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

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