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  Subjects -> EARTH SCIENCES (Total: 579 journals)
    - EARTH SCIENCES (427 journals)
    - GEOLOGY (64 journals)
    - GEOPHYSICS (27 journals)
    - HYDROLOGY (17 journals)
    - OCEANOGRAPHY (44 journals)

EARTH SCIENCES (427 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (1 follower)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (2 followers)
Acta Geophysica     Hybrid Journal   (7 followers)
Acta Geotechnica     Hybrid Journal   (8 followers)
Acta Meteorologica Sinica     Hybrid Journal   (2 followers)
Advances in High Energy Physics     Open Access   (12 followers)
Advances In Physics     Hybrid Journal   (6 followers)
Aeolian Research     Hybrid Journal   (1 follower)
African Journal of Aquatic Science     Hybrid Journal   (13 followers)
Algological Studies     Full-text available via subscription   (2 followers)
Alpine Botany     Hybrid Journal   (2 followers)
AMBIO     Hybrid Journal   (13 followers)
Anales del Instituto de la Patagonia     Open Access   (2 followers)
Andean geology     Open Access   (5 followers)
Annales Henri Poincaré     Hybrid Journal   (2 followers)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (1 follower)
Annals of Geophysics     Full-text available via subscription   (9 followers)
Annals of GIS     Hybrid Journal   (14 followers)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (9 followers)
Applied Clay Science     Hybrid Journal   (2 followers)
Applied Geochemistry     Hybrid Journal   (6 followers)
Applied Geomatics     Hybrid Journal   (6 followers)
Applied Geophysics     Hybrid Journal   (6 followers)
Applied Ocean Research     Hybrid Journal   (6 followers)
Applied Petrochemical Research     Open Access   (3 followers)
Applied Remote Sensing Journal     Open Access   (6 followers)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (19 followers)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (6 followers)
Artificial Satellites     Open Access   (11 followers)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (2 followers)
Asian Journal of Earth Sciences     Open Access   (16 followers)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (3 followers)
Atmosphere-Ocean     Full-text available via subscription   (3 followers)
Atmospheric and Climate Sciences     Open Access   (14 followers)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (11 followers)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (7 followers)
Bragantia     Open Access   (2 followers)
Bulletin of Earthquake Engineering     Hybrid Journal   (9 followers)
Bulletin of Geosciences     Open Access   (7 followers)
Bulletin of Marine Science     Full-text available via subscription   (12 followers)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (2 followers)
Bulletin of the Seismological Society of America     Full-text available via subscription   (15 followers)
Bulletin of Volcanology     Hybrid Journal   (11 followers)
Canadian Journal of Plant Science     Full-text available via subscription   (10 followers)
Canadian Mineralogist     Full-text available via subscription   (1 follower)
Canadian Water Resources Journal     Hybrid Journal   (17 followers)
Carbonates and Evaporites     Hybrid Journal   (3 followers)
CATENA     Hybrid Journal   (3 followers)
Central European Journal of Geosciences     Hybrid Journal   (5 followers)
Central European Journal of Physics     Hybrid Journal   (2 followers)
Chemical Geology     Hybrid Journal   (9 followers)
Chemie der Erde - Geochemistry     Hybrid Journal   (3 followers)
Chinese Geographical Science     Hybrid Journal   (3 followers)
Chinese Journal of Geochemistry     Hybrid Journal   (2 followers)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (3 followers)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (8 followers)
Coastal Management     Hybrid Journal   (17 followers)
Comptes Rendus Geoscience     Full-text available via subscription   (5 followers)
Computational Geosciences     Hybrid Journal   (10 followers)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (2 followers)
Computers and Geotechnics     Hybrid Journal   (5 followers)
Continental Journal of Earth Sciences     Open Access   (1 follower)
Continental Shelf Research     Hybrid Journal   (6 followers)
Contributions to Mineralogy and Petrology     Hybrid Journal   (7 followers)
Contributions to Plasma Physics     Hybrid Journal   (2 followers)
Coral Reefs     Hybrid Journal   (17 followers)
Cretaceous Research     Hybrid Journal   (3 followers)
Cybergeo : European Journal of Geography     Open Access   (3 followers)
Developments in Geotectonics     Full-text available via subscription   (1 follower)
Developments in Quaternary Science     Full-text available via subscription   (3 followers)
Développement durable et territoires     Open Access   (2 followers)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (2 followers)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (3 followers)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (105 followers)
Earth Interactions     Full-text available via subscription   (7 followers)
Earth Science Research     Open Access   (5 followers)
Earth Surface Processes and Landforms     Hybrid Journal   (10 followers)
Earth System Dynamics     Open Access   (4 followers)
Earth System Dynamics Discussions     Open Access   (3 followers)
Earth's Future     Open Access   (1 follower)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (7 followers)
Earthquake Spectra     Full-text available via subscription   (11 followers)
Ecohydrology     Hybrid Journal   (11 followers)
Ecological Questions     Open Access   (5 followers)
Electromagnetics     Hybrid Journal   (2 followers)
Energy Efficiency     Hybrid Journal   (9 followers)
Energy Exploration & Exploitation     Full-text available via subscription   (2 followers)
Environmental Earth Sciences     Hybrid Journal   (10 followers)
Environmental Geology     Hybrid Journal   (10 followers)
Environmental Geosciences     Full-text available via subscription   (4 followers)
Erwerbs-Obstbau     Hybrid Journal  
Estuaries and Coasts     Hybrid Journal   (1 follower)
Estuarine, Coastal and Shelf Science     Hybrid Journal   (15 followers)
Estudios Geográficos     Open Access  
European Journal of Mineralogy     Full-text available via subscription   (6 followers)

        1 2 3 4 5 | Last

Applied Clay Science    [4 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0169-1317
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.999]   [H-I: 63]
  • Sulfonated nanoClay minerals as a recyclable eco-friendly catalyst for the
           synthesis of quinoxaline derivatives in green media
    • Abstract: Publication date: Available online 22 January 2014
      Source:Applied Clay Science
      Author(s): Mahgol Tajbakhsh , Maasoomeh Bazzar , Seideh Fatemeh Ramzanian , Mahmood Tajbakhsh
      Sulfonated nanoClay was prepared by reacting a mixture of nanoClay mineral particles with 3-aminopropyltriethoxysilane (APTES) in dry toluene under N2 and subsequent treatment with propane sultone. The synthesized sulfonated nanoClay was characterized with FTIR spectroscopy, elemental analysis, thermogravimeteric analysis (TGA), SEM and atomic force microscopy (AFM). The result showed particle sizes between 30 and 38nm. TGA indicated a 70% loading of SO3 − group which was confirmed by elemental analysis. Synthesized sulfonated nanoClay was tested in the synthesis of quinoxaline derivatives via the condensation of 1,2-diamines with 1,2-diketones in ethyl alcohol as a green medium at room temperature. Using this method, the title compounds were prepared in high yields and short reaction times. The catalyst was recovered and reused several times without significant loss of catalytic activity. AFM and SEM of recycled catalyst showed a uniform distribution with a particle size of 40nm and little aggregation.
      Graphical abstract image

      PubDate: 2014-01-24T00:02:27Z
       
  • Using fly ash to partially substitute metakaolin in geopolymer synthesis
    • Abstract: Publication date: Available online 20 January 2014
      Source:Applied Clay Science
      Author(s): Zuhua Zhang , Hao Wang , Yingcan Zhu , Andrew Reid , John L. Provis , Frank Bullen
      Metakaolin-based geopolymers containing between 0 and 40% fly ash were prepared, to study the influence of fly ash substitution on the reaction process and products. At constant liquid/solid ratio, the partial replacement of metakaolin by fly ash reduces the rate of reaction, but the reaction continues for an extended duration and so is still able to achieve a relatively high extent of reaction and provide a comparable 28-day compressive strength when the replacement is less than 30%. The replacement of 10% of the metakaolin by fly ash gives an increased reaction extent (as measured by isothermal conduction calorimetry), and also a higher 28-day compressive strength, by 15%. The porosity of the geopolymer increases with the level of fly ash replacement, and pore refinement and ongoing reaction of fly ash particles during the first month of curing are also apparent.
      Graphical abstract image

      PubDate: 2014-01-24T00:02:27Z
       
  • Adsorption characteristics, isotherm, kinetics, and diffusion of modified
           natural bentonite for removing the 2,4,5-trichlorophenol
    • Abstract: Publication date: Available online 23 January 2014
      Source:Applied Clay Science
      Author(s): H. Zaghouane-Boudiaf , Mokhtar Boutahala , Sousna Sahnoun , Chafia Tiar , Fatima Gomri
      Adsorption of the 2,4,5 trichlorophenol (TCP) from aqueous solution onto the surface of organo-bentonites was investigated spectrophotometrically. Natural bentonite was activated with sulfuric acid at 90°C and exchanged with a set of 4 alkyltrimethylammonium bromides (alkyl=C12, C14, C16 and C18) to evaluate the effect of carbon chain length on the TCP adsorption. X-ray diffraction was used to study the change in the structural properties of the samples. The basal spacing of the activated-bentonite (AB) increased from 13.4 to 21.5Å by intercalation of the cationic surfactants in the interlayer space of the clays. The intercalated cationic surfactants were characterized by Fourier transform infrared spectroscopy (FTIR). The surface areas of organo-bentonites were found to be much lower than that of AB. The contact time on the adsorption process was studied and the adsorption of TCP onto organo-bentonites followed pseudo-second-order kinetics. Adsorption isotherms were established and found to correlate with the Langmuir model with correlation coefficient of 0.998. Adsorption capacity of organo-bentonite increased with increasing the alkyl chain length. Results showed that TCP strongly interacted with AB exchanged with octadecyltrimethylammonium bromide (C18).


      PubDate: 2014-01-24T00:02:27Z
       
  • Restricting layer collapse enhances the adsorption capacity of
           reduced-charge organoclays
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Runliang Zhu , Junbo Zhao , Fei Ge , Lifang Zhu , Jianxi Zhu , Qi Tao , Hongping He
      By restricting layer collapse, and increasing the exposure of siloxane surfaces, in the interlayer space of organoclays, their capacity for adsorbing hydrophobic organic contaminants has been enhanced. The organoclays were prepared by replacing a proportion (20–80%) of the Li+ ions, occupying interlayer sites in montmorillonite, with tetramethylammonium (TMA) ions. The TMA-exchanged samples were then heated at 200°C for 12h to induce migration of most interlayer Li+ ions into the silicate layers, and as a result of which the layer charge was reduced. Finally, the remaining Li+ cations in the reduced-charge montmorillonite were exchanged with TMA. The structural and adsorptive characteristics of the novel reduced-charge organoclays (N-TMA-Mt) are compared with those of their traditional counterparts (T-TMA-Mt), obtained by direct intercalation of TMA into reduced-charge montmorillonites. As layer charge decreased, both the specific surface area and adsorption capacity (for nitrobenzene) of T-TMA-Mt increased to a maximum, and then declined. In the case of N-TMA-Mt, however, both parameters increased as layer charge decreased. When the layer charge of N-TMA-Mt decreased to approximately 60% of the value for the original montmorillonite, the adsorption capacity of the sample was greater than that of T-TMA-Mt. XRD analysis indicates that the layer structure of N-TMA-Mt is more rigid than that of T-TMA-Mt. The above results indicate that the pre-exchanged TMA cations in the interlayer space of N-TMA-Mt act as pillars, restricting layer collapse (during thermal treatment), and increasing the exposure of siloxane surfaces. As a result, the capacity of N-TMA-Mt for adsorbing hydrophobic organic contaminants is superior to that of traditional organoclays.
      Graphical abstract image

      PubDate: 2014-01-24T00:02:27Z
       
  • Structure and photoluminescence of composite based on ZnO particles
           inserted in layered magadiite
    • Abstract: Publication date: Available online 16 January 2014
      Source:Applied Clay Science
      Author(s): Yufeng Chen , Gensheng Yu , Fei Li , Junchao Wei
      A magadiite–ZnO (Mag–ZnO) composite was synthesized from Na–magadiite by two-step ion-exchanges and thermal treatment. Various techniques have been used to characterize the composite. X-ray diffraction (XRD) results found that the basal spacings of the derivatives were different from that of the Na–magadiite. Scanning electron microscope equipped with energy dispersive X-ray (SEM–EDX) was used to estimate the chemical composition of the Mag–ZnO composite. Photoluminescence (PL) spectrum of the Mag–ZnO presents a luminescent peak at 356nm and a weak shoulder at 456nm under the excitation of 280nm. This luminescent peak showed markedly blue shift compared with that of the uncovered ZnO (455nm), which may be due to the quantum confinement effect of nanoparticles. UV–visible transmission spectra suggested that the Mag–ZnO composite is characteristic of magadiite and ZnO. TEM observation revealed that the ZnO nanoparticles were inserted in the magadiite, and its sizes were estimated to be about 2.5nm. These results confirmed the formation of Mag–ZnO composite, along with improved photoluminescence of ZnO inserted in the magadiite.


      PubDate: 2014-01-20T00:02:40Z
       
  • Synthesis of polyisoprene–montmorillonite nanocomposites via
           differential microemulsion polymerization and application of PIP–Mt
           in natural rubber
    • Abstract: Publication date: Available online 16 January 2014
      Source:Applied Clay Science
      Author(s): Parat Boonchoo , Garry L. Rempel , Pattarapan Prasassarakich
      Polyisoprene–montmorillonite (PIP–Mt) nanocomposites with an average particle size of 30±7.2nm and narrow size distribution (20–50nm) were successfully synthesized via differential microemulsion polymerization. X-ray diffractometry analysis revealed that PIP was intercalated in the Mt layers expanding the d spacing of the Mt layer from 3.1nm to 3.8nm. The SDS (surfactant) concentration, isoprene monomer (IP) to water ratio and Mt loading were all found to affect the IP conversion level, and the solid content and particle size of the obtained PIP–Mt nanocomposites. An IP conversion level of 81% and a solid content of 20% were achieved at 0.25wt.% 2,2-azoisobutyronitrile (AIBN), 10wt.% Mt, 10wt.% SDS and an IP:H2O ratio of 0.24:1. These PIP–Mt nanocomposites could be used as an effective nano-filler in natural rubber (NR) latex for the preparation of NR/PIP–Mt composites, improving the mechanical properties compared to the unfilled NR. NR filled with PIP–Mt at 2wt.% showed a 1.6 and 1.1 fold higher tensile strength and a modulus of elasticity at 300% elongation, respectively. Furthermore, NR/PIP–Mt composites at 2wt.% Mt loading improved the thermal aging compared to unfilled NR, with an 87.6%, 96.2% and 84.0% retention of the tensile strength, elongation at break and modulus of elasticity, respectively compared to 52.5%, 88.9% and 58.8% for the unfilled NR.
      Graphical abstract image

      PubDate: 2014-01-20T00:02:40Z
       
  • Dissolution kinetics of metakaolin in sulfuric acid: Comparison between
           heterogeneous and homogeneous reaction methods
    • Abstract: Publication date: Available online 17 January 2014
      Source:Applied Clay Science
      Author(s): P.E.A. Lima , R.S. Angélica , R.F. Neves
      A kinetic study of metakaolin dissolution in sulfuric acid was carried out with the application of homogeneous and heterogeneous reaction methods. The comparison between them was not found in literature. The results showed small differences for activation energies, with an average of 96.8kJ/mol, and leaching reaction of the first order with respect to aluminum from metakaolin. The kinetic study of metakaolin dissolution process in acid solution can be carried out by applying relatively easy-to-use homogeneous reaction methods that require short time for their application.


      PubDate: 2014-01-20T00:02:40Z
       
  • Technological fingerprints of Black-Gloss Ware from Motya (Western Sicily,
           Italy)
    • Abstract: Publication date: Available online 19 January 2014
      Source:Applied Clay Science
      Author(s): Caterina De Vito , Laura Medeghini , Silvano Mignardi , Diletta Orlandi , Lorenzo Nigro , Federica Spagnoli , Pier Paolo Lottici , Danilo Bersani
      Black-Gloss Ware artifacts, unearthed at the Phoenician-Punic site of Motya (Sicily, Italy), dating back from the end of 6th to the early 4th century BC, have been investigated. Mineralogical, petrographical and chemical characterization has been performed to elucidate the technological aspects, to distinguish locally manufactured pottery from those imported and to provide information on raw materials used for their production. A multi-analytical approach based on optical microscopy, μ-Raman spectroscopy, scanning electron microscopy and X-ray diffraction investigations has been used. Results show that the internal body is composed of quartz, K-feldspar, plagioclase feldspar, pyroxene, mica, gehlenite and hematite. In addition, magnetite, hercynite and amorphous carbon occur in the black gloss. On the basis of these mineralogical assemblages, we can infer that the ceramic artifacts were exposed to similar firing temperatures and fO2, i.e. estimated T in the range 950–1100°C under oxidizing–reducing–oxidizing conditions.
      Graphical abstract image

      PubDate: 2014-01-20T00:02:40Z
       
  • Ability of natural, acid-activated, and surfactant-modified Terra Rossa
           soils to sorb triazine herbicides and their degradation products
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Sanja Stipičević , Lavoslav Sekovanić , Vlasta Drevenkar
      Two Terra Rossa soils that were collected in the Mediterranean region of Croatia and Turkey were tested in their natural, acid-activated, and surfactant-modified forms as sorbents for hydrophobic triazine groundwater pollutants in terms of their potential application to the multi-mineral landfill barriers. The soils were predominantly composed of kaolinite, followed by quartz, calcite, iron-bearing oxides/oxyhydroxides, and several other types of clay. The natural soils were poor in organic carbon (OC ≤2%), were similar in chemical composition, and were significantly different in their cation-exchange capacity (CEC). Sorption experiments were conducted with hydrophobic, weakly basic and ionisable triazine herbicides (atratone, ametryn, and atrazine) and three atrazine dealkylated degradation products. The Freundlich sorption parameters were evaluated and compared with respect to the physicochemical properties of the sorbates and sorbents. The low affinities of the natural soils for the sorption of all of the tested triazines were significantly enhanced by soil acid activation. The highest fractions of sorbed triazines were observed in the acid-activated soil with the higher CEC: 90% for the most basic and partially protonated atratone and ametryn and 78% and 61% for the more polar degradation products deisopropylatrazine and didealkylated atrazine, respectively. The enrichment of natural soils with OC by the sorption of the cationic surfactant hexadecyltrimethylammonium bromide (HDTMA) was more efficient in soil with higher CEC. The sorption intensities of all of the triazines except the most polar didealkylated atrazine increased significantly with increasing soil OC and correlated positively with the hydrophobicity of the compound. The sorption capacities of the HDTMA-modified soils were greater for most compounds than the capacities of the acid-activated soils. Based on the calculated sorbate fractions that were resistant to desorption, atratone and ametryn would be expected to be retained longest in the acid-activated soils, while the soil modification with HDTMA primarily prolonged the retention of ametryn and atrazine. The results indicated that, unlike natural Terra Rossa soils, their acid-activated or surfactant-modified forms could be applicable as components of an organophilic layer in multi-mineral barriers for retention of triazines and similar chemicals.


      PubDate: 2014-01-16T00:02:42Z
       
  • Molecular dynamic study of capillary forces on clay particles
    • Abstract: Publication date: Available online 15 January 2014
      Source:Applied Clay Science
      Author(s): Priyanthi M. Amarasinghe , A. Anandarajah , Pijush Ghosh
      Capillary forces between discrete colloid particles are of interest in many areas of science and engineering. This study used molecular dynamics (MD) to examine capillary phenomena that develop in a clay–water–air system, which requires an understanding of capillary forces, contact angles, and meniscus curvatures. The capillary formed between two parallel pyrophyllite clay particles and pure water was studied using MD for various system parameters which included particle separation, particle thickness, and strength of the clay–water van der Waals force. For a given set of potential energy parameters, the contact angle was independent of particle separation (≈550), the radius of curvature depended on particle separation, and particle thickness had a negligible influence on contact angles and meniscus radii. The van der Waals energy parameters, however, had a profound influence on contact angles and meniscus radii. In all cases, capillary forces on clay particles calculated by MD agreed with values calculated using the classical Young–Laplace equation. When the separation distance is 40Å, the force was calculated to be 9.87×10−10 N by Young–Laplace equation and 8.37×10−10 N by MD.
      Graphical abstract image

      PubDate: 2014-01-16T00:02:42Z
       
  • Cd(II) adsorption from aqueous solution by raw and modified kaolinite
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Ahmet Sari , Mustafa Tuzen
      This study aimed to investigate the adsorption and desorption potential of raw kaolinite (Kaol) and manganese oxide (MnO2)-modified kaolinite (MnO-Kaol) for the removal of cadmium (Cd(II)) ions from aqueous solution and waste water. The chemical and morphological characterizations of kaol and MnO-Kaol were carried out by using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FT-IR) analysis methods. The BET surface analysis results showed that the specific surface area of kaol increased by about 68% after MnO2 modification. The cadmium adsorption feasibility of MnO-Kaol was examined systemically by evaluating the effects of initial pH of solution, contact time, adsorbent concentration, and temperature of solution on the adsorption efficiency. From the Langmuir model, the adsorption capacities of kaol and MnO-Kaol were found to be 14.11 and 36.47mgg−1. The Dubinin–Radushkevich (D–R) model showed that the Cd(II) adsorption onto MnO-Kaol was progressed essentially by chemical ion-exchange. The recovery test demonstrated that the MnO-Kaol has good reusability performance after repeated ten times adsorption–desorption cycles. The thermodynamic studies revealed that the adsorption process of Cd(II) onto MnO-Kaol has exothermic nature and more feasible with increasing temperature of solution. The kinetic investigations also denoted that the adsorption process better fits the pseudo-second-order kinetic model.


      PubDate: 2014-01-16T00:02:42Z
       
  • Promoting effect of cerium on the characteristic and catalytic activity of
           Al, Zr, and Al–Zr pillared clay
    • Abstract: Publication date: Available online 11 January 2014
      Source:Applied Clay Science
      Author(s): S. Mnasri-Ghnimi , N. Frini-Srasra
      A series of pillared interlayered clays (PILCs) including Al-, Zr- and Al–Zr-PILC have been prepared and characterized by X-ray diffraction, elemental analyses, N2 adsorption, cationic exchange capacity and IR measurements after n-butylamine adsorption. Cerium introduced in the Zr4+ and/or Al3+ intercalated solution allows for an improvement of the stability and crystallinity of PILC and creates pillared clays with new properties. The resulting materials were used for the synthesis of 1,3-dioxolane. The addition of cerium has a major influence in this reaction.


      PubDate: 2014-01-12T00:02:30Z
       
  • Long-term behavior of lime–metakaolin pastes at ambient temperature
           and humid curing condition
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): A. Santos Silva , A. Gameiro , J. Grilo , R. Veiga , A. Velosa
      This paper presents the reaction behavior of lime and metakaolin (MK) pastes submitted to long term aging at ambient temperature and relative humidity of 95±5%. The results presented are the basis for an extensive research pointing towards the formulation of lime based mortars for conservation of historic buildings, namely in humid environments. MK, when mixed with calcium hydroxide, in the presence of water, originates a set of major hydrated compounds, specifically, stratlingite, monocarboaluminate and calcium aluminate hydrate. The type of hydrated compounds formed is dependent on the lime/MK ratio, being some of them unstable over time. This instability can compromise the mechanical properties of lime–MK mortars. From this work different reaction kinetics with aging were perceived, being the best results in terms of the pozzolanic reaction obtained with 50% MK content. Pastes with less than 25% of MK also present reliable stability.
      Graphical abstract image

      PubDate: 2014-01-12T00:02:30Z
       
  • Geotechnical properties of lime-treated gypseous soils
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): A. Aldaood , M. Bouasker , M. Al-Mukhtar
      This paper presents the results of an experimental research study on the behavior of gypseous soils treated with lime. The aim of this work was to investigate the effect of a wide range of gypsum content and curing conditions on two important geotechnical properties: the mechanical strength and swell potential of lime-treated fine-grained soil. For this purpose, soil samples were prepared with different gypsum content (0%, 5%, 15% and 25%), treated with lime and assessed at different curing times and temperatures. The results for untreated gypseous soil showed that the unconfined compressive strength increases and the swell potential enhances with the presence of gypsum. The geotechnical properties of the lime-treated gypseous soil depend not only on the gypsum content but also on the curing conditions. An approximate doubling of the unconfined compressive strength of soil samples cured for 28days was observed when the curing temperature was increased from 20°C to 40°C. Moreover, the swell potential increased with curing times and decreased with curing temperature in the lime-treated gypseous soil. The tests carried out at the microscopic level showed the formation of calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH), which are responsible for strength development in the treated soil samples. Further, the ettringite mineral, which induces swelling, was also observed in the treated soils.


      PubDate: 2014-01-12T00:02:30Z
       
  • Role of electrostatic interactions in the adsorption of cadmium(II) from
           aqueous solution onto vermiculite
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Erika Padilla-Ortega , Roberto Leyva-Ramos , Jovita Mendoza-Barron
      The adsorption equilibrium data of Cd(II) on vermiculite was obtained in a batch adsorber. The adsorption data were interpreted with the Langmuir, Freundlich and Prausnitz–Radke (PR) isotherm models, and the PR isotherm best fitted the experimental data. The adsorption capacity of vermiculite towards Cd(II) was increased by raising the solution pH and temperature. The first effect was attributed to electrostatic interactions and competition between the protons and Cd(II) for the cationic sites. The second trend indicated that the adsorption was endothermic. The desorption of Cd(II) adsorbed on vermiculite at pH=7, was irreversible and reversible when the pH of desorption solution was 7 and 3, respectively. The maximum uptake of Cd(II) on vermiculite was greater than the cationic exchange capacity. This result revealed that the adsorption of Cd(II) on vermiculite occurred by other adsorption mechanisms besides ion exchange. It was demonstrated that the greater the uptake of Cd(II) on vermiculite, the higher the reduction of the negative charge of the surface. Hence, the electrostatic interactions between the Cd2+ cations in solution and the negative zeta potential of the surface played an important role on the adsorption capacity of vermiculite. Hence, the adsorption of Cd(II) on vermiculite is mainly due to the mechanisms of ion exchange and electrostatic attraction.


      PubDate: 2014-01-08T00:02:36Z
       
  • Montmorillonite as a multifunctional adsorbent can simultaneously remove
           crystal violet, cetyltrimethylammonium, and 2-naphthol from water
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Runliang Zhu , Qingze Chen , Hanyang Liu , Fei Ge , Lifang Zhu , Jianxi Zhu , Hongping He
      The adsorptive behaviors of crystal violet (CV), cetyltrimethylammonium (CTMA), and 2-naphthol to montmorillonite (Mt) using a simultaneous-adsorption process were studied in this work. The adsorption results showed that under the experimental concentrations both CV and CTMA were almost completely removed by Mt. XRD and FTIR characterization results showed that the adsorbed CV and CTMA formed CTMA–CV aggregates within the interlayer spaces of Mt, and these aggregates served as accommodation spaces for the adsorption of 2-naphthol. The adsorption isotherms of 2-naphthol fitted linear equation well in the simultaneous-adsorption process, suggesting that partition should be the dominant mechanism for uptaking 2-naphthol. Combining the fact that CV alone formed aggregates showed nonlinear adsorption isotherms and much weaker adsorption capacity towards 2-naphtol than CTMA alone formed aggregates, one would expect that CTMA played a dominant role in the adsorption of 2-naphthol to CTMA–CV aggregates. In addition, the CTMA–CV aggregates have better adsorption capacity towards 2-naphthol than the combination of CTMA aggregates and CV aggregates do. FTIR results showed that CV could adjust the arrangement of CTMA in the CTMA–CV aggregates, which might be the reason for the enhanced adsorption capacity. Results of this work suggest that montmorillonite can be used as a low-cost and high-efficient adsorbent for the simultaneous removal of different types of organic contaminants from water.
      Graphical abstract image

      PubDate: 2014-01-08T00:02:36Z
       
  • Some consequences of the fluorination of brucite-like layers in layered
           double hydroxides: Adsorption
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Enrique Lima , Heriberto Pfeiffer , Jorge Flores
      Hydrotalcite-like compounds were synthesised by co-precipitation method. The originality of the work is the replacement of structural OH− by F−. Fluoride anions were incorporated as a part of the brucite like layers not as compensating anions. The resulting adsorptive properties of fluorinated materials are very different than those observed for the fluorine-free sample. The polarity and polarisability parameters were calculated by using dyes and xenon as molecular probes. The hydrogen bond accepting character and acido-basicity are the main properties enhanced because of the fluorination of hydrotalcite-like compounds, helping to diversify adsorption sites for chromophores or water.
      Graphical abstract image

      PubDate: 2014-01-08T00:02:36Z
       
  • Synthesis, characterization and electrochemical behavior of
           montmorillonite poly(o-toluidine) nanocomposites
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): R. Baby Suneetha , C. Vedhi
      Toluidine was polymerized with montmorillonite (Mt) by the chemical oxidation method using potassium perdisulfate by varying the toluidine to clay ratio. The solubility of the chemically prepared clay-polymer nanocomposites (CPN) was ascertained and it showed good solubility in DMSO and DMF. The in situ intercalative polymerization of o-toluidine (POT) within the Mt layers was analyzed by FTIR, UV–visible, XRD, SEM and TEM. The analyses of UV visible and FTIR spectroscopy demonstrated that o-toluidine has been polymerized to POT in its conducting emeraldine form. The conformation adopted by POT chains in the Mt interlayer depended on the molar ratio of o-toluidine to montmorillonite. FTIR spectra showed that amine vibration peak observed at 1593cm−1 was shifted to lower wave numbers when the CPN were formed. SEM analysis showed the variation in morphology from granular agglomerate to layered flaky structure as the clay mineral concentration was increased. Elemental analysis was done by EDAX which shows the presence of Na, Mg Al, Si, C and N. Thermal stability of the CPN was studied using TGA/DTA and DSC studies. The X-ray diffraction studies revealed the formation of nano sized (28nm) crystalline CPN. Cyclic voltammetric studies of the synthesized CPN exhibited good adherent behavior on electrode surface at pH1.0. It exhibited one oxidation peak at 0.405V and one reduction peak at 0.299V. By varying the atmosphere it was found that the CPN modified electrode exhibited oxygen reducing capacity.


      PubDate: 2014-01-08T00:02:36Z
       
  • Impact of high-pH fluid circulation on long term hydromechanical behaviour
           and microstructure of compacted clay from the laboratory of Meuse-Haute
           Marne (France)
    • Abstract: Publication date: February 2014
      Source:Applied Clay Science, Volumes 88–89
      Author(s): Olivier Cuisinier , Dimitri Deneele , Farimah Masrouri , Adel Abdallah , Nathalie Conil
      The main object of the study was to depict couplings between the hydromechanical behaviour of compacted clayey soil and the mineralogical and microstructural transformations induced by high-pH water. This high-pH water could be generated by the degradation of concrete lining of deep galleries in the context of the storage of nuclear wastes in deep facilities. The tested material is the clay that comes from the laboratory of the Meuse-Haute Marne laboratory (MHM-clay). Compacted MHM-clay samples were subjected to the circulation of high-pH water or natural site water over an 18-month period. The hydromechanical properties, microstructural characteristics and some physicochemical properties of the samples were then determined (i.e., shear strength, swelling properties, retention curve, mineralogy and microstructure). After the circulation of high-pH water, a strong reduction of the swelling properties associated to an increase in friction angle was evidenced, whereas the hydrodynamic properties remained stable. These modifications were associated with an alteration of the fabric of the samples, i.e., the dissolution of the initial clay minerals and the precipitation of neoformed illite, which is a non-swelling mineral. The results demonstrated that chemo-hydromechanical couplings occurred during the circulation of high-pH water and resulted in the modification of the material's mineralogy. Thus, these processes are likely to alter the sealing characteristics of a backfill constructed from a compacted MHM-clay in the very long term.


      PubDate: 2014-01-04T00:02:32Z
       
  • Evaluation of anion adsorption properties of nanocomposite polymer
           hydrogels containing layered double hydroxides
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Toshiyuki Hibino
      The feasibility of nanocomposite polymer hydrogels as anion adsorbents was explored by using agarose-layered double hydroxide (LDH) hybrids. Also, to obtain fundamental data for possible applications such as slow drug release of more complex hybrid hydrogels such as ionic polymer–LDHs, the absorption ability of LDH highly dispersed in an uncharged polymer, agarose, was evaluated. An aqueous colloidal dispersion of LDH containing lactate was mixed with agarose and water. Then, the mixture was boiled to dissolve the agarose and cooled to form a gel. It was confirmed by SEM that LDH nanoplates were uniformly dispersed in the resulting nanocomposite hydrogels. LDH restacked from the colloidal dispersion by evaporation of water was used for comparison. Samples were treated with an acetate-buffer/NaCl solution to replace lactate anions in LDHs with Cl− anions and to exclude contaminating carbonate anions from LDHs. Adsorption ability for SO4 2− was evaluated as the amount of adsorbed anion per unit quantity of LDH by normalizing the amounts of adsorbed anion by the Al content (mol/mol). The adsorption ability of the LDH nanoplates in the hybrid gels was lower than that of the restacked LDH when the LDH contents were low. When LDH/agarose ratio was lower, agarose polymer probably covered the LDH nanoplates more, which may have hindered anion access to the LDH nanoplates. When the LDH content was increased so that the ratio of LDH to agarose approached 1:1 by weight, the adsorption ability of the LDH nanoplates was about the same as or slightly greater than that of the restacked LDH. In addition, when LDH:agarose=1:1, anion selectivity among SO4 2− , I− and HPO4 2− was about the same between the hybrid gel and the restacked LDH.
      Graphical abstract image

      PubDate: 2013-12-31T00:12:08Z
       
  • Retention of iodide by the Callovo-Oxfordian formation: An experimental
           study
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): G. Montavon , A. Sabatié-Gogova , S. Ribet , C. Bailly , N. Bessaguet , D. Durce , E. Giffaut , C. Landesman , B. Grambow
      The Callovo-Oxfordian (COx) clayed formation is chosen in France as the possible site for an underground nuclear waste disposal. The question raised in this paper concerns the ability of the COx to sorb iodine. Experimental set-ups working in both batch and dynamic systems have been designed for the accurate determination of weak retention factors (i.e. <0.1L/kg) under conditions relevant to the geological formation. Adsorption data measurements were combined with speciation studies performed by anion exchange chromatography. Iodide was shown to be the only form of iodine present in the system regarding both the natural pristine iodine content of the samples and iodine added to the samples. A weak but significant adsorption was observed at 20°C (Kd<0.31L/kg). The adsorption process is reversible when working under fixed PCO2 (1% CO2) with the necessity to consider a kinetic-controlled process under dynamic conditions. When the partial CO2 pressure was not controlled, a part of iodine was shown to be irreversibly bound, probably in a newly precipitated carbonate phase. A Kd value in the range of 0.01–0.14L/kg can be given under controlled PCO2 to describe the adsorption of trace concentrations of iodine by the COx formation.


      PubDate: 2013-12-31T00:12:08Z
       
  • Adsorption of pentachlorophenol to a humin-like substance–bentonite
           complex prepared by polycondensation reactions of humic precursors
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Masami Fukushima , Ryo Okabe , Ryo Nishimoto , Shigeki Fukuchi , Tsutomu Sato , Motoki Terashima
      Humic substances have natural surfactant characteristics and have a relatively high affinity for pentachlorophenol (PCP). However, humic substances cannot be loaded into bentonite (Bent) via intercalation because of their larger size. In the present study, a humin-like substance (HuLS) was prepared by polycondensation reactions of humic precursors, such as glycine and catechol, and the product was loaded into Bent. XRD patterns showed that the basal spacing, calculated from the montmorillonite peak, for the HuLS–Bent complex was larger than that for Bent itself, indicating that the intercalation of HuLS was successful. The adsorption capabilities of PCP were evaluated from adsorption isotherms at pH4.0, 5.5 and 6.5. At all pH values, the linear adsorption coefficients of PCP, K d (Lkg−1), for the HuLS–Bent complex (37 at pH6.5, 247 at pH5.5 and 804 at pH4.0) were significantly larger than those for Bent itself (not determined at pH6.5, 40 at pH5.5 and 94 at pH4.0). These results show that the adsorption capabilities of PCP can be enhanced by loading HuLS onto Bent. In addition, the K d values for Bent and the HuLS–Bent complex were found to be pH-dependent, in that the K d value decreased with increasing pH. Because of the pK a for PCP (4.75), more than 90% of the PCP was present as the anionic form at pH5.5 and 6.5. In addition, the values for the Zeta potentials for Bent and the HuLS–Bent complex remained negative at pH2–12 and decreased with increasing pH. It thus appears that electrostatic repulsion between the anionic form of PCP and the adsorbents can affect the adsorption capabilities.
      Graphical abstract image

      PubDate: 2013-12-31T00:12:08Z
       
  • Formulation and antibacterial profiles of clay–ciprofloxacin
           composites
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): A.R. Hamilton , G.A. Hutcheon , M. Roberts , E.E. Gaskell
      The ability of clay minerals to adsorb and desorb drugs, including antibacterial molecules, is an attractive and exciting prospect for healthcare applications. The antibacterial ciprofloxacin was adsorbed onto kaolin, montmorillonite K-10, and Laponite® RD then the subsequent antibacterial activity of the composites formed was confirmed. The effects of time, pH, and CIP concentration were investigated. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to confirm the mechanism of ciprofloxacin adsorption onto the clay minerals. Dispersion pH was the most important variable influencing the adsorption of ciprofloxacin onto the clay minerals and the mechanism of adsorption was confirmed as cation exchange. Adsorption isotherms and application of Langmuir and Freundlich models showed that a ciprofloxacin monolayer was formed at different concentrations on each of the clay minerals tested. Kinetic studies showed that maximal CIP adsorption was achieved within the first hour of adsorption. Antibacterial activity of clay–ciprofloxacin composites against the common skin bacteria Staphylococcus epidermidis and Propionibacterium acnes was demonstrated. This work showed that clay–ciprofloxacin composites are potential delivery systems for ciprofloxacin molecules. As a result, this could make them ideal candidates to take forward for healthcare applications, including the development of novel wound dressings.
      Graphical abstract image

      PubDate: 2013-12-31T00:12:08Z
       
  • Stress relaxation behavior of organically modified montmorillonite filled
           natural rubber/nitrile rubber nanocomposites
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Hanna J. Maria , Nathalie Lyczko , Ange Nzihou , Kuruvilla Joseph , Cherian Mathew , Sabu Thomas
      To reduce material consumption, it is important to have reinforced material with longer life time. Incorporation of nanoparticles to reinforce and compatibilize polymer blends is one of the widely undergoing research areas in polymer science technology. A series of natural rubber and nitrile rubber (NR/NBR) nanocomposite vulcanazite, reinforced with two different organically modified clay (OMt) were prepared. To predict the performance of a material over long periods of time, stress relaxation studies with both the reinforced systems were done. The effects of loading, blend composition, filler polarity and temperature on stress relaxation of OMt reinforced NR/NBR nanocomposites were carefully measured. Based on the stress relaxation measurements, it was observed that due to its polarity difference, O1Mt (Mt modified with dimethyl, benzyl, HT modification provided by Southern Clay Products) was preferentially located at the NBR phase while O2Mt (Mt modified with mercapto silane provided by English India Clay) had more affinity with natural rubber in the NR/NBR nanocomposites. The preferential localization of OMt has been analyzed by HRTEM. The nature of interaction of the nanoclay was found to influence the stress relaxation rate. NR/NBR nanocomposites with higher filler loading showed higher rates of relaxation rate due to the presence of more filler–filler interactions. At 70°C, the viscosity ratio was found to influence the reinforcement, and consequently relaxation rate of the 50/50 NR/NBR nanocomposites. It was found that the rearrangements of the polymer chains are dependent on the blend composition, temperature, filler/polymer interactions etc. To explain and predict observed phenomena, the stretched-exponential Kohlrausch equation and Maxwell–Weichert model were used. For both models, the experimental curve fitted well with the theoretical models.
      Graphical abstract image

      PubDate: 2013-12-31T00:12:08Z
       
  • Zeolite occurrence and genesis in the Late-Cretaceous Cayo arc of Coastal
           Ecuador: Evidence for zeolite formation in cooling marine pyroclastic flow
           deposits
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): L. Machiels , D. Garcés , R. Snellings , W. Vilema , F. Morante , C. Paredes , J. Elsen
      This paper describes the quantitative mineralogy, the mineral chemistry and the distribution of natural zeolites over the outcrop area of the Late Cretaceous Cayo Formation of Coastal Ecuador (>1000km2) and develops a model for zeolite alteration in the Cayo volcanic arc. Different zeolite types were identified: Ca-heulandite-type zeolites (clinoptilolite and heulandite), mordenite, laumontite, analcime, stilbite, epistilbite, chabazite, thomsonite and erionite. Zeolites occur over nearly the entire outcrop area and the entire stratigraphical thickness of the Cayo Formation, in percentages varying between less than 20 and nearly 100wt.%. A substantial amount of the analysed samples (1/8) has zeolite contents higher than 50wt.% and could potentially be used in agriculture, aquaculture, for waste water treatment or as supplementary cementitious materials. A clear difference in zeolite type and content was observed when comparing the lower and upper units of the Cayo Formation and the distribution of these units determines the zeolite distribution over the outcrop area. In the upper unit, Ca-HEU-type zeolites are the main zeolite minerals and rarely laumontite and analcime occur. A smectite-rich smectite/chlorite (C/S) is the major associated alteration mineral, while quartz contents are relatively low. In the lower unit, the zeolite mineralogy is more variable and mordenite, Ca-HEU-type zeolites and laumontite are common. Stilbite, epistilbite and analcime occur rarely. Further quartz, albite, C/S and celadonite occur as associated alteration minerals. Little burial metamorphism or volcanically induced hydrothermal alteration has affected the deposits of the Cayo formation. Mineral alteration occurred mainly by interaction of hot pyroclastic glass with marine water, present as pressurized steam in cooling pyroclastic flow deposits on one hand or by low temperature diagenesis of already cooled pyroclastic or epiclastic deposits on the other hand. A model similar to the “geoautoclave” model is proposed to explain the genesis of zeolites, in which an autoclave is formed by the hydrostatic pressure exerted by the marine water column overlying the pyroclastic deposits, preventing gas escape and promoting glass dissolution, zeolite formation and, conversion to higher-grade phases possible if heat can be maintained for a long enough period.


      PubDate: 2013-12-31T00:12:08Z
       
  • Editorial Board
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87




      PubDate: 2013-12-31T00:12:08Z
       
  • Ion exchange in amorphous alkali-activated aluminosilicates: Potassium
           based geopolymers
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Taisiya Skorina
      Ion exchange properties of pure potassium-based geopolymer (pure K-GP) formulated with Si/Al=2.1 and K/Al=1.0±0.02 atomic ratios have been studied. For pure K-GP, the maximum ion-exchange level of K+ with respect to Na+ and Cs+ is 77 and 61%, respectively, as determined by exhausted exchange with 1M solutions of appropriate nitrates at 22±2°C. The geopolymer shows a slight preference for K+ over Cs+ as indicated by the normalized Cs/K-GP isotherm obtained under noncompetitive exchange. Parent geopolymer yields a pure geopolymer when it is extensively washed with deionized water until neutral pH is obtained and equilibrated with aqueous solution of KNO3 resulting in changing in composition and textural properties. As calculated from N2 sorption–desorption isotherms, surface specific area and cumulative pore volume for parent K-GP are 5.5m2 g−1 and 0.01cm3 g−1, respectively, whereas for pure K-GP surface specific area and cumulative pore volume are 270m2 g−1 and 0.4cm3 g−1, respectively.


      PubDate: 2013-12-31T00:12:08Z
       
  • A hydrodynamic method for the measurement of Laponite-RD caffeine binding
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Kellen J. Sorauf , Daniel E. Connors , Todd A. Wells , Keith E. Miller
      A novel flow-based technique to determine effective binding constants between caffeine and dispersed Laponite-RD particles in aqueous dispersions is presented. The technique, which is based on wide-bore hydrodynamic chromatography principles, exploits diffusion coefficient and flow profile differences between caffeine and Laponite-RD. A high-pressure liquid chromatography pump is used to create a laminar flow of mobile phase through a 0.25mm diameter capillary; flow conditions are optimized in the capillary to exploit differences in diffusion coefficients of the dispersed Laponite-RD particles and caffeine. Different flow profiles for Laponite-RD and caffeine result enabling a deconvolution algorithm to determine the concentrations of caffeine associated with the Laponite-RD, a model nanoparticle, as well as the caffeine free in solution. Using these data, binding isotherms are presented from which an effective binding constant of caffeine associated with Laponite-RD can be obtained.


      PubDate: 2013-12-31T00:12:08Z
       
  • Use of 29Si and 27Al MAS NMR to study thermal activation of kaolinites
           from Brazilian Amazon kaolin wastes
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Ana Áurea Barreto Maia , Rômulo Simões Angélica , Roberto de Freitas Neves , Herbert Pöllmann , Chris Straub , Kay Saalwächter
      The study of thermal activation of kaolinite at various temperatures to produce highly reactive metakaolinite from Brazilian Amazon kaolin wastes was studied using 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR). The wastes used in the current study came from the Capim and Jari regions in northern Brazil. The mineralogical and chemical characterizations of Jari kaolin (KJ) waste were performed by XRD, FTIR, DTA–TGA, SEM and chemical analyses. The results indicate that the Jari and Capim kaolins (KC) wastes are composed primarily of kaolinite and that KJ is composed of a typical kaolinite with a low degree of structural order. The ideal temperature to produce highly reactive metakaolinite is 600°C for KJ and 700°C for KC, suggesting that the degree of structural order of kaolinite has a definite influence on its dehydroxylation temperature. These results were confirmed when zeolite NaA was synthesized from metakaolins produced at temperatures used in this work.


      PubDate: 2013-12-31T00:12:08Z
       
  • Use of polymer as template in microwave synthesis of saponite. Study of
           several factors of influence
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Fiseha B. Gebretsadik , Pilar Salagre , Yolanda Cesteros
      Several saponites were synthesized at pH=8 by microwaves or conventional hydrothermal aging with different slurry dilutions (H2O/Si molar ratios of 250, 125 and 50) at 453K under autogenic pressure. The influence of using a polymer as template, during the synthesis, and its molecular mass was investigated. The saponite prepared with medium dilution slurry by microwaves had the best incorporation of Al3+ in tetrahedral positions (AlT/AlO =9.2), in agreement with its highest C.E.C. (0.87mEq/g). Additionally, this sample showed the highest surface area (461m2/g). In general, the increase of the slurry concentration and the presence of polymer improved the order in the tetrahedral sheet and decreased the amorphous silica content. The effect of polymer, on the stacking, was low but depended on the dilution and heat source (microwaves or conventional). The use of polymer and its molecular mass modified the saponite porosity and the incorporation of Al3+ in the tetrahedral sheet.


      PubDate: 2013-12-31T00:12:08Z
       
  • Synthesis and thermal decomposition of metal hydroxide intercalated
           saponite
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): N. Nityashree , Ujjal K. Gautam , Michael Rajamathi
      Chlorite-like nanocomposites in which the anionic clay layers are intercalated between the cationic clay layers were prepared by mixing an aqueous colloidal dispersion of exfoliated layers of copper hydroxysalt or α-cobalt hydroxide with an aqueous colloidal dispersion of exfoliated saponite layers. The nanocomposites showed a different thermal decomposition behavior compared to the parent layered solids. The thermal decomposition of the chlorite-like nanocomposites resulted in nanocomposites in which metal oxide (CuO/Co3O4) nanoparticles are uniformly distributed in saponite matrix. The particle size of the oxide nanoparticles in the nanocomposite could be varied by varying the decomposition parameters such as the temperature and duration of decomposition.
      Graphical abstract image

      PubDate: 2013-12-31T00:12:08Z
       
  • Long-term effect of water chemistry on the swelling pressure of a
           bentonite-based material
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Qiong Wang , Yu-Jun Cui , Anh Minh Tang , Pierre Delage , Behrouz Gatmiri , Wei-Min Ye
      Compacted bentonite-based materials have been proposed as possible sealing and backfill materials in geological repositories for the high-level radioactive waste disposal in several countries. During the long time lifespan of a repository, as the chemical composition of pore water can change, the swelling and sealing capacity of the material may also change. From a point of view of storage safety assessment, it is important to evaluate this possible change of swelling capacity. In this study, a mixture of bentonite and crushed Callovo-Oxfordian claystone was investigated. The long-term effect of pore water chemistry on the swelling pressure was studied at constant-volume conditions for 700days. Distilled water and synthetic water having the chemical composition similar to that of in-situ pore water were used for hydration. The results obtained in an initial period of 100h revealed no significant influence of the water composition on the swelling pressure evolution, and the maximum swelling pressures observed were close to 4.30MPa for a dry density of 1.70Mg/m3. Over a longer time period, on the contrary, the swelling pressure eventually decreased for all samples, especially for the sample saturated with synthetic water. In addition, comparison of a one-step soaking test with a multi-step soaking test showed no wetting procedure effect on the long term swelling behaviour. All the results are analysed by considering the physico-chemical interaction between the minerals of claystone, minerals of bentonite and different fluids involved.


      PubDate: 2013-12-31T00:12:08Z
       
  • Hydraulic properties of smectite rich clay controlled by hydraulic
           gradients and filter types
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Laith Al-Taie , Roland Pusch , Sven Knutsson
      The common practice in geotechnical laboratories is to apply high hydraulic gradients for getting results in reasonable time but this can jeopardize the accuracy. In this paper, the hydraulic conductivity of a smectite rich clay from Iraq was determined under different hydraulic gradients (5 to 10,000m/m) using several densities and two permeants. Also, two types of filters were used, ordinary stainless steel sintered filter and sand/silt filter, in order to examine the possible effect of clogging by dragged clay gel particles. It was concluded that the outflow filter can affect the evaluated conductivity especially when applying high hydraulic gradients. For sintered filters the hydraulic conductivity was reduced as the gradient increased, while the conductivity increased as the hydraulic gradient increased when using sand/silt filters. For salt water the impact of the gradient was less obvious than for distilled water. A theoretical model was derived for selecting safe hydraulic gradients as a function of dry density, swelling pressure and permeant type. A major conclusion was that the gradient in laboratory testing should not exceed 100m/m.


      PubDate: 2013-12-15T10:38:02Z
       
  • Impact of clay mineral particle morphology on the rheological properties
           of dispersions: A combined X-ray scattering, transmission electronic
           microscopy and flow rheology study
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Christian Blachier , Alain Jacquet , Martin Mosquet , Laurent Michot , Christophe Baravian
      The rheological features of aqueous dispersions of three clay minerals, illite, kaolinite and montmorillonite are analyzed using the notion of effective volume fraction that links the morphological properties of the suspended solids to their hydrodynamical behavior. The morphological information obtained from an appropriate treatment of the flow curves is confronted to the results obtained by small and wide angle X-ray scattering and transmission electron microscopy. The excellent agreement obtained by independent measurements proves that rheology can be used as a relevant tool to obtain information about the morphology of clay mineral particles. The fruitfulness of this approach is further evidenced by analyzing the influence of the presence of various clay minerals on the rheology of a concentrated calcareous sand. It was proved that using effective volume fractions, the behavior of various sand–clay mineral mixtures can be easily rationalized.
      Graphical abstract image

      PubDate: 2013-12-15T10:38:02Z
       
  • Using design of mixture experiments to optimize triaxial ceramic tile
           compositions incorporating Cambodian clays
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Bun Kim Ngun , Hasmaliza Mohamad , Ken-ichi Katsumata , Kiyoshi Okada , Zainal Arifin Ahmad
      Two Cambodian clay deposits were used for the development of tile formulations using the statistical design of mixture experiments. The tile formulation also included addition of feldspar and silica sand and Malaysian industrial clay was used for comparison. The specimens were pressed (30MPa) before firing (1170°C) and then characterized for their linear firing shrinkage, water absorption and modulus of rupture. Regression models were calculated by relating the sintered properties with the compositions. The significance and adequacy of the models were confirmed by statistical analysis and experimental verification. It was found that Cambodian clays are suitable to be used as raw material in the ceramic tile industry and that the regression models can be used to select the optional compositions with respect to the standard ceramic tile specifications. The models were not tested with the lack-of-fit test as this is only a preliminary study to evaluate the properties of the fired ceramics.


      PubDate: 2013-12-15T10:38:02Z
       
  • Biodegradation and adsorption of crude oil hydrocarbons supported on
           “homoionic” montmorillonite clay minerals
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Uzochukwu C. Ugochukwu , Martin D. Jones , Ian M. Head , David A.C. Manning , Claire I. Fialips
      The role of “homoionic” montmorillonites in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clay mineral used for this study was montmorillonite which was treated with the corresponding metal chloride salt to produce Na-, K-, Mg-, Ca-, Zn-, Al-, Cr-, and Fe-montmorillonites used in this study. The study indicated that Zn- and K-montmorillonites were inhibitory to biodegradation of the crude oil hydrocarbons and appears to do so as a result of extensive adsorption of the hydrocarbons. However, Na-, Ca- and Fe-montmorillonites with relatively high surface area and cation exchange capacity (CEC) were stimulatory to biodegradation of the crude oil hydrocarbons. This study reveals that whereas surface area and the ‘local bridging effect’ were important factors from the clay minerals that conferred stimulatory effect on the biodegradation of the hydrocarbons, the hydrolysis of the interlayer water by trivalent cations of the clay to generate protons and increase acidity of the medium is suggested to be inhibitory to biodegradation of the crude oil hydrocarbons. The interlayer cations (trivalent cations) that impart the highest local bridging effect which is stimulatory to biodegradation also impart the highest hydrolysis of interlayer water which is inhibitory. This study showed that interlayer cations play a crucial role on the ability of the clay mineral to influence biodegradation of the hydrocarbons.


      PubDate: 2013-12-15T10:38:02Z
       
  • Producing protein intercalated bentonite — Equilibrium, kinetics and
           physical properties of gelatin–bentonite system
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Rashid M. Shamsuddin , Casparus J.R. Verbeek , Mark C. Lay
      Protein intercalated bentonite was produced using gelatin with calcium (CaBt), sodium (NaBt) and octadecylamine-modified bentonite (amine Bt). Adsorption isotherms and rates were investigated from pH3 to pH9 and 4 to 20mg/ml initial gelatin concentrations using 3g of adsorbent loading per 100ml solution. At 20mg/ml gelatin solution, the highest gelatin adsorption obtained for CaBt was 372mg/g or 58.9% gelatin recovery between pH3 to pH5.23 while NaBt showed the best adsorption between pH7 to pH9 with 405mg/g or 60.4% gelatin recovery. Amine Bt showed consistently poor adsorption with the highest gelatin adsorption of 222mg/g or 33.5% recovery at pH3. Basal spacing (d-value) for CaBt increased from 16.3 to 20Å while NaBt increased from 12.4 to 20–23Å, indicating that intercalation had occurred. Adsorption equilibriums were modelled using the Langmuir, Freundlich, Langmuir–Freundlich and Temkin isotherms. The best regression coefficients were given by the Langmuir–Freundlich isotherm for CaBt and NaBt, and by the Freundlich isotherm for amine Bt. Adsorption was rapid with gelatin–bentonite solutions reaching equilibrium within 10–20min. Adsorption rates decreased with increasing initial gelatin concentration suggesting that protein diffusion decreased due to increased solution viscosity.


      PubDate: 2013-12-11T03:01:53Z
       
  • Organoclays with hexagonal rotator order for the paraffinic chains of the
           compensating cation. Implications on the structure of clay polymer
           nanocomposites
    • Abstract: Publication date: Available online 9 December 2013
      Source:Applied Clay Science
      Author(s): Valeria Cipolletti , Maurizio Galimberti , Marco Mauro , Gaetano Guerra
      Organically modified clays (OC) were prepared by reacting montmorillonite (Mt) and dimethyl ditallow ammonium chloride (2HTCl), optionally adding either stearic acid (SA) or 2-stearamidoethyl stearate (SAES). Reactions were performed either at the solid state, in the absence of any other chemical substance, or with the help of solvents such as water and alcohol, or in poly(1,4-cis-isoprene) as the reaction medium. Characterization was performed by means of TGA, XRD, DSC, IR analyses. Two types of OC were identified, with 3.6–4.0nm and about 6nm as d 001 basal spacing, independently of the synthetic route. The 3.6–4nm value could be explained with the bilayer placement of the tilted paraffinic chains of the ammonium cation. The 6nm value could arise from the perpendicular placement of the paraffinic chains, associated with the presence in the interlayer space of either the acid or the amide. For the first time, it is documented the occurrence of hexagonal rotator order in the packing of the long hydrocarbon tails of the 2HT compensating cation. SA and, in particular, SAES were found to enhance this type of order. A third type of OC, with 2.5nm as d 001 basal spacing was obtained through solvent extraction of the above mentioned OC. Results reported in this work show that the crystalline structure of an OC depends on type and amount of low molecular mass substances present in the interlayer spa compensating cations and guests such as an acid and/or an amide. For a given compensating cation, the interlayer distance can be varied by changing the amount of the cation and by adding a guest. The Mt/2HT organoclay studied in this work reveals 2.5, 3.6–4.0 and 6.0nm as the interlayer distances of the minima of energy. Polymer chains are not involved in the OC crystalline structure, even if the OC synthesis is performed in the polymer matrix. This work strongly suggests that the best explanation for most interlayer spacing variation observed for clays in polymer nanocomposites is the different placement of intercalated low molecular mass substances, rather than the generally assumed polymer chain intercalation. Moreover, it presents the synthesis of OC at the solid state as a versatile method for preparing a large variety of clay polymer nanocomposites.


      PubDate: 2013-12-11T03:01:53Z
       
  • Polarization analysis of green sand and parameter optimization under
           exciting electric field
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Dequan Shi , Guili Gao , Dayong Li , Lihua Wang
      The polarization mechanism of green sand under direct current electric field was further analyzed by means of an equivalent mathematical model, and it was the absorption current that caused the polarization of green sand. However, the absorption current was essentially caused by the ions of the clay. Therefore, the clay was the source of the polarization and its content mainly determined the degree of polarization. Experiments based on the Taguchi method showed that the electrode area had the most important influence on the polarization, followed by the voltage amplitude and the frequency. The interactions of these three parameters did exist, and the interaction between the electrode area and the voltage amplitude had a bigger influence on the polarization than the frequency. The optimal exciting field parameters were that the voltage amplitude was 5V, the frequency was 1kHz and the electrode area was 2500mm2. The clay content and moisture content can be obtained by an artificial neural net according to AC voltage, DC voltage and DC voltage drop.


      PubDate: 2013-12-11T03:01:53Z
       
  • Preparation and characterization of montmorillonite modified with
           3-aminopropyltriethoxysilane
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Paula T. Bertuoli , Diego Piazza , Lisete C. Scienza , Ademir J. Zattera
      The modification of montmorillonite clay mineral (Mt) was performed using the 3-aminopropyltriethoxysilane (γ-APS) silylation agent in different synthesis solutions. The modified products (S-Mt) were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The XRD demonstrated that silane was intercalated in the interlayer space of Mt due to the increase in basal spacing. The basal spacing shown by some S-Mts suggests the presence of a double layer of aminopropyl molecules in the interlayer space of the clay mineral modified in water and in a hydroalcoholic media at both synthesis temperatures (50°C and 80°C). The TGA revealed the presence of peaks in the range of 200°C to 600°C due to the presence of adsorbed silanes, intercalated silanes and silanes chemically bonded between the clay mineral layers and/or the edges. Evidence showed that the presence of water in dispersant is essential for intercalation of the silane in the interlayer space of the Mt such that the S-MMTwater, S-MtE/A(50) e S-MtE/A(80) showed higher amount of silane and higher basal spacing in its structure. Qualitative evidence of the presence of γ-APS in the modified clay minerals was obtained by FTIR spectroscopy.
      Graphical abstract image

      PubDate: 2013-12-11T03:01:53Z
       
  • Comparative study on the application of ethanol–bentonite slurry and
           salt–bentonite slurry as effective injection materials for barrier
           sealing
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Larry Pax Chegbeleh , Sandow Mark Yidana , Makoto Nishigaki , Francis Achampong
      A deep geological repository for high level radioactive waste disposal is a multi-barrier system whose overall performance depends on the effective sealing of the barriers. Effective barrier sealing can be achieved by the use of good grouting materials. A good grouting or injection material is one that is capable of penetrating very narrow voids of injection medium and effectively sealing them. The effects of both organic and inorganic solvents (ethanol and aqueous salt) on the rheological and injection characteristics of bentonite (Bent) slurry were investigated experimentally, with the aim of choosing between the two, a better injection material for effective sealing. Wyoming Bent, used as the injection material, was mixed with various concentrations of ethanol and 4% salt solution to form two separate slurries: Ethanol–bentonite (Eth–Bent) slurry and Salt–bentonite (Salt–Bent) slurry respectively. Prepared slurries were injected into a synthetic fracture of apertures 100, 80 and 60μm under dynamic injection to determine the penetrability of the slurries into the apertures. The viscosities of the slurries were also determined. The results revealed that, both salt and ethanol are capable of suppressing the swelling property of Bent to form better injectable slurry than the slurry formed when fresh water is mixed with Bent. This was inferred from the successful injection behavior of the slurries through micro-fractures of aperture sizes 60–100μm. Though ethanol and salt have the capability of suppressing the swelling behavior of Bent, the effect was more pronounced with salt as the viscosities were lower for salt than ethanol. Salt–Bent slurry can conclusively be considered as a more effective grouting material than Eth–Bent slurry for effective sealing.


      PubDate: 2013-12-11T03:01:53Z
       
  • Influence of viscosity modifier nature and concentration on the viscous
           flow behaviour of oil-based drilling fluids at high pressure
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): J. Hermoso , F. Martinez-Boza , C. Gallegos
      This work deals with the effect of viscosity modifier nature and concentration on the rheological properties of model oil-based drilling fluids (OBM) submitted to high pressure. The oil-based fluids were formulated by dispersing, with a high shear mixer, two selected organobentonites in a mineral oil, at room temperature. The viscous flow behaviour of the corresponding dispersions was characterised as a function of pressure, organoclay nature and organoclay concentration, using a controlled-stress rheometer equipped with both pressure cell and coaxial cylinder geometries. A factorial Sisko–Barus model, which takes into account both shear and pressure effects in the same equation, fitted the experimental pressure–viscosity data fairly well. The influence of disperse phase concentration on the shear-thinning characteristics of these organoclay dispersions is related to the development of different microstructures, which depend on organoclay nature. In this sense, the resulting microstructure has been attributed to the cohesion energy between microgels domains. From the experimental results obtained, it can be concluded that the viscous flow behaviour of the OBM investigated is strongly affected by organoclay nature and concentration. The pressure–viscosity behaviour of these dispersions is mainly influenced by the piezoviscous properties of the oil and the properties of the continuous phase. The Sisko–Barus model proposed can be a useful tool, from an engineering point of view, for calculating pressure losses in the different sections of the bore, as well as being of significant help to solve other additional problems, such as hole cleaning, induced fracturing, and hole erosion during the drilling operation.


      PubDate: 2013-12-11T03:01:53Z
       
  • Synthesis of polyhedral oligomeric silsesquioxane-modified organic
           montmorillonites and their nanocomposites with poly(l-lactide)
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Dan Bi , Qifang Li , Guang-Xin Chen
      Novel montmorillonites (Mts) were prepared by reacting aminopolyhedral oligomeric silsesquioxane (POSS) with organic Mt (OMt). Poly(l-lactide) (PLLA)-based nanocomposites with Mt were produced by melt compounding. The effects of POSS modified OMt (POSS-OMt) on the gas transport, thermal properties, and morphology of PLLA were investigated. POSS in the interlayers of OMt exerted important effects on the properties of the clay polymer nanocomposites (CPN). XRD studies revealed that the layer spacing of OMt increased from 1.68nm to 3.74nm after intercalation with POSS. TEM findings indicated that the CPN consisted of a random dispersion of intercalated/exfoliated aggregates throughout the PLLA matrix. DSC results demonstrated that incorporation of 2mass% POSS-OMt results in a significant increase in crystallization temperature. TGA studies further showed that the CPN prepared from POSS-OMt displays a 31.2°C increase in decomposition temperature for 5% mass loss relative to virgin PLLA. Gas permeation analysis showed that increasing the Mt concentration in the polymer matrix leads to expected decreases in permeation values. The gas barrier properties of the CPN were comparable with those predicted by phenomenological models, such as those from Nielsen and Cussler.
      Graphical abstract image

      PubDate: 2013-12-07T00:01:29Z
       
  • Experimental study on the role of clays as sealing materials in the
           geological storage of carbon dioxide
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Emilio Galán , Patricia Aparicio
      The aim of this work is to further the knowledge of reactions that can occur between carbon dioxide, diffused or escaped from a geological storage, and the sealing rock (e.g. clay-rich sediments). This research provides experimental data on the reactive behaviour of saponite (Mg-smectite), kaolin and Common Clay (composed of illite with minor montmorillonite) samples with CO2 in the presence of water or under dry conditions. The mechanisms for physical and chemical retention of CO2 were determined, and the influence of pressure, temperature and relative humidity on the effective sealing of the rock was examined. Firstly, the saponite did not physically adsorb CO2, and an amorphous phase was formed due to carbonic acid attack. Nevertheless, the Mg-smectite exchange cations, lead to the precipitation of dolomite and increase the mineral CO2 trapping. Secondly, the smectite and illite of the Common Clay sample were partially destroyed and the smectite destruction leads to the precipitation of some carbonates. Thirdly, kaolin did not physically trap CO2 nor any chemical reaction. This paper has demonstrated that the cannibalization of saponite and Common Clays is not total and the precipitation of carbonates may occur, which could avoid the progressive destruction of the sealing rock.
      Graphical abstract image

      PubDate: 2013-12-07T00:01:29Z
       
  • Freeze-drying: A versatile method to overcome re-aggregation and improve
           dispersion stability of palygorskite for sustained release of ofloxacin
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Qin Wang , Junping Zhang , Aiqin Wang
      In order to overcome the re-aggregation of palygorskite nanofibers in the drying process, the palygorskite clay was freeze-dried instead of the traditional oven-drying after disaggregated by high-pressure homogenization. The effects of freeze-drying temperature on the microstructure and physicochemical properties of palygorskite clay were investigated by SEM, FTIR and BET. Further, the dispersion stability and rheological properties of the freeze-dried palygorskite clay as well as its adsorption and in vitro release properties for ofloxacin were studied. The results showed that the re-aggregation of palygorskite nanofibers can be successfully overcome by freeze-drying. Meanwhile, the structure and aspect ratio of palygorskite nanofibers were kept very well. Consequently, the dispersion stability and apparent viscosity of palygorskite in deionized water were enhanced compared with the traditional oven-dried sample. In addition, the freeze-drying of palygorskite induced more of the adsorbed ofloxacin to be released within 24h although no evident increase in adsorption capacity was observed. This means that the adsorbed ofloxacin molecules remained active and most of them could be released from the freeze-dried palygorskite, which is very important for a drug delivery vehicle. Moreover, the physicochemical properties of palygorskite and the cumulative release of ofloxacin could be tuned by the freeze-drying temperature according to practical applications.
      Graphical abstract image

      PubDate: 2013-12-07T00:01:29Z
       
  • Effect of environmental conditions on the adsorption behavior of Sr(II) by
           Na-rectorite
    • Abstract: Publication date: January 2014
      Source:Applied Clay Science, Volume 87
      Author(s): Ying Zhao , Zhenyi Shao , Changlun Chen , Jun Hu , Hongli Chen
      The adsorption behavior of Sr(II) by Na-rectorite was investigated as a function of various environmental parameters such as pH, ionic strength, humic acid (HA) and temperature under ambient conditions. The results indicated that the adsorption of Sr(II) on Na-rectorite was strongly dependent on pH and ionic strength. The presence of HA enhanced the adsorption of Sr(II) on Na-rectorite at low pH, whereas suppressed Sr(II) adsorption on Na–rectorite at high pH. The Langmuir model simulated the adsorption isotherms of Sr(II) better than the Freundlich model at three different temperatures of 293, 313 and 333K. The thermodynamic parameters (ΔH 0, ΔS 0 and ΔG 0) calculated from the temperature dependent adsorption isotherms indicated that the adsorption process of Sr(II) on Na–rectorite was spontaneous and endothermic. The adsorption of Sr(II) was dominated by outer-sphere surface complexation and ion exchange at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The results indicate that Na-rectorite may be a promising candidate for the treatment of radionuclides from large volume solution.


      PubDate: 2013-12-07T00:01:29Z
       
  • Pararosaniline and crystal violet tagged montmorillonite for latent
           fingerprint investigation
    • Abstract: Publication date: Available online 2 December 2013
      Source:Applied Clay Science
      Author(s): Şerife Sarıoğlan , Serkan Gürbüz , Tuğba İpeksaç , Merve Gürtekin Seden , Melek Erol
      Use of cationic pigment-intercalated bentonite (montmorillonite, Mt) as the latent print development powder was investigated. The cationic dyes, crystal violet (CV) and pararosaniline (PS), were substituted with sodium ions present in the interlayers of Mt by ion exchange mechanism. Organophilic montmorillonites (OMts) were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), elemental analysis and Fourier transform infrared spectroscopy (FTIR). TGA results determined the average amount of dye molecules in OMts as 52mmol/100g for both PS and CV. Modified bentonite powders were applied to develop fresh and aged (1, 7 and 15days) fingermarks deposited on non-porous surfaces such as glass, metal and porcelain using a fiberglass brush. Sharp and clear prints with complete ridge details were developed on glass and metal surfaces even for the 15-day-old fingermarks. Surprisingly, CV- and PS-intercalated fingerprint powders successfully worked for the development of the seven-month-old fingerprints on the glass surface. In contrast, physically mixed bentonite and dye mixtures were not very successful in the development of even fresh fingerprints on the glass surface. CV-tagged bentonite also exhibited strong fluorescence at around 500nm when excited at 450nm.
      Graphical abstract image

      PubDate: 2013-12-03T00:02:34Z
       
  • Exfoliation of vermiculites with chemical treatment using hydrogen
           peroxide and thermal treatment using microwaves
    • Abstract: Publication date: Available online 2 December 2013
      Source:Applied Clay Science
      Author(s): Celia Marcos , Irene Rodríguez
      This paper presents the investigation about chemical and thermal exfoliation of vermiculites from Santa Olalla (Huelva, Spain), Libby (Montana, USA) and Goiás (Brasil). Four experiments were made: 1) Reaction of each sample from Santa Olalla, Libby and Goiás with hydrogen peroxide solution of 30% and 50% respectively, at different times for each sample. 2) Irradiation of Libby and Goiás samples with microwaves for 20s. 3) Reaction of Goiás samples with hydrogen peroxide solutions of 30 and 50 mass%, respectively, into microwave oven for 20s. 4) Abrupt heating of Libby vermiculite at 1000°C for 1min in an oven once stabilized (~2h). The original and treated vermiculite samples were characterized by X-ray diffraction (XRD) and thermogravimetry; their chemical composition was obtained by electron microprobe and their morphology was examined with the scanning electron optical and microscopy. The results of this study, in relation to the treatments with hydrogen peroxide, showed that: 1) The purest samples like those from Santa Olalla suffered minor changes (slight structural disorder) and the exfoliation was lower; while others like Libby, with higher content of iron and interlayer potassium, could suffer major changes with the formation of a new phase through interstratified phases, and the exfoliation grade was higher. 2) The exfoliation speed of the samples increased with the peroxide hydrogen concentration and might be attributed to higher dissolution of dissolved and/or exchanged amounts of cations such as sodium, potassium, magnesium and iron. In relation to the microwave irradiation: 1) No major structural changes in the investigated samples were observed as no major changes were observed in the XRD patterns of the treated samples in relation to the untreated ones. 2) Samples like those from Goiás, which did not exfoliate when irradiated with microwaves, exfoliate when treated with hydrogen peroxide and simultaneously irradiated with microwaves for a few seconds.


      PubDate: 2013-12-03T00:02:34Z
       
  • Estimation of the electric double layer thickness in the presence of two
           types of ions in soil water
    • Abstract: Publication date: Available online 2 December 2013
      Source:Applied Clay Science
      Author(s): Kshirendra Kumar Mahanta , Govinda Chandra Mishra , M.L. Kansal
      The deficit of charges on the clay surface is balanced by the cations in soil water forming the electric double layer (EDL). In sodic soil monovalent Na+ ions are dominant and hence, thickness of the EDL (β) is more than in the nonsodic soil where bivalent Ca2+ ions are dominant. For reclaiming the sodic soil, gypsum is added as a source of Ca2+ ions to replace the Na+ ions from the EDL as well as for reducing β. In this paper, an analytical solution is derived to the nonlinear Poisson–Boltzman equation and the solution is used for computing β exactly. A comparison is made between β computed from the solutions of linearized and nonlinear Poisson–Boltzman equation. The solution to the linearized Poisson–Boltzman equation overestimates β. Therefore, it is appropriate to adopt the solution of the nonlinear Poisson–Boltzman equation for computing β.
      Graphical abstract image

      PubDate: 2013-12-03T00:02:34Z
       
  • Optimized removal of Reactive Navy Blue SP-BR by organo-montmorillonite
           based adsorbents through central composite design
    • Abstract: Publication date: Available online 2 December 2013
      Source:Applied Clay Science
      Author(s): F. Rasouli , S. Aber , D. Salari , A.R. Khataee
      In this study, the Montmorillonite K10 (MMT-K10) was activated by sulfuric acid, followed by modification with cetyltrimethylammonium bromide (CTAB). The central composite design (CCD) was applied to optimize the activation process of MMT-K10. The effects of activation parameters (acid concentration, temperature, and contact time) on the decolorization efficiency of MMT-K10 (R%) were studied, and the optimum conditions were defined. The optimum values of input variables were found to be 50°C (temperature), 3.6mol/L (acid concentration) and 2.2h (contact time). The predicted and experimental values of responses were in reasonable agreement with each other (R2 =0.968 and adj-R2 =0.940). The activated and modified MMT-K10 was characterized by FTIR, XRD, SEM and TEM techniques. The FT-IR analysis confirmed that acid-activation and modification caused the intercalation of CTAB in MMT-K10 layers and increase in specific surface area.


      PubDate: 2013-12-03T00:02:34Z
       
 
 
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