Electrochemical process for the production of chromic acid

Details Electrochemical process for the production of chromic acid Electrochemical process for the production of chromic acid

1989-08-15

1991-11-26

Niebling, John

Chemistry: electrical and wave energy

Processes and products

C25B 122

Patent

active

050680153

ABSTRACT:
A process for the production of chromic acid by the multistage electrolysis of dichromate and/or monochromate solutions in two-compartment electrolysis cells, of which the anode and cathode compartments are separated by cation exchanger membranes, at temperatures in the range from 50.degree. to 90.degree. C., the dichromate and/or monochromate solutions being obtained by the digestion of chrome ores and leaching, the improvement wherein, optionally after the removal of aluminum, vanadium and other impurities, the monochromate solution obtained after leaching is adjusted at 20.degree. to 110.degree. C. to a pH value of from 8 to 12 by the addition and/or in situ formation of carbonate in a quantity of from 0.01 to 0.18 mol/l (for 300 to 500 g/l Na.sub.2 CrO.sub.4, converted with CO.sub.2 under pressure into a dichromate-containing solution, the dichromate-containing solution is introduced into the anode compartment of the electrolysis cell, a solution containing chromic acid, in which the molar ratio of Na ions to chromic acid is from 0.45:0.55 to 0.30:0.70, is electrolytically produced and the chromic acid is worked up by crystallization, washing and drying.

REFERENCES:
Mulokozi et al., "Selective Separation of Chromium from Other Elements by Ion-Exchange-11"; vol. 22, No. 3, Mar. 1975, pp. 239-244.
Perry et al., Chemical Engineers' Handbook; 5th Edition, 1973, pp. 16-2 to 16-4 and 16-10 to 16-12.
"Ullmann's Encyclopedia of Industrial Chemistry"; Chromium Compounds; vol. A7; pp. 66-97.

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