Submitted to: Biofuels, Bioproducts, & Biorefining (Biofpr)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2021
Publication Date: 6/9/2021
Citation: Singh, R., Dien, B.S., Singh, V. 2021. Response surface methodology guided adsorption and recovery of free fatty acids from oil using resin. Biofuels, Bioproducts, & Biorefining (Biofpr). 15(5): 1485-1495. https://doi.org/10.1002/bbb.2255.
DOI: https://doi.org/10.1002/bbb.2255

Interpretive Summary: Biodiesel as its name implies is a sustainable substitute for fossil diesel that is suitable for use in trucks and heavy equipment and for blending with fossil diesel. The U.S. produces 2.5 billion gallons per year (2020), mostly from soy oil. Its advantages compared to fossil diesel are that it is much less polluting, supports farmers, and promises to create a market for messy fat, vegetable oil, and grease wastes. However, using less pristine sources of oils is challenging. Oils are comprised of two chemicals: fatty acids and glycerol. Oil in which even 3% has broken down to its original fatty acids cannot be used to make biodiesel, which is frequently the case with waste cooking oil. Here a new technology is described that not only removes the fatty acids from the oil, but also recovers these acids for other uses. The new technology involves the use of a solid resin that specifically removes fatty acids from oils. In lay terms, the resin acts like a dish towel that specially adsorbs fatty acids, and like a towel the resin can be cleaned (e.g., dried) and reused at least 3 times. This research should be of interest to the food industry, who generate used kitchen oil, and manufacturers of biodiesel.

Technical Abstract: The presence of free fatty acids interferes with conversion of plant oils to biodiesel. Four, strong and weak base resins were evaluated for free fatty acids (FFA) removal from oil. Amberlite FPA 51 showed the highest adsorption capacity of FFA. A resin concentration above 3% could enable a higher % FFA adsorption. The adsorption process fitted a pseudo-first-order kinetic model and achieved equilibrium in approximately 8 h to. A full factorial design was used to optimize the resin and FFA concentrations at a fixed temperature (40°C). A ratio of resin to fatty acid concentrations above 1.875 was sufficient for 70% adsorption and the amount adsorbed continued to increase with further added resin. A two-step washing of resin using hexane and ethanol recovered approximately 67.55 ± 4.05 % of the initially added fatty acid. The used resin was regenerated with 5 % NaOH and re-used for a minimum of 3 consecutive cycles. However, the adsorption capacity diminished to 75% of the initial cycle in cycles 2 and 3. Thus, the work presents a resin-based process for deacidification of oil to reduce fatty acid content of oil for biodiesel production.