Manganese Sulphate Stain

I dropped a few granuals of manganese sulphate on our KoolDeck porch (intended for the potted palms). After the first rain, we now have some rather ugly rust colored spots. Oxalic acid based rust remover had no effect.
Any cleaning thoughts are greatly appreciated.
Kevin
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Kevin wrote:

Have you tried a bleach, either chlorine or non-chlorine type?
Are you sure that the stain is from manganese sulphate? Here's what a message on sci.chem, 2001-09-03 13:37:55 PST said:
"Sodium bisulfite is much better, and can still be had in the few hobby stores that sell Perfect brand chemistry supplies, but you'll pay dollars per ounce there. It reduces the MnO2 to Mn2+, and manganese sulfate is quite soluble and essentially colorless."
You might also check with a local chemistry teacher.
Ray
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Yes, tried bleach without any effect. The label on the bag says manganese sulphate. The bag even says that it will stain driveways and concrete. Tried power washing within hours of the stain showing.
Thanks
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Manganese sulfate as I recall is reddish in color. Just because the stain looked like rust didn't mean it was rust and unfortunately you applied oxalic acid. Oxalic acid reacts with iron salts (true rust) yielding iron oxalates which are water soluble. However, you likely have produced manganese oxalate which is insoluble in water.
You might try a concentrated solution of Sal Ammonia (ammonium chloride) but my guess is that by this time the metal is bound to the organic matrix forming the KoolDeck and getting the stain out will not be possible. Sorry.
Sal ammonia used to be available in hardware and grocery stores as a cleaning product. Years ago it was used to clean silver tableware. It's not particularly toxic and was used orally to alter the pH of urine in some individuals.
RB
Kevin wrote:

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Actually oxalic acid is routinely used to remove manganese stains. It bleaches them nearly instantly and I used it when I had pounds of manganese to remove. The stain may come from a different metal and something like CLR or a similar rust and lime removal product should help.
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EJ

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Well per the bag ingrediants, Maganese sulphate was the only ingrediant. Full strength Oxalic acid lightened the shade only (maybe by 5%). I did try CLR and Fidazzle with is supposed to work with "salt crystal stains".
I'm beginning to think RB may be right and there was some other reaction with the KoolDeck composition.
Thanks

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I doubt that you were removing manganese. Manganese is a metal that isn't found in the typical home. You might have been removing a salt of manganese but to do it with oxalic acid seems unlikely since manganese oxalate is insoluble in water. The OP said he had manganese sulfate (looks somewhat like iron oxide) which is moderately soluble in water. That was the problem it dissolved in water and the water solution carried it into the KoolDeck material.
Since this was a plant food it probably wasn't ultra pure manganese sulfate and iron is typically found with manganese so there may well have been some iron as rust mixed in. The rust can be reacted with oxalic acid to produce a water soluble iron salt but you're still left with the manganese salt.
RB
EJ wrote:

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He's probably dealing with a permanganate.
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William W. Plummer wrote:

I understand. But that's a far cry from "manganese."
RB
(course VI)

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