A clay from the Mediterranean area classified as natural bleaching earth was comprehensively characterized and the quantitative phase content was determined. Morphology and surface characteristics were determined by environmental scanning electron microscopy (ESEM) and nitrogen adsorption. The BET surface area was >200 m2 g–1 and the average mesopore diameter was >10 nm. Thus the clay is suitable for bioseparation of larger proteins. X-ray diffraction (XRD), X-ray fluorescence (XRF), cation exchange capacity (CEC), layer charge measurement and simultaneous thermal analysis (STA) were used for mineralogical characterization. Determination of the phase content by Rietveld analysis was possible only after Sr2+ saturation, while Rietveld analysis of XRD patterns from Na+-saturated clay resulted in a strong overestimation of the amorphous content and masking of the sepiolite. The clay consists of sepiolite, dioctahedral smectite with high layer charge and low stack height, X-ray amorphous matter (probably mainly SiO2) and accessory feldspars.

The subarkosic-sublitharenitic Upper Cretaceous sandstone, which has up to 30% porosity and 585 md permeability, produces on salt diapir structures in the Oguendjo West Block, offshore Gabon. The porosity consists of 68% intergranular porosity of primary and secondary origin, 17% secondary intragranular and moldic porosity, and 15% microporosity. A microcrystalline quartz druse, which was derived from alteration of lithic fragments, coats framework grains and retards the development of syntaxial quartz overgrowths. Other cements are patchy ankerite (0·3–13·7 vol%) and kaolinite, which also occurs as a replacement of framework grains. The total kaolinite content ranges from 1·8 to 8·2 vol%. Kaolinite and remnants of altered and partially dissolved lithic fragments are susceptible to movement with fluid flow. Formation sensitivity tests showed that the kaolinite-rich sandstone was stable to 2% NaCl water, but introduction of freshwater caused permeability impairment. Acid treatment to remove damage produced sporadic results. Injection of HCl raised the permeability temporarily, indicating that fines were still being liberated within the pore network. Injection of HCl/HF immediately reduced permeability through partial disaggregation of the rock. Plugging of the formation face by drill mud also damages the reservoir. Reversal of flow at high pressure differentials will remove formation damage produced by face plugging. A guideline for this process established in the laboratory is to backflow with a pressure differential at least as high as the overbalance used in drilling. The combination of oil-based drilling fluids and underbalanced perforating with filtered diesel in the wellbore should eliminate most formation damage in this reservoir.

In this study, adsorption and adsorption kinetics of methyl violet dye from aqueous solutions onto kaolinite were investigated. The effects of adsorbent dosage, pH, ionic strength, contact time, temperature and initial dye concentration were studied. Kinetic and thermodynamic parameters were determined using experimental data. Adsorption capacity decreased with increasing ionic strength. Changes in the initial pH of the dye solution in a range close to the dye's natural pH (i.e. ∼ pH 5.0) values affected adsorption capacity slightly, indicating that adsorption studies could be carried out at the dye's natural pH. The adsorption process followed the Freundlich-type adsorption isotherms and pseudo-second order type adsorption kinetics. However, an intraparticle diffusion process was found to have effects in adsorption processes. Thermodynamic parameters were calculated from the experimental data and enthalpy of the adsorption, ΔH0, was found to be –6.82 kJ mol–1, indicating physisorption nature of the adsorption. Other thermodynamic parameters, ΔS0 and DG0, were also calculated. Negative values of ΔG0 indicated that the adsorption process for methyl violet on kaolinite is spontaneous.

The removal of lead and zinc from a binary solution by fixed bed depths (40, 80 and 120 mm) of a natural zeolite was examined at a flow rate of 1 mL/min. The results obtained were fitted to the Bed Depth Service Time (BDST) model and the parameters of the model (q and k) were used to design a column system for flow rates of 2 and 3 mL/min at a bed depth of 80 mm. The experimental results were in excellent agreement with those predicted and experimental breakthrough curves for the binary systems were obtained. This approach facilitates the design of effective binary column processes without additional experimentation. Two major design parameters, the Empty Bed Contact Time (EBCT) and the zeolite usage rate, were calculated. The highest EBCT value of 13.56 min represents the optimal conditions for the binary (Pb+Zn) solution.

Compositional and microstructural analysis of mullites in porcelain whitewares obtained by the firing of two blends of identical triaxial composition using a kaolin B consisting of ‘higher-crystallinity’ kaolinite or a finer halloysitic kaolin M of lower crystal order was performed. No significant changes in the average Al2O3 contents (near the stoichiometric composition 3:2) of the mullites were observed. Fast and slow firing at the same temperature using B or M kaolin yielded different mullite contents. The Warren–Averbach method showed increase of the D110 mullite crystallite size and crystallite size distributions with small shifts to greater values with increasing firing temperature for the same type of firing (slow or fast) using the same kaolin, as well as significant differences between fast and slow firing of the same blend at different temperatures for each kaolin. The higher maximum frequency distribution of crystallite size observed at the same firing temperature using blends with M kaolin suggests a clearer crystallite growth of mullite in this blend. The agreement between thickening perpendicular to prism faces and mean crystallite sizes <D110> of mullite were not always observed because the direction perpendicular to 110 planes is not preferred for growth.

This paper addresses the application of thermal analytical methods (DTA/DSC/TG/ MS) in soil investigations, especially the interrelation of exothermic effects and analytical or preparative parameters. For the superimposed decomposition/ oxidation reactions of siderites, FeCO3, the heating rate is shown to have a decisive influence because low heating rates tend to suppress the endothermic effect. In mixtures of small amounts of organic matter (glucose and starch) with talc, the phyllosilicate acts as a catalyst by influencing the intensity of combustion of the organic matter.

A montmorillonite clay and an X-ray amorphous Fe(II)-silicate were suspended in a synthetic groundwater solution under oxic and anoxic conditions at 23 and 70°C for 200 days. The clay samples were then analysed for total Fe, Fe(II), dithionite- and oxalate-extractable Fe (Fed and Feo), cation exchange capacity (CEC), and examined by X-ray diffraction (XRD) and diffuse reflectance spectrometry (DRS). The total iron content and Fe(II)/Fe(III) ratio of the clay increased with an increase in temperature and both were greater under anoxic than oxic conditions, as were the amounts of Fed and Feo. The CEC of the clay was lower in the presence of the Fe-silicate, suggesting that Fe-hydroxide had precipitated at the edges of the clay blocking some cation-exchange sites. No changes in the clay were detected by XRD or DRS after contact with the Fe-silicate, nor was there any evidence for Fe-hydroxide material in the interlayer region of the clay. However, it is shown that the amount and nature of iron associated with clay can be significantly altered and certain properties of the clay, such as CEC, can be affected when the clay is in contact with Fe(II)-containing materials.

Quartz-hematite veins in the St. Austell pluton feature an assemblage of authigenic kaolin, illite, chlorite and hematite. Similar assemblages occur in altered granites adjacent to the veins. Complex textures in the veins and altered granites show that kaolin was an initial precipitate from hydrothermal fluids that was subsequently replaced by illite, hematite and chlorite. The sequence of mineral precipitation reflects a kinetic control on crystal growth, with early nonequilibrium precipitation of kaolin from fluids with compositions appropriate for the equilibrium formation of illite. Hematite formed under relatively oxidizing conditions that subsequently became more reducing to permit the late precipitation of chlorite. Illite associated with the quartz-hematite veins differs texturally, mineralogically and chemically from the coarsely crystalline hydrothermal muscovite (sericite or gilbertite) associated with quartz-tourmaline veins and greisen. Quartzhematite veins are thus considered to record a distinct mineralization event that is not related to the early greisenization or the economic kaolinization.

Decomposition of decylammonium cations on vermiculite surfaces as a result of acidity has been studied. The vermiculite-decylammonium complex was treated with solutions of HCl in water and butanol, and solutions of chlordimeform in butanol. X-ray powder diffraction and IR spectroscopy data showed the presence after treatment of ammonium cations in addition to aliphatic chain compounds in the interlamellar space. The ammonium cation is produced by breaking of the C-N bond of alkylammonium due to the low pH of the medium and, when using butànol as solvent, to the dissociation of the scarce water molecules on the clay surface. The influence of the different solutions on the period of decomposition of alkylammonium cations is discussed. Vermiculite-decylammonium complex treated with HCl solutions for a year released structural Mg2+ due to the acidity of the medium. This Mg2+ partially displaced ammonium cations from the interlamellar space.

Clays are commonly used as liners in urban landfills. However, the reactive processes with landfill leachates, and in particular the role of accessory minerals is poorly known. The aim of this work is to evaluate the diffusion of a synthetic urban landfill leachate through compacted natural smectite-illitic clays containing carbonates and sulfates and to predict the functioning of the clay liner for different minor mineral proportions. The leachate, characterized by acidic pH conditions and high organic matter content, is a typical aqueous solution formed in the acetogenic phase of organic matter degradation in urban landfill areas. Medium-scale (11 cm) laboratory diffusion tests were performed over 77 days. Chloride diffusion coefficients, porosity changes, cation exchange constants and the sulfate reduction rate were quantitatively assessed by means of reactive transport modelling. The exchange capacity of the clays is responsible for NH4+ retention. However, the presence or absence of gypsum in the initial clay rock controls the functioning of the liner. Gypsum dissolution ensures a high sulfate concentration in the porewater and enhances the acetate consumption via sulfate reduction. Gypsum dissolution and the concomitant calcite precipitation do not significantly alter the porosity of the clay rock.

Zeolitic tuffs from the Xerovouni location of the Avdella area (Evros Prefecture, Greece) contain on average 54 wt.% HEU-type zeolite, 6 wt.% smectite, 4 wt.% mica (64 wt.% microporous minerals), 8 wt.% alkali feldspar, 9 wt.% plagioclase, 11 wt.% cristobalite and 8 wt.% quartz (36 wt.% non-microporous minerals). The chemical formula of the HEU-type zeolite is Ca2.4K0.6Na0.4Mg0.3Al6.7Si29.3O72·17H2O and the tuffs contain on average 72.3 wt.% SiO2, 11.9 wt.% Al2O3, 1.2 wt.% Fe2O3, 1.0 wt.% MgO, 2.8 wt.% CaO, 1.3 wt.% Na2O and 1.9 wt.% K2O. The zeolitic tuffs show an average ammonium exchange capacity of 144 meq/100 g. HEU-type zeolite accounts for the most of the ammonium exchange capacity, while smectite and mica contribute to a relatively small extent. The ammonium exchange capacity of the Xerovouni zeolitic tuffs showed positive correlations with (a) the HEU-type zeolite content, (b) the total microporous minerals content, (c) the loss on ignition content and (d) the CaOcontent. Such materials could be used in a large variety of agricultural, aquacultural, industrial and environmental applications.

Les auteurs étudient les produits de l'altération fumerollienne et météorique de Vulcano, Iles Eoliennes, Italie. Ces produits sont étudiés par diffraction des rayons X, analyse chimique classique, microscopie électronique et microsonde.

This investigation was carried out to determine whether the adsorptive and ion-exchange properties of faujasite (FAU) could be used to delivery locally the anticancer drugs gemcitanine hydrochloride (dFdU.HCl) and oxaliplatin (DACH-Pt). A soaking procedure was used for the determination of the maximum adsorption capacity of FAU and the mechanism described here was achieved. 274 mg dFdU.HCl/g FAU were adsorbed in 16 h, while 48 h were needed for the adsorption of 79.7 mg DACH-Pt/g FAU. Drug release studies were carried out by soaking the samples of loaded FAU in simulation body fluids (SBF). After only one hour 76% of dFdU.HCl was released while the release of DACH-Pt from the FAU was more normal since 38% of DACH-Pt was released in the first 24 h.

Electric fields were imposed on aqueous suspensions of the rigid asymmetric particles of crocidolite. Orientational order resulted in the field and the intensity of the light scattered by the medium changed. Such intensity changes were recorded for pulsed electric fields of up to 500 V cm−1 amplitude and 1·5 kHz frequency. When combined with data for the scattered intensity prior to the application of the field, the average particle mass (8 × 10−15 g), length of the rod-like particles (1·3 µm), rotary diffusion coefficient (2·4 s−1) and electrical polarizability (22 × 10−29 Fm2) were all evaluated for this sample. The relationship of the polarizability to the electric double layer structure of the sols is briefly discussed. The transient scattering method offers a reliable and rapid means of characterizing mineral sols.

The present study explores the effect of a magnetically modified halloysite (mHNT) surface on the structure and properties of biodegradable polymer nanocomposites based on poly ɛ-caprolactone (PCL). Halloysite nanotubes (HNTs) have been modified by a scalable and tunable procedure using magnetic Fe oxide particles prepared by microwave-assisted synthesis fromferrous sulfate at high pH. The HNT content in composites prepared in melt varied from 5 to 30 wt.%. Application of magnetically modified HNT to PCL resulted in the formation of soft magnetic materials. Analyses of the nanocomposite structure revealed that both natural and magnetized HNTs, as well as free magnetite particles are dispersed uniformly in the polymer matrix. Investigation of the mechanical and physical properties confirmed that the reinforcing ability of HNTs was not affected by magnetic modification.

Examination of rock samples from Job's Hill, St Mary, Jamaica, by chemical, X-ray, differential thermal, and infrared analyses showed predominant dickite with associated nacrite and kaolinite. The uniqueness of this deposit makes it possible that selected material could be used as a standard mineral.

Fourth-order relative sea level changes may have a significant impact upon burial diagenesis and reservoir quality through their effect upon surface and subsurface temperature. Relative sea level changes can induce sediment surface temperature changes of <20°C when the sediment surface changes from being close to or beneath the thermocline to being sub-aerially exposed. Such sea level changes typically occur on a timescale of half a million years. Approximately one quarter to one third of the magnitude of these temperature fluctuations will be propagated to 2500 m in the subsurface. Shorter timescale fluctuations of similar magnitude, resulting from glaciation, will not be significant below ~1000 m burial as there is not enough time to effect the change before the next surface temperature cycle occurs. Diagenesis is strongly controlled by temperature through its impact on the driving force and rate of geochemical processes. Burial diagenesis and cementation may thus be episodic on timescales associated with sequence stratigraphic events occurring on the surface, thousands of metres above the zone where diagenesis is occurring.

The Alto dos Quintos Mine, Rio Grande do Norte, northeast region of Brazil, is one of the few mines where a LCT (Li-Cs-Ta-enriched) pegmatite is exploited for the deep blue gemstone called “Paraiba Tourmaline (PT)”. Blue cuprian elbaite, a fault-bound pink montmorillonite bearing some relict apatite and newly-formed Ca-Al-phosphate of the Al-P-sulphate group (APS minerals) also occur in the underground mine. The montmorillonite was studied using extended clay mineralogical tools (XRD, IR spectroscopy, XRF, SEM-EDX, cation exchange capacity (CEC), DTA). The structural formula method for calculation of the smectite formula based on EDX data yielded an extremely Fe-poor montmorillonite: (Ca0.22+)(Al1.7Fe0.0Mg0.4)(Si3.8Al0.2). The charge on the tetrahedral sheets accounts for approximately 30% of the total permanent negative charge. However, based on the more precise Hofmann & Klemen test, tetrahedral charge values of 11% to 13% were calculated. This is indicative of the dominance of montmorillonite rather than beidellite among the smectite minerals, which is independently proved by a pronounced IR band at 630 cm-1. The formation of pink montmorillonite is not directly related to the emplacement of the Li-bearing PT pegmatite. The sheet silicate developed after a considerable hiatus (Mesozoic?), when the Neoproterozoic pegmatites had already undergone different stages of hypogene (cookeite) and supergene (illite, kaolinite) alteration, during which Li was flushed out to a degree that formation conditions of expandable Li-bearing phyllosilicates were no longer favoured. The nature of the pinkish tint is not yet clarified. The montmorillonite formed in a temperature regime close to 250°C, when apatite was transformed into Ca-bearing APS minerals under acidic conditions. Cainozoic volcanic activity and the reactivation of deep-seated fault zones are considered to be responsible for the formation of this pink P-bearing montmorillonitic clay.