Homebrew PCBs

Hi Stefan,

Copper is a much more serious problem in the environment. But once again 
dilution  moves into the realm of fertilizer. On a 100 X 300 foot lot  5 
pounds of elemental copper per year would be a high level of copper 
fertilizer. That's a lot of etching solution.

After reading up on methods of recovery and regeneration of copper and 
etching solutions it looks like a tough row to hoe for everyone 
involved. At the price of copper today and the cost of disposal it looks 
like it would be a good business to recover the metals and purify the 
water its in. Every one I have ever talked to about it tells me its not 
worth the hassle.

Gordon


Stefan Trethan wrote:
>
> On 6/27/07, Gordon Couger <gordon.couger@... 
> <mailto:gordon.couger%40gmail.com>> wrote:
> > The old saw, "Dilution is the solution to pollution", sure applies to
> > Ferric chloride. It is used in fertilizer in dilute amounts.
> > Neutralizing the acid and diluting it in 10 or 20 volumes of water makes
> > it pretty safe. I can assure you Radio Shack doesn't sell anything that
> > exposes them to much liability it's not good for the bottom line. Here
> > they use it in Compost 
> http://www.greenmeadowfarms.com/manuretreatment.htm 
> <http://www.greenmeadowfarms.com/manuretreatment.htm>
> >
> > The dose makes the poison. Things that are deadly toxins in large
> > amounts such a iron, zinc and copper are necessary to sustain all life
> > in small amounts.
>
> I don't think the etchant itself is any problem with most etchants,
> acids are quickly neutralised (otherwise the hydrochloric acid in the
> stomachs of our dead ancestors would have killed the planet long ago
> ;-).
> Just pour HCL on limestone if you don't believe it.
>
> The only problem might be copper, and remember radio shack does not
> sell etchant with copper in it, you add it. So no "clean" FeCl MSDS or
> disposal guideline does apply.
>
> Sea water also contains copper (horseshoe crabs even have a
> copper-based blue blood which is useful for medicine, and for the
> horseshoe crabs of course.)
>
> Deer (and probably most animals but i only know for sure with deer)
> need some copper for their development, and if they are kept on ground
> with not enough copper supplements must be given. I believe copper
> sulphate is used which is also "very poisonous" just not in very tiny
> amounts...
>
> It's all a matter of quantity and while i don't intentionally dispose
> of etchant via the sewer i don't hesitate washing PCBs and equipment
> in the sink which by necessity flushes down some copper chloride. I've
> also washed it on the grass and it didn't die. Tiny amounts......
>
> Now a PCB manufacturing company is another matter, they must have
> cascading washes and purify their waste, but they don't have tiny
> amounts.
>
> ST
>
>