A ternary metal alloy electrode, its preparation method and application

Abstract

The present invention provides a ternary metal alloy electrode, which uses at least one selected from titanium foam, iron foam, copper foam, nickel foam, aluminum foam and carbon nanofibers as the substrate, and copper, nickel and bismuth metals with a molar ratio of 1:0.1-1.5:0.05-0.8 are deposited on the substrate; the metal deposition amount on the substrate is 1-15 mg / cm<supgt;2< / supgt;. The electrode is prepared by an electrodeposition method. In the electrode of the present invention, the three active metals have a cooperative effect through a specific ratio, and particularly have obvious selectivity and reactivity to nitrate nitrogen, greatly improving the removal efficiency of nitrate nitrogen in wastewater. The electrode substrate has good adsorption performance for nitrate nitrogen. When applied to wastewater treatment, it can enrich more nitrate nitrogen in a shorter time, improve the mass transfer efficiency, and cooperate with the active metal to further improve the reaction efficiency. The electrode of the present invention can achieve 100% removal of nitrate nitrogen in 1 hour, and the total nitrogen removal rate can reach more than 65%.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode preparation, in particular to a ternary metal alloy electrode and its application. Background Art

[0002] Water is a necessary resource for human survival. For sustainable development, it is necessary to further remove nitrate during the wastewater treatment process. The electrocatalytic reduction technology for denitrification has the advantages of high efficiency, simple and easy control, and no need to introduce foreign ions, and has received more and more attention.

[0003] The core of the electrocatalytic reduction technology lies in the cathode material. A high-performance cathode reduction material can convert nitrate nitrogen into nitrogen with high selectivity. Therefore, it is necessary to develop an electrode with excellent performance. Among many cathode materials, copper electrodes and copper-nickel alloy electrodes have relatively excellent nitrate nitrogen reduction performance and long electrode life, and thus have received more and more attention from researchers.

[0004] Patent CN111792705A discloses a graphene oxide-supported carbon-based copper-nickel electrode, a preparation method and uses thereof. The electrode uses a graphite felt material as a substrate, and the substrate is sequentially electrodeposited with graphene oxide and copper-nickel bimetal to obtain the composite electrode. Using this composite electrode as the electrocatalytic reduction cathode, it can be used for the electrochemical reduction of nitrate, and its nitrate nitrogen reduction effect is significantly better than that of commercial electrodes on the market. Patent CN108585125A discloses a carbon-based copper-nickel composite electrode for reducing nitrate nitrogen in water, a preparation method and its application. Using a carbon material as a substrate, carbon nanotubes are first electro-deposited, and then copper-nickel bimetal is electro-deposited to obtain the composite electrode. Using this composite electrode as the cathode of the reaction device, it can be used for the electrochemical reduction of nitrate, and its nitrate nitrogen reduction rate is significantly better than that of a simple copper-nickel electrode. However, the above electrodes still have the disadvantage of low nitrate nitrogen reduction performance, and it is necessary to increase the reaction time to achieve complete removal of nitrate nitrogen. In addition, the selectivity for generating nitrogen is also relatively poor.

[0005] Yu-Jen Shih et al. (Yu-Jen Shih, Zhi-Lun Wu, Yao-Hui Huang, et al. Electrochemical nitrate reduction as affected by the crystal morphology and facet of copper nanoparticles supported on nickel foam electrodes (Cu / Ni), Chemical Engineering Journal. 383 (2020) 123157) prepared a copper-nickel metal alloy electrode. During the reduction process of nitrate nitrogen in water, although it showed excellent nitrate nitrogen reduction performance, the reduction product was mainly ammonia nitrogen, and the selectivity for generating nitrogen gas was poor. For the above reasons, it is necessary to develop an electrode with a simple preparation method, high nitrate nitrogen reduction performance, and high nitrogen gas selectivity. Summary of the Invention

[0006] To solve the deficiencies of the prior art, the present invention provides a preparation method of a ternary metal alloy electrode. By selecting and proportioning the substrate and ternary metal components, a ternary metal alloy electrode is obtained, which has a good effect in wastewater denitrification.

[0007] To achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0008] The technical objective of the first aspect of the present invention is to provide a ternary metal alloy electrode, which uses at least one selected from titanium foam, iron foam, copper foam, nickel foam, aluminum foam, and carbon nanofibers as the substrate, and copper, nickel, and bismuth metals are deposited on the substrate. The molar ratio of copper, nickel, and bismuth is 1:0.1~1.5:0.05~0.8, preferably 1:0.1~1:0.1~0.6, and more preferably 1:0.2~1:0.1~0.5; in the ternary metal alloy electrode, based on the weight of the three metals, the metal deposition amount on the substrate is 1~15mg / cm 2 , preferably 4~12mg / cm 2 , more preferably 6~9mg / cm 2 .

[0009] Furthermore, the titanium foam, iron foam, copper foam, nickel foam, aluminum foam, and carbon nanofibers are in the form of flakes, columns, blocks, filaments, etc. with a certain supporting ability and have good moisture absorption performance. As one of the more specific implementation methods, the porosity of the titanium foam, iron foam, copper foam, aluminum foam, and carbon nanofibers is 93~99%, and the density is 0.1~0.4g / cm 2 .

[0010] The technical object of the second aspect of the present invention is to provide a preparation method of a ternary metal alloy electrode, which uses at least one selected from titanium foam, iron foam, copper foam, nickel foam and aluminum foam as the substrate as the cathode, and uses an acidic solution of copper salt, nickel salt and bismuth salt as the electrolyte solution, and the molar ratio of copper, nickel and bismuth is 1:0.1-1.5:0.05-0.8, and is prepared by electrodeposition method.

[0011] Further, the acidic solution is one of concentrated nitric acid, concentrated sulfuric acid, concentrated hydrochloric acid and concentrated phosphoric acid, and the molar concentration of the acid is 0.3-0.5 mol / L.

[0012] Further, boric acid and a surfactant are added to the electrolyte solution, the addition amount of boric acid is 0.01-0.05 mol / L, the addition amount of the surfactant is 0.01-0.05 mol / L, and the surfactant is selected from at least one of sodium dodecyl sulfonate, sodium benzenesulfonate, sodium lauryl sulfate and cetyltrimethylammonium bromide.

[0013] Further, the copper salt, nickel salt and bismuth salt are at least one of copper, nickel, bismuth chloride salts, nitrate salts, sulfate salts, phosphate salts and acetate salts.

[0014] Further, the current density in the electrodeposition process is 1-20 mA / cm 2 and preferably 5-12 mA / cm 2 and the electrodeposition time is 1-50 min, preferably 10-30 min.

[0015] Further, the anode used in the electrodeposition process can be any one that can achieve the above deposition reaction in the prior art and is well known to those skilled in the art. As a specific implementation method, it is selected from one of a platinum electrode, a ruthenium-iridium electrode, a ruthenium-titanium electrode, a ruthenium-tantalum electrode, a ruthenium-iridium-titanium electrode, a ruthenium-iridium-tin electrode, a ruthenium-iridium-titanium-tin electrode, a lead dioxide electrode, a tin dioxide electrode and a carbon electrode.

[0016] Further, the above preparation method further includes a process of washing, cleaning and drying the surface of the substrate before the electrodeposition reaction, specifically, washing the substrate with acetone, sulfuric acid and deionized water in sequence.

[0017] Further, the above preparation method further includes a process of washing and drying the electrode after the electrodeposition reaction.

[0018] The technical object of the third aspect of the present invention is to provide a method for electrochemically removing nitrate nitrogen in wastewater, using a ternary metal alloy electrode as the cathode and using one selected from a platinum electrode, a ruthenium-iridium electrode, a ruthenium-titanium electrode, a ruthenium-tantalum electrode, a ruthenium-iridium-titanium electrode, a ruthenium-iridium-tin electrode, a ruthenium-iridium-titanium-tin electrode, a lead dioxide electrode, a tin dioxide electrode, a carbon electrode as the anode.

[0019] Further, the content of nitrate nitrogen in the wastewater is 50-300 mg / L.

[0020] Further, the current density is 5-50 mA / cm 2 , and the time for electrolytic removal of nitrate nitrogen is 20-80 min.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) In the electrode of the present invention, the three active metals have a cooperative effect through a specific ratio, and particularly have obvious selectivity and reactivity to nitrate nitrogen, greatly improving the removal efficiency of nitrate nitrogen in wastewater;

[0023] (2) The selected substrate in the electrode of the present invention has a high specific surface area, providing more reactive sites for the reaction;

[0024] (3) The electrode substrate of the present invention has good adsorption performance for nitrate nitrogen. When applied to wastewater treatment, it can enrich more nitrate nitrogen in a shorter time, improve the mass transfer efficiency, and cooperate with the active metal to further improve the reaction efficiency. The electrode of the present invention can achieve 100% removal of nitrate nitrogen in 1 hour, and the total nitrogen removal rate can reach more than 65%.

[0025] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation part. Description of the Drawings

[0026] Figure 1 . SEM image of the surface of the ternary metal alloy electrode prepared in Example 1. Specific Embodiments

[0027] The following non-limiting embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0028] The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0029] The nitrate nitrogen in the present invention is determined by the method of "Determination of Nitrate Nitrogen in Water - Phenol Disulfonic Acid Spectrophotometry" (GB / 7480), the nitrite nitrogen is determined by the method of "Determination of Nitrite Nitrogen in Water - Spectrophotometry" (GB / 7493), and the ammonia nitrogen is determined by the method of "Determination of Ammonia Nitrogen - Gas Phase Molecular Absorption Spectrometry" (HJT195).

[0030] The nitrate nitrogen residual rate, nitrite nitrogen generation rate, and ammonia nitrogen generation rate are respectively shown in the following formulas:

[0031]

[0032] The removal rate of nitrate nitrogen is:

[0033]

[0034] The total nitrogen removal rate (gaseous nitrogen generation rate) is calculated by the following formula:

[0035]

[0036] Wherein, (NO 3 - -N) 0 — the initial concentration of nitrate nitrogen, (NO 3 - -N) t , (NO 2 - -N) t , (NH 4 + -N) t are the instantaneous concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen at time t.

[0037] The energy consumption, that is, the electricity consumption (kWh (g NO 3 - -N) -1 ) consumed to remove 1 g of nitrate nitrogen, is calculated by the following formula:

[0038]

[0039] Wherein U is the battery voltage (V), I is the current (A), t is the degradation time (h), V is the solution volume (L), (NO 3 - -N) 0 and (NO 3 - -N) t are the NO 3 - -N (g L -1 ) at time 0 and the given time t, respectively.

[0040] The scanning electron microscope photos of the samples were measured by a Philips Fei Quanta200F field emission scanning electron microscope.

[0041] Example 1

[0042] Using titanium foam as the electrode substrate, the porosity of the titanium foam is 96%, and the density is 0.2 g / cm 2, the titanium foam substrate was washed successively with acetone, sulfuric acid, and deionized water, and then dried in an oven. Copper sulfate, nickel sulfate, and bismuth nitrate were dissolved in 0.4 mol / L nitric acid according to the molar ratio of copper, nickel, and bismuth of 2:2:1, and then 0.05 mol / L boric acid and 0.01 mol / L surfactant (cetyltrimethylammonium bromide) were added and mixed evenly by ultrasonic. Using the pretreated titanium foam substrate as the cathode and the tin dioxide electrode as the anode, electrodeposition was carried out under the conditions of a current density of 10 mA / cm 2 , and an electrodeposition time of 20 min. After electrodeposition, the electrode was washed and dried to obtain a ternary metal alloy electrode.

[0043] Figure 1 Figure 6 is the SEM image of the prepared copper nanoelectrode, and it can be seen that the electrode surface is dense and the texture is uniform.

[0044] It was measured that the total metal deposition amount on the substrate of the electrode was 6.3 mg / cm 2 .

[0045] The electrode was used for denitrification reaction:

[0046] Using the prepared ternary metal alloy electrode as the cathode and the platinum electrode as the anode, for the denitrification experiment of simulated wastewater containing 100 mg / L sodium nitrate and 20 g / L sodium sulfate, at a current density of 40 mA / cm 2 , 100% nitrate nitrogen removal was achieved in 40 min, the total nitrogen removal rate reached 77.6%, and the energy consumption was 0.187 (kWh (g NO 3 - -N) -1 ).

[0047] Example 2

[0048] The substrate was replaced with nickel foam, and the others were the same as in Example 1. The total metal deposition amount on the substrate of the obtained electrode was 6.6 mg / cm 2 . When applied to denitrification, 100% nitrate nitrogen removal was achieved in 50 min, the total nitrogen removal rate reached 69.5%, and the energy consumption was 0.223 (kWh (g NO 3 - -N) -1 ).

[0049] Example 3

[0050] The substrate was replaced with carbon nanofibers (density of 0.1 g / cm 2 ), and the others were the same as in Example 1. The total metal deposition amount on the substrate of the obtained electrode was 7.2 mg / cm 2When applied to denitrification of nitrogen, 100% removal of nitrate nitrogen is achieved in 40 min, the total nitrogen removal rate reaches 71.2%, and the energy consumption is 0.197 (kWh (g NO 3 - -N) -1 ).

[0051] Example 4

[0052] Adjust the molar ratio of copper, nickel and bismuth to 4:2:1, and the others are the same as in Example 1. The total metal deposition amount on the substrate in the obtained electrode is 8.1 mg / cm 2 When applied to denitrification of nitrogen, 100% removal of nitrate nitrogen is achieved in 40 min, the total nitrogen removal rate reaches 79.2%, and the energy consumption is 0.180 (kWh (g NO 3 - -N) -1 ).

[0053] Example 5

[0054] Adjust the molar ratio of copper, nickel and bismuth to 10:2:1, and the others are the same as in Example 1. The total metal deposition amount on the substrate in the obtained electrode is 9.6 mg / cm 2 When applied to denitrification of nitrogen, 100% removal of nitrate nitrogen is achieved in 60 min, the total nitrogen removal rate reaches 71%, and the energy consumption is 0.216 (kWh (g NO 3 - -N) -1 )

[0055] Example 6

[0056] Adjust the molar ratio of copper, nickel and bismuth to 10:5:1, and the others are the same as in Example 1. The total metal deposition amount on the substrate in the obtained electrode is 10.9 mg / cm 2 When applied to denitrification of nitrogen, 100% removal of nitrate nitrogen is achieved in 70 min, the total nitrogen removal rate reaches 66.7%, and the energy consumption is 0.224 (kWh (g NO 3 - -N) -1 )

[0057] Comparative Example 1

[0058] Except for not adding bismuth salt, the others are the same as in Example 1. For the same denitrification of nitrogen reaction, 78.4% of nitrate nitrogen removal can be achieved in 40 min, and the total nitrogen removal rate is 41.9%. It takes 80 min to achieve 100% nitrate nitrogen removal, and the total nitrogen removal rate is 56.7%, and the energy consumption is 0.275 (kWh (g NO 3 - -N) -1 )

[0059] Comparative Example 2

[0060] Except for not adding nickel salt, other conditions are the same as in Example 1. For the same denitrification reaction, 84.3% of nitrate nitrogen can be removed in 40 min, and the total nitrogen removal rate is 48.1%. It takes 80 min to achieve 100% removal of nitrate nitrogen, the total nitrogen removal rate is 69.2%, and the energy consumption is 0.291 (kWh (g NO 3 - -N) -1 ).

[0061] Comparative Example 3

[0062] Except for not adding copper salt, other conditions are the same as in Example 1. For the same denitrification reaction, 49.1% of nitrate nitrogen can be removed in 40 min, and the total nitrogen removal rate is 27.7%. It takes 100 min to achieve 100% removal of nitrate nitrogen, the total nitrogen removal rate is 66.3%, and the energy consumption is 0.329 (kWh (g NO 3 - -N) -1 )).

[0063] Comparative Example 4

[0064] Mix copper sulfate salt, nickel sulfate and bismuth nitrate according to the molar ratio of copper, nickel and bismuth of 12:6:1, and other conditions are the same as in Example 1. For the same denitrification reaction, 73.2% of nitrate nitrogen can be removed in 40 min, and the total nitrogen removal rate is 36.7%, and the energy consumption is 0.239 (kWh (g NO 3 - -N) -1 )). It takes 90 min to achieve 100% removal of nitrate nitrogen, the total nitrogen removal rate is 59.4%, and the energy consumption is 0.312 (kWh (g NO 3 - -N) -1 ).

Claims

1. A method for electrochemically removing nitrate nitrogen from wastewater, characterized in that, Using a ternary metal alloy electrode as the cathode, wastewater is electrolytically treated. The ternary metal alloy electrode uses at least one selected from titanium foam, iron foam, copper foam, nickel foam, aluminum foam, and carbon nanofibers as the substrate, and copper, nickel, and bismuth metals are deposited on the substrate. The molar ratio of copper, nickel, and bismuth is 1:0.1~1.5:0.05~0.

8. In the ternary metal alloy electrode, based on the weight of the three metals, the metal deposition amount on the substrate is 1~15 mg / cm 2 .

2. The method according to claim 1, characterized in that, the molar ratio of copper, nickel and bismuth in the ternary metal alloy electrode is 1:0.1 - 1:0.1 - 0.

6.

3. The method according to claim 2, characterized in that, the molar ratio of copper, nickel and bismuth in the ternary metal alloy electrode is 1:0.2 - 1:0.1 - 0.

5.

4. The method according to claim 1, characterized in that, In the ternary metal alloy electrode, the metal deposition amount on the substrate is 4 to 12 mg / cm 2 .

5. The method according to claim 4, characterized in that, In the ternary metal alloy electrode, the metal deposition amount on the substrate is 6-9 mg / cm 2 .

6. The method according to claim 1, characterized in that, The porosity of the titanium foam, iron foam, copper foam, aluminum foam and carbon nanofibers is 93 to 99%, and the density is 0.1 to 0.4 g / cm 2 .

7. The method according to claim 1, characterized in that, the ternary metal alloy electrode is prepared by the following method: using at least one selected from titanium foam, iron foam, copper foam, nickel foam and aluminum foam as the substrate as the cathode, using an acidic solution of copper salt, nickel salt and bismuth salt as the electrolyte solution, with the molar ratio of copper, nickel and bismuth being 1:0.1 - 1.5:0.05 - 0.8, and preparing by electrodeposition.

8. The method according to claim 7, characterized in that, the acidic solution is one of concentrated nitric acid, concentrated sulfuric acid, concentrated hydrochloric acid and concentrated phosphoric acid, and the molar concentration of the acid is 0.3 - 0.5 mol / L.

9. The method according to claim 7, characterized in that, boric acid and a surfactant are further added to the electrolyte solution, the addition amount of boric acid is 0.01 - 0.05 mol / L, and the addition amount of the surfactant is 0.01 - 0.05 mol / L.

10. The method according to claim 9, characterized in that, the surfactant is at least one selected from sodium dodecyl sulfonate, sodium benzenesulfonate, sodium lauryl sulfate and cetyltrimethylammonium bromide.

11. The method according to claim 7, characterized in that, the copper salt, nickel salt and bismuth salt are at least one of copper, nickel, bismuth chloride salts, nitrate salts, sulfate salts, phosphate salts and acetate salts.

12. The method according to claim 7, characterized in that, The current density in the electroplating process is 1 - 20 mA / cm 2 , and the electroplating time is 1 - 50 min.

13. The method according to claim 12, characterized in that, The current density of the electrodeposition process is 5 - 12 mA / cm 2 , and the electrodeposition time is 10 - 30 min.

14. The method according to claim 7, characterized in that, the anode used in the electrodeposition process is selected from one of a platinum electrode, a ruthenium - iridium electrode, a ruthenium - titanium electrode, a ruthenium - tantalum electrode, a ruthenium - iridium - titanium electrode, a ruthenium - iridium - tin electrode, a ruthenium - iridium - titanium - tin electrode, a lead dioxide electrode, a tin dioxide electrode and a carbon electrode.

15. The method according to claim 7, characterized in that, it further includes a process of washing and drying the surface of the substrate before the electrodeposition reaction, specifically washing the substrate with acetone, sulfuric acid and deionized water in sequence.

16. The method according to claim 1, characterized in that, the anode is selected from one of a platinum electrode, a ruthenium - iridium electrode, a ruthenium - titanium electrode, a ruthenium - tantalum electrode, a ruthenium - iridium - titanium electrode, a ruthenium - iridium - tin electrode, a ruthenium - iridium - titanium - tin electrode, a lead dioxide electrode, a tin dioxide electrode and a carbon electrode.

17. The method according to claim 1, characterized in that, The current density of electrolysis is 5 - 50 mA / cm 2 , and the time for electrolytic removal of nitrate nitrogen is 20 - 80 min.

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