Three aluminas were investigated with five eluents containing various amounts of water. The first water layer adsorption can be described by the Freundlich's model whilst adsorption of the following water layers can be interpreted with the Brunauer, Emmet and Teller model. Energetic identity of the three aluminas was proved and eight active sites per nm2were evidenced. Retention of solutes was interpreted with a logarithmic model in which the capacity factor logarithm varies linearly with the eluent water content logarithm.