No abstract

No abstract

Porous electrodes are important in many physical−chemical processes including capacitive deionization (CDI), a desalination technology where ions are adsorbed from solution into the electrostatic double layers formed at the electrode/solution interface inside of two juxtaposed porous electrodes. A key property of the porous electrode is the charge efficiency of the double layer, Λ, defined as the ratio of equilibrium salt adsorption over electrode charge. We present experimental data for Λ as a function of voltage and salt concentration and use this data set to characterize the double-layer structure inside of the electrode and determine the effective area for ion adsorption. Accurate experimental assessment of these two crucial properties of the electrode/solution interface enables more structured optimization of electrode materials for desalination purposes. In addition, detailed knowledge of the double-layer structure and effective area gives way to the development of more accurate dynamic process models describing CDI.

No abstract

No abstract

Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous carbon electrodes. In front of each electrode, an ion-exchange membrane is positioned, and between them, a spacer is situated, which transports the water to be desalinated. In this work, we demonstrate for the first time that up to 83% of the energy used for charging the electrodes during desalination can be recovered in the regeneration step. This can be achieved by charging and discharging the electrodes in a controlled manner by using constant current conditions. By implementing energy recovery as an integral part of the MCDI operation, the overall energy consumption can be as low as 0.26 (kW·h)/m(3) of produced water to reduce the salinity by 10 mM, which means that MCDI is more energy efficient for treatment of brackish water than reverse osmosis. Nevertheless, the measured energy consumption is much higher than the thermodynamically calculated values for desalinating the water, and therefore, a further improvement in thermodynamic efficiency will be needed in the future.

No abstract

No abstract