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  Subjects -> EARTH SCIENCES (Total: 589 journals)
    - EARTH SCIENCES (436 journals)
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EARTH SCIENCES (436 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Hybrid Journal   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 8)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 2)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances In Physics     Hybrid Journal   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 1)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 3)
AMBIO     Hybrid Journal   (Followers: 13)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 2)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 1)
Annals of Geophysics     Full-text available via subscription   (Followers: 9)
Annals of GIS     Hybrid Journal   (Followers: 15)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene Review     Hybrid Journal   (Followers: 1)
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 7)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 9)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 21)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 14)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 17)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 3)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 4)
Atmospheric and Climate Sciences     Open Access   (Followers: 14)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 8)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 9)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of Marine Science     Full-text available via subscription   (Followers: 13)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 16)
Bulletin of Volcanology     Hybrid Journal   (Followers: 11)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 9)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 10)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 5)
Contemporary Trends in Geoscience     Open Access  
Continental Journal of Earth Sciences     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 7)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 18)
Cretaceous Research     Hybrid Journal   (Followers: 4)
Cybergeo : European Journal of Geography     Open Access   (Followers: 4)
Developments in Geotectonics     Full-text available via subscription   (Followers: 2)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 159)
Earth Interactions     Full-text available via subscription   (Followers: 8)
Earth Science Research     Open Access   (Followers: 6)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 1)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 11)
Earth System Dynamics     Open Access   (Followers: 4)
Earth System Dynamics Discussions     Open Access   (Followers: 3)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 1)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Spectra     Full-text available via subscription   (Followers: 11)
Ecohydrology     Hybrid Journal   (Followers: 11)
Ecological Questions     Open Access   (Followers: 6)
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  

        1 2 3 4 5 | Last

Journal Cover Applied Clay Science
   Journal TOC RSS feeds Export to Zotero [4 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0169-1317
     Published by Elsevier Homepage  [2563 journals]   [SJR: 0.999]   [H-I: 63]
  • Quantification and comparison of the reaction properties of FEBEX and
           MX-80 clays with saponite: Europium immobilisers under subcritical
           conditions
    • Abstract: Publication date: November 2014
      Source:Applied Clay Science, Volume 101
      Author(s): María Villa-Alfageme , Santiago Hurtado , Miguel A. Castro , Said El Mrabet , M. Mar Orta , M. Carolina Pazos , María D. Alba
      The evaluation of the retention mechanisms in FEBEX and MX-80 bentonites, selected as reference materials to construct engineered barriers, carries major implications in the safe storage of immobilisation capacity through a recently discovered chemical retention mechanism and the structural analysis of the reaction products. Hydrothermal treatments were accomplished with immobilisation capacity through a recently discovered chemical retention mechanism and the structural analysis of the reaction products. Hydrothermal treatments were accomplished with Eu(NO3)3 (151Eu and 153Eu, with 52.2% 153Eu) and spiked with radioactive 152Eu for the quantification of the reactions. Results were compared with saponite as the reference smectite. The strong dependence of the reaction parameters with temperature and time was quantified and the reaction velocity was evaluated. The velocity follows these trends: 240days are needed for the total retention of europium for temperatures over 200°C; below 150°C, significantly longer reaction times, on the order of three years, are required to complete the reaction. Clays do not influence velocity rates, but the retention capacity of bentonites remains lower than for saponite. At 300°C, the milliequivalents retained by the three clays are consistently over CEC. The structural analyses reveal not only adsorption of europium but also the presence of Eu(OH)3 precipitation and Eu2SiO3 confirming the existence of a chemical reaction.
      Graphical abstract image

      PubDate: 2014-09-18T03:20:16Z
       
  • Adsorption of chloroanilines from aqueous solutions on the modified
           halloysite
    • Abstract: Publication date: Available online 16 September 2014
      Source:Applied Clay Science
      Author(s): Beata Szczepanik , Piotr Słomkiewicz , Magdalena Garnuszek , Kamil Czech
      Batch removal of 3-, 4-chloroaniline and 3,4-dichloroaniline from an aqueous solution using unmodified and acid-activated halloysite was investigated in this study. The influence of acid concentration used for digesting the halloysite, contact time as well as the concentration of chloroaniline solutions was reported. The results show that the adsorption of 4-chloroaniline was greatly enhanced by using a sulfuric acid-treated halloysite, as compared to the unmodified halloysite. A comparison of kinetic models applied to the adsorption of chloroanilines on an acid-treated halloysite was evaluated for pseudo first-order, pseudo second-order, and intraparticle diffusion kinetic models. The chemisorption pseudo-second order kinetic model was found to correlate the experimental data well. The adsorption mechanism of acid-treated halloysite -chloroaniline system complied well with the Langmuir model in the case of 4-chloroaniline and 3,4-dichloroaniline and with the Freundlich model for 3-chloroaniline.


      PubDate: 2014-09-18T03:20:16Z
       
  • Stabilization of alkali earth metal cations in Na-4-mica
    • Abstract: Publication date: Available online 17 September 2014
      Source:Applied Clay Science
      Author(s): Jun Hyung Kim , Hong-Jin Kim , Man Park
      Na-4-mica, a highly charged swelling mica, has suffered from insufficient understanding of some fundamental features such as partial layer collapse and rearrangement of interlayered cations and layers during exchange reaction. This study focuses on elucidating the changes in chemical environments of divalent cations and in layered structure during the exchange reaction with divalent cations. Cation exchange reaction with a series of alkali earth cations led to significant changes in both XRD pattern and IR spectra. The extent of cation exchange reaction depended highly and systematically on cation size and hydration energy. Exchange reaction with Mg2+ and Ca2+ led to highly hydrated phases whereas that with Sr2+ to anhydrous phase and that with Ba2+ to remarkable degradation of layered structure. The hydrated divalent cations could be quickly stabilized in interlayer space in spite of localized incompatibility of both lattice and charge through formation of interstratified phases having various ratios of Na+/M2+ and Na+/H3O+. Therefore, divalent cations could be stably accommodated either in hydrated or anhydrous state within the cavities, preferably around crystal edges to obstruct their further uptake.


      PubDate: 2014-09-18T03:20:16Z
       
  • High morphological stability and structural transition of halloysite
           (Hunan, China) in heat treatment
    • Abstract: Publication date: November 2014
      Source:Applied Clay Science, Volume 101
      Author(s): Jing Ouyang , Zheng Zhou , Yi Zhang , Huaming Yang
      Halloysite is one of the nanoscale tubular minerals in nature. This article reports the mineralogical character, dispersion treatment, structural, and morphological stabilities of a 10Å-type halloysite mineral from Hunan, China. X-ray diffraction (XRD), transmission electron microscopy (TEM), particle-size distribution and N2 adsorption–desorption isotherms were adopted to characterize the raw and calcined minerals. Ammonium lauryl sulfate was used as the surfactant to obtain mono-dispersed halloysite nanotubes. The raw mineral is a kind of tubular nanotube with a hollow interior channel, the specific surface area is 56.7m2/g. Alunitization occurred in the impure mineral. Thermal treatment to the mineral induced shrinkage of the c-axis and yielded a 7Å-type structure. The tube wall was transformed to an amorphous structure in the dehydration process at 450°C. Phase segregation occurred to yield amorphous SiO2 and γ-Al2O3 at around 1000°C. The tubular morphology can be maintained even after it is calcined at 1100°C for 6h, and the specific surface area is enlarged slightly to 65.7m2/g. While after being calcined to 1300°C, the mineral will generate mullite and silica, accompanied with collapse of the tubular walls. A schematic diagram is proposed to illustrate the structural transformation procedure. The results provide assurance to the use of halloysite in high temperature circumstances, such as three-way catalysts.


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




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



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


      PubDate: 2014-09-14T02:52:55Z
       
  • Approaches to surface complexation modeling of Ni(II) on Callovo-Oxfordian
           clayrock
    • Abstract: Publication date: Available online 10 September 2014
      Source:Applied Clay Science
      Author(s): Z. Chen , G. Montavon , Z. Guo , X. Wang , S. Razafindratsima , J.C. Robinet , C. Landesman
      Callovo-Oxfordian formation (COX) is as potential host formation for emplacement of long-term nuclear waste repositories in France. The objective of this work is to assess whether a simplified “bottom-up” approach may explain the retention of Ni(II) by the COX considering two levels of ‘upscaling’: (i) from clay surfaces to rock clay fraction and (ii) from clay fraction to whole rock samples. To this end, Ni(II) adsorption was investigated by batch equilibrium, XPS, and EXAFS techniques on a representative sample extracted at the location where the storage is supposed to be built (clay content of about 50%) and on the corresponding carbonate-free <2μm fractions. The results showed that a simplified “bottom-up” approach based on published models available for illite and montmorillonite cannot explain Ni(II) adsorption on the <2μm fraction when the retention is controlled only by surface complexation on the reactive clay edge sites. An operational model based on the generalized composite modeling approach was used instead. The developed model considers an interaction between two Ni(II) species with one type of clay edge sites. The model developed for the clay fraction gives a satisfactory estimation of Ni(II) adsorption data for the representative clayrock sample. Complementary experiments were performed by X-ray photoelectron (XPS) and X-ray absorption (EXAFS) spectroscopies for both clay fraction and raw COX sample at high Ni(II) loadings. Spectroscopic data were characterized by similar fitting parameters considering formation of Ni phyllosilicate. This indicates that the clay fraction governs the retention of Ni(II), as it was concluded from the batch experiments. Complementary adsorption experiments preformed with COX samples having clay contents representative of the variability occurring at the formation scale (i.e. 1.5–47% in weight) show that one cannot neglect the retention properties of the non-clay phases, mainly dominated by calcite, when the clay content becomes the minority. Retention values in the range of 60–300L/kg can finally be given for describing adsorption properties of trace concentrations of Ni(II) for the clay contents representative of the majority of the Callovo-Oxfordian formation.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Catalytic cracking of rosin over acid-activated montmorillonite catalysts
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Dong Shen Tong , You Miao Zheng , Wei Hua Yu , Lin Mei Wu , Chun Hui Zhou
      A series of acid-activated montmorillonite were prepared and evaluated as catalysts for the catalytic cracking of rosin. All the samples were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), nitrogen adsorption–desorption, temperature-programmed desorption of NH3 (NH3-TPD), scanning electron microscopy (SEM) and thermal analysis (TGA-DSC). Their catalytic performances were evaluated by the cracking of rosin in a batch reactor. The experimental results showed that acid-activated montmorillonite catalysts were active in the catalytic cracking of rosin. The acidic value of the non-essential oil products significantly declined from 163.05mg/g to 0.43mg/g and the main component in the non-essential oil and essential oil was the C13 compound. The acid treatment of montmorillonite improved the specific surface area and the amount of surface SiOH2 + groups. The moderate (Brönsted) acidity on the acid-activated montmorillonite might be responsible for the cracking of rosin.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • Insight into the nature of Au-Au2O3 functionalized palygorskite
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Xi He , Liangjie Fu , Huaming Yang
      The Au/palygorskite (Au/Pal) composite was prepared via supporting gold species on the surface of palygorskite. Results indicated that the dehydration of palygorskite showed obvious effect on the Au0/Au3+ molar ratio, and the generated hydroxide radicals (−OH) played a special role in the formation of Au-Au2O3 coexistence system. Au2O3 nanoparticles were formed on the hydrated (010) palygroskite surface, while Au nanoparticles were mainly on the surface of unhydrated (100) palygroskite. The decomposition of Au2O3 to metallic Au was promoted by increasing calcination temperature. However, this process would be hindered by –OH radicals produced at high temperature. The Au0/Au3+ molar ratio changed nonlinearly with the calcination temperature. The dehydration was beneficial to the formation of the chemical bonds between Au species and palygroskite. Au-Au2O3 coexistence expanded the application of gold supported composites. Atomic-level interfaces between Au species and palygorskite surface were also investigated. Realizing Au-Au2O3 coexistence by dehydration of palygorskite could provide a novel method for the synthesis of advanced mineral-based composites.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • From used montmorillonite to carbon monolayer–montmorillonite
           nanocomposites
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Qingze Chen , Runliang Zhu , Weixian Deng , Ying Xu , Jianxi Zhu , Qi Tao , Hongping He
      Summary background Montmorillonite (Mt) as a low-cost and high-efficient adsorbent for cationic dyes has a promising application in dye wastewater treatment. However, proper disposal of the used Mt is critical to its application. Objective In this work, the used Mt after the adsorption of crystal violet (CV) was calcined under the protection of N2, with the purpose of transforming the used Mt into carbon monolayer–Mt nanocomposites. Methods Mt, the used Mt after CV adsorption, and the calcined Mt have been characterized by XRD, FTIR, Raman spectra, thermal analysis and elemental analysis. Results X-ray diffraction results showed that calcination led to the decrease of basal spacing of the used Mt from 2.06nm to 1.34nm. As such, the interlayer spacing of the calcined Mt is 0.38nm, close to the thickness of a single graphene layer (0.34nm), suggesting the formation of carbon monolayer within the interlayer space of Mt. FTIR characterization results showed that the infrared absorption bands of CV, which were clearly displayed on the infrared spectra of the used Mt, disappeared after the calcination. On the other hand, Raman spectra clearly showed the presence of D-band and G-band on the calcined Mt. These spectroscopy characterization results further proved the formation of carbon monolayer within the interlayer spaces of Mt. Elemental analysis results showed that about 40% carbon and 22% nitrogen from CV were transformed into the carbon monolayer at 600 °C calcination, and the transformation ratios decreased to 37% and 12% respectively at 800 °C calcination. Therefore, the obtained carbon monolayer was an N-doped graphene-like material. Conclusions As such, this work provided an easy way to transform the used Mt after the adsorption of cationic dyes into carbon monolayer–Mt nanocomposites.
      Graphical abstract image

      PubDate: 2014-09-14T02:52:55Z
       
  • X-ray diffraction and rheology cross-study of polymer chain penetrating
           surfactant tethered layered double hydroxide resulting into intermixed
           structure with polypropylene, poly(butylene)succinate and
           poly(dimethyl)siloxane
    • Abstract: Publication date: October 2014
      Source:Applied Clay Science, Volume 100
      Author(s): Fabrice Leroux , Antoine Dalod , Mohammed Hennous , Laura Sisti , Grazia Totaro , Annamaria Celli , Christian Coehlo , Vincent Verney
      A series of layered double hydroxides interleaved with surfactant using saturated alkyl chain carboxylate anions CH3(CH2)mCOOH, even number m between 6 (C8) and 16 (C18), obtained by coprecipitation method was dispersed by melt polymer extrusion into polypropylene (PP), poly(butylene)succinate (PBS) and polydimethylsiloxane (PDMS). The hybrid LDH materials were investigated by means of X-ray diffraction and Fourier transform IR spectroscopy resulting in the presence of contracted basal spacing over the entire variation of m. Dispersion into polymer was found to yield intermixed polymer structures regardless of either the polymer or of the alkyl chain length. PP polymer chain was able to diffuse into the interlayer space, long alkyl chains (m≥14) were found to reinforce while shorter chains (m≤12) induced a plasticizing effect. For PBS and PDMS, a chain-extender-type behavior was observed. The relative change in viscosity within the frequency sweep stress linear response was visualized by the Cole-Cole representation. The molecular weight change relative to polymer free of filler and obtained from the power-law of the zero-shear viscosity η′0 was found to be linearly dependent of the basal spacing increase in the three cases. Such cross-study using XRD and melt polymer rheology was able to unravel the attritive or plastizicing role of the organoclay as function of the basal spacing expansion in the intermixed polymer structure, and to respond whether LDH interleaved platelets were of interest for polar and non-polar polymer and finally to predictively monitor the interfacial attrition by the alkyl chain length of the surfactant molecule tethered to the LDH platelets.
      Graphical abstract image

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


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


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


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

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

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

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

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

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


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

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

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




      PubDate: 2014-09-14T02:52:55Z
       
  • The effect of cetyltrimethylammonium ion and type of smectites on the
           luminescence efficiency of bis(8-hydroxyquinoline)zinc(II) complex
    • Abstract: Publication date: Available online 4 September 2014
      Source:Applied Clay Science
      Author(s): Patcharaporn Pimchan , Nithima Khaorapapong , Makoto Ogawa
      A luminescence metal complex, bis(8-hydroxyquinoline)zinc(II) (Znq2), was incorporated into the interlayer space of smectites (a natural montmorillonite and a synthetic saponite) by two different ways; colloidal processes via the in situ formation of bis(8-hydroxyquinoline)zinc(II) in cetyltrimethylammonium-smectites (CTA-smectites) and the adsorption of cetyltrimethylammonium coated bis(8-hydroxyquinoline)zinc(II) (Znq2CTA) into hydrophilic smectites. The UV–Vis spectra confirmed the formation and the incorporation of bis(8-hydroxyquinoline)zinc(II) in the interlayer space of smectites. The photoluminescence bands of Znq2CTA@montmorillonite and Znq2@CTA-montmorillonite (498nm) were blue shifted in comparison with the weak emission bands of Znq2CTA@saponite and Znq2@CTA-saponite (510nm), indicating the formation of different nanostructures and/or packing of bis(8-hydroxyquinoline)zinc(II) in the two types of smectites. The state of the intercalated cetyltrimethylammonium ions also played a key role to the luminescence intensities of the products due to the concentration quenching and self-absorption.
      Graphical abstract image

      PubDate: 2014-09-10T02:21:04Z
       
  • Synthesis and characterization of soy polyol-based polyurethane
           nanocomposites reinforced with silylated palygorskite
    • Abstract: Publication date: Available online 8 September 2014
      Source:Applied Clay Science
      Author(s): Chengshuang Wang , Qisheng Wu , Fang Liu , Jing An , Rong Lu , Hongfeng Xie , Rongshi Cheng
      Soy polyol-based polyurethane (PU) nanocomposites were synthesized with 3-glycidoxypropyltrimethoxysilane modified palygorskite (GPTMSPal). The GPTMSPal PU nanocomposites were characterized using XRD, DMA, TGA, SEM, and universal test machine. GPTMSPal increased the glass transition temperature as well as significantly improved tensile strength and Young's modulus of the GPTMSPal PU nanocomposites. Compared to neat PU, GPTMSPal PU nanocomposite with 12mass% GPTMSPal exhibited a 13.1°C increase in the glass transition temperature, a 303% improvement in tensile strength, and a 518% increment in Young's modulus, respectively. TGA results showed that the thermal stability of GPTMSPal PU nanocomposites improved with increased GPTMSPal loading. Furthermore, SEM revealed a uniform dispersion of GPTMSPal in the PU matrix.


      PubDate: 2014-09-10T02:21:04Z
       
  • The effect of magnesium chloride solution on the engineering properties of
           clay soil with expansive and dispersive characteristics
    • Abstract: Publication date: November 2014
      Source:Applied Clay Science, Volume 101
      Author(s): Murat Turkoz , Hasan Savas , Aykut Acaz , Hasan Tosun
      Because expansive and dispersive soils damage engineering structures, extensive studies on using additives to ameliorate the effects of these soils have been conducted. In this study, the effect of magnesium chloride (MgCl2) solution on the engineering properties of clay soils was evaluated. Previous studies on this subject have shown that MgCl2 is more commonly used as an anti-icing agent on roads than as a soil stabilizer. MgCl2 is also used to control dust and humidity on roads and to reduce the scattering of coarse particles from road surfaces. However, as the use of MgCl2 becomes more common, its potential to improve the geotechnical properties of problematic soils will receive increasing attention. To this end, the variation in the engineering properties of expansive and dispersive clay soil samples as functions of the added MgCl2 content was investigated. First, the physical and chemical properties of the soil sample were determined. Next, the swell percentage, swell pressure, crumb, pinhole and unconsolidated undrained (UU) triaxial compression tests were performed at different curing times on samples with and without the additive by compressing the sample to achieve particular compaction characteristics. Scanning electron microscopy (SEM) analyses were performed to observe the microstructures in the sample without the additive and with the amount of additive that most strongly improved the expansive and dispersive qualities of the clay. The results show that dispersive and expansive clay soils can be effectively improved using an additive MgCl2 solution.


      PubDate: 2014-09-10T02:21:04Z
       
  • Editorial Board
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99




      PubDate: 2014-09-04T01:28:23Z
       
  • Electrically induced reversible viscosity change in hectorite aqueous
           dispersion under an AC electric field
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Hiroshi Kimura , Mao Ueno , Shinya Takahashi , Akira Tsuchida , Keiichi Kurosaka
      The electrically induced viscosity change of a deionized hectorite aqueous dispersion under an alternating current (AC) electric field was investigated. The hectorite dispersion showed a reversible viscosity change when an AC electric field (<ca. 0.01Hz) of the order of a few V/mm was applied and removed thereafter, although it showed an incomplete reversibility when a direct current (DC) electric field was applied. Regarding the mechanism of reversible viscosity change, it can be considered that the hectorite is well dispersed as individual layers or as small flocs without an electric field. These form a three-dimensional network structure, which returns to the original dispersion state upon removal of the alternating electric field.


      PubDate: 2014-09-04T01:28:23Z
       
  • Preparation of photopolymerized nanocomposites through intercalating
           multifunctional acrylated siloxane into montmorillonite
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Han Xie , Qianghua Wu , Wenfang Shi
      The multifunctional acrylate-intercalated montmorillonite (TA-Mt) was prepared by intercalating the cetyltrimethyl ammonium bromide (CTAB)-modified Mt (CTAB-Mt) with a trifunctional acrylated siloxane (TAS). The TA-Mt was further formulated with epoxy acrylate and 1,1,1-propanetrimethanol tris(3-mercaptopropionate) (PTTM) in an equimolar ratio of thiol group to acrylate double bond, and a trace amount of 0.5wt.% photoinitiator. This formulation was then exposed to UV light to form the polymer/Mt nanocomposites through the thiol-ene click reaction. The FT-IR, XRD, and TGA analysis confirmed the successful grafting of TAS to the Mt interlayers. The TEM and HR-TEM micrographs together with further XRD measurement indicated that the UV-cured nanocomposites possess an intercalated structure. The TGA and DMA analyses demonstrated the better thermal stability and excellent compatibility. The Tg increased with the TA-Mt content increasing in the nanocomposites.


      PubDate: 2014-09-04T01:28:23Z
       
  • Enhancement of β phase crystallization and dielectric behavior of
           kaolinite/halloysite modified poly(vinylidene fluoride) thin films
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Pradip Thakur , Arpan Kool , Biswajoy Bagchi , Sukhen Das , Papiya Nandy
      Poly(vinylidene fluoride) with different contents (1–15 mass%) of clay minerals (kaolinite and halloysite) has been synthesized by solution-casting method to investigate the electroactive β-phase formation mechanism and the dielectric properties of the clay polymer nanocomposite (CPN) films. X-ray diffraction spectra, Fourier transform infrared spectroscopy, micro-Raman spectroscopy and differential scanning calorimetry confirmed the formation of electroactive β-phase in PVDF matrix after the addition of clay minerals. Field emission scanning electron microscope images showed interfacial interaction in CPN between the polymer matrix and the clay minerals resulting in enhanced electroactive β-phase nucleation and large dielectric constant of the CPN thin films.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • Assessment of three Spanish clays for their use in pelotherapy
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): M.I. Carretero , M. Pozo , J.L. Legido , M.V. Fernández-González , R. Delgado , I. Gómez , F. Armijo , F. Maraver
      The mineralogy, geochemistry and physical and physicochemical properties of three Spanish clays and their mixtures with distilled water were determined. These results were compared with the data obtained by other authors for peloids from spas in Spain and Turkey. The main clay minerals of the samples studied were montmorillonite in Clay1, saponite in Clay2 and kerolite–stevensite in Clay3. The results obtained showed that all three clays share some properties with clays already in use, but Clay1 and Clay2, that are quite rich in smectite, are more suitable when the typical smectite features are needed for therapy. The peloid from saponite was the most suitable for thermotherapy while the kerolite–stevensite sample was not suitable for the preparation of peloids for this use.


      PubDate: 2014-09-04T01:28:23Z
       
  • Effect of curing temperature on geopolymerization of metakaolin-based
           geopolymers
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Bing-hui Mo , He Zhu , Xue-min Cui , Yan He , Si-yu Gong
      The effects of different curing temperature (within the range 20 to 100°C) on electrical conductivity in geopolymerization process were systematically discussed with Impedance Analyzer. The variations of setting time conducted by Vicat apparatus can be described as the influence of curing temperatures on the geopolymerization of metakaolin-based geopolymers. Simultaneously, the impacts on the microstructure and mechanical properties of the geopolymer samples are discussed. The results indicated that elevating curing temperature will accelerate the dissolution, polymerization, reprecipitation processes of the geopolymerization reaction. The optimum curing temperature of geopolymer is about 60°C at which the geopolymer samples present the best mechanical properties with the compressive strength of 97.95MPa after cured for 7days.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • Preparation of rare earth metal ion/TiO2Hal-conducting polymers by ions
           imprinting technique and its photodegradation property on tetracycline
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Xiuna Yu , Ziyang Lu , Naichao Si , Weichao Zhou , Tingting Chen , Xun Gao , Minshan Song , Yongsheng Yan , Pengwei Huo , Chunyong Yan
      Rare earth metal ions had been immobilized on TiO2Hal with conducting polymers by ions imprinting technique. The as-prepared ions imprinting photocatalysts had been characterized by SEM, XRD, FT-IR, UV–vis DRS and ICP-AES. The results demonstrated that there were rare earth metal ions in the photocatalysts. The photocatalytic activity of the ions imprinting photocatalysts was studied by the degradation of tetracycline simulated wastewater under the visible light irradiation. Moreover, a series of synthetic factors were also investigated, the results indicated that it was better to choose o-phenylenediamine as functional monomer, the photocatalytic activity of degradation of tetracycline solution could be improved by adding the rare earth metal ions, Y3+ was the most appropriate ion and the best synthetic concentration of Y3+ was 0.02g. Under the optimal conditions, the photodegradation rate could reach 78.80%.


      PubDate: 2014-09-04T01:28:23Z
       
  • Evaluation of glauconite rock color stability during firing
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): V. Valanciene , R. Siauciunas , Z. Valancius
      The paper analyses the influence of the firing temperature on the mineralogical composition and color stability of glauconite rock—a potential natural color-changing additive in ceramics. By XRD, Mössbauer spectroscopy and colorimetric analysis it has been established that the tint of glauconite rocks' color depends on the amount of iron incorporated into hematite and magnesioferrite. The intensity of red color rises as the amount of iron in hematite increases. The ceramic body becomes darker, when more iron is incorporated into magnesioferrite and the difference between the amount of iron in magnesioferrite and hematite is higher. Firing temperature intervals in which the color of glauconite rocks does not change have been determined. The color of the rock in each interval remains stable but the tint of the ceramic body fired in different temperature ranges varies. Therefore, glauconite rock is suitable for adjustment of the color of easily fusible clay.


      PubDate: 2014-09-04T01:28:23Z
       
  • Palygorskite polypyrrole nanocomposite: A new platform for electrically
           tunable drug delivery
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Yong Kong , Hanli Ge , Jianxin Xiong , Shixiang Zuo , Yong Wei , Chao Yao , Linhong Deng
      A clay polymer nanocomposite (CPN) based on aspirin-loaded palygorskite (Pal) modified polypyrrole (PPy) was prepared by in situ electropolymerization of pyrrole monomer in the presence of Pal as the modifier and aspirin as the drug source. This drug-loading approach was simple and convenient, since colloid templates such as polystyrene microspheres used in conventional drug-loading system were not needed. The resulting CPN was characterized by TEM, XRD, cyclic voltammetry (CV), chronocoulometry, electrochemical impedance spectroscopy (EIS) and FTIR. The CPN was used as a new platform for aspirin delivery, which could significantly enhance aspirin loading capacity of the system and control aspirin release by external electrical stimulus. The results indicated that the proposed novel drug-delivery system might be promising as an implantable device where drug release could be electrically tuned according to the patient's requirement.


      PubDate: 2014-09-04T01:28:23Z
       
  • Time of reactions in a lime treated clayey soil and influence of curing
           conditions on its microstructure and behaviour
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Marta Di Sante , Evelina Fratalocchi , Francesco Mazzieri , Erio Pasqualini
      A research programme has been set up to investigate the sequence of physical and chemical reactions in compacted soil–lime mixtures and their influence on the mechanical and hydraulic performance with time. The paper illustrates a method set up to monitor sequence and development of soil–lime reactions with curing time based on pH measurement. The method was also used, together with SEM observations and chemical analyses, to properly analyse results of hydraulic conductivity and oedometer tests performed on compacted soil–lime samples cured in saturated and unsaturated conditions. It was found that the hydraulic conductivity significantly decreases by increasing the time spent in unsaturated condition and it tends to appreciably reduce with time. In terms of compressibility, higher compression index resulted in saturated curing conditions. These differences were found to be due to a different microstructure. A crystalline, more brittle structure was detected in the case of immediate saturation with an ununiformed distribution in pore size. Unsaturated curing conditions give rise to amorphous, uniformly distributed pozzolanic products, with a more homogeneous pore size distribution.


      PubDate: 2014-09-04T01:28:23Z
       
  • Synthesis and characterization of organosaponites. Thermal behavior of
           their poly(vinyl chloride) nanocomposites
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): S. Albeniz , M.A. Vicente , R. Trujillano , S.A. Korili , A. Gil
      The aim of this work was to synthesize and characterize the structural properties of the materials resulting from the combination of a synthetic saponite with several organic molecules, namely, Arquad 2HT-75, octadecylamine, 3-aminopropyltriethoxysilane, trimethyloctadecylammonium bromide and tetraethoxysilane, or combinations of them, and with or without the addition of HCl during synthesis. The ratios organic molecule/saponite and HCl/organic molecule were considered as synthesis variables. Structural characterization was based on X-ray diffraction (XRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and infrared spectroscopy (FTIR). The chemical composition of the materials was determined through X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS), and their morphology was analyzed through scanning electron microscopy (SEM). The values obtained for the basal spacings were a function of the type and amount of the organic molecule. Otherwise, HCl did not significantly influence the basal spacing, but it had the capacity to significantly modify the morphology and the chemical composition of the samples. From the results found, the solids modified with tetraethoxysilane and 3-aminopropyltriethoxysilane were selected to incorporate various titanium precursors. These new organo-modified saponites were used in the formulation of PVC nanocomposites and their thermal behavior was evaluated at two temperatures (70 and 180°C).


      PubDate: 2014-09-04T01:28:23Z
       
  • Silylated montmorillonite as nanofillers for plasticized PVC
           nanocomposites: Effect of the plasticizer
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Tatiane F. Silva , Bluma G. Soares , Stephane C. Ferreira , Sebastien Livi
      Poly(vinyl chloride) (PVC) nanocomposites were prepared by compounding PVC with different clay minerals, which were previously dispersed into dioctyl phthalate (DOP) or epoxidized soybean oil (ESO) as plasticizers, with the help of an ultrasonication. Sodium montmorillonite (Na+-Mt) and those obtained from its functionalization with N-(2-aminoethyl-)-3-aminopropyl-trimethoxy-silane (NH2-Mt) or 3-mercaptopropyl-trimethoxy-silane (SH-Mt), as well as a commercial organoclay, Cloisite 30B, were employed as the nanoparticles. The incorporation of amino or mercaptosilane on the Na+-Mt surface was estimated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The clay PVC nanocomposites containing 2.5phr of different clay minerals were characterized by XRD, dynamic mechanical analysis, thermal degradation and dielectric analysis. It was found a high exfoliation degree for the nanocomposites containing silylated clays, as suggested by the absence of reflections. Na+-Mt also displayed a high exfoliated structure for system plasticized with ESO. The presence of different clay minerals resulted in an increase of the storage modulus without affecting the glass transition temperature. Regarding thermal stability, those systems plasticized with ESO presented the best results obtained from thermogravimetric analysis, and the presence of Cloisite 30B, a clay mineral modified with ammonium salt, presented the worst performance in both plasticized systems.


      PubDate: 2014-09-04T01:28:23Z
       
  • Characterization of halloysite-water nanofluid for heat transfer
           applications
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): J.A. Alberola , R. Mondragón , J.E. Juliá , L. Hernández , L. Cabedo
      Nanofluids based on water with halloysite (Hal) nanotubes were prepared and characterized in order to evaluate its suitability to be used as a heat transfer fluid. A characterization of the Hal powder nanoparticles was performed by means of SEM, TEM, WAXS, FTIR and TGA so that chemical composition, size and shape were determined. Stability of nanofluids was analyzed by means of zeta potential and light transmission measurements. Thermal conductivity, specific heat and viscosity of nanofluids prepared at different solid contents (0.5, 1, 3 and 5% volume fraction) and temperatures (40, 60 and 80°C) were obtained in order to optimize the Prandtl number. The nanofluids exhibited a good performance for its application as heat transfer fluids, with low Prandtl numbers compared to other commonly used nanofluids. High thermal conductivity enhancement with moderate viscosity and good stability results was obtained for the Hal nanofluid.


      PubDate: 2014-09-04T01:28:23Z
       
  • Thermo-physical performance of organoclay coatings deposited on the
           surfaces of glass fibre-reinforced epoxy composites using an atmospheric
           pressure plasma or a resin binder
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Baljinder K. Kandola , Piyanuch Luangtriratana
      This work reports the thermal barrier and flame retardant efficiency of an organically modified clay (organoclay, OC), when deposited on the surface of glass fibre-reinforced epoxy (GRE) composites. Two approaches were undertaken: 1) the OC was deposited on the surface of the epoxy composite and then polymerised using an atmospheric argon plasma in the presence and absence of a silicon-containing monomer and 2) the OC was dispersed in a phenolic resin binder and applied as a surface coating. Fourier transform infrared spectrometry confirmed the polymerisation of the silicon-containing monomer by plasma treatment. The adhesion between the coating and the substrate was measured using the tape pull method, which indicated that the OC was tightly embedded in the resin matrix after plasma treatment or with the resin binder. The surface morphology of coated surfaces was studied using scanning electron and digital microscopies. The thermal barrier effect of the OC-containing coatings studied by a cone calorimeter at 35kW/m2 heat flux was demonstrated by increase in time-to-ignition and time-to-peak heat release rate, and decrease in the peak heat release of the coated samples compared to the control sample. However, for the coatings to be effective enough to be self-extinguishing, the presence of an additional flame retardant element in the coating or on the surface layer of the GRE composite and beneath the clay layered coating is required.


      PubDate: 2014-09-04T01:28:23Z
       
  • Montmorillonite-PLGA nanocomposites as an oral extended drug delivery
           vehicle for venlafaxine hydrochloride
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Shilpa Jain , Monika Datta
      The objective of the present study is to develop montmorillonite (Mt) based PLGA nanocomposites for oral and controlled release carrier for an antidepressant drug, venlafaxine hydrochloride (VF). VF loaded CPN were prepared using double emulsion solvent evaporation technique. The synthesized CPN were compared with respect to morphology, particle size, physical status of VF and Mt and in vitro drug release to the corresponding biodegradable PLGA nanoparticles. Mt based VF-PLGA nanocomposites suggest the possibility of designing the oral and controlled release formulations to minimize the drug administration frequency and the occurrence of side effect thereby increasing the effectiveness of drug and hence improving patient compliance.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • Bentonite binders in the presence of mycotoxins: Results of in vitro
           preliminary tests and an in vivo broiler trial
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): A.C. Pappas , E. Tsiplakou , M. Georgiadou , C. Anagnostopoulos , A.N. Markoglou , K. Liapis , G. Zervas
      The use of two bentonites differing in composition as potential binders of three mycotoxins present in broiler diets was examined with both an in vitro preliminary test and an in vivo trial. In the in vitro test, the adsorbing and desorbing ability of the two bentonites added at 1% was investigated. Concentrations of aflatoxin B1 (AFB1), ochratoxin A (OTA) and zearalenone (ZEA) were determined with LC–MS/MS and were 0.02ppm, 0.1ppm and 2ppm respectively. In the in vivo trial, a total of 300 day-old, as hatched, broilers were randomly distributed in five dietary treatments with four replicate pens per treatment. In T1 treatment, broilers were fed a basal diet with neither mycotoxins nor bentonite added; in T2 broilers were fed the same diet with 1% m/m bentonite A added. In T3, broilers were fed the same diet with 1% m/m bentonite A added and three mycotoxins (AFB1, OTA and ZEA) added at levels not exceeding the EU maximum. In T4 treatment, broilers were fed the same diet with 1% m/m of bentonite B added and in T5 broilers were fed the same diet with 1% m/m of bentonite B added and mycotoxins at the same levels. Broiler performance and several biochemical and hematological parameters were examined. The in vitro test indicated a complete adsorption of 0.02ppm AFB1 by both bentonites, present at 1%. No desorption was observed for AFB1. Adsorption and desorption of ZEA and OTA were low. The in vivo trial revealed that the overall performance of broilers did not differ between treatments. Aspartate aminotransferase was found lower in broilers fed mycotoxin contaminated diets but within normal range. The study revealed that the examined bentonites may maintain optimum broiler performance when mycotoxin levels present in the diet do not exceed EU limits and guidance values possibly by ameliorating the negative effects of other mycotoxins, not regulated by EU, present at the same time in the diet.


      PubDate: 2014-09-04T01:28:23Z
       
  • Tailoring the reactivity of bio-surfactants as a tool for montmorillonite
           exfoliation in epoxy thermosets
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Laura Puchot , Pierre Verge , Valérie Toniazzo , David Ruch , Thierry Fouquet , João A.S. Bomfim
      It is well established that the chemical structure of surfactants used to promote the dispersion of clay minerals in polymers plays a major role in clay polymer nanocomposites preparation. However, much less explored is the incorporation of reactive surfactants capable of covalently grafting to monomers and polymer chains. In this work, the effect of the reactivity degree of bio-based surfactants onto the exfoliation of montmorillonite in epoxy is evidenced. For this purpose, 3 surfactants were prepared from a derivative of Cardanol, incorporating reactive groups: N(CH3)2, NH2 or two NH2 functions. In each case, the organomodification of the clay mineral results in a similar interlayer space increase. Combined chemical derivatization and MALDI-TOF/MS was used to evidence the differences of the residual reactivity of the intercalated surfactants. Finally each organomodified clay mineral was used for the preparation of epoxy nanocomposites. Interestingly, for the most reactive surfactant, X-ray diffraction analysis evidenced a fully exfoliated structure while semi-exfoliation or intercalated structure was found for the less reactive surfactants.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • First evidence of singlet oxygen species mechanism in silicate clay for
           antimicrobial behavior
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Jiun-Chiou Wei , Yi-Ting Wang , Jiang-Jen Lin
      Nanoscale silicate platelets (NSPs) from the natural silicate clay minerals were shown to have antimicrobial ability through physical trapping mechanism. The NSP could inhibit the growth of drug-resistant species such as methicillin-resistant Staphylococcus aureus and silver ion-resistant Escherichia coli. We further found that the NSP generated singlet oxygen species under ultraviolet irradiation. This is the first time to report the ability of generating singlet oxygen species by the platelets of ca. 80×80×1nm in geometric shape. The ability to emit singlet oxygen species of the NSP clay provides an explanation for “physical trapping” antimicrobial mechanism.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • Rheology of concentrated bentonite dispersions treated with sodium
           pyrophosphate for application in mitigating earthquake-induced
           liquefaction
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Marika Santagata , Julia P. Clarke , Antonio Bobet , Vincent P. Drnevich , Chadi S. El Mohtar , Pao-Tsung Huang , Cliff T. Johnston
      The paper investigates the effectiveness of sodium pyrophosphate (SPP) to engineer the rheology of concentrated bentonite dispersions for their use in treating sands susceptible to earthquake-induced liquefaction. This application requires that on the short term the rheological properties of the dispersion allow its permeation inside a porous medium, but that once inside the sand pores, the dispersion regains its gel structure. The testing program focuses on 10% bentonite dispersions (expressed in terms of mass of bentonite by total mass of the dispersion) prepared using a commercial Wyoming sodium-bentonite, pure water and SPP at dosages ranging from 0% to 2% by mass of the bentonite. Rheological tests are conducted using a Physica MCR 301 rotational rheometer to probe the flow and viscoelastic properties of the dispersions over time. Tests conducted at early ages suggest that dispersions with SPP≥0.5% are likely to be suitable permeation materials. Tests conducted over a period of two years show a significant evolution of the rheology, with all dispersions returning to exhibit response typical of gel-like materials, including thixotropic behavior; the greater the SPP%, the more delayed the formation of the gel. Custom rheological tests establish the independence of the behavior of the SPP dispersions on the frequency of the applied load. These results suggest the ability of these dispersions to mitigate liquefaction during subsequent seismic events, and further support their use in the application considered.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • Effect of polyethylene oxide (PEO) and shear rate on rheological
           properties of bentonite clay
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): L. Hammadi , N. Boudjenane , M. Belhadri
      In this paper, the influence of polyethylene oxide (PEO) and shear rate on rheological properties of bentonite suspensions is studied. The model of Herschel–Bulkley which is used to fit the flow curves of the mixture which based on the bentonite-polyethylene oxide and the Generalized Kelvin–Voigt model has been successfully applied to fit the creep and recovery data and to analyze the viscoelastic properties of mixture. The addition of polyethylene oxide (PEO) in a concentration range between 0 and 2% in 4% of bentonite induces not only an increase of the yield stress and the consistency index of bentonite but also a decrease of the flow index of bentonite. It is also the addition of PEO between 0 and 2% to 4% that may cause an increase in the viscoelastic properties of bentonite. For constant shear rate applied on the 4% bentonite at the 20°C in which a thixotropic behavior was observed and analyzed by using a modified model of Herschel–Bulkley a structural parameter λ is included in order to account for time dependent effect.


      PubDate: 2014-09-04T01:28:23Z
       
  • Clay–polymer nanocomposites (CPNs): Adsorbents of the future for
           water treatment
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Emmanuel I. Unuabonah , Andreas Taubert
      Today's world is burdened with the need for potable water even with the numerous water bodies that exist. Among several other techniques, adsorption has become widely used for the removal of inorganic and organic micropollutants from aqueous solution and numerous adsorbents for water treatment have therefore been prepared over the years. A class of adsorbents currently receiving growing attention is the clay–polymer nanocomposite (CPN) adsorbents. CPNs effectively treat water by adsorption and flocculation of both inorganic and organic micropollutants from aqueous solutions. Some of these CPNs – when modified with biocides – also have the ability to efficiently remove microorganisms such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans from water. CPNs are far more easily recovered from aqueous media than neat clay. They also exhibit far better treatment times than either polymer or clay adsorbents. They have higher adsorption capacity and better life cycles compared with clay alone. CPNs therefore show an excellent potential as highly efficient water and waste treatment agents. This article reviews the various CPNs that have been prepared recently and used as adsorbents in the removal of micropollutants (inorganic, organic and biological) from aqueous solutions. A special focus is placed on CPNs that are not only interesting from an academic point of view but also effectively reduce the concentration of micropollutants in water to safe limits and also on new developments bordering on CPN use as water treatment agent that have not yet realized their full potential.
      Graphical abstract image

      PubDate: 2014-09-04T01:28:23Z
       
  • Acid-base properties of organosmectite in aqueous suspension
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Noureddine Hamdi , Ezzeddine Srasra
      Surfactant modified smectite was prepared using hexadecyltrimethylammonium bromide (HDTMAB) at three CEC levels (0.5, 1 and 2 CEC). Potentiometric titration behavior of Na-smectite and organosmectites was investigated and interpreted according to surface complexation theory. The point of zero charge (PZC) was determined by both the methods potentiometric and mass titrations. The PZC of Na-smectite is about 6.2 and that of the organosmectites (H0.5, H1 and H2) is 6.8, 7.7 and 8, respectively. The titration data was modulated using the ProtoFit program in order to determine the PZC and the equilibrium constants (pKas). The results give a good agreement between the experimental and modeling study.


      PubDate: 2014-08-01T22:34:09Z
       
  • Interactions of the dye, Rhodamine B with kaolinite and montmorillonite in
           water
    • Abstract: Publication date: September 2014
      Source:Applied Clay Science, Volume 99
      Author(s): Krishna G. Bhattacharyya , Susmita SenGupta , Gautam Kumar Sarma
      Two of the most common clay minerals, kaolinite and montmorillonite, were allowed to interact with the cationic dye, Rhodamine B in aqueous solution. The clay minerals were used along with those modified by treatment with 0.25 and 0.50M H2SO4. The influences of pH, interaction time, clay mineral amount, dye concentration and temperature on the adsorption process were monitored and explained on the basis of physico-chemical characteristics of the clay minerals and the behaviour of the dye molecules. The optimum pH for Rhodamine B adsorption was 4.0. The interactions attained equilibrium in ~180min and the rate processes followed second order kinetics. It was observed that montmorillonite had a Langmuir monolayer capacity of more than eight times that of kaolinite. The modified clay minerals showed slightly higher adsorption capacity than the raw clay minerals. Adsorption was endothermic with enthalpy of adsorption increasing with rise in temperature and the endothermic interactions were driven by increase in entropy and decrease in Gibbs energy. The results suggested that the dye can be separated from aqueous solution by both clay minerals.


      PubDate: 2014-08-01T22:34:09Z
       
 
 
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