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Biowaste-Derived Carbon Electrodes for Capacitive Deionization

Wednesday, 3 October 2018: 09:20
Universal 3 (Expo Center)
J. Lado (Electrochemical Processes Unit, IMDEA Energy), L. A. M. Ruotolo (Federal University of Sao Carlos), and R. L. Zornitta (Federal University of São Carlos)
Capacitive Deionization (CDI) is one of the most relevant emerging desalination technologies. CDI is based on the electrosorption of salts using a pair of electrically charged porous electrodes. In this way the CDI process consists on charging (ion removal)/discharging (ion desorption) cycles using the same operational principles of the supercapacitors. Therefore, CDI cells might potentially allow to recover part of the energy consumed in the desalination process while delivering drinking water.

One of the key elements in this technology are, as in the supercapacitor field, the electrodes. In accordance with this, intensive research has been conducted in order to find the best electrode candidates in terms of specific surface area (SSA), porosity, electrical conductivity, surface chemistry and optimized chemical surface charge of the electrode. The combination of these properties are expected to provide higher values of salt adsorption capacity (SAC) and average salt adsorption rate (ASAR). Moreover, it should be also remarked that one of the critical requirements in order to make CDI competitive with current desalination technologies (such as reverse osmosis or electrodialysis) is the cost of the electrode materials. In order to address this challenge, the preparation of carbon electrodes from abundant biowaste precursors was studied as a low cost and green alternative to more innovative carbon composite complex materials.

In this work the authors decided to evaluate different activation treatments of a biowaste precursor in order to obtain suitable activated carbons for capacitive deionization. The different structural properties (BET SSA, pore size distribution, chemical surface groups) of the synthesized AC’s were correlated not only with their electrochemical response (specific capacitance) but also with the CDI performance (SAC, electrosorption kinetics, charge efficiency and the energy consumption).