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Seeking high performance adsorbents for highly efficient treatment of wastewater containing organic dyes has become increasingly imperative worldwide. Herein, with a specific surface area (SSA) of 2,745.4 m2·g−1, trace N-doped porous biochar nanospheres (NPBs) are derived for the first time from affluent waste corn roots, via a hydrothermal conversion followed by a mild calcined activation by K2CO3 (KC) in the presence of low virulent melamine. Melamine acts as N source and synergistic activator for significant promotion in SSA, pore volume, and surface defects. The obtained NPBs (CHC-0.5N-4KC-900) are confirmed as superior adsorbents for removal of organic dyes rhodamine B (RhB, qm = 1,630.7 mg·g−1) and Congo red (CR, qm = 1,766.2 mg·g−1) as well as their mixtures, within not only a low (< 50 mg·L−1) but also a high (> 50, esp. 250–1500 mg·L−1) concentration range. The values for qm are far beyond commercially activated carbon (AC) as well as most reported biomass derived carbons, undoubtedly revealing the NPBs as great promising candidate adsorbents for disposal of real industrial wastewater. In addition, the adsorption of RhB is fitted by Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models. The kinetic analysis indicates that the adsorption before equilibrium conforms to the pseudo-second-order model, and the hydrogen bonding, electrostatic attraction, and esp. π–π interaction have contributed to the superior adsorption performance of the NPBs.

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Publication history
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Acknowledgements

Publication history

Received: 24 September 2022
Revised: 25 October 2022
Accepted: 26 October 2022
Published: 23 December 2022
Issue date: February 2023

Copyright

© Tsinghua University Press 2022

Acknowledgements

Acknowledgements

This work was supported by the State Key Laboratory of Chemical Engineering, China (No. SKL-ChE-21A02), State Key Laboratory of Organic-Inorganic Composites, China (No. oic-202101009), and the Natural Science Foundation of Shandong Province, China (No. ZR2022MB075), the National Natural Science Foundation of China (No. 22075304), and Beijing Natural Science Foundation, China (No. 3222050).

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