| 摘要 |
A process for the production of chromic acid, comprising (a) dissolving ferrochrome in sulphuric acid and mother liquor from the subsequent crystallization of ammonium chrome alum, optionally with the addition of at least one of catholyte and anolyte overflow from the subsequent electrolysis, (b) removing undissolved constituents by filtration, (c) removing dissolved iron by the addition of at least one of ammonia and ammonium sulphate to the filtrate obtained, crystallizing iron ammonium sulphate and filtering, (d) crystallizing and filtering ammonium chrome alum from the remaining solution and returning the filtrate for dissolving ferrochrome in step (a), (e) dissolving the ammonium chrome alum in water, (f) precipitating and separating chromium-(III) hydroxide from the resulting solution by adding a base, optionally under reducing conditions, (g) dissolving the separated chromium hydroxide in chromic acid and optionally sulphuric acid so that either a single solution in chromic acid is obtained or two solutions are obtained, one in chromic acid and another in sulphuric acid, (h) separating the solution(s) from undissolved constituents, and (i) utilizing the solution of chromium hydroxide in chromic acid as anolyte in the electrolytic production of chromic acid in an electrolytic cell divided by a membrane, and either utilizing the same solution as catholyte in the above mentioned electrolytic cell divided by a membrane or utilizing the solution of chromium hydroxide in sulphuric acid as catholyte in the above mentioned electrolytic cell divided by a membrane, hydrogen and metallic chromium being deposited electrolytically at the cathode and/or chromium (II) ions being produced electrolytically at the cathode.
|
