Removal of impurities from waste oil using eggshell and its active carbon

Waste oil is an inexpensive source for biodiesel production, but the high amount of impurities present (free fatty acids, oxidation products) impedes its practical application. The aim of this work is to assess the purification efficiency of the adsorption process with eggshell and its active carbon. Carbonization of eggshell was done at 200 ºC for 4 hours. For activation of the resultant carbon, sulfuric acid was used, and finally, thermal activation (600 ºC, 1 hour) was performed. The quality parameters of waste oil (free fatty acid, peroxide value, color indices, viscosity, and density) were determined before and after the adsorption process. The results showed an improvement pattern in the measured parameters after the adsorption. Reduction in peroxide and acid value were 71.7% and 51.72%, respectively. Also, produced biodiesel from treated waste oil has better quality indices including acidity, viscosity and specific gravity. Biodiesel yield also increased up to 40 percent.