Stability. Strong oxidizing agents,

such as nitric or chromic acid, rapidly

degrade ion exchange resins. Slower

degradation with oxygen and chlorine

may be induced catalytically. For this

reason, certain metal ions, for

example, iron, manganese and

copper, should be minimized in an

oxidizing solution. With cation

exchangers, attack is principally an

the polymer backbone

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0032/0901b803800326ca.pdf?filepath=liquidseps/pdfs/noreg/177-01837.pdf&fromPage=GetDoc

Thanks for your interest in the problem.  I have a metal-free system, but perhaps ring chlorination is still a problem.  Pre-chlorinating the resin might be an option.

You don't mention the type of ion exchange resin you are using.  Recovery should be OK with cation exchange resins provided they are free from transition metal or amine contamination.  Hypochlorite will react quantitatively with anion exchange materials which results anion exchange site decomposition.

Chris-

Actually, it's a quat anion exchange resin (Dowex 1X8), which is why I'm a bit mystified. Hard to imagine what the quaternary ammonium group might be doing, so I wonder if it's chlorination of rings or of residual styrene groups.

-Jim

Hypochlorite reacts directly with the quat.  At low ppm levels the hypochlorite conversion is quantitative to chloride.  But the quat is destroyed in the process and eventually no ion exchange sites remain.  See the following advice from Dow (http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_07d0/0901b803807d05a9.pdf?filepath=liquidseps/pdfs/noreg/177-01744.pdf&fromPage=GetDoc ).  Note their comments, especially the treatment of last resort comment on page 1.

Chris-

I have that document on hand - it suggests that the resins are reasonably stable to oxidation, which is not consistent with what I'm seeing: complete consumption of chlorine, over the course of hours at room temperature.  I can imagine formation of O-Cl species from cation exchange resins, but oxidation of a quat ammonium salt seems pretty far-fetched.  I'm working at neutral pH, not alkaline, which means different species (HOCl and CL2) in solution. 

I'll have a combustion analysis done, to see if the backbone is being chlorinated.

James,

They do say it's a measure of last resort. But from my own experience it seems to me to be unconscionable to even suggest its use with anion exchange resins. I actually use hypochlorite as a way to destroy anion exchange sites routinely in the lab so I know for fact that it destroys the quaternary site. I've looked but have been unable to determine what the reaction products are so if you do find that there is chlorine in the product that would be an interesting clue. Please post your results here.

Chris-

Thanks for that bit of unpublished wisdom.  I would guess that in strong base, you get a bit of the ylide, ArCH--N+Me3, which would quickly oxidize to ArCHCl-N+Me3. It would be downhill quickly from there in an alkaline solution.  I'll check for chloride in my solution as well.

The Dow publication leaves a great deal unsaid.  Example II of the attached patent also suggests that I should not be having problems.  This is quite the mystery... there may be more to the resin than Dow lets on.

I love this community- What a great source of knowledge.

Can I assume that monochloramine is also harmfull to mixed bed?

James Demers

Chris Pohl

Mushtaq Ahmad

Your assumption is correct. However, it will take a lot of water flux to have a material impact on your anion exchange resin if the source of your chloramine is drinking water since the levels in drinking water are typically 1-2 ppm chloramine.

Hi Chris,

Re your experience: "I actually use hypochlorite as a way to destroy anion exchange sites routinely in the lab so I know for fact that it destroys the quaternary site."

Did you mean only Ar-CH2-Quat type or other types of linkers between Ar and Quat are sensitive to active chlorine too?

I have used this method with both styrenic quaternary anion exchange polymers and hyperbranched anion exchange polymers. I haven't tried it with methacrylate anion exchange polymers, though. I expect that the reaction will work in that case as well. It is a great way to fix suppressors if they become contaminated with anion exchange materials as happens on occasion when I am testing new phases. Just pass a couple of milliliters of 5% sodium hypochlorite solution through the suppressor and let it sit for 15 minutes at room temperature. Rinse with DI water and dilute sulfuric acid and rinse again with DI water and the suppressor will be good as new.