Magnesium salt removal from manganese electrolyte via low-temperature crystallisation

In the electrolytic manganese industry, magnesium accumulation in the electrolyte is detrimental to production systems. Therefore, in this study, magnesium was removed from manganese electrolytes via low-temperature crystallisation. The Mg2+ concentration was reduced from 43.00 to 23.33 g L–1 at the optimal experimental conditions: crystallisation temperature of −5°C, crystallisation time of 1 h, H2SO4 concentration of 80 g L–1, whereas the Mn2+ concentration was minimally affected. The resulting crystal products were primarily composed of Mg(NH4)2(SO4)2·6H2O and a small amount of Fe(NH4)2(SO4)2·6H2O. This process does not require the addition of a precipitant during crystallisation, therefore considerably reducing the magnesium removal cost and facilitating clean production.