Magnesium aluminum silicate surface

Insoluble solids, regardless of particle size, that have a relatively low interfacial tension and are readily wetted by water are called hydrophilic solids. These solids include clays (bentonite, kaolin, talc, magnesium aluminum silicate) bismuth salts, barium sulfate, carbonates, hydroxides, or oxides of calcium, magnesium, zinc, and aluminum and titanium dioxide. The hydro-philicity of a powder surface can be investigated with the help of moisture absorption studies in which the solid particles are exposed to varying relative humidities. Insoluble powders that absorb moisture below relative humidities of 70-80% at room temperature are said to be hydrophilic solids. 

Pongjanyakul, T. Suksri, H. (2009). Alginate -magnesium aluminum silicate films forbuccal delivery of nicotine. Colloids and Surfaces B Biointerfaces. Vol. 74, pp. 103-113. 

Interestingly, impurities such as aluminum, calcium, magnesium or zinc were reported to reduce both the rate of dissolution and the solubility of silica at equilibrium. Nitric acid-cleaned silica was immersed in solutions of Al, Be, Fe, Ga or Gd ions at pH from 2 to 9. A drastic reduction of the solubility of silica was observed. In particular, the introduction of Al ions rendered silica insoluble at pH 9. This effect was attributed to the formation of a monolayer of insoluble silicate which lowered the silica solubility to that of the surface compound [17]. Seemingly, silicates involving metal ions are formed even at pH values apparently non-aggressive for silica. However, the amount of metal silicate is not specified and the formation of only a silicate monolayer is purely speculative. 

The refractory condensate model has fallen out of favor, including with Lewis (1988). Nevertheless, it is a useful end-member case. Goettel (1988) calculated the composition of the silicate portion of an ultrarefractory Mercury (Table 2, column 2). This model composition contains no FeO or volatiles, and has large concentrations of the refractory elements—aluminum, calcium, and magnesium. We calculated the thorium and uranium contents of such refractory condensates by assuming chondritic Al/Th and Al/U ratios. A surface of this composition will contain many of the phases in calcium-aluminum-rich inclusions (CAls), such as forsterite, anorthite, spinel, perovskite, hibonite, and melilite. 

Acid-functionalized polybutadienes are most effective with fillers such as calcium carbonate and aluminum and magnesium hydroxides but are not as effective with silicas and other silicates. As with the succinic anhydride derivatives discussed above, it is assumed that the anhydride functional polymers react with the filler surface by... 

---