| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method for producing alkali metal silicofluoride and nitric acid with high purity as valuables with a waste liquid of mixed acid of hydrofluoric acid and nitric acid as raw material. <P>SOLUTION: The production method uses a waste liquid of mixed acid of used hydrofluoric acid and used nitric acid as raw material, and performs treatment in order of the following (a) to (c): (a) hydrofluoric acid included in a waste liquid is reacted with a surplus silicon oxide compound to be converted into hydrosilicofluoric acid; (b) a surplus alkali metal salt is added to the waste liquid after the conversion into the hydrosilicofluoric acid to produce an alkali metal silicofluoride; and (c) after the production of the alkali metal silicofluoride by the (b), the separated liquid and an aluminum compound or a boron compound are reacted with each other, and fluorine as the constituent element of the hydrosilicofluoric acid contained in the liquid is converted into nonvolatile fluoroaluminic acid or borofluoric acid having a high boiling point, and then, nitric acid is produced by a distillation process. According to the method, high purity alkali metal silicofluoride and nitric acid can be produced. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
