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  Subjects -> EARTH SCIENCES (Total: 645 journals)
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EARTH SCIENCES (466 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal  
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Open Access   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 8)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 4)
Advances in High Energy Physics     Open Access   (Followers: 16)
Advances In Physics     Hybrid Journal   (Followers: 9)
Aeolian Research     Hybrid Journal   (Followers: 3)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 5)
AMBIO     Hybrid Journal   (Followers: 13)
Anales del Instituto de la Patagonia     Open Access   (Followers: 1)
Andean geology     Open Access   (Followers: 4)
Annales Henri Poincaré     Hybrid Journal   (Followers: 2)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 2)
Annals of Geophysics     Full-text available via subscription   (Followers: 9)
Annals of GIS     Hybrid Journal   (Followers: 18)
Annals of Glaciology     Full-text available via subscription   (Followers: 2)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 12)
Anthropocene     Hybrid Journal  
Anthropocene Review     Hybrid Journal   (Followers: 3)
Applied Clay Science     Hybrid Journal   (Followers: 3)
Applied Geochemistry     Hybrid Journal   (Followers: 8)
Applied Geomatics     Hybrid Journal   (Followers: 5)
Applied Geophysics     Hybrid Journal   (Followers: 8)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 12)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 35)
Arctic Science     Open Access   (Followers: 6)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 9)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 14)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 21)
Asian Review of Environmental and Earth Sciences     Open Access  
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: 15)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 12)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 11)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 10)
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: 17)
Cadernos de Geociências     Open Access  
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 15)
Canadian Mineralogist     Full-text available via subscription   (Followers: 2)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 18)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 4)
Chemical Geology     Hybrid Journal   (Followers: 11)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 4)
Chinese Geographical Science     Hybrid Journal   (Followers: 5)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 2)
Ciencia del suelo     Open Access   (Followers: 2)
Ciencias Espaciales     Open Access  
Climate and Development     Hybrid Journal   (Followers: 12)
Coastal Management     Hybrid Journal   (Followers: 23)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 7)
Computational Geosciences     Hybrid Journal   (Followers: 13)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Contemporary Trends in Geoscience     Open Access   (Followers: 2)
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: 16)
Cretaceous Research     Hybrid Journal   (Followers: 6)
Cybergeo : European Journal of Geography     Open Access   (Followers: 3)
Depositional Record     Open Access  
Developments in Geotectonics     Full-text available via subscription   (Followers: 3)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 1)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 2)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 73)
Earth and Space Science     Open Access   (Followers: 1)
Earth Interactions     Full-text available via subscription   (Followers: 11)
Earth Science Research     Open Access   (Followers: 7)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 3)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 19)
Earth System Dynamics     Open Access   (Followers: 7)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 4)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Science     Hybrid Journal   (Followers: 8)
Earthquake Spectra     Full-text available via subscription   (Followers: 14)
Ecohydrology     Hybrid Journal   (Followers: 9)
Ecological Questions     Open Access   (Followers: 6)
Electromagnetics     Hybrid Journal   (Followers: 2)

        1 2 3 4 5 | Last

Journal Cover Applied Clay Science
  [SJR: 1.17]   [H-I: 71]   [3 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2801 journals]
  • Characteristics and industrial application of the Lower Cretaceous clay
           deposits (Bouhedma Formation), Southeast Tunisia: Potential use for the
           manufacturing of ceramic tiles and bricks
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Slim Boussen, Dalel Sghaier, Fredj Chaabani, Bassem Jamoussi, Ali Bennour
      The assessment of the possible applications of the Lower Cretaceous clays, belonging to the Bouhedma Formation, as raw materials in ceramic applications, was performed on the basis of the mineralogical, chemical, thermal and physical properties. The characterization was carried out by Atomic Emission Spectrometry (ICP-AES), X-ray diffraction (XRD) and Thermogravimetric–Differential Thermal Analysis (TG-DTA) techniques. Physical properties were determined by specific surface area, particle size distribution, dilatometry and consistency limits. The data showed that these materials were composed of illite, kaolinite, and chlorite and mixed layered clay minerals in variable amounts. Quartz, feldspars and dolomite were also detected. The plasticity presented a medium value; suggesting that these clays are plastic. The firing shrinkage and the expansion were limited. Mixtures of clays were prepared from the Bouhedma clays, and heated to the desired temperature to obtain different earthenware products. Semi-industrial processed mini-bricks revealed promising characteristics and were visibly free of defects. Ceramic tiles had a bending strength complying with the required standards. Therefore, the technological properties of the investigated deposits make the Bouhedma clays suitable for the production of high-quality common bricks.


      PubDate: 2016-02-12T15:24:45Z
       
  • Dissolution kinetics of pyroaurite-type layered double hydroxide doped
           with Zn: Perspectives for pH controlled micronutrient release
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Ahmad Imran, Sandra López-Rayo, Jakob Magid, Hans Christian Bruun Hansen
      Layered double hydroxides (LDH) have a high potential for use as a source of micronutrients for plants since their dissolution rates may be controlled within the pH range observed in rhizospheres of plants in need of nutrients. Here the Zn2+ release from a pyroaurite-type LDH host at different pH was investigated. Zinc doped Mg–Fe(III) LDH intercalated with nitrate (PY(Zn)NO3) was synthesized by co-precipitation. For reference, both the nitrate and carbonate forms without Zn doping (PYNO3 and PYCO3) were also synthesized. The LDH with a Mg:Fe(III) molar ratio of 2 were found to be pure. LDH dissolution was monitored at a constant pH (4–8) to study the release of framework metal cations, dissolution stoichiometry and release kinetics. The LDH dissolved incongruently, releasing Mg2+ and Zn2+, and leaving an Fe(III)-enriched residue. The stoichiometry of metal release at a particular pH remained the same throughout the dissolution. Release kinetics of Zn2+ and Mg2+ from PY LDH was ‘first order’ with respect to the metal cations in the LDH, providing rate constants in the range of 0.16×10−3 to 10.1×10−3 min−1, with the highest rate constants at low pH. Metal ion (M) release had a fractional order with respect to [H+], resulting in overall release kinetics according to: rate=kH ×[M][H+]n with n in the range 0.25–0.43. The type of interlayer anion did not affect the overall release kinetics. Lower amounts of Zn2+ were released with respect to Mg2+ as pH increased, indicating that Zn2+ was increasingly retained in the residual Fe(III)-enriched phase. The present study demonstrates not only the pH-controlled release of micronutrient metal cations doped into the LDH framework but also points to resorption as critical parameters for optimizing the release profile. Furthermore, the present study indicates how the incorporation of the desired metal cation within the structure of the LDH may be adapted for other micronutrient/s such as Mn or Cu with the intention of using them as fertilizer.


      PubDate: 2016-02-12T15:24:45Z
       
  • Al–Mn-silicate nanobubbles phase as an intermediate in zeolite
           formation
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Amal Bejar, Semy Ben Chaabene, Maguy Jaber, Jean-François Lambert, Latifa Bergaoui
      Manganese (II) carbonate, silicic acid and aluminum nitrate were treated hydrothermally at different temperatures (120–210°C) and for different durations (6–72h) in an aqueous basic medium. Different compositions of starting mixtures were used. The synthetized materials were characterized by powder X-ray diffraction, FTIR-spectroscopy, N2 adsorption analysis, Transmission Electron Microscopy (TEM), energy dispersive X-ray analysis (EDX), thermal analysis (TG-DTG), Temperature-programmed reduction (TPR), X-fluorescence, X-ray photoelectron spectroscopy (XPS), electronic paramagnetic resonance (EPR) and 29Si and 27Al MAS-NMR spectroscopy. The formation of kaolinite, smectite-like and Mn-containing lamellar phases was observed, but only in minor amounts contrary to previous studies. The majority phase was an original Al–Mn silicate with nanobubble-like morphology, a high surface area and mesoporosity, containing both Mn(IV) in lattice positions and Mn2+ as exchangeable cations. This amorphous Al–Mn-silicate nanobubbles phase seems to be an intermediate in a zeolite formation. Indeed, the increase of the reaction temperature, the reaction time or the reagent concentrations promoted the crystallization of a zeolite of the analcime type by transformation of the Al–Mn-silicate nanobubbles.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Effects of mechanical and thermal activation on pozzolanic activity of
           kaolin containing mica
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Biljana Ilić, Vlastimir Radonjanin, Mirjana Malešev, Miodrag Zdujić, Aleksandra Mitrović
      Kaolin from a Serbian deposit, characterized by high content of impurities, such as mica and quartz, disordered kaolinite and high specific surface area, was subjected to thermal and mechanical activation on a large scale. Activations were carried out with a goal to investigate the effects of applied methods on the chemical, structural and morphological changes that occurred in the kaolin, and their influence on the pozzolanic activity. The changes were monitored using XRD, FTIR, TG/DTA, PSD, BET and SEM analyses. Pozzolanic activity was evaluated by determination of the 7-day compressive strength conducted on the lime mortars. The results showed that mechanical activation by milling the kaolin for 20h in the conventional horizontal ball mill was competitive for obtaining pozzolana as thermal activation. Pozzolanic activity of thermally activated kaolin was mainly influenced by formation of metakaolin. Combined effects (such as significant specific surface area increase, as well as partial kaolinite and complete mica phase amorphization) were dominant in pozzolanic activity of mechanically activated kaolin.


      PubDate: 2016-02-12T15:24:45Z
       
  • Measurement of hydraulic properties of bentonite cake formation deposited
           on base soil medium
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Dongseop Lee, Kiseok Kim, Hyobum Lee, Jeehee Lim, In-Mo Lee, Hangseok Choi
      Bentonite cake and filter cake on the surface of porous media result from the filtration of stabilizing slurry into the adjacent porous formation. This paper provides measurements of hydraulic conductivities of bentonite cake formed on Korean standard sand under various pressure levels. Two types of bentonite (Tixoton and Bentonil GTC4) were used to create the slurries with three different concentrations (4, 6, and 8% by weight). An estimation of the hydraulic conductivity of the bentonite cake based on the filtration theory was carried out. The range of hydraulic conductivities of the bentonite cake was from 2.1×10−11 m/s to 5.7×10−10 m/s. The hydraulic conductivity of the bentonite cake deposited on Korean standard sand were compared with that of the bentonite cake deposited on filter paper to show the effect of the filter medium. The slurry concentration of 6% seems to be a value that most stimulates the effect of the filter medium on the permeability of the Bentonil GTC4 bentonite cake. In addition, a simple approach was developed to characterize the hydraulic properties of the filter cake, which has usually been confused with the bentonite cake in recently published literature.


      PubDate: 2016-02-12T15:24:45Z
       
  • Plate-like Ni–Mg–Al layered double hydroxide synthesized via a
           
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Weichen Du, Liping Zheng, Xuewen Li, Jie Fu, Xiuyang Lu, Zhaoyin Hou
      Layered double hydroxide (LDH) is widely used in adsorption, additive, catalyst precursor and support. In this work, a solvent-free synthesis approach of plate-like Ni–Mg–Al LDH and its application in hydrogenolysis of D-sorbitol was reported. It was found that mainly hexagonal plate-liked LDH crystals (with a diameter of 25–30nm and a thickness of 7.0–10.5nm) formed in Ni3.6Mg2.4Al2(OH)16CO3-SF that synthesized via solvent-free routine. Ni3.6Mg2.4Al2(OH)16CO3-SF possessed higher crystallinity, bigger specific surface area and stronger basicity than its counterpart that synthesized in traditional coprecipitation method. Bi-functional Ni/solid-base catalyst with homogenously dispersed Ni clusters (with a mean diameter of 3.3nm) on separated plate-liked Mg2.4Al2O5.4 sheets could be prepared after controlled calcination and reduction of Ni3.6Mg2.4Al2(OH)16CO3-SF. Ni3.6/Mg2.4Al2O5.4-SF catalyst was highly active and stable for the hydrogenolysis of D-sorbitol under mild conditions.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Preparation and investigation of hydrophilic, photocatalytic, and
           antibacterial polyacrylic latex coating containing nanostructured
           TiO2/Ag+-exchanged-montmorillonite composite material
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Ali Olad, Rahimeh Nosrati, Hamideh Najjari, Katayoon Nofouzi
      In order to prepare a self cleaning and antibacterial coating, nanostructured TiO2/Ag+-exchanged-montmorillonite composite material was prepared and used as additive in a commercial grade polyacrylic latex coating. FT-IR and UV–visible spectroscopy, X-ray diffraction patterns and FESEM were used to characterize the composition and structure of the nanocomposites and coatings. The polyacrylic coatings, prepared by the using of TiO2/Ag+-exchanged-montmorillonite additive, showed better UV and visible light absorption, hydrophilic property, photodegradation of organic pollutants, stability in water and antibacterial properties than pristine commercial grade polyacrylic latex coating. According to the results, the modified polyacrylic coating containing 3%w of nanostructured TiO2/Ag+-exchanged-montmorillonite composite material as additive, with TiO2 to Ag+-exchanged-montmorillonite ratio of 2:1, was the best coating considering most of the useful properties such as low water contact angle, high photodegradation efficiency, and high water resistivity. The water contact angle for unmodified polyacrylic latex coating was 68° while it was decreased to about 10° or less for modified coating after 24h LED lamp illumination.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Pore distribution of water-saturated compacted clay using NMR relaxometry
           and freezing temperature depression; effects of density and salt
           concentration
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Takahiro Ohkubo, Moe Ibaraki, Yukio Tachi, Yasuhiko Iwadate
      The estimation of water population in water-saturated compacted clay was studied with 1H NMR relaxometry and freezing point depression. The clay samples and saturated condition were Na-montmorillonite at 0.8 and 1.4g/cm3 saturated by three salt concentrations (deionized water, 0.1mol/L and 1.0mol/L). The water-saturated compacted samples were prepared in PCTFE cylinder by immersed in the liquid under vacuum for 1month. All NMR measurements were conducted using intact PCTFE vessel, which was possible to keep confinement condition during experiment. In order to distinguish interlayer with four hydrated state and non-interlayer water, we assumed four T 1 thresholds corresponding to 1-, 2-, 3, and 4 hydrated layers, which were 1.2, 2.3, 3.5, and 4.7ms, respectively. The populations of hydrated state and non-interlayer water were calculated from these thresholds at 30°C. The sample with lower density exhibits higher population of non-interlayer water up to 55%. Low-temperature 1H NMR experiments were also conducted to support these results in view of freezing point depression against pore size. Mesopore water in approximately 4nm space observed in the calorimetric study was considered as non-interlayer water and the threshold temperature, which was equivalent to a freezing point of −12.5°C from Gibbs–Thomson equation. The result showed that population of non-interlayer water by expected from freezing point depression agreed with 1H NMR relaxometry within 10%. Correlation experiments were also conducted between longitudinal (T 1) and transverse relation times (T 2) at −10°C to obtain dynamical information on water. A small peak was obtained close to a T 1/T 2 line of 1.0 at a clay density of 1.4g/cm3, suggesting that high-mobility bulk-like water molecules existed in this sample.


      PubDate: 2016-02-12T15:24:45Z
       
  • Effects of molecular mass of polymer and composition on the compressive
           properties of hydrogels composed of Laponite and sodium polyacrylate
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Hiroyuki Takeno, Chikaki Sato
      Recent studies have shown that hydrogels prepared by simple mixing of a polyelectrolyte (sodium polyacrylate (PAAS)) and clay (Laponite) with a dispersant (tetrasodium pyrophosphate) are mechanically tough. In this study, the mechanical and structural properties of such hydrogels were investigated in detail as a function of both the molecular mass of the polymers and the hydrogel composition by means of compression measurements and synchrotron small-angle X-ray scattering analysis to clarify the origin of the mechanical toughness. The hydrogels prepared under optimum conditions were not broken, even after 90% compression. The elastic moduli of the hydrogels gradually decreased with increasing concentrations of PAAS, whereas they reached a maximum with respect to the concentration variation of the dispersant. The gels prepared at the compositions where the modulus was maximal were mechanically tough. These composition dependencies of the mechanical properties were related to structural inhomogeneity in the gel; thus, the results of this study demonstrate that inhomogeneity substantially lowers the mechanical properties of these hydrogels. At high clay concentrations, the elastic moduli of the hydrogels were not affected by the molecular mass of PAAS; in contrast, at low clay concentrations, they substantially decreased with decreasing the molecular mass of PAAS. The results of this study reveal that PAAS with a molecular mass greater than ~106 is necessary for fabricating the mechanically tough hydrogels.


      PubDate: 2016-02-12T15:24:45Z
       
  • Mg–Al layered double hydroxides modified clay adsorbents for
           efficient removal of Pb2+, Cu2+ and Ni2+ from water
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Facui Yang, Shiqi Sun, Xiaoqi Chen, Yue Chang, Fei Zha, Ziqiang Lei
      Highly effective clay adsorbents of Mg–Al layered double hydroxides modified palygorskite were prepared from the mixture of metal salts, urea and palygorskite by the in situ hydrothermal crystallization method. The obtained adsorbents were characterized by FT-IR, TG, XRD and SEM/EDS. The adsorption performances were evaluated for the removal of Pb2+, Cu2+ and Ni2+ in the aqueous solution. The adsorption capacities of the three metal cations at variable pH, contact times and metal concentrations were determined by atomic adsorption spectrometry. The adsorption capacities of the three metal cations on Mg–Al layered double hydroxides modified palygorskite were higher than those of palygorskite and Mg–Al layered double hydroxides at the initial metal ion concentration of 100mg/L and initial pH of 5.0. The experimental data showed a good compliance with the Langmuir isotherm and the pseudo-second-order kinetic model. Taking advantage of the combined benefits of palygorskite and Mg–Al layered double hydroxides, the as-prepared adsorbents exhibit selective and fast rating adsorption for Pb2+.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Immobilization of selenium by Mg-bearing minerals and its implications for
           selenium removal from contaminated water and wastewater
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Einstine M. Opiso, Tsutomu Sato, Tetsuro Yoneda
      This study examines the possible immobilization of Se(VI) by Mg-bearing hydrotalcite and serpentine-like minerals. Selenate immobilization was carried out via adsorption and coprecipitation reactions under alkaline conditions. The effects of Mg/Al ratios, temperature and initial Se concentration on the adsorption and/or coprecipitation of Se6+ onto these Mg-bearing minerals were examined. The sorption mechanism of Se(VI) was examined by XAFS analysis to give account of its local coordination environment. The results showed that Se(VI) sorption behavior by hydrotalcite and serpentine-like minerals was mainly influenced by their Mg/Al ratio. Higher removal efficiency of Se(VI) (> 60 and 90% at 100 and 10ppm initial Se concentration) was observed during coprecipitation onto hydrotalcite and serpentine-like phases with Mg/Al ratios of 2 and 1.25, respectively. The formation of Mg-bearing minerals was enhanced at higher temperature (at 75°C) but the effect of temperature in Se(VI) immobilization was very minimal. Selenate was mainly retained via outer-sphere complexation but an irreversible fraction of sorbed selenate (about 20%) was observed in these mineral phases. In overall, this study has several important implications in the possible application of hydrotalcite and aluminian serpentine in Se(VI) immobilization.


      PubDate: 2016-02-12T15:24:45Z
       
  • Assessment of aflatoxin B1 adsorption efficacy of natural and processed
           bentonites: In vitro and in vivo assays
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): G.R. Nazparvar Soufiani, M. Razmara, H. Kermanshahi, A.L. Barrientos Velázquez, A. Daneshmand
      The presence of aflatoxin B1 in livestock's feed results in contamination of milk and its products with aflatoxin M1. Different sequestering agents have been added to cows' ration to adsorb these toxins, although influence of processed bentonites on aflatoxins adsorption has not been evaluated yet. This experiment was carried out to assess the effects of incorporating natural and processed bentonite (local or commercially available), to the diet of Holstein dairy cows subjected to an aflatoxin B1 diet, and the transfer of aflatoxin metabolites (AFM1) to milk. Aflatoxin sequestering capacity, pH, CEC, XRD and XRF of natural and processed bentonites were measured. Then, twelve Holstein dairy cows were assigned to 3 treatments as the following: 1) local processed bentonite (G.Bind™), 2) local unprocessed bentonite (F), and 3) commercially available bentonite (M). Aflatoxin content in feed and milk was evaluated and transfer rate was measured. Results of the present study showed that the aflatoxin contents of milk were remained unchanged except for treatment G.Bind™ that considerably decreased aflatoxin M1 in milk after the second and third weeks of the experiment. G.Bind™ lowered the transfer rate of aflatoxin B1 from 1.17% at the beginning of the experiment to 0.43% and 0.39% after the first and second weeks, respectively. Processing of bentonites (basic processing in present study) can considerably help to adsorb aflatoxin from feed and also to decrease aflatoxin transfer to milk.


      PubDate: 2016-02-12T15:24:45Z
       
  • The structure and rheology of organo-montmorillonite in oil-based system
           aged under different temperatures
    • Abstract: Publication date: May 2016
      Source:Applied Clay Science, Volumes 124–125
      Author(s): Guanzheng Zhuang, Zepeng Zhang, Jinlong Sun, Libing Liao
      This work aims to study the structure of organo-montmorillonite (OMt), structure of OMt/oil gels and the rheology of OMt/oil fluids aged under different temperatures. Most important, we focused on the relationship among OMt, OMt/oil and temperatures. The results of XRD and contact angle test demonstrated that surfactants loading deeply influenced the structure and surface properties of OMt. The results of XRD, optical microscope and gel volume of OMt/oil indicated that the structure of OMt in oil went through three stages with the temperature rising: swelling→continuous swelling→exfoliation→shrinking. The enwinding, absorption and other attraction among absorbed surfactants bridged individual OMt sheets, particles and aggregates, forming the gel structure. The swelling and gel formation of OMt/oil were influenced by the surface/interface properties, basal spacing, surfactants loadings and temperature. Dynamic rheological curves demonstrated that OMt/oil followed the Bingham plastic model at high shear rate (often ≧20s−1) while deviation emerged at low shear rate range. The viscosity, gel strength and thixotropy of OMt/oil were relevant to the structure which was influenced by multiple elements, such as surface/interface properties, basal spacing, surfactants loadings, temperature, etc. The best performance of individual element did not automatically lead to the greatest rheological properties. Higher surfactants loading, higher d001 without very ordered internal lattice and moderate polarity of surface/interface of OMt were expected. For oil-based drilling fluids containing OMt prepared with cetyl trimethyl ammonium bromide (CTAB), the operating temperature was advised below 150°C.


      PubDate: 2016-02-12T15:24:45Z
       
  • Photodegradation of aniline in water in the presence of chemically
           activated halloysite
    • Abstract: Publication date: May 2016
      Source:Applied Clay Science, Volumes 124–125
      Author(s): Beata Szczepanik, Piotr Słomkiewicz
      Photocatalytic degradation of aniline was investigated in aqueous solutions containing halloysite (Hal) nanotubes, chemically activated halloysite (AHal), and photocatalysts: TiO2 (anatase) and commercial titania P25, under UV illumination. Powder X-ray diffraction (XRD), UV–Vis/DR spectra and nitrogen adsorption isotherms were carried out to characterize the activated halloysite. The effects of the AHal and titania photocatalyst amount as well as aniline concentration were examined. It is observed that the photodegradation of aniline has a similar course in the presence of AHal and in the presence of P25 and TiO2, both with respect to the decomposition of aniline and in decreasing the amounts of photoproducts being formed during the irradiation of aniline. The photodegradation of aniline is clearly slower in presence of Hal nanotubes than for AHal and P25. The disappearance of aniline follows approximately according to the Langmuir–Hinshelwood kinetics. The values of rate photodegradation constant are decreasing in the following order: P25>TiO2 >AHal>Hal nanotubes. These results have indicated that halloysite containing titanium dioxide could be employed during photocatalytic removal of aniline from the aqueous solution, similarly to commercial titania photocatalysts.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Effects of solution concentration and vertical stress on the swelling
           behavior of compacted GMZ01 bentonite
    • Abstract: Publication date: May 2016
      Source:Applied Clay Science, Volumes 124–125
      Author(s): Yong-Gui Chen, Chun-Min Zhu, Wei-Min Ye, Yu-Jun Cui, Bao Chen
      Compacted bentonite has been considered as buffer/backfill material in radioactive waste disposal. This study deals with the effects of the concentration of infiltration saturation and vertical stress on the swelling behavior of compacted GMZ bentonite. One-dimensional swelling tests were performed on specimens at an initial dry density of 1.7Mg/m3. NaCl solutions with concentrations of 0 (de-ionized water), 0.1, 0.5 and 1.0mol/L were used to saturate the specimens while three vertical stresses of 0.06, 0.062 and 1.85MPa were applied. Results show that, for all the infiltration solutions, the swelling strain decreases with increasing vertical stress; the impact of the vertical stress is more significant for low vertical loads while it is less patent when the high salinity solution is infiltrated. For all the vertical stresses applied, the swelling strain decreases with the increase in concentration of the infiltration solution; the impact of the concentration of infiltration solution is not only related to the vertical stress, but also to the soil permeability. Furthermore, the coefficient of primary swelling decreases with the increase in concentration and vertical stress. The concentration of infiltration solution has significant restricting effect on the secondary swelling deformation in case of low vertical stress, while it has no or few effects on the secondary swelling deformation in case of higher vertical stress.


      PubDate: 2016-02-12T15:24:45Z
       
  • Flexible polyurethane foam nanocomposites with modified layered double
           hydroxides
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Sandra Gómez-Fernández, Lorena Ugarte, Cristina Peña-Rodriguez, Manuela Zubitur, M. Ángeles Corcuera, Arantxa Eceiza
      A carbonate intercalated Mg/Al layered double hydroxide (LDH-CO3) was subjected to a calcination–rehydration treatment in order to intercalate two different phosphorus containing anions (HPO4 −2 and bis(2-ethylhexyl) phosphate, HDEHP−) into the hydroxide layers. The X-ray diffraction analysis showed that the anions were successfully intercalated presenting different crystallinity degree and crystallite size, being LDH-CO3 the most crystalline, followed by LDH-HDEHP and LDH-HPO4. The effect of the addition of unmodified and modified LDH in different quantities (1, 3 and 5pphp) to a flexible polyurethane foam matrix containing a castor oil based polyether was studied. Depending on the crystallinity of the LDH, different dispersion degree was achieved in the nanocomposites affecting the properties differently. Density and firmness increased with the addition of LDH while lower resilience values were obtained in foams containing 3pphp of LDH-CO3 and LDH-HPO4. In addition, thermal behaviour of nanocomposites was analysed by thermogravimetric analysis (TGA) and pyrolysis flow combustion calorimetry (PCFC) and was compared to the reference foam. A decrease in heat release rate was observed in the second stage of degradation, especially for LDH-HDEHP containing foam.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Electrocatalytical effect of montmorillonite to oxidizing ibuprofen:
           Analytical application in river water and commercial tablets
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): A. Loudiki, H. Hammani, W. Boumya, S. Lahrich, A. Farahi, M. Achak, M. Bakasse, M.A. El Mhammedi
      The electrochemical oxidation of ibuprofen was investigated at a montmorillonite-doped carbon paste electrode (Mt–CPE). A well-defined oxidation peak was observed at around 1.02V/AgCl in phosphate buffer (pH8). The experimental condition was optimized by varying chemical and electrochemical parameters. The oxidation peak current is linear to the ibuprofen concentration in the ranges 1.0×10−3–1.0×10−6 molL−1 and 1.0×10−6 −1.0×10−7 molL−1 with a detection limit of 6.80×10−8 molL−1. The precision (n=8) assessed as relative standard deviation (R.S.D.) were 1.24% for 1.0×10−6 molL−1 and 1.07% for 4.0×10−5 molL−1 respectively. Possible interferences were tested and evaluated in 1.0×10−5 molL−1 ibuprofen in the presences of common organic and inorganic interfering agents. Based on its high sensitivity and good selectivity, the Mt–CPE was successfully applied to determine ibuprofen in river water and commercial tablets. The satisfactory obtained results confirm the applicability of this sensor in practical analysis.


      PubDate: 2016-02-12T15:24:45Z
       
  • Influence of the temperature on the rheological properties of bentonite
           suspensions in aqueous polymer solutions
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): K. Ben Azouz, K. Bekkour, D. Dupuis
      Dispersions of clay particles in aqueous polymer solutions generally exhibit complex rheological behaviours depending on the mechanical history of the material. In this paper, the effect of the temperature on the rheological properties of bentonite dispersions in aqueous carboxymethylcellulose solutions is examined. The bentonite concentration was fixed to 5% w/w while the polymer is 0.5 or 1% w/w. For stresses lower than a yield stress, the systems behaved as a gel and, above the yield stress, they flowed as liquids. The samples were characterized both in permanent and oscillatory shear flow. In the liquid like regime, the viscosity of the fluids decreased as the temperature increased. In the solid like regime, when the temperature increased, the experimental results displayed unusual behaviours of the viscosity and of the shear moduli. The increase of the chain mobility induced by the Brownian motion combined with a dissociation of the aggregates of particles could result in the formation of an elastic network with more crosslinks. This could explain why a dramatic increase of the solid-like character of the dispersions was observed.


      PubDate: 2016-02-12T15:24:45Z
       
  • Continuous water adsorption states promoted by Ni2+ confined in a
           synthetic smectite
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): M.A.S. Altoé, L. Michels, E.C. dos Santos, R. Droppa, G. Grassi, L. Ribeiro, K.D. Knudsen, H.N. Bordallo, J.O. Fossum, G.J. da Silva
      The water adsorption isotherms of Ni-fluorohectorite have been obtained from the relative humidity dependence of X-ray diffraction intensities, and continuous transitions between the stable hydration states were observed. This behavior is significantly different from previous studies of Na-fluorohectorite and Li-fluorohectorite smectites. It was also observed that the environmental history of the clay mineral samples is important for the behavior displayed by these isotherms. In addition, based on thermogravimetric and differential scanning calorimetry measurements, it was observed that a complete Ni-fluorohectorite dehydrated state can only be reached at long times (several hours) at 70°C, or at shorter times (minutes) above 150°C. Our observations are consistent with the existence of various forms of Ni2+–H2O complexes in Ni-fluorohectorite, and we suggest that the present results can be extended to other smectites with transition metals as interlayer charge compensating cations, and consequently have significant practical consequences in materials science and other areas.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Mesoporous silica derived from kaolin: Specific surface area enlargement
           via a new zeolite-involved template-free strategy
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Zhu Shu, Tiantian Li, Jun Zhou, Yun Chen, Zimo Sheng, Yanxin Wang, Ximing Yuan
      A novel zeolite-involved template-free strategy is proposed and demonstrated to process natural kaolin into mesoporous silica with enlarged specific surface area (SBET). Kaolin was calcined and alkali-treated into aluminosilica zeolite, and then transformed into amorphous mesoporous silica with SBET of 751.5m2/g and pore size of ~4.0nm at the maximum probability in a subsequent acid-treatment. The alkali-treatment and the formation of zeolite intermediate were found to be the key for the SBET enlargement. The mechanisms were studied by XRD, XRF, SEM, TEM and N2 adsorption/desorption. The mesoporous silica shows favorable adsorption ability towards methylene blue with a monolayer adsorption capacity of up to 756.5mg/g, indicating its promising potential in adsorption application.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Performance of Ni/Si-pillared clay catalytic extrudates for benzene
           hydrogenation reaction
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): A. Louloudi, N. Papayannakos
      Ni supported on Si-pillared montmorillonite systems have been prepared and studied as catalysts for the test reaction of benzene hydrogenation. The Ni/Si-pillared clay catalytic systems were characterized as to their crystallographic structure, specific surface area, specific volume and apparent density. Their reactivity was evaluated over a temperature range of 70–150°C under atmospheric pressure, in a differential bench scale reactor, and compared with other Ni catalysts supported on conventional carriers, such as γ-Al2O3 and Vycor. Apart from the intrinsic catalytic rates, the effect of both internal and external mass transfer limitations was also studied for particle sizes commonly used in industrial praxis. The change of the overall reaction rates with particle size was investigated. The mass transfer effects were examined for diluted catalytic beds of three extrudate sizes and diffusional limitation within the particles were decoupled from external mass transfer resistances. Particle diffusional limitations and their dependence on process temperature and particle porosity were determined and discussed.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Adsorption of reactive dyes from aqueous solution by dirty bentonite
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Kheira Chinoune, Kahina Bentaleb, Zohra Bouberka, Abdelouahab Nadim, Ulrich Maschke
      The preparation of magnesium hydroxide coated bentonite, B–Mg(OH)2 composite, and its capacity to remove anionic reactive dyes; Procion blue HP (PB) and Remazol brilliant blue R (RB) from aqueous solution were reported in this study. The adsorbent was characterized by X-ray fluorescence analysis, X-ray powder diffraction, thermal gravimetric analysis, Brunauer Emmett Teller surface area analysis; scanning electron microscopy, and Fourier transform infrared spectroscopy. The effectiveness of B–Mg(OH)2 composite to remove dyes was examined at different initial concentrations, pH, temperature and ionic strengths. At pH=2, the maximum dye adsorption was found as 98.2% for RB and 87.8% for PB. Kinetic studies revealed that adsorption follows a pseudo-second-order model, and rate constants were evaluated. The Langmuir monolayer adsorption capacities of PB and RB in aqueous solution were estimated at 298K as 40.22 and 66.90mg/g, respectively. A temperature uptake from 278K to 313K induced an increase of adsorption for both dyes and the process was found to be physiosorptive, endothermic and spontaneous. Higher concentration or more valence of anions of electrolytes in dye solution caused decreasing dye adsorption efficiency of B–Mg(OH)2 composite.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Adsorption of two fungicides on natural clays of Morocco
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Said Azarkan, Aránzazu Peña, Khalid Draoui, C. Ignacio Sainz-Díaz
      North of Morocco is becoming one of suppliers of tourism sites and agricultural products for Europe. Thus, environmental risks from this region are important for the future of these activities. The presence of pesticides in soils and waters can become a serious environmental problem. Clay minerals can be used for mitigation of this problem. In this work, the adsorption of two fungicides, metalaxyl and tricyclazole, on natural Northern Moroccan clays was investigated using the batch equilibration method and several techniques, such as, X-ray diffraction (XRD), thermal analysis (TGA/DSC), and surface area measurement (BET) were used for clay characterization. The data from kinetic and adsorption studies were fitted to different models. The adsorption kinetics of these fungicides followed a pseudo-second-order model. Adsorption data, higher for metalaxyl than for tricyclazole, were fitted the Freundlich model. A natural stevensite was the clay with the highest adsorption capacities for both fungicides.


      PubDate: 2016-02-12T15:24:45Z
       
  • Optimization of hexadecylpyridinium-modified montmorillonite for removal
           of perchlorate based on adsorption mechanisms
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Wuhui Luo, Tsuyoshi Hirajima, Keiko Sasaki
      Adsorption of perchlorate (ClO4 −) onto hexadecylpyridinium-modified montmorillonite (OMt) was investigated by in situ and ex situ methods. For the in situ method, ClO4 − was initially bound by hexadecylpyridinium (HDPy+) in the form of HDPy-ClO4 which together with the excess HDPy+ were simultaneously captured by Mt. The ex situ strategy was performed by adding synthesized OMt into ClO4 −-bearing solution, where conventionally dried OMt (II-OMt) and innovative OMt (I-OMt) without drying and washing procedure were compared as adsorbents. The adsorption capacity of ClO4 − and amount of HDPy released into equilibrium solution were evaluated, where surfactant release was rarely addressed in previous publications. I-OMt showed relatively high adsorption capacity of ClO4 − and negligible release of HDPy. The lower adsorption capacity of ClO4 − onto II-OMt was caused by the washing procedure which removed the unstably anchored HDPy. Inhibition of HDPy release of I-OMt was explained by reconfiguration of HDPy after ClO4 − adsorption as supported by results of X-ray diffraction and attenuated total reflection Fourier transform infrared spectroscopy. In addition, for anion adsorption onto conventionally synthesized OMt, the difference between the amounts of released counter ion and that of entrapped target anion is generally ignored. Such phenomenon was critically considered in this study, and the results showed that the difference between adsorbed ClO4 − and released Cl− decreased with an increase of HDPy loading and was more significant in I-OMt. This is rationalized by the desorption of HDPy+ and formation of HDPy-ClO4 according to the results of 13C nuclear magnetic resonance spectra and the adsorption energy evaluated by the Dubinin–Radushkevich model.
      Graphical abstract image

      PubDate: 2016-02-12T15:24:45Z
       
  • Modeling the transport of water and ionic tracers in a micrometric clay
           sample
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Pauline Bacle, Jean-François Dufrêche, Benjamin Rotenberg, Ian C. Bourg, Virginie Marry
      Brownian dynamics simulations were performed to examine the self-diffusion of cationic (Na+), anionic (Cl−), and water tracers in a saturated compacted clay at the micrometric scale. Clay minerals particles, representing stacks of montmorillonite layers, are modeled as cylindrical platelets with characteristics that depend on the dry bulk density of the porous medium, ρ b . The tracers are allowed to diffuse between the platelets with their diffusion coefficient in bulk aqueous solution as well as inside the platelets with a diffusion coefficient that depends on the hydration level of the interlayer pores as determined from experiments or molecular dynamics simulations. The probability for a tracer to enter a platelet is related to its charge as predicted by the Poisson–Boltzmann equation. The apparent diffusion coefficients are calculated as a function of ρ b for various salinities and compared with the values obtained from tracer diffusion experiments available in the literature. Despite the simplicity of the clay model, the simulations predict most features of the experimental data and keep the door open for further improvements.


      PubDate: 2016-02-12T15:24:45Z
       
  • Organoclay-epoxy nanocomposites modified with polyacrylates: The effect of
           the clay mineral dispersion method
    • Abstract: Publication date: May 2016
      Source:Applied Clay Science, Volumes 124–125
      Author(s): Adriana A. Silva, Bluma G. Soares, Karim Dahmouche
      Organically modified montmorillonite (OMt) was employed to prepare clay/epoxy/acrylate polymer ternary composites. Two different procedures were used for the clay mineral dispersion: i) OMt was dispersed in an epoxy matrix previously modified with acrylate polymers or ii) the clay mineral was swollen in the acrylate monomers and the monomer was in situ polymerized followed by dispersion in the epoxy matrix. For the acrylate polymers, poly(methyl methacrylate) (PMMA) or a methyl methacrylate-co-2-ethylhexyl acrylate copolymer (PMMA-co-PEHA) were used. The nanostructure of the corresponding hybrid materials was investigated by X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The combination of these techniques confirmed the improved dispersion of the OMt in the thermosetting networks prepared by using the previous polymerization of acrylate monomers on the swollen clay mineral. Also this method resulted in ternary epoxy-based nanocomposites with outstanding impact resistance, higher storage modulus and improved thermal stability.


      PubDate: 2016-02-12T15:24:45Z
       
  • Extended and local structural description of a kaolinitic clay, its fired
           ceramics and intermediates: An XRD and XANES analysis
    • Abstract: Publication date: May 2016
      Source:Applied Clay Science, Volumes 124–125
      Author(s): L. Andrini, M.R. Gauna, M.S. Conconi, G. Suarez, F.G. Requejo, E.F. Aglietti, N.M. Rendtorff
      The thermal transformations processes of kaolinite (K) in kaolinitic clays is known to consist of a dehydroxylation into metakaolin (MK) at ≈600°C, followed by the formation of a spinel type aluminosilicate (SAS) at ≈980°C, and finally the development of mullite (M) at higher temperatures (1200–1300°C). The structural characterization of these materials is generally based on X-ray diffraction (XRD) studies, where the XRD features of K and M are well defined due to their crystalline nature, but as consequence of the low crystallinity of MK and SAS, the precise characterization of these phases is not possible using this technique. In this study the nature of aluminum atoms in the different materials obtained by thermal treatments of a kaolinite is investigated using Al K-XANES and compared with other well-known aluminum containing materials. XRD and SEM characterization were also carried out. The results confirm the potentiality of this synchrotron based techniques for the characterization of natural materials and ceramics especially with low crystallinity. Particularly the mullite aluminums Al K-XANES spectra were not reported before.


      PubDate: 2016-02-12T15:24:45Z
       
  • Desiccation of NaCl-contaminated soil of earthen heritages in the Site of
           Yar City, northwest China
    • Abstract: Publication date: May 2016
      Source:Applied Clay Science, Volumes 124–125
      Author(s): Y. Zhang, W.M. Ye, B. Chen, Y.G. Chen, B. Ye
      The Site of Yar City (formerly known as the ancient city of Jiaohe) is regarded as the largest, oldest and best-preserved earthen site in the present world. However, during the long-term exposure to the environment, remaining earthen structures suffered serious deterioration caused by many influencing factors. The shallow surfaces of the earthen walls can be fully saturated by the concentrated and heavy rains to form flowing slurry, which will be turned into strongly cracked surface crusts during the following intense evaporation and peeled off by wind deflation. In the meantime, salts could be accumulated in the remains to a quite high content, which could exacerbate the deterioration conversely. In this work, desiccation tests were conducted in laboratory on the initially saturated slurry specimens with different thicknesses and NaCl contents and thicknesses. Development of crack patterns on the surface of the specimen was monitored with a digital camera and analyzed using commercialized software. Results indicated that the evaporation process of NaCl-contaminated specimens could be identified as three stages, which has the same configuration as that of salt-free specimens. Cracking behavior of soil that closely correlates to the evaporation process was also influenced. As the NaCl content increases, the CIF values, intersection number, segment number as well as the total crack length decreases. A non-orthogonal crack pattern and orthogonal crack pattern were dominant for thin and thick specimens, respectively.


      PubDate: 2016-02-12T15:24:45Z
       
  • The potential of phosphate removal from dairy wastewater and municipal
           wastewater effluents using a lanthanum-modified bentonite
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Eyal Kurzbaum, Oded Bar Shalom
      Adsorption is gaining interest as an effective advanced method for treatment of wastewater effluents with a high phosphorus concentration. The present work investigated the use of a bentonite–lanthanum clay (Phoslock®) which effectively reduced the amount of dissolved phosphate. Batch experiments were carried out in order to obtain adsorption equilibrium isotherms and kinetics with phosphate-spiked synthetic solutions. Different doses of Phoslock® clay were examined for their efficiency in removing phosphate from dairy wastewater and from two types of domestic wastewater treatment plant effluents (a sequenced batch reactor (SBR) and an activated sludge plant). The average maximum adsorption capacity ratio was 69mg Phoslock® per 1mg of phosphate removed from the phosphate-spiked synthetic solution. Nevertheless, a ratio of 100, 300 and 400mg Phoslock® per 1mg of phosphate was found for complete phosphate removal from the effluents of the dairy, the SBR and the activated sludge plant, respectively. The higher ratios are probably due to the presence of dissolved organic matter in the wastewater. Phosphate removal from the effluents was more efficient and faster with the increase in Phoslock® doses (up to 100% removal in the first 15min for the dairy wastewater). This study shows that bentonite–lanthanum clay can be used to design an adsorption treatment process for phosphate removal from water and wastewater with a low hydraulic retention time and minimal infrastructure.


      PubDate: 2016-02-12T15:24:45Z
       
  • Preparation of economical and environmentally friendly
           graphene/palygorskite/TiO2 composites and its application for the removal
           of methylene blue
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Hao Zhao, Fengxian Qiu, Jie Yan, Jie Wang, Xin Li, Dongya Yang
      A novel economical and environmentally friendly graphene/palygorskite/TiO2 (GR/Pal/TiO2) composites adsorbent was prepared and characterized by X-ray diffractometry (XRD), Fourier transform infrared (FTIR), N2 adsorption/desorption isotherms, transmission electron-microscopy (TEM) and scanning electron microscopy (SEM). The GR/Pal/TiO2 was applied to removal dye methylene blue (MB) and the optimum conditions of adsorption were investigated. The obtained results indicated that when the dosage of GR/Pal/TiO2, reaction temperature and time of the composite are 15mg/mL, 40°C and 1h, respectively, the adsorption efficiency can reach 100%. The adsorption kinetic of MB followed the pseudo-second-order model while the adsorption isotherm confirms to the Langmuir model. The adsorption process is spontaneous and endothermic by thermodynamic study. Compared with other different reported materials, the novel GR/Pal/TiO2 composite exhibits a high adsorption ability for MB removal. The obtained results demonstrate that the prepared GR/Pal/TiO2 composites are very promising material for the removal of MB from wastewater.


      PubDate: 2016-01-18T10:50:22Z
       
  • Improved photocatalytic activity of SnO2–ZnAl LDH prepared by one
           step Sn4+ incorporation
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): G. Mendoza-Damián, F. Tzompantzi, A. Mantilla, R. Pérez-Hernández, A. Hernández-Gordillo
      SnO2–ZnAl LDH with a molar ratio Zn/(Al+Sn) 3/1 (Sn4+ contents 0.1–0.4mol%) were prepared in one step by the co-precipitation method. The ZnAl LDH intercalated with carbonate ions and the composite of ZnAl LDH formed together with SnO2 were characterized by XRD, SEM, HRTEM and complementary spectroscopies such as FTIR, XPS and UV–Vis. The EDX and AAS was performed for the compositional analysis. The effect of the Sn4+ content on the opto-electronic properties of the dried SnO2–ZnAl LDH composites were evaluated on the phenol photodegradation under UV light irradiation. The mineralization degree of the photocatalysts was determined after 2h of reaction by TOC analysis. The SnO2–ZnAl LDH composites that showed the highest photocatalytic activity were compared with ZnAl LDH sample impregnated with Sn4+ cations. The effect of the presence of the Zn5(CO3)2(OH)6 as precursor for the formation of the ZnAl LDH as well as the methodology of synthesis on the photocatalytic properties of the composites were studied. A possible mechanism of the OH radical formation and electron–hole charge separation in the improvement photocatalytic reaction were discussed.
      Graphical abstract image

      PubDate: 2016-01-18T10:50:22Z
       
  • Relationship between the fractal structure with the shear complex modulus
           of montmorillonite suspensions
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): M. Gareche, A. Allal, N. Zeraibi, F. Roby, N. Azril, L. Saoudi
      In this work, we characterized and studied the rheological behavior of montmorillonite suspensions. Our objective was to establish the link between the structure of these suspensions and their rheological behavior. We have characterized these suspensions using several techniques: X-ray scattering to determine their composition and structure, the light scattering to determine the diffusion coefficient of the clay particles and their size. We also measured their densities and their rheological properties in linear and non-linear viscoelasticity. The rheological measurements show that the bentonite particles are structured to form a fractal network. We have determined experimentally the moduli and yield stresses. Using Piau model, we have derived its fractal dimension (D =1.74±0.08). The light scattering measurements allowed us to determine the particles size and the characteristic time of diffusion of the clay particles in the suspension. Finally, knowing the structure of our suspensions and characteristic time, we tried to model their viscoelastic behavior G∗(Ω) using Chambon and Winter model.


      PubDate: 2016-01-18T10:50:22Z
       
  • Editorial Board
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122




      PubDate: 2016-01-18T10:50:22Z
       
  • Ceramics from clays and by-product from biodiesel production: Processing,
           properties and microstructural characterization
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): S. Martínez-Martínez, L. Pérez-Villarejo, D. Eliche-Quesada, B. Carrasco-Hurtado, P.J. Sánchez-Soto, G.N. Angelopoulos
      The production of biodiesel generates a by-product called glycerine which contains glycerol that cannot be re-integrated into the same manufacturing process. The ceramic bricks are an interesting option to set in their structure a wide range of by-products and residues materials and composites, sometimes serving only as a reservoir for the inert residue, and other, having a positive effect on the ceramic material or process. In the present work, the incorporation of this waste in raw clays has been studied. The raw materials: clay and glycerine was characterized by XRD, XRF, CNHS analysis, higher heating value and thermal analysis and after, using conventional moulding and sintering processing methods to prepare clay–glycerine composites, the influence of the amount of waste added to clay has been evaluated. To do this, percentages of glycerine were added to the clay from 5% to 20% and evaluated by a series of technological properties such as compressive strength, absorption and suction of water, bulk density, the study of porosity generated by adsorption–desorption isotherms of N2, thermal conductivity and finally by the compressive strength after freezing-thaw. it was considered as the maximum permissible rate of addition of glycerol 10–15% in weight, because higher additions have a strong effect on the properties of the obtained materials such as compression strength and bulk density which descending dramatically due to the large amount of porosity generated as reflected by high values of absorption and suction experiments. It was concluded that adding 5% glycerol to the ceramic paste generated plasticity in clay to achieve be moulded, with values of compressive strength of 84MPa while gets to reduce the density apparent by almost 5%.


      PubDate: 2016-01-18T10:50:22Z
       
  • Synthesis of methotrexatum intercalated zinc–aluminum-layered double
           hydroxides and the corresponding cell studies
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Wei-Yuan Wang, Hong Liu, Shu-Ping Li, Xiao-Dong Li
      To study the influence of morphology on release property, drug efficacy and other properties, a series of methotrexate intercalated zinc–aluminum-layered double hydroxides (MTX/ZnAl-LDHs) hybrids were synthesized through the traditional coprecipitation method, by the way of changing pH value and using different solvents. X-ray diffraction (XRD) patterns and fourier transform infrared spectroscopy (FTIR) investigations manifested the successful intercalation of MTX anions for all hybrids. TEM photographs indicated that low pH value was in favor of improving the morphologies, and addition of polyethylene glycol (PEG) in solvent would lead to the formation of regular particles. Lastly, in-vitro release and the bioassay tests showed that regular particles had much longer release duration and were more efficient in the suppression of the tumor cells.
      Graphical abstract image

      PubDate: 2016-01-18T10:50:22Z
       
  • Effect of heating temperature on the sequestration of Cr3+ cations on
           montmorillonite
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Runhong Zhu, Runliang Zhu, Fei Ge, Yin Xu, Jing Liu, Jianxi Zhu, Hongping He
      Montmorillonite (Mt) has been considered as low-cost and high efficient adsorbent for heavy metal cations, and thermal treatment can be a facile approach for sequestration of the adsorbed heavy metal cations on Mt. This work was intended to study the effects of heating temperature on the sequestration efficiency of Cr on Mt. Toward this aim, thermal treatment of the spent Mt after adsorption of Cr3+ was carried out at different temperatures, both in air and in nitrogen atmosphere. The heated samples were characterized by X-ray diffraction (XRD) and X-ray photon spectroscopy (XPS), and the sequestration efficiency of Cr on Mt was further examined by ammonium acetate and HCl washing. The results indicated that heating temperature can significantly affect the sequestration efficiency. For the samples heated in air atmosphere, Cr can be effectively sequestered at a relatively low temperature (e.g., 200°C), as Cr3+ ions can migrate into the Mt layers because of its small ion radius. As the temperature increased to 300°C, however, the oxidation of Cr3+ into Cr6+ would promote the desorption of Cr. As the temperature further increased to above 400°C, the collapse of Mt layers in combination with the formation of Cr2O3 then can help in sequestering Cr. Only after heating at 700°C, efficient sequestration of Cr on Mt could be achieved by the significant damage of the layered structure. When heated at 900°C, the desorption of Cr was un-detectable due to the formed amorphous silica structure. On the other hand, as Cr3+ could not be oxidized in nitrogen atmosphere, the sequestration efficiency continually increased with rising temperature. The results of this work showed that heating temperature should be cautiously chosen for the effective sequestration of oxidizable heavy metal cations on Mt.
      Graphical abstract image

      PubDate: 2016-01-18T10:50:22Z
       
  • Copper-complexed clay/poly-acrylic acid composites: Extremely efficient
           adsorbents of ammonia gas
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Erming Liu, Binoy Sarkar, Liang Wang, Ravi Naidu
      Work reported in this manuscript takes into consideration the possible use of NH3 gas by terrorists and the potential for an effective and rapid removal of such toxic substance from air using a modified clay material. In this study, a series of clay/polymer composites were synthesised for ammonia gas (NH3) adsorption. The adsorbents were prepared by polymerisation of acrylic acid with N,N′-methylenebisacrylamide (MBA) as cross-linker in the presence of a large amount of highly dispersed clay nanoparticles, followed by interaction with copper ions (Cu2+). Two kinds of clays were used. One was an acid-treated bentonite that had a specific surface area (SSA) of 395m2/g and the other was natural palygorskite with a SSA of 87m2/g. The materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption and Fourier transform infrared spectroscopy (FTIR). The materials' ability to remove NH3 was investigated using NH3 breakthrough dynamic test while the strength of NH3 retention was characterised by Thermogravimetric Analysis (TGA) coupled with FTIR. The results indicate that clay/poly-acrylic acid composites are highly efficient adsorbents of NH3 after binding with Cu2+. Trapping NH3 on such adsorbents can lead to colour change and this makes it possible to predict the lifetime of the adsorption bed visually. In addition, the result of NH3 release from the material following adsorption showed that majority of the adsorbed NH3 desorbed at temperature above 180°C. The clay/polymer composites can potentially be used in air filters. They may provide an effective and cheap way for removing NH3 from contaminated air.
      Graphical abstract image

      PubDate: 2016-01-18T10:50:22Z
       
  • Evaluation of the mixed oxides produced from hydrotalcite-like compound's
           thermal treatment in arsenic uptake
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Manuel Sánchez-Cantú, José Alberto Galicia-Aguilar, Deisy Santamaría-Juárez, Luis E. Hernández-Moreno
      In this work, hydrotalcite-like compounds (prepared by a simple and environmentally-friendly method) were evaluated as adsorbent's precursors for arsenic (V) removal in water. Materials were characterized by X-ray powder diffraction, N2 adsorption-desorption at −196°C and thermogravimetric analyses. It was revealed by the XRD characterization that the calcined samples exhibited the characteristic reflections of the MgO and spinel crystalline phases. The thermal treatment increase gave rise to a specific surface area increment achieving a maximum at 550°C. The effect of adsorbents' activation, reaction time, adsorbent amount, pH and initial arsenic concentrations were evaluated. Results showed that removal efficiency of arsenate increased with the increment of the annealing temperature reaching a maximum removal with the calcined sample at 550°C. The adsorption isotherms can be well described by Freundlich model and adsorption kinetics of arsenate was adjusted by the pseudo-second-order, indicating that chemisorption was the limit step. It was demonstrated that removal capacity depends on the initial arsenic concentration where more than 98% removal was achieved with initial concentrations below 250μg/L.
      Graphical abstract image

      PubDate: 2016-01-18T10:50:22Z
       
  • Experiments and modeling of non-linear viscoelastic responses in natural
           rubber and chlorobutyl rubber nanocomposites
    • Abstract: Publication date: April 2016
      Source:Applied Clay Science, Volume 123
      Author(s): Ajesh K. Zachariah, Arup Kumar Chandra, P.K. Mohammed, Jyotishkumar Parameswaranpillai, Sabu Thomas
      The filler–filler and rubber–filler interactions in polyisoprene (natural rubber — NR) and chlorine substituted poly isoprene–isobutyl rubber (chlorobutyl rubber — CIIR) were monitored by non-linear viscoelastic measurements (Payne effect). The experimental results have been modeled using the famous Maier–Göritz equation and by the tradition approach of Kraus theory. It was observed that the filler–filler network formation in NR/organoclay nanocomposites was very strong while the interactions in CIIR/organoclay nanocomposites were very poor. The network formation and dispersion of nanoclay platelets were observed using AFM and TEM techniques. Using the DSC technique, the effects of filler–filler and filler–polymer interactions on glass transition temperature (T g ), confinement of polymer chains (χ i ) and the variations in heat capacity (ΔCp) were analyzed. These analyses revealed that the nanofiller loading in rubber matrix developed a rigid amorphous region due to the confinement of polymer chains. The T g of the natural rubber nanocomposites was increased and then decreased as the filler loading increased from 0 to 10phr. The mechanical percolation behavior of rubber nanocomposites were estimated using the Huber–Vilgis approach by calculating the excess modulus. The application of this approach pointed out to a cluster–cluster aggregation model (CCA), where space filling clusters were formed. The diffusion of liquids through the nanocomposites was carefully evaluated for explaining the nanofiller interaction with the two rubber matrices. Finally, the Kraus, Lorentz–Parks and Cunneen–Russell models were applied to quantify the degree of reinforcing action of the fillers in both elastomer matrices.


      PubDate: 2016-01-14T11:13:48Z
       
  • Swelling and geo-environmental properties of bentonite treated with
           recycled bassanite
    • Abstract: Publication date: Available online 4 January 2016
      Source:Applied Clay Science
      Author(s): Aly Ahmed, M. Hesham El Naggar
      This paper describes an investigation of the use of recycled bassanite, which is derived from plasterboard waste, as an additive material to mitigate the swelling potential of bentonite considering its environmental impact. Recycled bassanite was mixed with furnace cement and with lime at 2:1 ratios, and then the admixture was mixed with the tested bentonite at four different content ratios. The effects of adding bassanite admixture on the swelling properties, mechanical properties, environmental properties, microstructure, and mineralogical composition of the tested bentonite were investigated. The test results indicated that recycled bassanite has the potential for use as a stabiliser to mitigate swelling in expansive clay. Increasing the admixture content reduced the potential for swelling, the plasticity, the montmorillonite intensity, the percentage of sodium ions and the cation exchange capacity of the bentonite. The compressive strength, unit weight and percentage of calcium ions were increased for all admixture contents used. The different bassanite–cement/lime admixture contents resulted in approximately the same reduction in the swelling potential of the tested bentonite. The bassanite–cement/lime admixture had much more pronounced effects on the swelling and mechanical properties of the bentonite than bassanite alone. The bentonite treated with 6% admixture content exhibited the greatest reduction in swelling potential; hence, this admixture content ratio is considered optimal for stabilising bentonite and mitigating its swelling. The measurements of hydrogen sulphide gas, fluorine solubility and pH of the treated bentonite were found to be within the acceptable limits, indicating that bassanite–cement/lime admixtures used did not have any negative environmental effects. However, bassanite is not recommended for use alone as an amendment for expansive clay because it releases fluorine at amounts that may exceed the allowable limit in some cases.


      PubDate: 2016-01-06T13:33:44Z
       
  • Determination and reduction of Fe(III) incorporated into Mg–Fe
           layered double hydroxide structures
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Kazuya Morimoto, Kenji Tamura, Hirohisa Yamada, Tsutomu Sato, Masaya Suzuki
      The syntheses of Mg–Fe(III) layered double hydroxides with different compositions at varied temperature through a co-precipitation method were attempted. The well-crystallized and white colored layered double hydroxides with chloride anions were obtained from the samples adjusted to the composition of Mg/Fe=4 and aged at higher temperature. The Fe species in the white colored Mg–Fe layered double hydroxides were evaluated as all Fe(III) species by a Mössbauer measurement. The synthesized Mg–Fe(III) layered double hydroxide was treated with a sugar alcohol at temperature above its melting point in order to reduce Fe(III) incorporated into the hydroxide layers. The Mg–Fe layered double hydroxide resulting from a sugar alcohol treatment showed the reduction property in an aqueous solution.
      Graphical abstract image

      PubDate: 2016-01-02T13:11:09Z
       
  • Carboxymethyl cellulose capsulated layered double hydroxides/drug
           nanohybrids for Cephalexin oral delivery
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Soroush Barkhordari, Mehdi Yadollahi
      In this paper, pH sensitive carboxymethyl cellulose (CMC) beads were proposed as a protective capsule for layered double hydroxides-drug (LDH-Drug) nanohybrids in gastrointestinal tract conditions. Cephalexin (CPX), as a model drug, was intercalated between LDH layers through co-precipitation method. The resulting nanohybrid (LDH-CPX) was used to prepare nanocomposite hydrogel beads by association with carboxymethyl cellulose. The synthesized products were characterized using FTIR, XRD and SEM analysis. In vitro drug delivery tests were carried out in conditions simulating the gastrointestinal tract to prove the effectiveness of these novel nanocomposite beads as a controlled drug delivery system. The drug release tests revealed a better protection against stomach pH and a controlled liberation in the intestinal tract conditions for CMC encapsulated LDH-CPX nanohybrids.


      PubDate: 2016-01-02T13:11:09Z
       
  • Accelerated weathering performance of polylactide and its montmorillonite
           nanocomposite
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Cevdet Kaynak, Burcu Sarı
      The goal of this study was to compare accelerated weathering performance of neat polylactide (PLA) and its 1 mass% organically modified montmorillonite (Mt) nanocomposite; compounded and shaped by twin-screw extrusion melt mixing and injection molding, respectively. Accelerated weathering test system applied consecutive steps of UV irradiation and humidity in accordance with ISO 4892-3 standards for 200h. Chain scission reactions such as photolysis, photooxidation and hydrolysis resulted in significant decrease in the molecular weight of PLA; consequently reductions in the mechanical properties of modulus, strength, ductility and toughness of the specimens occurred. However, after comparing mechanical properties of PLA and Mt–PLA before and after 200h accelerated weathering, use of PLA with only 1 mass% Mt was extremely beneficial not only for “indoor applications” but also for “outdoor applications”. This was due to the effective nanoscale reinforcing and barrier actions of intercalated/exfoliated Mt layers. For example, flexural strength was 6% beneficial before weathering, but after weathering the benefit was 88%.


      PubDate: 2016-01-02T13:11:09Z
       
  • Three-way catalytic performances of Pd loaded halloysite-Ce0.5Zr0.5O2
           hybrid materials
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Zheng Zhou, Jing Ouyang, Huaming Yang, Aidong Tang
      Halloysite (Hal) hybridized Ce0.5Zr0.5O2 solid solutions (CZ and CZHal) were prepared using the evaporation induced self-assembly (EISA) method. X-ray diffraction (XRD), scanning electronic spectroscopy (SEM), transmission electronic spectroscopy (TEM), energy dispersion spectrum (EDS) and elements mapping techniques were used to characterize the thermal, morphological and structural status of the obtained samples. Three way catalytic (TWC) performances of the samples were tested after being loaded onto dichroite ceramics. Pd was used as the catalysis centers by impregnation method (Pd/CZ and Pd/CZHal). The results revealed that, Hal hybridized with Ce0.5Zr0.5O2 very well, according to the TEM figures. The hybridizing of CZ with halloysite enhanced the TWC performances in forms of decreased light-off temperature and increased catalytic efficiency to CO, C3H8 and NOx. Even, the TWC performances of CZHal displayed higher efficiency than the reference commercial sample at working temperature (450°C). After catalysis tests, halloysite in the CZHal sample remained their tubular morphology. The obtained CZ and CZHal sustained their phase stability at thermal treatment up to 1100°C, continual calcinations will cause phase segregation and solid reaction to yield ZrSiO4 in the contacting area between the halloysite and CZ matters. The mineral probably acted as the channels for gases go into and out of the inner part of the CZ matrix, which will facilitate the redox reactions in the inner areas, and finally enhanced the TWC performances.


      PubDate: 2015-12-29T09:56:07Z
       
  • Modelling reactions between alkaline fluids and fractured rock: The
           Maqarin natural analogue
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Claire Watson, James Wilson, David Savage, Steven Benbow, Simon Norris
      Cement and concrete will be used as fracture grouts, shotcretes, tunnel seals, and as matrices for waste encapsulation in many radioactive waste geological disposal facility concepts. Alteration of the disposal facility host rock and/or swelling clay in waste package buffers and tunnel backfills by alkaline solutions leached from cement/concrete may have implications for system performance. The Maqarin natural analogue has received considerable attention over the last twenty-five years as it represents some of the conditions of interest for a cementitious radioactive waste disposal system; as naturally-occurring high pH waters have been transported through fractures passing through clayey marls, causing mineralogical alteration in the wall-rock and sealing of the fractures as minerals precipitate. In this study, reactive-transport simulations were constructed of the mineral–fluid interactions at the Maqarin site with a particular emphasis on mineral formation in fractures, including armouring of surfaces, and how this can be simulated in geological environments that may host a radioactive waste disposal facility. The evolution of fractures is important as they may act as pathways for water and contaminant transport. In a ‘base case’ reactive-transport model, a pseudo 2-D approach was used to simulate flow along a fracture and diffusion of solutes into the rock matrix. The model predicts that ettringite, thaumasite and C–S–H (jennite and tobermorite), dominate the fracture-filling minerals, whereas alteration products forming at the expense of the primary silicates in the rock matrix include scolecite (Ca–zeolite), ettringite, C–S–H and small amounts of sepiolite, in broad agreement with observations of the rock present at Maqarin. A more realistic conceptual model of mineral precipitation in the fracture has also been developed, whereby minerals precipitated on the fracture walls in an ‘armoured’ layer rather than uniformly throughout the fracture cells, thus impeding diffusion into the rock matrix. In this model only jennite and calcite precipitated in the fracture, eventually filling it. The modelling carried out here confirms that, where alkaline fluids derived from cement degradation come into contact with rocks saturated with neutral pH, bicarbonate-rich groundwaters, sealing of fractures may occur. However, fracture sealing is complex and is dependent upon a range of factors such as: rock composition (mineralogy, grain size, porosity); groundwater composition and flow rates; and mineral reaction kinetics inter alia. Although the precise timing of fracture sealing at Maqarin is unknown, the consideration of a number of uncertainties in reactive-transport modelling conducted here would suggest that sealing is moderately rapid (of the order of hundreds of years). The geochemical modelling approach used here could be applied to potential fractured host rocks for radioactive waste disposal facilities, in order to elucidate the evolution of water flow and contaminant transport pathways.


      PubDate: 2015-12-25T09:29:11Z
       
  • Nanocomposite based on erucic acid modified montmorillonite/sulfited
           rapeseed oil: Preparation and application in leather
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Bin Lyu, Jianjing Gao, Jianzhong Ma, Dangge Gao, Hongdi Wang, Xuewu Han
      Montmorillonite was modified by cis-13-docosenoic acid also known as erucic acid via intercalation reaction. The as-prepared erucic acid modified montmorillonite (EA-Mt), rapeseed oil, ethylene diamine, acrylic, and sodium bisulfite were employed to prepare the EA-Mt/modified rapeseed oil (EA-Mt/MRO) nanocomposite. X-ray diffraction (XRD) indicated that erucic acid successfully intercalated into the interlayer space of montmorillonite (Mt) with the basal spacing of Mt increasing from 1.24nm to 1.48nm. The thermal stability of EA-Mt/MRO nanocomposite was effectively improved after adding the EA-Mt by thermogravimetric analysis (TGA). Then, EA-Mt/MRO nanocomposite as fatliquoring agent was applied in the leather fatliquoring process of goatskin garment. Erucic acid intercalated Mt was dispersed on the collagen fibers of the leather as confirmed by SEM and EDX. The flame retardancy of the leather treated with EA-Mt/MRO nanocomposite was found to be improved in a significant way. Compared with that of leather treated with modified rapeseed oil (MRO), the highest LOI value of leather treated with EA-Mt/MRO reached 27.9% from 23.7% with 8% EA-Mt. The leather had superior softness, physical and mechanical properties.


      PubDate: 2015-12-25T09:29:11Z
       
  • Novel strategy for palygorskite/poly(acrylic acid) nanocomposite hydrogels
           from bi-functionalized palygorskite nanorods as easily separable adsorbent
           for cationic basic dye
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Longxiang Zhu, Jinshan Guo, Peng Liu, Shibin Zhao
      A novel strategy was developed for the preparation of a palygorskite/poly(acrylic acid) nanocomposite (Pal/PAA) hydrogel with a 3-D network structure, by the surface-initiated redox radical solution polymerization of acrylic acid (AA) with the bi-functionalized palygorskite (BF-Pal) nanorods, in which the amino groups acted as the initiating groups, and the CC groups acted as the crosslinking groups. The effect of the synthesis conditions on the component in the Pal/PAA nanocomposite hydrogels were investigated with TGA analysis. The designed Pal/PAA hydrogel exhibited a remarkably high adsorption capacity for methylene blue (MB) of 833.9mg/g.
      Graphical abstract image

      PubDate: 2015-12-25T09:29:11Z
       
  • Impact of organic pollutants on the macro and microstructure responses of
           Na-bentonite
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): A.R. Goodarzi, S. Najafi Fateh, H. Shekary
      Bentonite (Bent) is a favorable buffer material for waste containment barriers, although its properties may be affected by the pore fluid chemistry. Hence, this study investigates the role of different organic pollutants including methanol, acetone, acetic acid, and citric acid on the macro and microstructure responses of Na+-Bent. The chemicals at various concentrations (0 to 80% by the volume of distilled water) were separately added to the soil samples which were then subjected to a set of tests. The results indicate that an increase in the concentration of organic permeants by decreasing the dielectric constant (ε) reduces the plasticity index, compressibility and swelling potential of soil; whereas, the permeability increases. Such changes are ascribed to a tighter packing of the clay particles, as clearly confirmed by the SEM micrographs and XRD patterns. The decrease in the absolute value of soil zeta potential also supports the development of coagulated structure in the artificially contaminated samples upon reducing the ε of solution. However, the results reveal that the sensitivity of soil properties to the variations in the ε value is pronounced at the intermediate stages of concentration (i.e. the organic fluid/water ratio<60%) when the ε is higher than 50. In addition, at relatively low concentration, the acidic permeants dramatically alter the soil fabric due to having lower pH, causing remarkable effects on the hydro-mechanical parameters as compared to the other chemicals. Overall, the organic pollutants, depending on their type and concentration, exert negative impact on the barrier performance of Na+-Bent which are not precisely comparable only with reference to the changes in the dielectric constant of pore fluid, and thereby may not be completely explained by the diffuse double layer (DDL) theory.


      PubDate: 2015-12-25T09:29:11Z
       
  • Applied properties of oil-based drilling fluids with montmorillonites
           modified by cationic and anionic surfactants
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Daojin Zhou, Zepeng Zhang, Jialun Tang, Fanwen Wang, Libing Liao
      Montmorillonites modified by cationic surfactants have been used in oil-based drilling fluids for a period of time, while few studies focused on the use of montmorillonites modified by both cationic and anionic surfactants in oil-based drilling fluids. Compared with cationic surfactants, anionic surfactants have an advantage in thermal stability. Here, two parts of work were described. First, montmorillonites were modified by cationic and anionic surfactants through mechanochemistry. The structure and properties of organomontmorillonites were studied by X-ray diffraction, thermal analysis, contact angles and dispersion. Second, the applet properties including thixotropy, viscosity properties, gel properties and filtration loss resistance of oil-based drilling fluids with organomontmorillonites as additives were further studied at both room temperature (25°C) and higher temperatures (200–220°C). Characterizations indicated that cationic and anionic surfactants had intercalated into the interlayer spaces of montmorillonites, and the cationic–anionic organomontmorillonites had high surface polarity, better thermal stability and dispersion in high polar solvent than cationic organomontmorillonites. The properties of oil-based drilling fluids under both room and high temperatures showed that cationic and anionic organomontmorillonites performed better thixotropy, and had better rheological properties and less filtration loss than cationic organomontmorillonites in different oil–water ratio oil-based drilling fluids. The novel cationic and anionic organomontmorillonites have the potential to be widely applied in oil-based drilling fluids.


      PubDate: 2015-12-21T09:18:26Z
       
  • Dexketoprofen and aceclofenac release from layered double hydroxide and
           SBA-15 ordered mesoporous material
    • Abstract: Publication date: March 2016
      Source:Applied Clay Science, Volumes 121–122
      Author(s): Soledad San Román, Gonzalo Nuno Almeida, Margarita del Arco, Cristina Martín
      Two non-steroidal anti-inflammatory drugs, dexketoprofen (Dx) and aceclofenac (Ac), were incorporated in two different matrixes, layered double hydroxide and ordered mesoporous silica, SBA-15. The matrixes and the samples were characterized by different techniques, PXRD, SEM, TEM, FT-IR, N2 adsorption at −196°C and the drug release speed was also measured. The total amount of incorporated drug to the different matrixes was higher in the LDH than in mesoporous silica. The release studies showed a higher drug release speed from the layered double hydroxide than from the ordered mesoporous silica, but even so slower than the one found for the pure drugs, what shows that these solids can be used as drug controlled release matrixes.
      Graphical abstract image

      PubDate: 2015-12-21T09:18:26Z
       
 
 
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