A process for in-situ repair of organic nitrogen using three-dimensional electrodes

Abstract

The present invention introduces a process for in-situ repair of organic nitrogen using a three-dimensional electrode, which includes: step S1, using a Peterson mud sampler to collect surface samples of river sediments and overlying water; step S2, preserving and treating the surface samples of the water area and the overlying water collected in step S1; step S3, stirring and mixing the surface samples of the water area and the overlying water in step S2; step S4, using a device for in-situ repair of organic nitrogen using a three-dimensional electrode to treat the mixture obtained in step S3; the device for in-situ repair of organic nitrogen using a three-dimensional electrode includes: an electrolytic cell, a DC power supply, an anode and a cathode; the positive electrode of the DC power supply is connected to the anode; the negative electrode of the DC power supply is connected to the cathode; the anode is located at the bottom of the electrolytic cell; the cathode is located on the water surface in the electrolytic cell; the anode material is an active electrode material; the anode is a three-dimensional porous structure. The present application can take into account both the complex environment and solid-liquid of river and lake sediments, and realize the in-situ removal of nitrogen elements.

Description

Technical Field

[0001] The invention belongs to the field of preparation and application of environmental remediation equipment, and specifically relates to a process for in-situ repair of organic nitrogen using a three-dimensional electrode. Background Art

[0002] In order to avoid water pollution caused by excessive nitrogen, the treatment of organic nitrogen is particularly important. Organic nitrogen mainly includes urea, amino acids, proteins, nucleic acids, uric acid, fatty amines, organic bases, amino sugars and other nitrogen-containing organic substances. There are many methods for treating organic nitrogen, but the effects are not very good.

[0003] For example, Chinese patent CN111087049A discloses a method for treating wastewater containing refractory organic nitrogen, which comprises the following steps: adding wastewater containing refractory organic nitrogen and wastewater containing bromine into an electrolytic cell in a certain proportion, and subjecting the electrolytic reaction to a certain period of time, wherein the bromide ions in the wastewater are oxidized into bromine, and the bromine rapidly reacts with water to generate highly oxidizing hypobromous acid, which can oxidize and degrade the organic nitrogen in the wastewater. After treatment by the present invention, more than 90% of the refractory organic nitrogen can be removed. The method described therein is a method of treating waste with waste, with low treatment cost and wide pH applicable range, and can be widely used in the treatment of various wastewater containing refractory organic nitrogen. However, it uses bromine, which increases the cost of river and lake water treatment.

[0004] Although the organic nitrogen in the water body has been degraded, the sediments (mud) in the river and lake system can be both the "source" and "sink" of organic nitrogen, so it is imperative to remove the adsorbed organic nitrogen in the solid phase. Chinese patent CN109607990A provides a treatment method for electrolytic denitrification and phosphorus fixation in heavily polluted river sediments, but the electrode of this patent is a planar structure, with low current utilization, small contact area with sludge, and low treatment efficiency; the magnesium-aluminum alloy as the anode releases metal magnesium ions, causing secondary pollution. In the foreign literature Treatment of pollute driver sediment by electrochemical oxidation: Changes of hydrophilicity and acute cytotoxicity of dissolved organic matter——Chemospher, the electrode is designed as a planar structure, and the anode and cathode are inserted into the sediment / sediment at the same time. The nitrate nitrogen overflowing from the sediment cannot be reduced to N2 by the cathode, which has the risk of further aggravating the eutrophication of the water body. Similarly, the foreign literature Reduction of nitrogen and phosphorus loading from polluted sediment by electrolysis - Ecological Engineering only used cathode materials to reduce nitrate nitrogen. A large amount of organic nitrogen in the sediment could not be effectively degraded by the reduction reaction. The removal of organic nitrogen in the sediment requires the synergistic effect of oxidation and reduction reactions.

[0005] Regardless of the technical means of the above-mentioned patent or the electrolysis method used in other existing technologies, chemical agents will be widely used, resulting in waste of resources and further pollution. Moreover, it can only achieve electrocatalytic oxidation of organic nitrogen, and cannot achieve reduction and denitrification. This results in the nitrogen element still remaining in the water body, and still cannot solve the water pollution problem. Moreover, in the treatment process, the electrodes used are mostly column-type parallel electrodes, which are all vertically and parallelly located in the water body. This results in a small electrolysis area and cannot complete the nitrogen treatment of the entire water area, let alone achieve nitrogen electrolysis at different water depths. Summary of the invention

[0006] In order to solve the above problems and take into account the complex environment and solid-liquid of river and lake sediments, electrode electrolysis is used and by changing the electrode shape and electrode distribution pattern, the conversion of nitrogen elements is achieved, thereby achieving the technical effect of repairing organic nitrogen pollution.

[0007] In order to achieve the above-mentioned effects, the present invention designs a process for in-situ repair of organic nitrogen using a three-dimensional electrode.

[0008] A process for in-situ repair of organic nitrogen using a three-dimensional electrode, comprising the following steps:

[0009] Step S1, using a Peterson mud sampler to collect sediment surface samples and overlying water with relatively serious sediment pollution;

[0010] Step S2, preserving the sediment surface sample and overlying water collected in step S1 respectively;

[0011] Step S3, stirring and mixing the sediment surface sample and overlying water in step S2;

[0012] Step S4: using a three-dimensional electrode in-situ repair device for organic nitrogen to treat the mixture obtained in step S3.

[0013] Preferably, in step S4, the three-dimensional electrode in-situ repair organic nitrogen device comprises: an electrolytic cell, a DC power supply, an anode and a cathode; the DC power supply positive electrode is connected to the anode;

[0014] The negative electrode and cathode of the DC power supply are connected;

[0015] The anode is located at the bottom of the electrolytic cell;

[0016] The cathode is located on the water surface in the electrolytic cell;

[0017] The anode material is an active electrode material;

[0018] The anode is a three-dimensional porous structure.

[0019] Preferably, in step S2, the sediment surface sample and the overlying water are stored as follows: freeze-dry the sediment surface sample, pass it through a 100-mesh sieve, place it in a brown screw-mouth glass sampling bottle, place it in a refrigerator, and store it frozen at -20°C for future use; store the overlying water at 4°C.

[0020] Preferably, the anode is constructed by connecting a plurality of small electrode plates.

[0021] Preferably, the projected sizes of the anode and cathode are the same.

[0022] Preferably, the material of the anode is one or more combinations of Ti / RuO2-IrO2, PbO2 and SnO2.

[0023] Preferably, the electrolytic cell is made of acrylic plate.

[0024] Preferably, the cathode material is one or more combinations of foamed iron, carbon fiber, graphene and titanium mesh.

[0025] Preferably, the effective current of the DC power supply is 0-64V, and the effective voltage is 0-5A.

[0026] Preferably, the DC power supply is Dahua KXN-645D.

[0027] The advantages and effects of this application are as follows:

[0028] 1. The present application designs a process for in-situ repair of organic nitrogen by three-dimensional electrodes, which specifically includes: step S1, using a Peterson mud sampler to collect sediment surface samples with relatively serious sediment pollution and overlying water on the bottom of the sediment; step S2, respectively preserving and treating the sediment surface samples and overlying water collected in step S1; step S3, stirring and mixing the sediment surface samples and overlying water in step S2; step S4, using a three-dimensional electrode in-situ repair of organic nitrogen device to treat the mixture obtained in step S3. By using the above 4 steps, the present application can simulate the removal of nitrogen from sediments with complex components in a solid-liquid two-phase environment of river and lake bottom mud environment, and realize nitrogen electrolysis at different water depths.

[0029] 2. This application only uses a single electrode electrolysis method. Through electrocatalytic oxidation of organic nitrogen and electrocatalytic reduction denitrification, organic nitrogen and inorganic nitrogen can be directly converted into N2 and removed from the sediment and water body. In addition, the equipment designed in this application is simple and easy to operate. It takes into account the complex environment of river and lake sediments and both solid and liquid. By continuously moving the electrodes, large-scale sediment organic nitrogen remediation projects can be achieved. There is no need to add any chemical agents, which is green and clean.

[0030] 3. The anode used in this application is a three-dimensional porous structure, which is composed of multiple small electrode plates. By designing the three-dimensional porous structure, it has a larger surface area, thereby increasing the contact area between the bottom mud and the anode. Compared with the existing design, the reaction speed is faster and the effect is better.

[0031] 4. The anode material of the present application is heavier and is placed in the river and lake sediments through pressure or its own gravity, while the cathode material is fixed on the water, ensuring the mobility of the electrode device, which is suitable for repairing large-scale polluted sediments.

[0032] 5. The electrocatalytic reaction process of this application does not use other chemical substances and will not cause secondary pollution. It only requires electrode materials and direct current to repair organic nitrogen pollution.

[0033] 6. The material of the anode electrode used in this application can be a variety of active electrode materials such as RuO2-IrO2, PbO2, SnO2, etc., and the cathode electrode material can be new cathode materials such as carbon fiber, graphene, titanium mesh, etc.; this application provides a variety of electrode materials for easy selection in actual operation.

[0034] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application so that it can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings as follows.

[0035] Based on the detailed description of the specific embodiments of the present application in combination with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0037] Figure 1 A front view of a three-dimensional electrode in-situ repair device for organic nitrogen provided by the present invention;

[0038] Figure 2 A structural diagram of a three-dimensional electrode in-situ repair device for organic nitrogen provided by the present invention;

[0039] Figure 3 The SEM images of Ti / RuO2-IrO2 left and foam iron right electrodes;

[0040] Figure 4 It is a line graph of the removal effect of electrocatalysis on total nitrogen, nitrate nitrogen and ammonia nitrogen in sediments;

[0041] Figure 5 The removal effect of total nitrogen, nitrate nitrogen and ammonia nitrogen in the overlying water by electrocatalysis;

[0042] Figure 6 A comparison of the removal rates of nitrogen from sediments by the three-dimensional electrode designed for this application and the existing planar electrode;

[0043] Figure numerals: 1. electrolytic cell; 2. DC power supply; 3. anode; 4. cathode. DETAILED DESCRIPTION

[0044] To make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all of the embodiments. In the following description, specific details such as specific configuration and components are provided only to help fully understand the embodiments of the present application. Therefore, it should be clear to those skilled in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, for clarity and brevity, the description of known functions and structures is omitted in the embodiment.

[0045] It should be understood that the references to "one embodiment" or "this embodiment" throughout the specification mean that the specific features, structures, or characteristics associated with the embodiment are included in at least one embodiment of the present application. Therefore, the references to "one embodiment" or "this embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0046] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0047] The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" in this article describes another type of association object relationship, indicating that there can be two relationships. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the previous and next associated objects are in an "or" relationship.

[0048] The term "at least one" in this article is only a description of the association relationship of associated objects, indicating that there may be three relationships. For example, at least one of A and B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0049] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusions.

[0050] Example 1

[0051] This embodiment mainly introduces a three-dimensional electrode in-situ repair organic nitrogen device designed by this process, which includes an electrolytic cell, a DC power supply, an anode and a cathode, wherein the positive electrode of the DC power supply is connected to the anode; for the specific structure, please refer to Figure 1 and Figure 2 .

[0052] The negative electrode and cathode of the DC power supply are connected;

[0053] The anode is located at the bottom of the electrolytic cell;

[0054] The electrolytic cell is filled with nitrogen-containing water that is severely polluted by sediments;

[0055] The cathode is located on the water surface in the electrolytic cell;

[0056] The anode material is an active electrode material;

[0057] The anode is a three-dimensional porous structure.

[0058] Preferably, the anode is constructed by connecting a plurality of small electrode plates.

[0059] Preferably, the projected sizes of the anode and cathode are the same.

[0060] Preferably, the material of the anode is one or more combinations of Ti / RuO2-IrO2, PbO2 and SnO2; the material of the cathode is one or more combinations of foamed iron, carbon fiber, graphene and titanium mesh; the materials of the anode and cathode can be found in Figure 3 , Figure 3 SEM images of Ti / RuO2-IrO2 on the left and foam iron on the right electrodes.

[0061] Preferably, the electrolytic cell is made of acrylic plate.

[0062] Preferably, the DC power supply is Dahua KXN-645D.

[0063] Preferably, the effective current of the DC power supply is 0-64V, and the effective voltage is 0-5A.

[0064] This application only uses a single electrode electrolysis method. Through electrocatalytic oxidation of organic nitrogen and electrocatalytic reduction denitrification, organic nitrogen and inorganic nitrogen can be directly converted into N2 and removed from the sediment and water body. In addition, the equipment designed in this application is simple and easy to operate. It takes into account the complex environment of river and lake sediments and both solid and liquid. By continuously moving the electrodes, large-scale sediment organic nitrogen remediation projects can be achieved. There is no need to add any chemical agents, and it is green and clean.

[0065] Similarly, the device designed in this embodiment is enlarged, and only the DC power supply, anode and cathode are retained, connected and powered on, and used directly in rivers and lakes; the anode is naturally sunk to the bottom to treat organic pollutants in river and lake sediments (bottom mud) and nitrogen on the water surface.

[0066] The anode used in this application is a three-dimensional porous structure, which is composed of multiple small electrode plates. By designing the three-dimensional porous structure, it has a larger surface area, thereby increasing the contact area between the bottom mud and the anode. Compared with the existing design, the reaction speed is faster and the effect is better.

[0067] The anode material of the present application is heavier and is placed in the river and lake bottom mud through pressure or its own gravity, while the cathode material is fixed on the water, ensuring the mobility of the electrode device, which is suitable for repairing large-scale polluted bottom mud.

[0068] The electrocatalytic reaction process of the present application does not involve the use of other chemical substances and will not cause secondary pollution. It only requires electrode materials and direct current to repair organic nitrogen pollution.

[0069] The material of the anode electrode used in this application can be a variety of active electrode materials such as RuO2-IrO2, PbO2, SnO2, etc., and the cathode electrode material can be new cathode materials such as carbon fiber, graphene, titanium mesh, etc.; this application provides a variety of electrode materials for easy selection in actual operation.

[0070] Example 2

[0071] Based on the above-mentioned Example 1, this example mainly introduces step S1, using a Peterson mud sampler to collect sediment surface samples with relatively serious sediment pollution and overlying water on the bottom layer of the sediment; step S2, respectively preserving and treating the sediment surface samples and overlying water collected in step S1; step S3, stirring and mixing the sediment surface samples and overlying water in step S2; step S4, using a three-dimensional stereoscopic electrode in situ repair organic nitrogen device to treat the mixture obtained in step S3.

[0072] Specifically:

[0073] 1. Sediment sample collection and pre-treatment are based on:

[0074] A Peterson mud sampler was used to collect 10 cm surface samples from rivers and lakes with serious sediment pollution. The samples were placed in a preservation box and taken back to the laboratory for freeze-drying. The samples were sieved through a 100-mesh sieve and placed in a brown screw-mouth glass sampling bottle and frozen in a refrigerator (-20°C) for future use. At the same time, the bottom overlying water at 20 cm from the sediment-water interface was collected and stored at 4°C.

[0075] 2. Electrocatalytic deposition:

[0076] The electrolytic cell used in this embodiment is a rectangular parallelepiped tank with a volume of 400mL, and the material is made of acrylic plate. Dahua KXN-645D is selected as a DC power supply, and its effective current and effective voltage are 0-64V and 0-5A respectively. This experiment uses a three-dimensional structure of Ti / RuO2-IrO2 as an anode, and foamed iron as a cathode, and the projection size of the electrode is 6cm × 4.5cm. The anode material is a three-dimensional electrode built using multiple small electrode plates. Before treatment, 200g of sediment was first extracted, and then 250mL of overlying water from the outer sea of ​​Dianchi Lake was added. After sufficient stirring, the electrode plate was inserted for electrocatalytic treatment. In the three gaps between the anode and the cathode, three parallel samples were taken after 0, 6, 12, 24, 48, 72, 120, 168 and 240h, respectively, to determine the contents of organic nitrogen, ammonium nitrogen, nitrate nitrogen and total nitrogen in the sediment and overlying water. The anode Ti / RuO2-IrO2 is placed in the river and lake bottom mud by pressure or gravity, inserted 5-10cm, and the cathode material is fixed in the overlying water, with a distance of 10-20cm between the anode and the cathode. When the DC power supply is turned on, the principle chemical reaction process is: anode: H2N-R-NO2+e-→NH3+NO3-; NH3+e-→NO3-+N2↑; cathode: NO3+e-→N2↑.

[0077] The present application designs a process for in-situ repair of organic nitrogen using a three-dimensional electrode, which specifically includes: step S1, using a Peterson mud sampler to collect sediment surface samples and overlying water on the bottom of the sediment with relatively serious sediment pollution; step S2, respectively preserving and treating the sediment surface samples and overlying water collected in step S1; step S3, stirring and mixing the sediment surface samples and overlying water in step S2; step S4, using a three-dimensional electrode in-situ repair of organic nitrogen device to treat the mixture obtained in step S3. The present application can simulate the removal of nitrogen from sediments with complex components in a solid-liquid two-phase environment in a river and lake bottom mud environment by using the above 4 steps.

[0078] Example 3

[0079] Based on the above-mentioned embodiments 1-2, this embodiment mainly introduces the effect verification of this process.

[0080] Figure 4 It is a line graph showing the removal effect of total nitrogen, nitrate nitrogen and ammonia nitrogen in sediments by electrocatalysis; Figure 4It can be clearly concluded that the total nitrogen content adsorbed on the sediment particles decreases significantly with the increase of electrode time, indicating that the oxidant produced by electrocatalysis reacts with the organic matter on the sediment. According to the increase in the concentrations of nitrate nitrogen and ammonia nitrogen, it can be inferred that the organic nitrogen is degraded into inorganic nitrogen. The concentration of nitrate nitrogen first increases rapidly, indicating that the degradation of organic nitrogen produces a large amount of nitrate nitrogen, and then the concentration slowly decreases. Part of it is desorbed from the sediment into the water body, and part of it is converted into N2 or ammonium nitrogen through electrocatalytic denitrification reaction. The concentration of ammonia nitrogen also increases significantly at first, indicating that the degradation of organic nitrogen produces a large amount of ammonia nitrogen, and then slowly decreases. Part of it is desorbed from the sediment into the water body, and part of it is converted into N2 or ammonium nitrogen through electrocatalysis.

[0081] Figure 5 The removal effect of total nitrogen, nitrate nitrogen and ammonia nitrogen in the overlying water by electrocatalysis; Figure 5 It can be clearly concluded that the total nitrogen content in the overlying water first rises rapidly. The main reason is that the organic nitrogen and inorganic nitrogen adsorbed on the surface of the sediment are degraded after electrocatalytic reaction and then desorbed into the aqueous solution. As the electrocatalysis proceeds, the N element in the water is gradually oxidized or reduced to N2 and escapes from the system, achieving a decrease in the total nitrogen concentration. The concentration of nitrate nitrogen first increases rapidly, because the degradation of organic nitrogen produces nitrate nitrogen. At the same time, N on the sediment is desorbed into the water body. As the electrocatalytic reaction proceeds, the nitrate nitrogen is reduced and converted into N2 or ammonium nitrogen. The concentration of ammonia nitrogen also increases rapidly first, because the degradation of organic nitrogen produces ammonia nitrogen. At the same time, ammonia nitrogen on the sediment is desorbed into the water body. As the electrocatalytic reaction proceeds, the ammonia nitrogen is oxidized and converted into N2 or nitrate nitrogen.

[0082] Figure 6 Comparison of nitrogen removal rates in sediments by the three-dimensional electrode designed for this application and the existing planar electrode; Figure 6 It can be clearly concluded that the nitrogen removal rate in the deposit by this process is much greater than that of the existing planar electrode device.

[0083] The above description is only the preferred embodiment of the present invention, which does not limit the protection scope of the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Within the spirit and principle of the present invention, any change, modification, replacement, integration and parameter change of these embodiments by conventional substitution or capable of achieving the same function without departing from the principle and spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A process for in-situ repair of organic nitrogen using a three-dimensional electrode, characterized in that: It includes the following steps: Step S1, using a Peterson mud sampler to collect sediment surface samples and overlying water with relatively serious sediment pollution; Step S2, preserving the sediment surface sample and overlying water collected in step S1 respectively; Step S3, stirring and mixing the sediment surface sample and overlying water in step S2; Step S4, treating the mixture obtained in step S3 using a three-dimensional electrode in-situ repair device for organic nitrogen; In step S4, the three-dimensional electrode in-situ repair organic nitrogen device comprises: an electrolytic cell (1), a direct current power supply (2), an anode (3) and a cathode (4); the positive electrode of the direct current power supply (2) is connected to the anode (3); The negative electrode of the DC power supply (2) is connected to the cathode (4); The anode (3) is located at the bottom of the electrolytic cell (1) and is placed in the river or lake bottom mud; The cathode (4) is located on the water surface in the electrolytic cell (1) and is fixed in the overlying water; The material of the electrolytic cell (1) is an acrylic plate; The anode (3) material is an active electrode material; it is one or more combinations of Ti / RuO2-IrO2, PbO2 and SnO2; The anode (3) is a three-dimensional porous structure; it is constructed by connecting a plurality of small electrode plates; The material of the cathode (4) is one or more combinations of foamed iron, carbon fiber, graphene and titanium mesh.

2. The process for in-situ repair of organic nitrogen using a three-dimensional electrode according to claim 1, characterized in that: In step S2, the sediment surface sample and the overlying water are stored as follows: freeze-dry the sediment surface sample, pass it through a 100-mesh sieve, place it in a brown screw-mouth glass sampling bottle, place it in a refrigerator, and store it frozen at -20°C for later use; store the overlying water at 4°C; the mass ratio of the sediment surface sample to the overlying water is 1g:1.25ml.

3. The process for in-situ repair of organic nitrogen using a three-dimensional electrode according to claim 2, characterized in that: The projection sizes of the anode (3) and cathode (4) are the same.

4. The process for in-situ repair of organic nitrogen using a three-dimensional electrode according to claim 2, characterized in that: The effective current of the DC power supply (2) is 0 to 64 V, and the effective voltage is 0 to 5 A.

5. A process for in-situ repair of organic nitrogen using a three-dimensional electrode according to any one of claims 2 or 4, characterized in that: The DC power supply (2) is Dahua KXN-645D.

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