Shang Jianying, Flury Markus, Harsh James B, Zollars Richard L
Department of Crop and Soil Sciences, Center for Multiphase Environmental Research, Washington State University, Pullman, WA 99164, USA.
J Colloid Interface Sci. 2008 Dec 15;328(2):299-307. doi: 10.1016/j.jcis.2008.09.039. Epub 2008 Sep 20.
We compared five different methods, static sessile drop, dynamic sessile drop, Wilhelmy plate, thin-layer wicking, and column wicking, to determine the contact angle of colloids typical for soils and sediments. The colloids (smectite, kaolinite, illite, goethite, hematite) were chosen to represent 1:1 and 2:1 layered aluminosilicate clays and sesquioxides, and were either obtained in pure form or synthesized in our laboratory. Colloids were deposited as thin films on glass slides, and then used for contact angle measurements using three different test liquids (water, formamide, diiodomethane). The colloidal films could be categorized into three types: (1) films without pores and with polar-liquid interactions (smectite), (2) films with pores and with polar-liquid interactions (kaolinite, illite, goethite), and (3) films without pores and no polar-liquid interactions (hematite). The static and dynamic sessile drop methods yielded the most consistent contact angles. For porous films, the contact angles decreased with time, and we consider the initial contact angle to be the most accurate. The differences in contact angles among the different methods were large and varied considerably: the most consistent contact angles were obtained for kaolinite with water, and illite with diiodomethane (contact angles were within 3 degrees); but mostly the differences ranged from 10 degrees to 40 degrees among the different methods. The thin-layer and column wicking methods were the least consistent methods.
我们比较了五种不同方法，即静态 sessile 滴法、动态 sessile 滴法、Wilhelmy 板法、薄层毛细作用法和柱形毛细作用法，以测定土壤和沉积物中典型胶体的接触角。选择这些胶体（蒙脱石、高岭石、伊利石、针铁矿、赤铁矿）来代表 1:1 和 2:1 层状铝硅酸盐粘土以及三氧化物，它们要么以纯形式获得，要么在我们实验室合成。将胶体以薄膜形式沉积在载玻片上，然后使用三种不同测试液体（水、甲酰胺、二碘甲烷）进行接触角测量。胶体薄膜可分为三种类型：（1）无孔隙且具有极性液体相互作用的薄膜（蒙脱石），（2）有孔隙且具有极性液体相互作用的薄膜（高岭石、伊利石、针铁矿），以及（3）无孔隙且无极性液体相互作用的薄膜（赤铁矿）。静态和动态 sessile 滴法得到的接触角最为一致。对于多孔薄膜，接触角随时间减小，我们认为初始接触角最为准确。不同方法之间接触角的差异很大且变化显著：高岭石与水、伊利石与二碘甲烷得到的接触角最为一致（接触角在 3 度以内）；但大多数情况下，不同方法之间的差异在 10 度到 40 度之间。薄层和柱形毛细作用法是最不一致的方法。
