Greensand Filter and KMnO4

[Sefrick]

Hello All,

I'm a new guy here and I'll start with a brief into. I'm a mecahnical engineer working at a co that engineers industrial water purification systems. I've got a good grip on the fluid/mechanical aspect of my job, but I'm struggling with the chem.

Right now one of our systems tht we're working on will be using a greensand filter with KMnO4 dosed into the feed to regen the greensand media so it can continue to remove Fe and Mn. I'd like to understand this process thoroughly beginning with the chemical formula for what this reaction would look like. If anyone can help out with that it would be GREAT!!

What confuses me the most is why are you feeding KMnO4, which contains Mn into a filter used to remove Mn?

Many thanks for any info

Sef

 

[SteveWag]

You may try these:

http://www.nesc.wvu.edu/ndwc/pdf/OT/TB/OT_HowTo_w03.pdf

http://www.clackcorp.com/water/pdf/manganese_greensand_2349.pdf

If you are feeding Permanganate continuously to the influent you are oxidizing the Manganese prior to filtration and operating the filter as a filter and as a “sponge” to adsorb any excess Permanganate. Greensand filters CAN be regenerated by adding Permanganate to the backwash water. Larger filters are not usually operated in that way. The advantage of regen during backwash is that it is hard to have “red water” production. The advantage of a continuous feed is economy of Permanganate and then “red water” is prevented by the greensand.
Steve

 

[bimr]

Reactions involved in iron and manganese removal by potassium permanganate and manganese greensand include the oxidation of iron by chlorine (if used) and permanganate:


2Fe2+ + Cl2 ? 2Fe3++ 2Cl

3Fe(HCO3)2+ KMnO4+ 7H2O ? MnO2 + 3Fe(OH)3 + KHCO3+ 5H2CO3


the oxidation of manganese by permanganate:

3Mn(HCO3)2 + 2KMnO4 + 2H2O ? 5MnO2 + 2KHCO3 + 4H2CO3


and the reduction of any excess potassium permanganate by the manganese greensand (where Z represents manganese greensand "zeolite") to manganese dioxide:

3Z•MnO + 2KMnO4 + H2O ? 3Z•MnO2 + 2KOH + 2MnO2


Conversely, the oxidation of soluble iron or manganese by the manganese greensand when the oxidant demand on the raw water has not been fully met:

_________Fe2+ ____________ Fe3+

Z•MnO2 + Mn2+ ? Z•Mn2O3 + Mn3+

___________________________ Mn4+


This technical paper provides a complete description:

http://www.hungerfordterry.com/techdata_iron.htm

 

[Sefrick]

many thanks to the both of you