Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I design my own boards using positive acting pre-sensitized boards.

My developer solution is made of 1/2 teaspoon Sodium Hydroxide in
300ml water.

My etch solution is made up of 1 part 31% Hydrochloric acid (HCl),
and 2 parts 3% Hydrogen Peroxide (H2O2).

The above chemical solutions work very well for me, and are extremely
fast. I'm not looking to find a better way. I am looking to reduce
the waste that goes to the hazard waste facility.

I'm not a chemist, didn't even take high school chemistry. Anyway
here is an experiment I did with the above chemicals, to try and
reduce the amount of waste.

Safety first, wear chemical goggles, gloves, apron, and work in a
well ventilated area

Hydrochloric acid (HCl) is very acidic, PH1. Sodium Hydroxide (NaOH)
is very alkaline, PH14. When you mix an acid with an alkaline and
adjust the solution to PH7 they become table salt and water.
HCl + NaOH = NaCl + H2O2

It takes a lot of Sodium Hydroxide to move from PH1 to PH2, but it
takes very little to move from PH6 to PH7. And if the solution is
very alkaline it takes a lot of Hydrochloric acid to move from PH14
to PH13, and very little to move from PH8 to PH7.

I mixed the spent etchant and developer together and started to
neutralize the mixture. At about PH6 what I believe to be copper
chloride started to precipitate out of solution. After the solution
had set for about 12 hours, a blue sludge had formed at the bottom of
the container and what I believe to be saltwater solution was at the
top.

I siphoned off most of the water being careful not to disturb the
sludge.

I tested the PH of the water that had been removed from the sludge
container and it is still approximately PH7, and is crystal clear.

I have reduced the 3 liters of chemicals down to less than 250ml of
sludge.

Am I on the right track?
Is the blue sludge copper hydroxide?
Can the sludge be reduced even more by drying?
If so how can it be safely dried?
Is there an issue storing copper hydroxide in powder form?