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Applied Clay Science

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ISSN (Print) 0169-1317
Published by Elsevier

[2564 journals]

Organic free montmorillonite-based flexible insulating sheaths for Nb3Sn superconductor magnets
- Abstract: Publication date: Available online 21 May 2013
  Source:Applied Clay Science
  Author(s): Eric Prouzet , Alexandre Puigségur , André Larbot , Jean-Michel Rey , Françoise Rondeaux
  Nb3Sn is a superconductor that exhibits higher performances than NbTi alloy currently used in superconducting magnets, regarding both the critical magnetic field and critical current. However, Nb3Sn is an intermetallic compound prepared by thermal treatment, which loses ductility and plasticity once reacted. Since organic materials cannot be used as insulating sheaths and applied before the thermal treatment required for the synthesis of Nb3Sn, a clay mineral-based organic-free sheath was prepared, which can be applied to Nb3Sn magnetic coils prepared by the wind & react method, before the thermal process. This process allows for facile shaping of the superconductor precursor, before reaction, along with the application of the insulating coating, the sintering of this coating being achieved by the thermal treatment required for the synthesis of Nb3Sn. This process has been designed for industrial developments and facile scale-up. The final material is an organic-free ceramic ribbon that can be stored before further use as an insulating sheath of Nb3Sn wires, and electrical and magnetic tests on both the material and a specific demonstrator made with a 20m superconducting reel, demonstrate that this material can be used as an insulating sheath, with no side-effect on superconductor properties.
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  PubDate: 2013-05-22T23:03:24Z
Effects of interlayer interactions on the nanoindentation behavior and hardness of 2:1 phyllosilicates
- Abstract: Publication date: Available online 19 May 2013
  Source:Applied Clay Science
  Author(s): Jianhong Zhang , Liming Hu , Rohit Pant , Yuzhen Yu , Zhongxin Wei , Guoping Zhang
  Six non-expandable, hydrous 2:1 phyllosilicate minerals with different layer charges, including pyrophyllite and talc from the pyrophyllite-talc group and biotite, two muscovites, and margarite from the mica group, were nanoindented to probe their nanoscale deformation behavior and hardness. Remarkably different deformation responses were obtained, which are highly dependent upon the type and strength of interlayer interactions controlled by Coulomb or van der Waals forces. Concave load–displacement curves were observed on the micas with stronger Coulomb forces as interlayer interaction, while convex curves on the other group with weaker van der Waals attractions as interlayer interaction. The hardness increases with layer charge both within each group and between the two groups, ranging from 3.86GPa for talc to 16.34GPa for margarite, with the highest being four times greater than the lowest. Owing to their layered structure that favors kink band formation and layer delamination, pop-ins of varied extensions occur randomly in the load–displacement curves. An observed apparent indentation size effect is attributed to the pop-in events. The dependence of hardness on interlayer interactions between 2:1 layers instead of the atomic bonds within the 2:1 layer suggests that the interlayer interactions can be used as a hardness or plastic signature for phyllosilicate minerals.
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  PubDate: 2013-05-22T23:03:24Z
Removal of Acid Green 68:1 from aqueous solutions by calcined and uncalcined layered double hydroxides
- Abstract: Publication date: Available online 17 May 2013
  Source:Applied Clay Science
  Author(s): Rodrigo Morais Menezes dos Santos , Rosembergue Gabriel Lima Gonçalves , Vera Regina Leopoldo Constantino , Liovando Marciano da Costa , Luis Henrique Mendes da Silva , Jairo Tronto , Frederico Garcia Pinto
  Magnesium aluminum layered double hydroxide (LDH) was synthesized by the co-precipitation method followed by calcination. The resulting materials were characterized by X-ray diffraction (PXRD) and attenuated total reflectance with Fourier transform infrared spectroscopy (FTIR/ATR) and simultaneous thermogravimetric analysis/differential scanning calorimetry coupled to mass spectrometry (TGA–DSC–MS). Calcined and non-calcined LDHs were used as adsorbents to remove azo dye Acid Green 68:1 in an aqueous solution. Adsorption experiment results indicated that calcined LDH possesses greater adsorption capacity (154.8mgg−1) than non-calcined LDH (99.1mgg−1). Isotherms showed that adsorption of the dye was more consistent with the Langmuir model. Kinetic experiments of calcined LDH adsorption showed that for low concentration (50, 100 and 200mgL−1), the system reached the adsorption equilibrium in 1, 2, and 4h, and for higher concentration after 10h. The best kinetic model was the pseudo-second order. Adsorption studies also showed that the capacity for adsorption of the dye by calcinated LDH does not significantly diminish with pH level variation.
  
  PubDate: 2013-05-18T23:03:09Z
Reconstruction of calcined MgAl- and NiMgAl-layered double hydroxides during glycerol dehydration and their recycling characteristics
- Abstract: Publication date: Available online 17 May 2013
  Source:Applied Clay Science
  Author(s): Szilvia Mészáros , János Halász , Zoltán Kónya , Pál Sipos , István Pálinkó
  MgAl- and NiMgAl-layered double hydroxides (LDHs) were prepared by the co-precipitation method. On calcination MgAl and NiMgAl mixed oxides were formed. Crystalline MgO and NiO could be identified, while aluminium ions were well-dispersed on these oxides. The mixed oxides were effective in the transformation of glycerol to currently more valuable products like acetol (hydroxyacetone) and acrolein. Acetol was found to be the main product and some part was further dehydrated to acrolein. During the reaction, full reconstruction of the LDH structure occurred. The used catalysts could be reactivated by repeated calcination.
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  PubDate: 2013-05-18T23:03:09Z
Synthetic organofluoromica/poly(lactic acid) nanocomposites: Structure, rheological and thermal properties
- Abstract: Publication date: Available online 17 May 2013
  Source:Applied Clay Science
  Author(s): D.H.S. Souza , K. Dahmouche , C.T. Andrade , M.L. Dias
  Organically modified fluoromica/poly(lactic acid) (PLA) nanocomposites were prepared by melt processing at different compositions in an internal mixer at the same conditions. Gel permeation chromatography (GPC) was used to measure the molar masses of PLA alone, before and after processing. The results indicated that PLA presented some degradation during melt mixing. With the addition of the organically-modified fluoromica, higher reduction in the polymer molar masses was found. The structure of the synthetic mica and of the clay polymer nanocomposites (CPN) was studied by small-angle X-ray scattering (SAXS), which revealed the presence of nanometer-sized clay mineral aggregates. Dynamical rheological measurements were carried out in the linear viscoelastic region for both PLA and CPN molten samples. A predominantly viscous behavior was obtained for the polymer samples, whereas the CPN presented a pronounced elastic behavior. Addition of mica to PLA also had a significant effect on the complex viscosity of PLA, imparting an increasing shear thinning behavior with increasing mica composition. Below Tg, dynamical mechanical analysis results showed a substantial decrease of rigidity of the CPN in relation to PLA alone, attributed to the presence of high content of organic intercalant in the synthetic fluoromica. Lower cold crystallization rate was detected for the CPN in comparison with processed PLA alone.
  
  PubDate: 2013-05-18T23:03:09Z
The effect of particle size of clay on the viscosity build up property of mixed metal hydroxides (MMH) in the low solid-drilling mud compositions
- Abstract: Publication date: Available online 17 May 2013
  Source:Applied Clay Science
  Author(s): Barsha Baruah , Mridusmita Mishra , Chira R. Bhattacharjee , Mool C. Nihalani , Santosh K. Mishra , Shashi D. Baruah , Paran Phukan , Rajib L. Goswamee
  Mixed metal hydroxide (MMH) is a purely inorganic viscosifier of montmorillonite suspensions, having environmental and thixotropic advantages over conventional viscosifiers. It was observed that the particle size distribution of the clay plays a crucial role in building up viscosity of clay–MMH suspensions. Two drilling clays, their separated <2μm fractions and a pharmaceutical grade bentonite were studied. It was found that in a clay with 80% (w/w) particles below the 2μm level the yield point (YP) rise of 2.5% (w/w) aqueous clay suspension is not stopped even on 0.3% (w/v) MMH treatment, whereas in a clay with less than 30% (w/v) particles below the 2μm level the YP reaches a constant level of 8lb/100ft2 after 0.1% MMH (w/v) treatment. When the <2μm separated fraction is taken from the latter clay and hydrated it was found that YP rises even above the constancy level. On further homo-ionising this separated fraction to Na form and treating with MMH the YP rise was found still higher. When some carefully separated fraction containing a high amount of particles with less than <1μm fraction was treated with MMH the YP rise was even higher. With the decrease of the particle size of the clay there is associated an increase of cation exchange capacity (CEC). Therefore, both CEC and particle size play a vital role in viscosity buildup which is due to the formation of an extended gel-network of clay and LDH particles at the prevailing alkaline pH of the system giving rise to high thixotropy. Finally, to reach a bench mark level of YP≈20lb/100ft2 with the latter clay one must opt for a base mud concentration of a minimum of 4% (w/v) aqueous system.
  Highlights ► Paper deals with an inorganic viscosifier for drilling grade bentonite suspensions. ► It also deals with the effect of particle size of bentonite on its flow behavior.
  
  PubDate: 2013-05-18T23:03:09Z
Acid-activated montmorillonites as heterogeneous catalysts for the esterification of lauric acid acid with methanol
- Abstract: Publication date: Available online 18 May 2013
  Source:Applied Clay Science
  Author(s): Leandro Zatta , Luiz Pereira Ramos , Fernando Wypych
  A standard clay mineral was systematically subjected to activation with phosphoric acid under different concentrations and activation times. The materials were evaluated with regard to their structure, presence of functional groups, textural properties and the presence of Brönsted and Lewis acid sites. After characterization, the best catalyst was evaluated in the esterification of lauric acid with methanol. High conversions were observed in short times (between 91.63 and 96.67%) and relatively mild reaction temperatures, revealing the potential of acid-activated clays as esterification catalysts for industrial applications such as biodiesel production. For comparison purposes, some experiments were also carried out with a standard solid acid catalyst (montmorillonite K10) and conversions of 95.03% were obtained in comparison to the best catalyst obtained in the present study (96.67%).
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  PubDate: 2013-05-18T23:03:09Z
Adsorption of chromium(VI) from aqueous solutions onto amine-functionalized natural and acid-activated sepiolites
- Abstract: Publication date: Available online 14 May 2013
  Source:Applied Clay Science
  Author(s): V. Marjanović , S. Lazarević , I. Janković-Častvan , B. Jokić , Dj. Janaćković , R. Petrović
  Chromium(VI) adsorption onto amine-functionalized sepiolites from aqueous solution at 298K was investigated. Natural and acid-activated sepiolites were functionalized by covalent grafting [3-(2-aminoethylamino)propyl]trimethoxy-silane to the silanol groups onto the sepiolite surface. Functionalization was proved by differential thermal analysis and the point of zero charge, pHpzc, determinations. The adsorption isotherms suggested that the adsorption capacity of the functionalized acid-activated sepiolite was higher than that of the functionalized natural sepiolite, for all investigated initial solution pH values. Adsorption efficiency of the functionalized sepiolites was improved by decreasing solution pH value. Due to the high value of pHpzc and large buffer capacity of adsorbents, a very low initial solution pH value was required to achieve high protonation of the surface amine groups and provide electrostatic attraction of Cr(VI) anionic species. The maximum chromium(VI) removal was achieved at an initial pH of 2.0; ca. 60mg/g of functionalized acid-activated sepiolite and ca. 37mg/g of functionalized natural sepiolite. Equilibrium data for both functionalized sepiolites at an initial solution pH value of 2.0 fitted well to the Freundlich model. The adsorption process followed pseudo-second-order kinetics. The values of the thermodynamic parameters indicate a spontaneous adsorption process of a prevalently physical nature.
  
  PubDate: 2013-05-14T23:03:39Z
Charge transport in diatomaceous earth studied by broadband dielectric spectroscopy
- Abstract: Publication date: Available online 14 May 2013
  Source:Applied Clay Science
  Author(s): V. Saltas , F. Vallianatos , E. Gidarakos
  In the present work, broadband dielectric spectroscopy measurements in the frequency range of 10mHz to 1MHz and at elevated temperatures (room temperature up to 950°C) were carried out in industrial diatomaceous earth samples, in order to study charge transport phenomena which play a key role to the transport of both organic and inorganic contaminants in this kind of minerals. Cole–Cole plots of complex impedance measurements may serve to distinguish the contributions of grain interior, grain boundaries and electrode polarization to the overall electrical behavior of diatomite. Complex electrical conductivity and electric modulus representations have been combined under the fulfillment of the BNN relationship over a wide temperature range, in order to investigate the temperature dependence of diffusion coefficients and concentration of charge carriers in thermally modified diatomite. Both diffusivity and mobility follow the same Arrhenius-type behavior at two distinct temperature regions as DC-conductivity does. The related activation energies were estimated and ascribed to proton conduction (Ea≈1.00eV) at low temperatures (T<650°C) and hopping conduction of small polarons (Ea≈1.67eV) at higher temperatures, due to the presence of transition metals in diatomite sample. The thermal treatment of diatomite at 950°C enhances the available charge carriers and increases the diffusivity which might improve its adsorption capacity.
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  PubDate: 2013-05-14T23:03:39Z
Effects of montmorillonite on the chemical degradation kinetics of metsulfuron methyl in aqueous media
- Abstract: Publication date: Available online 14 May 2013
  Source:Applied Clay Science
  Author(s): Maximiliano Brigante , Graciela Zanini , Marcelo Avena
  The degradation kinetics of the sulfonylurea herbicide metsulfuron methyl (MM) has been studied in batch experiments by UV–VIS spectroscopy, and the effects of pH and the presence of a clay mineral (Na-montmorillonite) are reported. The proposed UV–VIS method gives kinetic results that are comparable to those obtained with chromatographic methods. In aqueous solutions, the chemical degradation of MM is undetectable at pH6.5–9.5, but increases about 500 times by decreasing the pH from 6 to 2, and 300 times by increasing pH from 9.5 to 11.5. For example, the half-life of MM is shorter than 1d at pH2 and 11.5, but longer than a year at pH6. Na-montmorillonite has an inhibitory effect on MM degradation. A combination of adsorption–desorption studies and degradation kinetic measurements demonstrates that in the presence of Na-montmorillonite only MM that remains in solution is subject to degradation; adsorbed MM is protected by the clay from being degraded. However, since adsorption only occurs at low pH (around 3) it can be envisaged that montmorillonite and supposedly other phyllosilicate clays do not affect significantly the chemical degradation rate of MM in soils and other natural systems.
  
  PubDate: 2013-05-14T23:03:39Z
Editorial Board
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  
  PubDate: 2013-05-14T23:03:39Z
Influences of quartz and muscovite on the formation of mullite from kaolinite
- Abstract: Publication date: Available online 9 May 2013
  Source:Applied Clay Science
  Author(s): H.M. Zhou , X.C. Qiao , J.G. Yu
  A kaolin containing muscovite and quartz (K-SZ) and a pure kaolin (K-SX) with the addition of potassium feldspar, K2SO4 and quartz, respectively, were used to investigate the influences of muscovite and quartz on the formation of mullite from kaolinite in the temperature range 1000–1500°C. In K-SZ formation of mullite began at 1100°C, and in K-SX at 1000°C. In K-SZ quartz accelerated the formation of cristobalite and restrained the reaction of mullite and silica. Muscovite in K-SZ acted as a fluxing agent for silica and mullite before 1400°C and accelerated the formation of cristobalite. The FTIR band at 896.8cm−1 was used to monitor the formation of orthorhombic mullite.
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  PubDate: 2013-05-10T23:04:06Z
A 1H and 27Al NMR investigation of yttrium(III) and europium(III) interaction with kaolinite
- Abstract: Publication date: Available online 9 May 2013
  Source:Applied Clay Science
  Author(s): Nina Huittinen , Priit Sarv , Jukka Lehto
  Sorption of the trivalent metals Eu3+ and Y3+ on a natural kaolinite mineral was investigated with solid-state 1H and 27Al NMR. The metal ion concentration in the samples was varied between 4×10−6 M and 8×10−5 M, while the kaolinite concentration and ionic strength with respect to Na+ were kept constant at 5g/l and 1mM, respectively. The aqueous samples were equilibrated for at least six days at pH8.0±0.1 before the mineral was separated from the supernatant, recovered, and dried. Metal ion addition to the kaolinite samples had no influence on recorded 27Al spectra, which show a center peak at 6.15ppm corresponding to octahedrally coordinated aluminum in the gibbsite-like sheets of kaolinite. The 27Al measurements were, however, imperative to perform as potential mineral dehydroxylation was monitored from the 27Al spectra before and after drying treatment and normalization of 1H spectra was based on the acquired 27Al data. The attachment of Y3+/Eu3+ on the kaolinite surface was shown to reduce 1H resonances with chemical shifts at 2.3–3.5ppm, 1.6, 1.3, 0.9 and 0.7–0.3ppm. The loss of proton signal could be attributed to metal ion attachment to isolated Al–OH groups on the kaolinite edge surfaces and possibly to bridging Al–OH–Al hydroxyls on the gibbsite-like basal plane of the mineral.
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  PubDate: 2013-05-10T23:04:06Z
Catalytic oxidation of VOCs over Al- and Fe-pillared montmorillonite
- Abstract: Publication date: Available online 4 May 2013
  Source:Applied Clay Science
  Author(s): Dan Li , Chunshan Li , Kenzi Suzuki
  Al- and Fe-pillared montmorillonite (Al- and Fe-PILCs) were prepared and examined as catalysts in the deep oxidation of toluene and chlorobenzene. The catalysts before and after reaction were characterized by X-ray powder diffraction, N2 adsorption, scanning electron microscopy, and energy dispersive X-ray spectrometer. Results show that Al- and Fe-PILCs with layer structures increase the surface area. For the catalytic oxidation of volatile organic compounds (VOCs), Fe-PILCs exhibit higher performance than fresh montmorillonite and Al-PILCs. Higher concentration of Fe also resulted in higher catalytic activity. Fe-PILCs also exhibited higher stability than Al-PILCs. Even at a low temperature (100°C), Fe-PILCs still exhibited certain activity. Lifetime evaluation results show that the activity of Fe-PILC (3) did not vary after a 96-hour reaction. BET and XRD results indicate that these pillared catalysts have very stable structures even after prolonged reaction. Hence, Fe-PILCs are potential materials for VOC decontamination.
  
  PubDate: 2013-05-06T23:04:32Z
Chemistry, morphology and structural characteristics of synthetic Al–Ni and Al–Co-lizardites
- Abstract: Publication date: Available online 4 May 2013
  Source:Applied Clay Science
  Author(s): María Bentabol , María Dolores Ruiz Cruz
  Al–Ni and Al–Co lizardites have been synthesized at hydrothermal conditions. The two phases display different morphologies: thin, dominantly curved platelets (Al–Ni); and stacks of very thin platy particles (Al–Co). The X-ray diffraction and transmission/analytical electron microscopy studies have been used to make accurate distinctions among different structural types and chemical populations. Al–Ni bearing lizardite includes a 1M polytype and probably very subordinate amounts of chlorite. Al–Co bearing lizardite includes two 1M polytypes with different cell-parameters, one of these consisting of an apparently modulated structure. Chemically, Al–Ni- and specially Al–Co lizardite consist of a mixture of two populations with tetrahedral compositions ~Si1.8Al0.2 and Si2.0. In contrast with previously described Al-rich serpentines, our serpentines are characterized by an asymmetrical Al distribution, with VIAl on the order of 1.0 atom per formula unit.
  
  PubDate: 2013-05-06T23:04:32Z
Electrooxidation of p-nitrophenol on organobentonite modified electrodes
- Abstract: Publication date: Available online 4 May 2013
  Source:Applied Clay Science
  Author(s): A. Abu Rabi-Stanković , Z. Mojović , A. Milutinović-Nikolić , N. Jović-Jovičić , P. Banković , M. Žunić , D. Jovanović
  A natural bentonite, modified with different quaternary ammonium cations, hexadecyl trimethylammonium, (HDTMA), dodecyl trimethylammonium (DTMA) and tetramethylammonium (TMA), was used as an electrode material in a p-nitrophenol (p-NP) electrooxidation. On the basis of electrochemical response, TMA-modified bentonite (TMA-B) electrode was chosen for further investigations. The influence of TMA loading on the electrochemical properties of the TMA-B electrodes toward p-NP electrooxidation was examined. Electrode sensitivity toward p-NP was performed. The detection limit for p-NP of 1·10−6 moldm−3 was obtained.
  
  PubDate: 2013-05-06T23:04:32Z
Differentiating response of 2,7-dichlorofluorescein intercalated CTAB modified Na-MMT clay matrix towards dopamine and ascorbic acid investigated by electronic, fluorescence spectroscopy and electrochemistry
- Abstract: Publication date: Available online 4 May 2013
  Source:Applied Clay Science
  Author(s): Sangita Haloi , Priyanka Goswami , Diganta Kumar Das
  2,7-Dichlorofluorescein incorporated cetyl-trimethyl ammonium bromide modified montmorillonite clay could distinguish dopamine (DA) and ascorbic acid (AA) by fluorescence, UV/visible spectroscopy (as aqueous dispersion) and by square wave voltammetry (as an electrode modifying agent). DA enhances the fluorescence of the modified clay while AA quenches it. The absorbance in the UV/visible spectra of the modified clay increases on interaction with DA but AA has no effect on the absorbance. As an electrode modifying agent the modified clay can separate the oxidation peaks of DA and AA by 0.170V.
  
  PubDate: 2013-05-06T23:04:32Z
Effects of copper-exchanged montmorillonite, as alternative to antibiotic, on diarrhea, intestinal permeability and proinflammatory cytokine of weanling pigs
- Abstract: Publication date: Available online 2 May 2013
  Source:Applied Clay Science
  Author(s): Juan Song , Ya li Li , Cai hong Hu
  The two copper-exchanged montmorillonites (Cu-MMT), Cu2+-exchanged Ca-montmorillonite (Cu*Ca-MMT) and Cu2+-exchanged Na-montmorillonite (Cu*Na-MMT), were used as alternative to chlortetracycline on growth performance, diarrhea, intestinal permeability and proinflammatory cytokine in weanling pigs. Ninety six piglets weaned at 21±1d age were allocated to the four groups: (1) control; (2) control+1.5g/kg Cu*Ca-MMT; (3) control+1.5g/kg Cu*Na-MMT; and (4) control+75mg/kg chlortetracycline. The results showed that as compared with the control group, supplementation with Cu*Ca-MMT and Cu*Na-MMT both improved (P <0.05) average daily gain (ADG) and gain/feed ratio, lowered (P <0.05) fecal scores and the total viable counts of Clostridium and Escherichia coli in ileum and proximal colon, reduced (P <0.05) plasma d-lactate and diamine oxidase (DAO), decreased (P <0.05) interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in ileal mucosal. No difference was observed in the efficiency of the Cu*Ca-MMT group and Cu*Na-MMT group. Supplementation of Cu-MMT was as effective as chlortetracycline for alleviating diarrhea and inflammation, and improving intestinal microflora and mucosal barrier integrity of weanling pigs. The results indicated that Cu-MMT could be a good candidate as an antibiotic alternative in weanling pigs.
  
  PubDate: 2013-05-06T23:04:32Z
Study on the elastic–plastic interface and large deformation of axisymmetric disks under rotating status
- Abstract: Publication date: Available online 28 April 2013
  Source:Applied Clay Science
  Author(s): Shaowei Hu
  When the angular velocity of a circular disk at room temperature is gradually increased the disk first of all behaves elastically, then, at a certain velocity, plastic yielding begins and proceeds, with work-hardening, until all the material of the disk has reached the initial yield point, Further increase in speed causes unrestricted plastic flow to take place. The system is stable as long as an increase in speed is necessary to produce further plastic flow. In the paper, theoretical analysis in polar coordinate of the elastic–plastic interface under rotating status was finished, The calculated results are given out in exact solution. The formula of large deformation analyses of rotating disk were derived out of an equation group which could become into seven independent equations with seven unknowns and can be solved by COLSYS software. Then, some calculated examples were given out. The bursting speed of rotating disk was analyzed.
  
  PubDate: 2013-04-28T23:05:46Z
Structural and thermal properties of polystyrene nanocomposites containing hydrophilic and hydrophobic layered double hydroxides
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  Author(s): Ahmed M. Youssef , Tamás Bujdosó , Viktória Hornok , Szilvia Papp , Abou el Fotouh Abdel Hakim , Imre Dékány
  Zn–Al layered double hydroxide (LDH) was synthesized and modified using sodium dodecyl benzene sulfonate (DBS). Hydrophilic and hydrophobic LDHs were applied as fillers in a free-emulsion polymerization of styrene monomer, which enhance their thermal stability, and strengthen their structure. In order to increase structural stability we modified the surface of LDH with anionic surfactant and examined its effect on the exfoliation in the polystyrene (PS) matrix. The structure of polystyrene–LDH nanocomposites was investigated by X-ray diffraction pattern technique (XRD), and small angle X-ray scattering (SAXS). Furthermore, thermal analysis (TGA and DSC) was evaluated and the prepared nanocomposites show significantly improved thermal stability at higher temperature. Both XRD and SAXS results confirmed the totally delaminated state of the LDH in the polymer matrix. It was established that the hydrophilic filler has a better exfoliation effect than the hydrophobic LDH in the hydrophobic polymer structure.
  Graphical abstract
  
  PubDate: 2013-04-28T23:05:46Z
Evaluation of hectorites, synthesized in different conditions, as soot combustion catalysts after impregnation with copper
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  Author(s): T. Sánchez , F.B. Gebretsadik , P. Salagre , Y. Cesteros , N. Guillén-Hurtado , A. García-García , A. Bueno-López
  Two microporous hectorites were prepared by conventional and microwave heating, and a delaminated mesoporous hectorite by an ultrasound-assisted synthesis. These three hectorites were impregnated with copper. The characterization techniques used were XRD, N2 adsorption, TEM and H2 reduction after selective surface copper oxidation by N2O (to determine copper dispersion). The catalytic activity for soot combustion of the copper-free and the copper-containing hectorites was tested under a gas mixture of 500ppm NOx/5% O2/N2 (and 5% O2/N2 in some cases), evaluating their stability through three consecutive soot combustion experiments. The delaminated hectorite showed the highest surface area (353m2/g) allowing the highest dispersion of copper. This copper-containing catalyst was the most active for soot combustion among those prepared and tested in this study. We have also concluded that the Cu/hectorite-catalyzed soot combustion mechanism is based on the activation of the O2 molecule and not on the NO2-assisted soot combustion.
  
  PubDate: 2013-04-24T23:04:36Z
Influence of crack initiation length on fracture behaviors of reinforced concrete
- Abstract: Publication date: Available online 17 April 2013
  Source:Applied Clay Science
  Author(s): Xiangqian Fan , Shaowei Hu
  For the purpose of discussing the fracture features of high strength reinforced concrete, under the conditions of the fundamental assumptions to reinforced concrete, the calculating process of fracture parameters for three point bending beam of high strength reinforced concrete is given, and through a total of 16 specimens with the same sizes, with the different initial crack length 40mm to 100mm on three point bending beam of high strength reinforced concrete, it is performed to examine the calculation method. The results show that the fracture features of high strength reinforced concrete are different from normal concrete, both the initiation toughness and the unstable toughness of high strength reinforced concrete gradually increase with the crack-to-depth ratios, and the ratios of initial load to maximum load are different depending on the initial crack length, the bigger the crack-to-depth ratios, the lower the ratio, and the ductility is best to the high strength reinforced concrete.
  
  PubDate: 2013-04-20T23:04:07Z
Thiamine pyrophosphate intercalation in layered double hydroxides (LDHs): An active bio-hybrid catalyst for pyruvate decarboxylation
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  Author(s): M. Baikousi , Ag. Stamatis , M. Louloudi , M.A. Karakassides
  The intercalation of thiamine pyrophosphate (TPP) into Zn–Al and Mg–Al layered double hydroxides has been investigated using two different methods: the co-precipitation procedure (at different pH values) and the ion-exchange reaction. The structure of the hybrid materials was studied by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy verifying that the TPP molecules prefer creating a bilayer arrangement at pH=7.5, 7.75 and 8, while in the case of pH=7 a monolayer of TPP molecules coexists in the interlayer space of LDHs. In addition, the thermal decomposition of the bio-hybrid materials was examined by thermogravimetry and differential thermal analysis (TG–DTA). The total amount of the deintercalated TPP molecules from LDHs was calculated after de-intercalation reactions in the presence of carbonate ions by Ultraviolet (UV) spectroscopy. Furthermore, the hybrid materials (TPP/LDH) have been tested as biomimetic catalysts for decarboxylation of pyruvic acid showing a comparable activity to the homogenous system (TPP). Our combined data confirm that thiamine pyrophosphate can be safely loaded and stored into LDH's layers forming a new bio-active hybrid material.
  Highlights ► We examine the intercalation of thiamine pyrophosphate (TPP) into LDHs. ► The intercalation procedures lead to a new bio-active hybrid material. ► The hybrid materials (TPP/LDHs) show a remarkable activity as biomimetic catalysts. ► We examine the deintercalation of loaded molecules in the presence of CO3 2−. ► Our data confirm that TPP can be safely loaded into LDH's layers.
  
  PubDate: 2013-04-20T23:04:07Z
Editorial Board
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  PubDate: 2013-04-20T23:04:07Z
Thermal stability of montmorillonite polyacrylamide and polyacrylate nanocomposites and adsorption of Fe(III) ions
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  Author(s): Piotr Natkański , Piotr Kuśtrowski , Anna Białas , Zofia Piwowarska , Marek Michalik
  Poly(sodium acrylate), polyacrylamide and their copolymers were introduced into the interlayer spaces of raw montmorillonite (Mt) by in-situ polymerization. The obtained clay polymer nanocomposites (CPN) retained the layered structure. The polymers were intercalated at an intended polymer-to-clay mass ratio of 1:1. Differences in the mechanism of decomposition of samples depended on the type of polymer functional groups. The CPN were tested as adsorbents of Fe3+ ions. The highest adsorption capacity was achieved for samples containing poly(sodium acrylate), which was due to their high swelling capacity and the attraction of iron ions by carboxyl groups.
  Highlights ► Clay mineral/poly(sodium acrylate-co-acrylamide) hydrogel nanocomposites were studied. ► A relatively high amount of raw montmorillonite was introduced to the CPN. ► Effect of polymer composition on the thermal stability of CPN was observed. ► Swelling and adsorption capacity was determined by the hydrogel type. ► High adsorption efficiency in Fe(III) removal was achieved for the studied CPN.
  
  PubDate: 2013-04-20T23:04:07Z
Exfoliation and dispersion of micrometer-sized LDH particles in poly(ethylene terephthalate) and their nanocomposite thermal stability
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  Author(s): Kongli Xu , Guangming Chen , Jianquan Shen
  Effect of surface modification on exfoliation and dispersion of micrometer-sized layered double hydroxide (LDH) in poly(ethylene terephthalate) (PET) and the thermal stability of the resultant PET/LDH nanocomposites or composite have been studied. First, large micrometer-sized LDH with carbonate anions was prepared by urea hydrolysis method. Then, various anions including nitrate (NO3 −), dodecyl sulfate (DS−) or dodecyl benzene sulphonate (DBS−) were intercalated into the interlayer space via anion exchange reaction. By solution intercalation process, PET/LDH_DS and PET/LDH_DBS nanocomposites were successfully obtained, while the LDH_NO3 could not be exfoliated enough in the PET matrix. Finally, the thermal stabilities of the PET/LDH nanocomposites or composite were investigated.
  Highlights ► Micrometer-sized LDH in lateral size was exfoliated and dispersed in PET matrix. ► Effect of surface modification of LDH was studied. ► PET/LDH nanocomposites were successfully prepared by solution intercalation. ► The thermal stabilities of PET/LDH nanocomposites or composite were investigated.
  
  PubDate: 2013-04-20T23:04:07Z
Morphological properties of vermiculite particles in size-selected fractions obtained by sonication
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  Author(s): Marc X. Reinholdt , Fabien Hubert , Michaël Faurel , Emmanuel Tertre , Angelina Razafitianamaharavo , Gregory Francius , Dimitri Prêt , Sabine Petit , Emile Béré , Manuel Pelletier , Eric Ferrage
  The objective of this study is to determine the morphological properties of vermiculite particles obtained by sonication followed by separation into different size fractions (0.1–0.2, 1–2 and 10–20μm). These size fractions were chosen because they represent the wide range of particle sizes encountered in natural media. As previously reported, the crystal-chemistry of this vermiculite from Santa Olalla (Huelva, Spain) was found to be unaffected by the sonication process, although a loss of crystallinity and an increase in structural disorder might have occurred for the finest fraction. Using low-pressure argon adsorption analyses and a suite of microscopy techniques (i.e., atomic force, optical and transmission electron microscopy), the geometrical properties of the particles, including the distribution of the basal and lateral surfaces and aspect ratios, were obtained. Good agreement was observed between the gas adsorption experiments when applying the derivative isotherm summation procedure and the atomic force or optical microscopy analyses. However, the surface area was overestimated by transmission electron microscopy, which was attributed to the sample preparation technique. All of these data demonstrated that the particle aspect ratios are similar for all fractions, and the finest particles tend to show slightly more elongated surface morphologies than the coarser particles. Finally, a comparison of the distribution of lateral, basal and interlayer adsorption sites to the experimental cation-exchange capacity (CEC) showed that only the basal and interlayer sites are available in the conditions of CEC analysis. Based on these findings, the pertinence of using these size fractions as models to better understand the interactions between swelling clay minerals and water/solutes is discussed.
  Graphical abstract
  
  PubDate: 2013-04-20T23:04:07Z
Effects of layered lanthanum phenylphosphonate on flame retardancy of glass-fiber reinforced poly(ethylene terephthalate) nanocomposites
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  Author(s): Yuanzheng Cai , Zhenghong Guo , Zhengping Fang , Zhenhu Cao
  Effects of layered metal phosphonate lanthanum phenylphosphonate (LaPP) on the thermal stability, flame retardancy and mechanical properties of glass-fiber reinforced poly(ethylene terephthalate) (PET/GF)/microencapsulated red phosphorus (MRP) systems were investigated. The result of transmission electron microscopy (TEM) measurements indicated that LaPP particles were homogenously dispersed in PET matrix and no obvious signs of LaPP aggregation were detected. Thermogravimetric (TG) analysis showed that incorporating LaPP into PET/GF-MRP enhanced the thermal stability and increased the char residue compared to the sample without LaPP. In the existence of LaPP, the PET/GF-MRP composites could pass the UL 94 V-0 rating test, and the limited oxygen index (LOI) could be enhanced. The structures of char residues observed by scanning electron microscopy (SEM) demonstrated that LaPP could promote to form the homogenous and compact char layer. What is more, the presence of LaPP improved the tensile strength and storage moduli of PET/GF-MRP composites.
  Graphical abstract
  
  PubDate: 2013-04-20T23:04:07Z
In situ incorporation of arsenic, molybdenum, and selenium during precipitation of hydrotalcite-like layered double hydroxides
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  Author(s): Susanta Paikaray , M. Jim Hendry
  Magnesium (Mg2+) and iron (Fe3+) are common cations and their precipitation as MgFeCO3-type hydrotalcite-like layered double hydroxide (HTlc) may influence contaminant mobilization in, for example, mine drainage sites. The extent of As(V), Mo(VI), and Se(VI) incorporation during HTlc precipitation in alkaline media under normal atmospheric conditions was evaluated and its effect on physico-chemical properties was examined. Even after solute entrapment, the HTlcs were characterized by strong agglomeration. The affinity for solute inclusion in the HTlcs varied in the order As(V)>Mo(VI)>Se(VI). The incorporation of solutes resulted in slight decreases in interlayer thickness, degree of crystallinity, and crystallite size compared to the solute-free MgFeCO3-type HTlc. Open air conditions allowed a substantial mass of CO3 2− to occupy the HTlc interlayer together with the metal(loid)ic oxyanions. The incorporation of As(V), Mo(VI), and Se(VI) into the HTlcs resulted in the addition of Raman spectral vibrations at ~810, ~898, and ~835cm−1, respectively. With solute incorporation, additional mass loss occurred in multiple stages upon heating; however, the thermal stability of the solute-incorporated HTlcs was unchanged compared to solute-free counterpart. Additional surface absorption of H2O and structural incorporation of CO3 2− were evident in the solute-incorporated HTlcs.
  
  PubDate: 2013-04-20T23:04:07Z
Electric-field-induced structuring and rheological properties of kaolinite and halloysite
- Abstract: Publication date: June 2013
  Source:Applied Clay Science, Volumes 77–78
  Author(s): Zbigniew Rozynek , Tomáš Zacher , Marián Janek , Mária Čaplovičová , Jon Otto Fossum
  Electric-field-induced structuring of kaolinite and halloysite particles was studied in respect to their electrorheological (ER) response in silicone oil and in paraffin dispersions. The structural and morphological properties of both clay minerals were studied by XRD, FTIR, SEM, TEM and TGA techniques. The dipolar arrangement induced under application of an electric field was investigated by 2D-WAXS and optical microscopy techniques. The ER response of the samples was measured by both the shear rate controlled method and bifurcation tests. Kaolinite particle dispersions were found to have an improved ER response relative to dispersions of halloysite particles. Finally, the electric currents of these ER fluids were measured and the results revealed differences in the current-magnitude between halloysite- and kaolinite-based silicone oil dispersions.
  
  PubDate: 2013-04-16T23:04:22Z
Enantioselective separation of tryptophan by Mg–Al layered double hydroxides intercalated with tartaric acid derivative
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  A series of tartaric acid derivatives, such as di-p-toluoyl-L-tartaric acid (L-DTTA), di-p-toluoyl-D-tartaric acid (D-DTTA), dibenzoyl-L-tartaric acid (L-DBTA) and dibenzoyl-D-tartaric acid (D-DBTA), were intercalated into layered double hydroxides (LDHs) by the ion-exchange method in this paper. The supramolecular products, DTTA-LDHs and DBTA-LDHs characterized by XRD and FTIR, were explored to recognize tryptophan enantiomers according to the different opticity active of different tartaric acid derivatives in the interlayer of LDHs. Batch studies were carried out to address various experimental parameters such as contact time, pH, temperature and initial tryptophan concentration. The results show that levo compounds modified LDH trend to adsorb D-tryptophan, while L-tryptophan trend to be adsorbed by LDHs intercalated with dextrorotary compounds. The recognition process was confirmed to be a chemisorption process according to the kinetic studies. Separation of tryptophan from aqueous solution using DTTA-LDHs and DBTA-LDHs has been well described by pseudo-second-order kinetic model. The adsorption isotherms showed that the adsorption data fitted the Freundlich isotherm equations well. The thermodynamic parameters indicated that the adsorption process was a spontaneous and endothermic chemisorption process.
  Graphical abstract Highlights • Tartaric acid derivatives DTTA and DBTA were intercalted into LDHs. • DTTA-LDHs and DBTA-LDHs can be applied to separate tryptophan enantiomers. • Contact time, pH, temperature and the tryptophan concentration were investigated. • The recognition process was confirmed to be a chemisorption process.
  
  PubDate: 2013-04-12T23:04:49Z
Effect of doubly organo-modified vermiculite on the properties of vermiculite/polystyrene nanocomposites
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Vermiculite (Verm)/polystyrene (PS) nanocomposites were prepared by dispersing a doubly organo-modified Verm (DOVerm) in PS via in situ polymerization (DOVerm/PS 1/99, 3/97, 5/95, and 7/93 mass/mass ratios). The morphology of Verm/PS nanocomposites evolved three stages as the content of DOVerm decreased in the nanocomposites: intercalation at high filler content, intermediate state of intercalation to exfoliation, and exfoliation of Verm in PS matrix with a low filler content. The morphological changes of Verm/PS nanocomposites were confirmed by the X-ray diffraction (XRD) patterns and the transmission electron microscopy (TEM) images. Compared with the pure PS, the nanocomposites filled with Verm showed significant enhancements on thermal stability and dynamic mechanical properties. Interestingly, the nanocomposites filled with 1 and 7 mass% of DOVerm exhibited more pronounced effects of Verm on the properties. It was proved that the double organo-modification clearly enhanced the ultimate properties of the Verm/PS nanocomposites.
  Graphical abstract
  
  PubDate: 2013-04-12T23:04:49Z
Role of the interlayer space of montmorillonite in hydrocarbon generation: An experimental study based on high temperature–pressure pyrolysis
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  The interlayer clay–organic complex is an important clay–organic association in sedimentary environments. However, the effects of organic matter storage in the interlayer space of clay minerals on the thermal degradation of organics and the generation of hydrocarbons have not been investigated. In this study, montmorillonite (Mt) and 12-amoniolauric acid (ALA) were used to prepare an interlayer Mt–ALA complex and a Mt–ALA complex in which Mt and ALA were simply mixed. Pyrolysis experiments on the ALA and Mt–ALA complexes were conducted in a confined gold capsule system at a fixed temperature and pressure of 350°C and 36MPa, respectively. X-ray diffraction, elemental analysis and Fourier transform infrared spectroscopy were used to characterize the Mt–ALA complexes, and automatically controlled gas chromatography along with a pyrolysis furnace was used to detect the volatile components released during pyrolysis. In the absence of Mt, the pyrolysis of ALA yielded only a small amount of C1–5 hydrocarbons and CO2. The amounts of C1–5 hydrocarbons released from the pyrolysis of the interlayer Mt–ALA complex and the mixed Mt–ALA complex are approximately 43 and 5 times greater than the amounts released from ALA alone, respectively. The Brønsted acid sites in the interlayer space of Mt, which arise from the interlayer dissociated water, significantly promote the cracking of hydrocarbons through a carbocation mechanism, the isomerization of normal hydrocarbons and alkene–alkane conversion through hydrogenation, resulting in high i-alkane/n-alkane and alkene/alkane ratios in the pyrolysis products. The Lewis acid sites of Mt are primarily involved in the decarboxylation of ALA during pyrolysis and are responsible for CO2 generation.
  
  PubDate: 2013-04-12T23:04:49Z
Role of vermiculite and zirconium–vermiculite on the formation of zircon–cordierite nanocomposites
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  The Zr4+–vermiculites were studied in their new role of the zircon precursor in the clay minerals mixtures which were prepared for firing of the zircon–cordierite nanocomposites. Currently there is a lack of data available about the structure of Zr4+–vermiculites, on which this study was performed. The modeling of the arrangement of interlayer material in the Zr4+–vermiculite led to new findings that water molecules are attracted more strongly by Mg2+ cations than by Zr-tetrameric cations, and that both the tetrameric cations [Zr4(OH)14(H2O)10]2+ and [Zr4(OH)8(H2O)16]8+ may be present in the interlayer space of the Zr4+–vermiculites. Vermiculites from two different localities Czech Republic (Verm1) and from Brazil (Verm2) were intercalated using the zirconyl chloride (ZrOCl2–30% solution in HCl) and the prepared Zr4+–vermiculites were designated as Zr4+–Verm1 and Zr4+–Verm2, respectively. Influence of the Zr4+–Verm1 and Zr4+–Verm2 in the mixtures of clay minerals on the properties of zircon–cordierite nanocomposites were investigated by their comparison with the properties of the zircon–cordierite nanocomposites, which were prepared using saturation of the clay minerals mixtures containing Verm1 and Verm2 with the zirconyl chloride (ZrOCl2–30% solution in HCl). The zircon–cordierite nanocomposites fired from the clay mineral mixtures containing Zr4+–Verm1 and Zr4+–Verm2 showed a maximum porosity of P=58 and 60%, skeletal density SD=3.2 and 3.6, and the smallest pores with a median pores diameter MDP=18 and 15μm, respectively, in comparison with the zircon–cordierite nanocomposites fired from the clay mineral mixtures containing Verm1 and Verm2 and saturated with zirconyl chloride solution. The type of vermiculite Verm1 or Verm2 in the clay mineral mixtures did not affect the contents of the crystalline mineral phases in cordierite and zircon–cordierite nanocomposites.
  Graphical abstract
  
  PubDate: 2013-04-12T23:04:49Z
Photocatalytic degradation of humic acid in the presence of montmorillonite
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Humic acids (HA) representing the major fraction of the naturally occurring humic substances (HS) are composed of highly functionalized carbon rich polydisperse organic fractions. Clay minerals which are responsible for the transport of inorganic and organic contaminants constitute the main component of the dispersed inorganic material in natural waters. The understanding of interactions between humic substances and clay minerals is an important task for the achievement of an effective water treatment performance. The aim of this research was to investigate the influence of montmorillonite as a representative clay mineral on the TiO2 photocatalytic removal of humic acids as the model compound of natural organic matter. The interactions prevailing between humic acid, montmorillonite and TiO2 surface were assessed prior to the application of photocatalysis in order to address the adsorptive and photolytic behavior of humic acids. The changes attained in humic acid were described by UV–vis spectroscopic i.e. color forming moieties (Color436) and UV absorbing centers (UV365 and UV254), and dissolved organic carbon (DOC) contents. Application of the pseudo first order kinetic model revealed both an enhancement and retardation with respect to the applied montmorillonite dose. The overall effect of montmorillonite on the photocatalytic degradation of humic acid was also evaluated in terms of molecular size distribution profiles (0.45μm filtered fraction, 100kDa fraction, 30kDa fraction and 3kDa fraction) described by the specified and DOC normalized specific UV–vis parameters.
  
  PubDate: 2013-04-12T23:04:49Z
Novel nanocomposites based on reactive organoclay of l-tyrosine and amine end-capped poly(amide–imide): Synthesis and characterization
- Abstract: Publication date: May 2013
  Source:Applied Clay Science, Volumes 75–76
  
  In the present study, a series of nanocomposite materials were successfully prepared using a poly(amide–imide) (PAI) matrix and novel reactive organoclay as a reinforcing agent. The organoclay was synthesized from Cloisite Na+ and protonated form of l-tyrosine amino acid via ion-exchange reaction. It was confirmed by Fourier transform infrared spectroscopy, X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetry analysis techniques. An optically active PAI was synthesized via solution polycondensation reaction of N,N′-(pyromellitoyl)-bis-phenylalanine diacid chloride and 4,4′-diaminodiphenylether. Then it was end-capped with amine end groups near the completion of the reaction to interact chemically with organoclay. Organoclay/PAI nanocomposite films containing different amounts of organoclay were prepared via solution intercalation method through blending of organoclay with the PAI solution. The nanostructures and properties of the organoclay/PAI hybrids were investigated using different techniques. Thermogravimetry analysis results indicated that the addition of organoclay into the PAI matrix increased the thermal decomposition temperatures of the resulting hybrid materials. The presence of amino acids as a biodegradable segment in both novel organoclay and optically active PAI, made the resulting nanostructure materials susceptible for biodegradation.
  Graphical abstract
  
  PubDate: 2013-04-12T23:04:49Z
Synthesis and mechanical properties of novel composites of inorganic polymers (geopolymers) with unidirectional natural flax fibres (phormium tenax)
- Abstract: Publication date: Available online 8 April 2013
  Source:Applied Clay Science
  
  This study reports the synthesis and mechanical properties of new inorganic polymer (geopolymer) composites unidirectionally reinforced with 4–10vol.% natural cellulose-based fibres (NZ flax, phormium tenax). The geopolymer matrix was derived from dehydroxylated kaolinite-type clay. The mechanical properties of the fibre-reinforced composites improve with increasing fibre content, achieving ultimate flexural strengths of about 70MPa at 10vol.% fibre content. This represents a significant improvement on the flexural strength of the unreinforced geopolymer matrix (about 5.8MPa), and all the composites show graceful failure, unlike the brittle failure of the matrix. Scanning electron microscopy was used to study the morphology of the fibre-matrix regions and a combination of thermogravimetric analysis (TGA) and thermal shrinkage measurements of these composites suggests that despite the formation of microcracks due to water loss from the geopolymer matrix, the fibres are thermally protected by the matrix up to 400°C. The flax fibres do not appear to be compromised by the alkaline environment of the matrix, suggesting new possible applications for these low-cost simply prepared construction materials.
  
  PubDate: 2013-04-08T23:03:11Z
Effects of surfactant concentration on alkyl chain arrangements in dry and swollen organic montmorillonite
- Abstract: Publication date: Available online 6 April 2013
  Source:Applied Clay Science
  
  To investigate the effects of surfactant concentration on alkyl chain arrangements in dry and swollen organic montmorillonite (OMt), Na+-montmorillonite (Na+-Mt) was modified with cationic surfactants with different alkyl chain lengths, including tetradecyl-trimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB) and steartrimonium bromide (STAB), at a series of concentrations. The properties of dry and swollen OMt were characterized by thermal analysis and X-ray diffraction. Two kinds of novel arrangement of alkyl chains were found for dry CTAB-Mt. The surfactant polar head showed two arrangements when the CTAB concentration increased from 0.23 to 0.45 cation exchange capacity (CEC). The arrangement of the paraffin-type bilayer had a larger tilting angle at 1.93 CEC than that of reported research, leading to a maximum d-spacing of 5.81nm. For swollen CTAB-Mt in the solvent, the d-spacing first increased and then remained constant with increase in the amount of added CTAB. The swelling behavior was proposed, including three distinct stages: solvent-controlling stage, surfactant concentration-controlling stage, and alkyl chain length-controlling stage. The alkyl chain arrangements of dry and swollen OMt were further confirmed by TTAB-Mt and STAB-Mt.
  Graphical abstract
  
  PubDate: 2013-04-08T23:03:11Z
Untreated coffee husk ashes used as flux in ceramic tiles
- Abstract: Publication date: Available online 6 April 2013
  Source:Applied Clay Science
  
  The agro-industrial activities are responsible for the production of large amounts of solid wastes, which, so far, have found scarce reuse alternatives. Among the former, coffee bean beneficiation generates an equal amount of coffee husks whose highest reuse potential is as fuel. The resulting ashes are frequently an object of illegal covert disposal and a serious source of environmental impact. However, coffee husk ashes (CHA) are particularly rich in alkaline and alkaline-earth metals, and might be adequate to replace the traditional feldspars, which are used in high content as fluxes in clay-based ceramic formulations but are becoming scarce and costly. In this work, the fluxing effect of CHA additions to an industrial clay-based mixture was evaluated. Based on the characterization results and the mullite–silica–leucite phase diagram, additions of 5 to 20wt.% CHA were made to the clay-based mixture and the resulting compositions were evaluated after sintering at temperatures between 1100 and 1200°C (60min soaking time). The results obtained show that firing temperatures near 1180°C and ~10wt.% CHA addition lead to linear shrinkage, water absorption and flexural strength values that fall within the range specified by floor tile standards (NBR 13817, EN 176 and ISO 13006), requiring no significant changes in processing parameters. Coffee husk ashes can thus advantageously replace feldspars in the role of fluxing material, with the potential to reduce not only natural ceramic raw material consumption, but also production and landfill costs as well as waste disposal area requirements.
  
  PubDate: 2013-04-08T23:03:11Z
A critical review of laboratory and in-situ hydraulic conductivity measurements for the Boom Clay in Belgium
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  The Boom Clay has been investigated for more than 30years as a candidate host formation for the disposal of high-level and long-lived radioactive waste in Belgium. The very low hydraulic conductivity (on the order of 10−12 m/s) in combination with limited hydraulic gradients over the host formation (0.02–0.04) results in water flow in the Boom Formation being negligible and diffusion the dominant transport mechanism. The assessment of the long-term barrier function of the host clay formation in the framework of radioactive waste disposal requires rigorous quantitative characterization of key formation properties such as the hydraulic conductivity (K). Hydraulic conductivities of Boom Clay measured through various testing techniques in the laboratory, i.e. tracer percolation experiments, constant head permeameter experiments and isostatic experiments, exhibit similar K values in the order of 10−12 m/s. Based on a large set of test samples, the impact of sample scale, hydraulic gradient range adopted in the tests, stress controlled methods and pre-existing fissures in the sample on the K value is shown to be quite limited. In situ measurements obtained from both several-centimetre long piezometer filters and percolation into a 7-metre long gallery and 21-metre long shaft at the HADES underground research facility yield K values that are very similar to values measured in the laboratory on samples of a few centimetres. This indicates that the K measurements for the Boom Clay obtained through various techniques are very consistent. K values measured on a centimetre-scale are also representative at the metre-scale, which is often the size of grid cells used in numerical simulations for long-term safety assessments. Spatial analysis of K values across the Boom Clay at the Mol site reveals a typical profile with a very homogenous 61-m thick central part, i.e. the so-called Putte and Terhagen Members, which is also the least permeable part of the Boom Clay. The geometric mean of the vertical (Kv ) and horizontal (Kh ) hydraulic conductivities for the Putte and Terhagen Members at the Mol site are 1.7×10−12 and 4.4×10−12 m/s, respectively, with a vertical anisotropy Kh /Kv of about 2.5. Higher K values, but still low (10−12 to 10−10 m/s), are observed in the more silty zones above and below the Putte and Terhagen Members, i.e. the Belsele–Waas Member and the Boeretang Member, as well as in the double band of the lower Putte Member. A regional analysis of vertical K variability of the Boom Clay in the northeast of Belgium based on test results from five boreholes shows an increase in hydraulic conductivity from the east towards the west. Statistical analyses indicate that the effect of the samples' stratigraphic position on hydraulic conductivity is strongly related to different grain-size characteristics. However, a general K–grain-size model does not explain the geographical differences in K values satisfactorily. Geographical differences can be best explained by different K–grain-size relationships at the different boreholes. The regional variation in K could be attributed in part to porosity, which in turn is related to the burial depth of the clay.
  
  PubDate: 2013-04-05T08:04:45Z
Analysis of non-linear consolidation of soft clay by differential quadrature method
- Abstract: Available online 3 April 2013
  Publication year: 2013
  Source:Applied Clay Science
  
  Due to the complexity of the non-linear consolidation of soft clay, numerical method is always adopted to its solution. The differential quadrature method (DQ method) equaling to a high precision finite difference method can obtain highly accurate numerical solutions of differential equations using less grid points. This numerical method is always used to solve the complicated nonlinear physical problem governed by partial equations. In this paper, DQ method is implemented to one dimensional non-liner consolidation equation and the boundary conditions. Euler forward scheme is used to solve the discrete equation, and the pore pressure and consolidation curves are prepared. The present numerical results are compared with the analytical solutions. Compared with the other numerical method, the method of solving the non-linear consolidation equation by the DQ method in this paper is very simple and reasonable. The DQ method is successfully implemented to the soft clay consolidation analysis and can assure satisfied numerical results with less grid points.
  Graphical abstract Highlights
  
  PubDate: 2013-04-05T08:04:45Z
Strategies for the successful preparation of homoionic smectites
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Many chemical, mechanical and thermal properties of smectites depend on the interlayer cations. Therefore, homoionic exchanged smectites are prepared in order to investigate the reaction exchange mechanisms and to improve their behavior as function of the interlayer cation. Presently no general protocol exists and many of the suggested procedures lack proof of achieved exchange. Thus, the aim of the present study was to depict strategies and to determine factors for successful preparation of homoionic smectites. Three natural bentonites and one purified bentonite were saturated by different compensator cations using different (Na+, Li+, K+, Ca2+, Mg2+, Cu2+, or Zn2+) chloride solutions. Concentration of the cations in solution varied between 1 and 20 times of CEC. The exchange was repeated one to three times. Extent of smectite interlayer saturation was studied by measurements of cation exchange capacity (CEC) and subsequent determination of the exchanged interlayer cations. Chemical properties of used solution salts influence pH and the surface properties of the smectites. As a result CEC of the smectites was altered by changing contribution from edge charges. It is established that divalent cation exchange was more successful than monovalent cation exchange (Bergaya et al., 2006). Moreover, fractions of high charged 2:1 layers could also hinder homoionic exchange. Finally, successful cation exchange reaction was strongly influenced by soluble accessory minerals and experimental setup. It was found that there is no simple recipe which is equally applicable for all smectites and bentonites, but there is a general protocol considering the following parameters: mineral composition of the sample, smectite CEC and/or layer charge, chemical and mechanical pretreatment, initial interlayer cations, type and concentration of saturating salt, solid–liquid ratio, reaction time, number of repetitions and washing procedure. Finally, proof of interlayer occupation is mandatory.
  
  PubDate: 2013-04-05T08:04:45Z
Nanocomposites of halloysite and polylactide
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Naturally occurred halloysite (Hal) nanotubes compounded with polylactide (PLA) via melt mixing formed biodegradable and biocompatible clay polymer nanocomposites (CPN). The hydrogen bonding interactions between Hal and PLA were confirmed by Fourier transform infrared spectroscopy (FTIR). The modulus, strength and toughness of the Hal-PLA nanocomposites were substantially higher than those of neat PLA. Storage modulus and glass transition temperature of the Hal-PLA nanocomposites also increased with Hal loading as observed by dynamic mechanical analysis. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that Hal was uniformly dispersed and oriented in the CPN. X-ray diffraction (XRD) of the CPN showed the absence of Hal reflection at around 20°, indicating interactions of the PLA molecular chains in the interlayer space of Hal. Hal could nucleate PLA, leading to the decreased cold crystallization temperature and increased crystallinity. The vicat softening temperature and the degradation temperature of the CPN increased with Hal loading. Owing to the high performance and biocompatibility of the CPN, the prepared Hal-PLA nanocomposites had potential applications in biodegradable plastic and biomedical areas.
  Graphical abstract
  
  PubDate: 2013-04-05T08:04:45Z
Composition and mechanical characteristic of riverbed soil in lower Yellow River
- Abstract: Available online 3 April 2013
  Publication year: 2013
  Source:Applied Clay Science
  
  Yellow River is a typical wandering channel with large sediment content. Lack of systemic data about composition of riverbed and indexes of mechanical characteristic, the influence of composition and indexes of mechanical characteristic of riverbed was considered difficultly in physical and mathematical models. Mechanical characteristic of soil considered, identification standard of soil layer about riverbed was carried out based on strength resistance of cone tip and the ratio of friction resistance between lateral cone and cone tip, and comparative analysis is worked out with identification standard of indoor geotechnical test. Taking the typical wandering section of river from Baihe to Yiluo outfall as the example, cone penetration tests were carried out and indoor tests were worked out. Firstly, huge data about composition and mechanical characteristic of riverbed are achieved, it shows that the main components of riverbed in lower Yellow River are silty clay, silty loam, sandy loam, sand and so on. Secondly, physical and mechanical indexes of riverbed soil keep strong regularity. Finally, formation cause and change trend are achieved through the basic data of riverbed soil, thus it will improve the development of technology of (Line No. 1) physical model and numerical method for river research (Line No. 2).
  Graphical abstract
  
  PubDate: 2013-04-05T08:04:45Z
Influence of the powder dimensions on the antimicrobial properties of modified layered double hydroxide
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Nano-hybrids of layered double hydroxides (LDHs), or hydrotalcite-like compounds, containing the antimicrobial anions of o-hydroxybenzoate (o-BzOH), also known as salicylate, were synthesized by a direct coprecipitation method. Elemental analysis indicated the chemical formula [Zn0.65Al0.35(OH)2] (C7H5O3)0.35 ∗0.7 H2O with a value of the molar fraction x=MIII/MIII +MII of 0.35. FT-IR spectroscopy and X-ray diffractograms confirmed the presence of o-hydroxybenzoate anions into the clay galleries, and indicated the presence of small size and disordered crystallites. The initial powder dimensions, reported as “surface weighted mean”, D[3,2], were reduced by using high energy ball milling (HEBM) technique for 1min, 2min, and 5min. Also the morphology, investigated by SEM, was influenced by HEBM: big agglomerated particles were found for the pristine samples, while well-defined platelets with uniform and thinner size were present in the milled samples. The release of the o-hydroxybenzoate anion into a saline solution was measured for the initial powder with 25.0μm of D[3,2] and for the powder with the smallest dimensions (D[3,2]=8.2μm). It was observed that the lower the powder dimensions the higher the percentage of active anions released into the saline solution. Also the diffusion parameter was found higher for the lower dimension powders. The antimicrobial activity against Escherichia coli was found much more effective for the sample with the lower powder dimensions, and even a slow but progressive reduction was noted after 24h. In the presence of particles of 8.2 μm the microbial growth after 96 h of incubation is not evident.
  
  PubDate: 2013-04-05T08:04:45Z
Adsorption of bacteria onto layered double hydroxide particles to form biogranule-like aggregates
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Biogranulation is a key process in biological treatment of wastewater, which forms biogranules from the agglutination of bacteria and suspended solid in wastewater. In this paper, the adsorption behaviors of bacteria onto layered double hydroxides (LDH) are investigated, and the biogranulation mechanism between bacteria and LDH particles is elucidated. It is found that NiFeCO3-LDH is able to absorb 45–55mg/g of Bacillus subtilis under various conditions. The adsorption follows the first-order Lagergren model. Scanning electron microscope (SEM) images support the formation of bacteria-LDH aggregates. Mechanism study shows that electrostatic interaction between LDH and bacteria should be the most important for the adsorption of bacteria onto LDH. Furthermore, one bacterium adhering to a few LDH particles is suggested, which maximizes the interactions between bacteria and LDH particles. The present results provide a possible means for biological treatment of wastewater through bacterial granulation with LDHs.
  Graphical abstract Highlights ► The feasibility of improving sludge granulation by Ni/Fe LDH was investigated. ► The structural characteristics of bacteria-LDH aggregates were examined. ► The effect of temperature, pH and ionic strength on the adsorption was revealed. ► The mechanism was postulated to bacteria & LDH's structural and compositional.
  
  PubDate: 2013-04-05T08:04:45Z
Peloids and pelotherapy: Historical evolution, classification and glossary
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  Targets, concepts, principles, methods, historical evolution, interactions with other sciences, systems, and implications on society are common fundamentals to any science or scientific field. With regard to concepts they can be expressed differently by people from different educational backgrounds and experiences, but preserving the fundamental ideas. Concepts can also evolve over times. This paper shows the changes undergone by the concept of peloid since the creation of this term and meaning in 1933, and the arguments that justified those changes. Also, the systems or classifications of peloids have evolved since the first classification proposed in 1937. This paper shows the classifications which have been proposed since then and the fundamentals on which they were based upon. Also a new, short and concise definition and classification of peloids are proposed. Relevant inconsistencies are found in the scientific literature regarding both nomenclature and definition of terms used in health resort medicine or spa therapy, skin care, balneology, balneotherapy, hydrotherapy, mud therapy, pelotherapy, thalassotherapy, climatology, and climatotherapy. Even the international general acceptance of these methods and terms is not fully recognized. A glossary with the terms and corresponding technical definitions does not exist. A glossary in English, the idiom worldwide used for science communication, prepared by an ad hoc Working Group constituted by the authors of the present paper is herewith proposed.
  Highlights ► Historical evolution of peloid definition and proposal of a new peloid definition ► Peloid typology and historical evolution of peloid classification ► Differentiation between natural peloid, peloid, mud therapy and peloid therapy ► Differentiation between medical peloid and cosmetic peloid ► Glossary of terms used in mud therapy and peloid therapy
  
  PubDate: 2013-04-05T08:04:45Z
Characterization and friction performances of Co–Al-layered double-metal hydroxides synthesized in the presence of dodecylsulfate
- Abstract: May 2013
  Publication year: 2013
  Source:Applied Clay Science, Volumes 75–76
  
  In this paper, Co–Al-layered double-metal hydroxides (CAD-LDHs) were synthesized by co-precipitation in the presence of dodecylsulfate (DDS) and characterized by XRD, FT-IR, TG–DSC, SEM. In addition, their frictional features were evaluated by four-ball friction tester, gear tester and air compressor. The results showed that synthesized CAD-LDHs have a hexagonal platelet morphology. Most crystallites have a disk diameter of around 150–250nm and a thickness of about 20nm, with a 0 = b 0 =0.31nm, c 0 =8.33nm, d-spacing=2.78nm and gallery height=2.30nm. The specific surface area is 78m2/g. DDS anions entered the interlayer of LDHs and were perpendicular to the LDH layer in a monolayer array. As a lubricant, CAD-LDH powder has excellent dispersability and suspension stability in the lubrication oil, and can significantly reduce friction coefficient (50.7%) and wear of friction pairs (17.9%). At the same time, they can reduce the temperature of lubrication oil (6.1%) and power consumption of driving motor (2.6–6.8%). Accordingly, CAD-LDHs may broadly be used as lubrication and anti-frictional materials.
  
  PubDate: 2013-04-05T08:04:45Z
Effective concentration of dichromate anions using layered double hydroxides from acidic solutions
- Abstract: Available online 26 March 2013
  Publication year: 2013
  Source:Applied Clay Science
  
  Chromate anion was effectively concentrated on an anion exchanger, layered double hydroxide (LDH), from aqueous solution. The LDHs used in this study were synthesized by hydrothermal reactions using urea hydrolysis as reported previously (Ogawa and Kaiho, 2002). The ion exchange was conducted at pH=3 to concentrate larger amount of dichromate (Cr2O7 2−). The adsorption isotherms indicated the strong interactions of chromate anions with LDHs. Among the tested LDHs (MgAl, NiAl, CoAl, and LiAl-LDHs), LiAl-LDH gave the best result in terms of the adsorbed Cr amount. Since the reaction was started from carbonate forms of layered double hydroxides, only the carbonate anions are released to the environment after the anion exchange. All these facts indicated that the present layered double hydroxides are promising materials for the environmental remediation from Cr contaminated water. If compared with commercially available LDHs and those synthesized by the conventional co-precipitation methods, the LDHs synthesized by hydrothermal reaction using urea hydrolysis were shown to be superior because of the stability and the ease of solid–liquid separation after the ion exchange.
  Graphical abstract Highlights ► Effective adsorption of chromates from water on layered double hydroxides was achieved. ► The adsorption capacity of chromates on layered double hydroxides is very high. ► The adsorption of dichromate was preferred from acidic aqueous solution at pH of 3. ► The layered double hydroxides used in this study are stable in acidic solutions.
  
  PubDate: 2013-03-28T00:03:42Z
Characterization of alkali activated kaolinitic clay
- Abstract: Available online 14 March 2013
  Publication year: 2013
  Source:Applied Clay Science
  
  Low cost building materials have been developed by chemical activation of Jordanian Hiswa kaolinite with a sodium hydroxide solution. The effect of the main parameters of synthesis and processing on the development of compressive strength was studied. An investigation of the physical, thermal, mineralogical and microstructural properties was performed. A compressive strength of 32MPa was obtained for a mixture cured at 80°C for 24h. The mineralogical and microstructural results on the hardened material indicate the formation of sodium zeolite phases and feldspathoids with a Na/Al ratio of one. The high compressive strength observed is directly related to the formation of the new phases that fill the pore spaces and bind the matrix.
  Highlights ► Kaolinite can be alkali activated. ► Zeolite-like reaction products are formed. ► Compressive strengths above 40MPa can be obtained. ► The environmental impact (CO2 emission) is smaller than for geopolymers.
  
  PubDate: 2013-03-16T00:03:15Z