Saturation capacity recovery method of resin for removing ammonia nitrogen and chlorine radicals in cobalt carbonate wastewater

Abstract

The invention discloses a saturation capacity recovery method of resin for removing ammonia nitrogen and chlorine radicals in cobalt carbonate wastewater, belongs to the field of ion exchange resin, and solves the problems that the saturation capacity of the resin is reduced and the service life is shortened. The method comprises the following steps: firstly, analyzing the saturated cation resin subjected to ammonia nitrogen removal adsorption by using ammonia water, so that anions adsorbed in the cation resin are thoroughly analyzed; then, pure water is used for flushing; ammonia nitrogen adsorbed on the cationic resin is desorbed by using hydrochloric acid; finally, pure water is used for flushing; the method comprises the following steps of: firstly, analyzing the anion resin which is saturated in chlorine ion removal adsorption by using hydrochloric acid, so that cations adsorbed in the anion resin are thoroughly analyzed; then, pure water is used for flushing; ammonia water is used for analyzing chloride ions adsorbed on the anion resin; finally, pure water is used for flushing. According to the method, the problem of incomplete analysis of a traditional method is solved, the saturation capacity recovery rate of the resin reaches 95% through periodic backwashing regeneration, and the service life of the resin is obviously prolonged.

Description

Technical Field

[0001] This invention belongs to the field of ion exchange resins, and specifically relates to a method for restoring the saturation capacity of a resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater. Background Technology

[0002] When cobalt carbonate wastewater is utilized for resource recovery, the condensate produced by MVR evaporation contains ammonia nitrogen and chloride ions, as well as trace amounts of calcium, magnesium, sodium, and cobalt ions. Ammonia nitrogen is removed from this condensate using a cationic resin, and chloride ions are removed and conductivity is reduced using an anion exchange resin.

[0003] Extensive experiments have revealed that cation exchange resins, while adsorbing ammonia nitrogen, also adsorb cobalt ions, magnesium ions, sodium ions, calcium ions, and a small amount of chloride ions in condensate; anion exchange resins, while removing chloride ions, also adsorb cobalt ions, calcium ions, magnesium ions, sodium ions, etc.

[0004] Typically, after the primary ammonia nitrogen removal cation exchange resin becomes saturated, it is backwashed with hydrochloric acid. This process uses hydrogen ions to desorb the ammonium, cobalt, calcium, magnesium, and sodium ions adsorbed on the resin. However, hydrochloric acid cannot desorb the chloride ions adsorbed on the resin. Similarly, after the secondary chloride ion exchange resin becomes saturated, it is backwashed with ammonia. This backwash only desorbs chloride ions, not cations. Therefore, with increasing usage time and flow rate, these ions accumulate in the resin, causing a rapid decrease in adsorption rate and saturation capacity. This necessitates more frequent backwashing and regeneration, leading to a rapid decline in the resin's lifespan.

[0005] To restore the saturation capacity of the resin and improve its service life, this invention optimizes and innovates the resin backwashing process for removing ammonia nitrogen and chloride ions to reduce conductivity. Summary of the Invention

[0006] The purpose of this invention is to provide a method for restoring the saturation capacity of resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater, so as to solve the problems of decreased resin saturation capacity and shortened service life.

[0007] The technical solution of this invention is: a method for restoring the saturation capacity of a resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater, as follows: For cation exchange resins that are saturated with primary ammonia nitrogen adsorption, first use ammonia water to desorb and fully soak the resin to completely remove the anions (chloride ions) adsorbed on the resin. Then, rinse the resin with pure water until the pH of the effluent reaches 7. Next, use hydrochloric acid to desorb the ammonia nitrogen adsorbed on the resin and fully soak it. Finally, rinse the resin with pure water until the pH of the effluent reaches 7. For anion exchange resins saturated with secondary chloride adsorption, hydrochloric acid is first used for elution and thorough soaking to completely remove the cations (cobalt, calcium, magnesium, sodium, and ammonium ions) adsorbed on the anion exchange resin. Then, the anion exchange resin is rinsed with pure water until the pH of the effluent reaches 7. Next, ammonia water is used to elute the chloride ions adsorbed on the anion exchange resin and the resin is thoroughly soaked. Finally, the anion exchange resin is rinsed with pure water until the pH of the effluent reaches 7.

[0008] As a further improvement of the present invention, the mass fraction of ammonia water used is 6-8%; the mass fraction of hydrochloric acid used is 6-8%.

[0009] As a further improvement of the present invention, the amount of ammonia and hydrochloric acid used in each analysis is not less than three times the volume of the resin.

[0010] As a further improvement of the present invention, the soaking time is not less than 4 hours each time the analysis is performed.

[0011] The beneficial effects of this invention are as follows: This invention improves upon the traditional backwashing process. For cation exchange resins saturated with primary ammonia nitrogen removal adsorption, ammonia water is first used for soaking to thoroughly dissolve the anions (chloride ions) adsorbed in the cation exchange resin. Then, hydrochloric acid is used to dissolve the ammonia nitrogen adsorbed on the cation exchange resin. For anion exchange resins saturated with secondary chloride ion removal adsorption, hydrochloric acid is first used for soaking to thoroughly dissolve the cations (cobalt ions, calcium ions, magnesium ions, sodium ions, and ammonium ions) adsorbed in the anion exchange resin. Then, ammonia water is used to dissolve the chloride ions adsorbed on the anion exchange resin. Through these methods, various anions and cations adsorbed on the resin are thoroughly dissolved. This ensures that the resin can effectively adsorb the corresponding cations and anions when it is reused. This invention solves the problem of incomplete dissolution in traditional methods. Through periodic backwashing and regeneration, the resin's saturation capacity recovery rate reaches 95%, significantly extending the resin's service life. Detailed Implementation

[0012] The present invention will be further described in detail below with reference to specific embodiments.

[0013] Example 1 In this embodiment, Kehaisi T-42 cation exchange resin is used for ammonia nitrogen removal, and A-21 anion exchange resin is used for chloride removal and conductivity reduction. The two cation exchange columns for ammonia nitrogen removal are connected in parallel. The water after the first stage of ammonia nitrogen removal enters an intermediate storage tank, and is then pumped into two parallel anion exchange columns for chloride removal. The daily condensate flow rate is approximately 400 cubic meters, with an ammonia nitrogen content of 10-50 mg / L and a chloride content of 10-50 mg / L. Under these conditions, the expected service life of the resin is approximately one year, and the backwash regeneration frequency is approximately once a week. However, in actual use, after three months, the resin's saturation capacity drops rapidly, and the backwash regeneration frequency gradually decreases from 5-6 days to 4 days, 1 day, and then 0.5 days. In response to the declining effective saturation capacity and increased backwashing frequency of the ammonia nitrogen removal and chloride removal resins, the backwashing and regeneration process of the ammonia nitrogen removal and chloride removal resins was adjusted. However, even by increasing the concentration of hydrochloric acid and ammonia in the backwash solution, the saturation capacity of the resins could not be restored.

[0014] Extensive experiments revealed that the T-42 cation exchange resin for removing ammonia nitrogen also removes small amounts of cobalt, calcium, sodium, magnesium, and chloride ions from the condensate. Similarly, the A-21 anion exchange resin for removing chloride also removes small amounts of cobalt, calcium, magnesium, and sodium ions from the condensate. Therefore, simply using the eluent that adsorbs the corresponding cation or anion cannot elute the chloride ions adsorbed on the ammonia nitrogen removal resin, nor the cobalt, calcium, magnesium, and sodium ions adsorbed on the chloride removal resin.

[0015] The method for restoring the saturated capacity of the resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater according to the present invention is as follows: For a cation exchange resin saturated with primary ammonia nitrogen removal, the resin is first desorbed using 6% ammonia solution (volume fraction). The volume of ammonia solution entering the ion exchange column is three times the volume of the cation exchange resin. The resin is soaked for 4 hours to ensure complete desorption of the anions (chloride ions) adsorbed on the cation exchange resin. Then, the cation exchange resin is rinsed with pure water until the pH of the effluent reaches 7. Next, 6% hydrochloric acid is used to desorb the ammonia nitrogen adsorbed on the cation exchange resin. The amount of hydrochloric acid entering the ion exchange column is three times the volume of the cation exchange resin. The resin is soaked for 4 hours. Finally, the cation exchange resin is rinsed with pure water until the pH of the effluent reaches 7. For anion exchange resins saturated with secondary chloride adsorption, the resins are first desorbed using 6% hydrochloric acid. The volume of hydrochloric acid entering the ion exchange column is three times the volume of the anion exchange resin. The resins are soaked for 4 hours to ensure complete desorption of the cations (cobalt, calcium, magnesium, sodium, and ammonium ions) adsorbed on the anion exchange resin. Then, the anion exchange resins are rinsed with pure water until the pH of the effluent reaches 7. Next, 6% ammonia water is used to desorb the chloride ions adsorbed on the anion exchange resin. The volume of ammonia water entering the ion exchange column is three times the volume of the cation exchange resin. The resins are soaked for 4 hours. Finally, the anion exchange resins are rinsed with pure water until the pH of the effluent reaches 7.

[0016] Using this analytical process, the saturation capacity of anion exchange resin and cation exchange resin can reach 95% after more than 3 months of use.

[0017] Example 2 The resin used in this embodiment is the same as that in Example 1. The method for restoring the saturated capacity of the resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater according to the present invention is as follows: For cation exchange resins saturated with primary ammonia nitrogen removal adsorption, the resin is first desorbed using 8% ammonia solution (volume fraction). The volume of ammonia solution entering the ion exchange column is three times the volume of the cation exchange resin. The resin is soaked for 4 hours to ensure complete desorption of the anions (chloride ions) adsorbed on the cation exchange resin. Then, the cation exchange resin is rinsed with pure water until the pH of the effluent reaches 7. Next, 8% hydrochloric acid is used to desorb the ammonia nitrogen adsorbed on the cation exchange resin. The amount of hydrochloric acid entering the ion exchange column is three times the volume of the cation exchange resin. The resin is soaked for 4 hours. Finally, the cation exchange resin is rinsed with pure water until the pH of the effluent reaches 7. For anion exchange resins saturated with secondary chloride adsorption, the resins are first desorbed using 8% hydrochloric acid. The volume of hydrochloric acid entering the ion exchange column is three times the volume of the anion exchange resin. The resins are soaked for 4 hours to ensure complete desorption of the cations (cobalt, calcium, magnesium, sodium, and ammonium ions) adsorbed on the anion exchange resin. Then, the anion exchange resins are rinsed with pure water until the pH of the effluent reaches 7. Next, 8% ammonia water is used to desorb the chloride ions adsorbed on the anion exchange resin. The volume of ammonia water entering the ion exchange column is three times the volume of the cation exchange resin. The resins are soaked for 4 hours. Finally, the anion exchange resins are rinsed with pure water until the pH of the effluent reaches 7.

[0018] Using this analytical process, the saturation capacity of anion exchange resin and cation exchange resin can reach 95% after more than 3 months of use.

Claims

1. A method for restoring the saturated capacity of a resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater, characterized in that: For cation exchange resins saturated with ammonia nitrogen adsorption, first use ammonia water to desorb and fully soak the resin to completely remove the anions adsorbed in it; then use pure water to rinse the resin until the pH of the effluent reaches 7; next, use hydrochloric acid to desorb the ammonia nitrogen adsorbed on the resin and fully soak it; finally, use pure water to rinse the resin until the pH of the effluent reaches 7. For anion exchange resins saturated with chloride adsorption, first use hydrochloric acid to precipitate and soak them thoroughly to completely remove the cations adsorbed in the anion exchange resin; then rinse the anion exchange resin with pure water until the pH of the effluent reaches 7; next, use ammonia water to precipitate the chloride ions adsorbed on the anion exchange resin and soak them thoroughly; finally, rinse the anion exchange resin with pure water until the pH of the effluent reaches 7.

2. The method for restoring the saturated capacity of the resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater according to claim 1, characterized in that: The mass fraction of the ammonia water used is 6-8%; the mass fraction of the hydrochloric acid used is 6-8%.

3. The method for restoring the saturated capacity of the resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater according to claim 1 or 2, characterized in that: During each analysis, the amount of ammonia and hydrochloric acid used should be no less than three times the volume of the resin.

4. The method for restoring the saturated capacity of the resin used for removing ammonia nitrogen and chloride ions from cobalt carbonate wastewater according to claim 1 or 2, characterized in that: The soaking time should be no less than 4 hours for each analysis.