Magnetically active MnFe₂O₄@hydrochar composite as a high-performance adsorbent for amoxicillin removal from water

Water pollution caused by antibiotics is an emerging issue for aquatic ecosystems and public health due to their stability and biological activity. Due to low removal rates of pharmaceuticals from water, conventional wastewater treatment cannot effectively remove antibiotics. Amoxicillin (AMX) is among the most frequently utilized β-lactam antibiotics and can often be detected in water sources, causing antibiotic resistance and environmental threats. Therefore, there is an urgent need for developing effective and economical materials that can be used to remove AMX from water sources. The synthesis of a hybrid MnFe₂O₄@hydrochar nanocomposite was carried out using an in situ coprecipitation technique, and the nanocomposite was characterized, demonstrating its ability to remove AMX from aqueous media. The presence of crystalline phases of MnFe₂O₄ nanoparticles within the hydrochar matrix was evidenced by XRD. SEM and TEM were used to examine nanoparticle dispersions and morphological features. FTIR analysis of the nanocomposite showed peaks indicating the presence of functional groups containing oxygen with metal-oxygen bonds. PSA indicates a broad hydrodynamic particle size distribution, with an average intensity-based diameter of 8487.4 nm, reflecting aggregation of the particles in suspension. This further confirmed the successful synthesis of MnFe₂O₄@hydrochar with abundant functional groups and magnetic properties, which are suitable for efficient adsorption of amoxicillin from aqueous environments. Batch adsorption experiments demonstrated a maximum AMX removal efficiency of 94.7% under the optimized conditions of pH 7. Kinetic analysis, evaluated through the pseudo-first-order and pseudo-second-order kinetic models, showed that the pseudo-first-order model gave a better fit with higher adjusted R ² values (0.95513-0.99665) and lower χ ², SSE and RMSE values. The equilibrium adsorption data were best described by the Langmuir isotherm model with a maximum adsorption capacity (q _max) of 4.99 mg g^-1 (R = 0.9846). Furthermore, the MnFe₂O₄@hydrochar nanocomposite was reused for five regeneration cycles and was easily recovered using an external magnet, which demonstrated that it is a stable, reusable, and environmentally sustainable adsorbent for the removal of antibiotics from contaminated wastewater.