10 - Electrochemically active carbon nanotube (CNT) membrane filter for desalination and water purification

Abstract

Recently, extraordinary breakthroughs have been made toward applying nanostructured materials such as carbon nanotubes (CNTs), porous graphene membranes in water purification, and desalination applications. In this regard, the potential of the electrochemically active CNT membrane has been highly strengthened for the last few decades. One of the main advantages of such approach is the capability of CNT channel to permit the water flow easily. The perusal of the literature showed that the performance of CNT-based membrane can be three times higher than that of the conventional membrane devices. The unique and excellent characteristics of CNT membrane can outperform the conventional polymer membranes. The CNT membrane has been widely used to adsorb chemical and biological contaminants as well as ion separation from seawater due to their high stability, great flexibility, and large specific surface area. Electrochemically active CNT filters deliver further electrooxidation of the adsorbed contaminants. Usually, polymeric membranes have flexible chains for which it fails to have well-defined pores necessary for filtration. On the contrary, CNT-based filters can provide pores with appropriate sizes and configurations by tailoring the growth parameters. The narrow pores of CNTs are capable of filtering water while eliminating ions (Na+/Cl−). Even this type of membrane is capable of removing bacteria from water and heavy hydrocarbon from petroleum. However, the success of desalination entirely depends on the basic design of the CNT-based filter with detailed optimization of the process parameters. Polymer filters cannot be recurrently used through several cycles since the elimination of fouling ingredients is difficult. Even though electrochemically active CNT-based membranes have lot of advantages due to their hydrophobic nature, high porosity and specific area; there are numerous traits, which are yet to be considered and optimized. Thus, the intrinsic properties of CNT and the fabrication of the membrane could be critical factors for their applicability in various water treatment processes. This chapter provides an explicit and systematic overview of the recent progress of electrochemically active CNT membranes addressing the current prevalent problems associated with water treatment and desalination. The physiochemical aspect including the working principles of this type of membrane have been discussed. The prevailing challenges and future perceptions are also discussed.