Application of electrodes with redox mechanisms for the desalination of water

Abstract: Capacitive deionization is a promising technology for purification and desalination of brackish water with great advantages over current technologies due to its low operating cost and high-water recovery ratio. Most of the system studied relies on the adsorption/desorption capacity of activated carbon electrodes due to its high surface area. However, its specific adsorption capacity is limited since the adsorption is predominantly on the surface of the electrodes. In this thesis we propose the use of polyaniline as a chloride-ion adsorption material. Polyaniline is a redox polymer able to accommodate anions in several of its three states when subjected to an external voltage. To this end, we synthesized polyaniline by electrodeposition technique and its electrochemical behavior was studied. A hybrid CDI system was assembled, using PANI as anode material and activated carbon cloth as cathode, showing outstanding adsorption of 37.26 mg/g Cl at current densities of 250 A/g. The energy consumption of this system was of 0.4979 kWh/m3. Its stability was evaluated over 50 cycles with negligible capacity loss. Along with its use in a CDI system, the aim of this thesis was to understand the mechanisms of operation of this material, by means of its physical and electrochemical characterization, as well as its efficiency and stability through the use of this material in capacitive deionization cells.