Wastewater containing organic dyestuff has caused worldwide concern, hence, it is imperative to develop materials to remove organic dyes from wastewater. Herein, we report the synthesis of carbon fiber-based bimetallic oxide nanocomposite with high efficiency for the adsorptive removal of Congo red (CR), a typical anionic dye. Composite nanosheets of nickel(II) oxide (NiO) and zinc oxide (ZnO) were in situ grown over electrospun carbon fibers via one-step oil bath coprecipitation and subsequent calcination in air at 350 degrees C. The C/NiO-ZnO nanocomposite fibers exhibited fast adsorption rates towards CR at circumneutral pH, and maximal adsorption capacity according to the Langmuir model reached 613 mg g(-1), much higher than aggregated NiO-ZnO microspheres and the carbon fiber alone. The high adsorption capacity of the C/NiO-ZnO nanocomposite was attributed to its high specific surface area (222 m(2) g(-1)), hierarchically porous structure with abundant mesopores and macropores, and the positive surface charge at circumneutral pH. Therefore, the flexible and easily recyclable C/NiO-ZnO nanocomposite fibers can become an alternative adsorbent for the treatment of anionic dye wastewater. (C) 2018 Elsevier Inc. All rights reserved.