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Waste Treatment of Chrome from PVD Process

We do a thin layer of Chrome plating by PVD process (app 02-0.3µ) on nickel plated brass parts.Rework components are stripped using HCl. Our effluent contains almost 25 -50 ppm of chromium. How to neutralise the effluent and precipitate chromium effectively?

Ramasubramanian Sankaran
Plating shop employee - India
June 19, 2011

Add a very small amount of ferrous sulfate ⇦this on eBay or Amazon [affil links] (50 - 100 mg/l) just in case some of the Cr is hexavalent, though it should not be.

Then, elevate the pH to 9 - 9.5 with a bit of calcium hydroxide slurry. Add flocculant to settle solids.

That should do the trick.

Dave Wichern
Consultant - The Bronx, New York
June 21, 2011

Assuming that all of the chromium is trivalent, all that you need to do is to adjust the pH to between 8.5 and 9, add a flocculant and then settle or filter out the precipitated metals.

Lyle Kirman
consultant - Cleveland Heights, Ohio
June 22, 2011

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