Purification of biodiesel using adsorbents and saturated salt solution

Abstract

This research studied the purification of biodiesel using adsorbents and saturated salt solution. The biodiesel was synthesized by the transesterification of palm oil with methanol at 6:1 molar ratio of methanol:oil, 1 %wt of sodium hydroxide and reaction temperature of 60C for 1.50 hours. The crude biodiesel was subjected to wash with three types of saturated salt solution including sodium chloride, potassium chloride and ferric sulfate. It was found that the saturated salt solution of sodium chloride gave the best result for removal of soap and the optimum conditions were 1:1 ratio of crude biodiesel and saturated salt solution of sodium chloride, one time of washing for 30 seconds at room temperature. By washing crude biodiesel with saturated salt solution of sodium chloride, the soap content could be reduced from 3500 ppm to 28 ppm. Then, the biodiesel was further purified by using adsorbents including silica gel, activated carbon and activated clay. This process gave the quality of biodiesel as analogous to water washing process and values of acid number, viscosity, flash point and free and total glycerin passed the specification of biodiesel standard.