(101c) Advances in Electrosorption By Mesoporous Carbon Materials for Water Desalination

Electrosorption of ions from aqueous solutions by porous carbon electrodes has been investigated for the desalination of saline water through the capacitive deionization (CDI) process. Mesoporous carbon materials of 10-nm average pore size, synthesized at Oak Ridge National Laboratory (ORNL), have been proven suitable for CDI because of their high surface area associated with an optimum pore size for ion transport.  To study ion transport in mesoporous carbon electrodes, we employed the neutron imaging technique, which is a non-destructive in-situ method for providing information on the local concentration of ions in the electrodes as a function of time. Neutron imaging of ions in mesoporous carbon was conducted to determine the effective diffusivity of ions under different conditions of applied potential. It was also found that an oscillating voltage component superimposed on the applied direct-current (dc) voltage that is usually applied in capacitive deionization enhances the rates of adsorption and desorption of ions. Using neutron imaging, it was determined that the effective diffusion coefficient increased by 35% when the oscillating potential was superimposed onto the dc potential of 1.2 V. Thus, modulation of the electrical signal applied in CDI processes can be used to enhance the kinetics of CDI and increase the competitiveness of this process in real water-treatment and reuse applications.