Electrodialysis for the Recovery of Acetate from Microbial Electrosynthesis Effluents

Microbial electrosynthesis (MES) is a promising bioelectrochemical technologyforconvertingCO2 into value-added products. However, downstream processing remains a majorconstraint for its applicationat larger scales.Thereis limited understanding of which separation technologies can be effectively integrated with MESeffluents, and how key operatingconditions impact on the product recovery and energyefficiency.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, and7.5), applied current density(1.9,3.8,9.5,and15.0mAcm−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 to34.97±0.63%. Under these conditions, theEDsystemrecovered1.12 ± 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 MESsystems, helping to address key bottlenecks faced by this technology.