[dorkbotpdx-blabber] printed circuit board chemistry

Thu Feb 26 23:58:59 EST 2009

This is a good write up.  I will only add a few safety tips.

To etch the copper you need strong acid.

To precipitate the CuOH you need a strong base.

Mixing a strong acid with a strong base to quickly leads to explosions.  This is how I blow up my first chemistry laboratory.  Side note: when someone says "RUN!!" run in the same direction as the person shouting.  Otherwise you have to spend some time in the showers like my former lab partners, but I digress.

So my recommendation is freeze the base.  Freezing your Sodium Hydroxide solution will make it more dense than the acid solution.  When the two are mixed, it creates a bi-layer where the chemistry can take place in a slow controlled manner.  Once added, leave it alone.  Do not mix.  Entropy will do all the mixing for you and agitation will lead to smaller CuOH crystals.  

Before filtration, cool the solution down further with an ice bath.

Don't recommend baking soda.  Baking soda will give you CuCO3 instead of CuOH.  The carbonate is more soluble the the hydroxide.

Good luck kids, don't melt you face off.  That reminds me of another story from graduate school but I will save it for latter.  Eventually his vision returned, if only he was wearing his safety glasses.  better to look like a dork then a blind person, I always say.  But what do I know..

Scott W.

if your not part of the solution, your part of the precipitate.

Date: Wed, 25 Feb 2009 11:17:25 -0800
Subject: Re: [dorkbotpdx-blabber] printed circuit board chemistry
From: gunterhausfrau at gmail.com
To: dorkbotpdx-blabber at dorkbot.org

So, depends on what you want. You can use the solution (assuming HCl/H2O2 was the etchant) once it is "used up" by copper etching as a source for plating copper. Not that difficult, a DC wall wart, a few bits of wire, a bolt and you can start plating (on another metal).

The other way to get the copper out is with sodium hydroxide. This is a strong base, and will burn you if not treated with respect (as will HCl)

CuCl2 + 2 Na(OH)2 ->Cu(OH)2 + 2 NaCl

The NaOH will neutralize the solution, and the copper hydroxide will percipicate out. You can then deal with the small amount of Cu(OH)2 driving off water to form copper metal or the oxide.

I imagine that if you don't want to deal with sodium hydroxide, even baking soda should raise the pH to the point where the solids will ppt. The reaction will be essetially the same.

if you heat the hydroxide to >185c you'll end up with a stable copper oxide (black). That is about as safe to dispose of as any other rock.

Likely lots of bubbling and spurting (think about the vinegar/baking soda volcanos you used to make, now thing more) work slow, don't dump.

o.k. assuming you don't wish to be disfigured, blinded, etc. Outside. gloves. eye protection, etc.

blinking LEDs are much less entertaining when you can't see them.

off the cuff, take with grain of salt, don't do this, I wasn't here, I don't even know you people.

On Wed, Feb 25, 2009 at 10:36 AM, Eric Garner <garnere at gmail.com> wrote:

the 3 most common etchants are ferric chloride, sodium or ammonium
persulphate, and HCl/H202, of the three only the HCl/H2O2 is
theoretically reusable. FeCl and the persulphates i usually tale to
the household hazardous waste collection sites at the Metro waste
transfer stations.

---------- Forwarded message ----------
From: Daniel Johnson <teknotus at gmail.com>
Date: Wed, Feb 25, 2009 at 10:27 AM
Subject: Re: [dorkbotpdx-blabber] printed circuit board chemistry
To: "A discussion list for dorkbot-pdx (portland,  or)"
<dorkbotpdx-blabber at dorkbot.org>

> I think even more than recovering removed copper from solution, most of us
> would just like to know the proper (bonus: cheap+easy) way of
> disposing/recycling of waste from this process without killing
> fish/trees/babies.

I just got this back from my friend.

"What I first need to know is what type of solution you are using to
dissolve the copper. If the chief concern is killing
fish/trees/babies, then there are probably more chemicals of concern
than just the copper. I don't think RETRIEVING the copper for reuse is
hugely practical.  There are simple ways to remove or complex copper
but I can't help until I have the solution components. If you know the
NAMES of the solutions, they most likely contain an analyte list
(ingrediant list) on the back, and it is required to have an
associated MSDS (Material Safetey Data Sheet) online. "
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--
--Eric
_________________________________________
Eric Garner

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