An electro-catalytic oxidation catalyst for high-salt high-ammonia-nitrogen wastewater treatment and a preparation method and application thereof

Abstract

The application discloses an electro-catalytic oxidation catalyst for high-salt and high-ammonia-nitrogen wastewater treatment and a preparation method and application thereof. The catalyst takes excessive metals such as Cu, Fe and Zn as active components of the catalyst, takes modified natural zeolite as a carrier, and loads the active components on the modified natural zeolite carrier through impregnation. The catalyst prepared by the application is used in the electro-catalytic oxidation treatment of high-salt and high-ammonia-nitrogen wastewater, and has the characteristics of mild reaction condition, no need of adding any chemical agent, strong impact load resistance, no secondary pollution, high ammonia-nitrogen removal efficiency and the like.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalytic materials and environmental pollution control, and relates to an electrocatalytic oxidation catalyst for the treatment of high-salt and high-ammonia nitrogen wastewater, its preparation method and application. Background Technology

[0002] Electrocatalytic oxidation technology is a novel and highly efficient wastewater treatment method. Due to its advantages such as requiring only electricity, no need to add other reagents, no introduction of new impurities, a clean electrolysis process, no environmental pollution, high degree of automation, and simple and convenient operation, it has been increasingly applied in recent years to the treatment of complex, high-concentration, toxic, harmful, and recalcitrant organic wastewater, especially high-salt, high-concentration organic wastewater. However, cases involving the treatment of high-salt, high-ammonia-nitrogen, or high-salt, high-ammonia-nitrogen, high-concentration organic wastewater are still relatively rare. Electrocatalytic oxidation technology utilizes a series of strong oxidants generated on the surface of an active anode or a filled catalyst, such as hydroxyl radicals (·OH) and superoxide anion radicals (O2). ·- Ozone (O3), superoxide radicals [·HO2], reactive oxygen atoms [O], etc., when chloride ions (Cl) are present - When present, it will also produce hypochlorous acid (HClO) and hypochlorite ions (ClO). - The process involves using oxidants such as chlorine (Cl2) to oxidize and decompose ammonia nitrogen into nitrogen gas, while simultaneously oxidizing and decomposing some large organic molecules into smaller organic molecules, and oxidizing some organic matter into carbon dioxide and water, ultimately achieving the goal of removing pollutants. In another method, the catalyst support is loaded with transition metal active components. During the electrocatalytic oxidation process, after the catalyst is added, the catalyst support acts as an adsorbent, adsorbing the oxidant, ammonia nitrogen, and organic matter onto the catalyst surface, triggering a series of chain chemical reactions that decompose ammonia nitrogen into nitrogen gas and some organic matter into carbon dioxide and water. This improves the efficiency of electrocatalytic oxidation and shortens the electrocatalytic oxidation time.

[0003] Electrocatalytic oxidation catalysts can use natural zeolite, molecular sieve, alumina, and activated carbon as catalyst supports. Among them, natural zeolite is a hydrous alkali metal or alkaline earth metal aluminosilicate mineral with a unique internal structure and crystal chemistry. Its interior is filled with tiny pores and channels, which have adsorption, ion exchange, catalytic, and acid and heat resistance properties. Therefore, it is widely used as an adsorbent, ion exchanger, and also a good electrocatalytic oxidation catalyst support, which can undergo synergistic oxidation with the supported active components.

[0004] Through research and application of electrocatalytic oxidation technology, it has been found that this technology is more suitable for treating wastewater with high salinity, high ammonia nitrogen, and high chlorine levels. Factors affecting nitrogen removal via electrocatalytic oxidation mainly include the active catalytic oxidation component, current density, electrolyte concentration, wastewater pH, and temperature. Currently, electrocatalytic oxidation technology is limited by wastewater electrolyte concentration, wastewater pH, and temperature, resulting in numerous problems such as high investment costs, high energy consumption, and low nitrogen removal efficiency.

[0005] Patent CN113019382A, "An Electrocatalytic Oxidation Catalyst for Landfill Leachate, Its Preparation Method and Uses," discloses a method for preparing an electrocatalytic oxidation catalyst for landfill leachate. The catalyst is prepared by blending and granulating alumina and activated carbon as raw material powders, using one or two of copper, lanthanum, or nickel as active components, and employing impregnation and calcination processes. The anode of the electrocatalytic oxidation reactor is made of titanium-based plate, and the cathode is made of stainless steel. The prepared catalyst is loaded into the reactor, and the reaction is carried out at a wastewater pH of 2-3 and a current density of 15 mA / cm². 2 Under certain conditions, catalytic oxidation of concentrated landfill leachate reduced ammonia nitrogen concentration from 100-150 mg / L to below 10 mg / L, and COD from 100-3500 mg / L to below 60 mg / L, achieving excellent results. However, the catalyst reaction occurred under acidic conditions, and the pH was adjusted to neutral with alkali after the reaction. This consumed large amounts of acid and sodium hydroxide, increasing the salinity of the wastewater. This not only increased wastewater treatment costs but also caused secondary environmental pollution and added difficulty to subsequent treatment facilities.

[0006] Patent CN115246668A, entitled "A Catalytic Wet Electro-oxidation Degradation Device and Method for Ammonia Nitrogen Pollutants in Wastewater," discloses a catalytic wet electro-oxidation degradation device for ammonia nitrogen pollutants in wastewater. The anode in the reactor uses a titanium-based coating material, and the cathode uses either titanium or stainless steel. The device degrades model wastewater at a reaction temperature of 160–270℃ and a reaction pressure of 5–7 MPa. The model wastewater is prepared with ammonium chloride and 0.5% sodium chloride is added. After catalytic wet electro-oxidation, the total nitrogen concentration decreased from 500 mg / L to 40 mg / L, achieving excellent results. However, this patented device has certain drawbacks: the active component coating is on the anode, and the electrode is inside the reactor, making disassembly inconvenient and sealing difficult; the reaction conditions are high temperature and pressure; the electrode life is short due to corrosion under high temperature and pressure; the reactor is prone to corrosion under high temperature and pressure; the titanium alloy material used makes reactor manufacturing difficult and increases equipment investment; and the high reaction temperature results in high energy consumption.

[0007] To address the problems of high energy consumption, harsh reaction conditions, and secondary environmental pollution in electrocatalytic oxidation technology, this invention provides an electrocatalytic oxidation catalyst for the treatment of high-salt and high-ammonia-nitrogen wastewater, its preparation method, and its application. Summary of the Invention

[0008] The electrocatalytic oxidation catalyst for high-salt and high-ammonia-nitrogen wastewater provided by this invention is a heterogeneous catalyst that operates at room temperature and pressure and has high stability and catalytic activity.

[0009] The technical solution adopted in this invention is as follows:

[0010] An electrocatalytic oxidation catalyst for treating high-salt, high-concentration ammonia nitrogen wastewater includes a support and a metal active component.

[0011] The carrier is preferably a modified natural zeolite carrier, and the carrier diameter is... The length is 3–15 mm. The support is 92–99 wt% of the catalyst weight, preferably 95–98.5 wt%.

[0012] Apart from the carrier, the remaining components are metal active components; the preferred metal active component salts are copper nitrate, ferric nitrate, and zinc nitrate.

[0013] The electrocatalytic oxidation treatment of high-salt, high-ammonia-nitrogen wastewater is preferably at least one of the following: wastewater from refining catalyst production, wastewater from coal chemical catalyst production, coal chemical wastewater, and landfill leachate.

[0014] The preparation method of the modified natural zeolite carrier includes the following steps:

[0015] (1) Preparation of modified natural zeolite

[0016] Add natural zeolite to a 0.2–1.5 wt% silver nitrate solution and stir for 6–12 hours. Rinse repeatedly with deionized water until no Ag is detected in the washing solution. + Dry at 70-110℃ for 2-4 hours and then seal for later use.

[0017] (2) Preparation of modified natural zeolite carrier

[0018] A mixture of 50–90 wt% modified natural zeolite and 10–50 wt% pseudoboehmite was prepared using a 0–5 wt% nitric acid solution as a molding aid. The mixture was then shaped using an extruder. The shaped solid was dried at 20–120°C for 2–6 h and then calcined at 300–600°C for 3–6 h to obtain a modified natural zeolite carrier.

[0019] A method for preparing an electrocatalytic oxidation catalyst for treating high-salt, high-concentration ammonia nitrogen wastewater includes the following steps:

[0020] (1) Add a certain amount of 100-200 mesh natural zeolite to a 0.2-1.5 wt% silver nitrate solution, stir for 6-12 hours, and rinse repeatedly with deionized water until no Ag is detected in the washing solution. + Dry at 70–110℃ for 2–4 hours and then seal for later use.

[0021] (2) Weigh 50-90 wt% of the modified natural zeolite and 10-50 wt% of the pseudoboehmite from step (1) and mix them. After mixing, add 0-5 wt% nitric acid solution and stir to mix. Shape the mixture using an extruder with the speed adjusted to 900-1500 rpm. Use a perforated plate. To determine the aperture size, the shaped solid is dried at 20–120℃ for 2–6 hours, then calcined in a 300–600℃ furnace for 3–6 hours. After natural cooling, the shaped material is crushed and sieved to obtain the aperture size. Modified natural zeolite carrier with a length of 3–15 mm;

[0022] (3) Prepare a solution of the metal active component salt with a concentration of 5-30 wt% for later use; the amount of the metal active component salt is 3-35 wt% of the carrier, preferably 5-30 wt%;

[0023] (4) Immerse the modified natural zeolite carrier in step (2) into the solution in step (3) at room temperature and pressure with equal volume for 4 to 24 hours.

[0024] (5) Take out the catalyst from step (4) and dry it in an oven at 20-120°C for 2-6 hours. After drying, cool it to room temperature.

[0025] (6) Take out the catalyst from step (5), place it in a roasting furnace at 300-600℃ for 3-6 hours, and take it out after cooling down to obtain an electrocatalytic oxidation catalyst for the treatment of high-salt and high-ammonia-nitrogen wastewater.

[0026] Preferably, the concentration of silver nitrate in step (1) is 0.4–0.6 wt%.

[0027] Preferably, the diameter of the modified natural zeolite carrier in step (2) is... Length 8–12 mm;

[0028] Preferably, in step (3), the active metal component salt is prepared into a solution with a mass concentration of 8-30 wt%.

[0029] Preferably, the roasting temperature in step (6) is 400-550℃.

[0030] The use of the modified natural zeolite catalyst provided by this invention or the catalyst obtained by the preparation method described above in the treatment of high-salt, high-ammonia-nitrogen wastewater.

[0031] The modified natural zeolite catalyst is used in the treatment of high-salt and high-ammonia-nitrogen wastewater. The device and reaction conditions are as follows: ambient temperature and pressure, wastewater is injected into the electrocatalytic oxidation device, the electrocatalytic oxidation device is filled with a cross-arranged anode and cathode electrode, and the catalyst filling rate is 30-80%.

[0032] The electrocatalytic oxidation device uses a titanium-based ruthenium-iridium coated electrode, commonly used in industry, as the anode, and a titanium plate as the cathode. The electrode spacing is 3–50 mm, and the current density is 20–100 mA / cm². 2 .

[0033] The electrocatalytic oxidation device has a reaction time of 1 to 6 hours.

[0034] The electrocatalytic oxidation catalyst prepared by the above-mentioned technical solution of this invention has the following advantages:

[0035] (1) The electrocatalytic oxidant is used, the reaction conditions are mild, and it works at normal temperature and pressure. The wastewater does not need to be acidified or alkaliified to adjust the pH value, does not increase the pollutants in the wastewater, and has no secondary pollution.

[0036] (2) Make full use of the high salt content in wastewater, especially the high chloride ion concentration, and use electrocatalytic oxidation catalyst to improve the removal of ammonia nitrogen and organic matter from high-concentration chloride ion pollutants, so as to achieve the purpose of treating waste with waste and realize the harmlessness and resource utilization of wastewater without the need to add any chemical agents.

[0037] (3) It has strong resistance to impact loads, and changes in pollutant concentration have no effect on the performance of the catalyst;

[0038] (4) The ammonia nitrogen pollutant removal rate is high, the energy consumption is low, the operating cost is low, and the ammonia nitrogen concentration in the effluent can meet the requirements of subsequent biochemical treatment facilities. Attached Figure Description

[0039] Figure 1 This invention relates to the relationship between different catalytic oxidation times and the removal rates of ammonia nitrogen, total nitrogen, and TOC pollutants during the electrocatalytic oxidation treatment of refining catalyst production wastewater using Cu / modified natural zeolite catalyst in Example 1 of this invention.

[0040] Figure 2 This invention, in Example 2, uses Fe / Cu / modified natural zeolite catalyst to electrocatalyze the treatment of refining catalyst production wastewater, showing the relationship between different catalytic oxidation times and the removal rates of ammonia nitrogen, total nitrogen, and TOC pollutants.

[0041] Figure 3 This invention, in Example 2, describes the relationship between different catalytic oxidation times and the removal rates of ammonia nitrogen, total nitrogen, and TOC pollutants during the electrocatalytic oxidation treatment of refining catalyst production wastewater using a Cu / Fe / Zn / modified natural zeolite catalyst. Detailed Implementation

[0042] The present invention will now be described in detail with reference to specific embodiments.

[0043] Example 1

[0044] (1) Add an equal volume of 100-mesh natural zeolite to a 0.5 wt% silver nitrate solution for modification, stir for 6 hours, remove and rinse repeatedly with deionized water until no Ag is detected in the washing solution. + Dry at 90℃ for 3 hours;

[0045] (2) Modified natural zeolite and pseudoboehmite were mixed at a weight ratio of 8:2, with 4wt% nitric acid solution as a binder. After extrusion molding, the mixture was dried at 80℃ for 2 hours, and then calcined at 550℃ for 5 hours to obtain a diameter of... A catalyst support with a length of 10 mm was prepared. A 16.6 wt% copper nitrate solution was prepared, and the prepared catalyst support was mixed with the copper nitrate solution and impregnated for 12 h. It was then dried at 105 °C for 2 h and calcined at 550 °C for 5 h to obtain a modified natural zeolite catalyst with a Cu content of 1.5%.

[0046] (3) The prepared catalyst was loaded into the electrocatalytic oxidation device with a filling rate of 50%, and the wastewater from the refining catalyst production was injected. The electrocatalytic oxidation device was operated at room temperature and pressure, voltage of 5.5V, and current density of 45mA / cm². 2 Electrocatalytic oxidation was carried out under a plate spacing of 5 mm, and water samples were taken every 1 hour to analyze the values ​​of ammonia nitrogen, total nitrogen and TOC.

[0047] (4) Results of electrocatalytic oxidation are shown in Figure 1 It can be seen that the Cu / modified natural zeolite catalyst, when used for electrocatalytic oxidation treatment of refining catalyst production wastewater at room temperature and pressure, achieved ammonia nitrogen removal rate of 82%, total nitrogen removal rate of 74%, and TOC removal rate of 58% after 4 hours of electrocatalytic oxidation, demonstrating good catalytic activity.

[0048] Example 2

[0049] (1) Add an equal volume of 100-mesh natural zeolite to a 0.5 wt% silver nitrate solution for modification, stir for 6 hours, remove and rinse repeatedly with deionized water until no Ag is detected in the washing solution. + Dry at 90℃ for 3 hours;

[0050] (2) Modified natural zeolite and pseudoboehmite were mixed at a weight ratio of 7:3, with 4wt% nitric acid solution as a binder. After extrusion molding, the mixture was dried at 80℃ for 2 hours, and then calcined at 550℃ for 5 hours to obtain a diameter of... A catalyst support with a length of 10 mm was prepared. A 30 wt% ferric nitrate solution was prepared, and the prepared catalyst support was mixed with the ferric nitrate solution. The mixture was impregnated at 60 °C for 12 h, dried at 105 °C for 2 h, and then calcined at 550 °C for 5 h to obtain a modified natural zeolite catalyst with a Fe content of 2%.

[0051] (3) The prepared catalyst was loaded into the electrocatalytic oxidation device with a filling rate of 50%, and the wastewater from the refining catalyst production was injected. The electrocatalytic oxidation device was operated at room temperature and pressure, voltage of 5.5V, and current density of 45mA / cm². 2 Electrocatalytic oxidation was carried out with a plate spacing of 5 mm, and water samples were taken every 1 hour to analyze the values ​​of ammonia nitrogen, total nitrogen and COD.

[0052] (4) The results showed that the Fe / modified natural zeolite catalyst, when used for electrocatalytic oxidation treatment of refining catalyst production wastewater at ambient temperature and pressure, achieved ammonia nitrogen removal rate of 59%, total nitrogen removal rate of 53%, and TOC removal rate of 52% after 4 hours of electrocatalytic oxidation. The catalyst exhibited good catalytic activity.

[0053] Example 3

[0054] (1) Add an equal volume of 100-mesh natural zeolite to a 0.5 wt% silver nitrate solution for modification, stir for 6 hours, remove and rinse repeatedly with deionized water until no Ag is detected in the washing solution. + Dry at 90℃ for 3 hours;

[0055] (2) Modified natural zeolite and pseudoboehmite were mixed at a weight ratio of 7:3, with 4wt% nitric acid solution as a binder. After extrusion molding, the mixture was dried at 80℃ for 2 hours, and then calcined at 550℃ for 5 hours to obtain a diameter of... A catalyst support with a length of 10 mm was prepared. A solution of 18.6 wt% ferric nitrate and 8.3 wt% copper nitrate was prepared. The prepared catalyst support was mixed with the prepared salt solution, impregnated at 60 °C for 12 h, dried at 105 °C for 2 h, and then calcined at 550 °C for 5 h to obtain a modified natural zeolite catalyst containing 1% Fe and 1% Cu.

[0056] (3) The prepared catalyst was loaded into the electrocatalytic oxidation device with a filling rate of 50%, and the wastewater from the refining catalyst production was injected. The electrocatalytic oxidation device was operated at room temperature and pressure, voltage of 5.5V, and current density of 45mA / cm². 2 Electrocatalytic oxidation was carried out under a plate spacing of 5 mm, and water samples were taken every 1 hour to analyze the values ​​of ammonia nitrogen, total nitrogen and TOC.

[0057] (4) Results of electrocatalytic oxidation are shown in Figure 2 It can be seen that the Cu / Fe modified natural zeolite catalyst, when used for electrocatalytic oxidation treatment of refining catalyst production wastewater at ambient temperature and pressure, achieved ammonia nitrogen removal rate of 88%, total nitrogen removal rate of 79%, and TOC removal rate of 62% after 4 hours of electrocatalytic oxidation, demonstrating good catalytic activity.

[0058] Example 4

[0059] (1) 100-mesh natural zeolite was added to a 0.5 wt% silver nitrate solution for modification. After stirring for 6 hours, the mixture was removed and rinsed repeatedly with deionized water until no Ag was detected in the washing solution. + Dry at 90℃ for 3 hours;

[0060] (2) Modified natural zeolite and pseudoboehmite were mixed at a weight ratio of 8:2, with 4wt% nitric acid solution as a binder. After extrusion molding, the mixture was dried at 80℃ for 2 hours, and then calcined at 550℃ for 5 hours to obtain a diameter of... A catalyst support with a length of 10 mm was prepared with a solution of 18.6 wt% iron nitrate, 8.3 wt% copper nitrate and 5.3 wt% zinc nitrate. The prepared catalyst support was mixed with the prepared salt solution, impregnated at 80℃ for 24 h, dried at 105℃ for 2 h, and then calcined at 550℃ for 5 h to obtain a modified natural zeolite catalyst containing 1% Fe, 1% Cu and 0.5% Zn.

[0061] (3) The prepared catalyst was loaded into the electrocatalytic oxidation device with a filling rate of 50%, and the wastewater from the refining catalyst production was injected. The electrocatalytic oxidation device was operated at room temperature and pressure, voltage of 5.5V, and current density of 45mA / cm². 2 Electrocatalytic oxidation was carried out with a plate spacing of 5 mm, and the values ​​of ammonia nitrogen, total nitrogen and TOC in the water sample were analyzed every 1 hour.

[0062] (4) Results of electrocatalytic oxidation are shown in Figure 3 It can be seen that the Fe / Cu / Zn / modified natural zeolite catalyst can effectively treat the wastewater from the production of refining catalysts at room temperature and pressure. After 3 hours of electrocatalytic oxidation, the ammonia nitrogen removal rate reached 93%, the total nitrogen removal rate reached 89%, and the TOC removal rate reached 78%. The catalyst showed good catalytic activity and shortened the electrocatalytic oxidation time.

Claims

1. A method for preparing an electrocatalytic oxidation catalyst for treating high-salt, high-concentration ammonia nitrogen wastewater, characterized in that, Includes the following steps: (1) Add 100-200 mesh natural zeolite to a 0.2-1.5 wt% silver nitrate solution, stir for 6-12 hours, and rinse repeatedly with deionized water until no Ag is detected in the washing solution. + Dry at 70–110℃ for 2–4 hours and then seal for later use. (2) Weigh 50-90 wt% of the modified natural zeolite and 10-50 wt% of the pseudoboehmite from step (1) and mix them. After mixing, add 4-5 wt% nitric acid solution and stir to mix. Shape the mixture using an extruder with the speed adjusted to 900-1500 rpm. Use a perforated plate. With an aperture of 2–8 mm, the shaped solid is dried at 20–120℃ for 2–6 hours, then calcined in a 300–600℃ furnace for 3–6 hours. After natural cooling, the shaped material is crushed and sieved to obtain a diameter of 2–8 mm. Modified natural zeolite carrier with a diameter of 2-8 mm and a length of 3-15 mm; (3) Prepare a solution of the metal active component salt with a concentration of 5-30 wt% for later use; the amount of the metal active component salt is 3-35 wt% of the carrier; the metal active component salt is copper nitrate, ferric nitrate and zinc nitrate; (4) Immerse the modified natural zeolite carrier from step (2) into the solution from step (3) at room temperature and pressure with equal volume for 4 to 24 hours. (5) Take out the catalyst from step (4) and dry it in an oven at 20-120°C for 2-6 hours. After drying, cool it to room temperature. (6) Take out the catalyst from step (5), place it in a calcining furnace at 300-600℃ for 3-6 hours, and take it out after cooling to obtain the electrocatalytic oxidation catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of silver nitrate is 0.4–0.6 wt%; in step (2), the diameter of the modified natural zeolite carrier is… 4-6 mm, length 8-12 mm; in step (3), the active metal component salt is prepared into a solution with a mass concentration of 8-30 wt%; in step (6), the calcination temperature is 400-550℃.

3. The application of the electrocatalytic oxidation catalyst prepared by the preparation method described in claim 1 or 2 in the treatment of high-salt and high-ammonia nitrogen wastewater.

4. The application according to claim 3, characterized in that, Wastewater is injected into the electrocatalytic oxidation device at normal temperature and pressure; the electrocatalytic oxidation device is filled with the electrocatalytic oxidation catalyst, with a catalyst filling rate of 30-80%.

5. The application according to claim 3, characterized in that, The electrocatalytic oxidation device uses an industrially mature titanium-based ruthenium-iridium coated electrode as the anode and a titanium plate as the cathode, with an electrode spacing of 3–50 mm and a current density of 20–100 mA / cm². 2 .

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