Method for electrochemical treatment of nitrate nitrogen in electroplating wastewater and copper-iron misfit layered composite electrode plate

Abstract

The application provides a method for reducing nitrate nitrogen in electroplating wastewater by electrochemical treatment and a copper-iron mislayer combined electrode plate of an electrochemical reactor, wherein the electroplating wastewater is adjusted to pH 2-4 by acid, then is reduced in a high-voltage pulse electrochemical reactor until the reaction water is obtained, then alkali is added to adjust the pH to 8-10, and finally a flocculating agent is added for precipitation. The electrode of the high-voltage pulse electrochemical reactor is a copper-iron mislayer combined electrode plate composed of several electrode plates, the distance between the two electrode plates is 3-5 cm, a single electrode plate is formed by welding a half copper plate and a half iron plate, the copper and iron parts of adjacent electrode plates are placed in a mislayered manner and are fixed by positioning members; the copper has better conductivity and thermal conductivity than the iron, the mislayered distribution reduces current loss and reduces the cost of sewage treatment, the iron as a relatively active metal can better reduce nitrate ions, and the nitrate nitrogen is efficiently reduced to NO, N2O, N2, NH4 + or NH3, and is removed by precipitation or gas generation, thereby reducing the content of nitrate ions in the electroplating wastewater and reducing the emission of harmful substances.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for electrochemically treating nitrate nitrogen in electroplating wastewater and a copper-iron staggered electrode plate. Background Technology

[0002] Electroplating is a surface treatment technique that deposits metal ions onto the surface of an object to form a metallic coating. This process is achieved through electrolysis, where the base metal to be plated acts as the cathode, and a salt solution containing the metal to be plated serves as the electrolyte. During electroplating, the cations of the pre-plated metal in the plating solution deposit on the surface of the base metal, forming a metallic film. The purpose of electroplating is to prevent metal oxidation (such as rust), improve wear resistance, conductivity, reflectivity, corrosion resistance, and enhance aesthetics.

[0003] In electroplating, nitric acid or nitrates are often used in processes such as chemical polishing. Nitrates (NO3) - Nitrate is the most stable form of nitrogen compound in an aerobic environment and the final product of the inorganic decomposition of nitrogen-containing organic matter. Nitrate wastewater is highly toxic, capable of disrupting the ecological balance of aquatic bodies and causing the death of aquatic plants and animals. The high proportion of nitrate nitrogen in nitrate wastewater increases the difficulty of its treatment.

[0004] The electrochemical treatment method reduces nitrate nitrogen in nitrate wastewater to NO, N2O, N2, and NH4. + And NH3, thereby reducing NO3 in wastewater - To reduce the content of nitrate ions and minimize environmental harm, most electrochemical methods for treating nitrate wastewater currently suffer from incomplete reduction of nitrate ions, leading to an excess of NO3- in the treated wastewater. - The content is still relatively high. In addition, due to the poor conductivity of the electrode plates in the electrochemical reactor, the current loss is large when using electrochemical treatment for wastewater, resulting in high cost and environmental problems. Summary of the Invention

[0005] This invention provides a method for electrochemically treating nitrate nitrogen in electroplating wastewater and a copper-iron staggered electrode plate, aiming to solve the technical problems of poor effect and large current loss in the electrochemical reduction of nitrate ions in electroplating wastewater in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods, comprising:

[0008] S1. The electroplating wastewater containing nitrate nitrogen is collected into the pH adjustment tank, and the pH is adjusted to 2-4 with acid to obtain acidic wastewater;

[0009] S2. The acidic wastewater is fed into a high-voltage pulse electrochemical reactor for electrochemical reduction until the reaction water is discharged. Then, alkali is added to adjust the pH to 8-10.

[0010] The high-pressure pulse electrochemical reactor is equipped with electrodes, which are copper-iron staggered composite plates. The copper-iron staggered composite plates are composed of several plates, with a spacing of 3-5 cm between adjacent plates. Each plate is welded together from half copper plate and half iron plate. The copper and iron portions of adjacent plates are staggered and the plates are fixed together by positioning components.

[0011] S3. Add flocculant, and then let the wastewater flow into the sedimentation tank for sedimentation.

[0012] In a preferred embodiment, the electrode plate includes a positioning plate and a fixing plate. The positioning plate has at least three positioning holes. The positioning element is inserted into and fixed in the positioning holes. The positioning plate and the fixing plate are placed alternately, and the fixing plate abuts against the positioning element.

[0013] The upper half of the positioning plate is made of iron, and the lower half is made of copper. The upper half of the adjacent fixing plate is made of copper, and the lower half is made of iron. Alternatively, the upper half of the positioning plate is made of copper, and the lower half is made of iron. The upper half of the adjacent fixing plate is made of iron, and the lower half is made of copper. The positioning plate and the fixing plate are placed in a staggered manner.

[0014] Based on the above scheme, the positioning plate and the fixing plate are separated by the positioning component, which helps to increase the contact area between the wastewater and the electrode plate and improve the electrolysis efficiency. Since copper has better conductivity than iron, the electrode plates are placed in a staggered manner with copper plates and iron plates to improve the conductivity of the electrochemical reactor and reduce current loss.

[0015] In a preferred embodiment, in step S1, the acid is sulfuric acid, and the pH of the wastewater is adjusted to 2-3 using sulfuric acid.

[0016] Based on the above scheme, sulfuric acid is a very strong acid. Adding an appropriate amount of dilute sulfuric acid can be used to adjust the pH of the reaction system to promote the reaction. Adjusting the pH to acidic with sulfuric acid is beneficial because, according to the indirect reduction mechanism of nitrate nitrogen, hydrogen ions are essential for the degradation of nitrate nitrogen, and a lower pH is more conducive to the degradation of nitrate nitrogen.

[0017] In a preferred embodiment, in step S2, the acidic wastewater flows from the bottom into a high-voltage pulsed electrochemical reactor for an electrochemical reduction reaction.

[0018] In a preferred embodiment, in step S2, the bottom of the high-voltage pulse electrochemical reactor is equipped with a stirring system.

[0019] In a preferred embodiment, the stirring system is a suspension aeration device.

[0020] Based on the above scheme, a stirring system is set at the bottom of the high-voltage pulse electrochemical reactor. The stirring system adopts a suspended aeration device, which plays the role of stirring the reaction and blowing off the gas generated after the reaction. Moreover, the suspended aeration device does not generate vibration, the blower does not need to be equipped with a sound insulation device, the equipment is lightweight, does not require a special foundation, and the installation and layout are simple and flexible.

[0021] In a preferred embodiment, in step S2, the voltage of the high-voltage pulse electrochemical reactor is 60V-90V, the current is 30A-60A, the duty cycle is 35%-50%, and the frequency is 1500Hz-2000Hz.

[0022] In a preferred embodiment, in step S4, the alkali is sodium hydroxide, and sodium hydroxide is added to adjust the pH to 9.

[0023] Based on the above scheme, sodium hydroxide can quickly adjust the pH of water, increase its alkalinity, increase its conductivity, and precipitate heavy metal ions and copper and iron ions generated by electrolysis in electroplating wastewater.

[0024] In a preferred embodiment, in step S3, the flocculant is polyacrylamide.

[0025] Based on the above scheme, polyacrylamide is used as a flocculant, which has the characteristics of high efficiency, environmental protection and safety. Polyacrylamide can quickly coagulate heavy metal ions and suspended matter in electroplating water, without causing any pollution to the environment.

[0026] Secondly, the present invention provides a copper-iron staggered composite electrode plate for an electrochemical reactor, comprising several electrode plates, with a spacing of 3-5 cm between adjacent electrode plates. Each electrode plate is welded together from half copper plate and half iron plate, and the copper and iron portions of adjacent electrode plates are staggered and fixed between the electrode plates by positioning components.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. This invention provides a method for electrochemically treating nitrate nitrogen in electroplating wastewater and a copper-iron staggered electrode plate combination in the electrochemical reactor. This method can efficiently oxidize and decompose pollutants, improve the completeness of the nitrate nitrogen reduction reaction, and reduce nitrate nitrogen to NO, N2O, N2, and NH4. + Alternatively, NH3 can be removed through precipitation or gas generation, reducing the content of nitrate ions in electroplating wastewater, decreasing the emission of harmful substances, thereby enhancing the wastewater treatment effect and reducing the harm of nitrate nitrogen to the environment.

[0029] 2. The electrochemical reactor used in this invention employs copper-iron staggered electrode plates as electrodes. Copper has better electrical and thermal conductivity than iron, and the staggered distribution reduces current loss and lowers wastewater treatment costs. Iron, as a relatively reactive metal, can better reduce nitrate ions. Simultaneously, the use of a high-frequency pulse power supply can reduce energy consumption and maintenance costs, improving the efficiency and sustainability of wastewater treatment. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram comparing the changes in current intensity between the iron electrode plate and the copper-iron staggered composite electrode plate provided by this invention.

[0032] Figure 2 This is a schematic diagram of the assembly structure of the copper-iron staggered combined electrode plate in this invention.

[0033] Figure 3 This is a schematic diagram of the connection structure in the copper-iron staggered composite electrode plate of the present invention.

[0034] Explanation of the attached drawing numbers:

[0035] 1-Positioning plate; 2-Fixing plate; 3-Positioning component. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the protection scope of the present invention.

[0037] Example 1:

[0038] This embodiment provides a method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods, including:

[0039] S1. The electroplating wastewater containing nitrate nitrogen is collected into the pH adjustment tank, and the pH is adjusted to 2-4 with acid to obtain acidic wastewater;

[0040] S2. The acidic wastewater is fed into a high-voltage pulse electrochemical reactor for electrochemical reduction until the reaction water is discharged. Then, alkali is added to adjust the pH to 8-10.

[0041] The high-pressure pulse electrochemical reactor is equipped with electrodes, which are copper-iron staggered composite plates. The copper-iron staggered composite plates are composed of several plates, with a spacing of 3-5 cm between adjacent plates. Each plate is welded together from half copper plate and half iron plate. The copper and iron portions of adjacent plates are staggered and the plates are fixed together by positioning components 3.

[0042] S3. Add flocculant, and then let the wastewater flow into the sedimentation tank for sedimentation.

[0043] In order to improve the conductivity and thermal conductivity of the electrode plate and reduce current loss, based on the above scheme, in step S2, the electrode plate includes a positioning plate 1 and a fixing plate 2. The positioning plate 1 is provided with at least three positioning holes. The positioning member 3 is inserted into and fixed in the positioning holes. The positioning plate 1 and the fixing plate 2 are placed alternately, and the fixing plate 2 abuts against the positioning member 3.

[0044] The upper half of the positioning plate 1 is made of iron, and the lower half is made of copper. The upper half of the adjacent fixing plate 2 is made of copper, and the lower half is made of iron. Alternatively, the upper half of the positioning plate 1 is made of copper, and the lower half is made of iron. The upper half of the adjacent fixing plate 2 is made of iron, and the lower half is made of copper. The positioning plate 1 and the fixing plate 2 are placed in a staggered manner.

[0045] Specifically, the positioning element 3 can be a plastic tube or a plastic ring, etc. The electrode spacing can be adjusted according to actual needs. In a preferred embodiment, the electrode spacing can be 4cm, etc.

[0046] In step S1, the acid is sulfuric acid, which is used to adjust the pH of the wastewater to 2-3.

[0047] Specifically, the acid is used to adjust the pH of the electroplating wastewater to acidic. Sulfuric acid or the like can be used to adjust the pH of the electroplating wastewater to 2-4. A lower pH is more conducive to the degradation of nitrate nitrogen. A more preferred option is to adjust the pH to 2-3.

[0048] In step S2, the acidic wastewater flows from the bottom into the high-pressure pulse electrochemical reactor for an electrochemical reduction reaction. The bottom of the high-pressure pulse electrochemical reactor is equipped with a stirring system, which is a suspended aeration device.

[0049] Specifically, the acidic wastewater flows into the electrochemical reactor from the bottom inlet to undergo an electrochemical reduction reaction, reducing nitrate nitrogen to NO, N2O, N2, and NH4. + And NH3. The system employs a bottom-inlet acidic wastewater and top-outlet design. The stirring system selected in this embodiment uses a suspended aeration device installed at the bottom of the reactor, which serves to stir and remove the gas generated after the reaction.

[0050] The high-voltage pulse electrochemical reactor has a voltage of 60V-90V, a current of 30A-60A, a duty cycle of 35%-50%, and a frequency of 1500Hz-2000Hz.

[0051] Specifically, the voltage, current, duty cycle, and frequency of the high-voltage pulse can be adaptively adjusted to meet the needs of practical applications. This applies to electroplating wastewater with high COD, total heavy metal ions, and NO3 levels. - The higher the nitrogen concentration, the higher the selected power supply regulation parameters. In this embodiment, the power supply regulation is 60-90V, 30-60A, 35%-50% duty cycle, and 1500-2000Hz frequency, as long as the final effluent contains NO3. - N should be less than 60 mg / L.

[0052] Additionally, in step S4, the alkali is sodium hydroxide, and sodium hydroxide is added to adjust the pH to 9.

[0053] Specifically, the alkali is used to adjust the pH value of the wastewater. Sodium hydroxide or similar substances can be used. It is sufficient to adjust the pH value of the electroplating wastewater to 8-10. A better option is to adjust the pH value of the electroplating wastewater to 9.

[0054] After adjusting the pH of the electroplating wastewater to alkaline, a flocculant is added to precipitate heavy metal ions or suspended solids. The flocculant can be polyacrylamide, etc.

[0055] Example 2:

[0056] This embodiment provides a copper-iron staggered composite electrode plate for an electrochemical reactor. Each electrode plate is welded together from half copper plate and half iron plate. The electrode plate spacing is 3-5cm, and the copper and iron parts of adjacent electrode plates are staggered. Adjacent electrode plates are fixed together with plastic rings.

[0057] Specifically, the selected electrode is a copper-iron staggered composite electrode plate. The electrode plate spacing can be 4cm, etc. A single electrode plate is made by welding half copper plate and half iron plate together. An electrode plate is placed in the reactor at intervals of 3-5cm. The copper and iron parts of adjacent electrode plates are staggered. That is, if the first electrode plate has the copper plate on top and the iron plate on the bottom, the adjacent electrode plates will have the iron plate on top and the copper plate on the bottom, and so on. Adjacent electrode plates can be fixed with positioning parts such as plastic rings.

[0058] In addition, the electroplating wastewater described in this invention has a COD of <500 mg / L, total heavy metal ions of <200 mg / L, and NO3- of <500 mg / L. - N < 200 mg / L.

[0059] The invention will be further explained and illustrated below with reference to specific experiments:

[0060] 1. Place the electroplating wastewater containing nitrate nitrogen into a pH adjustment tank and add sulfuric acid to adjust the pH to 2.5;

[0061] 2. Acidic wastewater is fed into the electrochemical reactor from the bottom inlet to carry out an electrochemical reduction reaction. The reaction time is set to 60 minutes. The selected reactor has a volume of 600L (length * width * height = 1 * 0.5 * 1.2m) and an effective volume of 500L. The reactor adopts a bottom inlet and top outlet method.

[0062] Among them, see Figure 1 A comparison of the conductivity of the copper-iron staggered composite electrode plate and the iron electrode plate shows that the conductivity of the copper-iron staggered composite electrode plate is significantly better than that of the iron electrode plate.

[0063] See Figure 2 The electrodes selected in this experiment were copper-iron staggered composite plates, with a plate spacing of 4 cm. Each individual electrode plate measures 500*500 cm (4 mm thick) and is constructed by welding one half copper plate and the other half iron plate together; for example, a 500*500 cm copper plate and an iron plate of the same size are welded together to form a single 500*500 cm electrode plate. Electrodes were placed in the reactor at 4 cm intervals, with the copper and iron portions of adjacent plates staggered. That is, if the first electrode plate had its copper plate on top and its iron plate on the bottom, the adjacent plates would have their iron plate on top and their copper plate on the bottom, and so on. The electrodes were fixed together with plastic rings. Twenty electrodes were placed in the selected 600 L container.

[0064] 3. The effluent from the top of the electrochemical reactor is sent to the pH adjustment tank, where sodium hydroxide is used to adjust the pH to between 9 and 9. Then, the alkaline electroplating wastewater flows into the reaction sedimentation tank, where flocculants are added to carry out reaction sedimentation, thereby settling the heavy metal ions and suspended solids in the wastewater.

[0065] 4. Test Results

[0066]

[0067] The experimental results show that the content of nitrate nitrogen in electroplating wastewater treated with iron as the electrode plate was effectively reduced, but the content was still relatively high, with a reduction of 115.4 mg of nitrate nitrogen per liter. However, the content of nitrate nitrogen in electroplating wastewater treated with a copper-iron layered combination as the electrode plate was significantly reduced, with a reduction of 153.6 mg of nitrate nitrogen per liter. This indicates that using a copper-iron layered combination as the electrode plate allows for more complete reduction of nitrate nitrogen and has a stronger ability to treat wastewater.

[0068] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods, characterized in that, include: S1. The electroplating wastewater containing nitrate nitrogen is collected into the pH adjustment tank, and the pH is adjusted to 2-4 with acid to obtain acidic wastewater; S2. The acidic wastewater is fed into a high-voltage pulse electrochemical reactor for electrochemical reduction until the reaction water is discharged. Then, alkali is added to adjust the pH to 8-10. The high-pressure pulse electrochemical reactor is equipped with electrodes, which are copper-iron staggered composite plates. The copper-iron staggered composite plates are composed of several plates, with a spacing of 3-5 cm between adjacent plates. Each plate is welded together from half copper plate and half iron plate. The copper and iron portions of adjacent plates are staggered and the plates are fixed together by positioning components. S3. Add flocculant, and then let the wastewater flow into the sedimentation tank for sedimentation.

2. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, The electrode plate includes a positioning plate and a fixing plate. The positioning plate is provided with at least three positioning holes. The positioning element is inserted into and fixed in the positioning holes. The positioning plate and the fixing plate are placed alternately, and the fixing plate abuts against the positioning element. The upper half of the positioning plate is made of iron, and the lower half is made of copper. The upper half of the adjacent fixing plate is made of copper, and the lower half is made of iron. Alternatively, the upper half of the positioning plate is made of copper, and the lower half is made of iron. The upper half of the adjacent fixing plate is made of iron, and the lower half is made of copper. The positioning plate and the fixing plate are placed in a staggered manner.

3. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, In step S1, the acid is sulfuric acid, and the pH of the wastewater is adjusted to 2-3 using sulfuric acid.

4. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, In step S2, the acidic wastewater flows from the bottom into the high-voltage pulse electrochemical reactor to carry out an electrochemical reduction reaction.

5. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, In step S2, a stirring system is provided at the bottom of the high-voltage pulse electrochemical reactor.

6. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 5, characterized in that, The stirring system is a suspension aeration device.

7. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, In step S2, the voltage of the high-voltage pulse electrochemical reactor is 60V-90V, the current is 30A-60A, the duty cycle is 35%-50%, and the frequency is 1500Hz-2000Hz.

8. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, In step S2, the alkali is sodium hydroxide, and sodium hydroxide is added to adjust the pH to 9.

9. The method for treating nitrate nitrogen in electroplating wastewater using electrochemical methods according to claim 1, characterized in that, In step S3, the flocculant is polyacrylamide.

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