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-MoS_2, 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.