Deterioration of ion exchange capacity 2

[ie416]

Hello,
I work on ion exchange resins on a laboratory scale.I regenerate the resin with Sodium salt of a particular concentration(Say 80 g /ltr of solution) and measure the capacity in terms of equivalents of ions detected per litre of the resin bed.

When i reduce the salt concentration in the regenerant by half (40 g/ltr of solution), the measured capacity is reduced by a factor of 4.Is such a drastic reduction acceptable?
Apart from the obvious change in salt concentration and resin degradation/fouling , are there any other factors that contribute to reduction in capacity ?

 

[m777182]

We experienced detrimental effect of oxidants, e.g H2O2, at low concentration levels at lab, pilot scale and full operation scale. The process was abandoned some years ago due to row material change.
m777182

 

[quark]

Generally you require 2 Na+ ions (monovalent) to exchange each of Ca++ or Mg++ (bivalent)ions. That is why your softening capacity is getting reduced by 4 times.

 

[BenThayer]

i have to disagree with quark. all things being equal, reducing half of the regenerant would reduce half of the capacity.

however, all things are not equal. in resin regeration, you are typically relying on a complete saturation of the resin. frequently, you are regenating with something the resin would rather not have. in your case, if you put a mixture of calcium chloride and sodium chloride through a resin that had been regenated with acid (H+), it would preferentially remove the calcium.

with regards to valence, the Ca++ is why the ppm levels of the calcium "stick" better than equivalent ppm level of Na+.

when the regenerant conc. is cut in half,this becomes more of a kinetics/equilibrium question.

water treatment systems will frequently try and increase regenerant volumes and concentrations to try and compensate for fouling of the resin.

 

[quark]

Ben,

You must trust me, if I say, I have been waiting for somebody to negate my comment after I posted it.

At first thought this didn't seem to me as a problem with degradation or fouling as that should have effected when we used actual concentration also. Then I required a quick answer and thus I overlooked simple algebra. Further, I thought that the original poster was comparing both the results with respect to inlet concentration (yes, I agree that it is a silly idea and includes some magical numbers)

Having said this, I still feel it is natural. As you already stated in your reply that a bivalent ion has greater tendency to stick to the resins than a monovalent ion and we do reuire strong concentration to reverse the effect.

Thanks for pointing out.

Regards,