The hydroxyl orientations in 31 dioctahedral and trioctahedral 2:1 phyllosilicate structures have been determined by electrostatic energy calculations. These structures included micas, brittle micas, and other related minerals exhibiting ordered as well as disordered cation distributions. The dioctahedral micas and brittle micas were examined with and without the interlayer cation. A range of orientations from 1.3° to 183.3° (the angle ρ between the O-H and (001) measured with respect to the M1 site) were found. The orientations for the dioctahedral structures represent a continuum of values whereas the trioctahedral species exhibit two possible orientations separated by an energy barrier. One orientation is near 90° the other is near 180°. The latter orientation results from a concentration of charge on the interlayer (IC) and tetrahedral (T) sites at the expense of the octahedral (M) sites. A multiple regression analysis of all 31 structures, using as predictors the a and b cell parameters, d001, and the charges for T, IC, M1, and M2 sites, was performed. This analysis indicated that the important factors are the charges for IC, T, and M2 sites. When treated as a separate group, one finds the same factors for the dioctahedral structures. The trioctahedral orientations are determined by the charge on the M2 site and the amount of tetrahedral rotation. Using these two predictor equations, the value of ρ can be estimated with a standard deviation of 4.7° and 2.9° for the dioctahedral and trioctahedral cases, respectively.

Mineralogical, chemical, and geological aspects of four types of clay deposits in Las Aguilas Formation northwest of Barker in Buenos Aires Province, Argentina, indicate that these products of lateritic alteration of Precambrian granite are predominantly kaolinitic with minor amounts of halloysite, illite, and chlorite. Minor amounts of quartz, feldspars, and ferric oxides are also present. Of the four types, one is suitable for high quality refractories, another can be used for wall tiles and china, and a third, the most abundant, can be used for red ceramics; the fourth has no special use. The abundance of the clays is calculated to exceed eleven million metric tons.

Infrared and Mössbauer spectroscopy show that the extent of the reduction of nontronite is dependent on the chemical composition of the nontronite and on the nature of the reducing agent. Hydrazine reversibly reduces about 10% of the iron in all of the nontronites studied irrespective of composition and it is suggested that the resulting ferrous iron occurs only in distorted octahedral sites. Similar conclusions are reached for the dithionite reduction of the nontronites containing little tetrahedral iron, but for those with more than one in eight silicons replaced by iron, changes brought about by dithionite treatment are irreversible due to dissolution of appreciable quantities of iron. Results from both spectroscopic techniques suggest that iron in tetrahedral sites is preferentially dissolved and that up to 80% of the structural iron can be reduced.

Evidence is presented for the formation in these extensively reduced nontronites of a small amount of a mica-like phase resembling celadonite or glauconite, and, as dithionite is used for the pretreatment of soils, the implication of this observation is briefly discussed.

The use of deuterated hydrazine as a reducing agent has enabled the nontronite absorption band near 850 cm-1 to be assigned to a Si-O (apical) stretching vibration, which is inactive in the infrared for perfect hexagonal symmetry, but which is activated by distortions in the tetrahedral layer.

The conditions under which an exchanger phase will behave as an ideal mixture are established from thermodynamic principles. It is shown that, if a stoichiometric cation-exchange reaction is reversible, the exchanger phase will exhibit ideal behavior if the Vanselow selectivity coefficient is independent of the exchanger composition. This criterion is applied to some recently published data for Na+-trace metal cation exchange on Camp Berteau montmorillonite. An analysis of the data suggests that, so long as the exchange process is reversible, Na+-trace metal cation exchange produces an exchanger phase that behaves as an ideal mixture.

The rates of dehydroxylation of smectites intercalated with the decomposition products of Ni(phen)3SO4 are from 2 to 4 times greater than those of clays without the heat-stable intercalate. These results suggest that the intercalated material, in keeping the clay sheets separated, provides a more ready avenue for water loss during the dehydroxylation process.

The roles of different forms of Fe(III) impurities in a hectorite with respect to the oxidation of benzidine in aqueous suspension have been evaluated using electron spin resonance and UV-visible spectroscopy. Natural surface-adsorbed Fe(III) showed no detectable activity in the oxidation process, while very small quantities of structural octahedral Fe(III) apparently promoted a relatively rapid conversion to the radical cation. However, extremely small quantities of benzidine were oxidized in comparison to the exchange capacity of the clay. Freshly adsorbed Fe3+ cations effectively oxidized benzidine, but lost much of this ability upon aging. The Fe(III)-benzidine electron transfer could be distinguished from an O2-benzidine reaction, since the latter reaction was slow and limited by the rate of O2 diffusion into the clay-water system. The O2-benzidine reaction was also inhibited at high pH. The existence of two reaction mechanisms and the involvement of only a small fraction of the total structural iron, as shown by comparison of the hectorite and a montmorillonite, may explain the conflicting interpretations in the literature. The benzidine blue reaction not only requires an oxidizing agent to form the radical, but also a clay surface to adsorb and stabilize it against further oxidation.

The adsorption-catalyzed degradation of parathion on clay surfaces is a hydrolysis process, proceeding either directly or through a rearrangement step. The rate and mechanism of degradation are dependent on the nature of the clay, its hydration status, and saturating cation. A mechanism for parathion degradation at adsorption sites on clay surfaces, in the absence of a liquid phase, is proposed.

Montmorillonite-aminocaproic acid complexes (monomer complexes) were prepared by the intercalation of 6-aminocaproic acid to various homoionic (Na+, Ca2+, Mg2+, Co2+, and Cu2+) montmorillonites. Infrared spectra of the monomer complexes indicated that the interaction between the exchangeable cations and the 6-aminocaproic acid increased in the following order: Na-, Ca-, and Mg- < Co- < Cu-montmorillonite-aminocaproic acid complex. Montmorillonite-nylon complexes (polymer complexes) were prepared by thermal treatment of the monomer complexes, which was confirmed by X-ray powder diffraction and infrared spectroscopy the results of which indicated the condensation of 6-aminocaproic acid in the interlayer space.

Thermal degradation of montmorillonite-nylon complexes was studied by thermogravimetry. It was found that the thermal stability of the polymer complexes increased in the following order: Cu- < Co- < Na- < Mg- < Ca-montmorillonite-nylon complex.

It was suggested that the difference in thermal stability depended upon the length of the polymer chain which might be influenced by the interaction between the exchangeable cations and the 6-aminocaproic acid. The activation energy for the thermal degradation of each montmorillonite-nylon complex was obtained, and the value for Cu-montmorillonite-nylon complex was smaller than that for the other cation-exchanged montmorillonite-nylon complexes.

The adsorption of butanol, hexanol, and octanol on alkylammonium montmorillonites of different chain length is similar to the distribution of alcohol between an organic solvent and water in bulk solution. Successive expansion of the clay layers starts at critical alcohol/cation ratios of 0.6 or lower which are biased mean values due to the heterogeneity of the cation density of the mineral. In the interlamellar phase autoassociation of the alcohols occurs in contrast to their behavior in aqueous solution. The intrinsic association constants (kM ~ 7) are of the same magnitude of the values found in cyclohexane. The alcohols can associate with molecules fixed on specific sites of the mineral and on free monomers. The ratio of fixed to free monomers is of the order of 10/1.

Natural erionite was exhaustively ion exchanged with Na+ to give the anhydrous unit-cell composition (K1.9Na5.4Ca0.1Mg0.1)[(AlO2)7.4(SiO2)28.6]. A thermodynamic study of alkali and alkaline earth metal ion exchange in this zeolite was made and the selectivity series found to be Rb > Cs ≥ K > Ba > Sr > Ca > Na > Li. In all cases approximately two K+ ions per unit cell (probably those in the cancrinite cages) could not be replaced by conventional ion exchange. It was also found that two Na+ ions per unit cell are extremely difficult to replace with alkaline earth ions. It is believed that complete replacement of the approximately six Na+ cations in the two large cages per unit cell of erionite would result in a non-uniform, divalent cation population in these cages. A more stable anhydrous composition is (K2Ca2Na2)[(AlO2)8(SiO2)28] in which each large cage contains one Ca2* or other alkaline earth cation and one Na+ ion.

The charge density distribution among different classes of a series of reduced charge mont-morillonites is heterogeneous as in the parent Camp Berteau clay. In addition, charge reduction proceeds inhomogeneously. Up to 20% differences in charge density can be accounted for by aikyl chains extending at the edges of the clay particle. A realistic charge density-cation-exchange capacity relationship for hec-torite, Otay montmorillonite, and a series of reduced charge montmorillonites of Camp Berteau is obtained by accounting for the influence of particle radius and for the extent of alkyl chains lying outside the clay layers in the charge density calculations.

Nephelometric (light scattering) methods for the determination of Ca and Ba in the 0–30 ppm range, and their application to the estimation of the cation exchange capacity (±10%) of small (≤30 mg) samples of clay minerals, are described and evaluated.

The diffusion of water in the title intercalate has been measured by quasielastic neutron scattering. The diffusion coefficient (6.1 × 10−7 cm2 s−1 at 23.5°C) is one order less than that found previously for a sodium-exchanged montmorillonite which, however, contained 4 times as much water in the interlamellar space. The activation energy for the motion has been deduced to be 18 kJ mol−1. Also it has been demonstrated that upon the time scale of the neutron scattering events (faster than 10−9 s) the hydroxyl groups of the clay lattice are not in motion.