Mechanism of adsorption of cations by silicate minerals

• Main Author: Armstrong, Milton Glen
• Format: Others
• Published: BYU ScholarsArchive 1953
• Subjects: Cations; Silicates
• Online Access: https://scholarsarchive.byu.edu/etd/8157; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=9157&context=etd

Adsorption of cations by clays has been a subject of investigation for many years. Many proposals have been advanced to explain this process of adsorption. Two proposals have been prominent in recent years. The Marshall "charged lattice" theory attributes adsorption of cations by clays to an electrostatic attration of the clay particles for cations. This charge on the clay particles is attributed to various isomorphic substitutions in the lattice of the clay which result in an unbalanced charge on the particle. This isomorphic substitution can take place either in the silicon-oxygen tetrahedra of the silicate structure or with the aluminum layer of the particle. The Cook "ion-pair" theory make the assumption that the charge on the clay particle is caused by the neutral clay chemisorbing hydroxyl molecules in the compact double layer thus giving the particle its negative charge. Cations are then attracted electrostatically to the diffuse outer layer. Experimental adsorption data is used to evaluate the validity of these two theories. Equations are set up representing mathematically the two mechanisms of adsorption and are tested graphically with the experimental data. These various graphs, in every case, show that the Marshall "charged lattice" mechanism is inconsistent with the experimental data. The Cook theory adequately represents a consistent agreement with this rather complete set of experimental data.