No abstract

This work investigates the use of ceramic membranes with different molecular weight cut-offs (MWCOs: 5, 10 and 20 kDa) to desolventize azeotropic solvent mixtures (ethanol/n-hexane and isopropyl alcohol/n-hexane) from soybean oil/azeotrope micelles. Results show that a decrease in the MWCO of a membrane and an increase in the solvent mass ratio in the mixture resulted in a significant reduction in the permeate flux. The 20 kDa membrane presented the highest permeate flux, 80 and 60 kg/mh for the soybean oil/n-hexane/isopropyl alcohol and soybean oil/n-hexane/ethanol azeotropes, respectively, for an oil to solvent ratio of 1:3 (w/w). The highest oil retention was found using the n-hexane/isopropyl alcohol azeotrope, around 25% in the membrane with the lowest MWCO, that is, 5 kDa. It is shown that the azeotropic mixtures provided intermediate characteristics compared to the original pure solvent behavior.

Separation of refined soybean oil/n-hexane miscellas was studied using different commercial ultra-and nanofiltration membranes, with cutoffs in the range of 1 to 5 kDa and salt rejection higher than 97% (MgSO 4). Commercial soybean oil and n-hexane miscellas with 1:3 and 1:1 mass ratios were permeated in a dead-end module. The effects of the feed pressure (2-25 bar) on oil and n-hexane fluxes and rejection were investigated. Oil rejection ranged from negative values to 30.8%, soybean oil flux from 28.9 to 617.8 g/m-2 h-1 and n-hexane flux from 8.5 to 1,078.5 g m-2 h-1. Membrane fouling was observed at all experimental conditions studied. The membrane separation process has proven to be a promising alternative to solvent recovery in soybean oil extraction.