Abstract
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 × 10-11 m2/s at 1.2 V DC and 1.1 × 10-10 m2/s at 1.2 V DC with pulsed potential added.
Original language | English |
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Pages (from-to) | 18-24 |
Number of pages | 7 |
Journal | Separation and Purification Technology |
Volume | 129 |
DOIs | |
State | Published - May 29 2014 |
Funding
This research was conducted at the Oak Ridge National Laboratory and supported by the U.S. DOE Office of Energy Efficiency and Renewable Energy (EERE), under Contract DE-AC05-0096OR22725 with Oak Ridge National Laboratory, managed by UT-Battelle, LLC. A portion of this research at Oak Ridge National Laboratory’s High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Partial support to C. Tsouris, S. Yiacoumi and K. Sharma was provided by Campbell Applied Physics, Inc. and the National Science Foundation, under Grant No. CBET-0651683. The authors are thankful to Charles R. Schaich for his help with the neutron imaging cell; Hyacinth Igwe and Chidera Ozurumba for their help with CDI experiments; and Bob Campbell, Bill Bourcier, Tom Dorow, Sunita Kaushik, and Fred Seamon of Campbell Applied Physics, Inc., for frequent discussions on CDI. Notice: This paper has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this paper, or allow others to do so, for United States Government purposes.
Keywords
- Capacitive deionization
- Desalination
- Electrosorption
- Neutron imaging
- Pulsed voltage