Synthesis under Microwave Irradiation, Characterization and Application of Alkyliminodimethylenediphosphonic Acids in Solvent Extraction of Iron (III)

The synthesis under microwave irradiation, characterization and application of new alkyliminodimethylenediphosphonic acids in solvent extraction of iron (III) has been investigated. The alkyliminodimethylenediphosphonic acids synthesized were: hexadecyliminodimethylenediphosphonic acid (HIDMP, H4L1) and decyliminodimethylenediphosphonic acid (DIDMP, H4L2). After purification, these products were characterized by elemental analysis and by FT-IR, 1H NMR, 13C NMR, 31P NMR spectroscopy. In this study, we proposed a tentative assignment for the shifts of those two ligands and their specific complexes with iron (III). We also carried out the extraction of Fe (III) by HIDMP and DIDMP from [chloroform+2-octanol (v/v: 90%/10%)] solutions at an aqueous to organic phase ratio (1/1) and at room temperature. Experimental results showed that HIDMP and DIDMP are synthesised efficiently and rapidly in good yields (85-88%) under microwave irradiation. The extraction yields are more significant in the case of the HIDMP (99%) which is equipped with a hydrocarbon chain, longer than that of the DIDMP (95%). Logarithmic plots of the iron (III) distribution ratio vs. pHeq and the extractant concentration showed that the ratios of extractant to extracted iron (III) are 3:1. The metal complexes formed in organic phase are [Fe (H3L1)3. 3H2O] and [Fe (H3L2)3. 3H2O] with HIDMP and DIDMP, respectively. A spectroscopic analysis of the metal complexes has showed that coordination of iron (III) takes place via oxygen atoms in the phosphonic groups, whereas the nitrogen atom remains rather uncoordinated. The equilibrium constants for the extraction of iron (III) were found to be 10.44x10-3 and 1.98x10-3 for HIDMP and DIDMP, respectively.