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  Subjects -> EARTH SCIENCES (Total: 615 journals)
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EARTH SCIENCES (453 journals)                  1 2 3 4 5 | Last

Acta Geodaetica et Geophysica     Hybrid Journal   (Followers: 1)
Acta Geodaetica et Geophysica Hungarica     Full-text available via subscription   (Followers: 2)
Acta Geophysica     Hybrid Journal   (Followers: 7)
Acta Geotechnica     Hybrid Journal   (Followers: 8)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 2)
Advances in High Energy Physics     Open Access   (Followers: 12)
Advances In Physics     Hybrid Journal   (Followers: 9)
Aeolian Research     Hybrid Journal   (Followers: 2)
African Journal of Aquatic Science     Hybrid Journal   (Followers: 13)
Algological Studies     Full-text available via subscription   (Followers: 2)
Alpine Botany     Hybrid Journal   (Followers: 5)
AMBIO     Hybrid Journal   (Followers: 12)
Anales del Instituto de la Patagonia     Open Access   (Followers: 2)
Andean geology     Open Access   (Followers: 5)
Annales Henri Poincaré     Hybrid Journal   (Followers: 1)
Annales UMCS, Geographia, Geologia, Mineralogia et Petrographia     Open Access   (Followers: 1)
Annals of Geophysics     Full-text available via subscription   (Followers: 10)
Annals of GIS     Hybrid Journal   (Followers: 17)
Annals of Glaciology     Full-text available via subscription   (Followers: 1)
Annual Review of Marine Science     Full-text available via subscription   (Followers: 11)
Anthropocene Review     Hybrid Journal   (Followers: 2)
Applied Clay Science     Hybrid Journal   (Followers: 2)
Applied Geochemistry     Hybrid Journal   (Followers: 6)
Applied Geomatics     Hybrid Journal   (Followers: 7)
Applied Geophysics     Hybrid Journal   (Followers: 6)
Applied Ocean Research     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 3)
Applied Remote Sensing Journal     Open Access   (Followers: 9)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 21)
Arctic, Antarctic, and Alpine Research     Full-text available via subscription   (Followers: 8)
Artificial Satellites     Open Access   (Followers: 15)
Asia-Pacific Journal of Atmospheric Sciences     Hybrid Journal   (Followers: 2)
Asian Journal of Earth Sciences     Open Access   (Followers: 18)
Atlantic Geology : Journal of the Atlantic Geoscience Society / Atlantic Geology : revue de la Société Géoscientifique de l'Atlantique     Full-text available via subscription   (Followers: 3)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 6)
Atmospheric and Climate Sciences     Open Access   (Followers: 17)
Australian Journal of Earth Sciences: An International Geoscience Journal of the Geological Society of Australia     Hybrid Journal   (Followers: 11)
Boletim de Ciências Geodésicas     Open Access  
Boreas: An International Journal of Quaternary Research     Hybrid Journal   (Followers: 10)
Bragantia     Open Access   (Followers: 2)
Bulletin of Earthquake Engineering     Hybrid Journal   (Followers: 10)
Bulletin of Geosciences     Open Access   (Followers: 8)
Bulletin of the Lebedev Physics Institute     Hybrid Journal   (Followers: 1)
Bulletin of the Seismological Society of America     Full-text available via subscription   (Followers: 17)
Bulletin of Volcanology     Hybrid Journal   (Followers: 13)
Canadian Journal of Plant Science     Full-text available via subscription   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 1)
Canadian Water Resources Journal     Hybrid Journal   (Followers: 20)
Carbonates and Evaporites     Hybrid Journal   (Followers: 4)
CATENA     Hybrid Journal   (Followers: 3)
Central European Journal of Geosciences     Hybrid Journal   (Followers: 5)
Central European Journal of Physics     Hybrid Journal   (Followers: 1)
Chemical Geology     Hybrid Journal   (Followers: 10)
Chemie der Erde - Geochemistry     Hybrid Journal   (Followers: 3)
Chinese Geographical Science     Hybrid Journal   (Followers: 3)
Chinese Journal of Geochemistry     Hybrid Journal   (Followers: 2)
Chinese Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 3)
Ciencia del suelo     Open Access  
Climate and Development     Hybrid Journal   (Followers: 11)
Coastal Management     Hybrid Journal   (Followers: 18)
Comptes Rendus Geoscience     Full-text available via subscription   (Followers: 5)
Computational Geosciences     Hybrid Journal   (Followers: 11)
Computational Mathematics and Mathematical Physics     Hybrid Journal   (Followers: 1)
Computers and Geotechnics     Hybrid Journal   (Followers: 6)
Contemporary Trends in Geoscience     Open Access   (Followers: 1)
Continental Shelf Research     Hybrid Journal   (Followers: 8)
Contributions to Mineralogy and Petrology     Hybrid Journal   (Followers: 8)
Contributions to Plasma Physics     Hybrid Journal   (Followers: 2)
Coral Reefs     Hybrid Journal   (Followers: 18)
Cretaceous Research     Hybrid Journal   (Followers: 4)
Cybergeo : European Journal of Geography     Open Access   (Followers: 5)
Developments in Geotectonics     Full-text available via subscription   (Followers: 2)
Developments in Quaternary Science     Full-text available via subscription   (Followers: 3)
Développement durable et territoires     Open Access   (Followers: 2)
Diatom Research     Hybrid Journal  
Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
E3S Web of Conferences     Open Access  
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 216)
Earth and Space Science     Open Access  
Earth Interactions     Full-text available via subscription   (Followers: 9)
Earth Science Research     Open Access   (Followers: 7)
Earth Surface Dynamics (ESurf)     Open Access   (Followers: 1)
Earth Surface Processes and Landforms     Hybrid Journal   (Followers: 12)
Earth System Dynamics     Open Access   (Followers: 6)
Earth System Dynamics Discussions     Open Access   (Followers: 4)
Earth's Future     Open Access   (Followers: 1)
Earth, Planets and Space     Open Access   (Followers: 1)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7)
Earthquake Science     Hybrid Journal   (Followers: 8)
Earthquake Spectra     Full-text available via subscription   (Followers: 13)
Ecohydrology     Hybrid Journal   (Followers: 11)
Electromagnetics     Hybrid Journal   (Followers: 1)
Energy Efficiency     Hybrid Journal   (Followers: 11)
Energy Exploration & Exploitation     Full-text available via subscription   (Followers: 4)
Environmental Earth Sciences     Hybrid Journal   (Followers: 11)
Environmental Geology     Hybrid Journal   (Followers: 11)
Environmental Geosciences     Full-text available via subscription   (Followers: 4)
Environmental Geotechnics     Open Access  
Erwerbs-Obstbau     Hybrid Journal  

        1 2 3 4 5 | Last

Journal Cover   Applied Clay Science
  [SJR: 0.999]   [H-I: 63]   [4 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0169-1317
   Published by Elsevier Homepage  [2589 journals]
  • Effects of organobentonites on imidacloprid release from alginate-based
           formulation
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Li Jiang , Junyong Mo , Zhijie Kong , Yanping Qin , Lintao Dai , Yajing Wang , Lin Ma
      To provide effective delay in release, organobentonites with different loading levels of dodecyltrimethylammonium chloride (DTMA) and hexadecyltrimethylammonium chloride (HTMA) were used as modifying agents in the alginate-based controlled release formulation (CRF) containing imidacloprid. The structure of organobentonites was characterized by FTIR and XRD, and adsorption toward imidacloprid was investigated. The results were utilized to reveal the effects of organobentonites on the release of imidacloprid as well as its mechanism, and to evaluate the potential use of organobentonites to modulate the release of imidacloprid. The results showed that organobentonites could reduce the release of imidacloprid from alginate-based granules, different from the natural bentonite that accelerated the release of imidacloprid. The time taken for 50% of the active ingredient to be released, T 50, for CRF incorporating organobentonites with DTMA at loading level of 50, 75, 100 and 125% of the clay's cation exchange capacity was 2.12, 1.59, 1.55 and 1.38 times of the value for the formulation without modifying agent, respectively. The values for those incorporating organobentonites with HTMA at the same loading level were 2.61, 2.20, 1.89 and 1.88 times. It was suggested that imidacloprid released via an anomalous transport kinetics predominated by Fickian diffusion and was influenced by the addition of bentonite and organobentonites due to the change of matrix permeability and the interaction with organobentonites. The enhancement of matrix permeability and imidacloprid release resulting from the addition of natural bentonite might be attributed to the lamellar structure and swellability of bentonite in water. In contrast, the matrix permeability and imidacloprid release decreased when organobentonites were used as modifier agents, as a consequence of the hydrophobicity of organobentonite. The results also suggested the feasibility of regulating imidacloprid release via controlling the structure of the organobentonites. An increase in loading level of quaternary ammonium ions could result in an enhancement of the release, while the extension of the alkyl chain slowed down the release of imidacloprid.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Novel polyamidoamine dendrimer-functionalized palygorskite adsorbents with
           high adsorption capacity for Pb2+ and reactive dyes
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Shouyong Zhou , Ailian Xue , Yan Zhang , Meisheng Li , Kang Li , Yijiang Zhao , Weihong Xing
      Novel polyamidoamine (PAMAM) dendrimer-functionalized palygorskite (Pal) adsorbents, up to generation 4.0, with high adsorption capacity, were designed and efficiently synthesized by grafting PAMAM onto 3-aminopropyltriethoxysilane-modified palygorskite (NH2-Pal) surfaces. This was carried out using a divergent method including the Michael addition of methyl acrylate (MA) and amidation of the resultant ester moieties with ethylenediamine (EDA). The optimal conditions for Michael addition were achieved using 88.8mmol MA (relative to 4.0g NH2-Pal) at 323K for 24h. The optimal conditions for amidation of the resultant esters were achieved using 179.3mmol EDA (relative to 2.1g Pal-PAMAM G0.5) at 323K for 48h. All of the amino-terminated Pal-PAMAM G(n) (n =0, 1, 2, 3 and 4) adsorbents exhibited very high density amino-terminated groups and adsorption capacities for both Pb2+ and Reactive Red 3BS, which increased with increasing generation number. The maximum adsorption capacity for Pb2+ at 293K was 68.5±3.3, 151.1±5.7, 196.5±6.1, 389.1±9.6 and 694.4±12.9mg/g for Pal-PAMAM G(n) (n =0, 1, 2, 3 and 4), respectively. The maximum adsorption capacity for Reactive Red 3BS at 293K was 34.2±2.7, 69.9±4.3, 122.0±6.4, 242.7±7.1 and 322.6±6.9mg/g for Pal-PAMAM G(n) (n =0, 1, 2, 3 and 4), respectively.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • African terra sigillata from Henchir Es-Srira archaeological site, central
           Tunisia: Archaeological provenance and raw materials based on chemical
           analysis
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Siwar Baklouti , Lara Maritan , Néjia Laridhi Ouazaa , Claudio Mazzoli , Samia Larabi Kassaa , Jean-Louis Joron , Boutheina Fouzaï , Lluís Casas Duocastella , Moufida Labayed-Lahdari
      Terra sigillata from the Henchir Es-Srira archaeological site in central Tunisia was analysed by X-ray fluorescence (XRF), and chemical data were statistically treated by multivariate (principal component and cluster) analyses, which defined a geochemically homogeneous reference group. According to our results, potsherds from Henchir Es-Srira are compositionally compatible with the six reference samples from the same site already published in the literature, and form a single group. A larger reference group is now well established for this site. In addition, comparisons with previous data from other sites in both northern and central Tunisia show that terra sigillata from Henchir Es-Srira is chemically more similar to that of the northern sites than the central ones. Neutron activation analysis (NAA), an extremely valuable tool for provenance studies, was also performed on a set of selected potsherds from Henchir Es-Srira and clay materials collected nearby, with the aim of identifying the possible clayey raw materials used for this ceramic production. Comparisons of both bulk chemical composition and trace and rare earth element (REE) patterns show that most of the objects were locally produced from a Neogene base-clay, probably collected from the “Saouaf Formation”.


      PubDate: 2015-02-28T14:28:42Z
       
  • Characterization of urea-modified Palabora vermiculite
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Herminio F. Muiambo , Walter W. Focke , Maria Atanasova , Aida Benhamida
      Replacing the exchangeable interlayer ions in Palabora vermiculite with magnesium, aluminum or iron (III) ions does not affect the exfoliation onset temperature (456±11°C). However, co-intercalation of minor amounts of urea lowers the exfoliation onset temperature to 209±35°C. This significant decrease is attributed to the low thermal stability of urea which releases ammonia and water as blowing agents. Thermo-mechanical analysis indicates that the expanded vermiculite exhibits spring-like properties. Part of the original expansion is recovered when the applied force is removed. The observed hysteresis is attributed to the progressive flattening of warped/buckled sheets that make up the expanded worm-like structure. Provided the expanded flake has not been heated beyond 450°C, it can be reconstituted by applying a sufficiently high compressive force followed by equilibration with distilled water. Such flakes show the conventional exfoliation behavior when heated again.


      PubDate: 2015-02-28T14:28:42Z
       
  • Multi-step removal mechanism of pyrophosphate using CaFe-layered double
           hydroxide at high pH
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Jizhi Zhou , Xiaoman Li , Wentao Li , Feng Wei , Yongwen Su , Jia Zhang , Zhi Ping Xu , Guangren Qian
      Pyrophosphate (PP) is frequently used as a ligand in the electroplating process at high pH. This research investigated PP removal over Ca2Fe-layered double hydroxide (LDH) at pH12. The maximum amount of PP removal was up to 7.4mmol (as P) at the LDH dosage of 1.0g/L. As represented by the concentration of total phosphate ([TP]), the isotherm with increasing initial PP reveals that PP removal over LDH underwent multi-processes: (1) at initial [TP]<3.2mmol/L, PP removal was attributed to Ca2P2O7·2H2O formation while at initial [TP]=3.2–6.9mmol/L PP removal kept at 3.2mmol/g due to the competitive formation of CaP2O7 2− instead of Ca2P2O7·2H2O; (2) At [TP]=6.9–12.0mmol/L, formed CaP2O7 2− is incorporated into the LDH framework and reconstruct the layered structure to remove PP together with Ca2P2O7·2H2O precipitation; (3) At [TP]>12.0mmol/L, CaP2O7 2− incorporation becomes predominant in PP removal. Interestingly, in the structure of CaP2O7 2−-incorporated LDH, CaP2O7 2− is intercalated with Ca2+ being supposedly incorporated into the LDH hydroxide vacant site. Therefore, the result provides a possible way to remove a large PP amount using Ca2Fe-LDH at high pH.


      PubDate: 2015-02-28T14:28:42Z
       
  • Functional organo-Mt/copolymer nanoarchitectures. Microwave-assisted rapid
           synthesis and characterisation of
           ODA–Mt/poly[NIPAm-co-(MA-alt-2,3-2H-DHP)] nanocomposites
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Zakir M.O. Rzayev , Ayşe Uzgören-Baran , Ulviye Bunyatova
      In this work, novel octadecyl amine–montmorillonite (ODA–Mt) copolymer nanocomposites were synthesised by interlamellar microwave-assisted complex-radical copolymerisation. The microwave method is found to be a facile and highly effective means to clay polymer nanocomposites (CPNs) that provide a higher rate of interlamellar copolymerisation and conversion of micro- and nanoparticles. The chemical and physical structures, surface morphologies and thermal behaviours of the prepared CPN were investigated by FTIR and 1H (13C) NMR spectroscopy, XRD, SEM, TEM, thermal (DSC and TGA) and dynamic mechanical (DMA) analysis methods. That copolymerisation was accompanied by in situ complex formation (charge transfer complex and H-bonding similar with known copolymerisation without ODA–Mt) and the intercalative amidisation of anhydride units with the octadecyl amine groups of Mt was determined. These observed chemical and physical interfacial interactions as effective in situ processing play an important role in the formation of hybrid systems and micro- and nanocomposites with stimuli-responsive NIPAm polymer chains.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Editorial Board
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106




      PubDate: 2015-02-28T14:28:42Z
       
  • Effects of bentonite on different cell types: A brief review
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Janaína Nones , Humberto Gracher Riella , Andrea Gonçalves Trentin , Jader Nones
      Bentonites, clays considered to be good adsorbents, have numerous applications because of their structural characteristics, their abundance in nature, low cost and availability. Research suggests that bentonites may be excellent cell protectors and that they can reduce some of the side effects of drugs such as those used for cancer treatment. Once inside the human or animal body, bentonite particles are efficient at promoting growth (acting as adsorbents of toxins), improving health (reducing the harmful effects of drugs) and promoting well being (active principles in cosmetics and pharmaceuticals). The effects of bentonite vary depending on the type of cell they reach. For this reason, it is necessary to determine the adequate dosage and exposure time as well as evaluate their toxicity in vitro and in vivo. In certain concentrations bentonites may cause undesired effects, such as apoptotic cell death, oxidative stress and damage of the cell membrane. On the other hand, the same concentrations can also contribute to an increase in viability and the survival of other cell types. In this paper, the main chemical characteristics of bentonites are reviewed and some pharmacological applications are described. It was finally reviewed how bentonites interact with different types of cells and new perspectives are briefly discussed.


      PubDate: 2015-02-28T14:28:42Z
       
  • Effects of solvothermal process on the physicochemical and adsorption
           characteristics of palygorskite
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Zhifang Zhang , Wenbo Wang , Aiqin Wang
      Palygorskite (PAL) was treated with various organic solvents including methanol (MT), ethanol (ET), isopropanol (IPA), dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) via a facile solvothermal process. The effects of various solvents and reaction parameters on the microstructure, morphology and adsorption properties of PAL were intensively investigated. Fourier transformation infrared spectrometry (FTIR) and thermogravimetric (TG) analyses confirmed that some solvent molecules could be encapsulated in the tunnels of PAL and the polarity of solvent molecules plays an important role for their interaction with PAL. Field-emission scanning electron microscopy (FESEM) shows that the solvothermal treatment results in a better dispersion of PAL crystal bundles. The treated PAL by various solvents has relatively higher adsorption capacity (from 119mg/g to 154mg/g) and removal efficiency for methylene blue (MB) than the raw PAL, and the improved electrostatic and hydrogen-bonding interactions between MB and PAL are mainly responsible for the enhancement of adsorption properties. The adsorption properties of PAL for MB were greatly affected by the characters of solvents, and DMF-treated PAL gives the best adsorption and removal capabilities for MB.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Selective adsorption of CO2 on a regenerable amine-bentonite hybrid
           adsorbent
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Ali E.I. Elkhalifah , M. Azmi Bustam , A.M. Shariff , T. Murugesan
      The ability of magnesium form of bentonite modified by monoethanolammonium cations (MEA+-Mg-bentonite) to reversibly and selectively adsorb CO2 over other light gases, such as CH4 and N2 has gravimetrically been investigated using a Magnetic Suspension Balance (MSB) equipment. Before CO2 adsorption measurements, untreated bentonite and MEA+-Mg-bentonite were characterized by XRD, FTIR, TGA and BET techniques to establish their structural characteristics, thermal stability and specific surface area and porosity characteristics. The results showed that MEA+-Mg-bentonite adsorbed higher CO2 amount compared to untreated bentonite under similar conditions. The equilibrium isotherms for CO2 adsorption on untreated bentonite and MEA+-Mg-bentonite were measured at 25, 50 and 75°C and a pressure range of 01.0bar. It was found that MEA+-Mg-bentonite has static CO2 adsorption capacities of 0.79, 0.69 and 0.56mmol/g, compared to 0.45, 0.36 and 0.30mmol/g for untreated bentonite at temperatures of 25, 50 and 75°C and a pressure of 1bar, respectively. The calculated values of the thermodynamic parameters revealed that the process involving CO2 adsorption on MEA+-Mg-bentonite adsorbent was a physical, spontaneous and exothermic. Moreover, the results showed moderate and slightly high equilibrium selectivities for CO2 over CH4 on MEA+-Mg-bentonite with the values of 1.36, 4.85 and 3.43 at 25, 50 and 75°C, respectively. However, MEA+-Mg-bentonite showed equilibrium selectivity for CO2 over N2 as high as 13.79, 9.91 and 6.32 at 25, 50 and 75°C, respectively. Regenerative ability in short runs of isothermal CO2 adsorption–desorption cycles revealed that MEA+-Mg-bentonite adsorbent was able to undergo several CO2 adsorption–desorption cycles without noticeable decrease in its adsorption capacity. Clearly, amine-bentonite hybrid adsorbents are promising inexpensive materials for CO2 capture.


      PubDate: 2015-02-28T14:28:42Z
       
  • Experimental studies on the desorption of adsorbed sodium poly(acrylic
           acid) from crude kaolin particles
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Feridun Demir
      Background The controlled stability and fluidity of highly concentrated kaolin dispersion is a crucial problem when kaolin is used in industry due to the charge heterogeneity of its surface. To solve the common industrial problems of dispersions prepared at high solid loadings in terms of their rheological behavior, some organic and inorganic dispersing agents have to be added into the system to modify the particle surfaces. Objective Adsorption and desorption behaviors of sodium poly(acrylic acid) (NaPAA) on the surface of kaolin particles were investigated to elucidate the adsorption mechanism of the PAA–kaolin dispersion system within the scope of the rheology and the colloidal stability. We also investigated the structural changes in the kaolin particles due to the extraction of Si4+ and Al3+ ions when a dispersing agent was used. Method Kaolin dispersions were prepared using NaPAA, and investigated in terms of the adsorption and desorption behaviors, the rheological and the electrokinetic properties and the extracted Al3+ and Si4+ ions from the particles. Results As expected, PAA was strongly adsorbed on the positively charged alumina sites of the particles. According to the results obtained in the experiments of adsorption density, viscosity, ζ-potential and the dissolution of metal ion measurements for the adsorption/desorption, a strong and irreversible adsorption was observed between PAA and the surface of the kaolin surface, indicating the existence of unbreakable chemical bonds. This is due to the adsorption of negatively charged carboxylic acid groups (–COO−) from the PAA onto the positive alumina sites on the edges of the kaolin surface by electrostatic attraction. Due to the negative charge, no adsorption was observed on the silica surface of the particles within the working pH range of 5.3 to 8.4. Conclusion The adsorption mechanism of PAA–kaolin interaction is attributed to chemical adsorption with the formation of chemical bonds between the charged carboxylic acid groups (–COO−) of the polymer and the alumina sites on the edges of the kaolin.


      PubDate: 2015-02-28T14:28:42Z
       
  • Development of transition metal oxide–kaolin composite pigments for
           potential application in paint systems
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Swagata Roy , Subrata Kar , Biswajoy Bagchi , S. Das
      The present work deals with a simplified process for synthesizing metal oxides of Cu(II), Ni(II), Cr(III) and Fe(III) imbibed kaolin pigments and characterizing those samples using X-ray diffraction, Fourier transform infrared spectroscopy, FESEM and EDS in addition to the visual classification by color. Furthermore, PEG analysis and antimicrobial potency of these samples were investigated thoroughly which conferred positive impact depicting the fact that these metal oxides incorporated kaolin composites can serve as a good and promising ceramic pigment material in paint systems. Due to easy availability of kaolin and involvement of low temperature, the production cost of these synthesized pigments is highly reduced which can be an added advantage to the paint industry.


      PubDate: 2015-02-28T14:28:42Z
       
  • Organic modification of montmorillonite for application in plasticized PVC
           nanocomposites
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Henrik Petersen , Ignacy Jakubowicz , Jonas Enebro , Nazdaneh Yarahmadi
      A new type of organic compound for modifying clay minerals suitable for use in plasticized polyvinyl chloride was selected and studied. The theory of Hansen solubility parameters was used to predict the miscibility between potential organomodifiers and polyvinyl chloride. In a series of systematic experiments using four very different solvents (i.e., water, ethanol, tetrahydrofuran and chloroform) and three different types of Mt (i.e., Mt-Na+, Mt-PGV and Mt-Ca++), the importance of various parameters to the process of clay mineral intercalation was investigated. The effects of each combination were evaluated employing wide-angle X-ray diffraction and thermogravimetry. The results of swelling experiments on clay mineral in various solvents correlated well with the results of a theoretical preliminary study using Hansen solubility parameters. The extent of swelling followed the order H2O>EtOH>THF>chloroform. The d-spacing seemed to be little affected by the type of solvent used in the modification, while the type of Mt used was important to the intercalation results. Organomodification of Mt-Na+ increased the d-spacing by nearly 0.7nm when tributyl citrate was used as a chelating agent. Similar modification of Mt-Ca++ showed an increase of 0.3nm only. Furthermore, thermogravimetry and DTG curves showed significant structural differences between Mt-Na+ and Mt-Ca++.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Removal of basic dyes from aqueous solution by adsorption onto binary
           iron-manganese oxide coated kaolinite: Non-linear isotherm and kinetics
           modeling
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Tabrez A. Khan , Equbal A. Khan , Shahjahan
      Adsorption of basic fuchsin (BF) and crystal violet (CV) dyes onto iron-manganese oxide coated kaolinite (IMK) was investigated. The adsorbent was characterized using FT-IR, XRD spectra, EDX and SEM images. The effect of various parameters such as initial dye concentration, contact time, adsorbent dose and initial solution pH was examined. The data were fitted into non-linear two-parameter Langmuir, Freundlich, Dubinin–Radushkevich (D–R) and three-parameter Toth isotherm models. The data best fitted the Langmuir and Toth models. Langmuir saturation adsorption capacity (Qo ) at 308K for BF and CV was found to be 10.36mg/g and 20.64mg/g, respectively. The value of apparent energy of adsorption obtained from non-linear D–R model (1.10–2.38kJ/mol) suggested physical adsorption of the dyes. The adsorption process followed pseudo-second order kinetics. The negative value of free energy change (2.27–6.125kJ/mol) and positive value of enthalpy change (6.70–6.68kJ/mol) indicated the feasibility, spontaneity and endothermic nature of the adsorption process. The positive value of entropy change (0.028kJ/molK) revealed increased randomness at the adsorbent–adsorbate interface. The results showed that iron-manganese oxide coated kaolinite is a promising low cost adsorbent for the removal of BF and CV dyes from wastewater.


      PubDate: 2015-02-28T14:28:42Z
       
  • Effect of the montmorillonite intercalant and anhydride maleic grafting on
           polylactic acid structure and properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Kahina Issaadi , Abderrahmane Habi , Yves Grohens , Isabelle Pillin
      The goal of this work is to prepare maleic anhydride grafted poly(lactic acid) (PLAgMA) according to a method described by Hwang et al. in order to investigate its effect as matrix and as compatibilizer on the dispersion of two organic nanofillers into PLA matrix, as well as its effect as compatibilizer on rheological and barrier properties of clay mineral–PLA nanocomposites. Two different montmorillonites, Cloisite® 20A and Cloisite® 30B, are used in this study. The latter is classically used in pristine PLA nanocomposites. The clay mineral polymer nanocomposites are prepared by the incorporation of 3 mass % of each layered silicate into PLA, PLAgMA and PLA/PLAgMA via melt blending. Transmission electron microscopy micrographs of the PLAgMA/Cloisite® blends showed the presence of intercalated and partially exfoliated areas with Cloisite® 20A and re-aggregation of the layered silicates with Cloisite® 30B. These results are confirmed by rheological behaviors, which showed their dependence on the content of maleic anhydride and nature of montmorillonite. Water vapor permeations (WVP) were strongly reduced by the incorporation of Cloisite®, and the better results are obtained with C20A/PLA containing 5 mass % of PLAgMA.


      PubDate: 2015-02-28T14:28:42Z
       
  • About differences of swelling pressure — dry density relations of
           compacted bentonites
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): S. Kaufhold , W. Baille , T. Schanz , R. Dohrmann
      The swelling capacity is one of the most characteristic properties of bentonites. This property, along with others, made bentonite a candidate material for the safe disposal of high-level radioactive waste (HLRW). For HLRW-barrier systems the swelling pressure is of particular interest because it basically controls sealing properties (a large swelling pressure generally results in low permeability). Commonly, the swelling pressure is investigated as a function of compaction and hence plotted against the density, usually the dry density. Different dry density/swelling pressure relations of bentonites were published. Therefore, the aim of the present study was to identify reasons for these differences. To be able to compare a significant set of different bentonites, a small scale swelling pressure device was developed which is based on measuring a swelling pressure related value of 500mg bentonite powder. This device allowed recording about 200 single values (in duplicate) and hence dry density/swelling pressure relations of thirty six different bentonites. The differences of the dry density/swelling pressure plots of different bentonites could be explained by i) different ways to obtain a range of dry densities (either constant load or constant water content), ii) different portions of uncompactable porosity of the different bentonites, and iii) different smectite contents.


      PubDate: 2015-02-28T14:28:42Z
       
  • Surface chemistry and rheology of Laponite dispersions — Zeta
           potential, yield stress, ageing, fractal dimension and pyrophosphate
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Au Pek-Ing , Leong Yee-Kwong
      The ageing behaviour of Laponite gels at the phase boundary of attractive gel and flocculated state (ionic strength~0.01M 1:1 electrolyte) was investigated due to a lack of study in this region. Zeta potential and yield stress measurement revealed that freshly prepared Laponite dispersion took time to reach the surface chemical equilibrium (SCE) state. The higher the ionic strength, the shorter was the time needed. This well-defined structural state was employed at the commencement of ageing study. The ageing behaviour was characterised by a rapidly increasing yield stress region followed by a gradually increasing region and then by a plateau region. Both the initial and fully aged yield stress of Laponite gels increased with ionic strength and solid loading. Both the Leong and the two-parameter logarithmic time models described the ageing behaviour quite well. The relationship between the yield stress at the SCE state and at the fully recovered or rejuvenated state, and volume fraction obeyed a power law model. The fractal dimension of the two states was the same 2.0. This study also investigated the yield stress-pH behaviour of Laponite gel with and without pyrophosphate additive. Pure Laponite dispersion displayed a maximum yield stress at high pH. A drop in yield stress occurred at low pH region and eventually approaching zero yield stress. A totally opposite trend was observed with pyrophosphate additive. No yield stress was detected at high pH region and a maximum yield stress was located at pH5 followed by a drop in yield stress until pH2. This drop in the yield stress regardless of the presence of pyrophosphate, was due to the particle agglomeration promoted by low pH.


      PubDate: 2015-02-28T14:28:42Z
       
  • Removal characteristics of ammonium nitrogen from wastewater by modified
           Ca-bentonites
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Zhiming Sun , Xiaosuo Qu , Gaofeng Wang , Shuilin Zheng , Ray L. Frost
      A modified inorganic bentonite (Na/Al) based on purified Ca-bentonite was prepared through exchanging Al and Na ions in the interlayer space of Ca-bentonite. The structural properties of purified and modified bentonites were characterized by XRD and SEM analysis. Batch experiments were performed for the adsorption of ammonium nitrogen and different experimental conditions were studied in order to investigate the optimum adsorption conditions. Comparative experiments were also carried out for natural Ca-bentonite (RB), unmodified purified bentonite (PB) and modified purified bentonite (MB). Through the thermodynamic analysis, the ammonium nitrogen adsorption process can be spontaneous, the standard heat was −41.46kJmol−1, and the adsorption process based on ion exchange adsorption. The ammonium nitrogen adsorption capacity of MB (46.904mg/g) was improved compared to raw bentonite (RB) (26.631mg/g), which was among the highest values of ammonium nitrogen adsorption compared with other adsorbents according to the literatures. The described process provides a potential pathway for the removal of ammonium nitrogen at low concentrations encountered in most natural waters.


      PubDate: 2015-02-28T14:28:42Z
       
  • Red clay application in the utilization of paper production sludge and
           scrap glass to fabricate ceramic materials
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Vsévolod Mymrin , Walderson Klitzke , Kirill Alekseev , Rodrigo Eduardo Catai , André Nagalli , Ronaldo Luis dos Santos Izzo , Cezar Augusto Romano
      The article describes the compositions with red clay, as principal component, for utilization of paper production sludge and scrap glass to fabricate red ceramics at sintering temperatures of 700°, 800°, 850°, 900°, 1000°, 1050° and 1100°C. The raw and final materials were analyzed by XRF, XRD, SEM, EDS and LAMMA methods. The flexural strength tests of obtained ceramics reached till 11.7MPa, water absorption till 12.6%, bulk densities varied from 1.79 to 1.86g/cm3, and shrinkage till 1.4%. These properties can be attributed to the sintering at 700° and 1100°C of ceramics with glassy structures and small inclusions of new crystalline minerals, such as mullite, albite, orthoclase and nepheline.


      PubDate: 2015-02-28T14:28:42Z
       
  • Thermally treated clay sediments as geopolymer source material
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): C. Ferone , B. Liguori , I. Capasso , F. Colangelo , R. Cioffi , E. Cappelletto , R. Di Maggio
      The management of reservoirs for water supply is a great environmental problem, since regular de-silting operations produce huge quantities of sediments. Among the recycling possibilities, the use of clay sediments for the manufacture of geopolymer-based materials seems to be an interesting alternative to disposal, due to their low cost and easy availability. In particular, two sediments, coming from reservoirs located in Southern Italy, were firstly characterized by X-ray diffraction, differential thermogravimetry, Fourier transformed infrared (FTIR) spectroscopy and 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy. The reactivity of raw and thermally treated clay sediments in alkaline media was also investigated. Finally, geopolymeric samples were produced and chemically, physically and mechanically characterized. The results showed that the calcined clay sediments can be suitable source materials in polycondensation reactions and that the increase of the calcination temperature from 400 to 750°C resulted in an increased reactivity. Moreover, good mechanical properties were obtained by all the geopolymers prepared with heat-treated sediments.


      PubDate: 2015-02-28T14:28:42Z
       
  • Influence of gibbsite and quartz in kaolin on the properties of
           metakaolin-based geopolymer cements
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): H.K. Tchakoute , C.H. Rüscher , J.N.Y. Djobo , B.B.D. Kenne , D. Njopwouo
      Three different kaolins (K1, K2, K3) from sources in Cameroon were applied for producing geopolymer cements. The kaolins differ significantly in their gibbsite and quartz contents. Thermal transformation (700°C, 4h) into their metakaolins MK1, MK2, MK3 shows the total loss of crystalline kaolinite and reveal the typically rather broad bump in the X-ray pattern. Gibbsite becomes dehydrated into γ and χ-Al2O3. Geopolymer cements (GP1, GP2, GP3) were obtained using freshly prepared sodium silicate solutions (NWG) with a ratio NWG/MK=0.87. It could be observed that the initial (60/80/90min) and final (90/140/160min) setting time increases and their 28day compressive strength (49/39/30MPa) decreases in the course GP1/GP2/GP3. It is discussed that the higher content of quartz in K1 (up to 22wt.%), compared to K2 (10wt.%) and K3 (8wt.%) promotes higher strength values and decreased setting times. Gibbsite was not present in K1, but up to 11wt.% in K2 and 28 wt.% in K3, transformed in its dehydrated forms remains unreacted during geopolymerization. Therefore, the higher content of gibbsite in the kaolinite could be related to a lower strength. The reacted volumes and compositions of the geopolymer become almost the same in all three cases. A content of 30–50% of unreacted metakaolin was proved in all cases.


      PubDate: 2015-02-28T14:28:42Z
       
  • Template-free synthesis of kaolin-based mesoporous silica with improved
           specific surface area by a novel approach
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Tiantian Li , Zhu Shu , Jun Zhou , Yun Chen , Dongxue Yu , Ximing Yuan , Yanxin Wang
      A novel template-free method is proposed and demonstrated to develop the facile top-down strategy of preparing mesoporous materials from natural minerals. In the process, kaolin was pre-calcined, alkali-activated and finally acid-etched into mesoporous silica (MS) of improved specific surface area (604m2/g) and large pore size (4.41nm) at the maximum probability. The characterizations of XRF, XRD, TG, FT-IR, SEM, TEM and N2 adsorption/desorption were carried out and the material evolution mechanism was clarified. The as-resulted MS showed favorable adsorption ability toward methylene blue with the monolayer adsorption capacity up to 652.9mg/g, indicating its promising potential in adsorption application. The template-free method proposed may benefit not only the clay products but also the wide application of mesoporous materials cost-effectively.


      PubDate: 2015-02-28T14:28:42Z
       
  • Exfoliation and intercalation of montmorillonite by small peptides
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Karin A. Block , Adrianna Trusiak , Al Katz , Alexandra Alimova , Hui Wei , Paul Gottlieb , Jeffrey C. Steiner
      Understanding structural changes in clay minerals induced by complexation with organic matter is relevant to soil science and agricultural applications. In this study, the effect of peptide storage in montmorillonite and the thermal stability of peptide–clay complexes were examined through characterization by X-ray diffraction (XRD), electron microscopy, UV absorption, and thermogravimetric analysis (TGA). XRD analysis of small peptide–montmorillonite clay complexes produced profiles consisting of reflections associated with the smectite 001 reflection and related peaks similar to that produced by a mixed layer clay mineral structure. Shifts in higher order diffraction maxima were attributed to disorder caused by the intercalation with the peptides. Increasing peptide concentrations resulted in greater shifts toward smaller 2θ from 6.37° (1.39nm) to 5.45° (1.62nm) as the interlayer space expanded. The expansion was accompanied by broadening of the 001 reflection (FWHM increases from 0.51 to 1.22° 2θ). The XRD line broadening was interpreted as caused by poorer crystallinity resulting from intercalation and tactoid exfoliation. SEM images revealed montmorillonite platelets with upwardly rolled edges that tend toward cylindrical structures with the production of tubules. High-resolution TEM images revealed bending of montmorillonite platelets, confirming exfoliation. The distribution of basal spacings in the micrographs was determined from the spatial frequencies obtained by Fourier analysis of density profiles. The distribution indicated the presence of discrete coherent crystallite domains. XRD and TGA results indicated that higher peptide concentrations resulted in a greater fraction of intercalated peptides and that surface adsorption of peptides mediated intercalation. Therefore, higher peptide concentration led to more stable organoclay complexes. However, UV absorption and TGA found that peptide adsorption onto montmorillonite had a finite limit at approximately 16% by weight.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Synthesized palygorskite/polyaniline nanocomposite particles by oxidative
           polymerization and their electrorheology
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Hyun Sik Chae , Wen Ling Zhang , Shang Hao Piao , Hyoung Jin Choi
      Palygorskite (Pal) clay coated with semiconducting polyaniline (PANI) nanocomposite particles was prepared by oxidative polymerization using aniline monomer in the presence of Pal. The morphological characteristics of the synthesized Pal/PANI composite particles were examined by both field emission scanning electron microscopy and transmission electron microscopy. A rotational rheometer was also used to examine the rheological behavior of the Pal/PANI composite-based electrorheological (ER) fluid when the nanocomposite particles were dispersed in silicone oil. From its flow curve of shear stress vs. shear rate investigated under an applied electric field, the typical ER behavior of the Pal/PANI-based ER fluid was observed. In addition, polarizability and relaxation time of the ER system obtained from the dielectric spectra were well correlated with its ER performance.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Development of sustainable fired clay bricks by adding kindling from vine
           shoot: Study of thermal and mechanical properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Pedro M. Velasco , María Pilar M. Ortiz , Manuel Antonio M. Giró , Daniel M. Melia , Jorge H. Rehbein
      This paper studies the addition of kindling from vine shoots in the production of fired clay bricks in order to achieve a better insulation of the buildings enclosure and a new way for recycling vine shoots, a waste which is widely produced in vineyards. Therefore, the influence of kindling addition on the thermal and mechanical properties of the fired clay bricks has been investigated in partnership with a local brick factory. As result, it could be concluded that the amount of kindling that can be added is around 11%, whereby the brick's mechanical and physical properties abide by settled regulations for structural clay bricks, in accordance with current regulations. The added waste has improved bricks conductivity properties by reducing it up to 62% compared to the brick made without any waste. This means an improvement up to 34% for the equivalent thermal transmittance of a typical single-leaf wall assembly.


      PubDate: 2015-02-28T14:28:42Z
       
  • Pre-historic production of ceramics in the Amazon: Provenience, raw
           materials, and firing temperatures
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Suyanne Flavia Santos Rodrigues , Marcondes Lima da Costa , Herbert Pöllmann , Dirse Clara Kern , Maura Imazio da Silveira , Renato Kipnis
      The chemical–mineralogical properties of prehistoric ceramics found in the Amazon were investigated with the aim of elucidating the production technology, the raw materials used, and the origin of these materials. For this, sherds were obtained from three archeological sites located in distinct regions of the basin. The mineralogical composition of the samples was determined by X-ray diffraction, optical microscopy, thermal analyses, FT-IR, and SEM-EDS, while the chemical composition was measured using ICP-OES and ICP-MS. The manufacturing process consisted of the coiling technique with the smoothing of surfaces, and the addition of organic and mineral non-plastic materials. The pots were fired at ±600°C, leading to the formation of an amorphous metakaolinite matrix in which a number of different types of non-plastic materials can be found. These non-plastic materials, together with the phosphates found in the samples, represent the principal differences in the chemical and mineralogical composition of the sherds from different sites. The raw material (clay) used for the production of the ceramic sherds from the Da Mata and Jabuti sites had the same geological origin, and were distinct from those of Monte Dourado 1 in relation to the intensive use of crushed rock. Cariapé was found throughout the region, and the shells reflect the proximity of the Jabuti site to the ocean. The phosphates found in the matrix probably formed during the use of the pots to prepare food, and could not have been part of the raw material, given that they would not have resisted the firing temperature. The evidence indicates that the potters used the materials available locally for the production of ceramics. The use of cariapé at all the sites confirmed that this practice was widespread in the region, representing an important cultural trait of the production of ceramics in the prehistoric Amazon.


      PubDate: 2015-02-28T14:28:42Z
       
  • Photoelectrochemical properties of dye-dispersing allophane–titania
           composite electrodes
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Hiromasa Nishikiori , Naohiro Kanada , Rudi Agus Setiawan , Koji Morita , Katsuya Teshima , Tsuneo Fujii
      Dye-dispersing allophane–titania composite electrodes were prepared from titanium alkoxide sols containing dye and allophane. The photoelectric conversion properties of the electrodes were investigated by photoelectrochemical measurements. The photocurrent values in the UV range decreased with an increase in the allophane content, whereas those in the visible range were increased by adding 1.0% (Al/Ti ratio) allophane. As a small amount of allophane nanoparticles were highly dispersed in the titania electrodes, the dye molecules were dispersed in the electrodes without decreasing the efficiency of the electron injection from the dye to the titania conduction band. The dye molecules dispersed on the titania nanoparticle surface were capped with allophane nanoparticles which prevented desorption. The dye molecules strongly interacted with the titania nanoparticle surface and efficiently injected the excited electrons into the titania conduction band.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Novel vanadium-chromium-bentonite green catalysts for cyclohexene
           epoxidation
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Noureddine Belaidi , Sumeya Bedrane , Abderrahim Choukchou-Braham , Redouane Bachir
      The aim of this work is the valorization of bentonite-type clay from Maghnia (Algeria) as green catalyst for the production of added value fine chemicals. The modification of the clay structure by acid activation and impregnation of transition metals, such as chromium and vanadium, enhanced redox properties and increased Lewis and Brønsted acidity. Various samples of vanadia supported on chromium-containing acid-activated bentonite, were prepared and characterized by diffuse-reflectance UV–vis spectroscopy, surface acidity followed by FT-IR, X-ray diffraction, nitrogen adsorption–desorption isotherms and scanning electron microscopy (SEM) coupled with EDX. The catalysts prepared were studied in the cyclohexene epoxidation, using tert-butyl hydroperoxide as oxidant. The influences of vanadium content, catalyst weight, reaction temperature and oxidant amount on the evolution of the epoxidation reaction were checked. The experimental results showed an interesting catalytic activity of 43% and a selectivity towards epoxide of about 71%, when TBHP was used as oxidant and heptane as solvent.


      PubDate: 2015-02-28T14:28:42Z
       
  • Porous 3D network rectorite/chitosan gels: Preparation and adsorption
           properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Yajing Lu , Peter R. Chang , Pengwu Zheng , Xiaofei Ma
      Ultra-light porous 3D network rectorite (Rec) gels were prepared by crosslinking chitosan with glutaraldehyde in a simple process of aqueous gel precursor freezing, solvent exchange, and ethanol drying instead of expensive supercritical drying technology. The porous structures of Rec gels were composed of randomly oriented Rec layers. Rec gels with densities of 28.8 to 79.6mg/cm3 withheld liquids such as water up to 13–26 times, DMSO 12–35 times, and soybean oil 9–20 times the weight of the gel. However, the crosslinked chitosan components, which were used to consolidate the porous 3D network, delayed methylene blue (MB) adsorption of Rec gels. After calcination at 500°C most of the polymer was burnt away from gels, though the porous structure was maintained and could still contain liquid. The process for MB dye adsorption by the obtained gel was studied. The kinetic adsorption fit the pseudo second-order well, and the isotherm data followed the Langmuir models. The maximum adsorption capacity reached 162.6mg/g. The calcined REC gels could effectively remove the cationic dye from aqueous solutions.


      PubDate: 2015-02-28T14:28:42Z
       
  • Influence of hydrated lime on the surface properties and interaction of
           kaolinite particles
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Yadeta C. Chemeda , Dimitri Deneele , George E. Christidis , Guy Ouvrard
      Lime is a widely used chemical additive in the stabilization of problematic soils. However, the physico-chemical mechanism involved, particularly in the short-term, is still not fully understood. In the present work, the influence of hydrated lime (Ca(OH)2) on the rheological properties of kaolinite dispersion has been investigated. The influence of the type of cation and pH on the interfacial chemistry and particle interaction were also examined. The result showed that kaolinite predominantly adsorbs Ca2+ and CaOH+ at pH=7 and pH=12.6 respectively. With increasing concentration of Ca(OH)2, the value of storage modulus (G′), Bingham yield stress (τB) and cohesive energy density (Ec) initially decreased at lower concentration (≤5.5mmol/l) followed by increase at higher concentration (≥11mmol/l); in contrast these parameters decreased monotonously with increasing the concentration of NaOH. The strain hardening characteristic of loss modulus (G″) curve was found to be very sensitive to change in surface chemistry and the associated particle organization. The modification in the mechanical properties of the kaolinite with varying amount of Ca(OH)2 was attributed to the aggregation microstructure of kaolinite particles. The Ca-ion at higher pH promotes linkage between particles and provides the most efficient way to form dense, tightly packed flocs, which behave as individual coarse grained materials (silt or sand).
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Theoretical studies of the interaction of terephthalate anion in
           MgAl-layered double hydroxides
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Inna M. Nangoi , Viviane S. Vaiss , Wladmir F. Souza , Sandra S.X. Chiaro , Alexandre A. Leitão
      We used first principles calculations based on Density-Functional Theory to investigate the structural and electronic properties of Mg–Al-TA (TA=terephthalate anion) layered double hydroxides for the relations x = N Al/(N Al + N Mg) equal to 1/4, 1/3 and 1/2. Value of x =1/2 is unusual in the literature due to the so-called cation avoidance rule; notwithstanding, some experimental results have demonstrated that it is possible to be obtained using TA as counterion. The calculated geometric parameters are in good agreement with available experimental data. The gauge-including projector augmented wave method was applied to compute solid state nuclear magnetic resonance chemical shifts of terephthalate's carbons for structure with x =1/3. A good correlation between the minimum energy for TA rotating angle and the chemical shifts was obtained. The interlayer interactions were discussed on the basis of electronic density differences and Bader charge analysis. Our calculations show that the electron density in the interlayer region does not change significantly while the molar ratio x increases. This result is in line with the Bader analysis. The calculations show that there is a major change in the difference of charge density between water molecules and layer than anion and layer when the molar ratio x increases. This result demonstrates the importance of water molecules in the stabilization of LDHs with higher layer charge. Also, a geometric factor helps in the formation of structures with x =1/2. That is, the area occupied by each positive charge in the layers needs to be large enough to have the TA anions in the interlayer space along the c structural vector.


      PubDate: 2015-02-28T14:28:42Z
       
  • Editorial Board
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107




      PubDate: 2015-02-28T14:28:42Z
       
  • Biological beneficiation of kaolin: A review on iron removal
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Mohammad Raouf Hosseini , Ali Ahmadi
      Application of mineral bio-beneficiation to remove iron oxyhydroxides from kaolinite clays has been the center of interest in recent decades, and many research works over the world have been dedicated to study the potential of this approach for upgrading the clay whiteness and refractoriness while preserving the inherent specifications and therefore improving the commercial value of kaolin. Microbial purification methods are preferred since they are environmentally benign (neither use nor release hazardous chemicals), not energy intensive, low in initial and operational costs, and they preserve the crystal structure of the clay. The present review offers the general concepts and fundamentals of the process along with an outline and critical assessment of the latest studies carried out on the biological dissolution of iron from kaolinite clays.


      PubDate: 2015-02-28T14:28:42Z
       
  • X-ray absorption spectroscopy study of Cu(II) coordination in the
           interlayer of montmorillonite
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Sung Pil Hyun , Kim F. Hayes
      Cu(II) coordination in the interlayer of an expandable clay mineral montmorillonite is studied using X-ray absorption spectroscopy (XAS) along with electron paramagnetic resonance (EPR) and X-ray diffraction (XRD). Ab initio calculations are performed using FEFF code to reproduce the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) portion of the experimentally measured XAS spectra. Cu(II) coordination changes depending on the Cu(II) loading and hydration state of the interlayer. XRD shows that the Cu-saturated montmorillonite has d 001-spacing values corresponding to the interlayer thickness of four and one water layer(s) for the hydrated and dehydrated interlayers, respectively. EPR shows that Cu(II) in the fully hydrated, unsaturated interlayer behaves similarly to free Cu(II) ion in a bulk aqueous solution, while Cu(II) forms a square planar complex in the dehydrated interlayer. Cu(II) in the fully hydrated, Cu-saturated montmorillonite has a characteristic singlet 1st derivative XANES spectrum. FEFF calculations show that this singlet feature originates from a quasi-regular octahedral coordination of water molecules around the interlayer Cu(II) atom. All other samples and model compounds including the dry Cu-saturated montmorillonite, wet and dry unsaturated montmorillonite, aqueous Cu(II), cupric nitrate salt (Cu(NO3)2·4.5H2O), and Cu(II) hydroxide precipitates have doublet 1st derivative XANES spectra. FEFF calculations suggest that the doublet features arise from an axially elongated octahedral coordination under the Jahn–Teller effect or square planar coordination. FEFF calculations of the EXAFS spectra as a function of the axial oxygen bond length demonstrate that a destructive interference between backscattering from equatorial oxygen (Oeq) and that from axial oxygen (Oax) atoms leads to an apparent coordination number (CN) less than six expected for the tetragonal coordination, with the farther, loosely bound axial oxygen atoms making a minor, yet negative contribution to the CN determined by the EXAFS analysis. This study shows that Cu(II) has interchangeable octahedral, tetragonal, and square planar coordinations in the interlayer of montmorillonite, depending on Cu(II) loading and degree of hydration. The quasi-regular octahedral coordination of the interlayer Cu(II) in montmorillonite is a new finding of this study.


      PubDate: 2015-02-28T14:28:42Z
       
  • Boron isotopic fractionation in aqueous boric acid solutions over
           synthetic minerals: Effect of layer and surface charge on fractionation
           factor
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Gökhan Elmaci , Okan Icten , Ahmet Nedim Ay , Birgül Zümreoglu-Karan
      Boron isotopic fractionation in boric acid solutions during adsorption on synthetic manganese oxides (birnessite “B” and cryptomelane “C”) and Mg–Al-layered double hydroxide “LDH” was investigated. The materials were characterized by elemental analyses, powder X-ray diffraction, FTIR spectra, BET surface area and zeta potential measurements. Batch experiments were conducted without changing the solution pH to correlate the boron sorption properties of the adsorbents with isotopic fractionation in the associated boric acid solutions. The results showed that boron isotopic composition of the contact solution is heavily dependent on the selective adsorption of B(OH)3 or B(OH)4 − species due to the charge properties of the minerals. With B and C, possessing negatively charged surfaces, 10B(OH)4 − was preferentially fractionated in the solution due to the transfer of the Lewis acidic 11B(OH)3 species while with LDH selective adsoption of 10B(OH)4 − by positive layers was favorable resulting in the enrichment of the heavier isotope in the solution.


      PubDate: 2015-02-28T14:28:42Z
       
  • Synthesis of Cu–Al layered double hydroxide nanofluid and
           characterization of its thermal properties
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Samarshi Chakraborty , Ishita Sarkar , Krishnayan Haldar , Surjya Kanta Pal , Sudipto Chakraborty
      Synthesis of pristine Cu–Al layered double hydroxide (LDH) nanofluid via one step method and study of its thermal properties are the core essence of the current work. Nitrate salts of Cu, Al and Na were mixed in a particular molar ratio at constant pH to produce desired Cu–Al LDH. Different dispersion techniques were utilized to uniformly disperse Cu-Al LDH in water to obtain Cu–Al LDH nanofluids. Broadly used characterization techniques were implemented to identify and characterize pristine Cu–Al LDH nanoparticle. These techniques were used to determine crystallite size, composition, morphology and characteristics vibration of interlayer anion present in the nanoparticle. The nanofluids were characterized for particle size, cluster size, surface tension and thermal conductivity. Particle size analysis was carried out to confirm the formation of nanofluid. Dynamic light scattering (DLS) method had been employed to measure the clustering tendency of nanofluid. Effect of nanofluid loading on thermal conductivity was studied in depth. Influence of particle size, shape and composition on thermal conductivity of nanofluid had also been selected as an essential topic of investigation. Zeta potential and visual phase separation study were carried out to measure the stability of concerned nanofluid.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Designing and optimization of separation process of iron impurities from
           kaolin by oxalic acid in bench-scale stirred-tank reactor
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): M. Taran , E. Aghaie
      Kaolin leaching by oxalic acid in a bench-scale stirred-tank reactor using response surface methodology and face centered central composite design based on three variables: oxalic acid concentration (X 1: 0.1–0.3M), temperature (X 2: 30–80°C) and duration of the leaching test (X 3: 2–4days) was investigated. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis by Design-Expert 7 software and were analyzed by analysis of variance (ANOVA). According to ANOVA, all factors (X 1, X 2 and X 3) influenced the response (dissolved iron concentration) and a positive regression coefficient of variables suggested an increase in dissolved iron concentration with an increase in oxalic acid concentration, temperature and time of leaching but there was not any interaction between them. The 3-D response surface plot and the contour plot derived from the mathematical model were applied to determine the optimal conditions. The optimum leaching conditions for maximum dissolved iron concentration were found to be oxalic acid concentration of 0.21M, temperature of 77°C and duration of the leaching test of 4days. After the washing stage of kaolin, in those experiments that pH was above 4, iron oxalate precipitate was formed and the percentage of residual iron in the sample after leaching was higher than expected. In general, the minimum amount of residual iron in the kaolin was 0.75% (w/w) that was obtained in tests where the oxalic acid concentration, temperature, time of the leaching and pH of final solution were 0.3M, 30°C, 2days and 3, respectively.


      PubDate: 2015-02-28T14:28:42Z
       
  • Sequestration of heavy metal cations on montmorillonite by thermal
           treatment
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Runhong Zhu , Qi Chen , Runliang Zhu , Ying Xu , Fei Ge , Jianxi Zhu , Hongping He
      Clay minerals are low-cost, high-efficient, and environmentally-friendly adsorbents for heavy metal cations. Proper disposal of the spent clay minerals, however, is still a big challenge holding back their wide applications in environmental remediation. In this work, the spent montmorillonites (Mt) after the adsorption of Cu2+ or Cd2+ were thermally treated, with the aim of in-situ sequestrating the adsorbed heavy metal cations. The structural characteristics of the calcined Mt samples were investigated using X-ray diffraction and X-ray photon spectroscopy, and the sequestration efficiency was tested by ammonium acetate and HCl washing. The results of this work demonstrated that Cu2+ cations could migrate into both the ditrigonal cavities on the tetrahedral sheet and vacant sites on the octahedral sheet of Mt after thermal treatment due to its small ion radius. In this case, Cu2+ cations could be efficiently sequestrated on Mt layers, e.g., less than 3.2% desorption by ammonium acetate washing and less than 5% desorption by HCl washing for the 400°C treated Cu–Mt. As for Cd2+ cations, they could hardly migrate into Mt layers, and thus much higher calcination temperature (e.g., 700°C) was needed to efficiently sequestrate them on Mt. In this case, Cd2+ cations were mainly sequestrated by the collapse of Mt layers and/or the deformation of Mt structure, which could block the desorption pathway for Cd2+ cations. Interestingly, as the thermal treatment temperature increased to a critical value (i.e., 400°C for Cu–Mt and 500°C for Cd–Mt), the structural Al3+ could be preferably dissolved by HCl than the adsorbed heavy metal cations; ammonium acetate could hardly dissolve the structural Al3+. This work demonstrated that thermal treatment could be a practical method for safe disposal of the spent Mt after the adsorption of heavy metal cations.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Synthesis of Fe2O3–NiO–Cr2O3 composites from NiFe-layered
           double hydroxide for degrading methylene blue under visible light
    • Abstract: Publication date: April 2015
      Source:Applied Clay Science, Volume 107
      Author(s): Jianfeng Ma , Jiafan Ding , Liangmin Yu , Liangyin Li , Yong Kong , Sridhar Komarneni
      To develop a low-cost and highly efficient photocatalyst under the visible illumination, Ni3Fe–CO3–LDH (referred to hereafter as NiFe-layered double hydroxide or NiFe–LDH) was used as a precursor to synthesize Fe2O3–NiO–Cr2O3 composite. The NiFe–LDH was prepared by co-precipitation and then it was exchanged with dichromate. After calcining at 600°C, the Fe2O3–NiO–Cr2O3 composite was obtained. The composites' absorption edge intensely extended up to ca. 700nm covering the full visible light spectrum and showed high catalytic activity at natural pH under the visible light illumination. A very high methylene blue degradation of 91.2% was achieved with the aid of H2O2 in 120min with no detectable Cr in solution.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Porous hollow tubes processed by extrusion of ceramic emulsions
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): N. Vitorino , C. Freitas , M.J. Ribeiro , J.C.C. Abrantes , J.R. Frade
      The processing of ceramic materials by extrusion is widely used to obtain products with constant cross section. Most of them are framed with applications as catalysis, filtration, building, fuel cells, isolators, etc., mainly if they are porous with special designed microstructural characteristics as pore size/distribution, liquid and gas permeability, mechanical properties, etc. Thus, in this work we combine a cellular ceramic preparation strategy based on a synergy of emulsification process and gel casting, with the extrusion process to obtain porous hollow tubes. Tree ceramic emulsions were extruded under different ram speeds and its effect was studied using Benbow-Bridgwater model.


      PubDate: 2015-02-28T14:28:42Z
       
  • Thickness, modulus and strength of interphase in clay/polymer
           nanocomposites
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Yasser Zare , Hamid Garmabi
      The aim of the present work is to quantify the properties of interphase between the polymer matrix and the nanoclay in clay/polymer nanocomposites (CPN). Two micromechanics models, Ji and Pukanszky, are simply used to measure the modulus, strength and thickness of interphase by mechanical properties of nanocomposites. The suggested approach is applied to calculate and evaluate the interphase properties in various samples reported in the literature. The calculations clearly demonstrate the different properties of interphase compared to matrix and nanoclay phases. It is shown that the interphase usually has a significant thickness, modulus and strength in CPN which cannot be neglected in the final properties of nanocomposites.


      PubDate: 2015-02-28T14:28:42Z
       
  • 12-Phosphotungstic acid immobilized on activated-bentonite as an efficient
           heterogeneous catalyst for the hydroxyalkylation of phenol
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Ran Liu , Xinnian Xia , Xiaozhen Niu , Guozhong Zhang , Yanbing Lu , Rufeng Jiang , Shili He
      12-Phosphotungstic acid (PTA) supported on commercially activated-bentonite (BNT) was demonstrated to be efficient in the synthesis of bisphenol F (BPF) by hydroxyalkylation of phenol. In the series of PTA (10–40wt.%) impregnated-BNT catalysts prepared, 20% PTA/BNT showed the highest product yield (93%) and selectivity (97%), which was higher than that of parent PTA and BNT individually, due to the excellent dispersion of PTA on BNT leading to the redistribution of Brönsted and Lewis acid sites on BNT. NH3-TPD studies of various catalysts revealed that an appropriate combination of both strong and weak acid sites could contribute to a higher yield of BPF compared to the catalyst Al-MCM-41, and the Brönsted acid sites were more crucial in achieving a higher selectivity to 4,4′-isomer than Lewis acid sites.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Experimental investigation of the effect of henna extract on the swelling
           of sodium bentonite in aqueous solution
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Aghil Moslemizadeh , Seyed Reza Shadizadeh , Mehdi Moomenie
      This paper reports for the first time the effect of Henna extract as a new, naturally occurring, and ecofriendly additive on swelling of sodium bentonite in aqueous solution. This is performed via a number of methods including dynamic linear swelling test in two distinct temperatures of 28°C and 82°C, sodium bentonite inhibition and sodium bentonite sedimentation tests. The results indicated that inhibition properties of Henna extract are a function of its concentration and are comparable with potassium chloride and polyamine as the two most common clay stabilizers. Inhibition mechanism was assessed using adsorption measurements obtained by conductivity technique, contact angle measurements via the sessile drop method, and scanning electron microscopy (SEM) analysis. Results of adsorption measurements indicated that Henna extract has a lower adsorption isotherm in alkaline medium (pH=9) compared to natural medium (acidotic). Adsorption of Henna extract increases hydrophobicity of sodium bentonite particle surface; nevertheless, this adsorption mechanism is slightly weakened in alkaline medium due to the effect of caustic soda as a pH adjustment agent. SEM analysis demonstrated that sodium bentonite particles have an extended area when exposed to Henna extract solution instead of distilled water indicating sodium bentonite particle stability. Henna extract has deflocculating properties at low concentrations (especially up to 0.2mass%); yet it indicates good inhibition properties to sodium bentonite swelling at a concentration several times higher than that of deflocculating concentration, about 3mass%. Inhibition properties could be attributed to the hydrogen bonding between the hydroxyl group of Henna extract constituents and oxygen atoms available on silica groups of sodium bentonite, especially to the lawsone (2-hydroxy-1,4 napthaquinone) constituent.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Valorization and inertization of galvanic sludge waste in clay bricks
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): L. Pérez-Villarejo , S. Martínez-Martínez , B. Carrasco-Hurtado , D. Eliche-Quesada , C. Ureña-Nieto , P.J. Sánchez-Soto
      Galvanic sludge wastes (GSW) are produced by the physico-chemical treatments of wastewater generated by electroplating plants. These materials have a significant potential for the production of clay ceramic bricks. This paper focuses on the viability of the inertization of heavy metals from GSW mixed with clays. The original materials were obtained by mixing three types of raw clay (red, yellow and black) in equal parts with GSW. These mixtures were characterized by XRD, XRF, and chemical elemental analysis CHNS. The dosage of GSW in the clay–GSW bricks was up to 5wt.%. The bricks were then manufactured using conventional processes. The influence of the amount of GSW was evaluated after firing the clay–GSW composites at 950°C for 1h. The engineering properties of the fired samples, such as density, water absorption, open porosity, water suction and compressive strength, with and without the GSW, were determined. The incorporation of GSW into the clay mix clearly decreased the linear shrinkage and bulk density of the bricks in comparison with the fired clay used as a control. These GSW–clay composites also showed lower open porosity. According to the results obtained for the bulk density of the bricks, samples with GSW addition showed slightly lower values of open porosity than clay bodies, indicating that the GSW–clay samples had slightly higher closed porosity values. This was also shown by SEM. The open porosity, SEM and pore size distribution tests indicated that the porosity generated by the addition of GSW was mainly closed and, therefore, GSW bricks had excellent mechanical properties. The environmental risks of the incorporation of GSW, rich in heavy metals (Cr, Zn, Ni and others), to a clay matrix were evaluated by leaching tests of the fired products. The results indicated a successful inertization of the pollutants.


      PubDate: 2015-02-28T14:28:42Z
       
  • Release of surfactants from organo-modified montmorillonite into solvents:
           Implications for polymer nanocomposites
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Yining Xia , Maria Rubino , Rafael Auras
      A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to measure the surfactant released from organo-modified montmorillonite (OMMt) into different solvents used as food simulants. Two types of OMMt (Nanomer I.44P and Cloisite 93A) containing different quaternary alkylammonium surfactants were selected. The release of surfactant from clay suspensions was investigated by taking three factors into consideration: temperature, sonication and simulant type. At room temperature (22°C), the amount of surfactant (in percentage) released from the OMMt into pure ethanol was about 25% (from the I44P clay) and 11% (from the Cloisite clay). However, more surfactant was released into ethanol when the clay suspensions were held at higher temperatures, and a two-fold amount of surfactant was released when the suspensions were sonicated. The maximum surfactant release from both types of OMMt was achieved when the clays were dispersed in pure ethanol, while significantly less surfactant was released into 50% ethanol (ethanol/water, 1:1) or pure water. Finally, the affinity between the solvent and the surfactant was discussed based on solubility parameters and correlated with the surfactant release into different solvents.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • The effect of the substitution of hydrated lime with phyllite on mortar
           quality
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Thays F. de Oliveira , Márcia H. Beck , Pedro V. Escosteguy , Edson C. Bortoluzzi , Marcio L. Modolo
      In Brazil, phyllite began to be used as a substitute for hydrated lime for binary cement/lime mortar. Phyllite is cheaper and contributes more to the health of the workers than hydrated lime. However, this substitution has generated problems in coatings. Here we evaluate the effect of this substitution on a binary cement/phyllite mortar quality. The cement:phyllite:sand ratio tested was 1:0.4:6.5, which is the more common ratio used in Brazil, providing greater savings. The chemical and mineralogical compositions of hydrated lime and phyllite as well as some mortar properties were characterized. Overall, our results show that phyllite mortars have greater porosity, lower linear retraction, and lower pullout strength. These characteristics are due to the properties of expansion and retraction of the material and the absence of lamellar structure in hydrated lime. Although phyllite has been used as a substitute for hydrated lime due to economic and health reasons, our study indicates that the contribution of phyllite for mortar quality is lower than that of lime, therefore decreasing mortar quality rather than improving it.


      PubDate: 2015-02-28T14:28:42Z
       
  • Study on the preparation and characterization of a titanium-pillared
           clay-supported CrCe catalyst and its application to the degradation of a
           low concentration of chlorobenzene
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Shufeng Zuo , Menglin Ding , Jing Tong , Lucong Feng , Chenze Qi
      In the present study, Ti-pillared clay (Ti-PILC) with a large surface area, uniform mesopores and high thermal stability was prepared and used as carrier to support CrCe oxides. Performance of the catalysts in catalytic chlorobenzene degradation was investigated. Ti-PILC had a significantly larger basal space and higher specific surface area and pore volume compared with those of Na-montmorillonite. These improvements accelerated the mass transfer of the gas in the gas–solid reaction, as the gas was transferred through the bigger pores of the catalysts. The porous structure of the carrier remained stable after calcination at 550°C, and the supported active constituent was evenly dispersed without aggregation, indicating that the material was a class of catalyst well suited for the catalytic degradation of chlorobenzene. Notably, CrCe(6:1)/Ti-PILC enabled the complete degradation of a low concentration of chlorobenzene at approximately 250°C and displayed outstanding performance compared with other types of catalysts.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Design of experiments to evaluate clay swelling inhibition by different
           combinations of organic compounds and inorganic salts for application in
           water base drilling fluids
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Rosangela de Carvalho Balaban , Emanuella Layne Ferreira Vidal , Maurício Rodrigues Borges
      In this study the synergistic behavior that occurs when three different cationic inhibitors for clay swelling were associated with brines containing NaCl and KCl was evaluated. These commercial inhibitors are based on a cationic quaternary polyamine chloride with quaternary ammonium group (INIB 1), on a cationic polyacrylamide chloride with quaternary ammonium group (INIB 2) and on a quaternary ammonium chloride salt (INIB 3). Each inhibitor was characterized considering the amount of chlorides and content of active matter. The tests were performed with a commercial bentonite. Capillary suction timer (CST) and linear swell meter (LSM) were used for the evaluation of clay–water interaction in the presence of various fluids. For a better interpretation of the experimental results statistical analysis (DOE — design of experiments) via response surface methodology (RSM) was used, taking into account the type and concentration of inhibitors, the type and concentration of brines as well as the contact time of the inhibitor solutions with clay. The results showed different efficiencies, in other words, inhibitors mixed with brines were more effective than the inhibitors alone. The best results were obtained for cationic polyacrylamide chloride with quaternary ammonium group at 7lb/bbl (pounds per barrel) in KCl brine at 18.74lb/bbl with contact time of brine and clay of 7.6h. Solutions containing these combinations presented greater inhibition of clay swelling. However, for field operations, other parameters should be considered as operating cost, environmental requirements and the application time of each product.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Sensitive determination and electro-oxidative polymerization of azodyes on
           a carbon paste electrode modified with bentonite
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): Elif Türker Acar , Sinem Ortaboy , Gül Hisarlı , Gülten Atun
      A new composite carbon paste electrode incorporating bentonite (BentMCPE) was developed and used for extremely sensitive determination and electro-oxidative polymerization of azodyes using cyclic voltammetry. Lanaset Red 2B (LR2B) was selected as a model molecule for optimization of operational parameters such as amount of modifier, the pH of buffer medium, scan rate and dye concentration. Performance analyses showed that BentMCPE allows determination of LR2B, Acid Blue 113 (AB113) and Acid Yellow 17 (AY17) dyes as low as (6–8)×10−10 mol/L at pH5.5. The peak intensities increased with the repetitive scans due to electro-catalytic anodic polymerization of the dyes. The results of multiple scans in single binary and ternary dye solutions showed that all of the dyes whether hydroxyl substituted (LR2B and AY17) or not (AB113) can be polymerized on the BentMCPE surface. Two possible electro-polymerization pathways were proposed by assuming formation of different radical intermediates produced from azo/hydrazone tautomers of the dyes. A comparison of FT-IR spectra recorded after the first and tenth repetitive scans confirmed that the electro-polymerization process proceeds by head to tail interactions of the radicals with dye monomers deposited on the electrode surface.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
  • Perturbation induced by EDTA on HDO, Br- and EuIII diffusion in a
           large-scale clay rock sample
    • Abstract: Publication date: March 2015
      Source:Applied Clay Science, Volumes 105–106
      Author(s): R.V.H. Dagnelie , P. Arnoux , J. Radwan , D. Lebeau , P. Nerfie , C. Beaucaire
      Clay rocks are widely studied in the context of waste landfill leachates or as geological barriers for nuclear waste management. The release of organic co-contaminants by wastes may alter clay rocks, depending on the ratio between the volume of wastes and the mass of rock. In this work, a 10mM EDTA plume was injected in a large-scale clay rock sample with a low V/m ratio (<< 1.0Lkg-1) close to environmental conditions. The chemical perturbation was monitored for 450days, as well as its effect on HDO, Br-, and EuIII diffusion. Alteration of carbonates and iron-rich phases was evidenced in addition to the decrease of tracer concentration. Negatively charged complexes of EDTA and Eu are slightly adsorbed on minerals surface and display a desorption hysteresis. Transport parameters including diffusion anisotropy of HDO, Br, and EDTA complexes are estimated. Results are discussed with emphasis on determination of the mechanisms governing such a perturbation and the corresponding transitory state.
      Graphical abstract image

      PubDate: 2015-02-28T14:28:42Z
       
 
 
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