Study on adsorption and desorption behaviors of microplastics toward antibiotics mediated by hydrodynamic conditions

Abstract

[Objective] To investigate the adsorption and desorption behaviors and associated environmental risks of polyethylene(PE) microplastics toward four antibiotics(SDZ, SMX, NOF, OFL) under hydrodynamic conditions. [Methods] A horizontal oscillating grid tank was employed to simulate actual aquatic environments. Adsorption-desorption experiments were performed to analyze the adsorption and desorption characteristics of PE toward antibiotics. Additionally, the effects of microplastic concentration and turbulence intensity on the adsorption process were examined. [Results] The adsorption process reached equilibrium after 40 hours. Kinetic model fitting result indicated that the adsorption was mainly governed by chemisorption and jointly controlled by internal and external diffusion, while the desorption process was dominated by physical desorption. An increase in PE concentration ultimately reduced the unit adsorption capacity by about 30%, and a gradual increase in turbulence intensity led to an approximate 10% increase in adsorption capacity. [Conclusion] Both PE concentration and hydrodynamic turbulence intensity affect the adsorption capacity of PE: High PE concentration leads to particle aggregation, thereby reducing adsorption efficiency. Strong turbulence conditions enhance adsorption by accelerating molecular diffusion and particle dispersion. The desorption process exhibits potential chemical interactions, which may increase the environmental transfer risk of antibiotics. The dual role mechanism of PE as a carrier of antibiotics under hydrodynamic conditions is revealed, providing a theoretical basis for assessing the ecological risks of combined pollution.

Keywords

microplastics / antibiotics / hydrodynamic conditions / adsorption / desorption / influencing factors