Production of electrolytic battery active manganese dioxide

Abstract

This process concerns the direct electroconversion of low grade manganese ores to high purity manganese dioxide product, which, among other applications, is ideally suited for use in dry cells. The process operating conditions are controlled such that impurities in the ore are substantially eliminated from the product. A decrease in impurity levels in excess of 100 fold can be achieved between the product and the ore feed.

What I claim is: 
     
       1. A process for the production of high grade γMnO 2  from manganese dioxide ore in an electrochemical cell having one or more inert anodes, immersed in an aqueous anolyte having a solution manganese content of 20 g/l Mn to 200 g/l Mn and an acidity of up to 5N, and one or more inert cathodes, immersed in a slurry consisting of particulate manganese dioxide ore and an aqueous catholyte having a solution manganese content of 30 g/l Mn to 220 g/l Mn and a pH below 7, the anodes and cathodes disposed on opposite sides of one or more porous diaphragms, the process consisting of applying a direct current potential between the anodes and cathodes to reduce the manganese dioxide slurry to ionic manganese which diffuses through the diaphragms and is oxidised at the anodes where γMnO 2  is formed, the anode current density being 20 to 250 Amp/m 2  at a cell temperature of from .[.15 to 25° C..]. .Iadd.80° to 100° C. .Iaddend.or 1,000 to 4,000 Amp/m 2  at a cell temperature of .Badd..[.80° to 100° C..]..Baddend. .Iadd.15° to 25° C. .Iaddend.and the cathode current density being 5 to 400 Amps/m 2 . 
     
     
       2. A process as in claim 1 in which the electrolyte comprises the anion group, sulphate. 
     
     
       3. A process as claimed in claim 1 in which the electrolyte comprises the anion group, chloride. 
     
     
       4. A process as claimed in claim 1 in which the electrolyte comprises the anion group, nitrate. 
     
     
       5. A process as claimed in claim 1 in which the current density is from about 30 to 140 Amp/m 2 . 
     
     
       6. A process as claimed in claim 1 in which the anolyte contains about 80 to 130 g/l Mn and about 2N acid. 
     
     
       7. A process as claimed in claim 1 in which the cathode current density is 25 to 100 Amp/m 2 . 
     
     
       8. A process as claimed in claim 1 in which the ore content of the catholyte is about 20 to 350 g/l. 
     
     
       9. A process as claimed in claim 1 in which the ore content of the catholyte is about 50 to 200 g/l. 
     
     
       10. A process as claimed in claim 1, in which the acid content is such that the pH is in the range of about pH4 to pH0.5.