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  Subjects -> EARTH SCIENCES (Total: 609 journals)
    - EARTH SCIENCES (448 journals)
    - GEOLOGY (67 journals)
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EARTH SCIENCES (448 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: 8)
Aeolian Research     Hybrid Journal   (Followers: 2)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 4)
AMBIO     Hybrid Journal   (Followers: 12)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 1)
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: 16)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 10)
Anthropocene Review     Hybrid Journal   (Followers: 1)
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 7)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 9)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 21)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 15)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 18)
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: 6)
Atmospheric and Climate Sciences     Open Access   (Followers: 17)
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: 10)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 17)
Bulletin of Volcanology     Hybrid Journal   (Followers: 13)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 11)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 11)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 6)
Contemporary Trends in Geoscience     Open Access   (Followers: 1)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 8)
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: 5)
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: 202)
Earth and Space Science     Open Access  
Earth Interactions     Full-text available via subscription   (Followers: 8)
Earth Science Research     Open Access   (Followers: 7)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 1)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 12)
Earth System Dynamics     Open Access   (Followers: 6)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 1)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Science     Hybrid Journal   (Followers: 8)
Earthquake Spectra     Full-text available via subscription   (Followers: 12)
Ecohydrology     Hybrid Journal   (Followers: 11)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 10)
Environmental Geology     Hybrid Journal   (Followers: 11)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access  
Erwerbs-Obstbau     Hybrid Journal  

        1 2 3 4 5 | Last

Journal Cover Applied Clay Science     [SJR: 0.999]   [H-I: 63]
   [4 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2584 journals]
  • Experimental studies on the desorption of adsorbed sodium poly(acrylic
           acid) from crude kaolin particles
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Feridun Demir
      Background The controlled stability and fluidity of highly concentrated kaolin dispersion is a crucial problem when kaolin is used in industry due to the charge heterogeneity of its surface. To solve the common industrial problems of dispersions prepared at high solid loadings in terms of their rheological behavior, some organic and inorganic dispersing agents have to be added into the system to modify the particle surfaces. Objective Adsorption and desorption behaviors of sodium poly(acrylic acid) (NaPAA) on the surface of kaolin particles were investigated to elucidate the adsorption mechanism of the PAA–kaolin dispersion system within the scope of the rheology and the colloidal stability. We also investigated the structural changes in the kaolin particles due to the extraction of Si4+ and Al3+ ions when a dispersing agent was used. Method Kaolin dispersions were prepared using NaPAA, and investigated in terms of the adsorption and desorption behaviors, the rheological and the electrokinetic properties and the extracted Al3+ and Si4+ ions from the particles. Results As expected, PAA was strongly adsorbed on the positively charged alumina sites of the particles. According to the results obtained in the experiments of adsorption density, viscosity, ζ-potential and the dissolution of metal ion measurements for the adsorption/desorption, a strong and irreversible adsorption was observed between PAA and the surface of the kaolin surface, indicating the existence of unbreakable chemical bonds. This is due to the adsorption of negatively charged carboxylic acid groups (–COO−) from the PAA onto the positive alumina sites on the edges of the kaolin surface by electrostatic attraction. Due to the negative charge, no adsorption was observed on the silica surface of the particles within the working pH range of 5.3 to 8.4. Conclusion The adsorption mechanism of PAA–kaolin interaction is attributed to chemical adsorption with the formation of chemical bonds between the charged carboxylic acid groups (–COO−) of the polymer and the alumina sites on the edges of the kaolin.


      PubDate: 2015-01-26T02:47:41Z
       
  • African terra sigillata from Henchir Es-Srira archaeological site, central
           Tunisia: Archaeological provenance and raw materials based on chemical
           analysis
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Siwar Baklouti , Lara Maritan , Néjia Laridhi Ouazaa , Claudio Mazzoli , Samia Larabi Kassaa , Jean-Louis Joron , Boutheina Fouzaï , Lluís Casas Duocastella , Moufida Labayed-Lahdari
      Terra sigillata from the Henchir Es-Srira archaeological site in central Tunisia was analysed by X-ray fluorescence (XRF), and chemical data were statistically treated by multivariate (principal component and cluster) analyses, which defined a geochemically homogeneous reference group. According to our results, potsherds from Henchir Es-Srira are compositionally compatible with the six reference samples from the same site already published in the literature, and form a single group. A larger reference group is now well established for this site. In addition, comparisons with previous data from other sites in both northern and central Tunisia show that terra sigillata from Henchir Es-Srira is chemically more similar to that of the northern sites than the central ones. Neutron activation analysis (NAA), an extremely valuable tool for provenance studies, was also performed on a set of selected potsherds from Henchir Es-Srira and clay materials collected nearby, with the aim of identifying the possible clayey raw materials used for this ceramic production. Comparisons of both bulk chemical composition and trace and rare earth element (REE) patterns show that most of the objects were locally produced from a Neogene base-clay, probably collected from the “Saouaf Formation”.


      PubDate: 2015-01-26T02:47:41Z
       
  • Multi-step removal mechanism of pyrophosphate using CaFe-layered double
           hydroxide at high pH
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Jizhi Zhou , Xiaoman Li , Wentao Li , Feng Wei , Yongwen Su , Jia Zhang , Zhi Ping Xu , Guangren Qian
      Pyrophosphate (PP) is frequently used as a ligand in the electroplating process at high pH. This research investigated PP removal over Ca2Fe-layered double hydroxide (LDH) at pH12. The maximum amount of PP removal was up to 7.4mmol (as P) at the LDH dosage of 1.0g/L. As represented by the concentration of total phosphate ([TP]), the isotherm with increasing initial PP reveals that PP removal over LDH underwent multi-processes: (1) at initial [TP]<3.2mmol/L, PP removal was attributed to Ca2P2O7·2H2O formation while at initial [TP]=3.2–6.9mmol/L PP removal kept at 3.2mmol/g due to the competitive formation of CaP2O7 2− instead of Ca2P2O7·2H2O; (2) At [TP]=6.9–12.0mmol/L, formed CaP2O7 2− is incorporated into the LDH framework and reconstruct the layered structure to remove PP together with Ca2P2O7·2H2O precipitation; (3) At [TP]>12.0mmol/L, CaP2O7 2− incorporation becomes predominant in PP removal. Interestingly, in the structure of CaP2O7 2−-incorporated LDH, CaP2O7 2− is intercalated with Ca2+ being supposedly incorporated into the LDH hydroxide vacant site. Therefore, the result provides a possible way to remove a large PP amount using Ca2Fe-LDH at high pH.


      PubDate: 2015-01-26T02:47:41Z
       
  • Characterization of urea-modified Palabora vermiculite
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Herminio F. Muiambo , Walter W. Focke , Maria Atanasova , Aida Benhamida
      Replacing the exchangeable interlayer ions in Palabora vermiculite with magnesium, aluminum or iron (III) ions does not affect the exfoliation onset temperature (456±11°C). However, co-intercalation of minor amounts of urea lowers the exfoliation onset temperature to 209±35°C. This significant decrease is attributed to the low thermal stability of urea which releases ammonia and water as blowing agents. Thermo-mechanical analysis indicates that the expanded vermiculite exhibits spring-like properties. Part of the original expansion is recovered when the applied force is removed. The observed hysteresis is attributed to the progressive flattening of warped/buckled sheets that make up the expanded worm-like structure. Provided the expanded flake has not been heated beyond 450°C, it can be reconstituted by applying a sufficiently high compressive force followed by equilibration with distilled water. Such flakes show the conventional exfoliation behavior when heated again.


      PubDate: 2015-01-26T02:47:41Z
       
  • Functional organo-Mt/copolymer nanoarchitectures. Microwave-assisted rapid
           synthesis and characterisation of
           ODA–Mt/poly[NIPAm-co-(MA-alt-2,3-2H-DHP)] nanocomposites
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Zakir M.O. Rzayev , Ayşe Uzgören-Baran , Ulviye Bunyatova
      In this work, novel octadecyl amine–montmorillonite (ODA–Mt) copolymer nanocomposites were synthesised by interlamellar microwave-assisted complex-radical copolymerisation. The microwave method is found to be a facile and highly effective means to clay polymer nanocomposites (CPNs) that provide a higher rate of interlamellar copolymerisation and conversion of micro- and nanoparticles. The chemical and physical structures, surface morphologies and thermal behaviours of the prepared CPN were investigated by FTIR and 1H (13C) NMR spectroscopy, XRD, SEM, TEM, thermal (DSC and TGA) and dynamic mechanical (DMA) analysis methods. That copolymerisation was accompanied by in situ complex formation (charge transfer complex and H-bonding similar with known copolymerisation without ODA–Mt) and the intercalative amidisation of anhydride units with the octadecyl amine groups of Mt was determined. These observed chemical and physical interfacial interactions as effective in situ processing play an important role in the formation of hybrid systems and micro- and nanocomposites with stimuli-responsive NIPAm polymer chains.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Property-based assessment of soil mineralogy using mineralogy charts
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Oksana Paykov , Harmonie Hawley
      It is essential to determine soil mineralogy as soils containing high amounts of smectites pose a hazard to geotechnical structures and increase susceptibility to soil erosion and landslides. The everyday use of analytical techniques in geotechnical engineering practice is considered expensive and time consuming. Prior studies suggest that physico-chemical properties of soil can be used to estimate the soil mineralogy. The current study evaluated specific surface area and liquid limit as possible parameters to estimate soil mineralogy. Mineralogy charts are introduced to estimate the percentage of montmorillonite, kaolinite, and illite in a sample. The degree of accuracy is highly dependent on the method used to determine the soil properties. Mineralogy ChartSSA yielded as accurate results as artificial neural network based models. Prediction of soil mineralogy based on liquid limit of the soil yielded a wide range of correlation coefficients between the measured and calculated values.


      PubDate: 2015-01-26T02:47:41Z
       
  • Effective phosphate adsorption by Zr/Al-pillared montmorillonite: insight
           into equilibrium, kinetics and thermodynamics
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Weiya Huang , Jie Chen , Fei He , Jinpeng Tang , Dan Li , Yi Zhu , Yuanming Zhang
      Zirconium-pillared montmorillonite (Zr-Mt) and zirconium/aluminum-pillared montmorillonite (Zr/Al-Mt) were prepared by intercalating Zr4+ and Zr4+/Al3+ polyhydroxy-cations into the interlayer spaces of natural montmorillonite (Mt). Zr-Mt and Zr/Al-Mt exhibited greater specific surface areas and pore volumes, as compared with Mt. In particular, the enhancement in the phosphate removal performance of Zr/Al-Mt was more significant in terms of phosphate adsorption capacity and rate, in relation to Zr-Mt. Herein, several important parameters, such as contact time, temperature, initial solution pH and competing anion, were investigated in detail to evaluate the phosphate adsorption performances of Zr/Al-Mt. The pseudo-second-order kinetic model fitted our acquired phosphate adsorption data best, in comparison with the use of the pseudo-first-order or the pseudo-third-order kinetic model. The Langmuir model appeared to fit the adsorption process better than that of the Freundlich model, with a maximum phosphate adsorption capacity of 17.2mg P/g at 25°C. The thermodynamic parameters (ΔG°, ΔH° and ΔS°) were also determined, which revealed that the phosphate adsorption process was spontaneous and endothermic in nature. A high adsorption capacity was observed at pH=3.0, which decreased by increasing pH. The presence of competitive ions, e.g. Cl−, NO3 −, and SO4 2−, slightly impacted the phosphate adsorption; whereas the introduction of CO3 2− caused the greatest adverse effect. The study on the Zr/Al-Mt leaching strongly suggested that the risk of Zr4+ leakage during adsorption process be negligible within a wide pH range of 3.0–9.0. After three adsorption-desorption cycles, there was no significant loss in the adsorption performance of Zr/Al-Mt.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Temperature and concentration dependence of J-aggregate of a cyanine dye
           in a Laponite film fabricated by Langmuir–Blodgett technique
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Santanu Chakraborty , D. Bhattacharjee , Honami Soda , Makoto Tominaga , Yasutaka Suzuki , Jun Kawamata , Syed Arshad Hussain
      In this communication, we report the temperature and concentration dependence of J-aggregate of a cyanine dye N, N′-dioctadecylthiacyanine perchlorate (NK) in the Laponite film fabricated by Langmuir–Blodgett technique. Surface pressure area per molecule isotherm revealed the formation of stable Langmuir monolayer at the air–water interface. Spectroscopic characterization confirmed the formation of J-aggregates in the NK LB film without Laponite. In the hybrid film, J-aggregate forms at lower Laponite concentration (1ppm), higher deposited surface pressure and at lower subphase temperature. Both the J-aggregated films were found to be optical second harmonic generation (SHG) active and mechanically very stable, although intrinsically NK is SHG inactive.


      PubDate: 2015-01-26T02:47:41Z
       
  • Preparation of copper oxide in smectites
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Nithima Khaorapapong , Nuttaporn Khumchoo , Makoto Ogawa
      Copper oxide nanoparticles were prepared in the interlayer spaces of sodium- and cetyltrimethylammonium–smectites by a titration of an aqueous solution of copper nitrate at 70°C in the presence of dispersed smectites. The resulting hybrids were characterized by powder XRD, SEM, TEM, TG-DTA, as well as FT-IR and UV–visible spectroscopies. A massive blue shift (from 490nm to 232–478nm) of the UV–visible absorption observed for the hybrids confirmed the formation of nanometer-sized copper oxide (3–7nm) in the interlayer spaces. A small amount of larger CuO particle with the size of around 0.6–2.9μm formed at the external surface of clay mineral particles. The nature of the broad absorption band (at around 490nm) of pure copper oxide and the hybrids with high copper oxide loading was attributed to the overlapping of the Cu2+ to O2− charge transfer as well as d–d transition of copper oxide. The interactions with smectites played a role in stabilizing and protecting the formed copper oxide nanoparticles.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Durability of alkali activated cement produced from kaolinitic clay
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Faten Slaty , Hani Khoury , Hubert Rahier , Jan Wastiels
      Alkali activated products were synthesized by activation of kaolinitic clay from Hiswa area, Jordan with a sodium hydroxide solution. These specimens were subjected to long-term durability tests under different environmental and chemical conditions. The geopolymer specimens undergo very low drying shrinkage. The specimens perform well under ambient, de-ionized water, wet–dry cycles, sea water, and sodium sulfate conditions. The newly developed material from Hiswa clay shows a stable strength under all these conditions. The specimens are however attacked by acid solutions and lose about 9.7% of their mass after 90days of exposure. The alkali–silica reaction has highly affected the geopolymer specimens as indicated by cracking, expansion and loss of mechanical strength.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • CO2 capture by kaolinite and its adsorption mechanism
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Yen-Hua Chen , De-Long Lu
      The low-cost and naturally abundant clay mineral kaolinite was studied for use an adsorbent for CO2 capture. Samples of kaolinite were subjected to acid treatments to improve their textural properties, namely, its surface area and pore volume. It was found that the kaolinite sample treated with 3M H2SO4 for 10h reaction exhibited the highest Brunauer–Emmett–Teller (BET) surface area (18.9–74.3m2/g) and pore volume (0.11–0.31cm3/g). The CO2 adsorption capacity of kaolinite, which was ~0mg-CO2/g-sorbent at 25°C, increased to 3.4mg-CO2/g-sorbent after the acid treatment. Moreover, it was found that the CO2 adsorption capacity of kaolinite was greater at room temperature than at higher temperatures. The CO2 adsorption by kaolinite, which was investigated using X-ray diffraction analysis, Fourier transform infrared spectroscopy, and CO2 adsorption isotherm measurements, was found to be mainly attributable to physical adsorption.


      PubDate: 2015-01-26T02:47:41Z
       
  • Shear resistance of bentonite backfill materials and their interfaces
           under varying hydraulic conditions in a deep rock nuclear waste repository
           
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Gowthaman Sinnathamby , Leena Korkiala-Tanttu , Laura Torres Salvador
      This paper presents the shear behaviour and the shear resistance of different bentonite based clay backfill materials and their interfaces of Finnish KBS-3V type nuclear waste repository, under varying hydraulic conditions. The interfaces between proposed precompressed Friedland clay blocks (FCB) and other granular backfill materials (GM) such as bentonite pellets (QSEP) and granules of bentonite (GB) were tested in a conventional direct shear box apparatus under various hydraulic test conditions. The main objective of this study was to get insight into the shear behaviour of different backfill interfaces and to determine their interface shear parameters. Tests were done by changing the salinity of the interface water and the amount of interface water itself. Test results showed that the internal shear strength of QSEP and GB decreased with increasing water content due to the lubricating effect of the free-water between the granules. Furthermore, test results showed that the interface shear parameters of the FCB–FCB interface increased with increasing salinity of the interface water, which produced rough FCB surfaces and asperities as the water was absorbed. The interface friction and cohesion of the FCB–GM (i.e. QSEP and FCB) interfaces under varying amounts of interface water were investigated through two different scenarios. In scenario 1, natural FCB surface was tested against GM with varying water contents, and in scenario 2, the amount of water on the FCB surface was varied whilst the water content of the GM was fixed as high as possible at around 60% (by weight). The test results showed that in scenario 1, the interface shear of FCB–GM (both FCB–QSEP and FCB–GB) decreased with increasing water contents of GM. At water contents (of GM) less than 40% (by weight), the failure took place at the interface, whilst at water contents above 40%, the failure occurred within the GM itself. Greater interface shear was observed when the FCB was wetted (i.e. in FCB–QSEP and FCB–GB interfaces) in scenario 2, compared with natural FCB surface in the same interfaces. The interface shear results obtained from this study will be incorporated in the detailed modelling of the buffer–backfill interaction of the KBS-3V.


      PubDate: 2015-01-26T02:47:41Z
       
  • Raman spectroscopy — Useful tool for studying the catalysts derived
           from Mo and V-oxyanion-intercalated layered double hydroxides
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Iuliana Daniela Dobrea , Cristina Elena Ciocan , Emil Dumitriu , Marcel Ionel Popa , Eddy Petit , Vasile Hulea
      Layered double hydroxides with Me-based oxyanions (MeMo, V) in the interlayer gallery were prepared by ion exchange and used as efficient catalysts for the mild oxidation of organic sulfides with H2O2. Raman spectroscopy was used as the main and very efficient technique for the advanced characterization of these materials during their preparation and catalytic use. First, it served for monitoring the progression of the ion exchange during the preparation of the catalysts, and then the Raman spectroscopy provided precise information regarding the type of the oxyanions located in the catalyst structure, before and after the oxidation reaction.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Occurrence of iron and aluminum sesquioxides and their implications for
           the P sorption in subtropical soils
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Edson C. Bortoluzzi , Carlos A.S. Pérez , José D. Ardisson , Tales Tiecher , Laurent Caner
      The effect of the pedo-climatic variation in qualitative and quantitative soil sesquioxide contents and soil phosphorus (P) sorption capacities has been studied. In four soils (samples from A horizons) located along a southern Brazilian environmental gradient (EG) shown a decrease in crystallized iron oxides with the increase of altitude. Hematite and goethite were found at low EG altitudes in association with low soil organic carbon content, and goethite–ferrihydrite and gibbsite were found at high altitudes in association with high organic carbon content. The adsorbed soil P (measured by the remaining P) was predicted by the goethite content, and the desorbed P (measured by successive P extractions using anion exchange resin membranes) was predicted mainly by the goethite and clay content. In subtropical soils, even a smooth environmental gradient could determine the qualitative and quantitative iron and aluminum sesquioxide distributions that control soil P sorption capacities.


      PubDate: 2015-01-26T02:47:41Z
       
  • Technical feasibility of reusing coal combustion by-products from a
           thermoelectric power plant in the manufacture of fired clay bricks
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): B. Sena da Fonseca , C. Galhano , D. Seixas
      This paper intends to study the suitability of reuse a waste produced by thermoelectric power plants in the clay bricks industry. One of the main by-products is bottom ash and currently only half of these residues are reused; therefore a new environmentally-friendly solution is researched. Besides a chemical and mineralogical characterization of bottom ash, clay bodies were moulded by using clay pastes with 2.5, 5, 10, 15 and 20wt.% of bottom ash. Then the green bodies were fired at 900, 1000 and 1100°C and thereafter studied. This bottom ash shows particular features of a fluxing agent which reduces the melting point of the liquid phase, and so the water absorption and open porosity tend to decrease with the increasing amount of waste, while the bulk density increases. Improvements were found; some regarding the mechanical strength and salt fog resistance due to bottom ash incorporation, especially in the case of samples fired at 900°C with 20% of bottom ash. Since ceramics made from these mixtures reveal good performance at all levels, the bottom ash shows high potential to be used in the ceramic industry.


      PubDate: 2015-01-26T02:47:41Z
       
  • Oral extended release of dexamethasone: Montmorillonite–PLGA
           nanocomposites as a delivery vehicle
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Shilpa Jain , Monika Datta
      Dexamethasone (DEX) is a potent synthetic member of the glucocorticoid class of steroid drugs that has anti-inflammatory and immunosuppressant effects. It is 25 times more potent than cortisol in its glucocorticoid effect, while having a minimal mineralocorticoid effect. Due to the hydrophobicity and short half-life of the drug, high doses are required to maintain its therapeutic level in the blood plasma which has undesirable side effects. Therefore, a new drug delivery system capable of overcoming the drawbacks associated with dexamethasone is required at present. The present study is aimed at developing an extended release carrier for DEX using montmorillonite (Mt) and polylactic-co-glycolic acid (PLGA) nanocomposites suitable for oral administration. The synthesized clay polymer nanocomposites (CPN) were characterized with respect to morphology, particle size, physical status etc. The in-vitro drug release behavior of DEX from Mt–PLGA nanocomposites and PLGA particles in simulated gastrointestinal fluids has been investigated. In-vitro drug release profiles of CPN in simulated gastrointestinal fluid indicate an extended release of DEX as compared to DEX–PLGA particles and pure DEX.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • A study of the effects of electrode spacing on the cementation region for
           electro-osmotic chemical treatment
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Chang-Yu Ou , Shao-Chi Chien , Ren-Hao Liu
      Previous laboratory studies have shown that injection of the calcium chloride solution can cause soil to be cemented near the cathode during electro-osmosis. In order to predict the size of the cementation region, a series of electro-osmotic chemical tests was conducted using different electrode sizes, electric voltages, and electrode spacing. After the tests, the concentration of calcium ions and pH values over the entire sample were analyzed and the cementation near the cathodes was inspected. Results show that the contours of the Ca2+ concentration, contours of the pH values and the cementation region were consistent to each other. Cementation often occurs near the cathode in an alkaline environment where the pH values are higher than 8.3 to 8.7. The cementation region was highly related to the applied voltage and electrode spacing but slightly related to the size and shape of the cathodes. When the electric field intensity was amplified by N times, the radius of the cementation region was increased by N times. This relationship can be used to predict the cementation region around the cathode and to design a rational spacing between two cathodes for multiple pairs of electrodes.


      PubDate: 2015-01-26T02:47:41Z
       
  • Production of montmorillonite/polypyrrole nanocomposites through in situ
           oxidative polymerization of pyrrole: Effect of anionic and cationic
           surfactants on structure and properties
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Sílvia D.A.S. Ramôa , Guilherme M.O. Barra , Claudia Merlini , Wido H. Schreiner , Sébastian Livi , Bluma G. Soares
      Montmorillonite/polypyrrole (Mt/PPy) nanocomposites were prepared through in situ oxidative polymerization of pyrrole in aqueous dispersions of unmodified montmorillonite (Na+–Mt) with three different surfactants (dodecylbenzenesulfonic acid (DBSA), sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB)), using iron (III) chloride hexahydrate (FeCl3⋅6H2O) as an oxidant. In order to investigate the effect of the anionic and cationic surfactants used in the pyrrole polymerization, Mt/PPy nanocomposites were also prepared without surfactant. The anionic surfactants promoted the intercalation and partial exfoliation of the clay, while clay polymer nanocomposites (CPN) prepared with cationic CTAB (Mt/PPy.CTAB) and without surfactant (Mt/PPy.Cl) were partially intercalated. High electrical conductivity (10.8Scm−1) was observed for the Mt/PPy.SDS nanocomposites due to the highly site-specific interaction between the protonated PPy (N+) and the negatively-charged Si–O–Si groups of the Mt. Finally, the thermal stability of the CPN was higher than that found for the corresponding PPy samples, with the exception of the Mt/PPy.CTAB nanocomposite, due to the protective effect of the clay layers.


      PubDate: 2015-01-26T02:47:41Z
       
  • Intergranular pore space evolution in MX80 bentonite during a long-term
           experiment
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Lukas M. Keller , Lorenz Holzer , Philippe Gasser , Rolf Erni , Marta D. Rossell
      Focused ion beam nanotomography (FIB-nt) was applied to MX80 bentonite samples from the long-term Alternative Buffer Material (ABM) experiment in order to study the evolution of the intergranular pore space under similar condition that is supposed to prevail in repositories of nuclear waste. The applied high-resolution imaging method revealed the presence of two different types of pore filler. The first type is related to corrosion of iron and is represented by newly formed heavy minerals. Extensive formation of heavy minerals occurred only near the iron parts of the experimental set up. Based on comparison with other studies, the second filler type was interpreted as clay-gel that was likely formed during water uptake and swelling. A large fraction of the initial pore space was filled with such a clay gel. By attributing filled pores to the present open porosity, the initial intergranular porosity (radii>10nm) of the starting material was in the range of 4.3–4.6vol.%, which was reduced to <1vol.% during the experiment. A finite scaling approach was applied to the initial pore space (i.e. pores with radii>10nm), which yielded percolation thresholds with critical porosities ϕ in the range of 3–19vol.%. Thus, the residual open porosity was far below the percolation threshold. The initial porosity of one sample was above the percolation threshold, but also in this material percolation was restricted to one spatial direction. This indicated anisotropy with respect to percolation. The formation of a clay-gel and heavy minerals led to a decrease in intergranular porosity, which in turn affected connectivity of the pore network. Using results from pore-network modelling in combination with percolation theory illustrates that a minor reduction of porosity led to a substantial decrease in pore connectivity. Depending on water saturation within the observed intergranular pore space, air permeability decreases exponentially over three to four orders of magnitude within a narrow porosity range of about 1vol.%. Based on observations and calculations, gas transport along the intergranular pore space of MX80 bentonite from the ABM experiment is not considered as a possible scenario and can reasonably be excluded.


      PubDate: 2015-01-26T02:47:41Z
       
  • Minimal interference of glucose and ethanol on aflatoxin B1 adsorption by
           smectites
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Sabrina Sharmeen Alam , Youjun Deng , Joe B. Dixon
      Due to stringent regulations on aflatoxins in food and feed, and an increased demand for biofuel, it is reasonable to direct aflatoxin-contaminated corn to biofuel production. Of great concern is the up to three-fold mycotoxin enrichment in distiller's grains, a co-product of ethanol biofuel production. The objective of this study was to test the interferences of ethanol and glucose on aflatoxin adsorption by smectites. Ethanol and glucose are two of the major soluble compounds present in fermentation solutions. The aflatoxin adsorption capacities of four smectites from Mississippi (2MS, 3MS, and 4MS) and Alabama (MBBO1) were evaluated in water and in ethanol/glucose. The highest aflatoxin B1 adsorption capacity (Qmax) of the four smectites in water was 0.59molkg−1 (184gkg−1). Batch adsorption experiments suggested that smectites effectively adsorbed aflatoxin B1 from the simulated fermentation solutions. Aflatoxin adsorption from 10% (w/v) glucose and 20% (v/v) ethanol to clay was 90% of aflatoxin adsorption to clay from pure distilled water. X-ray diffraction analysis indicated that aflatoxin–smectite complexes formed in water, 10% glucose, and 20% ethanol solutions responded similarly to heat treatment and maintained basal spacings >1.2nm up to 300°C, whereas the smectite without aflatoxin treatment collapsed to 1.0nm at 150°C. The greater basal spacing after heat treatment suggested that smectite interlayers were accessible to aflatoxin in the presence of high glucose and ethanol concentrations. Infrared spectra of aflatoxin–smectite complexes formed in the simulated fermentation solutions were nearly identical to infrared spectra of aflatoxin–smectite complexes formed in distilled water. This suggests that ethanol and glucose had little influence on the type or strength of bonding between aflatoxin and smectite and that washing with water easily removed any adsorbed ethanol and glucose. The distinct two-carbonyl bond in-phase stretching vibration at 1727cm−1 revealed irreversible aflatoxin B1 bonding in smectite interlayers. It can be concluded that glucose and ethanol interferences with aflatoxin adsorption to smectites is minimal.


      PubDate: 2015-01-26T02:47:41Z
       
  • Mechanism of soil cementation by electroosmotic chemical treatment
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Chang-Yu Ou , Shao-Chi Chien , Ching-Cheng Yang , Chun-Tao Chen
      The injection of calcium chloride solution through the anode during electroosmosis has been shown to be effective in strengthening soft clay. The objective of this study was to investigate the mechanism responsible for this improvement using a kaolinite. Several types of samples were prepared, including a sample directly taken from the clay near the cathode after the completion of an electroosmotic chemical treatment test and samples of kaolinite mixed with different concentrations of calcium ion solutions and cured for various times. A mechanical strength test and chemical and mineralogical analyses were performed to examine the properties and compositions of the samples. Results showed that some crystalline products could be formed in an alkaline environment of pH around 10 or after a short treatment time. The products filled some of the clay voids, causing a moderate increase in clay strength. In a strongly alkaline environment, calcium silicate and/or aluminum hydrate would be formed with a longer curing time, leading to a substantial increase in clay strength. Therefore, raising the concentration of the injected calcium chloride solution, enlargement of the applied electric voltage and extension of treatment time could result in greater clay strength.


      PubDate: 2015-01-26T02:47:41Z
       
  • The preparation and characterization of lactone form of
           10-hydroxycamptothecin-layered double hydroxide nanohybrids
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Xiujiang Pang , Junmei Cheng , Li Chen , Dongxiang Li
      10-Hydroxycamptothecin (HCPT) as a hydrophobic anticancer drug brings many challenges in the clinical applications due to its poor water solubility and its facile structure transformation to inactive structure. In this work, the lactone form of HCPT–LDH nanohybrids with high drug loading was prepared by a two-step method. Firstly, the carboxylate form of HCPT-intercalated LDH was prepared by a coprecipitation method using a microchannel reactor. Secondly, dilute acetic acid was added into the as-precipitates to perform a structure recovery of HCPT in the nanohybrids from carboxylate form to bioactive lactone form because the lactone–carboxylate equilibrium of HCPT is reversible and pH-dependent. The dispersity of HCPT–LDH nanohybrids was obviously improved as compared with particles prepared by conventional method, and the average particle size increased with the drug loading. It was found that the content of HCPT in the nanohybrids with bioactive lactone form reached 95% after treated with acetic acid. For cancer cells, the lactone form of HCPT–LDH was found to be significantly more potent than raw HCPT, and it provided an important foundation for the development and application of nanohybrid delivery system.


      PubDate: 2015-01-26T02:47:41Z
       
  • Bentonite protects neural crest stem cells from death caused by aflatoxin
           B1
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Janaína Nones , Jader Nones , Humberto Gracher Riella , Nivaldo Cabral Kuhnen , Andrea Trentin
      Bentonites, which have been shown to be good mycotoxin adsorbents, have a wide range of biochemical and industrial uses. Although many in vitro studies have shown the effects of bentonite on a variety of cell types, there is no comparable information regarding its effects on neural crest (NC) stem cells. The NC is a collection of multipotent and oligopotent progenitors endowed with both neural and mesenchymal potentials. NC cells originated at trunk level can become peripheral nervous system cells, melanocytes and smooth muscle cells. For this reason, the NC is considered an ideal model for studying the role of different substances on cell differentiation, survival and growth. We have recently shown that aflatoxin B1 (AFB1) decreases the viability and reduces the population of NC cells. In the present work, we have characterized bentonite extracted from the South of Brazil and investigated its effects on NC differentiation and survival, when challenged with AFB1. The results have highlighted the high content of SiO2, Fe2O3 and K2O present in bentonite, with content of MnO, MgO, CaO, Na2O, TiO2 and P2O5 lower than 1%. These results have also shown that bentonite at 0.6mg/mL is not toxic to NC cells in culture. Furthermore, bentonite increased the viability of NC cells previously treated with AFB1 without affecting cell differentiation. The evidence suggests that AFB1 interacted with bentonite by occupying the interlayer spaces, which might have contributed to a reduction of AFB1 availability and, consequently, a reduction in NC damage and an increase in the total number of cells. Our study contributes to a better understanding of the effects of clay minerals on the NC and may help to create new, more effective pharmacological applications to reduce or eliminate the toxic effects of AFB1.


      PubDate: 2015-01-26T02:47:41Z
       
  • Characterization of inorganic and organic clay modified materials: An
           approach for adsorption of an insecticidal terpenic compound
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Marie Goletti Mbouga Nguemtchouin , Martin Benoît Ngassoum , Richard Kamga , Stéfano Deabate , Serge Lagerge , Emmanuelle Gastaldi , Pascale Chalier , Marc Cretin
      Two organic molecules and two inorganic polymers have been used to modify the structure of bentonites as to obtain a high adsorption capacity of thymol, an insecticidal terpenic compound. The selected organic molecules were cetyl and phenyl trimethyl ammonium chlorides (CTMA and PTMA); the inorganic compounds were aluminium hydroxyl and iron hydroxyl polymers. Organic bentonites were obtained after treatment with CTMA and PTMA solutions. Inorganic bentonites were obtained after treatment with polymeric solutions of Alx(OH)y and Fex(OH)y. Materials were characterized by several physicochemical techniques including X-ray diffraction (XRD), thermal gravimetric and differential analysis (TGA, TDA), infrared spectroscopy (FTIR) and nitrogen adsorption–desorption. Adsorption capacities of modified and unmodified bentonites for terpenic compounds were also carried out. Results show that the organic cations have been intercalated successfully into the bentonite interlayer space. XRD measurements show that PTMA and CTMA induce an interlayer space expansion of 4.1Å and 10.5Å, respectively. The increase of specific surface areas (SSA) of materials treated with metallic polycations attests the occurrence of exfoliation. The highest adsorption capacity of thymol is obtained with bentonites modified by alkylammonium, which proves that the modification of the interlayer space is an interesting way to improve adsorption properties of clays usable as support for natural insecticides.


      PubDate: 2015-01-26T02:47:41Z
       
  • Organic modification of bentonite and its effect on rheological properties
           of paper coating
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Hunan Liang , Zhu Long , Shuhui Yang , Lei Dai
      Objective The effect of organic modified bentonite on rheological behavior of paper coating was studied to extend the use of bentonite in the paper industry. Background In the coating process, the paper coating was performed in various shear forces. Therefore, the rheological properties of the coating had profound effects on the quality of coated paper. In order to achieve the good rheology, paper coating required the addition of thickener or rheology modifiers. Organic bentonite was a kind of thixotropic ge1, which was extensively used in a number of applications as rheology modifier to modify the rheology and control the stability of systems. Method Na+-bentonite was modified with diallyl dimethylammonium chloride and dodecyl trimethylammonium chloride, respectively. The organic bentonite was characterized by XRD and TGA and the rheological properties of paper coating containing organic bentonite were measured by rheometer. Results The XRD spectra showed that the 001 reflection of bentonite was shifted to a lower 2θ after the modification. Moreover, the modification with DTAC had more pronounced effect than with DADMAC. The TGA curve showed that one dehydration stage in the range of 30–155°C was observed. For organic bentonite, thermal degradation took place in two stages. The first step was obtained in the temperature range of 250–600°C and the second step took place between 600 and 900°C. The addition of modified organic bentonite resulted in the increases of yield stress and viscosity of coating, and they increased when the amount of organic bentonite was increased. The flow characteristics fitted well with the Herschel–Bulkley model, and the rheological properties of paper coatings exhibited typical pseudoplastic behavior. Conclusion (1) The organic modifying agents were successfully inserted into the interlayer space of bentonite, the bonded amount of DADMAC and DTAC was 0.107g/1g Bent-DADMAC and 0.124g/1g Bent-DTAC, respectively; (2) organic bentonites had the thickening and promoting rheological function for paper coating; and (3) the paper coating containing organic bentonite exhibits the pseudoplastic fluid.
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      PubDate: 2015-01-26T02:47:41Z
       
  • Hydrothermal synthesis of dioctahedral smectites: The Al–Fe3+
           chemical series. Part II: Crystal-chemistry
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): S. Petit , A. Decarreau , W. Gates , P. Andrieux , O. Grauby
      The crystal-chemistry of a series of synthetic Al–Fe3+ smectites was studied in detail using near and mid infrared spectroscopy. Chemical and NIR data indicated a quite complete range of octahedral Al for Fe3+ substitution, and therefore, the solid-solution between beidellite and nontronite end-members was continuous and complete. The wavenumbers of several infrared absorption bands were correlated with the chemistry of the synthetic smectites, providing a useful tool to constrain their structural formulae and also for assisting in assignments of similar bands in natural smectites. The Al and Fe3+ cations were shown to be randomly distributed in the octahedral sheet of synthesized smectites. Despite the high availability of iron during synthesis, generally only a small amount of tetrahedral Fe3+ was observed.


      PubDate: 2015-01-26T02:47:41Z
       
  • Intercalation compounds of a synthetic alkylammonium-smectite with
           alkanolamines and their unique humidity response properties
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Kazuko Fujii , Hideo Hashizume , Shuichi Shimomura , Katsuhiko Ariga , Toshihiro Ando
      Triethanolamine (TEA) and diethylethanolamine (DEEA) were introduced into the interlayer space of a synthetic alkylammonium smectite (Synth A-Sm) in order to prepare novel intercalation compounds. The inorganic and organic moieties bond covalently with each other in Synth A-Sm. The intercalation compounds prepared (Synth A-Sm TEA and DEEA) showed unique humidity response. A wide range of preparation conditions was tested for the intercalation of the alkanolamines. Then it was revealed that the intercalation was achieved with alkanolamines/Synth A-Sm ratios x of 20–375mmol/g from room temperature (RT) to 180°C. X-ray diffraction (XRD) analysis showed that the basal spacing increased by the intercalation of TEA or DEEA in the interlayer space of the Synth A-Sm. The basal spacing was independent of x, indicating that TEA was intercalated less than or equal to the saturation value. The interlayer space of Synth A-Sm did not infinitely swell with the introduction of TEA. The basal spacing did not change under dry nitrogen flow in the case of the Synth A-Sm TEA compounds. On the other hand, the basal spacing decreased under dry nitrogen flow in the case of Synth A-Sm DEEA compounds. DEEA easily deintercalated under nitrogen flow at RT. Fourier transform infrared (FT-IR) spectra of the prepared intercalation compounds were simple superimpositions of the spectra of Synth A-Sm and the guest alkanolamines (TEA or DEEA). The Synth A-Sm TEA compounds prepared were characterized under controlled relative humidity. The XRD measurements indicated that the basal spacing was independent of the relative humidity. However, as relative humidity increased, the X-ray reflections from the Synth A-Sm TEA compounds drastically weakened. The XRD analysis was performed under repeated humidification-drying cycles. The XRD results revealed that the unique humidity response is reversible.
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      PubDate: 2015-01-26T02:47:41Z
       
  • Matrix-enhanced adsorption removal of trace BPA by controlling the
           interlayer hydrophobic environment of montmorillonite
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Zheng-Ming Wang , Hiroko Ooga , Takahiro Hirotsu , Wen-Long Wang , Qian Yuan Wu , Hong-Yin Hu
      There is an increased concern recently toward Bisphenol A (BPA), a typical phenolic type estrogenic endocrine disruptor compound, because of its potential impact toward both human beings as well as wildlife at a trace concentration level. In this research, the surfactant-modified montmorillonite materials were used aiming at the complete removal of trace BPA in water environment. Through a detailed examination on the intercalation properties of alkyltrimethylammonium ions, the interlayer hydrophobic environment properties of the clay minerals, and their relationship with the BPA equilibrium adsorption, it is concluded that BPA at a trace concentration level can be completely removed through increasing the chain length of the surfactant intercalates. Sufficient interlayer hydrophobicity, realized by near or excess cation exchange capacity intercalation of longer chain surfactants, is found significant to the enhancement of selective adsorption of BPA while coexisting with matrix organic substances, which is substantially instructive to the removal of other kinds of non-ionic emerged organic contaminants.
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      PubDate: 2015-01-26T02:47:41Z
       
  • Halloysite–CeO2–AgBr nanocomposite for solar light
           photodegradation of methyl orange
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Xiazhang Li , Chao Yao , Xiaowang Lu , Zonglin Hu , Yu Yin , Chaoying Ni
      Halloysite nanotube supported hybrid CeO2–AgBr nanocomposite was synthesized by a facile microwave mediated method. The molar ratio of CeO2 and AgBr in the halloysite–CeO2–AgBr nanocomposite was adjusted so that r = n Ag/( n Ag +n Ce) was selected as 0.0, 0.25, 0.33, 0.40, 0.45, and 0.50 respectively. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–Visible diffused reflectance spectroscopy (UV–Vis) were employed to investigate the structure and optical properties of the nanocomposites. Results indicate that among the pure halloysite and CeO2–AgBr loaded halloysite nanocomposites, the molar fraction r has a critical effect on the photocatalytic activity, which increases as the AgBr content increases to r ≤0.4 and decreases when r >0.4. The highest conversion of methyl orange reached 99% within 80min by using halloysite–CeO2–AgBr at r =0.4, which was much higher than pure halloysite and CeO2–AgBr. As an exploratory study, the introduction of AgBr species was found to extend the spectral response from UV to visible region and improve the separation of electron–hole pairs. The repeatable use of the nanocomposite photocatalyst with little depreciation was also confirmed.
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      PubDate: 2015-01-26T02:47:41Z
       
  • Physicochemical characterization of amino functionalized synthetic
           clay/Nafion nanocomposite film with embedded platinum nanoparticles for
           PEM fuel cells
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): B. Narayanamoorthy , S. Balaji
      A novel aminopropyl functional group bearing magnesium phyllosilicate clay (AC)/Nafion nanocomposite films with embedded platinum nanoparticles (Pt/AC/N) was prepared by sol–gel method followed by solution casting for various compositions of AC in Nafion. The as prepared nanocomposite films were subjected to surface characterization by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The thermal and mechanical stabilities were analyzed by thermogravimetric analysis (TGA) and nanoindentation coupled scanning probe microscopy analysis (SPM). The protonic conductivity of AC/Nafion nanocomposite films with and without Pt nanoparticles was measured by electrochemical impedance spectroscopy (EIS) using a two-probe conductivity cell. It was found that 6wt.% AC/Nafion possesses a high proton conductivity of 1.38×10−4 Scm−1, a thermal stability of up to 360°C (60°C higher than pristine Nafion) and a high mechanical stability (78.76MPa) among the different compositions studied. The catalytic activity of the optimized nanocomposite film containing Pt nanoparticles (Pt/6wt.% AC/N) towards oxygen reduction reaction (ORR) was investigated by cyclic voltammetry (CV) and linear scan voltammetry (LSV) techniques under hydrodynamic conditions. It was observed that 35.4μgcm−2 Pt/6wt.% AC/N composite film has higher ORR limiting current density of 4.2mAcm−2, and also it is interesting to note that this composition exhibited a high conductivity of 1.75×10−3 Scm−1 indicating that the nanocomposite catalyst film could be used as a proton conductor as well as a catalyst layer for the fabrication of membrane electrode assemblies in PEM fuel cells.
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      PubDate: 2015-01-26T02:47:41Z
       
  • Exploring an alternative route for meixnerite synthesis. The impact of the
           gaseous environment on the reconstruction of the lamellar structure and
           the catalytic performances
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Octavian Dumitru Pavel , Rodica Zăvoianu , Ruxandra Bîrjega , Emilian Angelescu , Guylene Costentin , Michel Che
      This work investigates the possibility to obtain the meixnerite structure Mg6Al2(OH)18·4H2O in carbonate-free environment by direct co-precipitation of Mg and Al nitrates using only NaOH solution as precipitation agent as well as the physico-chemical and catalytic performances of the mixed oxide (MO) obtained by thermal decomposition of this layered material at 460°C under nitrogen flow. The influence played by different gaseous environments, air or nitrogen, during the hydration of the above mentioned mixed oxide on the structural characteristics and catalytic performances of the derived reconstructed layered double hydroxide (LDH) materials (RLDH-A and RLDH-N, respectively) is also scrutinized. The characterization of the solids was performed by chemical and elemental analyses, XRD, DRIFTS, N2 adsorption–desorption isotherms and adsorption of molecules with different pKa in order to determine their basicity. The catalytic activity for cyanoethylation was discussed in relation with the structural properties of the catalytic materials. The results showed that the co-precipitation method employed leads to the formation of an LDH containing also NO3 − and CO3 2− anions besides HO−. Also, low amounts of C and N (<1%) were still present in the derived mixed oxide as well as in the reconstructed layered materials. The use of different gaseous environments, air or nitrogen, during the reconstruction leads to different structural properties which affected the catalytic activity of the solids. It has been noticed that the presence of carbonate anion in the structure of parent LDH-materials as well as that of carbonate low amounts in the LDH-derived mixed oxide improved the ability of the latter to recreate the lamellar structure through memory effect. However this fact is not accompanied by an increase of catalytic activity since the presence of carbonate anions decreases the basicity of the solid. Among the layered materials, the sample reconstructed under nitrogen (RLDH-N) which has a low crystallinity, and hence a larger number of defects, has also the highest number of HO− base sites and is the most active for catalytic cyanoethylation.
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      PubDate: 2015-01-26T02:47:41Z
       
  • Study of Pb2+ adsorption in a packed bed column of bentonite using CFD
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Cezar A. da Rosa , Indianara C. Ostroski , Joziane Gimenes Meneguin , Marcelino L. Gimenes , Maria A.S.D. Barros
      Objectives In this study, experiments and CFD (Computational Fluid Dynamics) simulations were conducted to investigate lead ion (Pb2+) adsorption in bentonite. Method Experiments were carried out in a fixed bed column at 30°C,pH=4.0 and average particle diameter of 0.127mm. The influence of the flow rate on the breakthrough curves was examined with constant inlet concentration equal to 0.88meqL-1. The CFD technique was used for the simulation of flow patterns and ion concentration profiles inside the fixed bed column during the adsorption process. A 2D axisymmetric model based on Navier-Stokes and diffusion-convection equations was used for simulating the fluid phase. Results Experimental data obtained for different inlet flow rates and Pb2+ concentrations were used for validating the model. Conclusion The CFD simulations predicted the experimental behavior of the fixed bed adsorption very well in all conditions under study.


      PubDate: 2015-01-26T02:47:41Z
       
  • Physicochemical characterization, elemental speciation and
           hydrogeochemical modeling of river and peloid sediments used for
           therapeutic uses
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Margaret Suárez Muñoz , Clara Melián Rodríguez , Alina Gelen Rudnikas , Oscar Díaz Rizo , Miren Martínez-Santos , Estilita Ruiz-Romera , Juan R. Fagundo Castillo , Aurora Pérez-Gramatges , Nadia V. Martínez-Villegas , Dagoberto Blanco Padilla , Rebeca Hernández Díaz , Patricia González-Hernández
      The present study was conducted to characterize the river sediment and the final peloid from San Diego de los Baños Thermal Center (Pinar del Rio, Cuba), based on its original sedimentary geochemistry and composition, in order to establish the physicochemical and geochemical properties for its inorganic quality assessment in therapeutic uses. The original sediment was extracted from the estuary of San Diego River, and then maturated with thermal waters, yielding a peloid with known anti-inflammatory and dermatological properties. A comparative study of total content and geochemical speciation of seven transition metals (Cr, Cu, Fe, Ni, Mn, Pb and Zn) in the sediments was performed using a sequential extraction procedure and Inductively Couple Plasma Emission (ICP) techniques, as well as hydrogeochemical modeling to predict and correlate species under the physicochemical conditions measured for the river and peloid sediments. The results showed that the main differences originated from maturation process are closely related to the changes in electric conductivity (EC) and redox potential (Eh). These variations are reflected in the composition of major elements, and at a lesser extent, in the total content of the transition metals. Most of the elements studied in this investigation appeared in the less mobile fractions, which suggested low availability in the sediments, under the studied conditions. In the case of Mn, species are mainly located in the most leachable fractions, which together with its relatively high content, indicates a need for regular monitoring of this element in the peloids used in the Thermal Center. The findings were useful to predict the behavior of these transition metals regarding solubility, potential motility and availability in the river and final peloid sediments, and led to classify the San Diego de los Baños peloid as mud or fangi. It was concluded that most of the metals are strongly retained in the peloid through the maturation process, as many factors contribute to the low mobility, such as the nearly neutral pH, the presence of organic matter, redox conditions, and the presence of carbonates and salts. The sediments were finally characterized regarding possible contamination, according to USEPA and background criteria, and were considered as non-polluted/non-contaminated except for Mn, which showed a moderate contamination factor. The results from the present work show the relevance of physicochemical and elemental characterization to peloid classification and quality assessment. Moreover, it evidences the importance of performing geochemical speciation using both experimental and theoretical techniques, for proper assessment of mobility and distribution mechanisms of soluble and solid mineral species present in these sediments.


      PubDate: 2015-01-26T02:47:41Z
       
  • Compressive strength and microstructure of soft clay soil stabilized with
           recycled bassanite
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Aly Ahmed
      This paper investigates the microstructure and mineralogical compositions of soft clay soil stabilized with bassanite that is produced from gypsum waste materials. Bassanite was mixed in different ratios with cement and lime, as a solidification agent, to prevent the solubility of bassanite. Different amounts of these admixtures were mixed with the tested soil. Scan electron microscopic (SEM) and X-ray diffraction (XRD) were used to identify the microstructure and mineralogical compositions of stabilized soil specimens, respectively while unconfined compression test was used to examine the compressive strength. Test results showed that the addition of recycled bassanite improves the strength of the tested soil. The improvement in the soil strength, based on compressive strength, is in agreement with the SEM and XRD results. The XRD results revealed the presence of various cementation compounds in the soil matrix when recycled bassanite was added. Both the content and ratio of the admixture had a significant effect on the formation of the cementation compounds and the improvement of compressive strength. The formation of ettringite increased with the increase of admixture content in soil mixture for both admixtures used. The ratio of admixture had a clear effect on the reduction of the formation of ettringite in the case of bassanite–cement admixture while it had no significant effect in the case of bassanite–lime admixture. Curing time had a significant effect on the formation of ettringite and the improvement of compressive strength. These results support the suitability of using recycled bassanite produced from gypsum wastes as a low cost and efficient stabilizer material in ground improvement projects.


      PubDate: 2015-01-26T02:47:41Z
       
  • A new ball milling method to produce organo-montmorillonite from anionic
           and nonionic surfactants
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Guanzheng Zhuang , Zepeng Zhang , Jingshu Guo , Libing Liao , Jiali Zhao
      Background Organo-montmorillonite (OMt) is widely used in oil well drilling fluids, paint, grease, cosmetics, and personal care products. Nanocomposites which are prepared using organoclays and polymers. Generally, organo-montmorillonite can be prepared using ion-exchange reactions with cationic surfactants. However, cationic-organo-montmorillonite (COMt) has poorer thermal stability. In addition, the preparation process of traditional OMt uses a large amount of water. The process would emit a large amount of effluent and increase cost. Objective The aim of this work is to prepare nonionic-organo-montmorillonite (NOMt) and anionic-nonionic-organo-montmorillonite (ANOMt) using ball milling method. And NOMt and ANOMt are of better thermal stability than COMt. Method Organo-montmorillonite was prepared using ball milling method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Thermogravimetric (TG) analysis, differential thermal analysis (DTA) and contact angle test. Results XRD analysis indicated that the interlayer spacing of Ca2+-montmorillonite (Ca-Mt) was expanded. ANOMt showed a large d-spacing above 5.0nm. SEM analysis demonstrated that the ANOMt was flaky in substance. FT-IR spectra proved that the chemical environment of the surfactants changed. TG and DTA results showed that the thermal stabilities of NOMt and ANOMt were better than that of COMt. FT-IR and thermal analysis indicated that the interlayer water was replaced. The contact angle tests of the samples indicated that NOMt and ANOMt were of oleophilic property. Conclusion Ca-Mt was modified with nonionic surfactant and anionic surfactant by ball milling method, without any added water. NOMt and ANOMt were prepared. The thermal stabilities of NOMt and ANOMt are better than COMt. Dual mechanisms of intercalation and stacking were proposed.


      PubDate: 2015-01-26T02:47:41Z
       
  • Delamination of organically modified montmorillonite for reducing the
           filler networking with carbon black in poly(1,4-cis-isoprene) based
           nanocomposites
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Maurizio Galimberti , Michele Coombs , Stefano Pandini , Theonis Riccò , Valeria Cipolletti , Lucia Conzatti , Gaetano Guerra
      This work presents the correlation between the organization of an organically modified montmorillonite (OMt) and the dynamic-mechanical properties of polymer nanocomposites containing a hybrid filler system, based on carbon black (CB) and OMt. Clay polymer nanocomposites (CPN) were prepared by melt blending synthetic poly(1,4-cis-isoprene) (PI), carbon black (CB) and OMt. Two types of OMt were used: with ammonium cations intercalated between the clay mineral layers (I-OMt) and delaminated (D-OMt). The latter was obtained via ball milling of I-OMt and presented a degree of delamination higher than 95%, as revealed by X-ray diffraction (XRD) analysis. The structure of CPN was studied with XRD and transmission electron microscopy (TEM) analyses. The mechanical behavior of uncrosslinked masterbatches and of nanocomposites crosslinked with sulfur based systems was assessed with dynamic shear experiments, by measuring the time needed to recover the initial modulus after a large strain perturbation and by obtaining master curves for the dependence of the storage modulus on frequency. I-OMt is shown to promote the filler networking phenomenon more easily than D-OMt: the storage modulus has a stronger reduction with the strain amplitude and a longer rubbery plateau is featured on the frequency scale. Modulus recovery measurements revealed that the structure of CPN can be restored after the application of large strain amplitudes. The extent of OMt delamination is presented as a key feature to control the dynamic-mechanical properties of CPN containing a filler, such as CB, suitable to establish an intimate interaction with OMt. The partial substitution of CB with D-OMt allowed the preparation of crosslinked nanocomposites with lower Payne effect.


      PubDate: 2015-01-26T02:47:41Z
       
  • Storage stability and rheological properties of asphalt modified with
           waste packaging polyethylene and organic montmorillonite
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104
      Author(s): Ruien Yu , Changqing Fang , Pei Liu , Xiaolong Liu , Yan Li
      In this paper, asphalt was modified using waste packaging polyethylene (WPE) and organic montmorillonite (OMt) and the storage stability and rheological properties of the resulting material were investigated. Simultaneously, the structure and morphology were also studied in an attempt to explain the changes in the material properties. The results showed that the addition of OMt improved the storage stability of WPE modified asphalt, but does not compromise its excellent high temperature rheological properties. Fluorescence microscopic images of the material revealed that the OMt slenderized and orientated the WPE micro-fibers promoting improved dispersion of the WPE in the base asphalt. Exfoliated OMt layers in the asphalt played a key role in the WPE microfibers' orientation and promoted its uniform distribution in the asphalt. In addition, scanning electron microscopic images showed the potential low temperature properties advantages of WPE modified asphalt.


      PubDate: 2015-01-26T02:47:41Z
       
  • Editorial Board
    • Abstract: Publication date: February 2015
      Source:Applied Clay Science, Volume 104




      PubDate: 2015-01-26T02:47:41Z
       
  • Effect of dry grinding on chemically modified kaolin
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Khalil Shahverdi-Shahraki , Tamal Ghosh , Kamal Mahajan , Abdellah Ajji , Pierre J. Carreau
      The effect of dry grinding on the morphology and structure of kaolin particles treated with potassium acetate (KAc) and dimethyl sulfoxide (DMSO) has been investigated. After treatment with KAc, the d-spacing of kaolin increased from 0.72 to 1.03, 1.30, and 1.38nm due to the combined effects of humidity and orientation of KAc molecules. The d-spacing was increased to 1.13nm in the case of DMSO treatment. A combination of XRD, TGA, and FT-IR showed that the crystalline structure of kaolin–DMSO and kaolin–KAc were significantly altered by grinding. The intensity of XRD diffraction peaks of ground samples was decreased due to the deterioration of the crystalline structure, and for longer grinding times those peaks almost disappeared. After grinding, the dehydroxylation temperature generally shifted to lower values and a smaller weight loss was observed. The variations of particle size and surface characteristics were also investigated.


      PubDate: 2015-01-26T02:47:41Z
       
  • The anti-inflammatory activity of natural allophane
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Javiera Cervini-Silva , Antonio Nieto-Camacho , Virginia Gómez-Vidales , Stephan Kaufhold , Benny K.G. Theng
      This paper presents evidence of the novel anti-inflammatory properties of natural allophane collected from New Zealand, Japan, and Ecuador. Allophanes were assessed by (i) the mouse-ear edema method using 12-O-tetradecanoylphorbol-13-acetate (TPA) as inflammatory agent; and (ii) the myeloperoxidase (MPO) enzymatic-activity method. After 4h, applying 1mgear−1 allophane conveyed edema inhibition (EI; p ≤0.01) in up to 39%, while MPO content inhibition (CI) values surpassed 60%. Pearson's correlation analysis between EI and MPO data showed that edema was mediated by the migration of neutrophils at t =4h (p <0.05), but not at t =24h. The lack of variation in cellular migration with time was explained because of a reaction of zero-order kinetics. EPR spectra for allophanes showing higher anti-inflammatory activity denoted a broad signal centered at g =2, and an intense spin–spin interaction, typical of a low-spin, octahedral Fe3+ environment (S =1/2); and overlapping signals typical for Ni, with octahedral coordination, explained either by oxidation states +1 (Ni1+), +3 (Ni3+), or bulk Ni2+ ions.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Sensitive determination and electro-oxidative polymerization of azodyes on
           a carbon paste electrode modified with bentonite
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Elif Türker Acar , Sinem Ortaboy , Gül Hisarlı , Gülten Atun
      A new composite carbon paste electrode incorporating bentonite (BentMCPE) was developed and used for extremely sensitive determination and electro-oxidative polymerization of azodyes using cyclic voltammetry. Lanaset Red 2B (LR2B) was selected as a model molecule for optimization of operational parameters such as amount of modifier, the pH of buffer medium, scan rate and dye concentration. Performance analyses showed that BentMCPE allows determination of LR2B, Acid Blue 113 (AB113) and Acid Yellow 17 (AY17) dyes as low as (6–8)×10−10 mol/L at pH5.5. The peak intensities increased with the repetitive scans due to electro-catalytic anodic polymerization of the dyes. The results of multiple scans in single binary and ternary dye solutions showed that all of the dyes whether hydroxyl substituted (LR2B and AY17) or not (AB113) can be polymerized on the BentMCPE surface. Two possible electro-polymerization pathways were proposed by assuming formation of different radical intermediates produced from azo/hydrazone tautomers of the dyes. A comparison of FT-IR spectra recorded after the first and tenth repetitive scans confirmed that the electro-polymerization process proceeds by head to tail interactions of the radicals with dye monomers deposited on the electrode surface.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Design of experiments to evaluate clay swelling inhibition by different
           combinations of organic compounds and inorganic salts for application in
           water base drilling fluids
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Rosangela de Carvalho Balaban , Emanuella Layne Ferreira Vidal , Maurício Rodrigues Borges
      In this study the synergistic behavior that occurs when three different cationic inhibitors for clay swelling were associated with brines containing NaCl and KCl was evaluated. These commercial inhibitors are based on a cationic quaternary polyamine chloride with quaternary ammonium group (INIB 1), on a cationic polyacrylamide chloride with quaternary ammonium group (INIB 2) and on a quaternary ammonium chloride salt (INIB 3). Each inhibitor was characterized considering the amount of chlorides and content of active matter. The tests were performed with a commercial bentonite. Capillary suction timer (CST) and linear swell meter (LSM) were used for the evaluation of clay–water interaction in the presence of various fluids. For a better interpretation of the experimental results statistical analysis (DOE — design of experiments) via response surface methodology (RSM) was used, taking into account the type and concentration of inhibitors, the type and concentration of brines as well as the contact time of the inhibitor solutions with clay. The results showed different efficiencies, in other words, inhibitors mixed with brines were more effective than the inhibitors alone. The best results were obtained for cationic polyacrylamide chloride with quaternary ammonium group at 7lb/bbl (pounds per barrel) in KCl brine at 18.74lb/bbl with contact time of brine and clay of 7.6h. Solutions containing these combinations presented greater inhibition of clay swelling. However, for field operations, other parameters should be considered as operating cost, environmental requirements and the application time of each product.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Study on the preparation and characterization of a titanium-pillared
           clay-supported CrCe catalyst and its application to the degradation of a
           low concentration of chlorobenzene
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Shufeng Zuo , Menglin Ding , Jing Tong , Lucong Feng , Chenze Qi
      In the present study, Ti-pillared clay (Ti-PILC) with a large surface area, uniform mesopores and high thermal stability was prepared and used as carrier to support CrCe oxides. Performance of the catalysts in catalytic chlorobenzene degradation was investigated. Ti-PILC had a significantly larger basal space and higher specific surface area and pore volume compared with those of Na-montmorillonite. These improvements accelerated the mass transfer of the gas in the gas–solid reaction, as the gas was transferred through the bigger pores of the catalysts. The porous structure of the carrier remained stable after calcination at 550°C, and the supported active constituent was evenly dispersed without aggregation, indicating that the material was a class of catalyst well suited for the catalytic degradation of chlorobenzene. Notably, CrCe(6:1)/Ti-PILC enabled the complete degradation of a low concentration of chlorobenzene at approximately 250°C and displayed outstanding performance compared with other types of catalysts.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • The effect of the substitution of hydrated lime with phyllite on mortar
           quality
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Thays F. de Oliveira , Márcia H. Beck , Pedro V. Escosteguy , Edson C. Bortoluzzi , Marcio L. Modolo
      In Brazil, phyllite began to be used as a substitute for hydrated lime for binary cement/lime mortar. Phyllite is cheaper and contributes more to the health of the workers than hydrated lime. However, this substitution has generated problems in coatings. Here we evaluate the effect of this substitution on a binary cement/phyllite mortar quality. The cement:phyllite:sand ratio tested was 1:0.4:6.5, which is the more common ratio used in Brazil, providing greater savings. The chemical and mineralogical compositions of hydrated lime and phyllite as well as some mortar properties were characterized. Overall, our results show that phyllite mortars have greater porosity, lower linear retraction, and lower pullout strength. These characteristics are due to the properties of expansion and retraction of the material and the absence of lamellar structure in hydrated lime. Although phyllite has been used as a substitute for hydrated lime due to economic and health reasons, our study indicates that the contribution of phyllite for mortar quality is lower than that of lime, therefore decreasing mortar quality rather than improving it.


      PubDate: 2015-01-26T02:47:41Z
       
  • Valorization and inertization of galvanic sludge waste in clay bricks
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): L. Pérez-Villarejo , S. Martínez-Martínez , B. Carrasco-Hurtado , D. Eliche-Quesada , C. Ureña-Nieto , P.J. Sánchez-Soto
      Galvanic sludge wastes (GSW) are produced by the physico-chemical treatments of wastewater generated by electroplating plants. These materials have a significant potential for the production of clay ceramic bricks. This paper focuses on the viability of the inertization of heavy metals from GSW mixed with clays. The original materials were obtained by mixing three types of raw clay (red, yellow and black) in equal parts with GSW. These mixtures were characterized by XRD, XRF, and chemical elemental analysis CHNS. The dosage of GSW in the clay–GSW bricks was up to 5wt.%. The bricks were then manufactured using conventional processes. The influence of the amount of GSW was evaluated after firing the clay–GSW composites at 950°C for 1h. The engineering properties of the fired samples, such as density, water absorption, open porosity, water suction and compressive strength, with and without the GSW, were determined. The incorporation of GSW into the clay mix clearly decreased the linear shrinkage and bulk density of the bricks in comparison with the fired clay used as a control. These GSW–clay composites also showed lower open porosity. According to the results obtained for the bulk density of the bricks, samples with GSW addition showed slightly lower values of open porosity than clay bodies, indicating that the GSW–clay samples had slightly higher closed porosity values. This was also shown by SEM. The open porosity, SEM and pore size distribution tests indicated that the porosity generated by the addition of GSW was mainly closed and, therefore, GSW bricks had excellent mechanical properties. The environmental risks of the incorporation of GSW, rich in heavy metals (Cr, Zn, Ni and others), to a clay matrix were evaluated by leaching tests of the fired products. The results indicated a successful inertization of the pollutants.


      PubDate: 2015-01-26T02:47:41Z
       
  • Experimental investigation of the effect of henna extract on the swelling
           of sodium bentonite in aqueous solution
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Aghil Moslemizadeh , Seyed Reza Shadizadeh , Mehdi Moomenie
      This paper reports for the first time the effect of Henna extract as a new, naturally occurring, and ecofriendly additive on swelling of sodium bentonite in aqueous solution. This is performed via a number of methods including dynamic linear swelling test in two distinct temperatures of 28°C and 82°C, sodium bentonite inhibition and sodium bentonite sedimentation tests. The results indicated that inhibition properties of Henna extract are a function of its concentration and are comparable with potassium chloride and polyamine as the two most common clay stabilizers. Inhibition mechanism was assessed using adsorption measurements obtained by conductivity technique, contact angle measurements via the sessile drop method, and scanning electron microscopy (SEM) analysis. Results of adsorption measurements indicated that Henna extract has a lower adsorption isotherm in alkaline medium (pH=9) compared to natural medium (acidotic). Adsorption of Henna extract increases hydrophobicity of sodium bentonite particle surface; nevertheless, this adsorption mechanism is slightly weakened in alkaline medium due to the effect of caustic soda as a pH adjustment agent. SEM analysis demonstrated that sodium bentonite particles have an extended area when exposed to Henna extract solution instead of distilled water indicating sodium bentonite particle stability. Henna extract has deflocculating properties at low concentrations (especially up to 0.2mass%); yet it indicates good inhibition properties to sodium bentonite swelling at a concentration several times higher than that of deflocculating concentration, about 3mass%. Inhibition properties could be attributed to the hydrogen bonding between the hydroxyl group of Henna extract constituents and oxygen atoms available on silica groups of sodium bentonite, especially to the lawsone (2-hydroxy-1,4 napthaquinone) constituent.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • 12-Phosphotungstic acid immobilized on activated-bentonite as an efficient
           heterogeneous catalyst for the hydroxyalkylation of phenol
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Ran Liu , Xinnian Xia , Xiaozhen Niu , Guozhong Zhang , Yanbing Lu , Rufeng Jiang , Shili He
      12-Phosphotungstic acid (PTA) supported on commercially activated-bentonite (BNT) was demonstrated to be efficient in the synthesis of bisphenol F (BPF) by hydroxyalkylation of phenol. In the series of PTA (10–40wt.%) impregnated-BNT catalysts prepared, 20% PTA/BNT showed the highest product yield (93%) and selectivity (97%), which was higher than that of parent PTA and BNT individually, due to the excellent dispersion of PTA on BNT leading to the redistribution of Brönsted and Lewis acid sites on BNT. NH3-TPD studies of various catalysts revealed that an appropriate combination of both strong and weak acid sites could contribute to a higher yield of BPF compared to the catalyst Al-MCM-41, and the Brönsted acid sites were more crucial in achieving a higher selectivity to 4,4′-isomer than Lewis acid sites.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
  • Thickness, modulus and strength of interphase in clay/polymer
           nanocomposites
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Yasser Zare , Hamid Garmabi
      The aim of the present work is to quantify the properties of interphase between the polymer matrix and the nanoclay in clay/polymer nanocomposites (CPN). Two micromechanics models, Ji and Pukanszky, are simply used to measure the modulus, strength and thickness of interphase by mechanical properties of nanocomposites. The suggested approach is applied to calculate and evaluate the interphase properties in various samples reported in the literature. The calculations clearly demonstrate the different properties of interphase compared to matrix and nanoclay phases. It is shown that the interphase usually has a significant thickness, modulus and strength in CPN which cannot be neglected in the final properties of nanocomposites.


      PubDate: 2015-01-26T02:47:41Z
       
  • Porous hollow tubes processed by extrusion of ceramic emulsions
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): N. Vitorino , C. Freitas , M.J. Ribeiro , J.C.C. Abrantes , J.R. Frade
      The processing of ceramic materials by extrusion is widely used to obtain products with constant cross section. Most of them are framed with applications as catalysis, filtration, building, fuel cells, isolators, etc., mainly if they are porous with special designed microstructural characteristics as pore size/distribution, liquid and gas permeability, mechanical properties, etc. Thus, in this work we combine a cellular ceramic preparation strategy based on a synergy of emulsification process and gel casting, with the extrusion process to obtain porous hollow tubes. Tree ceramic emulsions were extruded under different ram speeds and its effect was studied using Benbow-Bridgwater model.


      PubDate: 2015-01-26T02:47:41Z
       
  • Effects of organobentonites on imidacloprid release from alginate-based
           formulation
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Li Jiang , Junyong Mo , Zhijie Kong , Yanping Qin , Lintao Dai , Yajing Wang , Lin Ma
      To provide effective delay in release, organobentonites with different loading levels of dodecyltrimethylammonium chloride (DTMA) and hexadecyltrimethylammonium chloride (HTMA) were used as modifying agents in the alginate-based controlled release formulation (CRF) containing imidacloprid. The structure of organobentonites was characterized by FTIR and XRD, and adsorption toward imidacloprid was investigated. The results were utilized to reveal the effects of organobentonites on the release of imidacloprid as well as its mechanism, and to evaluate the potential use of organobentonites to modulate the release of imidacloprid. The results showed that organobentonites could reduce the release of imidacloprid from alginate-based granules, different from the natural bentonite that accelerated the release of imidacloprid. The time taken for 50% of the active ingredient to be released, T 50, for CRF incorporating organobentonites with DTMA at loading level of 50, 75, 100 and 125% of the clay's cation exchange capacity was 2.12, 1.59, 1.55 and 1.38 times of the value for the formulation without modifying agent, respectively. The values for those incorporating organobentonites with HTMA at the same loading level were 2.61, 2.20, 1.89 and 1.88 times. It was suggested that imidacloprid released via an anomalous transport kinetics predominated by Fickian diffusion and was influenced by the addition of bentonite and organobentonites due to the change of matrix permeability and the interaction with organobentonites. The enhancement of matrix permeability and imidacloprid release resulting from the addition of natural bentonite might be attributed to the lamellar structure and swellability of bentonite in water. In contrast, the matrix permeability and imidacloprid release decreased when organobentonites were used as modifier agents, as a consequence of the hydrophobicity of organobentonite. The results also suggested the feasibility of regulating imidacloprid release via controlling the structure of the organobentonites. An increase in loading level of quaternary ammonium ions could result in an enhancement of the release, while the extension of the alkyl chain slowed down the release of imidacloprid.
      Graphical abstract image

      PubDate: 2015-01-26T02:47:41Z
       
 
 
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