Separation of Sunflower Oil from Hexane by Use of Composite Polymeric Membranes

Vegetable oil extraction, as performed today by the oilseed-crushing industry, usually involves solvent extraction with commercial hexane. After this step, the vegetable oil-hexane mixture (miscella) must be treated to separate its components by distillation. If solvent-resistant membranes with good permeation properties can be obtained, membrane separation may replace, or be used in combination with, conventional evaporation. Two tailor-made flat composite membranes, poly(vinylidene fluoride) (PVDF-Si and PVDF-CA) and a commercially available composite membrane (MPF-50), were used to separate a crude sunflower oil-hexane mixture. The effects of temperature, cross-flow velocity (v), transmembrane pressure (Delta p), and feed oil concentration (C (f)) on membrane selectivity and permeation flux were determined. The PVDF-Si membrane achieved the best results, being stable in commercial hexane and having promising permselectivity properties for separation of vegetable oil-hexane miscella. Improved separation performance was obtained at C (f) = 25%, Delta p = 7.8 bar, T = 30 A degrees C, and v = 0.8 m s(-1); a limiting permeate flux of 12 Lm(-2) h(-1) and 46.2% oil retention were achieved. Low membrane fouling was observed under all the experimental conditions studied.