A one-step nitric acid/ethanol pretreatment strategy for scalable and sustainable cellulose nanofibrils production from sugarcane bagasse

Abstract

Cellulose nanofibrils (CNFs) hold immense potential across industries, yet their commercialization remains hindered by energy-intensive production processes and reliance on costly, purified pulp feedstocks. Herein, this study presents a nitric acid/ethanol treatment strategy for the sustainable production of CNFs from sugarcane bagasse by integrating delignification, defibrillation, fiber size reduction, and surface functionalization. This method achieved 94.3% lignin removal while preserving cellulose crystallinity (∼75%) and minimizing cellulose degradation. Compared to commercial bleached sugarcane bagasse pulp, the treated fibers showed 59.0% shorter length and 442.9% higher fines content, enabling energy-efficient fibrillation. Mechanistic studies revealed selective lignin–carbohydrate complex cleavage, aromatic nitration, and hydroxyl-to-carboxyl oxidation. Without further pretreatment, the derived CNFs exhibited uniform nanostructures (1–10 nm diameter, 100 nm–2 μm length) and suspension stability (>6 months) after homogenization. Notably, the nitric acid/ethanol reaction medium enables solvent recovery through simple distillation, facilitating process sustainability. By synergizing the dual role of nitric acid as an oxidant/delignification agent with lignin solvation of ethanol, this process offers a scalable, sustainable route for CNF production.