Method for continuous production of electrolytic manganese dioxide

Claim 2

IN A METHOD FOR CONTINUOUS PRODUCTION OF ELECTROLYTIC MANGANESE DIOXIDE BY ELECTROLYSIS OF AN AQUEOUS MANGANESE SULFATE - SUFLURIC ACID SOLUTION CONTAINING 30 G/L OR MORE OF MAGANESIUM IN THE FORM OF MAGNESIUM SULFATE AS IMPURITY WHEREIN CONSUMED MANGANESE IS MADE UP FOR BY SUPPLYING A NEUTRAL AQUEOUS MANGANESE SULFATE SOLUTION PREPARED BY LEACHING OF MANGANESE ORE WHICH CONTAINS MAGNESIUM AS IMPURITY WITH SPENT ELECTROLYTE AND SULFURIC ACID FOLLOWED BY NEUTRALIZATION AND FILTRATION, THE IMPROVEMENT COMPRISING CONCENTRATING THE WHOLE AMOUNT OF OR A PART OF THE NEUTRAL MANGANESE SULFATE SOLUTION IN A VACUUM AT A TEMPERATUE OF BETWEEN 40*C. AND 60*C TO PRODUCE A SOLUTION HAVING A CONCENTRATION CORRESPONDING TO A SATURATION POINT AT FROM 15*C. TO 60*C., AND THEN RAPIDLY COOLING THE RESULTANT SOLUTION TO 15*C. - 25*C., TO GIVE CRYSTAL CONTAINING MAGNESIUM SULFATE, FILTERING AWAY THE CRYSTAL AND FEEDING THE FILTRATE TO THE ELECTROLYTIC CELL TO MAKE UP FOR THE WHOLE AMOUNT OF

Claim 3

Method as defined by claim 1 wherein said spent electrolyte contains 10 - 40 g/l of manganese in the form of manganese sulfate and 30 - 45 g/l of magnesium in the form of magnesium sulfate.

Claim 4

Method as defined by claim 1 wherein said neutral aqueous manganese sulfate solution contains 40 - 70 g/l of manganese in the form of manganese sulfate and 30 - 50 g/l of magnesium in the form of magnesium sulfate.

Claim 5

Method as defined by claim 1 wherein electrolysis is carried out while blowing in live steam.

Claim 6

In a method for production of electrolytic manganese dioxide by electrolysis of an aqueous manganese sulfate - sulfuric acid solution containing 10 - 40 g/l of manganese in the form of manganese sulfate and as impurity 30 - 45 g/l of magnesium in the form of magnesium sulfate, wherein consumed manganese is made up for by supplying a neutral manganese sulfate solution containing 40 - 70 g/l of manganese in the form of manganese sulfate and 30 - 50 g/l of magnesium in the form of magnesium sulfate, said neutral solution being prepared by leaching manganese ore containing magnesium as impurity with a spent electrolyte followed by neutralization and filtration; the improvement comprising concentrating the whole amount of or a part of said neutral aqueous solution of manganese sulfate in a vacuum at a temperature between 40*C. and 60*C. to produce a solution having a concentration corresponding to a saturation point at from 15*C. to 60*C., and then rapidly cooling the resultant solution to 15*- 25*C., to give crystal containing magnesium sulfate, filtering away the crystal and feeding the filtrate to the electrolytic taNk to make up for the whole amount of or a part of consumed manganese, whereby the content of magnesium in the form of magnesium sulfate in the electrolyte is maintained at not more than 45 g/l.

Claim 7

In a method for production of electrolytic manganese dioxide by electrolysis of an aqueous manganese sulfate - sulfuric acid solution containing 10 - 40 g/l of manganese in the form of manganese sulfate and as impurity 30 - 45 g/l of magnesium in the form of magnesium sulfate, wherein consumed manganese is made up for by supplying a neutral manganese sulfate solution containing 40 - 70 g/l of manganese in the form of manganese sulfate and 30 - 50 g/l of magnesium in the form of magnesium sulfate, said neutral solution being prepared by leaching manganese ore containing magnesium as impurity with a spent electrolyte followed by neutralization and filtration; the improvement comprising concentrating the whole amount of or a part of said neutral aqueous solution of manganese sulfate in a vacuum at a temperature between 40*C. and 60*C. to produce a solution having a concentration corresponding to a saturation point at from 15*C. to 60*C., and then rapidly cooling the resultant solution to 15*- 25*C., to give crystal containing magnesium sulfate, filtering away the crystal and feeding the filtrate to the electrolytic taNk to make up for the whole amount of or a part of consumed manganese, whereby the content of magnesium in the form of magnesium sulfate in the electrolyte is maintained at not more than 45 g/l.