Process for recovering nitric acid and hydrofluoric acid from waste pickle liquors
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United States of America Patent
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Jul 24, 1990
Grant Date -
N/A
app pub date -
Oct 27, 1988
filing date -
Nov 18, 1987
priority date (Note) -
Expired
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Abstract
A method for regenerating a waste liquor containing nitric acid and hydrofluoric acid to recover highly pure nitric and hydrofluoric acids therefrom. The method comprises adding hydrofluoric acid, or an acid mixture of nitric and hydrofluoric acids having a major content of the hydrofluoric acid, to a nitric acid and hydrofluoric acid waste liquor, and subjecting the resulting mixture to dialysis with an ion-exchange electrodialyzer to recover the dialyzed acids. The acid-removed solution is neutralized to cause a precipitate to form and the precipitate is separated. The resultant solution is subjected to an ion-exchange membrane electrodialyzer using a combination of a bipolar membrane, an anion-exchange membrane and a cation-exchange membrane for separation into the acids and the alkali, which are subsequently recovered. The process has a high current efficiency and high recovery rates for acids.
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