High-efficiency and targeted Hg(II) adsorption on sulfur-functionalized mesoporous silica via thiol-ene click chemistry: Dual-site coordination, performance, and mechanisms.

Mercury (Hg) contamination in industrial wastewater poses a significant environmental and health threat. Efficient and targeted removal of Hg(II) is essential to prevent its release into aquatic environments. In this study, sulfur-functionalized mesoporous silica (SFMS) was synthesized via a thiol-ene click chemistry strategy to introduce thiol and thioether groups onto a mesoporous silica framework for Hg(II) capture. SFMS exhibited a strong affinity for Hg(Ⅱ), attributed to dual sulfur coordination sites, enabling efficient removal even under competitive ion conditions. The distribution coefficient (KD = 9.72 × 106 mL/g) confirmed its high selectivity in multi-ionic systems. Rapid adsorption kinetics were observed, with over 99% Hg(II) removal at initial concentrations of 2.50 and 5.00 mg/L. SFMS also maintained stable performance across a wide pH range (3-10). Furthermore, SFMS demonstrated consistently high Hg(II) removal efficiencies (>95%) across various water matrices. Compared with commercial activated carbon, SFMS maintained removal efficiencies above 95% over a wide concentration range (1-20 mg/L). These results highlight the potential of thiol-ene click chemistry as a simple and mild strategy for constructing dual-site sulfur-functionalized adsorbents for efficient Hg(II) removal.