Energy and Environment Directorate, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99354, USA.
J Hazard Mater. 2013 Jan 15;244-245:160-70. doi: 10.1016/j.jhazmat.2012.11.028. Epub 2012 Nov 21.
Xanthan gum solutions are shear thinning fluids which can be used as delivery media to improve the distribution of remedial amendments injected into heterogeneous subsurface environments. The rheological behavior of the shear thinning solution needs to be known to develop an appropriate design for field injection. In this study, the rheological properties of xanthan gum solutions were obtained under various chemical and environmental conditions relevant to delivery of remedial amendments to groundwater. Higher xanthan concentration raised the absolute solution viscosity and increased the degree of shear thinning. Addition of remedial amendments (e.g., phosphate, sodium lactate, ethyl lactate) caused the dynamic viscosity of xanthan solutions to decrease, but they maintained shear-thinning properties. Use of mono- and divalent salts (e.g., Na(+), Ca(2+)) to increase the solution ionic strength also decreased the dynamic viscosity of xanthan and the degree of shear thinning, although the effect reversed at high xanthan concentrations. A power law analysis showed that the consistency index is a linear function of the xanthan concentration. The degree of shear thinning, however, is best described using a logarithmic function. Mechanisms to describe the observed empiricism have been discussed. In the absence of sediments, xanthan solutions maintained their viscosity for months. However, the solutions lost their viscosity over a period of days to weeks when in contact with site sediment. Loss of viscosity is attributed to physical and biodegradation processes.
黄原胶溶液是剪切稀化流体，可用作输送介质，以改善注入非均质地表环境中的补救性添加剂的分布。为了制定现场注射的适当设计，需要了解剪切稀化溶液的流变特性。在这项研究中，获得了与将补救性添加剂输送到地下水中有关的各种化学和环境条件下黄原胶溶液的流变性质。较高的黄原胶浓度提高了绝对溶液粘度，并增加了剪切稀化的程度。补救性添加剂（如磷酸盐、乳酸钠、乳酸乙酯）的添加会降低黄原胶溶液的动态粘度，但它们保持剪切稀化特性。使用一价和二价盐（如 Na(+)、Ca(2+)）来增加溶液的离子强度也会降低黄原胶的动态粘度和剪切稀化程度，但在高黄原胶浓度下，效果会逆转。幂律分析表明，稠度指数是黄原胶浓度的线性函数。然而，剪切稀化程度最好用对数函数来描述。已经讨论了描述观察到的经验主义的机制。在没有沉积物的情况下，黄原胶溶液可以保持数月的粘度。然而，当与现场沉积物接触时，溶液在数天到数周的时间内失去了粘度。粘度的损失归因于物理和生物降解过程。
