Deacidification of Used Cooking Oil: Modeling and Validation of Ethanolic Extraction in a Liquid-Liquid Film Contactor

Large quantities of used cooking oil (UCO) are produced globally, primarily in densely populated urban centers. Although UCO is highly heterogeneous due to degradation during cooking, it still contains a significant fraction of triacylglycerols (TG) that could be used as raw materials in oleochemical biorefineries. A major challenge in reintegrating this residue into productive cycles is the presence of free fatty acids (FFA), which can affect subsequent catalytic or enzymatic transformations. Conventional processes for FFA removal are energy-intensive, require alkaline feedstocks, and generate problematic residues. To overcome these issues, alcoholic extraction of FFA is considered a promising pretreatment for UCO, enabling the extraction of FFA for subsequent esterification. In this regard, liquid-liquid film contactors (LLFC) have shown potential to intensify FFA extraction because they operate under mild conditions and at laminar flow regime, reducing energy consumption and enhancing productivity. This work presents the modeling and validation of a FFA extraction process suitable for deacidifying UCO using a LLFC with ethanol as a solvent. Experimental data were used to fit model parameters, which were optimized using a genetic algorithm. The validated LLFC model revealed that increasing the UCO mass flow rate and the ethanol-to-UCO ratio enhanced FFA mass transfer. Furthermore, a cascade configuration of three LLFCs was able to reduce the FFA content in UCO to 0.9 wt.%. It is anticipated that this technology will enable the pretreatment of UCO for further transformation into value-added oleochemicals and facilitate the exploitation of recovered FFA via subsequent ethanolic esterification.