A sulfide-nitrate collaborative purification method and device

Abstract

The present invention discloses a sulfide-nitrate collaborative purification method, comprising: Ru / WO supported on carbon paper 3‑x The catalyst is the cathode, and the nitrate solution with a pH value of 0 to 7 is used as the cathode electrolyte. x The catalyst serves as the anode, a sulfide solution with a pH of 12 to 14 serves as the anolyte, and a proton exchange membrane is placed between the cathode and anode to construct a flow battery that performs a catalytic redox reaction to purify sulfide and nitrate. The present invention also discloses a sulfide-nitrate coordinated purification device corresponding to the flow battery structure. This device utilizes a catalytic redox reaction to simultaneously convert sulfide and nitrate into thiosulfate and ammonia, while also generating electrical output.

Description

Technical Field

[0001] The present invention relates to a sulfide-nitrate purification method and device, and in particular to a sulfide-nitrate coordinated purification method and device. Background Art

[0002] Sulfide and nitrate are both common waste pollutants in industrial processes and require purification to meet emission standards. Traditional methods for sulfide purification include physical adsorption, chemical wet absorption and dry oxidation, and enzyme catalysis, while traditional methods for nitrate purification include chemical redox and biological denitrification. These methods cannot be used simultaneously, and sulfide and nitrate purification usually need to be carried out separately. Summary of the Invention

[0003] In view of the above-mentioned defects of the prior art, the present invention provides a sulfide-nitrate collaborative purification method. The present invention also provides a sulfide-nitrate collaborative purification device to achieve simultaneous purification of sulfide and nitrate.

[0004] The technical solution of the present invention is as follows: A sulfide-nitrate collaborative purification method comprising: using Ru / WO loaded on carbon paper 3-x The catalyst is the cathode, and the nitrate solution with a pH value of 0 to 7 is used as the cathode electrolyte. x The catalyst is used as the anode, a sulfide solution with a pH value of 12 to 14 is used as the anode electrolyte, and a proton exchange membrane is set between the cathode and the anode to construct a liquid flow battery for catalytic redox reaction to purify sulfide and nitrate.

[0005] Furthermore, the nitrate concentration of the cathode electrolyte is 0.1 to 1 mol / L.

[0006] Furthermore, the sulfide concentration of the anolyte is 0.1 to 1 mol / L.

[0007] Furthermore, the nitrate is one or more of sodium nitrate, potassium nitrate, calcium nitrate and ammonium nitrate.

[0008] Furthermore, the sulfide is one or more of sodium sulfide, potassium sulfide, calcium sulfide and ammonium sulfide.

[0009] Furthermore, the reaction temperature during the catalytic redox reaction is 25-80°C.

[0010] Another technical solution of the present invention is: a sulfide-nitrate coordinated purification device, comprising a flow battery consisting of a first guard plate, a first conductive bipolar plate, a cathode electrode, a proton exchange membrane, an anode electrode, a second conductive bipolar plate and a second guard plate stacked in sequence, wherein the first conductive bipolar plate is provided with a cathode electrolyte flow channel for passing a nitrate solution with a pH value of 0 to 7, the second conductive bipolar plate is provided with an anode electrolyte flow channel for passing a sulfide solution with a pH value of 12 to 14 as the anode electrolyte, and the cathode electrode is Ru / WO supported on carbon paper. 3-x Catalyst, the anode electrode is NiS supported on nickel foam x catalyst.

[0011] The advantages of the technical solution provided by the present invention are:

[0012] (1) Nitrate solution undergoes reduction reaction at the cathode, and Ru / WO 3-x Under the action of the catalyst, ammonia, an important agricultural fertilizer and chemical raw material, is produced. (2) The sulfide solution undergoes oxidation reaction at the anode, and NiS x Under the action of the catalyst, thiosulfate is generated, which is an antidote in the medical field and a fixer in the photography field. (3) The coordinated purification of nitrates and sulfides is achieved and products with production value are generated. At the same time, chemical energy is converted into electrical energy, resulting in power output. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of the sulfide-nitrate collaborative purification device of the embodiment.

[0014] Figure 2 This is the potential-pH diagram for nitrate reduction and sulfide oxidation reactions.

[0015] Figure 3 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 0, the anolyte pH is 14, the concentration is 1 mol / L, and the reaction temperature is 25°C.

[0016] Figure 4 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 7, the anolyte pH is 14, the concentration is 1 mol / L, and the reaction temperature is 25°C.

[0017] Figure 5 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 14, the anolyte pH is 14, the concentration is 1 mol / L, and the reaction temperature is 25°C.

[0018] Figure 6This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 0, the anode electrolyte pH is 12, the concentration is 1 mol / L, and the reaction temperature is 25°C.

[0019] Figure 7 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 0, the anolyte pH is 14, the concentration is 0.5 mol / L, and the reaction temperature is 25°C.

[0020] Figure 8 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 0, the anolyte pH is 14, the concentration of both is 0.1 mol / L, and the reaction temperature is 25°C.

[0021] Figure 9 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 0, the anolyte pH is 14, the concentration is 1 mol / L, and the reaction temperature is 60°C.

[0022] Figure 10 This is the polarization curve of the sulfide-nitric acid flow battery when the cathode electrolyte pH is 0, the anolyte pH is 14, the concentration is 1 mol / L, and the reaction temperature is 80°C.

[0023] Figure 11 The pH of the cathode electrolyte is 0, the pH of the anolyte is 14, the concentration of both is 1 mol / L, the reaction temperature is 25 °C, and the operating current density is 25 mA cm -2 The chronopotentiometry curve of the sulfide-nitric acid flow battery and the production rate of the products ammonia and thiosulfate are shown. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the following examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading this description, various equivalent modifications to this description by those skilled in the art fall within the scope defined by the claims appended to this application.

[0025] Please combine Figure 1 As shown, the sulfide-nitrate co-purification device involved in this embodiment is a liquid flow battery constructed by a membrane electrode flow reactor. Specifically, it includes a first protective plate 1, a first conductive bipolar plate 2, a cathode electrode 3, a proton exchange membrane 4, an anode electrode 5, a second conductive bipolar plate 6, and a second protective plate 7 stacked in sequence. The first protective plate 1 and the second protective plate 7 are insulating polyetheretherketone plates. The first conductive bipolar plate 2 and the second conductive bipolar plate 6 are titanium plates with serpentine flow channels, and the reaction area is 2cm×2cm. The cathode electrode 3 is Ru / WO supported on carbon paper. 3-x Catalyst, for its synthesis please refer to Nat. commun. 2022,13 ,5382(DOI: 10.1038 / s41467-022-33007-3)and Energy Environ. Sci. 2025, 18 , 818-830 (DOI: 10.1039 / D4EE03970J), the anode electrode 5 is NiS supported on nickel foam x Catalyst, for its synthesis please refer to Green Chem. 2021, 23 , 6975–6983 (DOI: 10.1039 / d1gc01857d) and Angew. Chem. Int. Ed. 2024, 63 , e202411977 (DOI: 10.1002 / anie.202411977), the reaction area of ​​the cathode electrode 3 and the anode electrode 5 are both 2 cm × 2 cm. A torque wrench is used for assembly and tightening, with a torque of 6 N·m.

[0026] Sulfide-nitrate collaborative purification is to pass the nitrate solution as the cathode electrolyte into the serpentine flow channel of the first conductive bipolar plate, and pass the sulfide solution as the anode electrolyte into the serpentine flow channel of the second conductive bipolar plate. Figure 2 The potential-pH diagram shown in the figure shows that the standard electrode potential of the nitrate reduction reaction is always higher than the standard electrode potential of the sulfide oxidation reaction. Therefore, the two constitute a primary cell that can output current. Nitrate reduction reaction occurs at the cathode of the battery. 3-x Ammonia can be generated under the action of the catalyst. Ammonia is an important agricultural fertilizer and chemical raw material. Sulfide oxidation reaction occurs at the anode. x Under the action of catalyst, thiosulfate can be generated. Thiosulfate is an antidote in the medical field and a fixer in the photography field.

[0027] By controlling the pH gradient difference between the cathode electrolyte and the anode electrolyte, the concentration of the reactants, and the reaction temperature, the constructed flow battery was tested for battery performance. Specifically, the steady-state chronopotentiometry was used to obtain the battery polarization curve. The battery discharge power density was then calculated using the formula (discharge power density = discharge voltage × discharge current density) to obtain the battery discharge power density curve. The cathode electrolyte used in each test was a potassium nitrate solution, and the anode electrolyte was a sodium sulfide solution. It should be noted that the nitrate forming the cathode electrolyte can be one or more of sodium nitrate, potassium nitrate, calcium nitrate, and ammonium nitrate, and the sulfide forming the anode electrolyte can be one or more of sodium sulfide, potassium sulfide, calcium sulfide, and ammonium sulfide.

[0028] The reaction was carried out at 25°C using 1 mol / L potassium nitrate solution as the cathode electrolyte and 1 mol / L sodium sulfide solution as the anode electrolyte. Figures 3 to 6As shown in the polarization curve, when the pH of the cathode electrolyte is 0 and the pH of the anode electrolyte is 14, the flow battery can reach 26.52 mW / cm 2 Peak discharge power density: When the pH of the cathode electrolyte is increased to 7 and the pH of the anolyte is 14, the maximum discharge power density of the flow battery drops to 6.54 mW / cm 2 When the pH of the cathode electrolyte is raised to 14 and the pH of the anolyte is also 14, the device becomes an electrolyzer rather than a primary battery, and therefore cannot achieve power output. When the pH of the cathode electrolyte is 0 and the pH of the anolyte is 12, the maximum discharge power density of the flow battery drops to 13.68 mW / cm 2 Therefore, the pH of the cathode electrolyte is selected to be 0-7, and the pH of the anode electrolyte is selected to be 12-14. The reduction of the pH gradient difference between the two-stage electrolyte will reduce the battery discharge power density and even transform it into an electrolytic cell.

[0029] The reaction was carried out at 25°C using potassium nitrate solution with a pH of 0 as the cathode electrolyte and sodium sulfide solution with a pH of 14 as the anode electrolyte. Figure 3 、 Figure 7 and Figure 8 As shown in the polarization curve, when the concentration of potassium nitrate solution and sodium sulfide solution is 1 mol / L, the flow battery can reach 26.52 mW / cm 2 Peak discharge power density: When the concentration of potassium nitrate solution and sodium sulfide solution is 0.5 mol / L, the maximum discharge power density of the flow battery drops to 25.74 mW / cm 2 When the concentration of potassium nitrate solution and sodium sulfide solution is 0.1 mol / L, the maximum discharge power density of the flow battery drops to 22.85 mW / cm 2 Therefore, increasing the electrolyte concentration is beneficial to enhancing the discharge power density of flow batteries.

[0030] The reaction was carried out at different temperatures using a 1 mol / L potassium nitrate solution with a pH of 0 as the cathode electrolyte and a 1 mol / L sodium sulfide solution with a pH of 14 as the anode electrolyte. Figure 3 、 Figure 9 and Figure 10 As shown in the polarization curve, when the reaction temperature is 25 ° C, the peak discharge power density of the flow battery is 26.52 mW / cm 2 When the reaction temperature is further increased to 60 °C, the peak discharge power density of the flow battery is 27.72 mW / cm 2 When the reaction temperature reaches 80℃, the peak discharge power density of the flow battery is 28.32 mW / cm 2 Therefore, increasing the reaction temperature is also beneficial to enhancing the discharge power density of flow batteries.

[0031] Finally, 1 mol / L potassium nitrate solution with pH 0 was used as the cathode electrolyte, and 1 mol / L sodium sulfide solution with pH 14 was used as the anode electrolyte. -2 The stability of the flow battery and the rate of production of ammonia and thiosulfate were tested at different current densities. Ammonia was quantified using the indophenol blue method and thiosulfate was titrated using the iodine titration method. Figure 11 As shown in the chronopotentiometry curve and product generation rate diagram, the voltage of the flow battery gradually decreases with the extension of reaction time. This is because the cathode and anode reactions consume acid and base, and the pH gradient difference between the two electrodes gradually decreases. In addition, the average ammonia generation rate increases from 0.0651 mmol h -1 cm -2 Increased to 0.0724 mmol h -1 cm -2 , while the average generation rate of thiosulfate increased from 0.0822 mmol h -1 cm -2 Increased to 0.0932 mmol h -1 cm -2 Therefore, this flow battery has the potential to convert nitrates and sulfides into ammonia and thiosulfate, respectively.

Claims

1. A sulfide-nitrate collaborative purification method, characterized in that: include: Ru / WO supported on carbon paper 3-x The catalyst is the cathode, and the potassium nitrate solution with pH value 0 is used as the cathode electrolyte. x The catalyst is used as the anode, and a sodium sulfide solution with a pH value of 14 is used as the anode electrolyte. A proton exchange membrane is set between the cathode and the anode to construct a liquid flow battery to catalyze the redox reaction to purify sodium sulfide and potassium nitrate.

2. The sulfide-nitrate collaborative purification method according to claim 1, characterized in that: The potassium nitrate concentration of the cathode electrolyte is 1 mol / L.

3. The sulfide-nitrate collaborative purification method according to claim 1, characterized in that: The sodium sulfide concentration of the anolyte is 1 mol / L.

4. The sulfide-nitrate collaborative purification method according to claim 1, characterized in that: The reaction temperature during the catalytic redox reaction is 25-80°C.

5. A sulfide-nitrate collaborative purification device, characterized in that: The invention relates to a flow battery comprising a first protective plate, a first conductive bipolar plate, a cathode electrode, a proton exchange membrane, an anode electrode, a second conductive bipolar plate and a second protective plate stacked in sequence. The first conductive bipolar plate is provided with a cathode electrolyte flow channel and is fed with a potassium nitrate solution with a pH value of 0. The second conductive bipolar plate is provided with an anolyte flow channel and is fed with a sodium sulfide solution with a pH value of 14 as the anolyte. The cathode electrode is a Ru / WO2 supported on carbon paper. 3-x Catalyst, the anode electrode is NiS supported on nickel foam x catalyst.

6. The sulfide-nitrate collaborative purification device according to claim 5, characterized in that: The potassium nitrate concentration of the cathode electrolyte is 1 mol / L.

7. The sulfide-nitrate collaborative purification device according to claim 5, characterized in that: The sodium sulfide concentration of the anolyte is 1 mol / L.

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