Bifunctional solid-state ionic liquid supported amidoxime chitosan adsorbents for Th(IV) and U(VI): Enhanced adsorption capacity from the synergistic effect

Abstract

Uranium and thorium of symbiotic relationship commonly appear in one kind of raw or spent ore. The simultaneous enrichment toward both metals in the first step is essential during many hydrometallurgy processing. Therefore bifunctional solid-state ionic liquid supported amidoxime chitosan (ACS) adsorbents were developed to simultaneously adsorb the two metal from the aqueous solution. The adsorption capacity of the bifunctional adsorbents toward uranium and thorium were significantly superior to the ionic liquid-free amidoxime chitosan, obviously proving the synergistic effect. For both uranium and thorium, the adsorption capacity in the consequence of ACS-[N₄₄₄₄][DEHP], ACS-[N₄₄₄₄][EHEHP], ACS-[N₁₈₈₈][DEHP] and ACS-[N₁₈₈₈][EHEHP] prove the steric effect and PO bonding played important roles in the adsorption. Study on isotherms and kinetics demonstrated the adsorption of ionic liquid-ACS adopted monolayer and chemical way. The ΔG^o of very small negative values highlighted ionic liquid-ACS were prone to adsorb uranium and thorium. The study showed feasibility of bifunctional solid-state ionic liquid supported amidoxime chitosan adsorbents for Th(IV) and U(VI).

Keywords: Adsorption; Chitosan; Ionic liquid; Thorium; Uranium.