Preparation of Mangosteen Shell-Derived Activated Carbon Via KOH Activation for Adsorptive Refining of Crude Biodiesel

Mangosteen shell-derived activated carbons (ACs) were prepared by potassium hydroxide (KOH) activation for refining crude biodiesel derived from the transesterification of waste cooking oil and methanol via an alkali catalyst. Effects of the KOH/char (w/w) ratio (0.50-1.50), activation temperature (500-900 A degrees C), adsorption time (15-180 min) and dosage of activated carbon (3-11 g/L) on the efficiency of the adsorptive refining of biodiesel were explored. The AC prepared at a KOH/char (w/w) ratio of 1.25 at 800 A degrees C exhibited the best ability to remove impurities contained in the crude biodiesel, and enhanced the purity of the biodiesel by up to 97.18 wt% at a dosage of 9 g/L and 120 min adsorption time. This was better than that refined by the conventional wet washing method (96.03 wt%). Equilibrium adsorption data fitted well with Freundlich isotherms, and the adsorption mechanism was controlled by the transport of impurities from the bulk solution to the surface of the AC.