Electrodialysis for the Recovery of Acetate from Microbial Electrosynthesis Effluents

Abstract Microbial electrosynthesis (MES) is a promising bioelectrochemical technology for converting CO2 into value-added products. However, downstream processing remains a major constraint for its application at larger scales. There is limited understanding of which separation technologies can be effectively integrated with MES effluents, and how key operating conditions impact on the product recovery and energy efficiency. This study assesses the use of electrodialysis (ED) as a solvent-free downstream separation process for acetate recovery from a multicomponent simulated MES effluent. The effects of operating pH (3, 5.5, and 7.5), applied current density (1.9, 3.8, 9.5, and 15.0 mA cm–2), and operation mode (continuous or fed-batch) were investigated. The highest acetate titer (13.73 ± 1.65) in the concentrate stream was reached at pH 5.5, a current density of 1.9 mA cm–2, and under fed-batch operation. Ion competition was identified as the primary limiting factor, with preferential Cl– transport, which reduced the Coulombic efficiency of acetate transport to 34.97 ± 0.63%. Under these conditions, the ED system recovered 1.12 ± 0.03 kg of acetate per kWh, corresponding to approximately 5% of the total energy demand associated with MES production. Overall, this study provides quantitative guidance on the optimization of electrodialysis as a recovery technology from a simulated MES effluent as a low-energy downstream solution for MES systems, helping to address key bottlenecks faced by this technology.