Open-Framework Vanadate as Efficient Ion Exchanger for Uranyl Removal.

The elimination of uranium from radioactive wastewater is crucial for the safe management and operation of environmental remediation. Here, we present a layered vanadate with high acid/base stability, [Me 2 NH 2 ]V 3 O 7 , as an excellent ion exchanger capturing uranyl from highly complex aqueous solutions. The material possesses an indirect band gap, ferromagnetic characteristic and a flower-like morphology comprising parallel nanosheets. The layered structure of [Me 2 NH 2 ]V 3 O 7 is predominantly upheld by the H-bond interaction between anionic framework [V 3 O 7 ] n n - and intercalated [Me 2 NH 2 ] + . The [Me 2 NH 2 ] + within [Me 2 NH 2 ]V 3 O 7 can be readily exchanged with UO 2 2+ . [Me 2 NH 2 ]V 3 O 7 exhibits high exchange capacity ( q m = 176.19 mg/g), fast kinetics (within 15 min), high removal efficiencies (>99%), and good selectivity against an excess of interfering ions. It also displays activity for UO 2 2+ ion exchange over a wide pH range (2.00-7.12). More importantly, [Me 2 NH 2 ]V 3 O 7 has the capability to effectively remove low-concentration uranium, yielding a residual U concentration of 13 ppb, which falls below the EPA-defined acceptable limit of 30 ppb in typical drinking water. [Me 2 NH 2 ]V 3 O 7 can also efficiently separate UO 2 2+ from Cs + or Sr 2+ achieving the highest separation factors (SF U/Cs of 589 and SF U/Sr of 227) to date. The BOMD and DFT calculations reveal that the driving force of ion exchange is dominated by the interaction between UO 2 2+ and [V 3 O 7 ] n n - , whereas the ion exchange rate is influenced by the mobility of UO 2 2+ and [Me 2 NH 2 ] + . Our experimental findings indicate that [Me 2 NH 2 ]V 3 O 7 can be considered as a promising uranium scavenger for environmental remediation. Additionally, the simulation results provide valuable mechanistic interpretations for ion exchange and serve as a reference for designing novel ion exchangers.