Lignin-intercalated WS₂ with synergistic adsorption for efficiency lead removal

Tungsten disulfide (WS₂), a two-dimensional adsorbent material, has garnered great attention in removing lead ions (Pb²⁺) from water due to their extensive exposed adsorption sites. However, WS₂ nanosheets inevitably agglomerated and stacked during the preparation and adsorption process, leading to reduced adsorption efficiency. Current method of enhancing WS₂ dispersion is mainly blending with synthetic polymers, but these synthetic polymers themselves do not possess adsorption properties, resulting adsorption effect enhancement poorly. Here, lignin extracted from walnut shells (WS) was intercalated into bulk WS₂ to prepare highly dispersible Lignin/WS₂ composites with synergistic adsorption effects. The spatial resistance and electrostatic repulsion of the intercalated lignin effectively exfoliated bulk WS₂ and stabilized their dispersion. The synergistic adsorption arises from lignin's oxygen-containing groups and WS₂ nanosheets' sulfur-rich surface, which significantly enhanced Pb²⁺ removal (∼66.9 mg/g). This value surpassed pure lignin and bulk WS₂ by 1.7 and 25.0 times, respectively. Adsorption follows pseudo-second-order kinetic and Freundlich isotherm model, indicating that the adsorption of Pb²⁺ by the Lignin/WS₂ composite belongs to multi molecular layer chemical adsorption. This work provides a novel strategy for lignin-based adsorbents in water remediation.