A method for treating wastewater containing copper complexes in a fuel cell

Abstract

The present invention relates to a method for treating wastewater containing copper complexes in a fuel cell, comprising: using a MoS2 / GF electrode as a positive electrode, a Zn plate as a negative electrode, using a bipolar ion exchange membrane to separate positive and negative electrode chambers, adding wastewater containing copper complexes to the positive electrode chamber, and recovering metallic copper and obtaining treated wastewater through a primary cell reaction. Compared with the prior art, the present invention realizes the recovery of metallic copper and synchronous power generation by using a primary cell method through the strong catalytic effect of MoS2 on the decomposition of copper-containing complexes, and has the advantages of high removal / recovery efficiency, reusable catalysts, etc., and can also output electrical energy, further reducing the energy consumption of electrochemical treatment of copper-containing wastewater, and has good practicality.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical reduction treatment of difficult-to-biodegrade heavy metal organic complexes in industrial wastewater, and relates to a fuel cell treatment method for copper complex wastewater, and in particular to a method for efficiently recovering copper and synchronously generating electricity from copper complex wastewater using a MoS2 positive electrode catalyst. Background Art

[0002] With the development of my country's economy in recent years, electroplating, chemical industry, printing and dyeing and other industries have made great progress. These industries are all heavily polluting industries, and their production processes will produce a large amount of industrial wastewater containing heavy metals. The most typical is heavy metal copper wastewater. However, these coppers are not free, and usually react with complexing agents commonly used in these industries, which increases the difficulty of separating heavy metal ions from wastewater. These copper-containing complexes are highly stable and difficult to recycle. To make matters worse, the highly toxic effects of metal organic complexes in water environments show serious harm to specific cells, aquatic plants and microorganisms. However, the effective treatment of metal organic complex wastewater remains a huge challenge. Compared with ionic metals, due to the shielding and protection of ligands, the complexed metals cannot be effectively removed using conventional methods (such as adsorption, ion exchange or chemical precipitation). Therefore, it is quite necessary to develop more powerful purification technologies.

[0003] Electrochemical direct reduction is a promising method that can directly achieve the decomposition of copper-containing complexes and the recovery of copper. The ligands that are decoordinated from copper ions can be recycled or removed by biological methods with low energy consumption. The electrochemical reduction method has high spontaneity in thermodynamics, but in order to achieve high selectivity and low energy consumption reduction, it needs to rely on powerful electrocatalysts. In addition, since the oxidation state of copper has a relatively high electrode potential, it provides the possibility of designing electrochemical reactors with spontaneous energy output. By rationally designing electrode catalysts and primary cell systems, the multifunctional application of copper complex wastewater removal / copper recovery and electricity generation can be achieved. Summary of the invention

[0004] The purpose of the present invention is to provide a method for treating copper-containing complex wastewater fuel cell in view of the drawbacks of the existing heavy metal copper complex wastewater treatment method, such as complexity and high energy consumption, so as to realize the recovery of copper resources and synchronous power generation. The process operation method is simple, and only the copper-containing complex wastewater needs to be used as the positive electrode electrolyte, and the copper-containing complex can be broken and the metal copper can be recovered by in-situ deposition on the MoS2 cathode by the original cell method. MoS2 has strong catalytic performance for the reduction process of copper-containing complex molecules, which can significantly reduce the activation energy required for its breaking process, and therefore has higher reaction activity than the traditional graphite cathode.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for treating wastewater containing copper complexes, comprising:

[0007] With MoS2 / GF electrode as the positive electrode and Zn plate as the negative electrode, a bipolar ion exchange membrane is used to separate the positive and negative electrode chambers. The copper complex wastewater is added to the positive electrode chamber, and the metallic copper is recovered through the galvanic cell reaction to obtain the treated wastewater.

[0008] Furthermore, the positive electrode electrolyte is sodium sulfate, and the negative electrode electrolyte is KOH.

[0009] Furthermore, the copper complex wastewater contains at least one of ethylenediaminetetraacetic acid copper (CuEDTA), citrate copper or diethylenetriaminepentaacetic acid copper.

[0010] Furthermore, in the primary cell reaction, an inert gas is continuously introduced into the positive electrode chamber.

[0011] Furthermore, the preparation method of the MoS2 / GF electrode includes: mixing a molybdenum source and a sulfur source in a solution to obtain a MoS2 precursor solution; placing graphite felt in the MoS2 precursor solution and performing a hydrothermal reaction to obtain a MoS2 / GF electrode.

[0012] Furthermore, the molybdenum source is sodium molybdate, and the sulfur source is thiourea.

[0013] Furthermore, the molar ratio of sodium molybdate to thiourea is 1:(4-6).

[0014] Furthermore, in the hydrothermal reaction, the reaction temperature is 180-220° C. and the reaction time is 22-28 h.

[0015] Furthermore, the graphite felt is rolled into a column and stands upright in the MoS2 precursor solution.

[0016] Furthermore, before being placed in the MoS2 precursor solution, the graphite felt is ultrasonically cleaned using dichloromethane, hydrochloric acid, ethanol and water in sequence.

[0017] The present invention realizes the recovery of metallic copper and synchronous power generation by using the primary cell method through the strong catalytic effect of MoS2 on the decomposition of copper-containing complexes, and has the advantages of high removal / recovery efficiency and reusable catalyst, and can also output electrical energy, further reducing the energy consumption of electrochemical treatment of copper-containing wastewater, and has good practicality.

[0018] Compared with the prior art, the present invention has the following characteristics:

[0019] 1) MoS2-loaded graphite felt electrode was prepared by hydrothermally modifying graphite felt with MoS2. The electrode was used as cathode to treat wastewater containing copper complex by constant current method, so as to achieve the removal of copper complex and direct recovery of metallic copper on the electrode and output of electric energy. The mechanism is:

[0020] Near the positive electrode, the pollutant CuEDTA transfers mass to the cathode surface driven by the electrochemical potential, and then CuEDTA undergoes a decomplexation process, transforming from a complexed state to a free metal ion. Finally, the free copper ions are reduced to metallic copper particles by electrons, and the ligands return to the solution driven by the electrochemical potential. On the Zn negative electrode, a spontaneous oxidation reaction occurs driven by the electrochemical potential, generating free Zn ions that transfer to the solution and leaving free electrons on the electrode. Driven by the potential difference, the free electrons flow to the positive electrode through the external circuit and perform work externally. Since MoS2 has a strong catalytic effect on the reduction of CuEDTA, the reduction efficiency of CuEDTA on the cathode surface is higher than that of the inactive electrode, which can provide a larger output current and output electrical work. Through the spontaneous redox reaction between the anode and cathode, the removal of copper-containing organic complexes and the output of electrical energy are achieved, which effectively utilizes the chemical energy contained in the CuEDTA molecules and achieves the dual functional effects of pollution control and resource utilization;

[0021] 2) The raw materials for preparing the electrode used in the present invention, carbon felt and sodium thiourea molybdate, are both cheap and readily available, and the preparation method is simple, so the production cost of the electrode is relatively low, and it is suitable for large-scale application;

[0022] 3) The present invention destroys the molecular structure of pollutants by removing heavy metal ions in the complex in advance, improves BOD5 / COD, makes wastewater more suitable for subsequent biochemical treatment, and is conducive to the final discharge of effluent meeting the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the CuEDTA-Zn primary battery in Example 2;

[0024] Figure 2 The figure is a comparison of the battery output characteristics of different cathodes in the CuEDTA-Zn primary battery in Example 2;

[0025] Figure 3 The output characteristic curve of the MoS2 / GF positive electrode primary battery during the cycle use process in Example 3;

[0026] Figure 4 It is the removal rate and Faraday efficiency of the MoS2 / GF positive electrode primary battery during the recycling process in Example 4. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] A method for treating wastewater containing copper complexes, comprising:

[0029] like Figure 1 As shown, the MoS2 / GF electrode is used as the positive electrode, the Zn plate is used as the negative electrode, and the bipolar ion exchange membrane is used to separate the positive and negative electrode chambers. The copper complex wastewater is added to the positive electrode chamber, and under magnetic stirring, an inert gas is continuously introduced into the positive electrode chamber. Then, the copper complex wastewater is subjected to electrodeposition treatment by a constant current method, so as to recover metallic copper and generate electricity simultaneously.

[0030] Among them, the positive electrode electrolyte is sodium sulfate and the negative electrode electrolyte is KOH.

[0031] In some specific embodiments, the positive / negative electrolyte may be other readily soluble salts.

[0032] In some specific embodiments, the copper complex-containing wastewater contains at least one of CuEDTA, copper citrate or copper diethylenetriaminepentaacetic acid.

[0033] The preparation method of the MoS2 / GF electrode includes: dissolving a molybdenum source and a sulfur source in water and transferring the solution to a Teflon-lined reactor to obtain a MoS2 precursor solution; placing cleaned graphite felt in the MoS2 precursor solution, and preparing the MoS2 / GF electrode by a hydrothermal reaction in an oven.

[0034] The molybdenum source is sodium molybdate, the sulfur source is thiourea, the molar ratio of sodium molybdate to thiourea is 1:(4-6), and in the hydrothermal reaction, the reaction temperature is 180-220°C, and the reaction time is 22-28h.

[0035] In some specific embodiments, the graphite felt is rolled into a column and stands upright in a MoS2 precursor solution.

[0036] In some specific embodiments, the cleaning process of the graphite felt includes: ultrasonic cleaning using dichloromethane, hydrochloric acid, ethanol, and water in sequence.

[0037] This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0038] In the following examples, unless otherwise specified, the volume of each electrode chamber is 30 mL and the electrode geometric area is 3 cm 2 , the positive electrode electrolyte is 0.5M sodium sulfate, and the negative electrode electrolyte is 1M KOH. The concentration of the copper complex is 1mM. The constant current detection equipment is an electrochemical workstation. The electrodeposition time is 60min. The Zn plate is a 99.99% high-purity zinc plate.

[0039] Embodiment 1:

[0040] A one-step hydrothermal preparation method of a MoS2 / GF electrode comprises the following steps:

[0041] S1: Cleaning of graphite felt:

[0042] Take 2×6cm 2 The graphite felt was washed with dichloromethane, 1M hydrochloric acid, ethanol, and ultrapure water in turn, and then ultrasonically cleaned to remove impurities attached to the surface of the graphite felt, and then dried in an oven at 60°C for later use;

[0043] S2: Preparation of MoS2 precursor solution:

[0044] Use an electronic balance to weigh 0.21 g of sodium molybdate and 0.38 g of thiourea, dissolve them in 30 mL of ultrapure water, and stir to fully dissolve them to obtain a MoS2 precursor solution;

[0045] S3: Preparation of MoS2 / GF electrode:

[0046] The MoS2 precursor solution was transferred to a 50 mL Teflon hydrothermal reactor, and the graphite felt was rolled into a column and placed upright in the MoS2 precursor solution. The hydrothermal reactor was placed in an oven and subjected to a hydrothermal reaction at 200 °C for 24 h. The prepared electrode material was taken out and cleaned with ultrapure water, and then dried in a vacuum oven. The dried electrode material was cut into 2 × 2 cm 2 The small piece is set aside to obtain the MoS2 / GF electrode.

[0047] Embodiment 2:

[0048] This example is used to study the effect of different cathode materials on CuEDTA wastewater treatment:

[0049] The Zn plate is the negative electrode, and a bipolar ion exchange membrane is used to separate the positive and negative electrode chambers. The copper complex wastewater is added to the positive electrode chamber, and an inert gas is continuously introduced into the positive electrode chamber under magnetic stirring. The copper complex wastewater is then subjected to electrodeposition treatment by a constant current method to remove / recover metallic copper and generate electricity simultaneously.

[0050] Among them, two different electrode materials were selected for the positive electrode, namely MoS2 / GF and graphite felt, and the current linear scanning method was used to measure the output characteristic curve of the battery.

[0051] The results are as follows Figure 2 As shown in the figure, it can be seen that for the MoS2 / GF positive electrode, the original battery is at 1.95mA / cm 2 1.05mW / cm 2 The maximum power density output of graphite felt primary battery is only 1.39mA / cm 20.51mW / cm 2 The maximum power density output is . This embodiment fully demonstrates that the selected active cathode has better catalytic activity than the traditional inactive cathode in the CuEDTA-Zn sewage fuel cell.

[0052] Embodiment 3:

[0053] This example is used to study the output performance of MoS2 / GF in a CuEDTA-Zn sewage fuel cell.

[0054] The only difference compared with Example 2 is that MoS2 / GF is used as the positive electrode and the current density is 0.5 mA / cm 2 , the rest is the same as Example 2.

[0055] The results are as follows Figure 3 As shown in the figure, it can be seen that the CuEDTA-Zn sewage fuel cell with MoS2 / GF positive electrode can output 1.9 J of electrical work in a single cycle. This example fully illustrates the output performance of the selected MoS2 / GF in the CuEDTA-Zn sewage fuel cell.

[0056] Embodiment 4:

[0057] This example is used to study the circulation effect of MoS2 / GF in a CuEDTA-Zn sewage fuel cell.

[0058] The only difference compared with Example 2 is that MoS2 / GF is used as the positive electrode and the current density is 0.5 mA / cm 2 The same experimental operation was performed three times in a row with an experimental cycle of 1 h. After the third time, the MoS2 / GF positive electrode was soaked in a saturated amine tetraacetic acid solution to regenerate the electrode, and the experiment was repeated.

[0059] The results are as follows Figure 4 As shown in the figure, it can be seen that with the continuous operation, the Faradaic efficiency and removal efficiency gradually decrease, and the performance of the electrode is fully restored after regeneration. This example fully illustrates the practical application value of the selected MoS2 / GF in CuEDTA-Zn sewage fuel cells.

[0060] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for treating wastewater containing copper complexes, characterized in that: include: With MoS2 / GF electrode as positive electrode and Zn plate as negative electrode, bipolar ion exchange membrane is used to separate positive and negative electrode chambers, wastewater containing copper complex is added to the positive electrode chamber, and metallic copper is recovered through the galvanic cell reaction to obtain treated wastewater; The preparation method of the MoS2 / GF electrode comprises: mixing a molybdenum source and a sulfur source in a solution to obtain a MoS2 precursor solution; The graphite felt is placed in a MoS2 precursor solution and subjected to a hydrothermal reaction to obtain a MoS2 / GF electrode.

2. A method for treating wastewater containing copper complex according to claim 1, characterized in that: The positive electrode electrolyte is sodium sulfate and the negative electrode electrolyte is KOH.

3. A method for treating wastewater containing copper complex according to claim 1, characterized in that: The copper complex wastewater contains at least one of ethylenediaminetetraacetic acid copper, citric acid copper or diethylenetriaminepentaacetic acid copper.

4. A method for treating wastewater containing copper complex according to claim 1, characterized in that: In the primary cell reaction, an inert gas is continuously introduced into the positive electrode chamber.

5. A method for treating wastewater containing copper complex according to claim 1, characterized in that: The molybdenum source is sodium molybdate, and the sulfur source is thiourea.

6. A method for treating wastewater containing copper complex according to claim 5, characterized in that: The molar ratio of sodium molybdate to thiourea is 1:(4-6).

7. A method for treating wastewater containing copper complex according to claim 1, characterized in that: In the hydrothermal reaction, the reaction temperature is 180-220° C. and the reaction time is 22-28 hours.

8. The method for treating wastewater containing copper complex according to claim 1, characterized in that: The graphite felt is rolled into a column and stands upright in the MoS2 precursor solution.

9. The method for treating wastewater containing copper complex according to claim 1, characterized in that: The graphite felt is ultrasonically cleaned in sequence using dichloromethane, hydrochloric acid, ethanol and water before being placed in the MoS2 precursor solution.

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