Improved gravitational grain size separation method

A low energy method for grain size separation in heterogeneous sediments without using chemicals and in thermostatic condition, was tested in order to preserve unchanged the physical and chemical properties of the porous medium. The method consisted of wet sieving, to divide the sandy fraction from the fine fraction (< 63 µm), and of wet gravitational separation to divide the clayey from the silty fraction. Deionised water was used as dispersive phase for sequential gravitational separation of silt and clay. Stokesʹ law was applied to calculate the settling time for the silty fraction in order to siphon out the resulting supernatant containing the clay particles. The procedure was systematically tested and proved to be highly reproducible and the degree of purity was 90% for silt and 95% for clay. This method can be conveniently applied in many studies on contaminant fate and partitioning between liquid and solid phases, where physical and chemical integrity of each granulometric fraction is a prerequisite.