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  Subjects -> EARTH SCIENCES (Total: 621 journals)
    - EARTH SCIENCES (458 journals)
    - GEOLOGY (67 journals)
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EARTH SCIENCES (458 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: 9)
Aeolian Research     Hybrid Journal   (Followers: 2)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 5)
AMBIO     Hybrid Journal   (Followers: 12)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 1)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 2)
Annals of Geophysics     Full-text available via subscription   (Followers: 10)
Annals of GIS     Hybrid Journal   (Followers: 17)
Annals of Glaciology     Full-text available via subscription   (Followers: 2)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 11)
Anthropocene Review     Hybrid Journal   (Followers: 2)
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 7)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 9)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 21)
Arctic Science     Open Access  
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 9)
Artificial Satellites     Open Access   (Followers: 15)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 18)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 3)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 7)
Atmospheric and Climate Sciences     Open Access   (Followers: 17)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 11)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 18)
Bulletin of Volcanology     Hybrid Journal   (Followers: 15)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 10)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 11)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 11)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 6)
Contemporary Trends in Geoscience     Open Access   (Followers: 1)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 8)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 18)
Cretaceous Research     Hybrid Journal   (Followers: 5)
Cybergeo : European Journal of Geography     Open Access   (Followers: 5)
Depositional Record     Open Access  
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: 4)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 221)
Earth and Space Science     Open Access  
Earth Interactions     Full-text available via subscription   (Followers: 9)
Earth Science Research     Open Access   (Followers: 7)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 2)
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: 2)
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: 11)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 11)
Environmental Geology     Hybrid Journal   (Followers: 11)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)

        1 2 3 4 5 | Last

Journal Cover   Applied Clay Science
  [SJR: 1.17]   [H-I: 71]   [4 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2588 journals]
  • Photoactive hybrid material based on kaolinite intercalated with a
           reactive fluorescent silane
    • Abstract: Publication date: Available online 12 March 2015
      Source:Applied Clay Science
      Author(s): Samuel Sas , Martin Danko , Kamil Lang , Juraj Bujdák
      The main strategies to modify layered silicates with dyes have been based on ion exchange reactions. In this work, the modification was performed via the chemisorption of reactive rhodamine on the surface of kaolinite (Kaol) particles. The reactive dye (RhAptes) was synthesized via the reaction of rhodamine B (RhB) with 3-aminopropyl-triethoxy silane. Efficient modification of the Kaol surface was achieved after the pre-expansion of its structure with dimethyl sulfoxide. RhAptes reacted with the hydroxyl groups of the expanded mineral. The structural characteristics and optical properties of the hybrid material (Kaol-RhAptes) were characterized by X-ray diffraction and spectroscopy in the visible region. Absorption and fluorescence spectra of Kaol-RhAptes were similar to its dye precursors, RhB and RhAptes. Time-resolved fluorescence spectra proved only minor molecular aggregation of bound rhodamine. Partial fluorescence quenching was confirmed by fluorescence quantum yield measurements. We assume that other materials based on Kaol intercalated with various photoactive molecules could be synthesized by the strategy used in this work. Modifications of kaolinite could lead to special materials and might expand their range of applications.
      Graphical abstract image

      PubDate: 2015-03-16T20:01:05Z
       
  • Chemical modification routes of synthetic talc: Influence on its
           nucleating power and on its dispersion state
    • Abstract: Publication date: Available online 14 March 2015
      Source:Applied Clay Science
      Author(s): Brice Fiorentino , René Fulchiron , Véronique Bounor-Legaré , Jean-Charles Majesté , Jérome Crépin Leblond , Jannick Duchet-Rumeau
      New synthetic talcs were incorporated into a polyolefin matrix to prepare synthetic talc polypropylene (PP) nanocomposites via melt mixing. Different routes of physicochemical modifications of short range (cation exchange or silane grafting) or long range (compatibilizer) order were carried out to achieve an optimized dispersion state. A statistical TEM image analysis methodology was developed to evaluate more quantitatively the dispersion state of the talc particles within the PP matrix. Natural talc was taken as a reference in order to compare its nucleating power and its dispersion capacity with that of the synthetic talcs in the same grade of PP. Even though natural talc acts as the most efficient nucleating agent, the organophilic surface treatment enhances significantly the nucleating effect of the synthetic talcs. By coupling the incorporation of a compatibilizer with a suitable organophilic surface treatment, the synthetic talcs can be also better dispersed than their natural counterpart, giving rise to the formation of a heat shield that delays the thermal degradation of the filled matrix.


      PubDate: 2015-03-16T20:01:05Z
       
  • Effect of commercial clays on the properties of SEBS/PP/oil thermoplastic
           elastomers. Part 1. Physical, mechanical and thermal properties
    • Abstract: Publication date: Available online 14 March 2015
      Source:Applied Clay Science
      Author(s): Hugo M. Tiggemann , Vanda F. Ribeiro , Fabricio Celso , Sônia M.B. Nachtigall
      Thermoplastic elastomers based on SEBS/PP/oil blends show good flexibility at low temperatures, allowing complex shapes molding with good finishing. In this study, three different commercially available clays were used as fillers in these blends through melt mixing processes to produce clay polymer nanocomposites (CPN) with improved thermal and mechanical properties. The physicomechanical properties, melt flow index, density and thermal stability of the materials were studied. It was found that optimum concentration was 2phr for all fillers. At this concentration, the mechanical properties reached a maximum while higher filler loading proved to be less beneficial. CPN prepared with Novaclay, a Brazilian clay organically modified with silane, showed the best properties, reaching 60% increase of mechanical resistance in comparison to the non-modified TPE matrix.


      PubDate: 2015-03-16T20:01:05Z
       
  • BiOCl dispersed on NiFe–LDH leads to enhanced photo-degradation of
           Rhodamine B dye
    • Abstract: Publication date: Available online 14 March 2015
      Source:Applied Clay Science
      Author(s): Jianfeng Ma , Jiafan Ding , Liangmin Yu , Liangyin Li , Yong Kong , Sridhar Komarneni
      BiOCl–NiFe–LDH composites were synthesized using NiFe–Cl–LDH and Bi(NO3)3 as precursors and the composites were characterized by XRD, SEM and FTIR. Photocatalytic degradation of Rhodamine B (RhB) dye was tested with BiOCl–NiFe–LDH composite and NiFe–Cl–LDH and BiOCl materials under the same conditions and the composite was found to be superior to both NiFe–Cl–LDH and BiOCl for RhB degradation. The superior performance of the BiOCl–NiFe–LDH composite was related to better dispersion of BiOCl particles on the surface of NiFe–LDH materials. After three-times of recycling, the RhB degradation efficiencies were 93.3%, 90.1% and 87.9% during the first, second and third cycles, respectively. The BiOCl–NiFe–LDH composite prepared here appears to be an efficient and stable composite photocatalyst, which may have potential applications in wastewater treatment field.
      Graphical abstract image

      PubDate: 2015-03-16T20:01:05Z
       
  • Structural and physicochemical aspects of drug release from layered double
           hydroxides and layered hydroxide salts
    • Abstract: Publication date: Available online 14 March 2015
      Source:Applied Clay Science
      Author(s): Ricardo Rojas , Yamila Garro Linck , Silvia L. Cuffini , Gustavo A. Monti , Carla E. Giacomelli
      Layered double hydroxides (LDHs) and Zn layered hydroxide salts (LHSs) present different physicochemical and interfacial properties derived from their dissimilar structure and composition, which affect the release behavior of the intercalated drug. In this work, these aspects are studied using LDHs and LHSs intercalated with ibuprofen (Ibu), naproxen (Nap) or ketoprofen (Ket) to understand the behavior of intercalation compounds as drug carriers. The structure of the solids and the interaction mode between the drugs and the layers were determined by chemical analysis, PXRD, FTIR and NMR. Further, the interfacial properties (potential zeta and hydrophilic/hydrophobic character) of the solids, as well as their drug release profiles were also comparatively studied. The drugs were attached by electrostatic interactions to LDH layers while coordinate bond was produced in the case of LHSs. The different interaction modes, together with the higher drug density between LHS layers produced more crystalline solids with larger basal spacing values than the corresponding LDH. This detailed structural study allowed for establishing the correlations between structure, interactions, morphology, interfacial properties and drug release behavior. Thus, the different interaction modes determined the surface charging behavior, while the solubility of LHS layers led to a fast drug release in neutral media. Finally, the loose drug arrangement in the hybrids caused a solubility increase in acid media. These correlations are helpful to predict and optimize the behavior of drug delivery systems based on both LDHs and Zn–LHSs.
      Graphical abstract image

      PubDate: 2015-03-16T20:01:05Z
       
  • Ultrafine hydrotalcite particles prepared with novel technology to improve
           the flame retardancy of polypropylene
    • Abstract: Publication date: Available online 10 March 2015
      Source:Applied Clay Science
      Author(s): Sheng Xu , Meng-Chen Liao , Hong-Yan Zeng , Zhi-Qing Zhang , Xiao-Jun Liu , Pei-Han Zhu
      Ultrafine Mg/Al hydrotalcite particles (RMAH) were synthesized by co-precipitation in high-gravity environment generated by a rotating packed bed reactor with (NH4)2CO3 as precipitant. Sodium tripolyphosphate modified RMAH (S-RMAH) was investigated as potential flame retardant for polypropylene (PP) material. The RMAH and S-RMAH materials were characterized using XRD, SEM/EDS, TG–DTG, FT-IR, BET, particle size distribution, pH point of zero charge and so on. The S-RMAH particles which were coated by P3O10 5− possessed smaller particle sizes and narrower sizes range, and their surface property was modified from hydrophilic to hydrophobic nature. As novel functional fire-retarding nanofillers, the RMAH and S-RMAH were used to prepare PP/RMAH and PP/S-RMAH composites, aiming to investigate the effect of the nanofillers on the flammability, compatibility and mechanical properties of PP material. The thermal stability, morphological and flame retardant properties of the two composites were determined by SEM, TGA, LOI and UL94 analyses, and their mechanical properties were also characterized. The results showed that the RMAH and S-RMAH could significantly enhance the thermal stability, flammability and mechanical properties of PP material, and the S-RMAH had better performances as a flame retardant for PP than the RMAH. It offered a new approach to preparing ultrafine hydrotalcite nanoparticles with high anti-flaming performances.


      PubDate: 2015-03-12T19:49:36Z
       
  • Calcium-free geopolymer as a stabilizer for sulfate-rich soils
    • Abstract: Publication date: Available online 10 March 2015
      Source:Applied Clay Science
      Author(s): Mo Zhang , Mengxuan Zhao , Guoping Zhang , Peter Nowak , Adam Coen , Mingjiang Tao
      The expansion and heaving of sulfate-rich soils is a long-lasting challenge for soil stabilization with calcium based stabilizers, such as lime and cement. It is caused by the formation of an expansive mineral, ettringite, when calcium and water are introduced to a sulfate concentrated soil. This study aims to explore the feasibility of using calcium-free geopolymer, which is an inorganic aluminosilicate cementitious material, as a stabilizer for sulfate-rich soils. To this end, metakaolin based geopolymer (MKG) was used to stabilize a synthetic lean clay premixed with 1000, 5000 and 10,000ppm gypsum (equivalent to the sulfate concentration of 565, 2825 and 5650ppm, respectively). The clay samples were stabilized with MKG at 8 and 13wt.%, and their mechanical properties and swelling potential were determined through unconfined compression test and water bath soaking, respectively. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometer (XRD) tests were performed to further examine the microstructural and mineralogical characteristics of the clay samples. In addition, control sample sets, including unstabilized clay, lime- and cement-stabilized clay, were prepared and tested for providing a reference baseline to evaluate if MKG is an effective stabilizer for sulfate-rich soils. The unconfined compressive strength, Young's Moduli and failure strain of the clay samples were significantly increased after the stabilization with MKG. The swelling strain of the samples stabilized with the geopolymer was much lower than that of 4% lime stabilized counterparts after soaking in water. Geopolymer gels, but no ettringite crystal, were observed in geopolymer stabilized clay samples, as confirmed with the SEM–EDX results and XRD spectra. The results from this study confirmed that calcium-free geopolymer can be an effective stabilizer for sulfate-rich soils without excessive expansions. Using higher concentrations of geopolymer and geopolymers synthesized from industrial wastes is worth being studied in the future to further develop geopolymer-based stabilization technique for sulfate-rich soils.
      Graphical abstract image

      PubDate: 2015-03-12T19:49:36Z
       
  • Effect of clay modifier on morphology, thermal properties and flammability
           of newly synthesized poly(sulfide–sulfone–amide)
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Meisam Shabanian , Mansooreh Varvanifarahani , Mohsen Hajibeygi , Hossein Ali Khonakdar , Sattar Ebrahimi , Seyed Hassan Jafari
      A novel polyamide bearing sulfide and sulfone units was synthesized through a direct polycondensation reaction between 2,2′-(phenylmethylene)bis(sulfanediyl)diacetic acid and 4,4′-diaminodiphenylsulfone. The resulting poly(sulfide–sulfone–amide) (PSA) exhibited high solubility in organic solvents such as tetrahydrofuran. A series of nanocomposites based on the synthesized functional polyamide loaded with a reactive organoclay containing triazine ring (Mt-Traz) and also with Cloisite 15A (Mt-15A) as reinforcing agents were prepared through a solution technique. Flammability and thermal stability of the neat PSA and corresponding nanocomposites were studied by microscale combustion calorimetry (MCC) and thermogravimetric analysis (TGA) techniques. Thermal properties of the nanocomposites were strongly influenced by the nature of the modifiers. Use of Mt-Traz led to a more improved flame retardancy and higher thermal stability as compared to Mt-15A. According to the MCC data, by introducing 5 mass% of Mt-Traz into PSA matrix a reduction of about 25% in the peak heat release rate and 47% in total heat release values was observed, while incorporation of Mt-15A led to a reduction of about 13% and 27% in those values.
      Graphical abstract image

      PubDate: 2015-03-12T19:49:36Z
       
  • Incorporation of paper sludge in clay brick formulation: Ten years of
           industrial experience
    • Abstract: Publication date: Available online 12 March 2015
      Source:Applied Clay Science
      Author(s): J.A. Cusidó , L.V. Cremades , C. Soriano , M. Devant
      The large amounts of sewage sludge (11million tonnes in Europe in 2005) produced in paper manufacturing plants require the introduction of recycling and/or alternative recovery solutions to minimize the amounts of generated waste, such as its use in soil remediation or in the cement industry. A feasible alternative to valorize that waste is the use of paper sludge as raw material in the production of structural ceramic or clay bricks. Previous studies tried to incorporate sewage sludge from different sources into ceramic matrices, unfortunately with little success in the final result for most types of sludge. However, those experiments carried out using as additive sludge from the paper industry succeeded in producing a material suitable for the red ceramic industry. In this paper, binary mixtures of clay and paper sludge under different formulations were produced and their physico-chemical properties were studied. Increasing the paper sludge content in the clay mixture provides the material with improved properties regarding its thermal and acoustic insulation, but in turn it decreases its mechanical strength. However, this fragility of the material is compensated by an increased ductility. Regarding metal leaching, the studied ceramics have no environmental restrictions as far as their use as building material is concerned, as the obtained results were virtually identical to those for the blank samples (100% clay). Results showed that the presence of dichloromethane (373.2μgm−3) and propanone (61.2μgm−3) in the samples with added sludge was relatively relevant with respect to concentrations in samples made of 100% clay. All monocyclic aromatics detected showed a concentration level far below their odor threshold. In general, thus, it can be concluded that volatile organic compound (VOC) emissions during firing of the new ceramic material do not involve any particular problem. Finally, the experience obtained after more than 10years of industrial production of this new mixed ceramic product was also analyzed. This analysis allowed confirmation that clay brick production with incorporation of paper sludge waste is a feasible solution from a technical point of view. As a key outcome, this fact has helped the reduction in a large proportion the amount of sludge produced by the Spanish paper industry ending up in landfills.


      PubDate: 2015-03-12T19:49:36Z
       
  • Effects of bentonite concentration and solution pH on the rheological
           properties and long-term stabilities of bentonite suspensions
    • Abstract: Publication date: Available online 6 March 2015
      Source:Applied Clay Science
      Author(s): Ko Yeon Choo , Kang Bai
      The influences of bentonite concentration and solution pH on the rheological properties and long-term stabilities of bentonite suspensions were studied in this research. Rheological properties were measured at bentonite concentrations of 5, 7, and 9wt.%. It was found that the viscosity and shear stress increased with increasing bentonite concentration and storage time. The initial shear stress of the 9wt.% bentonite suspension grew larger with increasing storage time than did the yield stress value obtained from Herschel–Bulkley model fitting. The result showed that a significant yield value was required to break the particle network due to the large cohesion force between the particles. Rheological properties and zeta potentials were measured with various amounts of a 1M HCl solution added to a 5wt.% bentonite suspension. The amount of HCl solution added had a significant impact on the zeta potential of the bentonite suspension. The absolute value of the zeta potential decreased as the added amount of HCl solution increased. Therefore, particle aggregation was facilitated due to a decrease in the stability of the suspension. Comparing the shear stress obtained from the upward flow curve at a shear rate of 3.4 1/s with the yield stress obtained from the downward flow curve fitted with the Herschel–Bulkley model or Bingham model, as a function of the added amount of HCl solution, showed that the difference between the two values was large in acidic media with high HCl content, but insignificant in neutral or basic media. In addition, the large shear stress phenomenon at a shear rate of 3.4 1/s diminished with increasing storage time, which was due to the change in the pH of the suspension from acidic through neutral, to basic with increasing storage time.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Synthesis and characterisation of geopolymer from Nigerian Clay
    • Abstract: Publication date: Available online 7 March 2015
      Source:Applied Clay Science
      Author(s): Mary B. Ogundiran , Sanjay Kumar
      Nigerian Ikere-clay has been characterised for its possible use in synthesis of geopolymer binder. The significance of endothermic peaks at the dissolution/hydrolysis stage on alkaline reactivity of the clay and geopolymer strength development was also investigated. The clay, which was of kaolin type, was thermally treated to convert it into amorphous metakaolin which is more reactive precursor for geopolymer synthesis. Geopolymer has been synthesised at ambient temperature using sodium hydroxide and/or sodium silicate solution. The characteristics of clay and clay derived geopolymer were evaluated using x-ray fluorescence (XRF), x-ray diffraction (XRD), Fourier transform infra-red spectrometry (FTIR), laser particle size analyser and scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX). The reactions occurred during geopolymerisation were monitored using isothermal conduction calorimeter. FTIR revealed the existence of Al-O and Si-O stretching vibrations of amorphous alumino-silicate network for clay and geopolymers. SEM-EDX images confirmed the presence of reaction product corresponding to NASH (N=NaO, A=Al2O3, S=SiO2, H=H2O) gel. Attempts were made to correlate the microstructure with strength development. The maximum compressive strength of 28.2MPa was obtained for geopolymer that was synthesised with NaOH/Na2SiO3 solution and cured at 27°C for 28days. The samples with good compressive strength showed compact microstructure. The results demonstrated the suitability of Nigerian kaolinitic clay for synthesis of geopolymer at ambient temperatures.


      PubDate: 2015-03-08T17:43:15Z
       
  • Effects of solvothermal process on the physicochemical and adsorption
           characteristics of palygorskite
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Zhifang Zhang , Wenbo Wang , Aiqin Wang
      Palygorskite (PAL) was treated with various organic solvents including methanol (MT), ethanol (ET), isopropanol (IPA), dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) via a facile solvothermal process. The effects of various solvents and reaction parameters on the microstructure, morphology and adsorption properties of PAL were intensively investigated. Fourier transformation infrared spectrometry (FTIR) and thermogravimetric (TG) analyses confirmed that some solvent molecules could be encapsulated in the tunnels of PAL and the polarity of solvent molecules plays an important role for their interaction with PAL. Field-emission scanning electron microscopy (FESEM) shows that the solvothermal treatment results in a better dispersion of PAL crystal bundles. The treated PAL by various solvents has relatively higher adsorption capacity (from 119mg/g to 154mg/g) and removal efficiency for methylene blue (MB) than the raw PAL, and the improved electrostatic and hydrogen-bonding interactions between MB and PAL are mainly responsible for the enhancement of adsorption properties. The adsorption properties of PAL for MB were greatly affected by the characters of solvents, and DMF-treated PAL gives the best adsorption and removal capabilities for MB.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Novel polyamidoamine dendrimer-functionalized palygorskite adsorbents with
           high adsorption capacity for Pb2+ and reactive dyes
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Shouyong Zhou , Ailian Xue , Yan Zhang , Meisheng Li , Kang Li , Yijiang Zhao , Weihong Xing
      Novel polyamidoamine (PAMAM) dendrimer-functionalized palygorskite (Pal) adsorbents, up to generation 4.0, with high adsorption capacity, were designed and efficiently synthesized by grafting PAMAM onto 3-aminopropyltriethoxysilane-modified palygorskite (NH2-Pal) surfaces. This was carried out using a divergent method including the Michael addition of methyl acrylate (MA) and amidation of the resultant ester moieties with ethylenediamine (EDA). The optimal conditions for Michael addition were achieved using 88.8mmol MA (relative to 4.0g NH2-Pal) at 323K for 24h. The optimal conditions for amidation of the resultant esters were achieved using 179.3mmol EDA (relative to 2.1g Pal-PAMAM G0.5) at 323K for 48h. All of the amino-terminated Pal-PAMAM G(n) (n =0, 1, 2, 3 and 4) adsorbents exhibited very high density amino-terminated groups and adsorption capacities for both Pb2+ and Reactive Red 3BS, which increased with increasing generation number. The maximum adsorption capacity for Pb2+ at 293K was 68.5±3.3, 151.1±5.7, 196.5±6.1, 389.1±9.6 and 694.4±12.9mg/g for Pal-PAMAM G(n) (n =0, 1, 2, 3 and 4), respectively. The maximum adsorption capacity for Reactive Red 3BS at 293K was 34.2±2.7, 69.9±4.3, 122.0±6.4, 242.7±7.1 and 322.6±6.9mg/g for Pal-PAMAM G(n) (n =0, 1, 2, 3 and 4), respectively.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Selective adsorption of CO2 on a regenerable amine-bentonite hybrid
           adsorbent
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Ali E.I. Elkhalifah , M. Azmi Bustam , A.M. Shariff , T. Murugesan
      The ability of magnesium form of bentonite modified by monoethanolammonium cations (MEA+-Mg-bentonite) to reversibly and selectively adsorb CO2 over other light gases, such as CH4 and N2 has gravimetrically been investigated using a Magnetic Suspension Balance (MSB) equipment. Before CO2 adsorption measurements, untreated bentonite and MEA+-Mg-bentonite were characterized by XRD, FTIR, TGA and BET techniques to establish their structural characteristics, thermal stability and specific surface area and porosity characteristics. The results showed that MEA+-Mg-bentonite adsorbed higher CO2 amount compared to untreated bentonite under similar conditions. The equilibrium isotherms for CO2 adsorption on untreated bentonite and MEA+-Mg-bentonite were measured at 25, 50 and 75°C and a pressure range of 01.0bar. It was found that MEA+-Mg-bentonite has static CO2 adsorption capacities of 0.79, 0.69 and 0.56mmol/g, compared to 0.45, 0.36 and 0.30mmol/g for untreated bentonite at temperatures of 25, 50 and 75°C and a pressure of 1bar, respectively. The calculated values of the thermodynamic parameters revealed that the process involving CO2 adsorption on MEA+-Mg-bentonite adsorbent was a physical, spontaneous and exothermic. Moreover, the results showed moderate and slightly high equilibrium selectivities for CO2 over CH4 on MEA+-Mg-bentonite with the values of 1.36, 4.85 and 3.43 at 25, 50 and 75°C, respectively. However, MEA+-Mg-bentonite showed equilibrium selectivity for CO2 over N2 as high as 13.79, 9.91 and 6.32 at 25, 50 and 75°C, respectively. Regenerative ability in short runs of isothermal CO2 adsorption–desorption cycles revealed that MEA+-Mg-bentonite adsorbent was able to undergo several CO2 adsorption–desorption cycles without noticeable decrease in its adsorption capacity. Clearly, amine-bentonite hybrid adsorbents are promising inexpensive materials for CO2 capture.


      PubDate: 2015-03-08T17:43:15Z
       
  • Development of transition metal oxide–kaolin composite pigments for
           potential application in paint systems
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Swagata Roy , Subrata Kar , Biswajoy Bagchi , S. Das
      The present work deals with a simplified process for synthesizing metal oxides of Cu(II), Ni(II), Cr(III) and Fe(III) imbibed kaolin pigments and characterizing those samples using X-ray diffraction, Fourier transform infrared spectroscopy, FESEM and EDS in addition to the visual classification by color. Furthermore, PEG analysis and antimicrobial potency of these samples were investigated thoroughly which conferred positive impact depicting the fact that these metal oxides incorporated kaolin composites can serve as a good and promising ceramic pigment material in paint systems. Due to easy availability of kaolin and involvement of low temperature, the production cost of these synthesized pigments is highly reduced which can be an added advantage to the paint industry.


      PubDate: 2015-03-08T17:43:15Z
       
  • Thermally treated clay sediments as geopolymer source material
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): C. Ferone , B. Liguori , I. Capasso , F. Colangelo , R. Cioffi , E. Cappelletto , R. Di Maggio
      The management of reservoirs for water supply is a great environmental problem, since regular de-silting operations produce huge quantities of sediments. Among the recycling possibilities, the use of clay sediments for the manufacture of geopolymer-based materials seems to be an interesting alternative to disposal, due to their low cost and easy availability. In particular, two sediments, coming from reservoirs located in Southern Italy, were firstly characterized by X-ray diffraction, differential thermogravimetry, Fourier transformed infrared (FTIR) spectroscopy and 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy. The reactivity of raw and thermally treated clay sediments in alkaline media was also investigated. Finally, geopolymeric samples were produced and chemically, physically and mechanically characterized. The results showed that the calcined clay sediments can be suitable source materials in polycondensation reactions and that the increase of the calcination temperature from 400 to 750°C resulted in an increased reactivity. Moreover, good mechanical properties were obtained by all the geopolymers prepared with heat-treated sediments.


      PubDate: 2015-03-08T17:43:15Z
       
  • Influence of gibbsite and quartz in kaolin on the properties of
           metakaolin-based geopolymer cements
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): H.K. Tchakoute , C.H. Rüscher , J.N.Y. Djobo , B.B.D. Kenne , D. Njopwouo
      Three different kaolins (K1, K2, K3) from sources in Cameroon were applied for producing geopolymer cements. The kaolins differ significantly in their gibbsite and quartz contents. Thermal transformation (700°C, 4h) into their metakaolins MK1, MK2, MK3 shows the total loss of crystalline kaolinite and reveal the typically rather broad bump in the X-ray pattern. Gibbsite becomes dehydrated into γ and χ-Al2O3. Geopolymer cements (GP1, GP2, GP3) were obtained using freshly prepared sodium silicate solutions (NWG) with a ratio NWG/MK=0.87. It could be observed that the initial (60/80/90min) and final (90/140/160min) setting time increases and their 28day compressive strength (49/39/30MPa) decreases in the course GP1/GP2/GP3. It is discussed that the higher content of quartz in K1 (up to 22wt.%), compared to K2 (10wt.%) and K3 (8wt.%) promotes higher strength values and decreased setting times. Gibbsite was not present in K1, but up to 11wt.% in K2 and 28 wt.% in K3, transformed in its dehydrated forms remains unreacted during geopolymerization. Therefore, the higher content of gibbsite in the kaolinite could be related to a lower strength. The reacted volumes and compositions of the geopolymer become almost the same in all three cases. A content of 30–50% of unreacted metakaolin was proved in all cases.


      PubDate: 2015-03-08T17:43:15Z
       
  • Template-free synthesis of kaolin-based mesoporous silica with improved
           specific surface area by a novel approach
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Tiantian Li , Zhu Shu , Jun Zhou , Yun Chen , Dongxue Yu , Ximing Yuan , Yanxin Wang
      A novel template-free method is proposed and demonstrated to develop the facile top-down strategy of preparing mesoporous materials from natural minerals. In the process, kaolin was pre-calcined, alkali-activated and finally acid-etched into mesoporous silica (MS) of improved specific surface area (604m2/g) and large pore size (4.41nm) at the maximum probability. The characterizations of XRF, XRD, TG, FT-IR, SEM, TEM and N2 adsorption/desorption were carried out and the material evolution mechanism was clarified. The as-resulted MS showed favorable adsorption ability toward methylene blue with the monolayer adsorption capacity up to 652.9mg/g, indicating its promising potential in adsorption application. The template-free method proposed may benefit not only the clay products but also the wide application of mesoporous materials cost-effectively.


      PubDate: 2015-03-08T17:43:15Z
       
  • Exfoliation and intercalation of montmorillonite by small peptides
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Karin A. Block , Adrianna Trusiak , Al Katz , Alexandra Alimova , Hui Wei , Paul Gottlieb , Jeffrey C. Steiner
      Understanding structural changes in clay minerals induced by complexation with organic matter is relevant to soil science and agricultural applications. In this study, the effect of peptide storage in montmorillonite and the thermal stability of peptide–clay complexes were examined through characterization by X-ray diffraction (XRD), electron microscopy, UV absorption, and thermogravimetric analysis (TGA). XRD analysis of small peptide–montmorillonite clay complexes produced profiles consisting of reflections associated with the smectite 001 reflection and related peaks similar to that produced by a mixed layer clay mineral structure. Shifts in higher order diffraction maxima were attributed to disorder caused by the intercalation with the peptides. Increasing peptide concentrations resulted in greater shifts toward smaller 2θ from 6.37° (1.39nm) to 5.45° (1.62nm) as the interlayer space expanded. The expansion was accompanied by broadening of the 001 reflection (FWHM increases from 0.51 to 1.22° 2θ). The XRD line broadening was interpreted as caused by poorer crystallinity resulting from intercalation and tactoid exfoliation. SEM images revealed montmorillonite platelets with upwardly rolled edges that tend toward cylindrical structures with the production of tubules. High-resolution TEM images revealed bending of montmorillonite platelets, confirming exfoliation. The distribution of basal spacings in the micrographs was determined from the spatial frequencies obtained by Fourier analysis of density profiles. The distribution indicated the presence of discrete coherent crystallite domains. XRD and TGA results indicated that higher peptide concentrations resulted in a greater fraction of intercalated peptides and that surface adsorption of peptides mediated intercalation. Therefore, higher peptide concentration led to more stable organoclay complexes. However, UV absorption and TGA found that peptide adsorption onto montmorillonite had a finite limit at approximately 16% by weight.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Synthesized palygorskite/polyaniline nanocomposite particles by oxidative
           polymerization and their electrorheology
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Hyun Sik Chae , Wen Ling Zhang , Shang Hao Piao , Hyoung Jin Choi
      Palygorskite (Pal) clay coated with semiconducting polyaniline (PANI) nanocomposite particles was prepared by oxidative polymerization using aniline monomer in the presence of Pal. The morphological characteristics of the synthesized Pal/PANI composite particles were examined by both field emission scanning electron microscopy and transmission electron microscopy. A rotational rheometer was also used to examine the rheological behavior of the Pal/PANI composite-based electrorheological (ER) fluid when the nanocomposite particles were dispersed in silicone oil. From its flow curve of shear stress vs. shear rate investigated under an applied electric field, the typical ER behavior of the Pal/PANI-based ER fluid was observed. In addition, polarizability and relaxation time of the ER system obtained from the dielectric spectra were well correlated with its ER performance.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Development of sustainable fired clay bricks by adding kindling from vine
           shoot: Study of thermal and mechanical properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Pedro M. Velasco , María Pilar M. Ortiz , Manuel Antonio M. Giró , Daniel M. Melia , Jorge H. Rehbein
      This paper studies the addition of kindling from vine shoots in the production of fired clay bricks in order to achieve a better insulation of the buildings enclosure and a new way for recycling vine shoots, a waste which is widely produced in vineyards. Therefore, the influence of kindling addition on the thermal and mechanical properties of the fired clay bricks has been investigated in partnership with a local brick factory. As result, it could be concluded that the amount of kindling that can be added is around 11%, whereby the brick's mechanical and physical properties abide by settled regulations for structural clay bricks, in accordance with current regulations. The added waste has improved bricks conductivity properties by reducing it up to 62% compared to the brick made without any waste. This means an improvement up to 34% for the equivalent thermal transmittance of a typical single-leaf wall assembly.


      PubDate: 2015-03-08T17:43:15Z
       
  • Pre-historic production of ceramics in the Amazon: Provenience, raw
           materials, and firing temperatures
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Suyanne Flavia Santos Rodrigues , Marcondes Lima da Costa , Herbert Pöllmann , Dirse Clara Kern , Maura Imazio da Silveira , Renato Kipnis
      The chemical–mineralogical properties of prehistoric ceramics found in the Amazon were investigated with the aim of elucidating the production technology, the raw materials used, and the origin of these materials. For this, sherds were obtained from three archeological sites located in distinct regions of the basin. The mineralogical composition of the samples was determined by X-ray diffraction, optical microscopy, thermal analyses, FT-IR, and SEM-EDS, while the chemical composition was measured using ICP-OES and ICP-MS. The manufacturing process consisted of the coiling technique with the smoothing of surfaces, and the addition of organic and mineral non-plastic materials. The pots were fired at ±600°C, leading to the formation of an amorphous metakaolinite matrix in which a number of different types of non-plastic materials can be found. These non-plastic materials, together with the phosphates found in the samples, represent the principal differences in the chemical and mineralogical composition of the sherds from different sites. The raw material (clay) used for the production of the ceramic sherds from the Da Mata and Jabuti sites had the same geological origin, and were distinct from those of Monte Dourado 1 in relation to the intensive use of crushed rock. Cariapé was found throughout the region, and the shells reflect the proximity of the Jabuti site to the ocean. The phosphates found in the matrix probably formed during the use of the pots to prepare food, and could not have been part of the raw material, given that they would not have resisted the firing temperature. The evidence indicates that the potters used the materials available locally for the production of ceramics. The use of cariapé at all the sites confirmed that this practice was widespread in the region, representing an important cultural trait of the production of ceramics in the prehistoric Amazon.


      PubDate: 2015-03-08T17:43:15Z
       
  • Photoelectrochemical properties of dye-dispersing allophane–titania
           composite electrodes
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Hiromasa Nishikiori , Naohiro Kanada , Rudi Agus Setiawan , Koji Morita , Katsuya Teshima , Tsuneo Fujii
      Dye-dispersing allophane–titania composite electrodes were prepared from titanium alkoxide sols containing dye and allophane. The photoelectric conversion properties of the electrodes were investigated by photoelectrochemical measurements. The photocurrent values in the UV range decreased with an increase in the allophane content, whereas those in the visible range were increased by adding 1.0% (Al/Ti ratio) allophane. As a small amount of allophane nanoparticles were highly dispersed in the titania electrodes, the dye molecules were dispersed in the electrodes without decreasing the efficiency of the electron injection from the dye to the titania conduction band. The dye molecules dispersed on the titania nanoparticle surface were capped with allophane nanoparticles which prevented desorption. The dye molecules strongly interacted with the titania nanoparticle surface and efficiently injected the excited electrons into the titania conduction band.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Theoretical studies of the interaction of terephthalate anion in
           MgAl-layered double hydroxides
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Inna M. Nangoi , Viviane S. Vaiss , Wladmir F. Souza , Sandra S.X. Chiaro , Alexandre A. Leitão
      We used first principles calculations based on Density-Functional Theory to investigate the structural and electronic properties of Mg–Al-TA (TA=terephthalate anion) layered double hydroxides for the relations x = N Al/(N Al + N Mg) equal to 1/4, 1/3 and 1/2. Value of x =1/2 is unusual in the literature due to the so-called cation avoidance rule; notwithstanding, some experimental results have demonstrated that it is possible to be obtained using TA as counterion. The calculated geometric parameters are in good agreement with available experimental data. The gauge-including projector augmented wave method was applied to compute solid state nuclear magnetic resonance chemical shifts of terephthalate's carbons for structure with x =1/3. A good correlation between the minimum energy for TA rotating angle and the chemical shifts was obtained. The interlayer interactions were discussed on the basis of electronic density differences and Bader charge analysis. Our calculations show that the electron density in the interlayer region does not change significantly while the molar ratio x increases. This result is in line with the Bader analysis. The calculations show that there is a major change in the difference of charge density between water molecules and layer than anion and layer when the molar ratio x increases. This result demonstrates the importance of water molecules in the stabilization of LDHs with higher layer charge. Also, a geometric factor helps in the formation of structures with x =1/2. That is, the area occupied by each positive charge in the layers needs to be large enough to have the TA anions in the interlayer space along the c structural vector.


      PubDate: 2015-03-08T17:43:15Z
       
  • X-ray absorption spectroscopy study of Cu(II) coordination in the
           interlayer of montmorillonite
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Sung Pil Hyun , Kim F. Hayes
      Cu(II) coordination in the interlayer of an expandable clay mineral montmorillonite is studied using X-ray absorption spectroscopy (XAS) along with electron paramagnetic resonance (EPR) and X-ray diffraction (XRD). Ab initio calculations are performed using FEFF code to reproduce the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) portion of the experimentally measured XAS spectra. Cu(II) coordination changes depending on the Cu(II) loading and hydration state of the interlayer. XRD shows that the Cu-saturated montmorillonite has d 001-spacing values corresponding to the interlayer thickness of four and one water layer(s) for the hydrated and dehydrated interlayers, respectively. EPR shows that Cu(II) in the fully hydrated, unsaturated interlayer behaves similarly to free Cu(II) ion in a bulk aqueous solution, while Cu(II) forms a square planar complex in the dehydrated interlayer. Cu(II) in the fully hydrated, Cu-saturated montmorillonite has a characteristic singlet 1st derivative XANES spectrum. FEFF calculations show that this singlet feature originates from a quasi-regular octahedral coordination of water molecules around the interlayer Cu(II) atom. All other samples and model compounds including the dry Cu-saturated montmorillonite, wet and dry unsaturated montmorillonite, aqueous Cu(II), cupric nitrate salt (Cu(NO3)2·4.5H2O), and Cu(II) hydroxide precipitates have doublet 1st derivative XANES spectra. FEFF calculations suggest that the doublet features arise from an axially elongated octahedral coordination under the Jahn–Teller effect or square planar coordination. FEFF calculations of the EXAFS spectra as a function of the axial oxygen bond length demonstrate that a destructive interference between backscattering from equatorial oxygen (Oeq) and that from axial oxygen (Oax) atoms leads to an apparent coordination number (CN) less than six expected for the tetragonal coordination, with the farther, loosely bound axial oxygen atoms making a minor, yet negative contribution to the CN determined by the EXAFS analysis. This study shows that Cu(II) has interchangeable octahedral, tetragonal, and square planar coordinations in the interlayer of montmorillonite, depending on Cu(II) loading and degree of hydration. The quasi-regular octahedral coordination of the interlayer Cu(II) in montmorillonite is a new finding of this study.


      PubDate: 2015-03-08T17:43:15Z
       
  • Stabilization treatment of a dispersive clayey soil using granulated blast
           furnace slag and basic oxygen furnace slag
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): A.R. Goodarzi , M. Salimi
      Dispersive clays may pose considerable distress if not adequately taken care of. On the other hand, the treatment of problematic soils with waste materials has been recently proved to be a useful option from economic and environmental view point. Hence, in this research, the potential use and effectiveness of dispersive soil stabilization using two types of industrial by-product, including granulated blast furnace slag (GBFS) and basic oxygen furnace slag (BOFS) were investigated. The slags were separately added (ranging from 2.5 to 30%) to a laboratory dispersed sample and a set of experiments were performed to study the physicochemical, mechanical and microstructural changes of the stabilized soil. The results indicate that the soil dispersion can be eliminated upon adding 10% BOFS. This is attributed to the exchange of interlayer sodium ions on the clay surfaces by multivalent cations from the agent. Besides, an increase in the ion concentration of soil-additive mixtures induces a more depression of the diffuse double layer that decreases the soil dispersivity potential. With increasing the curing time, an improvement in the strength of composite samples is observed. The formation of cementitious compounds due to the pozzolanic reactions is responsible for such a treatment, as confirmed by the XRD analyses and SEM micrographs. It appears that the GBFS has a lower activity as compared to BOFS, therefore causes less influence on the soil engineering parameters and a higher percentage (20–25%) of GBFS is required to govern soil dispersion. Overall, utilization of the studied slags particularly of BOFS is very effective to overcome the problems associated with dispersive soils.


      PubDate: 2015-03-08T17:43:15Z
       
  • Mineralogical study of calcined coal waste in a pozzolan/Ca(OH)2 system
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Rosario García , Raquel Vigil de la Villa , Moisés Frías , Olga Rodriguez , Sagrario Martínez-Ramírez , Lucía Fernández-Carrasco , I.S. de Soto , E. Villar-Cociña
      Activated carbon mining waste influences the formation of hydrated phases, their saturation indexes and mineral stability fields during pozzolanic reactions. The behavior of these reactions is predicted in this study by examining the influence of carbon waste at 600°C over 2h, by means of a thermodynamic model running on a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations (PHREEQC program: pH-REdox-Equilibrium in Program C). Experimental analysis of the solid phases shows early formation of monosulfoaluminate hydrate, C–S–H phases and subsequent precipitation of laminar minerals, tetracalcium aluminate hydrate, layered double hydroxide compounds (phyllosilicate/carbonate) (LDH) and stratlingite. Monosulfoaluminate hydrate was formed on day one of the reaction for samples with activated coal mining waste. The thermodynamic calculations confirmed the experimental observations.


      PubDate: 2015-03-08T17:43:15Z
       
  • Synthesis, optimisation and characterisation of the zeolite NaA using
           kaolin waste from the Amazon Region. Production of Zeolites KA, MgA and
           CaA
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Ana Áurea B. Maia , Roberto F. Neves , Rômulo S. Angélica , Herbert Pöllmann
      This study aimed to use industrial kaolin waste from the Capim (KC) and Jari (KJ) regions of northern Brazil in the synthesis of the zeolite NaA. A temperature of 110°C was kept constant throughout the synthesis process of the zeolite NaA, and the durations and Na/Al ratios were altered. The results of X-ray diffraction (XRD) analysis showed that high purity zeolite NaA with a high degree of structural order was produced in the following conditions: a Na/Al ratio of 1.64 for KC and KJ and synthesis durations of 18h for KC and 20h for KJ. According to the XRD results, which indicated the formation of the zeolites KA, MgA and CaA, the process of cation exchange between the Na from zeolite NaA and the K, Mg and Ca from the solutions was efficient.


      PubDate: 2015-03-08T17:43:15Z
       
  • Boron isotopic fractionation in aqueous boric acid solutions over
           synthetic minerals: Effect of layer and surface charge on fractionation
           factor
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Gökhan Elmaci , Okan Icten , Ahmet Nedim Ay , Birgül Zümreoglu-Karan
      Boron isotopic fractionation in boric acid solutions during adsorption on synthetic manganese oxides (birnessite “B” and cryptomelane “C”) and Mg–Al-layered double hydroxide “LDH” was investigated. The materials were characterized by elemental analyses, powder X-ray diffraction, FTIR spectra, BET surface area and zeta potential measurements. Batch experiments were conducted without changing the solution pH to correlate the boron sorption properties of the adsorbents with isotopic fractionation in the associated boric acid solutions. The results showed that boron isotopic composition of the contact solution is heavily dependent on the selective adsorption of B(OH)3 or B(OH)4 − species due to the charge properties of the minerals. With B and C, possessing negatively charged surfaces, 10B(OH)4 − was preferentially fractionated in the solution due to the transfer of the Lewis acidic 11B(OH)3 species while with LDH selective adsoption of 10B(OH)4 − by positive layers was favorable resulting in the enrichment of the heavier isotope in the solution.


      PubDate: 2015-03-08T17:43:15Z
       
  • Designing and optimization of separation process of iron impurities from
           kaolin by oxalic acid in bench-scale stirred-tank reactor
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): M. Taran , E. Aghaie
      Kaolin leaching by oxalic acid in a bench-scale stirred-tank reactor using response surface methodology and face centered central composite design based on three variables: oxalic acid concentration (X 1: 0.1–0.3M), temperature (X 2: 30–80°C) and duration of the leaching test (X 3: 2–4days) was investigated. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis by Design-Expert 7 software and were analyzed by analysis of variance (ANOVA). According to ANOVA, all factors (X 1, X 2 and X 3) influenced the response (dissolved iron concentration) and a positive regression coefficient of variables suggested an increase in dissolved iron concentration with an increase in oxalic acid concentration, temperature and time of leaching but there was not any interaction between them. The 3-D response surface plot and the contour plot derived from the mathematical model were applied to determine the optimal conditions. The optimum leaching conditions for maximum dissolved iron concentration were found to be oxalic acid concentration of 0.21M, temperature of 77°C and duration of the leaching test of 4days. After the washing stage of kaolin, in those experiments that pH was above 4, iron oxalate precipitate was formed and the percentage of residual iron in the sample after leaching was higher than expected. In general, the minimum amount of residual iron in the kaolin was 0.75% (w/w) that was obtained in tests where the oxalic acid concentration, temperature, time of the leaching and pH of final solution were 0.3M, 30°C, 2days and 3, respectively.


      PubDate: 2015-03-08T17:43:15Z
       
  • Synthesis of Cu–Al layered double hydroxide nanofluid and
           characterization of its thermal properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Samarshi Chakraborty , Ishita Sarkar , Krishnayan Haldar , Surjya Kanta Pal , Sudipto Chakraborty
      Synthesis of pristine Cu–Al layered double hydroxide (LDH) nanofluid via one step method and study of its thermal properties are the core essence of the current work. Nitrate salts of Cu, Al and Na were mixed in a particular molar ratio at constant pH to produce desired Cu–Al LDH. Different dispersion techniques were utilized to uniformly disperse Cu-Al LDH in water to obtain Cu–Al LDH nanofluids. Broadly used characterization techniques were implemented to identify and characterize pristine Cu–Al LDH nanoparticle. These techniques were used to determine crystallite size, composition, morphology and characteristics vibration of interlayer anion present in the nanoparticle. The nanofluids were characterized for particle size, cluster size, surface tension and thermal conductivity. Particle size analysis was carried out to confirm the formation of nanofluid. Dynamic light scattering (DLS) method had been employed to measure the clustering tendency of nanofluid. Effect of nanofluid loading on thermal conductivity was studied in depth. Influence of particle size, shape and composition on thermal conductivity of nanofluid had also been selected as an essential topic of investigation. Zeta potential and visual phase separation study were carried out to measure the stability of concerned nanofluid.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Sequestration of heavy metal cations on montmorillonite by thermal
           treatment
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Runhong Zhu , Qi Chen , Runliang Zhu , Ying Xu , Fei Ge , Jianxi Zhu , Hongping He
      Clay minerals are low-cost, high-efficient, and environmentally-friendly adsorbents for heavy metal cations. Proper disposal of the spent clay minerals, however, is still a big challenge holding back their wide applications in environmental remediation. In this work, the spent montmorillonites (Mt) after the adsorption of Cu2+ or Cd2+ were thermally treated, with the aim of in-situ sequestrating the adsorbed heavy metal cations. The structural characteristics of the calcined Mt samples were investigated using X-ray diffraction and X-ray photon spectroscopy, and the sequestration efficiency was tested by ammonium acetate and HCl washing. The results of this work demonstrated that Cu2+ cations could migrate into both the ditrigonal cavities on the tetrahedral sheet and vacant sites on the octahedral sheet of Mt after thermal treatment due to its small ion radius. In this case, Cu2+ cations could be efficiently sequestrated on Mt layers, e.g., less than 3.2% desorption by ammonium acetate washing and less than 5% desorption by HCl washing for the 400°C treated Cu–Mt. As for Cd2+ cations, they could hardly migrate into Mt layers, and thus much higher calcination temperature (e.g., 700°C) was needed to efficiently sequestrate them on Mt. In this case, Cd2+ cations were mainly sequestrated by the collapse of Mt layers and/or the deformation of Mt structure, which could block the desorption pathway for Cd2+ cations. Interestingly, as the thermal treatment temperature increased to a critical value (i.e., 400°C for Cu–Mt and 500°C for Cd–Mt), the structural Al3+ could be preferably dissolved by HCl than the adsorbed heavy metal cations; ammonium acetate could hardly dissolve the structural Al3+. This work demonstrated that thermal treatment could be a practical method for safe disposal of the spent Mt after the adsorption of heavy metal cations.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Synthesis of Fe2O3–NiO–Cr2O3 composites from NiFe-layered
           double hydroxide for degrading methylene blue under visible light
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Jianfeng Ma , Jiafan Ding , Liangmin Yu , Liangyin Li , Yong Kong , Sridhar Komarneni
      To develop a low-cost and highly efficient photocatalyst under the visible illumination, Ni3Fe–CO3–LDH (referred to hereafter as NiFe-layered double hydroxide or NiFe–LDH) was used as a precursor to synthesize Fe2O3–NiO–Cr2O3 composite. The NiFe–LDH was prepared by co-precipitation and then it was exchanged with dichromate. After calcining at 600°C, the Fe2O3–NiO–Cr2O3 composite was obtained. The composites' absorption edge intensely extended up to ca. 700nm covering the full visible light spectrum and showed high catalytic activity at natural pH under the visible light illumination. A very high methylene blue degradation of 91.2% was achieved with the aid of H2O2 in 120min with no detectable Cr in solution.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Organic modification of montmorillonite for application in plasticized PVC
           nanocomposites
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Henrik Petersen , Ignacy Jakubowicz , Jonas Enebro , Nazdaneh Yarahmadi
      A new type of organic compound for modifying clay minerals suitable for use in plasticized polyvinyl chloride was selected and studied. The theory of Hansen solubility parameters was used to predict the miscibility between potential organomodifiers and polyvinyl chloride. In a series of systematic experiments using four very different solvents (i.e., water, ethanol, tetrahydrofuran and chloroform) and three different types of Mt (i.e., Mt-Na+, Mt-PGV and Mt-Ca++), the importance of various parameters to the process of clay mineral intercalation was investigated. The effects of each combination were evaluated employing wide-angle X-ray diffraction and thermogravimetry. The results of swelling experiments on clay mineral in various solvents correlated well with the results of a theoretical preliminary study using Hansen solubility parameters. The extent of swelling followed the order H2O>EtOH>THF>chloroform. The d-spacing seemed to be little affected by the type of solvent used in the modification, while the type of Mt used was important to the intercalation results. Organomodification of Mt-Na+ increased the d-spacing by nearly 0.7nm when tributyl citrate was used as a chelating agent. Similar modification of Mt-Ca++ showed an increase of 0.3nm only. Furthermore, thermogravimetry and DTG curves showed significant structural differences between Mt-Na+ and Mt-Ca++.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Removal of basic dyes from aqueous solution by adsorption onto binary
           iron-manganese oxide coated kaolinite: Non-linear isotherm and kinetics
           modeling
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Tabrez A. Khan , Equbal A. Khan , Shahjahan
      Adsorption of basic fuchsin (BF) and crystal violet (CV) dyes onto iron-manganese oxide coated kaolinite (IMK) was investigated. The adsorbent was characterized using FT-IR, XRD spectra, EDX and SEM images. The effect of various parameters such as initial dye concentration, contact time, adsorbent dose and initial solution pH was examined. The data were fitted into non-linear two-parameter Langmuir, Freundlich, Dubinin–Radushkevich (D–R) and three-parameter Toth isotherm models. The data best fitted the Langmuir and Toth models. Langmuir saturation adsorption capacity (Qo ) at 308K for BF and CV was found to be 10.36mg/g and 20.64mg/g, respectively. The value of apparent energy of adsorption obtained from non-linear D–R model (1.10–2.38kJ/mol) suggested physical adsorption of the dyes. The adsorption process followed pseudo-second order kinetics. The negative value of free energy change (2.27–6.125kJ/mol) and positive value of enthalpy change (6.70–6.68kJ/mol) indicated the feasibility, spontaneity and endothermic nature of the adsorption process. The positive value of entropy change (0.028kJ/molK) revealed increased randomness at the adsorbent–adsorbate interface. The results showed that iron-manganese oxide coated kaolinite is a promising low cost adsorbent for the removal of BF and CV dyes from wastewater.


      PubDate: 2015-03-08T17:43:15Z
       
  • Effect of the montmorillonite intercalant and anhydride maleic grafting on
           polylactic acid structure and properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Kahina Issaadi , Abderrahmane Habi , Yves Grohens , Isabelle Pillin
      The goal of this work is to prepare maleic anhydride grafted poly(lactic acid) (PLAgMA) according to a method described by Hwang et al. in order to investigate its effect as matrix and as compatibilizer on the dispersion of two organic nanofillers into PLA matrix, as well as its effect as compatibilizer on rheological and barrier properties of clay mineral–PLA nanocomposites. Two different montmorillonites, Cloisite® 20A and Cloisite® 30B, are used in this study. The latter is classically used in pristine PLA nanocomposites. The clay mineral polymer nanocomposites are prepared by the incorporation of 3 mass % of each layered silicate into PLA, PLAgMA and PLA/PLAgMA via melt blending. Transmission electron microscopy micrographs of the PLAgMA/Cloisite® blends showed the presence of intercalated and partially exfoliated areas with Cloisite® 20A and re-aggregation of the layered silicates with Cloisite® 30B. These results are confirmed by rheological behaviors, which showed their dependence on the content of maleic anhydride and nature of montmorillonite. Water vapor permeations (WVP) were strongly reduced by the incorporation of Cloisite®, and the better results are obtained with C20A/PLA containing 5 mass % of PLAgMA.


      PubDate: 2015-03-08T17:43:15Z
       
  • About differences of swelling pressure — dry density relations of
           compacted bentonites
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): S. Kaufhold , W. Baille , T. Schanz , R. Dohrmann
      The swelling capacity is one of the most characteristic properties of bentonites. This property, along with others, made bentonite a candidate material for the safe disposal of high-level radioactive waste (HLRW). For HLRW-barrier systems the swelling pressure is of particular interest because it basically controls sealing properties (a large swelling pressure generally results in low permeability). Commonly, the swelling pressure is investigated as a function of compaction and hence plotted against the density, usually the dry density. Different dry density/swelling pressure relations of bentonites were published. Therefore, the aim of the present study was to identify reasons for these differences. To be able to compare a significant set of different bentonites, a small scale swelling pressure device was developed which is based on measuring a swelling pressure related value of 500mg bentonite powder. This device allowed recording about 200 single values (in duplicate) and hence dry density/swelling pressure relations of thirty six different bentonites. The differences of the dry density/swelling pressure plots of different bentonites could be explained by i) different ways to obtain a range of dry densities (either constant load or constant water content), ii) different portions of uncompactable porosity of the different bentonites, and iii) different smectite contents.


      PubDate: 2015-03-08T17:43:15Z
       
  • Removal characteristics of ammonium nitrogen from wastewater by modified
           Ca-bentonites
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Zhiming Sun , Xiaosuo Qu , Gaofeng Wang , Shuilin Zheng , Ray L. Frost
      A modified inorganic bentonite (Na/Al) based on purified Ca-bentonite was prepared through exchanging Al and Na ions in the interlayer space of Ca-bentonite. The structural properties of purified and modified bentonites were characterized by XRD and SEM analysis. Batch experiments were performed for the adsorption of ammonium nitrogen and different experimental conditions were studied in order to investigate the optimum adsorption conditions. Comparative experiments were also carried out for natural Ca-bentonite (RB), unmodified purified bentonite (PB) and modified purified bentonite (MB). Through the thermodynamic analysis, the ammonium nitrogen adsorption process can be spontaneous, the standard heat was −41.46kJmol−1, and the adsorption process based on ion exchange adsorption. The ammonium nitrogen adsorption capacity of MB (46.904mg/g) was improved compared to raw bentonite (RB) (26.631mg/g), which was among the highest values of ammonium nitrogen adsorption compared with other adsorbents according to the literatures. The described process provides a potential pathway for the removal of ammonium nitrogen at low concentrations encountered in most natural waters.


      PubDate: 2015-03-08T17:43:15Z
       
  • Surface chemistry and rheology of Laponite dispersions — Zeta
           potential, yield stress, ageing, fractal dimension and pyrophosphate
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Au Pek-Ing , Leong Yee-Kwong
      The ageing behaviour of Laponite gels at the phase boundary of attractive gel and flocculated state (ionic strength~0.01M 1:1 electrolyte) was investigated due to a lack of study in this region. Zeta potential and yield stress measurement revealed that freshly prepared Laponite dispersion took time to reach the surface chemical equilibrium (SCE) state. The higher the ionic strength, the shorter was the time needed. This well-defined structural state was employed at the commencement of ageing study. The ageing behaviour was characterised by a rapidly increasing yield stress region followed by a gradually increasing region and then by a plateau region. Both the initial and fully aged yield stress of Laponite gels increased with ionic strength and solid loading. Both the Leong and the two-parameter logarithmic time models described the ageing behaviour quite well. The relationship between the yield stress at the SCE state and at the fully recovered or rejuvenated state, and volume fraction obeyed a power law model. The fractal dimension of the two states was the same 2.0. This study also investigated the yield stress-pH behaviour of Laponite gel with and without pyrophosphate additive. Pure Laponite dispersion displayed a maximum yield stress at high pH. A drop in yield stress occurred at low pH region and eventually approaching zero yield stress. A totally opposite trend was observed with pyrophosphate additive. No yield stress was detected at high pH region and a maximum yield stress was located at pH5 followed by a drop in yield stress until pH2. This drop in the yield stress regardless of the presence of pyrophosphate, was due to the particle agglomeration promoted by low pH.


      PubDate: 2015-03-08T17:43:15Z
       
  • Montmorillonite reinforced polymer nanocomposite antibacterial film
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Lemiye A. Savas , Mehmet Hancer
      In this work, montmorillonite (Mt) was first ion-exchanged with silver ions (Ag+Mt) then organically modified with cetyltrimethylammonium bromide, CTAB (Ag+OMt). Active carrier Mt-layers were then compounded into low density polyethylene (LDPE) polymer using a high shear force co-rotating twin screw extruder. The order of Ag ion and CTAB adsorption on to Mt was revised in order not to form AgBr nano particles of which existence was reported in previous studies. Antibacterial activity of the Ag+OMt–LDPE nanocomposite films was then investigated against powerful gram negative Escherichia coli (E. coli) bacteria. It seems there is strong synergetic effect between silver ions and OMt nanoparticles as evidenced by the bacterial inhibition properties of thin blow molded Ag+OMt–LDPE nanocomposite film samples using liquid surface bacterial testing at a much lower active component concentration than similar studies appeared in the literature.


      PubDate: 2015-03-08T17:43:15Z
       
  • Estimation of the heat of reaction in traditional ceramic compositions
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): S. Ferrer , A. Mezquita , M.P. Gomez-Tena , C. Machi , E. Monfort
      Most energy studies on the traditional ceramic manufacturing process focus on the firing stage because this is the process stage that consumes the greatest amount of thermal energy. At present in Europe, using typical technologies, about 50% of the energy input in the firing stage is still lost through the kiln stacks. A key issue in energy studies is the accurate determination of the energy efficiency of the process, an issue that may become crucial in coming years to enable the energy management of different facilities and products to be compared. To reliably determine energy efficiency, accurate determination is required of the energy needed for the necessary physico-chemical transformations to develop in the material in the firing stage. This energy is also the only strictly unrecoverable energy, as the energy contained in other streams could, potentially at least, be partly recoverable. The present study was undertaken to develop an analytical methodology for estimating the heat of reaction of seven different traditional ceramic products, involving a broad spectrum of compositions, with peak firing temperatures ranging from 850°C to 1200°C. The following industrial ceramic compositions were studied: four ceramic tile compositions (red-body stoneware tile, porcelain tile, red-body earthenware wall tile, and white-body earthenware wall tile); two structural ceramic compositions (white brick and roof tile), and a porcelain tableware composition. To estimate the energy involved in the physico-chemical reactions in the firing stage, an analytical methodology was developed, based on the mineralogy data of the unfired body composition and on the enthalpy of formation of the minerals in the fired tiles. The methodology was validated by comparing the results with experimental data.


      PubDate: 2015-03-08T17:43:15Z
       
  • Anisotropic clay–polystyrene nanocomposites: Synthesis,
           characterization and mechanical properties
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Henrik Mauroy , Tomás S. Plivelic , Jussi-Petteri Suuronen , Fredrik S. Hage , Jon Otto Fossum , Kenneth D. Knudsen
      Recent studies on clay–polymer nanocomposites have shown prominent improvements in thermal and mechanical properties with the addition of quite small amounts of nanometer sized clay particles. The present work presents characterization of anisotropic clay–polystyrene nanocomposites synthesized via a guided self-assembly technique, employing electric fields to align the clay particles into chain-like structures inside the polymer matrix. Four different kinds of surface modified clay were used as particle additives, namely Hectorite, Laponite, Na-Montmorillonite and Li-Fluorohectorite. The microstructure of the nanocomposites was examined with wide angle X-ray scattering (WAXS), X-ray computed microtomography (XMT) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) was further employed to examine the high-temperature resilience of the nanocomposites before determination of the mechanical properties during compression. The results showed that the nanocomposites were of the intercalated type with the clay dispersed as ~15–70nm thick crystallites which in turn aggregated into micrometer sized particles. Alignment of the clay particles into chains inside the polymer matrix led to differences in mechanical properties compared to nanocomposites having a random orientation of the clay particles. In particular the aligned polystyrene–fluorohectorite nanocomposite displayed large improvements compared to its non-aligned counterpart. It was also observed that differences in yield strength depended on the compression direction.


      PubDate: 2015-03-08T17:43:15Z
       
  • Rheological properties of clay material at the solid/solution interface
           formed under quasi-free swelling conditions
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Rasmus Eriksson , Timothy Schatz
      One scenario of interest for the long-term safety assessment of a spent nuclear fuel repository involves the loss of bentonite barrier material through contact with dilute groundwater at a transmissive fracture interface. Small-scale, flow-through, artificial fracture experiments demonstrated that the quasi-free swelling of compacted montmorillonite into thin, horizontal fractures in the presence of dilute aqueous solutions leads to the formation of an inner, rigid gel-like phase and an outer, sol phase, with a distinct interface separating these two phases. The mechanical strength of the solid phase at this interface was assessed through a set of rheological measurements performed at various salt and montmorillonite solids concentrations. “Sol/gel” phase transformations were identified in suspensions containing between 2 and 4vol.% solids content with electrolyte concentrations below 17mM NaCl. At 4vol.% solids content all of the examined suspensions displayed gel-like properties. The results and analysis further revealed that it can be considered highly unlikely that mechanical forces due to groundwater flow in natural rock fractures would be sufficiently strong to remove any clay material at the solid/solution interface.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Red clay application in the utilization of paper production sludge and
           scrap glass to fabricate ceramic materials
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Vsévolod Mymrin , Walderson Klitzke , Kirill Alekseev , Rodrigo Eduardo Catai , André Nagalli , Ronaldo Luis dos Santos Izzo , Cezar Augusto Romano
      The article describes the compositions with red clay, as principal component, for utilization of paper production sludge and scrap glass to fabricate red ceramics at sintering temperatures of 700°, 800°, 850°, 900°, 1000°, 1050° and 1100°C. The raw and final materials were analyzed by XRF, XRD, SEM, EDS and LAMMA methods. The flexural strength tests of obtained ceramics reached till 11.7MPa, water absorption till 12.6%, bulk densities varied from 1.79 to 1.86g/cm3, and shrinkage till 1.4%. These properties can be attributed to the sintering at 700° and 1100°C of ceramics with glassy structures and small inclusions of new crystalline minerals, such as mullite, albite, orthoclase and nepheline.


      PubDate: 2015-03-08T17:43:15Z
       
  • Porous 3D network rectorite/chitosan gels: Preparation and adsorption
           properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Yajing Lu , Peter R. Chang , Pengwu Zheng , Xiaofei Ma
      Ultra-light porous 3D network rectorite (Rec) gels were prepared by crosslinking chitosan with glutaraldehyde in a simple process of aqueous gel precursor freezing, solvent exchange, and ethanol drying instead of expensive supercritical drying technology. The porous structures of Rec gels were composed of randomly oriented Rec layers. Rec gels with densities of 28.8 to 79.6mg/cm3 withheld liquids such as water up to 13–26 times, DMSO 12–35 times, and soybean oil 9–20 times the weight of the gel. However, the crosslinked chitosan components, which were used to consolidate the porous 3D network, delayed methylene blue (MB) adsorption of Rec gels. After calcination at 500°C most of the polymer was burnt away from gels, though the porous structure was maintained and could still contain liquid. The process for MB dye adsorption by the obtained gel was studied. The kinetic adsorption fit the pseudo second-order well, and the isotherm data followed the Langmuir models. The maximum adsorption capacity reached 162.6mg/g. The calcined REC gels could effectively remove the cationic dye from aqueous solutions.


      PubDate: 2015-03-08T17:43:15Z
       
  • Novel vanadium-chromium-bentonite green catalysts for cyclohexene
           epoxidation
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Noureddine Belaidi , Sumeya Bedrane , Abderrahim Choukchou-Braham , Redouane Bachir
      The aim of this work is the valorization of bentonite-type clay from Maghnia (Algeria) as green catalyst for the production of added value fine chemicals. The modification of the clay structure by acid activation and impregnation of transition metals, such as chromium and vanadium, enhanced redox properties and increased Lewis and Brønsted acidity. Various samples of vanadia supported on chromium-containing acid-activated bentonite, were prepared and characterized by diffuse-reflectance UV–vis spectroscopy, surface acidity followed by FT-IR, X-ray diffraction, nitrogen adsorption–desorption isotherms and scanning electron microscopy (SEM) coupled with EDX. The catalysts prepared were studied in the cyclohexene epoxidation, using tert-butyl hydroperoxide as oxidant. The influences of vanadium content, catalyst weight, reaction temperature and oxidant amount on the evolution of the epoxidation reaction were checked. The experimental results showed an interesting catalytic activity of 43% and a selectivity towards epoxide of about 71%, when TBHP was used as oxidant and heptane as solvent.


      PubDate: 2015-03-08T17:43:15Z
       
  • Influence of hydrated lime on the surface properties and interaction of
           kaolinite particles
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Yadeta C. Chemeda , Dimitri Deneele , George E. Christidis , Guy Ouvrard
      Lime is a widely used chemical additive in the stabilization of problematic soils. However, the physico-chemical mechanism involved, particularly in the short-term, is still not fully understood. In the present work, the influence of hydrated lime (Ca(OH)2) on the rheological properties of kaolinite dispersion has been investigated. The influence of the type of cation and pH on the interfacial chemistry and particle interaction were also examined. The result showed that kaolinite predominantly adsorbs Ca2+ and CaOH+ at pH=7 and pH=12.6 respectively. With increasing concentration of Ca(OH)2, the value of storage modulus (G′), Bingham yield stress (τB) and cohesive energy density (Ec) initially decreased at lower concentration (≤5.5mmol/l) followed by increase at higher concentration (≥11mmol/l); in contrast these parameters decreased monotonously with increasing the concentration of NaOH. The strain hardening characteristic of loss modulus (G″) curve was found to be very sensitive to change in surface chemistry and the associated particle organization. The modification in the mechanical properties of the kaolinite with varying amount of Ca(OH)2 was attributed to the aggregation microstructure of kaolinite particles. The Ca-ion at higher pH promotes linkage between particles and provides the most efficient way to form dense, tightly packed flocs, which behave as individual coarse grained materials (silt or sand).
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
  • Editorial Board
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107




      PubDate: 2015-03-08T17:43:15Z
       
  • Biological beneficiation of kaolin: A review on iron removal
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Mohammad Raouf Hosseini , Ali Ahmadi
      Application of mineral bio-beneficiation to remove iron oxyhydroxides from kaolinite clays has been the center of interest in recent decades, and many research works over the world have been dedicated to study the potential of this approach for upgrading the clay whiteness and refractoriness while preserving the inherent specifications and therefore improving the commercial value of kaolin. Microbial purification methods are preferred since they are environmentally benign (neither use nor release hazardous chemicals), not energy intensive, low in initial and operational costs, and they preserve the crystal structure of the clay. The present review offers the general concepts and fundamentals of the process along with an outline and critical assessment of the latest studies carried out on the biological dissolution of iron from kaolinite clays.


      PubDate: 2015-03-08T17:43:15Z
       
  • Morphology and rheology of (styrene-butadiene
           rubber/acrylonitrile-butadiene rubber) blends filled with organoclay: The
           effect of nanoparticle localization
    • Abstract: Publication date: May 2015
      Source:Applied Clay Science, Volume 108
      Author(s): Alireza Monfared , Azam. Jalali-Arani
      In this study, immiscible acrylonitrile butadiene rubber/styrene butadiene rubber (NBR/SBR) blends and their nanocomposites with cloisite 15A (C15A) and cloisite 30B (C30B) nanoparticles were prepared via a melt mixing method. The structure and morphology of the prepared samples were investigated by theoretical methods and by using equipment including X-Ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The experimental results proved that the C30B, the more hydrophilic organoclay (OC) tended to confine in the NBR, the more polar rubber phase, and in the interface whereas C15A, the less hydrophilic one was located at the SBR and interface. This was in agreement with the results obtained by the calculation of the wetting parameter. The EDS results showed that the average area of the NBR droplets in the SBR/NBR (80/20) blend decreased from 1.13 to 0.8 and 0.76μm2 in the presence of C30B and C15A, respectively. The use of epoxidized natural rubber (ENR) in conjunction with the OC caused more reduction of the NBR droplet size. Rheo-mechanical spectroscopy displayed the significant effect of OC localization on viscoelastic properties of the blends. Meanwhile, the rheological behavior of the blends was quantitatively similar to that predicted by Palierne's model extended to filled immiscible blends. This model was applied to obtain morphological and interfacial information for the SBR/NBR nanocomposite.
      Graphical abstract image

      PubDate: 2015-03-08T17:43:15Z
       
 
 
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