Abstract
3, 5-Dinitro (3, 5-DNBPHA) and 2, 4-dinitro derivatives (2, 4-DNBPHA) of N-benzoyl-N-phenylhydroxylamine (BPHA) were synthesized. Their acid dissociation constants and distribution constants between chloroform and 0.1mol dm-3 potassium chloride solution were determined by a spectrophotometric method and a liquid-liquid distribution method, respectively. The solvent extraction of lanthanoids (Ln) with 3, 5-DNBPHA in chloroform was studied. The selected lanthanoids (Yb, Ho, Eu, Pr and La) were all found to extract with compounds as self-adducts of the form LnL3(HL)2, where L and HL denote the ligand anion and neutral ligand, respectively. The extraction constant and separation factor were compared with those of the methoxy derivatives of BPHA previously reported. It has become apparent that the lower is the pKa value of the extractant, the larger is the extraction constant; further, the separation of lanthanoids becomes poorer as pKa decreases.
