A method for preparing an electrocatalyst and an integrated device for recovering ammonium sulfate

Abstract

The present invention discloses a method for preparing an electrocatalyst and an integrated device for recovering ammonium sulfate. The method for preparing the electrocatalyst comprises the following steps: placing the cut NF into appropriate amounts of acetone, 1 mol·L ‑1 The NFs were ultrasonically treated in a solution of hydrochloric acid and an appropriate amount of anhydrous ethanol for 15 minutes each to remove trace oils and oxides from the NF surface and enhance the substrate's hydrophilicity. A certain amount of urea, Cu(NO₃)₂·, and NH₄F were ultrasonically dissolved in deionized water and transferred to the autoclave liner to prepare a Cu₂O / NF electrode. The pretreated NFs were tilted and placed on the inner wall of the autoclave liner. The autoclave was placed in an oven and heated at 105°C for 6 hours. After the autoclave cooled naturally to room temperature, the resulting electrode was washed three times alternately with distilled water and anhydrous ethanol and vacuum-dried at 60°C for 6 hours. The present method for preparing in situ grown cuprous oxide heterojunction electrocatalysts using nickel foam as a support is simple, mild, easy to operate, and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the field of water treatment material preparation, and in particular to a method for preparing an electrocatalyst and an integrated device for recovering ammonium sulfate. Background Art

[0002] Nitrate is the most oxidized form of nitrogen and exists in natural water bodies and various types of industrial wastewater. Excessive nitrate in the environment can lead to eutrophication of water, which in turn affects human health. − It is converted into nitrite anions in the human body, which is closely related to various adverse health consequences, including liver damage, colorectal cancer, bladder cancer, breast cancer and thyroid disease; Currently, various methods for removing NO3 − Treatment technologies are very common, including physical adsorption, biological denitrification, electrodialysis, ion exchange, reverse osmosis and catalytic hydrogenation; however, these technologies all have certain drawbacks, such as low reaction efficiency, high operating costs, and serious influence of environmental conditions; selective electrocatalytic reduction of nitrate to NH4 using renewable electricity + It is attracting considerable research interest because it requires simpler operating conditions and less energy loss and does not produce sludge; more attractive is that in NO3 − NH4 produced in + It can be recycled as a value-added product, such as (NH4)2SO4 fertilizer.

[0003] Ammonium sulfate is a physiologically acidic fertilizer with broad applicability in agriculture. It is suitable for general soil and crops. It can promote vigorous growth of branches and leaves, improve fruit quality and yield, and enhance the resistance of crops to disasters. It can be used as base fertilizer, topdressing and seed fertilizer.

[0004] Electrocatalytic reduction of NO3 − It is a promising technology with low demand for chemicals before and after the reaction, relatively low investment cost, flexible operating conditions, easy control of reaction by-products, small footprint, and automatic control. It uses electrochemical reduction to remove NO3 − It has attracted widespread attention; by applying voltage in the reactor, the electrons between ions are transferred in a directional manner, thereby achieving NO3 − The change in the valence state of nitrogen promotes its reduction to NH4 + ; Metal materials are widely used in NO3 −Reduction, such as Fe, Cu, Zn, Ni, Pd and Pt; bimetallic electrodes have been widely studied because they can combine the advantages of two metals at the same time; among metal electrode materials, Pd and Pt are effective electroreduction materials with wide application; studies have shown that platinum group metals have high electrocatalytic activity, and Pd in ​​the platinum group metals has high N2 selectivity, but the use of precious metal Pd also increases NO3 − The reduction cost; Currently, electrochemical reduction of NO3 − Presence of NO3 − The problem of low reduction efficiency; however, NO3 − Converted into non-toxic NH4 + The current technology is not mature enough. The main problems are that there are many by-products and high energy consumption. Therefore, it is necessary to develop a product with excellent stability and high NH4 + Selective and low energy consumption electrode material; copper is a metal with highly occupied d orbitals, and its energy level is similar to that of NO3 − The similarity between the lowest unoccupied molecular π* orbitals of NO3 − Can be reduced to NH4 smoothly and quickly + ; Nickel foam is a common 3D metal material with low price, uniform porosity and network structure, excellent chemical and mechanical stability, and large specific surface area. Ni foam has been widely used in adsorbents, catalysts, and battery materials; therefore, it is worth looking forward to proposing a simple preparation method of copper and nickel foam bimetallic electrocatalyst for the reduction of nitrate. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a method for preparing an electrocatalyst and an integrated device for recovering ammonium sulfate.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A cuprous oxide heterojunction electrocatalyst is in situ grown on a nickel foam sheet as a carrier. The catalyst is composed of cuprous oxide particles and copper hydroxide particles loaded on the surface of the nickel foam sheet. The copper particles are stably attached and a heterogeneous structure is formed between the interfaces of different types of copper.

[0008] Furthermore, the preparation method of the electrocatalyst comprises the following steps:

[0009] S1: Place the cut nickel foam sheets into acetone, 1 mol·L -1 The nickel foam was ultrasonically treated in hydrochloric acid and anhydrous ethanol for 15 min each to remove trace grease and oxides on the surface of the nickel foam and enhance the hydrophilicity of the substrate;

[0010] S2: Urea, copper salt, and ammonium fluoride were ultrasonically dissolved in 70 mL of deionized water and transferred into the autoclave liner to prepare the Cu2O / NF electrode;

[0011] S3: The pretreated nickel foam sheet is placed obliquely on the inner wall of the autoclave liner, and the autoclave is placed in an oven for heating;

[0012] S4: After the autoclave is cooled to room temperature, the obtained electrode is washed alternately with distilled water and anhydrous ethanol three times and dried in vacuum at 60 °C for 6 h.

[0013] Furthermore, the mass of the urea is 0.7-2.8 g, the amount of the copper salt is 0.1-1 mol, and the mass of the ammonium fluoride is 0.05-0.3 g.

[0014] Furthermore, the copper salt is any one of copper sulfate, copper nitrate, copper chloride, and copper carbonate.

[0015] Furthermore, the hydrothermal deposition temperature is 80-120° C., and the hydrothermal deposition time is 4-8 hours.

[0016] Furthermore, a method for electrocatalytic reduction of nitrate ions by in situ growing a cuprous oxide heterojunction electrocatalyst using a nickel foam sheet as a carrier is provided, and the specific steps are as follows: a three-electrode system is constructed using the cuprous oxide heterojunction electrocatalyst grown in situ using the nickel foam sheet as a carrier as a working electrode, an iridium ruthenium titanium composite electrode as a counter electrode, and a saturated Ag / AgCl electrode as a reference electrode, the simulated wastewater is in units of 150 ml, the nitrate concentration is 50 mg / L, and 0.05 mol / L Na2SO4 is selected as the electrolyte; nitrate is electrocatalytically reduced at a voltage of -1.1 to -1.5.

[0017] Furthermore, the pH during the electrocatalytic nitrate reduction reaction is 4 to 10.

[0018] Furthermore, an integrated device for recovering ammonium sulfate includes a wastewater tank and a physical filtration tank, the water inlet of the physical filtration tank is connected to the wastewater tank, the water outlet of the physical filtration tank is fixedly connected to a closed electrolytic cell, the upper end of the closed electrolytic cell is fixedly connected to an electrochemical workstation, the lower end surface of the closed electrolytic cell is fixedly provided with a guide outlet, the guide outlet is fixedly connected to a product recovery device, the product recovery device includes a first chamber and a second chamber, a gas diffusion port is provided between the first chamber and the second chamber, a gas diffusion membrane is fixedly installed in the gas diffusion port, a product discharge port is fixedly provided on the second chamber, a product discharge valve is fixedly installed at the product discharge port, the closed electrolytic cell includes the first electrolytic cell and the second electrolytic cell, a connecting pipe is provided between the first electrolytic cell and the second electrolytic cell, a cation exchange membrane is fixedly installed in the connecting pipe; an electrochemical controller and a reference electrode electrically connected to the electrochemical controller, a cathode plate, a water level sensor and an electrocatalyst release device; the electrocatalyst release device includes a working electrode and a cathode plate of an iridium ruthenium-titanium counter electrode.

[0019] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a cuprous oxide heterojunction electrocatalyst grown in situ on a nickel foam sheet as a carrier, which is synthesized by a one-step hydrothermal method and has a unique rhombic structure; after hydrothermal deposition, cuprous oxide and copper hydroxide are loaded on the surface of the nickel foam to form a strong heterojunction interface; the interface heterostructure not only provides more active sites, but also improves the electronic environment and accelerates electron transport, thereby enhancing the ability of electrocatalytic reduction of nitrate ions; therefore, the cuprous oxide heterojunction electrocatalyst has significantly improved activity compared to traditional Cu@CF electrocatalysts and has stronger denitrification performance.

[0020] The preparation method of the cuprous oxide heterojunction electrocatalyst grown in situ using a nickel foam sheet as a carrier is simple, has mild conditions, is easy to operate, and has no environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The cuprous oxide heterojunction electrocatalyst prepared by the present invention is grown in situ using nickel foam as a carrier;

[0022] Figure 2 This is a SEM image of the in-situ grown cuprous oxide heterojunction electrocatalyst prepared by the present invention using nickel foam as a support;

[0023] Figure 3 This is the XPS Cu2p image of the in-situ grown cuprous oxide heterojunction electrocatalyst prepared by the present invention using nickel foam as a support;

[0024] Figure 4 This is a HRTEM image of the in-situ grown cuprous oxide heterojunction electrocatalyst using nickel foam as a support, prepared by the present invention;

[0025] Figure 5 This is a graph showing the change in removal rate of nitrate nitrogen over time in the electrocatalytic reduction of nitrate by the catalyst prepared by the present invention;

[0026] Figure 6 This is a graph showing the change in the generation rate of ammonium nitrogen over time in the electrocatalytic reduction of nitrate by the catalyst prepared by the present invention;

[0027] Figure 7 Flow chart of the preparation of the catalyst of the present invention;

[0028] Figure 8 This is a schematic structural diagram of the integrated device for recovering ammonium sulfate of the present invention.

[0029] Figure numerals: 1. Wastewater tank; 3. Physical filtration chamber; 4. Sealed electrolytic cell; 5. Electrochemical workstation; 6. Product recovery device; 61. First chamber; 62. Second chamber; 63. Gas diffusion membrane; 64. Product discharge valve; 41. First electrolytic cell; 42. Second electrolytic cell; 43. Cation exchange membrane; 51. Electrochemical controller; 52. Reference electrode; 53. Cathode plate; 10. Water level sensor; 54. Electrocatalyst release device. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0031] See also Figure 8 As shown, an integrated device for recovering ammonium sulfate includes a wastewater tank and a physical filtration tank. The water inlet of the physical filtration tank is connected to the wastewater tank. The water outlet of the physical filtration tank is fixedly connected to a closed electrolytic cell. The upper end of the closed electrolytic cell is fixedly connected to an electrochemical workstation. The lower end surface of the closed electrolytic cell is fixedly provided with a guide port, which is fixedly connected to a product recovery device. The product recovery device includes a first chamber and a second chamber. A gas diffusion port is provided between the first chamber and the second chamber. A gas diffusion port is fixedly installed in the gas diffusion port. The membrane is fixedly provided with a product discharge outlet on the second chamber, and a product discharge valve is fixedly installed at the product discharge outlet. The sealed electrolytic cell includes a first electrolytic cell and a second electrolytic cell, and a connecting pipe is provided between the first electrolytic cell and the second electrolytic cell, and a cation exchange membrane is fixedly installed in the connecting pipe; an electrochemical controller and a reference electrode electrically connected to the electrochemical controller, a cathode plate, a water level sensor and an electrocatalyst release device; the electrocatalyst release device includes a working electrode of a heterojunction electrocatalyst and a cathode plate of an iridium ruthenium-titanium counter electrode.

[0032] The present invention also discloses an in-situ grown cuprous oxide heterojunction electrocatalyst using a nickel foam sheet as a carrier. The catalyst is composed of cuprous oxide particles and copper hydroxide particles loaded on the surface of the nickel foam sheet. The copper particles are stably attached and a heterogeneous structure is formed between the interfaces of different types of copper.

[0033] Example 1: Preparation of Cu(I / II)@NF-urea 1.4 electrode

[0034] (1) Place the cut NF (nickel foam sheet) into appropriate amounts (just enough to cover the nickel foam sheet) of acetone, 1 mol·L -1 The NFs were ultrasonically treated in hydrochloric acid and an appropriate amount of anhydrous ethanol for 15 min each to remove trace oils and oxides on the surface of the NFs and enhance the hydrophilicity of the substrate.

[0035] (2) 1.4 g of urea, 0.96 g of Cu(NO3)2·3H2O, and 0.15 g of NH4F were dissolved in 70 mL of deionized water and then transferred to the autoclave liner (100 mL).

[0036] (3) The pretreated NF was tilted onto the lining wall of the autoclave. The autoclave was placed in an oven and heated at 105 °C for 6 h. The obtained electrode was washed and then vacuum dried at 60 °C for 6 h.

[0037] Figure 1 This is the SEM image of the Cu(I / II)@NF-urea 1.4 electrocatalyst prepared in Example 1. The SEM image shows that Cu nanoparticles can be uniformly loaded on NF and have a unique diamond structure.

[0038] Figure 2 This is the XPS image of the Cu(I / II)@NF-urea 1.4 electrocatalyst prepared in Example 1. The XPS image confirms that Cu species with different valence states are successfully loaded on the surface of nickel foam.

[0039] Figure 3 This is the HRTEM image of the Cu(I / II)@NF-urea 1.4 electrocatalyst prepared in Example 1. The HRTEM image shows that an obvious heterogeneous structure is formed between copper hydroxide and cuprous oxide.

[0040] Example 2: The Cu(I / II)@NF-urea 1.4 electrode prepared in Example 1 was used to investigate its effect on the electrochemical reduction of nitrate to ammonia.

[0041] The Cu(I / II)@NF-urea 1.4 electrode prepared in Example 2 was used as the working electrode to carry out the electrocatalytic reduction of nitrate. Meanwhile, Cu@NF was used as the control. The results of the change of nitrate nitrogen removal rate over time in the electrocatalytic reduction of nitrate were shown in the figure below. Figure 5The results of the graph of the amount of ammonium nitrogen produced over time are shown as follows. Figure 6 The results show that when Cu (I / II) @ NF-urea 1.4 catalyst electrode is used as the working electrode, the removal rate of nitrate nitrogen continues to rise. After 6 hours of reaction, the removal rate reaches 100%, and the NH4 + The amount of -N produced is 44.09 mg, NH4 + -N selectivity was 88.18%; under the same conditions, the removal efficiency of Cu@NF was 51.6%, and NH4 + The amount of -N produced is 12.27 mg, NH4 + The selectivity of -N was 47.55%, which proved that the Cu(I / II)@NF-urea 1.4 catalyst electrode had high activity and selectivity for ammonia production in the electrocatalytic reduction of nitrate.

[0042] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. A method for preparing an in-situ grown cuprous oxide heterojunction electrocatalyst using nickel foam as a support, characterized by: The catalyst is composed of cuprous oxide particles and copper hydroxide particles loaded on the surface of a nickel foam sheet, the copper particles are stably attached and a heterogeneous structure is formed between the interfaces of different types of copper; The preparation method comprises the following steps: S1: Place the cut nickel foam sheets into acetone, 1 mol·L -1 The nickel foam was ultrasonically treated in hydrochloric acid and anhydrous ethanol for 15 min each to remove trace grease and oxides on the surface of the nickel foam and enhance the hydrophilicity of the substrate; S2: Urea, copper salt, and ammonium fluoride were ultrasonically dissolved in 70 mL of deionized water and transferred into the autoclave liner to prepare the Cu2O / NF electrode; S3: The pretreated nickel foam sheet is placed obliquely on the inner wall of the autoclave liner, and the autoclave is placed in an oven for heating; S4: After the autoclave is cooled to room temperature naturally, the obtained electrode is washed alternately with distilled water and anhydrous ethanol three times and vacuum dried at 60°C for 6 h.

2. The method for preparing a cuprous oxide heterojunction electrocatalyst by in-situ growth using nickel foam as a support according to claim 1, characterized in that: The mass of the urea is 0.7-2.8 g, the amount of the copper salt is 0.1-1 mol, and the mass of the ammonium fluoride is 0.05-0.3 g.

3. The method for preparing a cuprous oxide heterojunction electrocatalyst by in-situ growth using nickel foam as a support according to claim 1, characterized in that: The copper salt is any one of copper sulfate, copper nitrate, copper chloride and copper carbonate.

4. A method for electrocatalytic reduction of nitrate using a catalyst prepared by the method of any one of claims 1 to 3, characterized in that: The specific steps are as follows: a three-electrode system is constructed by in-situ growing a cuprous oxide heterojunction electrocatalyst on a nickel foam sheet as a working electrode, an iridium-ruthenium-titanium composite electrode as a counter electrode, and a saturated Ag / AgCl electrode as a reference electrode. The simulated wastewater is in units of 150 ml, the nitrate concentration is 50 mg / L, and 0.05 mol / L Na2SO4 is selected as the electrolyte; nitrate is electrocatalytically reduced at a voltage of -1.1 to -1.

5.

5. The method for electrocatalytic reduction of nitrate according to claim 4, wherein: The pH value during the electrocatalytic nitrate reduction reaction is 4 to 10.

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