Adsorption of petroleum organic compounds on natural Wyoming montmorillonite

Adsorption of petroleum organic compounds on natural Wyoming montmorillonite clay is an irreversible process, as most of organic species still remain adsorbed on mineral after aging. The process is conditioned by the petroleum paraffinic content and by molecules containing alkane chains, as only these type of compounds easy intercalate within the clay interlayer. Such adsorption also involves an irreversible displacement of part of the clay interlayer water. The partial dissolution of the clay matrix is indicated by XRD as an irreversible modification of the clay structure. On the contrary, adsorption of n-heptane or toluene molecules on the same clay are reversible processes, since the clay mineral recover its original crystalline structure after aging and evaporation of the organic species.