Pre-treatment of waste cooking oil by combined activated carbon adsorption and acid esterification for biodiesel synthesis via two-stage transesterification

The abundance of waste cooking oil (WCO) makes it an attractive alternative for biodiesel production. To date, research emphasizing biodiesel production via two-step transesterification from WCO, with the pre-treatment of WCO using combined activated carbon adsorption and acid esterification, is limited. Therefore, it is the aim of this study to (1) reduce the free fatty acid of WCO through a combination of pre-treatment using activated carbon and esterification of acid catalysis simultaneously, (2) maximize the production of biodiesel via a two-step transesterification process, and (3) compare the converted biodiesel against the biodiesel standards. The amount of activated carbon and the reaction time for each step of the transesterification process are varied. The combination pre-treatment method has successfully reduced the FFA content in WCO from 9.297% to below 3%. The produced biodiesel is verified as fully converted biodiesel via solubility testing in ethanol. The optimum conditions for biodiesel production are pre-treatment using 5 g of powdered activated carbon and a reaction time for each transesterification step of 30 min. The biodiesel generated under these conditions meets the biodiesel standards. It has the highest content of saturated fatty acid, with the maximum biodiesel yield of 52.78%.