Gebze Institute of Technology, Department of Chemical Engineering, Cayirova, Gebze 41400, Kocaeli, Turkey.
J Colloid Interface Sci. 2011 Oct 15;362(2):524-31. doi: 10.1016/j.jcis.2011.06.060. Epub 2011 Jul 7.
In this work, the effect of SDS anionic surfactant on the diffusion-controlled evaporation rate of aqueous solution drops placed on TEFLON-FEP substrate was investigated with 11 different SDS concentrations. Drop evaporation was monitored in a closed chamber having a constant RH of 54-57% by a video camera. The initial contact angle, θ(i) decreased from 104±2° down to 68±1° due to the adsorption of SDS both at the water-air and the solid-water interfaces. The adsorption of SDS on the solid surface was found to be 76% of that of its adsorption at the water-air interface by applying Lucassen-Reynders approach. An equation was developed for the comparison of the evaporation rates of drops having different θ(i) on the same substrate. It was found that the addition of SDS did not alter the drop evaporation rate considerably for the first 1200 s for all the SDS concentrations. The main difference was found to be the change of the mode of drop evaporation by varying the SDS concentration. The constant θ mode was operative up to 80 mM SDS concentration, whereas constant contact area mode was operative after 200 mM SDS concentrations due to rapid drop pining on the substrate.
在这项工作中，通过使用 11 种不同的 SDS 浓度，研究了 SDS 阴离子表面活性剂对放置在 TEFLON-FEP 基底上的水溶液液滴的扩散控制蒸发速率的影响。通过摄像机在具有恒定 RH（54-57%）的密闭室中监测液滴蒸发。由于 SDS 在水-空气和固-水界面的吸附，初始接触角θ（i）从 104±2°下降到 68±1°。通过应用 Lucassen-Reynders 方法发现，SDS 在固-液界面上的吸附量为其在水-空气界面上吸附量的 76%。为了比较在同一基底上具有不同θ（i）的液滴的蒸发速率，开发了一个方程。结果发现，对于所有 SDS 浓度，在最初的 1200 秒内，SDS 的添加并没有显著改变液滴的蒸发速率。主要的区别在于通过改变 SDS 浓度改变液滴蒸发的模式。在 80mM SDS 浓度下，恒定θ模式起作用，而在 200mM SDS 浓度后，由于液滴快速固定在基底上，恒接触面积模式起作用。
