Iron(III) extraction from sulfate solutions with D2EHPA in the presence of organic proton-donor additives

Abstract

Abstract The effect of organic proton-donor additives (HA) on the extraction of iron(III) from sulfuric acid solutions with di(2-ethylhexyl)phosphoric acid (HR) in decane and toluene was studied. It was shown that adding the additives into the organic phase causes an antagonistic effect. Iron(III) extraction in the presence of additives decreases in the series octyl alcohol ≈ 4-tert-butyl phenol > octanoic acid. The low activity of octanoic acid is attributed to self-association and the formation of dimers in the organic phase, which significantly prevents the formation of intermolecular associates between D2EHPA and monocarboxylic acid. Octanol and 4-tert-butyl phenol form stable associates with D2EHPA leading to a decrease in the ferric iron extraction efficiency thus facilitating efficient iron stripping from the loaded organic phase. In the D2EHPA and octyl alcohol system [FeR2·HR2] is formed. The stripping of iron from the HR and octyl alcohol mixtures was shown to be much more efficient than that from D2EHPA alone and can be successfully achieved using ~4.5 mol/L H2SO4 or H2SO4 (~3.5 mol/L) and NaCl (1.0 mol/L) mixture. Extraction systems containing D2EHPA and aliphatic alcohols can be used to recover iron from various industrial solutions, in particular, from those derived from zinc, nickel production, and others.