Abstract: Anion negative adsorption by montmorillonite colloid surface with overlapping flat double layers was determined and the influence of the overlappping degree of the flat double layers and the electrolyte concentration on the anion negative adsorption is discussed. The experimental results are concluded as following: (1) the overlapping degree of the flat double layers can be described by the variation of the ratio of the electric potential at the midplane,φ_d, to the electric potential at the Outer Helmhotz Plane(OHP), φ_δ; (2) the overlapping degree of the flat double layers, φ_d/φ_δ, raises with the increase of the applied pressure; (3) the anion negative adsorption decreases with the increase of the overlapping degree of the flat double layers and the increase of the electrolyte concentration.

Key words: Electric double layer, Montmorillonite colloid, Anion negative adsorption