Protolytic Weathering of Montmorillonite, Described by Its Effective Surface Fractal Dimension

Octahedral coordinated aluminum is released by the attack of protons from clay minerals like montmorillonite. Apart from other effects, this leads to an alteration of the form of the surface of the clay particles. We used fractal geometry to describe this change in form. The effective surface fractal dimension (D) was determined before and after acid treatment by using the dependency: number of yardsticks necessary to cover the surface versus size of the yardstick area. We used n-alkanols with different cross sectional areas to determine this dependency. This resulted in a D: 2.55 for the untreated and a D: 2.85 for the acid treated clay.