Abstract Aqueous solutions of chromic acid containing metallic contaminants dissolved therein are purified by electrodialysis of the solution in a cell having an anolyte compartment containing an anode and a catholyte compartment containing a cathode, the anolyte and catholyte compartments being separated by a cation permeable membrane. The chromic acid solution is contained in the anolyte compartment and comprises the anolyte of the process, and an aqueous solution of at least one ionizable organic compound is contained in the catholyte compartment and comprises the catholyte of the process. An electric current is passed between the anode and the cathode through the anolyte and catholyte to cause contaminating metal cations to migrate from the anolyte through the cation permeable membrane into the catholyte. The anions of the ionizable organic compounds are oxidized to gaseous oxidation products and water when reacted with the chromic acidcontaining anolyte, the solubility of said ionizable organic compounds is such that the total concentration thereof in the catholyte is at least 1 Normal, and the dissociation of said organic compounds is such that the conductivity of the catholyte is at least 1.0 X 10 4 mho/cm.
IN THE PROCESS FOR REMOVING DISSOLVED METALLIC CATION CONTAMINANTS FROM AN AQUEOUS SOLUTION OF CHROMIC ACID BY ELECTRODIALYSIS IN AN ELECTRODIALYSIS CELL HAVING AN ANOLYTE COMPARTMENT CONTAINING AN ANODE AND A CATHOLYTE COMPARTMENT CONTAINING A CATHODE, SAID ANOLYTE AND SAID CATHOLYTE COMPARTMENTS BEING SEPARATED BY A CATION PERMEABLE MEMBRANE, IN WHICH PROCESS THE CONTAMINATED CHROMIC ACID SOLUTION IS CONTAINED IN SAID ANOLYTE COMPARTMENT AND COMPRISES THE ANOLYTE OF SAID CELL, AN AQUEOUS SOLUTION OF AN IONIZED ELECTROLYTE IS CONTAINED IN SAID CATHOLYTE COMPARTMENT AND COMPRISES THE CATHOLYTE OF SAID CELL, AND AN ELECTRIC CURRENT IS PASSED BETWEEN SAID ANODE AND SAID CATHODE THROUGH SAID ANOLYTE AND SAID CATHOLYTE TO CAUSE CONTAMINATING METAL CATIONS TO MIGRATE FROM THE ANOLYTE THROUGH THE CATION PERMEABLE MEMBRANE INTO THE CATHOLYTE.
Claim 2
Dependent Claim
126 words
IN THE PROCESS FOR REMOVING DISSOLVED METALLIC CATION CONTAMINANTS FROM AN AQUEOUS SOLUTION OF CHROMIC ACID BY ELECTRODIALYSIS IN AN ELECTRODIALYSIS CELL HAVING AN ANOLYTE COMPARTMENT CONTAINING AN ANODE AND A CATHOLYTE COMPARTMENT CONTAINING A CATHODE, SAID ANOLYTE AND SAID CATHOLYTE COMPARTMENTS BEING SEPARATED BY A CATION PERMEABLE MEMBRANE, IN WHICH PROCESS THE CONTAMINATED CHROMIC ACID SOLUTION IS CONTAINED IN SAID ANOLYTE COMPARTMENT AND COMPRISES THE ANOLYTE OF SAID CELL, AN AQUEOUS SOLUTION OF AN IONIZED ELECTROLYTE IS CONTAINED IN SAID CATHOLYTE COMPARTMENT AND COMPRISES THE CATHOLYTE OF SAID CELL, AND AN ELECTRIC CURRENT IS PASSED BETWEEN SAID ANODE AND SAID CATHODE THROUGH SAID ANOLYTE AND SAID CATHOLYTE TO CAUSE CONTAMINATING METAL CATIONS TO MIGRATE FROM THE ANOLYTE THROUGH THE CATION PERMEABLE MEMBRANE INTO THE CATHOLYTE.
Claim 3
Dependent Claim
24 words
The process according to claim 1 in which the catholyte contains a chelating agent for the contaminant metal ions transferred thereto from the anolyte.
Claim 4
Dependent Claim
26 words
The process according to claim 1 in which the water soluble ionizable organic compound comprises a saturated aliphatic carboxylic acid having 1 to 5 carbon atoms.
Claim 5
Dependent Claim
27 words
The process according to claim 1 in which the water soluble ionizable organic compound comprises a substituted Alpha -hydroxy fatty acid having 2 to 7 carbon atoms.
Claim 6
Dependent Claim
25 words
The process according to claim 4 in which the organic compound comprises gluconic acid reacted with sodium hydroxide to a pH of at least 12.
Claim 7
Dependent Claim
26 words
The process according to claim 1 in which the water soluble ionizable organic compound comprises an aliphatic dicarboxylic acid having 2, 3, or 5 carbon atoms.
Claim 8
Dependent Claim
31 words
The process according to claim 1 in which the water soluble ionizable water compound comprises citric acid reacted with ammonium hydroxide to a pH of from about 5.2 to about 7.6.
Claim 9
Dependent Claim
22 words
The process according to Claim 7 in which the ammoniated citric acid solution has a pH of from about 6 to 7.
Claim 10
Dependent Claim
23 words
The process according to claim 1 in which the water soluble ionizable organic compounds comprise a mixture of ammoniated citric and gluconic acids.
Claim 11
Dependent Claim
24 words
The process according to claim 1 in which the water soluble ionizable organic compounds comprise a mixture of ammoniated citric acid and ammonium oxalate.
Claim 12
Dependent Claim
23 words
The process according to claim 1 in which the water soluble ionizable organic compounds comprise a mixture of ammoniated citric and formic acids.