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Showing 1 - 200 of 1205 Journals sorted alphabetically
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Journal Cover
Applied Clay Science
Journal Prestige (SJR): 0.992
Citation Impact (citeScore): 4
Number of Followers: 6  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0169-1317
Published by Elsevier Homepage  [3162 journals]
  • Corrigendum to “A molecular dynamics framework to explore the structure
           and dynamics of layered double hydroxides” [Appl. Clay Sci., 163,
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Germán Pérez-Sánchez, Tiago L.P. Galvão, João Tedim, José R.B. Gomes
  • Impact of field conditions on the strength development of a geopolymer
           stabilized marine clay
    • Abstract: Publication date: Available online 13 October 2018Source: Applied Clay ScienceAuthor(s): Mohammadjavad Yaghoubi, Arul Arulrajah, Mahdi Miri Disfani, Suksun Horpibulsuk, Stephen Darmawan, James Wang A soft marine clay was stabilized with fly-ash (FA) and slag (S) based geopolymers. FA and S with combined contents of 10, 20 and 30% were added to the soft clay and activated with a liquid alkaline activator (L) at various contents. The clay was a marine clay which was dominated by quartz, illite and feldspar. The effect of a number of preparation and curing factors including water content and temperature variation, wetting-drying cycles and mixing time and method were evaluated. The objective of this research was to evaluate the effect of these factors that are likely to occur in ground improvement applications, such as deep soil mixing, on the unconfined compressive strength (UCS), microstructure and mineralogy of the mixtures. Results showed that increasing the FA + S content increased the UCS values significantly through the geopolymerization process, which was evident when increasing the FA + S content from 10% to 20%. Moreover, higher UCS values were achieved when the curing temperature was increased and the strength development was accelerated as a result of accelerated precipitation of FA and S. Furthermore, strength development was enhanced when the L/(FA + S) ratio was increased from 0.75 to 1.0, followed by a decrease at L/(FA + S) ratio of 1.25. Similar trends of strength development were observed by varying the water contents of 0.75, 1.0 and 1.25 liquid limit (LL) of the soil. The increased amount of liquid, L and water, caused less favorable environment, such as lower L molarity and less particle contact, for proper strength development. The UCS values decreased for up to 6 cycles of wetting and drying, where the geopolymeric network was not sufficiently stable, and remained almost constant afterwards. Increasing the mixing time caused more dissolution of FA and S, which resulted in enhancement of the UCS values. Adding FA + S and L to the soil separately resulted in higher UCS values compared to when FA + S and L were mixed together initially and then added to the soil. The microstructure and mineralogy analyses indicated that increasing the curing temperature, as well as the L/(FA + S) ratio resulted in more dissolution of FA and S and formation of calcium sodium aluminum silicate hydrate (CNASH) products.
  • Study on corrosion behavior of low carbon steel under different water
           conditions in bentonite of China-Mock-Up
    • Abstract: Publication date: Available online 12 October 2018Source: Applied Clay ScienceAuthor(s): Xin Wei, Yuemiao Liu, Junhua Dong, Shengfei Cao, Jingli Xie, Nan Chen, Fang Xue, Changgang Wang, Wei Ke In China-Mock-Up, the transition of water conditions in bentonite and its influence on the corrosion behavior of four low carbon steel electrochemical sensors buried in bentonite along horizontal direction were investigated by in situ electrochemical impedance spectroscopy (EIS) with the infiltration of groundwater from outside to inside. The results show that in the initial stage of EIS measurement, water in bentonite around the electrochemical sensors from outside to inside is hygroscopic water and chemical bonding water successively. With increasing time, water in the outer bentonite transforms from hygroscopic water to free water. Meanwhile, water in the inner bentonite transforms from chemical bonding water to hygroscopic water. As water in bentonite exists as the chemical bonding water, the equivalent circuit can be described as a pure capacitor, which does not cause the corrosion of low carbon steel. When water in bentonite exists as hygroscopic water, it can be described as a circuit consisting of two leakage capacitors in series, which causes the slight corrosion of the steel. While, in the presence of free water, the equivalent circuit can be described as a free water resistance and two leakage capacitors in series, which causes the serious corrosion of the steel.
  • Photocatalytic degradation of trimethoprim on doped Ti-pillared
    • Abstract: Publication date: Available online 12 October 2018Source: Applied Clay ScienceAuthor(s): Beatriz González, Raquel Trujillano, Miguel A. Vicente, Vicente Rives, Sophia A. Korili, Antonio Gil Montmorillonite pillared with titanium and doped with Cr3+ or Fe3+ has been tested for the photo-degradation of the antibiotic trimethoprim (trimethoxybenzyl-2,4-pyrimidinediamine) under different conditions, namely, in the dark or in UV light, with or without catalyst, finding excellent catalytic performance under photocatalytic conditions. The degradation by-products were preliminary analysed by mass spectrometry. The results suggested that the molecule broke in two halves, corresponding to its two existing rings. The process continued with the breakage of new fragments from the trimethoxybenzene half, these fragments later reacted with the methoxy groups in this part of the molecule, giving species with m/z values higher than that for the starting molecule, and with the breakage of new fragments.
  • Adsorption of reactive red 136 onto chitosan/montmorillonite intercalated
           composite from aqueous solution
    • Abstract: Publication date: Available online 10 October 2018Source: Applied Clay ScienceAuthor(s): Jin Li, Jun Cai, Lian Zhong, Huali Cheng, Han Wang, Qimin Ma Chitosan/montmorillonite intercalated composite (CTS/MMT) was used as an effective adsorbent for removal of reactive red 136 (RR136). Taguchi method attached grey relational analysis was applied to determine the optimal adsorption conditions, including pH, initial concentration of dye, temperature, adsorbent dosage and contact time, for achieving simultaneous maximization of removal percentage and adsorption capacity. The percentage contribution of each adsorption condition was determined in the analysis of variance and shown that the most effective parameter is initial concentration of dye. The optimal adsorption conditions were found in pH 3, initial concentration of dye 240 mg/L, temperature 20 °C, adsorbent dosage 0.4 g/L and contact time 135 min. Under the optimal condition, the removal percentages and adsorption capacity were 74.7% and 445.38 mg/g, respectively. The adsorption behaviors showed that the adsorption isotherms and kinetics were in best agreement with the Toth isotherm and Brouers-Weron-Sotolongo model, respectively. Applicability of mechanistic models exhibited that film diffusion and intra-particle diffusion were involved in the current adsorption processes and intra-particle diffusion was not the only rate-controlling step. CTS/MMT before and after adsorption were characterized through FT-IR, XRD and SEM. The results indicated that the RR136 adsorption process was not only surface adsorption but intercalation, and OH, CONH2, NH2 and SiO group of CTS/MMT were involved in the adsorption process. Moreover, the desorption and regeneration experiments revealed CTS/MMT showed excellent adsorption performance even after 15 adsorption-desorption cycles.
  • Determination of loamy resources impact on granulation of ceramic
           proppants and their properties
    • Abstract: Publication date: Available online 10 October 2018Source: Applied Clay ScienceAuthor(s): Joanna Szymanska, Pawel Wisniewski, Paulina Wawulska-Marek, Jaroslaw Mizera Currently, the global oil & gas sector is focused on enhanced natural gas exploration from unconventional rock formations. The potential deposits are located within large-scale basins of impermeable shales (hydrocarbons accumulated in closed pores) with plastic zones at great depths with high reservoir pressure. These severe geological conditions determine the application of granulated propping agents, named “proppants”. They are pumped with hydraulic fluid during hydraulic fracturing and subsequently locate tightly inside created rock fractures. Proppants function as a prop to facilitate gas flow up the wellbore. Quartz sands are applied mainly for low pressure basins. However, only ceramic proppants, granules produced from raw clays in a mechanical granulation and sintering process, are proper for deeper shales due to their homogeneity, higher sphericity, and mechanical and chemical stability.Aim of this research was verification of the impact of natural loamy resources (aluminosilicates in powder form) mixed with binder on ceramic proppants quality. Utility of the clays was estimated by their particle size distribution (PSD by laser diffraction method) and thermal stability (thermogravimetry - TGA). The unique platy morphology was determined by scanning electron microscopy (SEM), while energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF) and X-ray diffraction (XRD) revealed chemical-phase composition. Moreover, aluminosilicates were subjected to analysis of specific surface area (BET method) – very crucial for powder consolidation into granules in mechanical granulation.Quality of the granulated, and consequently sintered, bodies was evaluated by calculations of roundness and sphericity coefficient, specific gravity and bulk density, combined with microtomography (μCT) - a key investigation of porosity and proppant settlement in fracture. SEM studies also revealed phase transitions due to high temperature exposition of the green proppants and the correlation with proppant strength, evaluated in crush tests. Moreover, measurements of turbidity and solubility in acids revealed risk of the granules' decay in the shale gas wells.The obtained outcomes show dependence of the proppant's structure on the binder and the loamy materials ratio, proving the utility of the applied natural resources in the granules production. In consequence, these proppants can be used for hydraulic fracturing in severe mining conditions in accordance to the strict international ISO standards.Graphical abstractUnlabelled Image
  • Assembling polypyrrole coated sepiolite fiber as efficient particle
           adsorbent for chromium (VI) removal with the feature of convenient
    • Abstract: Publication date: Available online 9 October 2018Source: Applied Clay ScienceAuthor(s): Qi Zhou, Junlong Huang, Xing Zhang, Yun Gao To overcome the inherent defect of particle adsorbent that difficult to be recycled from waterbody, a new adsorbent was successfully prepared based on the surface polypyrrole (PPy) functionalized sepiolite fiber (SEP), with properties of magnetism and floatation. This adsorbent can be recovered easily from water surface by a magnet. The resultant MSEP/PPy retains the feature of sepiolite fiber template, along with a large surface area to have more surface adsorption sites. Batch experiment shows the experiment data is in good agreement with the pseudo-second order kinetic and Langmuir isotherm model. The adsorption mechanism reveals that the ion exchange occurs between Cl− and Cr(VI), followed by the reduction of Cr(VI) to Cr(III) via the surface PPy moiety. Additionally, most of the adsorption capacity of the adsorbent can be maintained in the cyclic regeneration, ranging from 87.93 to 58.36 mg/g even in the incomplete desorption.Graphical abstractUnlabelled Image
  • The pH influence on the intercalation of the bioactive agent ciprofloxacin
           in fluorohectorite
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): E.C. dos Santos, W.P. Gates, L. Michels, F. Juranyi, A. Mikkelsen, G.J. da Silva, J.O. Fossum, H.N. Bordallo Biocompatible encapsulated drug delivery materials are highly desired as they provide for controlled release of bioactive agents, thereby improving the effectiveness of medical treatments. Some of the key properties of better materials for drug delivery include high adsorptive capacity, which can be realized by smectites, a family of clay minerals. Here the influence of pH on encapsulation of the bioactive molecule ciprofloxacin (CIPRO), an antibiotic, by fluorohectorite (FHt), a synthetic smectite, was investigated. Aspects of the clay structure itself were also investigated. By means of X-ray powder diffraction (XRD), thermogravimetric analysis coupled to Fourier transform infrared spectroscopy (TGA/FTIR) and inelastic neutron scattering (INS), it is demonstrated that the capture of ciprofloxacin is more efficient at acidic pH. Geometric considerations based on the XRD results and mass calculations based on the TGA results provided evidence that at acidic pH, the CIPRO-FHt complex contained one CIPRO molecule per unit cell, while at neutral pH the CIPRO content was about half, despite having similar interlayer volume available. Finally it is shown that adsorption of CIPRO by FHt facilitated removal of residual water from the interlayer, providing additional evidence that intercalation is the main adsorptive mechanism at acidic pH. These results lead to a deeper understanding concerning the capture of amphoteric drug molecules by smectites, as well as concerning their molecular interactions, which may lead to more feasible application of clay minerals as a carrier for drug molecules.
  • Pore water salinity effect on the intrinsic compression behaviour of
           artificial soft soils
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Yongfeng Deng, Tongwei Zhang, Yujun Cui, Yonggui Chen, Tingting Deng, Xiaorong Zhou The framework of the intrinsic compression behaviour of normally consolidated soft clay proposed by Burland (1990) is widely adopted in engineering practices. However, further investigations should be conducted on its validity in the coastal and offshore environments to verify the effect of pore water salinity. In the present work, oedometer tests were performed on remoulded artificial soft clays (mixtures of kaolin and bentonite with 0%, 5%, 10%, and 20% of bentonite by mass). The artificial clays were salinized with sodium chloride solutions at concentrations 0 mol/L (distilled water), 0.17 mol/L, 0.51 mol/L, 0.86 mol/L, and 1.70 mol/L at water contents equal to 1.0–1.5 times of the liquid limits. The results showed that the ‘intrinsic’ properties of clays, including the compression index Cc⁎(100–1000 kPa), void ratio e100*, and compression line based on the void index Iv, changed with the pore water salinity. Following the empirical correlation proposed by previous researchers, the decrease in Cc⁎ caused by pore water salinity could be generally characterised by the liquid limit and void ratio at the liquid limit (eL). The dispersed correlation between the predicted e100⁎ and the experimental results in this study were caused by the significant changes in e0/eL controlled by pore water salinity. The relationships between void index Iv and vertical stress σv’ deviated from the intrinsic compression line (ICL) under the saline environment. For the artificial clay rich in smectite, the slopes of Iv–log σv’ before yielding increased with pore water salinity at the initial water content. Pore water salinity affected the intrinsic compression behaviour of soft clays primarily composed of kaolinite to a lesser extent.
  • Combined thermal and saline effects on the swelling pressure of densely
           compacted GMZ bentonite
    • Abstract: Publication date: Available online 6 October 2018Source: Applied Clay ScienceAuthor(s): Yong-Gui Chen, Xin-Xin Dong, Xu-Dong Zhang, Wei-Min Ye, Yu-Jun Cui Sufficient swelling pressure of compacted bentonite upon wetting is necessary to provide long-term stability to an engineered barrier system under conditions of thermal gradient and variable water chemistry in a high-level radioactive waste repository. To investigate the combined thermal and saline effects on the swelling pressure of Gaomiaozi (GMZ) bentonite, constant-volume swelling pressure tests were performed on densely compacted specimens inundated with deionized water, NaCl, and CaCl2 solutions at 20 °C and 60 °C. The results indicate that high temperature and saline solutions decrease the swelling pressure. Crystalline swelling dominates the constant-volume swelling of densely compacted bentonite. For a given cation type, a higher temperature or higher solution concentration resulted in a lower swelling pressure. The decreasing surface potential and increasing osmotic suction with solution concentration both weaken the clay swelling. The effects of temperature on the swelling pressure are explained by the role of the lattice contraction. The degeneration of the interlamellar adsorbed water at high temperature weakens the crystalline swelling. The effects of cation types are interpreted by their difference in chemical activity. Ca2+ ions possess higher exchange capacity and larger hydrated radius than those of the Na+ ions. When densely compacted Na-bentonite is wetted with CaCl2 solution, the possible change of the interlamellar cations from Na+ to Ca2+ ions would promote the crystalline swelling. The osmotic suction imposed by CaCl2 solution may offset the role of the cation exchange to a small extent. The effect of temperature on the swelling pressure exceeds that of the cation types. For a given solution concentration, the specimen wetted with NaCl solution developed lower swelling pressure than that with CaCl2 solution at 20 °C, whereas the opposite tendency appeared at 60 °C. In addition, specimens saturated with deionized water and NaCl solution at 20 °C obtained insignificant difference in pore size distribution, whereas identifiable differences in pore size distribution occured at 60 °C. The combined thermal and saline effects on the swelling pressure may be explained by the role of the lattice contraction at varied clay structure. When CaCl2 solution is used, the quasicrystals contain more montmorillonite layers than the case of the NaCl solution. The role of the lattice contraction at high temperature is expected to decrease the swelling pressure to a greater degree in the case of the CaCl2 solution. The remarkable increase in the osmotic suction at high temperature and high solution concentration could also enlarge the decrease in the swelling pressure. These conjectures, however, still require quantitative interpretations via microscopic tests such as X-ray powder diffraction tests on bulk samples.
  • Changes in the structure and porosity of hollow spherical allophane under
           alkaline conditions
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Shun Wang, Peixin Du, Peng Yuan, Xuemin Zhong, Yaqi Liu, Dong Liu, Liangliang Deng This work investigated changes in the chemical composition, structure and porosity of hollow spherical allophane under alkaline conditions, which are significant not only for understanding its fate in natural environment but also for its functional applications. Hollow spherical allophane with a silicon/aluminium (Si/Al) molar ratio of 0.77 was hydrothermally synthesised followed by treatment with dilute sodium hydroxide (NaOH) solutions with different concentrations (indicated by pH values). The allophane and its alkali-treated products were then characterized using a combination of techniques, such as Fourier-transform infrared spectroscopy, nuclear magnetic resonance and nitrogen physisorption analysis. Allophane showed a weak structural stability in alkaline conditions. At pH ≤ 11.0, the framework of allophane particles was almost intact; its polymerised silicates showed only slight dissolution. At a higher pH (> 11.0), desilication and dealumination enhanced, resulting in the destruction of the imogolite local structure (ImoLS) along the edges of defect pores and the formation of amorphous materials. Most of the defect pores increased in size, becoming accessible to nitrogen and the textural parameters of the micropores reached their maximum values at a pH of 12.5. However, the damage to some secondary pores and the collapse of some hollow spherules reduced total pore volume (Vtotal). At a pH of 13.0, most of the hollow spherules were observed to have collapsed, resulting in remarkable decrease in the textural parameters. However, some unbroken and/or mildly broken allophane particles might remain, deduced from the relatively high BET specific surface area (SSA) and Vtotal and the considerable proportion of micropores for Allo13.0. These results reveal the dissolution behaviour of allophane in alkaline conditions and the mechanism underlying this behaviour, providing essential insights into the mineral's potential applications.
  • Preparation and characterization of ultra-thin poly ether block
           amide/nanoclay nanocomposite membrane for gas separation
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Zahra Amini, Morteza Asghari Supported Mixed Matrix Membrane (SMMM) Polyether block amide/nanoclay (PEBA/Cloisite 30b), based on Polyacrylonitrile on nonwoven Polyester (PAN/PE), was fabricated by the spin coating method, following optimization of fabrication conditions for Single-Layer Mixed Matrix Membranes (SLMMMs). Cloisite 30b is a type of montmorillonite modified from nanoclays family. The fabricated membranes were examined structurally through The X-ray Diffraction (XRD), The Field Emission Scanning Electron Microscopy (FESEM), The Fourier-transform infrared spectroscopy (FTIR), and The Atomic force microscopy (AFM) analyses, and evaluated operationally by conducting permeability tests of the pure gases of CO2, CH4 and N2. The effect of different Cloisite 30b loadings and the varying pressures on the gas separation performance of the membranes was investigated. Elevation of the loading up to 0.2 wt% Cloisite 30b increased the permeability and the selectivity, whereas further increase up to 1 wt% reduced the permeability and selectivity. After an increase in pressure from 4 to 14 bar, an elevated permeability and selectivity was observed. The membrane with a Cloisite 30b loading of 0.2 wt% had the best performance in the separation of the pure gases of CO2, CH4, and N2 such that the permeability of CO2, along with the selectivity of CO2/N2, and CO2/CH4 had increase of about 55.55%, 26.45% and 38% in comparison with the Single Layer Neat Membrane (SLNM). The permeability of CO2, the selectivity of CO2/N2, and the selectivity of CO2/CH4 of SMMM with a Cloisite 30b loading of 0.2 wt% also indicated an increase of about 364%, 18% and 47.8% in comparison to the Supported Neat Membrane (SNM). Furthermore, CO2 permeability through SMMM with cloisite30b loading of 0.2 wt% indicated a growth of about 562.5% in comparison to SLMMM with the same loading.Graphical abstractUnlabelled Image
  • Alkali activation behaviour of un-calcined montmorillonite and illite clay
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Alastair Marsh, Andrew Heath, Pascaline Patureau, Mark Evernden, Pete Walker Using alkali activation, un-calcined soils have potential as precursors for low carbon, low cost, geopolymer-stabilised construction materials. This technology has been recently promoted as a lower impact alternative to cement stabilisation for walling materials in construction around the world. There is a lack of fundamental understanding around the alkali activation of un-calcined montmorillonite and illite, which, along with kaolinite, are clay minerals commonly found in soils. Kaolinite, as a 1:1 clay mineral, has been shown to form crystalline hydrosodalite when alkali-activated, but 2:1 montmorillonite and illite could form stronger geopolymer structures due to the higher Si:Al ratio in the precursor mineral. The lack of understanding of the underlying mechanisms at work with 2:1 clay minerals is a barrier to knowing how viable un-calcined geopolymer stabilised soil materials are for the range of soil types found in nature. In this study, montmorillonite and illite precursors were activated with a range of sodium hydroxide concentrations, compacted, and then cured at 80 °C for 24 h. The cured samples were characterised using a variety of advanced analytical techniques, including powder XRD, SEM, TGA, 27Al and 29Si-MAS-NMR, and FTIR. For the first time it was confirmed that alkali activation of uncalcined montmorillonite forms a NASH or (N,C)ASH geopolymer as the major product phase, which increases in quantity with increasing Na:Al molar ratio of the system. Although it has a similar Si:Al ratio, alkali activation of illite seems to result in structural alteration and increased porosity for Na:Al ≥ 0.5. The behaviour of these individual clay minerals suggests that the alkali activation of un-calcined 2:1 clay minerals is complex. Although alkali activation of montmorillonite can form a geopolymer, alkali activation of soils containing illite may lead to poor quality materials. This research has shown that the focus of future development work should be around montmorillonite-based clays.Graphical abstractUnlabelled Image
  • Synthesis of iron-rich tri-octahedral clay minerals: A review
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Liva Dzene, Jocelyne Brendlé, Lionel Limousy, Patrick Dutournié, Christelle Martin, Nicolas Michau Examples in materials science and in geology show an interest for iron-rich tri-octahedral clay mineral synthesis in large amounts and with well-defined characteristics. This review summarizes previously reported methods and conditions for iron-rich tri-octahedral clay mineral synthesis. Two approaches of hydrothermal synthesis have been applied: using gel or solid precursors. The most common synthesis approach is the hydrothermal synthesis using gel precursor. The synthesis of 1:1 type clay minerals were performed in reducing conditions in neutral or alkaline pH at various temperature and time ranges. The experimental conditions for 2:1 type clay mineral synthesis were in most cases similar to 1:1 type clay minerals, with in addition acidic pH and oxidizing conditions. The most commonly used methods for identifying and characterizing these minerals are X-ray diffraction, infra-red and Mössbauer spectroscopies as well as transmission electron microscopy. The thermodynamic stability of synthesized phases, as well as the reason for elements adopting a definite configuration and distribution in solid phase remain open questions.Graphical abstractUnlabelled Image
  • “Nano in micro” architecture composite membranes for
           controlled drug delivery
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Reshmi C.R., Suja P. Sundaran, Subija T., Sujith Athiyanathil A novel “nano in micro” architecture composite electrospun membrane has been fabricated with Poly (ɛ-caprolactone) (PCL). Nano sheets of montmorillonite (Mt) can act as drug cargoes in PCL electrospun membranes. The fiber morphology and diameter of PCL/Mt. electrospun membranes were tuned by optimization of various electrospun parameters. Higher concentration of Mt. loaded electrospun membranes exhibited improved crystallinity and hydrophilicity. The in vitro degradation studies of PCL/Mt. electrospun membranes explored a new scenario of degradation mechanism. PCL/40Mt membranes showed enhancement in human dermal fibroblast (HDFs) adhesion and proliferation. The vitamin B12 loaded Mt. nano-sheets incorporated in electrospun membranes exhibited extended release of the drugs over 15 days. Moreover, the pH responsive nature of PCL/40Mt electrospun membranes was also investigated. Gentamicin is the antibacterial drug loaded on PCL/40Mt membrane and showed bioactivity against E. coli for 15 days. The newly fabricated nano in micro architecture membranes can be used as potential material for tissue engineering and sustained drug delivery.Graphical abstractUnlabelled Image
  • Investigation of Re(VII) diffusion in bentonite by through-diffusion and
           modeling techniques
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Tao Wu, Zhifen Wang, Yanhua Tong, Yongya Wang, Luc R. Van Loon The interlayer cation of bentonite has obviously influence on the diffusion behavior of radionuclides. The diffusion behavior of Re(VII) in Na+- and Ca2+-bentonites was investigated by a through-diffusion method at bulk dry densities from 1000 kg/m3 to 1800 kg/m3. A modified multi-porosity model (APM), which subdivided the porosity into the interlayer porosity (εil), the diffuse double layer porosity (εddl) and free layer porosity (εfree) in compacted bentonite, is employed to describe the distribution of the three porosities as a function of the bulk dry density and to explain the lower effective diffusion coefficient (De) and accessible porosity (εacc) of Re(VII) in Na+-bentonite compared to that in Ca2+-bentonite. With increasing bulk dry density, εacc decreased, leading to a decrease of De for Re(VII). εddl and εil are both related to the montmorillonite bulk dry density. Moreover εddl is also related to the external surface area (Aext) and the ionic strength. APM was successful in reproducing trends of εacc data for Re (this work), 35Cl and 125I (data from the literature) as a function of the bulk dry density. Compared to Ca2+-bentonite, Na+-bentonite had higher εil and εddl at the same compaction, indicating a less proportion of large pores. After combing with Archie's law, the dependency of De on bulk dry density was reproduced with a cementation factor of 2.2 and 2.6 for Na+- and Ca2+-bentonites, respectively.Graphical abstractUnlabelled Image
  • Recycled clay/PET nanocomposites evaluated by novel rheological analysis
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Milan Kracalik Clay-polymer nanocomposites exhibit complex rheological behavior due to physical and also possibly chemical interactions between individual phases. Up to now, rheology of clay-polymer nanocomposites has been usually described by evaluation of complex viscosity curve (shear thinning phenomenon), storage modulus curve (G´ secondary plateau) or plotting parameters characterizing damping behavior (e.g. Van Gurp-Palmen-plot, Cole-Cole plot). On the contrary to evaluation of damping behavior, new approach – based on evaluation of rigidity behavior – was tested, where the values of cot δ were calculated and called as „storage factor“, analogically to broadly used loss factor. Afterwards, values of storage factor were integrated over measured frequency range and called as “cumulative storage factor”. In this contribution, clay-PET nanocomposites with different organoclays have been prepared and characterized by both conventional as well as novel analysis approach. Rheological results have been supported by AFM micrographs.
  • Palygorskite mixed with Ho-based perovskite as a promising cathode
           material for solid oxide fuel cell
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Xiufang Zhu, Linzhi Zhai, Lijing Zhang, Jiadong Zhang, Xuemei Liu, Jie Song Porous palygorskite (Pal) was mixed with Ho0.9Sr0.1Cr0.5Fe0.5O3-δ (HSCF) perovskite to prepare a novel cathode material for SOFC due to large specific surface area and nano-scaled internal channels. Calcination of HSCF was preceded under 1000 °C by Thermogravimetry and differential scanning calorimetry techniques (TG-DSC) and X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and IR manifested that Pal was mixed homogeneously with HSCF. Brunauer-Emmett-Teller (BET) analysis proved that surface areas of cathode increased from 0.18 m2 g−1 to 4.23 m2g−1after mixing with palygorskite. In addition, the performances of the single cell (NiO-GDC GDC HSCF-GDC and NiO-GDC GDC HSCF-Pal-GDC) were also measured at 450–550 °C when the 99% H2 and ambient air were fuels of anode and cathode, respectively. Corresponding the maximum power density were 14.32 mW·cm−2 and 28.43 mW·cm−2 at 500 °C. When the single cell operating temperature was raised to 550 °C, the performance of single cell NiO-GDC GDC HSCF-GDC continues to enhance, while another ome decreased sharply. BET values of the cathode with mixing Pal after cell test declined from 4.23 m2 g−1 to 0.11 m2 g−1, which indicated the collapsing of the pores in Pal at the cell operating temperature and impeded the performance of the cell. The operating temperature of the single cell after mixing Pal in electrode couldn't exceed 500 °C. The electrochemical impedance spectra (EIS) was also used to analysis the factors influencing cell performance. Therefore, HSCF-Pal as a promising cathode can be used as low temperature solid oxide fuel cell.
  • Rock fabric and origin of the expandable phyllosilicates in the sands of
           the Ashdown Formation, East Sussex, UK
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Javier Cuadros, Jana Schweigstillová Phyllosilicate minerals have the potential to be used as indicators of past environmental conditions and climate. However, the appropriate use of this tool requires that the origin of the phyllosilicates be ascertained to correspond to the age under investigation, as mineralogical changes postdating it would lead to wrong conclusions. The soft sandstone of the Ashdown Formation (south-central and southeaster UK) contains fine-grained Al-phyllosilicates of limited interlayer expandability that have been described by other authors as vermiculite, smectite, interstratified illite-vermiculite and interstratified illite-smectite. The origin of these mineral phases is not yet agreed, with some authors reporting them as detrital and some as authigenic, generated by the weathering of detrital mica in the sandstone. In order to investigate whether or not these fine-grained minerals are detrital, four samples of the sandstone of variable softness were studied because they most likely had different clay content and because the different clay content could be possibly due to differential weathering. Investigation of mineralogy (X-ray diffraction), chemistry (bulk and SEM-EDS microanalysis) and rock fabric (image analysis of SEM micrographs) indicated that the sandstone consists of quartz, microcline, albite, anorthite, muscovite/illite, kaolinite, interstratified illite-smectite and smectite, where smectite layers expand only partially. Kaolinite is mainly detrital. Rock hardness was controlled by quartz abundance in the original sediment, not by later weathering. Alteration of the investigated sandstone samples after deposition was limited but reaction models are compatible with partial (
  • One-step synthesis of Ru/montmorillonite composite from gel system of
           RuCl3-Na2O-ZnO-Al2O3-SiO2-F-H2O and applications in nitrobenzene
           hydrogenation catalysis
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Peng Zhang, Fujie Zhu, Xiaoling Tan, Wenqing Li, Shaonan Xu, Peiping Zhang, Cundi Wei, Shiding Miao One-step synthesis of Ru/montmorillonite (Ru/Mt) without using any organic ligands has been successfully implemented from a gel system of RuCl3-Na2O-ZnO-Al2O3-SiO2-F−–H2O, and the catalytic application was demonstrated in the hydrogenation of nitrobenzene (NB). The synthesized materials were characterized by X-ray diffraction, infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Due to the particular structure of which Ru(0)-nanoparticles were encapsulated by clay layers, the catalytic activity of Ru/Mt. was found to experience no significant deactivation after runs of reactions. The catalytic performance of Ru/Mt. was determined as a function of Ru loading amount with respect to NB. The conversion of NB to aniline was found to reach 99.42% within 2.0 h (PH2 = 5.0 Pa; T = 90 °C), and the turnover frequency was higher than activated carbon- or Al2O3-supported- ruthenium catalysts (Ru/AC, Ru/Al2O3). The method has its priority in getting pure clay supports, and high catalytic activity was obtained by avoiding the paramagnetic ions from natural clays.Graphical Unlabelled Image
  • Saponin loaded montmorillonite-human serum albumin nanocomposites as drug
           delivery system in colorectal cancer therapy
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Oznur Akbal, Tayfun Vural, Soheil Malekghasemi, Betül Bozdoğan, Emir Baki Denkbaş This study reports the synthesis and application of new saponin (SAP)-loaded montmorillonite-human serum albumin (Mt-HSA) nanocomposites (NCs) as an anticancer drug delivery agent. When the biodegradable and biofriendly HSA was combined with Mt., which possesses excellent mucoadhesive properties, the resulting NCs could pass through the gastrointestinal barrier easily. SAP-Mt-HSA NCs were prepared by a modified desolvation technique in which ethanol and glutaraldehyde (GA) were used as precipitating and crosslinking agents, respectively. The efficacy of these NCs was assessed in a colorectal cancer cell line (DLD-1) as an in-vitro gastrointestinal model and L929 fibroblast cells as a healthy cell model. The release profile of SAP and the cytotoxic effect and cellular uptake of NCs were evaluated. The results clearly demonstrated that SAP-Mt-HSA NCs can induce dose-dependent cancer cell death with little or no toxicity toward healthy cells.Graphical abstractUnlabelled Image
  • Preparation and formation mechanism of pure phase Ca2Al-layered double
           hydroxides nanosheets synthesized by a T-type microchannel reactor:
           Application as hardening accelerator for mortar
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Xiujiang Pang, Yuan Liu, Li Chen, Yi Zhong, Zaifeng Li, Meng Liu, Shaoxiang Li CaAl-LDH has its special application such as crystal seeds in mortar to improve the early strength. But it is hard to prepare pure phase CaAl-LDH by traditional coprecipitation method and to avoid the byproducts like aluminum hydroxide and calcium carbonate. In this paper, pure phase Ca2Al-LDH nanosheets could be obtained by controlling Rb/s (mole ratio between base and salt solution) of 1.5 using a T-type microchannel reactor. The so-obtained Ca2Al-LDH nanosheets had a two-dimensional structure with lateral size of 30–100 nm and thickness of 2–3 nm. By correlating characterizations of pH titration with zeta potential, detailed information was obtained during the formation process of LDH prepared by the microchannel reactor and traditional coprecipitation, respectively. Tracking zeta potential of LDH prepared by microchannel reactor revealed that Ca2Al-LDH nanosheets were formed through one-step reaction between salts and base solutions in microspace. While for the case of traditional coprecipitation method, results revealed LDH formed through three stages: Al(OH)3 formation, mixing of trace Ca2+ into Al(OH)3, and their transformation into LDH. As a hardening accelerator for mortar, a dosage of only 0.35 wt % Ca2Al-LDH nanosheets prepared using microchannel reactor exhibited greatly enhanced performances in both the early tensile strength and compressive strength of the mortar, which increased by 62% and 36%, respectively.
  • Investigation of the hydration kinetics and microstructure formation
           mechanism of fresh fly ash cemented filling materials based on hydration
           heat and volume resistivity characteristics
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Bo Yin, Tianhe Kang, Jianting Kang, Yuejuan Chen, Linlin Wu, Mingze Du Fly ash cemented filling materials (FCFM) have received a great deal of attention in recent years as more sustainable solutions to the large-scale utilization problems of fly ash and coal gangue. Based on the hydration heat and the volume resistivity characteristics, this study examined the changes in the fresh FCFM properties from the thermodynamic and electrical perspectives, which reflected the characteristics of the hydration kinetics and microstructure formation mechanism of the FCFM. The results showed that the hydration exothermic process of the FCFM exhibited a rapid reaction stage, an induction stage, an acceleration stage, a deceleration stage and a stable stage. Compared with cement, the mixture of fly ash and coal gangue resulted in a substantially lower hydration heat. The volume resistivity of the FCFM changed over time, initially increasing, then decreasing, then increasing again. The hydration kinetics of the FCFM could be described by three processes: nucleation and crystal growth (NG), interactions at the phase boundaries (I) and diffusion (D). The NG process dominated in the early stage of hydration, and the I and D processes gradually became dominant as the hydration degree increased. Compared with cement, changing the hydration kinetics required a higher degree of hydration in the mixture of fly ash and coal gangue. The improvement in the hydration reaction rate of FCFM due to additives was primarily reflected in the early hydration stage. The calculated data on the C-S-H gel content of the FCFM paste agreed well with the changes in the uniaxial compressive strength (UCS) and plane porosity over time. Remarkable negative correlations between the plane porosity and the UCS and between the plane porosity and the C-S-H gel content were found, along with a significant positive correlation between the C-S-H gel content and UCS. A microstructure formation mechanism model of the FCFM was constructed, and the hydration process of the filling material was divided into a dissolution period, a hydration period and a flocculated-structure formation and growth period. These findings provide new insights into the hydration kinetics and microstructure formation mechanism of fresh FCFM.
  • Development and characterization of bentonite/wGLP systems
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Andrea Y. Mansilla, Matias Lanfranconi, Vera A. Alvarez, Claudia A. Casalongué Bentonite (Bent) clay is a component of soil with useful properties for enzyme adsorption. In this work, the previously characterized antioxidant superoxide dismutase (SOD) enzyme named wGLP by wheat germin-like protein was immobilized in raw (Bent) and modified bentonites (Bent-DDA). The physicochemical characterizations of both supports were carried out. Successful adsorption of wGLP onto Bent and Bent-DDA occurred on the surface and within the interlayer spacing as was revealed by X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). The release of wGLP at different times and pHs was tested. While wGLP remained almost totally immobilized into Bent-DDA up to 96 h, it was released from Bent to reach nearly 60% after 72 h at pH 7.5 and preserving its SOD activity. Since tomato cell viability under the presence of Bent-wGLP was maintained, Bent-wGLP complexes are potential carriers of antioxidants in tomato cell suspension cultures.
  • Silver nanoparticles assembled on modified sepiolite nanofibers for
           enhanced catalytic reduction of 4-nitrophenol
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Junhua Zhang, Zhaoli Yan, Liangjie Fu, Yi Zhang, Huaming Yang, Jing Ouyang, Deliang Chen Acid-activated sepiolite nanofibers (ASep) were organically modified with (3-aminopropyl) triethoxysilane (APTES) to produce the amino-functionalized nanofibers (NH2-ASep). Due to the amino groups, highly dispersed silver nanoparticles (AgNPs) were assembled on the surface of NH2-ASep by a simple chemical reduction approach, and the AgNPs were smaller than those directly deposited onto ASep surface. The as-synthesized Ag/NH2-ASep nanofiber catalysts exhibited an excellent catalytic activity in the reduction process of 4-nitrophenol to 4-aminophenol with full conversion within 150 s in the presence of NaBH4 as the reductant. The results indicated that Ag/NH2-ASep nanofiber catalysts exhibited excellent catalytic activities because the highly dispersed of small-sized AgNPs were exposed on the surface of highly dispersed nanofibers with amino functional groups, allowing effective contact with the reactants and catalysis of the reaction. Moreover, the Ag/NH2-ASep nanofiber catalysts are stable and easy to use for the catalytic reaction due to their one-dimensional nanofiber structure with functional amino groups.Graphical abstractUnlabelled Image
  • Preparation of NiAlZr-terephthalate LDHs with high Al and Zr content and
           their mixed oxides for cyclohexane dehydrogenation
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Santiago Arias, Lenivaldo V. Sousa, Celmy B.M. Barbosa, Antonio Osimar S. Silva, Roger Fréty, Jose Geraldo A. Pacheco Hydrotalcite-like materials were synthesized by pH-controlled precipitation method with Ni2+ and Al3+ cations and terephthalate as the compensation anion. Ni/Al ratios were 1.0 and 0.3, both high in aluminum content for what has been commonly reported in the literature for this type of materials. The incorporation of Zr(IV) in the structure of the materials was evaluated substituting Al(III) for Zr(IV), using Al/Zr ratios of 3.0 and 0.3. Characterization techniques, such as X-ray diffraction, thermogravimetric analysis, infrared spectroscopy and chemical analysis, demonstrated that NiAlZr-terephthalate hydrotalcite-like materials were obtained simultaneously with amorphous phases of ZrO2 and Al(OH)3. The mixed oxides, produced by the calcination of the hydrotalcites, had interesting characteristics that could be useful for potential unsupported mesoporous nickel catalysts, with high surface areas, nanoparticles, variable reducibility temperature, thermal stability and different kinds of interaction of nickel with aluminum and zirconium, depending on the metal content. These NiAlZr oxides were evaluated as catalysts for cyclohexane dehydrogenation reaction after a reduction process. The resulting catalysts presented a high cyclohexane conversion and in some cases selectivity to benzene close to 90%, especially when zirconium was added and nanosized cristallites of NiO were formed.Graphical abstractUnlabelled Image
  • A palgorskite-based nanocomposite effectively reducing the incidence of
           powdery mildew
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Hao Hu, Jun Ni, Dongqing Cai, Huilan Zhang, Minghao Li, Xian Shu, Caiguo Tang, Lifang Wu Wheat powdery mildew (PM) is one of the world's top 10 most destructive fungal plant pathogen and the routine control of this disease is by application of fungicides and disease-resistant cultivars. In this study, a nanocomposite composed of amino silicon oil (ASO) and palygorskite (Pal) was developed and can effectively inhibit the pathogen. The results demonstrated that the morphology and microstructure of Pal could be effectively modified by ASO via hydrogen bonds between –NH2 of ASO and − OH of Pal, resulting in an increase of hydrophobic surface groups. Further analysis showed that nanonetworks were formed by Pal-ASO interaction, which could effectively segregate Blumeria graminis f. sp. tritici (Bgt) conidia from wheat leaf surface and reduce the disease index by 98%. This work provides an economic and environmentally friendly approach to control the wheat powdery mildew disease.
  • Adsorption behavior of hydroxypropyl guar gum onto montmorillonite and
           reducing adsorption in the reservoir
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Zichen Yin, Yanling Wang, Jingshan San Hydroxypropyl guar gum (HPG) is a kind of thickener commonly used in the field of oilfield chemistry. The adsorption behavior of HPG onto Montmorillonite (Mt) was investigated in this article. The maximum adsorption amount of HPG on Mt. was 3.6 mg/g at the HPG concentration of 2 g/L. The effect of pH, temperature, salts, alcohols and hydrolyzed polyacrylamide (HPAM) on adsorption behavior was revealed. The results showed that adsorption capacity increased with pH ranging from 3 to 13. The adsorption capacity was slightly influenced at temperature from 20 °C to 60 °C. The adsorption amount decreased at the presence of NaCl, KCl, CaCl2 or MgCl2, while it increased with addition of Na2SO4 or Na3PO4. The adsorption capacity was found no change at the presence of monobasic alcohol, while it significantly increased with the increasing concentration of polybasic alcohol. The adsorption density reduced with the addition of HPAM. Scanning electron microscope (SEM) and X-ray Diffraction (XRD) confirmed that adsorption behavior occurred on the exterior surface of Mt. Besides, the adsorption was attributed to Van der Waals' forces and electrostatic interaction. The Fourier Transform infrared spectroscopy (FTIR) showed that adsorption behavior occurred on Mt. surface via physisorption rather than chemisorption. The adsorption behavior of HPG on Mt. surface obeyed the Langmuir adsorption isotherm which showed that the adsorption was monolayer adsorption. The adsorption mechanism would be characterized as exterior surface adsorption, physical adsorption and monolayer adsorption.
  • Doped nafion-layered double hydroxide nanoparticles as a modified ionic
           polymer metal composite sheet for a high-responsive humidity sensor
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Fahimeh Beigi, Matin Sadat Saneei Mousavi, Faranak Manteghi, Mohammadreza Kolahdouz In this paper, a novel Ionic Polymer Metal Composite (IPMC) has been fabricated by chemical electroless plating integrated with doping Layered Double Hydroxide (LDH) nanoparticles in the nafion polymeric matrix. Platinum, as a noble metal, was used for electrode deposition of the prepared doped nafion and successfully act as a high-quality electrode to transfer electrical signal. This IPMC, in fact, is a smart material suggesting to acts as a high responsive mechanical humidity sensor in biomedical devices since it produced a remarkably higher voltage with higher sensitivity and responsivity in comparison to the previous IPMC humidity sensors in literature. LDH nanoparticles own a layered ionic structure, which makes them highly hydrophilic. This property increases the water uptake of the IPMC. By increasing the penetration of water molecules in the nafion channels, the separation of positive and negative charges becomes easier and leads to higher and faster humidity sensing application. The humidity sensing applications of undoped and LDH-doped IPMC fabricated by facile chemical plating method were measured and compared at different bending angles. It was found that 1% doped nafion sheet had the highest water uptake of 30%, and consequently better humidity sensing compared to the undoped, 0.5%, 1.5%, 2% and 3% doped nafion. This means that doping concentration and modification has an optimized value.
  • Highly effective adsorption of crystal violet dye from contaminated water
           using graphene oxide intercalated montmorillonite nanocomposite
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Chandni Puri, Gajjala Sumana Herein, graphene oxide intercalated montmorillonite nanocomposites were prepared by a facile chemical route and then used for the adsorption of crystal violet dye from contaminated water. Structural characterization of the nanocomposites were performed using Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, zeta potential, X-ray diffraction, specific surface area and pore volume measurements. The isothermal data obtained using batch adsorption technique were fitted using Langmuir and Freundlich equations and it was found that the experimental data is well described by the Langmuir isotherm model with a very high adsorption capacity of 746.27 mg g−1. The kinetics of the adsorption process showed rapid dynamics and conformed to pseudo-second-order model with a correlation coefficient of R2 > 0.99. The influence of interaction time and initial dye concentration on the adsorption efficiency were also investigated. Additionally, thermodynamic studies revealed that the adsorption process was spontaneous and endothermic. Further, the results indicated that the synthesised nanocomposites adsorb crystal violet dye efficiently (∼96%) with a small decrease in removal efficiency even after five cycles of adsorption and could be employed in wastewater treatment for the removal of cationic dyes.Graphical abstractUnlabelled Image
  • One-pot synthesis of metakaolin/g-C3N4 composite for improved
           visible-light photocatalytic H2 evolution
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Xuelin Wang, Zhengliang Zhao, Zhu Shu, Ying Chen, Jun Zhou, Tiantian Li, Wenbin Wang, Yigen Tan, Na Sun The conversion of solar energy to chemical energy via photocatalysis is a potential pathway for future energy supplying, and the development of graphitic carbon nitride (g-C3N4) for visible-light photocatalytic hydrogen evolution reaction (HER) has attracted increasing attention. In this work, raw kaolinite was used to enhance the photocatalytic performance of g-C3N4 by constructing the metakaolin/g-C3N4 composites. A facile one-pot method, heat-treating their mixed precursors, was employed. The as-prepared MK/CN-70.4% exhibits a favorable hydrogen evolution rate of 288 μmol g−1 h−1, which is 1.5 times that of bulk g-C3N4. The improved HER benefits from both the electronegativity of metakaolin and the nanosizing of g-C3N4. The proposed strategy has the potential to inspire the utilization of other clay minerals to improve the photocatalytic activity of g-C3N4.
  • Towards mass production of Au nanoparticles supported on montmorillonite
           microspheres for catalytic reduction of 4-nitrophenol
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Fengyan Xiao, Yawei Qin, Ning Wang, Dawei Pan Noble metals supported on substrates have been proven as highly efficient catalysts for the reduction of nitro-compounds. However, their large-scale applications are still limited by the problems of fouling and transport during the mass production process. Herein, we first fabricated a spherical montmorillonite (Mt) substrate via spray drying technique, followed by the deposition of Au NPs through polydopamine chemistry to synthesize spherical Au nanoparticles supported Mt (Au@Mt) microspheres. The Au loading is 14.5 wt%, whereas the specific surface area of the Au@Mt microspheres is 47.3 m2 g−1, endowing the prepared Au@Mt microspheres with excellent catalytic activity to the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4 with the optimized apparent reduction rate constant higher than 1.05 min−1. Furthermore, the microspheres can be easily recycled with self-sedimentation without any devices involved and showed excellent stability and recyclability for at least 20 cycles without almost unchanged spherical morphology and catalytic performance. Our straightforward strategy to solve the issue of the mass production process through granulation of amorphous nanomaterial substrate facilitates the practical application of these catalysts in the reduction of nitro-compounds.Graphical abstractUnlabelled Image
  • Remarkably improving the fire-safety of polypropylene by synergism of
           functionalized ZrP nanosheet and N-alkoxy hindered amine
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Huali Xie, Xuejun Lai, Hongqiang Li, Xingrong Zeng Realizing the high efficiency of halogen-free flame retardant is one of the biggest challenges and the most urgent issues in the development of high performance polypropylene (PP). Coupling the catalytic carbonization and free-radical quenching mechanism is proposed to be an efficient method to address this issue. In this work, a functionalized zirconium phosphate (F-ZrP) with good catalytic carbonization capability was synthesized, and was combined with N-alkoxy hindered amine (NOR) to flame-retard PP. The composition showed high flame-retardant efficiency. When the content of NOR, F-ZrP and ammonium polyphosphate were 0.2 wt%, 4.95 wt% and 14.85 wt%, respectively, the flame retardant PP reached a limiting oxygen index of 36.0% and achieved a UL-94 V-0 rating. Meanwhile, the peak heat release rate, average heat release rate, total heat release, peak smoke production rate and total smoke production were declined by 95.6%, 90.6%, 73.3%, 93.5% and 80.6%, respectively. It revealed that F-ZrP formed closed micron-scale char-cages via interfacial carbonization. In the char-cages, the nitroxyl radicals generated by NOR efficiently quenched the active free-radicals produced by PP and induce their cyclization reaction. Under the further catalytic effect of ZrP, graphitized crystalline char with extraordinary thermostability and barrier effect was generated quickly and protected the polymer from burning.
  • Cs+ sorption onto Kutch clays: Influence of competing ions
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Anna S. Semenkova, Mariia V. Evsiunina, Parveen K. Verma, Prasanta K. Mohapatra, Vladimir G. Petrov, Irina F. Seregina, Mikhail A. Bolshov, Victoria V. Krupskaya, Anna Yu. Romanchuk, Stepan N. Kalmykov The sorption of Cs+ onto raw Kutch clay (India) over a wide range of concentrations and pH levels was studied and compared with its sorption onto the well-studied FEBEX clay (Spain). The principal clay mineral in both samples is montmorillonite. Non-linear sorption isotherms were measured for both clays. The shapes of the isotherms prompted the use of a two-site exchange thermodynamic model to describe the experimental data. However, differences in the highly selective sorption sites (Type 1) were observed for the two studied clays. It was found that the presence of different cations (H+, Ca2+, Mg2+, etc.) in solution affected the sorption of Cs+. A model accounting for the competition process was developed for predicting the behavior of the raw clay in complex solutions.
  • New developments in low clinker cement paste mineralogy
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): M. Frías, R. Vigil de la Villa, R. García, S. Martínez-Ramírez, L. Fernández-Carrasco The use of industrial waste as a cement addition often changes the composition and development of the hydrated phases and with them matrix performance and durability, in particular at later ages. The effect of the presence in blended cement of 20% to 50% kaolinite based activated carbon waste (ACW) on paste hydration has been characterized by means of XRD, SEM/EDX, TG/DTG, NMR and FTIR to identify and monitor the mineralogical phases forming in materials at ages of up to 180 d. The results showed that the main reaction products forming in the first 7 d included C-S-H gels, C4ACH12 and C4AH13 (hydroxy-AFm). Whilst monocarboaluminate (Mc) content declined with rising percentages of ACW, the amount of hexagonal phase hydroxy-AFm rose. Then microstructure of the C-S-H gels developing in the OPC and the 50% additioned paste differed. Compact C-S-H gel plates, and phyllosilicate-like laminar spongy microplates with high polymerised C-S-H gel formed in the blended cement paste.
  • Insights on the role of organic matters of some Egyptian clays in methyl
           orange adsorption: Isotherm and kinetic studies
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Ahmed M. Zayed, Mahmoud S.M. Abdel Wahed, Essam A. Mohamed, Mika Sillanpää The role of organic matters (OM) of some Egyptian clay in Methyl Orange (MO) adsorption from aqueous solutions was tested for the first time. To elaborate this role, the raw Organic Matters-Rich Clays (OMRC) was calcinated at 500 °C/4 h to remove their associated OM by oxidation. Then the MO removal efficiency by both OMRC and its calcinated derivative (COMRC) was tested at different experimental parameters. The adsorption of MO by the studied adsorbents was pH- and time-dependent process and the equilibrium was attained after 60 min. The pseudo-second-order model with high determination coefficients (R2 > 0.999) fitted well the adsorption kinetics, while the intra-particle diffusion was not the rate governing step in MO adsorption by both adsorbents. The MO adsorption characteristics revealed that equilibrium data of OMRC and COMRC fitted well to the Freundlich and Langmuir models, respectively. Electrostatic interaction was the primary but not the only governing mechanism for MO adsorption by the investigated adsorbents; participation from hydrogen bonding mechanism was involved, with some preference for COMRC. The superiority of OMRC over COMRC in MO adsorption can be attributed to the involvement of oxygen- and nitrogen-bearing groups of both OM and clay minerals in the adsorption process on the contrary of COMRC in which only oxygen-bearing groups of the clay minerals were incorporated.
  • Ceramic materials from Cuatrovitas archaelogical site (Spain). A
           mineralogical and chemical study for determining the provenance and the
           firing temperature
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Isabel González, Antonio Romero-Baena, Emilio Galán, Adolfo Miras, José Carlos Castilla-Alcántara, Paloma Campos The characterization of ceramic materials from archaeological sites is of great importance to learn about the human traditions and regional History. In this work, 12 pieces of ceramics of the Cuatrovitas Archaelogical Site (Bollullos de la Mitación, Seville, Spain) were studied to approach the provenance of the raw material and the firing temperature. In addition, raw materials, from possible sources areas used for the manufacture of those ceramics, were also studied. Mineralogical characterization by XRD and chemical analyses of major, trace and rare earth elements were performed on both raw and ceramic materials. Thin sections, SEM-EDS analyses and micro-XRF mapping were carried out to complete the mineralogical and chemical characterization. The results show that there are two types of ceramic materials, probably prepared by mixtures of different clays and sandy materials. A feasible source area for those raw materials could be the alluvial of the Guadiamar River. According to the mineralogy of the high-temperature phases found in the ceramic pieces, two firing temperatures can be approached: one at 800–850 °C owing to the presence of calcite, and another at 900–950 °C because of the presence of diopside and gehlenite.
  • Mechanism of electro-osmotic chemical for clay improvement: Process
           analysis and clay property evolution
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Zhijia Xue, Xiaowei Tang, Qing Yang, Zhifeng Tian, Yao Zhang, Wei Xu Electro-osmotic chemical methods were applied in a series of geotechnical studies in which various solutions were injected into clay samples, increasing the undrained shear strength of the clay. Such methods resulted in a series of phenomena and in clay property evolution. In this study the current, temperature, settlement, drainage volume, and electrical potential distribution during the electro-osmotic experiments were monitored as process data, and the electrical conductivity in clay, calcium content, pH, water content, and undrained shear strength after the electro-osmotic chemical experiments were measured as clay property evolution data. Based on the process data, clay property data, and relevant theories, the mechanism of clay reinforcement with electro-osmotic chemicals was comprehensively explained. The development of an electro-osmotic permeability coefficient difference and the permeable drainage boundary condition resulted in a negative pore water pressure distribution shaped as an arch, which resulted in the water content having the same distribution and induced settlement. Because of the gathering of Ca2+ and H+ near the anode, a chemical cement reaction occurred near the cathode. The electrical potential gradient near the anode was lower than that near the cathode. Because of the chemical cement reaction between Ca2+, OH−, and SiO32−, the undrained shear strength near the cathode was much higher than that near the anode. In addition, a coupling analysis of the electro-osmotic chemical process and clay property evolution is presented at the end of the discussion.
  • Degradation of aqueous ketoprofen by heterogeneous photocatalysis using
           Bi2S3/TiO2–Montmorillonite nanocomposites under simulated solar
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Lila Djouadi, Hussein Khalaf, Horiya Boukhatem, Hocine Boutoumi, Amina Kezzime, J. Arturo Santaballa, Moisés Canle The photocatalytic degradation of Ketoprofen (KP), 2-(3-benzoylphenyl)-propionic acid was studied under near UV–Vis irradiation (NUV-Vis) using supported photocatalysts. Bi2S3/TiO2-montmorillonite (Bi2S3/TiO2-Mt) photocatalysts were synthesized using a two- step ion exchange and impregnation method, and characterized using different techniques: Fourier transform infrared spectra (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and photo-electrochemistry. Successful intercalation of TiO2 and Bi2S3 in the montmorillonite (Mt) was carried out, and the corresponding energy diagram for the Bi2S3/TiO2 heterojunction has been proposed. The resulting Bi2S3/TiO2-Mt nanocomposites were able to degrade KP under NUV–Vis irradiation. KP photodegradation was monitored by HPLC. The kinetics of photocatalytic transformation followed the Langmuir-Hinshelwood kinetic model. Pseudo-first-order kinetics adequately fitted the experimental data (t½ca. 17 min at pH 11, t½ca. 44 min at pH 3. 0.5 g·L−1 Bi2S3/TiO2 (25/75)-Mt nanocomposite). Factors affecting the kinetics of the process, such as the different Bi2S3/TiO2 ratio and initial pH solution have been discussed. KP photoproducts were identified using HPLC-MS, and the corresponding reaction mechanism has been proposed. Photodegradation of KP over Bi2S3/TiO2-Mt nanocomposites under NUV-Vis irradiation starts with the decarboxylation of KP and subsequent hydroxylation by HO• and oxidation by HO• and other reactive oxygen species (ROS) leads to the formation of photoproducts. TiO2 and Bi2S3 intercalated in the montmorillonite are cheap and efficient nanocomposites for the abatement of persistent organic pollutants (POP), such as KP, using NUV-Vis light.Graphical abstractUnlabelled Image
  • N-doped TiO2/sepiolite nanocomposites with enhanced visible-light
           catalysis: Role of N precursors
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Feng Zhou, Huaibing Song, Hongquan Wang, Sridhar Komarneni, Chunjie Yan Several nitrogen-doped TiO2/Sepiolite (N-TiO2/Sep) photocatalysts were prepared via microwave-hydrothermal treatment using four different types of nitrogen sources: ammonium hydroxide, urea, ethylenediamine and triethylamine. The obtained nanocomposites were characterized by using XRD, TEM, BET, XPS and UV–vis techniques. The results revealed that the chemical and morphological properties of the nanocomposites were significantly dependent on the nitrogen source. The interstitial N doping occurred in the form of N-O-Ti-O and the surfaces of the samples were modified by carbon species from dopants. As compared to that of the undoped sample, N-doped samples exhibited a red shift in the band gap transition. The results of simulated solar light photocatalytic activities demonstrated that NTS-EDA exhibited better photocatalytic activity than singly N-doped (i.e., no carbon) or undoped TiO2/Sep sample. The enhanced solar-light activity is attributed to the low band gap energy with N-doping, the high adsorption capacity and uniform distribution of titania nanoparticles with sepiolite as support, and the appropriate carbon content of the dopants.
  • Evolution of fine microstructure during firing of extruded clays: A small
           angle neutron scattering study
    • Abstract: Publication date: 15 December 2018Source: Applied Clay Science, Volume 166Author(s): Alberto Viani, Radek Ševčík, Marie-Sousai Appavou, Aurel Radulescu The microstructure of extruded fired-clay bodies in the interval 800–1100 °C has been investigated with small angle neutron scattering. The evolution of the retrieved pore size distribution is compatible with the coarsening of the pore network with increasing temperature. The analysis of the scattering curves in combination with results of electron microscopy, indicated a multiscale nature for the pore-matrix microstructure. A structural parameter obtained from the analysis of the scattering curves, is proposed as indicator of maximum firing temperature through the implementation of a linear calibration curve. Such method has been successfully tested on a material of industrial production and can be considered of interest for the production of custom made replacement materials in the conservation of cultural heritage or for the characterization of the manufacturing process of archaeological fired-clay objects. Textural features originated by the forming process of extrusion have been detected as anisotropy of the pore network. They are still present above 1000 °C and, because of the use of screw extrusion, they are observed in both sections cut parallel and perpendicular to the direction of extrusion.
  • Identification of iron in Earth analogues of Martian phyllosilicates using
           visible reflectance spectroscopy: Spectral derivatives and color
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Manuel Sánchez-Marañón, Javier Cuadros, Joseph R. Michalski, Manuel Melgosa, Vesselin Dekov A range of phyllosilicate compositions have been detected spectroscopically on Mars, but the largest fraction by far corresponds to clay minerals rich in Fe and Mg. Given that most of our understanding of Martian clays comes from remote sensing data, it is critically important to explore the details of how compositional variation affects spectral features of phyllosilicates. The greatest efforts have focused so far on near-infrared (NIR) spectroscopy. Recently, ambiguities have been detected in the NIR spectra of 2:1 phyllosilicates with intermediate FeMg content that preclude mineral and chemical discrimination. Such ambiguities highlight the relevance of exploring the visible spectral range as a complementary tool to characterize Martian phyllosilicates precisely. This article reports the investigation of laboratory reflectance spectra (330–800 nm) from 34 Earth analogues of Martian phyllosilicates with a wide range of MgFe composition, including nontronite, celadonite and saponite end-members, as well as interstratified glauconite-nontronite, talc-nontronite, and talc-saponite. The spectra indicated the presence of Fe(III) by absorption modulations and a decrease in total reflectance, especially in samples with tetrahedral Fe(III). Absorption bands at 370 and 420 nm were diagnostic of octahedrically and tetrahedrally coordinated Fe(III), respectively. Band amplitudes in the second derivative of the Kubelka-Munk function correlated positively with Fe(III) content (R2 > 0.8). Standard color analyses of the visible reflectance spectra under the CIE illuminant D65 indicated that the CIELAB color parameter a*10 was positively correlated with tetrahedral Fe(III), b*10 was positively correlated with octahedral Fe(III), and L*10 was negatively correlated with Fe(III) in both structural sites. Because Fe(II) was in relatively low amount, it did not provide clear spectral evidence. Multiple regression models using the amplitude of the diagnostic absorption bands predicted well absolute Fe content in the phyllosilicates (R2 = 0.89) and the ratio Fe/(Fe + Mg + Al) (R2 = 0.84). CIELAB color parameters improved the prediction of total Fe (R2 = 0.92) and the ratio Fe/(Fe + Mg + Al) (R2 = 0.93). Application of these analyses to Martian data has challenges set by Fe oxide dust coating and spatial and spectral resolution. However, these results mark an avenue to develop testable tools using visible-wavelength spectral data from both satellite and lander probes to help establishing Fe content and mineral identification of Martian phyllosilicates.
  • Transport behaviour of low molecular weight organic compounds in
           multi-mineral clay systems. A comparison between measured and predicted
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Y. Chen, M.A. Glaus, L.R. Van Loon, U. Mäder Determining the retardation properties of argillaceous media for dissolved low molecular weight organic compounds (LMW—OC's) is still an open issue in the assessment of the migration behaviour of 14C in the near and far field of a deep geological repository of radioactive wastes. Here we report retardation factors of potential carriers of organic 14C (carboxylates and alcohols) in binary clay mixtures (kaolinite and illite) as well as in Opalinus Clay (OPA), the favoured host rock for the deep geological disposal of radioactive waste in Switzerland. The percolation technique with a pulse injection of the LMW-OC's was used for all measurements. The transferability of sorption values of the LMW-OC's gained on the single-mineral systems (kaolinite and illite, respectively) to the binary clay mixtures and to clay rock (OPA) was tested.For binary clay mixtures, percolation experiments were carried out using tritiated water and 36Cl− as the reference tracers. The retardation factors predicted by the component additivity approach (CA) were consistent with the measured ones. Deuterated water and bromide were used as reference tracers in experiments with OPA. Complex breakthrough curves of bromide and the test compounds were observed here. Heterogeneities of the pore space are proposed as the main reason to explain the complex structure of breakthrough curve. Additionally, (a)biotic degradation or transformation of the organic compounds over the long experimental duration possibly further added to the complexity of the results in some cases. The derivation of sorption distribution ratios (Rd), determined from the breakthrough curves was therefore inherently associated with large uncertainties. The transferability of retardation data gained on less complex systems to the conditions of OPA was tested using the CA and the global composite (GC) approach. Significant discrepancies were found between the measured values and those predicted by the CA approach. The discrepancies were found to be smaller using the GC approach. In that case, the results obtained for single- and binary clay systems were also used for calibration purposes. Retardation factors of the LMW-OC's in OPA were then predicted based on two empiric relationships. The observed discrepancies are most probably related to the different chemical composition of the aqueous solution (e.g. ionic strength, pH), the various mineralogical features (e.g. compaction), and the different hydraulic conditions within the clay systems (e.g. Darcy flux). The absence of anion-sorption in OPA may be particularly explained by differences in the pH of the OPA pore water and the pore water in compacted kaolinite samples.
  • Migration of clay and its role in droplet morphology establishment during
           melt mixing of clay polyethylene/polyamide nanocomposites
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Pascal Mederic, Fatima Fneich, Julien Ville, Thierry Aubry The migration of clay particles during mixing of organically montmorillonite polyethylene/polyamide nanocomposites was investigated. Special attention was paid to the observation of PA droplet morphology establishment as well as clay localization and exfoliation at different mixing times. During the incorporation step in internal mixer, the simultaneous mixing of all components favors the presence of a great number of micrometric clay agglomerates within the matrix. The migration of clay particles from the polyethylene (PE) matrix towards the polyamide (PA) dispersed phase is a very short process that takes about 1 min. From the beginning of the dispersion step (~2 min), clay particles are exclusively localized at the PA droplet frontier. Then, they are sheared and redistributed, forming a nanometric interphase. The correlation between droplet morphology establishment and clay migration mechanisms until the formation of a developed interphase is discussed.Graphical abstractUnlabelled Image
  • Transparent, UV-proof and mechanically strong
           montmorillonite/alginate/Ca2+ nanocomposite hydrogel films with solvent
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Xing Su, Biqiong Chen Fully swollen montmorillonite/alginate/Ca2+ (Ca2+-MtAlg) nanocomposites with a specific chemical composition are expected to show well-ordered microstructure, excellent mechanical properties, unique optical properties and solvent sensitivities. Inspired by nacre, Ca2+-MtAlg nanocomposite hydrogel films with high montmorillonite mass contents (≥ 20%) were synthesised by solution casting, followed by subsequent ionic crosslinking. The fully swollen Ca2+-MtAlg nanocomposite films were mechanically flexible and stable in water. By regulating the relative content of alginate and Mt, it was possible for the hydrogel films to reach a high tensile strength of 28 MPa. Ca2+-MtAlg hydrogel films also showed acceptable transparency and high efficiency in blocking ultraviolet light. Furthermore, they demonstrated solvent sensitivity; the hydrogels lost water in either methanol or acetone, the one with an Mt/Alg mass ratio of 1:4 coiled seriously in acetone while those with a lower mass ratio were more stable in either methanol or acetone. Overall, Ca2+-MtAlg nanocomposite hydrogel films have the potential for use in stimuli-responsive load-bearing biomedical applications, skin care and beyond.Graphical abstractUnlabelled Image
  • Insights into phosphate adsorption behavior on structurally modified ZnAl
           layered double hydroxides
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): E.M. Seftel, R.G. Ciocarlan, B. Michielsen, V. Meynen, S. Mullens, P. Cool The present study focuses on the phosphate uptake by synthetic ZnAl-layered double hydroxides having different charge density due to the modification of the cationic ratio (Zn2+/Al3+) within the brucite-like sheets. The structure of the as-synthesized ZnAl-LDH was confirmed by X-ray diffraction and 27Al NMR and micro-Raman spectroscopy characterization techniques. The materials were applied for sorption of phosphate anions in aqueous media under relevant conditions. Parameters affecting the sorption process were thoroughly investigated, such as the layer cationic ratio, the exchangeable interlayer anion, thermal treatment and competitive sorption in the presence of co-existing anions. The sorption data provided information regarding the relationship between the phosphate uptake and the physical-chemical properties of these materials. The phosphate adsorption onto the non-calcined LDH occurred via the anionic exchange mechanism while both structural reconstruction and precipitation mechanisms were observed for the calcined materials. The obtained results suggest that the Zn containing LDH are suitable candidates for the phosphate recovery or removal from aqueous media in wastewater treatment processes.Graphical abstractUnlabelled Image
  • Role of pH in green rust preparation and chromate removal from water
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Abdullah Al Mamun, Aina Onoguchi, Giuseppe Granata, Chiharu Tokoro The removal of hexavalent chromium from water by sustainable methods still presents challenging aspects. Green rust (GR) is a mixed Fe(II)-Fe(III) layer double hydroxide intercalated with anions and water molecules that was recently found capable of immobilizing low concentrations of chromate. Nevertheless, the influence of pH on GR preparation and chromate removal mechanism has not been fully clarified yet. This work elucidated the influence of pH on GR preparation and chromate removal by sulfate-GR. Two types of GR were prepared at two different pH, namely pH 8.75 (GR8.75) and 7.50 (GR7.50), and were used in chromate removal experiments at pH 5 and 9. XRD, XPS and XAFS analysis were carried out to assess the change of phase composition, surface oxidation state and crystal structure. Increasing the preparation pH from 7.50 to 8.75 produced a larger inclusion of SO42− and Na+ within the GR interlayer and resulted in a larger crystal lattice and more surface area. GR8.75 was 1.7 times more efficient than GR7.50 and 6.7 times more efficient than ferrihydrite as Fe required to remove 10 mg/L of chromate from water. While removing chromate, GR7.50 released a larger amount of SO42− than GR8.75 in spite of a lower initial content. At pH 5, GR8.75 reduced chromate and oxidized mostly to goethite, whereas magnetite was the main oxidation product at pH 9. In contrast, GR7.50 removed chromate and transformed into Cr-intercalated ferrihydrite. XPS results confirmed the larger passivation of GR8.75. All results indicated that GR8.75 removed chromate mainly via surface reduction whilst GR7.50 removed it mostly via replacement of SO42− in the interlayer prior to reduction. EXAFS analysis of solid residues highlighted the presence of bidentate mononuclear FeCr2O4-like CrFe bonding as well as Cr2O3-like CrO and CrOCr bonding under all investigated conditions. The increase of FeFe edge sharing and double corner sharing coordination numbers in the final solid product upon chromate removal by GR8.75 suggests a surface-based reaction between GR and chromate. In contrast, for GR7.50 upon chromate removal, the increase of single corner sharing FeFe coordination via oxygen can be resulted from lateral insertion of chromate into GR interlayer.Graphical abstractUnlabelled Image
  • Facile fabrication of CdS/ZnAlO heterojunction with enhanced
           photocatalytic activity for Cr(VI) reduction under visible light
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Chao-Rong Chen, Hong-Yan Zeng, Sheng Xu, Jia-Chao Shen, Guo Hu, Run-Liang Zhu, Jin-Ze Du, Yun-Xin Sun Cadmium sulfide (CdS) is an excellent visible light responsive material for the appropriate band gap, but the high electron-hole recombination and particle aggregation of CdS seriously limited its practical application in photocatalysis. In this work, the CdS/ZnAlO heterostructures photocatalyst was synthesized via a facile hydrothermal method. The structural characterizations showed that the particles aggregation of CdS and the separation of photogenerated electron-hole pairs were obviously improvement. The CdS/ZnAlO composite showed the highest photocatalytic activity for Cr(VI) reduction under visible light within 120 min. The enhanced photocatalytic activity might be attributed to the synergistic effect of the effective separation of photogenerated electron-hole and the adsorption of Cr(VI) on the interface of the catalyst. In addition, the possible mechanism of Cr(VI) reduction over CdS/ZnAlO was also proposed. The present work is devoted to synthesise a high efficient and stable photocatalyst for Cr(VI) contaminated wastewater treatment.Graphical The CdS/ZnAlO heterojunction photocatalyst was designed and prepared to improve the charge transfer and the particle aggregation of CdS, which demonstrated highly efficient photocatalytic activity and stability for Cr(VI) reduction under visible light irradiation.Unlabelled Image
  • Al+for+the+design+of+efficient+antibacterial+ceramics&rft.title=Applied+Clay+Science&rft.issn=0169-1317&">Ternary layered double hydroxides (LDH) based on Cu- substituted ZnAl for
           the design of efficient antibacterial ceramics
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Geetanjali Mishra, Barsha Dash, Sony Pandey, Diptipriya Sethi Cu-substituted ZnAl layered double hydroxides (LDH) were synthesized via co-precipitation method by varying the amount of Cu and explored as efficient antibacterial materials. The as-synthesized materials were characterized with various methods including elemental analysis, X-ray diffraction, transmission electron microscopy and scanning electron microscopy, particle size analyzer etc. which revealed that LDH materials were well crystallized. In addition, the flakes of LDH were well dispersed, one flake being easily distinguished from another. The as-synthesized Cu-LDH was calcined at a temperature range of 400–800 °C to get perfect spinel and corresponding oxide phase. Particle size analysis revealed that the size of the corresponding oxides decreases to nano size from micron size. As an application, antibacterial activity of the ternary LDH were investigated against both gram positive and gram negative bacteria. Furthermore, the antibacterial performance of corresponding spinels and oxides were compared with the as-synthesized materials and the result could prove the efficiency of spinel materials with that of LDH materials. The calcined composite was added with Portland cement in different ratios like 3:1, 1:1 and 1:3, 1:10, 1:15 and 1:20 and it was found that up to the ratio of 1:20, the mixture is an effective antibacterial material against E.coli. Therefore, Cu substitution in ZnAl ternary LDH could be a straightforward approach for designing efficient antibacterial materials with various potential applications such as ceramics, cement add-ons etc.Graphical abstractUnlabelled Image
  • The prospect of layered double hydroxide as bone implants: A study of
           mechanical properties, cytocompatibility and antibacterial activity
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Feng Peng, Donghui Wang, Dongdong Zhang, Huiliang Cao, Xuanyong Liu With the ability to host anions or neutral drugs, layered double hydroxide (LDH) are hot spots in the field of biomaterials. Intensive works so far only have focused on their application in surface modification or injectable medicine. Yet, little literatures report the potential of LDH as bone implants. In the present study, four types of LDH (MgAl, MgFe, ZnAl and ZnFe) were prepared via a coprecipitation method. Our results showed that the synthetic LDH powders can be pressed into discs in the absence of binder. The discs can maintain their shape after immersed in culture medium for 10 days, not including MgAl LDH disc. The elastic modulus of all discs was between 9 and 35 GPa, which was close to cortical bone (5–23 GPa). ZnAl LDH and ZnFe LDH showed higher cytotoxicity than MgAl LDH and MgFe LDH whether in the form of suspension or extract. Furthermore, even up to 10 mg/mL, the extract of MgAl LDH and MgFe LDH showed no cytotoxicity, while cells were totally died in the extract of ZnAl LDH and ZnFe LDH. Compared with cells, bacterial showed an even lower tolerance concentration to ZnAl LDH and ZnFe LDH. This study indicates that Mg-containing LDH show better cytotocompatibility, while Zn-containing LDH show better antibacterial property. With proper elastic modulus and controllable biological effect, LDH are promising to be used as bone implants.
  • Investigation of the initial stages of the montmorillonite acid-activation
           process using DFT calculations
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Carla G. Fonseca, Viviane S. Vaiss, Fernando Wypych, Renata Diniz, Alexandre A. Leitão Many important properties of the clay minerals such as montmorillonite (Mt) arise from their surface chemistry especially when this material is submitted to an acid activation process which will result in materials catalytically active for a variety of reactions. The acid activation preferentially occurs on the edge surfaces, in this sense ab initio calculations were performed in order to determinate the most probable models for (010) and (110) surfaces in both pyrophyllite and Mt clay minerals, the edge stability, the initial stages of the acid activation process and the main acid sites present in the structures. The calculations predicted that the (110) edge surface is more stable than the (010) edge surface at pyrophyllite, on the other hand, at Mt the (010) surface has shown to be more stable, thus the pyrophyllite edge surfaces should not be used as representative models of Mt edge surfaces. The microstructural evolution of the Mt during the acid activation was investigated by 29Si and 27Al SSNMR simulations and these calculations could assist in the correct assignment of the silicon and aluminum chemical environments. The reactivity of the surfaces was evaluated and the calculations indicate that the acid character of the acid-activated Mt mainly comes from the H sites present in silanol and aluminol groups. These sites might be responsible for the catalytic activity of these materials.
  • Synthesis of 3D mesoporous alumina from natural clays for confining CdS
           nanoparticles and enhanced photocatalytic performances
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Xiaoyu Li, Kang Peng A spatial confinement effect of CdS nanoparticles in mesoporous alumina, which is synthesized through evaporation-induced self-assembly (EISA) method, post-impregnation approach and microwave irradiation process, was investigated to verify the enhanced catalytic activity and stability with less aggregation of CdS crystallites during decoloration of organic dyes under visible-light irradiation. In this work, we utilize inexpensive natural clays for preparing mesoporous alumina via evaporation-induced self-assembly method, and used as the host for confining CdS nanoparticles to suppress the crystallite growth and aggregation. The loading amount and grain size of CdS nanoparticles significantly altered catalytic activity and stability. CdS clusters confined inside the mesoporous channels provided abundant reactive sites for photocatalytic reaction through spatial confinement effect, quantum size effect and sulfide-support interaction, thus greatly enhancing the reaction activity. CdS/MAl composites have large special surface area, strong visible light absorption and high quantum yields. CdS/MAl-25 photocatalyst has exhibited remarkably enhanced visible light photoactivities as compared to other catalysts, and the overall decoloration rate was up to 97.5% after visible light irradiation for 60 min. The CdS/MAl composites exhibit potential applications in the wastewater treatment under visible light irradiation.Graphical Mesoporous alumina from natural clays for confining CdS nanoparticles (CdS/MAl) were successfully prepared through evaporation induced self-assembly, post-impregnation and microwave irradiation as a novel photocatalyst for organic pollutants removal.Unlabelled Image
  • Analysis of the structural changes of a pellet/powder bentonite mixture
           upon wetting by X-ray computed microtomography
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Agustín Molinero Guerra, Patrick Aimedieu, Michel Bornert, Yu-Jun Cui, Anh Minh Tang, Zhao Sun, Nadia Mokni, Pierre Delage, Frédéric Bernier Pellet/powder bentonite mixture is one of the candidate materials for sealing plugs in deep geological high-level radioactive waste disposal. This note presents an investigation on the structure changes of this mixture occurring during the saturation process by means of X-ray computed micro-tomography. The test was performed in an infiltration column (60 mm in inner diameter and 120 mm in height). Water was supplied to the two ends of the column and the changes of the sample morphology were observed during a period of 100 days of hydration. Digital Volume Correlation (DVC) technique was used to determine the vertical displacement field of the bentonite powder. A pressure transducer was used to measure the axial swelling pressure during the hydration. The results show that the initial distribution of powder in the inter-pellet pores was not homogeneous; the powder filled almost completely the pores in the zones close to the two ends while air-filled inter-pellet voids were observed in the middle of the column specimen. When water started to infiltrate inside the specimen from both ends, the pellets and the powder grains started to swell (because of the swelling properties of smectite, the principal mineral of bentonite) and filled the voids. That induced at the same time increase of swelling pressure and downward movement of powder grains. The results allowed a better understanding on the hydro-mechanical couplings, at the pellet scale, in the pellet/powder bentonite mixture upon wetting.
  • Assessment of potassium release threshold levels of Vertisols
           (shrink-swell soils) in different agro-ecological regions of India
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Priya P. Gurav, S.C. Datta, S.K. Ray, P.L. Choudhari, N. Ahmed Studies to evaluate the release threshold level of potassium in Vertisols (shrink-swell soils) in different agro-ecological regions of India and how that may help in K fertility interpretations are rare. Thus the objectives of this study were (i) to evaluate the K status of Vertisols through release threshold levels and (ii) to relate the findings with soil K release and fertilizer management. Three established soil series samples were collected from Vertisols of different agro-ecological regions of India. Release threshold level (RTL) was assessed after equilibrating soil with 0.01 M CaCl2 solution having series of soil: solution ratio, after which the remaining amount of exchangeable K was extracted with 1 N NH4OAc (pH 7). Total amount of K extracted (KT = K desorbed in CaCl2 solution plus K extracted with 1 N NH4OAc) remained more or less constant with decreasing K-level up to a certain value (say threshold value) below which KT increased sharply indicating K release from non-labile form. The threshold value in terms of K concentrations (Release Threshold Concentration) of Panjari, Nagpur, Maharashtra (Typic Haplusterts, Sub-humid dry), Teligi, Bellary, Karnataka (Sodic Haplusterts, Semi-arid dry) and Kheri, Jabalpur, Madhya Pradesh (Typic Haplusterts, Sub-humid moist) soils were 0.044–0.049, 0.034–0.062 and 0.043–0.11 mm, respectively. The high release threshold K levels in terms of concentration and activity ratio (AR) were observed in soils of Teligi and Kheri series as compared to soils of Panjari series due to high content of trioctahedral mica in the former two soils. The relationships between clay minerals, release threshold level, exchangeable potassium and non-exchangeable potassium determined by 1 N HNO3 and sodium tetra-phenyl borate (NaBPh4) have been discussed.
  • In−situ complexation of o−phenanthroline in the interlayer of
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Anand Kabadagi, Santosh Chikkamath, Jayappa Manjanna, Satoru Kobayashi The solid state reaction between Fe(II)−montmorillonite (Mt) and o−phenanthroline (L) resulted in the in-situ complexation of interlayer Fe(II) ions with L. The formation of the [FeL3]2+ complex in the interlayer was confirmed from X−ray diffraction (XRD), thermal analysis (TG/DTA), infrared (FT−IR) and diffused reflectance (DR) UV−Vis spectra. The basal spacing (d001) of this inorganic-organic hybrid material, Fe(II)−Mt−L, was found to be 18 Å at room temperature. The XRD pattern shows the self-oriented (stacked) layer structure, which is independent of relative humidity. The TG−DTA curve shows the decomposition of interlayer complex at about 450 °C. The FTIR spectra show the prominent C−H bending for L around 720 cm−1 and 845 cm−1 in addition to other structural features of clay mineral. The DR UV−Vis spectra shows the absorption at about 510 nm, which is a characteristic value for [FeL3]2+ complex. The FE−SEM image and magnetic behaviour of the Fe(II)−Mt−L are compared with Fe(II)−Mt. The Fe(II)−Mt−L was heated upto 500 °C, and it was found that the structural integrity remained same until 350 °C as indicated by XRD, FTIR and TG-DTA. The d001 was reduced to 11.7 Å at about 400 °C and then the clay interlayer collapsed irreversibly to d001 of 9.6 Å. These hybrid materials are expected to show selective adsorption and catalytic property in organic (ca. Bigineli-type) reactions. As a first step, we have focused here only on preparation and characterization of these modified clay minerals by innovative approach.Graphical abstractUnlabelled Image
  • The use of pottery clay for canvas priming in Italian Baroque – An
           example of technology transfer
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): David Hradil, Janka Hradilová, Katarína Holcová, Petr Bezdička In the Baroque European painting technology, various coloured clays had been used to prime canvases. These clays are generally considered to be carefully selected in terms of colour and other technological properties (adhesiveness, ductility etc.), as the painting represented the most delicate field of fine art. However, it seems that the availability of the material at a given place as well as its price often played a much more significant role than previously thought. It led to the usage of highly heterogeneous cheap pottery clays in painting, even though they often had to be additionally coloured. For the first time, a clear evidence is provided that a very similar pottery clay material was applied in three different technological ways: i) as a clay body of an unfired terracotta statue created in Florence or Bologna at the end of 16th century, ii) as a secondary putty on the Renaissance painting by Antonello da Saliba (1466–1535), and iii) as a preparation layer – ground – of an oil-on-canvas paintings attributed to Italian Caravaggists (17th century) or also to Carlo Maratta or workshop (1655–1713). The identity of the material was confirmed by mineralogical analyses as well as description of nannofossils, which enable to date the clay to Eocene – Oligocene.Graphical abstractUnlabelled Image
  • Effects of carbonaceous matter additives on kinetics, phase and structure
           evolution of coal-series kaolin during calcination
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Shuai Yuan, Yanjun Li, Yuexin Han, Peng Gao In this study, the influence of carbonaceous matter on the kinetics, phase, and structure evolution of coal-series kaolin during the calcination process was systematically investigated. The pyrolysis characteristics were studied by thermogravimetric–differential-thermal-gravity–differential-scanning-calorimetry (TG–DTG–DSC), and the kinetic parameters were calculated by the Coats–Redfern (CR) method and the Flynn–Wall–Ozawa (FWO) method. Furthermore, the changes in the mineral composition, chemical structure, and morphology of the samples during calcination were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) analyses. The kinetic analysis demonstrates that the calcination reaction behaviors of the coal-series kaolin without and with carbonaceous matter additives were according to the third-order reaction model (F3); the differential expression of the F3 mechanism is g(α) = (1 − α)−2 – 1. The activation energy (Ea) and pre-exponential factor (lnA) increased by 7–14% and 13–23%, respectively, with carbon content addition increased from 2% to 6%. The relative decomposition rate of the kaolinite in the coal-series kaolin increased, the absorption peaks of the kaolinite decreased gradually, and the scale-shaped lamellar structures of the coal-series kaolin samples became irregular and amorphous with increasing carbon content under similar calcination conditions. Carbonaceous-matter additives can promote the thermal decomposition of coal-series kaolin during the calcination process.
  • Analytical and experimental analyses for mechanical and biological
           characteristics of novel nanoclay bio-nanocomposite scaffolds fabricated
           via space holder technique
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): S. Sahmani, M. Shahali, A. Khandan, S. Saber-Samandari, M.M. Aghdam In the present work, bioactive nanoclay-TiO2 (NC-T) bio-nanocomposite scaffolds containing different TiO2 weight fractions are fabricated spacer for bone tissue engineering applications via the space holder technique using NaCl particles as the. The microstructure, surface morphology (porosity) and bioactivity potential of the manufactured bio-nanocomposite scaffolds are examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), and inductively-coupled plasma optical emission spectroscopy (ICP-OES) techniques. The scaffold with optimized mechanical properties is predicted as NC-15wt%T with proper interconnected porosity and micro/macro pore size within the range of 1–2 (μm) and 3–5 (μm), respectively. Also, its mechanical properties including compressive strength, elastic modulus and crystallite size are extracted equal to 5.74 MPa, 438 MPa and 70–120 nm, respectively. The feasibility of the fabricated scaffolds for bioactive bone tissue engineering application (apatite deposition) is also evaluated using simulated body fluid (SBF) and physiological saline (PS) solutions. At the end, the nonlinear bending and vibration characteristics of an axially loaded beam-type bone implant made of the NC-T/NaCl bio-nanocomposite scaffolds are predicted analytically. In general view, the obtained results indicate that the NC-15wt%T/NaCl bio-nanocomposite scaffold may have excellent advantages for future research in bone regenerative applications.
  • An insight into the comprehensive application of opal-palygorskite clay:
           Synthesis of 4A zeolite and uptake of Hg2+
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Zongshan Wu, Tianhu Chen, Haibo Liu, Can Wang, Peng Cheng, Dong Chen, Jingjing Xie To availably utilize opal-palygorskite clay, dry beneficiation technique was applied to separate opal and palygorskite clay. Based on separated opal from opal-palygorskite clay, 4A zeolite was successfully synthesized by using a hydrothermal method. Box-Behnken was used to optimize Na2O/SiO2, H2O/Na2O and SiO2/Al2O3 with cation exchange capacity (CEC) as the response value. The optimum parameters was determined to be Na2O/SiO2 = 1.0, H2O/Na2O = 40, and SiO2/Al2O3 = 2.0, and CEC got the maximum of 2.99 mmol/(g·dry zeolite) under the conditions. The as-obtained 4A zeolite was characterized by using X-ray diffraction (XRD), thermo gravimetric analysis (TG), acid-base titration, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and then was applied to remove Hg2+ from aqueous solution. The maximum removal capacity of Hg2+ was 41.99 mg/g and adsorption equilibrium was obtained with contact time of 2 h. Effects of pH, ionic strength, temperatures, metal cations, strippant kinds and cycle times on removal behaviors of Hg2+ onto 4A zeolite were investigated by batch experiments. The kinetics and isotherms of Hg2+ adsorption fitted well by pseudo-second kinetic and Langmuir models. When Hg2+-adsorbed 4A zeolite was desorbed using 1 mol/L NaNO3 solution, the adsorption efficiency was maintained about 70% after four cycles.
  • Reinforcing effect of organoclay in nitrile rubber - Effect of mill mixing
           and latex stage mixing
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Bhavya Bhadran, Dhanya Vijayan, Neena George, C.S. Julie Chandra, P.M. Sabura Begum, Rani Joseph The urge for materials with diverse applications has paved the way to fabricate composites based on, one-dimensional filler like nanoclays. The main aim of the work was to study the effect of mill mixing and latex stage mixing on the reinforcing effect of organoclay in Nitrile Rubber. The non-ionic surfactant assisted latex stage mixing route proved to be more efficient and feasible when compared to mill mixing. Mechanical properties were measured and, about 150% increase in tensile strength and 79% increase in tensile modulus were obtained for the latex based composites at 3 phr clay loading when compared to neat rubber composites. Dynamic strain sweep tests revealed that, the low strain modulus for latex mixed composites was higher. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) results indicated that the addition of organoclay hardly affected the thermal properties of the rubber matrix. Transmission Electron Micrographs revealed homogeneous dispersion of partially exfoliated and intercalated nanoclay platelets in the latex state substantiating the viability of latex mixing over mill mixing. The extent of reinforcement in the nanocomposites was also analyzed with the help of different micromechanical models.Graphical abstractUnlabelled Image
  • Green synthesis of nano-muscovite and niter from feldspar through
           accelerated geomimicking process
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Jiangyan Yuan, Jing Yang, Hongwen Ma, Shuangqing Su, Qianqian Chang, Sridhar Komarneni Synthesis of nano-muscovite has significant implications for applications such as electrical insulation, composite materials and paper-making. In this study, an energy-saving, efficient and sustainable route to synthesize muscovite from K-feldspar was developed by mimicking natural chemical weathering process of feldspar. Here, well-crystallized nano-muscovite of uniform flaky morphology with a thickness of 20–40 nm was obtained at 250 °C in just 18 h after treatment of K-feldspar under hydrothermal conditions. Moreover, additional potassium generated by the dissolution of K-feldspar into solution was collected as KNO3. This is truly a green chemical process for the synthesis of muscovite and niter in a closed system as it not only conserved all the starting chemicals for reuse but also generated two useful by-products, niter and CaSiO3.Graphical abstractUnlabelled Image
  • The adsorption of nortriptyline on montmorillonite, kaolinite and gibbsite
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Shahrzad Sadri, Bruce B. Johnson, Maika Ruyter-Hooley, Michael J. Angove Nortriptyline (NT) is a tricyclic antidepressant in common use in many countries. Its presence in drinking water indicates that current wastewater treatment practices fail to remove it effectively from effluents with consequent adverse effects on aquatic organisms. Since mineral surfaces readily remove many organic substance from effluent streams, this research sought to study the adsorption of NT on montmorillonite, kaolinite and gibbsite. Adsorption edge and isotherm experiments were performed to determine the relative effectiveness of the three substrates for NT removal, and X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were used in order to gain an understanding of the mode of adsorption. Adsorption of NT on all three substrates was effectively independent of pH in the range from 3 to 12. Both montmorillonite and kaolinite proved to be excellent adsorbents of NT with maximum adsorption capacities of 19.3 and 6.4 μmol m−2 respectively at pH 6.0, but gibbsite adsorbed relatively little. The XRD and ATR-FTIR results indicated that NT formed as a multilayer on montmorillonite with no evidence of intercalation. Both electrostatic and hydrophobic interactions appeared to play important roles in the adsorption.
  • The zone of incipient 40Ar* loss-monitoring 40Ar* degassing behavior in a
           contact metamorphic setting
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Annette Süssenberger, Klaus Wemmer, Susanne Theodora Schmidt The 40Ar* retentivity behavior was studied in the contact metamorphic aureole of the Torres del Paine intrusion (51°S, Chile) and provides constraints on the closure temperature in contact metamorphic settings. The temperature conditions of the regional anchizonal to epizonal metamorphosed pelitic host rock and the contact metamorphic pelite were recorded by illite crystallinities (Kübler Index) and by Raman spectroscopy on carbonaceous matter. K/Ar age determinations were carried out on illite fine fractions (
  • Mechanochemical activation of phlogopite to directly produce slow-release
           potassium fertilizer
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Ahmed Said, Qiwu Zhang, Jun Qu, Yanchu Liu, Zhiwu Lei, Huimin Hu, Zhigao Xu Phlogopite, one trioctahedral mica, was activated by solvent-free ball milling to serve directly as slow-release potassium fertilizer. Before the final breakdown of the crystal structure, phase transformation of trigonal phlogopite into monoclinic by milling at 300 rpm for 120 min was observed for the first time. Different solubility of the amorphous product and monoclinic crystalline product in water or 2% citric acid was also obtained. The content of water soluble potassium (quick acting potassium) and 2.0% citric acid soluble one (slow release potassium) in the products could be easily changed by adjusting the milling speed depending on the requirement for plant growth. 100.0% K extraction in 2.0% citric acid solution from the amorphous sample and near 30% K extraction in water from the sample milled at 300 rpm was achieved. Several analytical methods such as XRD, SEM, FT-IR and TG-DTG were used to characterize the activated sample and to understand the reason for the easier dissolution of potassium. The proposed process was economical and environment-friendly, which could help to maintain a balanced supply of potassium fertilizer for sustainable development of agriculture by compensating partially current high-cost chemical fertilizer.
  • Kinetic and thermodynamic assessment on isoniazid/montmorillonite
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Esperanza Carazo, Ana Borrego-Sánchez, Rita Sánchez-Espejo, Fátima García-Villén, Pilar Cerezo, Carola Aguzzi, César Viseras The properties of montmorillonite (Mt) as a natural nanocarrier of drugs have been fully reported. Isoniazid (INH), a first-line tuberculostatic drug, was intercalated into this inorganic matrix and the equilibrium and thermodynamic aspects of the adsorption process were evaluated. Adsorption experiments were performed at different times and temperatures in aqueous medium. The overall adsorption process was the result of two simple processes: INH adsorption on the activated sites of Mt. followed by a slight precipitation phase of INH molecules over the adsorbed monolayer. Formation of the nanohybrid was spontaneous, exothermic and exoentropic, obtaining an increase in the thermodynamic stability of the system. The hybrid material (Mt-INH) was successfully prepared with high drug loading. Solid state characterization of the pure materials and the resulting nanohybrid was carried out. Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), differential scanning calorimetry (DSC), surface charge, X-ray powder diffraction (XRPD) and high resolution transmission electron microscopy (HRTEM) coupled with energy dispersive spectroscopy (XEDS) and elemental X-ray maps served to correctly resolve the structure of the nanohybrid and to assess the nature and degree of the drug-clay interactions.Graphical abstractUnlabelled Image
  • Texture profile analysis (TPA) of clay/seawater mixtures useful for peloid
           preparation: Effects of clay concentration, pH and salinity
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Manuel Pozo, Francisco Armijo, Francisco Maraver, José Manuel Ejeda, Iluminada Corvillo The liquid phase of a peloid can be mineral-medicinal, marine or salt lake water. This study was designed to experimentally determine the interaction between two bentonites and one sepiolite, and seawater as well as dilutions thereof to verify the effect of salinity on instrumental texture measurements in clay-water mixtures prepared with these components. In all the clay-water mixtures tested, instrumental hardness and adhesiveness decreased with water content. For a given instrumental hardness or adhesiveness, bentonite retained more water in the mixture with distilled water than with seawater. In contrast, sepiolite retained more water in the mixture with seawater than with distilled water. These differences affected the thermal behaviour of the clay-water mixtures. Instrumental hardness and adhesiveness curves may be a suitable tool to tailor concentrated dispersions and after maturation could be used in thalassos and medical spas as peloids.
  • Influence of thermal loading on index and physicochemical properties of
           Barmer bentonite
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Rohini C. Kale, K. Ravi The concept of the deep geological repository (DGR) has been widely accepted for the safe disposal of high-level nuclear waste (HLW). Compacted bentonite/bentonite-sand mixture is considered as buffer material in the deep geological repository due to its favorable physicochemical and hydro-mechanical properties. The bentonite buffer is expected to be exposed to high temperature for a long duration because the heat released from the waste canister and due to the geo-thermal gradient inside the deep geological repository. The temperature from the waste canister can go initially as high as 200 °C and probably reduce to ambient temperature upon the decay of the waste material. This long duration temperature variation induces a thermal loading on the bentonite buffer, affecting its index, physicochemical and hydro-mechanical properties. Hence there is a need to critically examine the effect of the induced thermal loading on the long-term performance of the buffer as this study will be quite useful for the preliminary understanding before fixing its design values for the use as a part of engineered barrier system (EBS) in DGR. In the present study, two bentonites (Barmer 1 (B1) and Barmer 2 (B2)) from Barmer district of Rajasthan, India, was subjected to four temperature levels, i.e., 60 °C, 110 °C, 150 °C and 200 °C for a time duration of 3, 7, 15, 21, 28 days. Changes in the physicochemical properties of both bentonites were observed and reported. The decrease in the Atterberg's limit, swelling, specific gravity, optimum moisture content, pH and exchangeable monovalent cation and increase in maximum dry density was recorded with an increase in temperature as well as with the duration of heating.
  • Green synthesis and characterization of colored Tunisian clays: Cosmetic
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): S. Gamoudi, E. Srasra Colored clays are prepared by a solid state reaction of dried leaves of flowers with a Tunisian clay used for pharmaceutical and cosmetic applications. The structural properties, photo- and thermal stability of the resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Differential scanning calorimetry analysis (DSC) and UV–visible spectroscopy. The mineralogical structure, physicochemical properties and pharmacopoeial tests of the purified clay suggested that this clay mineral can function in cosmetic products. The XRD results of colored clays revealed a slight difference in values of basal spacing d001 when compared to values obtained from purified clay. FTIR analysis confirmed changes in functional groups and surface properties of purified clay. DSC results proved a high thermal stability for purified and modified clays. UV–visible spectra of colored materials displayed a new band compared to purified clay in 400–700 nm wavelength region. The microbiological tests revealed the suitability of all clays for the cosmetic products.Graphical abstractUnlabelled Image
  • A comparative study about superamphiphobicity and stability of
           superamphiphobic coatings based on Palygorskite
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Jie Dong, Qing Zhu, Qingyun Wei, Baohui Zheng, Shangbin Li, Junping Zhang Naturally rich clay minerals are receiving increasing attention recently in preparation of super anti-wetting coatings, superhydrophobic and superamphiphobic ones. Clay minerals are a class of very promising natural building blocks for constructing microstructures of the coatings. Clay minerals such as Palygorskite (Pal), kaolinite, halloysite nanotubes and montmorillonite have been used. However, the comparative study about the effects of source of clay minerals on properties of the coatings remains a gap to be filled. Here, the first comparative study about superamphiphobicity and stability of superamphiphobic coatings based on Pal from different sources was reported. The superamphiphobic coatings were fabricated by hydrolytic condensation of silanes in the presence of Pal followed by spray-coating the as-prepared dispersions onto substrates. Five Pal samples from Anhui, Jiangsu and Gansu Provinces of China were chosen, and their effects on superamphiphobicity and stability of the coatings were studied using various analytical techniques including scanning electron microscopy and X-ray photoelectron spectroscopy. The superamphiphobicity and stability depend on micro/nanostructures of the coatings, originating from the microstructures of Pal. The Pal sample from Anhui is more suitable for preparing superamphiphobic coatings than the others because of the higher Mg content and the higher aspect ratio of the Pal nanorods. The finding will shed light on the progress of the clay-based super anti-wetting coatings.Graphical abstractUnlabelled Image
  • Montmorillonite as a reinforcement and color stabilizer of gelatin films
           containing acerola juice
    • Abstract: Publication date: 1 December 2018Source: Applied Clay Science, Volume 165Author(s): Hálisson L. Ribeiro, Edy S. Brito, Men de sá M. Souza Filho, Henriette M.C. Azeredo Montmorillonite (Mt) is well known as reinforcing agent in films. Moreover, it stabilizes anthocyanin pigments. In this study, Mt has been added as both reinforcement and color stabilizer to gelatin films containing acerola juice. Films were produced with different Mt concentrations (0–6.5% on gelatin). Increasing Mt contents resulted in enhanced tensile strength and modulus, although the elongation has been decreased. Mt also reduced the water vapor permeability in up to 45%. Mt presented two effects on film color: first, it changed its color from yellowish to red; and second, it stabilized film color throughout storage, mainly when added at 3.9%. It has been suggested that metals from Mt (such as Fe3+ or Al3+) may have formed complexes to anthocyanins, changing and stabilizing their color.Graphical abstractUnlabelled Image
  • Cobalt-doped Ni–Mn layered double hydroxide nanoplates as
           high-performance electrocatalyst for oxygen evolution reaction
    • Abstract: Publication date: Available online 1 August 2018Source: Applied Clay ScienceAuthor(s): Yi Wang, Xiaohe Liu, Ning Zhang, Guanzhou Qiu, Renzhi Ma Active, stable and low-cost electrocatalysts are in high demand to replace the traditional noble metal catalysts towards efficient water splitting. Here we report a type of nickel-manganese (Ni–Mn) layered double hydroxide (LDH) with controllable doping content of cobalt as an oxygen evolution reaction (OER) electrocatalyst with excellent performance in alkaline media. Co-doped Ni–Mn LDH nanoplates were synthesized via a facile hydrothermal method. It was found that the doping content of cobalt significantly affected the OER activities. The best electrocatalyst was based on a doping ratio of 21.1% Co, exhibiting a low overpotential of ~310 mV at a current density of 10 mA cm−2, a Tafel slope of ~59 mV dec−1 as well as excellent stability. This work demonstrates a facile synthetic method of rationally doping transition-metal hydroxides to develop new OER electrocatalysts with remarkable performance in water splitting.Graphic abstractNiMn LDH nanoplates with tunable cobalt doping content could be successfully prepared via a simple hydrothermal method. The doping content of cobalt in NiMn LDH nanoplates has a significant influence on their OER activities. The 21.1% Co-doped NiMn LDH exhibited excellent OER efficiency realizing an overpotential of 310 mV, Tafel plot of 59 mV/decade and a stable operating potential without fluctuating above 5 mV for 9 h. This work demonstrates a facile synthetic method and doping strategy for exploring electrocatalysts with remarkable OER performance, which will promote the development of transition-metal based hydroxides as high-performance electrocatalyst for water splitting.Unlabelled Image
  • Kinetic re-evaluation on “Comparative adsorption of Pb(II), Cu(II) and
           Cd(II) on chitosan saturated montmorillonite: Kinetic, thermodynamic and
           equilibrium studies”
    • Abstract: Publication date: Available online 7 May 2018Source: Applied Clay ScienceAuthor(s): Yong-Son Hong
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
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