Extraction Equilibria of Copper (II) and Palladium (II) with 2-Hydroxy-1-Naphthaldoxime

Abstract

2-Hydroxy-1-naphthaldoxime (=HNO) containing an oxime group as a ligand was synthesized in order to develop a highly selective extractant for Cu (II) and Pd (II). The extraction selectivity of HNO in chloroform for various metal ions was examined from aqueous ammonium nitrate solution and hydrochloric acid in a batchwise method at 300 K. From aqueous ammonium nitrate solution, Pd (II) was selectively extracted over Cu (II) in the low pH region, while Cu (II) was selectively extracted over Pd (II) in the high pH region because Pd (II) -ammine complexes is attributable not to be extracted with HNO. From hydrochloric acid solution, HNO was found to be a high selective extractant for Cu (II) and Pd (II) over base metals.
Cu (II) was found to be extracted by the following extraction reaction from aqueous ammonium nitrate solution. HNO behaved as a chelating extractant.
Cu²⁺+2HR R₂Cu+2H⁺; K_Cu, K_Cu=1.6×1010² [-]
Pd (II) was found to be extracted by the following extraction reaction from hydrochloric acid solution. HNO behaved as a solvating extractant.
2HR+PdCl_Cu (HR) _CuPdCl_Cu; KPd, KPd=1.8×10⁷ (moldm^-3) ^-2