Synthesis, characterization and performance of graphene–magnetite nanocomposite for adsorption of sulfamethoxazole, ciprofloxacin, chloramphenicol and tetracycline from aqueous solution

Abstract

The presence of emerging contaminants (EC), such as antibiotics for human and veterinary medicine, in aquatic environments has raised concerns regarding environmental impacts and public health. Given the inefficiency of conventional treatment systems alternative materials for the removal of these compounds are required. In this study, a magnetic heterostructure of graphene oxide functionalized with magnetite (OGD-MAG) was synthesized from the oxidation of commercial graphite (GRF) via a modified Hummers method, followed by coprecipitation with Fe₃O₄. The material was characterized by XRD, BET, SEM-EDS, and determination of the point of zero charge (pH_ZPC), showing an increase in surface area (up to 118 m² g⁻¹) and the presence of magnetic phases. The adsorption efficiency of OGD-MAG was evaluated for the removal of the antibiotics sulfamethoxazole (SMX), ciprofloxacin (CIP), chloramphenicol (CFC), and tetracycline (TCT) in batch experiments at pH 5 and 9. The results indicated removal efficiencies between from 25% and 80%, with emphasis on TCT (80% at pH 5), attributed to π-π stacking, hydrogen bonding, and complexation with Fe²⁺/Fe³⁺ in magnetite. The influence of pH and the surface charge of the material proved to be relevant for adsorption, considering the acid-base and structural characteristics of the antibiotics. OGD–MAG showed consistent antibiotic removal of SMX, CIP, CFC, and TCT, with no statistically significant differences between pH 5 and 9, and with magnetic recovery at the end of the tests. These data indicate potential applicability, to be confirmed by regeneration assays and comparative studies.