Optimization of simultaneous bicarbonate recovery and energy generation in a carbon-capture reverse electrodialysis...

In this study, we aimed to simultaneously regenerate the absorbent and recover bicarbonate using reverse electrodialysis to evaluate the potential to replace the process that consumes a large amount of thermal energy during the regeneration of amine after absorption. Therefore, a carbon-capture reverse electrodialysis (CCRED) system for bicarbonate and energy recovery was optimized using response surface methodology (RSM). We aimed to optimize the applicability of the system for tertiary amine solutions, as the intermediate product carbamate is formed in the case of primary and secondary amines, which interferes with their behavior during reverse electrodialysis. Three tertiary amines, DMAE, MDEA, and TEA, were evaluated, with DMAE exhibiting the highest power density of 1.85 W/m² due to its superior ion transport properties. In contrast, TEA showed high internal resistance attributed to its elevated solution viscosity. Optimization of the RED parameters revealed that an asymmetrical flow rate (Q_LC > Q_HC) between low-concentration (LC) and high-concentration (HC) streams was advantageous when using viscous absorbents. A high LC flow rate sustained a steep concentration gradient, while a moderate HC flow rate ensured sufficient residence time for ion diffusion. Experimental validation using the RSM model yielded an error rate of less than 5%. These findings provide a foundation for developing CCRED systems tailored to the physicochemical properties of individual absorbents in integrated carbon capture and energy recovery processes.