Waste fish oil (WFO) as a potential biodiesel feedstock has a large amount of free fatty acids that should be treated before transesterification for biodiesel production. In the present study, the esterification of free fatty acids of waste fish oil was investigated
experimentally using sulfonated activated carbon as catalyst under
ultrasound irradiation. The best esterification reaction conditions were obtained using
the RSM method. The maximum conversion was observed in the catalyst loading of 11.04 wt%, ultrasonic power of 296.09 W, and methanol to oil molar ratio of 14.85. The experimental esterification conversion under these conditions using ultrasonic irradiation
and conventional mixing was 88% and 56%, respectively. The required reaction time under ultrasonic irradiation compared to conventional mixing method was significantly reduced because of cavitation phenomenon and subsequent increase in the overall mass
transfer and reaction rate. A valid quadratic predictive correlation between the independent variables and target variable was generated using RSM. The obtained mathematical correlation from the data analysis gave a good prediction at high significant level