Impact of polyimide on the recycling of waste expanded polystyrene into flat-sheet filtration membrane

Abstract

Expanded polystyrene (EPS) is one of major plastic pollutants which toxicity increased when exposed to UV irradiation. In this study, the feasibility of upcycling waste EPS (WEPS), which originates from food packaging, into a flat-sheet filtration membrane was explored. The membrane was fabricated using the wet-phase inversion method, with polyimide serving as a blending additive varied from 2 to 8 wt.%. Characterization was carried out using water contact angle measurements, SEM, and UV–Vis spectrophotometry. The experimental results indicated that all WEPS/PI membranes demonstrated microplastic rejection rates exceeding 80%, and they exhibited greater uniformity compared to the pristine WEPS membrane. Furthermore, protein rejection improved with the concentration of PI. The addition of 8 wt.% polyimide led to a 240% increase in protein rejection, with all membranes having hydrophilic surface. The SEM images revealed that the introduction of polyimide altered the membrane’s structure, enhancing its filtration properties by modifying the finger-like structure of the membrane. The addition of 8% polyimide to the WEPS dope solution decreased both pore size and porosity to the least value observed, while also enhancing the antifouling property by 67%. The experimental findings indicate that the WEPS/PI membrane holds significant promise to solve challenges of waste EPS accumulation, as well as offering sustainable solutions for addressing microplastic pollution by recycling the waste EPS into high-end filtration membrane.