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Ask the Expert Question-and-Answer Archive (Wastewater Treatment)

by Mike McGinness, EcoShield Environmental Systems, Inc.
September, 2012

Solubility of Metals with Changing pH

Q. Can you direct me to a chart, table, web site or whatever that shows the solubility of various metals through the pH range of 0 to 14? I'm particularly interested in iron removal from water but I also need data on other metals. Thanks.

A. EPA published one, the results of study, about 25-30 years ago. The minimum solubility was in the the 8-10 pH range. I think it was about 8.5 to 9.5, but the problem with that data is it does not include the synergistic effects of other metals, compounds, complexing agents like ammonium ions, and chelating agents, and waste water treatment compound additives. It also depends on each metal's valence, and or oxidation state as well as the pH, and other compounds and their concentrations.

These should be useful (links below), if you know the complete picture of the waste water and or have control of the various parameter limits, and can crunch the chemical engineering data ...

http://nepis.epa.gov/...

http://cpe.njit.edu/dlnotes/CHE685/Cls06-2.pdf

http://nepis.epa.gov/Exe/ZyNET.exe/

http://www.mtech.umd.edu/ummap/documents/pmg_metal_precip_man1.pdf

Hope this helps!

Let me know if I can be of further service.

Sincerely,

Mike McGinness



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