Deacidification and solvent recovery of soybean oil by nanofiltration membranes

Abstract

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 oil-hexane mixture. The effects of transmembrane pressure (Δp=10-20 bar), temperature (T=30-50ºC) and feed oil concentration (Cf=10-35 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 Cf = 25%, Δp = 20 bar, and T = 30°C, achieving a permeate flux of 20.3 Lm-2h-1, 80% oil retention, 58% FFA removal.