The Micropore Size Distributions of Clay Mineral Systems

Summary The micropore (<100 Å) size distributions of compacted clay mineral systems have been examined by means of low‐temperature N 2 sorption isotherms to saturation. The calculation of pore sizes was based on the application of the Kelvin equation, corrected for the adsorbed film thickness, to the parallel plate model. Clay‐mineral systems have been shown to exist with a high degree of parallel alignment of the plate‐shaped crystals. This results in a high proportion of microporosity and in relatively discrete pore sizes. In montmorillonite clays much intercrystalline overlap area in the dry matrix is inaccessible to N 2 sorption. The structure of these systems may be governed partly by the effect, in suspension, of electrostatic interaction between the charged particles on crystal size, but largely by mechanical interaction on sedimentation and the size of the exchangeable cations present.