bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled Polymerization of Metanilic Anion within the Interlayer of NiAl Layered Double Hydroxide
Authors: Tian Xiaofei , Wei Min , Evans David G. , Rao Guoying , Yang Heli 
Published: August 2006

AbstractThe controlled chemical oxidative polymerization of metanilic anion (m-NH2C6H4SO3−)$(m{\rm{ - N}}{{\rm{H}}_2}{{\rm{C}}_6}{{\rm{H}}_4}{\rm{SO}}_3^ - )$ within the interlayer of NiAl layered double hydroxide was performed using, for the first time, ammonium persulfate as the oxidizing agent. The quantity of oxidizing agent required for control of the interlayer polymerization was investigated systematically and it was found that interleaved polyaniline sulfonic (PANIS) was present in different oxidation states and protonation levels when different quantities of external oxidizing agents were added. A mechanism for the oxidative polymerization of metanilic anion in NiAl layered double hydroxide is proposed, based on the intercalation of the oxidizing agent and the interlayer polymerization of monomer. The resulting PANIS/NiAl LDH composites were characterized by powder X-ray diffraction, ultraviolet-visible absorption spectra, Fourier transform infrared and X-ray photoelectron spectroscopy.
Sorption of Nitroaromatics by Ammonium- and Organic Ammonium-Exchanged Smectite: Shifts from Adsorption/Complexation to a Partition-Dominated Process
Authors: Roberts Michael G. , Li Hui , Teppen Brian J. , Boyd Stephen A. 
Published: August 2006

AbstractNitroaromatic compounds (NACs) are components of munitions commonly found as soil contaminants at military training sites and elsewhere. These compounds pose possible threats to human health and ecological systems. Recent studies indicate that these compounds are strongly retained by smectite clays. The adsorption mechanisms are not fully reconciled, but it is known that the type of exchangeable cation strongly affects NAC affinity for smectites. This study examined the sorption of 1,3-dinitrobenzene, 2,4-dinitrotoluene and naphthalene from water by a smectite clay (SWy-2) saturated with ammonium, tetramethylammonium (TMA), trimethylphenylammonium (TMPA) and hexadecyltrimethylammonium (HDTMA). In all cases, we observed greater sorption of 2,4-dinitrotoluene compared with 1,3-dinitrobenzene. The sorption isotherms for 2,4-dinitrotoluene and 1,3-dinitrobenzene displayed a concave-downward curve for NH4-SWy-2 and TMA-SWy-2, whereas the isotherms for sorption of HDTMA-SWy-2 and TMPA-SWy-2 were essentially linear. The magnitude of sorption followed the order: NH4-SWy-2 > TMA-SWy-2 > TMPA-SWy-2 > HDTMA-SWy-2 for both compounds. The greater affinity of NACs for NH4- and TMA-SWy-2 is due in part to complex formation between the exchangeable cation and −NO2 groups. These clays also provide near optimal interlayer distances that approximate the molecular thickness of NACs hence promoting the simultaneous interaction of the planar aromatic rings with opposing siloxane surfaces and solute dehydration. Both processes are energetically favorable. In HDTMA-SWy-2, sorption of all solutes is via a partition-dominated process. Solute competition (diminished uptake of one solute in the presence of a second) was observed for TMA-SWy-2 but not HDTMA-SWy-2. This is consistent with an adsorptive mechanism for TMA-SWy-2 and a partitioning mechanism for HDTMA-SWy-2. This study demonstrates that the dominant molecular mechanism of NAC sorption by smectite changes fundamentally from complexation between −NO2 groups and the exchangeable cation (viz. NH4 and TMA) to partitioning for a systematic series of ammonium and quaternary ammonium cations in which the locus of positive charge (the central N atom) is progressively shielded by organic moieties of increasing size.
Studies on the Adsorption of Dyes to Kaolinite
Authors: Harris Rodney G. , Johnson Bruce B. , Wells John D. 
Published: August 2006

AbstractThe strong adsorption to kaolinite of four polyaromatic, cationic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O), which adsorb much less to alumina or silica, was investigated by means of acid-base titrations, measurements of adsorption at varying pH and dye concentration, and by ATR-FTIR spectroscopy. The four dyes adsorb to kaolinite to similar extents, with little change over the pH range 3–10, but at higher pH (above the pKas of the dyes) the adsorption of 9-aminoacridine and 3,6-diaminoacridine decreases, that of azure A increases, and that of safranin O stays approximately constant. Although the dyes adsorb to kaolinite much more strongly than metal ions do, titration and spectroscopic data show that there is only limited chemical interaction between the adsorbed dyes and the kaolinite surface. The results indicate that electrostatic interaction between the dye molecules and the kaolinite surface is necessary for adsorption, but that hydrophobic interactions also contribute. It is proposed that the relatively hydrophobic silica faces of kaolinite, which carry low-density permanent negative charge, facilitate aggregation and adsorption of the positively charged, flat, aromatic dye molecules.
Competitive Adsorption of Cd and Dyes to Kaolinite
Authors: Harris Rodney G. , Johnson Bruce B. , Wells John D. 
Published: August 2006

AbstractThe competitive adsorption to kaolinite between Cd(II) and four polyaromatic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O) was studied in 5 mM KNO3 at 25°C. Under these conditions, Cd adsorbs to the silica face of kaolinite between about pH 4 and 6.5, but at higher pH, adsorbed Cd is progressively relocated to the crystal edges. In the presence of dye, less Cd adsorbed to kaolinite below pH 7. If sufficient dye was added to saturate the kaolinite surface, Cd adsorption was totally suppressed up to ∼pH 6. At higher pH, Cd followed the characteristic pattern for edge adsorption. In separate experiments 9-aminoacridine and azure A displaced pre-adsorbed Cd from kaolinite. The displacement curves were initially linear, with one Cd ion being displaced for every 13 dye molecules adsorbed at pH 5.5, and one Cd ion for every 35 dye molecules at pH 7.5. The interpretation of these results is that the dyes bind to kaolinite much more strongly than Cd(II) does, but only to the silica face.
Modeling the Adsorption of Organic Dye Molecules to Kaolinite
Authors: Harris Rodney G. , Wells John D. , Angove Michael J. , Johnson Bruce B. 
Published: August 2006

AbstractSimple extended constant capacitance surface complexation models have been developed to represent the adsorption of polyaromatic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O) to kaolinite, and the competitive adsorption of the dyes with Cd. The formulation of the models was based on data from recent publications, including quantitative adsorption measurements over a range of conditions (varying pH and concentration), acid-base titrations and attenuated total reflectance-Fourier transform infrared spectroscopic data. In the models the dye molecules adsorb as aggregates of three or four, forming outer-sphere complexes with sites on the silica face of kaolinite. Both electrostatic and hydrophobic interactions are implicated in the adsorption processes. Despite their simplicity, the models fit a wide range of experimental data, thereby supporting the underlying hypothesis that the flat, hydrophobic, but slightly charged silica faces of kaolinite facilitate the aggregation and adsorption of the flat, aromatic, cationic dye molecules.
Redox Properties of Structural Fe in Ferruginous Smectite. A Discussion of the Standard Potential and its Environmental Implications
Authors: Favre Fabienne , Stucki Joseph W. , Boivin Pascal 
Published: August 2006

AbstractThe aim of this study was to compare the redox properties of oxides and smectite structural Fe (FeStr). Structural Fe in smectite often accounts for about half of the Fe pool in soils and sediments, and is naturally reduced by indigenous bacteria. This reaction is, however, seldom taken into account in environmental studies. The equation for the oxidation-reduction of FeStrand its application to the calculation of the standard electrode potential of FeStr,E0, are discussed on the basis of literature review. The resulting redox properties were used in a new analysis of previously reported field monitoring data. This agreed well with experimental observations that remained unexplained, and showed that if equilibrium conditions prevail, the FeStrpool in soils will reduce prior to the Fe in oxides. The FeStrpool is, therefore, likely to play a major role in controlling the bio-geochemistry of temporarily water-logged soils, and this reaction should be taken into account in further studies.
Differences in the Dehydration-Rehydration Behavior of Halloysites: New Evidence and Interpretations
Authors: Joussein Emmanuel , Petit Sabine , Fialips Claire-Isabelle , Vieillard Philippe , Righi Dominique 
Published: August 2006

AbstractTwo reference halloysites from New Zealand (Te Puke and Opotiki) were studied by X-ray diffraction under (1) various levels of relative humidity (RH) from 95 to 0% (dehydration), and (2) various temperatures increasing from 25 to 120°C (dehydration). They were also studied by differential thermal and thermogravimetric analyses at 40 and 0.2% RH. The impact of freeze drying along with the influence of cation saturation (Ca and K) on halloysite hydration were studied. The dehydration of the two halloysite samples upon decrease in RH started below 70% RH. However, the dehydration of Opotiki was still incomplete at ∼0% RH regardless of the saturation cation whereas Te Puke was completely dehydrated at ∼10% RH. For each sample, the decrease in RH and the increase in temperature induce similar dehydration behavior, but the dehydration processes of the Opotiki and Te Puke samples are different. The dehydration of Te Puke proceeds with one intermediate hydration state reacting as a separate phase due to the presence of ‘hole’ water molecules. The dehydration of the fully hydrated Opotiki halloysite gives a dehydrated phase and no 8.6 Å phase. The results suggest the presence of different types of water molecule, the ‘associated’ and the ‘hole’ water, controlling the dehydration behavior of halloysites. Freeze-dried halloysite samples are essentially dehydrated and the size of their coherent scattering domains is strongly reduced. Rehydration experiments performed after dehydration either at 95% RH or by immersing the sample in water for 3 months result in their partial rehydration. Calcium saturation promotes the rehydration process. The results suggest the presence of interlayer cations in the Opotiki sample, Ca ions being associated with the strongly held ‘hole’ water. As a result of this study, we assert that the (de)hydration behavior of halloysite is highly heterogeneous and cannot be generalized a priori.
Preparation of Porous Carbons from Halloysite-Sucrose Mixtures
Authors: Wang Ai-ping , Kang Feiyu , Huang Zheng-Hong , Guo Zhancheng 
Published: August 2006

AbstractPorous carbons rich in mesopores and with large pore volumes have been prepared by polymerization and carbonization of a carbon precursor, sucrose, within a matrix of the natural clay, halloysite. The carbon precursor was impregnated into the pores of halloysite and mostly deposited on the external surface of the halloysite rods during impregnation. The inorganic matrix was removed by washing the carbon-mineral composite with HF and HCl. The resultant carbons were characterized by nitrogen adsorption analysis and were found to possess a large specific surface area, a large total pore volume and significant mesoporosity, without an activation process being involved. The pore volume and mesoporosity were up to 1.86 cm3/g and 78%, respectively, even at low carbonization temperatures (500°C). The size of the mesopores of the resultant carbons is mainly between 3 and 30 nm and the dominant pore size is ∼3.7 nm. The carbonization temperature has significant effects on the pore-size distribution and structure of the resultant carbons and carbon-mineral composites, respectively. This process is relatively simple and expected to cost less than the high-temperature carbonization process in the preparation of mesoporous carbons with total pore volume and large specific surface areas.
Structural and Chemical Alteration of Glauconite under Progressive Acid Treatment
Authors: Hassan Mervat S. , Baioumy Hassan M. 
Published: August 2006

AbstractBoiling glauconite from the El-Gideda area of Egypt in different concentrations of HCl and H2SO4 for different periods led to a modified structure. Treatment resulted in progressive destruction of the structure, leaving X-ray amorphous silica and only relics of the original mineral. The glauconitic material was modified structurally in order to increase its adsorption activity. The glauconite was evaluated in terms of mineralogy, chemistry, morphology, structural modification, octahedral cation leaching rate, surface area and cation exchange capacity using X-ray diffraction, infrared spectroscopy, X-ray fluorescence, scanning electron microscopy and surface area analysis. The ratio of extracted octahedral cations to the total octahedral cations in the untreated glauconite was taken as a measure of octahedral sheet decomposition. A progressive decrease in crystallinity and the formation of X-ray amorphous silica Si-O vibration bands at 1100, 800 and 494 cm−1 accompanied octahedral cation depletion. Acid activation using 2 M and 4 M HCl for 6 h destroyed 30% and 61% of the octahedral sheet, respectively. In contrast, similar treatment using 2.9 and 5.5 M H2SO4 destroyed 48% and 93% of the octahedral sheet, respectively. Depending on the extent of cation depletion, the 4 M HCl product surface areas were as high as 259 m2/g, whereas the surface area of the 5.5 M H2SO4 product was only 63 m2/g. The progressive increase in surface area was due to glauconite morphology alteration. Acid-induced dissolution of Al, Fe, Mg cations from octahedral sheet edges led to a wedge-like splitting of the glauconite crystals, mesopore creation, and greater access to interlayer galleries.
Influence of Mechanical Compaction and Clay Mineral Diagenesis on the Microfabric and Pore-Scale Properties of Deep-Water Gulf of Mexico Mudstones
Authors: Aplin Andrew C. , Matenaar Ingo F. , McCarty Douglas K. , van der Pluijm Ben A. 
Published: August 2006

AbstractWe report on how the effects of mechanical compaction and clay mineral diagenesis have affected the alignment of phyllosilicates in a suite of Miocene-Pliocene mudstones buried to sub-seabed depths of between 1.8 and 5.8 km in the deep-water Gulf of Mexico. Mechanical compaction has reduced the porosity of the samples to 15% at 5 km, with modal pore sizes between 10 and 20 nm. High-resolution X-ray texture goniometry data show that the intense mechanical compaction has not resulted in a strongly aligned phyllosilicate fabric. The muds were apparently deposited with a weak or isotropic phyllosilicate fabric which was not substantially realigned by mechanical compaction. Unusually, X-ray diffraction of <0.2 µm separates shows that: (1) there is no illitization trend between 90 and 120°C; and (2) discrete smectite persists to ∼120°C, coexisting with R1 I-S or R0 I-S with 30–40% expandable layers. Between 120 and 130°C, discrete smectite disappears and the expandability of I-S decreases to ∼25–30%. We propose a two-stage diagenetic process involving (1) the alteration of volcanic glass to smectite and (2) the illitization of smectite and I-S; the alteration of glass results in smectite without a preferred orientation and retards the illitization reaction. We suggest that the lack of a strongly aligned phyllosilicate fabric reflects the apparently limited extent of illitization, and thus recrystallization, to which these mudstones have been subjected.
Pore-Scale Analysis of Bulk Volume Change from Crystalline Interlayer Swelling in Na+- and Ca2+-Smectite
Authors: Likos William J. , Lu Ning 
Published: August 2006

AbstractWater-vapor sorption experiments were conducted to quantify bulk volume change of compacted expansive clay specimens resulting from interlayer hydration and dehydration in the crystalline swelling regime. Effects of interlayer cation type and pore fabric are examined by comparing results for natural Na+-smectite and Ca2+-smectite specimens compacted over a range of initial bulk densities. Transitions in interlayer hydration states are reflected in the general shape of the sorption isotherms and corresponding relationships between humidity and volume change. Hysteresis is observed in both the sorption and volume-change response. Volume change for Ca2+-smectite specimens is significantly greater than for Na+-smectite over the entire range of packing densities considered. Loosely compacted specimens result in less volume change for both clays. Results are interpreted in light of a conceptual framework based on previous SEM and TEM observations of particle and pore fabric for Na+ and Ca2+ smectite at high suctions. A pore-scale microstructural model is developed to quantitatively assess changes in interlayer and interparticle void volume during hydration. Modeling suggests that the relatively small volume changes observed for Na+-smectite are attributable to a reduction of interparticle void volume as expanding quasicrystals encroach into surrounding larger-scale pores. Volume change hysteresis is attributed to unrecovered alterations in interparticle fabric required to accommodate the swelling process. The results provide new insight to address volume change upscaling, hysteresis, and the general evolution of bi-modal pore fabric during crystalline swelling.
The Elastomer Gage for Local Strain Measurement in Monotonic and Cyclic Soil Testing
Authors: Safaqah OA , Riemer MF 
Published: August 2006

Abstract
This study introduces a new type of local strain gages for soil testing called the elastomer gage. It is the first on-sample local strain gage that is flexible enough to be attached to the inside of a conventional latex membrane so that the gage is in full contact with the soil's sample surface. The gage has very versatile design characteristics including variable length and sensitivity, which enable measurement over a wide range of static and cyclic strains. The gage can be used in many testing systems including triaxial, torsional shear, and simple shear devices to directly measure axial, circumferential, and shear strains. The gage has been validated in triaxial and torsional testing systems using a “calibration sample” made of urethane with known stiffness.
New Apparatus for Evaluating Filter Performance for Dams Containing Cracks
Authors: Brandon TL , Park Y , Duncan JM 
Published: August 2006

Abstract
A new test apparatus has been developed to evaluate filter performance when both the filter and the core _base_ material have been cracked. This apparatus allows the orientation of the crack to be horizontal or vertical, and accommodates flow in the horizontal and vertical directions as well. The applied hydraulic gradient and the thickness of the crack can also be varied.Two apparatuses have been constructed and tested. The smaller apparatus allows testing of truncated cylindrical test specimens that are 10 cm in diameter by 20 cm long. The larger apparatus allows testing of specimens that are approximately 30 by 30 by 30 cm. An automated data acquisition system was developed to measure the pressures and flow rates through the test specimens as well as obtaining a video record of the filter performance. In successful tests, the filter slumped to fill the crack, the flow rate decreased, and the head water pressure increased. In failed tests, the filter never slumped to fill the crack, the flow rate remained high, and the head water pressure stayed very low. The relative success of failure of a filter system could be assessed by the video record as well.
Characterizing the Time- and Energy-Dependent Reactor n/γ Environment
Authors: Griffin PJ , Luker SM , King DB , DePriest KR , Cooper PJ 
Published: August 2006

Abstract
In a reactor pulse, the early radiation has a neutron/gamma component resulting from the prompt fission neutron and gamma radiation and from the neutron-induced secondary gammas. However, after the primary reactor pulse, the radiation environment also includes a time-dependent delayed neutron and gamma component. At even later times, the material activation dominates the source term. When active tests are conducted in the reactor, the radiation environment at a particular time may not be well characterized by the time-integrated spectrum provided by the typical radiation transport calculations. This paper defines the steps that are required to adequately model the time- and energy-dependent radiation environment in the reactor environment. This paper also compares the time-dependent response from a range of active dosimeters in a reactor pulsed environment and shows how the n/γ mixed-field response for the dosimeters and the changing radiation field can influence the interpretation of the dosimetry.
Ubiquitous Computing im Wissensmanagement. Die Bedeutung allgegenwärtiger Informationsstrukturen auf das Wissensmanagement (Ubiquitous Computing and Knowledge Management. Ubiquitous Information Infrastructures and Their Influence on Knowledge Management)
Authors: Aßmann Jörg , Resatsch Florian , Schildhauer Thomas 
Published: August 2006

Zusammenfassung
Die Vision allgegenwärtiger Informations- und Kommunikationstechnologie in einer, den Alltag der Menschen und die Prozesse in Unternehmen durchdringenden Art und Weise, schafft erweiterte Möglichkeiten des Wissensmanagements. Der vorliegende Beitrag führt theoriegeleitet herbei, wie sich der Fortschritt der technischen Entwicklungen auf das Wissensmanagement der Zukunft auswirkt und welche Voraussetzungen, sowie Elemente des ubiquitären Wissensmanagement zur Diskussion stehen. Vor diesem Hintergrund wird der Nutzen des Ansatzes von Ubiquitous Computing für das Wissensmanagement heraus gearbeitet.
Suchen & Finden im Knowledge Broker Network (Searching & Finding in the Knowledge Broker Network)
Authors: Löw Robert , Bleimann Udo , Rausch Monika 
Published: August 2006

Zusammenfassung
Dieser Artikel präsentiert einen praxisorientierten Ansatz für die Umsetzung des Wissensmanagements in Unternehmen. Das Konzept des Knowledge Broker Networks basiert auf einem Hybrid-System aus Mensch und Maschine. Dieses unterstützt sowohl das Auffinden von Informationen als auch die Herstellung eines Kontakts zwischen einer Person mit einer konkreten Aufgabenstellung und einer Person bzw. Personengruppe, die bei der Lösung hilfreich sein könnte. Um unsere Vision einer Optimierung des automatisierten Suchvorgangs innerhalb eines Knowledge Management Systems zu verdeutlichen, stellen wir diese anhand eines Szenarios beispielhaft dar. Zusätzlich werden die Ergebnisse unserer Untersuchung zu im Internet verfügbaren Kontakt- und Wissens-Austausch-Plattformen und einige ausgewählte Ergebnisse zu den Erwartungen potentieller Nutzer an ein Knowledge Management System aufgezeigt.