Seawater desalination via membrane separation to clean water offers us a cutting-edge and reliable approach to quench our thirsty world. However, most membranes are restricted by the low water flux because the membrane quality is challenged by the harsh conditions and/or the complex process in preparation, which lead to low water productivity, energy efficiency and membrane usage. Thus, it is essential to develop desalination membranes with high-flux.
Recently, a research group led by Prof. ZENG Gaofeng at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences collaborated with Prof. SHI Guosheng at Shanghai University developed graphdiyne composite membranes which achieve nearly complete salt rejections and ultrahigh-water-flux in the seawater desalination.
The results were published in Nature Water on September. 4th.
In this work, the submicron thick and nanopore structured graphdiyne membranes on porous Cu hollow fibers are fabricated directly from monomer of hexaethynylbenzene via the Glaser-Hay cross-coupling reaction under mild solvothermal conditions.
The graphdiyne membranes exhibited >99.9% rejections to the small ions of seawater and 1-3 orders of magnitude higher water fluxes than commercial membranes, such as zeolite membranes, metal-organic frameworks membranes and graphene-based membranes.The graphdiyne membranes also exhibited reliable stability in the long-term tests with hypersaline water, real seawater and pollutant-containing waters
The theoretical calculations suggested that the interfaces of saline-water/graphdiyne and saline-water/vapor contain 1-3 molecular layers of pure water without salt, which contributed to the complete salt rejections on graphdiyne membrane. Through a two-layered graphdiyne channel model, ultrahigh water fluxes were achieved, which is in line with the experimental observations.
These findings not only provide an adaptive method for preparing graphdiyne membranes but also indicate the potential of obtaining other alkadiyne containing membranes under similar methodology, which may be used for membrane separations, ions transfer and energy conversion.
Preparation, desalination performance and separation mechanism of graphdiyne membrane (Image by SARI)