The Swedish and Finnish nuclear waste repository design, KBS-3H, foresees horizontal emplacement of copper canisters-bentonite modules surrounded by a titanium shell. The interaction of titanium with bentonite was studied here using a combination of wet chemistry and a spectroscopic approach to evaluate the potential impact of Ti corrosion on the clay. For natural analogue clays with high Ti contents, spectroscopic investigations showed that titanium occurs as crystalline TiO2. In contrast, the Ti in the MX-80 bentonite occurs in the clay structure, presumably in the octahedral sheet. Hydrothermal tests conducted at 200°C using synthetic montmorillonite showed little if any change in the montmorillonite structure at near-neutral and acidic conditions. Under alkaline conditions, limited alteration was observed, including the formation of trioctahedral clay minerals and zeolite. These changes, however, occurred independently of the addition of Ti. In the batch tests conducted at 80°C, Ti did not occur as separate TiO2 particles. The comparison of experimental data with spectroscopic simulations provides sound evidence that Ti was incorporated in a neoformed phyllosilicate structure.

Montmorillonite (Mnt), belonging to the smectite group and representing a 2:1-type clay mineral with good cation-exchange and swelling capacities, is a common clay component of soils. It was observed that some Mnt preparations exhibit peroxidase-like (P-L) activity using N,N-diethyl-p-phenylenediamine sulfate salt as a substrate. Both native (non-swelling) and swelling Mnt exhibited similar P-L activity. Modification of Mnt with copper and iron influenced both P-L activity and phenol polymerization. Both free and textile-bound Cu-Mnt (Sigma-Aldrich) enabled phenol removal. Soil Mnt P-L activity is probably involved in lignin breakdown and decontamination of soils polluted with phenol-containing molecules.

The observation of clayey matrix on a thin-section under polarized transmitted light allows the analysis of the clay particle arrangements, the measurement of their orientations in 3-D, and finally the cartography of the different orientation modes by using a simple image analysis system connected to the optical microscope. The method is based on: (1) the analysis of the shape evolution of the grey-level diagram vs. the rotating stage angles; and (2) the mathematical decomposition of these grey-level diagrams into elementary gaussian curves. For each identified orientation mode, the standard deviation of the grey values gives the dispersion index of the oriented particles around the axial plane. The 3-D representation is performed on the Wulff stereonet. The horizontal orientations are measured by simple rotation of the revolving stage and the dip angles are deduced from the peak displacements along the abscissa of the grey-level diagram during the complete rotation of the revolving stage. The quantifications (percentage, isotropy and distribution index) are performed after a thresholding operation of each orientation mode.

Sulphur reduction catalysts represent a viable option for S reduction in the fluid catalytic cracking (FCC) process. In this paper, a kaolin in situ crystallization catalyst was modified with vanadium and evaluated in a fixed fluid bed (FFB) reactor. The relation between the acidity of the catalyst, the S reduction rate and the catalyst activity is discussed. The results show that increasing weak Lewis acid acidity favours S reduction in the FCC process. Increasing the V content enhances the weak Lewis acidity, so causing the S reduction rate to increase. The kaolin in situ crystallization catalyst modified with 0.6 wt.% of V leads to a 34.5% reduction in the S content of the liquid product. Comprehensive evaluation of the FFB results and the S reduction ability indicates that the catalyst modified with 0.45 wt.% V provided the best performance.

The partial and apparent molal volumes of K-bentonite in pure water and in 0·5 M KCl were determined using pycnometer density data. The values obtained were found to increase with particle concentration. Theoretical values of the electrostatic contribution to the volume of particles calculated from an assumed model based on the electric double layer theory, gave values different from those found experimentally. This is explained as due largely to the uncertainties in the value of the clay specific surface area as well as to the assumed ideality of the model used.

Compacted bentonite is to be used as a component of an engineered barrier system to retard the migration of radionuclides in the geological disposal of radioactive waste. In such an environment, montmorillonite in compacted bentonite might be altered to illite due to the hydrothermal reactions caused by the decay heat of radionuclides. In the present study, the diffusion and retention behaviour of Cs in compacted montmorillonite containing illitewas investigated using through-diffusion experiments. The experimental results showed that the flux of Cs attributed to the surface diffusion was independent of the sorption of Cs on illite, indicating that the Cs sorbed on illite was immobile or considerably less mobile than the Cs sorbed on montmorillonite. Consequently, the illite content in compacted bentonite is expected to enhance the sorption capacity of Cs without causing surface diffusion.

Bentonites are proposed to be used as buffers in high-level radioactive waste repositories. The elevated temperatures in repositories may, however, affect bentonites’ desired properties. For instance, heating under dry conditions can cause cation fixation, potentially affecting swelling properties. The kinetics of mineral dissolution and precipitation reactions will equally be influenced by temperature. Redistributions of Ca-sulphates and -carbonates have been observed, as well as illitization of smectite. Illitization, however, has only been observed in laboratory experiments at large solution/solid ratios, whereas it has not yet been unambiguously identified in large-scale experiments. In many large-scale tests, cation exchange is the first observable geochemical reaction. In addition, an enrichment of Mg close to the heater is found in many such tests. The thermal gradient and (incongruent) smectite dissolution are suspected to play a role with respect to the Mg enrichment, but the underlying mechanism has not been unravelled so far. To predict the long-term performance of a bentonite buffer, numerical modelling is required in order to be able to simulate the reactions of all accompanying mineral phases. Smectites, which dominate the bentonite composition, are therefore particularly difficult to characterise, as their dissolution is often observed to be non-stoichiometric. Various model approaches exist to simulate smectite reactions, mostly based on kinetic rate reactions, ideally considering the effect of pH (congruent or incongruent dissolution), temperature and the degree of saturation of the solution. Reassessing and improving the thermodynamic/kinetic data of smectites are prerequisites for improving long-term buffer performance assessment.

A new method for estimating the sulphide content of samples of impermeable rocks is described. It is based on the oxidation of reducing substances by nitric acid and titration with permanganate of the nitrous oxides absorbed by potash.

A number of Ni-hydroxy-montmorillonite complexes were prepared by titrating NiCl2 solutions with NaOH in the presence of charge-reduced and normal montmorillonite suspensions. These complexes were characterized by chemical analysis, CEC, XRD, IR and temperature-programmed reduction (TPR). The R (charge-reduced) Ni-hydroxy complexes proved to be merely mechanical mixtures of Ni(OH)2 and clay. The reducibility of Ni contained in these samples was not affected by preliminary heat treatments. The nature of the N (normal) Ni-hydroxy montmorillonites depended principally on the amount of Ni actually incorporated into the precipitates. Neither the OH/Ni ratio selected for the preparation or the quantity of Ni initially added completely determined the type of complex formed. TPR patterns of the N samples generally showed three reduction bands whose respective intensities varied with the quality and the amount of Ni present. One of these reduction bands, occurring at high temperature, measured the extent of incorporation of Ni into the silicate framework during the TPR run. The intensity of this high-temperature band with respect to lower temperature ones was increased by thermal pretreatments. The results emphasize that when TPR patterns of natural Ni-bearing clays are being interpreted it is important to recognize that thermal transformations may occur in the samples caused by the heat supplied during the TPR run itself.

Back-scattered scanning electron microscopy (SEM) images of Cr-chlorite crystals from Erzerum (Turkey) reveal that the crystals are chemically inhomogeneous and display complex but well defined crystal zoning characterized by growth bands with contrasting chemical features. The chemical zoning has been investigated at the micron scale using an integrated approach, combining BSEM images, in situ chemical analysis by electron microprobe and Raman spectroscopy. Enrichment in Cr, due to octahedral Al substitution, reaches up to 0.7 atoms per half formula, especially in bands where the Mg content is depleted. These substitutions are also depicted at the micron scale on Raman spectra by changes in the v(OH) band intensities and positions that correlate with the Cr content. The Cr-enrichment occurs thus during specific stages of crystal growth, probably in response to changes in the fluid chemistry controlling the relative availability of Cr, Mg and Al in solution.

The Tertiary sequences in northern Kyushu, Japan, contain several types of zeolite and clay minerals together with carbonaceous materials. A correlation between authigenic mineral zones and vitrinite reflectance reveals the delay in mineral authigenesis relative to the increase in vitrinite reflectance compared with similar studies in other regions. This may be ascribed to causes such as high paleogeothermal gradient, and chemical composition of pore-waters and host sediment.

Soil clay mineralogy at Rothamsted began in the early 1930s, and quickly focused on technique, swelling minerals, micas and sorption phenomena. By the mid-1940s interest had extended to the formation and spatial distribution of soil clays with the move of the Soil Survey of England and Wales to Rothamsted. These themes continued for the next 40 years. Considerable contributions were made to crystal chemistry and structure determinations, and the relationship of these to the sorption and desorption of water and organic molecules, and the behaviour of soil K. The pattern of soil clay mineralogy was determined for large parts of England and Wales, and absorbed into soil mapping. The work on X-ray diffraction appeared in the Mineralogical Society Monographs on this subject. These, and the Monograph on Clay Chemistry, which reached their final form in the 1980s, are the lasting monuments to soil clay mineralogical research at Rothamsted.

Reagent-based selective separations of minerals are of great industrial importance. The basis of these separations is the competitive differential adsorption of the reagent onto a number of minerals. An X-ray photoelectron spectroscopic (XPS) study of the adsorption of polyacrylamide onto kaolin, feldspar and quartz is described. Initial data confirmed the utility of XPS for the study of polyacrylamide adsorption onto silica glass slides. Further results indicated the utility of the technique for the direct measurement of adsorption of polyacrylamide onto individual aliquots of kaolin, feldspar and quartz. Adsorption was relatively greatest onto kaolin. Feldspar displayed less adsorption and quartz very little. An imaging method was used to characterize, at least relatively, the competitive adsorption of polyacrylamide onto kaolin in the presence of mixtures of kaolin and quartz. This is a potential new technique for study of competitive adsorption.

This work examines possible new applications for common, clay-based formulations. We processed spray-dried grains of a common clay (ZA-4) and collected fines/rejects from the production of lightweight aggregates (LWA), which were used as filtration beds for removal of Pb2+ and Ni2+ from aqueous solutions. Experiments were performed at different contaminant concentrations and by testing several operational conditions. The removal performance of both tested materials is strongly dependent on the particle-size distribution of the batch, being better for beds made of smaller grain size, since packing density and specific contact area for removal are greater. In general, the efficiency for removal of Pb2+ was greater than for Ni2+. When compared with granular activated carbon, clay-based beds performed well. In particular, finer fractions of LWA show stable behaviour, without saturation after consecutive runs. Saturated beds can potentially be reused, in appropriate amounts, for production of new lightweight aggregates or common ceramic items (e.g. bricks), since retained contaminants will be fixed by firing in the clay matrix. Calcination of pressed pellets made of contaminated filter grains created consolidated ceramic components and sorbed metallic species became inert.

Une étude expérimentale des équilibres d'échange entre gel de composition (A,B)O-SiO2-nH2O et solution aqueuse (A2+, B2+) a été réalisée avec les couples (A,B) suivants: Mn-Mg, Co-Mg, Co-Mn et Cu-Ni. Les coefficients de distribution (A/B)gel/(A2+/B2+)sol obtenus sont énormes, l'élément A se fixant presque totalement dans le gel et n'apparaissant le plus souvent qu'en traces dans la solution. Le dosage de celles-ci par activation neutronique a permis d'atteindre le domaine des concentrations où ces gels présentent un comportement idéal (loi de Henry) et de mesurer avec une précision accrue les enthalpies libres standard des réactions d'échange correspondantes.

Thermoporometry (TPM) was applied to hydrotalcite precipitates prepared with carbonate, bicarboxylic acids and chloride. It was used to measure the formation of an ice body between the hydrotalcite particles. Before TPM could be applied, the dried hydrotalcite precipitate had to be soaked for two weeks in water. The mean value of a factor F measured by TPM, which described the shape of the ice body in hydrotalcite, was 1.7. This value was between those of a purely cylindrical (F = 2) and a purely spherical ice body (F = 1), indicating the formation of ice lenses. From the radius of the ice body, Rn, ice volume, Vn and shape factor F, the corresponding specific surface area of the hydrotalcite particles could be assessed. The TPM indicated that the distance between the separate hydrotalcite crystals in water, which is equal to 2(Rn+0.9) nm, was a function of the type of anion incorporated at the interlayer, such as chloride and bicarboxylic acid. The pore volume and surface area of the hydrotalcite particles measured by TPM were compared with those determined by the traditional nitrogen sorption technique on dried hydrotalcite. It appeared that sorption of N2 yielded much lower values than TPM. This difference was interpreted as being due to slow penetration of N2 through the dried hydrotalcite samples to the interparticle voids.

The purpose of this study was to develop a simple and economic method for the preparation of porous bioceramics with controllable macrostructure. Raw materials, including very small organic foam balls as the pore-creating reagent, wax (or paraffin) as the solvent, and oleic acid as the surface active agent, were selected along with bioactive materials such as β-TCP ceramic powder as the main component. The selected components were mixed into a slurry at 30–120ºC and shaped into a green body with a hot die-casting machine at 30–90ºC. The green body was then sintered and porous bioceramics were obtained. The main characteristics of porous bioceramics such as weight loss, compressive strength, connection and size of pores, percolation rate of water, apparent porosity and bulk density were measured. The results indicated that the apparent porosity and the specific surface area were large; the pores were connected in three dimensions and the compressive strength was >1.6 MPa. This study demonstrated that the methods used here are simple and effective in generating porous bioceramics with controllable macrostructures.