Stefan RL, Szeri AJ
Department of Mechanical and Aerospace Engineering, University of California-Irvine, Irvine, California, 92697-3975
J Colloid Interface Sci. 1999 Apr 1;212(1):1-13. doi: 10.1006/jcis.1998.6037.
When bubbles rise through a liquid they are known to scavenge dissolved surface-active materials (surfactants). Small bubbles in the size range of tens of micrometers quickly become covered with surfactants in any but the cleanest conditions. This has the effect of immobilizing the bubble surface and affecting the drag and therefore the bubble rise speed. A large number of bubbles rising as a cloud toward a free surface will populate the bulk surface with surfactants at a richness that far exceeds that which would occur in the absence of bubbling. However, in addition to the increased deposition of surfactants on the bulk surface, the random and agitated motions of the rising bubbles induce mixing of the liquid. In a companion paper (R. L. Stefan and A. J. Szeri, submitted for publication) the mixing properties of a bubble cloud rising toward a free surface were determined. In the present work, a model for the uptake of surfactants by bubbles and subsequent deposition on the bulk surface is developed including the crucial feature of bubble-induced fluid mixing. It is found that the mixing of desorbed surfactant down into the bulk is key to predicting what will be the enrichment of the bulk surface. Copyright 1999 Academic Press.
当气泡在液体中上升时，众所周知它们会清除溶解的表面活性物质（表面活性剂）。在除了最清洁的条件之外的任何情况下，几十微米大小范围内的小气泡很快就会被表面活性剂覆盖。这会使气泡表面固定，并影响阻力，进而影响气泡上升速度。大量气泡以云状形式朝着自由表面上升，会使主体表面充满表面活性剂，其丰富程度远远超过无气泡情况下的情况。然而，除了表面活性剂在主体表面上的沉积增加之外，上升气泡的随机和搅动运动会引起液体的混合。在一篇配套论文（R. L. 斯特凡和A. J. 塞里，已提交发表）中，确定了朝着自由表面上升的气泡云的混合特性。在当前工作中，建立了一个气泡摄取表面活性剂并随后沉积在主体表面上的模型，其中包括气泡引起的流体混合这一关键特征。研究发现，解吸的表面活性剂向下混合到主体中是预测主体表面富集情况的关键。版权所有1999年学术出版社。
