Nitrogen adsorption and desorption isotherms were obtained for microcrystalline, platy crystals of synthetic Al-substituted goethites synthesized from the ferrous system and heated to 260°C. Specific surface area, cumulative pore area and frequency of mesopore wall-separations of 2–15 nm in size increased as Al substitution increased. Nanometre-size micropores developed at heating temperatures between 200 and 240°C and decreased during the growth of hematite crystals between 240 and 260°C. Aluminium substitution had little effect on micropore development and a moderate effect on mesopore development. The increases in micropore volume and specific surface area due to heating are much smaller than is reported in the literature for large, lath-like crystals of goethite that develop abundant slit-shaped micropores.

A high-iron content saponite, of the variety griffithite, was reduced using sodium dithionite and hydrazonium sulphate solutions. An important amount of Fe3+ was reduced during the treatments. When using sodium dithionite as reducing agent, the reduction was accompanied by the substitution of Ca2+ by Na+ as the exchangeable cation. When using hydrazonium sulphate, the reduction was accompanied by acid activation of the clay, the protons being released in the oxidation reaction of the hydrazonium cation. The charge balance in the clay layers is affected by the reduction processes. These structural changes do not significantly affect the pillaring ability of the clay, which is similar in the reduced solids and in the natural griffithite.

The interface performance between clay–sand mixtures and concrete structures is governed by the mixture's composition and its physical properties. Moisture content and particle-size distribution play important roles in deciding the mixture's arrangement of soil particles, porosity, hydraulic conductivity and behaviour under various mechanical loadings. Application of a polymer interfacial coating can improve the bond performance between soils and concrete mainly via interfacial friction/mechanical interlocking. The present work analyses the development of interfacial strength between clay–sand mixtures and a polymer coating with changes in particle gradation. The multi-scale mechanisms at the interface are investigated, giving primary attention to soil porosity. A 50:50 clay–sand mixture exhibited a greater interfacial adhesive performance compared to other soil mixtures. In addition, the moisture-controlled pores and gradation-controlled pores demonstrated differences in macroscale interfacial strength. Both mercury intrusion porosimetry (MIP) and 129Xe nuclear magnetic resonance (NMR) were utilized to detect the pore structure of the mixtures. 129Xe-NMR revealed the pore distribution of the mixtures as ranging from macropores to nanopores, and MIP complemented the pore information by determining the critical pore entry diameter in the macropore regime. Mesopores dominated with increasing fine sand content until a threshold value was reached; thereafter, merging of pores occurred and macropores dominated.

The effect of the firing schedule on some physical properties of a group of Etraria marls has been studied. Of particular interest are the thermal expansion and moisture expansion of the clays which reflect mineralogical changes occurring during the firing process.

An X-ray study of the chamosite occurring in the ironstone beds near Easton Neston, Northamptonshire, has shown that probably the whole of the worked ironstone at this point is part of the Main Oolitic Ironstone Group of the Northampton Sand Ironstone formation. The boundary between the Main Ironstone in this area and the Chamosite-Kaolinite beds which overlie it has hitherto not been clearly identifiable, but it is now certain that the boundary is not more than 2 ft. 6 ins. below the top of the worked ironstone.

Some predominantly kaolinitic tropical soil clays when examined by DTA in a nitrogen atmosphere gave two exothermic reactions (at ∼880°C and ∼950°C) instead of the usual single exotherm. During heating, iron present in the samples is reduced, possibly by organic carbon, and reacts with the metakaolin phase to form hercynite (FeAl2O4). The presence of Fe2+ also causes mullite to form at a lower temperature than normal. These reactions accompany the lower-temperature exotherm. The higher-temperature exotherm is due to formation of γ-alumina. Although this exothermic doublet is an artifact of the experimental conditions, its occurrence may help to elucidate the sequence of reactions involved in the metakaolinite recrystallization process.

A simple IR spectroscopy method for detecting hydrated and dehydrated halloysite in artificial mixtures with kaolinite is described. The method is based on the exclusive ability of RbCl among the alkali halides to form a complex with halloysite but not with kaolinite. This complex absorbs at 3500 cm−1 when hydrated halloysite or admixed halloysite is examined in RbCl disks, the limit of detection being 15% in the kaolin admixture. Heating the clay powders or corresponding RbCl disks at 110°C affects the 3500 cm−1 frequency. The development of this absorption band together with a decrease in the intensity ratio of the 3690/3620 cm−1 frequencies is proportional to increasing amounts of halloysite in the kaolin admixtures. This method has an analytical applicability and is relatively rapid.

Clays have been used widely as sorbents of potentially toxic elements, especially Pb. However, their adsorption efficiency has been studied mostly under static experimental conditions, which are labour-intensive. In this study, dynamic adsorption experiments were established using micro-columns to assess the adsorption behaviour of natural Fe-Mg-rich clays for Pb ions by varying the inlet solution pH, Pb concentration and flow rate. The clays, consisting of varying amounts of palygorskite and Fe-smectite, were diluted with quartz (Qz) sand to enhance their permeability. Greater adsorption capacity was observed for the mixed palygorskite/Fe-smectite-rich clay beds (45.2 ± 0.01 mg g–1) followed by the Fe-smectite-rich (35.7 ± 0.07 mg g–1) and palygorskite-rich (20.0 ± 0.03 mg g–1) clay beds. The results indicated that the greater adsorption efficiency of palygorskite/Fe-smectite-rich clays could be attributed to synergistic effects due to the coexistence of palygorskite and Fe-smectite clay phases, which have distinct physicochemical characteristics. Moreover, the results obtained showed good agreement with the static experiments, implying that the use of micro-columns could describe adsorption adequately over shorter experimental times.

Le dispositif expérimental utilisé comporte une série de sacs à dialyse renfermant des gels de silice, d'alumine, isolés, mélangés ou coprécipités et un sac renfermant un de magnésium hydraté ou un précipité d'hydroxyde de magnésium.

En fin d'expérience, les matériaux ont été recueillis et étudiés afin d'établir leur composition chimique et minéralogique.

On constate que, lorsque la silice a beaucoup migré, le magnésium a peu migré et vice versa. En effet, les rapports

et R(MgO) calculé de la méme façon sont relies approximativement par la formule suivante:

Si on considere les minéraux formés, on constate que, pour les valeurs élevées de R(SiO2), l'alumine évolue sous forme d'hydroxyde alors que, pour les fortes valeurs de R(MgO), on tend à obtenir l'hydrotalcite.

Les auteurs proposent une interprétation de ces différents comportements. Le fait le plus remarquable est que pour les très fortes values de R(MgO), on se trouve dans les conditions de l'adsorption.

Ces résultats signifient que, dans un système hétérogène renfermant des constituants peu solubles, il existe au voisinage de ces derniers des conditions de genèse particulières.

Tectonic observations in the Tethyan Himalaya reveal an important extensional event that succeeds the emplacement of SW-verging nappes. A major thrust, called the Kum Tso Thrust, has been backfolded and reactivated by normal faulting associated with this event.

Measurements of the Kübler index, coupled with characterization of clay-size paragenesis show the effect of normal faulting on the regional metamorphic zonation and indicate that important extension zones, like the Sarchu-Lachung La Normal Fault Zone (SLFZ), exist within the Tethyan Himalaya. Diagenetic limestones from within the SLFZ are characterized by the occurrence of mixed-layered clay phases, kaolinite and an illite with a 001 peak >0.4 Δ°2θ. This zone is bordered by two anchizonal-to-epizonal zones, where illite peaks become narrower. Further to the NE the successive appearance of biotite, chloritoid, garnet and garnet-staurolite-kyanite assemblages testifies to an increase in metamorphic grade. The cataclastic samples from the normal faults contain kaolinite, smectite and a ‘broad’ illite, indicating that extension occurs under diagenetic conditions.

Fe3+-doped K10 montmorillonite combined with 2,6-di-tert-butyl-4-methyl-phenol is a potent catalytic system for trans-2-methylene-1,3-dithiolane 1,3-dioxide as a dienophile. Cycloaddition occurs with cyclopentadiene and furan as a diene at room temperature in short time and with good yields (64% overall).

Plate-like α-Al2O3 particles are used to reinforce metal or ceramics to improve their mechanical properties. Here, we have demonstrated the production of alumina platelets using kaolin as a raw material in a sodium sulphate flux. When kaolin was sintered using Na2SO4 flux, the main phase formed in samples sintered at 900ºC was mullite, but alumina was produced at 1000ºC. Sintering at 1200ºC led to alumina and sodium aluminosilicate, with little of the mullite phase present. Plate-like α-Al2O3 particles were observed in samples sintered at 1200ºC, with diameters ranging from 1.5 to 4.5 µm and thicknesses from 0.05 to 0.1 µm. This production method is economically feasible because the raw materials have a low cost and the sintering temperature is low.

Three semi-empirical equations are derived to characterize the performance of the nozzle discharge centrifuge as a thickener for flocculated kaolinite slurries. The first equation relates mass throughput to machine size and speed, the number and size of nozzles and the product concentration. The second equation relates the maximum clear effluent rate to the settling characteristics of the slurry and to machine parameters. The third equation relates power consumption to product and effluent rates and to machine parameters. Finally a numerical example of the use of the equations is given.

The genesis of china-clays in the neighbourhood of Guiscriff is not related to the presence of the peat which is situated on top of the clay layer in the lower parts. The formation of this peat is subsequent to the formation of china-clay. This china-clay was formed under the action of fluids of deep-seated origin of which the remains are included in the quartz veins stretching along the quarry.

The EPR spectrum of a previously unreported paramagnetic centre formed in kaolin minerals by exposure to γ radiation is described. This centre, which is referred to here as the ‘C-centre’, was seen initially during an investigation of the radiation dose response of the EPR signal in the natural Lampang kaolin from northern Thailand, and its EPR properties are now presented for a purified sample from this material. They suggest a paramagnetic centre with rhombic symmetry based on O− associated with a single 27Al atom. Computer simulations suggest spin Hamiltonian parameters of g1 = 1.976, g3 = 2.0417 and A(27Al) = 2.10 mT, with g2 ≈ 2.01. This C-centre was also seen as a minor radiationinduced component in both crude and purified Ranong kaolin samples, along with a stronger signal from the B-centre radical. It seems to be associated with the kaolinite component, but was lost on annealing to 300°C after which only the signal from the A-centre was visible.

Difficulties experienced in the preparation of organo-clay derivatives from an English montmorillonite led to an investigation of its properties. The mineralogical composition, cation-exchange capacity, surface area, and relative particle size, of this and two other montmorillonites, were compared. The results indicated that the large differences which were occasionally found could be attributed to the exchangeable cation on the clay.

The adsorption behaviour of the herbicide clomazone on inorganic and organically modified montmorillonite from the Bogovina deposit in Serbia was investigated. Montmorillonite was modified first with NaCl and then with organic complexes such as hexadecyltrimethylammonium bromide (HDTMA) and phenyltrimethylammonium chloride (PTMA). Changes in the surface properties and morphology of the montmorillonite before and after the modification with various concentrations of organic complexes were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Adsorption of clomazone on all examined samples was investigated using the batch adsorption method. Montmorillonite modified with HDTMA-bromide displayed greater uptake of the clomazone compared to the PTMA-montmorillonite, and both organically modified montmorillonites displayed greater uptake of the herbicide compared to the inorganic montmorillonite. Comparing the Freundlich coefficient and maximum adsorbed clomazone quantity values obtained by Langmuir model, the levels of adsorption of clomazone decreased in the following order: HDTMA-montmorillonite with 1.00 cation-exchange capacity (CEC) saturation > HDTMA-montmorillonite with 0.75 CEC saturation > PTMA-montmorillonite with 1.00 CEC saturation > PTMA-montmorillonite with 0.75 CEC saturation > HDTMA-montmorillonite with 0.50 CEC saturation > HDTMA-montmorillonite with 0.25 CEC saturation > PTMA-montmorillonite with 0.50 CEC saturation > PTMA-montmorillonite with 0.25 CEC saturation > Na-montmorillonite > raw sample. The type and content of an organic cation plays an important role in the behaviour of clomazone in a solid/liquid system. It is concluded that organically modified montmorillonite from Bogovina might be used as an effective adsorbent for clomazone.

Resonance energy transfer (RET) in hybrid polymer/inorganic/organic layers in saponite films, prepared using the ‘layer-by-layer’ (LBL) method, was studied. This method allows the fabrication of a multicomposite molecular assembly based on electrostatic and/or other intermolecular interactions between the interacting species. The LBL films were designed by sequential deposition including positively charged polycations ( poly(diallyldimethyl ammonium), PDDA) and negatively charged saponite dispersions with donor molecules (rhodamine 6G) and saponite dispersions with acceptor molecules (rhodamine 3B). In this sequence, the layer of saponite donor molecules was placed on an adjacent layer of saponite acceptor molecules, while the layers were separated by inserting a PDDA polycationic layer. The adsorption process was studied using absorption spectroscopy. The linear deposition regime was completed when ten layers had been deposited. The process of REF was studied by fluorescence spectroscopy. In this case the donor molecules – rhodamine 6G – play the role of lightharvesting antennae and transfer the energy to the next layer covered by energy acceptor, i.e. rhodamine 3B molecules. The insertion of polycation layers is rationalized by the adhesion of negatively charged underlying layers and the stabilization of multicomponent systems. The energy transfer efficiency was affected heavily by changing the distances between the adjacent layers.