Lately I've been hearing our sales people commenting that customers don't think their cation softening resin is lasting as long as it used to. This is a general comment, not something we're surveying. Here is some food for thought:
Has the manufacturing process changed?
Yes. One of the relatively recent changes to the process came with the non-solvent resins. The greatest motivating factor behind the non-solvent resin came from the EPA. Simply put, the resin manufacturers had to stop manufacturing the resin using solvents because they couldn't put the by-products down the drain. So the resin we used to clean up the water had a manufacturing process that potentially contaminated the water. Makes sense!
Are the non-solvent cation resins lasting as long as the solvent based resins?
According to a major manufacturer non-solvent ion exchange resins are manufactured to meet the same standards of the solvent type. That is, both the solvent and non-solvent resins are 8% crosslink and will react similarly under the same set of circumstances. For instance, both resins, in the presence of 2 ppm chlorine, will react and break down.
Should the solvent free ion exchange resins be used in industrial applications?
According to the data sheets for Sybron C-249 NS and Purolite C-100, the answer to this is yes.
So what are some of the reasons we are seeing shortened life/capacity?
Is there chlorine in the feed water?
In the presence of chlorine or any oxidant, cation ion exchange resins will breakdown prematurely. You say - yes, but the chlorine has always been there. I agree. However, as our water infrastructure has aged have the municipalities been forced in some instances to add more chlorine to compensate?
Are there higher levels of iron in the water?
As we know cation resin will remove ferrous iron but regenerating the iron off of the resin is challenging. Over time there is a loss of capacity as a result of the iron being embedded into the cation bead.
Is the cation resin seeing higher temperatures?
Gel cation resin can tolerate high temperatures but the combination of higher temperatures and an oxidant such as chlorine will dramatically lessen the life of the resin.
We've been supplying ion exchange resins for over 25 years now. We have customers who call every three years, most commonly replacement of anion resin in a demineralizer application and other customers we hear from every 5 or even 7 years - softener applications. I can't say as I've seen a trend that points to bad manufacturing practices by manufacturers.
In my opinion, the overwhelmingly majority of the problems result from oxidants such as chlorine and chloramine and my favorite - Operator Error - Oops ... we just backwashed all the resin out!
