Valorization of soybean oil residue through advanced technology of graphene oxide modified membranes for tocopherol recovery

Abstract Soybean oil deodourization distillate (SODD) is a source of tocopherols used to produce vitamin E, in which α‐tocopherol is the isomer with higher biological activity and value‐added for the food industry. Hence, the aim of the present study was to modify the membrane surface with sulphonic groups, polyethyleneimine, and graphene oxide nanoparticles functionalized with tannic acid to recover SODD α‐tocopherol. First, the SODD saponification step was conducted followed by a liquid–liquid separation, which performed a pre‐concentration of α‐tocopherol approximately 28 times. The unsaponifiable material was dried and diluted in hexane, obtaining the feed solution for the membrane filtration processes. HPLC‐UV/DAD analysis showed that the modified membrane containing 1.12 mg of graphene oxide and 4.50 mg of tannic acid (M3) allowed to recover 82.00% of α‐tocopherol in the concentrate (14.16 wt.% of α‐tocopherol). From the characterizations of the modified membrane, it was observed that M3 presented hydrophobic properties and was able to be reused in two filtration cycles with a 64.39% flow recovery rate and a 71.96% recovery of α‐tocopherol. The results showed that the membrane modification with graphene oxide is a compelling methodology with low energy consumption and is eco‐friendly for the recovery and purification of α‐tocopherol from SODD.