Production of N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid by BMED process using porous P84 co-polyimide membranes

The P84 co-polyimide membranes are utilized in bipolar membrane electrodialysis (BMED) process to produce N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES). The porous membranes can decrease the transport resistance of HEPES− ions and yield high recovery ratio and current efficiency, while the dense membrane is unsuitable for BMED. The output of HEPES is increased significantly if the membranes have finger- or tear-like pores, as well as higher ion exchange capacity. The HEPES− recovery ratios are 52.3-61.6% after running 6 h under 40 V, which are higher than that of membrane CJMA-3 (46.5%). The current efficiency can reach up to 86.1% and the energy consumption is only 3.92 kWh/kg by using the optimal porous membrane M-1, which are better than membrane CJMA-3 (65.5%, 5.15 kWh/kg). Hence, the porous membranes have high potential for producing organic acid with high molecular weight.