Synthesis of Bentonite/Mil-68(Al) Composite for Hg 2+ Adsorption and Electrochemical Detection

Heavy metal contamination, particularly mercury ions (Hg²⁺), represents a critical environmental issue due to their toxicity and persistence in the environment. In this study, a composite based on the MOF MIL-68(Al) and bentonite (B/MIL-68(Al)) was synthesized and characterized to evaluate its performance in the adsorption and electrochemical detection of Hg²⁺. Structural characterization by XRD and FTIR confirmed the integration of the MOF into the bentonite, while textural analyses revealed a significant increase in surface area (430 m² g⁻¹) and microporosity, enhancing its adsorptive capacity. The material was employed in the modification of gold screen-printed electrodes (SPEAu), improving their conductivity and electrochemical response for Hg²⁺ detection via differential pulse anodic stripping voltammetry (DPASV), achieving a detection limit (LOD) of 10.14 µg L⁻¹. Additionally, adsorption studies demonstrated that the composite exhibited a higher Hg²⁺ removal capacity compared to pure bentonite, fitting the Freundlich model, which suggests adsorption on heterogeneous sites with variable affinities. These findings highlight the potential of the B/MIL-68(Al) composite as a promising material for environmental remediation and the development of sensitive and selective electrochemical sensors for Hg²⁺ detection in aqueous media.