Cork waste-based adsorbents for glycerol removal from biodiesel: a sustainable alternative to wet washing

This is the authors' abstract. We don't add key points for this paper.

This work aims to use activated carbon from industrial cork waste as a novel method for glycerol removal from crude biodiesel produced using waste cooking oil, combining two residues to obtain both high-quality biodiesel and highly adsorbent activated carbon. The study first optimizes the biodiesel production conditions, achieving the highest ester yield at 30 °C, with a 1:9 oil-to-ethanol molar ratio, 1 wt.% NaOH catalyst, and a reaction time of 1 h. Additionally, activated carbons were prepared and characterized from cork waste, showing significantly higher BET surface areas than the raw material. The most promising cork-based materials were then applied to optimize glycerol removal from crude biodiesel through adsorption. A preliminary study identified milled raw cork and its KOH-activated carbon (SBET = 2057 m2/g) as the most effective. Kinetic and equilibrium studies demonstrated that optimal glycerol removal was achieved after 6 h at 25 °C using 2 wt.% of KOH-activated cork-based adsorbent, resulting in 88% glycerol removal and a final glycerol content of 0.017 wt.%. These findings demonstrate that cork waste-derived activated carbon is highly effective for biodiesel purification, successfully meeting the quality specifications required by European Standard EN 14214:2012+A2:2019 and offering an innovative solution for waste valorization and sustainable fuel production.