Powell Kristin Conrad, Chauhan Anuj
Department of Chemical Engineering, University of Florida , Gainesville, Florida 32611, United States.
Langmuir. 2014 Oct 21;30(41):12287-96. doi: 10.1021/la503049m. Epub 2014 Oct 7.
Carboxyl-terminated carbon black (CB) particles have been proposed as readily available, biocompatible dispersants to stabilize oil-in-water emulsions after an oil spill. Since the reduction in interfacial tension and the increase in interfacial elasticity are the key parameters which relate interfacial mechanics to emulsion stability, this investigation explores the effect of CB adsorption and surface coverage on oil-water interfacial tension and elasticity. Flocculation of CB was explored as ionic strength was increased from 0 to 0.6 M, approximately the salinity of seawater. As salinity increases, CB aggregates into larger particles from 100 nm to 6 μm. The interfacial tension and dilational viscoelasticity were measured for two systems: a drop of a CB suspension in oil and an inverted oil drop in a CB suspension. For the arrangement of a CB suspension drop in oil, most of the CB settles and accumulates toward the bottom of the drop with only small surface adsorption and no appreciable effect is observed on the dynamic interfacial tension or the dilational viscoelasticity. On reversing the arrangement to an inverted oil drop in CB suspension and increasing the convection of the outer phase, the surface coverage increases considerably. The CB coverage becomes more uniform with higher convection with an average value of approximately 2.6 g/m(2), which is representative of the coverage in Pickering emulsions stabilized by CB particles. The CB coverage decreases the surface tension from about 30 to 8.5 mN/m accompanied by an increase in the surface elasticity to 20.7 mN/m. The sharp contrast between the results from the CB suspension drop and the oil drop could be partially due to the effect of the wetting characteristics of the particles or due to the significant differences between the convection in the two cases.
羧基封端的炭黑（CB）颗粒已被提议作为易于获得的生物相容性分散剂，用于在溢油后稳定水包油乳液。由于界面张力的降低和界面弹性的增加是将界面力学与乳液稳定性相关联的关键参数，因此本研究探讨了CB吸附和表面覆盖率对油水界面张力和弹性的影响。随着离子强度从0增加到0.6 M（约为海水盐度），研究了CB的絮凝情况。随着盐度增加，CB聚集成从100 nm到6 μm的更大颗粒。针对两个系统测量了界面张力和拉伸粘弹性：一滴CB悬浮液在油中以及一滴倒置的油滴在CB悬浮液中。对于CB悬浮液滴在油中的布置，大部分CB沉降并积聚在液滴底部，只有少量表面吸附，并且未观察到对动态界面张力或拉伸粘弹性有明显影响。将布置颠倒为倒置的油滴在CB悬浮液中并增加外相的对流时，表面覆盖率显著增加。随着对流增加，CB覆盖率变得更加均匀，平均值约为2.6 g/m²，这代表了由CB颗粒稳定的Pickering乳液中的覆盖率。CB覆盖率将表面张力从约30 mN/m降低到8.5 mN/m，同时表面弹性增加到20.7 mN/m。CB悬浮液滴和油滴结果之间的鲜明对比可能部分归因于颗粒润湿性的影响或两种情况下对流的显著差异。
