Multisite synergistic interaction induced selective adsorption of CB5-Ti3C2T2 complex for strontium ion: a combined theoretical and experimental study

Abstract

In this work, we use a well-defined water-soluble macrocyclic molecule cucurbit[5]uril (CB5) to modify 2D Ti₃C₂T₂ MXene and assemble a novel high-performance adsorbent CB5-Ti₃C₂T₂ for Sr ion by density functional theory and experimental methods. The structural stabilities of two distinct types of CB5-Ti₃C₂T₂ (T = F, O and OH) complexes, i.e., CB5-Ti₃C₂T₂(V) and CB5-Ti₃C₂T₂(P) configurations are proved by binding energy and ab initio molecular dynamics (AIMD) simulations. Calculations of adsorption properties reveal that all the considered CB5-Ti₃C₂T₂ complexes can act as efficient adsorbents for Sr ion, among which CB5-Ti₃C₂O₂ complex possesses the best performance. The high affinity (the calculated adsorption energies < −7.6 eV) and selectivity of CB5-Ti₃C₂T₂ complex for Sr ion are attributed to the synergistic effect between CB5 molecule and Ti₃C₂T₂ MXene in the adsorption process, which arises from the multisite interactions of portal carbonyl groups of CB5 and surface functional groups of Ti₃C₂T₂ towards Sr. Finally, CB5-Ti₃C₂T₂ complex was successfully synthesized, and experimental results confirm its synergistic effect, good selectivity and high removal efficiency for Sr ions. In the treatment of strontium-containing wastewater with low concentrations, the distribution coefficient and decontamination factor of CB5-Ti₃C₂T₂ for Sr were determined to be as high as 2.88×10⁵ mL/g and 144.9, respectively, and the separation factor (SF_Sr/Ca) achieved a notable value of 67. 5. This work is expected to present a new strategy for the construction of high-performance MXene-based adsorbent for radionuclide elimination.