Extraction of cadmium bromide and picrate by 18-crown-6 ether into various less-polar diluents: Analysis of overall extraction equilibria based on their component equilibria with formation of their ion pairs in water

► Extraction constants for Cd (II) salts-18-crown-6 ether systems are determined. ► Extraction-abilities and -selectivities of their systems are discussed. ► Individual distribution constants of cationic ion-pair complexes are evaluated. ► Their constants are reduced into ion-transfer potentials at interfaces. ► Interactions of neutral ion-pair complexes with water molecules are examined.