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  Subjects -> EARTH SCIENCES (Total: 587 journals)
    - EARTH SCIENCES (434 journals)
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EARTH SCIENCES (434 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Hybrid Journal   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 8)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 2)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances In Physics     Hybrid Journal   (Followers: 6)
Aeolian Research     Hybrid Journal   (Followers: 1)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 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: 14)
Annals of Glaciology     Full-text available via subscription  
Annual Review of Marine Science     Full-text available via subscription   (Followers: 9)
Anthropocene Review     Hybrid Journal  
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 6)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 8)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 20)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 7)
Artificial Satellites     Open Access   (Followers: 13)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 17)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 3)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 3)
Atmospheric and Climate Sciences     Open Access   (Followers: 14)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 8)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 9)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of Marine Science     Full-text available via subscription   (Followers: 13)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 16)
Bulletin of Volcanology     Hybrid Journal   (Followers: 11)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 11)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 17)
Carbonates and Evaporites     Hybrid Journal   (Followers: 3)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 9)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 10)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 5)
Contemporary Trends in Geoscience     Open Access  
Continental Journal of Earth Sciences     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 7)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 7)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 18)
Cretaceous Research     Hybrid Journal   (Followers: 4)
Cybergeo : European Journal of Geography     Open Access   (Followers: 4)
Developments in Geotectonics     Full-text available via subscription   (Followers: 2)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 140)
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  
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Spectra     Full-text available via subscription   (Followers: 11)
Ecohydrology     Hybrid Journal   (Followers: 11)
Ecological Questions     Open Access   (Followers: 6)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 9)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 10)
Environmental Geology     Hybrid Journal   (Followers: 11)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access  

        1 2 3 4 5 | Last

Journal Cover Applied Clay Science
   [4 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0169-1317
     Published by Elsevier Homepage  [2563 journals]   [SJR: 0.999]   [H-I: 63]
  • Enhancement of β phase crystallization and dielectric behavior of
           kaolinite/halloysite modified poly(vinylidene fluoride) thin films
    • Abstract: Publication date: Available online 9 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • Preparation and application of copolymer modified with the palygorskite as
           inhibitor for calcium carbonate scale
    • Abstract: Publication date: Available online 9 July 2014
      Source:Applied Clay Science
      Author(s): Xiaorui Guo , Fengxian Qiu , Ke Dong , Xinshan Rong , Kaichen He , Jicheng Xu , Dongya Yang
      The scale inhibitor copolymer modified with palygorskite was prepared from maleic anhydride, styrene sulfonic sodium and palygorskite. The conditions of preparing scale inhibitor were optimized. The structure and morphology of the copolymer were characterized by FT-IR, SEM and XRD. Using the static experiment method, the influences of copolymer concentration, temperature, time, and Ca2+ concentration of the system on the inhibition efficiency were investigated. The experimental results showed that the scale inhibitor copolymer modified with palygorskite had an excellent efficiency of scale inhibition, and nearly 98.97% of scale inhibition efficiency for CaCO3 was obtained. The prepared scale inhibitor could be used in the system of high temperature and high hardness water.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • Changing elemental uptake of radish seedlings grown in Cd and Pb polluted
           smectite substrates
    • Abstract: Publication date: Available online 9 July 2014
      Source:Applied Clay Science
      Author(s): Khadija Semhi , Norbert Clauer , Sam Chaudhuri
      Radish seedlings were grown for one month in a smectite substrate under controlled laboratory conditions. The purpose was avoiding as much as possible side effects such as heterogeneity of natural soils, as well as fertilizer and atmospheric supplies. One set of seedlings was watered at the beginning of the survey with plain deionized water, whereas the others were with the same water containing Cd or Pb at 0.5 and 1mg/L concentrations, to quantify the impact of these metal pollutions on the plants. Significant changes were observed in the uptake of the seedlings watered with the contaminated solutions: Na and K uptakes decreased, whereas those of Al, Fe, Ca and Mn increased. Changes were also detected in the uptake of some rare earths and trace elements after watering with Cd or Pb contaminated solutions. The most concerning uptakes are for the pollutants Cd and Pb that increase by about 795 and 1240 times, respectively, in the contaminated seedlings, suggesting a high tolerance by the radishes for these two metals. The overall increasing elemental uptakes result from replacement of an ion exchange process during growth in the unpolluted substrate by an ion complexation process in the case of growth in the polluted substrate. Occurrence of a significant Eu anomaly and disappearance of the Gd anomaly in the rare-earth distribution patterns of the contaminated radishes were necessarily induced by organic activity; they also explain the suggested changing uptake process. Rare-earth element distributions represent therefore an efficient tracer to evaluate how much soil pollution by a given metal potentially affects the uptake process of plants, and to postulate that some types of metal pollution, Cd and Pb here, affect specific functions of enzymes and/or of bacterial micro-organisms.


      PubDate: 2014-07-27T22:14:31Z
       
  • Clay–polymer nanocomposites (CPNs): Adsorbents of the future for
           water treatment
    • Abstract: Publication date: Available online 10 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • Enhanced heavy metal adsorption on functionalized nanotubular halloysite
           interlayer grafted with aminoalcohols
    • Abstract: Publication date: Available online 14 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • Effects of oxalic and citric acids on three clay minerals after incubation
    • Abstract: Publication date: Available online 14 July 2014
      Source:Applied Clay Science
      Author(s): Mingming Kong , Li Huang , Lifen Li , Zhiyi Zhang , Shixue Zheng , Ming Kuang Wang
      The release of silicon (Si) from and the structural changes to clay minerals (i.e., kaolinite, montmorillonite (Mt), and illite) were investigated after being batch incubated with low-molecular-mass organic acids (i.e., oxalic and citric acids, LMMOA) of varying concentrations (0–0.5molL−1) at 25°C. Two mineral acids (i.e., HCl and H2SO4) with varying concentrations were also reacted with Ca-montmorillonite (Ca2+-Mt). With increasing reaction time, the Si released from kaolinite and illite reached its maximum level after incubation with the varying LMMOA concentrations for 15days. Quantities of Si released from the clay minerals with the LMMOA ranged from 0.22 to 114.01μgmL−1 (Si). Quantity of Si released with oxalic acid was higher than that with citric acid. The Si released from the clay minerals increased with increasing organic acid concentrations. More Si was released from Mt than from kaolinite and illite when incubated with the same LMMOA concentration. With increasing organic acid concentrations, the X-ray diffraction (XRD) reflection intensities of the Mt weakened, and this trend was more remarkable in the clay treated with oxalic acid than citric acid. However, no relationship between the XRD reflection intensity and the acid concentrations was noticeable in the incubated kaolinite and illite. While incubating with hydrochloric acid (HCl) and sulfate acid (H2SO4) for 15 day incubation, amounts of Si released from Ca2+-Mt were generally higher than those reacting with organic acids, and more Si was released in the H2SO4 treatment than that of HCl. But the XRD reflection intensities of the Ca2+-Mt had no distinctly change compared with those treated with the organic acids.


      PubDate: 2014-07-27T22:14:31Z
       
  • Electrically induced reversible viscosity change in hectorite aqueous
           dispersion under an AC electric field
    • Abstract: Publication date: Available online 15 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • Preparation of photopolymerized nanocomposites through intercalating
           multifunctional acrylated siloxane into montmorillonite
    • Abstract: Publication date: Available online 15 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • One-step synthesis of highly ordered Pt/MCM-41 from natural diatomite and
           the superior capacity in hydrogen storage
    • Abstract: Publication date: Available online 16 July 2014
      Source:Applied Clay Science
      Author(s): Jiao Jin , Jing Ouyang , Huaming Yang
      Platinum-loaded mesoporous silica (xPt/MCM-41) with highly ordered structures and narrow pore size distributions were successfully synthesized via one-step hydrothermal method from natural diatomite. The samples were characterized using X-ray diffraction, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy and transmission electron microscopy. Hydrogen adsorption capacities of the samples were also investigated at room temperature. The samples display uniformly arrayed hexagonal pore structure in two-dimension with pore size around 3nm. Zero-valent Pt nanoparticles were synthesized and stabilized by the confinement effect of ordered mesoporous MCM-41 without destroying the integrity of mesoporous structure in the one-step synthetic procedure. These xPt/MCM-41 materials were also concluded to be promising mediums for physisorption-based hydrogen storage at room temperature. The hydrogen adsorption capacity of 0.5Pt/MCM-41 is 2.32wt.% at 2.5MPa and 25°C, determined from the isotherms, which is among the highest reported values under the same conditions. Hydrogen storage was benefited by these highly dispersed Pt nanoparticles and the refined structure properties of MCM-41 at room temperature. Meantime, the composition, structure and surface characteristics of 0.5Pt/MCM-41 remained the same after hydrogen adsorption. The uniform mesoporous structure plays a decisive role in inhibition of agglomeration and confinement of nanoparticles. This one-step synthetic procedure could offer a more benign approach for the synthesis of noble metal functionalized MCM-41 potentially for hydrogen storage at room temperature.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • Oil–water separation process with organoclays: A comparative
           analysis
    • Abstract: Publication date: Available online 17 July 2014
      Source:Applied Clay Science
      Author(s): Mariaugusta F. Mota , Meiry Gláucia F. Rodrigues , Fabricio Machado
      This work presents an experimental study focusing on the preparation and characterization of modified green clay with quaternary ammonium salts alkyl dimethyl benzyl ammonium chloride (ADMBAC) and distearyl dimethyl ammonium chloride (DSDMAC) intended to be used as adsorbent in the process of removing oil emulsion in an oil–water system using finite bath. X-ray diffraction (XRD), infrared spectroscopy (IR) and expansion test (adsorption capacity and Foster swelling) measurements were performed in order to evaluate the performance of the ion exchange reactions and the degree of affinity with oil products. There was an increase in the XRD basal spacing of the modified clays (1.96nm and 2.25nm for DSDMAC and ADMBAC salts, respectively) in comparison to the observed value (1.56nm) for the unmodified clay. The IR results revealed that salts were successfully incorporated to clay structure. Based on the expansion tests the organoclays presented the best efficiency of separation, independent on the kind of solvent used in comparison with the unmodified clay performance. The modified clays exhibit a very high capacity of adsorption. The predictions of multiple linear regression models determined based on the factorial design of experiments are excellent.


      PubDate: 2014-07-27T22:14:31Z
       
  • Effects of organic modification of montmorillonite on the performance of
           starch-based nanocomposite films
    • Abstract: Publication date: Available online 18 July 2014
      Source:Applied Clay Science
      Author(s): Yuling Gao , Yangyong Dai , Hui Zhang , Enjie Diao , Hanxue Hou , Haizhou Dong
      Objective The objective of this article is to study the effects of six quaternary ammonium salts (QASs) with various chain lengths and head groups on the physico-chemical properties of organically modified montmorillonites (OMts) and their starch nanocomposite films. Methods X-ray diffraction,FT-IR spectroscopy and TGA analysis of the OMts were performed. Mechanical properties, water vapor permeability (WVP) and glass transition temperature (Tg) of the nanocomposite films were determined. Results A perfect intercalation structure was formed between the QASs and the natural montmorillonite. The QASs with high molecular weight were beneficial to increasing the d-spacing and loaded more mass in the interlayer space. The highest and lowest d-spacing were 3.56nm for D1821Mt and 1.81nm for 1231Mt, respectively. With the increase in the molecular size of the QASs, the starch/OMt composite films exhibited greater tensile strength (TS, 6.16MPa), lower water vapor permeability (WVP, 1.80×10−10g·m / m2·s·Pa), lower glass transition temperature (Tg, 17.1 °C) and better heat-sealing performance. Conclusions The QASs with large molecular size were more suitable for the production of starch/OMt nanocomposite films.


      PubDate: 2014-07-27T22:14:31Z
       
  • Effect of polyaniline-modified clay on the processing and properties of
           clay polyimide nanocomposites
    • Abstract: Publication date: Available online 19 July 2014
      Source:Applied Clay Science
      Author(s): Jia Wang , Jude O. Iroh , Stephen Hall
      Polyaniline modified-clay/polyimide nanocomposite (PANi-CPN) containing highly intercalated montmorillonite was synthesized by in-situ double intercalation polymerization followed by thermal imidization. The presence of PANi-clay resulted in a decrease in the poly(amic acid) (PAA) solution viscosity during polymerization, and accelerated the polymerization procedure as the solution viscosity attained the maximum value at a shorter reaction time. The extent of imidization for PAA is largely improved compared with the organo-CPN prepared in the same condition. The PANi-CPN prepared in this study showed a characteristic polyaniline (PANi) UV/Vis absorption peak between 450 and 700nm. The Wide Angle X-ray diffraction (WAXD) patterns for PANi-CPNs cured at 70°C show a weak peak at a very low diffraction angle, indicating the formation of highly intercalated clays. This peak disappears for the PANi-CPN cured at higher temperatures, indicating fully exfoliated clay structure. The thermo-mechanical properties of the composites increased with increasing filler concentration.


      PubDate: 2014-07-27T22:14:31Z
       
  • Microstructure of different chain length ionic liquids intercalated into
           montmorillonite: A molecular dynamics study
    • Abstract: Publication date: Available online 19 July 2014
      Source:Applied Clay Science
      Author(s): Limei Wu , Chengxue Yang , Lefu Mei , Faxiang Qin , Libing Liao , Guocheng Lv
      This study employs molecular dynamics modeling to examine the interlayer microstructures of montmorillonite intercalated with different chains of CnmimCl montmorillonites with varying chain lengths, intercalation amount, arrangement and energy. C4mim+ and C8mim+ arrange themselves in monolayers, while C12mim+ and C16mim+ in parallel bilayers or tilt aligning. The basal spacing of montmorillonite and the corresponding energy increased as the chain length of organic cations is increased. It is indicated that no bond has been formed for N+ O due to the minimum distances of no less than 3.1Å and angles of 35°–45° between N+ in Cnmim+ and silicon–oxygen tetrahedron. These modeling results provide insights into the understanding of synthesized Cnmim+-montmorillonite microstructure and guidelines for relevant engineering applications.


      PubDate: 2014-07-27T22:14:31Z
       
  • Silylation of Al13-intercalated montmorillonite with trimethylchlorosilane
           and their adsorption for Orange II
    • Abstract: Publication date: Available online 19 July 2014
      Source:Applied Clay Science
      Author(s): Zonghua Qin , Peng Yuan , Shuqin Yang , Dong Liu , Hongping He , Jianxi Zhu
      The grafting reactions between trimethylchlorosilane (TMCS) and Al13-intercalated montmorillonite were investigated using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption–desorption isotherms. The influence of solvent on the grafting process is discussed. The grafting amount of TMCS was roughly controlled by choosing different solvents. The product prepared in anhydrous ethanol has a high specific surface area and a large pore volume but a low degree of grafting modification; by comparison, the product prepared in cyclohexane has a high loading amount of silane but a low surface area. These organic–inorganic montmorillonites have an excellent adsorption capability for the removal of the anion dye, Orange II. Orange II exists in the interlayer region, not only through the electrostatic interactions between the anionic sulfonic acid groups of Orange II and the interlayer Al polycations, but also through the hydrophobic interactions between Orange II molecules and grafted silane. With particular emphasis on the absorbents prepared in cyclohexane, the removal rate of Orange II remains at 98.7% when the initial concentration is 1000mgl−1. A continuous organic phase is formed in the interlayer space of the products prepared in cyclohexane. The removal of Orange II with this adsorbent is based on both the adsorption on the interface and the partition between the water and the interlayer organic phases.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • The effect of montmorillonite clay in alginate gel beads for
           polychlorinated biphenyl adsorption: Isothermal and kinetic studies
    • Abstract: Publication date: Available online 22 July 2014
      Source:Applied Clay Science
      Author(s): Salvatore Barreca , Santino Orecchio , Andrea Pace
      Beads of alginate montmorillonite have been used as sorbent for polychlorinated biphenyls from aqueous solutions. The structure and the differences between the different beads were established by IR spectroscopy (FT-IR). The adsorption at 25°C has been studied in a batch system, following its kinetics and assessing adsorbent dose, initial PCB concentrations, and pH effects. The results show that increasing the initial concentration of the PCBs and the adsorption time favored the adsorption. Adsorption isotherm data were modeled using Chapman, Freundlich and Langmuir adsorption isotherms and the appropriate parameters were calculated. Adsorption of trichlorobiphenyls on alginate–montmorillonite beads followed a Freundlich isotherm type model, while adsorption of tetra-, penta-, and hexachlorobiphenyls displayed a sigmoid-shaped (S-type) isotherm fitting the Chapman sigmoidal equation with the highest non-linear R2 values among the three tested models. By comparing the percentage adsorptions using the same number of beads (same volumes), best removals were obtained by using alginate montmorillonite beads. Kinetic models were investigated to determine the mechanism of adsorption showing a best fit for the pseudo-second order model (R2 from 0.998 to 0.982). Moreover, to underline the effect of montmorillonite in alginate gel beads, we have compared the isothermal adsorption curves between alginate montmorillonite and alginate beads.


      PubDate: 2014-07-27T22:14:31Z
       
  • Phosphate recovery by generating hydroxyapatite via reaction of calcium
           eluted from layered double hydroxides
    • Abstract: Publication date: Available online 22 July 2014
      Source:Applied Clay Science
      Author(s): Hideyuki Tsuji , Shigeo Fujii
      Ca/Fe ([Ca2+]/[Fe3+])-based layered double hydroxides (CF-LDHs) were designed and synthesized with the aim of developing an adsorbent that can recover phosphorous from aqueous solution and then be directly used as fertilizer. Fundamental properties of phosphate recovery and reaction mechanisms between CF-LDHs and phosphate were investigated. The adsorption isotherm of CF-LDH was fit by the Langmuir isotherm at a low Ca/Fe molar ratio (=1). However, CF-LDHs exhibited a larger adsorption volume of phosphate at high Ca/Fe molar ratios (=2 and 3) than low Ca/Fe molar ratios or conventional Mg/Al ([Mg2+]/[Al3+])-based LDHs. At high Ca/Fe molar ratios, CF-LDH reacted with phosphate through a reaction mechanism different from that of the conventional LDHs. Whereas ion exchange is the primary mechanism of the reaction between the conventional LDHs and phosphate, CF-LDHs released calcium into aqueous solution and the reaction of calcium and phosphate generated hydroxyapatite. The amount of phosphate recovered depended on the amount of calcium that eluted from CF-LDH and on pH, which is affected by the hydroxyl groups of CF-LDH. Hydroxyapatite was generated more efficiently under alkaline conditions, indicating the involvement of a supersaturated state in hydroxyapatite generation.


      PubDate: 2014-07-27T22:14:31Z
       
  • First evidence of singlet oxygen species mechanism in silicate clay for
           antimicrobial behavior
    • Abstract: Publication date: Available online 22 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • The influence of disaggregation procedures on soil gravitational
           separation
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Enzo Salemi , Umberto Tessari , Nicolò Colombani , Micol Mastrocicco
      The use of dispersants in particle size analysis is a common practice, but this could cause bias on the gravitational separation of the different particle fractions in natural soil. The study highlights the results obtained in gravitational separation of silty and clayey fractions by using hydrogen peroxide (H2O2) and sodium hexametaphosphate ((NaPO3)6) in different combinations. The efficiency of the different treatments was verified by comparison against the results obtained on the same sediments without any treatment. The separation method is based on Stokes law to calculate the settling time of particles in deionized water under controlled temperature. This method was applied to three different agricultural soils of the Po River Plain. The sample treated with H2O2 and (NaPO3)6 at 4% showed the best results in terms of particle size degree of purity, ranging from 95% to 97% for clay and from 91% to 95% for silt. The degree of purity indicates the percentage of sediment with the particles of the provided grain sizes.


      PubDate: 2014-07-27T22:14:31Z
       
  • Effect of polyethylene oxide (PEO) and shear rate on rheological
           properties of bentonite clay
    • Abstract: Publication date: Available online 26 July 2014
      Source:Applied Clay Science
      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: 2014-07-27T22:14:31Z
       
  • Study of the modification of montmorillonite with monofunctional and
           trifunctional vinyl chlorosilane
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Sanam Sepehri , Mehdi Rafizadeh , Mahmoud Hemmati , Hosein Bouhendi
      Montmorillonite (Cloisite®Na+) was modified with dimethylchlorovinylsilane (DMCVS) and trichlorovinylsilane (TCVS), in order to replace the silanol groups of clay mineral with silane vinyl groups (silylation reaction). The grafting reaction was studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Variation of the grafted amount and the grafting yield was evaluated as a function of the initial silane concentration. The grafted amount was increased with both mono- and trichlorosilane concentrations; where, the reaction yield decreased. Since the reaction will liberate HCl, the effect of the presence of NaHCO3 in the reaction media, was studied. Silylation with monofunctional silane leads to higher grafting amount compared to silylation with trifunctional one. The mechanism of silylation reaction was determined and the effect of the number of silane functional groups on the reaction mechanism was studied. The highest grafted amount and grafting yield were achieved with the initial silane concentration of ~4mmol/g of DMCVS. The basal spacing of the silylated montmorillonites (Mt) was observed to be more than the basal spacing of pristine Mt.


      PubDate: 2014-07-27T22:14:31Z
       
  • Clean production of CTAB-montmorillonite: formation mechanism and swelling
           behavior in xylene
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Wei Hua Yu , Qian Qian Ren , Dong Shen Tong , Chun Hui Zhou , Hao Wang
      Organo-montmorillonite (OMt) with high swellability in a hydrophobic medium such as xylene was successfully prepared. The process was realized by clean and simple modification of Ca2+-montmorillonite (Ca2+-Mt) with cetyltrimethylammonium bromide (CTAB) dispersed in very small amounts of water and ethanol. In the process, there were no needs for the steps of a Na+-exchange reaction and washing. The mechanisms of formation of OMt and its swellability in xylene were investigated. The distribution of cetyltrimethylammonium (CTA+) cations and CTAB molecules adsorbed in the interlayer spaces, CTAB molecules adsorbed on the external surfaces and free CTAB molecules in the resultant OMt products was determined by the thermogravimetric (TG) and differential thermogravimetry (DTG) of the washed and unwashed OMt. The arrangement models of CTA+ cations in the interlayer spaces were deduced from powder X-ray diffraction (XRD) patterns and Fourier transform infrared (FT-IR) spectra. The results suggested that CTA+ cations and CTAB molecules adsorbed in the interlayer spaces and CTAB molecules adsorbed on the external surfaces of OMt played a role in the modification of Ca2+-Mt by ion exchange, hydrophobic interactions and van der Waals forces. Addition of ethanol into the preparation mixture was favorable for binding more CTA+ cations and CTAB molecules in the interlayer spaces of OMt and enhanced dispersion of clay particles. A maximal 64.0% colloid yield in xylene for the OMt sample, which was higher than that of the commercial OMt produced by a multistep process, was achieved. The formation of good gel-like structure of OMt in xylene depended on proper distribution of CTAB molecules and CTA+ cations on the external and internal surfaces of OMt, ordered arrangements of CTA+ cations in the interlayer spaces of OMt and the small sizes of dispersed OMt particles. A large volume of the networks of OMt particles in xylene was formed by edge-to-edge, face-to-face and face-to-edge between neighboring Mt particles and multifacial linking.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • Evaluation of gas permeability and mechanical behaviour of soil barriers
           of landfill cap covers through laboratory tests
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): S. Rajesh , J.P. Gourc , B.V.S. Viswanadham
      The soil barrier is one of the commonly used impervious barriers which are required to sustain deformation and prevent the migration of biogas to the atmosphere. In the present study, a simple custom designed gas permeability–bending test setup was developed and used to evaluate the deformation behaviour of the soil barrier material in-relation with gas permeability measurements. A series of conventional beam bending tests, unconfined compression tests and gas permeability–bending tests was performed to evaluate the influence of loading pattern, compaction characteristics and fibre reinforcement on the deformation behaviour of the soil barrier material. The experimental results reveal that loading pattern was not found to have any significant influence on the flexural tensile strength of the soil; however, a considerable influence on the displacement corresponding to gas breakthrough was noticed mainly due to the variation in the cracking pattern. An increase in the moulding moisture content of the soil leads to a significant delay in crack initiation and gas breakthrough with a slight reduction in the flexural tensile strength. The percentage increase in the flexural tensile strength of the soil beam compacted with 2% and 4% wet of optimum, upon inclusion of fibres was found to be 33% and 92% respectively. Similarly, the percentage increase in the limiting displacement of the soil moist-compacted at 2% and 4% wet of optimum, upon inclusion of fibres was found to be 30% and 25% respectively, which implies that soil reinforced with fibres can sustain its integrity in-terms of gas intactness up to relatively larger distortion than an un-reinforced soil barrier material. The performance of the deformation behaviour of the soil barrier material has significantly improved in-terms of flexural tensile strength and gas intactness upon inclusion of discrete fibre inclusions within the soil.


      PubDate: 2014-07-27T22:14:31Z
       
  • Organoclay maleated natural rubber nanocomposite. Prediction of abrasion
           and mechanical properties by artificial neural network and adaptive
           neuro-fuzzy inference
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Mahsa Nematollahi , Azam Jalali-Arani , Karim Golzar
      Maleated natural rubber (MNR) was produced and employed in different amounts as compatibilizer in preparation of organoclay/natural rubber (OC/NR) nanocomposite. Oscillating disk rheometry, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, rheomechanical spectroscopy, dynamic mechanical analysis, tensile and abrasion tests were used to evaluate the prepared samples. The obtained results showed that the use of MNR caused an increase in the maximum torque of rheometry, curing rate index and crosslink density. XRD analysis indicated that using of MNR, especially in the amount of 8 parts, resulted in a greater intercalation of OC layers. SEM showed a good dispersion of the OC as well as higher interfacial interaction between NR molecules and OC. These lead to improvement of modulus, tensile strength and abrasion resistance. Then the obtained results were modeled by artificial intelligence techniques. Comparison made between experimental and predicted values, indicated that the modeling results were in good agreement with the corresponding experimental amounts.


      PubDate: 2014-07-27T22:14:31Z
       
  • Montmorillonite for starch-based barrier dispersion coating — Part
           1: The influence of citric acid and poly(ethylene glycol) on viscosity and
           barrier properties
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Erik Olsson , Caisa Johansson , Lars Järnström
      Starch-based coating formulations were draw-down coated on a paper substrate and the effect on the water vapor transmission rate, WVTR, upon montmorillonite, Mt addition was compared to that of the pure starch matrix and for poly(ethylene glycol), PEG, or citric acid, CA, as potential plasticizers. Both PEG and CA were added at a ratio of 3 to 10 to starch. Addition of CA to the starch substantially lowered the WVTR of the coated papers compared to coating with pure starch or PEG plasticized starch. The WVTR of the papers coated with just starch and CA was lower than that obtained for paper coated with the non-plasticized Mt–starch dispersion, and approximately the same as paper coated with Mt–starch dispersions plasticized with PEG or CA. Addition of Mt was effective in reducing the WVTR in the case of starch plasticized by PEG but not with CA. These differences in WVTR reduction were indicated to be due to differences in the viscosity and clay swelling indicating that CA and PEG affected the Mt dispersion differently. CA was also investigated as a dispersing agent by addition in small quantities to the montmorillonite at different pHs. When this Mt dispersion was added to a starch containing PEG, CA gave slightly reduced plastic viscosity and showed a potential to further reduce the WVTR.


      PubDate: 2014-07-27T22:14:31Z
       
  • Montmorillonite for starch-based barrier dispersion coating — Part
           2: Pilot trials and PE-lamination
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Erik Olsson , Caisa Johansson , Johan Larsson , Lars Järnström
      Montmorillonite, Mt, have been shown to improve the barrier properties of thermoplastic starch coatings. In this paper, it is shown that it is possible to scale-up a recipe containing poly(ethylene glycol)-plasticized starch and a citric acid-dispersed Mt to pilot scale and to achieve water vapor barrier properties which are comparable to those achieved in laboratory scale. The results are compared with those obtained with two commercial synthetic barrier dispersions. The combination of a polyethylene film laminated on top of a 3g/m2 starch-based coating showed the potential to give also oxygen barrier properties to the multilayer structure when applied on a paper substrate.


      PubDate: 2014-07-27T22:14:31Z
       
  • Chemical stability of Laponite in aqueous media
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Shweta Jatav , Yogesh M. Joshi
      In this work the stability of Laponite against dissolution in its aqueous dispersions is investigated as a function of initial pH of water before mixing Laponite, and concentration of Laponite. Dissolution of Laponite is quantified in terms of the concentration of leached magnesium in the dispersions. Interestingly the solvent pH is observed to play no role in the dissolution of Laponite in dispersion over the explored range of 3 to 10. Furthermore, contrary to the usual belief that Laponite dissolves when the pH of aqueous dispersion decreases below 9, the dissolution of the same is observed even though dispersion pH is above 10 for low concentrations of Laponite (1 and 1.7mass%). On the other hand, for dispersions having a high concentration of Laponite (2.8mass%) and pH in the similar range (>10) no dissolution is observed. Measurement of ionic conductivity of dispersion shows that the concentration of sodium ions in dispersion increases with the concentration of Laponite, which appears to have a role in preventing the dissolution of Laponite.


      PubDate: 2014-07-27T22:14:31Z
       
  • Structure and dynamic properties of water saturated CTMA-montmorillonite:
           molecular dynamics simulations
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Qing Zhou , Wei Shen , Jianxi Zhu , Runliang Zhu , Hongping He , Jinhong Zhou , Peng Yuan
      The interlayer structure of wet organoclays has attracted great interest due to its close relation with adsorption process but still remains ambiguous at the atomic level. In this study, the structure and dynamics of cetyltrimethylammonium (CTMA+) intercalated montmorillonite (Mt) in the water saturated condition were investigated by molecular dynamics (MD) simulations. Two Mt models with different cation exchange capacity (CEC) were selected and various amounts of CTMA+ were added to achieve different loading levels based on experiments. The simulation results show that as the surfactant loading level increases, the arrangement of CTMA+ transforms from bilayer to inclined paraffin-type with a large amount of water in the interlayer space, indicating a different configuration from dry systems. The conformations of CTMA+ are influenced by water molecules and surfactant loading level. Compared to the dry models, the percentage of gauche conformations of CTMA+ decreases in the water saturated condition. In the cases of incomplete cation exchange, the confinement from silicate surface may lead to more ordered structure of alkyl chains. In the cases of excessive surfactant loading, the percentage of gauche conformation decreases due to the steric hindrance. Moreover, the ammonium head groups of CTMA+ are found to locate close to the center of six-member ring of silicate surface and coordinated with 4–6 water molecules. Their mobility is low due to the electrostatic interactions while the alkyl chains show higher mobility. Mt with a higher CEC has a stronger confining effect on both alkylammonium and water, which then reduces the mobility of alkyl chains and water molecules within the interlayer space.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • Fatty acids promote fulvic acid intercalation by montmorillonite
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): William E. Dubbin , Jonathan P. Vetterlein , Jörgen L. Jonsson
      Organic matter (OM) adsorbed to the interlamellar surfaces of swelling clay minerals is particularly stable, with residence times as long as 2000 to 10,000years. Intercalation of OM by smectitic clay minerals may therefore increase the stable C reservoir in both soils and sediments. However, the precise mechanisms of adsorption and intercalation of the myriad organic constituents by swelling clay minerals in soils and sediments remain unresolved. Model adsorption experiments with montmorillonite (Mt), a ubiquitous expanding layer silicate, showed that environmentally relevant fatty acids possessing long-chain alkyl C facilitate the adsorption and subsequent intercalation of fulvic acid (FA). Palmityl palmitate, comprising two C16:0 chains, promotes greater FA adsorption than does stearic acid, the latter possessing a single C18:0 chain. Furthermore, maximum FA interlayer adsorption was observed where the fatty acid was adsorbed to Mt prior to introduction of the humic material; the alkyl C chains of the fatty acid evidently serving as attachment points to enhance uptake and optimize placement of FA at the margins of the interlayer space. These data reveal a previously unknown mechanism through which humic materials become intercalated by expanding layer silicates, thus contributing to the stable OM pool in soils and sediments.


      PubDate: 2014-07-27T22:14:31Z
       
  • Characterisation of montmorillonites simultaneously modified with an
           organic dye and an ammonium salt at different dye/salt ratios. Properties
           of these modified montmorillonites EVA nanocomposites
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): M.I. Beltrán , V. Benavente , V. Marchante , H. Dema , A. Marcilla
      In this work, a sodium montmorillonite (Na+-Mt) was modified with two molecules simultaneously, an organic dye, methylene blue (MB), and ethyl hexadecyl dimethyl ammonium (EHDDMA). The synthesised organo-montmorillonites (OMt) combining different proportions of the two molecules were thoroughly characterised and mixed with ethylene vinyl acetate copolymer (EVA) in order to check the ability of these OMt as pigments and reinforcing additives. The synthesised OMt combining both surfactants, MB and EHDDMA, present higher interlayer distances than those with only MB, which were employed in previous works as nanopigments. When these OMt were incorporated in the EVA matrix, the obtained clay polymer nanocomposites (CPN) showed a high exfoliation degree of the OMt in the polymer, in such a way that at 80% of the cationic exchange capacity (CEC) of the Mt exchanged with EHDDMA, most of the OMt was exfoliated. Moreover, all the obtained CPN showed an increase in the Young's Moduli compared to the EVA reference, and especially those containing higher amounts of MB. The thermal stability of the CPN also increases with the MB content, compared to other CPN including conventional surfactants. The hiding power and colouring power achieved in the CPN are higher even with a much lower load of MB when EHDDMA is exchanged in the Mt.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • pH sensitive halloysite-sodium hyaluronate/poly(hydroxyethyl methacrylate)
           nanocomposites for colon cancer drug delivery
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Kummara Madhusudana Rao , Saravanan Nagappan , Deok Jin Seo , Chang-Sik Ha
      A safe and efficient halloysite-nanocomposite hydrogel for colon cancer drug delivery was synthesized using biocompatible and biodegradable materials composed of sodium hyaluronate with poly(hydroxyethyl methacrylate). Fourier-transform infra-red spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy were performed to confirm the formation, crystallinity, thermal and morphological properties of the nanocomposite hydrogel. The hydrogels exhibited good swelling properties in a pH sensitive manner. 5-Fluorouracil (5-FU), an anticancer drug, was encapsulated successfully into these hydrogels as well as inside the halloysite nanotubes through equilibrium swelling followed by pulling and breaking the vacuum. Transmission electron microscopy showed that 5-FU was also encapsulated in the halloysite nanotubes. In vitro release experiments were performed at 37°C in stimulated gastric fluid (pH1.2) for 2h followed by stimulated intestinal medium (pH7.4). It was found that the release of 5-FU from nanocomposite hydrogels followed pH-dependent controlled release as compared to that of conventional hydrogels. From the in vitro release studies it was found that the nanocomposite hydrogels are more efficient for colon cancer drug delivery.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • Model evaluation of geochemically induced swelling/shrinkage in
           argillaceous formations for nuclear waste disposal
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Liange Zheng , Jonny Rutqvist , Hui-Hai Liu , Jens T. Birkholzer , Eric Sonnenthal
      Argillaceous formations are being considered as host rocks for geologic disposal of nuclear waste in a number of countries. One advantage of emplacing nuclear waste in such formations is the potential self-sealing capability of clay due to swelling, which is of particular importance for the sealing and healing of disturbed rock zones (DRZ). It is therefore necessary to understand and be able to predict the changes in swelling properties within clay rock near the waste-emplacement tunnel. In this paper, considering that the clay rock formation is mostly under saturated conditions and the swelling property changes are mostly due to geochemical changes, we propose a modeling method that links a THC simulator with a swelling module that is based on diffuse double layer theory. Simulations were conducted to evaluate the geochemically induced changes in the swelling properties of the clay rock. Our findings are as follows: (1) geochemically induced swelling/shrinkage occurs exclusively in the EBS–clay formation interface, within a few meters from the waste-emplacement tunnels; (2) swelling/shrinkage-induced porosity changes are generally much smaller than those caused by mineral precipitation/dissolution processes; (3) geochemically induced swelling/shrinkage of the host clay rock is affected by variations in the pore water chemistry, exchangeable cations, and smectite abundance. Neglecting any of these three factors might lead to a miscalculation of the geochemically induced swelling pressure.


      PubDate: 2014-07-27T22:14:31Z
       
  • Adsorption of arsenic on modified montmorillonite
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Xiaohui Ren , Zilong Zhang , Hanjin Luo , Bingjie Hu , Zhi Dang , Chen Yang , Luye Li
      Fe polycations and cetyltrimethylammonium bromide (CTMAB) were used to synthesize modified montmorillonite. Arsenic removal by modified montmorillonite was investigated through effects of reaction time, adsorbent dosage, solution pH, as well as the associated adsorption isotherms and kinetics. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to explore the characteristics of the raw and modified montmorillonite. It was found that CTMAB had entered the interlayer of the raw montmorillonite (Mont) while Fe polycations adsorbed on the outer surface and formed small flocculent particles. All adsorption processes reached equilibrium within 20min. Pseudo-second-order kinetics and Langmuir adsorption model fit the experimental well. The adsorption capacity on C–Fe–M and Fe–M were 8.85 and 15.15mgg−1 for As(V), respectively, and 13.89 and 16.13mgg−1 for As(III). The adsorption of As(V)/As(III) on modified montmorillonite was significant in the pH range of 4–10. The removal rate exceeded 99% under the condition of pH range 2–10 for As(V). All results showed that modified montmorillonite has a good affinity towards As(V) and As(III). The sorption mechanisms were mainly surface adsorption and electrostatic adhesion.


      PubDate: 2014-07-27T22:14:31Z
       
  • Delaminated and intercalated organically modified montmorillonite in
           poly(1,4-cis-isoprene) matrix. Indications of counterintuitive
           dynamic-mechanical behavior
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Maurizio Galimberti , Michele Coombs , Valeria Cipolletti , Anna Spatola , Gaetano Guerra , Angela Lostritto , Luca Giannini , Stefano Pandini , Theonis Riccò
      Montmorillonite (Mt) and Mt organically modified (OMt) with dimethyl ditalloyl ammonium cations were delaminated through ball milling. X-ray diffraction (XRD) analysis allowed the observation a more efficient delamination for OMt than for Mt. In fact, 90% delamination was obtained for OMt, without appreciable variations of the in-plane Mt order. About 60% delamination was obtained for pristine Mt, in the presence of a substantial reduction (up to 40%) of crystalline order in the structural planes. A reflection due to the rotator order of talloyl chains was found both in pristine and in extensively delaminated OMt samples. Polymer nanocomposites based on poly(1,4-cis-isoprene) were prepared with two types of OMt: OMt, unmilled, with the ammonium cation intercalated in the interlayer space (I-OMt) and 90% delaminated OMt (D-OMt). XRD analysis of clay polymer nanocomposites (CPNs) revealed the unaltered crystalline order of I-OMt and a nearly complete maintenance of the delaminated structure of D-OMt. Dynamic-mechanical characterization of CPN gave counterintuitive results. I-OMt revealed a higher tendency to give rise to the filler networking phenomenon, in samples crosslinked with a sulfur based system. Moreover, I-OMt gave rise to a more pronounced extension of the rubbery plateau at low frequencies, in uncrosslinked masterbatches. This behavior is attributed to the higher volume fraction of I-OMt, as the intercalated alkylammoniums contribute to the I-OMt volume, whereas they essentially act as compatibilizers in D-OMt. Delamination of OMt is thus presented as a powerful tool to reduce the dissipation of energy in dynamic-mechanical applications of polymer melts and elastomers.


      PubDate: 2014-07-27T22:14:31Z
       
  • Editorial Board
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98




      PubDate: 2014-07-27T22:14:31Z
       
  • Hydrothermally synthesized zeolites based on kaolinite: A review
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): E.B.G. Johnson , Sazmal E. Arshad
      Many types of zeolites have been developed based on kaolinite in previous years. This review focuses on the current reports of kaolinite-based zeolites and the important factors in their synthesis. Among the factors discussed in this review are the effect of SiO2/Al2O3 (Si/Al) molar ratio of the gel mixture, metakaolinization time and temperature, aging condition, alkalinity, and crystallization time and temperature. This review only covers the most recent kaolinite-based zeolite papers published from 2005 to present. A brief discussion on the evolution of zeolites is also included.


      PubDate: 2014-07-27T22:14:31Z
       
  • Influence of magnetic field on the adsorption of organic compound by clays
           modified with iron
    • Abstract: Publication date: August 2014
      Source:Applied Clay Science, Volumes 97–98
      Author(s): Aline Auxiliadora Tireli , Francielle Candian Firmino Marcos , Laís Ferreira Oliveira , Iara do Rosário Guimarães , Mário César Guerreiro , Joaquim Paulo Silva
      Insertion of iron into montmorillonite (Mt) resulted in two modified materials, when different treatments were used: i) pillared clay (FePILC) and ii) magnetic clay (FeMAG). The ability of the modified clays to remove the organic dye methylene blue (MB) by adsorption was tested. Additionally, we evaluated the effects of adsorption after exposure to a pulsed magnetic field, the results were monitored by UV–vis spectroscopy and chemical analysis of total organic carbon. All materials were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), temperature-programmed reduction (TPR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and specific surface area measurements. The catalytic activity of the clays modified with iron was evaluated in hydrogen peroxide decomposition reaction. The XRD patterns show the formation of crystalline iron phases on the surface of the clays, besides confirming the pillaring procedure for FePILC with a basal spacing of 1.79nm, an increase of 0.53nm over the montmorillonite. The specific surface area of FePILC was 210.9m2/g. FeMAG had part of this original structure broken, with an area of 177.1m2/g and magnetic properties demonstrated by the attraction to a permanent magnet. The TPR profiles and EDS indicated that the different heat treatments exerted great influence on the amount and phases of iron formed. The materials showed high capacity for removal of the MB dye, and the isotherms fit the Langmuir model. Adsorption of the dye significantly increased in the presence of a magnetic field, changing the Langmuir parameters and especially the maximum adsorption capacity for all materials. The best results were observed for FeMAG.
      Graphical abstract image

      PubDate: 2014-07-27T22:14:31Z
       
  • Dissolution of iron in salicylic acid and cation exchange between
           Fe(II)-salicylate and Na-montmorillonite to form Fe(II)-montmorillonite
    • Abstract: Publication date: Available online 2 June 2014
      Source:Applied Clay Science
      Author(s): Belenahalli M. Vinoda , Jayappa Manjanna
      Bentonite is used as part of engineered barrier in the geological disposal of high-level nuclear waste (HLW) from nuclear plants. Fe(II)-montmorillonite, Fe(II)-Mt, is a potential altered clay in such a system due to clay mineral interaction with the carbon steel (overpack material) under reducing water chemistry conditions. To understand the long-term integrity of the HLW, the basic studies on Fe(II)-Mt are needed. In this study, we have focused on the synthesis of homoionic Fe(II)-Mt by using weak ferrous complexe for cation-exchange with Na-Mt. We prepared Fe(II)-salicylate by dissolving Fe0 in salicylic acid at 80°C under N2 atmosphere. Dissolution rate constants are in the range of 0.8–1.6×10−3 min−1. A colorless Fe(II)-L, was reasonably stable in the inert atmosphere, but was rapidly oxidized in air to a red colored Fe(III)-L (λ max 475nm). The solution redox potential and UV–Vis absorption spectra of these complexes are recorded here. Na-Mt was subjected for ion-exchange reaction with Fe(II)-L to form Fe(II)-Mt. The formation of Fe(II)-Mt was confirmed from the interlayer Fe2+ ions released by interacting with 0.5M H2SO4. The cumulative amount of Fe2+ ions are equivalent to CEC of 1.10meq/g and Fe2+/Fetotal ≈1. The X-ray diffraction patterns (d001) and infrared spectra also support the formation of Fe(II)-Mt. The cation exchange achieved here was possible through dissociation of Fe(II)-L owing to its intermediate stability constant (log K=6.55), unlike the Fe(III)-L (log K=16.35). We believe the present method is one of the best approaches for obtaining homoionic Fe(II)-Mt.


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


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


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

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


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


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


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

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


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

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


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

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

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


      PubDate: 2014-06-14T17:11:06Z
       
 
 
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