Showing papers in "Clay science in 1993"

Study on clay mineralogical characteristics of calcareous and noncalcareous soils of bangladesh

Abstract: Clay mineralogical compositions of calcareous and noncalcareous floodplain soils which are most widely distributed over Bangladesh were investigated. The calcareous soils formed over the Gangese sediments are more alkaline having high extractable bases than the noncalcareous soils of the Bahmaputra sediments. The compositions of clay minerals of both the soils were constituted mainly of 14, 10 and 7A components. Of them, mica was commonly observed abundantly with the smaller amounts of kaolinite, chlorite and the interstratified minerals of these components. Especially, the noncalcareous soil clays were dominated by mica

EFFECT OF HEATING IN AIR ON Si- AND Ge-CONTAINING FERRIHYDRITES

Abstract: The transformation of two natural siliceous ferrihydrites to hematite has been observed by X-ray diffraction, Moessbauer spectroscopy, weight loss and colour change. Three synthetic ferrihydrites (a 2-line pure sample, a 7-line Si-containing sample and a 7-line Ge-containing sample) have been used for comparison. The inhibitory effect of Si on the transformation, as observed previously, has been confirmed, and Ge has been found to exert a similar effect. Adsorption of soluble silicate onto the 2-line pure ferrihydrite also produced an inhibitory effect. It was possible to reduce OH:Fe ratios in ferrihydrites to the order of 1:10 or less without an apparent phase change, and the essentiality of H 2 O and OH − in the ferrihydrite structure is questioned

Removal of methanethiol by sepiolite and various sepiolite-metal compound complexes in ambient air

Abstract: In ambient air having 60% relative humidity (RH) at 25°C, the adsorption of methanethiol by sepiolite was studied by comparison with that by coconut-shell active carbon. The amount of methanethiol adsorbed by sepiolite was as small as 0.12 μmol/g in the air with 1 ppm methanethiol, while, the amount by active carbon was as large as > 1.1 μmol/g in the air with ≤ 0.03 ppm methanethiol. Methanethiol was converted into dimethyldisulfide on active carbon. In ambient air having 60% RH at 25°C, the removal of methanethiol by the sepiolite-metal complexes was also studied by comparison with that by the corresponding metal compounds

Formation process of kaolinite from amorphous calcium silicate and aluminum chloride

Abstract: The formation process of kaolinite in the hydrothermal reaction of an amorphous calcium silicate with aluminum chloride was studied by XRD, IR, DTA-TG, TEM, and high-resolution solid state 29 Si-MAS/NMR. The amorphous calcium silicate prepared from diatomite and calcium hydroxide was hydrothermally treated with an aluminum chloride solution in a Teflon pressure vessel at 220°C for a reaction period varying from 1 to 144 h. As the first step of the reaction, the Q 2 state component of the starting material changed into an intermediate amorphous with the Q 3 state. The degree of silica-polycondensation of this state is identical to that of the intermedicate phased observed in the kaolinitization from the amorphous mixture of silica and alumina

Thermal evolution of nickel chlorite-like phase derived from montmorillonite.

Abstract: A nickel chlorite-like compound was derived from montmorillonite by intercalation of nickel hydroxide layer between the silicate layers. The hydroxide layer was dehydrated in a temperature range of 300° to 400°C, and remained as the oxide between the silicate layers. The structural OH groups of montmorillonite arc converted into the oxide ions by the reaction with the remained nickel oxide layer in a temperature range of 400° to 500°C. This conversion leads to a pronounced thermal stabilization of the silicate layers up to 800°C, though the untreated montmorillonite suffers a destructive dehydration starting at temperatures about 650°C

Synthesis of ferrihydrite and feroxyhyte

Abstract: Ferrihydrite and feroxyhyte were synthesized at room temperature from 0.1 M FeSO 4 . Ferrihydrite, with 6 to 7 diffraction lines, formed at pHs 5-11 in the presence of Si (Fe:Si = 10:1). The use of Ge, in place of Si, resulted in the same, with the same d-spacings of the diffraction peaks. This indicates that the Si or Ge is not in the structure of ferrihydrite, but forms Fe-O-Si (or Ge) at the periphery of «domain» of ferrihydrite. The presence of Si or Ge was a requisite for the formation of ferrihydrite, because their absence led, at the pHs investigated, to the formation of goethite or lepidocrocite

Study on clay mineralogical characteristics of hill and terrace soils of Bangladesh.

Abstract: Brown Hill Soil and five terrace soil types (Shallow Red Brown Terrace Soil, Deep Red Brown Terrace Soil, Brown Mottled Terrace Soil, Shallow Grey Terrace Soil and Deep Grey Terrace Soil) were investigated to characterize their clay mineralogical compositions as a part of the systematic studies of General Soil Types of Bangladesh The clay of Brown Hill Soil was rich in mica and hydroxy-Al interlayered vermiculite with relatively low contents of smectite, vermiculite, kaolinite and chlorite (less than 10%) In contrast to hill soil, all five terrace soil clays examined were differentiated by the trace or very low presence of smectite and vermiculite, which were also different from the clays of previously studied calcareous and noncalcareous soils

X-ray diffraction line profile of glauconitic clay from the minamishiraoi deposit and evaluation of its mixed-layer structure

Abstract: X-ray diffraction experiment of a granular glauconitic clay and the computer simulation of the X-ray diffraction line profile of the clays from the Minamishiraoi Kuroko-type deposit, southwestern Hokkaido, Japan, were carried out to elucidate its mixed layer structure The mixed layer structure which shows an intermediate property of glauconite and smectite were evaluated to be of a random-type interstratification somewhat deviated from random interstratification towards the direction of segregation structure of glauconite and smectite, through comparison of the measured and the calculated X-ray diffraction line profiles

Adsorption of fluorescent dyes to chrysotile asbestos

Abstract: Fluorescent xanthene dyes having carboxyl or hydroxyl group in their molecular structures were found to be dissociatively absorbed on chrysotile as carboxylate or phenolate. The dyes were preferentially absorbed on chrysotile more than on kaolinite because of the anionic adsorption. Fluorescence excitation and infrared spectra showed that deprotonated umbelliferone (7-hydroxycoumarin) was adsorbed on magnesium of chrysotile. Strong fluorescence intensities of these dyes adsorbed on chrysotile are expected to be utilized for a selective detection method of chrysotile asbestos

Preparation of lead oxide-montmorillonite complex.

Abstract: Lead oxide-montmorillonite complex (LMC), Pb 2.90 O 0.273 (Si 3.77 Al 0.23 )-Al 1.69 Mg 0.15 Fe 0.17 )O 10 (OH) 2 , was prepared by heating a basic lead carbonate-montmorillonite complex at 400°C. The properties of the LMC were characterized by X-ray powder diffractometry, infrared absorption spectroscopy and X-ray photo-electronic spectroscopy. The electron density obtained by a one-dimensional Fourier synthesis method showed that the LMC had a crystal structure in which lead oxide having two lead atomic planes intercalated between the 2:1 silicate layers