Abstract The instant invention relates to a process for changing the oxidation state of a compound or ionic species preferably a dissolved ionic species, and the novel electrochemical cell utilized therein. In the instant process, the compound or ionic species is passed through a porous electrode, which is maintained at a voltage sufficient to change the oxidation state of said compound or ionic species. This process is especially useful for oxidation-reduction processes, wherein said species is an ion having the same charge as the porous electrode. The porous electrode is isolated from the oppositely charged electrode by a semipermeable membrane, said membrane being impermeable to said dissolved species. In a much preferred embodiment, the dissolved species is chromium in the +3 oxidation state, e.g., the chromium available in chromic acid solutions which have been "used" in plastic etching processes or in processes for the oxidation of organic compounds; and the membrane is fluoro sulfonic acid membrane. In this embodiment the "used" chromic acid solutions may be substantially regenerated and cycled for reuse in the above-mentioned processes. The porous anode preferably used in the regeneration of chromic acid solutions comprises a lead alloy or compound.
In an electrochemical process for oxidizing chromium in the +3 oxidation state to the +6 oxidation state comprising the steps of: providing an electrochemical cell having an anode compartment containing an anode, a cathode compartment containing a cathode and a semipermeable membrane capable of preventing passage of chromium in the +3 oxidation state separating said anode compartment from said cathode compartment; providing an acidic catholyte solution in said cathode compartment, said catholyte solution being substantially free of chromium in the +3 oxidation state; providing an anolyte solution in the anode compartment, said anolyte solution containing chromium in the +3 oxidation state; and passing a current between said anode and said cathode; the improvement wherein said anolyte solution is passed through and fills a multiplicity of pores provided in said anode while current is passed between said anode and cathode.
Claim 2
Dependent Claim
139 words
In an electrochemical process for oxidizing chromium in the +3 oxidation state to the +6 oxidation state comprising the steps of: providing an electrochemical cell having an anode compartment containing an anode, a cathode compartment containing a cathode and a semipermeable membrane capable of preventing passage of chromium in the +3 oxidation state separating said anode compartment from said cathode compartment; providing an acidic catholyte solution in said cathode compartment, said catholyte solution being substantially free of chromium in the +3 oxidation state; providing an anolyte solution in the anode compartment, said anolyte solution containing chromium in the +3 oxidation state; and passing a current between said anode and said cathode; the improvement wherein said anolyte solution is passed through and fills a multiplicity of pores provided in said anode while current is passed between said anode and cathode.
Claim 3
Dependent Claim
14 words
The process of claim 1, wherein said semipermeable membrane is a fluorosulfonic acid membrane.
Claim 4
Dependent Claim
15 words
The process of claim 1, wherein said porous anode is a lead compound or alloy.
Claim 5
Dependent Claim
19 words
The process of claim 3, wherein said porous anode is maintained at a voltage of at least 1.6 volts.
Claim 6
Dependent Claim
23 words
The process of claim 4, wherein said anolyte solution comprises from about 3 to about 300 ounces per gallon Cr + 3 .