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

Abstract

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 K₁ = 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.