Suppression of D2EHPA-based Extraction of Trivalent Metals in the Presence of Amides

抄録

The effects of neutral organic compounds on the extraction of trivalent metals by di(2-ethylhexyl)phosphoric acid (D2EHPA) were investigated. Various ethers and ketones examined showed only minor influences on the extraction of Ga(III) and Fe(III). In contrast, amides significantly suppressed the extraction of Fe(III), In(III), and Ga(III), with a stronger effect observed for a diamide than for a monoamide. The decrease in Fe(III) extraction led to an increased separation factor between Fe(III) and In(III), which are otherwise difficult to separate using D2EHPA alone. Slope analysis of pH dependence and ¹H NMR measurements suggested that amides interact with D2EHPA through hydrogen bonding, potentially affecting its dimerization equilibrium and thereby reducing extractability. These results reveal a negative but useful effect of amides on D2EHPA-based extraction systems.