One-step extraction and solidification of uranium (VI) from sulfate leaching liquor using bifunctional ionic liquids

Abstract

Three bifunctional [DODMA]+[DGA]- ionic liquids were synthesized starting from [DODMA]+[Cl]- surfactant and N, N-dialkyl-diglycolamide acid (DGA), which were employed for extraction of U(VI) from real leach solution. The simultaneous purification and solidification of uranium (VI) were realized in one-step process in sulfuric acid medium, and the extracted solid captured more than 99 % uranium (VI) was found to aggregate at the biphasic interface. XPS, FT-IR, ESI-MS and TGA analysis revealed that U(VI) ions were assembled into uranium-containing solids by coordination of uranyl ions and dicarbonyl groups of [DGA]- anions using amphiphilic property of [DODMA]+ cations. An unusual multi-step extraction mechanism by anionic exchange was proposed to elucidate the excellent selectivity for U(VI). The present bifunctional ionic liquids exhibited the high affinity for U(VI) compared to 18 main elements assayed in ore leaching liquor. The key interfering ions such as Fe(III) and V(V) were hardly extracted to enrich in the extracted solid, and the good separation factors were obtained in 280 for U/Fe and 117 for U/V. Without further back-extraction, final precipitation and other relevant operation, the proposed one-step strategy was considered as a sustainable or promising process for easier recovery of U(VI) in sulfate leaching liquor.