Optimized ultrasonic-assisted oil extraction and biodiesel production from the seeds of Maesopsis eminii

Abstract

In this study, the central composite design of response surface methodology was employed as a design of an experiment to optimize the extraction of oil from Maesopsis eminii seeds using ultrasonic-assisted solvent extraction (UASE). The most appropriate values of operating variables such as extraction time and n-hexane to biomass ratio and its effects on oil yield were analyzed. The 7:1 n-hexane-to-biomass ratio (140 mL n-hexane/20 g seed powder) and the 20 min extraction time were found as optimum conditions to get an oil yield of 47.86 ± 0.09 %. Oil’s chemical characteristics and compositions include yellowish color, 0.90 g/mL density, 5.40 pH, 47.9 mm2/s kinematic viscosity, 39.63 MJ/kg high heating value, >200 °C flashpoint, and 0.36 ± 0.05 % free fatty acid content. The analyses of Fourier Transform Infrared Radiation (FTIR) and Gas Chromatography-Mass Spectrophotometry (GC–MS) revealed that oil from the M. eminii seeds has esters and looked-for fatty acids signifying its potential for biodiesel production. Major fatty acids include oleic (36.7 %), linoleic (24.3 %) and stearic (22.6 %) with minor components shared by palmitic (10.2 %), arachidic (2.6 %), y-linolenic (1.5 %), cis-11-eicosenoic (1.5 %) and behenic (0.5 %). The exploratory oil refining via UASE and transesterification resulted in 84.6 % biodiesel yield indicating its high conversion rate and demonstrating its potential as a feedstock for green diesel production. Hence, the coming of the liquid biofuel from the unexplored non-edible M. eminii seeds would benefit humanity and the environment as this would reduce the use of petroleum-based fuels that are known for producing much air pollution in the atmosphere.