I don't see why it would not regenerate with air. However, because the drug store H202 is only 3% you resultant solution is going be fairly weak in CuCl, you may need to evaporate the saved etchant to up the concentration. I have seen posts suggest 30% H202 is available at beauty supply outlets, used for hair bleaching.
I was able to find a gallon of 3% H202 at my local Smart and Final
warehouse grocery store, was fairly low cost. Its used in the food service industry as a sanitize. I don't worry about regeneration and just make up new each time but I have been evaporating the spent etchant and saveing the resulting CuCl for future use. Not sure I will use it as I am thinking of going back to ammonium persulfate because its nice and clean with no corossive fumes. You do have to heat the AP to make it work.
--- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@...> wrote:
>
> I am following up on a comment in an earlier thread, to the effect that starting with 2 parts drug store hydrogen peroxide + 1 part Muriatic acid, one cannot ever get to the point of having CuCl2. (BTW, please forgive & correct if I do not get the chemical formulas right. Chemistry was a LONG time ago!)
>
> I am concerned / disappointed, because I have been saving my used etchant, made from the above, thinking that I would eventually build a tank to bubble in air to regenerate it, etc. But now it sounds like I would do better to neutralize what I have and start over.
>
> 1) Is that right, or is there any way to use the used etchant I now have on hand?
>
> 2) What do I need to do to make up an etchant mix that WOULD serve as the base for CuCl2?
>
> Many thanks ...
>
> Andy
>