Electrolytic generation of manganese (III) ions in strong sulfuric acid using an improved anode
View Patent ↗An electrolytic cell and a method of electrochemical oxidation of manganese (II) ions to manganese(III) ions in the electrolytic cell are described. The electrolytic cell comprises (1) an electrolyte solution of manganese(II) ions in a solution of 9 to 15 molar sulfuric acid; (2) a cathode immersed in the electrolyte solution; and (3) an anode immersed in the electrolyte solution and spaced apart from the cathode. Various anode materials are described including vitreous carbon, reticulated vitreous carbon, and woven carbon fibers.
1. A method of electrochemical oxidation of manganese (II) ions to manganese (III) ions comprising the steps of:
providing an electrolyte comprising a solution of manganese (II) ions in an acid solution in an electrolytic cell wherein the electrolytic cell comprises an anode and a cathode, and wherein the anode comprises a material selected from the group consisting of vitreous carbon, reticulated vitreous carbon and woven carbon fiber;
applying a current between the anode and the cathode; and
oxidizing the electrolyte to form manganese(III) ions, wherein the manganese(III) ions form a metastable complex.
2. A method according to claim 1 wherein the acid solution comprises sulfuric acid.
3. The method according to claim 2 , wherein the platable plastic comprises acrylonitrile-butadiene-styrene or acrylonitrile-butadiene-styrene/polycarbonate.
4. A method according to claim 1 wherein the acid solution comprises 9 to 15 molar sulfuric acid solution.
5. The method according to claim 4 , wherein the sulfuric acid has a concentration of 12 to 13 molar.
6. The method according to claim 1 , further comprising the step of contacting platable plastic with the metastable complex for a period of time to etch the platable plastic.
7. The method according to claim 1 , wherein the manganese(II) ions are derived from a compound selected from the group consisting of manganese sulfate, manganese carbonate and manganese hydroxide.
8. The method according to claim 1 , wherein the solution additionally comprises colloidal manganese dioxide.
9. The method according to claim 1 , wherein the concentration of the manganese(II) ions in the electrolyte is between about 0.005 molar and saturation.
10. The method according to claim 1 , wherein the cathode comprises a material selected from the group consisting of platinum, platinized titanium, iridium/tantalum oxide, niobium and lead.
11. The method according to claim 10 , wherein the cathode comprises lead.
12. The method according to claim 10 , wherein the cathode comprises platinized titanium or platinum.
13. The method according to claim 1 , wherein the anode comprises vitreous carbon.
14. The method according to claim 1 , wherein the anode comprises woven carbon fibers.
15. The method according to claim 14 , wherein the woven carbon fibers have a turbostratic structure.
16. The method according to claim 14 , wherein the woven carbon fibers are produced from fibers of polyacrylonitrile.
17. The method according to claim 14 , where the woven carbon fibers comprise at least 95% carbon and are impregnated with less than 2% resin, based on the weight of the carbon fibers.
18. The method according to claim 1 , wherein an area of the anode is larger than an area of the cathode.
19. The method according to claim 1 , wherein the anode current density is between about 0.1 to about 0.4 A/dm 2 .
20. The method according to claim 1 , wherein the temperature of the electrolyte is maintained between about 30° C. and about 80° C.
21. The method according to claim 1 , wherein the electrolyte does not contain any permanganate.