- #1
Enigman
- 647
- 311
Why is the cation exchange always carried out before anion exchange in softening of hard water by ion exchange resins?
Plz. Help:(
Plz. Help:(
Click For Summary
SUMMARY
The discussion centers on the sequence of cation and anion exchange in water softening using ion exchange resins. Cation exchange is performed first to prevent the degradation of cation exchange resins by alkalis formed during anion exchange. The products of cation exchange include hydronium ions, while anion exchange produces hydroxyl ions, affecting the pH of the solution. The physical properties of the resulting compounds vary based on the order of the exchange processes, with acidic products resulting from cation exchange and basic products from anion exchange.
PREREQUISITES- Understanding of ion exchange processes
- Knowledge of cation and anion exchange resins
- Familiarity with chemical properties of acids and bases
- Basic chemistry concepts related to pH and solubility
- Research the mechanisms of cation and anion exchange in detail
- Study the physical properties of common ion exchange resin materials
- Explore the effects of pH on ion exchange processes
- Learn about the degradation mechanisms of ion exchange resins
Chemists, water treatment professionals, and anyone involved in the design and operation of ion exchange systems for water softening.
- #2
DrDu
Science Advisor
- 6,423
- 1,004
What compounds are predominantly formed in the two alternative exchange processes?
What are their physical properties?
What are their physical properties?
- #3
Enigman
- 647
- 311
DrDu said:
Ummm... Hydronium ions in cathode exchange and hydroxyl ion in anode exchange...products after cathode exchange are acidic if carried out first (H2SO4,HCl...etc.) if anion exchange is carried out first products will be basic (Ca(OH)2, Mg(OH)2...etc.)
So it has some thing to do with pH.
Are cation exchange resins reactive?
Cation exchange resins are styrene-divinyl benzene copolymers maybe the benzene ring is attacked by hydroxyl ions? Could you please confirm the solution?
or
Thanks in advance.
- #4
DrDu
Science Advisor
- 6,423
- 1,004
How soluble are the products?
- #5
Enigman
- 647
- 311
Don't think solubility has anything to do with it, the products are completely ionizable (all are bases, when anion exchange is carried out first.), so no ppt. should be formed. Unless if it is with the resin itself...
- #6
DrDu
Science Advisor
- 6,423
- 1,004
Well, if you don't take a hint, you have to find a solution on your own.
- #7
Enigman
- 647
- 311
I did, a book I issued from the library confirms my theory that when the sequence is reversed the alkali formed in anion exchange will attack the cation exchange resin (the mechanism isn't mentioned 
) and thus degrade it. While in the usual sequence the acid formed in cation exchange passes harmlessly through anion exchange resin.
Thanks for your help.
P.S. I still didn't get what you were trying to point me towards...
) and thus degrade it. While in the usual sequence the acid formed in cation exchange passes harmlessly through anion exchange resin.Thanks for your help.
P.S. I still didn't get what you were trying to point me towards...