"Wish we knew how to refresh the compound that binds up the freed iron.
I think I read it was a sulfer compound.
Firkin ????"
That's what they say--and that eventually there's a bunch of "iron sulfate". Which is, as expected singularly uninformative
Ferric sulfate or ferrous sulfate? Is it hydrated or oar there other ligands?...
The compound that finally binds up the freed irom is fairly cheap and readily available I think. The chelator is the expensive part--finely tuned to want the iron enough to yank it out of the rust, but still willing to release it later, to form the "iron sulfate" which
remains in solution. If the chelator wasn't expensive, why not just dump in a bunch--why bother with the transfer?
Normally a chelator which coordinates to a metal atom through two or more groups like a pincher (from which the name is derived I think) forms a complex with a metal ion that's MORE stable than something like a hydrated sulfate complex.-- Equlibria often favor chelated complexes by factors of tens to hundreds.
In their system, things are working in reverse, at least the part involving "iron sulfate". Which is pretty cute. Cute enough to make me think that the "sulfer containg" compound may be not be as simple as they make it sound.
Anyway, the only ways I see to "regenerate" this stuff is
1)Electrochemically reduce the iron to iron-zero which will precipitate out. (like getting silver from photography solutions) If the other ingredients are ssusceptable to reduction, then this won't work. Not a brilliant thing to attempt in total ignorance of the composition of the solution.
2)Add more stuff to bind iron. Only problem, is we don't know what it is! At some point solubility will be a problem, and crystals will come out, which wouldn't be real great if they grew in the rust pits that your'e trying to clean.
But if one got a hold of the patent (if this is patented), this approach might work for a while. Or the formulators may have pretty much concentrated things to the max already.
Just a note--There is also detergent in the stuff, to clean off grease and the like.
One of the fastest ways to get junk off of the surface and promote mixing is SONICATION. If you put a container of this into the water bath of a sonicator, I bet it would work much faster. Most of the energy transmits fine through glass, no need to goop up the sonicator bath.
Sorry, not much help.