The horse chestnut seed shell (HC) and chestnut seed shell (CT) were evaluated as renewable, sustainable, and cheap raw materials transformed into valuable products, “cellulose nanocrystals (CNCs).” Alkali and bleaching treatments were performed to obtain horse chestnut cellulose (HCS) and chestnut cellulose (CTS) and subsequently isolated to the horse chestnut cellulose nanocrystal (HC-CNC) and chestnut cellulose nanocrystal (CT-CNC) by sulphuric acid hydrolysis. Raw materials and their products were comparatively investigated at each stage of the isolation process. The cellulose, hemicellulose, and lignin content of HC and CT were determined via chemical composition analysis. The structural analysis was performed using Fourier transform infrared spectroscopy and X-ray diffraction technics for CNCs. Morphological analysis and size range determination of the samples were carried out via atomic force microscopy (AFM) and particle size analysis. Zeta potential and particle size distribution were determined by analyzing the surface and particle size. The thermal behaviors were investigated at different phases of treatments using thermal gravimetric analysis (TGA/DTG). HC-CNC demonstrates a higher crystallinity index value of 85.49% and a lower yield of 20.46%, whereas CT-CNC shows a lower crystallinity of 65.06% and a higher yield of 36.59%. A differentiation in structural, thermal, and morphological properties of extracted celluloses and isolated CNCs was observed depending on the source of the raw materials. However, a morphological alteration in CNC structures has emerged relative to precursor cellulose after the acid hydrolysis process as an essential finding via AFM studies. The solid wastes horse chestnut and chestnut seed shells offer great potential as suitable, sustainable, and environmentally friendly starting raw materials to produce CNC and in applications, including wastewater treatments, biosensing, wound dressing, and reinforcement for polymer composites due to their excellent thermal and structural properties.

Graphical abstract

中文翻译：

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七叶树和栗子壳固体废弃物中纳米晶纤维素的分离、表征和比较

七叶树籽壳 (HC) 和栗子壳 (CT) 被评估为可再生、可持续且廉价的原材料，可转化为有价值的产品“纤维素纳米晶体 (CNC)”。进行碱和漂白处理以获得七叶树纤维素（HCS）和板栗纤维素（CTS），随后通过硫酸水解分离到七叶树纤维素纳米晶（HC-CNC）和板栗纤维素纳米晶（CT-CNC）。在分离过程的每个阶段对原材料及其产品进行了比较研究。通过化学成分分析测定 HC 和 CT 的纤维素、半纤维素和木质素含量。使用傅里叶变换红外光谱和CNCs的X射线衍射技术进行结构分析。通过原子力显微镜（AFM）和粒度分析对样品进行形态分析和尺寸范围测定。Zeta电位和粒度分布通过分析表面和粒度来确定。使用热重分析 (TGA/DTG) 在不同处理阶段研究热行为。HC-CNC 的结晶度指数值较高，为 85.49%，收率较低，为 20.46%，而 CT-CNC 的结晶度较低，为 65.06%，收率较高，为 36.59%。根据原材料的来源，观察到提取的纤维素和分离的 CNCs 在结构、热和形态特性方面的差异。然而，在酸水解过程之后，CNC 结构的形态变化相对于前体纤维素已经出现，这是通过 AFM 研究的重要发现。固体废物七叶树和栗子壳作为合适、可持续和环保的起始原材料，具有巨大的潜力，可用于生产 CNC 和应用，包括废水处理、生物传感、伤口敷料和聚合物复合材料的增强，因为它们具有出色的热和结构特性。

图形概要