The removal of metals from edible oil by a membrane extraction procedure 355

Edible oils may contain traces of metals. In oil refining procedures these metals have to be removed to guarantee oxidatively stable products. In this study we present a hollow fiber membrane extraction system for the removal of metals from an oil. Several extraction liquids were tested, of which an ammonia solution gives the best distribution coefficient (m=11.7). From mass transfer calculation it follows that the resistance to mass transfer in the extraction phase in the fiber wall can be neglected compared to the resistances in the oil phase inside the fibers and the extraction phase outside the fibers. A cost evaluation shows that such a membrane extraction can be profitable in conventional refining if more than 1.5% bleaching earth has to be added in surplus to remove metals.