Thiol-functionalized metal-organic frameworks embedded with chelator-modified magnetite for high-efficiency and recyclable mercury removal in aqueous solutions

Aqueous mercury (Hg) pollution has aroused increasing concern due to its harmful effects on human health and environmental sustainability. The development of high-efficiency and recyclable adsorbents for Hg removal is of great significance in aqueous environments. Herein, we synthesize a Fe3O4@DTIM (4-(5)-imidazoledithiocarboxylic acid)-MOF (metal-organic framework)@SH composite as a high-efficiency and recyclable adsorbent for the removal of Hg2+. The typical MOF, known as HKUST-1, modified with Fe3O4@DTIM and ethanedithiol endow the material with recyclability and high efficiency, respectively. The optimized Fe3O4@DTIM-MOF@SH composite showed high affinity (adsorption rate constant K-1 = 0.29 g mg(-1) min(-1)) and adsorption capacity (756.9 mg g(-1)) for aqueous Hg2+ removal within 120 min. Fe3O4@DTIM-MOF@SH can be applied to adsorb Hg2+ in the pH range of 4.0 to 7.0. Additionally, the adsorbents showed high performance for Hg2+ adsorption after five cycles of utilization. State-of-the-art characterization and DFT calculations demonstrated that the sulfhydryl group on the Fe3O4@DTIM-MOF@SH composite played an important role in Hg2+ adsorption. Thus, this study provides a new strategy for the development of MOF-based adsorbents for the high-efficiency removal of mercury during remediation activities in aqueous solutions.