Oil and water don’t mix. This can be proven by simple adding a bit of olive oil to a glass f water and then mixing. The oil and water should separate into different layers no matter how much there mixed together. Now, if egg yolk is added and then the mixture is homogenised the oil shouldn’t separate out. This is because egg yolk is a natural emulsifier and the uniform mixture of oil and water is called an emulsion. Milk is an emulsion of oil in water and butter is an emulsion of water in oil. They can be formed because of the duality of the emulsifier. One end is hydrophilic, it loves water, and whenever it touches a water molecule this end will bind to it. The other end is oleophilic, a similar loving of oil. This means the emulsifier can hold both molecules in suspension and not allow them to separate.
Of course sometimes you don’t want oil and water to mix when unfortunately it has. The chemical industry produces, often highly salinated or acidic, oily water, which has in the past been cleaned by flocculation of precipitation. Both these methods take quite some time and are expensive compared to the product. Luckily a new method chemical membrane has been designed. By covering a glass fibre microlayer with silica spheres on a similar scale, a membrane has been produced that acts as an anti-emulsifier. One side is hydrophobic but when submerged in water becomes hydrophilic. The changing of nature means oil gets held by the membrane at the surface and water is held below it. This method seems to be very efficient and more importantly can be used in environments that are of low pH and high salt content, making it perfect for purification of this water.