Tortuosity of porous particles
Tortuosity of porous particles
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DOI：
10.1021/ac071377r
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发表时间：
2007-12-01
影响因子：
7.4
通讯作者：
Denoyel, R.
中科院分区：
文献类型：
--
作者：
Barrande, M.;Bouchet, R.;Denoyel, R.
在多孔介质传输特性模型中，弯曲度常被用作可调参数。这个参数，不能简化为经典的测量的微观结构参数，如比表面积，孔隙率，或孔径分布，反映了渗透路径的效率，这是链接到材料的拓扑结构。用电解质饱和的颗粒床的有效电导率的测量是评估弯曲度的简单方法。然而，由于在获得可靠的结果和解释数据方面存在真实的困难，它只得到很少的注意。值得注意的是，未解决颗粒间和颗粒内孔隙率对弯曲度的贡献之间的区别。据我们所知，没有模型能够在整个孔隙率范围内拟合悬浮液的曲折度的实验数据，更不用说颗粒床了。只有经验表达式已被提出，但它们不允许导出的多孔颗粒的intratortuosity。对于稀体系，麦克斯韦方程预测球形颗粒悬浮液的有效电导率作为本体电解质电导率和颗粒电导率的函数。粒子内弯曲度可以从粒子电导率导出，所述粒子电导率从应用于粒子无限稀释时的数据的麦克斯韦方程获得。然后，通过假设麦克斯韦方程是电导率作为孔隙率的函数的一阶近似，我们提出了通过电导率测量获得的多孔颗粒悬浮液的弯曲度τ的显式关系：τ = τ其中τ是悬浮液的总孔隙率，τ（p）是颗粒内弯曲度，而ε（p）是颗粒孔隙率。该关系在整个孔隙度范围内拟合实验数据，并且可以用于从仅一个孔隙度的实验确定τ（p）。最后，所获得的值tau（p）的一组用于色谱的多孔颗粒进行了讨论，并在文献中提供的数据进行比较。
Tortuosity is often used as an adjustable parameter in models of transfer properties through porous media. This parameter, not reducible to classical measured microstructural parameters like specific surface area, porosity, or pore size distribution, reflects the efficiency of percolation paths, which is linked to the topology of the material. The measurement of the effective conductivity of a bed of particles saturated with an electrolyte is a simple way to evaluate tortuosity. Nevertheless, it received only little attention because of the real difficulties in both getting reliable results and interpreting data. Notably, the discrimination between the contribution of interparticle and intraparticle porosities to the tortuosity is not resolved. To our knowledge, there is no model able to fit the experimental data of the tortuosity of a suspension, and a fortiori of a particle bed, in the whole porosity range. Only empirical expressions have been proposed, but they do not allow deriving intratortuosity of a porous particle. For a dilute system, Maxwell's equation predicts the effective conductivity of suspensions of spherical particles as a function of the bulk electrolyte conductivity and of particle conductivity. The intraparticle tortuosity can be derived from the particle conductivity obtained from the Maxwell equation applied to data at infinite dilution of particles. Then, by assuming that the Maxwell equation is a first-order approximation of the conductivity as a function of porosity, we propose an explicit relation of the tortuosity tau of a suspension of porous particles, obtained by conductivity measurement, as tau = tau(epsilon, epsilon(p), tau(p)), where epsilon is the total porosity of the suspension, tau(p) is the intraparticle tortuosity, and epsilon(p) is the particle porosity. This relationship fits the experimental data in the whole porosity range and can be used to determine tau(p) from an experiment at only one porosity. Finally, the obtained values of tau(p) for a set of porous particles used in chromatography are discussed and compared to the data available in the literature.