Electrospun Recycled EPS/CNT Membranes Modified with an Imidazolium Silane: Processing, Wettability and Gravity-Driven Oil–Water Separation

The conversion of expanded polystyrene (EPS) packaging waste into functional fibrous membranes offers a route for extending its use beyond conventional packaging applications. In this study, recycled EPS was electrospun with multi-walled carbon nanotubes (MWCNTs) and 1-methyl-3-[3-(triethoxysilyl)propyl]imidazolium chloride (MCPTS) to investigate the influence of modifier concentration on processing behavior and membrane properties. MWCNT content was fixed at 0.5 wt%, while MCPTS was varied from 1 to 9 wt% relative to EPS. MWCNT incorporation increased solution viscosity from 0.185 to 0.310 Pa·s. MCPTS produced a nonmonotonic response, with viscosity decreasing at 1–3 wt% before increasing to 0.340 Pa·s at 9 wt%. Scanning electron microscopy (SEM) showed interconnected fibrous deposits, and spectra obtained by Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR) showed the characteristic spectral features of polystyrene. Apparent water contact angle (WCA) increased from 125.27 ± 0.57° for neat EPS to 148.77 ± 0.85° for EPS/CNT/MCPTS-9. In three gravity-driven tests using distinct membranes and an initial mixture of 5.0 mL motor oil and 5.0 mL water, EPS/CNT/MCPTS-9 achieved a mean volumetric oil recovery of 94.0 ± 0.4% and a mean batch flux of 15.26 ± 0.06 L m−2 h−1 over 30 min. MCPTS-containing specimens retained 97.46–99.34% of their initial mass after the specified 20 s direct flame exposure. These findings identify MCPTS loading as an effective formulation variable for modifying recycled EPS membrane wettability and demonstrate a laboratory-scale route linking plastic-waste valorization with gravity-driven oil–water separation.