Novel phenylalanine-modified magnetic ferroferric oxide nanoparticles for ciprofloxacin removal from aqueous solution

The pollution of natural water bodies by pharmaceutical compounds has led to serious concerns regarding ecological and public health safety. In this study, novel recyclable phenylalanine (Phe)-modified magnetic ferroferric oxide nanoparticles (Fe₃O₄@Phe NPs) were successfully synthesized for the first time using a simple one-pot method to remove ciprofloxacin (CIP) from aqueous solutions. Fe₃O₄ and Fe₃O₄@Phe NPs were characterized using different techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Turbiscan analysis and vibrating-sample magnetometry (VSM). The results show that Fe₃O₄ NPs are fully encapsulated by Phe, exhibiting an average diameter of 200 nm, a high specific surface area (35.79 m² g^-1), good dispersion and superparamagnetic properties. The effects of Phe content, initial pH and ionic strength on CIP adsorption onto Fe₃O₄ and Fe₃O₄@Phe NPs are investigated. The maximal adsorption capacity of CIP onto Fe₃O₄@Phe NPs is determined to be 49.27 mg g^-1. The adsorption kinetics and isotherms show that the adsorption process follows the pseudo-second-order-kinetic and Langmuir isotherm models, respectively. This indicates that the adsorption involves a rate-controlled monolayer chemisorption process. The regeneration experiments show that Fe₃O₄ and Fe₃O₄@Phe NPs exhibit good reusability for CIP adsorption. Adsorption mechanisms include electrostatic interactions, hydrogen bonding, hydrophobicity and π-π interactions. This study presents a promising strategy for the design and preparation of multifunctional nanoparticles to remove contaminants from the environment.