Sarkar Arijit, Tirumkudulu Mahesh S
Department of Chemical Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400076, India.
Langmuir. 2009 May 5;25(9):4945-53. doi: 10.1021/la804186m.
We consider the drying of latex dispersions containing submicrometer-sized particles dispersed in water. It is well known that the consolidation of colloidal particles is influenced by a number of factors such as particle size and shape and interparticle potential. In this work, we focus on the effect of surface charge on the consolidation front. Recent experimental and theoretical investigations on the sedimentation of charged colloidal spheres have shown that the large mass difference between noninteracting colloids and ions sets up a macroscopic electric field, thereby enhancing the diffusivity of the particles and resulting in an inflated sedimentation profile. Our experimental measurements of the concentration profile during drying-induced consolidation also reveal similar charge effects. We present a model for the consolidation of charged particles that accounts for the presence of an induced external electric field. As expected, the predicted particle diffusivity is enhanced by the onset of the electric field at low particle concentration. Fluorescence and bright-field microscopy were used to detect the particle concentration variation in a dispersion dried in a capillary, and the measured profile agrees with the prediction confirming the influence of particle charge on consolidation.
我们考虑含有分散于水中的亚微米级颗粒的胶乳分散体的干燥过程。众所周知，胶体颗粒的固结受到许多因素的影响，如颗粒大小、形状和颗粒间电势。在这项工作中，我们重点关注表面电荷对固结前沿的影响。最近关于带电胶体球沉降的实验和理论研究表明，非相互作用胶体与离子之间的巨大质量差异会产生宏观电场，从而提高颗粒的扩散率，并导致沉降曲线膨胀。我们在干燥诱导固结过程中对浓度分布的实验测量也揭示了类似的电荷效应。我们提出了一个用于带电颗粒固结的模型，该模型考虑了感应外部电场的存在。正如预期的那样，在低颗粒浓度下，电场的出现会提高预测的颗粒扩散率。使用荧光显微镜和明场显微镜来检测在毛细管中干燥的分散体中的颗粒浓度变化，测量的曲线与预测结果相符，证实了颗粒电荷对固结的影响。
