Comparative study of mono (n-octyl) phosphinic and di(n-octyl) phosphinic acids as metal extractants

Abstract The extraction of Fe(III), Co(II), Zn(II), Cu(II), Cd(II) and Pb(II) from 1.0 M sodium nitrate solutions by mono(n-octyl)phosphinic acid (H[(O)(H)P]) and di(n-octyl)phosphinic acid (H[DOP]) dissolved in toluene was studied as a function of the extractant concentration and pH in the aqueous phase at 25°C. The predominant metal species extracted and their equilibrium constants were determined by slope analysis. The metal extraction behaviour, when a hydrogen attached to the phosphorus is replaced by an alkyl group in the molecule of phosphinic acid, was compared. Finally, the influence of the addition of basic extractants, such as trioctylphosphine oxide (TOPO) and trilaurylamine (TLA), to the phosphinic acids in the extraction of some metals was also analyzed.