<p>Microplastics (MPs, &lt; 5 mm) serve as critical vectors for hydrophobic pollutants, yet their role in transporting brominated flame retardants remains poorly understood. This study systematically investigated the adsorption of tetrabromobisphenol A (TBBPA), a pervasive brominated contaminant, onto polyethylene microplastics (PEMPs) under environmentally relevant conditions. Key findings revealed that TBBPA adsorption was maximized at a low PEMPs dosage (0.2 g/L), neutral pH (7.5), and 283 K, with equilibrium capacities of 1.32, 0.98, and 0.69 mg/g for 0.2, 0.4, and 0.6 g/L PEMPs, respectively. Thermodynamic analysis confirmed a spontaneous and exothermic (ΔG &lt; 0, ΔH &lt; 0) adsorption process dominated by physical interactions. Aging treatments (UV irradiation) significantly enhanced adsorption capacity (1.79-fold increase) by generating surface cracks and oxygen-containing groups, which elevated the specific surface area from 0.386 to 0.404 m²/g. Mass transfer mechanisms involved both film diffusion (Boyd model) and intra-particle diffusion, with the latter being rate-limiting. Notably, high ionic strength in simulated seawater (Na⁺, Ca²⁺ competition) and fulvic acid in freshwater reduced TBBPA adsorption by 55% and 70%, respectively. These disparities imply that PEMPs migrating from rivers to oceans may continuously accumulate TBBPA, amplifying ecological risks through long-range transport and localized contaminant release. Our findings underscore the necessity to regulate TBBPA-laden plastic waste and reevaluate microplastic-mediated contaminant fluxes in aquatic systems.</p> Graphical Abstract <p></p>