Charged Mineral Research Articles

Chemistry of water expelled from compacting clay layers: A model based on Donnan equilibrium

Equations are derived to follow the chemistry of solutions expelled from compacting clay suspensions which contain a uni-univalent electrolyte. The separated equilibrium solution contains more electrolytes due to negative adsorption of the charged clay minerals with compaction. Comparison with experimental data indicates that relatively low activity coefficients in the suspension tend to counterbalance this effect.

Ionic adsorption on variable charge mineral surfaces. Theoretical charge development and titration curves

A completely general theory is presented which can be used to describe both anion and cation adsorption on amphoteric oxide surfaces. It takes account of the fact that both the surfaces and adsorbing species are charged and that the surfaces change their charge when ionic adsorption takes place. The theory is applicable to both specific and non-specifically adsorbed ions. It is shown to account for the pH dependent charge curves of goethite, silica and two tropical soils.

Corrigenda - Ionic adsorption on variable charge mineral surfaces. Theoretical charge development and titration curves

A completely general theory is presented which can be used to describe both anion and cation adsorption on amphoteric oxide surfaces. It takes account of the fact that both the surfaces and adsorbing species are charged and that the surfaces change their charge when ionic adsorption takes place. The theory is applicable to both specific and non-specifically adsorbed ions. It is shown to account for the pH dependent charge curves of goethite, silica and two tropical soils.

The role of water in minerals

The interaction of water with clay minerals is central to a wide range of disciplines that span from fundamental particles used in materials science and engineering to applied aspects in soil science and geotechnical engineering. Because water is the most abundant molecule on the surface of the Earth, and clay minerals are ubiquitous mineral phases, it follows that clay–water interactions play many important roles in the biosphere. In fact, water is an integral component of many clay mineral structures. This chapter reviews key elements of the structure of water, its interaction with ions, and the interaction of water with clay minerals. Surface interactions include hydrogen bonding, ion–dipole, dipole–dipole, and van der Waals interactions involving both neutral and charged clay mineral surfaces. Recent spectroscopic and molecular modelling studies of clay mineral–water interactions are presented in the framework of molecular probes and reporter groups.