Comparative Adsorption of PET and PS Nanoplastics onto Graphene Oxide–Cellulose and Graphene Oxide–Chitosan Composites: Thermodynamic, Kinetic, and Isotherm Studies

Polyethylene terephthalate (PET) and polystyrene (PS) nanoplastics are major aquatic contaminants due to their high persistence, mobility, and potential ecological impacts. In this study, PET–NPs and PS–NPs were prepared by nanoprecipitation, and the adsorption of both types of nanoplastics by graphene oxide–chitosan (GO–CS), graphene oxide–microcrystalline cellulose 50µm (GO–MCC50µm), and graphene oxide–microcrystalline cellulose 90µm (GO–MCC90µm) composites was systematically investigated. The structural and physical properties of the materials were characterized using transmission electron microscopy (TEM), pHpzc analysis, Dynamic Light Scattering (DLS), zeta potential, and X-ray photoelectron spectroscopy (XPS). Batch adsorption experiments evaluated the effects of pH, contact time, initial concentration, and temperature on adsorption efficiency, while the adsorption mechanism was analyzed through kinetic, isotherm, and thermodynamic studies. The maximum Langmuir adsorption capacities for PS–NPs were 13.60, 12.59, and 11.19 mg·g−1 for GO–CS, GO–MCC50µm, and GO–MCC90µm composites, respectively. The maximum adsorption capacities for PET–NPs were 56.17, 33.33, and 23.20 mg·g−1 for GO–CS, GO–MCC50µm, and GO–MCC90µm composites, respectively. This study provides new insights into the effects of adsorbent surface chemistry, particle size, and nanoplastic morphology on adsorption processes, highlighting graphene oxide–polysaccharide composites as promising eco-friendly materials for nanoplastic removal from aqueous media.