| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus and method for efficiently removing hydrofluosilicic acid contained in fluoro-nitric acid waste solution by reducing the addition and residue of ions becoming impurities such as alkali or the like, reducing the wasted amount of hydrofluoric acid and nitric acid to highly efficiently recover a refined fluoro-nitric acid solution low in the concentration of hydrofluosilicic acid and high in the concentration of hydrofluoric acid and nitric acid.SOLUTION: An electrodialysis apparatus A includes first and second cation exchange membranes C1 and C2 arranged between a cathode 2 and an anode 3, first and second monovalent selective anion exchange membranes AS1 and AS2 arranged between the membranes C1 and C2, a desalting chambers 4 formed between the membranes AS1 and AS2, a concentrated solution chamber 5 formed between the membrane C1 and the membrane AS1, and a refined solution chamber 6 formed between the membrane AS2 and the membrane C2, a hydrofluosilicic acid-containing fluoro-nitric acid waste solution is introduced into the desalting chamber 4 and an electrolyte is transferred to the concentrated solution chamber 5 from the desalting chamber 4 to perform electrolysis and a refined solution is recovered from the refined solution chamber 6. A potassium salt or a base is added to the concentrated solution in a flocculation separator B to perform flocculation treatment and a formed precipitate is separated by a separator 24. |
