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  Subjects -> ENGINEERING (Total: 2272 journals)
    - CHEMICAL ENGINEERING (190 journals)
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    - ENGINEERING (1204 journals)
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ENGINEERING (1204 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 17)
AAPG Bulletin     Hybrid Journal   (Followers: 7)
AASRI Procedia     Open Access   (Followers: 15)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 245)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 6)
Advanced Science     Open Access   (Followers: 5)
Advanced Science Focus     Free   (Followers: 3)
Advanced Science Letters     Full-text available via subscription   (Followers: 8)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 7)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 26)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 29)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 12)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 37)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 1)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 4)
AIChE Journal     Hybrid Journal   (Followers: 31)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 28)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 17)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
Annals of Science     Hybrid Journal   (Followers: 7)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 6)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 16)
Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Network Science     Open Access   (Followers: 1)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 3)
Applied Sciences     Open Access   (Followers: 2)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 7)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 3)
Asia-Pacific Journal of Science and Technology     Open Access  
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 8)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 5)
Batteries     Open Access   (Followers: 5)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Motor Trade Survey     Full-text available via subscription   (Followers: 1)
BER : Retail Sector Survey     Full-text available via subscription   (Followers: 2)
BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 10)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 9)
Biomedical Science and Engineering     Open Access   (Followers: 4)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 2)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription   (Followers: 1)
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 9)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 22)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 43)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Thermal Engineering     Open Access   (Followers: 4)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 8)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 22)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 3)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 5)
Coatings     Open Access   (Followers: 4)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 26)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 266)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 185)
Composites Part B : Engineering     Hybrid Journal   (Followers: 278)
Composites Science and Technology     Hybrid Journal   (Followers: 180)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 14)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 17)
Computers & Geosciences     Hybrid Journal   (Followers: 28)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 5)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 4)
Computers and Geotechnics     Hybrid Journal   (Followers: 10)
Computing and Visualization in Science     Hybrid Journal   (Followers: 5)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 30)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 7)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 9)
Control Engineering Practice     Hybrid Journal   (Followers: 42)
Control Theory and Informatics     Open Access   (Followers: 8)
Corrosion Science     Hybrid Journal   (Followers: 25)
CT&F Ciencia, Tecnologia y Futuro     Open Access   (Followers: 1)
CTheory     Open Access  

        1 2 3 4 5 6 7 | Last

Journal Cover Applied Clay Science
  [SJR: 0.826]   [H-I: 83]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [3051 journals]
  • 4-Nitrophenol reduction catalysed by Au-Ag bimetallic nanoparticles
           supported on LDH: Homogeneous vs. heterogeneous catalysis
    • Authors: Nidhi Arora; Akansha Mehta; Amit Mishra; Soumen Basu
      Pages: 1 - 9
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Nidhi Arora, Akansha Mehta, Amit Mishra, Soumen Basu
      Bimetallic nanoparticles, which are composed of two metal elements in a particle, exhibit much higher catalytic activity than respective monometallic ones due to new bi-functional or synergistic effects, so-called a ligand and/or an ensemble effect. In this work, a novel homogeneous as well as heterogeneous AuAg bimetallic nanocatalyst have been synthesized and supported on layer double hydroxide (LDH) by a simple wet chemical process. The support of LDH has reduced the size as well as capped the bimetallic nanoparticles and hence prevents the agglomeration. The surface morphology and chemical composition of these bimetallic nanoparticles were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that alloy (40–60nm) and core-shell (15–30nm) AuAg bimetallic nanoparticles were formed for heterogeneous and homogeneous composites, respectively. Moreover, the different compositions of as-synthesized AuAg bimetallic nanoparticles were utilized for the catalytic reduction of 4-nitrophenol. The highest activity was observed for the AuAg nanoparticles prepared with AuAg ratio at 1:3 and the activity became 10 to 45 times higher than that of original monometallic Au or Ag nanoparticles. The rate kinetics was studied for both homogeneous and heterogeneous system on the reduction of 4-nitrophenol and observed that the rate of reduction was greater in case of homogeneous catalysts as compared to heterogeneous catalysts. Also, the heterogeneous catalysts were effortlessly recovered and reused (up to 5cycles) after completion of the reduction reaction.
      Graphical abstract image

      PubDate: 2017-10-26T21:56:46Z
      DOI: 10.1016/j.clay.2017.10.015
      Issue No: Vol. 151 (2017)
       
  • Copolymer microstructure, nanocomposite morphology and aqueous solution
           viscosity of styrene-modified polyacrylamides in situ synthesized in
           presence of clay mineral
    • Authors: Hossein Khakpour; Mahdi Abdollahi
      Pages: 10 - 19
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Hossein Khakpour, Mahdi Abdollahi
      Free-radical copolymerization of acrylamide (AM) with styrene (St) as a hydrophobic comonomer was carried out in the aqueous solution by potassium persulfate as an initiator in the presence of clay mineral. To investigate the influence of two kinds of clay minerals on the copolymer microstructure and nanocomposite morphology; hydrophilic Cloisite Na+ and hydrophobic Cloisite 30B were used in this work. Aqueous solution viscosity of the purified copolymers was also studied. Microstructural parameters were studied using 1H NMR spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), aqueous solution viscosity, molecular weight measurements and solubility. Results showed that a mechanism almost similar to the heterogeneous mechanism can be considered for the St/AM copolymerization with both Cloisite Na+ and Cloisite 30B. Nanocomposite morphology studies showed that copolymer chains intercalated significantly into the clay mineral interlayers only with Cloisite Na+. In the case of Cloisite Na+, some exfoliation of the clay mineral interlayers was also observed from TEM micrographs. The formation of St interchain aggregations and physical network was confirmed by DLS and aqueous solution viscosity in the various salt and temperature conditions.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.004
      Issue No: Vol. 151 (2017)
       
  • Adsorption properties and mechanisms of palygorskite for removal of
           various ionic dyes from water
    • Authors: Ran Yang; Dawei Li; Aimin Li; Hu Yang
      Pages: 20 - 28
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Ran Yang, Dawei Li, Aimin Li, Hu Yang
      In this study, an acid-treated palygorskite (PAL-O) with negatively charged layers has been used as an adsorbent for the removal of various types of ionic dyes including cationic [crystal violet (CV), cationic light yellow (7GL), and methylene blue (MB)] and anionic [methyl orange (MO) and acid green 25 (AG25)] ones from water. PAL-O showed efficient performance in the adsorption of all three cationic dyes because of electrostatic interactions. As regards the two anionic dyes, PAL-O also exhibited good adsorption efficiency for MO but had almost no effect on AG25. For detailed investigation of the adsorption mechanisms, PAL-O has been further treated by soxhlet extraction, using distilled water as solvent, to remove water-soluble matter such as metal ions. The efficiencies of the purified palygorskite (PAL-P) for adsorption of cationic dyes were slightly increased, but that of MO adsorption decreased evidently. This result indicated that the metal ions on the palygorskite played an important bridging effect for adsorption of anionic dyes. However, minimal AG25 uptake may occur because this bridging effect was too weak to be bonded for much stronger electrostatic repulsions between AG25 and palygorskite. In general, the charge properties and molecular structures of dyes play important roles in their adsorption behaviors.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.016
      Issue No: Vol. 151 (2017)
       
  • Modification of montmorillonite by Gemini surfactants with different chain
           lengths and its adsorption behavior for methyl orange
    • Authors: Hua-Ping Ren; Shao-Peng Tian; Min Zhu; Yu-Zhen Zhao; Ke-Xuan Li; Qiang Ma; Si-Yi Ding; Jian Gao; Zongcheng Miao
      Pages: 29 - 36
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Hua-Ping Ren, Shao-Peng Tian, Min Zhu, Yu-Zhen Zhao, Ke-Xuan Li, Qiang Ma, Si-Yi Ding, Jian Gao, Zongcheng Miao
      To investigate the effect of the alkyl chain length of Gemini surfactants on the adsorption behavior of corresponding organoclays for azo dye methyl orange (MO) removal in aqueous solution, they were prepared by modifying Na-montmorillonite (Na-Mt) using a series of commercialized Gemini surfactants, [C12H25-N+(CH3)2-CH2]2·2Br− (G12-2-12), [C16H33-N+(CH3)2-CH2]2·2Br− (G16-2-16), and [C18H37-N+(CH3)2-CH2]2·2Br− (G18-2-18), which were characterized by identical spacer chain length and different alkyl chain lengths. The structure, morphology and surface properties of organoclays were characterized via XRD, FTIR, TG, SEM, and water contact angle. The results revealed that the interlayer space, hydrophobicity, and dispersibility of organoclays increased significantly with increasing the alkyl chain length of the Gemini surfactants. The adsorption behavior of MO from aqueous solution onto the organoclays was determined. The results indicated that the adsorption capacity of the organoclays was in the order: G16-2-16-Mt>G18-2-18-Mt>G12-2-12-Mt. The highest adsorption capacity of G16-2-16-Mt can be reasonably attributed to the suitable interlayer space, hydrophobicity, and interlayer packing density of the surfactants of G16-2-16-Mt. Moreover, the effects of the pH of the MO solution, adsorption temperature, contact time and the initial MO concentration on the adsorption capacity of MO on Gemini surfactant-modified Mt was also investigated. The adsorption capacity of G16-2-16-Mt decreased with increasing pH and exhibited a maximum at 30°C. The adsorption isotherms of MO onto G16-2-16-Mt and G18-2-18-Mt were in good agreement with the Langmuir equation, and the adsorption kinetics can best be described by a pseudo-first-order model.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.024
      Issue No: Vol. 151 (2017)
       
  • Predictive modelling of the impact of silica nanoparticles on fluid loss
           of water based drilling mud
    • Authors: Richard O. Afolabi; Oyinkepreye D. Orodu; Ifeanyi Seteyeobot
      Pages: 37 - 45
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Richard O. Afolabi, Oyinkepreye D. Orodu, Ifeanyi Seteyeobot
      Research into the use of nanoparticles for drilling mud formulation is gaining momentum but a key challenge involves predicting the effect of nanoparticles on the properties of the modified mud. Mathematical models used in the description of drilling muds allow for a generalised computation of drilling performance. In other words, such models cannot quantitatively capture the contributions of nanoparticles to the overall performance of the nano-modified drilling mud. In this work, a new model was derived which describes the fluid loss of nanoparticle enhanced water based drilling mud under static filtration. This was done taking into account the structural kinetics of the bentonite suspension and colloidal behaviour of the nanoparticles. The new fluid loss model was compared with the known API static fluid loss model using statistical measures, Root Mean Square Error (RMSE) and Coefficient of Determination (R2). The new model compares favourably with the API static model with RMSE and R2 values of 0.41–0.81cm3 and 99.3–99.89% respectively. The new fluid loss model was able to predict a value for the maximum fluid loss. It also accounted for variation in mud cake permeability and solid fraction, which could not be explained by the API fluid loss model.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.09.040
      Issue No: Vol. 151 (2017)
       
  • Mechanism responsible for intercalation of dimethyl sulfoxide in
           kaolinite: Molecular dynamics simulations
    • Authors: Shuai Zhang; Qinfu Liu; Hongfei Cheng; Feng Gao; Cun Liu; Brian J. Teppen
      Pages: 46 - 53
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Shuai Zhang, Qinfu Liu, Hongfei Cheng, Feng Gao, Cun Liu, Brian J. Teppen
      Intercalation is the promising strategy to expand the interlayer region of kaolinite for their further applications. Herein, the adaptive biasing force (ABF) accelerated molecular dynamics simulations were performed to calculate the free energies involved in the kaolinite intercalation by dimethyl sulfoxide (DMSO). Additionally, the classical all atom molecular dynamics simulations were carried out to calculate the interfacial interactions between kaolinite interlayer surfaces and DMSO with the aim at exploring the underlying force that drives the DMSO to enter the interlayer space. The results showed that the favorable interaction of DMSO with both kaolinite interlayer octahedral surface and tetrahedral surface can help in introducing DMSO enter kaolinite interlayer. The hydroxyl groups on octahedral surface functioned as H-donors attracting the SO groups of DMSO through hydrogen bonding interaction. The tetrahedral surface featuring hydrophobic property attracted the methyl groups of DMSO through hydrophobic interaction. The results provided a detailed picture of the energetics and interlayer structure of kaolinite-DMSO intercalate.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.022
      Issue No: Vol. 151 (2017)
       
  • Zr-containing layered double hydroxides: Synthesis, characterization, and
           evaluation of thermodynamic properties
    • Authors: J. Poonoosamy; F. Brandt; M. Stekiel; P. Kegler; M. Klinkenberg; B. Winkler; V. Vinograd; D. Bosbach; G. Deissmann
      Pages: 54 - 65
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): J. Poonoosamy, F. Brandt, M. Stekiel, P. Kegler, M. Klinkenberg, B. Winkler, V. Vinograd, D. Bosbach, G. Deissmann
      Layered doubled hydroxides (LDH), consisting of positively charged octahedral brucite-type layers and interlayer anions, have been widely studied in the last decades because of their ability to control the mobility of various anions and cations in the environment. LDH may be relevant to the safety case of nuclear waste repositories due to their retention potential of anionic radionuclide species, for example 129I or 79Se. So far few studies were dedicated to Zr incorporation into LDH, which might be a relevant secondary phase in the repository environment due to the possible corrosion of Zr-bearing nuclear materials and the presence of 93Zr, a long-lived fission and activation product, in various nuclear waste streams. The focus of our study was to synthesize and characterize Cl-bearing Mg-Al-LDH (MgxAlyZrz(OH)2Cl(2x+3y+4z−2)) with different Zr-content and to evaluate their thermodynamic properties, especially their solubility as a function of temperature. The LDH were synthesized by a coprecipitation method at temperatures between 298.15 and 343.15K, aiming at Zr/(Zr+Al) ratios of 0.1 and 0.4, respectively. Our analytical techniques combining X-ray diffraction and scanning electron microscopy indicated that up to 5mol% Zr were incorporated into the brucite layer of the LDH. At higher Zr concentrations the precipitation of an amorphous hydrous Zr-oxide was observed. The structural uptake of Zr was lower than the value reported in literature for CO3 2– bearing LDH, suggesting that the interlayer anions may play a role with regard to the Zr uptake in the brucite layer. At low Zr contents, well defined crystalline LDH with the composition Mg0.72Al0.22Zr0.025(OH)2Cl0.20 were obtained at all syntheses temperatures. The solubility of this LDH decreases slightly with temperature and the stoichiometric saturation constant was found to satisfy the Van't Hoff equation. The thermodynamic properties of the Zr LDH (Gibbs free energy of formation, ΔG° f) were determined by considering an approach based on solubility data and Gibbs energy minimization and a calorimetric approach. The enthalpy of formation (ΔH° f) and the lattice entropy (S°) of the Zr-LDH were determined using calorimetric measurements to be −1181.01±4.98kJmol−1 and 83.9Jmol−1 K−1 respectively. Considering contribution of the configurational entropy, the standard entropy, S°, was evaluated at 97±7Jmol−1 K−1. The ΔG° f for Mg0.72Al0.22Zr0.025(OH)2Cl0.20*0.69H2O obtained from experimental measurements and that predicted by theory were evaluated at −1046±7 and −1046±13kJmol−1 respectively. Thus, the combination of solubility data and Gibbs energy minimization can be considered as good alternative for the evaluation of ΔG° f of LDH.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.013
      Issue No: Vol. 151 (2017)
       
  • Calcined Mg/Al layered double hydroxides as efficient adsorbents for
           polyhydroxy fullerenes
    • Authors: Yanping Zhu; Runliang Zhu; Qingze Chen; Minwang Laipan; Jianxi Zhu; Yunfei Xi; Hongping He
      Pages: 66 - 72
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Yanping Zhu, Runliang Zhu, Qingze Chen, Minwang Laipan, Jianxi Zhu, Yunfei Xi, Hongping He
      The environmental behaviors and pollution control of engineered nanomaterials are drawing increasing interests nowadays. This work showed that the calcined layered double hydroxides (LDH), i.e., layered double oxides (LDO), could effectively adsorb polyhydroxy fullerenes (PHF) from aqueous solution. The maximum adsorption capacity of LDO reached ~476mg/g, much higher than that on LDH (~47mg/g) and activated carbon (~28mg/g). All of the three equilibrium adsorption isotherms could be well fitted with the Langmuir equation. The high adsorption capacity of PHF on LDO can be attributed to the enhanced accessibility to the adsorption sites for PHF during structural reconstruction of LDO. In addition, the rehydrated LDH, with a net positive surface charge, has high affinity for negatively charged PHF through an electrostatic interaction. Cl−, CO3 2−, and SO4 2− could slightly enhance the adsorption of the PHF on LDO, while HPO4 2− showed an evident inhibiting effect in the whole concentration range of PHF. The adsorbents before and after the adsorption of PHF were characterized by XRD, FT-IR, and TG. The obtained results indicated that the adsorbed PHF could not intercalate into the interlayer spaces of the reconstructed LDH, but could effectively compete with CO3 2– during the adsorption process.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.018
      Issue No: Vol. 151 (2017)
       
  • Removal of Cs+ and Co2+ ions from aqueous solutions using poly
           (acrylamide-acrylic acid)/kaolin composite prepared by gamma radiation
    • Authors: M.I. El-Dessouky; H.H. Ibrahiem; E.H. EL-Masry; G.E. Sharaf El-deen; N.M. Sami; M.E. Moustafa; E.M. Mabrouk
      Pages: 73 - 80
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): M.I. El-Dessouky, H.H. Ibrahiem, E.H. EL-Masry, G.E. Sharaf El-deen, N.M. Sami, M.E. Moustafa, E.M. Mabrouk
      Synthesis of poly (acrylamide-acrylic acid)/kaolin composite (P(AM-AA)/K) using gamma radiation was carried out for removal of cesium and cobalt ions from aqueous solution. The prepared composite was characterized using FT-IR, SEM, XRD, TGA and DTA. Comparative adsorption behavior of poly (acrylamide-acrylic acid)/kaolin composite for adsorption of cesium and cobalt ions was studied. The adsorption studies were performed under different pH, temperature, and initial metal ion concentration. The obtained data are handled using adsorption kinetics, isotherm models and the thermodynamic behavior of the metal ion adsorption was calculated. It was found that the synthesized composite possesses a good swelling behavior due to the presence of kaolin. Pseudo-second-order kinetic model provided a better correlation for the experimental data in comparison to the pseudo-first-order kinetic model. The negative value of ΔG indicates the feasibility and spontaneity of the adsorption process. The positive ΔH suggests the endothermic nature of the adsorption.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.020
      Issue No: Vol. 151 (2017)
       
  • Pre-exfoliated nanoclay through two consecutive reaction systems: Silane
           functionalization followed by grafting of amino acid monomers
    • Authors: Mohammad Asgari; Uttandaraman Sundararaj
      Pages: 81 - 91
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Mohammad Asgari, Uttandaraman Sundararaj
      This work presents a novel way to produce a thermally stable nanoclay with an increased interlayer space, which are the essential requirements in fabricating clay-polymer nanocomposites. Sodium montmorillonite (Na-Mt) was functionalized through two separate, consecutive reaction systems. Functionalization with an aminosilane was first performed, in order to produce reactive groups at the silicate nanolayers. In the second step, amino acid monomers were employed for a further reaction with silane-modified nanoclay. X-ray diffraction results demonstrated an increased d001-value (24Å) using 10mmol γ-aminobutyric acid. The 001 reflection peak disappeared when 5mmol ω-aminoundecanoic acid/g Mt was used as the second type of amino acid. Transmission electron microscopy images of modified Mt with 10mmol ω-aminoundecanoic acid exhibited a well separated or exfoliated structure of nanolayers. Thermogravimetric measurements indicated a trend of increasing thermal stability of the modified nanoclays (350°C to 400°C) with increasing amounts of initial ω-aminoundecanoic acid. Based on these results, optimizing the modifiers and synthesis conditions can control the properties of modified nanoclay. Tensile modulus and strain at break of HDPE/2 mass% modified Mt showed 10% and 14% enhancements, respectively, due to the increased d001-value of the nanofiller, which results in greater filler-polymer interaction.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.021
      Issue No: Vol. 151 (2017)
       
  • Clay concrete and effect of clay minerals types on stabilized soft clay
           soils by epoxy resin
    • Authors: Salaheddin Hamidi; Seyed Morteza Marandi
      Pages: 92 - 101
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Salaheddin Hamidi, Seyed Morteza Marandi
      Clay soils, especially soft clay soils covered considerable parts of the earth. Cement and lime are used as traditional additives for clay soils stabilization but unable to increase the strength properties of clay soils significantly. So, it seems necessary to use new additives to increase the strength parameters of soft clay soils. Therefore, cement and epoxy resin are used for stabilization of soft clay soils in this study. The main objects of this study are the determination of the effect of epoxy resin on the mechanical parameters and microstructure properties of clay soils, the phenomenon of clay concrete and effect of clay minerals on its properties and also, using knowledge of the elastic modulus, toughness and elastic and plastic strain of the stabilized soft clay as a practical criterion for determination of the optimum additive percentage in soft clays stabilization in addition to UCS. In this study, two samples of clay soils with different clay minerals were investigated. Clay soil samples that tested experimentally were bentonite and kaolinite. A series of microstructure and macrostructure experiments were conducted on the samples. The results show that using epoxy resin increases strength parameters about 100 to 1000 times while UCS reaches to more than 50MPa in some samples based on the clay mineral types in the soils. Unlike the cement concrete, as the strength increases the failure strain and material toughness will increase simultaneously as well. In addition, the important and prominent result of stabilization by epoxy resin is the best efficiency in the weakest and the most sensitive soils.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.010
      Issue No: Vol. 151 (2017)
       
  • Study on non-darcian flow sand-clay mixtures
    • Authors: Shengwei Wang; Wei Zhu; Kang Fei; Chaoyang Xu; Nan Zhang
      Pages: 102 - 108
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Shengwei Wang, Wei Zhu, Kang Fei, Chaoyang Xu, Nan Zhang
      Compacted clay liners in landfills can easily develop fissures in a dry environment. To overcome this, sand is added to the clay. In this study, various mixes of sand-clay soils were tested for their hydraulic conductivity, threshold gradient, as well as bound forms of pore water. The water flow behavior in the sand-clay samples varied according to the sand content. When the sand content was no <50%, the compacted sand-clay permeability conformed to Darcy's law. When the sand content was >50%, the permeability deviated from Darcy's law and a threshold gradient became apparent. The lowest hydraulic conductivity was measured in the sand-clay sample with 30% sand content. Based on the seepage theory, the relation between the sand content and the soil's intrinsic permeability was obtained and a model representing the relation between the sand content and hydraulic conductivity was established. Based on analysis of the water morphology between the soil particles, the Hange-Poiseuille law was modified, showing that changing the sand content of the sand-clay can modify the effective apertures of the soil. When the sand content was 30%, the modified effective aperture was the smallest, which explains why the hydraulic conductivity was smallest and the threshold gradient was largest. Considering the empirical relationship between the modified effective aperture and threshold gradient derived in previous studies, this paper furthers our understanding of the development of the threshold gradient in sand-clay soils.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.028
      Issue No: Vol. 151 (2017)
       
  • Effect of metal nitrate concentration on the electrodeposition of
           hydrotalcite-like compounds on open-cell foams
    • Authors: Phuoc Hoang Ho; Erika Scavetta; Francesca Ospitali; Domenica Tonelli; Giuseppe Fornasari; Angelo Vaccari; Patricia Benito
      Pages: 109 - 117
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Phuoc Hoang Ho, Erika Scavetta, Francesca Ospitali, Domenica Tonelli, Giuseppe Fornasari, Angelo Vaccari, Patricia Benito
      Mg/Al hydrotalcite-like compounds were deposited on FeCrAlloy open-cell metal foams by the electro-base generation method in metal nitrate baths of different concentration (0.03, 0.06 and 0.10M, Mg/Al=3/1). The modifications of both electrochemical and chemical processes by the electrolyte concentration were investigated. For comparison purposes, experiments were carried out in KNO3 solutions and using FeCrAlloy plates as working electrodes. The reduction processes followed a surface reduction behaviour and were slowed down by the solid deposition or the ineffective solution replenishment at the electrode interface, being more remarkable with more concentrated baths. Hydrotalcite-like, brucite and probably gibbsite phases were deposited at −1.2V vs SCE for 100–2000s. The metal nitrate concentration determined both OH− production by nitrate reduction and OH− consumption by precipitation of cations, these processes not only governed the amount of solid deposited and its distribution on the support but also the solid growth mechanism, crystallinity of the phases and intercalating anions inside the hydrotalcite.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.019
      Issue No: Vol. 151 (2017)
       
  • Competitive adsorption of Cu (II) and Zn (II) on impregnate raw Algerian
           bentonite and efficiency of extraction
    • Authors: Djamila Bouazza; Hafida Miloudi; Mehdi Adjdir; Abdelkader Tayeb; Anne Boos
      Pages: 118 - 123
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Djamila Bouazza, Hafida Miloudi, Mehdi Adjdir, Abdelkader Tayeb, Anne Boos
      Impregnated homoionic raw Algerian bentonite (HB) with high basal spacing was prepared to remove a copper (Cu2+) and zinc (Zn2+) from 0.33M (Na+, H+)SO4 2− sulphate medium in aqueous solutions. The impregnated solid was characterized by X-ray diffraction (XRD), Fourier- Transform Infrared (FTIR) and Ultra-violet (UV). The effect of contact time, initial pH of a solution, heavy metal concentration and ligand concentration on the adsorption efficiency were investigated. Pseudo-first/s orders isotherms are applied to determine the efficiency of impregnate solid. The experimental data fitted well with the pseudo-second order model for Cu2+ and Zn2+ adsorption. Maximum capacities for Cu2+ and Zn2+ were 440mmol/kg and 32mmol/kg respectively. However, the adsorption is selective to copper in binary system. Moreover, impregnated solid was also regenerated and reused for subsequent recovery.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.026
      Issue No: Vol. 151 (2017)
       
  • Effects of different milling techniques on the layered double hydroxides
           final properties
    • Authors: Cinzia Pagano; Fabio Marmottini; Morena Nocchetti; Daniele Ramella; Luana Perioli
      Pages: 124 - 133
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Cinzia Pagano, Fabio Marmottini, Morena Nocchetti, Daniele Ramella, Luana Perioli
      Layered double hydroxides (LDHs) find many applications in the pharmaceutical field. Often, the synthetic product requires a suitable grinding procedure before starting any type of manufacturing process. Choosing the appropriate grinding procedure is important; it must reduce the particle size without modifying the LDH's native layered structure and crystal morphology. Using the LDH MgAl-NO3 as model sample, the aim of this paper was to investigate the influence of three common grinding procedures: knife mill, ball mill and jet mill, on particles size, morphology, specific surface area, crystallinity and flow character. Results highlighted that the jet milling procedure is the most appropriate method to induce particle size reduction while maintaining the original MgAl-NO3 features.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.030
      Issue No: Vol. 151 (2017)
       
  • Comparison of hydrocyclone and flotation ability in reduction of kaolin
           ore calcite
    • Authors: Mahdi Sadigh; Javad Vazifeh Mehrabani
      Pages: 134 - 139
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Mahdi Sadigh, Javad Vazifeh Mehrabani
      Kaolin, known as china clay, is a fine white clay with industrial usage. Kaolinite is the most common mineral in kaolin ores and iron, titanoferrous, and carbonate minerals are the major impurities. Calcium oxide (CaO) in carbonate form (CaCO3) is the recent critical issue for Zonuz kaolin plant located in the North West of Iran. Therefore, a number of practical and inexpensive processing methods were tried on a raw crushed Zonuz kaolin sample. The sample contained 3.56% CaO. First, sizing based methods like sieve screening and hydrocyclone were tested, because of the smaller size of kaolinite particles compared with most other impurities. However, CaO was removed poorly, much Al2O3 was wasted, and Fe2O3 was enriched in the product. Then, flotation tests were performed on the raw ore. The results were remarkable, because of the highest calcite removal with the lowest Al2O3 loss and Fe2O3 enrichment. Although CaO content was reduced to 1.33% or even less in finer sizes using flotation, these finer sizes led to more Al2O3 loss. Acidic leaching was not evaluated, due to intense reaction between acids and CaCO3, and damaging corrosive acidic conditions.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.027
      Issue No: Vol. 151 (2017)
       
  • Comparison of methylene blue adsorption on bentonite measured using the
           spot and colorimetric methods
    • Authors: Youko Miyoshi; Katsuhiro Tsukimura; Kazuya Morimoto; Masaya Suzuki; Tetsuichi Takagi
      Pages: 140 - 147
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Youko Miyoshi, Katsuhiro Tsukimura, Kazuya Morimoto, Masaya Suzuki, Tetsuichi Takagi
      The maximum amount of methylene blue (MB) adsorbed on montmorillonite in bentonite can be determined using a spot or colorimetric method to evaluate the quality of bentonite. The spot method differs from the colorimetric method in terms of the procedure used to add MB solution to a bentonite dispersion and the procedure to determine the maximum amount of MB. In the spot method, MB solution is added in a step-by-step process and the maximum amount is determined by observing a spot of MB and bentonite on filter paper. In the colorimetric method, MB is added only once and the maximum amount is determined using a spectrophotometer. This study revealed that the maximum amount of MB adsorbed onto bentonite measured using the spot method differs from that measured using the colorimetric method. The maximum amount measured using the colorimetric method can be estimated by multiplying the amount measured using the spot method by 0.937. To ascertain why the maximum amounts measured using the two methods differ, we examined bentonites using a newly proposed method (a step-by-step colorimetric method), in which MB is added in a step-by-step manner and the maximum amount is determined using a spectrophotometer. The maximum amount measured using the step-by-step colorimetric method showed that step-by-step addition of MB decreases the maximum amount. The decrease can be explained by the re-flocculation of montmorillonite particles in bentonite.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.023
      Issue No: Vol. 151 (2017)
       
  • Characteristics of clay minerals in soil particles from an argillic
           horizon of Alfisol in central China
    • Authors: Georges Martial Ndzana; Li Huang; Jin Bo Wang; Zhi Yi Zhang
      Pages: 148 - 156
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Georges Martial Ndzana, Li Huang, Jin Bo Wang, Zhi Yi Zhang
      The soil particles (<2000, 450–2000, 100–450 and 25–100nm) in an Alfisol were studied using inductively coupled plasma-optical emission spectroscopy (ICP-OES), conventional and synchrotron X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG) to investigate the mineral composition of clays and changes in crystalline structure in the particles of an argillic horizon. The results showed that the clay minerals in the particle fractions (<2000, 450–2000 and 100–450nm) were illite, kaolinite, vermiculite and a trace amount of hydroxy interlayered vermiculite and chlorite. In the nanoparticles (25–100nm), the main clay minerals were illite and kaolinite. The molar ratios of SiO2 to Al2O3 and SiO2 to R2O3 (Al2O3 and Fe2O3) were higher in the nanoparticles compared to other particle fractions. With decreasing particles size, kaolinite and vermiculite decreased gradually and illite increased. The Al-Mg-OH and Si–O–Si (Al) stretching modes of vermiculite were broadened in the 100–450nm particles and disappeared in nanoparticles while the hydroxyl group (OH) of clay minerals in the samples was reduced with decreasing particle fractions. The broadening of the band characteristics of clay minerals, the dehydration and dehydroxylation were less pronounced in particle fractions from the argillic horizon comparing to the topsoil. Clay minerals from 450 to 2000 and 100–450nm particle fractions were well ordered whereas illite and kaolinite were poorly ordered in nanoparticles of the argillic horizon. The “crystallinity” of clay minerals was weakly affected in the particle fractions of argillic horizon compared to topsoil.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.014
      Issue No: Vol. 151 (2017)
       
  • Impact of low normality of cesium chloride (n=0.3N) on the electrical
           features of nacrite-[(CsCl)n] nanohybrid subjected to excitation of
           frequency under controlled temperature
    • Authors: Nouha Jaafar; Hafsia Ben Rhaiem; Abdesslem Ben Haj Amara
      Pages: 157 - 163
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Nouha Jaafar, Hafsia Ben Rhaiem, Abdesslem Ben Haj Amara
      A series of nanohybrid materials with different (CsCl) n normalities (n = 0.05 N, 0.1 N, 0.3 N, 0.5 N, 1 N, 2 N and 3 N) was synthesized by indirect intercalation of nacrite. Systematic and kinetic X-ray diffraction surveys reveal that the optimal nanohybrid with the highest intercalation rate (τ=0.943) and degree of reaction (α=0.860) corresponds to (n = 0.3 N) normality value of aqueous CsCl solution and was labeled nacrite-[(CsCl) n = 0.3N ]. Its half-unit cell structural formula as deduced by agreement between experimental and simulated patterns (R p =7.30%) was Si 2 Al 2 O 5 (OH) 4 ·CsCl·H 2 O with a d002-value equals to 1.05nm. The atomic composition and the vibrational description of the nacrite-[(CsCl) n = 0.3N ] nanohybrid was made respectively by means of energy-dispersive X-ray spectroscopy coupled to transmission electron microscope and infrared spectroscopy techniques. The electrochemical impedance spectroscopy reveals that nacrite-[(CsCl) n = 0.3N ] nanohybrid material heated to higher temperatures exhibits an excellent ionic conductivity (σ ac ~10−2 S·m−1) and can be classified as a superionic conductor.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.09.027
      Issue No: Vol. 151 (2017)
       
  • Comparable study of vermiculites from four commercial deposits prepared
           with fixed ceria nanoparticles
    • Authors: Marta Valášková; Jana Kupková; Gražyna Simha Martynková; Jana Seidlerová; Vladimír Tomášek; Michal Ritz; Kamila Kočí; Volker Klemm; David Rafaja
      Pages: 164 - 174
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Marta Valášková, Jana Kupková, Gražyna Simha Martynková, Jana Seidlerová, Vladimír Tomášek, Michal Ritz, Kamila Kočí, Volker Klemm, David Rafaja
      Four commercial macroscopic vermiculites (Ver) from different exploited deposits were investigated regarding their chemistry and structural transformation stage from mica (phlogopite), and compared with selected raw vermiculites and “hydrobioties” known from literature, in which the chemical analyzes verified the existence of iron as Fe3+ and Fe2+. Subsequently prepared vermiculite/ceria (Ver/CeO2) nanoparticles composites were compared from the point of view of the fixation of ceria nanoparticles by using stability test and regarding their photocatalytic activity in the decomposition of N2O. The experimental methods used for these studies were X-ray fluorescence spectrometry, atomic emission spectrometry, X-ray powder diffraction, infrared (FR-IR) and Raman spectroscopy and transmission electron microscopy with high resolution (HRTEM). Negative layer charge of vermiculites produced by the local charge balance and distribution of Fe3+ in tetrahedral and octahedral sheets were related to the CeO2 nanocrystals fixation and orientation. Among the four Ver/CeO2 nanoparticles composite samples, the vermiculite in sample Ver-C/CeO2 exhibited the highest negative layer charge. The CeO2 crystallites were the smallest among all four samples. HRTEM found separated CeO2 nanocrystallites and CeO2 agglomerates of differently oriented nanocrystallites. Such forms of CeO2 nanocrystals influenced the position of the Raman CeO2 F2g and suppressed ability for photocatalytic N2O conversion.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.006
      Issue No: Vol. 151 (2017)
       
  • Cation exchange capacity of natural and synthetic hectorite
    • Authors: L. Delavernhe; M. Pilavtepe; K. Emmerich
      Pages: 175 - 180
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): L. Delavernhe, M. Pilavtepe, K. Emmerich
      Cation exchange capacity (CEC) of smectites is a function of both layer charge and lateral layer dimension, the later ones determining their edge surface area. Two trioctahedral smectites similar in layer charge, the Na-saturated hectorite SHCa-1<0.2μm and the synthetic Laponite® RD, were studied differing by morphology and particle size with a proportion due to the edge specific surface area of about 2.0% and 6.9%, respectively, considering single layers. The CEC of the materials was evaluated using the Cu-trien method over the pH range of 6 to 13. For this purpose, the Cu-trien method was evaluated for a use at pH above 10, out of the usual pH range of application. In addition, stability of clays was followed by analysing aqueous concentrations issued from the dissolution of the minerals. The CEC were measured at 83±1cmol(+) kg−1 at pH7.9 for HtCa-0.2Na and 79±1cmol(+) kg−1 at pH8.9 for Laponite® RD following the usual Cu-trien procedure without pH adjustment. The CEC ranged from 50 to 150 cmol(+) kg−1 over the pH range of 6 to 13. The strong CEC increase at pH>10 was correlated to the deprotonation of the silanol edge sites. The larger CEC development observed for Laponite® RD was related to its morphology and larger edge specific surface area. Estimation of the exchangeable cation population following the usual Cu-trien procedure led to an overestimation of Mg2+ and Li+ due to partial clay dissolution at pH<10.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.007
      Issue No: Vol. 151 (2017)
       
  • Stress relaxation of nitrile rubber composites filled with a hybrid
           metakaolin/carbon black filler under tensile and compressive forces
    • Authors: Elisson Brum Dutra da Rocha; Felipe Nunes Linhares; Cléverson Fernandes Senra Gabriel; Ana Maria Furtado de Sousa; Cristina Russi Guimarães Furtado
      Pages: 181 - 188
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Elisson Brum Dutra da Rocha, Felipe Nunes Linhares, Cléverson Fernandes Senra Gabriel, Ana Maria Furtado de Sousa, Cristina Russi Guimarães Furtado
      Stress relaxation of nitrile rubber composites filled with metakaolin and carbon black under tensile and compressive loading was assessed to determine the effect of the hybrid-system filler on the relaxation process. Nitrile rubber-filled formulations were designed with 50 parts of filler per hundred parts of rubber (phr), using carbon black-to-metakaolin ratios of 50:0, 35:15, 25:25, 15:35, and 0:50 phr. In addition, one unfilled vulcanized nitrile rubber (NBR) composite was prepared as reference. The results demonstrated that, although the presence of either filler system composition accelerated the relaxation process compared to the unfilled compound, the substitution of carbon black by metakaolin decreases the relaxation process for both the tensile and compressive tests. The lower stress relaxation caused by metakaolin in hybrid-system filler was ascribed to the reduction of filler-filler network and filler shape. Moreover, metakaolin imposed some constraints on the rubber chain movements when the load was applied in the tensile mode, but the opposite behavior was observed under compressive force.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.008
      Issue No: Vol. 151 (2017)
       
  • Characterization and comparison of thermal & mechanical properties of
           vermiculite polyvinylbutyral nanocomposites synthesized by solution
           casting method
    • Authors: Sevim İşçi; Yavuz İşçi
      Pages: 189 - 193
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Sevim İşçi, Yavuz İşçi
      The aim of the study is to determine the effect of the vermiculite (Vk) and its organoclays, which were prepared by using cationic and anionic surfactants, on polyvinylbutyral (PVB) nanocomposites. The PVB nanocomposites were synthesized by using solution casting method, concerning the changes on the mechanical, and thermal properties of PVB. Modification of vermiculites with surfactant extends the interlayer space of the vermiculite and increases the interactions of vermiculite and PVB. The structural, morphological characterizations of PVB nanocomposites were examined by XRD (X-ray diffraction), and TEM (Transmission electron microscopy), and mechanical, thermal properties of the nanocomposites were determined by DMA (Dynamical mechanical analysis), and DSC (Differential scanning calorimetry) methods. The results showed that addition of vermiculite or modified vermiculite increased the elastic modulus of PVB. Modification of vermiculite with anionic surfactant resulted in a better exfoliation and improved the mechanical and thermal properties compared with modification of vermiculite with cationic surfactant in PVB nanocomposites.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.009
      Issue No: Vol. 151 (2017)
       
  • Direct comparison among the formation of terephthalate- and
           carbonate-intercalated Mg-Al-LDH: The influence of the high aluminum
           content
    • Authors: Inna M. Nangoi; Arnaldo C. Faro; Wladmir F. Souza; Sandra S.X. Chiaro; Alexandre A. Leitão
      Pages: 194 - 200
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Inna M. Nangoi, Arnaldo C. Faro, Wladmir F. Souza, Sandra S.X. Chiaro, Alexandre A. Leitão
      First principles calculations based on Density Functional Theory (DFT) were used to investigate the standard thermodynamic potentials and also structural and electronic properties of terephthalate (TA) and carbonate intercalated Layered Double Hydroxides (LDH) with molar ratios, x = Al3+/Al3+ +Mg2+, equal to 0.25, 0.33 and 0.50. Herein we discuss how the interlayer species and formation of the LDH are influenced by the layer charge. Mg-Al-CO3 with high Al3+ content,x over 0.33, is hard to be obtained by synthetic methods in its pure phase, and LDH with high molar ratio is desirable for several applications such as intercalation reactions and obtainment of mixed oxides with better synergistic effects. This structure profile is easily to be acquired by the use of terephthalate as counterion than carbonate. The reason for this behaviour was found to be the competition among water molecules and anions for the interlayer sites. The dehydration process was simulated with excellent agreement with experimental data and showed important structural changes of TA in the interlayer space.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.011
      Issue No: Vol. 151 (2017)
       
  • Enhanced visible light photocatalytic activity of the mechanochemically
           prepared nanosized ZnxCd1-xS/Zn-Al layered double hydroxide precursor
           heterojunctions
    • Authors: Zhao Li; Qiwu Zhang; Xiaoman He; Min Chen
      Pages: 201 - 210
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Zhao Li, Qiwu Zhang, Xiaoman He, Min Chen
      ZnxCd1-xS/Zn–Al layered double hydroxide (LDH) precursor heterostructured composites were synthesized by a one-step mechanochemical method. X-ray diffraction, Fourier transform-infrared spectroscopy, SEM-EDS and thermogravimetric analysis confirmed the formation of the ZnxCd1-xS/Zn–Al LDH precursor composites. X-ray photoelectron spectroscopy indicated the formation of a heterojunction structure. The photocatalytic degradation activity for methyl orange of the heterostructured composites was observed even under visible light irradiation and exhibited a large enhancement with the increase in the molar ratio of sulfide solid solution to LDH as well as the increase in the ratio of Cd to Zn. A detailed investigation on the mechanism for the enhanced photocatalytic activity was performed, particularly regarding to the efficient separation of photogenerated electrons and holes with the heterostructure. This work provides a very simple and environment-friendly way to fabricate a series of heterostructured photocatalysts based on LDH precursor with transition metal sulfide well dispersed inside.
      Graphical abstract image

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.012
      Issue No: Vol. 151 (2017)
       
  • Clays for Efficient Disinfection of Bacteria in Water
    • Authors: Emmanuel I. Unuabonah; Chidinma G. Ugwuja; Martins O. Omorogie; Adewale Adewuyi; Nurudeen A. Oladoja
      Pages: 211 - 223
      Abstract: Publication date: January 2018
      Source:Applied Clay Science, Volume 151
      Author(s): Emmanuel I. Unuabonah, Chidinma G. Ugwuja, Martins O. Omorogie, Adewale Adewuyi, Nurudeen A. Oladoja
      Clay minerals are not only abundant in nature but can be easily engineered to make highly efficient materials for disinfection of water. A combination of their abundance and efficiency makes them a sustainable source of material for water disinfection. Several works have reported the use of clay minerals in modified form to make the removal of harmful pathogens from water sustainable and more efficient. This article reviews the various modified clay minerals that have been developed for the removal of these harmful pathogens from water. It also considers several operating factors that moderates the efficiencies of these materials during the pathogen removal process, techniques for measuring interaction between bacteria and clay-based adsorbents and future perspectives on their use in the treatment of potable water. It is believed that this will spur some interest in the quick development of very efficient and sustainable clay-based materials that will be useful for disinfection of water and wastewater in the near future.

      PubDate: 2017-11-09T03:47:07Z
      DOI: 10.1016/j.clay.2017.10.005
      Issue No: Vol. 151 (2017)
       
  • Effects of calcination temperature and the addition of ZnO on coal waste
           activation: A mineralogical and morphological evolution
    • Authors: Raquel Vigil de la Villa; Rosario García; Sagrario Martínez-Ramírez; Moisés Frías
      Pages: 1 - 9
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Raquel Vigil de la Villa, Rosario García, Sagrario Martínez-Ramírez, Moisés Frías
      Eco-efficient cements based on industrial wastes constitute a priority line of research for the sustainability of the cement sector, in response to the challenges of the circular economy at a European level. Eco-innovation and investigation of new alternative sources of primary materials from waste arise as potential actions directed at the achievement of greater efficiency in the use of resources. From among the broad range of industrial wastes, those that contain kaolinite (K) and phyllosilicates are ideal as active additions in the manufacture of cements, having previously undergone a process of thermal activation. Earlier works have indicated that the chemical reactivity of natural K (untreated kaolin) may be increased through the addition of ZnO as a chemical agent. In this study, the effect of ZnO as a chemical agent is for the first time studied, when added to coal waste in proportions of 0.5, 1.0, 1.5 and 3.0% by weight, prior to the thermal activation process of the waste that is calcinated at 550°, 600°, and 650°C for 2h. The mineralogy and the pozzolanic activity of the activated products are considered, and their influence on the evolution of the hydrated phases at 1, 7, and 28days of reaction in the pozzolan/lime system. Subsequently, the results are compared with those obtained from pure natural kaolinite activated at 600°C/2h, with ZnO addition and without chemical agent ZnO, with an added quantity of 1.0% in weight. The results showed important variations when the chemical activator (ZnO) was used for the natural kaolinite (NK) and the industrial waste. The chemical activator favors the disaggregation of the phyllosilicates from the aggregates, strengthening the pozzolanic reaction in the natural/lime kaolinite system. However, the activator in the coal waste/lime system, in addition to favoring the disaggregation of the aggregate, leaves epitaxial deposits on the surface and on the edges of the materials, saturating the substrate surface loading, with an inhibitory effect on the pozzolanic reaction. The abundance of metakaolinite (MK) and the partial dehydroxylation of the mica with its subsequent reorganization, explains the appearance of these minerals as one of the products of the reaction. With SEM/EDX, the existence of CSH gels of a spongy appearance may be observed following thermal activation of the coal waste; while if the activation is done under the combined effect of temperature and the addition of 1.0% ZnO, then the chemical activator favors the formation of long fibers and the appearance of gels, with compositions similar to LDH and calcium aluminates.

      PubDate: 2017-09-08T03:01:58Z
      DOI: 10.1016/j.clay.2017.08.031
      Issue No: Vol. 150 (2017)
       
  • Preparation and characterization of sodium lauroyl sarcosinate adsorbed on
           cetylpyridinium-montmorillonite as a possible antibacterial agent
    • Authors: Saadet Yapar; Mustafa Ateş; Günseli Özdemir
      Pages: 16 - 22
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Saadet Yapar, Mustafa Ateş, Günseli Özdemir
      An organo-montmorillonite was synthesized to generate a two-level antibacterial agent. The material (Mt-CP-SR) was prepared through the adsorption of sodium lauroyl sarcosinate (SR) on montmorillonite modified with cetylpyridinium (Mt-CP) and its structure was characterized by conducting ATR-FTIR, XRD, and SEM analyses. The results of the ATR-FTIR analyses indicated that SR on the surface could be detected when its amount exceeded the CEC of the Mt. The XRD analyses revealed that the adsorption of CP and SR causes the separation of Mt layers into smaller stacks. The adsorption and desorption study of SR onto and from 0.7 CEC Mt-CP were investigated to determine the amount of SR adsorbed at varying initial SR concentrations and the amount of SR released when diluted with water. Around 140mg of SR could be loaded on one gram of the Mt intercalated with 170mg of CP. The results indicated that desorption of SR from the surface is gradual and SR and CP have strong interactions on the montmorillonite (Mt) surface. The antibacterial activity of the material was tested against E. coli, S. aureus, and P. aeruginosa. Additionally, the SR solutions and CP+SR solutions in equimolar ratios were subjected to antibacterial tests for comparison purposes. SR proved to be effective against all three bacteria and the MIC values were found as 75mg/mL for E. coli, 37.5mg/mL for S. aureus, and 300mg/mL for P. aeruginosa. The MBC was 300mg/mL for E. coli and S. aureus. The solutions of CP+SR mixtures were ineffective against P. aeruginosa, whereas, they were effective against S. aureus. The prepared Mt-CP-SR samples were found to be effective against S. aureus and E. coli. These results indicate that the material could be used in antibacterial liquid soaps, in toothpaste formulations, personal care products, and topical applications against acne, and wounds without any negative contribution to the physico-chemical and detergency properties of the materials.

      PubDate: 2017-09-14T03:06:36Z
      DOI: 10.1016/j.clay.2017.08.025
      Issue No: Vol. 150 (2017)
       
  • Evaluation of organic modification of montmorillonite with ionic and
           nonionic surfactants
    • Authors: Jefferson Lopes Alves; Paulo de Tarso Vieira e Rosa; Ana Rita Morales
      Pages: 23 - 33
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Jefferson Lopes Alves, Paulo de Tarso Vieira e Rosa, Ana Rita Morales
      This work aims at evaluating the organophilization of montmorillonite with two different types of surfactants: one ionic, containing C16-C18 di(alkyl ester) dimethyl ammonium chloride (EA) and one nonionic, containing ethoxylated tallow amine (ETA). Aqueous dispersion and semi-solid routes were compared in terms of functionalization efficiency by statistical analysis, and supercritical CO2 was performed as a complementary and comparative method. Besides, the effect of the washing process after functionalization was evaluated. X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) and contact angle were used to evaluate the intercalation of surfactants into montmorillonite and process yield. The d001-value was improved by both surfactants intercalation, and the conformations of the species inside the clay minerals were suggested. The final arrangement of the organic species into Mt was modified as a function of the concentration of surfactant added, and by the washing steps. Most process parameters evaluated showed significant effects on d001-value and process yield. The semi-solid method was confirmed as a good alternative route due to its efficiency and it could be an environmentally friendly option to be used. ETA-modified montmorillonites showed similar d001-values (around 4.0nm) and higher thermal stability than EA-modified montmorillonite.

      PubDate: 2017-09-14T03:06:36Z
      DOI: 10.1016/j.clay.2017.09.001
      Issue No: Vol. 150 (2017)
       
  • Synthesis and characterization of 12-tungstophosphoric acid intercalated
           layered double hydroxides and their application as esterification
           catalysts for deacidification of crude oil
    • Authors: Yan Wu; Xinyue Liu; Yanqing Lei; Yue Qiu; Menglu Wang; Hao Wang
      Pages: 34 - 41
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Yan Wu, Xinyue Liu, Yanqing Lei, Yue Qiu, Menglu Wang, Hao Wang
      12-tungstophosphoric acid (H3PW12O40, HPW) intercalated layered double hydroxides (LDH) (M2+/Al3+ =2, M2+ =Mg2+, Zn2+, Ni2+) were prepared by an ion-exchange method. The as-prepared LDH show a strong reflection around 8.4° corresponding to a basal spacing of 1.05nm, which is considered as heteropolyacid salts or polytungstate intercalated LDH in almost all literature. Further systemic experiments and characterizations demonstrated that such reflection can be attributed to the intercalation of HPW, in which HPW may graft with the vacancies in the layer and orient in the interlayer with the C2 axis perpendicular to the layers. HPW intercalated LDH show higher catalytic activity than nitrate LDH for the esterification between ethylene glycol and naphthenic acids in crude oil. It is found that the total amount of acidic sites dominates the esterification activity. Due to the immobilized HPW active sites and the enlarged interlayer space, HPW intercalated LDH may act as an interlayer catalytic reactor to improve the esterification activity.
      Graphical abstract image

      PubDate: 2017-09-14T03:06:36Z
      DOI: 10.1016/j.clay.2017.09.007
      Issue No: Vol. 150 (2017)
       
  • A two-step technique for tensile strength of montmorillonite/polymer
           nanocomposites assuming filler morphology and interphase properties
    • Authors: Yasser Zare; Kyong Yop Rhee
      Pages: 42 - 46
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Yasser Zare, Kyong Yop Rhee
      This paper presents a two-step methodology for prediction of tensile strength in montmorillonite/polymer nanocomposites (MPN) assuming the effects of montmorillonite morphology (intercalation/exfoliation) and interphase properties. The suggested technique is evaluated by the experimental data of tensile strength in some samples. A good agreement is shown between experimental measurements and predictions, which can determine the intercalation/exfoliation level and interphase properties. A high aspect ratio of Mt platelets increases the interfacial interaction and mechanical involvement between polymer chains and nanoparticles causing high strengthening effect. Moreover, high concentration of well-exfoliated Mt as well as thick and strong interphase produces desirable tensile strength in MPN.

      PubDate: 2017-09-20T03:10:43Z
      DOI: 10.1016/j.clay.2017.08.026
      Issue No: Vol. 150 (2017)
       
  • Sustainable catalytic properties of silver nanoparticles supported
           montmorillonite for highly efficient recyclable reduction of methylene
           blue
    • Authors: Ning Wang; Yunxia Hu; Zongren Zhang
      Pages: 47 - 55
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Ning Wang, Yunxia Hu, Zongren Zhang
      Water contamination by organic dyes has become a serious environmental pollution. Here, a facile, green and cost-effective synthesis approach was developed to in situ grow silver nanoparticles (Ag NPs) on the eco-friendly and low cost natural material montmorillonite (Mt) through dopamine chemistry. The loading amount of silver on the montmorillonite reached 20 mass %. The Ag NPs supported montmorillonite (Ag NPs@Mt) exhibited excellent catalytic performances to reduce a model organic dye methylene blue in the presence of NaBH4 with catalytic efficiency higher than 98% and apparent reduction rate constant k app higher than 1.70min−1. More importantly, the Ag NPs@Mt was proven to show excellent recyclability for at least 20cycles and long-term stability for one month soaking in water. This low-cost and recyclable Ag NPs@Mt shows great potential in large scale application to treat dye containing wastewater.
      Graphical abstract image

      PubDate: 2017-09-20T03:10:43Z
      DOI: 10.1016/j.clay.2017.08.024
      Issue No: Vol. 150 (2017)
       
  • Clayey wastes-based lightweight aggregates: Heating transformations and
           physical/mechanical properties
    • Authors: M. Loutou; M. Hajjaji
      Pages: 56 - 62
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): M. Loutou, M. Hajjaji
      Heating transformations of pellets of selected binary blends of raw clay, cement kiln dust and phosphate sludge were investigated by using different techniques (XRD, DSC, FT-IR and SEM), and their main technical properties were followed as a function of temperature. It was found that calc-aluminosilicate phase (gehlenite/labradorite) neoformed at T<900°C from the breakdowns of kaolinite and chlorite, and lime of decomposed carbonates. Moreover, fluorapatite (a component of phosphate waste-containing blends) gave rise to calcium phosphate (Ca3(PO4)2) and melt, which played a chief role in the sintering process of the pellets. The melt abundance induced the dissolution of mullite, which was the major constituent of the cement kiln dust. The results also showed that the compressive strength of the pellets increased and water absorption together with density (except for the phosphate waste-clay blend) decreased with increasing temperature. These evolutions were discussed in relation to the microstructure changes. The suitability of the blends in LWAs manufacturing was evaluated basing on the magnitudes of the measured properties.

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.011
      Issue No: Vol. 150 (2017)
       
  • An insight into the carbonation of calcined clayey dolomite and its
           performance to remove Cd (II)
    • Authors: Hanlin Wang; Haibo Liu; Jingjing Xie; Hongwei Li; Tianhu Chen; Peng Chen; Dong Chen
      Pages: 63 - 70
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Hanlin Wang, Haibo Liu, Jingjing Xie, Hongwei Li, Tianhu Chen, Peng Chen, Dong Chen
      Highly active porous materials composed of calcite and periclase nanoparticles was prepared by the carbonation of thermally treated clayey dolomite, having great potential for heavy metal pollution control in water and soil. The effect of coexisting steam and hydration pretreatment on the carbonation of calcined clayey dolomite (CCD) was studied by fixed bed reactor and mass spectrum on-line monitoring. The phase, surface chemistry, thermal activity, pore type and morphology of CCD after carbonation were characterized by XRD, FTIR, TG, N2 adsorption–desorption isotherm and TEM. The results showed that the initial and complete carbonation temperatures of CCD under anhydrous conditions were 400°C and 600°C, respectively. The presence of 10% steam decreased the initial and complete temperatures by 100°C, respectively. The complete carbonation temperature was reduced to 400°C when the CCD was hydrated and dried before carbonation. However, the hydrated CCD which not dried can be directly carbonated at room temperature, and the carbonation rate (newborn calcite mass fraction) firstly decreased, then increased with the increase of temperature in the range of 50–500°C. According to the TG results, the decomposition temperatures of the newborn calcite produced by 650°C carbonation of CCD decreased by 50°C compared with that of common calcite. The research on cadmium removal showed that the removal efficiency of 50mg/L Cd (II) by 650°C carbonation of CCD rapidly reached 99.8% within 1h, while the equilibrium pH decreased by 2units compared with CCD without carbonation. The carbonation of CCD formed nano calcite of lower decomposition temperature and also hampered the hydroxylation to decrease the effluent pH. The experimental results displayed carbonation can control the physicochemical property of the CCD, and the carbonated product is potential to be used for the removal of Cd (II) from aqueous solution.

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.012
      Issue No: Vol. 150 (2017)
       
  • Stretchable dual nanocomposite hydrogels strengthened by physical
           interaction between inorganic hybrid crosslinker and polymers
    • Authors: Juan Du; Di Wang; Shimei Xu; Jide Wang; Yumei Liu; Jianbin Huang
      Pages: 71 - 80
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Juan Du, Di Wang, Shimei Xu, Jide Wang, Yumei Liu, Jianbin Huang
      Stretchable hydrogels have been developed by fabricating a dual nanocomposite structure by polymerization of hydrophilic monomers and sol-gel reaction of tetraethyl orthosilicate (TEOS) in the presence of Laponite. The mechanical enhancement of the hydrogels was markedly influenced by monomer structure and contents of TEOS and Laponite. The strong interaction between N-isopropylacrylamide (NIPAM) and inorganic hybrid crosslinker was examined by dyeing experiment, transparency and fluorescence measurement of Laponite/SiO2/monomer dispersions. This accounted for the excellent mechanical properties of Laponite/SiO2/PNIPAM dual nanocomposite hydrogel. Uniaxial tensile tests showed improved tensile property (elongation at break: 1845±3.46%; fracture stress: 271.41±6.26kPa), and elastic modulus of the hydrogel significantly increased with TEOS contents and reached 26.69±6.13kPa at 10:1.0 of mLaponite:mTEOS. Fracture compression strength could reach 7.06±1.25MPa (fracture energy: 1185.53±5.57Jm−2), meanwhile it showed remarkable fatigue resistance. The embedded nano-SiO2 accounted for the significantly improved stiffness of the hydrogels. Moreover, the dual nanocomposite mechanism (the covalent bonding of SiO2 with Laponite and strong physical interaction of polymer chains with inorganic hybrid crosslinker) made a big contribution to the toughness of the gels. The noncovalent entanglements between SiO2 and polymer chains could promote both strength and elongation of the hydrogel, but the effect is not as notable as the covalent one.
      Graphical abstract image

      PubDate: 2017-10-26T21:56:46Z
      DOI: 10.1016/j.clay.2017.09.008
      Issue No: Vol. 150 (2017)
       
  • Filler-matrix interaction in sodium montmorillonite-organosilica
           nanocomposite coatings for corrosion protection
    • Authors: Emanuela Callone; Riccardo Ceccato; Flavio Deflorian; Michele Fedel; Sandra Dirè
      Pages: 81 - 88
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Emanuela Callone, Riccardo Ceccato, Flavio Deflorian, Michele Fedel, Sandra Dirè
      Sodium montmorillonite/organosilica sol-gel coatings were obtained from a hydrolysed solution of 3-glycidoxypropyltrimethoxysilane (GPTMS), methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) with 2wt% of sonicated sodium montmorillonite (Mt). The effect of different sonication times (0, 1, 3, 12h) on the structure of both Mt and sol-gel clay-organosilica nanocomposites was investigated by means of 29Si and 27Al solid state nuclear magnetic resonance (NMR) and X-ray diffraction (XRD). Mt underwent relevant structural changes with the sonication treatment and the effect appeared time-dependent, although not linear. The structural changes induced on clay by the sonication process were kept in the clay-organosilica nanocomposite, according to 29Si NMR. Mt addition to the hybrid sol-gel network led to decreasing the amount of completely condensed silicon units by formation of new Si-O-Al hetero-metallic bonds, as shown by 27Al NMR results. Moreover, organosilica matrix and Mt appeared to interact even in the absence of the sonication treatment of the filler. The NMR study of GPTMS/MTES/Mt and TEOS/Mt samples clearly proves the interaction of Mt with the silsesquioxane (T) species in the obtained composites.
      Graphical abstract image

      PubDate: 2017-10-26T21:56:46Z
      DOI: 10.1016/j.clay.2017.09.016
      Issue No: Vol. 150 (2017)
       
  • Laser beam backscattering as a new tool to study the effect of inhibitors
           on shale particles-water interactions: A real-time analysis
    • Authors: Vinicius Kartnaller; Conny Cerai Ferreira; Santiago Villabona-Estupiñán; Elizabeth Roditi Lachter; Jorge de Almeida Rodrigues Junior; Regina Sandra Veiga Nascimento; João Cajaiba
      Pages: 89 - 97
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Vinicius Kartnaller, Conny Cerai Ferreira, Santiago Villabona-Estupiñán, Elizabeth Roditi Lachter, Jorge de Almeida Rodrigues Junior, Regina Sandra Veiga Nascimento, João Cajaiba
      The interaction between clay-rich shales formations and water is one of the most relevant factors for well instability in drilling operations, representing a significant challenge for the oil and gas industry. To minimize the problems related to water sensitivity, chemical additives or inhibitors are incorporated into water-based drilling fluids, acting over the water-shale interactions and maintaining the integrity of the sedimentary rock. In this work a novel approach is proposed to gain new information about the dynamics of the inhibitory process and to evaluate the shale inhibition efficiency of different chemical additives using a laser beam backscattering technique. This technique is based on the analysis of laser backscattering profiles promoted by dispersed particles in a suspension, which results in a particle chord length distribution (CLD). The technique was adequate for monitoring the consequences of the interactions between water and shales, differentiating its reactivities by monitoring the effect of different inhibitors on each system's CLD over time. Two cationic inhibitors (KCl and PDADMAC, a cationic polymer) were tested, and the obtained results showed that the inhibition phenomenon is more than the inhibitor itself, and it depends on the shale structure and the capability of the inhibitor to interact with its clay stacks. A methodology was also developed to calculate an inhibition efficiency score (IES), in which the technique's real-time factor enables it to estimate how much better an inhibitor is when compared to others over time. Among the evaluated systems, the inhibitor that achieved the biggest efficiency for shale was KCl, resulting in 69%.
      Graphical abstract image

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.010
      Issue No: Vol. 150 (2017)
       
  • Toxicological assessment of two silane-modified clay minerals with
           potential use as food contact materials in human hepatoma cells and
           Salmonella typhimurium strains
    • Authors: Sara Maisanaba; María Llana-Ruíz-Cabello; Silvia Pichardo; Ana Isabel Prieto; Ana M. Cameán; María Jordá-Beneyto; Ángeles Jos
      Pages: 98 - 105
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Sara Maisanaba, María Llana-Ruíz-Cabello, Silvia Pichardo, Ana Isabel Prieto, Ana M. Cameán, María Jordá-Beneyto, Ángeles Jos
      Reinforced technological properties can be achieved by adding small amounts of organo-modified clay minerals into traditional polymeric matrices. The result is a final product with improved characteristics destined to several applications, among them, food packaging. However, it is mandatory to evaluate the toxicity of novel food contact materials, as well as all new substances destined to this purpose. The present work shows for the first time in a human target cell line from hepatic origin (HepG2), and in Salmonella typhimurium, a prokaryotic system, the in vitro toxicological evaluation of Clay3 and Clay4, two silane-modified montmorillonites intended to be incorporated into food containers. Cytotoxic effects were evaluated (0 to 250μg/mL) after 24 and 48h of exposure and only Clay4 showed toxic effects. Once the mean effective concentration was calculated, different mechanistic biomarkers were investigated for Clay4: cell death, reactive oxygen species (ROS) production, glutathione content, mutagenicity, and standard and oxidative genotoxicity. Only a significant ROS production after both times of exposure, as well as a significant oxidative DNA damage after the longer time assayed were obtained with Clay4. Between both silane-modified clay minerals studied Clay3 is the better candidate to develop new reinforced packaging materials in base to its good toxicological profile.

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.018
      Issue No: Vol. 150 (2017)
       
  • CTAB modified large surface area nanoporous geopolymer with high
           adsorption capacity for copper ion removal
    • Authors: Aditi Singhal; Bhanu P. Gangwar; J.M. Gayathry
      Pages: 106 - 114
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Aditi Singhal, Bhanu P. Gangwar, J.M. Gayathry
      Nanoporous geopolymer was synthesized with and without using Cetyl trimethylammonium bromide (CTAB) by condensing the mixture of metakaolin and alkali solution at a fixed ratio at room temperature. The surface area of CTAB-geopolymer was found to be more (216m2/g) as compared to without CTAB added geopolymer (137m2/g). The experimental results verified that the geopolymer could adsorb copper ions completely at lower concentrations and partially at higher concentrations. Pseudo second order model fits well at all the concentration from 55 to 1700ppm as the values of the correlation coefficient lies between 0.96 and 0.99. Intraparticle diffusion model at the concentration 55ppm explains that there is only boundary layer diffusion (instantaneous) and after this step, all the Cu ions are exchanged by the nanoporous geopolymer. At 120ppm, intraparticle diffusion model shows multilinearity. Different adsorption models - Langmuir, Freundlich and Tempkin were also tested to evaluate the most appropriate model and it was found that adsorption follows Langmuir model. The adsorption capacity and pseudo second order rate constant is estimated to be 1.65meq/g which is significantly higher than the fly ash based nonporous geopolymer.

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.013
      Issue No: Vol. 150 (2017)
       
  • Insights into the formation mechanism of imogolite from a full-range
           observation of its sol-gel growth
    • Authors: Peixin Du; Peng Yuan; Antoine Thill; Faïza Annabi-Bergaya; Dong Liu; Shun Wang
      Pages: 115 - 124
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Peixin Du, Peng Yuan, Antoine Thill, Faïza Annabi-Bergaya, Dong Liu, Shun Wang
      Imogolite (Imo) was prepared via a sol-gel method. The time-dependent changes in its morphology, structure and texture during the whole synthesis process (from amorphous precursors to the final products through nanoscale intermediates) were monitored by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) and N2 physisorption. The results showed that a shape transition from a spherical open imogolite local structure (ImoLS) to a tubular open ImoLS occurred in the process of proto-imogolite (proto-Imo) formation. Based on the overall structure of the obtained solid products and the occurring main reactions, Imo synthesis process was described in five steps: i) formation of amorphous precursors by hydrolysis and condensation of Al and Si; ii) formation of proto-Imo with an open ImoLS at the expense of the amorphous precursors; iii) open ImoLS dominates; it grows and assembles into the first closed ImoLS (tubes and spheres); iv) closed ImoLS dominates and continues to form (mainly tubes) at the expense of open ImoLS; and v) no more open ImoLS; further growth of already-formed Imo via oriented aggregation. These findings provide new insights into the formation mechanism and structure of proto-Imo and Imo, which helps to clarify the Imo synthesis procedure.

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.021
      Issue No: Vol. 150 (2017)
       
  • Characterisation and identification of local kaolin clay from Ghana: A
           potential material for electroporcelain insulator fabrication
    • Authors: Abu Yaya; Elvis K. Tiburu; Mary E. Vickers; Johnson K. Efavi; Boateng Onwona-Agyeman; Kevin M. Knowles
      Pages: 125 - 130
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Abu Yaya, Elvis K. Tiburu, Mary E. Vickers, Johnson K. Efavi, Boateng Onwona-Agyeman, Kevin M. Knowles
      The aim of this work was to evaluate two kaolin clays from the southern part of Ghana, Assin-Fosu and Kumasi clays, as source clays for the fabrication of electroporcelain insulators. X-ray diffraction, differential thermal analysis, thermogravimetric analysis, chemical analyses and scanning electron microscopy observations showed the fired clay minerals have broadly similar characteristics, but with significant differences in their chemical composition. The alumina contents were determined to be 35±2wt% and 22±2wt% respectively for the two kaolins and the silica contents 49±3wt% and 58±3wt% respectively. It is concluded that Assin-Fosu kaolin is a reliable local source material for electroporcelain fabrication, while Kumasi kaolin is more suitable for making wall and floor tiles.

      PubDate: 2017-09-26T03:14:50Z
      DOI: 10.1016/j.clay.2017.09.015
      Issue No: Vol. 150 (2017)
       
  • Physical and mechanical properties improvement of a porous clay ceramic
    • Authors: Hiba Zouaoui; Jamel Bouaziz
      Pages: 131 - 137
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Hiba Zouaoui, Jamel Bouaziz
      This work deals with the chemical, physical, thermal and mechanical analyses of porous clay and non-plastic clays mixtures from Tunisia. Five mixtures which are M1 (70 mass% clay +30 mass% waste brick), M2 (70 mass% clay +15 mass% waste brick +15 mass% sand), M3 (70 mass% clay +30 mass% sand), M4 (70 mass% clay +30 mass% chamotte) and M5 (70 mass% clay +15 mass% chamotte +15 mass% sand) were sintered between 900 and 1100°C and were evaluated for their possible ceramic applications. Thermal analysis (DTA/TG), dilatometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and physical-mechanical analyses (tensile strength, water absorption and bulk density) were used to assess the thermal behavior, phase evolution and microstructure of the fired mixtures. The formations of both the anorthite phase and the vitreous phase have improved the required ceramic product performance. M1 has the highest values of tensile strength and bulk density at 1100°C. According to the European Norm EN 14411, all the mixtures belong to the BIII group which are suitable for the production of earthenware and unglazed stoneware.

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.002
      Issue No: Vol. 150 (2017)
       
  • Functionalization of halloysite nanotubes for the preparation of
           carboxymethyl cellulose-based nanocomposite films
    • Authors: Long-Feng Wang; Jong-Whan Rhim
      Pages: 138 - 146
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Long-Feng Wang, Jong-Whan Rhim
      Halloysite nanotubes (Hal) were treated with acid to prepare uniformly charged acid treated Hal (Hal-A). After acid treatment, the surface charge (zeta potential) of Hal changed from +0.08mV to −32.65mV. Functionalized Hal-A were prepared through adsorbing metal ions by immersing the Hal-A into saturated solutions of three different metal salts, silver nitrate, zinc nitrate, and copper acetate. The number of metal ions attached to the Hal-A and their functionality were dependent on the type of metal ions. The functionalized Hal-A exhibited strong antimicrobial activity against food-borne pathogenic bacteria, L. monocytogenes and E. coli. The CMC-based film showed a significant increase in mechanical, water vapor barrier, and thermal stability properties after forming a composite with Hal. In particular, CMC-based films incorporated with the functionalized Hal-A showed strong antimicrobial activity against both L. monocytogenes and E. coli.

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.023
      Issue No: Vol. 150 (2017)
       
  • Thermoexfoliated and hydrophobized vermiculites for oleic acid removal
    • Authors: Celia Marcos; Roberto Menéndez; Irene Rodríguez
      Pages: 147 - 152
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Celia Marcos, Roberto Menéndez, Irene Rodríguez
      The aim of the present study was to investigate the removal efficiency of oleic acid from aqueous solutions by thermally expanded and hydrophobized vermiculites. The expansion of the samples was carried out in a furnace at 1000°C for 2min. The hydrophobization using polymethyl-hydro-siloxane as hydrophobing derivatizing reagent was performed by immersion and hydrophobizing atmosphere methods. The investigation was started with two vermiculites from Brazil, the Goiás and Piauí states, respectively. After some previous tests the Goiás vermiculite was selected to investigate five effects: 1) Adsorption at different pH. 2) Adsorption at different concentrations of hydrophobizing reactive and different weights of vermiculite. 3) Adsorbent mass. 4) Influence of the number of stages of adsorption. 5) Influence of salinity. Oleic acid uptake was quantitatively evaluated using the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich (DKR) models. In addition, the adsorption equilibrium was described well by the DKR isotherm model, indicative of a cooperative process. The maximum adsorption capacity obtained with DKR model was of 1.29mol/g of oleic acid. The hydrophobization Goiás vermiculite and the adsorption of oleic acid were verified using infrared spectroscopy. The findings of this study showed that this thermally expanded and hydrophobized vermiculite: 1) was very suitable for the recovery of oleic acid in water; 2) the adsorption increased with the increase of the salinity of the aqueous medium; 3) it was possible to reuse vermiculite unsaturated to recover more oleic acid.

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.026
      Issue No: Vol. 150 (2017)
       
  • An experimental study on oven-drying methods for laboratory determination
           of water content of a calcium-rich bentonite
    • Authors: Lin Zhi Lang; Wei Xiang; Wei Huang; De Shan Cui; Tom Schanz
      Pages: 153 - 162
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Lin Zhi Lang, Wei Xiang, Wei Huang, De Shan Cui, Tom Schanz
      Studies on the dehydration of montmorillonites imply that the standard oven-drying method (drying at 110 ± 5°C) may underestimate the water content of bentonites. This study quantifies, identifies, explains, and removes the residual water in a calcium-rich bentonite dried using the standard oven-drying method. A thermogravimetric-differential scanning calorimetry (TG-DSC) test was performed to determine the true water content. According to this test, the effect of the drying time and temperature on the amount of residual water in the bentonite was examined, including the oven-drying and vacuum-drying methods. To identify and explain the residual water, specific surface area (SSA) derived from the nitrogen adsorption isotherm and dehydration reaction characterised by TG-DSC curves of samples with a residual water content of 0–13.38% were obtained. The experimental results demonstrate that the standard oven-drying method underestimates the water content of calcium-rich bentonites by 2.1–3.1%. The 2.1–3.1% of residual water includes both interlayer water and adsorbed water on the external surface. The 2.1–3.1% of residual water is the water forming the inner shell around Ca2+ cations in the interlayer and on the external surface of montmorillonite particles. It is impractical to distinguish between the adsorbed water and interlayer water only based on the dehydration reaction characterised by TG-DSC curves. Drying profiles of 12h of drying at 200°C in an oven and 1h of drying at 150–200°C under vacuum are sufficient for removing the adsorbed and interlayer waters from the bentonite.

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.022
      Issue No: Vol. 150 (2017)
       
  • Heating-freezing effects on the orientation of kaolin clay particles
    • Authors: Karam A. Jaradat; Zubin Darbari; Mohamed Elbakhshwan; Sherif L. Abdelaziz; Simerjeet K. Gill; Eric Dooryhee; Lynne E. Ecker
      Pages: 163 - 174
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Karam A. Jaradat, Zubin Darbari, Mohamed Elbakhshwan, Sherif L. Abdelaziz, Simerjeet K. Gill, Eric Dooryhee, Lynne E. Ecker
      The effects of temperature changes on the particle orientation of a consolidated kaolin are studied using XRD experiments. Two sets of equipment were utilized in this study: a benchtop equipment, and a synchrotron beamline at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. The kaolin specimens tested in the benchtop XRD were subjected to elevated and freezing temperatures ex-situ, while those used for the NSLS-II experiment were exposed to the temperature changes in-situ. The temperatures considered in this study range from freezing (−10°C) to elevated temperature below boiling (90°C). The thermally-induced reorientation of clay mineral particles is highly dependent on the relative orientation of the clay mineral particles with respect to the applied thermal gradient. For example, kaolin samples with kaolinite particles oriented perpendicular to the thermal gradient, and to the expected thermally-induced pore water flow, experience much higher particles reorientations compared to samples with particles initially oriented parallel to the thermal gradient. Moreover, freezing kaolin preserved its microstructure as ice crystals form.

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.028
      Issue No: Vol. 150 (2017)
       
  • Physico-mechanical and gas permeability characteristics of kaolin based
           ceramic membranes prepared with a new pore-forming agent
    • Authors: David O. Obada; David Dodoo-Arhin; Muhammad Dauda; Fatai O. Anafi; Abdulkarim S. Ahmed; Olusegun A. Ajayi
      Pages: 175 - 183
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): David O. Obada, David Dodoo-Arhin, Muhammad Dauda, Fatai O. Anafi, Abdulkarim S. Ahmed, Olusegun A. Ajayi
      The objective of this study was to prepare low-cost macroporous ceramic membranes using natural kaolin obtained from deposits in Nigeria and Ghana, and powdery high density polyethelene (PHDPE) as porogen agent. The ceramic membranes have been prepared with porogen content wt% between (0 and 20)% by die pressing. Pellets were fired at 1150°C and soaking time of 4h. The raw materials were characterized using TG/DTA, particle size distribution (PSD) and Zeta potential. The membranes cast as circular disks were subjected for characterization studies using XRD and SEM analysis. In a bid to correlate the physico-mechanical properties vis-à-vis pore former content, the effect of the sintering temperature and pore former (PHDPE) content on porosity, density, water absorption and mechanical strength were evaluated. The membrane corrosion resistance was found to be unaltered with experimental conditions. Obtained membranes showed good porosity with maximum at about 62% with a mechanical strength that does not exceed 18MPa. These membranes can be considered as efficient regarding the results shown in the gas permeation tests at different sintering temperatures. A PHDPE percentage of 20% and a sintering temperature of 1150°C were chosen as the optimum for gas permeation based on enlarged pore diameter of sintered membranes.

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.014
      Issue No: Vol. 150 (2017)
       
  • Structure and photoluminescence of a new binary Mg/Tb layered double
           hydroxide
    • Authors: Xiaoqing Wang; Yufeng Chen; Huajian Zhou; Kunlei Zhang
      Pages: 184 - 191
      Abstract: Publication date: 15 December 2017
      Source:Applied Clay Science, Volume 150
      Author(s): Xiaoqing Wang, Yufeng Chen, Huajian Zhou, Kunlei Zhang
      A series of binary Mg/Tb layered double hydroxides (Mg/Tb-LDH) with different Mg2+/Tb3+ molar ratios of 2.0, 3.0, 4.0, and 5.0 have been synthesized in ammonia water media by hydrothermal method. Various characterizations, including inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), and photoluminescent spectra (PL), etc., were used to study the composition, structure, and photoluminescent property of samples. Results revealed that the molar ratios of Mg2+/Tb3+ present in the samples approximated to that of the initial molar ratios of chemical reagents. All the Mg/Tb-LDH samples have similar hexagonal structure as that of the brucite Mg(OH)2 despite their lattice c values are greatly larger than that of the Mg(OH)2. These Mg/Tb-LDH exhibited good photoluminescence. Moreover, the emissions due to 5D4 → 7FJ (J=5, 6) transitions of Tb3+ gradually enhanced as the Mg2+/Tb3+ molar ratios varied from 5.0, 4.0 to 3.0; then markedly decreased with the Mg2+/Tb3+ molar ratio down to 2.0. The strongest emissions were observable to be at Mg2+/Tb3+ molar ratio of 3.0. This new binary Mg/Tb-LDH may be potential application as luminescent materials.
      Graphical abstract image

      PubDate: 2017-10-03T17:56:04Z
      DOI: 10.1016/j.clay.2017.09.025
      Issue No: Vol. 150 (2017)
       
 
 
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