Oil extraction from Calophyllum inophyllum L. seeds through ultrasonication with n-hexane and petroleum ether as solvents

Several renewable energy initiatives are being established worldwide as the demand for oil rises and the fossil-based resource depletes. In this study, the seeds of bitaog (Calophyllum inophyllum L.), a non-edible feedstock, were utilized as biomass in extracting oil. Oil extraction via ultrasonic-assisted solvent extraction (UASE), set at 35 µm resonance amplitude, was initially conducted using two solvents: n-hexane (n) and petroleum ethers (HPe). The best volumes of each solvent with the highest oil yields were used in the subsequent experiment and as a solvent ratio (n-HPe) variable. The effects of solvent ratio (n-HPe) and the extraction time on oil yield were considered in the design of experiments using Design Expert software’s response surface methodology. The oil extractions via UASE resulted in a yield of 60 ± 1.17% at a 1.38:1 n-HPe ratio and at 40 min extraction time. The oil was dark green with a density of 0.92 g/mL at room temperature, a pH value of 6.21, and a high heating value of 41.90 MJ/kg. The FTIR and GC–MS analyses showed the presence of carboxylic acids and ester carbonyl functional groups. The percentages of fatty acids present in the oil were stearic 14.57, palmitic 13.18, myristic 0.02, lauric 0.17, margaric 0.1, arachidic 0.67, oleic 45.83, palmitoleic 0.2, eicosenoic 0.2, linoleic 24.96, and linolenic 0.1. The unsaturated fatty acid of the extracted oil from C. inophyllum L. seeds was 71.29% of the total fatty acid, indicating that the oil can be converted to biodiesel. The remaining 28.71% is composed of saturated fatty acids. The oil yield via UASE extraction with n-HPe was 60% better compared to 56% and 30% for Soxhlet and traditional solvent extraction by stirring, respectively. The overall result illustrates the efficacy of ultrasonication in boosting oil extraction efficiency.