A green approach: Utilizing untreated pine pollen grains as a natural biosorbent for microplastic removal from water systems

Microplastics (MPs) are widespread pollutants that pose significant threats to aquatic ecosystems and human health. This study evaluates the potential of untreated pine (Pinus eldarica) pollen grains as an eco-friendly, chemical-free biosorbent for removing MPs from water. The heterogeneous and porous surface of pine pollen, enriched with functional groups, enables effective adsorption of MPs through electrostatic and hydrophobic interactions. Untreated pine pollen achieved a maximum removal efficiency of 66.2±2.54% for polystyrene (PS) MPs at a pollen concentration of 240 mg/L and with higher efficiencies of 87% for PVC (Polyvinyl Chloride) and 95.2% for PET (Polyethylene Terephthalate), reflecting differences in polymer hydrophobicity and density. Adsorption followed the Freundlich isotherm model (R2=0.977), suggesting heterogeneous binding sites, and removal efficiency for PS MPs was size-dependent, decreasing from approximately 78% for 75-150 μm particles to approximately 63% for 250-500 μm particles. Alkaline pH enhanced PS MP removal to 77.6±3.39%, while the presence of humic acid (15 mg/L) reduced efficiency to approximately 56%, and competitive anions, particularly H₂PO₄- (5 mM), decreased it further to 45.2±1.7%. Surfactants significantly improved MP removal; for instance, non-ionic Tween20 increased efficiency from the baseline 66.2% to approximately 98%, and cationic CTAB to approximately 94%. Pine pollen showed strong reusability, maintaining over 50% removal efficiency for PS MPs after four adsorption-desorption cycles. It also maintained effectiveness in real water samples, achieving approximately 59% removal in lake water, though performance decreased to around 45% in wastewater. These findings highlight untreated pine pollen as a natural, cost-effective, and sustainable alternative to chemical agents for mitigating MP pollution in aquatic environments.