A modified version of the metal-organic framework (MOF) UiO-66, known as Q-UiO-66-SH, was synthesized through post-synthetic modification to achieve selective adsorption of Hg(II) from solution. This was accomplished by controlled partial deligandation of UiO-66 at 350 °C in an air atmosphere. The deligandation process resulted in the formation of quasi UiO-66 (Q-UiO-66), which exhibited a significant increase in unsaturated zirconium sites. These unsaturated sites were capable of coordinating with cysteamine, leading to the formation of Q-UiO-66-SH. Importantly, this post-synthetic modification did not compromise the structural and thermal stability of the pristine UiO-66 framework. The influencing factors encompassing sorbent type, pH level, adsorbent dosage, and initial concentration of Hg (II) and coexisting ions were extensively investigated and thoroughly clarified. The maximum adsorption capacity in presence of thiol-functionalized Q-UiO-66 calculated 1400 mg.g-1 at pH 8.0 with a remarkable distribution coefficient of 6.7× 106 mL.g-1. The adsorption kinetics and isotherm model demonstrated a good agreement to pseudo-second-order kinetics and the Langmuir model, indicating monolayer chemisorption adsorption. From the perspective of thermodynamics, it became apparent that removing Hg (II) resulted in an endothermic reaction with the growing disorder as a spontaneous process. Moreover, Q-UiO-66-SH exhibits high removal efficiency and selectivity to mercury across a wide range of concentrations and pH in solution with the ability to remove mercury from the model sample, due to its thermal and chemical stability in aqueous environment. Therefore, the Q-UiO-66-SH sorbent shows immense potential as an effective and promising adsorbent for Hg (II) removal in water.
