A novel process on separation of manganese from calcium and magnesium using synergistic solvent extraction system

Abstract

The synergistic solvent extraction (SSX) system consisting of di-2-ethylhexyl phosphoric acid (P204) and alkyl-4-pyridinecarboxylate ester (4PC) in sulfonated kerosene was used to separate manganese from magnesium and calcium and to prepare pure manganese sulfate solutions with battery grade. In batch tests, over 99.9% of Mn2+ was extracted after a four-stage counter current extraction using an organic solution consisting of 0.25 mol/L P204 and 0.5 mol/L 4PC in sulfonated kerosene and a feed containing 22 g/L Mn2+, 4 g/L Mg2+ and 0.1 g/L Ca2+ with an A/O ratio of 1:6 at 25 °C for 10 min, while extractions of magnesium and calcium were negligible. After scrubbing using 0.025 mol/L H2SO4 at an A/O ratio of 1:8, the loaded organic solution was stripped using 0.7 mol/L H2SO4 at an A/O ratio of 1:8 to prepare pure manganese sulfate solutions with battery grade. The results of continuous operation test indicated that the mass ratios of Ca/Mn and Mg/Mn in strip liquors were below 5.6 × 10−5 and 2.5 × 10−4, respectively, further demonstrating the efficient separation of manganese from magnesium and calcium using the SSX system.