Deacidification and solvent recovery of soybean oil by nanofiltration membranes

Four tailor-made flat composite membranes of poly(vinylideneflouride) (PVDF) as a support and polydimethylsiloxane (PDMS) or cellulose acetate (CA) as coating layer, and a commercially available composite membrane (Solsep 030306) were used to remove hexane and free fatty acid (FFA) from crude soybean oilhexane mixture. The effects of transmembrane pressure (Delta p=1020 bar), temperature (T=3050 degrees C) and feed oil concentration (Cf=1035 w/w%) on membrane selectivity and permeation flux were determined. The PVDF-12% siloxane composite nanofiltration membrane achieved the best results, being stable in commercial hexane and having promising permselectivity properties to separate soybean oil/hexane miscella. Improved separation performance was obtained at C-f=25%, Delta p=20 bar, and T=30 degrees C, achieving a permeate flux of 20.3 Lm(-2) h(-1), 80% oil retention, 58% FFA removal.