An approach to produce pure manganese sulphate solution by Jarosite Process

Though India has a vast deposit of manganese ores, unfortunately the Indian manganese minerals do not occur in the form in which they are primarily required to function as an effective depolarizer. Indian deposits mostly occur as pyrolusite, cryptomelane, psilomelane, magnetite etc. Cryptomelane contains potassium as foreign ion in the lattice. In time of leaching /regeneration of spent electrolyte potassium of manganese dissolves in the sulphuric acid solution. It the potassium is not removed from the electrolyte it slowly builds in the solution and in time of electrolysis enters in the final product making lattice defect tunnel. A large volume presence of K+ will a change of gamma manganese dioxide to alpha (cryptomelane) manganese dioxide and activity drops. In this paper, removal of potassium from leached / regenerated electrolyte is described. At a pH of 2 and temperature around 100°C over 90% potassium is removed in 2hrs, when ferric iron added is 1½ times more than the stoichiometric equivalent to potassium present in the electrolyte for formation of jarosite.