Efficient and selective removal of Hg(II) from water using recyclable hierarchical MoS2/Fe3O4 nanocomposites

Developing practical and cost-effective adsorbents with satisfactory mercury (Hg) remediation capability is indispensable for aquatic environment safety and public health. Herein, a recyclable hierarchical MoS2/Fe3O4 nanocomposite (by in-situ growth of MoS2 nanosheets on the surface of Fe3O4 nanospheres) is presented for the selective removal of Hg(II) from aquatic samples. It exhibited high adsorption capacity (-1923.5 mg g-1), fast kinetics (k2 -0.56 mg g-1 min -1), broad working pH range (2-11), excellent selectivity (Kd > 1.0 x 107 mL g-1), and great reusability (removal efficiency > 90% after 20 cycles). In particular, removal efficiencies of up to-97% for different Hg(II) concentrations (10-1000 mu g L-1) in natural water and industrial effluents confirmed the practicability of MoS2/Fe3O4. The possible mechanism for effective Hg(II) removal was discussed by a series of characterization analyses, which was attributed to the alteration of the MoS2 structure and the surface co-ordination of Hg-S. The accessibility of surface sulfur sites and the diffusion of Hg(II) in the solid-liquid system were enhanced due to the advantage of the expanded interlayer spacing (0.96 nm) and the hierarchical structure. This study suggests that MoS2/Fe3O4 is a promising material for Hg(II) removal in actual scenarios and provides a feasible approach by rationally constructing hierarchical structures to promote the practical applications of MoS2 in sustainable water treatments.