SOLVENT EXTRACTION OF BASE METAL CATIONS SUCH AS IRON(Ⅲ) FROM HYDROCHLORIC ACID SOLUTIONS USING N,N'-SUBSTITUTED MALONAMIDES

摘要

The possibility of using new malonamides such as N,N'-dimethyl-N,N-diphenyltetradecyl malonamide (DMDPHTDMA) for the extraction of base metals from hydrochloric acid solutions has been evaluated. It has been shown that Fe(Ⅲ) may be selectively separated from other base metals such as Cu(Ⅱ), Zn(Ⅱ), Ni(Ⅱ) from hydrochloric acid solutions of concentration greater than 4 M. Iron(Ⅲ) is extracted as the tetrachloroferrate (Ⅲ) anion [FeCl_4]~-. Spectroscopic data - IR, UV, NMR -suggest an ion-pair mechanism for HCl concentration equal or greater than 10 M in which the DMDPHTDMA is mono or diprotonated, while a solvation mechanism should be considered for lower acid concentrations. The effect of variables including acidity and chloride concentration are discussed in relation to the extraction data. Comparisons are made with extraction data from nitric acid media. Overall DMDPHTDMA acts as a very weak base or ligand operating through an ion-pair or solvation mechanism, depending on the hydrochloric acid concentration.