Green synthesis of carbon nanotubes to address the water-energy-food nexus: A critical review

Carbon nanotubes are valuable materials that possess excellent physicochemical properties such as high electrical conductivity, thermal stability, mechanical strength, aspect ratio and surface area. These unique properties of CNTs make it possible to develop innovative technologies and materials that can be used in various applications such as agriculture (food), energy and water industries. Regardless of the high demand of CNTs, their cost remains the major problem due to their synthesis procedures that are high temperature dependent and require high capital costs to set-up. CNT costs only become cheaper when bought in large volumes e.g., tonnes. This paper reviews some of the greener methods used for the sustainable synthesis of CNTs in order to address the water-energy-food nexus. It also reports the challenges on green production processes and application of these nanomaterials. The intricate relationship between these resources (water, energy and food) requires a sustain ably integrated approach in ensuring water and food security as well as sustainable energy production. CNTs are advanced materials with the capability of solving these challenges and their application in the water, energy and food industry is reviewed.