Ann: High Purity Manganese Flowsheet Optimisation Progress Update, page-30

Fe goes in the liquor, it is dissolved alongside other metals (Al, Zn, etc). Fe and Al gets removed with ease on 2nd step (precipitation with cheap lime).

solvent extraction needed in my opinion last step to purify Manganese. Although there is some research of using Ion Exchange for that last step, enviro friendly depending on contaminant concentration.

I think getting final concentration of 99.7% MnSO4 is piece of cake. The tricky bit is to reach higher. Again, don't know how much higher is needed, will depend on VW or Tesla requirements.

however 99.7% is selling at US$1,400. And that is sufficient to make Megabucks per minute.