Modified electrospun nanofiber membranes to prevent fouling and pore wetting in membrane distillation: a review

Access to quality water remains a critical global issue. Membrane distillation (MD) has emerged as an up-andcoming technology for desalination and purification of water and wastewater, effectively removing various contaminants. The MD process stands out due to its lower fouling propensity than pressurized membrane processes and high rejection rate (100 % theoretical). However, the asymmetrical structure of phase inversion membranes limits their operational performance. Electrospinning, a technique that allows nanometer-scale fibres from a polymer solution and high applied voltage, offers a pathway to enhanced MD membranes. Electrospun nanofiber membranes (ENM) exhibit a high surface area, hydrophobicity, gas permeability, and smaller inter-fibrous pore size, making them attractive for MD applications. Despite these advantages, challenges associated with fouling and pore wetting persist. In this regard, this article sought to understand how additives contribute to the reduction of fouling and pore wetting in ENMs. Nanoparticles, polymeric materials, carbon-based materials, multilayer membranes and sustainable materials were studied. The reduction of fouling and pore wetting is associated with increased hydrophobicity, roughness and heat and mass transfer mechanisms. Additionally, some applications were discussed. Finally, several opportunities and challenges of ENMs for the MD process were considered, providing insights into the future directions of research and applications in this field.