High-efficiency and selective removal of Hg(Ⅱ) and Pb(Ⅱ) ions from aquatic system by 1T/2H mixed-phase MoSe2 nanoflowers: Performance and mechanism

Abstract

High-efficiency and selective removal of heavy metal ions from aquatic system is urgently needed and remains a major challenge. Endowed with rich Se atoms and unique 2D structure, MoSe2 should be promising for the removal of heavy metal ions. However, it remains challenging to balance the efficient exposure of active sites and the stability of materials, and the potential mechanism of the interactions between heavy metal ions and the interface of MoSe2 with different crystal phases and structures has yet to be comprehensively explored. Herein, mixed-phase 1T/2H MoSe2 nanoflowers featured with ultrathin nanosheets, high ratio of 1T phase, enlarged interlayer spacing, and defect-rich structure have been synthesized and demonstrated excellent performance for removing Hg(II) and Pb(II) ions from aquatic system, including high capacity (952.4 mg·g−1 for Hg(II); 217.9 mg·g−1 for Pb(II)), rapid kinetics, superior selectivity, and anti-interference ability. The ultrathin nanosheets and enlarged interlayer spacing ensured efficient exposure of Se atoms; the high ratio of 1T phase was beneficial for the binding of heavy metal ions (as confirmed by DFT calculations). The defect-rich structure not only provided additional channels for ions diffusion, but also produced more active sites for ion binding and charge transfer. Benefiting from these structural characteristics, 1T/2H MoSe2 could effectively and selectively remove Hg(II) and Pb(II) ions under the coexistence of various cations in practical water environment, the corresponding separation factors were greater than 170. Moreover, the interaction mechanism between two target ions and MoSe2 was elucidated byexperimentandDFT calculation. The present work not only explored advanced materials for the purification of heavy metal ions polluted water, but also may promote the exploration of MoSe2 in environmental remediation.