A method for recovering waste acid based on ion exchange separation technology

Abstract

This invention discloses a waste acid recovery method based on ion exchange separation technology, belonging to the field of waste acid recovery technology. The method includes the following steps: passing a waste nitric acid solution containing aluminum and chloride ions through a cation exchange resin to adsorb aluminum ions; adding silver nitrate solution to the adsorbed waste liquid to allow silver ions to react with chloride ions to form silver chloride precipitate; filtering out the silver chloride precipitate to obtain a nitric acid solution; removing the silver chloride precipitate, using aluminum foil as a reducing agent, and adding a small amount of hydrochloric acid to reduce the silver chloride to silver powder; washing the reduced silver powder and dissolving it in nitric acid to obtain a silver nitrate solution for recycling. This waste acid recovery method based on ion exchange separation technology solves the problem of excessive total nitrogen in wastewater discharge; it also significantly reduces waste acid treatment costs and improves economic efficiency.

Description

Technical Field

[0001] This invention relates to the field of waste acid recovery technology, specifically a waste acid recovery method based on ion exchange separation technology. Background Technology

[0002] In the production process of anodic etching foil for aluminum electrolytic capacitors, dilute nitric acid is used to chemically clean the aluminum foil to remove chloride ion impurities adhering to the surface of the foil. However, this process generates a large amount of waste nitric acid solution containing aluminum and chloride ions.

[0003] For the treatment of this type of wastewater, most manufacturers currently adopt the traditional method of neutralization with lime followed by sedimentation. Although this method is simple and easy to implement, it is difficult to fundamentally solve the environmental problem of excessive total nitrogen content in the discharged water. In contrast, only a few companies have adopted the more advanced electrodialysis technology to recover and reuse nitric acid. Although this technology can theoretically achieve effective resource recycling, its high investment cost and high energy consumption during operation result in poor overall economic benefits, thus facing significant difficulties in its widespread application in actual production.

[0004] Therefore, it is necessary to propose a waste acid recovery method based on ion exchange separation technology to solve the above problems. Summary of the Invention

[0005] (a) Technical problems to be solved The purpose of this invention is to provide a waste acid recovery method based on ion exchange separation technology, so as to solve the problems of excessive total nitrogen content and high treatment cost of existing waste acid treatment methods mentioned in the background art.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides a waste acid recovery method based on ion exchange separation technology, comprising the following steps: S1. The waste nitric acid solution containing aluminum ions and chloride ions is passed through a cation exchange resin to adsorb aluminum ions in the solution; S2. Add silver nitrate solution to the waste liquid after adsorption treatment so that silver ions react with chloride ions to form silver chloride precipitate. S3. Filter out the silver chloride precipitate to obtain a nitric acid solution; S4. Remove the silver chloride precipitate, use aluminum foil as a reducing agent, and add a small amount of hydrochloric acid to reduce the silver chloride to silver powder; S5. After washing the silver powder obtained from the reduction, dissolve it in nitric acid to obtain a silver nitrate solution for recycling.

[0007] Furthermore, the process includes the following steps: when the cation exchange resin is saturated with adsorption, an acid solution is introduced into it for regeneration; after regeneration, pure water is introduced into the cation exchange resin for rinsing.

[0008] Furthermore, the acid solution is dilute hydrochloric acid or dilute sulfuric acid.

[0009] Furthermore, the process includes the following steps: adding an appropriate amount of lime to the waste acid water generated during the regeneration process for neutralization, and then discharging the waste water after sedimentation.

[0010] A waste acid recovery system using the above-mentioned waste acid recovery method based on ion exchange separation technology includes an aluminum removal system and a chlorine removal system connected in sequence. The aluminum removal system includes a resin tank, the inlet of which is connected to a waste nitric acid tank. The dechlorination system includes a filter and a nitric acid recovery tank that are connected in a circulating manner. The inlet of the nitric acid recovery tank is connected to the outlet of the resin tank, and a dosing tank is connected to the infusion pipeline between the nitric acid recovery tank and the filter.

[0011] Furthermore, the inlet of the resin tank is connected to a pure water tank, a recycled water tank, and a regenerated liquid tank, and the outlet of the resin tank is connected to the inlet of the recycled water tank.

[0012] Furthermore, the dechlorination system comprises multiple sets, and the nitric acid recovery tanks of the multiple dechlorination systems are all connected to the resin tank. The inlet of the nitric acid recovery tank is equipped with a liquid valve.

[0013] (III) Beneficial Effects Compared with existing technologies, the present invention provides a waste acid recovery method based on ion exchange separation technology, which has the following beneficial effects: 1. This waste acid recovery method based on ion exchange separation technology uses ion exchange to treat waste nitric acid, which can replace aluminum nitrate with dilute nitric acid and then recover and reuse it. The recovery rate of nitrate ions reaches more than 90%, which solves the problem of excessive total nitrogen in wastewater discharge.

[0014] 2. This waste acid recovery method based on ion exchange separation technology achieves the recycling of silver nitrate, consuming only a small amount of aluminum foil and hydrochloric acid solution, thereby significantly reducing treatment costs and improving economic efficiency; at the same time, it effectively avoids the introduction of other impurity ions.

[0015] 3. This waste acid recovery method based on ion exchange separation technology produces waste acid water containing only a small amount of nitrate ions. After neutralization and sedimentation with lime, the total nitrogen content in the discharged wastewater can be significantly reduced, thus avoiding environmental pollution. Attached Figure Description

[0016] Figure 1This is a schematic diagram of the waste acid recovery system of the present invention.

[0017] In the diagram: 1. Pure water tank; 2. Recycled water tank; 3. Regenerated liquid tank; 4. Waste nitric acid tank; 5. Resin tank; 6. Filter; 7. Dosing tank; 8. Nitric acid recovery tank. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] A method for recovering waste acid based on ion exchange separation technology includes the following steps: S1. The waste nitric acid solution containing aluminum ions and chloride ions is passed through a cation exchange resin to adsorb aluminum ions in the solution; Specifically, a waste nitric acid solution containing aluminum and chloride ions is pumped into a cation exchange column at a stable and appropriate flow rate. The flow rate must be selected to ensure sufficient contact time between the cation exchange resin and the waste nitric acid solution so that aluminum ions are fully adsorbed.

[0020] S2. Add silver nitrate solution to the waste liquid after adsorption treatment so that silver ions react with chloride ions to form silver chloride precipitate. Specifically, the amount of silver nitrate solution required is calculated based on the concentration of chloride ions in the waste liquid after adsorption treatment and the volume of the waste liquid to be treated, to ensure that chloride ions can be completely precipitated.

[0021] S3. Filter out the silver chloride precipitate to obtain a nitric acid solution; Specifically, the waste liquid containing silver chloride precipitate is passed into filter 6, where the silver chloride precipitate is retained, while the clear nitric acid solution flows out through the filter paper.

[0022] S4. Remove the silver chloride precipitate, use aluminum foil as a reducing agent, and add a small amount of hydrochloric acid to reduce the silver chloride to silver powder; Specifically, because the chloride ion content in the waste nitric acid solution is relatively low, the amount of insoluble silver chloride obtained by filtration is also small. In order to reduce the equipment setup cost, aluminum foil is used for reduction treatment in the laboratory, with a small amount of hydrochloric acid as a medium, to obtain silver powder.

[0023] S5. After washing the silver powder obtained from the reduction, dissolve it in nitric acid to obtain a silver nitrate solution for recycling.

[0024] Specifically, the reduced silver powder is washed multiple times with deionized or purified water to remove residual impurities and hydrochloric acid. The washed silver powder is then placed in an appropriate amount of nitric acid and heated to a suitable temperature to promote its dissolution. Continuous stirring is necessary during the dissolution process to ensure a complete reaction between the silver powder and the nitric acid.

[0025] In some embodiments, the following steps are also included: When the cation exchange resin is saturated with adsorption, an acid solution is introduced into it for regeneration. After regeneration, pure water is introduced into the cation exchange resin for rinsing. Specifically, the acid solution is dilute hydrochloric acid or dilute sulfuric acid.

[0026] During operation, it is necessary to regularly monitor the ion concentration of the effluent, especially the concentration of aluminum ions. When the aluminum ion concentration in the effluent increases significantly, reaching or exceeding the set threshold, it can be determined that the cation exchange resin has become saturated. Once resin saturation is confirmed, ion exchange with the resin should be stopped immediately, and regeneration should be prepared.

[0027] Before introducing the acid solution, ensure the resin bed is completely emptied to avoid mixing solutions of different properties. Slowly introduce a 1-5% acid solution into the resin bed to ensure sufficient contact between the acid and the resin, and to fully dissolve and displace the adsorbed ions. The progress and effectiveness of the regeneration process can be assessed by monitoring the pH and ion concentration of the effluent. If the effluent still contains a significant amount of aluminum ions or other impurities, increase the amount of acid solution or extend the reaction time. After regeneration, rinse the resin bed with pure water to remove residual acid and impurities. Rinsing is considered complete when the pH of the effluent is close to neutral.

[0028] During the regeneration process of cation exchange resin, waste acid water containing acidic substances such as hydrochloric acid or sulfuric acid is generated. In order to avoid environmental pollution caused by the waste acid water generated during the regeneration process, this waste acid water is collected, and an appropriate amount of lime is added to it for neutralization reaction. After sedimentation, the waste water is discharged.

[0029] Please see Figure 1 As shown, a waste acid recovery system using ion exchange separation technology includes an aluminum removal system and a chlorine removal system connected in sequence. The aluminum removal system includes a resin tank 5, the inlet of which is connected to a waste nitric acid tank 4. The chlorine removal system includes a filter 6 and a nitric acid recovery tank 8 connected in a circulating manner. The inlet of the nitric acid recovery tank 8 is connected to the outlet of the resin tank 5. A dosing tank 7 is connected to the liquid delivery pipeline between the nitric acid recovery tank 8 and the filter 6.

[0030] Waste nitric acid solution containing aluminum and chloride ions is collected in waste nitric acid tank 4. The collected waste nitric acid solution is pumped into resin tank 5 by a liquid pump. The aluminum ions are adsorbed by the cation exchange resin inside resin tank 5. After adsorption treatment, the wastewater is fed into nitric acid recovery tank 8. Nitric acid recovery tank 8 is circulated into filter 6 by a liquid pump. During this process, silver nitrate solution is slowly added to it through dosing tank 7. The resulting silver chloride precipitate is filtered out by filter 6.

[0031] To facilitate the regeneration of the cation exchange resin, the inlet of the resin tank 5 is connected to the pure water tank 1, the recovery water tank 2, and the regenerated liquid tank 3, and the outlet of the resin tank 5 is connected to the inlet of the recovery water tank 2.

[0032] During the regeneration of cation exchange resin, the acid solution in the regeneration tank 3 is pumped into the resin tank 5 by a liquid pump for regeneration. The wastewater generated in this process is discharged. After regeneration is completed, pure water in the pure water tank 1 is pumped into the resin tank 5 by a liquid pump to rinse the resin. Finally, the rinsing wastewater is discharged into the recycling water tank 2 for collection, which is used for the first rinse of the resin after the next regeneration process, thereby achieving water conservation and optimized utilization.

[0033] There are multiple dechlorination systems, and the nitric acid recovery tanks 8 of the multiple dechlorination systems are all connected to the resin tank 5. The inlet of the nitric acid recovery tank 8 is equipped with a liquid valve.

[0034] By setting up multiple dechlorination systems and controlling their on / off state through liquid valves, these systems can be alternately connected to resin tank 5 to ensure that the aluminum ion processing flow is not interrupted while dechlorination is being performed, thereby improving overall processing efficiency.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for recovering waste acid based on ion exchange separation technology, characterized in that: Includes the following steps: S1. The waste nitric acid solution containing aluminum ions and chloride ions is passed through a cation exchange resin to adsorb aluminum ions in the solution; S2. Add silver nitrate solution to the waste liquid after adsorption treatment so that silver ions react with chloride ions to form silver chloride precipitate. S3. Filter out the silver chloride precipitate to obtain a nitric acid solution; S4. Remove the silver chloride precipitate, use aluminum foil as a reducing agent, and add a small amount of hydrochloric acid to reduce the silver chloride to silver powder; S5. After washing the silver powder obtained from the reduction, dissolve it in nitric acid to obtain a silver nitrate solution for recycling.

2. The waste acid recovery method based on ion exchange separation technology according to claim 1, characterized in that: It also includes the following steps: When the cation exchange resin is saturated with adsorption, an acid solution is introduced into it for regeneration; after regeneration, pure water is introduced into the cation exchange resin for rinsing.

3. The waste acid recovery method based on ion exchange separation technology according to claim 2, characterized in that: The acid solution is dilute hydrochloric acid or dilute sulfuric acid.

4. The waste acid recovery method based on ion exchange separation technology according to claim 1, characterized in that: It also includes the following steps: adding an appropriate amount of lime to the waste acid water generated during the regeneration process for neutralization reaction, and discharging the waste water after sedimentation.

5. A waste acid recovery system employing the waste acid recovery method based on ion exchange separation technology as described in any one of claims 1-4, characterized in that: This includes an aluminum removal system and a chlorine removal system connected in sequence; The aluminum removal system includes a resin tank (5), and the inlet of the resin tank (5) is connected to a waste nitric acid tank (4). The dechlorination system includes a filter (6) and a nitric acid recovery tank (8) connected in a circulating manner. The inlet of the nitric acid recovery tank (8) is connected to the outlet of the resin tank (5). A dosing tank (7) is connected to the infusion pipeline between the nitric acid recovery tank (8) and the filter (6).

6. The waste acid recovery system according to claim 5, characterized in that: The resin tank (5) is connected to a pure water tank (1), a recycled water tank (2) and a regenerated liquid tank (3) at its inlet. The resin tank (5) is connected to the inlet of the recycled water tank (2).

7. The waste acid recovery system according to claim 5, characterized in that: The dechlorination system has multiple sets, and the nitric acid recovery tanks (8) of the multiple dechlorination systems are all connected to the resin tank (5). The inlet of the nitric acid recovery tank (8) is equipped with a liquid valve.

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