The nexus between energy and water has gained significant attention in the last decade. This is mainly due to the tight relationship between these two elements, not only from the energy production point of view, in which water has a relevant role in hydropower generation and cooling systems of the nuclear power plants, but also from the production of water since desalination and water treatment plants required a significant amount of energy to function (pumping, distribution and aeration, mainly). The Water-Energy Nexus has been recently extended beyond energy production into the realm of energy storage. Here electrochemical devices, such as batteries and supercapacitors, have inspired a new class of water treatment technologies (desalination, pollutant removal and critical ion capture).
In this sense, among the emerging water treatment technologies, electrochemical technologies, and more precisely the electrochemical ion pumping technologies (EIPTs), have attracted the attention of the scientific community. With respect to EIPTS, Capacitive DeIonization (CDI) technology uses the advancements achieved in the field of supercapacitors to enhance energy efficient water treatment applications. The core of this technology has been in the use of novel materials with which to fabricate innovative electrodes having better capacity to remove target species. In CDI, the electrodes are mainly made of carbon in different configurations (activated carbons, nanotubes, fibers, graphene).
Researchers of the Electrochemical Processes Unit of IMDEA Energy have recently published their research about innovative 3D graphite felt electrodes modified with activated carbons (GF-Ac) employed in CDI for brackish water desalination. The novelty of this work is the synergy between the high electrical conductivity of the graphite felts in combination with the significant ion adsorption capacity of the activated carbons. Moreover, this material represents a great platform for simple electrode preparation leading to an easy to scale process for CDI technologies. This idea was inspired by our companion work on vanadium redox flow batteries which are employed in the energy storage field where these graphite electrodes are commonly employed.
The research recently published in the Chemical Engineering Journal* demonstrates the practical scaling of these electrodes from the laboratory to pilot plant levels for pre-commercial applications. The study illustrates the ability of these systems to scale by showing the electrochemical characterization of GF-AC in 1 cm2 to a 9-Cell Stack (300 cm2) both demonstrating excellent performance. The CDI stack showed that brackish water desalination could be performed at 2.26 LMH and 0.60 kWh m-3. Moreover, it was determined that the energy consumption could be even 50% lower if an electronic energy recovery system is implemented.
Currently, IMDEA researchers continue working on prototyping these systems using their knowledge in the energy storage field as a source of inspiration to further scale-up the CDI technology. Moreover, additional studies are ongoing examining means of improving electrode performance. In essence, we believe that GF-AC electrodes hold great promise for large-scale CDI practical applications.
This work is part of the research developed along with the companies GS INIMA Environment, S.A. and Proingesa in the framework of the DC-SOIAS project funded by the Ministry of Economy, Industry and Competitiveness (MINECO) through the State Program of Research, Development and Innovation Oriented Challenges of the Society. Collaboration Challenges 2015 (RTC-2015-3969-5).
(*) Wang, Y., Vázquez-Rodríguez, I., Santos, C., García-Quismondo, E., Palma, J., Anderson, M.A., Lado, J.J. Graphite felt 3D framework composites as an easy to scale capacitive deionization electrode for brackish water desalination. (2020) Chemical Engineering Journal, 392, 123698. https://doi.org/10.1016/j.cej.2019.123698
More information: Julio J. Lado. Postdoctoral Researcher, Electrochemical Processes Unit. Julio.firstname.lastname@example.org