Simultaneous improvement in solvent permeability and deacidification of soybean oil by nanofiltration

In this paper, soybean oil deacidification and hexane removal using laboratory scale solvent resistance nanofiltration membranes based technique is presented. Composite nanofiltration membranes made of different polymers poly(vinylideneflouride) (PVDF), polydimethylsiloxane (SI), polycarbonate (PC), and glycerol were tested to remove the hexane and free fatty acid (FFA) from soybean oil/hexane miscella (oil feed solution 10, 25, and 35% w/w) at 20 bar of transmembrane pressure and 30 °C, in a dead-end filtration set up. All membranes tested showed low fouling phenomena and high stability in the presence of hexane throughout the membrane pre-treatment and permeation procedure. The PVDF-10SI-1PC membrane showed the best performance achieving a miscella permeability of L_m = 6.8 × 10^-6 L (h m bar)^-1, oil and FFA sieving efficiency of β_(oil) = 0.21(80% of oil rejection) and β_FFA = 2.43 (27% of FFA removal), respectively, at oil feed concentration of 25%. Apart from these specific properties, the PVDF-10SI-1PC membrane presented excellent mechanical and chemical resistances and low reversible fouling. The results demonstrate that membrane technology can attain a high efficiency in the simultaneous solvent recovery and deacidification of oil/hexane miscella commonly processed in the soybean oil industry.