High-temperature hydrogen/propane separations in asymmetric carbon molecular sieve hollow fiber membranes

Nanoarchitectonics of carbon molecular sieve membranes with graphene oxide and polyimide for hydrogen purification

Hydrogen is an important energy carrier for the transition to a carbon-neutral society, the efficient separation and purification of hydrogen from gaseous mixtures is a critical step for the implementation of a hydrogen economy. In this work, graphene oxide (GO) tuned polyimide carbon molecular sieve (CMS) membranes were prepared by carbonization, which show an attractive combination of high permeability, selectivity and stability. The gas sorption isotherms indicate that the gas sorption capability increases with the carbonization temperature and follows the order of PI–GO-1.0%-600 °C > PI–GO-1.0%-550 °C > PI–GO-1.0%-500 °C, more micropores would be created under higher temperatures under GO guidance. The synergistic GO guidance and subsequent carbonization of PI–GO-1.0% at 550 °C increased H₂ permeability from 958 to 7462 Barrer and H₂/N₂ selectivity from 14 to 117, superior to state-of-the-art polymeric materials and surpassing Robeson's upper bound line. As the carbonization temperature increased, the CMS membranes gradually changed from the turbostratic polymeric structure to a denser and more ordered graphite structure. Therefore, ultrahigh selectivities for H₂/CO₂ (17), H₂/N₂ (157), and H₂/CH₄ (243) gas pairs were achieved while maintaining moderate H₂ gas permeabilities. This research opens up new avenues for GO tuned CMS membranes with desirable molecular sieving ability for hydrogen purification.

Hydrogen is an important energy carrier for the transition to a carbon-neutral society, the CMS membrane exhibited ultrahigh H₂/N₂ selectivity (117) and H₂ permeability, which have bright prospects for hydrogen purification.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.