Revealing the role of oxygen-containing functional groups on graphene oxide for the highly efficient adsorption of thorium ions.

Oxygen-containing functional groups on the surface of carbon materials can promote the adsorption capacity of radioactive thorium ions (Th(IV)), but their effect on the adsorption of Th(IV) has not been systematically revealed. Herein, to elucidate the nature of oxygen-containing group-mediated Th(IV) adsorption, a series of graphene oxide nanoflakes (GONFs) with different contents of oxygen-containing groups on the surface were prepared. The experimental results showed that the high adsorption of Th(IV) not only resulted from the oxygen content, but also was related to the type of oxygen-containing functional groups on GONFs. Subsequent density functional theory (DFT) calculations revealed that the high adsorption capacity for Th(IV) originated from the oxygen-containing groups and their adjacent activated sp2 carbon atoms. More importantly, the coordination of Th(IV) with oxygen functional groups induced the aggregation of GONFs, leading to the sedimentation of GONFs, which facilitated the separation of adsorbents and enabled the GONFs to be a more practical adsorbent for Th(IV). This work deepens our understanding of the role of oxygen-containing groups on Th(IV) adsorption and provides a new strategy for the design and synthesis of high-performance surface oxygen-containing carbon-based adsorbents with practical application potential.