This study aims to optimize strong acid hydrolysis-based production of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) from pre-extracted and fully bleached kraft pulp of loblolly pinewood, the most abundant and commercially significant softwood species in southeastern United States. The effect of four parameters, including acid concentration, temperature, duration and pulp particle size, on the yield and properties of CNCs was investigated using the central composite design (CCD) of response surface methodology (RSM) for process optimization. While CNC yield was significantly affected by acid concentration and hydrolysis temperature and was adequately explained by an empirical model, none of the characteristic properties of CNCs, including crystallinity index, surface charge and particle size, displayed any strong correlation to the process parameters within the experimental ranges tested. At different hydrolysis severities, we not only analyzed the waste streams to determine the extent of holocellulose degradation, but also evaluated the properties of leftover partially hydrolyzed pulp, called cellulosic solid residues (CSR), to gauge its potential for CNF production via mechanical fibrillation. Conditions that maximized CNC yields (60% w/w) were 60% acid concentration, 58 °C, 60 min and 40 mesh particle size. Twenty percent (w/w) of the pulp was degraded under these conditions. On the other hand, conditions that maximized CSR yields (60% w/w) were 54% acid, 45 °C, 90 min and 20 mesh particle size, which also produced 15% CNCs, caused minimal pulp degradation (< 5%) and imparted sufficient surface charge such that CSR was easily microfluidized into CNFs. Therefore, the strong acid hydrolysis process could be tuned to maximize the production of cellulose nanocrystals and nanofibers and obtain two products with different properties and applications through the process optimization.

中文翻译：

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通过预先提取的火炬松牛皮纸浆最大程度地生产纤维素纳米晶体和纳米纤维：响应面法

这项研究旨在优化以强酸水解为基础的纤维素松木的预提取和完全漂白牛皮纸浆的纤维素纳米晶体（CNCs）和纤维素纳米纤维（CNFs）的生产方法。松软的松木是美国东南部最丰富，最具商业意义的软木树种。使用响应表面方法（RSM）的中央复合设计（CCD）进行工艺优化，研究了酸浓度，温度，持续时间和纸浆粒度这四个参数对CNCs产量和性能的影响。尽管CNC产率受酸浓度和水解温度的影响很大，并且可以通过经验模型充分解释，但是CNC的任何特性都没有，包括结晶度指数，表面电荷和粒度，在测试的实验范围内显示出与工艺参数的任何强相关性。在不同的水解强度下，我们不仅分析了废物流以确定全纤维素的降解程度，而且还评估了剩余的部分水解的纸浆（称为纤维素固体残留物（CSR））的性能，以评估其通过机械原纤化生产CNF的潜力。使CNC产量最大化（60％w / w）的条件是60％的酸浓度，58°C，60分钟和40目粒度。在这些条件下，纸浆的百分之二十（w / w）被降解。另一方面，最大化CSR产量（60％w / w）的条件是54％的酸，45°C，90分钟和20目粒度，这也产生了15％的CNC，从而使纸浆降解最小（< 5％）并赋予足够的表面电荷，以使CSR易于微流化成CNF。因此，可以对强酸水解工艺进行调整，以最大程度地提高纤维素纳米晶体和纳米纤维的产量，并通过工艺优化获得具有不同性能和应用的两种产品。