Thiol‐Modified Halloysite‐Containing Gelatin/Chitosan Composite Hydrogel Adsorbent for Mercury Removal From Aqueous Solutions

ABSTRACT Mercury (Hg) is an extremely toxic heavy metal with no known beneficial biological function, representing a serious risk to both human health and the environment. As mercury contamination continues to rise, the development of efficient and sustainable strategies for its removal and recovery has become imperative. In this study, novel composite hydrogels were fabricated using chitosan (CTS) and gelatin (GE) as biopolymeric matrices, incorporating thiol‐functionalized halloysite nanotubes. The hydrogels were characterized by Fourier‐transform infrared spectroscopy (FT‐IR) and thermogravimetric analysis (TGA). Batch adsorption experiments were carried out to investigate the influence of various operational parameters, including contact time, pH, and initial Hg (II) concentration, on mercury removal from aqueous media. The adsorption mechanism was elucidated in detail, revealing the interactions between Hg (II) ions and the functional groups within the hydrogel matrix. Kinetic studies demonstrated that Hg (II) uptake proceeded rapidly and conformed well to the pseudo‐second‐order kinetic model. Equilibrium adsorption data were best described by the Langmuir isotherm model, indicating a maximum adsorption capacity of 415 mg/g. Thermodynamic evaluations at different temperatures showed that the adsorption process is exothermic (∆ H ° < 0) and spontaneous (∆ G ° < 0). Overall, the findings underscore the promise of CTS‐ and GE‐based composite hydrogels as effective, bio‐based adsorbents for mercury removal and environmental remediation applications.