Removal of tetracycline from water using ethylenediamine-modified magnetic chitosan

In this work, the magnetic chitosan nanoparticles were prepared by in-situ co-precipitation method and then modified by glutaraldehyde and ethylenediamine. The effect dose of crosslinking agents for adsorbent preparation on tetracycline (TC) adsorption was investigated. The experiment results showed that the modified chitosan (EMMCS-G) had the best adsorption performance, which was more than twice that of raw magnetic chitosan. EMMCS-G was characterized by SEM, TEM, VSM, FTIR, XRD and XPS. The effects of experimental parameters such as time, temperature, pH, adsorbent dosage and Cu2+ on TC adsorption by EMMCS-G were discussed. The result indicated that the optimal pH was 6.5. Under the conditions of an initial TC concentration of 50 mg/L and an EMMCS-G dosage of 50 mg, the removal rate reached an impressive 94%. The isotherm and kinetic studies of adsorption process illustrated that adsorption of TC onto EMMCS corresponded to Freundlich isotherm and pseudo-second-order kinetic models. The maximum adsorption capacity was 84 mg/g. Thermodynamic analysis revealed that adsorption process was both endothermic and spontaneous. The regeneration experiment suggested that the adsorbent possessed excellent reusability for further use. Moreover, the adsorption mechanisms of TC onto EMMCS-G mainly involved pore filling, π-π interactions, hydrogen bonding and electrostatic attraction.