Multisite synergistic interaction induced selective adsorption of CB5-TiCT complex for strontium ion: A combined theoretical and experimental study.

In this work, we use a well-defined water-soluble macrocyclic molecule cucurbit[5]uril (CB5) to modify 2D TiCT MXene and assemble a novel high-performance adsorbent CB5-TiCT for Sr ion by density functional theory and experimental methods. The structural stabilities of two distinct types of CB5-TiCT (T = F, O and OH) complexes, i.e., CB5-TiCT(V) and CB5-TiCT(P) configurations are proved by binding energy and ab initio molecular dynamics (AIMD) simulations. Calculations of adsorption properties reveal that all the considered CB5-TiCT complexes can act as efficient adsorbents for Sr ion, among which CB5-TiCO complex possesses the best performance. The high affinity (the calculated adsorption energies < -7.6 eV) and selectivity of CB5-TiCT complex for Sr ion are attributed to the synergistic effect between CB5 molecule and TiCT MXene in the adsorption process, which arises from the multisite interactions of portal carbonyl groups of CB5 and surface functional groups of TiCT towards Sr. Finally, CB5-TiCT 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-TiCT for Sr were determined to be as high as 2.88 × 10 mL/g and 144.9, respectively, and the separation factor (SF) 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.