Efficient extraction of polystyrene nanoplastics from water using an ionic liquid†

Nanoplastics (NPs) are garnering attention as an emerging type of plastic pollutant capable of causing detrimental effects on terrestrial, marine, and human health. Traditional water treatment methodologies, such as coagulation and flocculation, have shown limited effectiveness in eliminating different types of NPs. Ionic liquid-based liquid–liquid extraction (IL-LLE) stands out as a promising separation technique with notable potential for the effective removal of NPs in water treatment. In the current investigation, we present the use of the IL 1-octyl-3-methylimidazolium bistriflimide ([C₈mim][Tf₂N]) for the removal of three distinct polystyrene nanoplastics (PSNPs), including commercial PSNPs (∼70 nm), PSNPs synthesized with sodium dodecyl sulfate (SDS) (∼168 nm), and PSNPs synthesized with polyvinylpyrrolidone (PVP) (∼190 nm). The mass transfer behavior and mechanism of the removal process were examined under different pH, ionic strength, and water matrices to cover realistic conditions. The extraction procedure demonstrated an efficacy of >99% in removing commercial PSNPs and >95% for synthesized PSNPs. Finally, the performance of IL on the removal of PSNPs in real freshwater (Lake Tuscaloosa, Alabama, USA) was examined, demonstrating a removal rate >94% for CPS, 86% for PS-SDS, and 79% for PS-PVP, confirming the effectiveness of the treatment under real-world conditions.