A co-doped composite cathode Fe3O4 / CuO / NiO / Ti and a preparation method and application thereof

Abstract

The application discloses a kind of co-doped composite cathode Fe3O4 / CuO / NiO / Ti and preparation method and application thereof, belong to wastewater treatment technical field.The co-doped composite cathode is the titanium plate of multi-element Fe3O4 / CuO / NiO modification, and the hydrogen absorption capacity of titanium plate cathode can be improved by co-doping Fe3O4 / CuO / NiO, so that its reduction activity is greatly increased.The application constructs a new type of electrochemical reactor using the prepared co-doped composite cathode, which is applied in wastewater treatment, and by the way of reduction first and then oxidation, realizes efficient removal of absorbable organic halide (AOX) and chemical oxygen demand (COD) in wastewater and significant detoxification of biological acute toxicity, and the treatment process is fast, efficient and energy-saving.

Description

Technical Field

[0001] This application belongs to the field of wastewater treatment technology, specifically relating to a co-doped composite cathode Fe3O4 / CuO / NiO / Ti, its preparation method, and its application. Background Technology

[0002] According to statistics, the world's wastewater discharge reached 400 billion cubic meters in 23 years, polluting 5.5 trillion cubic meters of water bodies, 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, has a complex composition, is not easy to purify in water, and is also relatively difficult to treat. Absorbable halides (AOX) are an important indicator of water pollution, including chlorides, bromides, and iodides. They are carcinogenic and mutagenic. Among the 129 priority pollutants proposed by the U.S. Environmental Protection Agency, organohalides account for about 60%, and have become an international water quality indicator. Chemical oxygen demand (COD) refers to the amount of oxidant consumed when treating a water sample 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 salts, and sulfides. In the study of river pollution, the characteristics of industrial wastewater, and the operation and management of wastewater treatment plants, COD is a key and rapidly measurable parameter of organic pollution. With the continuous development of industry, acute biological toxicity testing of industrial wastewater has become another important link in evaluating water environmental quality. By comprehensively considering the interactions of multiple toxic substances, the direct relationship between the biological effects and mass concentration of toxic substances can be determined, thus providing effective scientific basis for the comprehensive evaluation and testing of water quality.

[0003] There are three main categories of common wastewater treatment processes in my country: 1) physical methods; 2) chemical methods; and 3) biological methods. Among these, electrolysis, a chemical method, utilizes an electrolytic cell composed of a power source, electrolyte, and electrodes. By applying an external voltage, cations in the electrolyte move towards the cathode and undergo reduction reactions, while anions move towards the anode and undergo oxidation reactions, thus converting electrical energy into chemical energy. Through these redox reactions, electrolysis can degrade organic matter and remove pollutants such as heavy metals from the electrolytic cell. Currently, electrochemical degradation methods are widely used in various wastewater treatment processes due to their stable performance, recyclability, small footprint of the electrolytic cell equipment, low environmental requirements, and ease of operation.

[0004] In electrolysis, insoluble materials, including stainless steel and graphite, are often chosen as anode materials. With the development of electrode materials, the emergence of Ti-based size-stabilized anode (DSA) electrodes has successfully overcome the shortcomings of traditional graphite electrodes (easily corroded) and precious metal electrodes (high cost). As a novel electrode material, it has achieved industrial production and application. Cathode materials are made of conductive materials, commonly including copper, aluminum, carbonaceous materials, stainless steel, and metal oxides. As a crucial component of the electrolytic cell, the cathode is responsible for accepting electrons and promoting reduction reactions, playing a vital role in energy production and pollutant degradation. Its reduction performance even determines, to a certain extent, the overall performance of the electrolytic cell. 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, making large-scale industrial application impractical. Metal oxides such as RuO2 and IrO2 exhibit good stability initially, but their reduction performance may rapidly decline after long-term use. Therefore, the development and design of cathode materials that are cost-effective, highly stable, and have effective catalytic activity remains a challenge to overcome. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the aforementioned problems, this invention provides a highly reducing-active co-doped composite cathode Fe3O4 / CuO / NiO / Ti, its preparation method, and its application. Based on this co-doped composite cathode, this invention constructs a novel electrochemical reactor that achieves stable and efficient removal of AOX from pharmaceutical wastewater through a reduction-oxidation process, while also effectively removing COD and detoxifying the wastewater by addressing acute biological toxicity.

[0007] 2. Technical Solution

[0008] The technical solution adopted in this invention is as follows:

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

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

[0011] S1: Preparation of the mixture

[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 calcination

[0014] The above mixture was coated onto a titanium plate, dried at 75–100°C, calcined at 350–600°C for 15–30 min, and then cooled to room temperature.

[0015] The coating, drying, and calcination processes were repeated until the above mixture was exhausted, resulting in a co-doped composite cathode of Fe3O4 / CuO / NiO / Ti.

[0016] Furthermore, in the above mixture, the amount of ethylene glycol is 30 ml, 40 ml, 50 ml, or 60 ml.

[0017] Furthermore, in the above mixture, the amount of polyethylene glycol is 10 ml, 15 ml, 20 ml, or 30 ml.

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

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

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

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

[0022] S1: Preparation of the mixture

[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 calcination

[0025] The above mixture was coated onto a titanium plate multiple times, dried in an oven at 90°C, calcined at 450°C for 20 minutes, and then cooled to room temperature.

[0026] Repeat the coating, drying, and calcination processes until the above mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

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

[0028] S1: Preparation of the mixture

[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 calcination

[0031] The above mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 400°C for 15 minutes, and then cooled to room temperature.

[0032] Repeat the coating, drying, and calcination processes until the above mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

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

[0034] S1: Preparation of the mixture

[0035] 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 to obtain a mixed solution;

[0036] S2: Coating, drying and calcination

[0037] The above mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 450°C for 20 minutes, and then cooled to room temperature.

[0038] Repeat the coating, drying, and calcination processes until the above mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

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

[0040] S1: Preparation of the mixture

[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 calcination

[0043] The above mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 450°C for 20 minutes, and then cooled to room temperature.

[0044] Repeat the coating, drying, and calcination processes until the above mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0045] The present invention also provides an electrochemical reactor comprising the aforementioned co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

[0046] Furthermore, the cathode region and anode region of the above-mentioned electrochemical reactor are separated by a proton exchange membrane, with the distance between the anode and the proton exchange membrane being 1-5 mm and the distance between the cathode and the proton exchange membrane being 1-5 mm.

[0047] Furthermore, the distance between the anode and the proton exchange membrane of the above 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 above 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 application of the above-mentioned co-doped composite cathode Fe3O4 / CuO / NiO / Ti and / or the above-mentioned electrochemical reactor in wastewater treatment, the application including the removal of AOX, the removal of COD and the detoxification of acute biological toxicity in wastewater.

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

[0051] S1: Set reaction conditions

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

[0053] Reaction time: The total time is 150-200 min, and the ratio of reaction time in the cathode area to that in the anode area is (1.5-2):(1-1.5).

[0054] Voltage: 8~15V;

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

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

[0057] pH: 7–9;

[0058] S2: Wastewater Treatment

[0059] The wastewater is first pumped from the inlet pool into the cathode area for reduction reaction by an inlet pump, and then pumped to the anode area for oxidation reaction by a reflux pump. After the reaction is completed, it is discharged through the outlet.

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

[0061] Voltage: 12V;

[0062] Current: 12mA / cm 2 ;

[0063] Sulfate electrolyte concentration: 0.05 mM;

[0064] pH: 8.

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

[0066] S1: Set reaction conditions

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

[0068] Reaction time: The total time is 150-200 min, and the ratio of reaction time in the cathode area to that in the anode area is (1.5-2):(1-1.5).

[0069] Voltage: 8~15V;

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

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

[0072] pH: 7–9;

[0073] S2: Wastewater Treatment

[0074] The wastewater is first pumped from the inlet pool into the cathode area for reduction reaction by an inlet pump, and then pumped to the anode area for oxidation reaction by a reflux pump. After the reaction is completed, it is discharged through the outlet.

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

[0076] Voltage: 12V;

[0077] Current: 12mA / cm 2 ;

[0078] Sulfate electrolyte concentration: 0.05 mM;

[0079] pH: 8.

[0080] 3. Beneficial effects

[0081] Compared with the prior art, the advantages of this invention are as follows:

[0082] (1) The present invention uses 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 transformed from antioxidant organic matter into easily oxidized reduction products in the cathode with high reduction activity, and then degraded through the oxidation of the anode, effectively improving the removal rate of AOX in wastewater, and even stabilizing close to 100%.

[0083] (2) The novel electrochemical reactor constructed based on the above co-doped composite cathode Fe3O4 / CuO / NiO / Ti can achieve a COD removal efficiency of over 75% and a detoxification efficiency of over 90% in wastewater by adopting a reduction-oxidation method, which effectively reduces the discharge of harmful substances in wastewater.

[0084] (3) The novel electrochemical reactor constructed based on the above co-doped composite cathode Fe3O4 / CuO / NiO / Ti does not require the addition of oxidant in the processing technology, and is not prone to secondary pollution; the whole operation is simple and convenient, reducing the cost of manpower and material resources. Attached Figure Description

[0085] Figure 1 This is a schematic diagram of the process flow for treating AOX in pharmaceutical wastewater using an electrochemical reactor. Detailed Implementation

[0086] The present invention will be further described below with reference to specific embodiments.

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

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

[0089] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0090] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[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” explicitly includes only A, only B, only C, and combinations thereof.

[0092] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as “less than about 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0093] The detection methods for each indicator in the embodiment are as follows:

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

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

[0096] Acute toxicity test method for biological substances: 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, including 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 above mixed solution was coated onto the titanium plate multiple times, dried in an oven at 90°C, and then calcined in a muffle furnace at 450°C for 20 minutes. After calcination, it was cooled to room temperature. 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 12.0×6.0cm.

[0102] S3: After cooling the fabricated co-doped composite cathode Fe3O4 / CuO / NiO / Ti to room temperature, seal it for later use.

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

[0104] The anode uses DSA material (purchased from the Ilka electrochemical space station, ruthenium-iridium-titanium electrode), with dimensions of 12.0 × 6.0 cm.

[0105] The aforementioned co-doped composite cathode Fe3O4 / CuO / NiO / Ti and the aforementioned DSA anode material were used as the cathode and anode of the novel electrochemical reactor. The reactor was separated by a proton exchange membrane (purchased from Leighton Electrochemical flagship store), with the distance between the anode and the proton exchange membrane set at 2.5 mm, and the distance between the cathode and the proton exchange membrane also set at 2.5 mm. The volume ratio of the anode region to the cathode region after separation by the exchange membrane was 1:1. The reaction conditions were optimized as follows:

[0106] a. Current density and voltage

[0107] Current density settings: 10, 12, 15, 18, 20 mA / cm² 2 The corresponding voltages are 9, 12, 15, 18, and 20V, respectively; the sulfate electrolyte concentration is 0.05mM; and the pH is 7.5. These conditions are used for wastewater treatment (in this invention, all wastewater originates from fermentation and pharmaceutical wastewater). When the voltage is 12V, the corresponding current density is 12mA / cm³. 2 The treatment effect is optimal, with AOX removal rate of 98.2%, COD removal rate of 79.4%, and acute biological toxicity reduced from highly toxic to non-toxic.

[0108] b. Electrolyte concentration

[0109] The above current density of 12 mA / cm² was selected. 2 The voltage was 12V, and sulfate electrolyte concentrations of 0.025, 0.05, 0.75, 0.1, and 0.15 mM, with a pH of 7.5, were selected for wastewater treatment. The wastewater treatment effect was best when the sulfate electrolyte concentration was 0.05 mM, with AOX removal rate of 99.3%, COD removal rate of 81.9%, and acute biological toxicity reduced from highly toxic to non-toxic.

[0110] c. pH

[0111] The above current density of 12 mA / cm² was selected. 2 The system was set with a voltage of 12V, a sulfate electrolyte concentration of 0.05mM, and pH values ​​of 6.5, 7, 7.5, 8, and 8.5 for wastewater treatment. The treatment effect was optimal at pH 8, with AOX removal rate of 99.5%, COD removal rate of 82.2%, and acute biological toxicity reduced from highly toxic to non-toxic.

[0112] d. Processing time

[0113] The above current density of 12 mA / cm² was selected. 2 The experiment was conducted with a voltage of 12V, a sulfate electrolyte concentration of 0.05mM, a pH of 8, and a total reaction time of 180min. The cathode reduction time was set to 10, 30, 60, 90, 120, 150, and 180min, while the corresponding anode oxidation time was 170, 150, 120, 90, 30, and 0min. Wastewater was treated according to these times. The optimal treatment effect was achieved when the cathode reduction time was 120min and the anode oxidation time was 60min, resulting in a 99.8% removal rate of AOX, an 83.1% removal rate of COD, and a reduction in acute biological toxicity from highly toxic to non-toxic.

[0114] In summary, the wastewater treatment conditions are ultimately set as follows: current density 12 mA / cm². 2 The voltage was 12V, the sulfate electrolyte concentration was 0.05mM, the pH was 8, the reduction reaction time in the cathode area was 120min, and the oxidation reaction time in the anode area was 60min.

[0115] (3) Wastewater treatment

[0116] like Figure 1 As shown, after the pharmaceutical wastewater is injected into the inlet tank, it is first pumped into the cathode area by the inlet pump for a reduction reaction for 120 minutes, and then pumped to the anode area by the reflux pump for an 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 the pharmaceutical wastewater was 99.6%, the removal rate of COD was 82.6%, and the acute biological toxicity was reduced from highly toxic to non-toxic.

[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, including the following steps:

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

[0121] S1: Mix 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 to obtain a mixed solution;

[0122] S2: The mixed solution is coated onto the titanium plate multiple times, dried in an oven at 90°C, and then calcined in a muffle furnace at 400°C for 15 minutes. After calcination, it is cooled to room temperature. The coating, drying and calcination operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0cm.

[0123] S3: After cooling the completed co-doped composite cathode to room temperature, seal and store it for later use.

[0124] (2) Construction and operation of novel electrochemical reaction systems

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

[0126] The construction and operation of the novel electrochemical reaction system differs in Example 1. The distance between the anode and the proton exchange membrane is 2.0 mm, and the distance between the cathode and the proton exchange membrane is 2.0 mm. All other aspects are 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 highly toxic to non-toxic.

[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, including the following steps:

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

[0133] S1: Mix 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 to obtain a mixed solution;

[0134] S2: The mixed solution is coated onto the titanium plate multiple times, dried in an oven at 90°C, and then calcined in a muffle furnace at 450°C for 20 minutes. After calcination, it is cooled to room temperature. The coating, drying and calcination operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0cm.

[0135] S3: After cooling the completed co-doped composite cathode to room temperature, seal and store it for later use.

[0136] (2) Construction and operation of novel electrochemical reaction systems

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

[0138] The setup and operation are the same as in 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 highly toxic to non-toxic.

[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, including the following steps:

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

[0145] S1: Mix 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 to obtain a mixed solution;

[0146] S2: The mixed solution is coated onto the titanium plate multiple times, dried in an oven at 90°C, and then calcined in a muffle furnace at 450°C for 20 minutes. After calcination, it is cooled to room temperature. The coating, drying and calcination operations are repeated until the mixed solution is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti with a size of 12.0×6.0cm.

[0147] S3: After cooling the completed co-doped composite cathode to room temperature, seal and store it for later use.

[0148] (2) Construction and operation of novel electrochemical reaction systems

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

[0150] The setup and operation are the same as in 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 to low.

[0154] Comparative Example 1

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

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

[0157] The preparation of CuO / NiO / Ti co-doped composite cathodes differs from that in Example 1, where the mixed solution prepared does not contain FeCl3·6H2O, and other operations are the same as in Example 1.

[0158] Fe3O 4 / The preparation of NiO / Ti co-doped composite cathodes differs from that in Example 1, where the mixed solution prepared does not contain CuCl2·2H2O, and other operations are the same as in Example 1.

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

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

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

[0162] (2) Construction and operation of novel electrochemical reaction systems

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

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

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

[0166] Table 1

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

[0168] As shown in Table 1, compared with the electrochemical reactors constructed from several co-doped composite cathodes in the comparative examples for wastewater treatment, the co-doped composite cathode Fe3O4 / CuO / NiO / Ti provided by this invention exhibits higher removal rates of AOX and COD in wastewater treatment, with a removal rate of 99.6% for AOX and 82.6% for COD. Furthermore, the co-doped composite cathode Fe3O4 / CuO / NiO / Ti provided by this invention also demonstrates better detoxification effects against acute biological toxicity in wastewater, achieving a non-toxic result after treatment.

[0169] Comparative Example 2

[0170] This comparative example provides the application of an electrochemical reactor for wastewater treatment using a co-doped composite cathode Fe3O4 / CuO / NiO / Ti system that integrates oxidation-reduction, simultaneous reduction-oxidation, reduction-oxidation reactions, and 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 separates 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 and cathode regions after the exchange membrane separation is 1:1. In application, unlike Example 1, wastewater is sequentially passed through the anode and cathode regions for a pre-oxidation and then reduction reaction. The voltage is set to 12V, and the current to 12mA / cm². 2 The sulfate electrolyte used had a concentration of 0.05 mM and a pH of 8. The total reaction time was 180 min, with the reaction times in the anode and cathode regions being 120 min and 60 min, respectively.

[0174] The simultaneous reduction-oxidation reaction system differs from the above-mentioned oxidation-reduction reaction system in that the reactor is not separated by a proton exchange membrane, and the reaction is carried out in the same volume for 180 min, with other reaction conditions being the same.

[0175] The reduction and oxidation reaction systems reacted separately for 180 minutes in the corresponding cathode and anode regions, with other reaction conditions remaining the same.

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

[0177] Table 2

[0178] reaction system AOX removal rate COD removal rate Acute biological toxicity Oxidation after reduction 99.6％ 82.6％ Non-toxic Oxidation followed by reduction 78.2％ 58.3％ Low toxicity Simultaneous reduction oxidation 55.2％ 34.8％ rise reduction 92.3％ 40.1％ Poisoning Oxidation 68.7％ 54.6％ Moderate to highly toxic

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

Claims

1. A method for preparing a co-doped composite cathode Fe3O4 / CuO / NiO / Ti, characterized in that, Includes the following steps: S1: Preparation of the mixture 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 calcination The mixture was coated onto a titanium plate, dried at 75-100°C, calcined at 350-600°C for 15-30 minutes, and then cooled to room temperature. Repeat the coating, drying, and calcination processes until the mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

2. The method for preparing the co-doped composite cathode Fe3O4 / CuO / NiO / Ti as described in claim 1, characterized in that, In the mixture Ethylene glycol is available in 30ml, 40ml, 50ml, or 60ml containers; and / or Polyethylene glycol is available in 10ml, 15ml, 20ml, or 30ml containers; 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 The amounts of NiCl2·6H2O are 1.5g, 2.0g, 2.5g, or 3.0g.

3. The method for preparing the co-doped composite cathode Fe3O4 / CuO / NiO / Ti as described in claim 1 or 2, characterized in that, In the preparation method described above S1: Preparation of the mixture 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 calcination The mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 450°C for 20 minutes, and then cooled to room temperature. Repeat the coating, drying and calcination operations until the mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti; or S1: Preparation of the mixture 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 calcination The mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 400°C for 15 minutes, and then cooled to room temperature. Repeat the coating, drying and calcination operations until the mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti; or S1: Preparation of the mixture 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 to obtain a mixed solution; S2: Coating, drying and calcination The mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 450°C for 20 minutes, and then cooled to room temperature. Repeat the coating, drying and calcination operations until the mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti; or S1: Preparation of the mixture 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 calcination The mixture was coated onto a titanium plate multiple times, dried at 90°C, calcined at 450°C for 20 minutes, and then cooled to room temperature. Repeat the coating, drying, and calcination processes until the mixture is exhausted to obtain a co-doped composite cathode Fe3O4 / CuO / NiO / Ti.

4. An electrochemical reactor, characterized in that, The electrochemical reactor comprises a co-doped composite cathode Fe3O4 / CuO / NiO / Ti prepared by the method described in any one of claims 1-3.

5. The electrochemical reactor as described in claim 4, characterized in that, The cathode and anode regions of the reactor are separated by a proton exchange membrane. The distance between the reactor anode and the proton exchange membrane is 1-5 mm, and the distance between the cathode and the proton exchange membrane is 1-5 mm.

6. The electrochemical reactor as described in claim 5, 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 reactor anode and the proton exchange membrane is 2.0 mm, and the distance between the cathode and the proton exchange membrane is 2.0 mm.

7. The application of the electrochemical reactor according to any one of claims 4-6 in wastewater treatment, characterized in that, This includes the removal of AOX and COD from wastewater, as well as the detoxification of acute biological toxicity.

8. The application as described in claim 7, characterized in that, Includes the following steps: S1: Set 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, with a reaction time ratio of (1.5~2):(1~1.5) between the cathode and anode regions; 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 zone for a reduction reaction, then enters the anode zone for an oxidation reaction, and is discharged through the outlet after the reaction is completed.

9. A wastewater treatment method, characterized in that, The treatment method uses the electrochemical reactor according to any one of claims 4-6 and includes the following steps: S1: Set 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, with a reaction time ratio of (1.5~2):(1~1.5) between the cathode and anode regions; 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 zone for a reduction reaction, then enters the anode zone for an oxidation reaction, and is discharged through the outlet after the reaction is completed.

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