Enhancement of Electrosorption Rates Using Low-Amplitude, High-Frequency, Pulsed Electrical Potential

The influence of low-amplitude, high-frequency, pulsed electrical potential on ion transport in mesoporous carbon electrodes has been investigated. Mesoporous carbon electrodes of approximately 10-nm average pore size were synthesized based on a soft-template method. The carbon electrodes were used in capacitive deionization experiments with salt solutions consisting of a mixture of ions of concentrations ranging from 5000 ppm to 10,000 ppm to investigate the effect of a pulsed potential on the ion removal rate. Higher rates of sorption and regeneration were observed when the pulsed potential was superimposed on a direct current (DC) offset of 1.2 V that is typically applied in capacitive deionization (CDI). The rate of ion sorption in CDI experiments was dependant on the amplitude and frequency of the pulsed potential. Conductivity measurements showed enhancement in transport rates due to the pulsed potential up to 130%. The effect was stronger during regeneration. Neutron imaging, a visualization technique, was also employed to quantify the diffusion of ions through mesoporous carbon electrodes under different conditions. Sequences of neutron images showed enhanced transport of gadolinium ions under the influence of pulsed potential. From the concentration histories of gadolinium ions inside the carbon electrodes, the effective diffusion coefficient of gadolinium ions was estimated at 8.3 +/- 0.4 x 10(-11) m(2)/s at 1.2 V DC and 1.1 x 10(-10) m(2)/s at 1.2 V DC with pulsed potential added. (C) 2014 Elsevier B.V. All rights reserved.