Development and characterization of sustainable cellulose nanofibers from passion fruit peel using citric and hydrochloric acids

Passion fruit peel is an abundant agro-industrial byproduct rich in lignocellulosic components, but its high pectin and lignin contents hinder cellulose valorization. This study produced cellulose nanofibers (CNFs) from passion fruit peel flour using three chemical extraction routes: citric acid (CA), hydrochloric acid (CL), and a sequential CA + CL treatment, followed by alkaline purification and mechanical fibrillation. Mass balance, yield analysis, preliminary life cycle assessment (LCA), and cost estimation were integrated with structural, chemical, thermal, and morphological characterization. CNF yields ranged from 24.8% to 29.4%, within values reported for agro-residue CNFs obtained under mild conditions. X-ray diffraction confirmed preservation of the cellulose Iβ crystalline structure with crystallinity indices above 80%. FTIR showed effective delignification and differences in hydrogen bonding. Thermogravimetric analysis indicated higher thermal stability for CL-derived CNFs, while SEM revealed nanofibers of 60–65 nm and some fibril bundling in CA + CL. Sustainability analysis showed CA used less water and produced fewer effluents, whereas CL achieved higher yields and lower production costs.西番莲果皮是一种储量丰富的农林工业副产物，富含木质纤维素类组分，但其较高的果胶与木质素含量会阻碍纤维素的高值化利用。本研究以西番莲果皮粉为原料，通过三条化学提取路径制备纤维素纳米纤维（Cellulose Nanofibers, CNFs）：柠檬酸（Citric Acid, CA）法、盐酸（Hydrochloric Acid, CL）法，以及柠檬酸-盐酸分步处理法，后续辅以碱性纯化与机械原纤化工艺。本研究将物料衡算、得率分析、初步生命周期评估（Life Cycle Assessment, LCA）与成本估算，与结构、化学、热学及形貌表征手段相结合。所得纤维素纳米纤维的得率介于24.8%至29.4%之间，与温和条件下制备的农林残渣源纤维素纳米纤维的已有报道值相符。X射线衍射分析证实，所得产物保留了纤维素Iβ晶型结构，结晶度指数高于80%。傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FTIR）结果表明，样品实现了有效的脱木质素处理，且氢键作用存在差异。热重分析结果显示，盐酸法制备的纤维素纳米纤维具有更高的热稳定性；扫描电子显微镜（Scanning Electron Microscopy, SEM）观测显示，产物为直径60~65 nm的纳米纤维，而柠檬酸-盐酸分步处理法所得样品存在部分原纤聚集现象。可持续性分析结果表明，柠檬酸法的用水量更少且产生的废水更少，而盐酸法则可获得更高的得率与更低的生产成本。