The wetting behavior of a nonionic surfactant on hydrophobized quartz sand

Abstract

The wetting behaviour of hydrophobized sand with a nonionic surfactant has been investigated. Wettability measurements with the apparent contact angle, drop penetration time, and water entry pressure were carried out at increasing TX-100 concentration on sands at different particle sizes functionalized with polydimethylsiloxane coatings. The relation between apparent contact angles, surfactant concentration and CMC with particle size was established. Differences in experimental results to the drop penetration time and water entry pressure are attributed to irregular particle morphology and sample structure being tested. Models are proposed to predict the apparent contact angles in a Cassie-Baxter state and predict the water entry pressure based on the effective pore size. Both are validated against the experimental results. Adsorption and work of adhesion are used to ascertain the distribution of surfactants at the solution-air and solution-particle surface in order to assist the interpretation of data. The findings pave the way for the modeling, design, and application of hydrophobized sand as functional construction materials.