Magnetic Fe3O4@Chitosan Carbon Microbeads: Removal of Doxycycline from Aqueous Solutions through a Fixed Bed via Sequential Adsorption and Heterogeneous Fenton-Like Regeneration

The adsorptive removal of antibiotics from aqueous solutions is recognized as the most suitable approach due to its easy operation, low cost, nontoxic properties, and high efficiency. However, the conventional regeneration of saturated adsorbents is an expensive and time-consuming process in practical wastewater treatment. Herein, a scalable adsorbent of magnetic Fe3O4@chitosan carbon microbeads (MCM) was successfully prepared by embedding Fe3O4 nanoparticles into chitosan hydrogel via an alkali gelation-thermal cracking process. The application of MCM composites for the adsorptive removal of doxycycline (DC) was evaluated using a fixed-bed column. The results showed that pH, initial concentration, flow rate, and bed depth are found to be important factors to control the adsorption capacity of DC. The Thomas and Yoon-Nelson models showed a good agreement with the experimental data and could be applied for the prediction of the fixed-bed column properties and breakthrough curves. More importantly, the saturated fixed bed can be easily recycled by H2O2 which shows excellent reusability for the removal of doxycycline. Thus, the combination of the adsorption advantage of chitosan carbon with catalytic properties of magnetic Fe3O4 nanoparticles might provide a new tool for addressing water treatment challenges.