Surface mechanistic insights into the simultaneous adsorptive removal of zidovudine and lamivudine from wastewater using waste-derived magnetic carbon nanostructures

The purpose of this study was to synthesize magnetic waste-derived carbon nanostructured material (Fe ₃ O ₄ @WDCNM) nanocomposite from potato peels and use it as an efficient adsorbent for the simultaneous removal of zidovudine (AZT) and lamivudine (3TC) in wastewater. The Fe ₃ O ₄ , WDCNM and Fe ₃ O ₄ @WDCNM materials were characterized using transmission electron microscopy (TEM); scanning electron microscopy - energy dispersive x-ray spectroscopy (SEM-EDS); fourier transform infrared spectroscopy (FTIR); X-ray diffraction (XRD); and brunauer–emmett–teller (BET) to determine their elemental composition, functional groups, structural morphology, and surface properties. The Fe ₃ O ₄ @WDCNM nanocomposite exhibited Fe, C, and O elements with C−O, O−H, =CH ₂ , C−C, and Fe−O significant functional groups. The nanocomposite also showed a crystalline nature. To assess the adsorption performance of the nanocomposite under varying conditions, including pH, adsorbent mass, and sample volume, batch experiments were conducted. The filtrates were analyzed using high-performance liquid chromatography with DAD. Under optimal conditions, the adsorption isotherm data fit the Langmuir model, indicating that AZT and 3TC adsorbed to form a monolayer on the homogeneous surface of the Fe ₃ O ₄ @WDCNM nanocomposite. Moreover, the mean free energies obtained from the Dubinin-Radushkevich (D-R) model were < 8 kJ/mol ^-1 , indicating that physisorption was the dominant interaction mechanism. Kinetic data best fit a pseudo-first-order (PFO) model, further supporting physisorption as the primary interaction mechanism. Thermodynamic experimental data confirmed the process to be spontaneous with ΔS°=73.02 J/mol K, ΔH°=18.93 kJ/mol, and ΔG° values ranging from -5.41 to -2.73 kJ/mol for 3TC; and ΔS°=34.53 J/mol K, ΔH°=6.10 kJ/mol, and ΔG° values ranging from -5.30 to -4.09 kJ/mol for AZT. The maximum removal efficiencies of 3TC and AZT were 96.65% and 96.42%, respectively, for real water samples.