Diamine and Diammonium Extractants

The application of di-tertiary amines and di-quaternary ammonium salts as extractants for metal ion separation is discussed. The versatility of the di-tertiary amines is illustrated. In these cases, two extraction mechanisms are postulated to coincide with the low and high pH conditions employed in the aqueous phases. The advantages in applying these two mechanisms for the selective extraction of metals from, and stripping to aqueous media are outlined. The potential advantages of these reagents over monoamines are discussed. Other features unique to diamine/diammonium extractants, e.g., differences in “acid effects” associated with these extractants, their differing tendencies towards third phase formation, etc., will be illustrated with extraction isotherms.