Synergistic adsorption and catalytic degradation of antibiotics in aquaculture effluents by iron-modified zeolite: Unveiling the adsorption-then-degradation dual-function mechanism

• Fe-zeolite boosted CIP, OTC, and SMX adsorption by 42%, 78%, and 143%. • NF+PDS system achieved 89.7% CIP removal via 1 O 2 dominant catalysis. • Removal follows pseudo-second-order kinetics and Langmuir isotherm models. • ntegrated "adsorption-then-degradation" ensures antibiotic mineralization. • Fe-zeolite shows high stability and performance across varied salinities. With the rapid growth of aquaculture, antibiotic residues in wastewater pose a global environmental challenge. Traditional treatment methods are often inefficient, making the search for cost-effective alternatives essential. This study explores iron-modified natural zeolite (Fe-zeolite) for removing antibiotics like ciprofloxacin (CIP), oxytetracycline (OTC), and sulfamethoxazole (SMX). .Iron modification enhanced the adsorption capacity of natural zeolite, increasing antibiotic removal by 41.6% for CIP, 78.4% for OTC, and 143% for SMX relative to the unmodified material. Kinetic and isotherm analyses showed that the adsorption behavior was better described by the pseudo-second-order and Langmuir models. Combined with FTIR characterization, competitive adsorption behavior, and matrix-dependent selectivity, the results suggest that specific surface interactions, particularly surface complexation on Fe-related domains, likely play an important role, although electrostatic interaction and ion exchange may also contribute. Beyond adsorption, Fe-zeolite activated peroxydisulfate (PDS) for catalytic degradation. In the NF/PDS system, the residual CIP concentration decreased to approximately 10.28% within 60 min under the optimized conditions, indicating efficient catalytic degradation following adsorption enrichment. The material enabled an integrated "adsorption-then-degradation" process, surface iron species promoted pollutant transformation after interfacial enrichment. Environmental factors such as salinity and natural organic matter (NOM) affect performance—salinity hinders CIP and OTC removal, while NOM enhances adsorption through bridging with Fe(oxyhydr)oxide domains. Reusability tests further showed that the material retained appreciable activity over three cycles, although a noticeable decline in performance was observed, highlighting both the practical potential and the stability limitations of this low-cost natural mineral-based system.