Bipolar membrane electrodialysis for efficient production of ferulic acid in alcohol/water mixed solvent

Abstract

In this study, bipolar membrane electrodialysis (BMED) was proposed to produce ferulic acid, as a kind of poorly water-soluble organic acids, in the alcohol/water mixed solvent system. Among the mixed solvents of EtOH/H2O, n-PrOH/H2O, and i-PrOH/H2O, high solubilities of both ferulic acid and sodium ferulate were achieved in the solvent of 50 v/v% n-PrOH/H2O. Meanwhile, the ionization of the produced ferulic acid was relatively low in the above system due to a feasible pKa of ferulic acid, resulting in a high purity of the product. Furthermore, a low current density of 10 mA/cm2 was recommended for the BMED process due to the stable membrane performance (no obvious membrane fouling observed) and low energy consumption. Moreover, the ionization of ferulic acid can be further lowered due to the solvation effects at a high feed concentration (0.5 mol/L, nearly saturated concentration). The low ionization of ferulic acid means that the migration of H+ ions instead of Na+ ions through cation exchange membrane can be suppressed efficiently, resulting in a high concentration of the product. Under the optimized parameters, the purity of ferulic acid, the current efficiency and energy consumption were 99.5%, 99.4%, and 0.30 kWh/kg ferulic acid, respectively. Also, the process economy estimation shows a low total process cost of 0.49 $/kg ferulic acid. Therefore, the BMED process exhibits an excellent economic competitiveness for efficient production of ferulic acid.