METHOD FOR RECOVERING NOBLE METAL ION

摘要

PROBLEM TO BE SOLVED: To provide a technology capable of recovering and reusing a noble metal ion simply and inexpensively from a pickling waste liq. containing the noble metal ion added for increasing a pickling rate of a stainless steel. SOLUTION: The noble metal is recovered and reused from the pickling waste liq. containing the noble metal ion by adding an I<-> (iodine ion) of >=1.5 times of the theoretical amount to be added obtained by a chemical reaction of the noble metal ion and the I<-> to a hydrochloric acid-nitric acid mixed pickling waste liq. used for pickling the stainless steel and containing the noble metal ion of 3-500mg/1 at <=40 deg.C to convert the noble metal ion into iodid, separating the iodide by filtering or settling and dissolving the separated iodide again into the hydrochloric acid-nitric acid mixed pickling waste liq.