Cementation Cathodic precipitation of a metal ion of a metal from solution by passing the solution over a more anodic (less noble) metal Cu 2+ +2e = Cu (cathodic precipitation Fe = Fe e (anodic dissolution) Cementation is less selective than gaseous reduction

Isolation techniques Ion exchange: organic resins on to which either cations or anions have been loosely bounded Solvent extraction: organic compounds – ethers, esters, ketones- provide high solubility of some metallic and complex metal ions Reverse osmosis: concentration of metal ions by passage of water from a dilute to a more concentrated solution through a semipermeable membranes

Electrowinning Electrowinning of a metal is based on the electrolysis of aqueous solutions or melts of metal salts with insoluble anode

Electrowinning

Electrorefining

Caron processs : laterite ore :  50% Fe - FeO.OH, 1-2% Ni - NiO,  0,1% Co - CoO Laterite ore Drying, Grinding Reduction roasting Ammoniacal leaching Partition Ni/Co Ni- liquor Boiling up/filtration NiCO 3.Ni(OH) 2 Calcination NiO Preparation of electrolyte Electrolysis Ni 99,9% H 2, CO NH 3 aq. (NH 4 )CO 3 Residue Na 2 S CoS H 2 SO 4 NH 3 vzduch