Expert: Dr. Henry Boyter, Jr. - 5/21/2007

Question
QUESTION: Hi Dr Henry, I am currently doing a research on Bioremediation of copper from distillery waste water. I have a water sample and i have found the total copper conc by atomic spectrophotometer, ad it was found to be 9.69ppm. Now i would like to find out what form is the copper present in the sample.i would like o know, if there id Cu+1 or Cu+2 in the sample. Is there any test which could help me distinguish between the two ionic state?. I am really confused and stuck in the middle of my research. Could you please guide me ? Thanking you, preeti

ANSWER: In normal water systems, copper will be present as Cu(II) with very little Cu(I) present unless you have ligands like cyanide which produces an insoluble complex.  The only way to really do speciation is to polarography, which is a very difficult technique that requires special equipment.
The only other method I know involves Neocuproine and is discussed in Standard Methods 3500-Cu-D (this is not available online).  It is also discussed in theis paper, but I am not sure that you can see it without paying.

http://www.rsc.org/ejarchive/AN/1991/AN9911600089.pdf

Speciation of copper in water is also very difficult, even when you just have the basic ions (see this paper).

http://chemse.oxfordjournals.org/cgi/content/abstract/31/7/689

All these methods depend on the copper being present in ionic form.  From a wastewater plant, that will be a rare case, so even if you use these techniques, the speciation will be questionable. You may find that they tell you there is no copper. For example, with phthalocyanine copper dyes, I know that the techniqies do not behave as they do with simple salt ions.

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QUESTION: For detection of cu(II), could I use simple qualitative test like addition of dilute sodium hydroxide, or dilute ammonia, till the color changes to deep blue?
Thanking you
preeti

Answer
If the copper is bound at all, the copper complexes may not form since the bound form will be more stable than the hydroxides and ammmonia complexes.  Also, the "level" of blue may not be enough to visually see.  You could try it but you need to do it by the method of standard additions to confirm the levels if you want quantitative results.  If all you want to know is if any Cu(II) is present, yes it should work, but as I said, if copper is present it will be mostly Cu(II).