Electrochemical removal device for inorganic nitrogen in pond culture tail water and application thereof

Abstract

This invention provides an electrochemical removal device for inorganic nitrogen in pond aquaculture effluent and its application. The device has an anode and a cathode at its two ends, with multiple sets of anion exchange membranes and cation exchange membranes alternately arranged from the anode to the cathode, forming a concentration chamber and a denitrification chamber in sequence, starting and ending with the concentration chamber. The concentration chamber containing the anode and cathode is referred to as the anode chamber and cathode chamber, respectively. In the denitrification chamber, nitrate, nitrite, and ammonium ions in the pond aquaculture effluent migrate to the concentration chamber, cathode chamber, and anode chamber under electrodialysis, resulting in a rapid decrease in ion concentration in the effluent, which is then directly discharged. The cathode is loaded with a copper-based metal catalyst, which can electrocatalytically reduce nitrate and nitrite nitrogen to nitrogen gas. The anode is loaded with a copper-based oxide or hydroxide catalyst, which can electrocatalytically oxidize ammonia nitrogen to nitrogen gas without the need for active chlorine, thus solving the adverse effect of the lack of chloride ions in pond effluent on ammonia nitrogen conversion.

Description

Technical Field

[0001] This invention belongs to the field of pond aquaculture wastewater treatment technology, specifically relating to an electrochemical removal device for inorganic nitrogen in pond aquaculture wastewater and its application. Background Technology

[0002] Pond aquaculture wastewater typically contains complex nitrogenous pollutants, including inorganic nitrogen such as ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen. If discharged directly without treatment, it can lead to eutrophication of the receiving water body, causing significant environmental damage.

[0003] Currently, the removal of inorganic nitrogen from pond aquaculture wastewater mainly employs ecological engineering technologies such as microbial transformation and aquatic plant uptake. These methods require a large land area, and their effectiveness is greatly affected by environmental conditions such as temperature and sunlight. Especially in winter, the activity of aquatic plants decreases and microbial metabolism slows down, leading to a significant drop in wastewater treatment efficiency. Furthermore, traditional treatment methods are mostly decentralized and in-situ, with limited capacity, making it difficult to handle the high-throughput wastewater generated during peak discharge periods or in large-scale aquaculture areas. During peak discharge periods, problems such as treatment delays and pollutant accumulation can easily occur, leading to shock pollution of surrounding water bodies after direct discharge of wastewater, posing significant environmental risks.

[0004] Electrochemical technology is a green water treatment technology that typically requires no additional reagents, produces fewer secondary pollutants, and operates under mild reaction conditions with minimal space requirements. Therefore, it has unique advantages in removing inorganic nitrogen from aquaculture wastewater. There are reports of electrochemical technology being used for treating mariculture wastewater. Its basic principle is to utilize the abundant chloride ions in seawater to generate active chlorine (such as hypochlorous acid) at the anode, thereby oxidizing ammonia nitrogen in the water into nitrogen gas, or oxidizing nitrite nitrogen into nitrate nitrogen. For example, patent application number 202420818533X is based on this principle and utilizes electrochemical treatment of mariculture wastewater.

[0005] However, there is currently no application of electrochemical technology for the removal of inorganic nitrogen pollutants from pond freshwater aquaculture wastewater. The reasons are: (1) pond wastewater lacks chloride ions, making it difficult to form active chlorine at the anode; (2) the concentration of inorganic nitrogen ions in the wastewater is low, significantly reducing the activity and selectivity of the electrochemical reaction; (3) it cannot effectively remove nitrate nitrogen, which is the dominant form of nitrogen in pond wastewater; (4) pond wastewater treatment requires a relatively fast treatment rate, resulting in a short residence time of reactants in the electrochemical reactor, making it difficult to achieve compliant discharge.

[0006] Therefore, there is an urgent need to develop an electrochemical technology for the removal of inorganic nitrogen pollutants from pond freshwater aquaculture tailwater. Summary of the Invention

[0007] To address the problems encountered by existing electrochemical technologies in treating inorganic nitrogen in pond effluent, this invention proposes an electrochemical removal device for inorganic nitrogen in pond aquaculture effluent. This device combines electrodialysis and electrocatalysis. The pond effluent first undergoes electrodialysis, rapidly reducing the concentration of inorganic nitrogen ions, and the effluent is then directly discharged. After the inorganic nitrogen ions in the effluent are concentrated, it undergoes further electrochemical treatment. A copper-based metal catalyst is loaded at the cathode to electrocatalytically reduce nitrate and nitrite nitrogen to nitrogen gas, while a copper-based oxide or hydroxide catalyst is loaded at the anode to electrocatalytically oxidize ammonia nitrogen to nitrogen gas. This process eliminates the need for active chlorine, thus overcoming the adverse effects of chloride ion deficiency in pond effluent on ammonia nitrogen conversion.

[0008] Specifically, the electrochemical removal device for inorganic nitrogen in pond aquaculture tailwater of the present invention is provided with an anode and a cathode at both ends, and multiple sets of anion exchange membranes and cation exchange membranes are alternately arranged from the anode to the cathode, thereby forming a concentration chamber and a denitrification chamber in sequence, starting and ending with the concentration chamber. The concentration chambers where the anode and cathode are located are referred to as the anode chamber and the cathode chamber, respectively.

[0009] Furthermore, both the anode and cathode are nickel foam or copper foam loaded with a copper-based catalyst. This enables the anode and cathode to electrocatalyze the conversion of inorganic nitrogen ions into nitrogen gas.

[0010] Furthermore, the catalyst is of the type of metal, oxide, or hydroxide.

[0011] Furthermore, the copper-based catalyst metal element is copper or one or more of copper and nickel, iron, cobalt, platinum, and iridium; wherein the proportion of copper element in the total metal element is 100% to 50%.

[0012] Furthermore, the concentration chamber, cathode chamber, and anode chamber of the device are connected by pipelines, and the liquid circulation is shared.

[0013] The present invention also provides an application of the electrochemical removal device for inorganic nitrogen in pond aquaculture tailwater as described above, wherein a portion of the pond aquaculture tailwater is used as electrode liquid and concentrate and is passed into the cathode chamber, anode chamber and concentration chamber, and circulates in the three chambers; the pond aquaculture tailwater is passed into the denitrification chamber, and after passing through the denitrification chamber, the tailwater is not circulated and is directly discharged.

[0014] After the pond aquaculture effluent is introduced into the denitrification chamber, the nitrate, nitrite and ammonium ions in the effluent migrate to the concentration chamber, cathode chamber and anode chamber respectively through the cation exchange membrane and anion exchange membrane under the action of electrodialysis. The ion concentration in the effluent of the denitrification chamber drops rapidly and the effluent is directly discharged.

[0015] Using electrodialysis technology, nitrate, nitrite and ammonium ions are enriched in the concentration chamber, cathode chamber and anode chamber. The concentration chamber, cathode chamber and anode chamber are connected by pipelines and share the liquid circulation. During the process, the anode and cathode loaded with copper-based catalysts carry out the electrocatalytic conversion of inorganic nitrogen ions into nitrogen gas in the cathode chamber and anode chamber.

[0016] This invention introduces electrodialysis technology into the electrocatalytic conversion process of inorganic nitrogen ions, which first enriches and then removes inorganic nitrogen in the effluent, thereby improving both the effluent treatment speed and the selectivity of inorganic nitrogen conversion into nitrogen gas.

[0017] The electrochemical removal device for inorganic nitrogen in pond aquaculture effluent proposed in this invention combines the functions of electrodialysis and electrocatalysis, separating the removal and conversion processes of inorganic nitrogen ions in the effluent. Inorganic nitrogen in the effluent is first enriched and then removed, which improves both the effluent treatment speed and the selectivity of inorganic nitrogen conversion to nitrogen gas. Specifically, compared with existing technologies, the beneficial effects of this invention are as follows: (1) In the denitrification chamber, nitrate, nitrite and ammonium ions in the pond aquaculture tailwater migrate to the concentration chamber, cathode chamber and anode chamber under the action of electrodialysis. The ion concentration in the tailwater drops rapidly and the effluent is directly discharged, which solves the problem of high-speed treatment of pond aquaculture tailwater.

[0018] (2) Electrocatalytic conversion of inorganic nitrogen ions into nitrogen gas is carried out in the cathode and anode chambers. The high concentration of inorganic nitrogen ions in the cathode and anode chambers avoids the adverse effects of low ion concentration in the raw effluent on the electrochemical reaction. The cathode is loaded with a copper-based metal catalyst, which can electrocatalytically reduce nitrate nitrogen and nitrite nitrogen into nitrogen gas, solving the problem of nitrate nitrogen removal in the effluent; the anode is loaded with a copper-based oxide or hydroxide catalyst, which can electrocatalytically oxidize ammonia nitrogen into nitrogen gas without the participation of active chlorine, thus solving the adverse effects of the lack of chloride ions in pond effluent on ammonia nitrogen conversion. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the electrochemical removal device for inorganic nitrogen in pond aquaculture wastewater according to the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0021] Example 1 This embodiment provides an application of an electrochemical removal device for inorganic nitrogen in pond aquaculture effluent. The device has an anode and a cathode at both ends. Figure 1As shown, two sets of anion exchange membranes and cation exchange membranes are alternately arranged from the anode to the cathode, forming a concentration chamber and a denitrification chamber in sequence. The concentration chamber containing the anode and cathode are referred to as the anode chamber and the cathode chamber, respectively. The concentration chamber, cathode chamber, and anode chamber of the device are connected by pipelines and share a common liquid circulation system.

[0022] The device uses nickel foam loaded with 100% metallic copper as the cathode and nickel foam loaded with 100% copper oxide as the anode. It has two denitrification chambers and one concentration chamber. The effective working area of ​​the device is 100 cm². 2 After filtration to remove particulate matter such as silt, the concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the pond effluent were 8.2 mg / L, 0.21 mg / L, and 0.53 mg / L, respectively. The total flow rate of the pond aquaculture effluent through the denitrification chamber was 5 mL / min, and the flow rate of the pond aquaculture effluent circulating through the concentration chamber, cathode chamber, and anode chamber was 50 mL / min. The volume of the concentrate was 200 mL. The electrolysis voltage was 40 V. After treatment by the device, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent were 2.3 mg / L, 0.025 mg / L, and 0.047 mg / L, respectively. The removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the concentrate were 1.77 mg / h, 0.062 mg / h, and 0.155 mg / h, respectively.

[0023] Example 2 This embodiment refers to Embodiment 1. The difference between this embodiment and Embodiment 1 is that in this embodiment, nickel foam loaded with copper-nickel alloy (copper molar fraction 50%) is used as the cathode. All other settings are the same as in Embodiment 1.

[0024] After treatment by the device, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent were measured to be 2.5 mg / L, 0.022 mg / L, and 0.035 mg / L, respectively. In the concentrate, the removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen were 1.71 mg / h, 0.065 mg / h, and 0.159 mg / h, respectively.

[0025] Example 3 This embodiment refers to Embodiment 1. The difference between this embodiment and Embodiment 1 is that in this embodiment, nickel foam loaded with copper-nickel alloy (75% copper molar fraction) is used as the cathode, and nickel foam loaded with copper-nickel oxide (50% copper molar fraction) is used as the anode. All other settings are the same as in Embodiment 1.

[0026] After treatment by the device, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent were measured to be 2.2 mg / L, 0.027 mg / L, and 0.031 mg / L, respectively. In the concentrate, the removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen were 1.80 mg / h, 0.063 mg / h, and 0.154 mg / h, respectively.

[0027] Example 4 This embodiment refers to Embodiment 1. The difference between this embodiment and Embodiment 1 is that in this embodiment, nickel foam loaded with copper-cobalt alloy (copper molar fraction 50%) is used as the cathode, and copper foam loaded with copper-cobalt hydroxide (copper molar fraction 50%) is used as the anode. All other settings are the same as in Embodiment 1.

[0028] After treatment by the device, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent were measured to be 2.8 mg / L, 0.023 mg / L, and 0.041 mg / L, respectively. In the concentrate, the removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen were 1.62 mg / h, 0.067 mg / h, and 0.151 mg / h, respectively.

[0029] Example 5 This embodiment refers to Embodiment 1. The difference between this embodiment and Embodiment 1 is that in this embodiment, nickel foam loaded with copper-iron alloy (copper molar fraction 50%) is used as the cathode, and copper foam loaded with copper-platinum alloy (copper molar fraction 50%) is used as the anode. All other settings are the same as in Embodiment 1.

[0030] After treatment by the device, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent were measured to be 2.9 mg / L, 0.021 mg / L, and 0.034 mg / L, respectively. In the concentrate, the removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen were 1.59 mg / h, 0.068 mg / h, and 0.155 mg / h, respectively.

[0031] Example 6 This embodiment refers to Embodiment 1. The difference between this embodiment and Embodiment 1 is that in this embodiment, foamed nickel loaded with copper-iron-cobalt alloy (copper:iron:cobalt molar fraction = 50%:25%:25%) is used as the cathode, and foamed copper loaded with copper-nickel-platinum alloy (copper:nickel:platinum molar fraction = 50%:40%:10%) is used as the anode. All other settings are the same as in Embodiment 1.

[0032] After treatment by the device, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent were measured to be 2.1 mg / L, 0.022 mg / L, and 0.031 mg / L, respectively. In the concentrate, the removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen were 1.83 mg / h, 0.068 mg / h, and 0.16 mg / h, respectively.

[0033] Example 7 This embodiment refers to Embodiment 1. The difference between this embodiment and Embodiment 1 is that this embodiment has 3 denitrification chambers and 2 concentration chambers.

[0034] The total flow rate of pond aquaculture effluent flowing through the denitrification chamber is 5 mL / min, while the flow rate of pond aquaculture effluent circulating through the concentration chamber, cathode chamber, and anode chamber is 10 mL / min. The volume of the concentrate is 400 mL. The electrolysis voltage is 60 V. After treatment, the average concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the effluent are 2.5 mg / L, 0.025 mg / L, and 0.043 mg / L, respectively. The removal rates of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen in the concentrate are 3.42 mg / h, 0.12 mg / h, and 0.32 mg / h, respectively.

[0035] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An electrochemical removal device for inorganic nitrogen in pond aquaculture wastewater, characterized in that: The device has an anode and a cathode at its two ends, and multiple sets of anion exchange membranes and cation exchange membranes are alternately arranged from the anode to the cathode. Concentration chambers and denitrification chambers are formed alternately in between, with the concentration chamber as the beginning and the end. The concentration chambers where the anode and cathode are located are called the anode chamber and the cathode chamber, respectively.

2. The apparatus according to claim 1, characterized in that: Both the anode and cathode are nickel foam or copper foam loaded with copper-based catalysts.

3. The apparatus according to claim 2, characterized in that: The catalyst is of the type of metal, oxide, or hydroxide.

4. The apparatus according to claim 2, characterized in that: The metal element of the copper-based catalyst is copper or one or more of copper and nickel, iron, cobalt, platinum and iridium; wherein the proportion of copper in the total metal element is 100% to 50%.

5. The apparatus according to claim 1, characterized in that: The concentration chamber, cathode chamber, and anode chamber of the device are connected by pipelines and share a common liquid circulation system.

6. The application of the electrochemical removal device for inorganic nitrogen in pond aquaculture wastewater according to any one of claims 1-5, characterized in that, A portion of the pond aquaculture wastewater is used as electrode solution and concentrate and is passed into the cathode chamber, anode chamber, and concentration chamber, where it circulates. The pond aquaculture wastewater is then passed into the denitrification chamber, where it does not circulate and is directly discharged.

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