Production of lactobionic acid by BMED process using porous P84 co-polyimide anion exchange membranes

Abstract

Abstract Porous P84 co-polyimide anion exchange membranes are prepared by phase inversion process using isopropanol (IPA) or water as the non-solvent. Membrane area resistances are in the range of 0.7–2.2 Ω cm2, lower than those of commercial anion exchange membrane AMX (2.0–3.5 Ω cm2) and dense P84 membrane (>80 Ω cm2). The ion exchange capacities (IECs) are in the range of 0.6–0.9 mmol/g and the water uptake (WR) values are 100–160%, both of which are higher than those of dense P84 membrane. The porous P84 co-polyimide membranes are utilized in bipolar membrane electrodialysis (BMED) process to produce lactobionic acid (LBA) and NaOH from sodium lactobionic. The pore morphology and IECs influence the output of LBA significantly. Membrane with big tear-like pores shows higher WR value and can produce 0.0555–0.0565 mol/L LBA. Sponge-like pores with IEC of 0.9 mmol/g can yield 0.0724 mol/L LBA after 180 min running under 20 V, while sponge-like pores with IEC of 0.7 mmol/g yield reduced LBA concentration of 0.0593 mol/L, illustrating that higher IEC is in favour of the passage of LB−. The porous P84 membranes have improved efficiency as compared with commercial membrane AMX (0.0451 mol/L) and the dense P84 membrane (merely 0.0162 mol/L) in the production of LBA. Meanwhile, the Na+ leakage through the porous membrane is similar to that of the commercial membrane. Hence, the porous membranes, due to their low resistances, can have high potential for producing organic acid with high molecular weight.