The rate of dissolution of phlogopite in an open system was measured at low temperature and pressure and at pH 3–5. The maximum dissolution rate was achieved by maintaining extremely low ionic concentrations in the solution using a cation-exchange resin (hydrogen form) as a trap for released cations. The resin also served as a source of hydrogen ions and acted as a buffer. The concentrations of ions adsorbed on the resin and remaining in solution were measured, along with surface area and cation-exchange capacity. The amount of phlogopite dissolved after 1010 hr was 67 times that dissolved using a CO2-buffered, closed-system method. During the first hour of the experiment, dissolution was incongruent, but later became congruent from 1 to 1010 hr. From 1 to 200 hr the reaction had linear kinetics. The dissolution rate for the first 200 hr of the reaction was 2.0 × 10−14 mole KMg3AlSi3O10(OH)2/cm2/sec. Since no evidence of parabolic kinetics was found, there is no reason to postulate the formation of a “protective layer.”

The pH, Eh, electrical conductivity (EC), and the amounts and valency of replaceable iron were measured periodically on Fe2+- and Fe3+-saturated montmorillonite and cation-exchange resin at three temperatures. Differences in the pattern of change of pH, Eh, and EC with time appear to be related more to the histories and modes of preparation of the systems than to intrinsic differences in the hydrolysis of the iron in them. Electron transfer reactions involving crystal components of the clay can cause oxidation of adsorbed Fe2+ ions; the activation energy (Ea) for oxidation on the clay's surface was 6 kcal/mole, less than a third of the activation energy reported for Fe2+ oxidation in solution. In the Fe2+-resin, where Ea = 10.7 kcal/mole, perturbed surface-water molecules may act as electron acceptors enhancing Fe2+ oxidation.

Polymerization and precipitation of the adsorbed iron is affected by the necessity to maintain electroneutrality, the ability of the iron-hydroxy ions and small polymers to move about in the voids of the ion exchanger, and the steric hindrance posed by the matrix of the ion exchanger to the formation of large polymers. In resin, little or no iron precipitates, probably due both to steric hindrance and the inability of the resin to release ionic components to maintain electroneutrality. In clays, steric hindrance is small, and Al and Mg are released from the crystal to maintain electroneutrality, thus the precipitation of iron is abundant and is controlled by the rate of release of Al and Mg from the crystal.

The formation of hydroxy-Al-interlayered montmorillonite was affected by complexing organic acids. Montmorillonite (<2.0 μm) was aged for three months at an initial pH of 5.0 or 6.0 in AlCl3 solutions containing citric or tannic acid at organic acid/Al molar ratios from 0 to 1.0. The Al/clay ratio in the system was 900 meq Al3+/100 g of montmorillonite. Ion-exchange experiments revealed that organically complexed Al ions have both positive and negative charges. Evidence from X-ray powder diffraction, electron microscopic examination, measurements of specific surface, cation-exchange capacity, organic carbon, and the nature of sorbed Al indicates that citric and tannic acids influence differently the hydroxy-Al interlayer formation in montmorillonite. Hydroxy-Al-citrate can be adsorbed as interlayers in montmorillonite, but hydroxy-Al-tannate exists principally as a separate phase binding the clay particles. The differences observed between the influence of citric and tannic acids on Al interlayering are probably due to their differences in molecular weight (size) and structure.

Montmorillonite-based catalysts were compared with an acidic ion-exchange resin of the type used industrially for the production of methyl t-butyl ether (MTBE) from methanol and isobutene or t-butanol. When 1,4-dioxan was used as solvent, Al3+-exchanged montmorillonites had about half the efficiency of the resin Amberlyst 15 at 60°C; they were, however, about twice as efficient at this temperature at Ti3+-montmorillonite or K10, a commercially available acid-treated bentonite. Montmorillonite exchanged with Chlorhydrol solutions to give interlayer [Al13O4(OH)2(H2O)12]7+ ions and pillared clays derived from such materials were poor catalysts, as was K306, a more drastically acid-treated bentonite- based commercial catalyst. Freeze-drying of the Al3+-clay before reaction to produce a more open, porous structure had no effect on its catalytic efficiency. The activation energy for the reaction of isobutene and methanol in dioxan was 44 kj/mole for an Al3+-clay catalyst compared with 25 kJ/mole for reactions catalyzed by Amberlyst 15. With no solvent (as in industrial processes), the rates of reaction were considerably slower for both the clay- and resin-catalyzed reactions. As has been found previously for resin-catalyzed reactions using stoichiometric amounts or an excess of methanol, the rate was proportional to the isobutene concentration, and the rate-determining step appeared to be protonation of the alkene. The performance of the Al3+-clay catalyst was increased by reducing the water content of the clay. In most reactions the clay catalysts were equilibrated at 12% relative humidity. Exposure of the clay to a low vacuum (10−1 torr) before use increased its catalytic activity from 50 to 60% of that of Amberlyst 15.