Reusable adsorbent of magnetite in mesoporous carbon for antibiotic removal

This study aims to evaluate the feasibility of an innovative reusable adsorbent through adsorption-degradation sequence for antibiotic removal from water. The magnetite/mesoporous carbon adsorbent was prepared using a two-step method of (i) in situ impregnation of magnetite precursor during resorcinol formaldehyde polymerization and (ii) pyrolysis at elevated temperature (800 °C). XRD spectra confirmed that magnetite (Fe₃O₄) was the only iron oxide species present in the adsorbent, and thermogravimetric analysis revealed that its content was 10 wt%. Nitrogen sorption analysis showed that Fe₃O₄/carbon features a high fraction of mesopores (> 80 vol.%) and a remarkable specific surface area value (246 m² g⁻¹), outstanding properties for water treatment. The performance of the adsorbent was examined in the uptake of three relevant antibiotics. The maximum adsorption uptakes were ca. 76 mg g⁻¹, ca. 70 mg g⁻¹, and ca. 44 mg g⁻¹ for metronidazole, sulfamethoxazole, and ciprofloxacin, respectively. All adsorption curves were successfully fitted with Langmuir equilibrium model. The regeneration of adsorbent was carried out using Fenton oxidation under ambient conditions. After three consecutive runs of adsorption-regeneration, Fe₃O₄/carbon maintained its performance almost unchanged (up to 95% of its adsorption capacity), which highlights the high reusability of the adsorbent.