Multicomponent Polymer Network Immobilizing MoS₂ Nanosheets for Stable Hg²⁺ Capture under Competitive Ion Conditions

Mercury-containing wastewater poses a severe threat to human health owing to the extreme toxicity and bioaccumulation of Hg²⁺. However, the practical application of Hg²⁺ adsorbents is often limited by insufficient structural stability, recyclability, and selectivity under competitive ion conditions. Herein, a natural polymer-based, recyclable adsorbent was constructed by immobilizing silane-modified MoS₂ nanosheets within a multicomponent carboxymethyl chitosan/poly(vinyl alcohol)/cellulose nanocrystal (CMC/PVA/CNC) network using glutaraldehyde as a cross-linker. This three-dimensional polymer framework effectively stabilizes MoS₂ nanosheets while maintaining the accessibility of sulfur-containing active sites. Under optimal conditions (MS loading of 40% and pH 5.5), the adsorbent achieved a maximum Hg²⁺ adsorption capacity of 216.49 mg·g^-1. More importantly, over 80% of the initial Hg²⁺ removal efficiency was retained after nine consecutive adsorption-desorption cycles, demonstrating excellent structural durability. The adsorbent exhibited pronounced selectivity toward Hg²⁺ in mixed-ion systems containing Cd²⁺, Cu²⁺, and Pb²⁺, with distribution coefficients 2 orders of magnitude higher than those of competing ions. Mechanistic investigations revealed that Hg²⁺ capture arises from cooperative coordination with -NH₂, -OH, and -SH functionalities accompanied by redox transformation to Hg₂SO₄. This work highlights a rational immobilization strategy for designing stable and selective adsorbents suitable for complex heavy-metal wastewater remediation.