Abstract
Extraction of polyunsaturated fatty acid ethyl esters (PUFA-Et) from aqueous silver nitrate solution was studied using supercritical (SC) ethane and ethylene and the extraction behaviors were compared with those of SC-CO2 extraction. For the SC-ethane extraction, PUFA esters were extracted faster than in SC-CO2 extraction. The concentration change for extracted PUFA esters was similar to that of CO2, and efficient DHA-Et separation was realized. The results of SC-ethylene extraction showed that the extraction rate was the fastest in the three kinds of supercritical fluids used and that SC-ethylene had little selectivity for the PUFA esters. This is because ethylene tends to form π-complex with Ag ion competitively.
Modeling of the semi-batch extraction process was carried out utilizing a simple mass balance relationship. All experimental extraction curves were successfully represented by this model with optimizing of apparent equilibrium constants.
