Imogolite solubility

The same group has also obtained composite materials based on imogolite and water-soluble polymers such as hydroxypropylcellulose (HPC) and poly (vinylalcohol) (PVA) [32]. HPC is a rigid rod polymer that has a cholesteric phase, whereas PVA is a random coil amorphous polymer. Significantly enhanced mechanical properties were only obtained in the case of the HPC composite materials. 

Secondary silicates form as clay minerals in soils after weathering of the primary silicates in igneous minerals. The secondary silicates include amorphous silica (opal) at high soluble silica concentrations and the very important aluminosilicate clay minerals kaolinite, smectite (montmorillonite), vermiculite, hydrous mica (il-lite), and others. Kaolinite tends to form at the low silicate concentrations of humid soils, whereas smectite forms at the higher silicate and Ca concentrations of arid and semiarid soils. The clay fraction of soils usually contains a mixture of these day minerals, plus considerable amorphous silicate material, such as allophane and imogolite, which may not be identifiable by x-ray diffraction. 

Gustafsson, J. P., D. G. Lumsdon, and M. Simonsson. 1998. Aluminium solubility characteristics of spodic B horizons containing imogolite-type materials. Clay Minerals 33, no. 1 77-86. 

Su, C. and Harsh, J.B. (1994) Gibbs free energies of formation at 298 K for imogolite and gibbsite from solubility measurements. Geochim. Cosmochim. Acta, 58, 1667-1677. 

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