Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej In situ carbothermal reduction synthesis of Fe nanocrystals embedded into N-doped carbon nanospheres for highly efficient U(VI) adsorption and reduction Kairuo Zhu a,b , Changlun Chen a,b,d, ⁎ , Mingwenchan Xu a , Ke Chen a , Xiaoli Tan a , M. Wakeel c , Njud S. Alharbi d a Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, PR China b Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, PR China c Department of Environment Sciences, Bahauddin Zakariya University, Multan, Pakistan d Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia GRAPHICAL ABSTRACT U(VI) adsorption and reduction by Fe nanocrystals embedded into N-doped carbon nanospheres. ARTICLE INFO Keywords: U(VI) Removal Fe nanocrystals Dopamine ABSTRACT In this work, magnetic porous nitrogen doped carbon structures containing well-dispersed active Fe nanocrystals (Fe/N-C) are fabricated conveniently via Fe 3+ -mediated polymerization of dopamine as precursor combined with in situ post carbonization process, thus allowing the entire encapsulation of active Fe nanocrystals in the interior. The obtained functional hybrid materials at 700 °C (Fe/N-C-700) show spherical structure, high pro- portion of metallic Fe nanocrystals, ultrahigh surface area, and easy magnetic separation property, affording excellent U(VI) removal capability (232.54 mg·g -1 ), surpassing the Fe/N-C samples pyrolyzed at different temperatures and nano zero-valent iron. During the adsorption process, effects of water chemistries (i.e., reaction time, pH, carbonates concentration and temperature) on U(VI) adsorption on Fe/N-C-700 are full explored, and the well-dispersed Fe nanocrystals play important role in reducing into U(IV). Meanwhile, nitrogen dopant could make function well in the electrostatic interaction and partial reduction of U(VI). The present study demon- strates that Fe/N-C-700 nanospheres derived from Fe-PDA have potential application for the preconcentration and immobilization of U(VI). http://dx.doi.org/10.1016/j.cej.2017.08.126 Received 11 July 2017; Received in revised form 24 August 2017; Accepted 24 August 2017 ⁎ Corresponding author at: Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, PR China. E-mail address: clchen@ipp.ac.cn (C. Chen). Chemical Engineering Journal 331 (2018) 395–405 Available online 01 September 2017 1385-8947/ © 2017 Elsevier B.V. All rights reserved. MARK