Letter 13077

Ion exchange resin regeneration 

How effect would lime regeneration of anion exchange resins be? Apart from calcium sulfate deposition would I encounter any other difficulties?

Ranjit M
- Mumbai, Maharashtra, India

Basically (pun intended) it will be very inefficient and likley will not work at all. You would have to filter to an extremely high degree the lime slurry so that it was essentially free of suspended solids. If you do not, it will foul the resin bed very very quickly. Further, the typical pH of lime slurry (and an indicator of hydroxyl strength necessary to effect the regeneration process) is fairly low as compared with sodium hydroxide at 4%. I believe the best you will probably get is around a pH of 11 or so - and weak at that.

There isn't much way around the fact that you need a heavy basicity and caustic soda is the best reagent for it.

Tom Baker
wastewater treatment specialist - Warminster, PA

Don't bring lime near your resin unless you intend to manufacture black speckled plaster for that different look.

John Tuohy
- Ireland

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