An improved method for the utilization of high or low grade manganese ore for the preparation of pure manganese sulphate and its application for the regeneration of the spent electrolytic manganese sulphate baths

Abstract

This investigation was undertaken to find an easily applied and cheap method for the preparation of pure manganese sulphate and to apply this to this regeneration of spent electrolytic manganese sulphate baths, preferably making use of low grade manganese ores containing high amount of iron , silica, phosphorous, etc., such as are usually dumped near the mine site. It has been found that artificial manganese dioxide and manganese ores og high or low grades (but mostly the pyrolusite variety) can be very easily reduced and manganese converted to manganese sulphate by digesting at about 100° c with various organic materials like glucose, molasses, sawdust, etc in the presence of dilute sulphuric acid, in the concentration present in the spent electrolyte. Even with very low grade manganese ore containing large amounts of iron, phosphorous and silica, etc., a solution of manganese sulphate was obtained completely free from those impurities. The maximum extraction of manganese from the ore was found to be near 95% of the manganese content in the ore. The spent sulphate liquor from electrolytic manganese or manganese dioxide baths containing about 2% free sulphuric acid could be regenerated in a one stage by digesting it for about 22-27 hours with sawdust and manganese ore of any grade, but the regenerated liquid under this condition was found to contain soluble organic matter in a considerable amount. By adopting a ‘two stage process of digestion’ with a total digestion period of 12-18 hours, a solution of manganese sulphate free from organic matter was obtained, which could be used for the production of pure metallic manganese or its dioxide by electrolysis.