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  Subjects -> EARTH SCIENCES (Total: 636 journals)
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EARTH SCIENCES (462 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     Open Access   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 9)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 4)
Advances in High Energy Physics     Open Access   (Followers: 11)
Advances In Physics     Hybrid Journal   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 3)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 12)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 6)
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: 1)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 2)
Annals of Geophysics     Full-text available via subscription   (Followers: 10)
Annals of GIS     Hybrid Journal   (Followers: 18)
Annals of Glaciology     Full-text available via subscription   (Followers: 2)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 11)
Anthropocene     Hybrid Journal  
Anthropocene Review     Hybrid Journal   (Followers: 3)
Applied Clay Science     Hybrid Journal   (Followers: 3)
Applied Geochemistry     Hybrid Journal   (Followers: 8)
Applied Geomatics     Hybrid Journal   (Followers: 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: 10)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 20)
Arctic Science     Open Access   (Followers: 4)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 9)
Artificial Satellites     Open Access   (Followers: 14)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 19)
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: 7)
Atmospheric and Climate Sciences     Open Access   (Followers: 15)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 12)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 10)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 9)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 18)
Bulletin of Volcanology     Hybrid Journal   (Followers: 16)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 13)
Canadian Mineralogist     Full-text available via subscription   (Followers: 2)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 4)
Chemical Geology     Hybrid Journal   (Followers: 10)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 5)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 2)
Ciencia del suelo     Open Access  
Ciencias Espaciales     Open Access  
Climate and Development     Hybrid Journal   (Followers: 12)
Coastal Management     Hybrid Journal   (Followers: 17)
Cogent Geoscience     Open Access  
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 6)
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 7)
Contemporary Trends in Geoscience     Open Access   (Followers: 2)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 8)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 16)
Cretaceous Research     Hybrid Journal   (Followers: 6)
Cybergeo : European Journal of Geography     Open Access   (Followers: 5)
Depositional Record     Open Access  
Developments in Geotectonics     Full-text available via subscription   (Followers: 3)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
E&S Engineering and Science     Open Access  
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 86)
Earth and Space Science     Open Access  
Earth Interactions     Full-text available via subscription   (Followers: 11)
Earth Science Research     Open Access   (Followers: 7)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 3)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 13)
Earth System Dynamics     Open Access   (Followers: 7)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 3)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Science     Hybrid Journal   (Followers: 8)
Earthquake Spectra     Full-text available via subscription   (Followers: 13)
Ecohydrology     Hybrid Journal   (Followers: 10)
Electromagnetics     Hybrid Journal   (Followers: 2)
Energy Efficiency     Hybrid Journal   (Followers: 12)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 3)
Environmental Earth Sciences     Hybrid Journal   (Followers: 12)

        1 2 3 4 5 | Last

Journal Cover   Applied Clay Science
  [SJR: 1.17]   [H-I: 71]   [3 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2807 journals]
  • Microstructural evolution, phase transformation, and variations in
           physical properties of coal series kaolin powder compact during firing
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Xiaohong Xu, Xinbin Lao, Jianfeng Wu, Yaxiang Zhang, Xiaoyang Xu, Kun Li
      Coal series kaolin (CSK) from coalmine in Shanxi, China was studied in the form of powder compact by using die-pressing technique. Mineralogical, morphological, and chemical characteristics of CSK were given. The microstructural evolution, phase transformation, and relevant variations in physical properties of the fired CSK with elevating temperature were investigated. Results indicated that mullite began to form at the temperature as low as 1002.8°C. Columnar mullite appeared when firing at 1500°C. Transformation of cristobalite to liquid phase favored the densification of the fired powder compacts and made them acquire the densest microstructure in 1580–1600°C temperature interval. Die-pressing technique and flake-like nature of CSK particle induced the interlocking texture on the plane perpendicular to die-pressing direction. Low content of impurities as TiO2 and Fe2O3 increased the formation temperature of the columnar mullite and endowed samples with high refractoriness (as high as 1600°C). The advantages of using CSK for industrial ceramic preparation are its high purity, low mullitization temperature, and high refractoriness.


      PubDate: 2015-07-28T20:48:25Z
       
  • Estimation of material and interfacial/interphase properties in
           clay/polymer nanocomposites by yield strength data
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Yasser Zare
      In this article, a new and simple approach is presented for calculation of material and interfacial/interphase properties in clay/polymer nanocomposites (CPN) by the experimental results of yield strength. The “B” interaction parameter from Pukanszky model is correlated with several material and interfacial/interphase characteristics such as yield strength of polymer matrix (σm), the aspect ratio of clay (α), the stress transfer parameter (s), thickness (ti) and strength (σi) of interphase. The suggested equations are applied to calculate and examine the material and interfacial/interphase properties for several samples of CPN. Also, the effects of all parameters on “σi” and “ti” are determined to predict the relations between material and interfacial/interphase properties. According to the suggested equations, low “B” and high “ti” produced insignificant “σi” in CPN. Furthermore, a thick interphase caused a large stress transfer from polymer matrix to clay at interphase region.


      PubDate: 2015-07-27T22:36:08Z
       
  • Fe2O3–palygorskite nanoparticles, efficient adsorbates for pesticide
           removal
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Affaf Ouali, Lala Setti Belaroui, Abdelkader Bengueddach, Alberto Lopez Galindo, Aránzazu Peña
      Recently, magnetic adsorbents have aroused a significant attention because of their excellent adsorption capacity. An Algerian palygorskite/magnetic iron oxide was prepared by chemical co-precipitation and characterized using infrared spectroscopy, X-ray diffraction and X-ray fluorescence. The results prove the formation of a red brick powder, with magnetic character, showing a high percentage of iron oxide on palygorskite. To verify the ability of the magnetic palygorskite for retaining organic pollutants, three different samples were evaluated for the adsorption of the fungicide fenarimol from aqueous samples: sifted palygorskite, purified palygorskite and Fe2O3/palygorskite. The effects of different variables were assessed: adsorbent mass, reaction time, initial pesticide concentration and desorption stability. Fenarimol adsorption kinetics followed a pseudo-second order model. The adsorption rates were 11%, 50% and 70%, for sifted, purified and Fe2O3/palygorskite, respectively. Both Langmuir and Freundlich models could be used to describe fenarimol adsorption on sifted and purified palygorskites. However only the Freundlich model could fit the adsorption data on Fe2O3/palygorskite, probably due to the adsorbent heterogeneity. Stability of fenarimol desorption from the three samples, where the fungicide had been previously preadsorbed, showed that the extent of desorbed fenarimol from Fe2O3/palygorskite remained constant along the studied period (15days).


      PubDate: 2015-07-27T22:36:08Z
       
  • Effect of metakaolin addition and seawater mixing on the properties and
           hydration of concrete
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Qiu Li, Haining Geng, Zhonghe Shui, Yun Huang
      The effect of metakaolin (MK) and seawater mixing on the properties and hydration products of concrete was studied by analytical techniques. MK improved compressive strength by refining pore structure without altering porosity. Seawater increased compressive strength at early age without altering pore structure. The combination of MK and seawater improved both early and later age strength. Hydration products in pastes containing MK were Portlandite, ettringite, hemicarboaluminate, monocarboaluminate and C-S-H gels. In pastes with seawater, instead of hemicarboaluminate and monocarboaluminate, hydrocalumite was identified. MK promoted hydrocalumite formation. MK decreased CH content with increase of MK content and age. Seawater increased CH content at early age with MK content. The combination increased CH content at early age and decreased later. At 28days, most chloride in seawater was immobilized by hydrocalumite. The combination improved properties of concrete at both early and later age.


      PubDate: 2015-07-27T22:36:08Z
       
  • Preparation and characterization of novel composite AlCr-pillared clays
           and preliminary investigation for benzene adsorption
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Menglin Ding, Shufeng Zuo, Chenze Qi
      In this study, a one-step high-temperature and high-pressure method was used to synthesize AlCr composite pillaring agents. Compared to conventional methods, the method greatly reduced the steps and material consumption. A series of composite AlCr-pillared clays (AlCr-PILC) were synthesized by ion exchange. The structure of the AlCr composite pillaring agent could be altered by changing the Al/Cr molar ratio, reaction temperature, and reaction time, thereby affecting the structure and properties of AlCr-PILC (including surface area, pore volume, pore diameter, and basal spacing). The structure and properties of the experimental materials were characterized by X-ray diffraction, N2 adsorption, high-resolution electron microscopy, and benzene adsorption and desorption experiments. The results indicated that after 4h of calcination at 550°C, the specific surface area, pore volume, and maximum basal spacing of AlCr-PILC reached 266–362m2/g, 0.16–0.22cm3/g, and 2.06nm, respectively. The benzene adsorption capacity of the synthesized AlCr-PILC was much larger than the capacity of the starting clays, reaching 48.3μmol/g. In addition, complete desorption could be achieved at 250°C. Therefore, the synthesized AlCr-PILC was a good material for adsorption.
      Graphical abstract image

      PubDate: 2015-07-23T22:22:40Z
       
  • Susceptibility of strength development by lime in gypsiferous soil—A
           micro mechanistic study
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Arvind Kumar Jha, P.V. Sivapullaiah
      The role of gypsum on the strength of lime treated soils after a long period of interaction is not well understood yet. The present study is performed to scrutinize the physical and strength behavior of lime treated soil with varying gypsum content. Lime and gypsum contents varying from 0 to 6% are considered in the present study for curing periods up to 28days. To understand the long-term effects, the work has been extended up to 365days, particularly with the use of 6% lime content and varying gypsum contents. Atterberg's limits turned out to be marginally affected by cation exchange. Unconfined compressive strength behavior of lime treated soil varies considerably with gypsum content and curing period. However, trivial alteration in strength is observed in the soil treated with lower lime content (up to 4%) and gypsum content up to 6%. On the contrary, strength of soil–6% lime mixture with addition of varying gypsum content shows acceleration in early strength at 14days curing period. However, the strength at 28days of curing declines but regains afterwards for 90days. The trend at longer curing period for 180 and 365days is, however, not unique but varies with gypsum contents. An attempt has been made to explain these changes on the basis of the form of gypsum, formation and conversion of reacted compounds (CASHH, CASH, CSH and Ettringite). The proposed explanations were supported by detailed characterization through thermal analysis, XRD, SEM and EDAX studies of soil–lime–gypsum mixtures.


      PubDate: 2015-07-23T22:22:40Z
       
  • Composition, firing behavior and ceramic properties of the Sejnène
           clays (Northwest Tunisia)
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): A. Bennour, S. Mahmoudi, E. Srasra, S. Boussen, N. Htira
      This study focuses on the results of various analyses and ceramic aptitude tests carried out on two representative clay samples of the Oligo-Miocene from Sejnène, in Northwest Tunisia. The original clays were characterized by chemical analysis, powder X-ray diffraction (XRD), TGA measurements, infrared spectroscopy, Bigot curves and evaluation of the plasticity. The mineralogical study proved that these clays are mainly composed of kaolinite and illite, with a small amount of interstratified I/S. The chemical analysis indicated that the clays of ClaySej1 are more siliceous than those of ClaySej2, which have higher levels of elemental fluxes (Fe2O3, Na2O, K2O and CaO). The mineralogical metamorphoses during the firing process were recorded via the X-ray diffraction of the raw clays and subsequent firing at 300, 600, 800, 1000 and 1200°C for 3h with a heating rate of 10°C/min. The main transformations were observed at 1000°C with the appearance of new crystalline phases especially in the ClaySej2 sample. The samples were hand-pressed in a rectangular mold and sintered at 950, 1050 and 1100°C with a heating rate of 10°C/min. The variations in flexural strength, linear shrinkage, water absorption and color were also determined and showed sensitivity to the chemical and mineralogical compositions.


      PubDate: 2015-07-23T22:22:40Z
       
  • Saponites containing divalent transition metal cations in octahedral
           positions — Exploration of synthesis possibilities using microwave
           radiation and NMR characterization
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): R. Trujillano, E. Rico, M.A. Vicente, V. Rives, I. Sobrados, J. Sanz
      The synthesis using microwave radiation of saponites containing Co2+, Zn2+ or Cu2+ in octahedral positions has been explored (in the case of Cu2+, together with Mg2+ or Ni2+). Pure saponite phases were formed under some synthesis conditions, although in other cases some impurities were also formed. Microwave treatment at 180°C favored the formation of ordered solids, but induced the crystallization of other phases in some cases. Cu2+-containing saponites were formed only if Mg2+ or Ni2+ were used as octahedral sheet co-cations. The solids were characterized by different techniques, including MAS-NMR spectroscopy, which gave very precise information in the case of Zn-saponite, allowing us to estimate the content of tetrahedral Al, but much more undefined information for samples with paramagnetic cations. Nevertheless, the presence of tetrahedral Fe3+ and octahedral Fe2+ species was evidenced. Cu2+ slightly perturbed the NMR signals, while Co2+ strongly perturbed 27Al, 23Na and especially 29Si NMR spectral signals.
      Graphical abstract image

      PubDate: 2015-07-23T22:22:40Z
       
  • Layered clay aqueous dispersion as a novel dye leveling agent in leather
           processing: Synthesis, characterization and application studies
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): Sujata Mandal, S. Natarajan, S. Suresh, R. Chandrasekar, G. Jothi, C. Muralidharan, Asit Baran Mandal
      Dyeing is an important process step of leather manufacture that is performed to obtain intended final color. Intensity variation and inconsistency in color characteristics among leathers processed in a batch are major concerns of tanners. Variations in final leather color result in either rework or rejection of leather leading to significant productivity and economic loss. Moreover, to produce certain natural-look leather products, uniform dyeing of the entire leather surface and color uniformity of the leathers among each batch are an absolute necessity. In this study, an aqueous dispersion of layered double hydroxide (LDH) has been synthesized and used as dye leveling agent in leather dyeing operation to enhance the shade intensity of the leather and color uniformity among different pieces of leathers. The physico-chemical characteristics of the LDH dispersion in water and its efficacy towards achieving the objective have been studied. Leathers processed using the aqueous dispersion of LDH showed excellent color uniformity and consistency with no detrimental effect on color fastness characteristics of the leather.
      Graphical abstract image

      PubDate: 2015-07-23T22:22:40Z
       
  • Mineralogical analysis of ceramic tiles by FTIR: A quantitative attempt
    • Abstract: Publication date: October 2015
      Source:Applied Clay Science, Volume 115
      Author(s): J.D. Jordá, M.M. Jordán, R. Ibanco-Cañete, M.A. Montero, J.A. Reyes-Labarta, A. Sánchez, M. Cerdán
      A method for quantitative mineralogical analysis by ATR-FTIR has been developed. The method relies on the use of the main band of calcite as a reference for the normalization of the IR spectrum of a mineral sample. In this way, the molar absorptivity coefficient in the Lambert–Beer law and the components of a mixture in mole percentage can be calculated. The GAMS equation modeling environment and the NLP solver CONOPT (©ARKI Consulting and Development) were used to correlate the experimental data in the samples considered. Mixtures of different minerals and gypsum were used in order to measure the minimum band intensity that must be considered for calculations and the detection limit. Accordingly, bands of intensity lower than 0.01 were discarded. The detection limit for gypsum was about 7% (mol/total mole). Good agreement was obtained when this FTIR method was applied to ceramic tiles previously analyzed by X-ray diffraction (XRD) or mineral mixtures prepared in the lab.


      PubDate: 2015-07-19T22:08:37Z
       
  • Nontronites as catalyst for synthesis of carbon nanotubes by catalytic
           chemical vapor deposition.
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Štefan Kavecký , Jana Valúchová , Mária Čaplovičová , Stefan Heissler , Pavol Šajgalík , Marián Janek
      Multiwall carbon nanotubes (MWCNT) were synthesized by catalytic chemical vapor deposition (CCVD) in a horizontal tube reactor using acetylene as the carbon source in a gas mixture with argon at 700°C and 30minute reaction time. As a catalyst was used the sodium forms of natural platy nontronite particles Sampor or Washington and their iron modified forms. Additionally, hydrothermally synthesized hematite α-Fe2O3 and/or its heterocoagulates with nontronite particles were used to test the catalytic activity. Catalyst nanoparticles were used to modify the conditioned Si wafer surface used as the catalyst support. Before CNT growth the catalyst nanoparticles were activated by applying a hydrogen stream in the tube reactor at 700°C. The effects of catalyst type and the reaction conditions on MWCNT growth such as C2H2/Ar ratio, time and reaction temperature were investigated. The growth of MWCNT was affected by the density of catalyst particles covering the surface e.g. for hematite, the amount deposited on a silicon surface. Depending on the type of catalyst located on the Si substrate, the bamboo-like, curly shaped and straight individual MWCNT were formed. The quality of the synthesized MWCNT was investigated using Raman spectroscopy. According to the cation exchange to Fe-forms, the iron content in nontronites was increased by about 14.5wt.%. However, by the addition of hematite particles, the iron content was increased by about 13.0wt.% of the total iron present. Raman spectroscopy has proved that good quality ordered graphite structure of the carbon sheets in CNT was also achieved by using pure Na-forms of natural nontronites applicable as the low-cost catalyst nanoparticles. Therefore, no ion exchange modification using iron salt is necessary for this type of material.


      PubDate: 2015-07-02T09:43:56Z
       
  • Analysis of strain anisotropy and hydroscopic property of clay and
           claystone
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Andrey Ponomaryov , Evgeniya Sychkina
      The paper presents an analysis of laboratory and field investigations of the anisotropy of natural early Permian claystone deformation behavior. Strain anisotropy in geotechnical engineering is of interest when calculating settlements and the ground base bearing capacity of a building foundation. The authors carried out pressuremeter tests, static stamp tests on claystone having an area of 600cm2 and a number of laboratory odometer tests of modern hard clay and claystone samples cut parallel and normal to stratification, as well as numerical modeling of these tests. The results obtained from the experiments and numerical modeling of claystone anisotropy deformability are reported and discussed. A number of the field and laboratory experiments made it possible to study the strain anisotropy of claystone in comparison with modern hard clay in the vertical and horizontal directions. In particular, modern clay shows less deformation under loading in the vertical direction than in the horizontal one. As for claystone, it shows less deformation under loading in the horizontal direction. The ratio is obtained to determine the parameters of the Jointed Rock model realized in the PLAXIS software package. The results of numerical modeling are in good agreement with the tests, thus supporting the numerical methods realized in the Jointed Rock model as a practical tool for the analysis of the soft rock stress–strain behavior. The mechanical properties of claystone are sensitive to water content and atmospheric air. Much attention is paid to the fulfillment of engineering and geological surveys, development of design documents, and foundations on claystones.


      PubDate: 2015-07-02T09:43:56Z
       
  • Polarization and depolarization currents in kaolin
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Ján Ondruška , Igor Štubňa , Viera Trnovcová , Igor Medveď , Tiit Kaljuvee
      Ceramic materials are considered dielectrics with ionic conductivity where polarization and depolarization effects play an important role. These effects take place when an external electric field is applied or removed. The measurement was performed on the kaolin samples, which contain 1.5mass % of the physically bound water, at room temperature. Since the polarization current did not reach zero value after a long period of time, it was deduced that both the ions and electrons are the charge carriers. At room temperature, H+ and OH− ions are the main charge carriers, a role of Na+ and K+ is negligible. Power functions, which describe the time dependent currents, suggest several polarization mechanisms. The best fit of the experimental relationships between the current and time showed a sum of three exponentials, i.e. three polarization and depolarization mechanisms should be considered. We ascribed them to 1) hopping of H+ ions, 2) migration of originally trapped and then released H+ ions, and 3) migration of OH− ions.


      PubDate: 2015-07-02T09:43:56Z
       
  • Water purification from perchlorate by a micelle–clay complex:
           Laboratory and pilot experiments
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Shlomo Nir , Ilya Brook , Yossi Anavi , Mark Ryskin , Julius Ben- Ari , Reuma Shveky- Huterer , Hanoch Etkin , Dikla Zadaka-Amir , Uri Shuali
      A technology for purification of water from perchlorate by filters including a complex between micelles of octadecyltrimethylammonium (ODTMA) and a clay-mineral, montmorillonite (Mt), or bentonite is presented. Laboratory filters of lengths of 20 and 40cm were filled with a powdered micelle (ODTMA)–Mt complex mixed with excess sand at ratios of 1:100 to 1:15 w/w. A pilot filter (60cm diameter∙110cm length) was filled with a 1:19 mixture. The complex exhibited a relatively large affinity to adsorb perchlorate; the presence of other anions, such as chloride, nitrate and sulfate at concentrations exceeding 1000-fold those of perchlorate had little effect on its removal from water by filtration. This high affinity was explained by the fact that the positively charged complex has abundance of hydrophobic regions, whereas perchlorate, is characterized by a large bare anionic radius, i.e., a loose hydration shell. A model which accounts for convection, adsorption and desorption was adequate in simulating and predicting the kinetics of filtration for two orders of magnitude variation in concentrations of perchlorate and one order of magnitude variations in concentrations of adsorbing sites, filter length, and flow velocities. Production of a granulated complex enabled to fill the filters exclusively with the complex and make the technology suitable for upscale. Based on the results of pilot experiments and model calculations, it is suggested that in comparison with other technologies, the micelle–clay filter has a relatively large capacity to remove perchlorate in the range of hundreds to thousands μg/l.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Ageing and collapse of Bentonite gels — Effects of Mg(II), Ca(II)
           and Ba(II) ions
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Pek-Ing Au , Prashanth Pillai , Yee-Kwong Leong
      The ageing and stability behaviour of Bentonite slurries were evaluated under the influence of Mg2+, Ca2+ and Ba2+ ions at concentration ranging from 0.005 to 1M. Stable gels were formed at low metal ion concentration of <0.05M. These gels displayed pronounced ageing or structural recovery behaviour. A well-defined initial state of ageing was employed. This was the surface-chemical equilibrium (SCE) state. The dissolved metal ion salt hastened the attainment of this SCE state of freshly prepared gel to less than 100min. As the structure recovered during ageing, the yield stress increased. The temporal ageing yield stress displayed an initial period of rapid increase, followed by a period of gradual increase and then a period of no increase. The Leong model described this ageing behaviour well. At metal ion concentration of 0.05M or greater, the gels became unstable and collapsed. In contrast, gel instability occurred at a much higher concentration of 0.5M for Na+, K+ and Cs+ ions. Also the settling layer of divalent metal ion weakened gels did not consolidate as effectively. The stability time of these weakened gels was found to decrease with increasing hydration bond length of the divalent metal ions, i.e. Ba(II)<Ca(II)<Mg(II).
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Identification of clay minerals in mixtures subjected to differential
           
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Paola Bruno Arab , Thiago Peixoto Araújo , Osni José Pejon
      The study of identification methods for clay minerals is very important because of the very fine particle size (less than 2μm) of these materials, which makes it difficult to recognize them with the naked eye. Because they consist of electrically charged particles, clay minerals exhibit distinct and dynamic behavior. From geotechnical standpoint, clay minerals are present in a wide variety of rocks and soils. Because their behavior is difficult to predict, careful consideration is necessary because they exert great influence on the design and construction of roads, tunnels, foundations, slopes, and many other types of infrastructure. Their characteristics may have a positive effect, e.g., when acting as clay liners, or a negative one, e.g., when their swelling characteristic causes buildings to lose their stability. In this context, the purpose of this work was to compare the reliability of two clay mineral identification methods: combined differential thermal analysis and thermogravimetry (DTA-TG) and the methylene blue adsorption test (MBAT). Proportional mixtures of kaolinite and bentonite were prepared in order to investigate the two methods. These two types of clay were chosen due to their distinct behaviors: kaolinite is a 1:1 clay mineral, and bentonite is composed mostly of montmorillonite, a 2:1 clay mineral. The two methods showed a positive and highly significant correlation. Moreover, the MBAT is a lower cost test that requires only ordinary chemistry laboratory equipment. Correlations revealed that the MBAT can provide thermal information related to DTA-TG tests.


      PubDate: 2015-07-02T09:43:56Z
       
  • Synthesis and characterization of layered double hydroxides intercalated
           by UV absorbents and their application in improving UV aging resistance of
           bitumen
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Song Xu , Jianying Yu , Weifei Wu , Lihui Xue , Yubin Sun
      Two different types of UV absorbents, 2-hydroxybenzoic acid and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, were intercalated into layered double hydroxides (LDHs) to synthesize organic LDH by anion-exchange method, and then the synthesized organic LDHs were applied to modify bitumen aiming to improve UV aging resistance of bitumen. According to the characterization with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM), the two UV absorbents were successfully intercalated into the galleries of LDH, leading to the expansion of interlayer distance of LDH. Thermogravimetry and differential scanning calorimetry (TG–DSC) and UV–vis absorbance analyses indicated that the thermal stability and UV absorptive ability of UV absorbents were enhanced significantly. Compared with LDH, organic LDH exhibited better improvement in UV aging resistance of bitumen by restraining the oxidation of bitumen and generation and stacking of asphaltenes cluster during UV exposure, which was due to the enhanced UV absorptive ability of organic LDH and compatibility between organic LDH and bitumen.


      PubDate: 2015-07-02T09:43:56Z
       
  • Synthesis of acidified palygorskite/BiOI with exceptional performances of
           adsorption and visible-light photoactivity for efficient treatment of
           aniline wastewater
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Yuan Guan , Hao Qian , JiaQing Guo , Shaogui Yang , Xin Wang , Shaomang Wang , Yongsheng Fu
      The acidified palygorskite/BiOI composites with different amounts of acidified palygorskite were synthesized using an ethylene glycol-assisted solvothermal method. The morphology, structure, surface area and pore-size distribution of the composites were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N2 adsorption–desorption isotherms. The BiOI microspheres consisting of numerous nanosheets were uniformly dispersed on the surface of acidified palygorskite. The composite with doping amount of 50wt.% acidified palygorskite manifested a large BET area of 118.5m2/g with mesoporous structure of 10.8nm. The surface chemistry was obtained by the determination of the point of zero charge. The introduction of acidified palygorskite made the composites have more acidic character. The adsorption of aniline onto acidified palygorskite/BiOI followed the pseudo-second-order model and the Freundlich equation. As pH increased, equilibrium adsorption concentration showed an upward trend, and reached a maximum at pH=7. The 50wt.%-acidified palygorskite/BiOI exhibited the optimal adsorption performance and visible-light photoactivity for 50mgL−1 of aniline solution. About 90wt.% of aniline was removed through combination of high adsorption and efficient photodegradation processes.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Study on the protective function of cloisite incorporated silane
           sol–gel coatings cured at different conditions
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): F. Ansari , R. Naderi , C. Dehghanian
      In this research, cloisite incorporated silane sol–gel coatings cured at different conditions were applied on 304L stainless steel to control its corrosion in 3.5% NaCl solution. At first step, the electrochemical noise data revealed the superior barrier function of the silane coating with cloisite compared to the neat one. As confirmed by the surface analysis, this was attributed to denser structure and increased coating thickness in the presence of cloisite nanoparticles. Then, the study focused on the impact of curing procedure on the performance of the hybrid silane film. The electrochemical data and results of FTIR, water contact angle and FESEM surface analysis showed that the heat treatment at sufficient temperature and time may lead to developing a reticulated coating which functions as an effective barrier to the diffusion of aggressive species.


      PubDate: 2015-07-02T09:43:56Z
       
  • Theoretical study of the anion exchange properties and the thermal
           decomposition of Zn5(OH)8(NO3)22H2O and Zn5(OH)8(NO3)22NH3
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Sérgio R. Tavares , Viviane S. Vaiss , Fernando Wypych , Alexandre A. Leitão
      The structures of the hydrated, ammoniated and anhydrous zinc hydroxide nitrate were studied by ab initio density-functional calculations so that some of their properties could be analyzed. The dehydrated structure is not yet refined from x-ray diffraction data and, therefore, several optimization calculations were conducted in order to test different sites to coordinated nitrate anions. Charge difference plots and projected density of states calculations (PDOS) were carried out to solve the interactions between the layers, which occur through the coordinated molecules and the nitrate anions. This result also validated our simulated dehydrated structure. Thermodynamical potentials and entropy of the dehydration and ammonia removal processes were also computed and it could be concluded that the water molecules leave the structure at different temperatures. In the case of Zn5(OH)8(NO3)2 2NH3, the dehydrated structure cannot be obtained by thermal treatment before the formation of zinc oxide, that was also studied for Zn5(OH)8(NO3)2 2H2O and its formation temperature corroborated the experimental works. We proposed and studied a chemical equation for the nitrate anion exchange reactions of the Zn5(OH)8(NO3)2 2H2O using fluoride, chloride, bromide and iodide and it could be concluded that all of the exchanges at 298.15K are thermodynamically spontaneous.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Evaluation of the exfoliation and stability of Na-montmorillonite in
           aqueous dispersions
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Samim Ali , Ranjini Bandyopadhyay
      In aqueous dispersion, Na-montmorillonite swells due to absorption of water and exfoliate into smaller entities, known as tactoids, with electric double layers on their surfaces. The exfoliation rate of such tactoids in aqueous Laponite dispersion was seen to be greatly reduced at the jamming transition and was reported by this group in a recent article [Langmuir, 2013, 29, 12663–12669]. The work reported here uses ultrasound attenuation spectroscopy experiments on Na-montmorillonite dispersions and shows that the complete exfoliation of tactoids is not achieved even below the jamming concentration. This behavior indicates that screened Coulomb repulsions between and within tactoids, as well as the osmotic pressure of hydrated Na+ ions, play very important roles in the exfoliation kinetics of tactoids. In this work, the phenomenon of tactoid exfoliation is studied systematically by changing clay mineral concentration, ionic conditions and the ages of the dispersions. A signature of an irreversible process of tactoid reformation under certain ionic conditions is also observed. Finally, electroacoustic measurements and rheometry are used to assess the influence of tactoid exfoliation on the stability and viscoelasticity of the arrested phases formed under different ionic conditions.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Physicochemical and index properties of loess stabilized with lime and fly
           ash piles
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Xiangjun Pei , Fanyu Zhang , Wanjiong Wu , Shouyun Liang
      This study examines physicochemical and index properties of loess modified by adding lime and fly ash piles. After curing for 28days, modified loess samples were obtained at various radial distances from the lime and fly ash piles (i.e., 5cm, 10cm 15cm, and 20cm). Various index properties were then measured: water content, density, Atterberg limits, and Equotip hardness value. The physicochemical properties were also measured, including specific surface area (SSA), cation exchange capacity (CEC), X-ray diffraction (XRD), and disintegration rate. The test results showed increases in SSA, CEC, water content, and liquid limit at distances from 5cm to 20cm, whereas density and the plastic limit decreased with radial distance. Moreover, the hardness value show an inverse relation with increasing radius for loess with lime and fly ash piles. The data obtained from XRD analysis and slake tests confirm that lime and fly ash migrate into loess surrounding the pile and consequently cause changes in physicochemical and index properties. These changes can be explained by the interaction between the structure and mineral composition. This interaction forms new cementitious products are formed by the hydration and pozzolanic reaction due to cation exchange, and consequently the interparticle flocculation and aggregate formation. These results indicate that lime and fly ash piles can be used as a convenient and efficient stabilization method to improve the performance of collapsing loess.


      PubDate: 2015-07-02T09:43:56Z
       
  • Influence of pH and antibiotic solubility on the removal of ciprofloxacin
           from aqueous media using montmorillonite
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): M. Eugenia Roca Jalil , Miria Baschini , Karim Sapag
      The ciprofloxacin (CPX) is a fluoroquinolone antibiotic that has been found in soils and aqueous media due to its vast use in both, human and veterinary health care. As a consequence the removal of this kind of compounds is widely studied. However, there are a few studies about the CPX removal from aqueous media by adsorption. This work is focused on the study of CPX removal by adsorption using an Argentinian montmorillonite (Mt). The influence of the pH media and the consequent antibiotic solubility in the adsorption process was analyzed. The experimental curve of CPX solubility versus pH media showed a strong correlation between them where the lowest value of solubility was obtained for the zwitterion species (CPX±). This result points out the fact that the solubility of the CPX species must be considered in adsorption experiments because of the antibiotic precipitation and the consequent overestimation of the adsorbent adsorption capacities. CPX adsorption kinetics and adsorption isotherms at different pH values showed that the adsorption processes obey pseudo-second order kinetics. The CPX adsorption capacity of the Mt, the affinity of the species towards its surface and the possible mechanisms involved in the adsorption process were assessed by Langmuir, Freundlich and Scatchard methods. The results showed that the adsorption mechanism of CPX on Mt is pH dependent, obtaining a negative cooperative mechanism at pH3, 6 and 7.5 and a positive cooperative mechanism at pH10. The highest CPX adsorption capacity on Mt was obtained at pH6. Infrared spectroscopy and X-ray diffractograms of the complexes obtained after the adsorption process provided information about the interaction between the functional groups of CPX and the adsorption sites on Mt and the changes in the basal space related with the molecular arrangements of the CPX on the sample, respectively. The CPX removal by this clay mineral is remarkably higher when it is compared with other materials and quite similar to previous data obtained with other bentonites.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Soil improvement by electroosmotic grouting of saline solutions with
           vacuum drainage at the cathode
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Jie Peng , Hanming Ye , Akram N. Alshawabkeh
      Electroosmotic grouting is a ground improvement method for soft soils that is not widely accepted for common application because the improvement of soil strength is not uniform. This paper proposed a new method to improve the non-uniform effect of electroosmotic grouting. Such method is electroosmotic grouting coupled with vacuum drainage at the cathode. The experimental study shows that the treatment effect of electroosmotic grouting with vacuum drainage at the cathode is not only better than general electroosmosis methods but also more uniform than such methods. In this study, the soil strength increased by 362%, 350%, and 438% at the locations close to the anode, between the anode and cathode, and close to the cathode, respectively. The results demonstrate that this technique could improve the treatment effect of electroosmotic grouting in soft soils.


      PubDate: 2015-07-02T09:43:56Z
       
  • FT-IR study of CO2 interaction with Na+ exchanged montmorillonite
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Elizabeth G. Krukowski , Angela Goodman , Gernot Rother , Eugene S. Ilton , George Guthrie , Robert J. Bodnar
      Carbon capture, utilization and storage (CCUS) in saline reservoirs in sedimentary formations has the potential to reduce the impact of fossil fuel combustion on climate change by reducing CO2 emissions to the atmosphere and storing the CO2 in geologic formations in perpetuity. At pressure and temperature (PT) conditions relevant to CCUS, CO2 is less dense than the pre-existing brine in the formation, and the more buoyant CO2 will migrate to the top of the formation where it will be in contact with cap rock. Interactions between clay-rich shale cap rocks and CO2 are poorly understood at PT conditions appropriate for CCUS in saline formations. In this study, the interaction of CO2 with clay minerals in the cap rock overlying a saline formation has been examined using Na+ exchanged montmorillonite (Mt) (Na+-STx-1) (Na+ Mt) as an analog for clay-rich shale. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used to discern mechanistic information for CO2 interaction with hydrated (both one- and two-water layers) and relatively dehydrated (both dehydrated layers and one-water layers) Na+-STx-1 at 35°C and 50°C and CO2 pressure from 0–5.9MPa. CO2-induced perturbations associated with the water layer and Na+-STx-1 vibrational modes such as AlAlOH and AlMgOH were examined. Data indicate that CO2 is preferentially incorporated into the interlayer space, with relatively dehydrated Na+-STx-1 capable of incorporating more CO2 compared to hydrated Na+-STx-1. Spectroscopic data provide no evidence of formation of carbonate minerals or the interaction of CO2 with sodium cations in the Na+-STx-1 structure.


      PubDate: 2015-07-02T09:43:56Z
       
  • Activation of clay surface sites of Bambouto's Andosol (Cameroon) with
           phosphate ions: Application for copper fixation in aqueous solution
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Jean Mermoz Siéwé , Emmanuel Djoufac Woumfo , Paul Djomgoue , Daniel Njopwouo
      The andosol collected from the mount Bambouto contains high ratio of amorphous mineral, especially an allophane which is known for its phosphate adsorption affinity. This andosol material also contains organic-matter which limits the phosphate adsorption. In the present work, H2O2 was used to remove organic matter with the aim of liberating the surface site as well as to increase the adsorption capacity of the sample. The effect of competitive ions such as: K+, Ca2+, NO3 −, CO3 2−, SO4 2− and Cl− on the adsorption of phosphate ions in our andosol's sample were investigated. In addition, the desorption of phosphate after saturation of andosol was also carried out in order to reuse the samples. The desorption study was done using a solution of NaOH with concentrations ranging from 1 to 10mmol/L and the effect of the dissolution of andosol's material under basic solution was also studied. The sample after adsorption of phosphate ions shows great affinity for copper ions removal in aqueous solution.


      PubDate: 2015-07-02T09:43:56Z
       
  • Kinetic pathway for thermal exfoliation of pyrophyllite
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Mostofa Shamim , Tapas Kumar Mukhopadhyay , Kausik Dana
      The thermal exfoliation of pyrophyllite on heating above 600°C was studied to discern its kinetic pathway and correlate it with dehydroxylation. The irreversible thermal expansion data of pyrophyllite was collected from a thermomechanical analyzer at different heating rates (β). Detailed kinetic analysis was performed on the data using model-free and regression analysis (both linear and non-linear) methods. Multivariate non-isothermal kinetic analysis was used to fit the expansion data at all heating rates simultaneously using eighteen kinetic models. It is found that, the exfoliation of pyrophyllite can be successfully fitted with three kinetic models, viz., n-dimensional Avrami (An), two-dimensional diffusion (D2) and three-dimensional diffusion (D3) model with acceptable kinetic parameters. D2 model (Ea, activation energy=392kJ·mol−1, regression coefficient=0.998) provides the most realistic mechanistic pathway by considering the planar geometric constraint of nucleation and growth in the layered structure of pyrophyllite. Electron microscopic images of exfoliated pyrophyllite shows distinct exfoliated layers indicating escape route for heated gas and supports the choice of D2 model. Although this exfoliation process is a consequence of dehydroxylation reaction, its complexity due to diffusional and geometric constraints is reflected by the high energy barrier (Ea) reported consistently by every kinetic model compared to that of dehydroxylation.


      PubDate: 2015-07-02T09:43:56Z
       
  • Microwave synthesis of delaminated acid saponites using quaternary
           ammonium salt or polymer as template. Study of pH influence
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Fiseha B. Gebretsadik , Deni Mance , Marc Baldus , Pilar Salagre , Yolanda Cesteros
      Mesoporous saponites were prepared at pH8 and 13 without and with template (surfactant or polymer) at 453K and autogenic pressure using microwaves or conventional oven during the hydrothermal ageing treatment. Acidity was obtained by calcination of the NH4-form. The effect of dilution (H2O/Si molar ratios of 250, 125 and 50) was studied for the samples prepared at pH8 with surfactant. In order to compare the effect of introducing surfactant during or after saponite synthesis, several samples prepared at pH13 were modified after synthesis by refluxing or by stirring at room temperature in a surfactant solution. Preparation of samples at pH13 favoured the ordering in the stacking direction, improved AlT/AlO ratio and led to samples with lower amorphous siliceous material content. The use of microwaves and surfactant for the synthesis at pH13 afforded a saponite with the highest surface area (603m2/g) and the smallest lamellae crystallite size (about 4nm). The properties of the samples synthesized at pH8 with surfactant depended on the dilution. Thus, the degree of delamination, the BET area and the AlT/AlO ratio increased whereas the amorphous siliceous material content decreased at lower slurry dilution. The incorporation of the surfactant by post-synthesis resulted in some degree of delamination especially when using refluxing. However, the degree of delamination was higher for the saponites prepared with the addition of the surfactant during the hydrothermal synthesis.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Fluorescence tuning of 2D montmorillonite optically active layers with
           beta-cyclodextrine/dye supramolecular complexes
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Marián Matejdes , Adriana Czímerová , Marián Janek
      Montmorillonite 2D-optically active layers were investigated using non-ionic Coumarine and cationic Pyronine dyes. The modification of thin montmorillonite films (MF) was done by single dye species and/or with β-cyclodextrine (CD) supramolecular complexes (SC). Equilibrium constants for SC formation were determined in the range 0.1·103 −6.0·103 for temperatures 283–323K. Thus amounts of dye incorporated in the SC with CD prepared at temperature 293K is more than 96% for Coumarine and more than 81% for Pyronine dye. Adsorption of SC in MF was proved by detection of increased first basal reflections using X-ray diffraction. The molecular transition moments for monomeric dye species in 2D MF of SC for Pyronine absorbing at 560nm were inclined 60° and co-adsorbed dimers or higher aggregates of molecules tilted around 33° towards montmorillonite surface. Coumarine absorption in the whole investigated spectral range indicated average molecule inclination around 28°. The angle of the Coumarine dye is favourable for the formation of J-aggregates with sufficient fluorescence intensity detected at 478nm for solid state applications.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Clay and clay minerals for fluoride removal from water: A state-of-the-art
           review
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): A. Vinati , B. Mahanty , S.K. Behera
      The presence of fluoride in water has become a matter of great concern around the world due to its chronic human carcinogenic behavior. Developing easily accessible and environmentally sustainable removal strategies is therefore a challenge for the scientists. Among the different treatment technologies, adsorption process for fluoride removal is considered cost-effective, flexible, and easy to design and operate. This review discusses the recent trends in scientific research and development on the exploitation of clay and clay minerals for fluoride removal from water, focusing on the effect of various factors on the adsorption, mechanism, isotherms and kinetics of the adsorption process.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Room temperature and high temperature sealing properties and compression
           properties of compressive gaskets made of micrometric vermiculite
           particles
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): A.N. Nguyen , L. Mirabel , L. Duclaux , L. Reinert , P. Dehaudt , J.F. Juliaa , A. Beziat
      Vermiculite gaskets obtained by pressing vermiculite powders in the range of 17.7–80MPa, were studied for their sealing (leak rate measurements) and compressive properties (compressibility and resiliency). The in plane permeability at room temperature was found to decrease strongly through increasing elaboration pressure, that reduced both the median pore radius (<30nm) and the macropore volume fraction (<45%), measured by mercury intrusion. After annealing at temperatures of up to 600°C, the out of plane permeability (measured at room temperature) was increasing from ~10−20 (at 200°C) to ~10−24 due to the increase in anisotropy related to the densification and the formation of interlayer bonds. The global leak rate was found to be determined exclusively by the contact leak rate and independent of the material's permeability. The leak rates measured at room temperature were also found to be dependent on the gasket's resiliency values. The global helium leak rate (2.5×10−2 atm·cm3·s−1·m−1, for 35MPa working pressure, under 5bar helium pressure) was relied neither on the working temperature (25°C to 800°C) nor the material porosity for gaskets pressed at 200°C and 80MPa. The resiliency (~5%) and compressibility (9%) values of these gaskets were reduced, as heating the materials to 800°C due to the densification induced by both pressure and temperature, increasing their rigidity.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Mechanical, dielectric and photoluminescence properties of
           alumina–mullite composite derived from natural Ganges clay
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Arpan Kool , Pradip Thakur , Biswajoy Bagchi , Nur Amin Hoque , Sukhen Das
      A highly dense mullite–alumina composite was developed utilizing external alumina and clay aggregates from the Ganges (India) bed in order to obtain a low-cost multifunctional composite. Thermal evaluation and phase formation were investigated by simultaneous differential thermal and thermo-gravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Both equiaxed and elongated whiskers of mullite were present along with alumina platelets. Mechanical characteristics of the mullite composites were measured in terms of relative density and Vicker's hardness and were found to be ~89% and ~4.5GPa at 1400°C. Dielectric constant of the composite was found to be ~18 at 1400°C which is higher than that of pure alumina or mullite. Structural defects and peculiar morphologies of the composite caused photoluminescence bands at around 310, 347, 436 and 460nm. Due to its remarkable density, Vicker's hardness, improved dielectric properties and prominent photoluminescence, the composite can be used as a multifunctional composite with structural, electrical and optical applications.


      PubDate: 2015-07-02T09:43:56Z
       
  • Preparation and antibacterial activity of chitosan-based nanocomposites
           containing bentonite-supported silver and zinc oxide nanoparticles for
           water disinfection
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Sarah C. Motshekga , Suprakas Sinha Ray , Maurice S. Onyango , Maggie N.B. Momba
      This study was conducted to develop novel chitosan nanocomposites and to optimize the minimum amount and contact time required to achieve complete inactivation of bacteria in water. Gram-negative Escherichia coli and Gram-positive Enterococcus faecalis bacteria were used to test the antibacterial activity of chitosan cross-linked with glutaraldehyde and chitosan nanocomposites in water. The silver and zinc oxide nanoparticles supported on bentonite were synthesized using microwave-assisted synthesis method. The resulting bentonite-supported silver and zinc oxide nanoparticles were dispersed in a chitosan biopolymer to prepare bentonite chitosan nanocomposites. The obtained bentonite chitosan nanocomposites were characterized with BET surface area measurements, FTIR, XRD, ICP-AES and SEM. When using cross-linked chitosan, it was demonstrated that factors such as pH, particle size and surface area influenced the inactivation of bacteria. For instance, the antibacterial activity of cross-linked chitosan was illustrated to increase with an increase in contact time. Meanwhile, an improvement in the inactivation activity was indicated with the introduction of silver and zinc oxide nanoparticles containing bentonite into the chitosan matrix. Although both silver and zinc oxide containing bentonite chitosan nanocomposites exhibited good antibacterial activity against bacteria, with removal efficiencies of at least 51%, the best antibacterial activity was demonstrated for silver–zinc oxide bentonite chitosan nanocomposite, with a removal efficiency of at least 78%. Furthermore, the antibacterial activity of bentonite chitosan nanocomposites was identified to be influenced by the amount of material, contact time and bacterial concentration. Finally, leaching tests demonstrated that bentonite chitosan nanocomposites were stable and, consequently, could be effectively used as antibacterial materials for water disinfection.
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      PubDate: 2015-07-02T09:43:56Z
       
  • Modified halloysite as an adsorbent for prometryn from aqueous solutions
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Danuta Grabka , Marta Raczyńska-Żak , Kamil Czech , Piotr Marek Słomkiewicz , Małgorzata Anna Jóźwiak
      Adsorption behavior of prometryn (2,4-bis (isopropylamino)-6-methylthio-s-triazine) on halloysite minerals has been studied in order to consider the application of such adsorbents in water purification. Halloysite, activated in various ways, was characterized by ASAP, SEM/EDS. Batch mode and flow system have been employed, using prometryn aqueous solutions. Various parameters were studied for both systems. Adsorption capacity was determined as a function of adsorbate concentration, of optimum contact time, optimum dose and adsorbent fragmentation. It was found that at pH=5 the best adsorptive properties for prometryn are obtained for halloysite treated with 96% H2SO4. Such adsorption matches Langmuir and Freundlich models and is in a good agreement with pseudo-second order kinetic model. The desorption of prometryn from halloysite was also studied. The performed studies show that halloysite treated with 96% H2SO4 holds the great potential for removal of water impurities such as prometryn.


      PubDate: 2015-07-02T09:43:56Z
       
  • Thermal decomposition behavior and de-intercalation mechanism of acetamide
           intercalated into kaolinite by thermoanalytical techniques
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Shenghui Zhang , Xuemei Ou , Yinghuai Qiang , Jinan Niu , Sridhar Komarneni
      De-intercalation is the inverse of the intercalation process, which can be easily and rapidly determined by thermal analysis. Research on the de-intercalation process is beneficial to exploring the intercalation mechanism that is still unclear in the case of kaolinite intercalation. The objectives of this study were (a) to investigate the thermal decomposition behavior of the intercalation compound of kaolinite and (b) to determine the kinetics of de-intercalation process by thermal analysis to study the mechanism of de-intercalation reaction in kaolinite. Here, the kaolinite–acetamide intercalation compound that was prepared by the direct intercalation method was investigated. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy results showed that acetamide molecules were inserted into the interlayer space of kaolinite and apparently formed new hydrogen bonds with the inner surface hydroxyl groups of kaolinite. The basal spacing of kaolinite increased from 0.721 to 1.102nm upon intercalation with acetamide. The thermogravimetric (TG) and differential scanning calorimetry (DSC) curves indicated that the decomposition process of the intercalation compound could be divided into two steps. The first step was attributed to the de-intercalation of the intercalated molecules at a temperature of about 181°C, and the second step corresponded to the dehydroxylation of kaolinite at a temperature of about 502°C. The completed kinetic triplet of the de-intercalation reaction was obtained through thermal analysis kinetics methods. The apparent activation energy Ea of the de-intercalation process was calculated to be about 73.6kJmol−1 by an iterative procedure. The pre-exponential factor A was estimated to be in the range of 1.06×1010 s−1 to 7.92×1010 s−1 by the Dollimore method. The optimized mechanism function of the de-intercalation process of acetamide was determined to be an nth-order chemical reaction through the Malek method. The mechanism function is G(α)=[1−(1− α)1− n ]/(1− n), f(α)=(1− α) n and experiments showed that the value of n increased with increased heating rate.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Hybrid material based on ZnAl hydrotalcite and silver nanoparticles for
           deodorant formulation
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): B. Ballarin , A. Mignani , F. Mogavero , S. Gabbanini , M. Morigi
      A simple method to prepare a hybrid material (ZnAl–AgNPs) based on silver nanoparticles and ZnAl layered double hydroxides (ZnAl LDHs), for possible use in a cosmetic formulation as deodorant, was reported. ZnAl–AgNPs, include the high adsorption capacity, the biocompatibility, the antacid properties of LDH and the antibacterial activity of AgNPs. According to the characterization with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM), it was possible to confirm that interaction of AgNPs with ZnAl LDH occurs by adsorption rather than intercalation of AgNPs in LDH. The deodorant activity of ZnAl–AgNPs was tested using the headspace solid phase micro-extraction gas chromatography (HS-SPME-GC) and the antibacterial property was monitored on gram-negative bacteria. For comparison raw ZnAl LDH was also investigated. The results showed that both raw ZnAl LDH and ZnAl–AgNPs have deodorant activity higher than that of zinc ricinoleate, normally used in commercial formulations.


      PubDate: 2015-07-02T09:43:56Z
       
  • Shear-thinning behaviour of dense, stabilised suspensions of plate-like
           particles. Proposed structural model.
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): J.L. Amorós , E. Blasco , V. Beltrán
      A structural model was developed to describe the shear-thinning behaviour of dense, stabilised suspensions of plate-like particles. The model is based on the following main assumptions: the particles are distributed in more or less compact layers, oriented parallel to the flow; the particles are assumed to behave as hard disks, disk thickness being the sum of crystal thickness plus twice the Debye length; when the shear stress increases, the orientation of the plate-like particles in the flow direction also increases, thus increasing layer compactness. In order to test the proposed model, a kaolin was selected and characterised. The kaolin was used to prepare more than 40 aqueous suspensions, modifying the solids volume fraction between ϕ =0.20 and ϕ =0.475 and the dispersant (sodium silicate) content between Xs =0.075 and Xs =0.225mg dispersant/m2 solid. The flow curves of all suspensions were determined in the quasi-steady state. The results confirmed the validity of the model to satisfactorily describe the combined effect of ϕ and XS on the flow curves in the shear-thinning range.


      PubDate: 2015-07-02T09:43:56Z
       
  • Immobilization of enzymes on clay minerals for biocatalysts and biosensors
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Ning An , Chun Hui Zhou , Xiao Yu Zhuang , Dong Shen Tong , Wei Hua Yu
      Many studies suggest that naturally-occurring layered clay minerals can be used as a class of biocompatible solid supports for immobilizing enzymes. The corresponding clay mineral enzyme hybrids prove to have great potentials in catalysis and biosensing. This article reviews latest advances in using clay minerals as supports for the immobilization of enzymes. The immobilization of enzyme onto clay minerals can be made via non-covalent adsorption and covalent bonding. The non-covalent immobilization involves van der Waals forces, electrostatic interactions, hydrogen bonding, and hydrophobic interactions. For avoiding desorption of enzymes, immobilization can be conducted through direct covalent bonding between enzymes and clay minerals. Organic modification of clay minerals and addition of linking molecules are made to improve the immobilization so as to increase the loading, activity and stability of enzymes. Regarding the applications of enzyme immobilized on clay minerals, recent studies are made mainly in biocatalytic processes and in biosensors. For manufacturing biosensing electrodes, clay minerals with metal nanoparticles, graphene and carbon nanotubes prove to be more effective owing mainly to the enhanced electron transfer. Future work on clay mineral enzyme hybrids could lie in integrating more additional functional materials with clay mineral enzyme hybrids to build hierarchical structured catalysts and electrodes.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Hydrotalcite derived (Cu, Mn)–Mg–Al metal oxide systems doped
           with palladium as catalysts for low-temperature methanol incineration
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Magdalena Jabłońska , Lucjan Chmielarz , Agnieszka Węgrzyn , Kinga Góra-Marek , Zofia Piwowarska , Stefan Witkowski , Ewa Bidzińska , Piotr Kuśtrowski , Anna Wach , Dorota Majda
      Hydrotalcite derived (Cu, Mn)–Mg–Al mixed metal oxides, synthesized by coprecipitation method, were found to be effective catalysts for methanol incineration. Copper and/or manganese oxides deposited on commercial γ-Al2O3 and MgO were used as the reference catalysts. Cu–Mg–Al–O mixed oxide system was found to be the most active catalysts in a series of the hydrotalcite originated metal oxides and supported samples. On the other hand, copper deposited on Al2O3 and MgO supports were significantly less active than the hydrotalcite derived catalysts. Activity of the catalysts was improved by deposition of small amount of palladium (0.5wt.%). Temperature-programmed surface reaction method (CH3OH-TPSR) and in situ Fourier-transform infrared spectroscopy (FT-IR) were employed to study the species formed on the catalyst surface during the process of methanol oxidation.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Preparation of Mg–Al layered double hydroxide/polyamide 6
           nanocomposites using Mg–Al–taurate LDH as nanofiller
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Dana Lennerová , František Kovanda , Jiří Brožek
      A novel method using Mg–Al layered double hydroxide (LDH) intercalated with taurate (2-aminoethanesulfonate acid) was applied for preparation of LDH/polyamide 6 nanocomposites via in situ intercalative polymerization. Two polymerization mechanisms were used — hydrolytic and anionic polymerization of ε-caprolactam, in which the Mg–Al LDH intercalated with taurate was dispersed. The obtained LDH/polyamide 6 nanocomposites were characterized by a combination of wide- and small-angle X-ray scattering, transmission electron microscopy, differential scanning calorimetry and thermogravimetric analysis. It was found that LDH filler was exfoliated in the polymer matrix and the LDH/polyamide 6 nanocomposites were successfully prepared by anionic polymerization of ε-caprolactam in the presence of dispersed LDH.


      PubDate: 2015-07-02T09:43:56Z
       
  • Zn–AL LDH reinforced nanocomposites based on new polyamide
           containing imide group: From synthesis to properties
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Mohsen Hajibeygi , Meisam Shabanian , Hossein Ali Khonakdar
      A new series of polyamide/Zn–Al layered double hydroxide (LDH) nanocomposites (PANC) was prepared by solution intercalation technique under ambient condition in dimethylformamide as solvent. The polyamide (PA) containing pyridine ring and imide group was synthesized using direct polycondensation reaction with good solubility and desired molar mass. Organo-modified Zn–Al LDH (OLDH) was produced by one-step method and used to improve mechanical, thermal and flame properties of PA. The extent of dispersion of OLDH sheets was quantified by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and the results showed a good dispersion for OLDH in the PA matrix. According to the results of mechanical tests, the tensile strength and the Young's modulus of PANC enhanced with increasing OLDH content. Thermal properties of PANC were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal property results in both nitrogen and air atmospheres showed that the addition of OLDH resulted in a substantial increase in the thermal stability and char yields of PANC as compared to the neat PA. Significant improvements in flame retardancy performance were observed for PANC from microscale combustion calorimeter (MCC) (reducing both the heat release rate and the total heat released).


      PubDate: 2015-07-02T09:43:56Z
       
  • Structural and chemical changes in kaolinite caused by flash calcination:
           Formation of spherical particles
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): M. Claverie , F. Martin , J.P. Tardy , M. Cyr , P. De Parseval , O. Grauby , C. Le Roux
      To understand the morphological changes of three commercial kaolins during flash calcination and to compare them with those obtained during traditional heat treatments in the laboratory (an electric furnace at 700°C for 5h), this paper presents the physical and chemical characteristics of metakaolins obtained from an industrial flash calciner. In the metakaolin products, kaolinite was not completed dehydroxylated during calcination, and the proportion of untransformed kaolinite was greater in flashed metakaolins than in traditional rotary-calcined metakaolins. Several particle morphologies were discernible in the metakaolins, including spherical particles that were formed in flash calcinations. These spherical particles were cut with a focused ion beam (FIB) and were revealed to contain a vitrified aluminum silicate phase with traces of mullite and various gases. These spherical particles were produced from the direct calcination of several submicron kaolinites near the flame of the calciner.


      PubDate: 2015-07-02T09:43:56Z
       
  • Synthesis and characterization of bentonite based
           inorgano–organo-composites and their performances for removing
           arsenic from water
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Jinming Hua
      Four modifiers, amorphous iron (hydr)oxides (Fex(OH)y), manganese oxides (MnxOy) and cationic surfactants, cetyltrimethylammonium bromide (CTMAB), and poly(dimethyldiallylammonium chloride) (PDMDAAC), were used to synthesize single and complex modified bentonite. Arsenic removal by modified bentonite was investigated through effects of the type, combination and adding level of modifiers. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption were used to explore the characteristics of the original and modified bentonite. It was found that the type, combination and adding amount of modifiers would have a noticeable influence on the structure and adsorption behavior of resulting bentonite adsorbents. The complex modified bentonite, with manganese oxides and then PDMDAAC at proper addition level, showed the best adsorption properties for arsenic, which could be due to a synergistic effect between PDMDAAC and manganese oxides during modification process. PDMDAAC was found to be favorable for coating of manganese oxides onto bentonite. The adsorbing capacity of modified bentonite depended not only on specific surface area (SSA), but mainly on composite components and/or their specific surface properties.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Mg–Al–CO3 hydrotalcite removal of persistent organic disruptor
           — Nonylphenol from aqueous solutions
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Bruno Kostura , Radim Škuta , Daniela Plachá , Jana Kukutschová , Dalibor Matýsek
      The paper addresses study of adsorption of widely used and persistent ionic surfactant nonylphenol (NP) onto Mg–Al–CO3 hydrotalcite (HT) and its calcined form (cHT). A combination of experimental techniques (gas chromatography, X-ray diffraction, and FTIR spectroscopy) was used for the characterization of adsorption products and for determination of the residual concentration of NP in the aqueous solution. NP deprotonation at equilibrium pH (7.22 for HT and 9.43 for cHT) was negligible. Adsorption efficiency of HT and cHT in the range 88.3–92.9% was achieved. It was found that for HT and cHT, the same adsorption mechanisms is applied, and depends on the initial concentration of NP in the solution. For the initial concentration c0 <3mgdm−3 the mono-layer adsorption occurs as a result of the polar interaction of the phenolic group of the NP — positively charged surface of HT or rehydratable cHT, whereas for c0 ≥3mgdm−3 multi-layered adsorption prevails. Intercalation of NP into the interlayer space of HT and cHT was not confirmed. The saturation capacity of HT and cHT in the event of the mono-layered adsorption was set at 1.80mgg−1. The physical nature of the adsorption suggests the possibility of easy regeneration of the adsorbent, and thus its reuse.


      PubDate: 2015-07-02T09:43:56Z
       
  • Determination of adsorption isotherms of aniline and 4-chloroaniline on
           halloysite adsorbent by inverse liquid chromatography
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Piotr M. Słomkiewicz , Beata Szczepanik , Magdalena Garnuszek
      Infrared spectroscopy (ATR FT-IR), X-ray fluorescence (WDXRF), and X-ray powder diffraction (XRPD) methods were used to investigate the structure and composition of halloysite mineral. On the basis of the results, we found that the chemical composition of Hal samples is typical as regards clay minerals with the exception of the high levels of iron and titanium oxides. The FTIR spectra of halloysite samples, before and after modifying, with aniline and 4-chloroaniline indicate successive incorporation of these compounds to the halloysite sample. Inverse chromatography is a quick and accurate method to determine adsorption equilibrium constants. The division peak method used previously to inverse gas chromatography was adapted in inverse liquid chromatography. Inverse liquid chromatography was used for aniline and 4-chloroaniline adsorption measurements on halloysite, which was an applying method of division peak. Both adsorption isotherms and enthalpy were determined. Physical significance of adsorption enthalpy was checked by the Boudart's criterion of entropy. In this paper proved that the division peak method of inverse liquid chromatography is useful because adsorption equilibrium constant can be determined with a single adsorbate dosage.


      PubDate: 2015-07-02T09:43:56Z
       
  • Effect of surfactant molecular structure on perchlorate removal by various
           organo-montmorillonites
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Wuhui Luo , Keiko Sasaki , Tsuyoshi Hirajima
      A series of organo-montmorillonites (organo-Mt) was synthesized using various cationic surfactants with different alkyl-chain lengths, head groups, and alkyl-chain numbers, which were systematically examined for perchlorate adsorption. The products were characterized by the specific surface area, field-emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In addition, the surfactant loadings and surface charges were investigated by CHN analysis and zeta potential measurements. The greatest adsorption capacity of 0.95mmol/g-composite was obtained on benzyloctadecyldimethylammonium-modified Mt. Increasing the alkyl-chain length significantly enhanced the capacity and selectivity for perchlorate adsorption, but resulted in decrease of adsorption rate. Compared with trimethylammonium and pyridinium with the same alkyl-chain length, the benzyldimethylammonium as a head group showed better performance in terms of adsorption capacity and selectivity of perchlorate because of higher hydrophobicity. Moreover, increasing the alkyl-chain number decreased adsorption rate, but enhanced adsorption capacity, because of dense packing of alkyl chains and high driving force for entrapment of counter ion-accompanying surfactant. The perchlorate adsorption performance of organo-Mt was synergistically influenced by the alkyl-chain length, head group and alkyl-chain number of the surfactants used for modification.


      PubDate: 2015-07-02T09:43:56Z
       
  • Effect of sludge from oil refining industry or sludge from pomace oil
           extraction industry addition to clay ceramics
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): D. Eliche-Quesada , R. Azevedo-Da Cunha , F.A. Corpas-Iglesias
      This work studies mixing sludge from oil refining industry (SOI) or sludge from pomace oil extraction industry (SPOEI) with clay in order to produce lightweight bricks for civil construction. Applied sludges and clay were previously characterized in terms of chemical and mineralogical composition and thermal behavior. Ceramic bricks were produced with different quantities of sludge (0–30wt.%) as raw material, with conformed bricks being fired at 950°C. In order to determine optimal mixing, physical, mechanical, thermal and chemical properties of bricks were assessed. Results indicated that the type and proportion of waste are important parameters in determining brick quality. Increasing content of SOI or SPOEI resulted in a loss of brick compressive strength and thermal conductivity, due to decreasing bulk density and increasing water absorption. Incorporating 5wt.% of SOI or 10wt.% of SPOEI barely alters properties of clay (control bricks). However, additions exceeding 10wt.% of SOI or 15wt.% of SPOEI led to bricks with low compressive strength due to increasing porosity caused by their content in organic substances, which, during combustion, act as pore forming agents, increasing clay porosity and providing energy support during a brick firing process. Leaching tests, performed according to TCLP standards on substituted brick samples, showed that the quantities of heavy metals leached from crushed bricks were within the regulatory limits.


      PubDate: 2015-07-02T09:43:56Z
       
  • Effects of feed palygorskite inclusion on pelleting technological
           characteristics, growth performance and tissue trace elements content of
           blunt snout bream (Megalobrama amblycephala)
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Ruiqiang Zhang , Xue Yang , Yueping Chen , Rui Yan , Chao Wen , Wenbin Liu , Yanmin Zhou
      The study aimed to investigate the effect of feed palygorskite inclusion on pelleting technological characteristics, growth performance and tissue trace elements content of blunt snout bream, Megalobrama amblycephala. Diets without (control group) or with 2% palygorskite were pelleted and were measured for pelleting technological characteristics. Then the diets were fed to two groups of fish in four replicates (30 fish per replicate) for six weeks. Compared with the control group, dietary 2% palygorskite inclusion enhanced pellet production rate, pellet durability and the degree of starch gelatinization of pellet, and reduced percentage of fines. There was no difference in the weight gain, feed conversion rate, condition factor, hepatosomatic index and viscera/body ratio of fish between groups. Palygorskite supplementation significantly enhanced the Fe content in the blood and muscle and Zn content in the muscle, but reduced muscular Cd concentration. However, the accumulations of Cu and Pb in the body were not affected by palygorskite. The results indicated that dietary palygorskite supplementation could enhance pellet production efficiency, pellet quality, and alter trace elements accumulation in the tissues without impairing growth performance of blunt snout bream.


      PubDate: 2015-07-02T09:43:56Z
       
  • A comparative study of tubular halloysite and platy kaolinite as carriers
           for the loading and release of the herbicide amitrole
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Daoyong Tan , Peng Yuan , Faïza Annabi-Bergaya , Faqin Dong , Dong Liu , Hongping He
      Nanosized tubular halloysite (Hal) and platy kaolinite (Kaol) were used as carriers for the loading and release of the herbicide amitrole (AMT). The AMT loading content in Hal was 17.5 mass% (69.9% greater than in Kaol). This result is attributed to the significant loading of AMT in the lumen of Hal. The methoxy modification of Hal and Kaol made their interlayer spaces available for the intercalation of AMT, which substantially promoted the AMT loading. The AMT loading content in methoxy-modified Hal was 30.5 mass%, corresponding to 27.9% intercalated AMT and 72.1% non-intercalated AMT. The AMT loading content in methoxy-modified Kaol was 20.8 mass%, corresponding to 47.6% intercalated AMT and 52.4% non-intercalated AMT. The release profiles of the AMT fit with the modified Korsmeyer–Peppas model. The methoxy-modified Kaol exhibited a slow release of AMT, which resulted from two factors: (i) the high proportion of intercalated AMT, the diffusion of which was restricted by the lamellar structure of the methoxy-modified Kaol, and (ii) the long diffusion path of intercalated AMT because of the large size of Kaol particles in comparison with Hal particles.
      Graphical abstract image

      PubDate: 2015-07-02T09:43:56Z
       
  • Montmorillonite colloids: I. Characterization and stability of dispersions
           with different size fractions
    • Abstract: Publication date: September 2015
      Source:Applied Clay Science, Volume 114
      Author(s): Knapp Karin Norrfors , Muriel Bouby , Stephanie Heck , Nicolas Finck , Rémi Marsac , Thorsten Schäfer , Horst Geckeis , Susanna Wold
      Bentonite is planned to be used as a technical barrier in the final storage of spent nuclear fuel and high level vitrified waste. In contact with ground water of low ionic strength, montmorillonite colloids may be released from the bentonite buffer and thereby enhance the transport of radionuclides (RNs) sorbed. In the present case, clay colloids represent aggregates of several clay mineral layers. It is of major importance to determine RN sorption properties for different sizes of montmorillonite aggregates, since size fractionation may occur during particle transport in natural media. In this study, a protocol for size fractionation of clay aggregates is developed, by sequential and direct centrifugation, in the presence and absence of organic matter. Seven colloidal fractions of different mean aggregate sizes are obtained ranging, when considering the mean equivalent hydrodynamic sphere diameter (ESD), from ~960nm down to ~85nm. Applying mathematical treatments (Jennings and Parslow, 1988) and approximating the clay aggregates to regular disc-shaped stacks of clay mineral sheets result in mean surface diameters varying from ~1.5μm down to ~190nm. All these colloidal fractions are characterized by XRD, IC and ICP-OES where they are found to have the same chemical composition. The number of edge sites (aluminol and silanol) is estimated (in mol/kg) for each colloidal fraction according to (Tournassat et al., 2003). It is calculated from the mean particle sizes obtained from AsFlFFF and PCS measurements, where the clay aggregates are approximated to regular disc-shaped stacks of clay mineral sheets. The estimated number of edge sites varies significantly for the different clay dispersions. In addition, stability studies using the various clay colloidal fractions are performed by the addition of NaCl, CaCl2 or MgCl2, in the presence or absence of organic matter, where no difference in stability is found.


      PubDate: 2015-07-02T09:43:56Z
       
 
 
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