[luckylinux]

As stated in the title I'm going to etch some PCBs using hydrochloric acid and hydrogen peroxide.
After a few etchs are done I'll be left with a cupric acid / copper chlorine solution (don't know how it's officially called, sorry).

Now the possibilities are (**if I cannot dispose of it in an authorized recycling center**: they may accept chemical solutions, but seem they need to be in their original box and non-mixed: since I'll obtain cupric chloride they may refuse to dispose of it if I bring it back in a Hcl / H2O2 bottle):
1. Neutralize it with baking soda, creating lesser dangerous compounds that may be poured down the drain (filter it before and keep the CuCO3 residue, then pour down the drain)
2. Adding some magnesium / alluminium to it, creating solid copper (that can be filtered) and other compounds that are less dangerous and may be poured down the drain
3. Electrolysis ? Not sure the materials that could be used for the anode and cathode electrode to get copper at the cathode and chlorine at the anode
4. Use it again: regularly bubble oxygen in it (through an air pump and a polyethylene tube carrying that air under the solution) to re-activate it and eventually add some HCl when too much chlorine has evaporated

I'm particularly interested in option 4: I suppose I may use a fairly big box to etch my PCBs, yet I don't really now if I can store it outside. Storing inside may cause corrosion due to the chlorine gaz that escapes the solution, yet storing outside in the heat and with exposition to the light may be even worse. Still I though that if I store it in an opaque box with no direct contact to sunlight, maybe in an other box that assures some kind of heat insulation, that may not be such a problem. For reference temps here go up to 34-36°C in the summer and down to -16 in the winter (if I recall correctly). This also avoids the "problem" to dispose of the solution (or at least this becomes less of a concern for now).

If anyone has experiences with option 3 please suggest. As far as I understood (and I'm an electrical engineer, not a chemist) the cathode electrode has to be less reactive than hydrogen, otherwise hydrogen will be generated (see http://www.mindset.co.za/resources//0000022572/0000029661/0000029601/default.htm for instance). Furthemore I seem to recall reading elsewhere that the cathode has to be of a different material than copper itself, since it's copper I want to get at the cathode. Not sure why and if it's true, but that would leave only silver as an option (?). Or would gold / platinum work too?

Thank you very much for your help.

[aliphatic]

 Option 4 is the way to go, get a nice liquor decanter with a ground glass stopper from a thrift store or garage sale, and pour your etchant in there. Opaque is not necessary. I've been working with the same batch of etchant for over a year now, and haven't had any problems. I keep mine in the basement.

The peroxide will decay, but there is so little of it the gasses released won't be an issue. The HCl is used up as well and is no longer anywhere near the 12M strength it was, so the fumes from this are neglegable as well.

For an etching box, I use a plastic shoebox made from polyethylene.

Bubbling oxygen might be more troublesome than adding a few capfuls of peroxide to freshen it up.

For option 3, you can use a piece of copper for your cathode, but you will be producing chlorine gas on the other end, which may not be desiresble.

Professional curiosity, what do you use to print your traces?