermal impregnation and heat treatment used in the production of this batch of three-dimensional electrode fillers are as follows:

[0064] 1) preparing a three-phase mixed solvent of ethylenediamine:ethanolamine:ethanol (volume ratio) of 2:3:2;

[0065] 2) Dissolve zinc acetate dihydrate and cobalt acetate tetrahydrate in the three-phase mixed solvent prepared in 1) to form Zn 2+ The concentration of the solution is 1 mol / L, and the amount of Co in the solution is 2+ Molar concentration of Zn 2+ 1.5 times;

[0066] 3) heating the finished steel slag particles as a carrier and the solution in 2) to 150° C. respectively, then completely immersing the steel slag particles in the solution, maintaining a constant temperature of 150° C., and vigorously stirring for a duration of 15 minutes every 8 minutes, for a total immersion duration of 3 hours;

[0067] 4) separating the steel slag particles after the immersion treatment in 3) from the solution, cooling them naturally to room temperature, then rinsing them with pure water four times, and then drying them with hot air at about 80° C. to a moisture content of less than 4%;

[0068] The hydrothermal impregnation raw material was subjected to a constant temperature heat treatment at 450°C for 6 hours. The heat treatment was performed using a linear ramp to the desired temperature (450°C) for 15 minutes. The cooling process during the heat treatment was divided into two stages, both of which should be continuous and uniform. The first stage was an accelerated cooling stage, cooling to 330°C for 25 seconds; the second stage was a decelerated cooling stage, cooling to room temperature using a linear ramp for 10 minutes.

[0069] In this embodiment, the average value of the three parallel sample test data is used as the characterization parameter of the batch of steel slag particle products. The characterization parameters of the batch of three-dimensional electrode fillers finally obtained are: BET (specific surface area) is 47.5m 2 / g, at 10mA / cm 2 The specific capacitance under current density conditions is 810.7F / g.

[0070] Example 5

[0071] In order to better verify the technical effects achieved by the present application, the fifth embodiment of the present application verifies the removal effect of the three-dimensional electro-catalytic oxidation system adopting the three-dimensional electrode filler prepared by the method of the present application on the characteristic pollutants by a three-dimensional electro-catalytic oxidation small test experiment, and the specific method is as follows:

[0072] The prepared three-dimensional electrode filler is filled in the electro-catalytic oxidation small test experiment device, and the characteristic pollutant phenol (influent concentration 5 mg / L) of petrochemical wastewater is used as the influent pollutant of the electro-catalytic oxidation small test experiment device to carry out the electro-catalytic oxidation small test experiment. It should be noted that phenol as a pollutant with benzene ring has poor biodegradability and certain biological toxicity, which makes the biodegradation treatment process less applicable.

[0073] The schematic diagram of the small test experiment device is shown in Figure 1 and Figure 2 . It includes a direct current power supply 1, an overflow weir 17, a cathode plate 3, an anode plate 4, a three-dimensional electrode filler supporting layer 18, an influent pipe 9, an influent distribution pipe 15, an effluent pipe 13, and a three-dimensional electrode filler 16. The small test experiment device (which is commonly used in the prior art and the principle is not described in detail) is a cuboid column structure with a size of L x B x H = 200 mm x 200 mm x 600 mm and is made of organic glass. The cathode plate 3 and the anode plate 4 are both titanium alloy plates with a size of L x B x H = 180 mm x 4 mm x 400 mm, and the distance between adjacent plates is 59 mm. The stacking height of the three-dimensional electrode filler 16 is the same as the height of the cathode plate 3 and the anode plate 4, which is 400 mm.

[0074] The operation parameters of the electro-catalytic oxidation small test experiment device are shown in Table 1, and the device is continuously operated for 30 days, and the phenol concentration (liquid chromatography) is measured once a day, and the effluent phenol concentration and removal rate are shown in Figure 3 .

[0075] Table 1 Operation parameters of the electro-catalytic oxidation small test experiment device

[0076] Run time period Run parameter 1-10 days HRT = 60 min, current intensity = 80 mA / cm 2 The corresponding direct current voltage is 69.4 V 11-20 days HRT = 60 min, current intensity = 50 mA / cm 2 corresponding direct current 44.1 V 21-30 days HRT = 40 min, current intensity = 50 mA / cm 2 corresponding to a direct current voltage of 44.1 V

[0077] It can be seen from Table 1 and Figure 3 that when HRT = 60 min, current intensity 80 mA / cm 2 , the phenol removal rate of the electro-catalytic oxidation small test experiment device filled with the three-dimensional electrode filler can reach more than 94%, and the effluent phenol concentration is less than 0.3 mg / L. On this basis, further reducing HRT (40 min) and current intensity (50 mA / cm 2), the phenol removal rate of the device can still basically reach more than 90%. In general, under the conditions of reasonable HRT and current intensity, the electro-catalytic oxidation small test device made by using the three-dimensional electrode filler of the application has high removal rate and running stability for phenol.

[0078] Example 6

[0079] Based on the previous example, in order to further verify the long-term running performance of the three-dimensional electrode filler of the application when dealing with real wastewater, the electro-catalytic small test device is optimized and improved to make an electro-catalytic oxidation pilot test device.

[0080] The schematic diagram of the pilot test device is shown in Figure 4 and Figure 5 . It includes a direct current power supply 1, a metal mesh 2, a cathode plate 3, an anode plate 4, an electrode plate unit connection point 5, a jet pipe 6, a backwashing air inlet pipe 7, a backwashing water inlet pipe 8, a water inlet pipe 9, a backwashing water outlet pipe 10, a first electromagnetic valve 11, a second electromagnetic valve 12, a water outlet pipe 13, a backwashing water and air distribution pipe 14, a water distribution pipe 15, and a three-dimensional electrode filler 16. The pilot test device (the applicant has previously applied for a patent based on the device, so the experimental principle is not described in detail) is a cuboid column structure with a size of LxBxH=0.6m x 0.6m x 1.2m and a material of organic glass with a wall thickness of 12mm. The cathode plate unit 3 and the anode plate unit 4 are both titanium alloy plates with a size of LxBxH=150mm x 8mm x 450mm, and the distance between adjacent electrode plates is 63mm. The height of the three-dimensional electrode filler is 1.0m.

[0081] Compared with the previous example, the device modification part is as follows: the overflow weir 17 of example 3 is replaced by the metal mesh 2 to meet the needs of trapping the filler during air-water backwashing; the air-water backwashing system is added; the electrode plate is not a whole titanium alloy plate, but is composed of multiple electrode plate units through the electrode plate unit connection point 5.

[0082] The electro-catalytic oxidation pilot test device takes the effluent of the secondary sedimentation tank of a wastewater treatment plant of a pharmaceutical enterprise as the influent and runs for 150 days. The influent water quality is shown in Table 2, the running parameters are shown in Table 3, the effluent is sampled once every 5 days to detect COD, and the effluent COD concentration and removal rate are shown in Figure 6 .

[0083] Table 2 Influent water quality of electro-catalytic oxidation pilot test device

[0084]

[0085] Table 3 Running conditions of electro-catalytic oxidation pilot test device

[0086]

[0087]

[0088] From the data of Table 2, it can be seen that the B / C of the influent of the pilot plant is 0.28, and the general B / C is below 0.6, which can be considered as poor biodegradability of the water quality, thus it can be considered that the influent of the pilot plant has poor biodegradability, and the COD of the influent is mostly refractory COD. In combination with Table 3 and Figure 6 It can be seen that the pilot plant has the best COD removal performance under the operating conditions of HRT = 60 min and current density = 80 mA / cm 2 (1-50 days), and the effluent COD concentration is all below 15 mg / L. In the following 51-100 days and 101-150 days, the current intensity and HRT are reduced to 50 mA / cm 2 and 40 min respectively, and the effluent COD concentration of the plant can still be stably maintained below 23 mg / L. In general, with the effluent of the secondary sedimentation tank of a wastewater treatment plant of a certain pharmaceutical enterprise as the influent of the pilot plant filled with the three-dimensional electrode filler for electro-catalytic oxidation, under the reasonable operating conditions, the pilot plant has good removal efficiency and operating stability for the refractory COD in the influent during the 150-day operation, and the effluent COD value can stably reach the Class IV water quality standard (Environmental Quality Standard for Surface Water (GB3838-2002)).

[0089] The above has described the present application and its embodiments in a schematic manner, and the description is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person of ordinary skill in the art is inspired thereby, without departing from the purpose of the present application, similar structural modes and embodiments can be designed without creativity, and all of them should belong to the protection scope of the present application.

Claims

1. A method for preparing a three-dimensional electrode filler, characterized in that: The three-dimensional electrode filler for electrocatalysis uses steel slag particles as a carrier and loads a ZnO-CoO composite metal oxide with a mesoporous structure on the steel slag particles; the steel slag particles have a particle size of 3-5 mm, a compressive strength greater than 15 MPa, and a specific surface area greater than 0.5 m 2 / g; The preparation method of the three-dimensional electrode filler includes: The raw steel slag is successively crushed, screened once, autoclaved, cleaned, dried and screened twice to obtain finished steel slag particles as a three-dimensional electrode filler carrier; The ZnO-CoO composite metal oxide with a mesoporous structure is loaded on the finished steel slag particles by hydrothermal impregnation and subsequent heat treatment; The hydrothermal impregnation treatment method specifically includes: S1: Prepare a three-phase mixed solvent of ethylenediamine:ethanolamine:ethanol with a volume ratio of 2:3:2; S2: Dissolve zinc acetate dihydrate and cobalt acetate tetrahydrate in the three-phase mixed solvent prepared in step S1 to form Zn 2+ The concentration of the solution is 1~1.5mol / L, and the Co 2+ Molar concentration of Zn 2+ 1.5 times; S3: heating the finished steel slag particles as a carrier and the solution obtained in step S2 to 150°C respectively, then completely immersing the steel slag particles in the solution, maintaining a constant temperature of 150°C, and vigorously stirring for 15-20 seconds every 5-10 minutes, with the immersion duration being 2-4 hours; S4: The steel slag particles after the immersion treatment in step S3 are separated from the solution, cooled naturally to room temperature, then rinsed with pure water 3 to 4 times, and then dried with 80°C hot air to make its moisture content less than 4%.

2. The method for preparing a three-dimensional electrode filler according to claim 1, wherein: The screening particle size of the primary screening is 10-15 mm, and the screening particle size of the secondary screening is 3-5 mm.

3. The method for preparing a three-dimensional electrode filler according to claim 1, wherein: The pressure of the autoclave process is 2 MPa and the duration is 5 to 6 hours.

4. The method for preparing a three-dimensional electrode filler according to claim 1, wherein: The heat treatment method is specifically to perform a constant temperature heat treatment of 450-470°C on the raw material after the hydrothermal impregnation treatment for 5-8 hours; The heat treatment process also includes a temperature rising process before isothermal heat treatment and a temperature falling process after isothermal heat treatment.

5. The method for preparing a three-dimensional electrode filler according to claim 4, wherein: The heating process before the constant temperature heat treatment is specifically to heat the temperature to 450-470° C. in a linear heating manner, with the heating time being greater than 15 minutes.

6. The method for preparing a three-dimensional electrode filler according to claim 4, wherein: The cooling process after the constant temperature heat treatment is divided into two stages. The first stage is the accelerated cooling stage, cooling to 330°C, and the cooling time is continuously controlled within 20-25 seconds. The second stage is the deceleration cooling stage, which uses linear cooling to room temperature and the cooling duration is greater than 10 minutes.

7. The method for preparing a three-dimensional electrode filler according to claim 6, wherein: The two stages of the cooling process are continuous and uniform.

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