Study on Adsorption Behaviors of Sulfadiazine on Degradable Microplastics
Microplastics can serve as new vectors for the adsorption of antibiotics in water,which may affect their environ-ment behaviors and toxic effects.However,most studies have focused on the nondegradable microplastics,and the research on the adsorption behaviors of antibiotics on different types of degradable microplastics is less.In this study,polylactic acid(PLA)and polybutylene terephthalate(PBAT)were selected as representatives of degradable microplastics due to their wide application.Sulfadiazine was used as the target antibiotic to systematically investigate its adsorption characteristics and mecha-nisms on the two microplastics.The results showed that the adsorption of sulfadiazine on PLA and PBAT reached equilibrium in 24 h,and their equilibrium adsorption amounts were 0.746 mg/g and 0.716 mg/g,respectively.The adsorption kinetics were well fitted by the pseudo-second-order kinetic model for both microplastics,indicating the adsorption process was affected by many factors,of which liquid film diffusion was the main rate-limiting step.The adsorption isotherms of sulfadiazine on PLA and PBAT were in accordance with the Freundlich model,indicating the heterogeneous muti-layer adsorption processes.The D-R model further suggested that physical adsorption was dominant.The effects of different pH values on the adsorption processes by the two microplastics were almost consistent.With the increase of pH in the range of 4～9,the adsorption capaci-ty decreased.The molecular structure,specific surface area and functional groups of the two microplastics were the major factors affecting their adsorption capacities and mechanisms.Van Der Waals interactions and hydrogen bond were responsible for sulfadiazine adsorption on PLA,while PBAT interacted with sulfadiazine mainly through Van Der Waals interactions,hydrogen bond and π-π interaction.These findings will be helpful to deeply understand the interactions between degradable microplastics and coexisting antibiotics in aqueous environments and reveal the ability of degradable microplastics as a vector for antibiotics,which will provide a theoretical basis for better evaluating the environmental risks of these two pollutants.
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维普
