well i suppose i might need to eat my words regarding the "trying new things isn't disrespectful to those who come before us" thing at least in terms of AGP (alkaline glycine process) for extraction of base metals. the regenerative property of the Copper(II) Chloride process does seem fairly robust, hands off, and reliable. reading more about it, once you have copper chloride in solution, it oxidizes the copper, which reacts to form more copper chloride with the free chloride ions in solution, and the H+ ions form more water with the dissolved oxygen in solution. all that being factored in, and ignoring, for simplicity, the contamination and depletion of copper chloride in solution by more reactive base metals, it really is as simple as adjusting three things to keep the solution viable:
- free chloride ions (addition of HCl)
- dissolved oxygen (air pump bubbling through solution)
- concentration of copper ions in solution (overall volume of solution relative to other substances)
according to a webpage written up about the details of a copper chloride etching system (tailored for hobbyist PCB fabrication), there is an optimal specific gravity at which to operate the etching vat, though from the information about managing each of the three parameters, it seems like the small numerical range translates to a rather large range in practice.
while i will give this whole methodology more credit than i initially did (back when i thought it was primarily just HCl putting copper into solution and being depleted), i am still hopeful about the possibility of copper electrowinning making the alkaline glycine process a viable closed-loop process.