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topic 9722

Removal Cr from Liquid Waste from Electroplating Cr


We have liquid waste from electroplating cr process and have tried to removal Cr in pH 13, but still have Fe and Zn in the solid hydroxide. Would you like to give me any sugesstion?

Moh.Yori Suaib
University of Indonesia - Jakarta


It's not easy to separate the chrome from the other metals, which is why the great majority of metal finishing waste water treatment systems don't attempt it.

But, from a theoretical viewpoint, I would look at removing the other metals with cation ion exchange; the chrome will not be removed because the metal is present as CrO3 anions. Naturally, it would be more practical to intervene earlier and remove the chrome with anion resin before mixing it with the other materials. Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


I don't fully understand the question but I have recently finished a university project on removal of Cr(VI) from waste waters. An up and coming technology in this area is bioremediation which in theory should be relatively cheap once set up. If you are currently trying to remove the Cr with an oxide/hydroxide then low pH's give more efficient uptake and uptake at pH 13 will be poor. Also if you have a high concentration of Cr in your water uptake will be very much better.

Hope this helps! Anna Royle
- England


If you wish to treat CrVI then you need to reduce it first to CrIII. Reduce pH to say 2.5 and use sodium bisulphite. Be careful because the reaction will produce Sulphur Dioxide and needs an extraction system.

Then if you raise the pH to say 10 the CrIII hydroxide can be filtered out.

Bernard Irving
- United Kingdom

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