Effect of clay mineralogy and exchangeable cations on water repellency in clay-amended sandy soils

Abstract

Artificial water-repellent sands were prepared in the laboratory from acid-washed sand and either cetyl alcohol or organics extracted from a natural water-repellent sand. Added clays (at 0.5% w/w) had no effect when gently mixed with a natural and the two artificial water-repellent sands. After a wetting and drying cycle, kaolinite reduced repellency to a low level in the natural sand and the artificial sand with extracted organics, but montmorillonite was not effective. Na+-saturated clays were generally more effective than Ca2+-saturated clays. In the cetyl alcohol sand, montmorillonite was more effective than kaolinite. Neither artificial sand was a perfect model of the natural system, although the extracted organic model was far superior. Kaolinite did not strongly adsorb hydrophobic molecules, but was effective because it was able to cover the hydrophobic sand surface. Application of kaolinite clay to a water-repellent sand appears promising.