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Showing papers in "Clay science in 2004"


Journal ArticleDOI
TL;DR: In this paper, the authors examined interaction of allophane with dilute NaOH solutions with pure nano-ball allophanes samples obtained by using less than 0.2 gm fraction from inner part of pumice grains.
Abstract: Allophane as a poorly ordered aluminum silicate is known to have lower tolerance to alkaline condition than layer silicates have, and easily dissolve completely under higher alkali concentrations. However, changes in structure and dissolution mechanism under dilute alkali concentrations are not clear. In this research, we examined interaction of allophane with dilute NaOH solutions (

17 citations



Journal ArticleDOI
TL;DR: In this article, the authors have shown that Zn-hectorites have expansion of the basal spacing (d 001 ) by the treatment with ethylene glycol on powder X-ray diffraction (XRD) patterns, and characterized by ZnO vibration in the around 660-670 cm -1 on FT-IR spectra, peaks assigned to Zn2p on XPS spectra and thermal dehydroxylation at lower temperature on thermogravimetry and differential thermal analysis.
Abstract: Both refluxing reaction under atmospheric pressure and hydrothermal reaction under autogenous water vapor pressure of two kinds of starting slurry with the initial molar ratio Na:Zn:Li:Si= 0.7:5.4:0.6:8.0 and 1.4:5.4:1.2:8.0 made from Zn-Si homogeneous precipitates, lithium fluoride and sodium hydroxide successfully have yielded Zn-hectorites containing Zn 2+ instead of Mg 2+ in the trioctahedral sheets. Zn-hectorites have expansion of the basal spacing (d 001 ) by the treatment with ethylene glycol on powder X-ray diffraction (XRD) patterns, and characterized by Zn-O vibration in the around 660-670 cm -1 on fourier transform infrared spectrometer (FT-IR) spectra, peaks assigned to Zn2p on X-ray photoelectron spectrometer (XPS) spectra and thermal dehydroxylation at lower temperature on thermogravimetry and differential thermal analysis (TG-DTA). It has also clarified that Zn-hectorite synthesized by hydrothermal reaction under autogenous water vapor pressure is relatively large massive particles and has a larger CEC, although it has lower MB adsorptive ability compared to a commercial Mg-hectorite as reference.

9 citations


Journal ArticleDOI
TL;DR: In this paper, the adsorption of phenol on mono, bis and tris(2,2'-bipyridine)nickel(II)-saponite intercalation compounds from aqueous solution was examined.
Abstract: Adsorption of phenol on mono, bis and tris(2,2'-bipyridine)nickel(II)- and tris(ethylenediamine)-nickel(II)-saponite intercalation compounds from aqueous solution was examined. Mono, bis and tris(2,2'-bipyridine)nickel(II)-saponites were prepared by the reactions of Ni(II)-form of a synthetic saponite (Sumecton SA) with 2,2'-bipyridine at the molar 2,2'-bipyridine to Ni(II) ratios of 1:1, 2:1 and 3:1. Tris(ethylenediamine)nickel(II)-saponite was prepared by the reactions of the Ni(II)-saponite with ethylenediamine at the molar ratio of 3:1 (ethylenediamine:Ni(II)). X-Ray diffraction and thermal analysis indicated that 2,2'-bipyridine and ethylenediamine were intercalated into Ni(II)-saponite to form mono, bis and tris(2,2'-bipyridine)nickel(II) and tris(ethylenediamine)nickel(II) complexes. The adsorption isotherms of phenol for the mono, bis and tris(2,2'-bipyridine)nickel(II)-saponites followed Langmuir type, indicating strong adsorbate-adsorbent interactions. The basal spacings of the mono, bis and tris(2,2'-bipyridine)nickel(II)-saponites did not change by the adsorption of phenol, indicating that the adsorbed phenol existed in the interlayer micropore formed by the pillaring with the complexes. The adsorption of phenol on the tris(ethylenediamine)nickel(II)-saponite was less effective than those on the (2,2'-bipyridine)nickel(II)-saponites, suggesting that the interactions between pyridine rings and phenol played an important role in the adsorption of phenol.

7 citations



Journal ArticleDOI
TL;DR: In this paper, the GainsThomas ion exchange selectivity coefficients, K GT of Cd 2+, Cu 2+, Pb 2+ and Zn 2+ on Ca-saturated kaolinite and bentonite were determined in comparison with Ca 2+.
Abstract: In order to grasp the adsorptive selectivities of heavy metal ions on the phyllosilicates, the GainsThomas ion exchange selectivity coefficients, K GT of Cd 2+ , Cu 2+ , Pb 2+ and Zn 2+ on Ca-saturated kaolinite and bentonite were determined in comparison with Ca 2+ . Adsorption mechanism was also estimated by the determination in desorption of the ions adsorbed on the phyllosilicates. The average K GT s (min.-max.) on the Ca-kaolinite were 1.0 (0.7-1.3) for Cd 2+ , 1.3 (0.5-2.1) for Cu 2+ , 4.5 (3.3-5.6) for Pb 2+ and 1.3 (0.6-2.1) for Zn 2+ . On the Ca-bentonite, the average K GT s (min.-max.) were 1.0 (0.7-1.9) for Cd 2+ , 1.4 (0.8-2.7) for Cu 2+ , 1.9 (1.5-2.5) for Pb 2+ and 1.7 (1.1-2.7) for Zn 2+ . These results indicated that Cd 2+ has the same adsorptive selectivity onto the surfaces of the phyllosilicates as Ca 2+ . The selectivity of Pb 2+ to kaolinite was found to be specifically higher than those of the other heavy metal ions. It was confirmed that Cu 2+ and Zn 2+ can be adsorbed on the surface of the phyllosilicates with the slightly higher selectivities than the alkaline-earth metal ion. Except for Pb 2+ on kaolinite, most Cd 2+ , Cu 2+ and Zn 2+ (>70%) adsorbed on the phyllosilicates can be desorbed with the 1 mol dm -3 (mol L -1 ) ammonium acetate extraction regardless of clay species and adsorptive equilibrium pH, indicating that many Cd 2+ , Cu 2+ and Zn 2+ are adsorbed on the phyllosilicates in fashion of ion exchange reaction. Half of Pb adsorbed on kaolinite was desorbed with the 1 mol L -1 ammonium acetate extraction and 25% was extracted by 1 mol L -1 HCl, implying the possibility of specific sorption of some Pb 2+ on the phyllosilicate.

6 citations


Journal ArticleDOI
TL;DR: The ultra thin films of fragile specimens for high-resolution transmission electron microscopy (HRTEM) observations can be successfully prepared by the simple preparation technique made by thinning the Mo-grids via argon ion milling.
Abstract: The ultra thin films of fragile specimens for high-resolution transmission electron microscopy (HRTEM) observations can be successfully prepared by our simple preparation technique. At first, the specimens are impregnated with a diluted epoxy-resin (ethanol-soluble) to prevent their breakdown. Chips are made of the impregnated specimens, and these are polished. The polished chips and glasses are adhered together using an adhesive wax at ca. 70•Ž. The adhered chips are thinned and polished, and they form petrographic thin sections. Mo-grids are attached onto the selected areas in the thin sections for HRTEM observations using an epoxy adhesive. Only Mo-grids attached to the selected areas can be detached from the thin sections in hot water ca. 70•Ž. The ultra thin films are made by thinning the Mo-grids via argon ion milling.

4 citations



Journal ArticleDOI
TL;DR: In this paper, the adsorption sites and behavior of Sr atoms on smectite were analyzed using EXAFS spectroscopy, and it was concluded that the Sr atoms are attracted stronger to the 2:1 sheets of smectites in the air-dried compacted samples than in the wet-paste samples because of the smaller Debye-Waller factors.
Abstract: To elucidate the adsorption sites and behavior of Sr atoms on smectite, EXAFS spectroscopy was performed at the Spring-8 using air-dried and wet-paste samples of Sr-adsorbed bentonite adjusted to pH 4.7 and 9.6. EXAFS analyses were conducted for the two-oxygen shell fit using a crystalline SrSO 4 as a reference compound. The first-neighbor shells consisted of 5.5 O atoms of water molecules at a distance of 2.58 A in the air-dried sample and 7.0 O at 2.60 A in the wet sample. The second shells consisted of 2.6 O atoms at a distance of 2.77 A and 2.5 O at 2.81 A for the air-dried and wet samples, respectively. Only the Debye-Waller factors of the second shells were affected by the pH, resulting to be smaller at pH 4.7 than those observed at pH 9.6. It is concluded from the EXAFS results that Sr atoms are attracted stronger to the 2:1 sheets of smectite in the air-dried compacted samples than in the wet-paste samples because of the smaller Debye-Waller factors in the air-dried compacted samples. The Sr atoms hovered on a triangle of the oxygen hexagonal cavity on the flat surface of 2:1 sheets and resided on the broken face of the octahedral sheets at the edge surface. In addition, they behaved as hydrated ions and formed incomplete outer-sphere complexes at high water content; however, they formed incomplete inner-sphere-like complexes together with oxygen atoms of the 2:1 sheets in the air-dried samples. The Sr atoms also played a role combining two sheets of the 2:1 layer of smectite in forming the edge-to-edge and edge-to-face associations.

3 citations


Journal ArticleDOI
TL;DR: In this paper, the mineralogy of soils from three representative soil series of AEZ 11, High Ganges River Floodplain, has been reported in this paper, and the soils were uniformly grouped into three types depending on the smectite content in the <2 ǫm clay fraction.
Abstract: Bangladesh has been divided into 30 Agroecological Regions (AEZs) and the applied agricultural research has currently been conducted on this basis. In context of the lack of enough information on mineralogy on the AEZ basis, an attempt has been taken to study mineralogy of important soils from all AEZs of Bangladesh in order to provide basic information for applied research. As a part of this attempt, the mineralogy of soils from three representative soil series of AEZ 11, High Ganges River Floodplain, has been reported in this paper. The clay content of the surface soils ranged from 8.9 to 30.4% and the texture was mostly silt loam. The 2-20 gm fraction was found to dominate over other fractions in all soils. This fraction was composed mainly of quartz, followed by mica, plagioclase and chlorite. Mica was the predominant mineral in the <2 gm clay fraction followed by smectite in seven soils and by chlorite in five soils. The soils were uniformly grouped into three types depending on the smectite content in the <2 ƒÊm clay fraction. The impact of mineralogy on the inherent potentiality of soils regarding crop production has been discussed.

2 citations


Journal ArticleDOI
TL;DR: In this article, the growth characteristics of mullite and changes in structural parameters were analyzed with the help of Rietveld technique, and the results showed that crystallization of the mullite increases with increase of temperature upto 1550•Ž.
Abstract: Kaolinite undergoes a phase and structural change on heating. In this paper we report the growth characteristics of mullite, and it's changes in structural parameters by analyzing with help of Rietveld technique. The results show that crystallization of mullite increases with increase of temperature upto 1550•Ž. X-ray diffraction analysis indicates mullite formation in kaolinite takes place in two steps. The crystal parameters (a, b, c), crystal size, strain change significantly during these two steps.

Journal ArticleDOI
TL;DR: In this paper, the alteration mechanism of biotite in granitic rock caused by crustose liche "Porpidia" was investigated by means of X-ray diffraction, optical microscope, EPMA and electron microscope with EDX.
Abstract: The alteration mechanism of biotite in granitic rock caused by crustose liche \"Porpidia\" was investigated by means of X-ray diffraction, optical microscope, EPMA and electron microscope with EDX. Vertical thin sections of lichen-rock interface were observed by a scanning electron microscope to make clear the physico-chemical phenomenon caused by lichens. The contact surfaces between lichen and a biotite were physically observed with this section, and were further investigated chemically by EPMA. As a result, physical destruction of biotite grains by lichen thallus was observed, and the formation of iron oxide or hydroxide was recognized. The chemical compositions of some parts of the biotite crystal were analyzed by EPMA, such as altered parts closed to lichen thallus, altered parts far from lichen thallus and fresh parts. Consequently, comparison of the different parts revealed increase in Si02 content on one hand and decrease in FeO and 1 (20 on the other hand from the fresh biotite crystal throughout the licheni alteration. Due to the lower solubility of Si02 and higher solubility of Fe203 and Al2O3 from minerals under strong acid condition, which is formed by lichen thallus, it seems that Si4+ content in tetrahedral site is increased by cation exchange. Also due to the low pH and activity of high molecular weight polymers, the possible weakening of the iron-xygen bonds will lead to the dissolution of Fe 3+ ions. Consequently, it is likely that, due to the increasing negative charge of biotite layers with dissolutio of Fe 3+, dissolution of K+ will be disturbed. Vermiculite-like minerals in biotite formed with the actio or effect of lichen were identified by quantitative chemical analysis as wt% of oxides and calculation of structural formulae on the basis of 22 oxygen atoms per unit cell.


Journal Article
TL;DR: In this article, the impact of mineralogical composition of soil on potassium fixation and release was studied with nine selected soils from three important Agroecological Regions of Bangladesh: Old Himalayan Piedmont Plain, Old Brahmaputra Floodplain and High Ganges River Floodplain.
Abstract: The impact of mineralogical composition of soil on potassium (K) fixation and release was studied with nine selected soils from three important Agroecological Regions of Bangladesh: Old Himalayan Piedmont Plain, Old Brahmaputra Floodplain and High Ganges River Floodplain. Mica, in variable amounts, was the most dominant mineral in all soils. In addition to mica, smectite and vermiculite were present in considerable amounts in the High Ganges River Floodplain and Old Brahmaputra Floodplain soils, respectively, while the Old Himalayan Piedmont Plain soils contained none of them. In the study of K fixation, three levels (0.3, 0.6 and 0.9 cmolc kg-1) of K were added to soils for three periods of incubation (15, 30 and 45 days) at two moisture conditions (continuous waterlogging and alternate wetting and drying). Potassium release was studied by successive xtractions using three concentrations of the HNO3 solution (1.0 M, 0.1 M and 0.01 M). Both the K fixation rate and K release potential were the highest in the High Ganges River Floodplain soils followed by the Old Brahmaputra Floodplain soils while the lowest were in the Old Himalayan Piedmont Plain soils. The K fixation and release behaviors of the soils could be related to their mineralogical make-up.


Journal ArticleDOI
TL;DR: In this paper, the weathering mechanism of pyroclastic rocks distributed at the landslides in Lembo area, Bana-Bangou district, was investigated from a mineralogical viewpoint.
Abstract: The weathering mechanism of pyroclastic rocks distributed at the landslides in Lembo area, Bana-Bangou district, was investigated from a mineralogical viewpoint. Specimens collected from the landslide profile were composed mainly of kaolinite, illite, chlorite, illite-smectite interstratified mineral, gibbsite, goethite, anatase, maghematite, hematite, quartz and feldspar. The landslide area (pyroclastic rock) was characterized by slow creep movement every raining season. The slip zone was recognized on the landslide profile. Chemical composition of the landslide materials showed the complete leaching of CaO and Na 2 O, whereas a small amount of K 2 O and MgO remained in the whole profile. Detail examinations of the microtexture indicated that the material showed aggregate skeletal matrix with high porosity. This process further caused the decrease of soil strengths and development of micro-texture characteristics that tended to increase the creeping landslide. This displacement rate of the creeping landslide mechanically depended mostly on the pore water pressure in the landslide profile. High pore water pressure always corresponded to the large displacement rate. The mechanism of the creeping landslide was considered from mineralogical characteristics.