Carbonaceous nanofibrous membranes with enhanced superhydrophilicity and underwater superoleophobicity for effective purification of emulsified oily wastewater

High performance oil–water separation membranes with stable physical–chemical properties are highly desirable for the treatment of emulsified oily wastewater in various conditions. Carbonaceous nanofibrous membranes are promising due to several merits, including good thermal resistance, chemical inertness, non-toxicity, and harmlessness. However, the hydrophobicity and oleophilicity of carbon, as well as the poor mechanical property of carbon nanofibers, make it challenging to use the corresponding membrane for the separation of oil-in-water emulsions. Herein, we demonstrate a facile and effective strategy to fabricate a superhydrophilic and underwater superoleophobic carbonaceous nanofibrous membrane. The mechanical property and surface wettability of the membrane could be well regulated through heteroatom doping and thermal induced oxidation. As a result, the obtained carbonaceous nanofibrous membrane exhibited intriguingly durable mechanical flexibility and oil–water selective wettability, which were comparable to that of polymeric membranes. In the meanwhile, a plausible mechanism for the underwater superoleophobicity of the membrane was proposed based on a series of structural analyses and molecular dynamic simulations. With the synergy of developed pores and high oil–water selective wettability, the obtained carbonaceous nanofibrous membrane was effective for separating various oil-in-water emulsions. Moreover, the membrane, thanks to its gratifying underwater anti-oil adhesion property, could be efficiently reused after a simple process of hydraulic washing, demonstrating great potential for the purification of emulsified oily wastewater.