RE: gEDA-user: used chemicals (plated holes, pc boards)

[John Griessen <john_g@cibolo.com>]

On Thu, 2003-06-12 at 12:06, EATON,JOHN (HP-Vancouver,ex1) wrote:

> I hope he tells us how he disposes of all the used
> chemicals.
> 
> John Eaton
For small scale uses of plating baths like sulfuric/copper or
hcl/copper, it's possible to be environment considerate if you are
careful.  The thing to avoid is releasing dilute metal solutions into
creeks...(or down the drain into your local treatment and river)...very
bad.  First of all avoid dilution! minimize washing -- squeegee first
and run the wash runoff into some rock dust or baking soda. 
 When your etching/plating baths get unusable, the conscientious thing
is to reverse plate out the metal onto some junk, then you can
concentrate the remains by evaporation, and use it as decorative
coloring for rock or other metal sculpture projects...if that's not your
hobby, you could also remove and drastically lower toxicity of acid
metal solutions by filtering through some limestone cutting leftovers
from your local garden wall and rock wall builders sawing operations --
the calcium carbonate rock dust goes into reaction with the metal to
make a green compound called copper carbonate, (whaddaya know..), which
is no big environmental hazard -- especially if you live in moutnains
with green rocks : -> The acid gets neutralized by the limestone and CO2
is released.  Fairly pure water is left.  Just don't put any lead or tin
in the same plating bath!   Tin I don't know how to handle -- it's used
for cooking pans, so not toxic itself, but may interfere with getting
copper out of solution if mixed in with it.... Also it pays to research
the know methods and see that HCl seems to be best utilized by industry
for continous process plating -- it's a reverible process -- cleanable,
rechargeable, etc.  Reversibility means you can etch, and then plate,
and minimize environmental impact that way.  None of this is for the
faint of heart, and I have not started it yet myself.  Another etch
process with sodium perchlorate sounds good.  Its spent bath woudl have
lots of copper chloride, so it may be possible to plate as HCl/Cu bath
with the spent bath from perchlorate etching as a starting point.  All
of this needs a little storage and processing building with nothing but 
plating stuff and lots of open trays of baking soda around on the
shelves and in the air flows.

John Griessen
EE, sculptor