Removal of textile microplastic fibers from water by photo-Fenton oxidation

Microplastic fibers (MFs) from synthetic garments pose a growing environmental challenge, as their release during domestic laundry cycles and persistence in wastewater have facilitated their dispersion in aquatic ecosystems, as well as their accumulation along the food chain. In this context, advanced oxidation processes (AOPs), capable of breaking down refractory organic pollutants, emerge as a promising alternative to mitigate this issue. In this study, the effectiveness of photo-Fenton to remove PET MFs was evaluated by quantifying their weight loss. Physical and chemical changes in the fibers were followed using scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (ATR-FTIR). Total organic carbon (TOC) of the effluents obtained after the photo-Fenton treatment was also measured to determine the degree of mineralization achieved. Moreover, the effect of hydrogen peroxide concentration and reaction time was investigated. A starting H₂O₂ concentration of 500 mg L^-1 was identified as optimal, yielding 40.6 % mass loss of PET MFs after 4 h. Under these conditions, 16 h tests resulted in 99 % mass loss, with high mineralization yields (TOC < 0.5 mg L^-1) . The degradation was successfully described by a cylindrical Shrinking Core Model (R² > 0.99). Progressive cavity and hole formation, and the appearance of oxygenated functionalities, were also observed upon treatment. Finally, the degradation of MFs fragments was examined to evaluate the role of morphology, and the effect of real fibers obtained from a washing cycle was also assessed.