Sterilization of Ion Exchange Resins

Background
One of the most common questions ion exchange manufacturers encounter, “What is the best method of sterilizing ion exchange resins?”
 
Synthetic resins were introduced over 70 years ago. Because carbon makes up a high proportion of these products matrix, they are susceptible to biological fouling if subjected to a contaminated supply. Synthetic resins are employed in sensitive applications, such as in the production of water for medical, foodstuff and beverages, as well as potable water. Therefore, being able to sterilize resins is important and routine sterilization should be done periodically as a precaution as part of routine maintenance and operation. For example, many hotel chains, hospitals, restaurant chains have their water softeners routinely sterilized as part of their service contracts.
 
Current Practice
Sterilization chemicals include dilute sodium hypochlorite, dilute hydrogen peroxide and many proprietary chemicals. In every case, however, these chemicals are strong oxidizing chemicals that will damage the resin to some extent each time they are used, so concentration and contact time are critical.
 
For example, oxidizing agents attack the cross-linking matrix resulting in loss of cation activity. On anion resins, they do the same damage and also attack the active amine group, which greatly affects performance.
 
It is important to realize that incorrect sterilization can destroy resin and result in irreversible damage to the plant performance.  
 
Best Practice
The chemical most preferred by Purolite for sterilization of synthetic ion exchange resins is peracetic acid. While it has some oxidative potential, peracetic acid with low hydrogen peroxide content used at low concentration with a contact time of several hours has yielded successful results with the slow loss of performance. It also has an advantage in that it can be used on both cation and anion resins and even anion resins in the regenerated form.
 
While peracetic acid is supplied with varying hydrogen peroxide content, you should always use the lowest concentration and dilute as per the instructions.
 
Purolite recommends routine testing of samples before and after treatment to ensure resin performance is maintained. If the plant is suffering from a severe biological attack, the most cost-effective and quickest solution is to give the plant full, strong sterilization and install new resin.
 
Peracetic Acid Procedure 
An outline procedure should be available from your local Purolite sales office and testing of samples can also be organized before and following treatment of the general resin characteristics.