Sulfide-nitrate synergistic purification method and device

Abstract

The invention discloses a sulfide-nitrate synergistic purification method which comprises the following steps: taking a Ru / WO3-x catalyst loaded on carbon paper as a cathode, a nitrate solution with the pH value of 0-7 as a catholyte, a NiSx catalyst loaded on foamed nickel as an anode and a sulfide solution with the pH value of 12-14 as an anolyte; a proton exchange membrane is arranged between the cathode and the anode to construct a flow battery at intervals for catalytic oxidation-reduction reaction to purify sulfide and nitrate. The invention also discloses a sulfide-nitrate synergistic purification device corresponding to the flow battery structure. Sulfide and nitrate can be converted into thiosulfate and ammonia at the same time through the catalytic oxidation-reduction reaction, and power output is achieved.

Description

Technical Field

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

[0002] Both sulfide and nitrate are common waste pollutants in industrial processes, and need to be purified to meet the discharge requirements. Traditional methods for purifying sulfide include physical adsorption method, chemical wet absorption and dry oxidation method, and biological enzyme catalysis method, etc. Traditional methods for purifying nitrate include chemical oxidation - reduction method and biological denitrification adsorption method, etc. These methods cannot be unified synchronously, and sulfide and nitrate usually need to be purified separately. Summary of the Invention

[0003] Aiming at the defects of the above - mentioned prior art, the present invention provides a method for synergistically purifying sulfide - nitrate, and the present invention also provides a device for synergistically purifying sulfide - nitrate, so as to realize the simultaneous purification treatment of sulfide - nitrate.

[0004] The technical solution of the present invention is as follows: A method for synergistically purifying sulfide - nitrate, comprising: using Ru / WO supported on carbon paper as the cathode, using a nitrate solution with a pH value of 0 - 7 as the cathode electrolyte, using NiS supported on nickel foam as the anode, using a sulfide solution with a pH value of 12 - 14 as the anode electrolyte, and arranging a proton exchange membrane between the cathode and the anode to separate and construct a flow battery for catalytic oxidation - reduction reaction to purify sulfide and nitrate. 3-x catalyst as the cathode, using a nitrate solution with a pH value of 0 - 7 as the cathode electrolyte, using NiS supported on nickel foam as the x catalyst as the anode, using a sulfide solution with a pH value of 12 - 14 as the anode electrolyte, and arranging a proton exchange membrane between the cathode and the anode to separate and construct a flow battery for catalytic oxidation - reduction reaction to purify sulfide and nitrate.

[0005] Further, the nitrate concentration in the cathode electrolyte is 0.1 - 1 mol / L.

[0006] Further, the sulfide concentration in the anode electrolyte is 0.1 - 1 mol / L.

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

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

[0009] Further, the reaction temperature during the catalytic oxidation - reduction reaction is 25 - 80 °C.

[0010] Another technical solution of the present invention is: a sulfide-nitrate synergistic purification device, including a flow battery composed of 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 for introducing a nitrate solution with a pH value of 0 to 7, and the second conductive bipolar plate is provided with an anode electrolyte flow channel for introducing a sulfide solution with a pH value of 12 to 14 as the anode electrolyte. The cathode electrode is a Ru / WO 3-x catalyst loaded on carbon paper, and the anode electrode is a NiS x catalyst loaded on nickel foam.

[0011] The advantages of the technical solution provided by the present invention are as follows: (1) The nitrate solution undergoes a reduction reaction at the cathode, and important agricultural fertilizers and chemical raw material ammonia are generated under the action of the Ru / WO 3-x catalyst. (2) The sulfide solution undergoes an oxidation reaction at the anode, and thiosulfate is generated under the action of the NiS x catalyst. Thiosulfate is an antidote in the medical field and a fixing agent in the photography field. (3) The synergistic purification of nitrate and sulfide is realized, and valuable products are generated. At the same time, chemical energy is converted into electrical energy to obtain power output. Brief Description of the Drawings

[0012] Figure 1 is a schematic structural diagram of the sulfide-nitrate synergistic purification device in the embodiment.

[0013] Figure 2 is a potential-pH diagram of the nitrate reduction and sulfide oxidation reactions.

[0014] Figure 3 is a polarization curve diagram of the sulfide-nitrate flow battery when the pH of the cathode electrolyte is 0, the pH of the anode electrolyte is 14, the concentrations are both 1 mol / L, and the reaction temperature is 25 °C.

[0015] Figure 4 is a polarization curve diagram of the sulfide-nitrate flow battery when the pH of the cathode electrolyte is 7, the pH of the anode electrolyte is 14, the concentrations are both 1 mol / L, and the reaction temperature is 25 °C.

[0016] Figure 5 is a polarization curve diagram of the sulfide-nitrate flow battery when the pH of the cathode electrolyte is 14, the pH of the anode electrolyte is 14, the concentrations are both 1 mol / L, and the reaction temperature is 25 °C.

[0017] Figure 6It is the polarization curve graph of a sulfide-nitric acid flow battery when the pH of the catholyte is 0, the pH of the anolyte is 12, the concentration of both is 1 mol / L, and the reaction temperature is 25 °C.

[0018] Figure 7 It is the polarization curve graph of a sulfide-nitric acid flow battery when the pH of the catholyte is 0, the pH of the anolyte is 14, the concentration of both is 0.5 mol / L, and the reaction temperature is 25 °C.

[0019] Figure 8 It is the polarization curve graph of a sulfide-nitric acid flow battery when the pH of the catholyte is 0, the pH of the anolyte is 14, the concentration of both is 0.1 mol / L, and the reaction temperature is 25 °C.

[0020] Figure 9 It is the polarization curve graph of a sulfide-nitric acid flow battery when the pH of the catholyte is 0, the pH of the anolyte is 14, the concentration of both is 1 mol / L, and the reaction temperature is 60 °C.

[0021] Figure 10 It is the polarization curve graph of a sulfide-nitric acid flow battery when the pH of the catholyte is 0, the pH of the anolyte is 14, the concentration of both is 1 mol / L, and the reaction temperature is 80 °C.

[0022] Figure 11 It is the chronopotentiometry curve graph of a sulfide-nitric acid flow battery and the production rate graph of products ammonia and thiosulfate when the pH of the catholyte 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 at this time. Specific Embodiments

[0023] The present invention will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading this description, various equivalent modifications of this description by those skilled in the art all fall within the scope defined by the appended claims of this application.

[0024] Please refer to Figure 1 As shown, the sulfide-nitrate synergistic purification device involved in this embodiment is a flow battery constructed by a membrane electrode flow reactor. It specifically 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. Among them, the first protective plate 1 and the second protective plate 7 are insulating polyether ether ketone 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 2 cm × 2 cm. The cathode electrode 3 is a Ru / WO supported on carbon paper 3-x catalyst, and its synthesis can be referred 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 x catalyst loaded on nickel foam, and its synthesis can be referred 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 areas of both the cathode electrode 3 and the anode electrode 5 are 2 cm × 2 cm. A torque wrench is used for assembly and compression, and the torque is 6 N·m.

[0025] In the sulfide - nitrate synergistic purification, the nitrate solution is introduced into the serpentine flow channel of the first conductive bipolar plate as the cathode electrolyte, and the sulfide solution is introduced into the serpentine flow channel of the second conductive bipolar plate as the anode electrolyte. Please combine with Figure 2 the potential - pH diagram shown. The standard electrode potential of the nitrate reduction reaction is always higher than that of the sulfide oxidation reaction. Therefore, the two form a primary battery and can output current externally. The nitrate reduction reaction occurs at the cathode of the battery and can generate ammonia under the action of the Ru / WO 3-x catalyst. Ammonia is an important agricultural fertilizer and chemical raw material. The sulfide oxidation reaction occurs at the anode and can generate thiosulfate under the action of the NiS x catalyst. Thiosulfate is an antidote in the medical field and a fixing agent in the photography field.

[0026] By regulating the pH gradient difference, reactant concentration, and reaction temperature of the cathode electrolyte and the anode electrolyte, the battery performance of the constructed flow battery was tested. Specifically, the polarization curve of the battery was obtained by using the steady - state chronopotentiometry method. Subsequently, the battery discharge power density curve was obtained by calculating the battery discharge power density through the formula (discharge power density = discharge voltage × discharge current density). Among them, the cathode electrolyte used in each test is potassium nitrate solution, and the anode electrolyte is 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 is one or more of sodium sulfide, potassium sulfide, calcium sulfide, and ammonium sulfide.

[0027] Using 1 mol / L potassium nitrate solution as the cathode electrolyte and 1 mol / L sodium sulfide solution as the anode electrolyte, the reaction is carried out at 25 °C. Please combine with 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 peak discharge power density of the flow battery can reach 26.52 mW / cm 2 ; when the pH of the cathode electrolyte is increased to 7 and the pH of the anode electrolyte 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 increased to 14 and the pH of the anode electrolyte is also 14, the device turns into an electrolytic cell rather than a primary battery, so power output cannot be achieved; when the pH of the cathode electrolyte is 0 and the pH of the anode electrolyte 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. Narrowing the pH gradient difference between the two electrolytes will reduce the battery discharge power density and even turn it into an electrolytic cell.

[0028] Using potassium nitrate solution with pH 0 as the cathode electrolyte and sodium sulfide solution with pH 14 as the anode electrolyte, the reaction is carried out at 25°C. Please combine Figure 3 、 Figure 7 and Figure 8 As shown in the polarization curve, when the concentrations of potassium nitrate solution and sodium sulfide solution are 1 mol / L, the peak discharge power density of the flow battery can reach 26.52 mW / cm 2 ; when the concentrations of potassium nitrate solution and sodium sulfide solution are 0.5 mol / L, the maximum discharge power density of the flow battery drops to 25.74 mW / cm 2 ; when the concentrations of potassium nitrate solution and sodium sulfide solution are 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 the flow battery.

[0029] Using 1 mol / L potassium nitrate solution with pH 0 as the cathode electrolyte and 1 mol / L sodium sulfide solution with pH 14 as the anode electrolyte, the reaction is carried out at different temperatures. Please combine 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 is 80°C, 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 the flow battery.

[0030] Finally, a 1 mol / L potassium nitrate solution with a pH of 0 was used as the cathode electrolyte, and a 1 mol / L sodium sulfide solution with a pH of 14 was used as the anode electrolyte. The stability of the flow battery and the production rates of the products ammonia and thiosulfate were tested at 25 °C and a current density of 25 mA cm -2 . Among them, ammonia was quantified by the indophenol blue method and thiosulfate was titrated by the iodometric method. Combining Figure 11 with the chronopotentiometry curve and the product production rate diagram shown, as the reaction time extended, the voltage of the flow battery gradually decreased because the anode and cathode reactions consumed acids and bases, and the pH gradient difference between the two electrodes gradually narrowed. In addition, the average production rate of ammonia increased from 0.0651 mmol h -1 cm -2 to 0.0724 mmol h -1 cm -2 , while the average production rate of thiosulfate increased from 0.0822 mmol h -1 cm -2 to 0.0932 mmol h -1 cm -2 . Therefore, this flow battery has the prospect of converting nitrate and sulfide 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 used as the cathode, and a nitrate solution with a pH value of 0 to 7 is used as the cathode electrolyte. The NiS supported on the nickel foam x The catalyst is used as the anode, and a sulfide solution with a pH value of 12 to 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 for catalytic redox reaction to purify sulfide and nitrate.

2. The sulfide-nitrate collaborative purification method according to claim 1, characterized in that: The nitrate concentration of the cathode electrolyte is 0.1-1 mol / L.

3. The sulfide-nitrate coordinated purification method according to claim 1, characterized in that: The sulfide concentration of the anode electrolyte is 0.1-1 mol / L.

4. The sulfide-nitrate coordinated purification method according to claim 1, characterized in that: The nitrate is one or more of sodium nitrate, potassium nitrate, calcium nitrate and ammonium nitrate.

5. The sulfide-nitrate coordinated purification method according to claim 1, characterized in that: The sulfide is one or more of sodium sulfide, potassium sulfide, calcium sulfide and ammonium sulfide.

6. The sulfide-nitrate coordinated purification method according to claim 1, characterized in that: The reaction temperature during the catalytic oxidation-reduction reaction is 25-80°C.

7. A sulfide-nitrate coordinated 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, 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 an anode electrolyte, the cathode electrode is Ru / WO supported on carbon paper 3-x Catalyst, the anode electrode is NiS supported on nickel foam x catalyst.

8. The sulfide-nitrate coordinated purification device according to claim 7, characterized in that: The nitrate concentration of the cathode electrolyte is 0.1-1 mol / L.

9. The sulfide-nitrate coordinated purification device according to claim 7, characterized in that: The nitrate concentration of the anolyte is 0.1-1 mol / L.

10. The sulfide-nitrate coordinated purification device according to claim 7, characterized in that: The nitrate is one or more of sodium nitrate, potassium nitrate, calcium nitrate and ammonium nitrate, and the sulfide is one or more of sodium sulfide, potassium sulfide, calcium sulfide and ammonium sulfide.

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