Comparative study on the electrosorption properties of carbon fabric, functionalized multiwall carbon nanotubes and solar-reduced graphene oxide for flow through electrode based desalination studies

Abstract

Removal of salt ions using capacitive deionization (CDI) is an efficient and environmentally friendly route to fulfill the necessity of fresh water. Carbon nanomaterials are preferred as electrode material for desalination studies. However, the design of the CDI cell and the structure of electrodes also plays an important role in deciding the salt removal efficiency. Here, we have fabricated a flow-through electrode capacitive deionization (FTE-CDI) cell to study the electrosorption performances of various carbon-based materials like; carbon fabric (CF), functionalized-multiwall carbon nanotubes (F-MWCNT), and solar reduced graphene oxide (SRGO). Surface morphology and elemental composition of all the electrodes were examined using a scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance was analyzed using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Specific capacitance and equivalent series resistance of about 49.91 F/g (2.18 Ω), 64.69 F/g (2.03 Ω), and 128.45 F/g (0.87 Ω) were achieved for CF, F-MWCNT, and SRGO respectively. Electrosorption capacity of 10.70, 31.22, and 37.54 mg/g was attained with the CF, F-MWCNT, and SRGO sponge electrodes respectively. The ion sorption followed the Langmuir isotherm and Pseudo-first-order kinetics. Hence, corresponds to monolayer physisorption of the salt ions on the surface of the electrodes. This work demonstrates the significance of the electro-active material, importance of an electrodes structure, and CDI cell architecture for desalination applications.