SELECTIVITY AND EQUILIBRIA IN EXTRACTION WITH MACROCYCLES IN SYNERGISTIC COMBINATION WITH ORGANOPHILIC ACIDS.

The authors report the behavior of several organophilic macrocyclic polyethers (crown ethers) as coordinative extraction synergists in combination with 1) a long-chain neo carboxylic acid, 2) an alkyl phosphoric acid, and 3) an alkyl-aryl sulfonic acid. Selected combinations of these organophilic cation exchangers and macrocyclic coordinators were examined as extractants for alkali, alkaline earth, and first-row transition elements from nitrate systems. Both synergistic and antagonistic effects were produced. Macrocycles having a cavity size to fit the metal ion usually produced the largest synergistic effect; however, the nature of the substituents on the macrocyclic ring also has a strong effect on selectivity. In general, alkali metal ions prefer to bond to benzo-substituted crown ethers while alkaline earth ions prefer to bond to cyclohexano-substituted ones. Iron, cobalt, and nickel extractions are antagonized by the macrocycles while copper is synergized only slightly and manganese and zinc moderately strongly.