Solid-liquid interface silicate adsorption

The dispersed systems are mostly silicates. The author discusses interparticle interactions as a tool for evaluating the stability of dispersions. Parameters such as heat of immersion at solid-liquid interfaces and adsorption capacity are determined, and the mathematical treatment for determining the enthalpy isotherms is described. The heat of wetting in amorphous silica dispersion and on zeolites is discussed. 

One of the essential features of the solid-liquid interface is that the adsorbing substance may not only be bound to the surface by relatively weak physical forces, but also may form true chemical bonding with molecules or ions located at the surface of the solid phase. This phenomenon, referred to as the chemisorption, may seem to invalidate the polarity equalization rule at the interface between a polar crystal (e.g. silicate or sulfide) and a polar medium (water) the adsorption due to chemical bond formation may occur in such a way that the hydrocarbon chains are facing the water phase (Fig. III-9, a). At sufficiently high concentrations of chemisorbing surfactant, when the entire solid surface is covered with a monolayer, the formation of a second, oppositely oriented, surfactant layer starts, i.e., regular surfactant adsorption... 

In our earlier works the adsorption layer at the solid/ liquid interface was employed as a nanophase reactor for the generation of nanocrystalline metal particles and for their stabilization in the presence of the clay mineral [17]. The procedure consists of adsorbing the precursor ions of the nanocrystalline material in the interfacial adsorption layer of solid particles dispersed in the liquid phase and the synthesis is carried out in the adsorption layer by introducing the reducing agent. The nanoparticles can be grown attached to the surface, in well-controllable number and size between the silicate layers. 

The surfaces of oxide colloidal particles or silicate minerals in contact with aqueous solutions are charged positively or negatively by adsorption or desorption of H+ ions. An electrical double layer at solid/liquid interface is formed by adsorbing counterions from the aqueous solution to its surface (Sen and Khilar, 2009). The charge developing process on the surfaces can be represented as follows (Cornell and Schwertmann, 1998) ... 

Secondary minerals are generally formed in nearsurface conditions. Secondary minerals include layer silicates or clay minerals, carbonates, phosphates, sulfur minerals, and different hydroxides and oxy-hydroxides of Al, Fe, Mn, Ti, and Si. Non-crystalline minerals such as allophane and imogoUte are also included among the secondary minerals. Secondary minerals, such as the clay minerals, may show specific surface areas in the range 20-800 m /g and up to 1000 m /g in the case of imogolite (Wada, 1985). Surface area is very important because most reactions in soil are surface reactions at the solid and liquid interface. A brief examination of layer silicates and soil colloids is useful for understanding the phenomena of adsorption, fixation, and weathering. 

---