| 摘要 |
Metallic contaminants, e.g. cobalt, iron, copper, and zinc are removed from an aqueous nickel solution by solvent extraction with a solution of a water-insoluble quaternary ammonium thiocyanate in a water-immiscible organic solvent. The quaternary ammonium thiocyanate contains at least two alkyl groups having carbon chains of 8 or more carbon atoms attached to the quaternary nitrogen atom and it may be dissolved in, for example, methyl isobutyl ketone, a naphtha, or one or more xylenes. The organic solution may also contain a water-insoluble quaternary ammonium chloride. After extraction of the contaminants and separation of the aqueous and organic phases, thiocyanate may be recovered from the organic phase for re-use by treating the latter with aqueous alkali metal hydroxide to precipitate the hydroxide of the contaminating metal or with a water-soluble sulphide or hydrogen sulphide to precipitate the sulphide, filtering and separating the aqueous phase. Recovery of thiocyanate from the nickel-bearing aqueous phase may be effected with a solution of a water-insoluble amine in a water-immiscible organic solvent, e.g. a trialkylamine in which the alkyl chains each contain from 8 to 10 carbon atoms dissolved in xylene, a naphtha, or a paraffin. Thiocyanate ions extracted by the amine may be regenerated by treating the organic phase with aqueous alkali metal hydroxide. Alternatively, thiocyanate ions may be removed from the aqueous nickel-bearing solution by precipitation as cuprous thiocyanate, which, after filtration, is treated with alkali metal hydroxide to regenerate thiocyanate ions in an aqueous solution. |
