Comparative performance of hierarchical 3D flower-like and 2D MoS2–Kaolin hybrid adsorbents for mercury remediation and antimicrobial applications

The critical environmental challenges associated with mercury pollution are attributed to its toxicity, persistence, and tendency to bioaccumulate throughout the food chain. In this study, kaolin–molybdenum disulfide (MoS2) composites engineered with two distinct morphologies, three-dimensional (3D) flower-like MoS2 (F-MoS2) and two-dimensional MoS2 (2D-MoS2), were synthesized and evaluated for mercury removal from aqueous solutions. MoS2 was hydrothermally synthesized and deposited onto kaolin to obtain K–F-MoS2 and K–2D-MoS2 composites. Comprehensive characterization confirmed well-defined 2D and 3D flower-like architectures and demonstrated their structural integrity following Hg2+ adsorption. K–F-MoS2 exhibited significantly higher performance than K–2D-MoS2 with maximum Langmuir capacities of 161.4 and 76.8 mg/g, respectively. The adsorption isotherms were best described by the Langmuir model for K–F-MoS2 and the Freundlich model for K–2D-MoS2. Both composites followed the pseudo-second-order kinetic model, indicating chemisorption-driven uptake, and mechanistic investigations confirmed Hg2+ binding was predominantly through covalent surface complexation with sulfur atoms on MoS2. Thermodynamic studies establish the endothermic nature of the adsorption process. K–2D-MoS2 and K–F-MoS2 exhibited antibacterial activity against S. aureus and Escherichia coli (BL21), with K–2D-MoS2 exhibiting a minimum inhibitory concentration (MIC) of 2.5 and 5 mg/mL, and for K–F-MoS2, 5 and 10 mg/mL, respectively. Both adsorbents also inhibited biofilm formation. These results demonstrate that kaolin–MoS2 hybrid systems are promising multifunctional materials for Hg2+ remediation and antimicrobial protection with strong potential for industrial applications.