Three-dimensional molybdenum disulfide/graphene hydrogel with tunable heterointerfaces for high selective Hg(II)...

A hierarchical and hybridized hydrogel with rational structure and composition as adsorbent possesses a series of distinct advantages, e.g., fast ion diffusion, high selectivity and good stability. Herein, a novel three-dimensional (3D) molybdenum disulfide (MoS₂)-reduced graphene oxide (rGO) hydrogel with two-dimensional heterointerfaces is fabricated by an eco-friendly one-pot hydrothermal method. The heterointerfacial area could be readily tuned by the regulation of MoS₂/rGO ratio, in order to improve the adsorption capacity and selectivity. The 3D MoS₂-rGO hydrogel with 70 wt% MoS₂ shows high selectivity for Hg(II) ions, with a distribution coefficient value (K_d) of 7.49 × 10⁶ mL g^-1 even in the presence of other coexisting ions. More attractively, the free-standing and flexible 3D MoS₂-rGO hydrogel can be used as a column-packed device, providing an efficient pathway for the fast removal of 80 mg L^-1 Hg(II) within 7 min to achieve a tolerable concentration of < 2 μg L^-1 in 30 mL water with 5 mg of 3D MoS₂-rGO hydrogel. Considering that the direct-contact adsorption is more efficient than oscillating adsorption, the 3D MoS₂-rGO hydrogel as nanobuilding block shows a promising potential for cleaning the point-of-use water.