As far as our imagination would stretch, we would have never thought that sand, as found on the beach embracing waters of breaking waves, would become hydro-phobic. Water-repelling sand is an example of how nanotechnology can lead to drastic changes in the behavior of materials.
To understand how hydrophobic sand works, you need to know some basic information about water molecules. Due to the unequal distribution of electrons in the molecule’s bonds between atoms, water molecules have slightly positively- and slightly negatively-charged ends. Positively- and negatively-charged ends of different molecules strongly interact with each other in the same way poles of a magnet do. These interactions known as “hydrogen bonds” are so strong that substances made up of non-polar molecules, such as that of oils and tar, cannot mix with water. Try to mix water with oil, and you will see the latter spreading across the water’s surface and not mixing with it.
Naturally, atoms on the surface of sand particles have charged ends that are attracted to the water molecules charged ends; that is why sand absorbs water. Applying nanotechnology, scientists have coated natural sand grains with a silicon-based compound that has a hydrophilic end, which is attracted to the sand particle, and a hydrophobic end that sticks out away from it. This process creates a hydrophobic water-repelling layer on the surface of the sand grain. However, other liquids will soak into the nano-modified sand, such as oils.
Hydrophobic sand is used in cleaning up petroleum oil spills due to its ability to absorb it. It has also been used to protect electric and telephone wires in extremely cold climates as it repels water and prevents it freezing around the junction boxes.
References
nanotech-now.com
mrsec.wisc.edu