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  Subjects -> EARTH SCIENCES (Total: 591 journals)
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EARTH SCIENCES (437 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Hybrid Journal   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 8)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 2)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances In Physics     Hybrid Journal   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 2)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 3)
AMBIO     Hybrid Journal   (Followers: 12)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 2)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 1)
Annals of Geophysics     Full-text available via subscription   (Followers: 9)
Annals of GIS     Hybrid Journal   (Followers: 15)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene Review     Hybrid Journal   (Followers: 1)
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 7)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 9)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 21)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 15)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 17)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 3)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 4)
Atmospheric and Climate Sciences     Open Access   (Followers: 14)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 8)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of Marine Science     Full-text available via subscription   (Followers: 13)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 17)
Bulletin of Volcanology     Hybrid Journal   (Followers: 11)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 9)
Coastal Management     Hybrid Journal   (Followers: 19)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 11)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 5)
Contemporary Trends in Geoscience     Open Access  
Continental Journal of Earth Sciences     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 7)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 18)
Cretaceous Research     Hybrid Journal   (Followers: 4)
Cybergeo : European Journal of Geography     Open Access   (Followers: 4)
Developments in Geotectonics     Full-text available via subscription   (Followers: 2)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 170)
Earth Interactions     Full-text available via subscription   (Followers: 8)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 1)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 11)
Earth System Dynamics     Open Access   (Followers: 4)
Earth System Dynamics Discussions     Open Access   (Followers: 3)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 1)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Spectra     Full-text available via subscription   (Followers: 12)
Ecohydrology     Hybrid Journal   (Followers: 11)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 10)
Environmental Geology     Hybrid Journal   (Followers: 11)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access  
Erwerbs-Obstbau     Hybrid Journal  

        1 2 3 4 5 | Last

Journal Cover Applied Clay Science
   Journal TOC RSS feeds Export to Zotero [4 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0169-1317
     Published by Elsevier Homepage  [2570 journals]   [SJR: 0.999]   [H-I: 63]
  • Micro porosity evolution in compacted swelling clays — A chemical
           approach
    • Abstract: Publication date: Available online 8 October 2014
      Source:Applied Clay Science
      Author(s): Majid Sedighi , Hywel R. Thomas
      This paper presents a new approach to investigate the variation of microscopic porosity/pore water interactions in compacted swelling clays. The aim of the research has been to develop a theoretical formulation for the prediction of micro-porosity variations with suction and temperature in compacted smectite. The model developed is based on a geochemical formulation of interlayer hydration/dehydration of smectite. An established theoretical approach based on regular solid-solution theory is adopted to describe the water adsorption/desorption in the interlayer of smectite. The thermodynamic parameters of the model for the case of two bentonite clays, namely MX-80 and FEBEX are presented. Thermodynamic parameters of the hydration model including Margules parameter (Ws ) and logarithm of the equilibrium constant (log Keq ) at ambient temperature were found to be −2420 cal/mol and −1.42, for compacted MX-80 and −3330 cal/mol and −2.79, for compacted FEBEX, respectively. Micro/macro-porosity evolutions with dry density and relative humidity are presented. The results are compared with alternative approximations reported in the literature which show a close correlation. Variations of the micro and macro-porosity in compacted bentonite with hydration processes are also studied through the application of the model under restrained swelling and isothermal conditions. The results provide an insight into the evolution of pore water in compacted bentonite during saturation and quantify the distribution of water in micro and macro pores.


      PubDate: 2014-10-12T07:00:37Z
       
  • The preparation of micro-porous membrane from a Tunisian kaolin
    • Abstract: Publication date: Available online 8 October 2014
      Source:Applied Clay Science
      Author(s): I. Hedfi , N. Hamdi , E. Srasra , M.A. Rodríguez
      The purpose of this work is the preparation of a low cost membrane from Tunisian kaolin in order to be used in a filtration process. This study has begun with the characterization of the raw material in order to choose the best condition of the membrane preparation. After the clay characterization, it has been pressed and sintered at 950°C for 2h to obtain the flat ceramic membranes of 25mm in diameter. Different characterizations were performed to determine the porosity, the density and the mechanical strength of these membranes; samples show good porosity (~30%), high compressive strength, around 60MPa, but relatively low permeability.


      PubDate: 2014-10-12T07:00:37Z
       
  • Effect of the chemical composition of smectites used in KF/Clay catalysts
           on soybean oil transesterification into methyl esters
    • Abstract: Publication date: Available online 11 October 2014
      Source:Applied Clay Science
      Author(s): L.C.A. Silva , E.A. Silva , M.R. Monteiro , C. Silva , J.G. Teleken , H.J. Alves
      Three smectites with distinct chemical compositions were treated with potassium fluoride and the catalysts thus obtained were used in the transesterification of soybean oil with methanol. The smectites and catalysts were examined by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and the BET gas adsorption method to verify if their chemical composition influences the properties of the resulting catalysts. An experimental design was applied to evaluate the effect of the variables of the transesterification reaction: temperature, mass ratio of the catalyst, and the molar ratio of oil to methanol. The results indicate that increasing the SiO2/Al2O3 ratio of the smectites causes an increase in the basicity of the catalysts, and hence, in the conversion rate into methyl esters.


      PubDate: 2014-10-12T07:00:37Z
       
  • Development of expandability charts for Ankara Kalecik Clay
    • Abstract: Publication date: Available online 8 October 2014
      Source:Applied Clay Science
      Author(s): Ahmet Ozguven
      The main aim of this study is to establish optimum working conditions and to propose expandability charts for Kalecik Clay using expansion ratio versus unit volume weight values via a statistical computer program (Design Expert 7.0). First of all, some suitable samples were collected from the Kalecik County (Ankara, Turkey). Later, the samples were crushed and milled up to 200μm clay size in the laboratory. Then, pellets with a 10mm diameter were dried in ovens and heated inside a furnace to expand in different temperatures. One heating operation began with 900°C and ended with 1200°C. In addition to that, the holding time periods were selected as 5, 10, 15 or 20min for each operation. In the final stage, the unit volume weight and expansion ratio of the produced aggregates were determined. As results of this study, both the optimum furnace holding time and furnace temperature values for the samples were determined in order to maximize the expansion ratio values and minimize the unit volume weight for Kalecik Clays. Some expandability charts were proposed for Kalecik Clay by using the findings. The charts allow one to assign expansion ratio and unit volume weight values in different working conditions including holding time inside the furnace and furnace temperature. The proposed charts are expected to be quite useful for more efficient production of expanded clay aggregates in construction industry.


      PubDate: 2014-10-12T07:00:37Z
       
  • Preparation and application of chemically modified kaolin as fillers in
           Egyptian kraft bagasse pulp
    • Abstract: Publication date: Available online 11 October 2014
      Source:Applied Clay Science
      Author(s): Ahmed El Gendy , Ramzi Khiari , Fedia Bettaieb , Nathalie Marlin , Alain Dufresne
      The application of kaolin modified with hemicellulose and carboxymethyl cellulose (CMC) in the presence of alum (Al2(SO4)3) as fillers in Egyptian kraft bagasse pulp was investigated. The kaolin content was 15% based on pulp and different amounts of alum i.e., 2, 4, 8, 12, 16, 18 and 20% based on filler were added. It was found that kaolin modified with CMC/alum could improve the physical properties of handsheets. The modification of kaolin with hemicellulose and CMC/alum could enhance significantly the physical properties of handsheets as well as the amount of the retained kaolin. The retention, the brightness and the opacity of the handsheets filled with modified kaolin were significantly improved compared with either the control handsheets or that filled with unmodified kaolin. SEM observations of the fillers confirmed the surface encapsulating effect of the modifiers on the filler. It can be deduced also from the obtained images of the paper-sheets that modified filler particles were more effectively adhered and bonded to the pulp fibers, in comparison to unmodified filler particles. The results indicated that the interaction of hemicellulose and CMC could be used as a source for production of a good retention aid in papermaking.


      PubDate: 2014-10-12T07:00:37Z
       
  • The development of unfired clay building material using Brick Dust Waste
           and Mercia mudstone clay
    • Abstract: Publication date: Available online 11 October 2014
      Source:Applied Clay Science
      Author(s): J.E. Oti , J.M. Kinuthia , R.B. Robinson
      This work reports the potential of using Brick Dust Waste (BDW) as a partial substitute for clay in the development of unfired clay building materials (brick, block and mortar). BDW is a waste material from the cutting of fired clay bricks. There are various reasons necessitating the cutting of bricks — corner bricks, construction of chimneys, and other uses needing bricks of various shapes and sizes. This results in the disposal of BDW as an environmental problem of concern. In order to investigate the clay replacement potential of BDW, four types of mixes were designed at varying BDW replacement levels — 5%, 10%, 15% and 20%. Ground Granulated Blastfurnace Slag, an industrial by-product from steel manufacture was activated using quick lime and the mixture was used to stabilise Mercia mudstone clay for unfired clay production. The 56day compressive results using cylinder test specimens showed a significant strength gain (up to 2.1N/mm2). Overall, the results suggest that it is possible to develop unfired clay building material using up to 20% BDW as partial substitutes for primary clay.


      PubDate: 2014-10-12T07:00:37Z
       
  • Mineralogy and pore space characteristics of traprocks from Central
           Siberia, Russia: Prerequisite of weathering trends and soil formation
    • Abstract: Publication date: Available online 11 October 2014
      Source:Applied Clay Science
      Author(s): Sofia Lessovaia , Stefan Dultz , Sergey Goryachkin , Michael Plötze , Yury Polekhovsky , Natalia Andreeva , Alexey Filimonov
      Pore space issues and mineral paragenesis of traprocks from the central part of the basaltic province (Central Siberia, Russia) were studied, as was the fine size fraction (<1μm) of well-drained soils from two groups — “shallow with hard rock” and “deeper and mature with saprolite.” The explanation of coexisting of these two groups was given via rocks' characteristics. The methods used included mercury intrusion porosimetry (MIP), impregnation of connective pores with a molten alloy (Wood's metal) combined with subsequent electron microscopy, optical microscopy, X-ray diffraction, and IR spectroscopy. Rock from the lithic contact is represented by slightly weathered dolerite and shows a tendency to bimodal pore size distribution with a second maximum in pore size at 10nm, which is due to the occurrence of phyllosilicates. Coarse pore systems are mainly due to cracks, which allow an easy exchange of water. Higher total porosity in the rock in one of two pits (~12vol.% compared with 4vol.%) appears to be a prerequisite for the formation of a deeper and more mature profile. Secondary products of dolerite weathering are smectites determining the association of clay minerals in both soil profiles and Fe-oxides. Most likely, desegregation and weathering of the rock fragments from soil horizons are fast enough to keep sufficient amounts of smectite only in the fine size fraction of the shallow profile. In the mature profile, pedogenesis leads to acidification of upper soil horizons and to a pronounced decrease in the smectite proportion, not only in the soil but also in the rock fragments from soil horizons. Thus, smectite(s) that was stable in early stages of rock weathering and soil formation and became unstable due to soil acidification illustrates the metastable nature of clay mineralogy in the well-drained soils from basic rock.


      PubDate: 2014-10-12T07:00:37Z
       
  • X-ray studies on the nano- and microscale anisotropy in compacted clays:
           Comparison of bentonite and purified calcium montmorillonite
    • Abstract: Publication date: Available online 5 October 2014
      Source:Applied Clay Science
      Author(s): Jussi-Petteri Suuronen , Michał Matusewicz , Markus Olin , Ritva Serimaa
      Exceptional water retention properties make compacted clays and clayrocks attractive materials in waste management applications, e.g. as buffer materials and barrier formations for radionuclide release in geological disposal of spent nuclear fuel elements. Consisting of particles with a very high aspect ratio, clay materials exhibit significant structural anisotropy with potential implications on their performance. In this work, the micron-scale and nanometer-scale anisotropy in compacted calcium montmorillonite and MX-80 bentonite were investigated and quantified under varying humidity conditions; the utilized novel experimental method combines X-ray microtomography (XMT) and small-angle X-ray diffraction to near-simultaneously characterize both the micron-scale 3D morphology and mineralogical properties such as clay platelet spacing in platelet stacks (tactoids) and tactoid orientation. Sedimentation during the purification process and lack of accessory minerals were found to induce much stronger orientation in purified Ca-montmorillonite as compared to the MX-80. In highly anisotropic samples, the orientation of microcracks visualized with XMT under low humidity conditions was found to correlate with the local orientation of clay tactoids measured with X-ray diffraction. The proposed experimental method can be applied to a wide range of similar materials, such as shales or samples from clayrock formations.


      PubDate: 2014-10-08T06:01:08Z
       
  • Formation mechanism of layered double hydroxides in Mg2+-, Al3+-, and
           Fe3+-rich aqueous media: Implications for neutralization in acid leach ore
           milling
    • Abstract: Publication date: Available online 6 October 2014
      Source:Applied Clay Science
      Author(s): Susanta Paikaray , Mario A. Gomez , M. Jim Hendry , Joseph Essilfie-Dughan
      Hydrotalcite-like layered double hydroxides (HT-LDHs) are important due to their extensive use in catalysis, polymer science, medicine, refractory materials, and the remediation of contaminated waters. The inclusion of several cations and anions in their structure can result in complex formation mechanisms depending on the chemical nature of the respective species. A systematic evaluation of the formation mechanism of HT-LDH from Mg2+Al3+Fe3+-rich aqueous media at ambient conditions was conducted to determine formation pathways in natural settings and in conditions observed in ore milling processes. Neutralization from pH1.7 to 12.5 (using NaOH) of individual M2+ and M3+ ions demonstrated that M3+-hydroxides precipitate first, followed by M2+-hydroxides in the order of Fe(OH)3, Al(OH)3, then Mg(OH)2. The rate of formation accelerates as pH increases. The addition of M2+ ions to M3+-hydroxides produces HT-LDH while the addition of M3+ ions to M2+-hydroxides does not. HT-LDH precipitates immediately under alkaline conditions (pH=13.2) with available M2+ +M3+ ions, while formation progresses slowly as initially acidic conditions (pH=1.7) are neutralized (to pH=12.5) via the precipitation of M3+-hydroxides and subsequently HT-LDH. This latter formation pathway is consistent with observations of the formation of MgFeAl HT-LDH during the neutralization process in an acid-leach process uranium mill: HT-LDH is first observed at pH~6.4 and is dominant at pH~8.0 or greater. At pH≥6.4, HT-LDH is co-associated with Fe3+-hydroxides. The early formation of M3+-hydroxides and substitution by M2+ ions into the structure appear to govern the overall HT-LDH formation mechanism, with the resulting excess positive charge counterbalanced by CO3 2− ions through atmospheric CO2 dissolution.
      Graphical abstract image

      PubDate: 2014-10-08T06:01:08Z
       
  • Assessment of clay consistency through conventional methods and indirect
           extrusion tests
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): R.D. Verástegui-Flores , G. Di Emidio
      The consistency of fine-grained soil is an essential parameter in soil mechanics. The most relevant consistency indices are the liquid limit and the plastic limit. The liquid limit is commonly determined through the Casagrande test or the fall cone test, while the plastic limit is determined through the hand rolling method. The greatest issue with some of these techniques is their low repeatability and operator dependency. In order to minimize those issues, an indirect-extrusion-based technique was evaluated as an alternative method to determine both consistency limits. The experimental work was carried out on mixtures of kaolin and bentonite to cover a wide range of plasticity. The results suggested that there is a specific extrusion pressure linked to each consistency limit and that the results are repeatable. The liquid limit obtained through the extrusion method closely matches the results of the fall cone test. Similarly, the plastic limit out of extrusion closely matches the results of the hand rolling method.


      PubDate: 2014-10-08T06:01:08Z
       
  • Electric–hydraulic–chemical coupled modeling of solute
           transport through landfill clay liners
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): Zhenze Li , Qiang Xue , Takeshi Katsumi , Toru Inui
      Pollutant migration in dense clay barriers appears to be strongly influenced by the electric double layer of colloidal surfaces. Osmosis that resulted from chemical potential or electric potential difference across the clay membrane has been successively described in a number of theoretical works. Streaming potential (SP) which is present in charged porous medium under hydraulic gradient has been recognized as a significant factor governing the mass migration in compacted clays. However, few studies have been carried out in geo-environmental area with regard to this physical phenomenon. A coupled model was proposed to account for the effects of electrical, chemical and fluidic fields on solute transport in porous medium in this study. The electrical field deals with both the streaming potential and the externally applied electrical potential. The coupled nonlinear partial differential equations are numerically simulated by finite element method. Both the steady state solution and the time-dependent solution were investigated with the consideration of a series of influential factors. The streaming potential coefficient and the electro-osmotic coefficient were found to control the solute transport process. The potential application of the materials with tendency of producing SP was discussed. With appropriate selection of materials and parameters, optimum barring effect could be obtained for soil barriers in waste containment applications.


      PubDate: 2014-10-08T06:01:08Z
       
  • Ceramic behaviour of some clay deposits from Guayas province, Ecuador:
           Preliminary study
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): M.M. Jordán , F. Pardo , T. Sanfeliu , S. Meseguer
      This note is a preliminary study from mineralogical and chemical points of view about the possibility of using local clays from Ecuador in industrial ceramics. The chemical and mineralogical composition of clays was determined by X-ray fluorescence (XRF) and X-ray diffraction (XRD). Also, the plasticity index (PI) was measured for each sample. Test samples were prepared by pressing and firing at different temperatures. Linear contraction (LC), water absorption capacity (WAC), and bending strength were performed to characterise the fired clays. The clay deposits studied were plastic raw materials with very high contents of quartz. The raw material in traditional ceramics in Ecuador is clay with approximate levels of silica at 60%, alumina 15%, low alkalis and carbonates, and high iron levels. The sample mineralogy indicates quartz as a primary mineral, followed by plagioclases, with hematite to a lesser extent in all the samples. Kaolinite, illite, and chlorite are the main clay minerals in the raw material samples. All the studied clays seem to be easily adaptable to a correct dry pressing ceramic process. The studied clays are an excellent raw material for the formulation of low porosity ceramic stoneware.


      PubDate: 2014-10-08T06:01:08Z
       
  • Hydrogeochemical evolution of the bentonite buffer in a KBS-3 repository
           for radioactive waste. Reactive transport modelling of the LOT A2
           experiment
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): Joaquin Salas , Clara Sena , David Arcos
      The Swedish Nuclear Fuel and Waste Management Company (SKB) is conducting a series of long term tests at the Äspö Hard Rock Laboratory to assess the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 repository for high level nuclear waste. The LOT A2 experiment consists of a vertical borehole with a central heater inside a copper tube surrounded by compacted bentonite. During four years, the temperature of the copper tube was maintained at 130°C, while the bentonite was progressively water saturated by the injection of groundwater. During this period, physical and hydro-geochemical data were collected. By using the code TOUGHREACT, a model was made to simulate the processes of solute transport which control the chemical and the mineralogical distribution observed in the bentonite at the end of the test. Additionally, a series of sensitivity analyses was performed to assess the influence of key parameters controlling the thermal–hydro-geochemical processes. Numerical results indicate that, within the first year, the heated bentonite blocks are completely water saturated, which agree with the measured data. The simulated transport of chloride, the dissolution/precipitation of Ca sulphate minerals, and the cation redistribution in the montmorillonite interlayer also agree with data measured at the end of the experiment.


      PubDate: 2014-10-08T06:01:08Z
       
  • Smectite synthesis at low temperature and neutral pH in the presence of
           succinic acid
    • Abstract: Publication date: Available online 6 October 2014
      Source:Applied Clay Science
      Author(s): Tomaso R.R. Bontognali , Francisca Martinez-Ruiz , Judith A. McKenzie , Anelize Bahniuk , Sylvia Anjos , Crisogono Vasconcelos
      In some modern natural environments, authigenic clays occur in close spatial association with microbial cells and biofilms. These clays may be the result of a microbially influenced mineralization process. To test this hypothesis, we conducted laboratory experiments with organic molecules that are commonly produced by microbes and may promote mineral nucleation within biofilms. Solutions used for the experiments contained different organic acids (i.e., oxalic acid, succinic acid, citric acid, and EDTA), sodium silicate, and different cations (i.e., Al, Mg, Ca, K). The solutions, with a pH adjusted to 7, were incubated at 25°C for 2.5 or 6months. Precipitates showing a crystalline habit formed exclusively in the presence of succinic acid. In the other experiments, amorphous silica was the only precipitated phase. Transmission electron microscopy (TEM) observations including analytical electron microscopy (AEM) analyses and selected area electron diffraction (SAED) patterns indicate that the minerals formed in the presence of succinic acid are smectites with variable Al and Mg octahedral occupancy. Mg-rich smectites show a composition broadly similar to stevensite. Succinic acid is commonly produced by aerobic microbes as intermediate product of the tricarboxylic acid cycle. Thus, this biological degradation process might promote the formation of authigenic smectites in a large variety of natural environments. Our results may lead to a revised interpretation of some smectites present in ancient sedimentary rocks, which may have formed through a microbially influenced mineralization process similar to that simulated with our experiments.


      PubDate: 2014-10-08T06:01:08Z
       
  • Using Agrawal integral equation to study the pyrolysis kinetics of
           exfoliated montmorillonite from a polyhedral oligomeric silsesquioxane
           surfactant and click chemistry
    • Abstract: Publication date: Available online 6 October 2014
      Source:Applied Clay Science
      Author(s): Hui-Wang Cui , Shiao-Wei Kuo
      In this study, the exfoliated montmorillonite was prepared through the click chemistry of a propargyl-containing intercalator with singly or multiply azido-functionalized polyhedral oligomeric silsesquioxane nanoparticles. Thermogravimetric analyses revealed that the pyrolysis kinetics had a close relationship to the layered structures, exfoliated structures, and cage-like molecules of polyhedral oligomeric silsesquioxane nanoparticles. The pyrolysis of exfoliated montmorillonite had a mechanism function of Avrami–Erofeev equation, and the kinetic compensation effect equation revealed the pyrolysis.


      PubDate: 2014-10-08T06:01:08Z
       
  • Study of cracking process of clay cap barrier in landfill using X-ray CT
    • Abstract: Publication date: Available online 6 October 2014
      Source:Applied Clay Science
      Author(s): T. Mukunoki , T. Nakano , J. Otani , J.P. Gourc
      In Japan, surface facilities are being considered, as is already the case in France, for the storage of low-activity nuclear wastes. At these sites, a compacted clay liner (CCL) in combination with different soil and geosynthetic layers is generally used as a cap barrier. The aim of the CCL is to limit the infiltration of moisture, especially that due to rainfall, through the barrier into the waste body and to inhibit the possible release of radon gas into the atmosphere. However, the cap cover may be subjected to differential settlement that could induce cracking and consequently cause loss of fluid toughness, namely; greenhouse gas emission. Indirect tensile tests, such as punching and bending tests, are carried out on the CCL to characterize its sensitivity to cracking. In this study, a method based on the use of an X-ray CT scanner is presented for determining the deformation field of the specimen. This paper first describes the X-ray CT scanner and then discusses the improved facility developed for the new device used for the bending test. It is demonstrated that this method is suitable for determining the evolution of cracking in the clay specimen. To improve the observation accuracy of the CCL due to loading, a bending apparatus is newly developed for an X-ray CT scanner. This allows the inner conditions of CCL, especially cracks, due to loading to be observed and evaluated with little disruption of the specimen behavior.


      PubDate: 2014-10-08T06:01:08Z
       
  • Direct electrochemical sensing for oxytetracycline in food using a zinc
           cation-exchanged montmorillonite
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): Junyong Sun , Tian Gan , Haijing Zhu , Zhaoxia Shi , Yanming Liu
      Direct voltammetric determination of oxytetracycline (OTC) at a zinc cation-exchanged montmorillonite modified glassy carbon electrode (Zn-Mt/GCE) was described. The OTC yielded one well-defined oxidation peak at the Zn-Mt/GCE. The experimental parameters, which influence the voltammetric responses of OTC, e.g., the pH value, scan rate and accumulation condition, were optimized. The oxidation peak current changed with the OTC concentration over the range from 0.80 to 40μM. The detection limit was 0.12μM for an accumulation time of 4min. The coefficient of variation, determined at 10μM OTC, was 3.4% (n=10). Using this method, OTC in the real food and feedstuff samples was determined.
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      PubDate: 2014-10-08T06:01:08Z
       
  • Single-stranded DNA adsorption characteristics by hollow spherule
           allophane nano-particles: pH dependence and computer simulation
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): Yoko Matsuura , Shuichi Arakawa , Masami Okamoto
      Clay mineral surfaces have been important for the prebiotic organization and protection of nucleic acids. The morphological observation to provide insight into the adsorption structure and characteristics of single-stranded DNA (ss-DNA) by natural allophane particles was presented. The molecular orbital (MO) computer simulation has been used to probe the interaction of ss-DNA and/or adenosine 5′-monophosphate and allophane with active sites. Our simulations predicted that the strand undergoes some extent of the elongation, which induces the alteration of the conformation of the phosphate backbone, base–base distance and excluded volume correlation among bases. This work demonstrates the ss-DNA adsorption by the allophane particles with novel insights into the morphological features and detailed molecular level information. The overall results support a general adsorption mechanism for the ss-DNA/allophane complexation.
      Graphical abstract image

      PubDate: 2014-10-08T06:01:08Z
       
  • Tolerance and efficacy study of palygorskite incorporation in the diet of
           laying hens
    • Abstract: Publication date: Available online 7 October 2014
      Source:Applied Clay Science
      Author(s): S. Chalvatzi , G. Arsenos , A. Tserveni-Goussi , P. Fortomaris
      The objective of this study was to assess the safety and effectiveness of palygorskite inclusion in the diet of laying hens. A total of 135 Lohmann Brown hens, aged 21weeks, were randomly assigned to one of three treatment groups (n=45): group C (control), group S (fed a diet with 1% palygorskite, standard-level) and group T (fed a diet with 9.1% palygorskite, multi-fold of standard-level). All hens were kept in commercial laying cages (3 hens per cage, 15 replicates per group). Hens of group T were used only for the first eight weeks (tolerance study period), while hens of groups C and S were kept for another sixteen weeks (efficacy study period). In each group, laying percentage, feed intake, feed conversion ratio, mortality and egg quality characteristics were assessed. The results showed that feeding a ration with 9.1% palygorskite (group T) did not have any negative effects on laying percentage (%), feed conversion ratio or health of hens. However, the body weight of hens in group T was significantly lower (P<0.001) while their feed intake was higher (P<0.001) compared to those of groups C and S for the 8-week experimental period. Furthermore, the produced eggs had significantly (P<0.001) lighter coloured egg yolk. The incorporation of 1% palygorskite in the ration for 24weeks improved laying percentage (by 2.6%, P<0.05) and feed conversion ratio (by 4.6%, P<0.05); feed intake and body weight of hens were unaffected. The produced eggs had significantly lighter eggshell and yolk colour (P<0.001) as well as increased eggshell thickness (P<0.05). It was concluded that palygorskite is a tolerable material which has the potential to improve laying hen performance and influence egg quality traits when used at recommended levels.


      PubDate: 2014-10-08T06:01:08Z
       
  • Novel method for preparation of calcined kaolin intercalation
           compound-based geopolymer
    • Abstract: Publication date: Available online 8 October 2014
      Source:Applied Clay Science
      Author(s): Lu Zeng , Dan-yang Cao , Yan Xu , Chun-wei Fan , Xiao-qin Peng
      This paper introduces a novel method for the preparation of a geopolymer using kaolinite intercalation compound which is calcined at a low temperature and forms a geopolymer by alkaline activation. The samples were characterized by X-ray diffraction (XRD), Thermogravimetric/Differential scanning calorimetry (TG/DSC) and Fourier transformed infrared spectroscopy (FTIR). Coal-bearing strata kaolin (CSK) mainly consisting of kaolinite and quartz was used to prepare the intercalation compound (CSK-K) with potassium acetate (KAc) and calcined below 400°C. The calcination temperature and the dosage of KAc were analyzed. The results showed that CSK calcined below 400 °C cannot be alkali-activated to harden and when the dosage of KAc was 30% by mass of CSK, CSK-K calcined between 350°C and 400°C can be alkali-activated to form the geopolymer with a high compressive strength around 31MPa. This was attributed to the formation of metakaolin and geopolymerization which were related to the effect of intercalation reaction and the content of K+. CSK-K calcined at low temperature has great potential as a novel material for the manufacture of geopolymers.


      PubDate: 2014-10-08T06:01:08Z
       
  • Rapid sedimentation of poly(methyl methacrylate) spheres and
           montmorillonite particles in water upon application of a DC electric field
           of the order of a few V/mm
    • Abstract: Publication date: Available online 5 October 2014
      Source:Applied Clay Science
      Author(s): Hiroshi Kimura , Shinya Takahashi , Akira Tsuchida
      It was discovered that the sedimentation velocity of colloidal particles (poly(methyl methacrylate) (PMMA) spheres and montmorillonite (Mt) particles) in water increased drastically when an electric field of the order of a few V/mmDC was applied. These particles showed up to several hundred times its sedimentation velocity in the case that the volume fraction of particles was 0.0001–0.001, and the electric field strength was less than or equal to 1.0V/mmDC. It is highly plausible that the particles gather each other and form some flocs, which leads to the increase in its sedimentation velocity. This phenomenon would appear for other various colloidal dispersions. This finding offers great potential for controlling the dispersion state of various colloidal particles in liquids using an electric field and application for a simple and efficient particle removal device.


      PubDate: 2014-10-08T06:01:08Z
       
  • Targeting of fluorescent palygorskite polyethyleneimine nanocomposite to
           cancer cells
    • Abstract: Publication date: Available online 5 October 2014
      Source:Applied Clay Science
      Author(s): Shuai Han , Feng Liu , Jiang Wu , Yu Zhang , Yujie Xie , Wenyu Wu , Weisheng Liu , Qin Wang , Yu Tang
      Palygorskite (Pal), a natural clay mineral, grafted by functional macromolecule polyethyleneimine (PEI) via the coupling grafting method, has further been modified by introducing both fluorescein isothiocyanate (FI) and folic acid (FA), with the aim of specifically targeting and detecting cancer cells. The formed Pal-PEI–FI–FA nanocomposite was nontoxic up to a concentration of 300μg·mL−1, and further could be specially taken up by HeLa cells via FA receptor-mediated endocytosis as shown by confocal microscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES) data. Therefore, it is concluded that the novel Pal-based nanocomposite has great potential for biomedical sensing, diagnosis, and therapeutics.
      Graphical abstract image

      PubDate: 2014-10-08T06:01:08Z
       
  • Introduction of aluminum to porous clay heterostructures to modify the
           adsorption properties
    • Abstract: Publication date: Available online 26 September 2014
      Source:Applied Clay Science
      Author(s): Moisés L. Pinto , Vipin Kumar Saini , José M. Guil , João Pires
      Porous clay heterostrucures (PCHs) are clay mineral based porous materials that have been mainly prepared by intercalation of structures with silica pore walls. In the present work the silica composition of the pore walls was modified by incorporating aluminum oxide, by a co-condensation methodology. Samples were characterized by nitrogen, water and toluene adsorption measurements. For the latter, heats of adsorption were measured using microcalorimetry. Characterization was also made by XRD, FTIR and chemical analysis by ICP and SEM-EDS. The materials were tested towards their selective adsorption properties, using chromatographic separation of toluene/n-heptane and toluene/cyclohexane mixtures. The amounts of aluminum that were introduced in the PCHs by the co-condensation methodology without disrupting the porous structure were limited but, still, they were able to modify the selective adsorption properties of the samples. Above a certain value it produces disruption of the pore structure.
      Graphical abstract image

      PubDate: 2014-10-02T05:00:38Z
       
  • Potential use of Argentine kaolinitic clays as pozzolanic material
    • Abstract: Publication date: Available online 26 September 2014
      Source:Applied Clay Science
      Author(s): Alejandra Tironi , Monica A. Trezza , Alberto N. Scian , Edgardo F. Irassar
      Different Argentine kaolinitic clays were selected to study their potential pozzolanic activity. The incidence of several factors such as the origin of deposits (primary or sedimentary clays), mineralogical composition, and the order/disorder degree of kaolinite structure on the pozzolanic activity was analyzed. Five clays were characterized by chemical analysis, X-ray diffraction (XRD), Fourier transformed infra-red spectroscopy (FTIR), differential thermal analysis combined with thermo-gravimetric analysis (DTA/TG), and Scanning Electron Microscopy (SEM). The crystallinity of kaolinite in raw clays was estimated by five indexes: FWHM-001, FWHM-002, Hinckley Index (HI), and R2 on the XRD patterns, whereas the P0 index was determined on the FTIR spectra. Clays were calcined at 700°C and ground until all mass passed through a 45μm sieve. Pozzolanic activity was evaluated by the Frattini test and the strength activity index (SAI) at 7, 28 and 90days using a blended cement containing 30% by weight of calcined clay. Complementary, the presence of remaining Ca(OH)2 in mortar was checked by XRD at 28 and 90days. Results indicate that four blended cements presented a very good pozzolanic activity evaluated by the Frattini test at 7 and 28days and they have a different compressive strength with a SAI>1 at 90days. In these blended cements, the Ca(OH)2 released by cement hydration was consumed. Analyzing the incidence of factors on pozzolanic activity, it can be concluded that clays containing more than 50% kaolinite provide enough amount of reactive material, and that the rate of the pozzolanic reaction is improved when the kaolinite mineral present in the clay has a disordered structure.


      PubDate: 2014-10-02T05:00:38Z
       
  • Synthesis and characterization of chlorhexidine acetate
           drug–montmorillonite intercalates for antibacterial applications
    • Abstract: Publication date: Available online 27 September 2014
      Source:Applied Clay Science
      Author(s): Kasturi Saha , B.S. Butola , Mangala Joshi
      In this study, a drug intercalated montmorillonite (Mt) has been prepared which can be useful in designing novel topical drug delivery system. The drug–Mt intercalates were synthesized by ion exchange route where interlayer cations i.e., K+, Na+ etc. of Na+–Mt exchange with the cation of the drug, chlorhexidine acetate (Ca++). The characterization of drug–Mt intercalates has been done using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric technique and energy dispersive X-ray analysis; all of which indicate successful intercalation of drug into the interlayer space. These drug–Mt intercalates strongly inhibited the growth of a wide range of microorganisms including both Staphylococcus aureus and Escherichia coli. In vitro release study of the antibacterial drug–Mt intercalates in phosphate buffer saline (pH7.4) media at 37°C was investigated. The pattern was found to be initially burst release followed by sustained release. The Ca++–Mt intercalates with a wide range of bioactivity against microbes and controlled release characteristics have the potential for application in the area of topical drug delivery.


      PubDate: 2014-10-02T05:00:38Z
       
  • Elaboration and characterization of materials obtained by pressing of
           vermiculite without binder addition
    • Abstract: Publication date: Available online 29 September 2014
      Source:Applied Clay Science
      Author(s): A.-N. Nguyen , F. Balima , P. Penhoud , L. Duclaux , L. Mirabel , L. Reinert , F. Muller , S. Le Floch , V. Pischedda , A. San Miguel , A. Beziat , P. Dehaudt , J.-F. Juliaa
      Vermiculite materials were obtained by uniaxial pressing of potassic vermiculite powders obtained by sonication without any binder addition. The vermiculite powders, made of aggregates of particles with nanometric thickness and micrometric in plane dimension, were pressed in the range 17.7–80MPa at room temperature and 200°C, and further annealed in the range 400–800°C. Pressing powders at 200°C instead of 25°C allowed the slight increase of the density of the formed materials (from 1.9 to 2g·cm−3) due to the desorption of the water molecules from the interaggregate and interparticle spaces, allowing a higher densification. The density was also increased by tailoring the particle size distribution. The pressed materials were formed of oriented arrangement of vermiculite aggregates. The porous structure, characterized by mercury porosimetry, scanning electron microscopy, and small angle X-ray scattering, was modelled by oriented oblate spheroidal pores formed in the voids between the stacked aggregates organized in a structure possessing a cylindrical symmetry. The porous structure was found to vary with the pressure and the annealing temperature.
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      PubDate: 2014-10-02T05:00:38Z
       
  • Impact of sulfate attack on mechanical properties and hydraulic
           conductivity of a cement-admixed clay
    • Abstract: Publication date: Available online 2 October 2014
      Source:Applied Clay Science
      Author(s): R.D. Verástegui-Flores , G. Di Emidio
      Context and purpose Treatment of clay with cement has been used for various ground improvement and geoenvironmental applications including vertical barriers to isolate contaminated areas. An important issue with cement-treated clays is their durability especially when applied in chemically aggressive environments. The purpose of this study is to evaluate the impact of chemical degradation on engineering properties of cement-treated clay. Methodology The mechanical and hydraulic behaviors of a cement-treated clay in contact with water and an aggressive sodium sulfate solution were investigated. Bender elements were installed in a flexible-wall hydraulic conductivity cell to simultaneously monitor the small-strain shear modulus (G0 ) and the hydraulic conductivity (k) of the cement-admixed clay. Results During permeation with clean water, an increase of G0 and a gradual decrease of k with time were observed due to cement hydration. Conversely, after permeation with the sulfate solution, a sudden decrease of G0 and a gradual increase of k were recorded. Conclusions G0 measurements provided evidence of immediate deterioration of the sample as it comes in contact with sulfates. However, in order to have significant impact on the permeability, a network of interconnected preferential flow paths had to first develop through the whole sample. Monitoring of G0 was shown to provide valuable additional information to study the impact of chemical degradation of cement-treated clays.


      PubDate: 2014-10-02T05:00:38Z
       
  • Micro- and nano-sized bentonite filled composite superabsorbents of
           chitosan and acrylic copolymer for removal of synthetic dyes from water
    • Abstract: Publication date: Available online 1 October 2014
      Source:Applied Clay Science
      Author(s): Ruma Bhattacharyya , Samit Kumar Ray
      Bentonite clay, chitosan and acrylic copolymer gels have been separately reported for the adsorption of dyes. In the present work these three kinds of adsorbents were combined to make composite hydrogels. The hydrogels were characterized by FTIR, XRD, DTA–TGA and SEM. The swelling, diffusion and network parameters of the hydrogels were also evaluated. These composite hydrogels were used for the removal of malachite green and methyl violet dyes from water. The composite hydrogels showed high adsorption and removal% of both of these dyes. The mass transfer coefficient, diffusion coefficient and thermodynamic parameters of the dye adsorption were also determined.


      PubDate: 2014-10-02T05:00:38Z
       
  • Quantification and comparison of the reaction properties of FEBEX and
           MX-80 clays with saponite: Europium immobilisers under subcritical
           conditions
    • Abstract: Publication date: November 2014
      Source:Applied Clay Science, Volume 101
      Author(s): María Villa-Alfageme , Santiago Hurtado , Miguel A. Castro , Said El Mrabet , M. Mar Orta , M. Carolina Pazos , María D. Alba
      The evaluation of the retention mechanisms in FEBEX and MX-80 bentonites, selected as reference materials to construct engineered barriers, carries major implications in the safe storage of immobilisation capacity through a recently discovered chemical retention mechanism and the structural analysis of the reaction products. Hydrothermal treatments were accomplished with immobilisation capacity through a recently discovered chemical retention mechanism and the structural analysis of the reaction products. Hydrothermal treatments were accomplished with Eu(NO3)3 (151Eu and 153Eu, with 52.2% 153Eu) and spiked with radioactive 152Eu for the quantification of the reactions. Results were compared with saponite as the reference smectite. The strong dependence of the reaction parameters with temperature and time was quantified and the reaction velocity was evaluated. The velocity follows these trends: 240days are needed for the total retention of europium for temperatures over 200°C; below 150°C, significantly longer reaction times, on the order of three years, are required to complete the reaction. Clays do not influence velocity rates, but the retention capacity of bentonites remains lower than for saponite. At 300°C, the milliequivalents retained by the three clays are consistently over CEC. The structural analyses reveal not only adsorption of europium but also the presence of Eu(OH)3 precipitation and Eu2SiO3 confirming the existence of a chemical reaction.
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      PubDate: 2014-09-18T03:20:16Z
       
  • High morphological stability and structural transition of halloysite
           (Hunan, China) in heat treatment
    • Abstract: Publication date: November 2014
      Source:Applied Clay Science, Volume 101
      Author(s): Jing Ouyang , Zheng Zhou , Yi Zhang , Huaming Yang
      Halloysite is one of the nanoscale tubular minerals in nature. This article reports the mineralogical character, dispersion treatment, structural, and morphological stabilities of a 10Å-type halloysite mineral from Hunan, China. X-ray diffraction (XRD), transmission electron microscopy (TEM), particle-size distribution and N2 adsorption–desorption isotherms were adopted to characterize the raw and calcined minerals. Ammonium lauryl sulfate was used as the surfactant to obtain mono-dispersed halloysite nanotubes. The raw mineral is a kind of tubular nanotube with a hollow interior channel, the specific surface area is 56.7m2/g. Alunitization occurred in the impure mineral. Thermal treatment to the mineral induced shrinkage of the c-axis and yielded a 7Å-type structure. The tube wall was transformed to an amorphous structure in the dehydration process at 450°C. Phase segregation occurred to yield amorphous SiO2 and γ-Al2O3 at around 1000°C. The tubular morphology can be maintained even after it is calcined at 1100°C for 6h, and the specific surface area is enlarged slightly to 65.7m2/g. While after being calcined to 1300°C, the mineral will generate mullite and silica, accompanied with collapse of the tubular walls. A schematic diagram is proposed to illustrate the structural transformation procedure. The results provide assurance to the use of halloysite in high temperature circumstances, such as three-way catalysts.


      PubDate: 2014-09-18T03:20:16Z
       
  • Contents
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100




      PubDate: 2014-09-14T02:52:55Z
       
  • Special Issue Advances in Applied Clay Science Intercalated nanomaterials:
           From functional clays to advanced hybrid lamellar compounds
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Runliang Zhu , Clément Sanchez , Faiza Bergaya



      PubDate: 2014-09-14T02:52:55Z
       
  • Integrative strategies to hybrid lamellar compounds: an integration
           challenge
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): F.M. Fernandes , H. Baradari , C. Sanchez
      During the past decades, the potential derived from the hybridization of inorganic materials, has been widely studied and presented. The capability of tuning materials’ performances, not only in terms of tailoring their physico-chemical properties to answer prerequisites of a given application, but also regarding the elaboration of novel concepts, opened a door to a radical new world in materials science. However, as a consequence of their diverse chemistry, structure, envisaged applications and historical background, each subgroup of inorganic lamellar compounds were usually discussed separately. This review intends to reflect upon the different categories of lamellar compounds and their hybridization strategies, regardless of their chemical and historical differences. The hybridization strategies of lamellar compounds are divided and presented under two main categories. Firstly, the intercalation/exfoliation approach, where the hybridization of lamellar compounds is operated in pre-formed inorganic layered materials. Secondly, the in situ synthesis methods, where the hybrid character of the layered compound is imparted simultaneously along with the layered inorganic compounds synthesis routes. Finally, in order to tackle the important question of “the place and role of hybrid lamellar compounds in consumer end-products, an integration challenge”, the proven concepts and potential applications defined for these organic-inorganic compounds are discussed.


      PubDate: 2014-09-14T02:52:55Z
       
  • Catalytic cracking of rosin over acid-activated montmorillonite catalysts
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Dong Shen Tong , You Miao Zheng , Wei Hua Yu , Lin Mei Wu , Chun Hui Zhou
      A series of acid-activated montmorillonite were prepared and evaluated as catalysts for the catalytic cracking of rosin. All the samples were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), nitrogen adsorption–desorption, temperature-programmed desorption of NH3 (NH3-TPD), scanning electron microscopy (SEM) and thermal analysis (TGA-DSC). Their catalytic performances were evaluated by the cracking of rosin in a batch reactor. The experimental results showed that acid-activated montmorillonite catalysts were active in the catalytic cracking of rosin. The acidic value of the non-essential oil products significantly declined from 163.05mg/g to 0.43mg/g and the main component in the non-essential oil and essential oil was the C13 compound. The acid treatment of montmorillonite improved the specific surface area and the amount of surface SiOH2 + groups. The moderate (Brönsted) acidity on the acid-activated montmorillonite might be responsible for the cracking of rosin.
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      PubDate: 2014-09-14T02:52:55Z
       
  • Insight into the nature of Au-Au2O3 functionalized palygorskite
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Xi He , Liangjie Fu , Huaming Yang
      The Au/palygorskite (Au/Pal) composite was prepared via supporting gold species on the surface of palygorskite. Results indicated that the dehydration of palygorskite showed obvious effect on the Au0/Au3+ molar ratio, and the generated hydroxide radicals (−OH) played a special role in the formation of Au-Au2O3 coexistence system. Au2O3 nanoparticles were formed on the hydrated (010) palygroskite surface, while Au nanoparticles were mainly on the surface of unhydrated (100) palygroskite. The decomposition of Au2O3 to metallic Au was promoted by increasing calcination temperature. However, this process would be hindered by –OH radicals produced at high temperature. The Au0/Au3+ molar ratio changed nonlinearly with the calcination temperature. The dehydration was beneficial to the formation of the chemical bonds between Au species and palygroskite. Au-Au2O3 coexistence expanded the application of gold supported composites. Atomic-level interfaces between Au species and palygorskite surface were also investigated. Realizing Au-Au2O3 coexistence by dehydration of palygorskite could provide a novel method for the synthesis of advanced mineral-based composites.
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      PubDate: 2014-09-14T02:52:55Z
       
  • From used montmorillonite to carbon monolayer–montmorillonite
           nanocomposites
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Qingze Chen , Runliang Zhu , Weixian Deng , Ying Xu , Jianxi Zhu , Qi Tao , Hongping He
      Summary background Montmorillonite (Mt) as a low-cost and high-efficient adsorbent for cationic dyes has a promising application in dye wastewater treatment. However, proper disposal of the used Mt is critical to its application. Objective In this work, the used Mt after the adsorption of crystal violet (CV) was calcined under the protection of N2, with the purpose of transforming the used Mt into carbon monolayer–Mt nanocomposites. Methods Mt, the used Mt after CV adsorption, and the calcined Mt have been characterized by XRD, FTIR, Raman spectra, thermal analysis and elemental analysis. Results X-ray diffraction results showed that calcination led to the decrease of basal spacing of the used Mt from 2.06nm to 1.34nm. As such, the interlayer spacing of the calcined Mt is 0.38nm, close to the thickness of a single graphene layer (0.34nm), suggesting the formation of carbon monolayer within the interlayer space of Mt. FTIR characterization results showed that the infrared absorption bands of CV, which were clearly displayed on the infrared spectra of the used Mt, disappeared after the calcination. On the other hand, Raman spectra clearly showed the presence of D-band and G-band on the calcined Mt. These spectroscopy characterization results further proved the formation of carbon monolayer within the interlayer spaces of Mt. Elemental analysis results showed that about 40% carbon and 22% nitrogen from CV were transformed into the carbon monolayer at 600 °C calcination, and the transformation ratios decreased to 37% and 12% respectively at 800 °C calcination. Therefore, the obtained carbon monolayer was an N-doped graphene-like material. Conclusions As such, this work provided an easy way to transform the used Mt after the adsorption of cationic dyes into carbon monolayer–Mt nanocomposites.
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      PubDate: 2014-09-14T02:52:55Z
       
  • X-ray diffraction and rheology cross-study of polymer chain penetrating
           surfactant tethered layered double hydroxide resulting into intermixed
           structure with polypropylene, poly(butylene)succinate and
           poly(dimethyl)siloxane
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Fabrice Leroux , Antoine Dalod , Mohammed Hennous , Laura Sisti , Grazia Totaro , Annamaria Celli , Christian Coehlo , Vincent Verney
      A series of layered double hydroxides interleaved with surfactant using saturated alkyl chain carboxylate anions CH3(CH2)mCOOH, even number m between 6 (C8) and 16 (C18), obtained by coprecipitation method was dispersed by melt polymer extrusion into polypropylene (PP), poly(butylene)succinate (PBS) and polydimethylsiloxane (PDMS). The hybrid LDH materials were investigated by means of X-ray diffraction and Fourier transform IR spectroscopy resulting in the presence of contracted basal spacing over the entire variation of m. Dispersion into polymer was found to yield intermixed polymer structures regardless of either the polymer or of the alkyl chain length. PP polymer chain was able to diffuse into the interlayer space, long alkyl chains (m≥14) were found to reinforce while shorter chains (m≤12) induced a plasticizing effect. For PBS and PDMS, a chain-extender-type behavior was observed. The relative change in viscosity within the frequency sweep stress linear response was visualized by the Cole-Cole representation. The molecular weight change relative to polymer free of filler and obtained from the power-law of the zero-shear viscosity η′0 was found to be linearly dependent of the basal spacing increase in the three cases. Such cross-study using XRD and melt polymer rheology was able to unravel the attritive or plastizicing role of the organoclay as function of the basal spacing expansion in the intermixed polymer structure, and to respond whether LDH interleaved platelets were of interest for polar and non-polar polymer and finally to predictively monitor the interfacial attrition by the alkyl chain length of the surfactant molecule tethered to the LDH platelets.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Palygorskite/polystyrene nanocomposites via facile in-situ bulk
           polymerization: Gelation and thermal properties
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Peng Liu , Longxiang Zhu , Jinshan Guo , Aiqin Wang , Yi Zhao , Zeran Wang
      Novel palygorskite/polystyrene (PLG/PS) nanocomposites were synthesized via the facile in-situ bulk radical polymerization of styrene in the presence of the organo-palygorskite (Org-PLG) nanorods, which was prepared by the modification of the acid-activated palygorskite (A-PLG) nanorods with the functional silane (γ-methacryloxypropyl trimethoxy silane (MPS)). The micro-gels with the Org-PLG nanorods as crosslinker were produced in the PLG/PS nanocomposites regardless of the polymerizing conditions, such as the feeding ratios of the Org-PLG, initiator and N2 atmosphere. Based on the gelation and thermal properties of the PLG/PS nanocomposites, the optimal preparation condition via the in-situ bulk polymerization was achieved and the crosslinking mechanism to the micro-gels was also depicted. This understanding should lead to a better design of clay mineral modifications for use in polymer nanocomposites.


      PubDate: 2014-09-14T02:52:55Z
       
  • Interaction between bentonite and Bacillus litoralis strain SWU9
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Qunwei Dai , Yulian Zhao , Faqin Dong , Bin Wang , Yunbi Huang
      Mineral–microbe interactions are of high importance for understanding mineral formation and dissolution. This study presents experimental results on the mineral–bacteria interaction system between bentonite and a Gram-negative Bacillus strain isolated from soil in liquid culture. Glucose consumption and pH changes were monitored and the variation of Ca2+ and Mg2+ concentrations in the solution, released from montmorillonite and chlorite in bentonite, was investigated. The influence of soil bacteria on the interlayer space was studied by X-ray diffraction analysis. The results show that bentonite acted as a good buffering effect against the decrease of pH, which enhanced the activity of the soil bacteria and promote consumption of the glucose. The release of Ca2+ and Mg2+ displayed a rising tendency with the increase of the bentonite content. The regular release of Ca2+ and Mg2+ caused by the action of the soil bacteria could be summarized as (i) CB , the net-enhancing effect of element concentrations; and (ii) dB , the net-enhancing effect per unit mass of bentonite. With the decrease of the bentonite content, the basal spacing of montmorillonite increased from 1.486nm to 1.769–2.021nm, which was induced by the bacterial metabolism. The interlayer space of montmorillonite increased in the range of 0.283–0.534nm with the decrease of mineral contents, and bacterial metabolism was responsible for this increase. The nanoparticle aggregation of mixture components was observed after the interaction between bacteria and bentonite, which may be explained by the release of Si4+, Al3+, etc. and coprecipitated into an amorphous precipitate.


      PubDate: 2014-09-14T02:52:55Z
       
  • An organoclay formula for the slow release of soluble compounds
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Guodong Yuan
      Slow-release formulations have been developed to enhance the effective use of active ingredients. In the case of fertilizers the formulations reduce nutrient leaching and greenhouse gas emissions. While polymer-coating is the dominant technology in producing slow-release fertilizers there is a demand for alternative options for different usages. To this end, a commercially available organoclay, with a basal spacing of 3.67nm, was used as matrix to produce pellets of CuSO4 and dicyandiamide (DCD) of different sizes by a die set and hand press. Both CuSO4 and DCD pellets showed a good slow-release performance in dissolution tests. Large pellets (1.2cm in diameter) of CuSO4 had a better performance in slow-release than small ones (0.7cm). For DCD pellets (0.7cm in diameter) it took 6days for a complete dissolution. The slow-release effect is probably due to the hydrophobic nature and high aspect ratio of the organoclay. The former makes soluble compounds between organoclay particles less susceptible to dissolution in water, whereas the latter hinders the dissolution of solutes inside a pellet by making their diffusion passage tortuous. The organoclay formulation is easy to make, and the rate of solute release can be adjusted by changing pellet size.


      PubDate: 2014-09-14T02:52:55Z
       
  • The protective effect of layered double hydroxide against damage to DNA
           induced by heavy metals
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Ping-xiao Wu , Wen Li , Ya-jie Zhu , Yi-ni Tang , Neng-wu Zhu , Chu-ling Guo
      The present study is part of an investigation of the protective effect of clay on DNA in adverse environmental conditions. In this paper, layered double hydroxide (LDH) was synthesized and examined as a possible gene protective material. Herring sperm DNA was intercalated into LDH by ion-exchange reaction after which the interlayer distance of LDH increased from 0.76 to 2.3nm. The DNA intercalated between the hydroxide layers and retained much of its structural integrity. After exposure of the LDH–DNA to a solution of Cd2+/Pb2+ solution, the structure of protected DNA released from LDH–DNA was virtually unchanged, in contrast to the unprotected DNA which sustained a structural damage as indicated by UV–vis spectroscopy, Cyclic voltammetry, Circular Dichroism (CD) spectroscopy and Electrophoresis. Following LDH–DNA exposure to the heavy metal solution, the concentration of Cd2+ and Pb2+ in the solution decreased from 200μg/mL to 17μg/mL and 12μg/mL, respectively, which indicates that they were also adsorbed by the clay. These data demonstrate that the LDH plays an important role in protecting the DNA against Cd2+ and Pb2+ by immobilizing metal ions. These findings give additional information on the potential implications for the clay used as gene reservoir.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Engineering small MgAl-layered double hydroxide nanoparticles for enhanced
           gene delivery
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Haiyan Dong , Min Chen , Shafiur Rahman , Harendra S. Parekh , Helen M. Cooper , Zhi Ping Xu
      In this paper we report an approach for engineering small MgAl-layered double hydroxide (sLDH) nanoparticles with the Z-average diameter of about 40nm. This method first requires co-precipitation of magnesium and aluminum nitrate solution with sodium hydroxide in methanol, followed by LDH slurry collection and re-suspension in methanol. The methanol suspension is then heated in an autoclave, followed by separation via centrifugation and thorough washing with deionized water. The nanoparticles are finally dispersed in deionized water into homogeneous aqueous suspension after 4–6day standing at room temperature. In general, sLDH nanoparticles have the Z-average size of 35–50nm, the number-average size of 14–30nm and the polydispersity index (PdI) of 0.19–0.25. The prepared sLDH suspension is stable for at least 1month when stored at fridge (2–8°C) or ambient (22–25°C) temperature. Moreover, sLDH nanoparticles are found to carry higher payloads of small double stranded DNA (dsDNA). More excitedly, sLDH nanoparticles transfect dsDNA into HEK 293T cells with a 5 to 6-fold greater efficiency compared to the larger LDH particles (Z-average diameter of 110nm).
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • High-capacity loading of 5-fluorouracil on the methoxy-modified kaolinite
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Daoyong Tan , Peng Yuan , Faïza Annabi-Bergaya , Dong Liu , Hongping He
      Kaolinite and methoxy-modified kaolinite were used as carriers for the loading of 5-fluorouracil (5FU) for the first time. The kaolinite products were characterized using X-ray diffraction, transmission electron microscopy, elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The loading mechanism of 5FU on kaolinite was as follows: the 5FU molecules were initially anchored to the external surface of kaolinite through hydrogen bonding, and the added 5FU then formed hydrogen-bonded aggregates with the anchored 5FU on the external surface of kaolinite. The surface-loaded 5FU was crystallite. The 5FU-loading content in the methoxy-modified kaolinite was 55.4mass%, which was 147.3% greater than that in unmodified kaolinite. The high-capacity loading of 5FU on methoxy-modified kaolinite resulted from two factors: (i) the interlayer space of the methoxy-modified kaolinite acted as an additional loading site that was available for the intercalation of 5FU; (ii) the loading of 5FU on the external surface of the methoxy-modified kaolinite was high because of the high affinity between 5FU and the methoxy-modified kaolinite. The 5FU-loading content of the interlayer-loaded 5FU and the surface-loaded 5FU in the methoxy-modified kaolinite was 14.6mass% and 40.8mass%, respectively. The interlayer-loaded 5FU was in an amorphous state, and of higher thermal stability than the surface-loaded 5FU. Methoxy-modified kaolinite is a promising drug carrier in pharmaceutical industry.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Enhanced heavy metal adsorption on functionalized nanotubular halloysite
           interlayer grafted with aminoalcohols
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Jakub Matusik , Anna Wścisło
      Nanotubular halloysite mineral with a 1:1 layered structure was interlayer grafted using diethanolamine and triethanolamine. The tailored materials which were stable in aqueous solutions had a constant interlayer gap equal to 3.1 or 3.6Å, respectively, and showed no swelling properties. The modification significantly improved the halloysite adsorption capacity with respect to Pb(II), Cd(II), Zn(II), and Cu(II). This was due to a two-step gradual diffusion of the metals into the interlayer space and their subsequent binding by amine nitrogen of the grafted aminoalcohol. In particular, the Cu(II) ions were preferentially removed from solution as they readily form complexes with N-donor ligands. The observed competitive protons adsorption on the amine nitrogen increased the pH of solution in contrast to system with raw halloysite where the pH decreased. The proton release in the latter system was due to domination of an ion-exchange and surface complexation removal mechanisms of the cations on the particles surface. The adsorption efficiency was related to the metal hydrolysis constants and in turn the size of the ions was less relevant. The adsorption isotherms and kinetic data in all cases followed the Langmuir and pseudo-second order equations, respectively. The applied desorption procedure illustrated a complex binding of the metals with the raw and modified mineral and showed that the materials cannot be completely recycled.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Pd hybridizing ZnO/kaolinite nanocomposites: Synthesis, microstructure,
           and enhanced photocatalytic property
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Xiaoyu Li , Huaming Yang
      A preparation strategy for constructing Pd-deposited ZnO/kaolinite was described in detail in this paper. Natural rod-like kaolinite served as a support to disperse ZnO nanoparticles through a thermal treatment. The ZnO nanoparticles were assembled on the surface of kaolinite rods to produce ZnO/kaolinite nanocomposites, which were then employed as a supporting material for the dispersion of Pd nanoparticles. The samples were characterized by XRD, FTIR, TEM, XPS, UV–vis spectroscopy, and photocatalytic property measurements. The results indicated that an obvious chemical binding existed between ZnO nanoparticles and the kaolinite surface. The shift of the binding energy of metallic Pd demonstrated a strong interaction between the metallic Pd and ZnO nanocrystals. The as-synthesized Pd–ZnO/kaolinite exhibited superior photocatalytic activity for the photodegradation of methylene blue compared with Pd/ZnO, ZnO/kaolinite, and pure ZnO, which indicated that the hybridization of the metal, kaolinite rods, and semiconductor could provide enhanced photocatalytic activity through a synergistic effect.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Simulated solar light photooxidation of azocarmine B over hydroxyl
           iron–aluminum pillared bentonite using hydrogen peroxide
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Tianyuan Xu , Yun Liu , Fei Ge , Yuting Ouyang
      Hydroxy iron–aluminum pillared bentonite (FeAlPBent) was synthesized with ion exchange method. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), BET, UV–vis diffuse spectra. The photo-Fenton catalytic activity of FeAlPBent was tested under a different reaction condition using azocarmine B (ACB) as model pollutant under simulated solar light irradiation. Response surface methodology based on Box–Behnken design was employed to investigate the effects of process variables on the removal of azocarmine B. The results indicated that hydroxy aluminum iron ions intercalated into the interlayer spaces of bentonite successfully and FeAlPBent had high photocatalytic activity. The optimum conditions for ACB removal were dye concentration of 80mg/L ACB, pH3, H2O2 concentration of 20mM and catalyst dosage of 0.6g/L. Under these conditions, the maximum ACB decolorization efficiency and TOC removal were 99.3% and 73.9%, respectively. In addition, the experiments also illustrated that FeAlPBent had a long-term stability. Furthermore, a tentative pathway for the oxidative degradation of ACB was postulated by Gaussian calculation and GC–MS analysis.


      PubDate: 2014-09-14T02:52:55Z
       
  • Adsorption–desorption behavior of naphthalene onto CDMBA modified
           bentonite: Contribution of the π–π interaction
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Liheng Xu , Ming Zhang , Lifang Zhu
      To enhance the removal of aromatic hydrophobic contaminants and to explore the π–π interaction between solute and adsorbent, organoclays modified with an aromatic long-chain alkyl surfactant, cetyldimethylbenzylammonium (CDMBA), were synthesized in this study. The adsorption–desorption behavior of naphthalene (NA) onto the resultant CDMBA-Bent (organoclays modified with CDMBA) was studied using batch-adsorption experiments. The structural characteristics of organobentonites were studied using X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR). The interlayer surfactant of CDMBA-Bent adopted similar packing pattern to that of CTMA-Bent (organoclays modified with CTMA), and the alkyl chain packing density of CDMBA-Bent was lower than that of CTMA-Bent under the same surfactant loading. The adsorption coefficients (k oc) of CDMBA-Bent towards NA were about 1.6 times higher than those of CTMA-Bent at all surfactant loadings tested. All desorption isotherms of NA from both CDMBA-Bent and CTMA-Bent showed hysteresis. The hysteresis index (calculated as k D/k A) of NA by CDMBA-Bent was much lower than that by CTMA-Bent, indicating a higher extent of irreversibility. A strong electron donor–acceptor interaction was explored between the aromatic rings of CDMBA and NA by 1H-NMR analysis. This specific π–π interaction may account for the high adsorption capacity and irreversibility of NA onto CDMBA-Bent. These results offered new insights of the adsorption mechanism of NA onto organoclay.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Synthesis of organoclays: A critical review and some unresolved issues
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Hongping He , Lingya Ma , Jianxi Zhu , Ray L. Frost , Benny K.G. Theng , Faïza Bergaya
      The synthesis of organoclays (OC) by intercalation of quaternary ammonium cation (QAC) into expanding clay minerals, notably montmorillonite (Mt), has attracted a great deal of attention during the past two decades. The OC have also found applications in the manufacture of clay polymer nanocomposites (CPN) and environmental remediation. Despite the wealth of information that exists on the formation and properties of OC, some problems remain to be resolved. The present contribution is an attempt at clarifying two outstanding issues, based on the literature and experimental data obtained by the authors over the past years. The first issue concerns the relationship between the cation exchange capacity (CEC) of the Mt and the basal spacing of the OC which, in turn, is dependent on the concentration and the nature of the added QAC. At a concentration less than 1 CEC, organo-Mt (OMt) formed using the QAC with a short alkyl chain length with nc <16 (e.g., dodecyl trimethylammonium) gives basal spacings of 1.4–1.6nm that are essentially independent of the CEC. However, for long-chain QAC with nc ≥16 (e.g., hexadecyl trimethylammonium), the basal spacing varies with the QAC concentration. For Mt with a CEC of 80–90meq/100g, the basal spacing of the OC increases gradually with the CEC and shows a sudden (stepwise) increase to 3.2–3.8nm at a QAC concentration of 1.5 CEC and to 3.5–4.0nm at a concentration of 2.0 CEC. The second issue pertains to the “locking” effect in QAC- and silane-modified pillared interlayered clays (PILC) and Mt. For silylated Mt, the “locking” effect results from the covalent bonding of silane to two adjacent layers within a single clay mineral particle. The same mechanism can operate in silane-grafted PILC but in this case, the “locking” effect may primarily be ascribed to the pillaring of adjacent basal surfaces by metal hydr(oxides).
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Editorial Board
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100




      PubDate: 2014-09-14T02:52:55Z
       
  • The effect of magnesium chloride solution on the engineering properties of
           clay soil with expansive and dispersive characteristics
    • Abstract: Publication date: November 2014
      Source:Applied Clay Science, Volume 101
      Author(s): Murat Turkoz , Hasan Savas , Aykut Acaz , Hasan Tosun
      Because expansive and dispersive soils damage engineering structures, extensive studies on using additives to ameliorate the effects of these soils have been conducted. In this study, the effect of magnesium chloride (MgCl2) solution on the engineering properties of clay soils was evaluated. Previous studies on this subject have shown that MgCl2 is more commonly used as an anti-icing agent on roads than as a soil stabilizer. MgCl2 is also used to control dust and humidity on roads and to reduce the scattering of coarse particles from road surfaces. However, as the use of MgCl2 becomes more common, its potential to improve the geotechnical properties of problematic soils will receive increasing attention. To this end, the variation in the engineering properties of expansive and dispersive clay soil samples as functions of the added MgCl2 content was investigated. First, the physical and chemical properties of the soil sample were determined. Next, the swell percentage, swell pressure, crumb, pinhole and unconsolidated undrained (UU) triaxial compression tests were performed at different curing times on samples with and without the additive by compressing the sample to achieve particular compaction characteristics. Scanning electron microscopy (SEM) analyses were performed to observe the microstructures in the sample without the additive and with the amount of additive that most strongly improved the expansive and dispersive qualities of the clay. The results show that dispersive and expansive clay soils can be effectively improved using an additive MgCl2 solution.


      PubDate: 2014-09-10T02:21:04Z
       
 
 
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