Influence of Physical and Chemical Activation of Coconut Shell Applied to Reduce Free Fatty Acids of Used Cooking Oil in Biodiesel Plant

Abstract

This research was conducted to compare the characteristics of activated carbon that synthesized via different methods, physical and chemical activation. It was applied to reduce Free Fatty Acids (FFA) in used cooking oil which will be used in the manufacture of biodiesel. Physical activation was carried out by heating dried coconut shell in a tube furnace at 900°C in N2 gas flowing, by varied the holding time; 2 hours, 3 hours, and 4 hours. Meanwhile, chemical activation was conducted using phosphoric acid solution with various concentrations: 9%, 10%, and 11%. The BET (Brunauer-Emmett-Teller) test was processed to determine the surface area of ​​the activated carbon. The FFA test was conducted to determine the FFA content in treated used cooking oil. The activated carbon with chemical activation has a surface area of ​​260.57 m2/gram, 323.55 m2/gram, and 162.21 m2/gram at concentrations of phosphoric acid 9%, 10%, and 11%, respectively. Meanwhile, for physical activation, the surface area were 278.58 m2/gram, 448.368 m2/gram, and 444.74 m2/gram with variations in heating holding time of 2 hours, 3 hours, and 4 hours, respectively. The lowest levels of FFA are found in cooking oil with a phosphoric acid concentration of 11%, which is 1.505%. The higher the concentration of chemical activator, the greater the adsorption power of an activated carbon. The lowest levels of fatty acids are found in cooking oil with a holding time of 4 hours, which is 1.805%. FFA (Free Faty Acid) test results show that the longer the heating holding time, the better the activated carbon will be.