To provide an efficient running method of a low running cost by solving the problems of the deficiency of an Fe removal rate in an iron extracting stage and the device, time and operator in a stage for diluting and adjusting the iron concn. of a waste hydronitrofluoric acid liquid in a recovery treatment of the waste hydronitrofluoric acid liquid by a solvent extraction method.
The supply rates of the waste liquid and org. solvent are adjusted in such a manner that the specified treating quantity of Fe and flow rate (OZ/A) of the org. solvent/waste liquid are attained with respect to a fluctuation in the Fe concn. of the waste hydronitrofluoric acid liquid used for pickling stainless steels without diluting the concn. of the waste hydronitrofluoric acid liquid at the time of recovering and reutilizing the hydronitrofluoric acid obtd. by executing the treatment to remove the Fe3+ ions in the waste hydronitrofluoric acid liquid by solvent extraction.
OYA SEIROKU
UCHINO KAZUHIRO
