Effect of Exopolymers on the Liquid Limit of Clays and Its Engineering Implications
Effect of Exopolymers on the Liquid Limit of Clays and Its Engineering Implications
复制标题
外聚合物对粘土液限的影响及其工程意义
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. Gambrell
中科院分区：
文献类型：
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作者：
R. Nugent;Guoping Zhang;R. Gambrell
实验研究，旨在了解微生物和粘土，特别是高岭石渗出的外聚合物之间的相互作用。两种生物聚合物-黄原胶，阴离子细菌胞外多糖，和瓜尔胶，中性电荷的植物多糖-被用作外聚合物类似物。测定了高岭石粘土的液限，在孔隙流体中具有不同的生物聚合物浓度和背景阳离子（Ca 2+、Na+或K+），以研究外聚物对粘土行为的影响。结果表明，高岭石的液限一般增加与生物聚合物浓度的孔隙流体作为一个结果，粘度增加，和背景阳离子存在于孔隙流体改变液限。采用五种类型的粘土颗粒、阳离子和生物聚合物之间的活性纳米级相互作用来解释结果：生物聚合物诱导的粘土颗粒聚集倾向于降低液限，二价阳离子引起的聚合物交联显著增加生物聚合物溶液粘度，从而提高液限;通过阳离子桥连和氢键形成的粘土-聚合物互联网络提高了液限;粘土表面上双电层厚度的减小降低了液限;单价阳离子在生物聚合物分子上的优选吸附降低了液限。液限的变化反映了这些相互作用在纳米尺度上相互竞争的宏观响应。工程意义也讨论了实验结果和粘土-生物聚合物相互作用的基础上。
An experimental study aimed at understanding the interactions between exopolymers exuded by microorganisms and clays, particularly kaolinite, is described. Two biopolymers–-xanthan gum, an anionic bacterial extracellular polysaccharide, and guar gum, a neutrally charged plant polysaccharide–-were used as exopolymer analogs. Liquid limits of a kaolinite clay were measured, with varied biopolymer concentrations and background cations (Ca2+, Na+, or K+) in the pore fluid, to study the influence of exopolymers on clay behavior. Results indicate that the liquid limit of kaolinite generally increases with the biopolymer concentration of the pore fluid as a result of increased viscosity, and the background cation present in the pore fluid alters the liquid limit. Five types of active nanoscale interactions between clay particles, cations, and biopolymers were adopted to interpret the results: biopolymer-induced aggregation of clay particles tends to decrease the liquid limit; polymer cross-linking caused by divalent cations significantly increases the biopolymer solution viscosity and hence the liquid limit; the formation of a clay–polymer interconnected network via cation bridging and hydrogen bonds increases the liquid limit; a reduction in the thickness of the electric double layer on the clay surface decreases the liquid limit; and preferred adsorption of monovalent cations over biopolymer molecules decreases the liquid limit. The variations in the liquid limit reflect the macroscopic response of these interactions competing with each other at the nanoscale. Engineering implications also are discussed on the basis of the experimental results and the clay–biopolymer interactions.