A Flexible Oxygenated Carbographite Nanofilamentous Buckypaper as an Amphiphilic Membrane

Here, for the first time, oxygenated amorphous carbon/graphite (a-CO_x/G) hybrid nanofilaments are produced and used as the building blocks of a buckypaper membrane. The nanofilaments are in fact the innovatively chopped version of brittle, highly graphitized polyacrylonitrile precursor nanofibers. The high temperature (1250 °C) graphitization and then fast cooling bring about biphasic nanofibers made of graphite and amorphous carbon, readily reoxidized during cooling. The combination of polar and nonpolar domains in the nanofilaments governs a desirable amphiphilicity, thus selectivity to a variety of polar/nonpolar water pollutants. Through electrostatic and π–π interactions, the membrane efficiently discriminates amphiphilic castor oil as well as cationic methylene blue dye from water. Moreover, the buckypaper-like structure of the membrane is 100% efficient in depth filtration of colloidal particles from water. The membrane's water flux is 16 times higher than that of commercial microfiltration membranes, promising an advanced energy/cost efficient filtration process. Thus, being multispectrally selective and highly water permeable, the a-CO_x/G nanofilamentous membrane is regarded potentially a next-generation, cost-effective, and sustainable alternative to the long-existing thin-film composite membranes for water treatment.