This study evaluated the leaching or release behavior of Bisphenol S (BPS), a common plastic additives, from Polyethersulfone (PES) and Polyphenylsulfone (PPSU) microplastics (MPs) that may derive from commercial products such as baby bottles and battery covers. Ultraviolet (UV) irradiation, temperature and humic acid (HA) were shown to affect the BPS release kinetics, which followed the first-order kinetics. The released BPS underwent immediate photolysis under UV254 irradiation. Under UV365 nm, the highest released concentration of BPS reached 473.6 μg●L-1 at 50°C, 7.9 times that at 35°C and 36.1 times that at 25°C, suggesting that the release kinetics sped up under high solution temperatures. As the HA concentration in water incrementally increased to 50 mg●L-1, the BPS release rate first increased and then declined, probably because HA primarily acted as a photosensitizer at low concentrations to increase light absorption on MPs with HA coating. However, at high HA concentrations, HA may shield the light and scavenge the reactive radicals responsible for the degradation of MPs. Our results also revealed that photo oxidation of MPs led to the breakage of diphenyl ether sulfone group due to the attack of reactive oxygen species (ROS), which contributed to the leaching mechanisms of BPS. Finally, the COMSOL Multi-physics simulation described the BPS release process of different MPs at 25°C and predicted a BPS release of up to 6862.1 μg per gram of MPs within 8000 h, which provides further understandings of the fate of aquatic MPs and secondary micropollutant release.

Leaching of bisphenol S from polyethersulfone (PES) and polyphenylsulfone (PPSU) microplastics during environmental weathering processes

ACS Fall 2021

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