Electrochemical reduction hydrogen storage method for industrial wastewater

Abstract

The application belongs to the technical field of electrochemical hydrogen storage, and particularly relates to an electrochemical reduction hydrogen storage method for industrial wastewater, which comprises the following steps: S1, mixing a solid catalyst, a polyacid and industrial wastewater to obtain a liquid as a cathode liquid for standby; S2, preparing a certain concentration of a protic solution as an anode liquid for standby; S3, using the cathode liquid and the anode liquid to build an electrochemical reactor, inserting a working electrode into the cathode liquid, inserting an anode electrode into the anode liquid, separating the cathode liquid and the anode liquid by using a proton membrane, and forming a current loop; and S4, after protective gas is introduced into the cathode chamber, turning on a power switch, introducing current into an electrolytic cell, and performing electrochemical reaction at a certain temperature, so that the treatment of the wastewater and the hydrogen storage target can be achieved. The application can realize the reduction treatment of the industrial wastewater and the preparation of a novel hydrogen storage energy in the cathode liquid, and the solid catalyst and the polyacid can be recycled and reused.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical hydrogen storage, and particularly relates to an electrochemical reduction hydrogen storage method for industrial wastewater. BACKGROUND

[0002] Nitrogen pollution in industrial wastewater is one of the important problems in environmental governance. A large amount of nitrogen-containing wastewater is discharged in the production processes of fertilizer production, petroleum chemical industry, pharmaceutical industry, food industry, etc., and the nitrogen in the wastewater mainly exists in the form of nitrate and nitrite. Once the wastewater is discharged into water bodies without treatment, it will cause eutrophication of the ecological system, pollute drinking water resources, and seriously threaten human health.

[0003] At present, common industrial wastewater denitrification technologies include biological denitrification, chemical nitrogen removal, membrane separation, etc. These technologies can effectively remove nitrogen pollutants in wastewater, but there are many limitations in the scope of application. The denitrification products cannot be effectively utilized or still need further treatment due to the influence of wastewater characteristics. Ammonia, as one of the most common chemical products in modern society, has been widely used in agriculture, medicine, textiles, etc. Its mature storage and transportation process and high energy density are expected to become a new type of hydrogen storage energy. In recent years, the electrochemical reduction of nitrogen oxides in industrial wastewater using renewable energy power has attracted widespread attention. Using green energy, high-valence nitrate and nitrite can be reduced to ammonia to realize hydrogen storage. This technology not only can replace the Haber-Bosch process with huge energy consumption, but also can effectively treat industrial wastewater to realize nitrogen cycle. However, the existing electrochemical treatment technology is affected by the concentration of nitrogen oxides in wastewater, especially the treatment effect of low-concentration nitrogen oxides is not good. Moreover, the reduction reaction of nitrogen oxides between the solid-liquid phases of the working electrode causes the problem of local mass transfer of reactants and intermediates, affecting the reaction efficiency.

[0004] In view of the above, it is of great application value to develop an efficient electrochemical reduction hydrogen storage method for industrial wastewater. SUMMARY

[0005] The purpose of the present application is to provide an electrochemical reduction hydrogen storage method for industrial wastewater, which can effectively solve the problem of heat and mass transfer of reactants and intermediates in traditional electrochemical methods, improve the reaction efficiency, and greatly reduce the treatment cost by adding polyacid and solid catalyst in the cathode liquid.

[0006] To achieve the above purpose, the present application provides an electrochemical reduction hydrogen storage method for industrial wastewater, comprising the following steps:

[0007] S1: mixing the solid catalyst, the polyacid and the industrial wastewater to obtain a catholyte; wherein the industrial wastewater contains nitrogen oxide compounds; the solid catalyst is a hydrogen transfer catalyst, which is used to promote the combination of the polyacid with protons and electrons to form a reduced polyacid, and to promote the reaction of the reduced polyacid with nitrogen oxide compounds;

[0008] S2: preparing a protic solution as an anolyte;

[0009] S3: assembling an electrochemical reactor, and placing the catholyte in a cathode chamber and the anolyte in an anode chamber, inserting a working electrode into the catholyte and an anode electrode into the anolyte, separating the cathode chamber and the anode chamber by a proton membrane, and forming a current loop;

[0010] S4: after introducing a protective gas into the cathode chamber, turning on the power supply, introducing an electric current into the electrochemical reactor through the working electrode and the anode electrode, and making the electrochemical reactor perform an electrochemical reaction at a preset temperature.

[0011] Further, the solid catalyst is one or more of platinum carbon, rhodium carbon, ruthenium carbon, palladium carbon and molybdenum sulfide; the polyacid is one or more of tungsten, titanium, molybdenum or antimony metal acid. The polyacid refers to polyoxometalate.

[0012] Further, the density of the electric current is 100-5000 mA / cm 2 , the temperature of the electrochemical reaction is 0-80℃, and the reaction time is 2-20h.

[0013] Further, the concentration of the nitrogen oxide compounds is 0.05 mmol / L-1.8 mol / L.

[0014] Further, the concentration of the polyacid in the catholyte is 0.01-0.5 mol / L, and the concentration of the solid catalyst in the catholyte is 0.4-8 g / L.

[0015] Further, the protic solution is an acidic solution, a basic solution or a salt solution, the acidic solution includes one or more of phosphoric acid, sulfuric acid and hydrochloric acid, the basic solution includes one or more of sodium hydroxide, potassium hydroxide and sodium bicarbonate, and the salt solution includes one or more of sodium phosphate, sodium sulfate and sodium chloride; the concentration of the protic solution is 0.1-5.0 mol / L.

[0016] Further, after the electrochemical reaction, the solid catalyst in the catholyte is recovered by filtration, the ammonium salt and the polyacid are obtained by cation and anion exchange separation of the filtered catholyte, and finally the solid product ammonium salt and the polyacid are obtained by evaporation crystallization. If the catholyte is a basic solution, ammonia water and ammonia gas can be obtained by heating.

[0017] Further, the industrial wastewater is derived from wastewater generated by chemical fertilizer production, petrochemical industry, pharmaceutical and food industry, printing and cleaning, or nuclear power station, and is prepared into catholyte for standby use after filtration treatment.

[0018] Further, the working electrode is a metal material electrode or a non-metal material electrode; the metal material electrode is selected from a nickel electrode, a copper electrode, a platinum electrode or a gold electrode; and the non-metal material electrode is selected from a carbon material electrode, including a graphite electrode, a graphene electrode or a carbon nanotube electrode.

[0019] Further, the anode electrode is a copper electrode, a platinum electrode, a rhodium electrode, a ruthenium electrode or a metal oxide electrode.

[0020] Further, the protective gas is argon, helium or nitrogen.

[0021] Overall, compared with the prior art, the above technical scheme conceived by the present application mainly has the following technical advantages:

[0022] 1. The electrochemical reduction hydrogen storage method for industrial wastewater provided by the present application makes the active hydrogen generated in the cathode chamber not escape in the form of hydrogen gas, but combine with polyacid to become an electron carrier under the action of electric energy and a catalyst; then, the nitrogen-oxygen compound in the catholyte reacts with the reduced polyacid under the action of the catalyst, the nitrogen-oxygen bond is gradually broken, and the active hydrogen released by the polyacid is combined at the same time, so that ammonia is finally generated to achieve the energy storage target. Therefore, compared with the prior art of electrochemical reduction of industrial wastewater, the present application solves the problem of local mass transfer of reactants and intermediates, thereby avoiding the influence of the concentration of nitrogen-oxygen compounds in different wastewaters on the reduction treatment of the wastewater, has extremely high reaction efficiency, and can effectively reduce low-concentration nitrogen-oxygen compounds.

[0023] 2. The present application uses polyacid as a reduction medium to transfer the reduction reaction of nitrogen-oxygen compounds between the solid and liquid phases of the working electrode to the liquid phase of the catholyte. Compared with the prior art of electrochemical treatment, the influence of the cathode competitive hydrogen evolution reaction on the reduction treatment of the wastewater is eliminated, and under the action of renewable energy power, the electrochemical reaction parameters and the types of catalysts can be flexibly controlled, so that efficient preparation and selection of products can be realized.

[0024] 3. The present application does not depend on the preparation of a composite electrode, and can flexibly select a conventional electrode, thereby greatly reducing the technical cost and having a broader application prospect.

[0025] 4. The polyacid and the solid catalyst used in the present application are stable and do not deteriorate during the reaction, and can be recycled and reused during the product extraction process. The recovery rate of the solid metal acid can be as high as 95% or more.

[0026] 5. In this invention, the electrolyte is preferably acidic, which can effectively provide abundant protons for the reduction of nitrogen oxides, and has a low energy barrier and ohmic resistance loss, thus filling the gap in the current electrochemical treatment of industrial wastewater in acidic systems. Attached Figure Description

[0027] Figure 1 The flowchart of the electrochemical reduction hydrogen storage method for industrial wastewater provided by the present invention is shown. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] like Figure 1 As shown, the electrochemical reduction hydrogen storage method for industrial wastewater provided by the present invention includes the following steps:

[0030] S1: Mix the solid catalyst, polyacid, and industrial wastewater to obtain a liquid that can be used as a cathode liquid.

[0031] The catholy solution contains 0.01-0.5 mol / L of polyacid, 0.4-8 g / L of solid catalyst, and 0.05 mmol / L-1.8 mol / L of nitrogen oxides. In practical applications, the concentration of polyacid can be adjusted according to the concentration of nitrogen oxides.

[0032] In a further preferred embodiment, the polyacid can be a metal acid of tungsten, titanium, molybdenum, or antimony, such as silicotungstic acid, phosphotungstic acid, phosphomolybdic acid, etc. The solid catalyst is one or more of platinum on carbon, rhodium on carbon, ruthenium on carbon, palladium on carbon, and molybdenum sulfide.

[0033] S2: Prepare a protonated solution of a certain concentration as the anolyte for later use.

[0034] The protonated solution can dissociate into protons (hydrogen ions) in the solution and pass through the proton exchange membrane into the catholyte, providing a sufficient hydrogen source for the reduction and storage of nitrogen oxides in industrial wastewater. In a further preferred embodiment, the protonated solution includes acidic solutions such as phosphoric acid, sulfuric acid, and hydrochloric acid; salt solutions such as sodium phosphate, sodium sulfate, and sodium chloride; and alkaline solutions such as sodium hydroxide, potassium hydroxide, and sodium bicarbonate.

[0035] S3: An electrochemical reactor (electrolytic cell) is constructed using the above-mentioned catholy and anolyte. A working electrode is inserted into the catholy and an anode electrode is inserted into the anolyte. The two chambers are separated by a proton exchange membrane, forming a current loop.

[0036] Specifically, the electrolytic cell adopts a three-electrode system, the working electrode adopts graphite, the counter electrode adopts platinum mesh, and the reference electrode adopts a silver / silver chloride electrode. The proton exchange membrane allows protons hydrogen in the anode liquid to pass into the cathode liquid, and effectively separates the anode liquid and the cathode liquid. Currently, Nafion-115, Nafion-117 membrane and the like can be used.

[0037] S4: After the protective gas is introduced into the above-mentioned cathode chamber, the power switch is turned on, the current is introduced into the electrolytic cell, and the electrochemical reaction is carried out at a certain temperature, so that the purposes of wastewater treatment and hydrogen storage can be achieved. According to the concentration of nitrogen oxide compounds in the wastewater, the current density and the reaction temperature can be adjusted to improve the electrolysis efficiency.

[0038] The reaction process of the electrochemical reactor constructed by the present application is as follows:

[0039] Cathode reaction 1:

[0040] Cathode reaction 2:

[0041] Anode reaction: Proton solution→oxygen+proton+electron.

[0042] Among them, the hydrogen storage wastewater refers to the wastewater in which the nitrogen oxide compounds are reduced to ammonia water or ammonium salt. The proton refers to the hydrogen ion, and the proton and the electron can combine to form active hydrogen. And because the reduction potential of the cathode polyacid is low, the hydrogen ion can be prevented from forming hydrogen gas overflow.

[0043] Under the action of electric energy and solid catalyst, the active hydrogen generated in the cathode chamber will not form hydrogen gas overflow, but will combine with the polyacid to become a reduced state polyacid, which becomes an electron carrier; further, under the action of the catalyst, the nitrogen oxide compounds in the cathode liquid react with the reduced state polyacid, the nitrogen-oxygen bond is gradually broken, and at the same time, the active hydrogen released by the polyacid is combined, and finally ammonia is generated to achieve the purpose of hydrogen storage.

[0044] Example 1

[0045] 25 mL of industrial wastewater was measured and rhodium carbon and silicotungstic acid were added into it, and the mixture was mixed to obtain a cathode liquid for standby, wherein the concentration of silicotungstic acid was 0.01 mol / L, the content of catalyst rhodium carbon was 0.4 g / L, and the concentration of nitrogen oxide compounds was 0.05 mol / L; a phosphoric acid solution with a concentration of 0.1 mol / L was prepared as an anode liquid for standby. Assemble an H-type electrolytic cell, separate the cathode liquid and the anode liquid with a Nafion-117 membrane, and then pour the cathode liquid and the anode liquid into the two sides of the electrolytic cell respectively. Insert a graphite electrode and a silver / silver chloride electrode into the cathode liquid, and insert a platinum mesh electrode into the anode liquid. The electrodes are connected by a constant current instrument. After argon gas is introduced into the cathode liquid for 20 min, the power is turned on, and the current density is set to 100 mA / cm2 The reaction temperature is 0°C, and the reaction time is 2 hours. After electrolysis, the separation of the reduction product, silicotungstic acid and solid catalyst is carried out. The specific separation method is as follows: the cathode liquid is collected and filtered to recover the solid catalyst rhodium carbon, and the filtrate is subjected to cation and anion exchange to obtain a silicotungstic acid aqueous solution and an ammonium salt solution. The two solutions are respectively subjected to evaporation and crystallization to obtain a solid ammonium salt and recover the silicotungstic acid.

[0046] Example 2

[0047] 25 mL of industrial wastewater is measured and silicotungstic acid and rhodium carbon are added thereto, and the mixture is fully mixed to obtain a cathode liquid for standby, wherein the concentration of the silicotungstic acid is 0.25 mol / L, the content of the catalyst rhodium carbon is 1 g / L, and the concentration of the nitrogen oxide is 0.5 mol / L. A phosphoric acid solution with a concentration of 2.5 mol / L is prepared as an anode liquid for standby. An H-type electrolytic cell is assembled, the middle is separated by a Nafion-117 membrane, the cathode liquid and the anode liquid are respectively filled into the two sides of the electrolytic cell, a graphite electrode and a silver / silver chloride electrode are inserted into the cathode liquid, and a platinum mesh electrode is inserted into the anode liquid. The electrodes are connected by a constant current instrument. After argon is introduced into the cathode liquid side for 20 minutes, the power is turned on, the current density is set to 1000 mA / cm 2 The reaction temperature is 30°C, and the reaction time is 4 hours. After electrolysis, the separation of the reduction product, silicotungstic acid and solid catalyst is carried out. The separation method is the same as that in Example 1.

[0048] Example 3

[0049] 25 mL of industrial wastewater is measured and silicotungstic acid and rhodium carbon are added thereto, and the mixture is fully mixed to obtain a cathode liquid for standby, wherein the concentration of the silicotungstic acid is 0.25 mol / L, the content of the catalyst rhodium carbon is 1 g / L, and the concentration of the nitrogen oxide is 0.5 mol / L. A phosphoric acid solution with a concentration of 2.5 mol / L is prepared as an anode liquid for standby. An H-type electrolytic cell is assembled, the middle is separated by a Nafion-117 membrane, the cathode liquid and the anode liquid are respectively filled into the two sides of the electrolytic cell, a graphite electrode and a silver / silver chloride electrode are inserted into the cathode liquid, and a platinum mesh electrode is inserted into the anode liquid. The electrodes are connected by a constant current instrument. After argon is introduced into the cathode liquid side for 20 minutes, the power is turned on, the current density is set to 1000 mA / cm 2 The reaction temperature is 30°C, and the reaction time is 4 hours. After electrolysis, the separation of the reduction product, silicotungstic acid and solid catalyst is carried out. The separation method is the same as that in Example 1.

[0050] Example 4

[0051] Take 25 mL of industrial wastewater, add tungstosilicic acid and rhodium carbon inside, mix well to get catholyte for standby, where the concentration of tungstosilicic acid is 0.5 mol / L, the content of catalyst is 8 g / L, and the concentration of nitrogen oxide is 1.8 mol / L; prepare 5 mol / L phosphoric acid solution as anolyte for standby. Assemble H-type electrolytic cell, separate with Nafion-117 membrane in the middle, fill the catholyte and anolyte into the two sides of the electrolytic cell respectively, insert graphite electrode and silver / silver chloride electrode in the catholyte, and platinum mesh electrode in the anolyte, connect the electrodes with constant current instrument. After argon is introduced into the catholyte side for 20 min, turn on the power, set the current density to 5000 mA / cm 2 , the reaction temperature is 80℃, and the reaction time is 12 h. After electrolysis, separate the reduction product, tungstosilicic acid, and solid catalyst, and the separation method is the same as that in Example 1.

[0052] Example 5

[0053] Take 25 mL of industrial wastewater, add tungstosilicic acid and rhodium carbon inside, mix well to get catholyte for standby, where the concentration of tungstosilicic acid is 0.5 mol / L, the content of catalyst is 8 g / L, and the concentration of nitrogen oxide is 1.8 mol / L; prepare 5 mol / L phosphoric acid solution as anolyte for standby. Assemble H-type electrolytic cell, separate with Nafion-117 membrane in the middle, fill the catholyte and anolyte into the two sides of the electrolytic cell respectively, insert graphite electrode and silver / silver chloride electrode in the catholyte, and platinum mesh electrode in the anolyte, connect the electrodes with constant current instrument. After argon is introduced into the catholyte side for 20 min, turn on the power, set the current density to 5000 mA / cm 2 , the reaction temperature is 80℃, and the reaction time is 12 h. After electrolysis, separate the reduction product, tungstosilicic acid, and solid catalyst, and the separation method is the same as that in Example 1.

[0054] Example 6

[0055] Take 25 mL of industrial wastewater, add tungstosilicic acid and rhodium carbon inside, mix well to get catholyte for standby, where the concentration of tungstosilicic acid is 0.5 mol / L, the content of catalyst is 8 g / L, and the concentration of nitrogen oxide is 1.8 mol / L; prepare 5 mol / L phosphoric acid solution as anolyte for standby. Assemble H-type electrolytic cell, separate with Nafion-117 membrane in the middle, fill the catholyte and anolyte into the two sides of the electrolytic cell respectively, insert graphite electrode and silver / silver chloride electrode in the catholyte, and platinum mesh electrode in the anolyte, connect the electrodes with constant current instrument. After argon is introduced into the catholyte side for 20 min, turn on the power, set the current density to 5000 mA / cm 2The reaction temperature was 80°C, and the reaction time was 20h. After electrolysis, the reduction product, phosphotungstic acid and the solid catalyst were separated, and the separation method was the same as that in Example 1.

[0056] The faradaic efficiency and ammonia yield of Examples 1-6 were calculated, and the formula for calculating the ammonia yield was The experimental results are shown in Table 1.

[0057] Table 1 Experimental results of treating industrial wastewater under different parameters in Examples 1-6

[0058] Examples Faraday efficiency (%) Ammonia yield (%) Example 1 94.3 90.3 Example 2 94.1 92.7 Example 3 97.0 94.2 Example 4 97.2 96.4 Example 5 98.1 96.9 Example 6 97.9 96.4

[0059] As can be seen from Table 1, the method for electrochemically treating industrial wastewater to store hydrogen provided by the application has high ammonia yield and faradaic efficiency, indicating that the reaction efficiency and energy conversion efficiency of the battery are high. When the concentration of nitrogen oxides in the industrial wastewater is only 0.05 mol / L, the yield is also high. When the concentration of nitrogen oxides in the industrial wastewater increases, the concentration of silicotungstic acid in the cathode liquid and the concentration of phosphoric acid in the anode liquid can be increased accordingly. In order to improve the reduction efficiency, the current density of the electrolytic cell can be further increased. The application can adapt to a wide range of electrolysis parameters, while having good electrolytic reduction effect.

[0060] Comparative Example 1

[0061] 25 mL of industrial wastewater was measured and silicotungstic acid was added inside to obtain a cathode liquid for standby, wherein the concentration of silicotungstic acid was 0.25 mol / L, and the concentration of nitrogen oxides was 0.5 mol / L; a phosphoric acid solution with a concentration of 2.5 mol / L was prepared as an anode liquid for standby. An H-type electrolytic cell was assembled, the middle was separated by a Nafion-117 membrane, the cathode liquid and the anode liquid were respectively filled into the two sides of the electrolytic cell, a graphite electrode and a silver / silver chloride electrode were inserted into the cathode liquid, and a platinum mesh electrode was inserted into the anode liquid. The electrodes were connected with a constant current instrument. After argon was introduced into the cathode liquid side for 20 min, the power was turned on, and the current density was set to 1000 mA / cm 2 The reaction temperature was 30°C, and the reaction time was 4h. After electrolysis, the reduction product and silicotungstic acid were separated, and the separation method was the same as that in Example 1.

[0062] In this comparative example 1, the faradaic efficiency was 30.5%, and the ammonia yield was 15.2%. It can be seen that when no catalyst is added to the cathode liquid, the hydrogen gas produced in the cathode liquid is difficult to combine with silicotungstic acid to form an electron carrier, thereby seriously affecting the reduction efficiency and yield of nitrogen oxides.

[0063] Comparative Example 2

[0064] Take 25 mL industrial wastewater, add sulfuric acid and 200 mg rhodium carbon inside, mix well to obtain catholyte for standby, wherein the concentration of sulfuric acid is 0.25 mol / L, and the concentration of nitrogen oxide is 0.5 mol / L; prepare a phosphoric acid solution with a concentration of 2.5 mol / L as anode liquid for standby. Assemble H-type electrolytic cell, separate the catholyte and anode liquid with Nafion-117 membrane, insert graphite electrode and silver / silver chloride electrode into the catholyte, and platinum mesh electrode into the anode liquid, and connect the electrodes with constant current instrument. After argon is introduced into the catholyte for 20 min, the power is turned on, the current density is set to 1000 mA / cm 2 After the electrolysis is completed, the reduction product, sulfuric acid and solid catalyst are separated, and the separation method is the same as that in example 1.

[0065] In the present comparative example 2, the faraday efficiency is 10.5%, and the ammonia yield is 7.2%, which is significantly lower than that of the examples. It can be seen that when no silicotungstic acid is added to the catholyte, the hydrogen generated in the catholyte is difficult to be supported and transferred to the catholyte, and therefore the problems and the competitive hydrogen evolution reaction in the cathode will reduce the reduction treatment effect of the wastewater.

[0066] In summary, by improving the specific parameters and conditions of the electrochemical treatment used in the wastewater treatment method, the present application has wide applicability and strong controllability compared with the existing wastewater denitrification technology. Compared with the existing electrochemical treatment technology, the present application can effectively solve the influence of reactants and intermediates on heat and mass transfer in the traditional electrochemical method, improve the reaction efficiency, and greatly reduce the wastewater treatment cost.

[0067] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electrochemical reduction hydrogen storage method of industrial wastewater, characterized by, The method comprises the following steps: S1: mixing a solid catalyst, a polyacid and industrial wastewater to obtain a catholyte; wherein the industrial wastewater contains nitrogen oxide compounds; the solid catalyst is a hydrogen transfer catalyst, which is used to promote the combination of the polyacid with protons and electrons to form a reduced polyacid, and promote the reaction of the reduced polyacid with nitrogen oxide compounds; S2: preparing a protic solution as an anolyte; S3: assembling an electrochemical reactor, placing the catholyte in a cathode chamber and the anolyte in an anode chamber, inserting a working electrode into the catholyte and an anode electrode into the anolyte, separating the cathode chamber and the anode chamber by a proton membrane, and forming a current loop; S4: after introducing a protective gas into the cathode chamber, turning on the power supply, introducing an electric current into the electrochemical reactor through the working electrode and the anode electrode, and making the electrochemical reactor perform an electrochemical reaction at a preset temperature; the solid catalyst is one or more of platinum carbon, rhodium carbon, ruthenium carbon, palladium carbon and molybdenum sulfide; the polyacid is one or more of tungsten, titanium, molybdenum or antimony metal acid; after the electrochemical reaction, the solid catalyst in the catholyte is recovered by filtration, and the ammonium salt and the polyacid are obtained by separating the cations and anions in the filtered catholyte, and finally the solid product ammonium salt and the polyacid are obtained by evaporation crystallization.

2. The method of claim 1, wherein the industrial wastewater is an aqueous solution of a metal salt. The density of the current is 100-5000 mA / cm 2 The temperature of the electrochemical reaction is 0-80℃, and the reaction time is 2-20h.

3. The method of claim 1, wherein the industrial wastewater is an aqueous solution of a metal salt. The concentration of nitrogen oxide compounds in the catholyte is 0.05 mmol / L-1.8 mol / L.

4. The method of claim 1, wherein the industrial wastewater is an aqueous solution of a metal salt. The concentration of the polyacid in the catholyte is 0.01-0.5 mol / L, and the concentration of the solid catalyst in the catholyte is 0.4-8 g / L.

5. The method of claim 1-4, wherein the method is characterized by, The protic solution is an acidic solution, an alkaline solution or a salt solution, the acidic solution comprises one or more of phosphoric acid, sulfuric acid and hydrochloric acid, the alkaline solution comprises one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate, and the salt solution comprises one or more of sodium phosphate, sodium sulfate and sodium chloride; the concentration of the protic solution is 0.1-5.0 mol / L.

6. The method of claim 1, wherein the industrial wastewater is an aqueous solution of a metal salt. The industrial wastewater is derived from the wastewater generated in the production of chemical fertilizers, petroleum chemical industry, pharmaceuticals and food, printing and cleaning, or nuclear power plants, and is prepared into the catholyte after filtration treatment.

7. The method of claim 1, wherein the industrial wastewater is an aqueous solution of a metal salt. The working electrode is a metal material electrode or a non-metal material electrode; the metal material electrode is selected from nickel electrode, copper electrode, platinum electrode or gold electrode; and the non-metal material electrode is a carbon material electrode, including graphite electrode, graphene electrode or carbon nanotube electrode. The anode electrode is a copper electrode, a platinum electrode, a rhodium electrode, a ruthenium electrode or a metal oxide electrode.

8. The method of claim 1, wherein the industrial wastewater is an aqueous solution of a metal salt. The protective gas is argon, helium or nitrogen.

Images