Microplastics and disposable face masks as “Trojan Horse” for radionuclides pollution in water bodies – A review with emphasis on the involved interactions

This review article focuses on the interaction of radionuclides (americium-241, uranium-232, radium-226, neptunium-237, cesium-137, iodine-125, strontium-90, thorium-234, and potassium-40) with different microplastics (polyamide (PN6), polyethylene (PE), polyvinyl chloride (PVC)) and single-use surgical face (SSF) masks. It has been shown that microplastics (MPs) and SSF masks can act as carriers of radionuclides thus helping the toxic pollutants to migrate and concentrate into the environment and possibly enter the food chain. High values of adsorption affinity were reported for various polymers, with the adsorption partition coefficient reaching up 2670 (L/kg) in the case of U-232 adsorption on polyamide (PN6). Generally, the type and the particle size of MPs, the solution pH, and the nature of the aquatic system (de-ionized water, groundwater, and seawater) are found to be significant factors in radionuclides’ adsorption onto MPs. The mechanism of adsorption depends on various parameters and the formation of outer- or inner-sphere complexes between the radionuclide and specific sites/functional groups on MPs surface. Desorption of the radionuclides is also an important aspect since for instance, a high desorption rate was noticed in low pH (pH<4) and using complexing agents such as EDTA. Future work should focus on the investigation of the interaction of MPs and radionuclides using real wastewater, column studies, and multi-component systems. Biofilms’ growth on the MPs surface and studying the interaction of biofilm-coated microplastics with radionuclides would also be of particular interest.