Recovery of manganese from leach solutions

A method of producing manganese carbonate from a leach liquor, the method comprising the steps of:

• a) providing a sulfurous acid leach solution comprising manganese and iron;
• b) oxidizing the ferrous iron in the solution to ferric iron by combining ozone with the solution while maintaining the oxidation potential of the solution between about 650 to about 800 mV measured with a platinum-silver/silver chloride electrode;
• c) selectively precipitating substantially all of the iron out of the solution as ferric hydroxide by combining milk of lime with the solution after the oxidizing step, wherein the solution pH is raised and maintained at about 3.9 to about 4.1 by the combination of milk of lime with the solution, and wherein the iron precipitating step leaves the solution with less than about 15 ppm of iron, and wherein the iron precipitating step lasts less than about one hour while maintaining substantially all of the manganese in solution;
• and
• d) selectively precipitating manganese out of the solution as manganese carbonate by the addition of sodium carbonate to raise and maintain the solution pH to about 8.0 or above;
• wherein the manganese precipitate provides a dry filter cake comprising at least about 98% wt manganese carbonate.

A method of producing manganese carbonate from a leach liquor, the method comprising the steps of:

• a) providing a sulfurous acid leach solution comprising manganese and iron;
• b) air sparging the solution to remove sulfur dioxide;
• c) oxidizing the iron in the solution by combining manganese dioxide with the solution while maintaining the oxidation potential of the solution between about 650 to about 800 mV measured with a platinum-silver/silver chloride electrode;
• c) selectively precipitating substantially all of the iron out of the solution as ferric hydroxide by combining an additional amount of manganese dioxide with the solution, wherein the iron precipitating step leaves the solution with less than about 15 ppm of iron, and wherein the iron precipitating step lasts less than about one hour while maintaining substantially all of the manganese in solution;
• and
• d) selectively precipitating manganese out of the solution as manganese carbonate by the addition of sodium carbonate to raise and maintain the solution pH to about 8.0 or above;
• wherein the manganese precipitate provides a dry filter cake comprising at least about 98% wt manganese carbonate.

A method of producing manganese carbonate from a leach liquor, the method comprising the steps of:

• a) providing a sulfurous acid leach solution comprising manganese and iron;
• b) air sparging the solution to remove dissolved sulfur dioxide from the solution;
• c) oxidizing the iron in the solution by combining manganese dioxide with the solution while maintaining the oxidation potential of the solution between about 650 to about 800 mV measured with a platinum-silver/silver chloride electrode;
• d) selectively precipitating iron out of the solution as ferric hydroxide in a kinetic reaction lasting about two hours or less while maintaining substantially all of the manganese in solution, wherein the step of precipitating substantially all of the iron comprises adding manganese dioxide to the solution after the step of oxidizing;
• and
• e) selectively precipitating manganese out of the solution as manganese carbonate by the addition of sodium carbonate.