Sustainable adsorption-photodegradation of doripenem using MIL-100(Fe)@TiO₂ metal-organic framework composite

The massive and uncontrolled use of antibiotics, especially doripenem, has led to increased contamination in aquatic environments. This compound is difficult to remove using conventional methods and may trigger bacterial resistance. This study aims to synthesize and evaluate MIL-100(Fe)@TiO₂ composite materials as hybrid adsorbents-photocatalysts for sustainable removal of doripenem. MIL-100(Fe) and MIL-100(Fe)@TiO₂ were synthesized by solvothermal methods and characterized by SEM-EDX, XRD, FTIR, nitrogen sorption, and DRS-Tauc to reveal their structures, crystallinity, porosity, and optical properties. Isotherm tests showed that doripenem adsorption followed the Langmuir model, with maximum capacities of 221.57 mg/g (MIL-100(Fe)) and 169.55 mg/g (MIL-100(Fe)@TiO₂) at 30 °C. The adsorption kinetics followed a pseudo-second-order model, while the photodegradation followed first-order kinetics with the rate constant (kapp) increasing with increasing temperature. The measured pH_pzc values of 4.5 for MIL-100(Fe) and 6.3 for MIL-100(Fe)@TiO₂ indicated that, under the experimental condition of pH 7.0, doripenem adsorption was governed mainly by hydrogen bonding, π-π interactions, and specific surface interactions rather than by dominant electrostatic attraction. The integration of TiO₂ significantly enhanced the photocatalytic activity through charge separation e^-/h⁺ and ROS formation. Five-cycle reusability tests showed higher stability of MIL-100(Fe)@TiO₂ (efficiency decreased from ~ 95 to 88%), compared to pure MIL-100(Fe) (~ 84 to 70%). These results confirmed that the MIL-100(Fe)@TiO₂ composite has the potential to serve as a sustainable, multifunctional material for the remediation of pharmaceutical waste containing antibiotics.