The method null of producing the chrome (vi) acid solution of a higher purity than the trivalent chrome or six value chrome or chrome content composition where both exist together

摘要

PURPOSE: To obtain a Cr (VI) oxide soln. from a waste soln. contg. Cr (II) and Cr (VI) salts by adding peroxide to a soln. of a Cr (III) complex contg. an org. carboxylic acid anion as a ligand and carrying out oxidation. ;CONSTITUTION: Floating impurities in a soln. to be treated are filtered off and org. carboxylic acid (salt) such as oxalic acid and a reducing agent such as a mixed soln. contg. dithionite and hydrogensulfite are added to the soln. to be treated under stirring while keeping pH 3-4. The amt. of the carboxylic acid added is 1-2 times (mol) as large as the total amt. of Cr in the soln. or 2 times if necessary. The reducing agent is added by an amt. enough to reduce Cr (VI) oxide or Cr (VI) salt in the soln. to Cr (III). The resulting soln. is allowed to stand for 1-6hr and adjusted to pH11 with an aq. NaOH soln. Peroxide such as an aq. hydrogen peroxide soln. is then added to the soln. of pH11 by 1.5-5mol per 1mol Cr (III) and this soln. is stirred, allowed to stand over night and heated to about 70C. A deposited precipitate is filtered off and a Cr (VI) oxide soln. contg. no org. carboxylic acid is obtd.;COPYRIGHT: (C)1993,JPO&Japio