Magnetic Trinity Platform Based on Renewable Humic Acid for Closed-Loop Management of Antibiotics via Adsorption-Detection-Catalytic Degradation Synergy

The ecological and life-health risks posed by excessive humic acid (HA) accumulation and persistent antibiotic contamination are urgent challenges requiring synergistic solutions. Herein, based on the amide reactions between the numerous carboxyl functional groups of biobased HA and the hollow mesoporous Fe3O4–NH2 nanoparticles, the multifunctional magnetic nanocomposite (Fe3O4@HA) was developed to overcome these challenges. Based on the synergistic advantages of the components, a green and economically Fe3O4@HA-based magnetic dispersive solid-phase extraction method was first constructed for the enrichment and detection of fluoroquinolone antibiotics (FQs) in three complex matrices. Satisfactory recovery rates were shown over a wide concentration range (0.005–50 μg·L–1). Particularly, thanks to the protective and well-dispersed nature provided by HA, Fe3O4@HA exhibits long-lasting and excellent degradation ability for antibiotics, while effectively reducing the leakage of Fe ions. Notably, the spent Fe3O4@HA serves dual environmental benefits, preventing secondary pollution through magnetic recovery and acting as a nutrient-rich soil amendment. This “three-birds-with-one-stone” strategy provides a feasible solution for eliminating the hazards of excessive HA, establishes a sustainable platform for long-term antibiotic monitoring and removal, and realizes agricultural reuse as well as the circular economy. This work is of great significance for promoting the rational use of renewable resources and sustainable development.