Maybe this question is better classified as "physics" than chemistry, but I'm trying it here. Suppose I'm concerned about a substance S that is highly soluble in water and less soluble in oil. I have a batch of oil that is nonetheless contaminated with traces of S, and I want to remove as much S from it as feasible.
I suspect that at an interface between this oil and water, S would diffuse from oil into water, since it's more soluble in water than in oil. I also suspect that diffusion of S across the oil-water interface would be slow, and I'd like to speed up the process if possible. In principle, I can think of three ways of doing that:
- Heating a vessel of oil and water to speed up diffusion
- Increasing the surface area of the oil-water interface by spreading the oil thinly over a large area of water
- Making an emulsion, either by mechanical agitation or with the addition of some emulsifying agent, and then breaking the emulsion later, hoping that S breaks out preferentially into the water fraction.
The last option seems most promising to me, but I don't know if it really works the way I suspect it does. Any pointers on how I might "wash" this oil? I am relatively unconcerned about traces of water remaining in the oil.