Characterization of polymeric membranes used in vegetable oil/organic solvents separation

The characterization of commercial membranes used in the separation of refined soybean oil/n-butane and n-hexane mixtures was studied in this work using different commercial ultrafiltration membranes, with cut-offs ranging from 1 to 5 kDa. The membranes were used in the permeation of refined soybean oil/pressurized n-butane mixtures at 1:3 (w/w) and 1:1 (w/w) mass ratios in a continuous tangential flow module and in the permeation of soybean oil/n-hexane mixtures in a dead-end flow module. The membranes were characterized by DSC (differential scanning calorimetry), FTIR (Fourier transform spectroscopy), contact angle measurement (Goniometer), zeta potential and SEM-EDS (scanning electron microscopy with X-ray microanalysis) aiming to better understanding the phenomena involved in the permeation process. Some membranes did not show any measurable permeation flux for refined soybean oil/n-butane mixtures, which may be related to their low hydrophobicity. Contact angle and zeta potential measurements showed that the membrane surface hydrophilicity changes after permeation. FTIR spectra showed that the membranes were fouled with oil even after washing with solvent. Results obtained in this work showed that permeation caused few modifications on the surfaces of the tested membranes at the experimental conditions investigated. It is shown that these polymeric membranes can be used in the separation of vegetable oils/organic solvents effectively without degradations.

Research highlights▶ The hydrophobicity of membranes’ surface was increased after permeation. ▶ Fouling could not be totally removed even after several washings with solvent. ▶ None of the membranes suffered morphological changes due to oil permeation.