| 摘要 |
PROBLEM TO BE SOLVED: To remove metallic ions from a waste solution of nitric-hydrofluoric acid containing the metallic ions of iron, chromium, nickel or the like, to regenerate nitric-hydrofluoric acid and to reuse the same as a pickling solution. SOLUTION: The hydroxide and/or carbonate of alkali metals is added to a waste solution of nitric-hydrofluoric acid containing metallic ions to control the pH of the waste solution to >=8, so that a metallic hydroxide is generated. Then, the generated metallic hydroxide is separated and removed from the waste solution, and the waste solution freed of the metallic hydroxide is made to contact the H<+> type cation exchange resin, so that the alkali metal ions are removed from the waste solution to obtain nitric-hydrofluoric acid.
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