Investigation of succinic acid recovery from aqueous solution and fermentation broth using polyimide nanofiltration membrane

A newly fabricated (PI) P84 NF membrane was introduced in this work for overcoming the separation challenges of bio-based succinic acid recovery. PI membranes were fabricated at different polymer concentrations and membrane thicknesses. The inherent properties of the membranes were evaluated using salt rejection, FESEM, a porometer, AFM and the surface zeta potential. The performances of PI membrane for succinic recovery were investigated from a simulated fermentation broth and an actual broth, consisting of succinate, formate, and acetate. The effect of various process conditions of different feed concentrations, pressures, stirring speeds and different concentration ratios of divalent to monovalent ions were investigated. From the results, 20 wt% PI membrane was successfully fabricated with average pore size diameter of 0.23nm, and Na2SO4 rejection of 80%. This membrane also exhibited high succinate rejection of 89-96% with a simulated broth, and that the rejection performance improved with increasing pressure and low feed concentration. Meanwhile, the succinate selectivity was improved by 20-51% with the increase in the stirring speed and the ratio of the divalent to monovalent ionic solute concentrations. With the actual broth, 92% succinate rejection was achieved, which was comparable to the rejection performance of the commercial membranes such as NF1 membrane. The membrane also showed excellent chemical stability in the broth based on the consistent FTIR and contact angle before and after the filtration. It can be concluded that the PI P84-based membrane has a great potential in applications for organic acids salts separation and recovery.