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Floc coating of filters

Q. Years ago we use to coat filter tubes with a coating of DIATOMACEOUS earth for removal of organics.

I need a procedure for this process.

Louis Hirbour
- Anaheim, California
2005

A. I think what you did was to precoat the tubes with DE, and then topcoat with activated carbon.

Jeffrey Holmes, CEF
Spartanburg, South Carolina

A. I think Jeffrey is right on. Although DE has a very large surface area compared to some materials, it's surface area is still orders of magnitude lower than activated carbon, and I doubt that it could be very effective in removing organics.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Louis,

To the best of my knowledge you aren't going to remove many "organics" with diatomacious earth unless they are in the solid form. DE improves particle retention by about 10X (smaller particles) than a conventional, oh say 10 micron cloth filter. If you want to improve organics removal, coat your filters with a bit of DE first, then add some activated carbon on top of the DE layer and change regularly. Not knowing your application, I'm basing this on a conventional disc filter system on a typical generic plating solution. You may want to contact your filter and/or chemistry vendors to see what they specifically recommend for your plant.

Trent Kaufman
electroplater - Galva, Illinois

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