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Adsorption mechanism and influencing factors of selenium under the coexistence of nanoparticles and microplastics

Desalination and Water Treatment 2024
Jianjun Lian, Shun Jiang, Hua-fei Si, Qiongjie Wang, Hongyan Wu, Xin-zhu Hong, Qiao-ping Kong, Bo Chen

Summary

Researchers investigated the adsorption of selenium(VI) onto polystyrene microplastics (PS), nano-titanium dioxide (TiO2), and their combination (PS+TiO2) in aqueous solution, finding that the process followed pseudo-second-order kinetics and the Freundlich isotherm model as an endothermic reaction. Humic acid and Ca2+ promoted selenium adsorption while PO43- inhibited it, with electrostatic adsorption and hydrogen bonding identified as the primary mechanisms for PS.

Polymers

Microplastics (MPs), as a common “vector” of pollutants in the aquatic environment, have a significant impact on the migration and transformation of heavy metals. In order to explore the mechanism and the influencing factors of the adsorption behavior of microplastics (MPs) on selenium (Se) in aqueous solution under the coexistence of nanoparticles, polystyrene microplastics (PS), nano-titanium dioxide particles (TiO2) and their coexisting compounds (PS+TiO2) were used as adsorbents to investigate the adsorption kinetics, isotherms and thermodynamic processes of Se. The effects of pH, humic acid concentration and coexisting ions on the adsorption behavior of Se(VI) were also analyzed. The results showed that the adsorption process of Se(VI) by PS and PS+TiO2 could be well fitted by pseudo-second-order kinetic model and Freundlich isotherm model, and it was an endothermic reaction with increased entropy. The adsorption capacity of Se(VI) by PS, TiO2, and PS+TiO2 were decreased with the increase of solution pH. Humic acid and Ca2+ promoted the adsorption of Se(VI), while PO43- significantly inhibited the adsorption of Se(VI) in the above three systems. The main adsorption mechanism of PS on Se(VI) was electrostatic adsorption and hydrogen bonding. The TiO2 adsorbed on the surface of PS mainly affected the adsorption behavior of PS on Se(VI) through hydrogen bonding.

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