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[keby9vam]

Hi all,

Ion exchange is used in water treatment applications. However, I would like to know how anion exchange resins (hydroxide functional group) are regenerated during water treatment. Is there any literature or source I can look at on this matter? I've tried searching on my own, but I seem to fall short. I found that the conventional method is to use KOH/NaOH, but is there any other way to regenerate the anion resin? Thank you in advance for your help.

Regards,

keby9vam

[kkala]

In the "BETZ Handbook of Industrial Water Conditioning", published by Betz laboratories Inc (several editions), data on Ion exchange regeneration can be found in Chapter "Ion Exchange, Part 1" (Next Chapter "Ion Exchange Part 2" deals with zeolite softenig). However data in the book does not look more extensive than in http://nzic.org.nz/ChemProcesses/water/13D.pdf; nevertheless BETZ distinguishes between strongly / weakly acidic and basic resins, so BETS is judged more clear and complete than the mentioned link (but brief). Probably resin suppliers can supply more data and give info more precise than this from BETZ presented below.
1. Strongly basic anion resins (e.g. HCl+ZOH-->Z^.Cl + H2O) are regenerated by "a strong alkali, such as caustic soda". Z^.Cl + NaOH -->ZOH + NaCl. No other means is reported. I have not heard of anything else, in the few desalination units met in factories. So there is doubt whether another "strong alkali" option can be more economical, under usual conditions.
2. Weakly basic anion resins (containing amine groups, -NH2) are "regenerated by applying caustic soda, soda ash (Na2CO3), or ammonia". Regeneration efficiency is higher compared to strong basic anion resins.
It is noted that these resins can absorb free mineral acids (e.g. H2SO4, HCl), but cannot absorb weakly ionized acids (H2SiO3, H2CO3); so they are used in conjunction with strongly basic anion resins in demineralizer units to reduce operating cost.
3. Above comes from paper info, so data from actual experience would be welcomed.

Edited by kkala, 04 July 2012 - 09:06 AM.