This study evaluated the most suitable pulse mode (pulse ON–OFF pattern) for transesterification of
waste cooking oil(WCO) using sodium hydroxide. Pulse sonication effect was investigated using ethanol,
methanol, and ethanol–methanol mixtures to convert waste cooking oil into biodiesel. The importance
of duty cycle (pulse-mode operation) and the role of reaction temperature during the conversion process
were discussed. A maximum biodiesel yield of 99% was obtained for a pulse ON–OFF combination of 7 s–
2 s at 150 W power output, and the optimum reaction conditions of 9:1 alcohol-to-oil molar ratio (50%-
ethanol, 50%-methanol), 1 wt.% of NaOH, and 1.5 min reaction time.
2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights
reserved.