No cost, no registration, no passwords -- just aloha, fun & authoritative answers
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Where the
world gathers for metal finishing
Q&As since 1989

-----

Waste water treatment

I am having problems with the precipitation of zinc. Please suggest any chemicals to remove zinc and at what pH they work best?

Thanks a lot.

Cpkuah
- Malaysia

You posted this as a student inquiry, Cpkuah, so can I assume you are a chemistry student dealing with a single test tube, rather than an industrial waste water treatment problem? Or is that a bad assumption?

Zinc theoretically precipitates best at a pH of about 10.2 per the chart (finishing.com/library/metalpH.html) from the EPA Technology Transfer series. But a few tenths of a point higher may actually help rather than hinder though, depending on what else is in solution, because such precipitation issues are usually co-precipitation issues and a slightly higher pH may pull out other stuff.

Calcium polysulfide or DTC will greatly reduce the solubility of zinc, but must be used with care due to toxicity. The terrible "White River fish kill" was caused by a discharge of way too much DTC. Good luck.

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

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully 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 might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: