Liquid-liquid extraction of sinapic acid from a mustard seed by-product using a hollow fiber membrane contactor

Abstract

This study focuses on the recovery of sinapic acid using liquid–liquid extraction (LLE) assisted by a hollow fiber membrane contactor (HFMC) from an aqueous feed obtained through the hydrolysis of mustard bran. The hydrolyste contains 230 ± 36 mg/L of sinapic acid, with a natural pH of 4. A screening was performed with solvents of different chemical nature (alcohol, ester, ketone, ether, cyclic ether). Data showed that all the solvents tested gave an extraction efficiency of more than 80 % for pH < 5, whereas the initial concentration of sinapic acid in the aqueous feed has little impact on the extraction efficiency. Four of the solvents tested were selected for use in the HFMC: two volatile (CPME, MIBK) and two non-volatile (octanol, octyl acetate). The solubility of the volatile solvents in the feed phase was found to be an important factor to consider in evaluating the HFMC (2.6 ± 0.5 % and 1.07 ± 0.05 % v/v with MIBK and CPME, respectively). Mass transfer coefficients with volatile solvents (25 ± 1 x10-6 and 15.3 ± 0.5 x10-6 m/s for MIBK and CPME, respectively) exceeded those of non-volatile solvents (4.1 ± 0.2 x10-6 and 4.5 ± 0.5 x10-6 for octanol and octyl acetate, respectively) by 4- to 6-fold. Extraction was intensified by increasing the initial concentration of sinapic acid in the feed phase and by increasing the feed-to-solvent ratio. CPME demonstrated optimal recovery efficiency at a phase ratio of 8:1 (v/v), yielding 0.9 g of sinapic acid per liter of CPME used.