Sorption kinetics and mechanism of various oils into kapok assembly

Sorption rates of kapok fibers on different oils, such as diesel, cooking oil, used motor oil, and motor oil, were quantitatively evaluated by using a wicking method. Kapok fibers absorbing different oils exhibited large differences in terms sorption coefficients. Microscopic observations of oil wetting on a single kapok showed that the four oils had varying wettability and adhesiveness to kapok, but that all of them penetrated into kapok lumens quickly because of the fiber's low surface energy, which was 40.64 mN/m, and extreme hydrophobicity, with a water contact angle up to 151°. After treatment with chloroform, there were slight changes in oil absorbencies to kapok, but the sorption coefficients for the four oils increased markedly. SEM demonstrated that chloroform treatments caused the smooth surface of the kapok fibers to become highly roughened, with densely vertical grooves that provided more available surface and a larger driving force for oil sorption through the fiber assembly.