Surface Hydrophobization of Glass Wool Fibers via Methyltrimethoxysilane Silanization for Polyethylene-Based Microplastic Filtration

Abstract

This study examines the surface modification of glass wool waste for the removal of polyethylene (PE) microplastics from aqueous suspensions. The modification strategy included sequential cleaning, pretreatment with NaOH at various concentrations (0.1, 0.5, and 1 M), and coating with methyltrimethoxysilane (MTMS) at various temperatures (room temperature (RT), 40, and 60 °C). The aim is to modify the surface properties of glass wool and evaluate its potential as a filtration medium. FTIR spectroscopy, scanning electron microscopy, contact angle measurements, and X-ray photoelectron spectroscopy (XPS) showed that alkaline pretreatment increases surface hydroxylation, facilitating effective silanization. The introduction of methyl groups resulted in a transition from hydrophilic to hydrophobic behavior, with contact angles for the modified samples exceeding 130°. XPS results showed an increase in surface carbon content, accompanied by decreases in oxygen and silicon signals, indicating the formation of an organosilane-based layer. Filtration experiments revealed that untreated glass wool exhibited unstable and limited microplastic retention, whereas the modified samples demonstrated significantly improved and more consistent results. Among the conditions tested, the best results were achieved with a combination of 1 M NaOH pretreatment and silanization at 60 °C, yielding low, stable turbidity values. The observed performance is attributed to the combined effect of enhanced hydrophobic interactions, increased surface roughness, and mechanical entrapment within the fibrous structure. Reusability tests showed that the modified material retained its microplastic-removal ability across multiple cycles, although some variability in performance was observed. Overall, this study demonstrates that an MTMS-based surface modification can improve the suitability of waste glass wool as a potential filtration medium for microplastic-containing suspensions.