-- The Home Page of the Finishing Industry
23+ years of serious education, promoting Aloha,
& the most fun you can have in metal finishing smiley
    no popups, no spam
on this site
current topics
topic 6021

Recycling Chromating Wastewater


Dear Sir/Madame,

We do clear & yellow Iridite. We are looking for an inexpensive way to recycle the waste water back into the system. For the time being we neutralize the nitric acid and reduce the hexa-chromium.

thank you.

Adel [last name deleted for privacy by Editor]
- nepeab, Ontario Canada


At today's cost structures, there may be no "inexpensive" way.

I have seen systems that employ ion-exchange to get the chromates out of the rinse water so that rinse water can be returned; they are fine but they only increase the overall chemical use compared to end-of-pipe neutralization.

Unfortunately, chromates--unlike most plating solutions--are not equilibrium processes wherein you can just add anodes and brighteners and keep things in balance. Rather, the chromates chemically react with the surface, and having done so they become exhausted contaminants which should not be returned to the tank, whereby they only would spoil it that much sooner.

I have seen more exotic and expensive systems where the regenerant and backwash from the ion-exchange systems goes into an electrolytic membrane separation system for regeneration, and it's probably a fine idea. But when you say "inexpensive", uh, I don't think so.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.