Electrochemical treatment of kaolinite-glass bead plugs in the presence of water and CaCl2 solutions produces dissolution of the glass beads, corrosion of the anodes, and transport of the released elements toward the cathodic zone. In this area, new mineral phases (both amorphous and crystalline) are synthesized. Most of these new phases, and especially the calcium silicate hydrate (CSH-1), are well known to exhibit important cementing properties. The nature and the extent of the modifications brought about by the treatment are dependent on the nature of the electrodes, the pH and the ionic strength of the circulating electrolyte, and the duration of the treatment.

Products resulting from the reaction of toluene with Cu(II)-montmorillonite were analyzed using GC/MS, HPLC/MS, GPC, and FTIR methods. Numerous oligomers of toluene were observed, extending at least as high as the resolution limit (1500 g/mol) of the GPC column. The FTIR spectrum of the nonvolatile components of the extract was very similar to that of liquid toluene. GC/MS data on the volatile components revealed dimers, trimers, and a multitude of transmethylated products. Oligomerization proceeded via both ring-ring (i.e., polyphenyl) and ring-methyl linkages. The primary trans-methylated products were tert-butylbenzene and isopropylxylene, indicating a competition between ringand side-chain methylations. The side-chain substitutions cannot be explained in terms of the aromatic radical cation intermediate which typically forms in arene/clay reactions. A consideration of alkylbenzene reactions observed in various other media suggests that the present transmethylation reactions occur via a benzyl cation intermediate.

The influence of pressure on the conductance of frozen montmorillonite suspensions was measured in the temperature range from 0°C to − 12°C on Na- and Ca-saturated samples. Pressures invariably increase the conductance of frozen suspensions. The change in conductance with pressure is postulated to be due to pressure melting of the ice in the frozen suspension. From swelling pressure data the increase in unfrozen water with pressure at constant temperature is calculated and shown to be consistent with the effect of pressure on conductance.

The Cretaceous sedimentary kaolin deposits of South Carolina and Georgia occur in a portion of the geologic column which contains abundant evidence of volcanic activity in Texas, Arkansas, Mississippi, and Puerto Rico. It is proposed that volcanic ash from eruptive centers in the Mississippi Embayment and Gulf Coastal region settled on land and was washed into adjacent valleys, lake basins, and possibly lagoons, along with varying amounts of residuum from the erosion surface; alteration of the volcanic ash to montmorillonite, and then to kaolinite, progressed under the influence of subaerial erosion in Cretaceous and later time whenever physical and chemical conditions were favorable.

Several perplexing and previously inadequately explained features of the deposits are clarified if we accept this hypothesis. These features include: (1) The purity of the deposits, being over 95 per cent clay mineral in many deposits 20 ft or more in thickness; (2) General absence of fossils; (3) Lack of bedding; (4) Prevalence of a small but nearly uniform content of TiO2 as minute crystallites of anatase; (5) Presence of elongate bevel-edged particles, now clay, which have the form of glass shards.

Both the “soft” and the “hard” clay are believed to have developed from the same source. At all places where seen in the field the hard clay occurs immediately beneath a prominent unconformity; its different properties are attributed to changes produced by subaerial weathering. Repeated wetting and drying, which resulted in a smaller particle size, and leaching of silica, resulting in a slight bauxitization, are considered important mechanisms.

The electrochemical properties of clays are discussed under four rules which arise from considerations of the bonding energy of ions associated with charged surfaces. The mean free bonding energy of a cation associated with a negatively charged surface is determined by calculation from conventional potentiometric measurements with membrane electrodes.

The first three rules are concerned with the effects of valency upon ionization. They arise directly from the method of calculating cationic mean free bonding energies, applicable to monofunctional surfaces as regards Rule 3, and to polyfunctional surfaces also as regards Rules 1 and 2.

The fourth rule (Jarusov’s rule) deals with mixtures of cations on polyfunctional surfaces. It may be expressed verbally by stating that the cation with the higher mean free bonding energy preempts those positions on the surface which manifest greater mean free bonding energy.

The incidence of each rule is examined, using data from studies of cationic activities in clay systems. The factors which cause deviations from these idealized rules are discussed. Graphical data are presented for Wyoming bentonite, Arizona bentonite (montmorillonite), and Putnam clay (montmorillonite group); illite, kaolinite and attapulgite.

The transfer of ions during the weathering of a Medford diabase, a granite from British Guiana, and of the Cheto Arizona tuff is traced by recasting the analyses of the fresh rocks and their altered counterparts into 160-oxygen rock cells, and by comparing algebraically the products of the weathering reaction with the original reactants.

Hydrolysis and hydration are the first steps in the reaction. H ions were added in the weathering environment of the diabase and granite, but Mg ions were added in the change of tuff to bentonite.

Silica and alkali metal ions are dissolved and removed during weathering of the diabase and granite, presumably under acid conditions, but it appears that the Cheto tuff was formed under a non-acid environment where Mg was added. During the hydrolysis of silicate rocks, H ions are concentrated temporarily in the clay minerals on land, while OH ions go to the ocean.

More examples of ion transfer during weathering than the three given herein are needed to define the reactions occurring in the many environments of alteration which rocks encounter.

The anhydrous structures of three-layer phyllosilicates are destroyed by heating, as in differential thermal analyses, over a range of temperatures starting from about 775°C, mean temperature for pyrophyllite, and rising to about 1075°C, a mean temperature for biotite. Parallel to the trend of increasing temperature of stability (and destruction) is an increased ratio of substituted Al for Si in the tetrahedral layers and, in some occurrences, of Mg for Al in the octahedral layers. These substitutions increase the degree of ionic bonding (and decrease the covalent bonding) within the oxygen framework. The electronegativity difference between the cation and oxygen increases as Al substitutes for Si, and Mg for Al. Increase in ionic character of a compound is compatible, from chemical considerations, with increase in thermal stability and susceptibility of the compound to alteration by water.

The principle illustrated by the phyllosilicates applies likewise to mineral groups of other silicate structure, such as the anorthite-albite series, the forsterite—fayalite series, and others.

Redox properties of iron-bearing mineral surfaces may play an important role in controlling the transport and transformation of pollutants into ground waters. Suspensions of seven iron-bearing minerals were reacted with pH and redox indicators under anaerobic conditions at the pH of the natural suspension. The responses of the indicators to the mineral surfaces were monitored by UV-visible spectroscopy using a scattered transmission technique. The Hammett surface acidity function (Hs) and the surface redox potential (Ehs) of these iron-bearing minerals were measured. These measured values were used to calculate Eh values for the seven minerals: goethite = +293 mV; chlorite = +290 mV; hematite = +290 mV; almandite = +282 mV; ferruginous smectite = +275 mV; pyrite = +235 mV; and Na-vermiculite = +223 mV. Calculated surface redox potentials of minerals are different from their potentials measured by platinum electrode in bulk suspensions. UV-visible spectroscopy provides a quick and non-destructive way of monitoring organic probe response at the mineral surface.

Recognition of the fact that clays exhibit both viscous and elastic response characteristics has led to the use of the theory of viscoelasticity for describing their mechanical behavior. This paper presents a brief outline of pertinent concepts from this theory to establish a framework for the presentation and interpretation of the experimental results. The experimental program was conducted on a water-washed Georgia kaolin at nominal moisture contents of 50%, 75%, and 100%, and included a series of oscillatory shear tests over a frequency range of two decades. These tests were performed on a Weissenberg Rheogoniometer with a cone-and-plate sample holder; this arrangement produces essentially homogeneous shear strains throughout the specimen.

The experimental results show that the stress-strain response of the clay is frequency-dependent and is definitely nonlinear, even at small strains. The greatest frequency dependence, as manifested in the complex shear modulus and phase angle, occurs in a region characteristic of many polymer systems. The logarithm of the complex shear modulus is found to vary approximately as the water content or consistency of the clay-water mixture.

Vermiculites have the potential to serve as effective catalysts if pillared with Al, but their high charge presents an obstacle to the pillaring process. The purpose of this study was to submit natural vermiculite to thermal treatments in the presence of water vapor in order to effect a reduction in the global negative charge and thereby to enhance its susceptibility to pillaring. The process of charge reduction in vermiculite under the conditions selected involved the extraction of 25% of IVAl accompanied by the extraction of structural Mg and charge-compensating cations (Ca2+, Na+, and K+). The results indicate a reduction of 35% in the global negative charge in vermiculite by the end of the treatment. Some of the VIAl content was not removed during acid washing, and probably remained in the solid in structural positions in the octahedral sheet.

Compacted bentonite–sand mixture is proposed widely as backfill in geological repositories for disposal of radioactive waste in many countries because this material has significant swelling capacity and low water permeability. Development of the swelling pressure of backfills upon hydration is related closely to the stability of the host rock in the geological repository. No systematic experimental studies have been carried out to explore the effect of a water phase on the swelling pressure and water retention of bentonite–sand mixtures with insignificant osmotic suction. The objective of the current study was to examine experimentally the influence of a water phase involving liquid water and water vapor on swelling pressure and water retention of a bentonite–sand mixture with insignificant osmotic suction. Swelling-pressure tests with suction control and water-retention measurements under constant-volume conditions were performed on the compacted bentonite–sand mixture with a dry density of 1.80 g/cm3. Osmotic and vapor equilibrium techniques were used to make identical specimens adsorb liquid water and water vapor, respectively. The experimental results showed that the water phase had almost no effect on the swelling-pressure patterns of the unsaturated bentonite–sand mixture upon hydration over a suction range from 27 to 3 MPa. The swelling pressure increased significantly with decreasing suction from 27 to 3 MPa, regardless of the mixture adsorbing either the liquid water or water vapor. Nevertheless, the water phase had a considerable impact on both the swelling pressure and water retention of the unsaturated bentonite–sand mixture upon hydration over the same suction range. For a given value of suction in the range above, the swelling pressure and the water content of the bentonite–sand upon adsorption of liquid water were greater than those upon adsorption of water vapor. The influence of the water phase on the swelling pressure and the water retention of the bentonite–sand mixture with insignificant osmotic suction is related mainly to the hydration or swelling mechanism of Ca-rich bentonite.