Synergistic Extraction of Europium into Nitrobenzene by Using Hydrogen Dicarbollylcobaltate and 2,6 – (Diphenylphosphino)Pyridine Dioxide

Solvent extraction of microamounts of europium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B–) in the presence of 2,6 – (diphenylphosphino)pyridine dioxide (DPPPDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL+, HL+2, EuL3+ 3 and EuL3+ 4 are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.