METHOD FOR REGENERATING AND RECOVERING ACID LIQUID MIXTURE SUCH AS WASTE NITRIC ACID-HYDROFLUORIC ACID MIXTURE

摘要

PROBLEM TO BE SOLVED: To recover hydrofluoric acid of desired concn. without need for several batches and consequently to remarkably reduce the starting time of a device in the method for removing metallic sludge from a waste liq. contg. a nitric acid-hydrofluoric acid mixture discharged in a metal pickling stage, etc., to regenerate and recover a nitric acid-hydrofluoric acid mixture. ;SOLUTION: An acid liq. mixture such as a waste nitric acid-hydrofluoric acid mixture is neutralized with alkali to deposit and separate metals, etc., the filtrate is supplied to a bipolar membrane device 4 provided with a bipolar membrane, cation-exchange membrane and anion-exchange membrane to separate acid and alkali, which are regenerated and recovered from the bipolar membrane device 4. In this method, a neutral salt generated in the neutralization stage 2 with alkali contg. the anionic component with the ratio of the anionic component constituting a mixed acid to be recovered into the total anionic composition in the mixed acid lower than the ratio to the total anionic composition in the filtrate is previously added before the filtrate is supplied to the bipolar membrane device 4.;COPYRIGHT: (C)1997,JPO