Cosolvent effect on the recovery of triglycerides from used frying oil with modified supercritical ethane

• Modified ethane may recover valuable undegraded triglycerides from used frying oil.
• A previous work with pure ethane resulted in 85% recovery of triglycerides.
• Triglycerides recovery in this work is increased up to 95% using modified ethane.
• Polar percentage of oily fraction recovered with pure ethane in former work was 17%.
• With modified ethane the undesired polar percentage is reduced from 17 to 11%.

Supercritical extraction with modified ethane was used for the separation of triglycerides from waste frying oil in a semicontinuous system. Cosolvents used to modify pure solvent behavior were ethanol, methanol, acetone, and hexane. They were selected because of their different capacity to form hydrogen bonds. The effect of cosolvent type on extraction yield and oil solubility followed the order: ethanol > methanol > acetone > hexane. However, their efficiency to separate triglycerides from polar species showed the opposite trend: ethanol < methanol < acetone < hexane. Regarding the effect of cosolvent concentration, yields and solute solubilities increased with increasing values of the variable. However, the separation efficiency was almost independent of cosolvent concentration. Finally, the extraction process was further analyzed in a continuous packed column. At the best conditions 95% of triglycerides were recovered, being the polar content of the extract only slightly higher than of the fresh oil.

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