Polystyrene waste-xanthan gum membranes: modification, preparation and evaluation as polyelectrolyte membranes

Abstract

The essential function of the proton exchange membrane in fuel cells is to enable the passage of proton from the anode to the cathode. In this work, new composite membranes consisting of sulfonated polystyrene and xanthan gum were prepared in dependance on the proportions of xanthan gum in the membranes. The solution-casting technique was employed for preparing the membranes. To assess the properties of the membranes the Fourier Transform Infrared spectroscopy and Scanning Electron Microscopy were used to analyze the membrane’s structure, Thermogravimetric analysis to evaluate its thermal stability, and examined its mechanical assets along with ethanol and water uptake. The composite membranes showed satisfactory thermal properties, maintaining their integrity up to 300 °C according to thermograms. One of the most noteworthy findings was the notable increase in the ion exchange capacity of the composite sulfonated polystyrene and xanthan gum membranes in contrast to the pure sulfonated polystyrene. The ion exchange capacity of the sulfonated polystyrene and xanthan gum composite with 0.05% xanthan reached 1.15 meq/g, surpassing the worth reported for Nafion 117 membranes (0.91 meq/g). The proton conductivity values undergo a noticeable increase, progressing from 0.12 S/cm reaching 0.18 S/cm for xanthan (0.06%). This achievement surpasses the documented figure for Nafion-117, which stands at 0.084 S/cm. The resulting sulfonated polystyrene and xanthan gum composite demonstrated favorable film-forming and structural properties, making it a promising option for polyelectrolyte membranes, with the added advantage of being cost-effective and utilizing waste materials.