The Maxwell-Stefan model 
The Maxwell-Stefan model of this applies for multicomponent systems. It is used to separate isotopes of uranium in gaseous compounds. This process is described by Fick's laws. This arises from the statistics of random particle movement and in the context of water and a semipermiable membrane it is called osmosis. For 10 points, name this movement from high concentration to low concentration.
The Maxwell-Stefan model of this applies for multicomponent systems.
diffusion