Defective iron-based metal-organic framework derived from discarded plastics for rapid and efficient adsorptive removal of methylmercury.

Metal-organic framework (MOF) has gained widespread attention as potential adsorbents for the removal of methylmercury (CHHg). This study synthesizes a defective MIL-88A(Fe) (D-MIL-88A(Fe)) from waste polyethylene terephthalate (PET). Structural characterization via XRD, SEM, N adsorption-desorption, and FT-IR confirmed the crystalline MIL-88A(Fe) framework with hierarchical porosity (0.6 nm micropores and 1.95 nm mesopores) and retained carboxyl/Fe-O functional groups, enhancing mass transfer and adsorption accessibility. Adsorption equilibrium studies revealed 93.4% CHHg removal with a maximum adsorption capacity of 4.91 mg/g (Langmuir model), indicating monolayer adsorption dominated by physical interactions. Kinetic analysis demonstrated ultrafast removal (90% within 500 min, k = 0.0076 min), aligning with pseudo-first-order kinetics. The material exhibited robust regeneration, retaining > 90% efficiency after five cycles. By utilizing discarded PET as a low-cost ligand source, this work not only reduces MOF production costs but also offers a dual solution for CHHg⁺-contaminated wastewater remediation and plastic waste value assessment.