Binding Mechanism of the Amidoxime Functional Group on Chelating Resins toward Gallium(III) in Bayer Liquor

Abstract

Amidoxime is of broad interest as a functional group for extraction and separation of different metals from aqueous solution due to its high affinity for a wide range of metal ions. Resins which contain an amidoxime group have exhibited good extractive properties for gallium and are adopted as the most efficient adsorbent for the recovery of gallium from Bayer liquor. However, the coordination mechanism between the amidoxime functional group of the resin and Ga(III) in Bayer liquor is unclear so far. Here, to identify the preferred action and the binding motif when amidoxime binds with Ga(III), we performed density functional theory (DFT) calculations and subsequent FT-IR spectra analysis for the amidoxime resin before and after adsorption of Ga(III) in Bayer liquor. Single-crystal X-ray diffraction was also used to validate the prediction. The fully relaxed structure and binding energy calculations of a series of complexes containing acetamidoximate (AO–) and gallium species, [Ga(OH)4-x(AO–)x]−, showed t...