Carbon nanotube membranes – Strategies and challenges towards scalable manufacturing and practical separation applications

Carbon Nanotube (CNT) membranes were shown to offer great potential for separation applications due to their attractive physicochemical, mechanical, thermal and electrical properties. This paper provides a critical review on the fabrication methods, properties and applications of CNT membranes and discusses the main challenges in both scaled-up production and advanced separation application for liquid and gas filtration. This review extends to offer in-depth insights on three main categories of CNT membranes, including vertically aligned (VA), mixed matrix (MM) and bucky paper (BP) CNT membranes. The impact of CNT structure on the membrane properties and performance is explained with highlighting multiple key parameters, such as CNT alignment, packing density and surface functionalization. The main challenge is how to integrate CNTs with their unique properties into a robust membrane structure with outstanding separation performance. This paper therefore deliberates novel trends of CNT membrane fabrication and their limitations in detail, followed by a thorough discussion on applying these CNT membranes in not only water treatment but also liquid and gas separation. Finally, concise challenges and prospects are outlined towards scaled-up production and commercialization of CNT membranes to highlight promising solutions for designing high-performance CNT membranes for advanced separation applications.