text: After leaching, the leach liquor must normally undergo concentration of the metal ions that are to be recovered.  Additionally, undesirable metal ions sometimes require removal. 
  *Precipitation is the selective removal of a compound of the targeted metal or removal of a major impurity by precipitation of one of its compounds.  Copper is precipitated as its sulfide as a means to purify nickel leachates.
  *Cementation is the conversion of the metal ion to the metal by a redox reaction.  A typical application involves addition of scrap iron to a solution of copper ions.  Iron dissolves and copper metal is deposited.
  *Solvent Extraction
  *Ion exchange
  *Gas reduction.  Treating a solution of nickel and ammonia with hydrogen affords nickel metal as its powder.
  *Electrowinning is a particularly selective if expensive electrolysis process applied to the isolation of precious metals.  Gold can be electroplated from its solutions.