Solvent extraction of iron(III) from hydrochloric acid solutions using N,N′-dimethyl-N,N′-diphenylmalonamide and N,N′-dimethyl-N,N′-diphenyltetradecylmalonamide

The use of N,N'-tetrasubstituted malonamides such as N,N'-dimethyl-N,N'-diphenylmalonamide (DMDPHMA) and N,N'-dimethyl-N,N'-diphenyl-tetradecylmalonamide (DMDPHTDMA) for the extraction of iron(III) from acid chloride solutions is investigated, in order to evaluate the possibility of using this family of compounds to extract base metal cations. In the present work, a mechanism for iron(III) extraction from chloride media by DMDPHMA and DMDPHTDMA is proposed, a comparison between their extraction behavior and involved mechanisms for both chloride and nitrate media being considered as well. Hydrochloric acid extraction, slope analysis and spectroscopic data-IR, UV, and NMR-were used to acquire information on the iron(HI) extraction reactions. The results suggest that DMDPHMA and DMDPHTDMA extract iron(III) through different mechanisms, thus showing the influence of the chemical structure on the metal ion transfer reactions to the organic phase. For DMDPHMA, an anionic-pair mechanism involving iron(III) extraction as the chlorocomplex FeCl4- seems to occur, while for DMDPHTDMA a solvation mechanism appears to be the predominant one. The stripping of iron(Ill) from the loaded organic phases is quantitatively achieved by a simple contact with water, and the selectivity towards iron(III) presented by both malonamide derivatives when several base metal cations co-exist in the,acid chloride aqueous solutions can be considered very promising.