Inorganic cations, clay minerals

Many inorganic ion exchangers have been studied for the removal of strontium and cesium ions, due to their high selectivity for specific cations, thermal and radiation stabilities [1 S], In spite of those advantages, they have been limted in their extensive applications because of the pressure drop problem in column operation when they are used in microcrystalline or powdered form. To solve this problem, in the case of synthetic zeolites, clay minerals are often used for pelletization, but it still causes dissolution of clay minerals in aqueous solution. 

The immobilization of metal complex catalysts on polymers and inorganic oxides has received considerable attention as a means of combining the best advantages of homogeneous and hetereo-geneous catalysis (1-6). The swelling layer lattice silicates known as smectite clay minerals have added an important new dimension to metal complex Immobilization. These compounds have mica-type structures in which two-dimensional silicate sheets are separated by monolayers of alkali metal or alkaline earth cations (7). The structure of a typical smectite, hectorite, is illustrated in Figure 1. 

Inorganic species are incorporated in low-rank coals in many ways as ion-exchangeable cations, as coordination complexes, and as a diverse array of discrete minerals. In some cases an element will be present in more than one form potassium, for example, occurs both as an exchangeable cation and in association with clay minerals. The variation in association of inorganics among the multiple modes of occurrence results in a very complex series of reactions and mineral transformations when low-rank coals are ashed. In low-rank coal utilization processes the behavior of the inorganic components can be at least as important to effective... 

When an alkaline solution is injected into a formation, the concentrations of OH, COs, and SiOs are increased. The increase in OH is from the injected alkaline solution. The increase in is from HCOs because high OH makes the reservoir an alkaline enviromnent and converts HCOs into COs. SiOs is a result of the reaction between the injected alkali and formation minerals. Strong alkalis dissolve the clay minerals and damage the rock surface electric charge and microstructures, which finally results in dispersion and migration of the clay minerals. If seawater is injected, S04 is increased. Ca " and Mg " are from the formation water, cation exchange, and reactions between the injected solution and rock minerals. Sometimes, there is Al. Several inorganic scales can be formed as follows ... 

Cations based on substituted silsesquioxanes have also been intercalated [7]. On heating the ion-exchanged clay minerals water is evolved, but oxycation or oxide pillars keep the siliceous layers apart. These materials have enhanced thermal stability compared with clay minerals expanded with organic cations. Expanded clay minerals cover at least as wide a range of accessibilities to the interlamellar micropore spaces as the zeolites, but the pore characteristics of clay minerals with inorganic pillars need more detailed investigation. 

---