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.

Stable organomineral derivatives are formed by reaction of organochlorosilanes with certain phyllosilicates. Organosiloxyl functions are grafted on silanol groups present at external mineral surfaces.

Water molecules adsorbed on external mineral surfaces may cause hydrolysis of the reactant organosilicon products, with liberation of HCl. This, in turn, may react with the silicate: octahedral cations are extracted from the lattice and fresh Si-OH groups, capable of further grafting, are formed on the mineral surface.

On the other hand, when difunctional reagents such as methylvinyldichlorosilane are used and if the ratio of adsorbed water to added reactive is adequate, then polymeric species with polysiloxane chains are grafted on the mineral.

Because of its high content of silanol groups, sepiolite forms organomineral compounds having a relatively high organic matter content. With chrysotile, the amount of organic matter grafted to the silicate, is considerably smaller, but it increases appreciably if water is added to the reacting products. This is attributed to hydrolysis of the organic reactant and subsequent destruction of external “brucitic” layers by acid attack.

Investigations concerning selective sorption and fixation of K and similar cations by clay minerals and soil clays and the mechanisms of these reactions are reviewed. In particular, recent observations on selective sorption of these ions in dilute solutions by weathered micas and vermiculite in relation to the interlayer structures are discussed in detail. Also, implications of the resistance to weathering of small mica particles to cation selectivity by soils are described. Despite the increased understanding of sorption and fixation reactions, the following aspects remain unclear.

First, the mechanism of the collapse of alternate layers in vermiculite on K or Cs sorption has not been unequivocally established. Second, factors that impart stability to the central core of mica particles so that K extraction becomes progressively difficult are not known. Third, inability of Ca or Mg ions to expand interlayers of Cs-saturated vermiculite in contrast to K-saturated vermiculite is not completely understood.

X-ray diffraction and electron microscopy were employed in conjunction with core flooding experiments to investigate clay migration phenomena.

Severe water sensitivity or loss of permeability was observed in a suite of sandstones in spite of the almost total absence of montmorillonite or swelling mixed layer clays. Clay migration was found to cause total or partial plugging even in sandstones of 500 millidarcy permeability. Bacterial plugging was ruled out by prefiltering and bactericide treatments of waters.

X-ray diffraction and electron microscopy analyses were performed on the sandstones and produced effluents. The direct cause of damage was displacement of submicroscopic natural clay crystals of needle-shaped mica and hexagonal-shaped kaolinite (Rex, 1965). The mobile clays were identified as authigenic crystals that are present on the pore walls and are dislodged by changes in water chemistry combined with water movement.

Flooding sandstones with alkali metal brines “sensitized” the cores, i.e. triggered clay dispersion upon subsequent flooding with fresh water. Flooding with divalent calcium brine prevented water sensitivity and suppressed the undesirable effect of alkali metal brines. A double layer expansion effect is suggested as the dispersion mechanism.

Montmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1–2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4·5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1–2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5–6).

It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1–2:2 intergrade clay mineral. The combined effects of low pH (below 4·5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4·5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization.

The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1–2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter.

Clay minerals in the upper 50 cm of sediment that surround the Cu- and Ni-rich manganese nodules in the North Equatorial Pacific form two fractions: terrigenous (mostly eolian) illite, chlorite, and kaolinite, and authigenic smectite. Smectite increases with depth in box cores from 26 to 39% and from 53 to 66% in the easternmost and westernmost areas respectively, and with distance seaward from the Americas from 26 to 53% in surface deposits. The change in the amount of smectite relative to other clay minerals is due to dilution by terrigenous debris; smectite probably forms at a uniform rate over much of the North Pacific deep-sea floor. The δO18 value for the smectite is +29.6‰ which suggests that it formed authigenically at a temperature characteristic of the deep-sea floor. The smectite is an Fe-rich montmorillonite that probably forms by the low-temperature chemical combination of Fe hydroxides and silica. Silica is derived from dissolution of biogenic debris, and the Fe hydroxide is from volcanic activity at the East Pacific Rise, 4000 to 5000 km to the east. Al in the authigenic montmorillonite may be derived from the dissolution of large amounts of biogenic silica or from river-derived Al that is adsorbed on Fe-Mn hydroxides in the oceans. The Fe-montmorillonite contains relatively abundant Cu, Zn, and Mn and is of possible economic importance as a source of these and other metals.

Retention of basic components of a crude oil by clay-containing reservoir sandstone was studied by flowing crude oil through cores and monitoring the concentration of bases in the effluent. Cores that were H-saturated, H-saturated then aged, and Na-saturated retained 0·82, 0·82, 0·70, and 0·20 meq base/100 g, respectively. Barium exchange capacity values were 0·86, 0·71, and 0·83 meq/100 g. Subsequent floods with water, toluene, and chloroform-acetone removed oil that had increasing concentrations of base and N, indicating that the basic fraction of crude oil was the most difficult fraction to extract from clay mineral surfaces. Retained bases were nitrogenous and the most tenaciously held bases had base/N ratios approaching unity.

Three kinds of opal-cristobalite, differentiated by the sharpness of the 4·1 Å XRD peak, were isolated from the Helms (Texas) bentonite by selective chemical dissolution followed by specific gravity separation. The δ18O value (oxygen isotope abundance) for these cristobalite isolates ranged from approximately 26–30‰ (parts per thousand), increasing with increased breadth of the 4·1 Å XRD peak. Opal-cristobalite isolated from the Monterey diatomite had a δ18O value of 34‰. These δ18O values are in the range for Cretaceous cherts (approximately 32‰) and are unlike the values of 9–11‰ obtained for low-cristobalite (XRD peaks at 4·05, 3·13, 2·4, and 2·49) formed hydrothermally or isolated from the vesicles of obsidian. The morphology pseudomorphic after diatoms, observed with the scanning electron microscope, was more apparent in the opal-cristobalite from the Monterey diatomite of Miocene age (approximately 10 million yr old) than in the spongy textured opal-cristobalite from the Helms bentonite, reflecting the 40 million yr available for crystallization since Upper Eocene.

The oxygen isotope abundance of Helms montmorillonite (δ18O = 26‰) indicates that it was formed in sea water while the δ18O values of the associated opal-cristobalite indicate that this SiO2 polymorph probably formed at approximately 25°C in meteoric water. Although both cristobalite and mont-montmorillonite in the bentonite were authigenic, the crystallization of the SiO2 phase apparently required a considerably longer period and occurred mainly after tectonic uplift.

In contrast to the results for cristobalite, quartz from the Helms and Upton (Wyoming) bentonites had δ18O values of 15 and 21‰ respectively. Such intermediate values, similar to those of aerosolic dusts of the Northern Hemisphere, loess, and many fluvial sediments and shales of the North Central United States (U.S.A.), preclude either a completely authigenic or a completely igneous origin for the quartz. These values probably result from a mixing of quartz from high and low temperature sources, detritally added to the ash or bentonite bed.

Wall-climbing robots work on large steel components with magnets, which limits the use of wireless sensors and magnetometers. This study aims to propose a novel autonomous localisation method (RGBD-IMU-AL) with an inertial measurement unit and a fixed RGB-D camera to improve the localisation performance of wall-climbing robots. The method contains five modules: calibration, tracking, three-dimensional (3D) reconstruction, location and attitude estimation. The calibration module is used to obtain the initial attitude angle. The tracking and 3D reconstruction module are used jointly to obtain the rough position and normal vector of the robot chassis. For the location module, a normal vector projection method is established to screen out the top point on the robot shell. An extended Kalman filter (EKF) is used to estimate the heading angle in the attitude estimation module. Experimental results show that the positioning error is within 0⋅02 m, and the positioning performance is better than that of the MS3D method. The heading angle error remains within 3⋅1°. The obtained results prove its applicability for the autonomous localisation in low-texture and magnetically disturbed environments.

The variation with time of exchangeable surface charge of amorphous ferric hydroxide in aqueous suspension was monitored by a titration technique. After 120 days, the surface charge of suspensions with initial pH from 8.5 to 10.5 was about one-fourth of the initial value, and goethite had formed from the ferric hydroxide. After the same time interval, the exchangeable surface charge of suspensions with initial pH from 5.5 to 8.0 was about two thirds the original value and the ferric hydroxide was still largely amorphous. The initial rate of crystallization and surface charge reduction increased with initial pH for suspensions with pH from 8.5 to 10.5, whereas the rate of surface charge reduction appeared to be independent of pH for suspensions with initial pH between 5.5 and 8.0. Based on these results it is suggested that at pH from 8.5 to 10.5 ferric hydroxide ages to goethite via a solution stage involving the Fe(OH)4- ion, whereas at pH values below 8.5 ferric hydroxide aging proceeds via mechanisms which do not involve the particle surface or bulk solution.

A deposit of kaolin clay, the site of the General Zaragosa Mine, located about 50 km northwest of San Luis Potosi, S. L. P., Mexico, has produced more than 250,000 tons of refractory clay by room and pillar mining methods during the last 32 years. The clay was formed by hydrothermal argillation of part of a fault block of rhyolite flow-breccia and probably welded tuff, presumably lower Tertiary in age. A silica-rich gossan now exposed at the surface caps the clay deposit.

Samples collected sequentially from the fresh rock to the most highly altered kaolin and studied by optical, X-ray, DTA, and chemical methods, show progressively:

1. Bleaching of the breccia matrix accompanied by mobilization of much of the iron, which was concentrated locally as spots of reddish oxide in the least altered areas.

2. Mobilization, and removal of considerable alkali and alkaline earth metals, in excess of that required to form montmorillonite; mobilization of silica, which was redeposited as fine anhedral quartz crystals disseminated within the montmorillonite and associated kaolinite-halloysite, or developed tripolitic, argillized rock peripheral to the clay ore body.

3. Further desilication of the silica and clay yielding relatively pure, but poorly ordered, kaolinite-halloysite as the most intense end product of argillation. Much silica removed during intense argillation was reprecipitated as tripolitic clay, as minor cristobalite in microscopic globules and massive aggregates characteristic of colloform opal, and in vastly larger amounts as opal and chalcedony replacing the rock overlying the clay (forming a silica gossan).

4. Minor amounts of alunite are present at two places in the deposit, which are interpreted tentatively as being the most probable loci of rising solutions.

Protein complexes of smectites in soils are difficult to detect if the usual smectite tests show no peculiarities. Andalusian black earths are typical examples. Investigation of the alkylam-monium derivatives, however, allows detection of adhered macromolecules which might be protein-like although this cannot be proved exactly.

Investigation of artificial clay-protein complexes reveals different types of clay protein interactions. Calcium smectites adsorb proteins mainly on the external surfaces, the macromolecules being anchored in the interlayer spaces. Sodium smectites give partial crystalline products in which the silicate layers are distributed in the protein matrix.

Exchange of alkylammonium ions can be used as a tool for detection of the protein. If this is adsorbed on external surfaces (calcium smectites) the increased layer separation during the cation exchange enables the macromolecules to slip between the layers and the basal spacing of the alkylammonium derivatives are changed in characteristic ways. The partial crystalline sodium clay-protein complexes are reorganized by alkylammonium ions to regular structures. The proteins are not displaced completely from the silicate surfaces so that the basal spacing of the alkylammonium derivatives are enhanced in comparison with pure montmorillonite.

The exchange of various alkylammonium cations from aqueous solution by sodium laponite has been studied. The affinity of the clay for these organic cations was linearly related to the molecular weight, molecular size or chain length of the alkylammonium ions. The affinity for the clay increases regularly with increasing chain length of the primary amines. A comparison of primary, secondary, and tertiary amines, containing the same alkylgroups shows that the affinity increases in the order R1NH3+ < R2NH2+ < R3NH+. These affinity sequences were attributed to important van der Waals contributions and changes in ion hydration states. The thermodynamic excess function, ΔGmE, was calculated and indicated that with respect to the pure homoionic forms the heterogeneous Na+-alkylammonium surface phases were more stable than they would be if the mixing were ideal.

Fibrous sepiolite crystals derive much of their commercial value from their molecular size channels and grooves. The crystals fold upon drying and these channels and grooves are lost. A model for the folding and unfolding of the crystals is presented. Extensive i.r., X-ray and thermogravimetric evidence shows that folding occurs when approximately half of the water of hydration, which is coordinated to the edge magnesium atoms inside of the channels, is removed. This occurs near 175°C under vacuum and near 300°C in air. When the crystals fold, all remaining water molecules enter a new environment, that of the hexagonal holes of the neighboring silica surface. A true anhydride is produced at about 500°C under vacuum when the final water is lost, but this final dehydration produces no important structural change. Rehydration of the anhydride to the normal hydrated sepiolite does not occur at room temperatures in 100% r.h. However, above, 60°C rehydration does occur.