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  Subjects -> ENGINEERING (Total: 2298 journals)
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ENGINEERING (1209 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: 19)
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: 252)
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: 9)
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: 26)
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: 11)
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: 30)
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: 40)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 2)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 5)
AIChE Journal     Hybrid Journal   (Followers: 32)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access   (Followers: 1)
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: 8)
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: 18)
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: 5)
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: 9)
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: 6)
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: 4)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 10)
Biomedical Engineering     Hybrid Journal   (Followers: 15)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 14)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 18)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 34)
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: 14)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 30)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 44)
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: 7)
CEAS Space Journal     Hybrid Journal   (Followers: 1)
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: 24)
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: 14)
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: 27)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 270)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 195)
Composites Part B : Engineering     Hybrid Journal   (Followers: 276)
Composites Science and Technology     Hybrid Journal   (Followers: 191)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 15)
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: 8)
Computer Science and Engineering     Open Access   (Followers: 19)
Computers & Geosciences     Hybrid Journal   (Followers: 29)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 6)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 4)
Computers and Geotechnics     Hybrid Journal   (Followers: 11)
Computing and Visualization in Science     Hybrid Journal   (Followers: 6)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 32)
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: 43)
Control Theory and Informatics     Open Access   (Followers: 8)
Corrosion Science     Hybrid Journal   (Followers: 25)
Corrosion Series     Full-text available via subscription   (Followers: 6)
CT&F Ciencia, Tecnologia y Futuro     Open Access   (Followers: 1)

        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  [3118 journals]
  • Influence of the pre-dispersion of montmorillonite on organic modification
           and the adsorption of perchlorate and methyl red anions
    • Authors: Wuhui Luo; Keiko Sasaki; Tsuyoshi Hirajima
      Pages: 1 - 9
      Abstract: Publication date: 15 March 2018
      Source:Applied Clay Science, Volume 154
      Author(s): Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima
      In this study, hexadecyl pyridinium chloride (HDPy-Cl) was applied to modify powdery and dispersed montmorillonite (pMt and dMt, respectively). Then, perchlorate (ClO4 −) and methyl red (MR) were selected as representatives of hazardous inorganic and organic pollutants, respectively, to investigate the influence of the dispersion of Mt on their adsorption using the obtained composites (pMt/HDPy and dMt/HDPy). Based on the X-ray diffraction patterns and water chemistry results, pre-dispersion of Mt resulted in a lower crystallinity of the obtained composite with slightly higher contents of HDPy+ (0.93mmol/g-Mt) and HDPy-Cl (1.41mmol/g-Mt) compared to the original powdery Mt (0.85 and 1.36mmol/g-Mt). Moreover, as supported by thermogravimetry results, the amount of HDPy distributed on the external surface of dMt/HDPy was greater than that on pMt/HDPy, which was opposite of the HDPy content in the interlayer space. The adsorption kinetic of ClO4 − and MR on two composites was studied and the results were fitted by three models, where the intra-particle diffusion model fitted the experimental data best. Similar adsorption capacities were obtained, and the slight differences in the adsorption kinetics as supported by the intra-particle diffusion model were ascribed to the differences in the HDPy contents and configuration. The pre-dispersion of Mt is not necessary when a modified composite is planned for use as an adsorbent of pollutants, but it would be beneficial to the synthesis of clay/polymer nanocomposites.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.032
      Issue No: Vol. 154 (2017)
       
  • A new one-step method for physical purification and organic modification
           of sepiolite
    • Authors: Guanzheng Zhuang; Jiahua Gao; Huiwen Chen; Zepeng Zhang
      Pages: 1 - 8
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Guanzheng Zhuang, Jiahua Gao, Huiwen Chen, Zepeng Zhang
      Organo-sepiolite (OSep) is conventionally prepared by two main steps, including purification of sepiolite (Sep) and organic modification procedure. These two steps were completed independently by two factories or production lines. In order to save more water, energy, cost and decrease polluted water, a one-step method to purify and organically modify Sep was proposed. Orthogonal test was used to optimize the conditions. X-ray diffraction demonstrated three impurities, i.e., quartz, calcite and talc, were include in the raw ore. The mass content of Sep in raw ore was 30%. By this one-step method, the crystalline impurities were completely removed. Organic modification did not influence on the crystal structure and morphology of Sep. The organic surfactant was not only used as organic modifier, but also used as flocculant, making OSep was easier to be separated from the dispersion. Zeta potential results demonstrated that dispersant increased the negative charges of Sep surface, enhancing the repulsive force between Sep. And the surfactant destroyed the electrical double layers and decrease the surface negative charges. Surfactant cations were adsorbed on the surface of Sep, resulting in hydrophobic surface. Contact angles and gel volumes indicated the compatibility between OSep and oil. The one-step method could not only purify Sep, but also efficiently modified the surface properties. This procedure is simple, environmentally friendly and cost saving, with high efficiency.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.045
      Issue No: Vol. 153 (2017)
       
  • A semi-analytical solution for one-dimensional elasto-viscoplastic
           consolidation of layered soft clay
    • Authors: Sheng-Feng Zou; Jin-Zhu Li; Xin-Yu Xie
      Pages: 9 - 15
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Sheng-Feng Zou, Jin-Zhu Li, Xin-Yu Xie
      The threshold yield stress plays a key role in controlling the rheological consolidation behaviour of soft clay. A semi-analytical theory combining numerical and analytical methods is introduced that excludes the effects of clay self-weight. The governing equations assume the clay is an elasto-viscoplastic material. Approximate solutions as well as computational programme to surface loading for two drainage boundary conditions are obtained, while the clay profile is separated into material which is overconsolidated and normally consolidated. The effects of threshold yield stress and time-dependent loading on the rheological behaviour of soft clays are explored using the solutions developed.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.042
      Issue No: Vol. 153 (2017)
       
  • Effects of calcium concentration and differential settlement on
           permeability characteristics of bentonite-sand mixtures
    • Authors: Sifa Xu; Mengdan Bian; Cuifeng Li; Xuehui Wu; Zhe Wang
      Pages: 16 - 22
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Sifa Xu, Mengdan Bian, Cuifeng Li, Xuehui Wu, Zhe Wang
      Liner systems consisting of clay or bentonite-sand mixtures can be installed on the bottom of landfills to prevent contaminants from seeping into the surroundings. Differential settlement of the foundation and presence of heavy metal or alkali metal ions in the leachate can vastly affect permeability characteristics of the liner system. In this study laboratory model tests were performed to investigate the influence of differential settlement and Ca2+ on permeability characteristics of bentonite-sand mixtures. The results showed that when the thickness of bentonite-sand mixtures was 100 and 200mm, cracks were formed within the bentonite-sand mixtures with respective deflections of 2.5 and 7.0mm. When the height of developed cracks exceeded 50% and 70% of the thickness, the permeability characteristics of bentonite-sand mixtures was >10−7 cm/s. Ca2+ concentration has great impact on the permeability characteristics of bentonite-sand mixtures. Na-bentonite will be converted to Ca-bentonite when the concentration of Ca2+ is two times greater than that of Na+ in the solution, and the anti-seepage performance of bentonite-sand mixtures will consequently deteriorate.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.029
      Issue No: Vol. 153 (2017)
       
  • Investigation of dynamic mechanical properties of Estonian clay Arumetsa
           during firing
    • Authors: Igor Štubňa; Tomáš Húlan; Tiit Kaljuvee; Libor Vozár
      Pages: 23 - 28
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Igor Štubňa, Tomáš Húlan, Tiit Kaljuvee, Libor Vozár
      Elastic and inelastic properties of ceramic clay from Estonian locality Arumetsa (59% of clay minerals, mostly illite; 25% of quartz, 12% of K-feldspars and 3% of carbonates) were investigated by a dynamical thermomechanical analysis during the heating and cooling stages of firing performed up to 900, 1000, and 1100°C. Complementary analyses DTA, TG, thermodilatometry, and XRD were also performed. During heating, the release of the physically bound water set the clay crystals closer to each other, which increases Young's modulus (YM) and decreases internal damping (ID). On the other hand, dehydroxylation did not influence YM and ID significantly. This means that the properties of the phase boundaries are more important for YM than the intrinsic mechanical properties of the crystals themselves. Heating above 700°C caused solid-phase sintering, later creation of the melt and an intensive liquid-phase sintering. The values of YM significantly depend on the maximal firing temperature. After heating to 900°C and 1000°C, YM reached low values (~8GPa) because sintering was not sufficient for substantially eliminating the porosity. The heating up to 1100°C brought the value of YM to 47GPa due to a high part of the glassy phase. As a result of the microcracks creation, the values of YM dropped down significantly from their highest values at 800°C. Their relative decrease represented 38% after firing at 1000°C and 1100°C and 36% after firing at 900°C.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.038
      Issue No: Vol. 153 (2017)
       
  • A new hydrotalcite-like absorbent FeMnMg-LDH and its adsorption capacity
           for Pb2+ ions in water
    • Authors: Hongguang Zhou; Zhenmao Jiang; Shiqiang Wei
      Pages: 29 - 37
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Hongguang Zhou, Zhenmao Jiang, Shiqiang Wei
      A new hydrotalcite-like material layered double hydroxide (FeMnMg-LDH) with potentials used as adsorbent was synthesized based on a co-precipitation method. The Fe/Mn/Mg molar ratio in its crystal structure is 1:1:2. Well lamellar structure of the synthesized FeMnMg-LDH has been proved by its transmission electron microscope (TEM) images and the diffraction peaks are similar to the characteristic peaks of typical LDHs. Its adsorption characteristics for heavy metals, taking Pb2+ as an example, were examined in this paper. The maximum Pb2+ adsorption capacity of FeMnMg-LDH was about 421.42mg/g at 25°C, which is much higher than those of the most other similar kind of absorbents. In addition, it could keep a Pb2+ removal efficiency higher than 97% from aqueous solution at a wide pH range (pH3–6). Thermodynamic parameters ΔH 0, ΔS 0 and ΔG 0 have been calculated. Positive value of ΔH and negative value of ΔG demonstrate an endothermic and spontaneous process of Pb2+ adsorption on the FeMnMg-LDH sample. The adsorption mechanisms mainly involve surface-induced precipitation and ion exchange. The coexisting divalent cations could compete with Pb2+ ions for the adsorption following a competing ability of Cu2+ >Cd2+ >Mg2+ >Ca2+. The results suggested that the synthesized FeMnMg-LDH material could be served as a potential material for the remediation of heavy metal contamination in water.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.033
      Issue No: Vol. 153 (2017)
       
  • Removal of Methylene Blue from aqueous solutions by adsorption on Kaolin:
           Kinetic and equilibrium studies
    • Authors: Lotfi Mouni; Lazhar Belkhiri; Jean-Claude Bollinger; Abdelkrim Bouzaza; Aymen Assadi; Amar Tirri; Farid Dahmoune; Khodir Madani; Houcine Remini
      Pages: 38 - 45
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Lotfi Mouni, Lazhar Belkhiri, Jean-Claude Bollinger, Abdelkrim Bouzaza, Aymen Assadi, Amar Tirri, Farid Dahmoune, Khodir Madani, Houcine Remini
      Removal of Methylene Blue (MB) from aqueous solutions is studied using a raw Algerian kaolin sample as a low-cost adsorbent. The effects of pH, contact time, dye concentration and temperature are all taken into consideration. The adsorption kinetics results are adjusted to best fit the pseudo-second order model. The experimental data are analyzed by Langmuir isotherms, revealing that the maximum adsorption capacity of MB on this kaolin sample equals 52.76mg/g at T=25°C and pH=6.0. The calculated thermodynamic data demonstrates that adsorption is spontaneous and enhanced at higher temperatures. Desorption studies with water indicate that the adsorbent could successfully retain MB, even after four cycles. From these results, it can be considered that the raw Algerian kaolin sample tested herein is effective in the removal of MB from aqueous solutions and moreover may be used as an alternative to high-cost commercial adsorbents.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.034
      Issue No: Vol. 153 (2017)
       
  • Calcined Mg/Al-LDH for acidic wastewater treatment: Simultaneous
           neutralization and contaminant removal
    • Authors: Minwang Laipan; Haoyang Fu; Runliang Zhu; Luyi Sun; Rachel M. Steel; Sujuan Ye; Jianxi Zhu; Hongping He
      Pages: 46 - 53
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Minwang Laipan, Haoyang Fu, Runliang Zhu, Luyi Sun, Rachel M. Steel, Sujuan Ye, Jianxi Zhu, Hongping He
      Acid drainage (AD) poses a significant concern for water pollution due to its strong acidity and the toxicity of its various contaminants (e.g., heavy metal ions). In order to minimize the harmful effects of AD, the acidity must be neutralized and the contaminants be removed. The capacity of calcined Mg/Al layered double hydroxide (Mg/Al-CLDH) for simultaneously neutralizing the pH of AD and removing various heavy metal cations and oxyanions (Cr(VI) and phosphate) was studied herein. The interactions throughout co-removal between metal cations (in short M) and oxyanions were particularly investigated. In the solution with only M, Mg/Al-CLDH was capable of neutralizing solution pH and removing M. The reconstruction of LDH from Mg/Al-CLDH produced OH– to neutralize pH and partially remove M through precipitation. FT-IR results suggested that forming H-bonds with the reconstructed LDH (R-LDH) might also contribute to M removal. In the solution containing both M and oxyanions, M and oxyanions could mutually affect their removal efficiency by Mg/Al-CLDH. M weakened the removal capacities of Cr(VI) and phosphate, because it could compete for adsorption sites on R-LDH. Cr(VI) and phosphate showed complex effects on the removal of M: Low concentrations of Cr(VI) promoted the removal of M by providing extra adsorption sites; high concentrations of Cr(VI), however, had the opposite effect, as a high concentration of Cr(VI) might largely occupy the adsorption sites on R-LDH. By contrast, phosphate inhibited the removal of M considerably, which might be ascribed to its strong buffering ability that maintained a relatively strong acidic nature of the solution. Our results, for the first time, showed that Mg/Al-CLDH is particularly suitable for the treatment of AD containing various contaminants.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.12.002
      Issue No: Vol. 153 (2017)
       
  • Direct production of ethanol from glycerol over Ni-substituted stichtite
           derived catalysts
    • Authors: Liping Zheng; Huaiyuan Zhao; Jie Fu; Xiuyang Lu; Zhaoyin Hou
      Pages: 54 - 60
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Liping Zheng, Huaiyuan Zhao, Jie Fu, Xiuyang Lu, Zhaoyin Hou
      Ethanol is a widely used chemical and its primary source is via the fermentation of crops (such as corn, sorghum, rice and barley) or biomass (such as sugarcane). Direct production of ethanol from over-supplying glycerol is of great significance. In this research, we want to report a synthesis route of ethanol from glycerol over a series of Ni-substituted stichtite derived Ni/MgCr2O4 catalysts. The best yield of ethanol reached 0.50g-ethanol/g-cat/h at 250°C over Ni2.4/Mg3.7Cr2.0O6.7. The transformation process from Ni-substituted stichtite to Ni/MgCr2O4 catalysts was characterized by TG-DSC, XRD, XPS and TEM. Characterization results inferred that the formation of MgCrO4 in calcined precursor played a crucial role for Ni dispersion and catalytic performance in the production of ethanol. Reaction mechanism for the formation of ethanol from glycerol was proposed.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.12.005
      Issue No: Vol. 153 (2017)
       
  • ZnAl layered double hydroxides impregnated with eucalyptus oil as
           efficient hybrid materials against multi-resistant bacteria
    • Authors: Marta Lobo-Sánchez; Gisel Nájera-Meléndez; Gilberto Luna; Verónica Segura-Pérez; José Angel Rivera; Geolar Fetter
      Pages: 61 - 69
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Marta Lobo-Sánchez, Gisel Nájera-Meléndez, Gilberto Luna, Verónica Segura-Pérez, José Angel Rivera, Geolar Fetter
      Bacterial contamination poses a serious hazard for human health. The use of bactericidal materials, such as layered double hydroxides, might constitute a way to reduce the risk of diseases. In this work, ZnAl layered double hydroxides were synthesized by microwave irradiation at different pH values and various metal molar ratios to be tested against multi-resistant bacteria. The synthesis conditions were chosen to form, in some cases, a composite containing zincite (ZnO), as both materials, zincite as well as the layered double hydroxide, are well known to be efficient antimicrobials. Eucalyptus extracted oil, which is a bactericidal compound, was extracted from eucalyptus leaves and used to impregnate some layered double hydroxide–zincite composites. The materials were characterized by X-ray diffraction, infrared spectroscopy, nitrogen physisorption and scanning electron microscopy. The samples were tested against Staphylococcus sp. and Pseudomonas aeruginosa, which are multi-resistant bacteria. It was found that Zn/Al molar ratio, pH and inclusion of eucalyptus oil in the layered double hydroxides synthesis determined the bactericidal activity. The best performing samples were those containing eucalyptus oil, which, at very low concentrations, were able to kill Staphylococcus sp. and inhibit the Pseudomonas aeruginosa growth.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.017
      Issue No: Vol. 153 (2017)
       
  • Hydroxy-interlayered minerals in the Holocene paleosol on the southernmost
           Loess Plateau, China
    • Authors: Chuan-Qin Huang; Mi-Nan Wang; Wen-Feng Tan; Ming-Kuang Wang; Luuk K. Koopal
      Pages: 70 - 77
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Chuan-Qin Huang, Mi-Nan Wang, Wen-Feng Tan, Ming-Kuang Wang, Luuk K. Koopal
      The presence and formation of hydroxy-interlayered minerals in the Holocene paleosol at the Wugong profile on the southernmost Chinese Loess Plateau were investigated by examining the <1μm and 1–2μm clay fractions of the 50–150cm horizon by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Prior to the analyses free Al and Fe phases were removed by dithionite-citric-bicarbonate (DCB) extraction. XRD patterns were obtained with air-dried, Mg-saturated, Mg-saturated with glycerol solvation (Mg-glycerol) and K-saturated and heated at 110, 250, 350, 450 and 550°C samples both before and after hydroxy-interlayered materials removal by sodium citrate extraction. The absorption bands at 3699 and 3430cm−1 in the FTIR spectra of both sub-fractions indicated the presence of hydroxy-interlayered minerals. The K-saturated and heated XRD patterns confirmed this by the progressive collapse of the 1.4nm reflection to a 1.0nm reflection. After removal of the hydroxy-interlayered materials no obvious increase of the relative XRD intensity of the 1.8nm reflection in Mg-glycerol pattern was observed and the 1.4nm reflection exhibited a stronger collapse to 1.0nm after K-saturation and increasing temperature treatment. This indicated that the hydroxy-interlayered minerals in the Holocene paleosol were mainly composed of hydroxyl-interlayer vermiculite. The hydroxyl-interlayer vermiculite was formed by the polymerization of Al/Fe-hydroxy materials within the interlayer space of vermiculite. Shoulder-like reflection at 1.2nm in the K-550°C pattern of the 1–2μm fraction indicated a higher degree of Al/Fe-hydroxylation in the coarse fraction than in the fine fraction, which was consistent with the lower extractable Al and Fe in the coarse fraction. The reflection at 1.38nm in the K-550°C pattern could be interpreted as pedogenic chlorite. Thus, transformation of vermiculite into hydroxy-interlayered vermiculite and finally into a chlorite-like mineral (pedogenic chlorite) has occurred in the Holocene paleosol on the southernmost Chinese Loess Plateau.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.007
      Issue No: Vol. 153 (2017)
       
  • Ternary hybrid system of halloysite nanotubes, polyacrylamides and
           cyclodextrin: an efficient support for immobilization of Pd nanoparticles
           for catalyzing coupling reaction
    • Authors: Samahe Sadjadi; Mohammad Atai
      Pages: 78 - 89
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Samahe Sadjadi, Mohammad Atai
      Taking advantage of the properties of polyacrylamide (P), the capability of cyclodextrin (CD) to form inclusion complex and outstanding features of halloysite nanoclay as catalyst support, a ternary hybrid system, Hal-P-CD, was designed and synthesized through growing polyacrylamide on the surface of functionalized halloysite nanotubes followed by introduction of β-cyclodextrin. The hybrid system was successfully used for immobilization of Pd nanoparticles and formation of a heterogeneous catalyst, Pd@Hal-P-CD. The structure of Pd@ Hal-P-CD was confirmed by using SEM/EDS, TEM, XRD, BET, ICP-AES, TGA, FTIR and elemental mapping analysis and its catalytic activity was studied for promoting ligand and copper-free Sonogashira coupling reaction in aqueous media (1:1 mixture of water and ethanol). The results established that Pd@Hal-P-CD could catalyze the coupling reaction to afford the desired products in high yields and short reaction times. Notably, the catalytic activity of Pd@Hal-P-CD was superior to those of Pd@Hal-P and Pd@Hal. The study of the reusability of the catalyst up to 7 reaction runs as well as Pd leaching confirmed the heterogeneous nature of the catalysis and the efficiency of Hal-P-CD for suppressing the Pd leaching. Additionally, this catalyst could also be successfully used for promoting Heck coupling reaction.
      Graphical abstract image

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.013
      Issue No: Vol. 153 (2017)
       
  • Effect of raw material milling on ceramic proppants properties
    • Authors: Anabella Mocciaro; Maria B. Lombardi; Alberto N. Scian
      Pages: 90 - 94
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Anabella Mocciaro, Maria B. Lombardi, Alberto N. Scian
      Low density and high breakage resistance ceramic proppants were developed from kaolin, bauxite and monoaluminum phosphate (MAP). The effect of the particle size on the raw materials over the density, the open porosity and the breakage resistance of the proppants was evaluated. The phase composition and the structure of the proppants due to the milling process were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pore size distribution by mercury intrusion. The proppants obtained with raw materials of smaller size improved its breakage resistance and developed a smaller open pore size, achieving an apparent density of 2.4g/cm3 with a breakage ratio of 9.61% under 64MPa. Some properties of the AG3 proppants with sand, low density ceramic proppants of the literature and commercial low density ceramics proppants were compared.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.009
      Issue No: Vol. 153 (2017)
       
  • Cobalt-boron loaded thermal activated Turkish sepiolite composites
           (Co-B@tSe) as a catalyst for hydrogen delivery
    • Authors: Esra Meşe; Aysel Kantürk Figen; Bilge Coşkuner Filiz; Sabriye Pişkin
      Pages: 95 - 106
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Esra Meşe, Aysel Kantürk Figen, Bilge Coşkuner Filiz, Sabriye Pişkin
      Cobalt-boron loaded thermal activated sepiolite composites (Co-B@tSe) are prepared with an impregnation-chemical reduction method and calcination step for use as a catalyst for sodium borohydride (NaBH4) hydrolysis, solvolysis, and methanolysis. The catalytic activity of Co-B@tSe can be improved by using a thermal-treated raw sepiolite as a catalyst support (Eskişehir, Turkey). The catalysts are analyzed using XRD, XRF, FT-IR, BET, DTA/TG, SEM/EDS and, TEM measurements. The catalytic performance for hydrogen generation is evaluated at room temperature. Research shows that cobalt-impregnated, heat treated, raw sepiolite at 500°C (Sample B-2) exhibits a high boron loading ability. These conditions, in conjunction with an appropriate calcination treatment, can improve catalytic activity. When the Co-B@tSe, in the form of Co3BO5 sized 6±1.8nm, is dispersed on sepiolite channels, the catalyzed hydrogen generation rate (HGR) shows a trend of more methanolysis than hydrolysis at room temperature.
      Graphical abstract image

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.008
      Issue No: Vol. 153 (2017)
       
  • Workability of clay mixtures
    • Authors: G.E. Barnes
      Pages: 107 - 112
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): G.E. Barnes
      Raw clays undergo mixing for the manufacture of structural clay products and ball clays and kaolins are carefully selected, processed, stored and blended in various proportions to produce consistent formulations for the wide range of fine ceramic products. The effects of blending different clays with a range of proportions have been investigated on the Atterberg plasticity limits and on the toughness-water content relationships. It is demonstrated that blending of raw and processed clays with different mineralogy and plasticity properties can produce liquid and plastic limits and toughness-water content relationships that do not follow a linear interpolation between the individual properties of the clays in relation to their proportions. Mixing of high plasticity clay with a lower plasticity clay produced a wider range of water contents over which the mixtures remained plastic, particularly with lower water contents which would be desirable when considering shrinkage properties. However, this resulted in increased toughness and harder workability, a less desirable factor.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.006
      Issue No: Vol. 153 (2017)
       
  • New model of ethylene glycol intercalate in smectites for XRD modelling
    • Authors: Marek Szczerba; Kristian Ufer
      Pages: 113 - 123
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Marek Szczerba, Kristian Ufer
      Several models of ethylene glycol (EG) intercalates were implemented in computer programs which are used to simulate XRD patterns of oriented clay minerals. So far the models assumed distributions of atomic positions perpendicular to the c* direction with similar or significantly higher temperature coefficients B for the EG molecules (B=1Å2 or 11Å2) than for atoms of crystal structure (approximately: B=1Å2). The temperature coefficients for the interlayer H2O molecules and Ca2+ cations (B=1Å2 or 1.68Å2) were close to these of clay minerals' atoms. This assumption is in disagreement with the distributions described recently with molecular dynamics (MD) simulations. An adjustable model of one and two EG planes in the interlayer is provided in this study. This new model is based on the results of MD simulations. A wide range of EG and H2O contents were considered in the simulated structures. Theoretical structures corresponding to certain basal spacings were chosen as representative for one- and two-plane intercalates. The electronic density profiles of EG molecules, H2O molecules, and Ca2+ ions were fitted with Gaussian functions. Their number was minimized to achieve the simplest but yet flexible model of the interlayer structures. The obtained new models show significant differences with regard to the former ones; especially in the atoms' positions. Based on the MD results, it was also possible to determine the relationships between positions of the atoms/molecules and basal spacing. For some atoms was also a relationship between basal spacing and intensity ratio of Gaussian distributions found. Temperature factors for interlayer species were larger than in the former models and Ca2+ ions can exist both as inner-sphere and/or outer sphere complexes, while its ratio can be optimized. All the relationships were implemented in the BGMN Rietveld refinement program. Using the new model it is possible to receive slightly better or similar matching between experimental and theoretical X-ray diffractograms, comparing to the former models. The new model shows limitations due to the fact that electronic distributions of water and EG molecules in the interlayer space are quite similar. Therefore, EG and water molecules in the interlayer space were not treated fully separately during the minimalization procedure.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.010
      Issue No: Vol. 153 (2017)
       
  • Chemical modification of commercial kaolin for mitigation of organic
           pollutants in environment via adsorption and generation of inorganic
           pesticides
    • Authors: Mohamed Khairy; Haytham A. Ayoub; Farouk A. Rashwan; Hanan F. Abdel-Hafez
      Pages: 124 - 133
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Mohamed Khairy, Haytham A. Ayoub, Farouk A. Rashwan, Hanan F. Abdel-Hafez
      Contamination of water supplies with different organic pollutants from industrial and agricultural activities has received high concern recent years. Thus, efficient removal of these organic pollutants and minimize their usage in environment are highly recommended. Herein, we report hydrothermal chemical modifications of commercial kaolin (CK) in presence of sodium hydroxide (alkaline-modified kaolin; AMK) and disodium hydrogen phosphate (phosphate-modified kaolin; PMK) reagents. Interestingly, these chemical modifications altered the physicochemical characteristics of CK in term of morphology, surface area and functionality which enhanced the adsorption capability of organic pollutants (i.e. methylene blue; MB) as well as offered an alternative inorganic pesticide that might reduce the consumption of organic pesticides. The results showed that, the equilibrium of MB adsorption is well described by Langmuir isotherm with maximum monolayer capacity of 434.78 and 476.19mg/g for AMK and PMK, respectively. Furthermore, AMK and PMK revealed reasonable latent entomotoxic effect against cotton leafworm (S. littoralis) compared to a highly toxic organic pesticide (i.e. Methomyl). Therefore, the naturally abundant kaolin can be utilized efficiently to mitigate the organic pollutants in environment through sequestering of organics and generation of alternative inorganic pesticides for green plant protection.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.014
      Issue No: Vol. 153 (2017)
       
  • Dendrimer-functionalized halloysite nanotubes for effective drug delivery
    • Authors: Joanna Kurczewska; Michał Cegłowski; Beata Messyasz; Grzegorz Schroeder
      Pages: 134 - 143
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Joanna Kurczewska, Michał Cegłowski, Beata Messyasz, Grzegorz Schroeder
      Halloysite nanotubes functionalized with polyamidoamine dendrimer were prepared and characterized. The material studied was applied as a carrier of three model therapeutic compounds - chlorogenic acid, ibuprofen and salicylic acid. It showed higher adsorption capacity for the drugs studied (123.16mg/g for chlorogenic acid; 182.72mg/g for ibuprofen; 39.52mg/g for salicylic acid) compared to raw halloysite and 3-aminopropyltrimethoxysilane functionalized – halloysite nanotubes. The experimental adsorption data fits the Langmuir model. As a result of surface functionalization of halloysite with the dendrimer, the release rate of chlorogenic and salicylic acid decreased, while the release profile of ibuprofen was similar to that of 3-aminopropyltrimethoxysilane functionalized nanotubes. The release kinetics of chlorogenic acid and salicylic acid followed Higuchi model and the release exponents indicated a Fickian diffusion mechanism. The release mode of ibuprofen followed the first order kinetics and the mechanism was described as non-Fickian (anomalous) transport. The in vivo toxicity studies showed that the dendrimer –functionalized halloysite had no effect on the living organisms used in the bioassays.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.019
      Issue No: Vol. 153 (2017)
       
  • Effect of different plasmonic metals on photocatalytic degradation of
           volatile organic compounds (VOCs) by bentonite/M-TiO2 nanocomposites under
           UV/visible light
    • Authors: Amit Mishra; Akansha Mehta; Shagun Kainth; Soumen Basu
      Pages: 144 - 153
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Amit Mishra, Akansha Mehta, Shagun Kainth, Soumen Basu
      Metal loaded clay/TiO2 nanocomposites have gained a huge attention to acting as an alternative and effective photocatalyst for the removal and complete degradation of toxic pollutants in the presence of UV/Visible light. Here, we have synthesized bentonite/M-TiO2 nanocomposites (M=Ag, Au, Pd) by a simple and facile method. Metal nanoparticles (NPs) of Ag, Au, and Pd were loaded (1% by wt.) on clay/TiO2 nanocomposites to study their impact on their photocatalytic activity. Oxidation states of the deposited metal NPs were analyzed by X-ray photoelectron spectroscopy (XPS). From HRTEM analysis, the particle size was found to be 8–10nm and 10–15nm for the metal NPs and TiO2 NPs respectively. The bentonite/M-TiO2 nanocomposites possessed higher surface area (119–125m2/g) as compared to unloaded bentonite/TiO2 nanocomposites (112m2/g). Localized surface plasmon resonance (LSPR) peaks corresponding to different metal NPs (502, 503 and 541nm for Pd, Ag and Au respectively) were observed from UV–Visible DRS spectra (diffuse reflectance spectroscopy). Metal NPs acted as electron sinks suppressing electron-hole recombination as depicted from PL spectra leading to an increase in exciton life time (2.50ns to 2.60ns) as observed from time resolved fluorescence spectroscopy. The prepared bentonite/M-TiO2 nanocomposites were found to be effective photocatalyst towards degradation of harmful volatile organic compounds (VOCs) like chlorobenzene and benzaldehyde under UV and visible light. The nanocomposite containing Ag was found to be highly active with a rate constant of 0.055 and 0.0178min−1 for chlorobenzene and 0.027 and 0.004min−1 for benzaldehyde degradation under UV and visible light respectively. One of the most important advantages of bentonite/M-TiO2 nanocomposites over the well-known commercial TiO2 photocatalyst, P25 was that it could be easily separated from aqueous dispersions by sedimentation after the reaction and could be reused for several times.
      Graphical abstract image

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.11.040
      Issue No: Vol. 153 (2017)
       
  • Structural characterization of sepiolite/polyamide6,6 nanocomposites by
           means of static and dynamic thermal methods
    • Authors: Cristina Fernandez-Barranco; Anna E. Kozioł; Marek Drewniak; Africa Yebra-Rodriguez
      Pages: 154 - 160
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Cristina Fernandez-Barranco, Anna E. Kozioł, Marek Drewniak, Africa Yebra-Rodriguez
      Clay Polymer Nanocomposites (CPN) are hybrid materials with improved technical characteristics with respect to the counterparts. Polyamide6,6 (PA66) is one of the most widely used as matrix. The α structure (triclinic) undergoes into the γ structure (pseudohexagonal) in a solid-to-solid transition when exposed to high temperatures. In recent years, sepiolite (Sep) has been used as reinforcing agent in polymer matrix as it enhances thermal properties of the nanocomposites without modification in the hydrogen bonds between PA66 chains. In this work we provide information about the structural changes occurring in neat PA66 and Sep/PA66 nanocomposites after the degradation process through a thermo-dynamic study combined with X-ray diffraction methods. In injection molded Sep/PA66 nanocomposites the sepiolite fibres locate between the polymer lamellae in a sloping suitable position, without involving large distortions in the lattice of PA66. Due to organophilization, no changes are induced by the sepiolite in the nanocomposite structure. The PA66…Sep contact promotes the occurrence of the CH…O hydrogen bonds in the typical reticulated structure between the sepiolite fibres and the polyamide chains, which renders thermal sability to the polymer crystals up to 150°C.
      Graphical abstract image

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.025
      Issue No: Vol. 153 (2017)
       
  • A novel electroosmotic chemical treatment for improving the clay strength
           throughout the entire region
    • Authors: Chang-Yu Ou; Shao-Chi Chien; Yu-Ting Syue; Chun-Tao Chen
      Pages: 161 - 171
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Chang-Yu Ou, Shao-Chi Chien, Yu-Ting Syue, Chun-Tao Chen
      Electroosmotic chemical treatment can be used to improve clay strength. However, this improvement is often limited to regions near the anode and/or cathode, while the areas between the electrodes remain weak. The objective of this study was to develop a suitable method to improve the clay strength throughout the entire sample. The characteristics of the test clay were studied by varying the concentration of the calcium chloride (CaCl2) solution, injecting a potassium hydroxide (KOH) solution to neutralize the acidic conditions in the anode area, using a fresh sodium silicate solution in the anode compartment, and constantly injecting deionized water after injection of the sodium silicate solution. The results indicated that an increase in the concentration of the CaCl2 solution reduced the efficiency of injecting the sodium silicate solution in the subsequent treatment stage. The use of a fresh sodium silicate solution may increase the efficiency of injecting the sodium silicate solution into clay, thereby extending the improvement range. When deionized water was injected constantly after injection of the sodium silicate solution, the Ca2+ ions in the clay migrated toward the cathode during treatment and, simultaneously, a highly alkaline condition formed near the cathode, leading to an enhancement of the pozzolanic reaction and a significant increase in the clay strength near the cathode. Based on these results, an ECT test was conducted using a fresh sodium silicate solution and constant injection of deionized water. The results indicated that the strength of the entire clay sample was improved.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.11.031
      Issue No: Vol. 153 (2017)
       
  • Layered double hydroxides: A brief review from fundamentals to application
           as evolving biomaterials
    • Authors: Geetanjali Mishra; Barsha Dash; Sony Pandey
      Pages: 172 - 186
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Geetanjali Mishra, Barsha Dash, Sony Pandey
      Layered double hydroxides (LDH) which are one type of layered materials and are also known as anionic clays, are promising layered materials due to some of their interesting properties, such as ease of synthesis, unique structure, uniform distribution of different metal cations in the brucite layer, surface hydroxyl groups, flexible tunability, intercalated anions with interlayer spaces, swelling properties, oxo-bridged linkage, and high chemical and thermal stability, ability to intercalate different type of anions (inorganic, organic, biomolecules, and even genes), delivery of intercalated anions in a sustained manner and also high biocompatibility. Considering the previous work on LDH as novel biomaterials, research on this particular materials has become one of the most interesting topic of today's research. LDH has become an important class of layered materials having prospects in the field of biomaterials, wherein great attention has been paid to the biocompatibility nature, exchange of the existing anion with the target anion, holding of guest species in between the interlayer space and its controlled release of the anion in a particular medium. This article, after deliberating the recent significant evolution in the structure and different methods of synthesis of different LDH materials and its applications in various extents especially its biological applications through their structural and functional properties, considers many typical examples. In particular, recent progress on the emerging strategies of LDH to improve their antimicrobial activity is also presented.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.021
      Issue No: Vol. 153 (2017)
       
  • Inorganic modification of layered silicates toward functional
           inorganic-inorganic hybrids
    • Authors: Thipwipa Sirinakorn; Kamonnart Imwiset; Sareeya Bureekaew; Makoto Ogawa
      Pages: 187 - 197
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Thipwipa Sirinakorn, Kamonnart Imwiset, Sareeya Bureekaew, Makoto Ogawa
      After careful investigation on the formation/preparation, the structures and the reactivity of a class of layered alkali silicates (kanemite, makatite, octosilicate, magadiite and so on) in 1960–80', the applications of the layered silicic acids and the alkaline metal silicates have extensively been investigated. The applications of these layered silicates range from the ion exchanger, adsorbent, catalyst and catalysts' support, bio-related one and so on. For the construction of functional nanomaterials, host-guest reaction has been applied to optimize materials performances as well as to find new functions. The functionalization of layered silicates with various organic functional groups has been investigated extensively and summarized in several review papers. In this review article, the functionalization of the layered alkali silicates and the silicic acids derived from with inorganic species will be summarized in order to highlight the present status of the materials chemistry on layered alkali silicates and their hybrids with inorganic species toward the practical application.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.011
      Issue No: Vol. 153 (2017)
       
  • Enhanced antimicrobial performance of cloisite 30B/poly (ε-caprolactone)
           over cloisite 30B/poly (l-lactic acid) as evidenced by structural features
           
    • Authors: Snigdha Sajeendra Babu; Nandakumar Kalarikkal; Sabu Thomas; Radhakrishnan E.K.
      Pages: 198 - 204
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Snigdha Sajeendra Babu, Nandakumar Kalarikkal, Sabu Thomas, Radhakrishnan E.K.
      Antimicrobial property of nanocomposites for biomedical applications demands the design of high performance materials. The molecular interactions among components of nanocomposites can be crucial in determining the release of antimicrobial components. In this study, the effect of polymer type on the antimicrobial property of cloisite 30B (C30B) was studied. Poly-ε-caprolactone (PCL) and Poly l-lactic acid (PLA) were the matrices used for cloisite 30B. These polymers are extensively used in tissue engineering and drug delivery applications. Nanocomposite formation was confirmed by AFM, FT-IR and X-ray diffraction. Antimicrobial analysis revealed that the PCL based nanocomposite was found to have synergistic antimicrobial activity against Staphylococcus aureus while PLA based one was antagonistic to the antimicrobial activity of C30B, due to higher level of interaction in C30B/PLA nanocomposite when compared to C30B/PCL. Higher degree of interactions could hinder release of antimicrobial agents from the nanocomposites. Results of the study provides an insight on the effect of matrix-filler interactions on bioactivity with promising applications in material engineering.
      Graphical abstract image

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.003
      Issue No: Vol. 153 (2017)
       
  • Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain
           but different functional groups in the presence of clay minerals
    • Authors: Hongmei Liu; Peng Yuan; Dong Liu; Hongling Bu; Hongzhe Song; Zonghua Qin; Hongping He
      Pages: 205 - 216
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Hongmei Liu, Peng Yuan, Dong Liu, Hongling Bu, Hongzhe Song, Zonghua Qin, Hongping He
      Organic matter (OM)-clay mineral complexes, especially OM-clay interlayer complexes, exist widely in soil, sediment, and source rock. These associations can influence the pyrolytic behaviors of OM. In addition, the nature of OM may also affect pyrolysis due to the variety and complexity of the structure and chemical composition of natural organics. In this study, to investigate the influences of the nature of OM as well as the interface association between OM and clay minerals on the pyrolysis of OM, interlayer clay-OM complexes and clay-OM mixtures were prepared and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) was adapted to monitor the pyrolytic temperatures and products of these complexes. A series of OM with the same alkyl main chain but different functional groups, i.e., Lauric acid (LA), Dodecylamine (DA), 12-Aminolauric acid (ALA) and Dodecyl trimethyl ammonium bromide (DTAB), was used, and montmorillonite (Mt) was selected as the representative clay mineral. The results showed that Mt decreased the decomposition temperature of the carboxyl groups that contained OM (LA and ALA), promoted the generation of CO2 via the catalysis of the Lewis acid sites of Mt, and delayed the decomposition of DA and DTAB. The interlayer Brønsted acid sites allowed the nitrogen-containing organics to undergo Hoffmann elimination. The pyrolytic behaviors of OM within the interlayers of Mt were more strongly affected than those on the external surface of Mt The pyrolytic performance of OM was closely related to the association ways between OM and clay minerals, the nature of clay minerals, and the nature of OM. The interlayer space was shown to be particularly important for the preservation and catalysis of organics.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.028
      Issue No: Vol. 153 (2017)
       
  • Thixotropic aging and its effect on 1-D compression behavior of soft
           reconstituted clays
    • Authors: Azmayeen Rafat Shahriar; Md. Zoynul Abedin; Rowshon Jadid
      Pages: 217 - 227
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Azmayeen Rafat Shahriar, Md. Zoynul Abedin, Rowshon Jadid
      The present study investigates the moisture content at which the thixotropic effect is maximum, as well as the effect of such aging on compression. For this research, samples were prepared at moisture contents ranging from 0.55–1.25 times their corresponding liquid limits, and fall cone and vane shear tests were administered to determine the shear strength. Oedometer tests were performed on both thixotropically aged and unaged samples to observe the effects of thixotropic aging on 1-D compression characteristics. It was observed that the maximum thixotropic strength was obtained at a moisture content close to 0.75 times the corresponding liquid limit for all samples, and thixotropic strength recovery was negligible at a moisture content of 0.55 times the corresponding liquid limit. Vane shear strength was found to be lower than fall cone strength, and an increase in the rate of strain resulted in lower estimation of thixotropic strength recovery. The thixotropic strength ratio was observed to be dependent on the plasticity index and activity of the clay sample. Of all of the clays examined, the thixotropically aged sample provided the highest yield stress. The study suggests that in situations where the effective vertical stress is less than 100kPa, the settlement calculation, using the conventional effective stress principle, needs to be rigorously revised. A scheme for considering both strength and compressibility behavior in design practice is also provided.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.029
      Issue No: Vol. 153 (2017)
       
  • Silane functionalization of sodium montmorillonite nanoclay: The effect of
           dispersing media on intercalation and chemical grafting
    • Authors: Mohammad Asgari; Uttandaraman Sundararaj
      Pages: 228 - 238
      Abstract: Publication date: 1 March 2018
      Source:Applied Clay Science, Volume 153
      Author(s): Mohammad Asgari, Uttandaraman Sundararaj
      This study investigated the effect of various dispersing media on the silane functionalization of sodium montmorillonite nanoclay (NaMt) to evaluate each medium's effectiveness on the intercalation and chemical grafting of silane coupling agent. The amount of intercalation was estimated using the equation that was developed in our previous work based on thermogravimetric analysis. The results showed that the amount of silane intercalation was the greatest for water and glycerol media (≈1.582mmol/g clay and ≈1.480mmol/g clay, respectively), which was in agreement with the d001-values calculated by the XRD analysis (≈19.6Å and ≈14.4Å, respectively). 29Si NMR results showed a new T site in addition to Q peaks for all modified nanoclays in different dispersing media, indicating the occurrence of silane chemical grafting at the surface of the nanolayers. The A T 3 A Q 3 in NMR spectra was used to compare the amount of chemically grafted silane in different dispersing media, a new approach for Mt material. Hydrogen-bonding solvents (water, glycerol and ethanol), and polar solvents (DMF and THF) showed greater T3 peak intensities compared to other dispersing media, indicating higher amounts of chemical grafting of silane molecules. This observation was in agreement with the broadening of FTIR peak at 1130–1000cm−1 , which is explained by the formation of extra SiOSi bonds; that is, in turn, due to silane chemical grafting at the surfaces of the nanolayers. The silane-nanofiller interactions were correlated with the Hansen solubility parameters of different dispersing media used for the modification. This research has potential to help design and improve the nanoclay modification processes, which are used in the fabrication of clay-polymer nanocomposites.

      PubDate: 2017-12-27T03:17:04Z
      DOI: 10.1016/j.clay.2017.12.020
      Issue No: Vol. 153 (2017)
       
  • Treatment of highly dispersive clay by lignosulfonate addition and
           electroosmosis application
    • Authors: Amir Hossein Vakili; Mohammad Kaedi; Mehdi Mokhberi; Mohamad Razip bin Selamat; Mahdi Salimi
      Pages: 1 - 8
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Amir Hossein Vakili, Mohammad Kaedi, Mehdi Mokhberi, Mohamad Razip bin Selamat, Mahdi Salimi
      Dispersive soils are clayey, high in sodium content, and washed easily when subjected to water with low salt concentrations. The works of stabilizing dispersive soils using chemical additives from throughout the world are well documented. In the current study, a highly dispersive clay was treated with various proportions of lignosulfonate, an environmentally friendly stabilizer. A 58% reduction in dispersivity of the soil was achieved by addition of 1.5% lignosulfonate by dry mass. Meanwhile, the electroosmosis technique is known as an effective and modern soil improvement method. In the subsequent stage of the study, the effects of electroosmosis treatment on the dispersive clay were investigated by using different potentials. The dispersivity of soils taken from around the anodes was found decreased by 52% after 7days of electroosmosis application under 48V potential. The above two methods were capable of reducing dispersivity however, when used alone, insufficient in bringing the treated soils into the non-dispersive category. Consequently, the simultaneous treatment by lignosulfonate addition and electroosmosis application was successful in reducing the dispersivity of the initially highly dispersive clay by 65% and qualifying it for the non-dispersive designation.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.039
      Issue No: Vol. 152 (2017)
       
  • Effects of processing on the mineralogy and solubility of carbonate-rich
           clays for alkaline activation purpose: mechanical, thermal activation in
           red/ox atmosphere and their combination
    • Authors: A. D'Elia; D. Pinto; G. Eramo; L.C. Giannossa; G. Ventruti; R. Laviano
      Pages: 9 - 21
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): A. D'Elia, D. Pinto, G. Eramo, L.C. Giannossa, G. Ventruti, R. Laviano
      The present study focuses on the assessment of the effects of different activation methods on carbonate-rich clays, to understand the mineralogical differences originated and to exploit such information to industry for traditional and innovative applications, especially as a precursor for alkali activated binders. Illite carbonate-rich clay samples were subjected to thermal activation in ox/red atmosphere between 400 and 900°C, mechanical activation (grinding for 5, 10 and 15min) and to a combination of such treatments. Mineralogical and textural changes in the activated samples were evaluated through X-ray powder diffraction, Fourier transform infrared spectroscopy and thermal techniques. The activated samples with the highest content of amorphous phase underwent leaching tests in a 3M NaOH solution by means of inductively coupled plasma-mass spectrometry. The application of the three processing routines, yielded three types of activated clays with different leaching modes of Si, Al, K and Ca: (1) high energy grinding preferentially delaminates clay minerals and reduces the grain size of calcite. K leaching reaches the highest values; (2) thermal heating at 800°C increases relatively the Si/Al solubility ratio, but the absolute concentrations of these elements are equal or lower than those obtained from ground clays. The relatively higher leaching of Ca is influenced by the formation of non-stoichiometric and poorly crystalline Ca-silicates and -aluminosilicates; (3) high energy grinding combined with heating treatment yields an extended amorphisation, mainly at the expense of clay minerals, with the highest leaching of Si and Al, and the lowest of Ca. New formed K-feldspars inhibit the concentration of K in alkaline solution.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.036
      Issue No: Vol. 152 (2017)
       
  • Facile preparation approach of nanocomposite based on water-soluble
           polymer and layered double hydroxides for the enhancement of leather
           dyeing
    • Authors: Lu Jia; Jianzhong Ma; Dangge Gao; Bin Lyu; Li Cheng
      Pages: 22 - 28
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Lu Jia, Jianzhong Ma, Dangge Gao, Bin Lyu, Li Cheng
      LDH/P(DMDAAC-AA-SAS) nanocomposites with LDH loading of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0% have been prepared by facile approach using water-soluble polymer dimethyl diallyl ammonium chloride-acrylic acid-sodium allyl sulfonate [P(DMDAAC-AA-SAS)] and layered double hydroxides (LDH) through ultrasound and self-assembly process. X-ray diffraction (XRD) and transmission electron microscope (TEM) of the nanocomposites show that the LDH are partly exfoliated, and the solubility of the LDH/P(DMDAAC-AA-SAS) can be affected by the LDH loading amount. Fourier transform infrared spectrometer (FTIR) analysis indicates that the nanocomposites are prepared. Different LDH loading amount LDH/P(DMDAAC-AA-SAS) nanocomposites have been applied in leather process. The results show that, the ‘L’ values of the 1wt% LDH loading LDH/P(DMDAAC-AA-SAS) nanocomposite treated black leather can be reduced to 21.56 while the control leather is 25.22, which indicating the better dyeing properties of LDH/P(DMDAAC-AA-SAS) nanocomposite. In addition, 1wt% LDH loading LDH/P(DMDAAC-AA-SAS) nanocomposite resulted in increment of leather thickening rate by 27.4% than control leather and physical characteristics of leather treated by nanocomposite can also be improved.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.017
      Issue No: Vol. 152 (2017)
       
  • Molecular dynamics study of the dissolution mechanism of kaolinite basal
           surfaces in alkali media
    • Authors: Zeinab Naderi Khorshidi; Xiaoli Tan; Qi Liu; Phillip Choi
      Pages: 29 - 37
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Zeinab Naderi Khorshidi, Xiaoli Tan, Qi Liu, Phillip Choi
      The geopolymerization process involves the dissolution of aluminosilicates in an alkali solution followed by the polymerization of the dissolved aluminate and silicate oligomers to form an amorphous geopolymer. It is generally accepted that the dissolution determines the nature of the oligomers formed, thereby the properties of the resultant geopolymer. Accordingly, in this work, a series of molecular dynamics (MD) simulations were carried out in the isothermal-isobaric (NPT) ensemble at 298K and 1atm to study the initial stage of dissolution process that takes place at the two basal surfaces (partially deprotonated octahedral and tetrahedral) of kaolinite in alkali media. Three different alkali media containing sodium (Na+), potassium (K+) and a mixture of 50/50 Na+/K+ cations were modeled at low (1M) and medium (5M) concentrations. The MD results showed that cations migrated to the vicinity of the deprotonated sites, trigging the dissociation of the nearby surface hydroxyl groups and increasing the interatomic distances between the aluminum atom that were adjacent to the deprotonated site and those attached such aluminum atom, thereby dissolving them in the form of aluminates into the alkali solution. Radial distribution functions and structural analyses indicated that the crystallinity of the model kaolinite decreased as simulation time and alkali solution concentration increased. The distortion occurred mostly on the octahedral surface that was attributed to the change of the coordination of aluminum from 6-fold octahedral to 5- and 4-fold tetrahedral. However, Na+ and K+ exhibited different dissolution mechanisms. In particular, Na+ with a higher charge density induced more dissociation of the surface hydroxyl groups, whereas K+ with a lower charge density resulted in more dissociation of aluminum atoms in the form of aluminates. In the case of the solution containing 50/50 Na+/K+, there was a synergistic effect of both cations that the solution led to more surface structure distortion as quantified by the number of 5- and 4-fold aluminum atoms.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.025
      Issue No: Vol. 152 (2017)
       
  • Experimental investigations on discrepancy in consolidation degrees with
           deformation and pore pressure variations of natural clays
    • Authors: Ling-Ling Zeng; Zhen-Shun Hong; Jie Han
      Pages: 38 - 43
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Ling-Ling Zeng, Zhen-Shun Hong, Jie Han
      Degrees of consolidation can be determined by two different methods using deformation and excess pore pressure variations for reconstituted and natural clays in laboratory tests and engineering practice. Theoretically, the relationship between the degrees of consolidation determined using the two methods should be unique. However, this study finds the experimental results from fifteen one-dimensional incremental load consolidation tests on five kinds of natural clays deviated from the theoretical line. The experimental relationships correlating the degrees of consolidation determined by the two methods are also found not unique, instead, consisting of a cluster of curves depending on different step stress increments. Two key causes are found to be responsible for the substantial discrepancy between experimental and theoretical results: (1) the nonlinear development of deformation during the dissipation of excess pore pressure; (2) the degree of consolidation determined by excess pore pressure measurements lower than 100% when the degree of consolidation determined based on the deformation-time curve becomes 100%. It is also found that the experimental relationships correlating the degrees of consolidation determined by the two methods are significantly affected by the values of degree of consolidation with excess pore pressure dissipation at 100% of consolidation degree with deformation observations.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.029
      Issue No: Vol. 152 (2017)
       
  • Adsorption of lead(II) ions from aqueous solutions onto Cr-pillared clays
    • Authors: Ana-Maria Georgescu; Françoise Nardou; Valentin Zichil; Ileana Denisa Nistor
      Pages: 44 - 50
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Ana-Maria Georgescu, Françoise Nardou, Valentin Zichil, Ileana Denisa Nistor
      The present paper presents the synthesis and characterization of porous nanomaterials, the Cr (III) being the metal oxide used as pillar intercalated between the layers of montmorillonite. The raw material used to obtain the pillared clays was a Romanian natural calcium bentonite, which was provided by S.C. Bentonita S.A. The main parameters were varied (metal ion for ion exchange process, aging temperature and duration for pillaring agent preparation, metal/clay ratio) in the aim of obtaining nanomaterials with high adsorption capacity of lead ions from waters. The modified clays were characterized by: nitrogen adsorption technique, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The determination of Pb(II) ions concentration was realized by atomic absorption spectrophotometry. The obtained results showed that the basal distance and specific surface area varied with the parameters of materials preparation. The nanomaterial with the best textural, structural and morphological properties was chosen in the aim of its using in Pb(II) adsorption from aqueous solution. The Langmuir and Freundlich models were used to fit the experimental data and these showed good correlations.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.031
      Issue No: Vol. 152 (2017)
       
  • Size-controlled self-assembly of anisotropic sepiolite fibers in rubber
           nanocomposites
    • Authors: Barbara Di Credico; Elkid Cobani; Emanuela Callone; Lucia Conzatti; Davide Cristofori; Massimiliano D’Arienzo; Sandra Dirè; Luca Giannini; Thomas Hanel; Roberto Scotti; Paola Stagnaro; Luciano Tadiello; Franca Morazzoni
      Pages: 51 - 64
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Barbara Di Credico, Elkid Cobani, Emanuela Callone, Lucia Conzatti, Davide Cristofori, Massimiliano D’Arienzo, Sandra Dirè, Luca Giannini, Thomas Hanel, Roberto Scotti, Paola Stagnaro, Luciano Tadiello, Franca Morazzoni
      The development of advanced polymer nanocomposites requires a strong filler-polymer interfacial interaction and an optimal filler nanodispersion. The incorporation of the clays into a polymer matrix frequently does not improve the composite mechanical properties, owing to both poor dispersion and macroscopic particle dimensions. In this work, pristine and organically-modified sepiolites (Sep) were structurally modified by an acid treatment, which provides nano-sized sepiolite (NS-Sep) fibers with reduced particle size and increased silanol groups on the surface layer. NS-Sep fibers were used to prepare styrene-butadiene rubber nanocomposites with enhanced mechanical properties. Dynamic-mechanical analysis of clay polymer nanocomposites demonstrated that the NS-Sep fibers provided an excellent balance between reinforcing and hysteretic behavior, compared to the large-sized pristine Sep and isotropic silica. This was related to the enhanced interfacial chemical interaction between NS-Sep and rubber, as well as to the size and self-assembly of anisotropic nanofibers to form filler network structures, as supported by transmission electron microscopy analysis. The preparation of nanocomposites, based on Sep nanofibers obtained by a simple and versatile acid treatment, can thus be considered an alternative approach for the designing of advanced clay polymer nanocomposites.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.032
      Issue No: Vol. 152 (2017)
       
  • Nitrate removal from model aqueous solutions and real water by calcined
           Mg/Al layered double hydroxides
    • Authors: Dana Ivánová; Peter Albert; Jana Kavuličová
      Pages: 65 - 72
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Dana Ivánová, Peter Albert, Jana Kavuličová
      Magnesium/Aluminium-carbonate layered double hydroxides were synthesized by two coprecipitation methods in conditions at low and high supersaturation with consequential calcination and application for nitrate removal. The different parameters such as adsorbent dosage, contact time, pH were observed in model solutions with various content of nitrates from 100 to 200mg/L to adjust optimal conditions for removal of nitrates from real water. The well water contained exceeded concentration limits of nitrates as well as cations such as magnesium, calcium, manganese and iron according to the required quality of drinking water. Nitrate concentration below the toxicity limit value was reached with removal efficiency of 72% and 84.6% for the first stage of adsorption by using of 15 and 20g/L of calcined adsorbent dose, respectively. In the second stage of adsorption after elimination of cations as well as coexisting anions in the first stage, the removal efficiency of nitrates was higher of 73.9%, 94.7%, 98.7% and 99.2% for calcined adsorbent dose from 5, 10, 15 and 20g/L, respectively.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.033
      Issue No: Vol. 152 (2017)
       
  • Combined EXAFS and ab initio study of copper complex geometries adsorbed
           on natural illite
    • Authors: David M.S. Martins; José P. Mirão; Jörg Göttlicher; Marco Molinari; Ralph Steininger; Stephen C. Parker; Mário A. Gonçalves
      Pages: 73 - 82
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): David M.S. Martins, José P. Mirão, Jörg Göttlicher, Marco Molinari, Ralph Steininger, Stephen C. Parker, Mário A. Gonçalves
      The adsorption of copper on the 2:1 clay mineral illite (0.4 to 20μm in size) was studied using a combination of extended X-ray adsorption fine structure (EXAFS) and hybrid-Density Functional Theory (DFT) modelling. The study evaluates the effect of varying pH and copper concentration on the mechanisms of copper adsorption in solutions at background electrolyte concentration typical of natural surface continental freshwaters in granitic environments. The EXAFS spectra revealed both the elongated square pyramidal and Jahn-Teller octahedral coordinated copper clusters as feasible with the former providing better fits using spertiniite (crystalline copper hydroxide) as model compound. Additionally, ab initio calculations also predicted the square pyramidal geometry to be more stable. Copper ions have four Oeq at an average distance of 1.95(1)Å and two independent Oax at average distances of 2.32(16)Å and 3.06(9)Å, with the latter decreasing to 2.97(2)Å as copper concentration and pH are increased. This may reveal different mechanism by which copper adsorbs on illite, as a weakly bound complex at low pH likely at exchange and edge sites and changing towards more strongly bound complexes at high affinity edge sites at higher pH and copper loads. Above 1% Cu model fits suggest formation of copper oligomers with average Cu-Cu distance of 3.10(2)Å. These occur at pH>6, where the correlation between Cu-Cu and Al-Al distances in the illite edge surfaces supports the formation of surface precipitates.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.034
      Issue No: Vol. 152 (2017)
       
  • Flocculation of aqueous kaolin suspension using a biodegradable flocculant
           system of poly (vinyl alcohol)-Acacia nilotica gum blends
    • Authors: Tanbir Nasim; Abhijit Pal; Abhijit Bandyopadhyay
      Pages: 83 - 92
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Tanbir Nasim, Abhijit Pal, Abhijit Bandyopadhyay
      Acacia nilotica gum (NG) was blended with high hydrolyzed grade biodegradable poly (vinyl alcohol) ( M n ¯ 14,000) in different mass proportions to produce a green and efficient flocculant for separartion of a low concentration of kaolin particles (3 mass%) from its suspension. Flocculation efficacy (settling time and turbidity number) was optimized with respect to flocculant dose, PVA-NG blend composition and pH of the medium. Results showed that PVA-NG73 (70% PVA and 30% NG) was the best performing flocculant at 25ppm dose when the pH of the medium was maintained at 2.6. Zeta potential (both before and after addition of flocculant), hydrodynamic size, isoelectric point and reduced viscosity number were measured to explain the sedimentation rate and turbidity numbers. The floc size was measured and was found to be comparative to the rate of sedimentation. The amount of water absorbed and lost during operation was found to be proportional with the floc size. Impact of inorganic salts on sedimentation was investigated at a neutral pH which showed a faster settling potential of both bivalent and trivalent salts at an optimized concentration (0.3M), at the best flocculant dose (25ppm).

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.035
      Issue No: Vol. 152 (2017)
       
  • Synergistic improvement of piezoelectric properties of PVDF/
           CaCO3/montmorillonite hybrid nanocomposites
    • Authors: Nusrat Jahan; Frej Mighri; Denis Rodrigue; Abdellah Ajji
      Pages: 93 - 100
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Nusrat Jahan, Frej Mighri, Denis Rodrigue, Abdellah Ajji
      Poly (vinylidene fluoride), PVDF, based hybrid nanocomposites (micro-CaCO3 +Montmorillonite (Mt)) containing varying amounts of CaCO3 (30–40 parts (wt.)) were developed via co-rotating twin-screw extrusion and were subjected to uniaxial stretching. A systematic study was performed to investigate the effect of micro-CaCO3 content of the hybrid filler and subsequent uniaxial stretching at various draw ratios, R (4–5), on the mechanical, dielectric, electrical and piezoelectric properties of hybrid nanocomposites. For the as-extruded hybrid nanocomposites (without post-extrusion stretching), both dielectric properties and DC volume resistivity improved significantly, probably due to the enhanced charge trapping capability of Mt. in the presence of CaCO3 micro-filler. Similarly, hybrid nanocomposite containing 40 parts of CaCO3 and 3 parts (wt.) of Mt. presented the maximum piezoelectric coefficient, d33 of 7.4pC/N. For stretched nanocomposites, the volume resistivity and dielectric properties of hybrid nanocomposite containing 40 parts of CaCO3 and 3 parts of Mt. decreased gradually with R presumably due to its porous structure, as observed in SEM. However, stretched hybrid nanocomposites consistently exhibited enhanced piezoelectricity where the highest d33 value of 30.6pC/N at R of 5 was obtained, which is attributed to the almost 100% β phase content and dipolar orientation induced by stretching and subsequent poling.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.10.036
      Issue No: Vol. 152 (2017)
       
  • Characterizing drying-induced clayey soil desiccation cracking process
           using electrical resistivity method
    • Authors: Chao-Sheng Tang; De-Yin Wang; Cheng Zhu; Qi-You Zhou; Shi-Kang Xu; Bin Shi
      Pages: 101 - 112
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Chao-Sheng Tang, De-Yin Wang, Cheng Zhu, Qi-You Zhou, Shi-Kang Xu, Bin Shi
      Desiccation cracking process negatively impacts both mechanical and hydraulic properties of clayey soils. Traditional methods applied for the characterization of soil cracking behaviors are mainly based on visual inspections or destructive approaches. The electrical resistivity method provides a non-destructive, sensitive and continuous evaluation of the spatiotemporal variations of many soil physical properties. In this study, an integrated experimental setup is configured to simultaneously capture the evolution of temperature, relative humidity, water content, crack morphology, and apparent electrical resistivity in clay during continuous drying. Apparent electrical resistivity measurements at 1.0cm electrode spacing are carried out to detect the initiation, propagation and coalescence of desiccation cracks. Image processing quantitatively describes the geometrical characteristics of shrinkage surface crack patterns. Experimental results indicate the strong correlation between the measured apparent electrical resistivity and cracking behavior of soil. As water content decreases during drying, the apparent electrical resistivity of initially saturated clayey soil decreases first before the onset of desiccation cracking, and then transits into the increasing trend. The evolution of apparent electrical resistivity in clayey soil is dominated by two competing effects, with one originated from the volumetric shrinkage-induced closer packing of soil fabric and higher concentration of ions in pore fluids, and another from the evaporation-induced water loss associated with hydration film contraction and desiccation crack insulation. The electrical resistivity method is an effective technique to characterize the development of desiccation cracks, and particularly reliable to map their positions. This study is expected to improve the fundamental understanding of desiccation cracking mechanisms in soils and provide insights on soil characterizations for enhanced stability and performance of earthwork structures.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.001
      Issue No: Vol. 152 (2017)
       
  • Effect of nanoclay localization on the peel performance of PE based blend
           nanocomposite sealants
    • Authors: Raziyeh S. Mohammadi; Seyed H. Tabatabaei; Abdellah Ajji
      Pages: 113 - 123
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Raziyeh S. Mohammadi, Seyed H. Tabatabaei, Abdellah Ajji
      Polyethylene (PE) based clay polymer nanocomposites (CPN) are of great importance to generate peelable seals in packaging industry. This study shows the significant effect of organoclay (OC) localization in PE-based blend sealants on their peel properties, for the first time. Two different immiscible blends composed of PE/ethylene-methyl acrylate copolymer (EMA) and PE/ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA) were examined for their potential to generate peelable seals upon addition of organo-modified montmorillonite (OMt). WAXD results and TEM observations reveal that OC is localized at the interface of PE/EMA phases while it is localized within the dispersed EMA-GMA phase in the PE/EMA-GMA blend, which is in agreement with the thermodynamic predictions. The incorporation of 4 phr OC converts the lock seal behavior of the PE/EMA blend seal to a peelable behavior over a wide peelable heat seal temperature range (over 35°C). In contrast, the OC/PE/EMA-GMA nanocomposite sealant, in which OC is mostly located within the EMA-GMA phase, shows lock seal performance similar to the PE/EMA-GMA neat blend.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.002
      Issue No: Vol. 152 (2017)
       
  • Sintering of red ceramics from yellow Amazonian latosols incorporated with
           illitic and gibbsitic clay
    • Authors: Igor Alexandre Rocha Barreto; Marcondes Lima da Costa
      Pages: 124 - 130
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Igor Alexandre Rocha Barreto, Marcondes Lima da Costa
      Latosols are part of the soil group with the widest geographic distribution in Brazil. This soil type consists of a yellowish to reddish clayey material, and it has been widely studied for its applicability to agriculture in tropical zones. Because of the wide distribution and mineral composition of latosols, it is important to evaluate the technical feasibility of using these materials for the production of red ceramics. The raw materials were characterized using X-ray diffraction, thermogravimetric and differential thermal analysis, inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, scanning electron microscopy, and a laser particle analyzer. To determine the physical and mechanical properties, 20 different mixtures of samples were produced with the latosols of Rondon do Pará and Mosqueiro combined with 0, 20, 30, and 40% illitic or gibbsitic clays; each composition was calcined at 950 and 1100°C. The technological properties of the samples (linear shrinkage, water absorption, apparent porosity, apparent density, and flexural strength) were investigated. The Mosqueiro latosol consists of quartz and kaolinite with additional minerals of anatase and goethite, whereas the Rondon latosol contains kaolinite and quartz as the dominant minerals, as well as goethite, anatase, and gibbsite. Only the Mosqueiro latosol, without the addition of other materials, demonstrated technological aspects that were favorable for its use in the production of ceramic products. However, the addition of illitic and gibbsitic clays significantly improved the technological characteristics of the two latosols studied.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.003
      Issue No: Vol. 152 (2017)
       
  • Immobilization of Rhus vernicifera laccase on sepiolite; effect of
           chitosan and copper modification on laccase adsorption and activity
    • Authors: Yaniv Olshansky; Segula Masaphy; Robert A. Root; Giora Rytwo
      Pages: 143 - 147
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Yaniv Olshansky, Segula Masaphy, Robert A. Root, Giora Rytwo
      The enzyme laccase, a multi-copper oxidase found in many plants and fungi, can be used in water treatment processes for the removal of pollutants. Commercially available laccase, derived from Rhus vernicifera, was adsorbed on sepiolite, sepiolite modified with chitosan, sepiolite plus Cu(II), and sepiolite modified with both chitosan and Cu(II) to investigate enzymatic activity. Adsorption of laccase on unmodified sepiolite increased its activity by 250±40% compared to the non-adsorbed enzyme, whereas for sepiolite-Cu–chitosan and sepiolite–chitosan the activity was enhanced by up to 700% and 500%, respectively. The stronger enhancement for the Cu-containing adsorbent suggests that exchangeable Cu has an effect on the adsorbed laccase. Desorption of the adsorbed laccase was <10%, and the non-desorbed enzyme retained high activity, indicating robust adsorption. This study suggests that chitosan-sepiolite based composites might be used as efficient support for laccase scaffolding and immobilization, thus providing in an effective adsorbent surface for catalytic oxidation of organic pollutants sensitive to laccase activity.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.006
      Issue No: Vol. 152 (2017)
       
  • Photocatalytic decolorization of cationic and anionic dyes over ZnO
           nanoparticle immobilized on natural Tunisian clay
    • Authors: Haithem Bel Hadjltaief; Sameh Ben Ameur; Patrick Da Costa; Mourad Ben Zina; Maria Elena Galvez
      Pages: 148 - 157
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Haithem Bel Hadjltaief, Sameh Ben Ameur, Patrick Da Costa, Mourad Ben Zina, Maria Elena Galvez
      In the present work we describe a simple and low-cost method for the decolorization of textile dyeing and printing wastewaters, using ZnO as photocatalyst supported on natural Tunisian clay (ZnO/Clay). This composite ZnO/Clay material was synthesized through a sol–gel method. X-ray diffraction (XRD), Nitrogen Physisorption (BET), Infrared Spectroscopy (FTIR), Scanning Electronic Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HRTEM) linked with Energy Dispersive X-ray (EDX), were performed in order to explain the characteristics of the ZnO/Clay photocatalyst. The XRD patterns, pointing to the presence of ZnO of very small crystal sizes, i.e. highly dispersed on the clay surface. The photocatalytic activity of ZnO/Clay was assayed in the decolorization of a cationic dye (Malachite Green, MG) and anionic dyes (Red Congo, RC) in aqueous solution as models pollutants under UV irradiation. In addition, the effects of different parameters such as pH of the solution, catalyst dosage, concentration of the dyes, irradiation source, as well as the influence of the presence of inorganic ions were investigated. The ZnO/Clay photocatalyst exhibited high photocatalytic activity of MG and CR decolorization under simulated solar compared to UV irradiation. The recyclability of the ZnO/Clay photocatalyst was as well validated.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.008
      Issue No: Vol. 152 (2017)
       
  • Sodium montmorillonite/ureasil-poly(oxyethylene) nanocomposite as
           potential adsorbent of cationic dye
    • Authors: Yanisleidys Hernández Bermúdez; Laurianne Truffault; Sandra Helena Pulcinelli; Celso Valentim Santilli
      Pages: 158 - 165
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Yanisleidys Hernández Bermúdez, Laurianne Truffault, Sandra Helena Pulcinelli, Celso Valentim Santilli
      A sodium montmorillonite/ureasil-poly(oxyethylene) clay-polymer nanocomposite was prepared using the sol-gel reaction of a U-PEO hybrid precursor/clay mineral suspension, with the aim of developing a sorbent for the removal of cationic dyes from aqueous media. The structural characteristics of the nanocomposite were studied by FTIR, XRD, UV–Vis spectroscopy, and SAXS. The XRD results revealed intercalation of the U-PEO in the silicate interlayer spaces. FTIR spectra indicated the existence of strong interactions between methylene blue (MB) dye and the clay mineral silicate layers. Time-resolved SAXS measurements during MB adsorption showed a decrease of the montmorillonite (Mt) peak area and an increase of the half-height width of the peak, indicating that water uptake during dye adsorption caused a reduction of the Mt. crystallite size. UV–Vis adsorption experiments showed that the kinetics of MB adsorption followed a pseudo-first order process and that the steady state equilibrium adsorption capacity followed the Langmuir model. The results showed that the nanocomposite is potentially applicable as an adsorbent of dyes present in contaminated waters.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.009
      Issue No: Vol. 152 (2017)
       
  • Particle arrangements in clay slurries: The case against the honeycomb
           structure
    • Authors: Amer Deirieh; Irene Y. Chang; Michael L. Whittaker; Steven Weigand; Denis Keane; James Rix; John T. Germaine; Derk Joester; Peter B. Flemings
      Pages: 166 - 172
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Amer Deirieh, Irene Y. Chang, Michael L. Whittaker, Steven Weigand, Denis Keane, James Rix, John T. Germaine, Derk Joester, Peter B. Flemings
      The properties of clay slurries (porosity ~0.75) impact a wide range of materials such as commercial clay dispersions and sedimentary deposits. Their material behavior, and in particular the gelation of clay slurries, is thought to be governed by clay particle interactions. In the literature, such interactions are rarely directly probed, but rather inferred from structures observed by cryo-electron microscopy. For example, the honeycomb structure is a widely accepted textbook model that is used to rationalize the observed behavior of clay slurries. Using high-pressure freezing, cryo-electron microscopy, and cryo-synchrotron wide-angle X-ray scattering, this study shows that the honeycomb-structure is an artifact of sample preparation. When samples are high-pressure frozen, individual clay particles and aggregates of particles arrange in a random orientation rather than the closed-cell structure dominated by face-face and face-edge contacts observed in plunge frozen samples. These results substantially contribute to the understanding of the gelation mechanism and particle interactions in colloidal clay slurries, and provide valuable input parameters for meso-scale modeling efforts of clay dispersions and sedimentary deposits to upscale their mechanical properties to the macroscale.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.010
      Issue No: Vol. 152 (2017)
       
  • Removal of acid orange 7 by surfactant-modified iron nanoparticle
           supported on palygorskite: Reactivity and mechanism
    • Authors: Guixiang Quan; Lijuan Kong; Yeqing Lan; Jinlong Yan; Bin Gao
      Pages: 173 - 182
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Guixiang Quan, Lijuan Kong, Yeqing Lan, Jinlong Yan, Bin Gao
      To improve the hydrophobic property of iron nanoparticle (INP) coated on palygorskite (P), cationic surfactant cetyltrimethyl ammonium bromide (CTMAB) was used to modify its surface properties through ion exchange. The structure of the composited P-INP/CTMAB was characterized by various analytical methods. The results showed that the long chain of CTMAB was coated on the surface of P-INP without intercalation effect. The morphology of P-INP was thus not obviously changed after the modification, but the special specific surface area increased from 30.63m2 g−1 to 127.04m2 g−1. The decoloration and degradation efficiency of P-INP/CTMAB towards acid orange 7 (AO7) was examined under different pH value, temperature and dosage conditions. The results showed that the reaction was preferred to the acidic environment and its first-order reaction rate constant (k obs) linearly depended on the dosage. With suitable conditions, the removal rate of AO7 and total organic carbon (TOC) by P-INP/CTMAB reached about 98.4% and 59.21% after 2h, respectively. These values were both higher than that of the unmodified composition P-INP, suggesting the synergistic effects in surface adsorption and the following removal reaction. The degradation intermediate products were investigated using HPLC-MS, and the potential degradation pathway of AO7 by P-INP/CTMAB was determined.
      Graphical abstract image

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.011
      Issue No: Vol. 152 (2017)
       
  • Experimental study to examine the independent roles of lime and cement on
           the stabilization of a mountain soil: A comparative study
    • Authors: L.K. Sharma; N.N. Sirdesai; K.M. Sharma; T.N. Singh
      Pages: 183 - 195
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): L.K. Sharma, N.N. Sirdesai, K.M. Sharma, T.N. Singh
      The durability, efficiency and the integrity of structures built within or over mountain soils are mainly controlled by the geotechnical properties. It is therefore imperative to analyse these properties before the commencement of such projects, and upgrade them when and where required. The current study focusses on the addressing the problems associated with soil failure that occur during the construction and widening of roads and highways in the area of interest. The soil samples, which were collected from the study area, were stabilized using two types of readily-available additives, namely, lime and cement. The outcomes of the study indicate the dependence of the geotechnical and microstructural properties on the type of additive used. The comparative analysis suggests that the cement has a relatively higher influence on the mechanical behaviour of soil when compared to that of lime. Additionally, the compressive strength of the samples that had been cured for 28days increased nearly four to six times than that of the untreated specimen, thereby suggesting the influence of curing time on the strength parameters. The increase in compressive strength can be attributed to the chemical transformations that occur in the soil on the addition of additives. The cation exchange and pozzolanic reactions resulted in the formation of cementitious compounds within the soil matrix, which was observed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis. The present study suggests that satisfactory strength can be achieved with the addition of 5% additives to the soil mixture, which will save the cost of stabilization subsequently.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.012
      Issue No: Vol. 152 (2017)
       
  • A novel study on the influence of cork waste residue on metakaolin-zeolite
           based geopolymers
    • Authors: Alcina Sudagar; Slavka Andrejkovičová; Carla Patinha; Ana Velosa; Amy McAdam; Eduardo Ferreira da Silva; Fernando Rocha
      Pages: 196 - 210
      Abstract: Publication date: February 2018
      Source:Applied Clay Science, Volume 152
      Author(s): Alcina Sudagar, Slavka Andrejkovičová, Carla Patinha, Ana Velosa, Amy McAdam, Eduardo Ferreira da Silva, Fernando Rocha
      The effect of industrial waste from the cork industry on the strength and adsorption properties of zeolite-metakaolin based geopolymers has been studied. Cork residue 20% by weight was added to geopolymers that contained 0%, 25%, 50%, 75% replacement of metakaolin by zeolite in the structure. The SiO2/Al2O3 and Na2O/Al2O3 molar ratios were kept at 1 to reduce the environmental impact of sodium silicate and sodium hydroxide to the minimum. The compressive strength evolution after 1, 14 and 28days in water and the heavy metals (Cd2+, Cr3+, Cu2+, Pb2+, and Zn2+) adsorption of the geopolymers were determined. It was found that addition of zeolite and cork residue in minor amounts concurrently aided in increasing the compressive strength of geopolymers. The adsorption properties, however, were dominated by the presence of cork residue and metakaolin which resulted in increasing adsorption of all heavy metal cations with increasing metakaolin in the structure. The adsorption was well fitted by the Langmuir model with R2 >0.98 and the trend of adsorption was found to be Pb2+ >Cd2+ >Cu2+, Zn2+ >Cr3+. The significant improvement in compressive strength, as well as adsorption capacity observed with the addition of cork waste residue, connotes that it can be efficient as filler in geopolymers.

      PubDate: 2017-12-13T10:44:03Z
      DOI: 10.1016/j.clay.2017.11.013
      Issue No: Vol. 152 (2017)
       
 
 
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