Advanced oxidation-aged microplastics as antibiotics’ supercarriers: from adsorption enhancement to complete gastrointestinal release

Current research often overlooks the polymer-specific aging behaviors of polar (PA) versus non-polar (PP) microplastics during advanced oxidation processes (AOPs). Addressing this gap, this study establishes a synergistic ultraviolet-persulfate (UV-PS) oxidation system to contrast the degradation mechanisms of PA against the natural photodegradation of PP, specifically examining their carrier effects for Doxycycline (DOX). The research has found that the sulfate radicals generated by the UV-PS system can efficiently attack the amide bonds in the PA molecule, resulting in a degradation level of the aging process being several times that of PP. Quantitative analysis reveals that the inherent polarity of the PA framework increases due to the oxidation-induced increase in active sites, resulting in an adsorption capacity for DOX that is 12 times that of non-polar PP and 27 times that of pure UV aging. However, this excellent enrichment ability aggravates its biological risk, and in vitro simulated digestion experiments confirm the "Trojan Horse" effect of aging PA. The adsorbed DOX was not permanently sealed, but the complete release of ~ 100% was achieved under the synergistic action of gastric fluid proton attack (about 70% of burst release) and increased solubility of intestinal bile salts. This study confirms that PS-PA as a high-risk "supercarrier" for antibiotics, highlighting the critical need for differentiated risk assessment for specific polymers in complex water treatment environments.