Construction Si–O–Mo bond via etching method: enhancing selective adsorption capacity of MoS2/montmorillonite to Pb2+

The inert substrate surface of MoS2 leads to unsatisfactory adsorption performance. Herein, an inert substrate surface activation strategy is proposed, and the resulted MoS2/montmorillonite (MMT) prepared via the hydrothermal method is immersed with NaF (F–Mt). The intercalation of Na + contributes to inducing the transformation of MoS2 from 2H phase to 1 T phase, thereby providing a large number of S vacancies and exposing available Mo4+. Meanwhile, the surface of MMT is activated due to the fact that partially [Si4O10]4- are etched by F-, which facilitates forming Si–O–Mo bonds to promote the charge transfer. The improved charge transfer rate can make S2- in MoS2 accumulate more negative charges, greatly enhancing the adsorption capacity to Pb2+. Moreover, the natural negative potential on the surface of MMT solves the problem of easy stacking for nanosheets, improving the availability of active sites on the edge, which are also benefit from the etching effect on MoS2 nanosheets with NaF. The maximum adsorption capacity achieves 97.09 mg/g. Additionally, density functional theory (DFT) calculations confirm the resulted S vacancies in MoS2 are in favor of removing Pb2+, which is also contributed by the electrostatic and chemical adsorption with MMT. Therefore, it suggests that F–Mt is an excellent adsorbent for Pb2+.