A hybrid ultrafiltration/nanofiltration/pervaporation membrane process for intensifying the refining of crude canola oil and solvent recovery

Abstract

Abstract Conventional edible oil processing methods with all their drawbacks have not changed over the past decades. Therefore, the main novelty of this study is to develop a three-stage hybrid membrane process to remove phospholipids, pigments, and solvent from the crude canola oil miscella by combining ultrafiltration, nanofiltration, and pervaporation processes. For the first and second stages, ultrafiltration and nanofiltration membranes were prepared by phase inversion method using polyethersulfone as polymer, and triethylene glycol and polyethylene glycol as additives. Pervaporation for the first time was conducted for solvent recovery, using commercial polydimethylsiloxane composite membranes with different active layer thicknesses. Almost full rejection of phospholipids (>99.9%) was obtained by addition of both additives, and approximately remained constant by changing the additive concentration. A 91.49% reduction in the color of crude oil with a flux of 1.17 L/m2.h was obtained at the end of the bleaching stage. The solvent recovery by the pervaporation process with the polydimethylsiloxane composite membranes showed the 100% oil rejection with acceptable flux. The proposed hybrid ultrafiltration/nanofiltration/pervaporation membrane process showed an excellent performance in terms of permeation flux, phospholipids rejection, and color reduction for refining crude canola oil and solvent recovery processes and meets the criteria of process intensification.