Size-controlled synthesis of polystyrene nanoparticles via concentration swing method and their size dependent sorption behavior

In this study, polystyrene (PS) nanoparticles with precisely controlled sizes and concentrations were synthesized using a concentration swing (CS) method without surface modification. By adjusting the concentration and volume of the CS-PS solution during the solvent shifting process, particle size and concentration were independently controlled. The resulting PS nanoparticles exhibited high reproducibility and stable dispersion without aggregation. Pollutant carrier properties of plastics with various particle sizes were evaluated using methylene blue as a model compound through sorption isotherms. As particle size decreased, the maximum sorption capacity per unit mass increased due to the larger specific surface area. However, the sorption capacity normalized by surface area was significantly higher in bulk plastics, showing nearly 1000-fold greater capacity compared to nanoplastics. Consequently, the difference in mass-based sorption capacity between nanoscale and bulk-scale plastics was limited to approximately a fourfold increase. These results challenge the prevailing notion that nanoparticles inherently pose significantly greater environmental risks due to their large surface area. This study highlights the need for comprehensive environmental management strategies that address plastic particles across a broad range of sizes.