Synergistic integration of Fe-MOF and biomass-derived activated carbon for enhanced ciprofloxacin adsorption: experimental insights and DFT-based mechanistic elucidation

This study reports the synthesis of an iron-based metal–organic framework (Fe-MOF) and its composite (Fe-MOF@AC) with activated carbon (AC). AC was derived from agricultural waste (mango leaves) to effectively remove ciprofloxacin (CIP), a hazardous contaminant in water. Both Fe-MOF and its composite were successfully characterized using advanced spectroscopic techniques. FTIR analysis confirmed the successful formation of both adsorbents due to the presence of the functional group (Fe–O) peak at 650 cm⁻¹, and XRD confirmed the degree of crystallinity. FESEM and EDX revealed the surface morphology and elemental composition, respectively, of the prepared materials. The composite exhibited superior adsorption performance (573.6 mg g⁻¹, 95.6%) compared with pristine Fe-MOF (368.2 mg g⁻¹, 61.4%), attributed to its enhanced surface area and synergistic functional group interactions. Maximum adsorption was observed at pH = 6, and the pseudo-second-order (PSO) model fitted the best (R² = 0.99), indicating chemisorption at active sites. Isothermal analysis revealed the Langmuir adsorption behavior of the composite (R² = 0.97), suggesting monolayer adsorption on homogeneous surfaces. Thermodynamic analysis indicated a spontaneous and exothermic process. DFT calculations provided qualitative electronic-level insights that were consistent with the Langmuir/PSO interpretation, suggesting favorable Fe–O–CIP interactions at pH 6. These results complemented but did not independently validate the experimental and mechanistic analysis. Reusability tests demonstrated minimal efficiency loss over five cycles, highlighting the composite's potential as a cheap and sustainable adsorbent for antibiotic-contaminated wastewater treatment.