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  Subjects -> EARTH SCIENCES (Total: 586 journals)
    - EARTH SCIENCES (433 journals)
    - GEOLOGY (65 journals)
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    - HYDROLOGY (17 journals)
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EARTH SCIENCES (433 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: 6)
Aeolian Research     Hybrid Journal   (Followers: 1)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 2)
AMBIO     Hybrid Journal   (Followers: 13)
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: 14)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene Review     Hybrid Journal  
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 6)
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: 8)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 20)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 13)
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: 3)
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: 9)
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: 15)
Bulletin of Volcanology     Hybrid Journal   (Followers: 11)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 17)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
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: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 10)
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: 7)
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: 135)
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)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Spectra     Full-text available via subscription   (Followers: 11)
Ecohydrology     Hybrid Journal   (Followers: 11)
Ecological Questions     Open Access   (Followers: 6)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 9)
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
   [4 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0169-1317
     Published by Elsevier Homepage  [2563 journals]   [SJR: 0.999]   [H-I: 63]
  • Metal oxide nanoparticles deposited onto carbon-coated halloysite
           nanotubes
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Yi Zhang , Jing Ouyang , Huaming Yang
      Halloysite nanotubes (HNTs) can serve as high aspect ratio templates for the deposition of functional nanoparticles to form novel nanocomposites. We reported here on the synthesis of carbon-coated HNTs (CCH) via the carbonization of sucrose-coated HNTs in the presence of sulfuric acid. Metal oxide (MO) nanoparticles (ZnO, TiO2) were subsequently deposited on the surface of the CCH to produce MO/CCH nanocomposites. The samples were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and N2 adsorption–desorption analysis. The results indicated that graphitic carbon could improve the conductivity of HNTs, and electron transfer across the interfaces between MO and graphitic carbon led to a significant change in photocatalytic properties. MO/CCH showed good photocatalytic performance for photodegradation of methylene blue dye. The nanocomposites had two excellent advantages as a result of the unique properties of carbon, and increased adsorption of pollutants and easy charge transportation. The as-synthesized nanocomposites could have potential application in the field of wastewater treatment.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Silica nanowires obtained on clay mineral layers and their influence on
           mini-emulsion polymerisation
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Mihai Cosmin Corobea , Ignac Capek , Raluca Ianchis , Dan Donescu , Raluca Somoghi , Marius Ghiurea , Cristina Lavinia Nistor , Violeta Purcar , Ludmila Otilia Cinteza , Constantin Radovici , Gabriel Prodan
      The increased interest in silica nanowires for nanophotonics, mechanical applications, microsurgery, chemical and biological sensors strongly motivates the search for new discoveries involving complex silica nanowire-clay mineral layers (SiNW), particularly focusing on their growth mechanism, their involvement during polymer synthesis and the generation of a new class of polymer nanocomposites. This paper addresses the major findings involving the growth mechanism of silica nanowires on the clay mineral layers as well as their high segmental mobility and influence on the kinetics of butylacrylate mini-emulsion radical polymerisation. The growth mechanism for the silica nanowires was a sol-gel process involving tetraethylorthosilicate at the edge groups of the clay layers after blocking the reactive sites with a monofunctional alkoxysilane. To demonstrate the mobility of the network, an indirect method was utilised, specifically the interaction between the ethoxylated molecules and Tween 60. No cross-linking side effects occurred in the silica nanowires. SiNW enhance the free radical polymerisation of butylacrylate in dispersed media, increasing the monomer conversion from 2.5% to 33%. The kinetics of the polymerisation process can be tuned by SiNW, modulating the system between emulsion- and mini-emulsion-like systems by acting on the pseudo-steady state interval of the radicals (10%–40% conversion).


      PubDate: 2014-06-14T17:11:06Z
       
  • Determination of optimum concentration of cloisite in an eco-friendly
           silane sol-gel film to improve corrosion resistance of mild steel
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): N. Asadi , R. Naderi , M. Saremi
      In this study, the effect of cloisite concentration on the protective performance of an eco-friendly silane sol-gel coating consisting of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and glycidyloxypropyltrimethoxysilane (GPS) applied on mild steel substrate was investigated using electrochemical techniques and surface analysis. Through taking advantage of electrochemical impedance spectroscopy, potentiodynamic polarization and electrochemical noise measurements, the optimum concentration of nanoparticles was determined. In the presence of the cloisite content, superiority of the hybrid silane film was connected to the enhanced barrier properties, confirmed by FE-SEM, FTIR and water contact angle studies. Moreover, a good trend correlation was observed between the noise resistance and low-frequency impedance modulus data.


      PubDate: 2014-06-14T17:11:06Z
       
  • Physicochemical and catalytic properties of montmorillonites modified with
           12-tungstophosphoric acid
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Aleksandra Pacuła , Katarzyna Pamin , Adam Zięba , Joanna Kryściak-Czerwenka , Zbigniew Olejniczak , Ewa M. Serwicka , Alicja Drelinkiewicz
      Background The catalytic performance of supported heteropolyacids in various liquid–solid and gas–solid heterogeneous reactions may be affected by the choice of support and/or the method of heteropolyacid deposition. Main methods Radioligand binding assays were used to quantify affinity, density and ratio of ET receptors. Design/methodology 12-tungstophosphoric acid (HPW) was dispersed throughout three matrixes: Na, H-exchanged montmorillonites (Na-Mt, H-Mt) derived from Polish bentonite and commercially available K10 montmorillonite (Mt-K10). Two series of catalysts were prepared via conventional and modified impregnations. Conventional procedure based on the incipient wetness impregnation method involved stirring of the aqueous dispersion of HPW and montmorillonite, followed by drying at elevated temperature. Modified preparation method employed ultrasonication as a means of the dispersion homogenization, followed by freeze-drying. The catalysts were characterized by XRD, N2 sorption, TG analysis, FT-IR and 31P solid-state MAS-NMR spectroscopy. The acidic properties of HPW/montmorillonites were examined in the conversion of ethanol, whereas their catalytic performance was evaluated in the transesterification of castor oil with methanol. Findings Intact Keggin anions were preserved on H-Mt and Mt-K10, while lacunary Keggin anions dominated on Na-Mt (especially after deposition aided by ultrasonication). Appropriate choice of the montmorillonite support and/or pretreatment allowed tailoring of the acidic function of the heteropolyacid supported catalysts. The use of H-Mt prepared under mild conditions resulted in enhanced acidity and high catalytic performance of acid catalysts, whereas the use of Na-Mt, aided by ultrasonication diminished their acidic function and catalytic activity. The most important achievement was to obtain HPW/montmorillonite system more active than unsupported HPW, via spreading heteropolyacid on H-Mt derived from Polish bentonite.


      PubDate: 2014-06-14T17:11:06Z
       
  • Chemo-mechanical modelling of lime treated soils
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): V. Robin , O. Cuisinier , F. Masrouri , A.A. Javadi
      Lime treatment has been widely used to improve mechanical properties of soils. However, less has been done to account for the effect of the treatment on constitutive relationships. In this study, a comprehensive programme of isotropic consolidation tests and drained triaxial experiments were designed and carried out on saturated specimens of a silt treated with quicklime. The chemical composition in hydrates, portlandite, and carbonates was determined using thermogravimetric analysis and differential thermal analysis. The modifications to the mechanical parameters of the soil were evaluated in the framework of the Cam Clay elastoplastic model. The experimental results revealed that the addition of lime leads to the modification of the critical state. For concentrations in lime higher than 1%, the treated specimens displayed a different normal compression line compared to the untreated state. Chemical analysis revealed the production of cementitious compounds for every concentration tested. A constitutive model was proposed to describe the observed behaviour of lime treated soils in the framework of the Structured Cam Clay. The model accounts for the modifications on the mechanical parameters of the soil. A chemo-mechanical coupling was established between the yield stress and the mass concentration in cementitious compounds.


      PubDate: 2014-06-14T17:11:06Z
       
  • Photocatalytic degradation of anionic and cationic dyes over TiO2 P25, and
           Ti-pillared clays and Ag-doped Ti-pillared clays
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): K. Sahel , M. Bouhent , F. Belkhadem , M. Ferchichi , F. Dappozze , C. Guillard , F. Figueras
      Ti-pillared clay and a Ag doped Ti-PILC have been synthesised and characterised and their photocatalytic efficiency in the degradation of methylene blue and Remazol black dyes was compared with the efficiency of P25 titanium oxide. In the dark, the adsorption of methylene blue on Ti-clays is total and fast. Ag doping of the clay increases this kinetics of adsorption, but does not alter the amount adsorbed. In that case adsorption, by cation exchange, is the cause of the disappearance of the reactant from the solution and photocatalytic properties cannot be investigated. In contrast, for Remazol black, the amount adsorbed is small, and decreases upon Ag doping in agreement with its adsorption properties. The comparison of the different solids in the photocatalytic degradation of Remazol black shows that TiO2 remains the best catalyst. The Ti-pillared beidellite shows a low activity, which is decreased by addition of Ag but increases proportionally to the content of Ti. The effect of ultrasonic treatment of the reaction medium containing the Ti-PILC has also been investigated and discussed taking into account the release of semiconductor and the decrease of diffusion.


      PubDate: 2014-06-14T17:11:06Z
       
  • Chromium VI adsorption from sodium chromate and potassium dichromate
           aqueous systems by hexadecyltrimethylammonium-modified zeolite-rich tuff
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): N. Salgado-Gómez , M.G. Macedo-Miranda , M.T. Olguín
      In the present investigation, zeolite-rich tuff from the state of Chihuahua, which was conditioned with a sodium chloride solution and subsequently modified with a hexadecyltrimethylammonium bromide solution, was used to evaluate the removal of Cr(VI) from aqueous systems prepared with Na2CrO4, K2Cr2O7 or a mixture of both Na2CrO4 and K2Cr2O7 salts. The zeolitic materials were characterized by scanning electron microscopy and X-ray diffraction, and their surface area was also determined. These experiments were performed in a batch system in which the influences of the pH, contact time between phases, and concentration of Cr(VI) in solution on the adsorption of Cr(VI) by surfactant-modified zeolite-rich tuff were investigated. The removal efficiency of chromium ions from aqueous solution is influenced by pH and the specific chromium species involved plays an important role in the adsorption process. The Cr(VI)-Na2CrO4 and Cr(VI)-K2Cr2O7 adsorption kinetics data were fit to a pseudo-second-order model, and the Langmuir isotherm adequately described the experimental results of these mono-component systems. In the Cr(VI)-Na2CrO4:Cr(VI)-K2Cr2O7 mixture, the surfactant-modified zeolite-rich tuff adsorbed more Cr(VI) depending on the initial ratio of Na2CrO4:K2Cr2O7 salts in the bi-component aqueous system.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Allophane–Pt nanocomposite: Synthesis and MO simulation
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Shuichi Arakawa , Yoko Matsuura , Masami Okamoto
      Allophane nanoparticles were synthesized through a hydrothermal treatment of precursor with Si/Al molar ratio of 0.75 at 100°C for 48h and characterized by using field emission scanning electron microscopy, pore-size distribution based on the Cranston–Inkley method, 29Si and 27Al magic angle spinning nuclear magnetic resonance, X-ray diffractometry, and energy dispersive X-ray spectroscopy. It is demonstrated that the synthetic allophane nanoparticle leads to a novel allophane–Pt nanocomposite with the metal particle size of ~2nm and narrow size distribution. The synthetic allophane particles promote the reduction of K2PtCl4 to Pt0 and act as a support substratum. The molecular orbital computer simulation was performed to provide insight into the structure and stability of Pt nanoparticles during complexation by the functional (OH)Al(OH2) groups on the wall perforations of the synthetic allophane.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Facile preparation of highly exfoliated and optically transparent
           polycarbonate (PC)/clay mineral nanocomposites using phosphonium modified
           organoclay mineral
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Supratim Suin , Nilesh K. Shrivastava , Sandip Maiti , B.B. Khatua
      Here, we focus on the morphology, mechanical and optical properties of the polycarbonate (PC) in the PC/clay mineral nanocomposites prepared through both the melt and solution blending technique at two different loadings (0.5 phr and 1 phr) of propyl triphenyl phosphonium modified montmorillonite (PTPP-Mt). The modified organo-Mt was prepared by ion exchange reaction and verified through FTIR spectroscopy, EDS study and XRD analysis. The outstanding thermal stability of the PTPP-Mt at the processing temperature of PC (280°C) made it a suitable candidate for the preparation of optically transparent PC/Mt nanocomposites. The XRD analysis over the PC/PTPP-Mt nanocomposites revealed the destruction of ordered geometry of the clay mineral, whereas, the presence of some localised zones of Mt was evident from transmission electron microscopic (TEM) analysis. Thermal analysis indicated an increase in glass transition temperature (Tg) and thermal stability of PC in the nanocomposites. The strength and modulus of the nanocomposites were increased with increase in Mt loadings. An increase in storage modulus in the nanocomposites was evident from the thermomechanical studies. Finally, the optical transparency of PC was retained without generation of any colour in the PC/PTPP-Mt nanocomposites.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Simultaneous purification and modification process for organobentonite
           production
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Z. Yeşilyurt , F. Boylu , K. Çinku , F. Esenli , M.S. Çelik
      Bentonites are commonly subjected to a water and energy intensive purification process in order to obtain high-grade montmorillonite, prior to modification to suit technological needs. In this study, the purification and modification processes were combined in order to minimize costs. A method for the production of organobentonite from roughly purified Na-bentonite from Reşadiye, Turkey, was proposed with a quaternary alkylammonium salt, hexadecyl trimethyl ammonium bromide. Further purification and ion exchange reactions were simultaneous within a centrifugal separation process, followed by the removal of excess modifier agent using the flotation method. The parameters of centrifugal force, feed solid content for Falcon concentrator and modification time, and the amount of alcohol for ion exchange reactions were optimized. Ammonium intercalated organoclays were characterized by X-ray diffraction analysis, thermogravimetric analysis, and swelling tests in organic liquids. An optimum flow sheet for the simultaneous purification and modification process yielding a 97% pure organobentonite with a 2.02nm basal spacing was developed.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Thermal stability and decomposition kinetics of styrene-butadiene rubber
           nanocomposites filled with different particle sized kaolinites
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Yude Zhang , Qinfu Liu , Jingjing Xiang , Ray L. Frost
      A series of styrene-butadiene rubber (SBR) nanocomposites filled with different particle sized kaolinites are prepared via a latex blending method. The thermal stabilities of these clay polymer nanocomposites (CPN) are characterized by a range of techniques including thermogravimetry (TG), digital photos, scanning electron microscopy (SEM) and Raman spectroscopy. These CPN show some remarkable improvement in thermal stability compared to that of the pure SBR. With the increase of kaolinite particle size, the residual char content and the average activation energy of kaolinite SBR nanocomposites all decrease; the pyrolysis residues become porous; the crystal carbon in the pyrolysis residues decrease significantly from 58.23% to 44.41%. The above results prove that the increase of kaolinite particle size is not beneficial in improving the thermal stability of kaolinite SBR nanocomposites.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Effect of pore water chemistry on the hydro-mechanical behaviour of
           Lianyungang soft marine clay
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Y.F. Deng , X.B. Yue , Y.J. Cui , G.H. Shao , S.Y. Liu , D.W. Zhang
      The effect of pore water chemistry on the hydro-mechanical behaviour of soft marine clay of Lianyungang was investigated. Field investigation and piezo-cone penetration tests at two sites with 0.56% and 4.91% salinity respectively were first performed, and a significant difference was observed in terms of Atterberg's limits (LL and PL), density, net tip resistance, sleeve friction and pore water pressure parameter, suggesting a significant effect of pore water chemistry. To confirm this observation, identification tests were extended to an artificial soil corresponding to a mixture of kaolinite/bentonite with different salinities. The results obtained confirm the significant effect of pore water chemistry. To further clarify this effect, oedometer tests were performed with both site water and deionised water. The results indicated that the compression index, swelling index, and secondary consolidation coefficient are higher in the case of deionised water, whereas the oedometer modulus, consolidation coefficient and hydraulic conductivity are larger in the case of site water. However, the ratio between secondary consolidation coefficient and compression (or swelling) index indicates no significant effect of pore water salinity. After completion of the oedometer tests, the microstructure features were studied by the mercury intrusion porosimetry. The results showed that deionised water led to an increase of porosity, whereas the site water led to a decrease of porosity.


      PubDate: 2014-06-14T17:11:06Z
       
  • Adsorption of Cu2+ and methylene blue on dodecyl sulfobetaine
           surfactant-modified montmorillonite
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Hongwei Fan , Limei Zhou , Xiaohui Jiang , Qiang Huang , Wencheng Lang
      The dodecyl sulfobetaine surfactant-modified montmorillonite (Mt-SB12) was synthesized using montmorillonite (Mt) and dodecyl sulfobetaine surfactant. The as-prepared material was used as adsorbent for removal of Cu2+ and methylene blue (MB) in single and binary systems. In the single systems, the results showed that the kinetics of adsorption followed the linear pseudo-second-kinetic model. The results of interlayer diffusion indicated that MB had higher diffusion rate than Cu2+. For the Mt-SB12, the isotherm results showed that MB adsorption followed the Langmuir and Cu2+ adsorption followed the Freundlich isotherm. The adsorption capacities for Cu2+ and MB at 298K and pH5 were (10.2 and 254.0) mg/g, respectively. For the Mt, Cu2+ and MB adsorptions both followed the Langmuir. The adsorption capacities for Cu2+ and MB at 298K and pH5 were (9.5 and 150.2) mg/g, respectively. So the dodecyl sulfobetaine surfactant-modified Mt is more beneficial to adsorb MB than Mt. Dubinin–Radushkevitch (D–R) equation indicated Cu2+ and MB adsorptions were chemical ion exchange adsorption and adsorption thermodynamics showed they were spontaneous and endothermic processes. In binary systems, Cu2+ and MB showed competitive adsorption. The adsorption capacity of Cu2+ or MB would be decreased with the increased concentration of another adsorbate. Mt-SB12 exhibited relative higher affinity and selectivity to MB.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • HT-XRD non-isothermal kinetics study of delamination of kaolinite from
           termite mound
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Petr Ptáček , Tomáš Opravil , František Šoukal , Jiří Brandštetr , Jaromír Havlica , Jiří Másilko
      The kinetics and mechanism of delamination including the destruction of kaolinite layered structure of kaolinite from termite nest were investigated by non-isothermal high-temperature X-ray diffraction analysis. The process is controlled by the rate of the 2nd order chemical equation described by the kinetic function F2 : (g( α )=(1−y)−1 −1). The apparent activation energy was assessed to be 417±9kJ·mol−1. The delamination is considered as the first step of the thermal transformation of kaolinite into metakaolinite but the temperature at which the maximum rate of dehydroxylation was reached is lower than the temperature for the maximum rate of delamination if a heating rate of ≤5°C·min−1 was applied and higher for heating rates ≥15°C·min−1. The superposition of both processes within the heating rates of 5 to 15°C·min−1 led to a significant decrease of activation energy. This behavior provides an option to modify the degree of metakaolinite delamination during the thermal treatment.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Pozzolanic consolidation of stabilized soft clays
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): V.R. Ouhadi , R.N. Yong , M. Amiri , M.H. Ouhadi
      The presence of soft clays underlying foundations has been responsible for failures in several geotechnical and geo-environmental projects. The three aspects of this study dealing with the stabilization of a soft clay through the addition of cement and lime include: (a) determination of the optimum proportions of both cement and lime needed to obtain a stabilized soil, (b) the phenomenon of pozzolanic consolidation which occurs in the cement–lime stabilized soft clay, and (c) using knowledge of the pre-consolidation stress and compression index of the stabilized soft clay as a practical criterion for determination of the optimum additive percentage in soft clays stabilization. The experimental research program designed to investigate the behavior of the soft clay before and after stabilization involved a series of tests that included sedimentation testing, cation exchange capacity measurement, X-ray diffractometry, unconfined compression and consolidation tests. The results indicate that pozzolanic reaction creates a form of pre-consolidation in the cement–lime stabilized soft clay. The reduction in soil settlement is attributed to the pozzolanic reaction in soil-additive interaction resulting in an increase in pre-consolidation stress of stabilized soil. The test results show that pozzolanic consolidation causes an increase in initial pre-consolidation stress of 70kN/m2 for a soft clay soil to 375kN/m2 for the stabilized soil with 6% lime, and to 385kN/m2 for stabilized soil with 6% cement. The series of XRD experiments conducted are used to study the micro-structural aspects of the stabilized soil. The results show that pozzolanic consolidation not only improves strength behavior of clay soils in general, but also reduces the potential for large settlements of the stabilized soft clays — indicating that there is considerable merit in using the consolidation behavior of the stabilized soft clays as a means for determining the required percentages of additives for cement–lime stabilization of soft clays and soft soils in general.


      PubDate: 2014-06-14T17:11:06Z
       
  • Solar photocatalytic degradation of methylene blue by mixed metal oxide
           catalysts derived from ZnAlTi layered double hydroxides
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Xiaorong Wang , Pingxiao Wu , Zhujian Huang , Nengwu Zhu , Jinhua Wu , Ping Li , Zhi Dang
      ZnAlTi layered double hydroxides (LDHs) with different Zn:Al:Ti ratios were synthesized by homogeneous precipitation method utilizing urea hydrolysis. The synthesized samples were calcined at 873K in order to obtain mixed metal oxides with high photocatalytic activity. Multiple characterizations such as XRD, FT-IR, TG–DSC, XPS, XRF, N2 adsorption–desorption isotherms and UV–vis DRS were carried out. The photocatalytic activity was evaluated by degradation of methylene blue (MB) dye under solar light irradiation. The experimental parameters such as the catalyst with different molar ratios, catalyst dose, initial MB concentration, and initial pH were studied in detail. A maximum of 99% photodegradation of MB was achieved with the catalyst loading of 1.0gL−1 and initial MB concentration of 10mgL−1, at the condition of neutral pH. The kinetic study indicated that the photocatalytic process was well fitted to the Langmuir–Hinshelwood model. Furthermore, after three cycles, the degradation of MB was still close to 90%, indicating that the photocatalyst had high stability for recycle.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Surfactant modified bentonite (CTMAB-bentonite) as a solid heterogeneous
           catalyst for the rapid synthesis of 3,4-dihydropyrano[c]chromene
           derivatives
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): M.E. Sedaghat , M. Rajabpour Booshehri , M.R. Nazarifar , F. Farhadi
      CTMAB-bentonite was found to be an efficient catalyst for the synthesis of 3,4-dihydropyrano[c]chromene derivatives by one-pot reaction of 4-hydroxycoumarin, aromatic aldehydes, and malononitrile in aqueous ethanol under mild condition. High yields, short reaction time, easy work-up, eco-friendly, non-toxic and reusable catalyst are the advantages of this procedure.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Fourier transform infrared spectroscopy analysis for hydrothermal
           transformation of microcrystalline cellulose on montmorillonite
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Lin Mei Wu , Dong Shen Tong , Li Zhi Zhao , Wei Hua Yu , Chun Hui Zhou , Hao Wang
      Specifying the interactions between montmorillonite and cellulose is helpful for understanding the evolution of biomass in soil and the geological formation of fossil fuels in nature. In this work, Fourier transform infrared spectroscopy was used to investigate the hydrothermal transformation of microcrystalline cellulose on montmorillonite. A series of samples were obtained from hydrothermal treatments of microcrystalline cellulose with montmorillonite in various ratios at 200°C for 16h. The resulting solid samples were analyzed by using Fourier transform infrared (FTIR) spectroscopy. The subtle changes before and after hydrothermal treatments were particularly studied by using mathematical methods to generate second derivatives of absorbance spectra. It was found that there were interactions between montmorillonite and microcrystalline cellulose during the hydrothermal process. In the presence of montmorillonite, the cellulose was transformed to yield a product with aliphatic CHx and aromatic groups. These were further confirmed by the FTIR spectra of the samples which were further treated by using an HCl/HF acid solution to remove the montmorillonite in them (demineralization). The structural parameters (‘A Factor’, ‘C Factor’ and CH3/CH2 ratio) were calculated. The values of the ‘A Factor’ and CH3/CH2 ratio of the resulting solid samples increased with the increase of montmorillonite. The values of ‘C Factor’ were little affected by the montmorillonite minerals. The findings suggested that montmorillonite-assisted hydrothermal treatment of cellulose was able to produce kerogen analogs.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Editorial Board
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95




      PubDate: 2014-06-14T17:11:06Z
       
  • Uses of near-infared spectra for the identification of clay minerals
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): J.L. Post , S.M. Crawford
      Aspects of clay mineralogy can be determined by the use of near-infrared (NIR) spectra. Beginning with fibrous clay minerals, the combination band spectra do not change position with changes in metal oxide content. Other clay mineral spectra were compared to determine whether this is unusual. These include NIR spectra of chlorite, micas and their alteration products, montmorillonites, and the kaolin group of clay minerals. None are fixed as sepiolite and palygorskite are. For all clay mineral IR spectra only the fibrous clay mineral spectra are fixed. The correlation of the OH fundamental and first overtone OH spectral wave numbers are a constant of 1.955. The kaolin group is readily differentiated by their combination band spectra, such as kaolinite and dickite.


      PubDate: 2014-06-14T17:11:06Z
       
  • Hydrotalcite-like compounds: A way to recover a hazardous waste in the
           aluminium tertiary industry
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): R. Galindo , A. López-Delgado , I. Padilla , M. Yates
      Magnesium–aluminium hydrotalcite-like compounds at ratios of 2:1, 3:1 and 4:1 were prepared using a non-conventional aluminium source, the hazardous wastes from the aluminium tertiary industry. The method consisted in a conventional coprecipitation at constant pH10 with magnesium chloride hexahydrate and stable solutions of Al3+ from dispersions of the fine powder from the sleeve filter suction system in the aluminium slag milling process. The characterisation of the resulting materials indicated that hydrotalcites were strongly dependent on the presence of iron in the layers, as well as the carbonate and chloride content in the interlayer which affected the final properties. XRD and SAED indicated low crystallinity for these materials. Furthermore, as can be seen by SEM, the formation of disordered tiny nuclei was significant causing small spherical agglomerates. The infrared spectra showed a change of symmetry in the interlayer for the different ratios and the textural data suggested the “ink-bottle shaped” mesopores and type IIb isotherms, similar to the results obtained for pillared clays, and the transition to H2 type in the hysteresis loops as a function of the higher ratio.


      PubDate: 2014-06-14T17:11:06Z
       
  • Dissolution of iron in salicylic acid and cation exchange between
           Fe(II)-salicylate and Na-montmorillonite to form Fe(II)-montmorillonite
    • Abstract: Publication date: Available online 2 June 2014
      Source:Applied Clay Science
      Author(s): Belenahalli M. Vinoda , Jayappa Manjanna
      Bentonite is used as part of engineered barrier in the geological disposal of high-level nuclear waste (HLW) from nuclear plants. Fe(II)-montmorillonite, Fe(II)-Mt, is a potential altered clay in such a system due to clay mineral interaction with the carbon steel (overpack material) under reducing water chemistry conditions. To understand the long-term integrity of the HLW, the basic studies on Fe(II)-Mt are needed. In this study, we have focused on the synthesis of homoionic Fe(II)-Mt by using weak ferrous complexe for cation-exchange with Na-Mt. We prepared Fe(II)-salicylate by dissolving Fe0 in salicylic acid at 80°C under N2 atmosphere. Dissolution rate constants are in the range of 0.8–1.6×10−3 min−1. A colorless Fe(II)-L, was reasonably stable in the inert atmosphere, but was rapidly oxidized in air to a red colored Fe(III)-L (λ max 475nm). The solution redox potential and UV–Vis absorption spectra of these complexes are recorded here. Na-Mt was subjected for ion-exchange reaction with Fe(II)-L to form Fe(II)-Mt. The formation of Fe(II)-Mt was confirmed from the interlayer Fe2+ ions released by interacting with 0.5M H2SO4. The cumulative amount of Fe2+ ions are equivalent to CEC of 1.10meq/g and Fe2+/Fetotal ≈1. The X-ray diffraction patterns (d001) and infrared spectra also support the formation of Fe(II)-Mt. The cation exchange achieved here was possible through dissociation of Fe(II)-L owing to its intermediate stability constant (log K=6.55), unlike the Fe(III)-L (log K=16.35). We believe the present method is one of the best approaches for obtaining homoionic Fe(II)-Mt.


      PubDate: 2014-06-14T17:11:06Z
       
  • 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: Available online 6 June 2014
      Source:Applied Clay Science
      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: 2014-06-14T17:11:06Z
       
  • An experimental investigation on the secondary compression of unsaturated
           GMZ01 bentonite
    • Abstract: Publication date: Available online 6 June 2014
      Source:Applied Clay Science
      Author(s): W.M. Ye , X.L. Lai , Q. Wang , Y.G. Chen , B. Chen , Y.J. Cui
      The secondary compression behavior of compacted GMZ01 bentonite was experimentally investigated by conducting a series of suction-controlled high-pressure oedometer tests. GMZ01 bentonite powder was first exposed to suction controlled conditions at 110MPa and then statically compacted to a dry density of 1.70g/cm3. Then, the compacted samples were hydrated to designed suctions using the vapor equilibrium technique and finally submitted to multi-staged loading oedometer tests. Corresponding results were presented in terms of stress–strain-time curves. Based on the test results, the incremental compression index C c ∗ and secondary compression index Cα were defined. Relationships between C c ∗, Cα , vertical stress and suction were analyzed. It is observed that both C c ∗ and Cα increase linearly with increasing vertical stress, which is different from the convex relationship reported by other researchers in saturated soils. Moreover, C c ∗ and Cα also increase with decreasing suction. The relationship between C c ∗ and Cα is linear in the considered stress range and the slope of this linear relationship (C α /C c ∗) increases with decreasing suction. Finally, a logarithm function is established between C α ∗/C c ∗ and suction s, which represents the coupling of suction, creep and stress of GMZ01 bentonite.


      PubDate: 2014-06-14T17:11:06Z
       
  • Lignosulfonate as dispersant for layered double hydroxide in
           nitrile–butadiene rubber composites
    • Abstract: Publication date: Available online 6 June 2014
      Source:Applied Clay Science
      Author(s): Suo Xiao , Yating Tan , Jianshuang Xu , Chen Xiong , Xi Wang , Shengpei Su
      Nitrile–butadiene rubber (NBR) based layered double hydroxide (LDHs) composites have been prepared through melt-compounding method using sodium lignosulfonate modified LDH (SLS–LDH) as a filler obtained by in-situ synthesis method. The composites were characterized in terms of LDH particles dispersion, mechanical properties and thermal properties. Both X-ray diffraction and scanning electron microscopy analysis data of the composites showed that layered SLS–LDH particles were obtained and SLS improved the dispersion of LDH particles in the NBR matrix. Experimental results indicated that both pristine LDH and SLS–LDH improved the mechanical properties of NBR composites while SLS–LDH showed a more obvious reinforcing ability compared with pristine LDH. The thermal stability of composites containing SLS–LDH was remarkably improved when 50% weight loss was selected as a point of comparison in thermogravimetric analysis. Differential scanning calorimetry analysis data showed that the glass transition temperature of the SLS–LDH/NBR composites increased when compared with LDH/NBR composites indicating the enhancement of interactions between NBR chains and LDH particles in the presence of SLS.


      PubDate: 2014-06-14T17:11:06Z
       
  • Hydro-mechanical analysis of GMZ bentonite–sand mixtures in the
           water infiltration process as the buffer/backfill mixture in an engineered
           nuclear barrier
    • Abstract: Publication date: Available online 6 June 2014
      Source:Applied Clay Science
      Author(s): Ming Zhang , Huyuan Zhang , Lang Zhou , Baoming Wang , Songjiang Wang
      A series of unsaturated tests on the GMZ bentonite–sand mixture at different dry densities and sand ratios are analyzed. This mixture is proposed as buffer/backfilling material in the Chinese concept for radioactive waste disposal. The water retention properties were studied under both confined and unconfined conditions; the results show that the water retention capacity is independent of the confined conditions and dry density if the suction is greater that about 4–5MPa, and by contrast, at low suctions (<4–5MPa) the confined conditions and dry density influence the water retention capacity. However, the water retention capacity is always influenced by the presence of sand. The unsaturated hydraulic conductivity was determined in the infiltration test by the special apparatus designed by the authors. The value of unsaturated hydraulic conductivity did not change significantly with the dry density changing from 1.50 to 1.90Mg/m3 or sand ratio increasing from 30% to 50%, always lower than 2.0×10−12 m/s. Furthermore, the swelling pressure at different position of specimen was monitored during the infiltration process, and the dry density distributions have also been determined at the end of the tests. Therefore, this method can be used for engineering purposes to predict the unsaturated hydraulic parameters at an early stage of a design to get an idea of the required design and hence, cost.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Industrially applicable methods of poly(methyl methacrylate)/organophilic
           montmorillonite nanocomposites preparation: Processes and cast materials
           characterization
    • Abstract: Publication date: Available online 6 June 2014
      Source:Applied Clay Science
      Author(s): Krzysztof Kowalczyk , Tadeusz Spychaj , Agnieszka Ubowska , Beata Schmidt
      The poly(methyl methacrylate) (PMMA)/organophilic montmorillonite cast nanocomposites were prepared via bulk free-radical polymerization of raw monomer (MMA) and PMMA/MMA syrup. Three types of commercial organophilic montmorillonites (o-Mt) (swelled in either MMA or syrup and additionally homogenized in a high-speed flow homogenizer or twin-screw extruder, respectively) have been utilized to PMMA panels manufacturing. An influence of o-Mt type and content as well as its dispersion methodology on mechanical, thermal and optical properties has been investigated. Although PMMA panels containing o-Mt exhibited similar tensile strength (in respect to unmodified PMMA samples), higher hardness (+2 HBa units) and flexural strength (+15% for PMMA prepared using raw monomer and unhomogenized o-Mt/MMA paste) have been observed. Moreover, introduction of o-Mt into polymeric matrix resulted in increased thermal stability, Vicat softening temperature (+5°C) and glass transition temperature value determined by DMTA technique (+5°C for PMMA/o-Mt composites prepared from syrup with non-extruded clay mineral paste). XRD and TEM analysis showed full or partial exfoliation of organophilic montmorillonites in polymer matrix, respectively.


      PubDate: 2014-06-14T17:11:06Z
       
  • Integrative strategies to hybrid lamellar compounds: an integration
           challenge
    • Abstract: Publication date: Available online 6 June 2014
      Source:Applied Clay Science
      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: 2014-06-14T17:11:06Z
       
  • EXAFS and XRD studies in synthetic Ni-fluorohectorite
    • Abstract: Publication date: Available online 6 June 2014
      Source:Applied Clay Science
      Author(s): Leander Michels , Luciano Ribeiro , Maria Suely Pedrosa Mundim , Marcelo Henrique Sousa , Roosevelt Droppa Jr. , Jon Otto Fossum , Geraldo José da Silva , Kleber Carlos Mundim
      In the present work the synthetic clay mineral fluorohectorite was studied by means of an extended X-ray absorption fine structure (EXAFS) in a powder sample with the intention to observe the number of neighboring atoms to the Ni interlayer cation. In addition X-ray diffraction (XRD) was performed in order to follow the hydration states of Ni-fluorohectorite in terms of basal-spacing measurements. The sample conditions were the same for both types of experiments. The EXAFS results show that Ni2+ forms a brucite-like structure in the form of Ni(OH)2, and that this structure coexists with the clay mineral particles. This shows that the Ni atom observed by means of our EXAFS measurements is predominantly the Ni which composes the brucite-like structure and not the interlayer Ni2+ cation. In order to confirm the formation of the brucite-like structure, the EXAFS data from Ni-fluorohectorite were compared to Ni-salt water solutions at various pH.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • A new method for determining platy particle aspect ratio: A kaolinite case
           study
    • Abstract: Publication date: Available online 7 June 2014
      Source:Applied Clay Science
      Author(s): Hongfei Cheng , Zhiliang Zhang , Qinfu Liu , Joseph Leung
      A technique based on the detection method of particle size is presented to calculate the aspect ratio of particles with known layered silicate minerals. The principle relies on the premise that objects placed in an electric field modify the current flow of that field. The accurate volume of the testing particle is obtained from the difference of the conductivity of the particles and that of the conductive liquid. Platy particles have a disc-like shape. Therefore, the thickness and diameter of the particle can be calculated from its volume. The aspect ratio of the platy particle is successfully obtained from the results. This study uses a spherical standard sample with a diameter of 10μm and two different kaolinites that vary in the conductivity of two electrodes by the particles as they pass through the aperture tube. According to the thickness of the particle size and the diameter (width and length) of the disc the particle extracted from the raw data, and the standard particles of the particle-size analyzer (Coulter Multisizer 3), a new method of determining the aspect ratio of the disc-shaped particle is obtained.


      PubDate: 2014-06-14T17:11:06Z
       
  • Intercalation of two phenolic acids in an ionic liquid–kaolinite
           nanohybrid material and desorption studies
    • Abstract: Publication date: Available online 11 June 2014
      Source:Applied Clay Science
      Author(s): Gustave Kenne Dedzo , Christian Detellier
      A new ionic liquid kaolinite nanohybrid material was obtained by the grafting of 1-(2-hydroxyethyl)-pyridinium chloride (HEPC) in the mineral interlayer spaces. The XRD of the resulting material confirmed the intercalation of the ionic liquid with an interlayer expansion of 5.7Å. Thermogravimetric analysis characterization highlighted the loss of organic matter and allowed the determination of the empirical formula of the composite: Al2O3Si2O2(OH)3(OH0.75)(HEPC)0.25. In this material, the associated anions remain free and can be replaced by other anions having a suitable size to fit into the interlayer. This was demonstrated by cyclic voltammetry after a pre-concentration step in a solution of Salicylic Acid (SA) or Gallic Acid (GA) in their anionic form. Intercalation/de-intercalation of these phenolic organic anions was then investigated. The kinetics of intercalation of these compounds was fast, with the equilibrium achieved after less than 30min. Maximum adsorption capacity (determined by the Langmuir model) for SA (781μmol/g) was close to the estimated value (867μmol/g). In the case of GA (484μmol/g), the smaller intercalated amount is plausibly due to the presence of GA in the form of di-anions. Desorption of these compounds performed in a 0.1M phosphate buffer solution at pH7 showed that SA was de-intercalated with fast kinetics (after 1min, release was almost complete). In the case of GA, the process was slower and the equilibrium reached after about 20min. These promising results demonstrate that the modified kaolinite may be used to store and control the release of chemical compounds, and also may be used as adsorbent for the removal of aqueous phenolic organic anions.


      PubDate: 2014-06-14T17:11:06Z
       
  • Preparation of amphoteric nanocomposite hydrogels based on exfoliation of
           montmorillonite via in-situ intercalative polymerization of hydrophilic
           cationic and anionic monomers
    • Abstract: Publication date: Available online 13 June 2014
      Source:Applied Clay Science
      Author(s): Xudong Nie , Abudurman Adalati , Juan Du , Huanhuan Liu , Shimei Xu , Jide Wang
      It is important for montmorillonite (Mt) -based nanocomposites to achieve good intercalation or exfoliation of Mt in composite structure. In this paper, N-[3-(dimethylamino)propyl] methacrylamide (DMAPMA), which is nonionic in neutral solution but cationic character in acid solution, and acrylic acid (AA) were used to modify Mt with AA together. Here DMAPMA and AA were used not only as the intercalators to disperse and intercalate Mt but also as the main monomers to form amphoteric nanocomposite hydrogels. The XRD and TEM results illustrated that an exfoliated or a highly intercalated nanocomposite structure was obtained. Compression strength of amphoteric nanocomposite hydrogel reached 54.4kPa under the water content of 99.8%. It should be emphasized that the excellent mechanical property of the hydrogels was reached without adding chemical crosslinking agents. Compared with the organic hydrogel, the hydrogels showed significant improvement in swelling capacity.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Preparation and characterization of carrageenan-based nanocomposite films
           reinforced with clay mineral and silver nanoparticles
    • Abstract: Publication date: Available online 12 June 2014
      Source:Applied Clay Science
      Author(s): Jong-Whan Rhim , Long-Feng Wang
      Antimicrobial bionanocomposite films were prepared with κ-carrageenan and silver nanoparticles (AgNPs) and organically modified clay mineral (Cloisite® 30B). AgNP-included nanocomposite films showed characteristic plasmonic effect of the AgNPs with the maximum absorption at 420nm and they also showed high UV barrier properties. Depending on the type of nanofillers, tensile strength (TS) of the nanocomposite films increased by 14–26% and water vapor permeability (WVP) decreased by 12–27% compared to those of the neat carrageenan film. The nanocomposite films exhibited characteristic antimicrobial activity against Gram-positive (Listeria monocytogenes) and Gram-negative (Escherichia coli O157:H7) pathogenic bacteria. While AgNP-included nanocomposite film showed strong antimicrobial activity against Gram-negative bacteria, the clay-included nanocomposite films showed strong antimicrobial activity against Gram-positive bacteria. On the contrary, the nanocomposite film with combined use of both nanofillers showed strong antimicrobial activity against both Gram-positive and Gram-negative bacteria.


      PubDate: 2014-06-14T17:11:06Z
       
  • Conversion of South African clays into high quality zeolites
    • Abstract: Publication date: Available online 13 June 2014
      Source:Applied Clay Science
      Author(s): Nicholas M. Musyoka , Roland Missengue , Melissa Kusisakana , Leslie F. Petrik
      Clays obtained from South Africa were used as feedstock materials for the synthesis of zeolites. The conventional alkaline hydrothermal treatment of the starting material (90°C for 8h) was preceded by a fusion step (550°C for 1.5h) to improve the solubility of aluminium and silicon. Various characterization techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed to probe the properties of the as-received clays as well as the resulting zeolitic phase. The synthesized zeolite X and hydroxy-sodalite were of high crystalline quality hence making clay materials a cheaper alternative for producing high quality zeolites.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Insights into the EPR characteristics of heated carbonate-rich illitic
           clay
    • Abstract: Publication date: Available online 13 June 2014
      Source:Applied Clay Science
      Author(s): Corina Ionescu , Volker Hoeck , Cristina Gruian , Viorica Simon
      The response of carbonate-rich illitic clay heated up to 1200°C was investigated by means of electron paramagnetic resonance (EPR) in order to define the factors influencing the shape of the resonance signals and to establish whether this method can be used for evaluation of firing temperature for clay-based ceramic objects. The results show that the dominating hyperfine sextet, at g≅2, due to Mn2+, is replaced over 700°C by a large signal, mainly due to Fe3+. Oxidation of Mn2+ (EPR active) to Mn3+ (EPR silent) or Mn4+, and Fe2+ (EPR silent) to Fe3+ (EPR active) respectively, combined with changes in their environment produce the resonance signals. The destruction of the carriers such as Fe-oxihydroxides, clinochlore, calcite, dolomite, altered biotite, illite and muscovite, as well as the formation of new minerals and glass are the main mineralogical processes influencing the width of the resonance signals. The results of this study can be used in conjunction with mineralogical and microstructural data for the investigation of technological conditions such as firing temperature and atmosphere related to archaeological ceramic objects. Data gathered from other methods may also help to constrain the EPR signal shape.


      PubDate: 2014-06-14T17:11:06Z
       
  • Crystallization mechanism of zeolite A from coal kaolin using a two-step
           method
    • Abstract: Publication date: Available online 13 June 2014
      Source:Applied Clay Science
      Author(s): Zhihui Zhou , Ge Jin , Hong Liu , Jianxiong Wu , Jinfeng Mei
      Zeolite A was synthesized from coal kaolin using a two-step method. The crystallization mechanism was studied. The synthesis was composed of pre-crystallization at a low temperature and crystallization at a high temperature. The influence factors on crystallinity were investigated, including calcination temperature of kaolin, crystallization time, pre-crystallization temperature and time, and composition of synthetic liquid. X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR) were used to characterize the nucleation and crystal growth processes. The results indicate that abundant nuclei were formed during the pre-crystallization period, whereas crystallization process during the first h in crystallization period was still a nucleation stage. Also, metakaolin had dissolved thoroughly after the synthesis liquid crystallized for 3h, and the nuclei were rapidly grown into zeolite A crystals at this time. An excess crystallization time results in a dissolution of as-synthesized crystals and a decrease of crystallinity as well as a too high concentration of OH−.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Efficient energy transfer of cationic iridium(III) complexes on the
           surface of a colloidal clay
    • Abstract: Publication date: Available online 14 June 2014
      Source:Applied Clay Science
      Author(s): Hisako Sato , Kenji Tamura , Masahiro Taniguchi , Akihiko Yamagishi
      In order to investigate energy transfer on a clay surface, blue- and red- emitting cationic iridium(III) complexes, [Ir(dfppy)2L]+ (dfppyH=2-(4′,6′-difluorophenyl)pyridine, L=4,4′-dimethyl-2,2′-bipyridine) and [Ir(piq)2L]+ (piqH=1-phenyisoquinoline) , respectively, were co-adsorbed by colloidally dispersed synthetic saponite in 1:3 (v/v) methanol/water. The stationary and transient emission results were analyzed on the basis of the Förster-type energy transfer mechanism. It was concluded that energy transfer took place from the excited blue emitter to the red one efficiently. The accumulation of the reactants on a clay particle was essential, since no energy transfer occurred in the absence of a clay in the similar concentration ranges.
      Graphical abstract image

      PubDate: 2014-06-14T17:11:06Z
       
  • Determination of key components and adsorption capacity of a low cost
           adsorbent based on sludge of drinking water treatment plant to adsorb
           cadmium ion in water
    • Abstract: Publication date: Available online 13 June 2014
      Source:Applied Clay Science
      Author(s): Eko Siswoyo , Yoshihiro Mihara , Shunitz Tanaka
      A low cost adsorbent based on sludge of drinking water treatment plant (DWTP), solid waste by-product of sedimentation process in the DWTP, was studied for adsorption of cadmium ion in water. Some parameters such as dose of the adsorbent, pH of solution, and shaking time were investigated in the batch system in order to know the optimum condition and adsorption ability of the adsorbent. Artificial sludge was prepared by following the process of DWTP and the effect of humic acid extracted from the DWTP sludge was examined in order to clarify the key component and adsorption capacity of the adsorbent. This study found that humic acid and iron oxide were the key components of the adsorbent material for adsorption of cadmium ion in water. The Langmuir isotherm adsorption model was fit and the adsorption capacity of the adsorbent based on sludge of Miyamchi and Nishino DWTP for Cd(II) was 5.3 and 9.2mg/g, respectively. The finding of this study is important for further development of a low cost adsorbent material in the near future.


      PubDate: 2014-06-14T17:11:06Z
       
  • In-situ synthesis of polyaniline coated montmorillonite (Mt) clay using
           Fe+3 intercalated Mt as oxidizing agent
    • Abstract: Publication date: Available online 6 April 2014
      Source:Applied Clay Science
      Author(s): Bhavana Gupta , A. Rakesh , Ambrose A. Melvin , Avinash C. Pandey , Rajiv Prakash
      Polyaniline (PAni) coated over montmorillonite clay (Mt) layers is reported through in-situ oxidative polymerization. A new approach of synthesis has been adopted in which oxidizing agent (FeCl3·6H2O) is first intercalated into organically modified montmorillonite clay (OMt) in THF solvent and this ferric ions intercalated clay layers are thereafter re-dispersed into aqueous solution of monomer for polymerization. Choice of THF and aqueous medium is governed by ease of intercalation of Fe+3 into OMt and subsequent diffusion of monomer into interlayer spaces during polymerization respectively. The intercalation of polymer within the interlayer spaces has been studied and confirmed using various techniques.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
  • Cement and lime mixture stabilization of an expansive overconsolidated
           clay
    • Abstract: Publication date: Available online 13 April 2014
      Source:Applied Clay Science
      Author(s): Mohamed Khemissa , Abdelkrim Mahamedi
      Urban areas of the wilaya of M'sila in Algeria nowadays experience a considerable development because of an unceasingly increasing demography, from where its extension towards virgin zones often less favorable than those already urbanized. This wilaya is located in a zone classified as semi-arid, whose geology comprises clayey formations characterized by a high variation of volume when the conditions of their equilibrium are modified (natural climatic phenomena due to a prolonged dryness, human activity by modification of the ground water level because of excessive pumping, configuration of constructions in their environment). This paper presents and analyzes the results of a series of normal Proctor compaction tests, methylene blue tests, California bearing ratio tests and undrained direct shear tests performed on Sidi-Hadjrès expansive overconsolidated clay treated with mixture of various cement and lime contents and compacted under the optimum Proctor conditions. These test results show that the geotechnical parameters values are concordant and confirm the bearing capacity improvement of this natural clay, which is translated by a significant increase in soil strength and its durability. However, the best performances are obtained for a mixt treatment corresponding to 8% cement and 4% lime contents.


      PubDate: 2014-04-25T20:00:03Z
       
  • Microwave assisted in situ ring-opening polymerization of polylactide/clay
           nanocomposites: Effect of clay loading
    • Abstract: Publication date: Available online 13 April 2014
      Source:Applied Clay Science
      Author(s): Pankil Singla , Rajeev Mehta , S.N. Upadhyay
      Poly (lactic acid)/clay nanocomposites were prepared through microwave-assisted in situ ring opening polymerization of lactide at various clay loadings. The polymerization rate was much faster with microwave heating compared to conventional heating. The synthesis of poly (lactic acid)/clay nanocomposites was catalyzed by stannous octoate (SnOct2) and dibutyltindimethoxide (DBTM). The monomer to initiator ratio was kept at 2500:1 and the temperature was maintained at 150°C. Three types of commercially available clays (Cloisite® 30B, 15A, and Na+) were employed to study the effect of clay loadings on the polymerization of lactide and in situ formation of polymer–clay nanocomposites. The percentage yield decreased with increase in the clay loading from 0.1 to 5% for both Cloisite® 30B and Cloisite® 15A but no product was formed with Cloisite® Na+ clay. The characterization of nanocomposites was done by using XRD (X-ray diffraction), TGA (thermo-gravimetric analysis), SEM (scanning electron microscopy) and TEM (transmission electron microscopy) analyses. This is the first report on the marked effect of clay mineral on in situ polymerization of lactide using microwave irradiation.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
  • The role of smectite composition on the hyperalkaline alteration of
           bentonite
    • Abstract: Publication date: Available online 13 April 2014
      Source:Applied Clay Science
      Author(s): Raúl Fernández , Ana Isabel Ruiz , Jaime Cuevas
      Cementitious materials will act as a source of alkaline fluids modifying the mineralogy, pH and physical–chemical properties of bentonite barriers implemented for long-term pollutants retention. A series of reactivity experiments in batch reactors at 175°C were performed for nearly 15months to evaluate the chemical and mineralogical responses of four different bentonites with potential use as buffer barriers against a hyperalkaline K–Na–OH-type solution. This solution simulates the early stage of an ordinary Portland cement leaching in a clay hosted nuclear waste repository. The tested buffer materials were three montmorillonitic bentonites: MX-80 (Wyoming type, USA), FEBEX (Almería, Spain), and a bentonite from Chile (MMT); and a saponitic bentonite from el “Cerro del Águila” (Toledo, Spain). Partial dissolution of smectite and precipitation of secondary phases such as analcime and K-feldspar (sanidine or orthoclase) were found as reaction products in the dioctahedral smectite-based bentonites whereas the trioctahedral character bentonite showed more resistance to alteration. In addition, mixed-layered illite/smectite (I–Sm) interstratification was observed in the four bentonites with different degrees of order. The most heterogeneous octahedral sheet with significant Fe and Mg occupations (FEBEX and MX-80 bentonites) altered to produce R0 random mixed-layered I–Sm (60–40% I), whereas virtually ideal Al–Mg octahedral sheet (MMT bentonite) altered to produce saponite and R≥1 ordered I–Sm (>80% I). The physical–chemical properties (CEC and SSA) were also altered differently in the four bentonites. The methodology used in this work is thought to develop a direct comparison of the performance of potential buffer materials in a nuclear or hazardous waste repository. The evaluation of other basic hydro-mechanical properties should be further evaluated to serve as an indicator of long-term stability of bentonites used in different reactive environments.


      PubDate: 2014-04-25T20:00:03Z
       
  • Lime consumption of different clayey soils
    • Abstract: Publication date: Available online 18 April 2014
      Source:Applied Clay Science
      Author(s): Muzahim Al-Mukhtar , Abdelmadjid Lasledj , J.F. Alcover
      This study focused on the lime consumption by 10% of lime treatment, of five soils containing different major clay minerals, kaolinite, illite, smectite–kaolinite, smectite–illite and smectite. Assessing the consumption of lime with respect to curing time, using an atomic absorption device, illustrates the lime–clay mineral reaction and the mechanisms involved in curing in the short- and long-term. X-ray diffraction and thermogravimetric analysis results show that clayey soils have different kinetic reactions depending on to their mineralogical composition, and that all soils consume the amount of lime added after a shorter or longer period of curing time. Two main reactions were assessed: the short-term reaction (cation exchange and flocculation) and the long-term reaction (pozzolanic reaction). These reactions are initiated due to the highly alkaline medium induced by the dissolution of lime in the water contained in the soil. The amount of lime consumed during the short-term reaction varies from nothing for kaolinite and maximum with sodium-smectite. The pozzolanic reaction present in all the clayey soils tested depends on the amount of lime available and is greatly accelerated by increasing the curing temperature from 20° to 50°C. This reaction induces structural and mineralogical changes in the treated soils due to the newly formed calcium hydrates.


      PubDate: 2014-04-25T20:00:03Z
       
  • Highly selective removal of nitrate and perchlorate by organoclay
    • Abstract: Publication date: Available online 18 April 2014
      Source:Applied Clay Science
      Author(s): Saeed Bagherifam , Sridhar Komarneni , Amir Lakzian , Amir Fotovat , Reza Khorasani , Wenyan Huang , Jianfeng Ma , Siqi Hong , Fred S. Cannon , Yujue Wang
      An organoclay was prepared using montmorillonite and hexadecylpyridinium chloride (HDPyCl) and tested for the removal of nitrate and perchlorate anions from aqueous solutions. The cationic surfactant modified organoclay was prepared at room temperature using HDPyCl corresponding to 4 times the cation exchange capacity (CEC) of Na-montmorillonite. Powder X-ray diffraction (XRD) analysis of the above organoclay showed a large basal spacing of 40.27Å with the intercalation of HDPy cations in the interlayers probably as a result of a paraffin-type bilayer arrangement. The adsorption data of nitrate and perchlorate were fitted to the Langmuir and Freundlich adsorption isotherms and pseudo-first order and pseudo-second order kinetic models to better understand their adsorption mechanisms. The nitrate and perchlorate uptakes by this organoclay could be described well using the Langmuir isotherm while their uptake kinetics fitted well to the pseudo-second order model. The maximum adsorption capacities of nitrate and perchlorate by the organoclay, HDPy-montmorillonite were calculated at 0.67 and 1.11mmolg−1, respectively. Nitrate and perchlorate uptake kinetics were found to be fast as equilibrium was reached within 4h. Furthermore, the uptakes of nitrate and perchlorate by HDPy-montmorillonite were found to be highly selective in the presence of Cl−, SO4 2− and CO3 2−, the most abundant naturally occurring anions. Therefore, the HDPy-montmorillonite could be used as a highly efficient adsorbent for the separation of nitrate and perchlorate from drinking or waste water and ground water.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
  • Evaluation of Zn–Al–SO4 layered double hydroxide for the
           removal of arsenite and arsenate from a simulated soil solution: Isotherms
           and kinetics
    • Abstract: Publication date: Available online 18 April 2014
      Source:Applied Clay Science
      Author(s): Saeed Bagherifam , Sridhar Komarneni , Amir Lakzian , Amir Fotovat , Reza Khorasani , Wenyan Huang , Jianfeng Ma , Yujue Wang
      The main objective of the present study was to evaluate the effectiveness of synthetic Zn–Al–SO4 layered double hydroxide (LDH) for the removal of arsenite and arsenate from a simulated soil solution. The Zn–Al–SO4 was synthesized using a hydrothermal method and the adsorption of arsenic was studied using Langmuir and Freundlich models. Moreover, the kinetics of adsorption was tested using pseudo-first, pseudo-second, intraparticle diffusion and Elovich models. The results of the experiments revealed that the adsorption isotherms of arsenite and arsenate on the Zn–Al–SO4 LDHs can be described well with Langmuir isotherm and maximum adsorption capacities were calculated to be 34.24 and 47.39mgg−1 for arsenite and arsenate, respectively. The adsorption kinetics of arsenate followed pseudo-second order while arsenite uptake showed better correlation with intra-particle diffusion model. Furthermore, the effects of two major coexisting and competing divalent anions such as SO4 2− and CO3 2− on the uptakes of arsenite and arsenate were studied and the results showed that CO3 2− had greater adverse effect on the uptakes of arsenite and arsenate by Zn–Al–SO4 than SO4 2−. Based on X-ray diffraction results, the main underplaying adsorption mechanism of arsenite and arsenate might be the exchange on the external surfaces and edges of Zn–Al–SO4 LDHs, but possibly some topotactic exchange may occur through the substitution of arsenic anions with sulfate in the interlayer region.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
  • Synthesis of clay/carbon adsorbent through hydrothermal carbonization of
           cellulose on palygorskite
    • Abstract: Publication date: Available online 21 April 2014
      Source:Applied Clay Science
      Author(s): Xueping Wu , Peng Gao , Xianlong Zhang , Guanping Jin , Yanqing Xu , Yucheng Wu
      Organophilic palygorskite/carbon composites were prepared through a green hydrothermal carbonization process using palygorskite clay and cheap cellulose as raw materials. The effects of reaction temperature (210°C to 250°C) and time (2h to 48h) on the product structures were investigated, and a potential reaction mechanism was proposed. Nanocarbon particles (10nm in diameter) were loaded onto the palygorskite surface (220–250°C, 12h or 210°C, 24–48h). Results from the Fourier transform infrared and X-ray photoelectron spectroscopy showed that the resultant palygorskite/carbon composites contained organic groups, including CH, CH2 , CHCH and CO. The coating mechanisms of palygorskite and nanocarbon were also discussed. The contribution of organic carbon to organophilic improvement was further confirmed by the static adsorption of phenol. The removal rate of phenol from aqueous solution increased with hydrothermal time and temperature, indicating that the loading of nanocarbon particles with organic groups made an important contribution for the organic modification of palygorskite. The palygorskite/carbon obtained at 250°C in 48h exhibited the highest adsorption (92wt.%) of phenol, which was slightly higher than that of commercial active carbon (90wt.%) and significantly higher than that of unmodified palygorskite (18wt.%).


      PubDate: 2014-04-25T20:00:03Z
       
  • Adsorption characteristics of montmorillonite clay modified with iron
           oxide with respect to methylene blue in aqueous media
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): L. Cottet , C.A.P. Almeida , N. Naidek , M.F. Viante , M.C. Lopes , N.A. Debacher
      Montmorillonite clay modified with iron oxide (MtMIO) was prepared for use as an adsorbent of methylene blue dye. Structural characterization of MtMIO was performed by field-emission scanning electron microscopy, energy-dispersive spectroscopy, surface area measurements, zeta potential analysis and Fourier transform infrared spectroscopy. Batch experiments were carried out under different conditions of initial dye concentration, contact time and temperature to investigate the adsorption of methylene blue onto MtMIO. Adsorption isotherms were experimentally determined and the Freundlich and Langmuir models were used to fit the data, better results being obtained for the latter with a maximum adsorption capacity of 71.12mgg−1 at 333K. Thermodynamic parameters, such as standard enthalpy, standard entropy and standard free energy changes were determined, indicating an endothermic and non-spontaneous process. Also, pseudo-first-order and pseudo-second-order kinetic models were applied, and the experimental data fitted the pseudo-second order model. The activation energy of +19.32kJmol−1 was determined using the Arrhenius equation.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
  • Modified clays as catalysts for the catalytic oxidation of ethanol
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Alejandro Pérez , Mario Montes , Rafael Molina , Sonia Moreno
      Two methods for modifying a clay mineral by pillaring and delamination were studied to obtain suitable catalyst supports for Co and Cu. The arrangement of the active species and the interaction that they may have with the support will be a fundamental feature for activity and selectivity in the oxidation reactions. Moreover, the use of natural materials such as clay minerals will add value to these materials and allow them to be excellent supports for environmental impact reactions. The combination of transition metals in equimolar ratios leads to cooperative effects between the species, resulting in the excellent catalytic performance in oxidation reactions of VOCs. Based on structural and morphological characterization using XRD, SEM, H2-TPR, textural analysis and the evaluation of the catalytic activity in the oxidation of ethanol, the delaminated system proved to be a more appropriate support.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
  • Removal of heavy metal ions from aqueous medium using Kuluncak (Malatya)
           vermiculites and effect of precipitation on removal
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Hikmet Sis , Turan Uysal
      The removal of heavy metal ions, Cr3+, Pb2+ and Zn2+, by vermiculite was studied by batch adsorption tests. Influence of experimental parameters (e.g., medium pH and initial ion concentration) on removal was examined separately. Metal hydroxide formation in the dispersions and their precipitation was also investigated to assess the effect of precipitation on ion removal. For this purpose, some removal tests were carried out in the absence of vermiculite at various pH and initial ion concentrations. Electrokinetic and other properties (e.g., specific surface area, thermal and chemical analysis) of vermiculite were determined to explain the experimental results and the interaction mechanisms between solid surface and the ions. Zeta potential data were found to be a very useful means to explain the interaction mechanism between the adsorbent and adsorbate. The affinity of vermiculite for ions changed in the order of Pb>Cr>Zn. At the lowest studied pH of 2.5, 15.81, 10.71 and 9.18mg of Pb, Cr and Zn ions could be removed by 1g of the adsorbent, respectively.


      PubDate: 2014-04-25T20:00:03Z
       
  • Influence of the synthesis parameter on the interlayer and framework
           structure of lamellar octadecyltrimethylammonium kanemite
    • Abstract: Publication date: June 2014
      Source:Applied Clay Science, Volume 95
      Author(s): Juan I. Corredor , Agustín Cota , Esperanza Pavón , Francisco J. Osuna , María D. Alba
      Inorganic–organic nanostructures, used as host materials for selective adsorption of functional molecules and as mesostructured material precursors, can be constructed by the interlayer modification of inorganic layered materials with surfactants. The formation mechanism is mainly determined by the surfactant assemblies in the 2D limited space. In this paper, a detailed structural analysis of the lamellar mesophases prepared from kanemite, a lamellar silicate, and octadecyltrimethylammonium (ODTMA) under various conditions was reported. The adsorbed amount of ODTMA and the long and short range structural orders were explored by TGA, XRD, IR/FT and MAS NMR spectroscopies. The results revealed that ODTMA molecules were efficiently intercalated in the interlayer space of kanemite and, in all synthesis conditions, an ordered lamellar structure was obtained. The ODTMA adsorption in kanemite caused changes not only in the interlayer space but also in the silicate framework, where five-member rings were formed. The characteristics of the final products were influenced by the synthesis conditions, although the separation mode, filtration or centrifugation, was not relevant. Therefore, the adsorption conditions of ODTMA in kanemite will contribute to the design of novel layered materials with potential environmental and technological use.
      Graphical abstract image

      PubDate: 2014-04-25T20:00:03Z
       
 
 
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