Minerals samples, surface areas

Chiou, C. T., and D. W. Rutherford. 1993. Sorption of N2 and EGME on some soils, clays and mineral oxides and determination of sample surface area by use of sorption data. Environ. Sci. Technol. 27 1587-1594. 

Experimental The majority of TG experiments were made with an STA 429 thermal analyser. The samples were separate crystals and powders prepared by milling of the natural minerals (magnesite, calcite, dolomite), and also chemically pure grade strontium and barium carbonates. The experiments were performed in a vacuum (n x 10 or n x 10 bar), in a CO2 atmosphere (1 bar), and in air. When calculating the molar enthalpy by the third-law method, the congruence of vaporization and the variation of the sample surface area during the course of the decomposition were taken into account. 

Example 4 Calculation of Sample Weight for Surface Moisture Content An example is given with reference to material with minimal internal or pore-retained moisture such as mineral concentrates wherein physically adhering moisture is the sole consideration. With this simphfication, a moisture coefficient K is employed as miiltipher of nominal top-size particle size d taken to the third power to account for surface area. Adapting fundamental sampling theory to moisture sampling, variance is of a minimum sample quantity is expressed as... 

Geochemists (e.g., Aagaard and Helgeson, 1982) commonly attribute such discrepancies to difficulties in representing the surface area As of minerals in natural samples. In the laboratory, the mineral is fresh and any surface coatings have been removed. The same mineral in the field, however, may be shielded with oxide, hy-... 

Mineral. Alumina used in this study was a high purity a- Linde sample purchased from the Union Carbide Corporation. BET surface area was determined to be 15.0 m /g. 

During reactions at high temperatures, the ceramic sample must be in contact with a container. Commonly used containers include alumina or zirconia boats or crucibles or noble metal foil-lined ceramic boats. It is important to be aware of possible reactions between the material being synthesized and the container which may be a source of foreign ions. For example, Al+S ions may be incorporated if alumina crucibles are employed. Forming the material into a pellet minimizes the surface area and helps limit reactions with containers. Both alumina and zirconia crucibles and boats can be cleaned with mineral acid washes and reused. 

The type of clay present in a soil influences triazine sorption (Brown and White, 1969). Furthermore, variations in surface properties among different samples of the same clay type greatly influence sorption. For instance, sorption of atrazine on 13 clay samples, of which smectite was the dominant mineral, ranged from 0% to 100% of added atrazine (Figure 21.7), and was inversely correlated to the surface charge density of the smectites (Laird et al., 1992). Such data illustrate the complexity of sorption processes and the reason why simple predictive models relying on % OC, % clay, or surface area normalizations may fail to predict accurately the sorption of triazine by a particular soil. 

Sample Preparation. The basalt was crushed and sieved, and the -120 + 230 mesh fraction was used. The grains were ultrasoni-cally washed in deionized water to remove very fine adhering particles. If these particles are not removed, they will preferentially dissolve under hydrothermal conditions, resulting in abnormally high rates of mineral-fluid reactions (10). Examination of samples of the basalt on a scanning electron microscope assured that all fines had been removed. Nitrogen B.E.T. specific surface area of the washed basalt was 2.7 m2/g. 

We monitored the pH and Eh of the column effluents by means of in-line sampling cells equipped with glass and platinum electrodes, respectively. Effluent samples were collected with a fraction collector. Three separate tests were conducted with columns of identical diameter but different lengths 11, 22, and 44 cm. The different column lengths allowed us to investigate the effect on solution chemistry of residence time in the column and surface area of minerals contacted by the solution. At the flow rates used in our experiment, the residence times were approximately 1, 2, and 4 days, respectively, for the three columns. The mineral surface area contacted by the solutions is proportional to the column lengths. 

Figure 6. Observed relationship between specific surface area (Sm) and Fe2 content of a chemically reduced series of ferruginous smectite (sample SWa-1 from the Source Clay Minerals Repository of The Clay Minerals Society). (Reproduced with permission from Lear,...

We have created pilot installation for CVD production of multiwall carbon nanotubes from ethylene in industrial scale. MWNT produced by this process have average diameter 12-20 nm, surface area near 200-500 m2/g, mass content of minerals 6-20% for non-purified NT and <1% for purified NT. Electron images of MWNT samples with different surface area (200, 390, and 500 m2/g) are shown in Figs. 1-3. 

Materials. Bone Mineral. Calorimetric measurements have been made on two samples of anorganic bone mineral obtained from Armour and Co. and designated as Ossar Femur Head lot 34 and lot 33-43, the latter being a mixture of two lots. Both samples were 20/40 mesh and had specific surface areas varying from 95 to 105 sq. meters per gram based on the weight of the dehydrated material. 

Layer charges can be calculated from mineral and chemical composition. Mineral composition can be determined by the comparison of x-ray diffraction and thermal analytical and surface area studies. Chemical composition is determined by a total chemical analysis of the sample. In the classical method, chemical analysis is made after acidic dissolution (Ross and Hendricks 1945). Nowadays, nondestructive analytical methods (e.g., electron microscopy, prompt gamma activation analysis, etc.) are also applied. Chemical composition is usually given as oxides (e.g., Si02, A1203, etc.). The cations are divided into three groups ... 

As usual for clay minerals, the internal surface area of montmorillonite is about 80%-95% of the total surface area. For different montmorillonite samples,... 

Mineral Composition, External Specific Surface Area, and Cation-Exchange Capacity of Some Hungarian Rock Samples... 

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