No abstract available

[en] The genesis and the most unique geological features of OUR active sites and of the ones expected to be operated are analyzed. The characteristics of our clays are described, and an overview of the current situation of the sector and its future prospects are given. (Author)

[en] Sorption of Eu(III) and Am(m) on attapulgite as a function of pH, ionic strength and Eu(III) and Am(III) concentrations was studied under ambient condition using batch technique. The results indicate that sorption of Eu(III) and Am(III) on attapulgite is strongly affected by pH values and weakly dependent on ionic strength. The sorption of both elements increases steeply with increasing pH from 2.5 to 5.5. Sorption of Eu(III) and Am(III) is mainly dominated by surface complexation, although ion exchange also contributes to Eu(III) and Am(III) sorption. (authors)

[en] The hydrothermal stability of smectite at temperatures less than 275 degrees C was investigated experimentally over a range of pH values. In the near-neutral pH region, the smectite to illite conversion predominated; in the mildly acid region, there was extensive formation of aluminum hydroxy interlayers in the clay; and in the alkaline region, framework silicates (feldspar and zeolites) were produced. The geological evidence for these reactions is also reviewed

No abstract available

[en] Smectite is a clay with a wide range applications derived from its specific proprieties i.e. adsorption and surface charge. This work The adsorption of Zn(II) onto a suspension of Na-saturated smectite from Elfahs (Tunisia), was studied as a function of the pH (3.0, 5.0 and 7.0) and ionic strength (0.5 M and 0.01 M NaCl). The results show that the adsorptive behaviour of Zn²⁺ ions was strongly dependent on the pH and the ionic strength with maximum Zn removal occurring at pH 7.0 and 0.01 M NaCl ionic strength with ion exchange as the basic mechanism. The adsorption data was then fitted to Freundlich and Langmuir isotherms models.

No abstract available

[en] The sorption of Cd(Ⅱ) on illite was studied as a function of pH, ionic strength, time and temperature under ambient conditions using batch technique. The results indicate that sorption of Cd(Ⅱ) on illite is strongly dependent on pH values and ionic strength. At low pH, the sorption is dominated by outer-sphere surface complexation and ion exchange on illite surfaces, whereas inner-sphere surface complexation is the main sorption mechanism at high pH. The adsorption of Cd(Ⅱ) on illite is found to follow pseudo-second-order kinetic model well. Sorption of Cd(Ⅱ) increase with increasing temperature and fit the Langmuir isotherm well. (authors)

[en] Water content measurement using a neutron moisture meter has a long tradition in the CSSR. The method of water content determination using neutron and gamma radiation was developed by the Research Institute of Building Materials in Brno for a number of materials, as e.g. coke, brown coal semi-coke, anthracite, glass sand, dolomite, soda, gravel, aggregates, cement sludge, slag, brick clay, intermediate products of the ceramics industry, refractory building materials, etc. The water content measurement of ceramic materials for the manufacture of wall tiles was performed in a special equipment by detection of the slowed-down neutrons with an accuracy of +-0.6% water (within the range from 5 to 11%) and of materials for the manufacture of floor tiles by means of neutron and gamma radiation with an accuracy of +-0.4% water (within the range from 5 to 8%). (author)

[en] Both shock recovery and thermal annealing experiments have been carried out on Riverside nontronite, an iron-rich smectite clay that closely matches the composition, but neither the color nor magnetic properties, of the Martian fines. Nontronite was recovered from peak shock pressures between 7 and 32 GPa, with calculated peak mean bulk temperatures ranging from 125⁰ to 1100⁰ C. Other nontronite samples were heated in air for one hour at temperatures ranging from 400⁰ to 1000⁰ C at 100⁰ C increments. Both shocked and heat-treated samples were analyzed by magnetic measurements, X ray diffraction, and Moessbauer spectroscopy. Nontronite powders shock-loaded to peak calculated temperature of 650⁰ C to 750⁰ C show a dramatic increase in ferromagnetic saturation magnetization (M/sub s/). A similar increase in magnetization in the same temperature range is observed in isothermally annealed powders at atmospheric pressure. The X ray diffraction and Moessbauer studies show, however, that for samples that experienced temperatures of 600⁰ C or more, the shocked material has little structural similarity to the isothermally annealed nontronite. This suggests that the ferromagnetic properties may be due to a minor phase. There is evicence from Moessbauer spectra for metallic iron in the shocked samples and for superparamagnetic Fe₂O₃ in the annealed samples. In addition to magnetic and structural changes, the shock and heating experiments altered the color of the nontronite from olive-yellow toward reddish-brown, yielding material that matches the observed properties of the Martian fines much more closely than the starting material does