METHOD OF TREATING NICKELAINING ETCHING WASTE FLUID

A method of regenerating an etching waste fluid, includes the steps of (a) dissolving HC l gas in an etching waste fluid at a temperature falling within a range of 20 DEG C to 50 DEG C and crystallizing NiC l 2 and FeC l 2 crystals, the etching waste fluid containing NiC l 2, FeC l 3, and FeC l 2 and being obtained by etching Ni or an Ni alloy with an etching solution consisting of an aqueous solution containing FeC l 3, (b) distilling a mother liquor at the atmospheric pressure upon crystallization to reduce the HC l concentration in the mother liquor, and (c) distilling, at a reduced pressure, a condensate obtained upon distillation at the atmospheric pressure to further reduce the HC l concentration, thereby obtaining an aqueous solution containing FeC l 3, or bringing the condensate obtained by distillation at the atmospheric pressure into contact with an iron oxide to cause HC l in the condensate to react with the iron oxide to further reduce the HC l concentration in the condensate, thereby obtaining the aqueous solution containing FeC l 3.