A review on electrochemically modified carbon nanotubes (CNTs) membrane for desalination and purification of water

Recently extraordinary breakthroughs have been made towards applying nano-structured materials such as carbon nanotubes (CNTs) and porous graphene membranes in water purification and desalination applications. In this regard, the potential of the electrochemically active carbon nanotube (CNTs) membrane has been highly strengthened for the last few decades. One of the main advantages for 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. CNT membrane has been widely used to adsorb chemical and biological contaminants as well as ion separation from sea water due to their high stability, great flexibility, and large specific surface area. Electrochemically active CNT filters deliver further Electro-oxidation 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 CNTs 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 membranes 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 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 as well as the fabrication of the membrane could be a critical factor 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 physio-chemical aspect including the working principles of this type of membrane have been discussed. The prevailing challenges and future perceptions are also discussed.