Desenvolvimento de eletrodos de carbono suportados em feltro de grafite para deionização capacitiva

Abstract

Capacitive deionization (CDI) is an emerging technology for water desalination, standing out for its efficiency and sustainability in the face of global challenges regarding access to drinking water. In this study, different treatments were applied to graphite felts (GF) with the aim of enhancing their physicochemical properties for use as a support for activated carbon (AC) in the production of electrodes for CDI applications. Characterizations performed on the materials, including thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Raman spectroscopy, indicated that, more significantly than surface chemical functionalization, the treatments induced defects in the graphitic structure of the felts. These findings suggested that CDI performance is primarily dependent on the degree of disorder in the carbon structure. Electrochemical impedance spectroscopy (EIS) analyses revealed increased charge transfer resistance in the treated materials, while cyclic voltammetry (CV) measurements showed increases in capacitance and specific capacitance of the electric double layer. Desalination tests, conducted in both potentiostatic and galvanostatic modes, showed that, overall, the treatments had positive effects on the materials’ performance, with improvements observed in salt adsorption capacity (SAC, 17.93 mg g⁻¹), average salt adsorption rate (ASAR, 0.75 mg g⁻¹ min⁻¹), water recovery (WR, 43.27%), water production (P, 591.01 L m⁻² h⁻¹), charge efficiency (Λcharge, 65%), coulombic efficiency (𝜂𝑐𝑜𝑢𝑙, 52%), and salt concentration reduction (Δc, 133.6 mg L⁻¹), along with reductions in energy consumption (Ev, 131.84 Wh m⁻³). Treated materials retained 83.5% of their salt adsorption capacity after 100-cycle testing, demonstrating the stability of the electrodes used. CDI experiments indicated that operational parameters such as flow rate, applied current, cell potential, and potential application time influenced the capacity and kinetics of salt removal. These results demonstrated that the treatments applied to the felts generally improved their performance as electrode materials for CDI, representing promising strategies for increasing the efficiency of water desalination processes.