Efficient Hg(Ⅱ) removed by l-cysteine modified UiO-66 through chemical adsorption via a facile partial ligand replacement strategy

In this work, UiO-66-l-cys with enhanced adsorption capacity for Hg(Ⅱ) in water was synthesized through a facile two-step partial ligand replacement strategy. The presence of the functional groups significantly enhanced the capacity of the material for Hg(Ⅱ). According to the Langmuir model, the maximum theoretical adsorption capacity was calculated to be 1321.4 mg/g, which is 20 times that of the original UiO-66. Thermodynamic study revealed that the adsorption of Hg(II) onto UiO-66-l-cys is a spontaneous and endothermic process, thus exhibiting an elevated adsorption capacity at higher temperatures. XPS results confirmed that the sulfhydryl (SH) and amino (NH₂) groups react with Hg(Ⅱ), enabling the material to adsorb a large quantity of Hg(Ⅱ). Through DFT theoretical calculation and simulation, it has been found that S atoms and N atoms exhibit significant attraction to Hg atoms. Moreover, the corrosion potential of UiO-66 in Hg solution becomes lower. It is demonstrated that it has a faster electron transfer rate, which is conducive to the adsorption process. Furthermore, UiO-66-l-cys exhibited an excellent cyclic stability, with only a 2.7 % decrease in adsorption capacity after five cycles. This method eliminates the necessity for the pre-synthesis of complex chemical ligands and intricate chemical reactions. It also streamlines the process, and lowers material costs. The UiO-66-l-cys exhibits considerable potential applications for the treatment of heavy metal pollution.