UV-water aging endows biodegradable poly (butylene adipate-co-terephthalate) (PBAT), unlike polystyrene, with abundant polar groups that markedly enhance its interaction with tetracycline and subsequent sorption, highlighting distinct antibiotic retention and release behavior for biodegradable versus conventional microplastics.

Microplastics (MPs) experience photo-induced surface modification in sunlit waters, yet the implications for contaminant binding differ fundamentally for biodegradable and conventional MPs. To simulate submerged aging, biodegradable poly (butylene adipate-co-terephthalate) (PBAT) and nondegradable polystyrene (PS) are exposed to ultraviolet A irradiation and river water for 30 days. Aged PBAT shows significant surface oxidation, including a 16% decrease in carbonyl index, a reversal of ζ-potential from slightly positive to −50 mV, and an increase in tetracycline (TC) sorption kinetics. In contrast, the nondegradable analog (PS) displays only modest oxidation (ΔCI ≈ 6%), a smaller charge shift, and a lower capacity increase (q _m ≈ 33 mg g⁻¹). Maximum TC uptake occurs at pH ≈ 7, whereas modest salinity increments (0.010–0.0105 M) attenuate retention, confirming the controlling influence of electrostatic forces. Fluorescence quenching (86% vs 74% for PBAT and PS) and Akaike information criterion/Bayesian information criterion-ranked model fits indicate that hydrogen bonding and electrostatic attraction dominate on the biodegradable surface, whereas π–π and hydrophobic interactions on the PS. This work confirms that submerged photo-oxidation turns biodegradable MPs into reactive, salinity-sensitive antibiotic sinks while conventional MPs remain inert transport vectors, emphasizing the need for MP-specific risk assessment and antibiotic pollution mitigation in aquatic settings.