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Topic: Preventing formation of copper (II) hydroxide in alkaline solution  (Read 3785 times)

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Offline _Espard_

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Is it possible to prevent the formation of insoluble copper hydroxides in aqueous solution (pH 9 -11) by complexing with a stronger ligand?

My thought would be to use a ligand that has a pKa that is in the acidic/neutral region and thus would be anionic at higher pH - this would allow it form a complex with the Cu(II) center. This would be done before adjusting pH up to alkaline region and (hopefully) prevent formation of any insoluble hydroxides.

Does this make sense, or is my assumption off-base? If not, does anyone have any ideas about how to go about doing something along theses lines (I'd like to stay away from any nitrogen-containing ligands, due to some other reasons).

Offline Hunter2

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #1 on: February 20, 2015, 10:49:12 AM »
In technical application EDTA, Quadrol or tartrate is in use. Application electroless copper bathes for electroless plating.

Offline Borek

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #2 on: February 20, 2015, 02:21:39 PM »
Have you ever added ammonia to copper(II) solution?
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Offline Hunter2

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #3 on: February 20, 2015, 02:28:15 PM »
But this will go in this way, that during adding the ammonia copper hydroxide precipitates and dissolve later on. The other mentioned complex agents prevent this phenomina.

Offline Borek

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #4 on: February 20, 2015, 04:29:19 PM »
All I was hinting at is that if the copper gets complexed by ammonia AFTER it first precipitated, finding a complexing agent capable of complexing copper to prevent precipitation in high pH shouldn't be a problem.
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Offline _Espard_

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #5 on: February 23, 2015, 01:23:14 PM »
Thanks for the insight you guys. Borek, I'd like to avoid the addition of any complexing agents that contain N-atoms as they contaminate my solution. Tartrate may be a good starting point as there it is only C, O.

Is there an ideal stoichiometric ratio for this? Or simply excess?

Offline _Espard_

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #6 on: February 23, 2015, 01:28:39 PM »
In technical application EDTA, Quadrol or tartrate is in use. Application electroless copper bathes for electroless plating.

Also, following the tartrate suggestion - would really most dicarboxylic acids work for this application? Or do the hydroxyl groups help complex the metal center in addition to the carboxylate groups?

Offline Borek

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Re: Preventing formation of copper (II) hydroxide in alkaline solution
« Reply #7 on: February 23, 2015, 04:54:19 PM »
Is there an ideal stoichiometric ratio for this? Or simply excess?

Whether you need an excess or not depends on the complex stability constant. But in general using small excess - if it doesn't interfere - would be a good idea, it keeps you on the safe side.
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