Recovery of acetic acid from simulated acetaldehyde wastewaters: Bipolar membrane electrodialysis processes and membrane selection

The recovery of acetic acid from simulated acetaldehyde wastewaters by BMED (bipolar membrane electrodialysis) process was studied in two steps. Firstly, selection of commercial membranes for acetic acid recovery was investigated through experimentation of diffusion dialysis, determination of membrane stability in acetic acid solution, and measurement of MER (membrane electrical resistance) of monomembranes and EIS (electrochemical impedance spectroscopy) of bipolar membranes. The results showed that Neosepta AMX and CMX membranes are the optimum monomembranes for BMED, and any bipolar membrane is suitable. Secondly, an improved BMED process was performed by changing the current density, adjusting the number of membranes, adding ion exchange resin in the cell, and including an additional cation exchange membrane. With the selected membranes, the optimum experimental condition in the BMED process was achieved, when two pieces of Neosepta AMX membranes and a current density of 10 mA/cm2 was adopted. Furthermore, the addition of a strong acid 001 type cation exchange resin into the feed compartment and a strong base 201 type gel anion exchange resin into the cathode compartment could substantially decrease the voltage drop across the membrane stack and reduce corresponding energy consumption. Finally, a low energy consumption of 0.61 kWh/kg and a relatively high current efficiency of 56.72% were achieved for acetic acid recovery under the optimum condition.