Regeneration of Ion Exchange Resin
Ion exchange resin used for a period of time, adsorption of impurities close to saturation, it is necessary to carry out regeneration treatment. The ions and other impurities adsorbed by the resin are removed by chemical eluting to restore its original composition and properties.
How to select regeneration agent
Resin regeneration should be based on the type of resin, characteristics and economic operation, the selection of appropriate regeneration agents and working conditions.
- The regeneration of strong acid and alkali resin is difficult, and the dosage of regeneration is much higher than the theoretical value.
- Weak acid or weak alkali resin is easier to regenerate, the regeneration dose is only slightly more than the theoretical value.
- The resins with large pores and low crosslinking degree are easy to regenerate.
- Gel type and resin with high crosslinking degree have longer regeneration reaction time.
The type of resin regenerating agent should be selected according to the ion type of resin, and the appropriate choice of low price acid, alkali or salt.
- The sodium resin was regenerated with 10% NaCl aq. and the dosage was twice the exchange capacity (117g/L NaCl was used).
- Hydrogen type strong acid resin regeneration with strong acid, sulfuric acid to prevent the resin adsorption of calcium and sulfuric acid reaction to generate calcium sulfate precipitation, should be first through 1-2% dilute sulfuric acid regeneration.
- Chlorine type strong alkaline resin, mainly in NaCl solution regeneration, adding a small amount of alkali can help the resin adsorption pigment and organic matter to dissolve and wash out, so usually use 10% NaCl+0.2% NaOH alkali salt solution regeneration, the conventional dosage is 150-200g NaCl per liter of resin, and 3-4g NaOH.
- OH - type strong alkali negative resin was regenerated with 4% NaOH aq.
- For the resin with serious pollution and difficulty in conventional regeneration treatment, acid or alkaline NaCl solution can be used for repeated treatment. In order to accelerate the chemical reaction of regeneration, the regeneration solution should be heated to 70-80 ºC.
What factors may affect resin regeneration
Quality of regenerating agent:
The higher the purity, the higher the regeneration degree of resin, the less ion leakage of water.
Dosage of regenerating agent:
Considering the reversible effects of exchange reaction, the dosage of regenerating agent should be 3-4 times of the theoretical amount, and the effect will not be improved by increasing the amount again, resulting in low economic benefit.
Regenerating agent concentration:
The concentration of regenerating agent needs to be controlled reasonably. Generally speaking, the higher the concentration of regenerating agent is, the higher the regeneration degree is, but when the amount of regenerating agent is constant, the regeneration effect decreases, resulting in the shortening of water preparation cycle, the increase of regeneration times, and the increase of acid and alkali dosage.
Regenerant velocity:
Should be appropriate to ensure full regeneration response, the longer the reaction time needed for the higher average valence, regenerant speed too fast, promotes the diffusion of ions, but reduce the contact time with the resin regeneration agent, regeneration effect may reduce instead, velocity is too small are not conducive to the ion diffusion, regeneration effect would also be affected.
Temperature of reclaimed liquid:
Increasing the temperature of reclaimed liquid can accelerate internal diffusion and external diffusion at the same time, but the temperature should not be too high, generally controlled at 25-40 degrees is appropriate.
In addition, the height of the resin layer, the flow rate of the regeneration solution, the concentration of the regeneration solution, the contact time between water and the resin, and the type of ion exchange resin will affect the regeneration of the resin.
