Process for the purification of manganese sulfate solutions and subsequent crystallization of high purity manganese sulfate monohydrate

A process for purifying a manganese sulfate solution and precipitating high purity manganese sulfate monohydrate crystals therefrom, comprising the steps of:

• (a) increasing the concentration of manganese sulfate in the manganese sulfate solution to produce a concentrated manganese sulfate solution;
• (b) removing calcium and magnesium from the concentrated manganese sulfate solution by precipitating calcium fluoride and magnesium fluoride through the addition of manganese fluoride produced in steps (f) and (g);
• (c) separating the precipitated calcium fluoride and magnesium fluoride from the concentrated manganese sulfate solution to produce a first clarified manganese sulfate solution;
• (d) a first crystallization step comprising combining the first clarified manganese sulfate solution with a recycle manganese sulfate solution and with manganese sulfate seed crystals to produce combined manganese sulfate solution and seed crystals, and heating and mixing the combined manganese sulfate solution and seed crystals to produce a crystal suspension comprising manganese sulfate crystals in a saturated manganese sulfate solution;
• (e) separating the manganese sulfate crystals from the crystal suspension, producing a process bleed stream comprising the saturated manganese sulfate solution;
• (f) treating the process bleed stream with a fluoride reagent to produce a slurry comprising manganese fluoride and a bleed solution depleted in manganese;
• (g) separating the manganese fluoride from the depleted manganese bleed solution and transferring the manganese fluoride to the concentrated manganese sulphate solution for the removal of calcium and magnesium in step (b);
• (h) redissolving the manganese sulfate crystals from step (e) in water and removing undissolved solids to produce a second clarified manganese sulfate solution;
• (i) a second crystallization step comprising combining the second clarified manganese sulfate solution produced in step (h) with manganese sulfate monohydrate seed crystals, and heating and mixing the combination to produce a final manganese sulfate monohydrate crystal product in a saturated manganese sulfate solution;
• and
• (j) separating the final manganese sulfate monohydrate crystal product produced in step (i) from the saturated manganese sulfate solution to produce solid high purity manganese sulfate monohydrate crystals and the recycle manganese sulfate solution.