When the resin is used for a certain period of time, when the adsorption capacity is reduced or the pollution is serious, the regeneration needs to be strengthened. The method is to add a 3%-5% hydrochloric acid solution 10CM higher than the resin layer to soak for 2-4 hours, and then perform leaching. column. Pass the column with 3-4 times the volume of the resin and the same concentration of hydrochloric acid solution, then wash with clean water until it is close to neutral; then soak in 3%-5% sodium hydroxide solution for 4 hours. Finally, the column was eluted and passed through the column with a sodium hydroxide solution of the same concentration 3-4 times the volume of the resin, and finally washed with clean water until the pH value was neutral, for use.
Although there are many methods for resin regeneration, the general processing procedures are similar. For example, in the laboratory, the “backwashing method” can be used to regenerate, that is, the resin to be treated is washed 1 to 3 times with an appropriate amount of distilled water, and then the resin is filled in the “regeneration tube or tower”, and then 2% sulfuric acid or 5﹪Hydrochloric acid is used as a regenerating agent. Pass through the resin column at a backwashing rate of 2-8VB/h. After the backwashing operation is completed, take it out and wash it with distilled water for 1 to 3 times. In ordinary households, the easiest way to regenerate is the “soaking method.” First of all, clean the resin to be regenerated with clean water to clean the impurities on the resin surface to ensure that the regenerated liquid can pass through the resin layer more freely and improve the regeneration efficiency. Then use dilute sulfuric acid or dilute hydrochloric acid as a regenerating solution to soak. At this time, the “hardness ions” absorbed by the resin can exchange reaction with the hydrogen ions in the acid solution. As a result, the resin can regain fresh hydrogen ions, which can be used for hard water. For softening. If the immersion method is operated only once, the regeneration procedure is completed, which is called “one-operation regeneration”. If the same operation is repeated again, it is called “secondary operation regeneration”, and so on. The more operations for each regeneration, the higher the regeneration rate or regeneration capacity of the resin. However, in the actual regeneration operation, in order to reduce the operating cost, it is necessary to appropriately control the number of operations and the amount of acid solution, so that the resin can be restored to the most economical and reasonable level, instead of 100% regeneration (impossible), or Close to 100% regeneration (not needed). Generally, it can control the regeneration rate up to 50 ~ 90%, and the resin can be reused, but 70 ~ 80% is the most suitable. If a higher regeneration rate is to be achieved, the regeneration acid solution must be greatly increased, and the number of operations will also increase. It’s not cost-effective. In the regeneration process of the soaking method, if 2%H2SO4 or 5%HCl is used as the regenerant, the operating dosage is usually 1.1 times the volume of the resin. When operating at room temperature, the regeneration efficiency is the highest in the initial operation, usually up to about 50~75%, the second operation can increase by about 5~10%, and the third operation can increase by about 3~5%. If the order of the number of times of each regeneration operation goes back, the regeneration efficiency will gradually decrease, but the total regeneration The efficiency is still increasing. For example, the “total regeneration efficiency” after three consecutive operations must be higher than the second operation. Similarly, the second operation must be higher than the first operation. In short, the “total regeneration efficiency” mainly depends on the resin type, characteristics, operating conditions (such as the number of operations and temperature), acid properties (such as type and concentration), and whether the resin adsorbs organic matter or not. When the “recycled resin” is used for a period of time and reaches a saturated state, and it must be regenerated for the second time, its average regeneration rate will drop slightly. It shows that the more the number of regenerations, the more the resin performance usually shows signs of gradual deterioration. Therefore, although Resin has the characteristics of regeneration ability, but it also has a life limit.
The regeneration characteristics of hydrogen resin are closely related to its type and structure. It is difficult to regenerate strong acid hydrogen resin. The dosage of regeneration acid is much higher than the theoretical value, and the contact time must be longer. In contrast, the regeneration of weakly acidic hydrogen resins is relatively easy, and the required dosage of the regeneration acid is only higher than the theoretical value, and long contact time is not required. It is generally believed that when the amount of sulfuric acid or hydrochloric acid is twice the total exchange capacity, the contact time of the regeneration resin and the regeneration acid solution is about 30-60 minutes for strong acidity and 30-45 minutes for weak acidity. In addition, the regeneration characteristics of hydrogen resins are also related to their “crosslinking degree”. The so-called cross-linking degree is the mass percentage of the cross-linking agent (such as styrene) contained in the quantitative resin. Generally, resins with a low degree of crosslinking are characterized by low polymerization density, more internal voids, large meshes, and good swellability to water, but they have weak ion selection, fast exchange reaction speed, and easier regeneration. The immersion contact time between the secondary regeneration resin and the regeneration acid solution is relatively short. Conversely, resins with a high degree of cross-linking require a longer time for the regeneration acid to contact the resin. The “crosslinking degree” of either strong acid or weak acid hydrogen type resin can be controlled at the time of manufacture. Because the mesh of the hydrogen resin not only provides good ion exchange conditions, but also like activated carbon, it can produce molecular adsorption and may also adsorb various organic substances, so it is susceptible to organic pollution, which affects its operating efficiency, and also makes The regeneration operation is difficult. If the resin adsorbs organic matter during use, especially macromolecular organic matter, the regeneration contact time must be longer, and usually the temperature (70 ~ 80℃) can be increased to remove most of the organic matter, so as to prevent its efficiency from being reduced too quickly. Operation at high temperature can also speed up the regeneration reaction time, so that the soaking contact time can be shortened. In this respect, sulfuric acid is the preferred regenerant, because sulfuric acid is quite stable when heated, while hydrochloric acid may produce toxic hydrogen chloride gas.
The chemical reaction of resin regeneration is the reverse reaction of its original exchange. According to the equilibrium principle of chemical reaction, increasing the concentration of reactants can promote the reaction to the other side. Therefore, increasing the acid concentration can accelerate the regeneration reaction rate and improve the regeneration efficiency. However, this does not mean that the higher the acid concentration, the better. If there is no experiment to evaluate the amount of acid required for the exchange resin, the problem of “excess is not enough” will occur. Although the concentration of the regeneration acid solution is insufficient, the regeneration rate of the resin is reduced, which will affect the subsequent hard water softening function to some extent. Conversely, if too much acid is used, the acid is wasted on weekdays, which increases the cost of regeneration, which is not cost-effective. In order to let consumers understand the dosage of regenerated acid, some manufacturers with better services will actively provide the most suitable concentration for reference. In addition, if the hydrogen ion concentration of the acid in the water exceeds 1mol/l, the regeneration reaction rate may be limited by the diffusion of the mesh. Therefore, the resin with a small mesh is not suitable to be regenerated with a high-concentration acid. Cause the phenomenon of wasting acid. In addition, although sulfuric acid is a good regenerating agent, it is still necessary to prevent the calcium ions absorbed by the resin from reacting with sulfuric acid, and the formation of calcium sulfate precipitates in the resin. To avoid this problem, you can use it during the first operation. Pour 1 ~ 2% sulfuric acid to soak and elute once, and then use higher concentration sulfuric acid for the second operation. Finally, if you plan to use “one-time regeneration” to complete the regeneration operation, you may consider increasing the operating concentration of the acid solution to increase its regeneration efficiency. Although this method of operation is the most convenient, the regeneration efficiency will not be as good as diluting the same amount of acid solution and immersing it in two or more times. However, if you need to perform multiple operations, you have to consider whether it is worth the effort to increase the regeneration efficiency.