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Adsorption behaviors of atrazine and imidacloprid on high temperature aged microplastics: Mechanism and influencing factors
Summary
Researchers investigated how aged polyethylene microplastics — the kind that have been weathered by UV light and heat in the environment — adsorb common agricultural pesticides, finding that microplastics can accumulate pesticides like atrazine and imidacloprid at high concentrations through hydrophobic (water-avoiding) interactions. This "Trojan horse" effect means microplastics can carry and potentially concentrate pesticides as they move through water environments.
The migration behavior of pesticides in water under the coexistence of microplastics is not sufficiently known. In this study, the effects of main environmental factors on the adsorption characteristics of atrazine (ATZ) and imidacloprid (IMD) on aged polyethylene (PE) microplastics in aqueous solution were investigated, and the adsorption mechanisms were also discussed. The results showed that the pseudo-first-order and Freundlich models fitted the adsorption kinetics and isotherms of ATZ and IMD on PE well. The adsorption capacity of PE toward ATZ and IMD could be reached to as high as 350.40 μg/g and 327.75 μg/g, respectively, at 298 K and pH 7. Moreover, the adsorption process of the two pesticides was a spontaneous and endothermic process. The removal amount of ATZ by PE was highest at pH= 3, and the removal rate decreased with the increasing of pH; while the removal rate of IMD by PE was best under neutral conditions. The increase in HA concentration reduced the adsorption capacity of ATZ (4.79–57.2 %) and IMD (3.94–30.02 %). Besides, the main adsorption mechanism of ATZ and IMD was hydrophobic interaction. This study provides a theoretical reference for investigating the effects of aging microplastics on the migration behavior of different pesticides in water environments. • The adsorption of ATZ and IMD on PE followed the pseudo-first-order kinetic model. • The adsorption of ATZ and IMD on PE conformed to the Friedrich isotherm model. • The adsorption of the two pesticides was a spontaneous and endothermic process. • The increase in HA concentration reduced the adsorption capacity of ATZ and IMD. • The main adsorption mechanism of ATZ and IMD was hydrophobic interaction.