Biodiesel dry purification with sugarcane bagasse

• Biodiesel purification using sugarcane bagasse as adsorbent.
• Addition of 0.5 wt% of sugarcane bagasse removed 40% of the glycerine from crude biodiesel.
• Sugarcane bagasse and Magnesol presented similar results for biodiesel purification.
• The maximum predicted adsorption is of 88.86 mg g−1.
• The adsorption process is controlled by chemisorption.

Biodiesel is an important renewable fuel that can be used as a substitute of petro diesel. Downstream processes represent a major concern in biodiesel production due to cost and because it is time consuming. The application of dry purification processes emerges as a promising alternative for biodiesel purification, but the applied adsorbent material should ensure biodiesel quality and process efficiency. Here we propose the application of sugarcane bagasse as a low cost adsorbent material for biodiesel treatment. Sugarcane bagasse was used in three different forms: raw sugarcane bagasse (as received), steam explosion pre-treated bagasse and bagasse ash. Equilibrium adsorption data showed that the addition of only 0.5 wt% of sugarcane bagasse removed 40% of the glycerine of the crude biodiesel and produced a purified biodiesel with less than 0.02 wt% of glycerine. The adjustment of equilibrium data to isotherm models showed that glycerine adsorption on sugarcane bagasse is not fully Langmuirian due to the heterogeneous surface of the adsorbent and the non-uniform distribution of heat of adsorption. Sugarcane bagasse proves to be a promising adsorbent for glycerine, with the maximum predicted glycerine adsorption of 88.86 mg g−1. The kinetic data of glycerine adsorption in raw sugarcane bagasse could be adjusted to the pseudo-second order model, which indicates that the rate-limiting step may be chemisorption. Kinetic data highlighted the fast nature of the process, since the glycerine removal was greater than 70% after only 10 min of adsorption process. Sugarcane bagasse presented results for biodiesel purification similar to those for the wet washing process or with Magnesol®. Thus, dry purification with sugarcane bagasse is a suitable alternative for biodiesel treatment in a low cost and efficient process.