What Is The Regeneration Of Ion Exchange Resin

First, conventional regeneration treatment
After the ion exchange resin is used for a period of time, the adsorbed impurities are close to the saturated state, and it is necessary to carry out regeneration treatment, and the ions and other impurities adsorbed by the resin are eluted with chemical agents to restore the original composition and properties. In practical application, in order to reduce the cost of regeneration, it is necessary to properly control the amount of regeneration agent, so that the performance of the resin can be restored to the most economical and reasonable regeneration level, usually the recovery degree of control performance is 70 to 80%. If a higher level of regeneration is to be achieved, the regeneration dose will be greatly increased and the utilization rate of the regenerant will be decreased.
The regeneration of resin should be based on the type of resin, characteristics, as well as the economy of operation, the selection of appropriate regeneration agents and working conditions.
The regeneration properties of resin are closely related to its type and structure. The regeneration of strong acid and strong basic resins is difficult, and the regeneration dose is much higher than the theoretical value. Weak acid or weak basic resin is easier to regenerate, and the regeneration dose is only slightly more than the theoretical value. In addition, the resin with large porosity and low crosslinking degree is easy to regenerate, while the resin with gel type and high crosslinking degree has a longer regeneration reaction time.
The type of regenerant should be selected according to the ion type of the resin, and the lower price of acids, bases or salts should be appropriately selected. For example, sodium-type strong acidic positive resin can be regenerated with 10%NaCl solution, and the amount of medicine is twice the exchange capacity (117g/ l resin with NaCl); The hydrogen type strong acid resin is regenerated with strong acid, and the calcium adsorbed by the resin should be prevented from reacting with sulfuric acid to form calcium sulfate precipitate. To this end, it is advisable to first pass 1-2% of dilute sulfuric acid regeneration.
Chlorine-type strong alkaline resin is mainly regenerated by NaCl solution, but adding a small amount of alkali helps dissolve and wash out the pigments and organic matter adsorbed by the resin. Therefore, alkaline salt solution containing 10%NaCl + 0.2%NaOH is usually used for regeneration. The conventional dosage is 150-200g NaCl per liter of resin, and 3-4g NaOH. OH type strong alkali negative resin is regenerated with 4%NaOH solution.
The chemical reaction of resin regeneration is the reverse reaction of the original exchange adsorption of resin. According to the principle of chemical reaction balance, increasing the concentration of a substance in a chemical reaction can promote the reaction to the other side, so increasing the concentration of regenerated liquid can accelerate the regeneration reaction and achieve a higher regeneration level.
In order to accelerate the regeneration chemical reaction, the regeneration liquid is usually heated to 70~80 ° C first. Its flow rate through the resin is generally 1~ 2 BV/h. It can also be used first fast and then slow method to give full play to the effectiveness of the regenerant. Regeneration time is about one hour. Then wash the resin with soft water for about one hour (water volume is about 4BV), after the washing water is drained, then wash with water back until the washing liquid is colorless and no turbidity.
After regeneration and backwashing, the pH value of some resins should be adjusted. Because the regenerated liquid often contains alkali, the resin is often alkaline after regeneration even after washing. Some decolorizing resins (especially weak alkaline resins) should work under slightly acidic conditions. At this time, dilute hydrochloric acid can be passed to reduce the pH value of the resin to about 6, and then wash with water, backwash each time.
After the resin is used for a long time, some impurities (especially macromolecular organic colloidal substances) absorbed by it are not easy to be eluted by conventional regeneration treatment, and gradually accumulate and pollute the resin, reducing the effectiveness of the resin. This should be handled in a special way. For example, cationic resin is contaminated by amphoteric compounds containing nitrogen, which can be treated with 4%NaOH solution to dissolve it and discharge it; The anion resin is contaminated by organic matter, and the NaOH concentration in alkali salt solution can be increased to 0.5~1.0% to dissolve organic matter.
Second, special regeneration treatment
More seriously polluted resins can be repeatedly treated with acid or alkaline salt solution, such as using 10%NaCl +1%NaOH alkali salt solution to dissolve organic matter, then using 4%HCl or 10%NaOH and 1%HCl respectively to dissolve inorganic matter, and then using 10%NaCl +1%NaOH treatment. Performed at about 70 ° C.
If the effect of the above treatment does not meet the requirements, it can be treated by oxidation method. That is, after washing the resin with water, the sodium hypochlorite solution with a concentration of 0.5% is injected, the flow rate is controlled by 2 to 4BV/h, the amount of 10 to 20BV is passed, and then washed with water and treated with salt water. It should be noted that oxidation treatment may oxidize the bonding bonds of macromolecules in the structure of the resin, resulting in the degradation of the resin, the expansion degree increases, and it is easy to fracture, so it is not suitable for common use. Usually 50 cycles are used before one oxidation treatment. Because the chlorine resin has strong oxidation resistance, the resin is treated with salt water before oxidation treatment to become chlorine, which can also avoid the change of pH value during the treatment process and make the oxidation more stable.
Third, the disposal of recycled waste liquid
Sugar factory resin decolorization, resin regeneration waste liquid contains a lot of pigment and organic matter, the color is very deep. When raw sugar is used to produce refined sugar, the amount of recycled waste liquid per 100 tons of sugar is about 6~9m3. It is also difficult to dispose of it before it can be discharged (or recycled).