Potassium Peroxymonosulfate vs. Sodium Monopersulfate

[TreeFiter]

I have always used Sodium Monopersulfate in the hot tubs I take care of, but I have come across other non-chlorine shocks that contain Potassium Peroxymonosulfate. I have tried the Potassium Peroxymonosulfate in a few tubs, but I don't think I'm getting the same result I was with Sodium Monopersulfate.

Should these two chemicals behave similarly? In my experience, with a bromine tub, Sodium Monopersulfate would re-activate the bromine in a matter of seconds. When I tried the Potassium Peroxymonosulfate, I didn't get any result even after several minutes.

Are they meant for different applications, or do they essentially serve the same purpose?

 

[JasonLion]

Potassium Peroxymonosulfate is also called Potassium Monopersulfate and MPS, different names for the same stuff. MPS will reactivate bromide to bromine fairly quickly.

Sodium Monopersulfate should be essentially identical, just with a sodium instead of potassium in a way that shouldn't make any difference in a pool/tub.

That suggests that whatever you were using that was labeled Potassium Peroxymonosulfate was not really Potassium Peroxymonosulfate.

 

[chem geek]

Are you sure you weren't using sodium persulfate (not monopersulfate)? This is not the same as potassium monopersulfate. The concentration is likely to be different so you need to dose by different amounts. Sodium persulfate is usually available in a more pure form while potassium monopersulfate is almost always in the triple salt so most products with it are no more than 43% MPS. If you were using persulfate, then it is an irritant unless silver ions are present in which case it breaks down producing powerful sulfate radicals that would quickly oxidize bromide to bromine. Persulfate by itself does not react with bromide (nor chloride, but it does react with iodide).

With monopersulfate, it takes longer to oxidize bromide to bromine. Ozone reacts faster and chlorine even faster (to oxidize bromide to bromine).

 

[TreeFiter]

I'm pretty sure I got the names right, but I'll check next time I service that particular tub. Thanks for the replies.

 

[TreeFiter]

I went back to this tub today, and the Spa Shock that was there is now gone. I'm not sure if this means someone dumped the whole thing in, or if it was misplaced or thrown away. What I did see was a high Total Chlorine, but no Free Chlorine. It seems to me that the Bromine in this tub is not being activated by this particular shock. I will be using an Oxidizing Shock that I have seen good results from in the past from now on, so I'm curious to see the difference it makes.

 

[chem geek]

So not reacting with bromide to from bromine is consistent with persulfate, not monopersulfate, so I'm pretty sure that it was sodium persulfate. The sodium vs. potassium is irrelevant with regard to reactivity. It's the persulfate (aka peroxydisulfate) vs. monopersulfate (aka peroxymonosulfate).