Comparison of three silane compounds to impart water repellency in an industrial sand

Abstract

Water repellent granular materials have been tested in water harvesting applications and proposed as landfill and slope covers. To achieve water repellency, sand particles are coated with waxes, oils or silanes. This paper focuses on silanes because they are widely used in glass coating applications, and thus pertinent for use on silicate minerals for enabling a high degree of water repellency to be attained. Three silane compounds were tested on medium-sized sand: dichlorodimethylsilane (DCDMS), octadecyltrichlorosilane (OTS) and trimethylchlorosilane. The aim was (a) to identify the minimum concentrations required to achieve the highest degree of water repellency, (b) to ensure its stability after treatment and (c) to determine potential conditions or factors to enhance water repellency. The results revealed that only a small amount of silanes, 0·001% by soil mass, was required for the treated sands to reach the maximum degree of water repellency with OTS achieving the highest (138°) and DCDMS the lowest (124°). From the findings, it can be concluded that the combination of OTS treatment in air-dried clean sand provides the highest and most stable water repellent behaviour, paving the way for future research in cover applications where water tightness is of paramount importance.