Surface Hydroxyl Groups Functionalized Porous CeO₂ for Enhanced Selective Adsorption of As(III)

The adsorption technique has been considered as one of the promising methods to remove arsenic ions in aqueous systems. However, the adsorbents are usually poorly selective and have low capacity. Herein, a kind of porous CeO₂ containing surface hydroxyl group which synthesized facilely possesses the great performance of selective adsorption of As(III) with 98.57% removal against 14 other coexisting metal ions. The results showed that the processes of As(III) and As(V) uptake were heterogeneous monolayer adsorptions and included external and intraparticle diffusions. The adsorption capacities at pH 2.5 reached 111.24 and 56.89 mg/g for As(III) and As(V), respectively. In addition, it also showed that As(III) could be oxidized to As(V) in the adsorption process. Density functional theory calculations revealed that the OH group in H₃AsO₃⁰ and the As atom in H₃AsO₄⁰ have affinity with lattice oxygen (O^2-) in CeO₂, while the O atom in H₂AsO₄^- preferred the Ce atom in CeO₂. This study provides a novel porous CeO₂ containing hydroxyl groups for selective and efficient removal of arsenic and elucidates the mechanism of As(III) and As(V) adsorptions.