Single-Walled Carbon Nanotube (SWCNT) Loaded Porous Reticulated Vitreous Carbon (RVC) Electrodes Used in a Capacitive Deionization (CDI) Cell for Effective Desalination.

Ali Aldalbahi,Abdulaziz Alrehaili,Mohammed Almoiqli,Abdelrazig Hamedelniel,Mostafizur Rahaman

doi:10.3390/nano8070527

Abstract

Acid-functionalized single-walled carbon nanotube (a-SWCNT)-coated reticulated vitreous carbon (RVC) composite electrodes have been prepared and the use of these electrodes in capacitive deionization (CDI) cells for water desalination has been the focus of this study. The performance of these electrodes was tested based on the applied voltage, flow rate, bias potential and a-SWCNT loadings, and then evaluated by electrosorption dynamics. The effect of the feed stream directly through the electrodes, between the electrodes, and the distance between the electrodes in the CDI system on the performance of the electrodes has been investigated. The interaction of ions with the electrodes was tested through Langmuir and Freundlich isotherm models. A new CDI cell was developed, which shows an increase of 23.96% in electrosorption capacity compared to the basic CDI cells. Moreover, a comparison of our results with the published results reveals that RVC/a-SWCNT electrodes produce 16 times more pure water compared to the ones produced using only CNT-based electrodes. Finally, it can be inferred that RVC/a-SWCNT composite electrodes in newly-developed CDI cells can be effectively used in desalination technology for water purification.

Highlights

Capacitive deionization (CDI) technology has become a new desalination technology developed in recent years with advantages such as energy saving, no secondary pollution, and simple operation, showing a broad prospect that this low-pressure and non-membrane desalination technology employs the basic electrochemical principle of adsorbing ions to high surface-area electrodes in a capacitive fashion such that the outgoing stream becomes devoid of the ions that were present in the incoming stream
The construction of a unique 3D electrode based on Acid-functionalized single-walled carbon nanotube (a-SWCNT)-coated reticulated vitreous carbon (RVC) composites has been performed in this study and their electrochemical performance has been checked by cyclic voltammetry
The effect of increasing a-SWCNT loading on the ion removal performance of a-SWCNT/RVC composite electrodes was investigated, which suggested that the composite electrodes can be effectively used in the capacitive deionization (CDI) cell for desalination technology

Summary

Introduction

Capacitive deionization (CDI) technology has become a new desalination technology developed in recent years with advantages such as energy saving, no secondary pollution, and simple operation, showing a broad prospect that this low-pressure and non-membrane desalination technology employs the basic electrochemical principle of adsorbing ions to high surface-area electrodes in a capacitive fashion such that the outgoing stream becomes devoid of the ions that were present in the incoming stream. There are studies based on the use of carbon nanotubes (CNTs) as CDI electrodes because of their exceptionally affordable functionality, structural stability, high surface area, and low electrical resistivity [13,14,15,16]. The electrosorption capacity of CNTs/PAni electrodes was found to be higher than the electrode made from only SWCNTs, where the electrodes based on composite materials were regenerated, indicating excellent recyclability. The observed excellent desalination behaviour of the composite electrodes is due to their higher electrical conductivity and surface area. It is necessary to develop CNT-based three-dimensional (3D) electrodes for better effectiveness in a CDI system because of their highly porous surface area and large amount of ion diffusion [20]

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