College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China.
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China.
Sci Total Environ. 2022 Aug 25;836:155579. doi: 10.1016/j.scitotenv.2022.155579. Epub 2022 May 1.
Fouling behaviors of polysaccharides vary with their structure, while the mechanisms underlying this phenomenon remain unexplored. This work was carried out to explore the thermodynamic fouling mechanisms of polysaccharides with different structure. Carrageenan and xanthan gum were selected as the model polysaccharides with structure of straight and branch chains, respectively. Batch filtration experiments showed that xanthan gum solution corresponded to a more rapid flux decline trend, and specific filtration resistance (SFR) of xanthan gum (2.32 × 10 m kg) was over 10 times than that of carrageenan (2.21 × 10 m kg). It was found that, xanthan gum possessed a more disordered structure and a rather higher viscosity (15.03 mPa·s V.S. 1.98 mPa·s for carrageenan). Calculation of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory showed higher adhesion energy of xanthan gum (-42.82 my m V.S. -23.26 mJ m for carrageenan). Scanning electron microscopy (SEM) analyses showed that xanthan gum gel layer had a more homogenous structure and rigid polymer backbone, indicating better mixing with water to form a gel. As verified by heating experiments, such a structure tended to contain more bound water. According to this information, Flory-Huggins lattice theory was introduced to build a bridge between polymeric structure and SFR. It was revealed that branch structure corresponded to higher chemical potential change during gel layer formation, and higher ability to carry bound water, resulting in higher filtration resistance during filtration process. This work revealed the fundamental thermodynamic mechanism of membrane fouling caused by polysaccharides with different structure, deepening understanding of membrane fouling.
多糖的污染行为因其结构而异，而这种现象的机制仍未得到探索。本工作旨在探索具有不同结构的多糖的热力学污染机制。选择角叉菜胶和黄原胶作为具有直链和支链结构的模型多糖。分批过滤实验表明，黄原胶溶液对应更快速的通量下降趋势，并且黄原胶的比过滤阻力（SFR）（2.32×10-9 m·kg-1）超过角叉菜胶的 10 倍（2.21×10-9 m·kg-1）。结果发现，黄原胶具有更无序的结构和更高的粘度（15.03 mPa·s V.S. 1.98 mPa·s 用于角叉菜胶）。扩展的德加古因-兰德奥韦尔拜克（XDLVO）理论计算表明黄原胶具有更高的粘附能（-42.82 my·m V.S. -23.26 mJ·m 用于角叉菜胶）。扫描电子显微镜（SEM）分析表明，黄原胶凝胶层具有更均匀的结构和刚性聚合物主链，表明与水更好地混合形成凝胶。通过加热实验验证，这种结构往往含有更多的结合水。根据这些信息，引入了弗洛里-哈金斯格子理论，在聚合物结构和 SFR 之间架起了一座桥梁。结果表明，支链结构在凝胶层形成过程中对应更高的化学势变化，以及携带结合水的更高能力，导致过滤过程中的过滤阻力更高。这项工作揭示了具有不同结构的多糖引起膜污染的基本热力学机制，加深了对膜污染的理解。
