A comprehensive review on dual-layer organic hollow fiber membranes fabrication via co-extrusion: Mechanistic insights, water treatment and gas separation applications

As a practical alternative to conventional separation processes, membrane technology has made significant progress in recent decades to address water scarcity, energy depletion and environmental contamination on a global scale. The advantages of membrane technology include selective permeation, lower energy consumption, and non-thermal processing of sensitive chemicals. The use of co-extrusion-based phase inversion technique to develop dual-layer hollow fiber (DLHF) membranes is a cutting-edge approach in membrane technology. There is a growing body of research focused on investigating the potential of DLHF membranes for both gas-phase and liquid-phase separation applications. There are a few reviews on the production of DLHF membranes by co-extrusion for specific applications, such as gas separation and membrane distillation. However, there is no comprehensive review covering all applications of DLHF membranes produced by co-extrusion. This review provides an overview of the significant advances in the fabrication of DLHF membranes using co-extrusion and phase inversion techniques. It also examines the role of various polymers, solvents, and nanomaterials in membrane fabrication, as well as the effects of spinning parameters and post-synthetic modifications on the structure and separation performance of DLHF membranes. Various applications of DLHF membranes including water purification and gas separation are discussed in detail. The study also discusses the challenges in membrane fabrication and operation, including delamination phenomena, substructure resistance, membrane fouling, and the plasticization effect. This study will help researchers to understand the mechanism of co-extrusion of DLHF membranes and their application in various separation processes.