Open Access Peer-reviewed Research Article

Tannin-Functionalized Hierarchical Porous Biochar from Lignocellulosic Waste for Simultaneous NH₄⁺ and NO₃⁻ Adsorption in Complex Wastewater via Ion-Exchange Synergy and Surface Complexation

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Submitted   Apr 11, 2026
Published   Jun 29, 2026
Issue    Vol 7 No 1 (2026)
DOI   10.25082/CR.2026.01.003

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Doaa F. Ahmed
Department of Basic Science, The Valley Institute for Engineering and Technology, El-Obour 11828, Egypt
Alaa Adel Abo Ella corresponding author
Department of Pharmaceutical Biotechnology, Badr University in Cairo (BUC), Badr City, Cairo 11829, Egypt
Sanaa Naeim
Faculty of Science, El-Azhar University, Cairo, Egypt
Mahmoud F. Mubarak
Petroleum Application Department, Egyptian Petroleum Research Institute (EPRI), Nasr City, Cairo 11727, Egypt
Mostafa Y. Nassar
Department of Chemistry, College of Science, King Faisal University, Al-Ahsa 31982, Saudi Arabia
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Abstract

The unregulated release of nitrogenous compounds from agricultural and industrial waste continues to pose a significant challenge for environmental remediation because of the differing chemical properties of cationic ammonium and anionic nitrate. This study sought to create a multifunctional adsorbent for concurrent nitrogen recovery by engineering a tannin-functionalized hierarchical porous biochar (T-HPB) derived from lignocellulosic wheat straw residues. The synthesis entailed a two-step procedure, including hydrothermal carbonization at 220 °C, succeeded by chemical activation with phosphoric acid (H₃PO₄) to create a hierarchical porous structure. The obtained biochar was subsequently functionalized with Bayberry tannin via glutaraldehyde-assisted crosslinking. Characterization results confirmed the formation of a well-developed porous architecture with a Brunauer–Emmett–Teller surface area of 842.5 m²/g Scanning electron microscopy revealed a hierarchical network of interconnected macro- and mesopores. Batch adsorption experiments revealed that T-HPB attained maximum adsorption capacities of 78.4 mg/g for ammonium and 52.1 mg/g for nitrate at 25°C and pH 7.0. Kinetic analyses revealed that the adsorption process adhered to a pseudo-second-order model, achieving roughly 90% equilibrium within 120 minutes. Mechanistic studies employing X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) demonstrated that ammonium removal was predominantly influenced by cation exchange and π–cation interactions with phenolic hydroxyl groups, while nitrate adsorption was primarily governed by surface complexation and electrostatic attraction at positively charged nitrogen-containing sites. The results indicate that T-HPB is an efficient and sustainable adsorbent for the concurrent removal and recovery of nitrogen species from intricate wastewater systems.

Keywords
lignocellulosic biochar, tannin-functionalized biochar, hierarchical porosity, simultaneous adsorption, nitrogen recovery, wastewater treatment

Article Details

Supporting Agencies
This work was supported by the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research, King Faisal University, Saudi Arabia [Grant No. KFU262099].
How to Cite
Ahmed, D. F., Ella, A. A. A., Naeim, S., Mubarak, M. F., Nassar, M. Y., Adam, M. S. S., Alfurayj, I., Hammud, H. H., Ayoup, M. S., & Masoud, E. M. (2026). Tannin-Functionalized Hierarchical Porous Biochar from Lignocellulosic Waste for Simultaneous NH₄⁺ and NO₃⁻ Adsorption in Complex Wastewater via Ion-Exchange Synergy and Surface Complexation. Chemical Reports, 7(1), 357-374. https://doi.org/10.25082/CR.2026.01.003
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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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