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About regeneration of ion exchanger

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Q. Thanks for your attention,

My question is: there is cation and anion resin in a mixed bed polisher; if both of them are to be used again, we must regenerate it. My problem is the anion and cation resin always need regeneration during service of 2 days. So what happens to the ion exchanger? Why does the ion exchanger have different regeneration? Why does the ion exchanger always take more reagents than my estimate?

Note : My Mixed bed polisher has 3 tanks; so is the ion exchange content of cation and anion the same capacity?

I hope you will send me the answer; thanks for your kindness.

Yohan Rini
- Bontang Kalimantan, Timur, Indonesia


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A. Your problem statement sounds vague. Perhaps if you studied how a mixed bed system works, some of what I think are your Qs will be answered.

When a mixed bed is set into regeneration, the first step is a type of a backwash, that separates the two resins. The anion resin is lighter than the cation resin, so it nicely settles on the top.

The regeneration chemicals are pumped separately to the two parts of the bed. Caustic comes in from the top, and exits near the center, while acid will enter near the center and exit at the bottom.

After the regeneration, the unit gets an air fluff, to mix the resins together.

Usually, the ratio is 60:40 anion to cation. Mixed beds will typically have much lower capacities than two bed units, but much higher quality. You may have calculated the resin capacities for a dual bed, or, you may have assumed the capacity of the resin to be what was given on the resin product data sheet, which is only good for new resin. To achieve the stated capacity, the chemical requirement is very high, making any capacity beyond 50-60% of stated capacity impractical.

Hopefully, that helps you.

Juzer Jangbarwala
- Brea, California


thumbsup2Very clear presentation Juzer. Thanks!

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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A. Maybe your pollution level is too high for resins capacity, even when new? Why don't you try to do an ECP pretreatment with mechanical filtration before resin filtration? It is possible with ECP technology, which means an electrolytic catalytic precipitation treatment and next a filtration of the oxides and minerals, and after that you will treat it by resins. Regards.

Dinu Damian
- Constanta, Romania


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Q. Dear Sir
Please let me Know how much Hydrochloric Acid (37% concentration) is required for regeneration of 600 ltr. ion exchange cation resin and How much caustic (KOH) for regeneration of 900 ltr. ion exchange anion resin. We are using these cation & anion beds for a water treatment plant of capacity of 15 ton per hour. We have two beds (Dual media & carbon bed) before these two beds.

With thanks & best regards,

Kh. Maksudul alam
- Mohakhali, Dhaka, Bangladesh


March 16, 2010

Q. How to regenerate anion and cation resin separately in a Laboratory. What are the instruments and equipments that we can use when doing this operation in a laboratory. Please send me what are the chemicals, concentrations and flow rates also..
Best Regards,

Ruvini Somaweera.
- Boralesgamuwa, Colombo, Sri Lanka


November 3, 2010

Q. Hi Sir

My Mixed bed has 300 kg of cation resin and 600 kg of anion resin. Regeneration protocol:
1. backwash
2. NaOH dosing together with dilution water
3. NaOH rinsing
4. HCl dosing together with dilution water
5. HCl rinsing
6. Air wash
7. Final rinsing

Resin supplier says that their resin can get the effluent water to around 0.2 ms/cm. But mine is near 2 ms/cm. What further procedure, or what else can I do?

August Adeleted
process engineer - Singapore


July 26, 2011

Q. I have a couple of questions. First I have a problem: my D.I. tanks are not lasting out in the field. I don't know if I am putting the right amount of chemicals in them. Would you have any formulas I could use and I have a 143 diameter tank I use for anion and cation resin. I put 45 cubic ft of resin into each tank. On the acid I put a full drum of acid, 55 gallons; and caustic I use 18" out of the 55 gallons I don't know if its enough or too little. Can you get back to me ASAP?

Manny Escobedo
- el paso, Texas

December 22, 2012

Please I need clarification regarding the mixed bed regeneration

Do the salt ions (e.g. NaCl) Na+ & Cl- replace the functional group (H+ amp; OH-) on both cation and anion resin in operation mode respectively according to the electronegativity "The strong ions replaces the weak ions"?

If yes, how can the regeneration be carried out as the H+ can't substitute for Na+ or OH- can't substitute for Cl- ?

Sayed Al-Neshawy
- Cairo, Egypt

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