Spent, acidic solutions comprising cupric chloride and hyrdrochloric acid
from the copper etching process are regenerated by a process in which the
acid is subjected to distillation with sulfuric acid. In one embodiment,
the process comprises (a) providing a spent etchant comprising at least
about 10% by weight chloride and at least about 5% dissolved copper; (b)
adding at least about 2 moles of sulfuric acid per mole of dissolved
copper to the spent etching solution, thereby converting copper chloride
into hydrochloric acid and precipitated copper sulfate; (c) distilling
the mixture from step (b) to vaporize at least a portion of the
hydrochloric acid; (d) condensing at least a portion of the vaporized
hydrochloric acid; (e) separating at least a portion of the precipitated
copper sulfate from the residual liquid, wherein said residual liquid
comprises sulfuric acid; and (f) reusing at least a portion of the
residual liquid as a sulfuric acid source in step (b).