Environmental Fate of 4-Methylbenzylidene Camphor: Adsorption Behavior on Textile-Derived Microplastic Fibers in Wastewater and Surface Water Systems

This study investigates the adsorption behavior of 4-methylbenzylidene camphor (4-MBC), a persistent ultraviolet filter, onto microplastic fibers (MPFs) released from domestic textiles, under environmentally relevant conditions. Two types of MPFs were used: MPF A, a heterogeneous blend of synthetic and natural fibers, and MPF B, a uniform polyester source. Adsorption experiments were conducted in municipal wastewater, Danube River surface water, and laundry effluent. Kinetic data best fit the pseudo-second-order model (R² > 0.95), and the Elovich model indicated chemisorption involving heterogeneous binding sites. MPF A exhibited superior adsorption capacities (qₑ = 85.4-90.1 µg/g) compared to MPF B (58.8-66.8 µg/g). Langmuir isotherms yielded maximum adsorption capacities of 204.9 µg/g for MPF A and 116.7 µg/g for MPF B (R² = 0.929-0.977), while D-R isotherm energies (12.0-21.7 kJ/mol) confirmed specific interactions, such as π-π stacking and hydrogen bonding. Adsorption efficiency was highest in municipal wastewater (total organic carbon-TOC = 13.12 mg/L, electrical conductivity-EC = 1152 µS/cm), followed by laundry and surface waters. These findings emphasize the critical role of polymer composition and matrix complexity in pollutant transport, suggesting MPFs are effective transporters of hydrophobic micropollutants in aquatic systems.