Structural effect of diamide extractants on the extraction behaviour of Fe(III) from hydrochloric acid

The extraction of Fe(III) from hydrochloric acid with N,N,N′,N′-tetrabutylmalonamide (TBMA), N,N,N′,N′-tetrabutyl-3-oxy-glutaramide (TBDGA) in toluene was studied and compared with the extraction result of N,N,N′,N′-tetrabutylsuccinamide (TBSA) in order to understand the relationship between the chemical structure of the extractants and their Fe(III) extraction behaviors. The extraction efficiency of the extractants toward Fe(III) in toluene increases in the order: TBMA < TBSA < TBDGA. The effect of hydrochloric acid concentration, extractant concentration and temperature on the extraction distribution ratio of Fe(III) was investigated to determine the thermodynamic parameters and the main extracted species. Spectroscopic data (UV-visible and IR) and density functional theory (DFT) were used to clarify the extraction mechanism.