Adsorption Behavior and Mechanism of Uranium on Polyethylene Terephthalate Microplastics in the Water Environment

As a kind of emerging contaminant, microplastics (MPs) widely exist in environments around the world and may carry other chemical pollutants. Besides, radioactive pollutants in water are getting more and more attention due to the discharge of wastewater from the Fukushima nuclear power plant. Among them, Uranium is an important fuel substance in nuclear power plants, which has toxicity of radioactivity and heavy metals. In order to research the interaction between MPs and uranium in water, batch experiments were conducted to study the adsorption behavior of radioactive heavy metal uranium (U(VI)) by ordinary PET MPs. The results showed that the adsorption amount of U(VI) onto PET increased (69.02%) after aging. The kinetic adsorption behavior of U(VI) could be explained by pseudo-second-order and Elovich models, and the isothermal adsorption behavior of U(VI) was well fitted by Langmuir and Sips models. The adsorption amounts were in the order of aged PET > virgin PET and ultrapure water > simulated freshwater. Besides, external diffusion and internal diffusion were included in the adsorption process. The adsorption capacity was affected by pH and salinity. The adsorption mechanisms included pore filling, electrostatic interaction, and surface complexation. The properties of MPs and the environment are the main factors affecting the adsorption process. The study elucidates the adsorption mechanism of U(VI) onto MPs in ultrapure water and simulated freshwater, aiming to assess the potential risk to aquatic environments where natural MPs and uranium ions coexist.

Graphical Abstract