Department of Chemical Engineering, City College of The City University of New York, NY 10031, USA.
J Colloid Interface Sci. 2011 Oct 1;362(1):235-41. doi: 10.1016/j.jcis.2011.05.077. Epub 2011 Jun 6.
The coalescence mechanism of a particle-laden drop resting at an oil-water interface has been studied. Two mechanisms for drop coalescence are observed; (i) complete coalescence, in which the drop experiences total coalescence in one event, and (ii) partial coalescence, where a drop is observed to separate during coalescence, producing a smaller secondary drop that rebounds and comes to rest at the planar oil-water interface. For particle-laden drops of approximately 4mm in diameter, we show the critical condition for partial to complete coalescence to be dependent on the particle concentration, and the interparticle interaction energy. Colloidal silica spheres dispersed in 10(-4) M KNO(3) electrolyte solution are highly charged and remain dispersed in the drop. By increasing the solids concentration, we measure the transition from partial to complete coalescence at 20 wt.%. However, this critical condition can be reduced by increasing the interparticle interaction energy. In 1 M KNO(3) electrolyte solution, the particle surface charge is sufficiently screened such that particle clusters readily form in the water drop. With particle clustering, transition from partial to complete coalescence is measured at 8 wt.% solids.
已研究了在油水界面处静止的含颗粒液滴的聚并机理。观察到两种液滴聚并机制：(i)完全聚并，其中液滴在一个事件中经历完全聚并，和(ii)部分聚并，其中观察到液滴在聚并过程中分离，产生较小的二次液滴，该液滴反弹并在平面油水界面处停止。对于直径约为 4mm 的含颗粒液滴，我们表明部分到完全聚并的临界条件取决于颗粒浓度和颗粒间相互作用能。在 10(-4) M KNO(3)电解质溶液中分散的胶体二氧化硅球带高度电荷，并在液滴中保持分散。通过增加固体浓度，我们在 20wt.%下测量从部分到完全聚并的转变。然而，通过增加颗粒间相互作用能，可以降低这种临界条件。在 1 M KNO(3)电解质溶液中，颗粒表面电荷被充分屏蔽，使得颗粒团簇在水滴中很容易形成。随着颗粒簇的形成，在 8wt.%固体下测量从部分到完全聚并的转变。
