Some aspects of organo-clay chemistry that have interested a growing number of scientists are reviewed and discussed. Particular attention is directed to published evidence for the “reality” of clay compounds, the possible effects of high energy radiation on clay properties, industrial applications of modified clays and the increasing number of patents being granted in this field of applied chemistry. A number of areas of inadequate information where further basic research could lead to useful applications is pointed out.

Bentonite is employed by industry to perform a multitude of jobs. Certain industrial applications become apparent from an understanding of the composition and structure of bentonite, and the properties they create. These properties are utilized chiefly when the material is suspended in a liquid, usually water; or as a dried powder or granule.

Most industrial applications involve the swelling property of bentonite to form viscous water suspensions. Depending upon the relative proportions of clay and water, these mixtures are used as bonding, plasticizing, and suspending agents.

Bentonites disperse into colloidal particles and, accordingly, provide large surface areas per unit weight of clay. This large surface area is a major reason why bentonite functions so well in stabilizing emulsions, or as a medium to carry other chemicals.

Bentonites react chemically with many organic materials to form compounds which are used chiefly as gelling agents in a variety of organic liquids.

Bentonites are selected for each industrial need on the basis of type and quality. This selection is based principally on physical properties, and chemistry of the bentonite becomes involved only to the extent that it influences the physical properties.

The clay mineral attapulgite derives its non-swelling needle-like morphology from its three-dimensional crystal structure. The shape and size of the needles result in unique colloidal properties, especially resistance to high concentrations of electrolytes, and give high surface area, high porosity particles when thermally activated. Examples of industrial applications of attapulgite are reviewed with emphasis on how these characteristic properties function in the various end-uses.

Kaolins are used in a multiplicity of industries because of unique physical and chemical properties. Shape, particle size, color, softness, and non-abrasiveness are physical properties that are especially important. Chemical properties, such as comparatively low base exchange capacity, as well as other chemical properties of the kaolin surface, and relative insolubility, are governing in many uses. In 1960, well over 2,000,000 tons of kaolin was used in the United States, more than one-half of which was consumed by the paper industry. The relationships between physical and chemical properties are discussed in the application of kaolin to paper, rubber, ceramics, plastics, ink, catalysis, insecticides, and numerous other uses. A few new uses of kaolin are discussed along with a short gaze into a crystal ball to see what the future may hold for that useful mineral, kaolin.

The clay minerals, generally characterized by their small particle size, affinity for water, and response to chemical changes in their environment, are noted for their gelling and viscosity-increasing abilities in aqueous systems. Rendered organophilic by association with long-ohain organic compounds, several of the clay minerals exhibit similar or even greater gelling abilities in various organic liquids.

Methods of preparing organophilic clays are discussed and data shown for ion exchange reactions between long-chain organic cations and montmorillonite minerals. Properties of modified clays in various liquid systems are illustrated, and industrial applications are cited.

The physical, chemical and mineralogical characteristics of clays used in the ceramics industries are briefly outlined. Clays used include ball clays, fireclays, high-alumina clays of the diaspore and burley types, and three-layer types. The high temperature phases and bonding characteristics are briefly reviewed as are the uses of these various clays in the structural clay products, whitewares and refractories.

The importance of clays in the past for ceramics and, in particular, refractories is reviewed and evaluated for future importance.

In Part I (Deeds and van Olphen, 1961) pycnometric data on expanding clays in water and in other displacement fluids were analyzed in terms of inaccessible void space within aggregates and of possible density anomalies of the adsorbed fraction of the displacement fluids.

Further details of this work are reported, and the consequences for the interpretation of core analysis data are discussed. It is concluded that in core analysis the density of the connate water can be assumed to be normal while the fraction of the total pore space which is filled with oil is computed, provided that the total pore space is determined by using water or a polar organic liquid. If a hydrocarbon liquid or an inert gas is used, a small correction for inaccessible pore space can be applied.

In the argillaceous fraction of a sedimentary series of petroliferous sandstones from the Sahara two successive diagenetic changes are considered. The first is kaolinization of the original silicates. This is followed by illitization of the kaolinite by saline waters. The same formation is kaolinitic where it produces petroleum and illitic where it is nonproductive.

A vitreous, perlitic rock near Etzatlân, west of Guadalajara, Mexico, has been argillized by hot spring activity. A continuous outcrop from fresh rock to relatively pure clay (halloysite) is exposed, and samples were collected along it to trace the progressive alteration. Alkali metals and silica were leached during argillation, as was shown by analyses of the solid samples and solutions from laboratory hydrolysis of the rock. The interpretation that the original clay mineral was endellite is supported by experiments treating the clay with K-acetate and ethylene glycol. The random arrangement of Si-O-Al in the glass is thought to have favored development of disordered stacking in the clay mineral formed, hence endellite, and random distribution of very fine-grained clay crystals in the mass of clay.

Studies have been made of the changes in physical and chemical properties of kaolinite produced by doses of 0.667 meV gamma-radiation ranging from 1018 to 1022 eV/g of ferrous ion dosimetry solution. Changes were observed in the degree of crystallinity, specific surface area, particle size, cation exchange capacity, and grinding properties. These changes are discussed in terms of the observed atomic displacements produced in the kaolinite structure by the radiation. Gamma-irradiation appears to provide a method for obtaining controlled variations in certain properties of kaolinite without the introduction of other complicating parameters.

Kaolin was irradiated with 0.67 meV gamma-rays from a Cs137 source. Irradiation dosages of more than 1019 eV/g retarded mullite formation whereas smaller dosages appeared to have enhanced mullite formation slightly. It appears that preferentially oriented mullite formation from kaolinite is energetically favored and is adversely affected by radiation-produced nb/3 shifting of the Al ions. A possible mechanism for the effects of the radiation on mullite formation is suggested.

The unit-cell characteristics and structures of sepiolite, ferri-sepiolites (xylotile, mountain wood, gunnbjarnite), loughlinite and palygorskite (attapulgite) and their structural relationships are discussed. The chemical, morphological and thermal properties are explained by their structures. The unit-cell characteristics and structures of sepiolite “anhydride”, loughlinite “anhydride” and palygorskite “anhydride” are given. Under low water vapor pressure the phase transformations sepiolite to sepiolite “anhydride” and palygorskite to palygorskite “anhydride” are reversible. It was not possible to synthesize sepiolite in the system MgO−SiO2−H2O under confined pressure within a range of 80° to 300°C

The possibility of the application of sepiolite and related compounds in industry, specially in the automobile industry, is referred to.

An exceptionally pure illitic clay is present in outcrops of the Blaylock Formation (Silurian) in the Ouachita Mountains of southeastern Oklahoma. Unweathered claystone samples from this unit in Beavers Bend State Park have been found to consist of a well-crystallized illite or hydrous mica. Impurities commonly found in illites such as non-clay minerals and non-micaceous clay minerals are conspicuously absent. The sample cannot be classified as a mica because it is hydrated and the particle-size distribution is in the clay size range. A detailed examination of the deposit suggests that it may have value as a reference illitic clay mineral.

Organic matter removal is accomplished rapidly and efficiently without removing carbonates by treating samples with a sodium hypochlorite solution. Quantities of organic matter left in samples by this treatment are commonly less than remain after hydrogen peroxide treatment of acidified samples.

Stable suspensions result from the use of a sodium carbonate-sodium bicarbonate solution to wash and sodium saturate the samples without dissolving or complexing sesquioxides.

At low cesium ion concentrations extremely high selectivities for cesium are exhibited by layer lattice silicates with unexpanded 10 Å c-spacing. The total amount of cesium which can be sorbed by these minerals depends on the edge area and the exchange capacity. At a concentration of 10−5 meq of cesium and 5 meq of sodium, a sample of biotite representing less than 0.025 meq of exchange capacity sorbed over 90 per cent of the cesium and a hydrobiotite with 50 percent vermiculite and representing 1.0 meq of exchange capacity sorbed 80 percent of the cesium.

After heating bentonites to 500–700° C more cesium is sorbed from solutions containing high sodium concentrations by the heated bentonite than the original material. The change in the amount of cesium sorbed as a result of heating may be a useful property for detecting the presence of montmorillonite in mixed or interlayered mineral systems. Lattice expansion of biotite results in improved cesium sorption; this behavior is due to generation of sufficient favorable exchange sites to offset the loss of edges with favorable 10 Å spacing.

The following recent work is reviewed.

In the Triassic basin of the Jura detrital illite changes into chlorite (chlorite and chloritie mixed layers) toward the middle of the basin.

In the profiles of podzolic soils and podzols, illite and chlorite change, through illite— vermiculite and chlorite-vermiculite stages, into vermiculite.

In Cambrian sandstones of the Sahara two successive diagenetic changes have taken place: early postdepositional kaolinization, and illitization by salt waters.

Neoformation of aluminomagnesian clays in the alkaline sediments of the Eocene basins in Africa produces a sedimentary and geochemical sequence of montmorillonite, attapulgite and sepiolite.

When siliceous neoformation is produced by crystal growth, the growth is regular in the production of quartz, and irregular or hindered in the formation of chalcedony or opal-cristobalite.

Kaolinite has been synthesized at low temperatures in dilute solutions.

Transformations of triphormic clay minerals in the hydrosphere consist of a progressive expansion of layers. Environment controls the equilibrium between interlayer cations and adjacent layers. Siliceous and argillaceous neoformation consists of organization of silica tetrahedrons; this organization depends on the environment and especially on the environmental cations. Transformation by diagenesis is more intense and allows direct passage from illite to kaolinite.

Clay mineral suites were extracted from 125 biocalcarenites, dolomites, mudstones and arenaceous rocks from the marine Keokuk, Warsaw and Salem formations of Mississippian age from southeast Iowa and nearby portions of Illinois and Missouri. Well crystallized illite, 2M1 polytype, randomly interstratified illite—montmorillonite, and quartz are in all clay suites. In the south part of the area, trioctahedral chlorite is absent or rare in Keokuk rocks, but is increasingly abundant upward in the section. Kaolinite is confined to the upper part of the section. In the north part of the area, the same upward order of appearance prevails, but the first appearances of chlorite and kaolinite are shifted downward in the stratigraphic section. This distribution of clay minerals is similar to that found by investigators in other areas: kaolinite confined near shore, chlorite in an intermediate position and illite concentrated farther from shore. Clay mineral evidence, combined with petrographic and stratigraphic data, strongly indicates that the type Mississippian strata of southeast Iowa were deposited in a southward regressing epicontinental sea.

Vermiculite and abundant mixed-layer illite-montmorillonite, weathering products of chlorite and illite, respectively, mark a local unconformity between lower and upper members of the Warsaw Formation on the crest of the Warsaw Anticline.

The investigation of clay minerals and argillaceous rocks started in the territory of Czechoslovakia as early as the later part of the eighteenth century and has continued up to today. During this long period many interesting results have been obtained. In about 1949 modern laboratory techniques were introduced. Most of the work in this country deals with the mineralogy, petrology, and geology of argillaceous rocks, the chemical composition and physical properties of clay materials which are useful for the purposes of the ceramic, glass, chemical, construction-engineering and mining industries, etc. This paper is subdivided into the following parts: (a) Classical research period; (b) Modern research period; (c) Kaolins (primary); (d) Other argillaceous rocks of sedimentary origin; (e) Bentonites; (f) Laterites and bauxitic rocks; (g) Clay minerals in sedimentary iron ores; (h) Clay minerals in carbonaceous rocks; (i) Clay minerals of hydro-thermal origin; (j) Kinds of apparatus for DTA and gravimetric thermal analysis; (k) Imbibometric study using water and organic liquids; (1) Problems of classification and terminology.

Experimental investigations of chemical weathering in which powders of potassium feldspar, albite, leucite, muscovite, tremolite, olivine, and volcanic glass are treated with pure water and with dilute solutions of sulfuric, carbonic, and hydrochloric acid have been performed in an apparatus in which the mineral powder is exposed to a circulating water flow. The experiments have been continued recently by treating kaolinite and montmorillonite. The course of decomposition of these minerals depends on water flow rate, grain size, temperature, and pH of the solutions. These experiments in open systems are compared with investigations reported in the literature and with the conditions of natural weathering.

Suspensions containing 3 percent sodium bentonite (Wyoming) and each of the four methylamine hydrochlorides were prepared so that the latter were present in amounts equal to 25, 50, 75, 100, 125, 200, 400, 600, 800, and 1000 percent of the exchange capacity of the clay. The flocculated clay was removed by decantation, and an oscillating -heating X-ray diffraction (Cu Kα.) pattern was made of the first-order diffraction maximum. With these patterns, the thermal stability, mixed layering, and multilayering of the amine-bentonite complex were followed. For methylamine, the data suggest that the first cations to enter lie in the holes with their C-N axes as close to the oxygen surface as possible. As additional methylamine hydrochloride enters, the C−N axis stands perpendicular in the holes to accommodate the chloride, and after all the holes are filled a second layer forms. Although the geometry of the dimethylamine cation permits it to occupy only two out of three holes, it also forms a second layer. The trimethylamine and tetramethyl ammonium cations are so large that they can occupy only one hole in three; this distribution satisfies the cation-exchange capacity, but a second layer does not form.