(660c) Self-Assembled Mesoporous Carbon for Capacitive Deionization of Water

Authors: 
Tsouris, C., Oak Ridge National Laboratory
DePaoli, D., Oak Ridge National Laboratory
Dai, S., Oak Ridge National Laboratory
Kiggans, J., Oak Ridge National Laboratory
Mayes, R., Oak Ridge National Laboratory
Hou, C., Georgia Institute of Technology
Yiacoumi, S., Georgia Institute of Technology


Self-assembled mesoporous carbon materials have been synthesized in our laboratories. Current work aims to translate the discovery of these materials into an industrially viable technology for water desalination via electrosorption or capacitive deionization. Mesoporous carbon sheets have been synthesized and used in a single-cell capacitive deionization reactor. Results have shown that the mesoporous carbon sheets are superior to carbon aerogel materials that are commercially available for capacitive deionization applications. A complex performance has been revealed when a mixture of ions were present in the solution, which is related to the competition of ion size and valence. When sodium chloride was used, ion competition was removed as evidenced from the performance of the reactor. Grand canonical Monte Carlo simulations were performed to study the fundamental aspects of electrosorption selectivity of electrolyte mixtures inside nanopores. Simulation results indicated that exclusion of coions is associated with the population of different counterions involved in the electrical double layer (EDL) formation. In the case of electrolyte mixtures, the competitive effects of asymmetries of ion charge and size can determine the pore accessibility. Divalent counterions have the energetic advantage of preferentially screening the surface charge. On the other hand, small counterions can access the pores and approach closer to the charged surfaces. Electrosorption selectivity of small monovalent versus large divalent ions depends on the magnitude of surface charge. This study is expected to lead to a competitive process for water desalination.