The Loeb-Sourirajan Membrane: How It Came About

In the early 1950's Professor Samuel Yuster at the University of California, Los Angeles (UCLA) conceived the idea of using the Gibbs adsorption equation as a guideline to find techniques for producing fresh water from brines (1,2). The Gibbs equation is given by: U = -( l/vRT ) (∂σ/∂1na)T,Ar (1) where U is the adsorption of solute per unit area of surface, ∂ is the number of ions into which the electrolyte can dissociate, R is the gas constant, T is the absolute temperature, σ is the surface tension of the solution, a is the activity of the solute, and Ar is the area of the surface of the solution. According to this equation, brines in contact with air or other hydrophobic surfaces, will have a layer of relatively pure water, 3 or 4 Angstroms thick, adjacent to the interface. Therefore it should be possible to 'skim off this fresh