In this study, the reaction between humus acids (humic acid and β-humus fulvic acid fraction) and bentonite and illite was studied at a variety of pH values. The degree of reaction was determined from the specific surface area and molar energy of adsorption. Characteristic parameters of adsorption isotherms for the formation of a mono-layer of the adsorbent, such as the constant C from the BET equation, mono-layer capacity (Nm), and standard error square (R2), were also included in the study. After the addition of humus acids, the specific surface area of illite and bentonite decreased at all pH values, reaching a minimum at pH 4. This indicates different degrees of reaction of humus acids with the clays and, probably, partial hydrophobization of the materials. The degree of reaction of humus acids with the minerals depended on the pH and, for certain combinations, it was highest at pH 4. This value is relatively close to that at which the humus acid fractions in question precipitate from solution.

Two zeolitized tuffs (ZTs), viz. a Neapolitan yellow tuff (NYT) and a clinoptilolite-bearing tuff (ZCL), were tested as pedotechnical materials to improve soil resilience against the impact of treatment by a ‘dirty’ municipal sewage system (DSW). Soils (surface horizon) were a sandy, alkaline Entisol (Typic Xeropsamment), and a sandy-loam, sub-acidic Alfisol (Ultic Palexeralf). Results showed that the presence of ZTs resulted in several favourable effects. Electrical conductivity (EC) decreased and pH was buffered. Ammonium was selectively taken up from the DSW, making the zeolitized tuffs almost saturated by NH4+, by exchanging both beneficial cations, such as K+ and Ca2+, thus improving their potential availability to plants, and undesirable cations such as Na+, thereby hindering the exchangeable sodium percentage (ESP) increase and concurrent soil salinization-alkalinization. At the same time, NH4+ was stored as a potentially slow-release nitrogen fertilizer. The mobility of Pb, Cu and Zn dropped off to a large extent. NYT produced the best effects, and the Entisol gained the greatest benefit from treatments.

Fluorescence and phase transitions of a new Mg-Al-Eu ternary layered double hydroxide (LDH) and their dependence on thermal treatment were studied for the first time. Phase transitions occurred as the temperature increased from 400 to 1100°C. The process of phase transition is discussed in detail. The emissions of Eu3+ ions described by the 5D0–7FJ transition (J = 1,2,3,4), and especially for the 5D0–7FJ transition (J = 1,2) varied markedly with phase transformations from LDH, MgO, to mixtures of MgO and MgAl2O4. Moreover,strong emissions of Eu3+ ions are present in these new host materials. These results indicate that Mg-Al-Eu ternary LDH may be a potential candidate for materials applied in fluorescent devices.

The purpose of this study was to develop a simple and efficient method for manufacturing porous bioceramics, in which small organic foam spheres were taken as the poremaking reagent and green bodies were made by hot die-casting in moulds. The raw materials (small organic foam spheres, paraffin, oleic acid and β-TCP powder) were mixed into a slurry at 30–120ºC and moulded into green bodies using a hot die-casting machine at 30–90ºC; the green bodies were then sintered and the porous bioceramics obtained. The main characteristics (structure and size of pores, water permeability, apparent porosity and shrinkage) were tested. The results indicated that the apparent porosity was high and directly proportional to the mass ratio between the small organic foam spheres and the β-TCP powder. The pores connected with each other in three dimensions; the size, distribution of the shapes and structures of the pores were clearly related to the dimensions of the small organic foam spheres. The water permeability was proportional to the hot die-casting pressures and the shapes of the samples could easily be controlled by selecting different moulds. This study indicated that the method can be used to manufacture porous bioceramics with controlled pore structures and different shapes effectively and easily by adding different amounts and sizes of small organic foam spheres, mixing the raw materials evenly, and by selection of the hot die-casting pressure and by the use of different moulds.

Hydrothermal alteration of Proterozoic granitic rocks in the Äspö underground laboratory, southestern Sweden, resulted in the formation of chlorite with large variations in textural and chemical characteristics, which reflect differences in formation temperatures, fluid composition, and reaction mechanisms. The mineral assemblage associated with chlorite, including Ca-Al silicates (prehnite, pumpellyite, epidote, and titanite), Fe-oxides, calcite, albite and K-feldspar, suggests that chloritization occurred at temperatures of between 200–350°C during various hydrothermal events primarily linked to magmatism and rock deformation. Petrographic and electron microprobe analyses revealed that chlorite replaced biotite, amphibole and magnetite, and hydrothermal chlorite phases filled fractures and vugs in the granitic rocks. While fracture-filling chlorite reduces fracture permeability, chloritization reactions in the host granite resulted in the formation of new localized microporosity that should thus be taken into consideration when evaluating the safety of the granitic basement rocks as a repository for nuclear waste. It is also important to take into account that similar alteration reactions may occur at the site of stored nuclear waste where temperatures in excess of 100°C might be encountered.

The genesis of the products of the alteration of acid pyroclastic material is discussed and interpreted on the basis of the distribution, sedimentation conditions, post-sedimentation activity, mineral and chemical compositions of pyroclastic deposits in Bulgaria and Slovakia.

It is found that the disordered nonequilibrium nature of the volcanic glass induces a diagenetic devitrification of the tuffs and formation of clinoptilolitic, adularia-cristobalite and bentonite rocks. With increasing temperature, the volcanic glass tends forward a stable state through a series of zeolite mineral associations: clinoptilolite-mordenite-analcime-feldspar. The change in mineral composition of this series of rocks occurs without a change in the chemical composition of the rocks, which could be explained by the closed nature of zeolite systems. The formation of bentonites is associated with the removal of alkaline ions under diagenetic conditions, while the formation of halloysite rocks is caused by hydrothermal activity.

The objective of this study was to build an automated size fractionator to process up to 16 samples at one time. Most parts used in the apparatus are inexpensive items, available from lawn irrigation, household appliance and aquatic pet supply stores. The device can be used to extract different silt and clay fractions by changing sedimentation time. A bentonite, a kaolin and an ironoxide-rich Oxisol were fractionated by this instrument to sequentially extract particles that have sizes equivalent to <2 µm, <5 µm, <10 µm and <20 µm quartz spheres. A laser diffraction particle size analyser revealed size differences in the different fractions and also showed that the silt fractions contained particles having slightly larger sizes than the assumed diameters of spherical quartz. Scanning electron microscope examination suggested that the greater particle size was mainly due to the non-spherical shapes of the particles and a reduced bulk density of the porous aggregates.

Natural zeolites have traditionally been used as supplements in animal nutrition with positive effects in terms of either faster growth or reduced incidence of diseases and death. The discovery that natural zeolites may act as drugs or coadjutants in pharmaceutical preparations has greatly enlarged the field of their applications in many sectors of biology and medicine, opening unexpected horizons for either basic or applied research. This review updates the state of the art of research in this sector, focusing on clinoptilolite-rich materials, with two main purposes: (1) trying to rationalize this subject, which is extremely variable and heterogeneous, and (2) raising doubts about unsuitable uses of natural zeolites in the light of their known properties and expected behaviour.

White clayey geomaterials were collected from northeast of the Nefza region (northern Tunisia). These deposits belong to the Mio-Pliocene molassic basins (basin of Tamra-Sidi Dris, Boukhchiba) and Oligocene Numidien in the area of El Aouinet. Analysis by X-ray diffraction showed associations of halloysite and kaolinite (Tamra), kaolinite and illite (Aouinet zone) and mixed layers, kaolinite and feldspars (Boukhchiba zone). Semi-industrial processed bricks showed promising characteristics and were visibly free of defects. Ceramic tiles had a bending strength that met the required standards but water absorption was somewhat high. So, to achieve higher quality, optimisation needs to be carried out in the formulation of batches or in the processing conditions. Finally, the incorporation in whitish sanitary-ware glaze formulations generated smooth coating layers that showed the required strong brightness and were free of defects.

An experimental pedology research project, based on a “process-system” pedogenetic model, was initiated to investigate the weathering of Phlegraean Yellow Tuff (PYT) – the yellow facies of the Campanian Ignimbrite with phillipsite > chabazite – as representative of the parent rock material as the soil-forming factor. PYT was weathered by water (W) and tannic acid solutions (TA) at concentrations ranging from 3 × 101 to 3 × 104 μmol l–1. The most concentrated TA solution (3 × 104 μmol l–1) showed the greatest extracting efficiency. Na and K were continually solubilized by W; Al, Ca and Mg contributed to the ionic composition of all the TA supernatants. A significant dissolution of the amorphous component and an associated decrease of the zeolite content, especially phillipsite, were noted. The features of PYT weathered outcomes fitted the “process-system” model very well. PYT showed a pedogenic potential, in being prone to weathering, as well as in releasing elements of importance for plant settlement and development, such as K, Ca, Mg and Fe.

The effect of mechanical activation on the ion-exchange selectivity of natural zeolites from Russia, namely clinoptilolite-bearing tuffs and chabazites, was studied. The structural modifications and thermal properties were investigated, and the specific surface area and porosity of mechanically activated zeolites were determined. At activation doses of up to 1.0 kJ g–1 the main processes are the breakdown of the zeolite particles and pore structure changes. At greater activation doses amorphization takes place. It was shown that during the initial stage of activation in most cases the clinoptilolite selectivity for Sr2+ increased slightly and then decreased; the selectivity for Cu2+ increased 100 times; and the selectivity of chabazite-1 for Sr2+ increased 300 times.