Pre-treatment and extraction of oil from Chlorella vulgaris microalgae by ultrasound

The oil extraction step from the microalgae is considered to be the most important and essential step in the production of biodiesel. In this research, the effect of time on the ultrasound method was optimized in the pre-processing and extraction stages. Chlorella vulgaris microalgae pretreatment was carried out with methods of pretreatment with hot water and ultrasound radiation in water solvent. Extraction of oil was done by two methods of solvent extraction by ultrasound and Bligh and Dyer at certain times and specific solvent ratios, and its fatty acid profile was investigated. The results showed that pre-treatment of C. vulgaris microalgae had an effect on extraction efficiency and increased extraction rate. Also, using ultrasonic waves accelerates the process of mass and energy transfer, decreases the operating temperature and the size of the equipment. Using hot water with 15 minutes of ultrasound radiation in pre-treatment and ultrasound extraction in 50 minutes increased extraction efficiency by 22.96%, which were 18.63% more than no pre-treatment and Bligh and Dyer. Investigating the composition and amount of fatty acids of C. vulgaris showed that ultrasound time has a significant positive effect on the amount of unsaturated fatty acids extraction.