Open Access

ARTICLE

Characterization of Cellulose Nanofibrils Prepared by Direct TEMPO-Mediated Oxidation of Coffee Grounds

Yujie Zhang, Yankai Zhao, Zhuang Zhao, Mengmeng Shan, Bochen Xu, Haoquan Xue, Junxuan Xu, Fan Wu, Qiang He^*
College of Mechanical Engineering, Jiamusi University, Jiamusi, China
* Corresponding Author: Qiang He. Email:
(This article belongs to the Special Issue: Recent Advances in Extraction, Characterization and Application of Cellulose Nanocrystals)

Journal of Polymer Materials https://doi.org/10.32604/jpm.2026.076617

Received 23 November 2025; Accepted 20 January 2026; Published online 04 February 2026

Abstract

This study presents a sustainable approach for the valorization of spent coffee grounds (CG) by converting them into carboxylated cellulose nanofibrils (CG-TCNF) via formic acid/hydrogen peroxide pretreatment followed by TEMPO/NaClO/NaClO₂-mediated oxidation. The pretreatment efficiently removed lignin, hemicellulose, and other non-cellulosic components, yielding purified cellulose (CG-C) with high crystallinity (CrI = 84%). Subsequent regioselective oxidation introduced carboxyl groups at the C6 position of cellulose chains, achieving a high carboxylate content of 1.4 mmol/g. The resulting CG-TCNF exhibited a well-dispersed nanofibrillar morphology with an average width of 3.57 nm and a high specific surface area of 265 m²/g. Comprehensive characterization confirmed the successful oxidation and nanofibrillation: Fourier Transform Infaraed (FT-IR) Spectroscopy revealed the characteristic carboxylate absorption bands, X-ray Diffraction (XRD) showed preserved cellulose I structure with a slight reduction in crystallinity (CrI = 79.2%), and zeta potential measurements indicated good colloidal stability (−45.23 mV) in aqueous suspension. Thermal analysis demonstrated that the introduced carboxyl groups reduced the thermal stability of the nanofibrils compared to the precursor cellulose. This work establishes a novel route for directly transforming coffee grounds into functional nanocellulose, highlighting its potential as a sustainable feedstock for high-value nanomaterials.

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Keywords

Spent coffee grounds; formic acid/hydrogen peroxide; TEMPO/NaClO/NaClO₂; carboxylated; cellulose nanofibrils

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