A sustainable one-step approach for the functionalized cellulose nanocrystal production using recyclable organic acids: Exploring structure-property dynamics.

The study presents a cutting-edge, sustainable approach for the high-yield production (59-62 %) of carboxyl-functionalized cellulose nanocrystals (CNCs) with impressive aspect ratio (20.65 ± 0.74 nm), high crystallinity (77-81 %), outstanding thermal stability (290 °C-343 °C) and varying degrees of functionalization. This innovative method harnesses the synergistic power of mild organic acid hydrolysis (10 %) and steam explosion, employing eco-friendly acids such as acetic, citric, malic, tartaric, and oxalic. These acids drive efficient esterification, as evidenced by zeta potential values (-16 mV to -34 mV) and the presence of ester carbonyl peaks in IR spectroscopy (1730 cm-1). This functionalization enhances the CNCs' colloidal stability by anchoring carboxyl functionalities, which serve as reactive sites for subsequent modifications to tune their hydrophilic or hydrophobic properties -making them versatile candidates for next-generation applications in packaging, biomedical technologies, and edible coatings. Additionally, the successful recovery of the organic acids further enhances the sustainability of this process. Rooted in the principles of green chemistry, this process ensures atom economy, reduced hazardous chemicals, and valorization of Elettaria cardamomum agromass, offering a transformative step towards a circular economy.