Capacitive Deionization (CDI) is an emerging technology that electrochemically adsorbs and recovers ions from concentrated solutions through capacitance. In CDI, ions migrate toward the oppositely charged porous electrode due to the applied potential difference, enabling their adsorption within the Electric Double Layer (EDL). This technology can be broadly implemented to the separation and recovery of carboxylates, such as acetate and butyrate, as well as other organic, and inorganic ions. This study aims to develop and solve a transient, two-dimensional fully coupled model to predict the adsorption and desorption dynamics of carboxylates at three potentials: 0.8, 1, or 1.2 V and three flowrates: 4, 6, or 8 mL/min. A prior study was conducted using a custom-designed flow-between CDI cell and activated carbon cloth as electrodes to capture concentration profiles and adsorption capacities under varying experimental conditions, with 10 mM carboxylate salt at pH 6.2 as influent. The experimental data was used to calibrate and validate the model. This work develops a model that incorporates diffusion, convection, electromigration, and EDL capacitance to predict the dynamic behavior of carboxylates during voltage application and removal under different conditions. The model offers a comprehensive understanding of how ion transports in a porous conductive medium due to capacitance induced by the applied potential difference. Model results are compared with experimental data, providing valuable insights for optimizing CDI operations and facilitating scale up for industrial applications.
