Co-doped composite cathode Fe3O4 / CuO / NiO / Ti and preparation method and application thereof

Abstract

The invention discloses a co-doped composite cathode Fe3O4 / CuO / NiO / Ti and a preparation method and application thereof, and belongs to the technical field of wastewater treatment. The co-doped composite cathode is a multi-element Fe3O4 / CuO / NiO modified titanium plate, and the hydrogen adsorption capacity of the titanium plate cathode can be improved by co-doping Fe3O4 / CuO / NiO, so that the reduction activity of the titanium plate cathode is greatly improved. The prepared co-doped composite cathode is utilized to construct a novel electrochemical reactor, the novel electrochemical reactor is applied to wastewater treatment, absorbable organic halides (AOX) and chemical oxygen demand (COD) in wastewater are efficiently removed and biological acute toxicity is remarkably detoxified in a mode of first reduction and then oxidation, and the treatment process is rapid, efficient and energy-saving.

Description

Technical Field

[0001] The present application belongs to the technical field of wastewater treatment, and specifically relates to a co-doped composite cathode Fe3O4 / CuO / NiO / Ti and a preparation method and application thereof. Background Art

[0002] According to statistics, the world's sewage discharge in 23 years reached 400 billion cubic meters, polluting 5.5 trillion cubic meters of water, accounting for more than 14% of the world's total runoff. Among them, water pollution caused by industrial production is the most serious. It contains many pollutants and has complex components. It is not easy to purify in water and is also difficult to treat. Absorbable halides (AOX) are an important sign of water pollution, including chloride, bromide and iodide, which are carcinogenic and mutagenic. Among the 129 priority pollutants proposed by the US Environmental Protection Agency, organic halides account for about 60%, which has become an international water quality indicator; Chemical oxygen demand (COD) refers to the amount of oxidant consumed when a water sample is treated with a certain strong oxidant under certain conditions. It is an indicator of the content of reducing substances in water, including organic matter, nitrite, ferrous salt and sulfide. In the study of river pollution, industrial wastewater characteristics and the operation and management of wastewater treatment plants, COD is a key and rapidly measurable organic pollution parameter; With the continuous development of industry, the detection of acute biological toxicity of industrial wastewater has become another important link in the evaluation of water environment quality. By comprehensively analyzing the interactions of multiple types of toxic substances, the direct relationship between the biological effects and mass concentrations of toxic substances can be determined, thereby providing an effective scientific basis for the comprehensive evaluation and detection of water quality.

[0003] There are three common treatment processes for various types of wastewater in my country: 1) physical method; 2) chemical method; 3) biological method. Among them, the electrolysis method in the chemical method uses a power supply, an electrolyte and an electrode to form an electrolytic cell. Through an external voltage, the cations in the electrolyte move to the cathode and undergo a reduction reaction at the cathode, and the anions move to the anode and undergo an oxidation reaction at the anode, thereby realizing the conversion of electrical energy into chemical energy. Through the above-mentioned redox reaction, the electrolysis method can achieve the degradation of organic matter in the electrolytic cell and the removal of pollutants such as heavy metals. The electrochemical degradation method is now widely used in various types of wastewater treatment due to its stable performance, recyclability, small footprint of electrolytic cell equipment, low environmental requirements, and convenient operation.

[0004] In the electrolysis method, the anode material is often selected from insoluble materials, including stainless steel and graphite. With the development of electrode materials, the emergence of Ti-based dimensionally stable anode (DSA) electrodes has successfully overcome the shortcomings of easy corrosion of traditional graphite electrodes and high cost of precious metal electrodes. As a new type of electrode material, it has been industrialized and applied; the cathode material is made of conductive materials, commonly copper, aluminum, carbonaceous materials, stainless steel, metal oxides, etc. The cathode is an important component of the electrolytic cell, responsible for accepting electrons and promoting the occurrence of reduction reactions, playing an important role in production capacity and pollutant degradation. Its reduction performance even determines the overall performance of the electrolytic cell to a certain extent. In order to improve the reduction reaction rate of cathode materials, common high-efficiency cathode materials such as platinum (Pt), iridium (Ir) and ruthenium (Ru) are all precious metals. Due to their rarity and high purity requirements, these materials are very expensive, and large-scale industrial application is not realistic; metal oxides such as RuO2 and IrO2 show good stability in the early stage, but their reduction performance may decline rapidly after long-term use. Therefore, the development and design of cathode materials with low cost, high stability and effective catalytic activity are still challenges that need to be overcome. Summary of the invention

[0005] 1. Problem to be solved

[0006] In view of the above problems, the present invention provides a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with high reduction activity and a preparation method and application thereof. Based on the co-doped composite cathode, the present invention constructs a novel electrochemical reactor, which realizes stable and efficient removal of AOX in pharmaceutical wastewater by reduction followed by oxidation, while effectively removing COD and detoxifying acute biological toxicity in the wastewater.

[0007] 2. Technical solution

[0008] The technical solution adopted by the present invention is as follows:

[0009] The invention provides a co-doped composite cathode Fe3O4 / CuO / NiO / Ti, comprising a titanium plate modified with multi-element Fe3O4 / CuO / NiO.

[0010] The present invention provides a method for preparing the co-doped composite cathode Fe3O4 / CuO / NiO / Ti, comprising the following steps:

[0011] S1: Prepare the mixed solution

[0012] Mix 30-60 mL of ethylene glycol, 15-30 mL of polyethylene glycol, 2.0-3.0 g of FeCl3·6H2O, 2.0-3.0 g of CuCl2·2H2O and 2.0-3.0 g of NiCl2·6H2O to obtain a mixed solution;

[0013] S2: coating, drying and calcining

[0014] The mixed solution is coated on a titanium plate, dried at 75-100°C, calcined at 350-600°C for 15-30 minutes, and cooled to room temperature after calcination;

[0015] Repeat the coating, drying and calcining operations until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0016] Furthermore, in the above-mentioned mixed solution, ethylene glycol is 30ml, 40ml, 50ml or 60ml.

[0017] Furthermore, in the above-mentioned mixed solution, the polyethylene glycol is 10ml, 15ml, 20ml or 30ml.

[0018] Furthermore, in the above-mentioned mixed solution, FeCl3·6H2O is 1.5g, 2.0g, 2.5g or 3.0g.

[0019] Furthermore, in the above-mentioned mixed solution, CuCl2·2H2O is 1.5g, 2.0g, 2.5g or 3.0g.

[0020] Furthermore, in the above-mentioned mixed solution, NiCl2·6H2O is 1.5g, 2.0g, 2.5g or 3.0g.

[0021] Furthermore, the preparation method of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti comprises the following steps:

[0022] S1: Prepare the mixed solution

[0023] 30 mL of ethylene glycol, 10 mL of polyethylene glycol, 1.5 g of FeCl3·6H2O, 1.5 g of CuCl2·2H2O and 1.5 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0024] S2: coating, drying and calcining

[0025] The mixed solution was coated on a titanium plate several times, dried in an oven at 90°C, calcined at 450°C for 20 min, and cooled to room temperature after calcination;

[0026] The coating, drying and calcining operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0027] Furthermore, the preparation method of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti comprises the following steps:

[0028] S1: Prepare the mixed solution

[0029] 40 mL of ethylene glycol, 15 mL of polyethylene glycol, 2.0 g of FeCl3·6H2O, 2.0 g of CuCl2·2H2O and 2.0 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0030] S2: coating, drying and calcining

[0031] The mixed solution was coated on a titanium plate several times, dried at 90°C, calcined at 400°C for 15 min, and cooled to room temperature after calcination;

[0032] The coating, drying and calcining operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0033] Furthermore, the preparation method of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti comprises the following steps:

[0034] S1: Prepare the mixed solution

[0035] 50 mL of ethylene glycol, 20 mL of polyethylene glycol, 2.5 g of FeCl3·6H2O, 2.5 g of CuCl2·2H2O and 2.5 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0036] S2: coating, drying and calcining

[0037] The mixed solution was coated on a titanium plate several times, dried at 90°C, calcined at 450°C for 20 min, and cooled to room temperature after calcination;

[0038] The coating, drying and calcining operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0039] Furthermore, the preparation method of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti comprises the following steps:

[0040] S1: Prepare the mixed solution

[0041] 60 mL of ethylene glycol, 30 mL of polyethylene glycol, 3.0 g of FeCl3·6H2O, 3.0 g of CuCl2·2H2O and 3.0 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0042] S2: coating, drying and calcining

[0043] The mixed solution was coated on a titanium plate several times, dried at 90°C, calcined at 450°C for 20 min, and cooled to room temperature after calcination;

[0044] The coating, drying and calcining operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0045] The present invention also provides an electrochemical reactor, which comprises the above-mentioned co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0046] Furthermore, the cathode region and the anode region of the electrochemical reactor are separated by a proton exchange membrane, the distance between the anode and the proton exchange membrane is 1 to 5 mm, and the distance between the cathode and the proton exchange membrane is 1 to 5 mm.

[0047] Furthermore, the distance between the anode and the proton exchange membrane of the reactor is 2.5 mm, and the distance between the cathode and the proton exchange membrane is 2.5 mm.

[0048] Furthermore, the distance between the anode and the proton exchange membrane of the reactor is 2.0 mm, and the distance between the cathode and the proton exchange membrane is 2.0 mm.

[0049] The present invention also provides the use of the above-mentioned co-doped composite cathode Fe3O4 / CuO / NiO / Ti and / or the above-mentioned electrochemical reactor in wastewater treatment, and the application includes the removal of AOX, COD and detoxification of acute biological toxicity in wastewater.

[0050] Furthermore, the application of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti and / or the electrochemical reactor in wastewater treatment comprises the following steps:

[0051] S1: Setting reaction conditions

[0052] Reaction volume: The volume ratio of the anode region and the cathode region is 1:1;

[0053] Reaction time: The total time is 150-200 minutes, and the ratio of the reaction time of the cathode area and the anode area is (1.5-2): (1-1.5);

[0054] Voltage: 8~15V;

[0055] Current: 10~20mA / cm 2 ;

[0056] Sulfate electrolyte concentration: 0.025~0.1mM;

[0057] pH: 7-9;

[0058] S2: Wastewater treatment

[0059] The wastewater is firstly pumped into the cathode region from the water inlet tank by the water inlet pump for reduction reaction, and then pumped to the anode region by the reflux pump for oxidation reaction, and then discharged through the water outlet after the reaction is completed.

[0060] Furthermore, in the above S1, the reaction conditions are set as follows:

[0061] Voltage: 12V;

[0062] Current: 12mA / cm 2 ;

[0063] Sulfate electrolyte concentration: 0.05mM;

[0064] pH:8.

[0065] The present invention also provides a wastewater treatment method, which uses the above electrochemical reactor and comprises the following steps:

[0066] S1: Setting reaction conditions

[0067] Reaction volume: The volume ratio of the anode region and the cathode region is 1:1;

[0068] Reaction time: The total time is 150-200 minutes, and the ratio of the reaction time of the cathode area and the anode area is (1.5-2): (1-1.5);

[0069] Voltage: 8~15V;

[0070] Current: 10~20mA / cm 2 ;

[0071] Sulfate electrolyte concentration: 0.025~0.1mM;

[0072] pH: 7-9;

[0073] S2: Wastewater treatment

[0074] The wastewater is firstly pumped into the cathode region from the water inlet tank by the water inlet pump for reduction reaction, and then pumped to the anode region by the reflux pump for oxidation reaction, and then discharged through the water outlet after the reaction is completed.

[0075] Furthermore, in the above S1, the reaction conditions are set as follows:

[0076] Voltage: 12V;

[0077] Current: 12mA / cm 2 ;

[0078] Sulfate electrolyte concentration: 0.05mM;

[0079] pH:8.

[0080] 3. Beneficial effects

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] (1) The present invention adopts a co-doped composite cathode Fe3O4 / CuO / NiO, which can improve the hydrogen adsorption capacity of the titanium plate cathode and greatly enhance its reduction activity. AOX is converted from antioxidant organic matter into easily oxidizable reduction products at the cathode with high reduction activity, and then degraded through the oxidation action of the anode, thereby effectively improving the removal rate of AOX in wastewater, and even stabilizing it to close to 100%.

[0083] (2) The novel electrochemical reactor constructed based on the co-doped composite cathode Fe3O4 / CuO / NiO / Ti of the present invention adopts a reduction-before-oxidation method to achieve a COD removal rate of more than 75% in wastewater, and a detoxification effect that can be stabilized at more than 90%, thereby effectively reducing the emission of harmful substances in wastewater.

[0084] (3) The novel electrochemical reactor constructed based on the co-doped composite cathode Fe3O4 / CuO / NiO / Ti of the present invention does not require the addition of additional oxidants in the treatment process and is not prone to secondary pollution; the entire operation is simple and convenient, reducing the cost of manpower and material resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 It is a schematic diagram of the process flow of treating AOX in pharmaceutical wastewater using an electrochemical reactor. DETAILED DESCRIPTION

[0086] The present invention is further described below in conjunction with specific embodiments.

[0087] It should be noted that the terms such as "upper", "lower", "left", "right", "middle", etc. cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of this application without substantially changing the technical content.

[0088] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0089] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0090] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement or value. The degree of flexibility for a particular variable can be easily determined by one skilled in the art.

[0091] As used herein, the term "at least one of" is intended to be synonymous with "one or more of." For example, "at least one of A, B, and C" expressly includes only A, only B, only C, and combinations of each thereof.

[0092] Concentration, amount and other numerical data can be presented in range format herein.It should be understood that such range format is only used for convenience and simplicity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all single numerical values ​​or sub-ranges contained in the range, just as each numerical value and sub-range are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including single numerals (such as 2,3,4) and sub-ranges (such as 1 to 3,2 to 4, etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5", which should be interpreted as including all the above-mentioned values ​​and ranges.In addition, no matter how the breadth of the described range or feature is, this explanation should be applicable.

[0093] The detection methods of each index in the embodiment are as follows:

[0094] AOX test method: HJ / T 83-2001;

[0095] COD detection method: HJ / T399-2007;

[0096] Biological acute toxicity test method: GB / T 15441-1995.

[0097] Example 1

[0098] This embodiment provides a method for preparing a co-doped composite cathode Fe3O4 / CuO / NiO / Ti and its application in wastewater treatment, comprising the following steps:

[0099] (1) Preparation of co-doped composite cathode Fe3O4 / CuO / NiO / Ti

[0100] S1: Mix 50 mL of ethylene glycol, 20 mL of polyethylene glycol, 2.5 g of FeCl3·6H2O, 2.5 g of CuCl2·2H2O and 2.5 g of NiCl2·6H2O;

[0101] S2: The mixed solution was coated on a titanium plate several times, dried in an oven at 90°C, calcined in a muffle furnace at 450°C for 20 min, and cooled to room temperature after calcination; the coating, drying and calcination operations were repeated until the mixed solution was exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0 cm;

[0102] S3: Cool the prepared co-doped composite cathode Fe3O4 / CuO / NiO / Ti to room temperature and then seal and store it for later use.

[0103] (2) Construction and operation of new electrochemical reactors

[0104] The anode used DSA material (purchased from Ileka Electrochemical Space Station, ruthenium iridium titanium electrode) with the same size of 12.0×6.0 cm.

[0105] The co-doped composite cathode Fe3O4 / CuO / NiO / Ti and the DSA anode material are used as the cathode and anode of the new electrochemical reactor; the reactor is separated by a proton exchange membrane (purchased from the Lurton electrochemical flagship store), and the distance between the anode and the proton exchange membrane is set to 2.5 mm, and the distance between the cathode and the proton exchange membrane is set to 2.5 mm. The volume ratio of the anode area and the cathode area separated by the above exchange membrane is 1:1. The reaction conditions are optimized as follows:

[0106] a. Current density and voltage

[0107] Set current density: 10, 12, 15, 18, 20 mA / cm 2 The corresponding voltages are 9, 12, 15, 18, and 20 V, respectively. The concentration of the sulfate electrolyte is 0.05 mM, and the pH is 7.5. The above conditions are used for wastewater treatment (the wastewater in the present invention is derived from fermentation pharmaceutical wastewater). When the voltage is 12 V, the corresponding current density is 12 mA / cm 2 The treatment effect is best when the AOX removal rate in the wastewater is 98.2%, the COD removal rate is 79.4%, and the biological acute toxicity is reduced from highly toxic to non-toxic.

[0108] b. Electrolyte concentration

[0109] Select the above current density 12mA / cm 2 , voltage 12V, selected sulfate electrolyte concentrations of 0.025, 0.05, 0.75, 0.1, 0.15mM, pH 7.5, respectively, for wastewater treatment. When the sulfate electrolyte concentration was 0.05mM, the wastewater treatment effect was best. The AOX removal rate in the wastewater was 99.3%, the COD removal rate was 81.9%, and the acute biological toxicity was reduced from highly toxic to non-toxic.

[0110] c. pH

[0111] Select the above current density 12mA / cm 2 , voltage 12V, sulfate electrolyte concentration 0.05mM, set the pH to 6.5, 7, 7.5, 8, and 8.5, and treat the wastewater respectively. When the pH is 8, the treatment effect is best. The removal rate of AOX in the wastewater is 99.5%, the COD removal rate is 82.2%, and the acute biological toxicity is reduced from highly toxic to non-toxic.

[0112] d. Processing time

[0113] Select the above current density 12mA / cm 2 , voltage 12V, sulfate electrolyte concentration 0.05mM, pH set to 8, total reaction time is 180min, among which the cathode reduction time is set to 10, 30, 60, 90, 120, 150, 180min, and the corresponding anode oxidation time is 170, 150, 120, 90, 30, 0min respectively. The wastewater is treated according to the above time. When the cathode reduction time is 120min and the anode oxidation time is 60min, the treatment effect is best. The removal rate of AOX in the wastewater is 99.8%, the COD removal rate is 83.1%, and the acute biological toxicity is reduced from high toxicity to non-toxic.

[0114] Based on the above, the wastewater treatment conditions were finally set as: current density 12mA / cm 2 , voltage 12V, sulfate electrolyte concentration 0.05mM, pH 8, cathode area reduction reaction time 120min, anode area oxidation reaction time 60min.

[0115] (3) Wastewater treatment

[0116] like Figure 1 As shown, after the pharmaceutical wastewater is injected into the water inlet pool, it is first pumped into the cathode area by the water inlet pump for reduction reaction for 120 minutes, and then pumped to the anode area by the reflux pump for oxidation reaction for 60 minutes. After the reaction is completed, it is discharged through the outlet.

[0117] After the above treatment, the removal rate of AOX in pharmaceutical wastewater was 99.6%, the removal rate of COD was 82.6%, and the acute biological toxicity was reduced from high toxicity to non-toxicity.

[0118] Example 2

[0119] This embodiment provides a method for preparing a co-doped composite cathode Fe3O4 / CuO / NiO / Ti and its application in wastewater treatment, comprising the following steps:

[0120] (1) Preparation of co-doped composite cathode Fe3O4 / CuO / NiO / Ti

[0121] S1: 40 mL of ethylene glycol, 15 mL of polyethylene glycol, 2.0 g of FeCl3·6H2O, 2.0 g of CuCl2·2H2O and 2.0 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0122] S2: coating the mixed solution on a titanium plate multiple times, drying it in an oven at 90°C, calcining it in a muffle furnace at 400°C for 15 minutes, and cooling it to room temperature after calcination; repeating the coating, drying and calcining operations until the mixed solution is exhausted, to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0 cm;

[0123] S3: Cool the manufactured co-doped composite cathode to room temperature and then seal it for storage.

[0124] (2) Construction and operation of new electrochemical reaction system

[0125] The anode material is the same as in Example 1.

[0126] Differences between the construction and operation of the novel electrochemical reaction system: In Example 1, the distance between the anode and the proton exchange membrane is set to 2.0 mm, the distance between the cathode and the proton exchange membrane is set to 2.0 mm, and the rest is the same as in Example 1.

[0127] (3) Wastewater treatment

[0128] The wastewater treatment process is the same as in Example 1.

[0129] After the above treatment, the removal rate of AOX in the wastewater was 97.8%, the removal rate of COD was 78.9%, and the acute biological toxicity was reduced from high toxicity to non-toxicity.

[0130] Example 3

[0131] This embodiment provides a method for preparing a co-doped composite cathode Fe3O4 / CuO / NiO / Ti and its application in wastewater treatment, comprising the following steps:

[0132] (1) Preparation of co-doped composite cathode Fe3O4 / CuO / NiO / Ti

[0133] S1: 60 mL of ethylene glycol, 30 mL of polyethylene glycol, 3.0 g of FeCl3·6H2O, 3.0 g of CuCl2·2H2O and 3.0 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0134] S2: coating the mixed solution on a titanium plate multiple times, drying it in an oven at 90°C, calcining it in a muffle furnace at 450°C for 20 minutes, and cooling it to room temperature after calcination; repeating the coating, drying and calcining operations until the mixed solution is exhausted, to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0 cm;

[0135] S3: Cool the manufactured co-doped composite cathode to room temperature and then seal it for storage.

[0136] (2) Construction and operation of new electrochemical reaction system

[0137] The anode material is the same as in Example 1.

[0138] The construction and operation are the same as Example 1.

[0139] (3) Wastewater treatment

[0140] The wastewater treatment process is the same as in Example 1.

[0141] After the above treatment, the removal rate of AOX in the wastewater was 93.2%, the removal rate of COD was 75.1%, and the acute biological toxicity was reduced from high toxicity to non-toxicity.

[0142] Example 4

[0143] This embodiment provides a method for preparing a co-doped composite cathode Fe3O4 / CuO / NiO / Ti and its application in wastewater treatment, comprising the following steps:

[0144] (1) Preparation of co-doped composite cathode Fe3O4 / CuO / NiO / Ti

[0145] S1: 30 mL of ethylene glycol, 10 mL of polyethylene glycol, 1.5 g of FeCl3·6H2O, 1.5 g of CuCl2·2H2O and 1.5 g of NiCl2·6H2O were mixed to obtain a mixed solution;

[0146] S2: coating the mixed solution on a titanium plate multiple times, drying it in an oven at 90°C, calcining it in a muffle furnace at 450°C for 20 min, and cooling it to room temperature after calcination; repeating the coating, drying and calcining operations until the mixed solution is exhausted, to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0 cm;

[0147] S3: Cool the manufactured co-doped composite cathode to room temperature and then seal it for storage.

[0148] (2) Construction and operation of new electrochemical reaction system

[0149] The anode material is the same as in Example 1.

[0150] The construction and operation are the same as Example 1.

[0151] (3) Wastewater treatment results

[0152] The wastewater treatment process is the same as in Example 1.

[0153] After the above treatment, the removal rate of AOX in the wastewater was 89.3%, the removal rate of COD was 69.6%, and the acute biological toxicity was reduced from high toxicity to low toxicity.

[0154] Comparative Example 1

[0155] This comparative example provides several methods for preparing co-doped composite cathodes and their applications in wastewater treatment, comprising the following steps:

[0156] (1) Preparation of several co-doped composite cathodes

[0157] Preparation of CuO / NiO / Ti co-doped composite cathode The difference between the mixed solution prepared in Example 1 and the mixed solution prepared in Example 1 does not contain FeCl3·6H2O, and the other operations are the same as those in Example 1;

[0158] Fe3O 4 / Preparation of NiO / Ti co-doped composite cathode The difference between the prepared mixed solution in Example 1 does not contain CuCl2·2H2O, and the other operations are the same as in Example 1;

[0159] Preparation of Fe3O4 / CuO / Ti co-doped composite cathode The difference between the prepared mixed solution in Example 1 does not contain NiCl2·6H2O, and the other operations are the same as in Example 1;

[0160] Preparation of Fe3O4 / Ti co-doped composite cathode is different from Example 1 in that the prepared mixed solution does not contain CuCl2·2H2O and NiCl2·6H2O, and other operations are the same as Example 1;

[0161] The preparation of the NiO / Ti co-doped composite cathode is different from that in Example 1, the prepared mixed solution does not contain FeCl3·6H2O and CuCl2·2H2O, and the other operations are the same as Example 1.

[0162] (2) Construction and operation of new electrochemical reaction system

[0163] The anode material is the same as in Example 1.

[0164] The construction and operation are the same as Example 1.

[0165] (3) The wastewater treatment process is the same as in Example 1. The treatment results are shown in Table 1 below.

[0166] Table 1

[0167] Co-doped composite cathode AOX removal efficiency COD removal rate Acute toxicity <![CDATA[Fe3O4 / CuO / NiO / Ti]]> 99.6％ 82.6％ Non-toxic CuO / NiO / Ti 74.2％ 52.6％ Low to medium toxicity <![CDATA[Fe3O4 / NiO / Ti]]> 78.8％ 55.7％ Low to medium toxicity <![CDATA[Fe3O4 / CuO / Ti]]> 76.5％ 54.3％ Low to medium toxicity <![CDATA[Fe3O4 / Ti]]> 60.8％ 41.7％ Medium to high poisoning NiO / Ti 58.3％ 39.4％ Medium to high poisoning

[0168] It can be seen from Table 1 that compared with the application of electrochemical reactors constructed with several co-doped composite cathodes in the comparative example in wastewater treatment, the co-doped composite cathode Fe3O4 / CuO / NiO / Ti provided by the present invention has a higher removal rate of AOX and COD in wastewater treatment, wherein the removal rate of AOX reaches 99.6%, and the removal rate of COD reaches 82.6%; the co-doped composite cathode Fe3O4 / CuO / NiO / Ti provided by the present invention also has a better detoxification effect on acute biological toxicity in wastewater, and can be non-toxic after treatment.

[0169] Comparative Example 2

[0170] This comparative example provides an application of an electrochemical reactor of an oxidation-reduction, synchronous reduction-oxidation, reduction-oxidation reaction system constructed by a co-doped composite cathode Fe3O4 / CuO / NiO / Ti in wastewater treatment, comprising the following steps:

[0171] (1) The preparation of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti is the same as in Example 1 above.

[0172] (2) Construction and operation of electrochemical reactors of different systems

[0173] The oxidation-reduction reaction system is to separate the reactor with a proton exchange membrane, the distance between the anode and the exchange membrane is 2.5 mm, and the distance between the cathode and the exchange membrane is 2.5 mm. The volume ratio of the anode area and the cathode area separated by the exchange membrane is 1:1. When used, the wastewater is first oxidized and then reduced by passing through the anode area and the cathode area in sequence. The voltage is set to 12V and the current is set to 12mA / cm 2 The concentration of the sulfate electrolyte used was 0.05 mM, pH 8, and the total reaction time was 180 min, of which the reaction times of the anode and cathode regions were 120 min and 60 min, respectively;

[0174] The synchronous reduction-oxidation reaction system is different from the above-mentioned oxidation-reduction reaction system. The reactor is not separated by a proton exchange membrane. The reaction is carried out under the same volume, the reaction time is 180 minutes, and other reaction conditions are the same.

[0175] The reduction and oxidation reaction systems reacted only in the corresponding cathode region and the corresponding anode region for 180 min, and other reaction conditions were the same.

[0176] (3) The results of the reactor wastewater treatment of the above-mentioned different systems are shown in Table 2 below

[0177] Table 2

[0178] Reaction system AOX removal efficiency COD removal rate Acute toxicity Reduction followed by oxidation 99.6％ 82.6％ Non-toxic Oxidation followed by reduction 78.2％ 58.3％ Low toxicity Synchronous reduction oxidation 55.2％ 34.8％ Elevated reduction 92.3％ 40.1％ Poisoning Oxidation 68.7％ 54.6％ Medium to high poisoning

[0179] It can be seen from Table 2 that compared with the reduction-then-oxidation reaction system constructed by the co-doped composite cathode Fe3O4 / CuO / NiO / Ti in the present invention, the reactors of the oxidation-then-reduction, simultaneous reduction-oxidation, and reduction and oxidation reaction systems in this comparative example have lower removal rates for AOX and COD in the wastewater; the reactors of the above-mentioned reaction systems can only achieve low toxicity at best for the detoxification effect of acute biological toxicity in the wastewater, and cannot achieve the non-toxic effect after treatment by the reduction-then-oxidation reaction system in the present invention.

Claims

1. A co-doped composite cathode Fe3O4 / CuO / NiO / Ti, characterized in that: The cathode includes a Fe3O4 / CuO / NiO modified titanium plate.

2. The method for preparing the co-doped composite cathode Fe3O4 / CuO / NiO / Ti according to claim 1, characterized in that: The following steps are involved: S1: Prepare the mixed solution Mix 30-60 mL of ethylene glycol, 10-30 mL of polyethylene glycol, 1.5-3.0 g of FeCl3·6H2O, 1.5-3.0 g of CuCl2·2H2O and 1.5-3.0 g of NiCl2·6H2O to obtain a mixed solution; S2: coating, drying and calcining The mixed solution is coated on a titanium plate, dried at 75-100° C., calcined at 350-600° C. for 15-30 min, and cooled to room temperature after calcination; The coating, drying and calcining operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

3. The method for preparing the co-doped composite cathode Fe3O4 / CuO / NiO / Ti as claimed in claim 2, characterized in that: In the mixed solution, 30ml, 40ml, 50ml or 60ml of ethylene glycol; and / or 10ml, 15ml, 20ml or 30ml of polyethylene glycol; and / or FeCl3·6H2O is 1.5g, 2.0g, 2.5g or 3.0g; and / or CuCl2·2H2O is 1.5g, 2.0g, 2.5g or 3.0g; and / or NiCl2·6H2O is 1.5g, 2.0g, 2.5g or 3.0g.

4. The method for preparing the co-doped composite cathode Fe3O4 / CuO / NiO / Ti as claimed in claim 2 or 3, characterized in that: In the preparation method, S1: Prepare the mixed solution 30 mL of ethylene glycol, 10 mL of polyethylene glycol, 1.5 g of FeCl3·6H2O, 1.5 g of CuCl2·2H2O and 1.5 g of NiCl2·6H2O were mixed to obtain a mixed solution; S2: coating, drying and calcining The mixed solution is coated on a titanium plate for multiple times, dried at 90° C., calcined at 450° C. for 20 min, and cooled to room temperature after calcination; Repeat the coating, drying and calcining operations until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti; or S1: Prepare the mixed solution 40 mL of ethylene glycol, 15 mL of polyethylene glycol, 2.0 g of FeCl3·6H2O, 2.0 g of CuCl2·2H2O and 2.0 g of NiCl2·6H2O were mixed to obtain a mixed solution; S2: coating, drying and calcining The mixed solution is coated on a titanium plate for multiple times, dried at 90°C, calcined at 400°C for 15 minutes, and cooled to room temperature after calcination; Repeat the coating, drying and calcining operations until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti; or S1: Prepare the mixed solution 50 mL of ethylene glycol, 20 mL of polyethylene glycol, 2.5 g of FeCl3·6H2O, 2.5 g of CuCl2·2H2O and 2.5 g of NiCl2·6H2O were mixed to obtain a mixed solution; S2: coating, drying and calcining The mixed solution is coated on a titanium plate for multiple times, dried at 90° C., calcined at 450° C. for 20 min, and cooled to room temperature after calcination; Repeat the coating, drying and calcining operations until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti; or S1: Prepare the mixed solution 60 mL of ethylene glycol, 30 mL of polyethylene glycol, 3.0 g of FeCl3·6H2O, 3.0 g of CuCl2·2H2O and 3.0 g of NiCl2·6H2O were mixed to obtain a mixed solution; S2: coating, drying and calcining The mixed solution is coated on a titanium plate for multiple times, dried at 90° C., calcined at 450° C. for 20 min, and cooled to room temperature after calcination; The coating, drying and calcining operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

5. An electrochemical reactor, characterized in that: The electrochemical reactor comprises the co-doped composite cathode Fe3O4 / CuO / NiO / Ti as described in claim 1.

6. The electrochemical reactor according to claim 5, characterized in that: The cathode region and the anode region of the reactor are separated by a proton exchange membrane. The distance between the anode of the reactor and the proton exchange membrane is 1 to 5 mm, and the distance between the cathode and the proton exchange membrane is 1 to 5 mm.

7. The electrochemical reactor according to claim 6, characterized in that: The distance between the reactor anode and the proton exchange membrane is 2.5 mm, and the distance between the cathode and the proton exchange membrane is 2.5 mm; or The distance between the anode of the reactor and the proton exchange membrane is 2.0 mm, and the distance between the cathode and the proton exchange membrane is 2.0 mm.

8. The co-doped composite cathode Fe3O4 / CuO / NiO / Ti according to claim 1, the preparation method of the co-doped composite cathode Fe3O4 / CuO / NiO / Ti according to any one of claims 2-4, and the use of the electrochemical reactor according to any one of claims 5-7 in wastewater treatment, characterized in that: It includes the removal of AOX in wastewater, the removal of COD and the detoxification of acute biological toxicity.

9. The use according to claim 8, characterized in that The following steps are involved: S1: Setting reaction conditions Reaction volume: the volume ratio of the anode region to the cathode region is 1:1; and / or Reaction time: 150-200 min, the ratio of cathode area to anode area reaction time is (1.5-2): (1-1.5); and / or Voltage: 8-15V; and / or Current: 10~20mA / cm 2 ; and / or Electrolyte concentration: 0.025-0.1 mM; and / or pH: 7-9; S2: Wastewater treatment The wastewater first enters the cathode region for reduction reaction, then enters the anode region for oxidation reaction, and is discharged through the outlet after the reaction is completed.

10. A method for treating wastewater, characterized in that: The treatment method uses the electrochemical reactor according to any one of claims 5 to 7, comprising the following steps: S1: Setting reaction conditions Reaction volume: the volume ratio of the anode region to the cathode region is 1:1; and / or Reaction time: 150-200 min, the ratio of cathode area to anode area reaction time is (1.5-2): (1-1.5); and / or Voltage: 8-15V; and / or Current: 10~20mA / cm 2 ; and / or Electrolyte concentration: 0.025-0.1 mM; and / or pH: 7-9; S2: Wastewater treatment The wastewater first enters the cathode region for reduction reaction, then enters the anode region for oxidation reaction, and is discharged through the outlet after the reaction is completed.

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