bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption of Dinitrophenol Herbicides From Water by Montmorillonites
Authors: Sheng Guangyao , Johnston Cliff T. , Teppen Brian J. , Boyd Stephen A. 
Published: February 2003

AbstractThe adsorption of two dinitrophenol herbicides, 4,6-dinitro-o-cresol (DNOC) and 4,6-dinitro-o-sec-butyl phenol (dinoseb), by two reference smectite clays (SWy-2 and SAz-1) was evaluated using a combination of sorption isotherms, Fourier transformation infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and molecular dynamic simulations. Clays were subject to saturation with various cations, and charge reduction. The DNOC adsorption decreased with increasing pH indicating that DNOC was primarily adsorbed as the neutral species. The FTIR spectra of DNOC-clay films showed that DNOC molecules are oriented parallel to the clay surface. Interlayer cations have a strong effect on adsorption depending largely on their hydration energies. Weakly hydrated cations, e.g. K+ and Cs+, resulted in greater sorption compared to more strongly hydrated cations such as Na+ or Ca2+. Lower hydration favors direct interactions of exchangeable cations with -NO2 groups of DNOC and manifests optimal interlayer spacings for adsorption. In the presence of sorbed DNOC, an interlayer spacing for K-SWy-2 of between 12 and 12.5 Å was maintained regardless of the presence of water. This d-spacing allowed DNOC molecules to interact simultaneously with the opposing clay layers thus minimizing contact of DNOC with water. The charge density of clays also affected sorption by controlling the size of adsorption domains. Accordingly, DNOC adsorption by low-charge clay (K-SWy-2) was much higher than by high-charge clay (K-SAz-1) and Li-charge reduction greatly enhanced dinoseb adsorption by K-SAz-1. Steric constraints were also evident from the observation that adsorption of DNOC, which contains a methyl substituent, was much greater than dinoseb, which contains a bulkier isobutyl group. Adsorption of DNOC by K-SAz-1 was not affected in the presence of dinoseb, whereas dinoseb adsorption was greatly reduced in the presence of DNOC.
On the Structural Stability of Montmorillonite Submitted to Heavy γ-Irradiation
Authors: Negron Alicia , Ramos Sergio , Blumenfeld Alexander L. , Pacheco Graciela , Fripiat Jose J. 
Published: February 2003

AbstractThe effect of heavy doses (up to 200 Mrad) of γ-radiation on the short-range structural organization in montmorillonite was studied using infrared (IR) spectroscopy and solid-state high-resolution 27Al and 29Si nuclear magnetic resonance (NMR). No change attributable to irradiation was observed. A small variation in the water content was noted but it is not systematic. The results show that the montmorillonite structure can accumulate high doses of radiation without damage and therefore this clay is a suitable material for use in the safe disposal of radioactive waste.
Tobelitization of Smectite During Oil Generation in Oil-Source Shales. Application to North Sea Illite-Tobelite-Smectite-Vermiculite
Authors: Drits Victor A. , Lindgreen Holger , Sakharov Boris A. , Jakobsen Hans Jørgen , Salyn Alfred L. , Dainyak Lidia G. 
Published: February 2003

AbstractIllite-smectite (I-S) minerals isolated from Upper Jurassic oil-source rock shales from Denmark and the North Sea have been investigated by X-ray diffraction, thermal analysis, infrared, Mössbauer, and solid-state nuclear magnetic resonance spectroscopies and chemical analysis. Detailed structures have been determined in order to reveal the diagenetic transformation mechanism in these shales. Generally, in oil-source rocks of sedimentary basins, oil generation takes place simultaneously with the diagenetic transformation of I-S. We demonstrate a link between the two reactions: NH3 released from kerogen during maximum oil generation is fixed as NH4+ in the NH4-bearing mica or tobelite layers formed from smectite or vermiculite layers in I-S, in a diagenetic interval which we name the ‘tobelitization window’. Due to this solid-state transformation, mixed-layer structures have been formed consisting of interstratified illite, tobelite, smectite and vermiculite layers (I-T-S-V) and having maximum ordering of illite + tobelite and smectite layers for R = 1. The tobelitization of smectite in I-S is probably typical for all oil-source rock shales.
Methods of Determining Cation Exchange Capacities for Clinoptilolite-Rich Rocks of the Logudoro Region in Northern Sardinia, Italy
Authors: Cerri Guido , Langella Alessio , Pansini Michele , Cappelletti Piergiulio 
Published: February 2003

AbstractClinoptilolite-rich materials from widespread pyroclastic and epiclastic deposits of northern Sardinia were investigated to assess their cation exchange properties and to find the most reliable experimental method to determine their cation exchange capacity (CEC). The CECs were evaluated using a cross exchange method (CEM) and a batch exchange method (BEM). The CEM resulted in values 30–35% lower than the theoretical or expected CEC calculated from the chemical analyses of the clinoptilolite-rich materials. The BEM resulted in CECs 6–12% lower than the expected CECs. Various parameters, such as the grain-size of powders (<64 µm and 125–250 µm) and replacement cation (Na+, K+, Li+, Cs+, NH4+, Ca2+, Mg2+, Sr2+) were evaluated in order to optimize the cation exchange process, i.e. enhance complete exchange. The particle size did not affect the exchange process appreciably. The type of replacement cation had a substantial effect on the experimental CEC determined by the BEM. The NH4+ and Cs+ replacement solutions resulted in the best experimental CECs ranging between 75% and 94% of the theoretical CEC with NH4+ as the replacement cation and 79% and 88% of the theoretical CEC with Cs+ as the replacement cation. The exchange efficiency was also measured as a function of ammonium concentration in the replacement solution (0.50, 1.00, 2.00 and 3.00 M). Experimental CECs ranged between 94% (0.5 M NH4Cl solution) and 99% (1 M NH4Cl solution) of the theoretical CEC for one epiclastic rock sample and between 79% (3 M NH4Cl solution) and 87% (2 M NH4Cl solution) of the theoretical CEC for one pyroclastic rock sample.
Crystal Chemistry of Fe-Sudoites From Uranium Deposits in the Athabasca Basin (Saskatchewan, Canada)
Authors: Billault Valérie , Beaufort Daniel , Patrier Patricia , Petit Sabine 
Published: February 2003

AbstractSudoites exhibit different crystal-chemical and textural properties which may be related to the structural and valence state of Fe. Mössbauer spectroscopic analysis shows that all Fe previously analyzed using a microprobe (from 1 wt.% to 7.2 wt.% total Fe as Fe2O3) is structural and occurs in both oxidation states (40% Fe2+and ∼60% Fe3+). Electron microprobe analyses from ∼200 sudoites indicate that Fe occurs in both octahedral sheets according to three main types of substitution: Fe3+= octahedral Al; Fe2+= Mg; and Fe3++ Fe2++ □ = 3Mg. Decreasing tetrahedral substitution balances Fe3+substitution in the trioctahedral sheet. Increasing octahedral Fe results in a more dioctahedral character of sudoite.X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA) and scanning electron microscope-transmission electron microscope (SEM-TEM) analyses showed that increasing octahedral Fe is associated with decreased stacking order and thermal stability due to the greater number of defects. In addition, with increasing octahedral Fe in sudoite, particles became smaller and more anhedral and consequently less stable with increasing Fe content. These structural and textural variations are interpreted as a result of the distortion of the sudoite structure by substitutions of Fe3+with larger ionic radii for Al and Mg octahedral cations and by the formation of octahedral vacancies.
Microbiotic Formation of Silicate Minerals in the Weathering Environment of a Pyroclastic Deposit
Authors: Kawano Motoharu , Tomita Katsutoshi 
Published: February 2003

AbstractBacterial mineralization in weathered pyroclastic deposits of the Kaimondake volcanic ash (4040 ybp) and the Koya pyroclastic flow (6400 ybp) was investigated to evaluate the impacts of bacteria on mineral formation, and to characterize the microbiogenic minerals in the weathering environment. The mineralogy of abiogenic weathering products was also investigated for comparison with the microbiogenic products, and mineral saturation indices were calculated for porewaters using the PHREEQC computer code. The results indicated that these weathered pyroclastic deposits contain 108–109 cells/g, consisting of spherical to rod-shaped bacteria. Associated abiogenic allophane had an Al/Si ratio ranging from 1.01 to 2.13. The bacterial cell surfaces were completely or partially covered by poorly-ordered silicate minerals, which could be divided into two groups based on their chemical and morphological characteristics. Group I was characterized by well developed fibrous to smectite-like flaky habits with variable Al, Si and Fe, corresponding to compositions between proto-imogolite allophane and chamosite. These Al-Si-Fe minerals were the most abundant and major microbiogenic products in both lithologies. Group II exhibited poorly-developed aggregates of allophane-like granular materials composed mainly of Al and Si with minor Fe. Geochemical calculations revealed that the porewaters were saturated with respect to allophane and other crystalline clay minerals such as halloysite, kaolinite, montmorillonite and nontronite. These microbiogenic minerals may be formed as the earliest phase of these clay minerals after interaction of the bacterial cell surfaces with dissolved cations mainly Si, Al and Fe, in the porewaters.
Significance of the Formation of Calcium Carbonate Minerals in the Pedogenesis and Management of Cracking Clay Soils (Vertisols) of India
Authors: Srivastava Pankaj , Bhattacharyya Tapas , Pal Dilip Kumar 
Published: February 2003

AbstractMicromorphological studies were performed in order to understand the factors and processes involved in the formation of calcium carbonate (CaCO3) in twenty three soil series of Vertisols representing sub-humid, semi-arid and arid climatic regions of Peninsular India. The study indicates that Vertisols contain both pedogenic calcium carbonate (PC) and non-pedogenic calcium carbonate (NPC) irrespective of the ecosystems to which they belong. The NPCs are part of the parent material of Vertisols. Dissolution of NPCs and recrystallization of dissolved Ca2+ ions are responsible for the formation of PCs. Vertisols of arid and semi-arid climates contain more PC in their soil control section (SCS) than those of sub-humid climates. Formation of PC is the prime chemical reaction responsible for the increase in pH, the decrease in the Ca/Mg ratio of exchange site with depth and in the development of subsoil sodicity. Petrographic and scanning electron microscopic (SEM) examination of quartz, feldspars and micas indicate little or no alteration, discounting the possibile formation of smectite during Vertisol formation. X-ray diffraction (XRD) analysis of clays indicates that smectites of Vertisols are fairly well crystallized and do not show any sign of transformation except for hydroxy interlayering. The preservation of the crystallinity of smectite and the lack of transformation of primary minerals thus validate the hypothesis of positive entropy change during the formation of Vertisols.The precise cause-effect relationship between CaCO3 of pedogenic and non-pedogenic origin, and exchangeable Mg, Na and Ca percentages (EMP, ESP and ECP) has been established in the study. This indicates that impoverishment of Ca2+ ions on the exchange sites of Vertisols needs to be controlled by rehabilitation methods that can replenish Ca2+ ions, and thus the study provides relevant information for future land resource management programmes not only on Vertisols of India but also on similar soils occurring elsewhere.
Influence of Gibbsite Surface Area and Citrate on Ni Sorption Mechanisms at pH 7.5
Authors: Yamaguchi Noriko U. , Scheinost Andreas C. , Sparks Donald L. 
Published: February 2003

AbstractWe investigated the sorption of Ni to gibbsite of two different surface areas at pH 7.5, in the presence and absence of citrate, over a time period of 180 days. Extended X-ray absorption fine-structure spectroscopy was employed to elucidate the sorption mechanisms at the molecular level. In agreement with former results, Ni-Al layered double hydroxide (LDH) formed in the presence of gibbsite of low surface area. However, gibbsite of high surface area suppressed the formation of the surface precipitate. Instead, two Al atoms neighboring Ni at distances of 2.95–2.98 Å indicated formation of an inner-sphere sorption complex, where each NiO6-octahedron shares edges with two AlO6-octahedra. Focused multiple scattering arising from Al atoms at a distance of 6 Å suggest that sorbed Ni(OH)2(OH2)4 monomers epitaxially extend the hexagonal arrangement of Al atoms in gibbsite. Only after 30 days or more was a small amount of LDH formed. The presence of citrate prevented the formation of LDH, while maintaining the formation of inner-sphere sorption complexes.
Effect of Acid and Alkali Treatments on Surface Areas and Adsorption Energies of Selected Minerals
Authors: Jozefaciuk Grzegorz , Bowanko Grzegorz 
Published: February 2003

AbstractBentonite, biotite, illite, kaolin, vermiculite and zeolite were acidified or alkalized with hydrochloric acid or sodium hydroxide at concentrations of 0.1, 1.0 and 5.0 mole dm−3 at room temperature for two weeks. In acid treatments, dissolution of Al prevailed over Si and the opposite was observed in alkali treatments. The XRD patterns showed severe alteration of the crystal structure after acid treatments, whereas sharpening of the XRD peaks after alkali treatments was observed. Illite and kaolin were most resistant to acid attack. with a few exceptions, the surface areas of the minerals computed from both water and nitrogen adsorption isotherms increased with acid and alkali treatments. with increasing reagent concentration, the nitrogen surface area increased faster than the water surface area. well-defined trends were not noted in either changes of average water or nitrogen adsorption energies or in relative amounts of adsorption sites, indicating that the effects of acid and alkali attack are controlled by the individual character of the minerals.
Emanation Thermal Analysis of Natural and Chemically-Modified Vermiculite
Authors: Poyato J. , Pérez-Maqueda L. A. , Justo A. , Balek V. 
Published: February 2003

AbstractEmanation thermal analysis (ETA), based on radon release measurements from previously labeled samples, was used for the first time in the characterization of the thermal behavior of natural Mg2+-vermiculite (Santa Olalla, Huelva, Spain) and of Na+- and NH4+-exchanged vermiculite samples. In addition, vermiculite samples subjected to a chemical treatment with an aqueous solution of (NH4)2SiF6 and partially or totally re-saturated with Na+ ions were also investigated by ETA. The ETA results of natural Mg2+-vermiculite, Na+-vermiculite and NH4+-vermiculite gave supplementary information about microstructure changes of the samples observed under dynamic heating conditions. The method has proved to be very useful for characterization of microstructure changes due to modification in the interlayer space of samples during the heat treatment. The crystallization of vermiculite into new phases, such as enstatite (for NH4+-vermiculite and Mg2+-vermiculite) and forsterite (for Na+-vermiculite) was also observed by ETA.
Preparation and Characterization of Eu-Magadiite Intercalation Compounds
Authors: Mizukami Naoko , Tsujimura Masashi , Kuroda Kazuyuki , Ogawa Makoto 
Published: February 2003

AbstractThe intercalation of europium ions (Eu3+) into the interlayer space of a layered silicate, magadiite, was conducted by ion-exchange reactions between magadiite and europium(III) chloride. X-ray diffraction and elemental analysis results indicated that Eu3+ cations were intercalated into the interlayer space of magadiite. The ion exchange between Eu3+ and Na+ occurred preferentially so that the adsorbed Eu3+ amounts were controlled quantitatively. Thermal transformation of the original layered structure was suppressed by the intercalation of Eu3+. The resulting intercalation compounds exhibited photoluminescence arising from the intercalated Eu3+. The luminescence intensity varied in accordance with the amount of Eu3+ absorbed, suggesting that the self-quenching occurred at higher loading levels. The luminescence intensity was also changed by the heat treatment, corresponding to the change in the surroundings of the Eu3+ adsorbed, induced by the removal of the adsorbed water molecules and the hydroxyl groups of the silicate.
Diagnosis of fetal acrania during the first trimester nuchal translucency screening for Down syndrome
Authors: Cheng C.‐C. , Lee F.‐K. , Lin H.‐W. , Shih J.‐C. , Tsai M.‐S. 
Published: February 2003

AbstractObjectives: Prenatal screening during the first‐trimester using fetal nuchal translucency (NT) measurement and maternal serum levels of free β‐human chorionic gonadotropin (hCG) and pregnancy‐associated plasma protein‐A (PAPP‐A) has become an established method for the detection of fetal Down syndrome. Increasing evidence has shown that some of the fetal structural abnormalities could be identified during NT scanning. Second trimester maternal serum alpha‐fetoprotein (MSAFP) measurements and ultrasound scans have been widely used in clinical practice to identify fetal neural tube defects (NTDs). In this study, we evaluated the effectiveness of early diagnosis of fetal acrania during NT scanning. Methods: We reviewed the medical records of 5890 pregnancies that were delivered in our hospital between January 1, 1999 and January 31, 2001. Among them, 3600 pregnant women received NT‐based Down syndrome screening at 10–13 weeks’ gestation. Pregnancies with fetal NTDs were evaluated and their maternal serum levels of free β‐hCG and PAPP‐A were compared with those of the normal control pregnancies. Results: Seven of the 3600 pregnancies were identified with fetal acrania and all of them were detected during first‐trimester NT scanning. Among the seven cases, five had measurements of maternal serum concentration free β‐hCG and PAPP‐A concentration, yet there were not significant difference between the pregnancies with fetal acrania and those of the control pregnancies (PAPP‐A, 1.13 vs. 0.96; free β‐hCG, 1.10 vs. 1.06; P>0.05). Two of the seven affected patients did not have maternal serum biochemical measurements due to the immediate termination of pregnancies. Conclusions: We demonstrated that pregnancies with fetal acrania could be easily identified at the time of NT scanning. Careful ultrasound inspection of fetal structure during NT measurements at 10–13 weeks of gestation provides an encouraging advantage for early diagnosis of fetal acrania.
Calcium–phosphorus–magnesium homeostasis in pregnant women after renal transplantation
Authors: Czajkowski K. , Wójcicka‐Bentyn J. , Grymowicz M. , Smolarczyk R. , Malinowska‐Polubiec A. , Romejko E. 
Published: February 2003

AbstractObjective: The aim of the study was the assessment of calcium–phosphorus–magnesium homeostasis in pregnant women after renal transplantation. Methods: The study covered 64 pregnant women in the third trimester of gestation including: 33 women after renal transplantation (the study group) and 31 healthy pregnant women (the control group). Women from both groups were at the similar age: 30.8±4.7 vs. 31.3±5.0 years (NS) and at the same gestational age 34.8±2.4 vs. 35.3±2.6 weeks (NS). The mean body mass index (BMI) in the women from the study group before pregnancy was 21.49±2.81 vs. 22.1±3.02 in the control group (NS), BMI before delivery was 25.43±3.05 vs. 26.0±3.35 (NS), the percentage of the BMI increase during pregnancy was 18.7±7.68 vs. 17.65±7.13 (NS) and BMI increase during gestation was 3.93±1.56 vs. 3.90±1.54, respectively (NS). Arterial blood pressure at the time of blood samples collection for biochemical tests was 151.4±26.8/92.5±16.9 in women from the study group comparing to 115.0±6.0/68.0±7.0 mmHg (P<0.001) in the patients from the control group. The maximal blood pressure during pregnancy was 169.2±20.7/102.7±14.0 vs. 118.0±7.0/70.0±8.0 mmHg (P<0.001), respectively. We estimated serum levels of: total Ca, ionized Ca2+, inorganic phosphorus (Pi), Mg, total protein, albumin and blood morphology. Moreover, urine levels of Ca, Pi, Mg and protein were assessed. Results: The pregnant women after renal transplantation presented increases in serum concentrations of total Ca (2.54±0.20 vs. 2.16±0.10 mmol/l; P<0.001) and ionized Ca2+ (1.322±0.104 vs. 1.12±0.07 mmol/l; P<0.001) and the decrease in Pi level (1.013±0.211 vs. 1.10±0.16 mmol/l; P<0.05), total protein (59.3±7.0 vs. 65±5 g/l; P<0.001) and albumin (461.6±65.65 vs. 493.2±59 μmol/l; P<0.05). Moreover, in the study group drop in red blood cells count to 3.71±0.56 vs. 4.01±0.35×1012/l (P<0.02) in the control group was detected. Despite increased volume of 24‐h urine collection in the kidney recipients we observed significantly decreased urine 24‐h calcium excretion 2.47±0.92 vs. 6.72±3.49 mmol (P<0.001) and simultaneous increase in urine Mg excretion 3.422±1.025 vs. 2.18±0.52 mmol/24 h (P<0.001). There was no difference in urine 24‐h Pi excretion between the study and the control group. The pregnant renal transplant recipients presented proteinuria of 1.19±1.9 g/24 h. Conclusions: Women after kidney grafting present vital aberrations in calcium–phosphorus–magnesium homeostasis during pregnancy. The most significant changes are associated with calcium metabolism (high increase in serum Ca levels and impairment of renal elimination of calcium). The observed changes may be influenced by the doses of immunosuppressive agents and disturbed renal function.