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  • Study on viscoelastic behaviors of bentonite/nitrile butadiene rubber nanocomposites compatibilized by different silane coupling agents
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-15
    Xin Ge, Zhijian Zhang, Huitao Yu, Bangwen Zhang, Ur Ryong Cho

    The influences of bentonite and different silane coupling agents (SCA) on the viscoelastic properties of nitrile butadiene rubber were studied in this work. The silane coupling agents compatibilized bentonite/nitrile butadiene rubber nanocomposites were fabricated by a novel green method. The viscoelastic behaviors of the nanocomposites and their vulcanizates were explored using a rubber processing analyzer (RPA) in the modes of strain sweep and frequency sweep. Storage modulus (G′) and elastic torque (S′) of nitrile butadiene rubber increased significantly with the incorporation of bentonite. In the SCA applied in this work, mercaptopropyltrimethoxysilane (MPTMS) contributed to high storage modulus (G′) of the nanocomposites because of thorough exfoliation of bentonite and short sulfur bonds formed during curing process. Meanwhile, multi-sulfur bonds in bis-[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) and reversible interactions from [3-(2-aminoethylamino)propyl] trimethoxysilane (AEAPTMS) resulted in lower storage modulus of the cured nanocomposites.

  • Chemically modified kaolinite nanolayers for the removal of organic pollutants
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-14
    Qiang Zhang, Zhaoli Yan, Jing Ouyang, Yi Zhang, Huaming Yang, Deliang Chen
  • Synthesis and characterization of PMMA and organic modified montmorilonites nanocomposites via in situ polymerization assisted by sonication
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-13
    Bruna Rosa Prado, Julio Roberto Bartoli

    A variety of organo-modified montmorillonite (OMMT) and poly(methylmethacrylate) (PMMA) nanocomposites (CPN) were synthetized by in situ polymerization in a chloroform solution under probe sonication at clay loadings of 3 mass%. A factorial experimental design was used to study the effects of the synthesis variables: Flory-Huggins (F-H) interaction parameters between PMMA and clay organomodifier (three grades of OMMT) and sonication energy (26.0 kJ, 30.3 kJ and 34.6 kJ), aiming clay dispersion at nanoscale levels into the polymeric matrix and improvements in CPN properties. The distinct surfactant side groups of commercial OMMT were: hydroxyl (C30B), aryl (C10A) or alkyl (C25A), considering their similar interlayer space. Multiple techniques of analysis to evaluate the level of clay dispersion were used. Small-amplitude oscillatory shear rheology (SAOS) indicated a high level of clay dispersion for the PMMA/C25A CPN and a tendency to form a percolated network structure from the low shear thinning exponent nω of complex viscosity, either at low (nω = −0.97) or high (nω = −0.83) sonication energy. However, the rheological results showed a low level of clay dispersion for PMMA/C10A (nω = −0.70) and PMMA/C30B (nω = −0.40). The F-H interaction parameter was the statistically significant factor for the shear thinning exponent nω response. X-ray diffraction (XRD) of CPN exhibited no discernible reflections for PMMA/C25A-26 kJ and PMMA/C10A-30.3 kJ CPN, suggesting that a high level of clay dispersion was achieved. Transmission electronic microscopy (TEM) images of PMMA/C25A-36.4 kJ and PMMA/C30B-26 kJ CPN showed exfoliated/intercalated and intercalated morphologies, respectively. Thermogravimetry presented a significant increase in PMMA chain scission temperature of up to 82 °C for all CPN when compared to pristine PMMA. The UV–visible transmittance of PMMA/C25A-26 kJ CPN showed to be around 4.5% lower in comparison with pristine PMMA. The CPN refractive index showed a slight reduction, which could even candidate them for new materials in optical electronic devices. The improvements in the verified properties for PMMA/C25A CPN were attributed to the lower F-H interaction parameter of C25A alkyl surfactant with chloroform when considering the others OMMT side groups. The chemical affinity of the alkyl chain to the chloroform could contribute to the diffusion of the solvent/monomer solution into the interlayer space of the clay, prior to polymerization, and then the polymer chain growth to push the layers apart.

  • Effect of optimum compaction moisture content formulations on the strength and durability of sustainable stabilised materials
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-09
    Mohamad Nidzam Rahmat, Norsalisma Ismail

    The achievement of Optimum Compaction Moisture Content (OCMC) of clay soil plays an important role in compaction as well as the durability and strength of compacted soil. This is due to its effect on the structure and orientation of the clay soil particles. Most researchers on stabilised systems involving soils and/or industrial waste by-product additives for applications in roads and buildings are faced with the problem of how to approach the establishment of OCMC, when the complex mixtures involved. This paper reports on the laboratory investigation of theoretical methods of two different approaches to establish the OCMC in the stabilisation of clay soil involving multi-binary binder in cementitious binder system. Furthermore, this research also explores the use of an industrial by-product, Pulverized Fuel Ash (PFA) as partial target material and ground granulated blastfurnace slag (GGBS), with a view to reducing the reliance on the traditional cementitious binders, such as lime and/or Portland Cement (PC), in stabilising Lower Oxford Clay (LOC) soil combining with PFA at 50:50 ratio. LOC + PFA was stabilised both in conventional manner using Lime and PC as control and using sustainable binders incorporating GGBS. The results show that there was no one particular approach to the establishment of the optimal compaction moisture content for best strength development and durability. The best approach being dependent on the period of curing, stabiliser content and whether GGBS was blended with Lime or with PC. Of the various stabilisers studied, the highest strength magnitudes were however recorded with LOC-PFA stabilised using the blended binders incorporating GGBS. For all 7, 28 and 56 days of curing periods, the PC-based stabilisers were observed to be less sensitive to the different approaches to compaction moisture content, relative to the lime-based systems.

  • 更新日期:2018-03-11
  • Identifying the differences between clays used in the brick industry by various methods: Iron extraction and NMR spectroscopy
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-09
    Julie Peyne, Ameni Gharzouni, Isabel Sobrados, Sylvie Rossignol
  • Reprint of ZnO/sepiolite heterostructured materials for solar photocatalytic degradation of pharmaceuticals in wastewater ☆ ☆☆
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-09
    M. Akkari, P. Aranda, C. Belver, J. Bedia, A. Ben Haj Amara, E. Ruiz-Hitzky
  • Hyperspectral remote sensing for mapping and detection of Egyptian kaolin quality
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-06
    Mahmoud E. Awad, Reda Amer, Alberto López-Galindo, Mahmoud M. El-Rahmany, Luis F. García del Moral, César Viseras

    This study aims to use spectral analysis and hyperspectral Hyperion remote sensing images of the Egyptian Abu Zenima Carboniferous and Cretaceous kaolin deposits, located in West-Central Sinai Peninsula, for mapping the spatial distribution of their qualities determined by their mineralogical and geochemical parameters. Mineral quantification has been made by X-ray diffractometry and chemical analysis, and kaolinite structural order-disorder degree was measured by mean of the Hinckley (HI), Stoch (IK) and Liètard (R2) indices. The geochemical characteristics classified the studied samples into ferruginous and non-ferruginous deposits. The mineralogical composition discriminated the studied sample grades into kaolin (>75% kaolinite), silty kaolin (75–50% kaolinite) and kaolinitic siltstone (<50% kaolinite). Abu Zenima kaolin quality is mainly influenced by quartz and Fe-Ti minerals contents. The Carboniferous kaolin samples are characterized by ordered kaolinite (HI or R2 > 1 and IK < 0.7), while the Cretaceous kaolins exhibited mainly disordered kaolinite (HI or R2 < 1 and IK > 0.7). Five EO-1 Hyperion Level 1 GST radiometrically and geometrically corrected images of April and May 2011 were used to identify the spatial distribution of Carboniferous and Cretaceous kaolin grades and the structural characteristics of kaolinite. The position, depth, full-width-half-maximum and 22SP-Index of the absorption features were calculated for the continuum-removed spectra in the range 350–2500 nm. Prominent absorption features spectra occur around ~1400, ~1900, ~2200 and 2300 nm, and there are shifting and changes in their position and morphology with the kaolinite richness and the structural order-disorder degree. Spectral Angle Mapper (SAM) supervised classifications proved successfulness for identifying the kaolinite spatial distribution on the Hyperion images using the measured spectra of kaolins with different qualities and structural order-disorders.

  • Microbially induced palygorskite-sepiolite authigenesis in modern hypersaline lakes (Central Spain)
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-03-03
    Pablo del Buey, Óscar Cabestrero, Xabier Arroyo, M. Esther Sanz-Montero
  • Calcium adsorption on clays: Effects of mineralogy, pore fluid chemistry and temperature
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-26
    Chinchu Cherian, Nikhil John Kollannur, Sandeep Bandipally, Dali Naidu Arnepalli

    The present study describes the calcium adsorption behavior of clays exhibiting distinct mineralogical composition. The adsorption characteristics were determined using conventional batch-equilibrium sorption method, and different theoretical models were applied to describe the equilibrium sorption isotherms. The variation in calcium adsorption capacity was determined as a function of clay mineralogy, temperature and pore fluid chemistry. Further, the thermodynamic parameters were also calculated to describe the nature of adsorption mechanisms. Significant variation in calcium adsorption potential was observed among the clays, primarily attributed to their mineralogical diversities and related unique surface charge properties. The adsorption density escalated with rise in calcium concentration, temperature and pH of the adsorption system. These observations can be attributed to surface charge modifications and mineral dissolution properties of the clays, which in turn resulted in higher electro-negativity of the clay surface and thereby enhancing the affinity for calcium ions.

  • Interactions between kaolinite and phosphinate-based flame retardant in Polyamide 6
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-22
    M.A. Batistella, R. Sonnier, B. Otazaghine, C.O. Petter, J.-M. Lopez-Cuesta

    The interactions between kaolinite and a commercially available phosphinate-based flame retardant (Exolit® OP1311) were evaluated as flame retardant systems in Polyamide 6 (PA6). The thermal degradation and flammability of PA6 composites were studied by TGA and cone calorimeter tests. Characterizations were conducted using FTIR, EDX and XRD. Cone calorimeter results showed a reduction in peak heat release rate (pHRR) as a function of filler loading and type with a greater reduction for OP1311 containing composites. Interestingly, OP1311 can be partially substituted by kaolinite without detrimental effect on peak of release rate (pHRR) measured by cone calorimeter. FTIR, EDX and XRD analysis of cone calorimeter residues showed that kaolinite may trap some phosphorous compounds in condensed phase leading to the formation of a glassy structure on sample residue. To assess possible interactions between kaolinite and phosphinate, a controlled thermal degradation was carried out on kaolinite, OP1311 and kaolinite/OP1311 (50:50) blends. The residues were analyzed by EDX and XRD. Results showed that almost all phosphorous present in the initial sample remains in residue for Kaolinite/OP1311 blend versus only about 60% for OP1311 alone. Also, XRD results showed that during combustion, new crystalline phases can be formed in the sample when kaolinite is combined with OP1311. These results suggest that some interactions between both components may occur and could explain the observed fire behavior of the composites containing kaolinite and phosphinate.

  • 更新日期:2018-02-22
  • Durable and fluorine-free superhydrophobic coatings from palygorskite-rich spent bleaching earth
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-22
    Penglin Zhang, Shuantao Dong, Bucheng Li, Xudong Wei, Junping Zhang
  • Effective removal of emulsified oil from oily wastewater using surfactant-modified sepiolite
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-21
    Yunfei Li, Maoxin Wang, Dejun Sun, Yujiang Li, Tao Wu
  • Mineral abundances quantification to reveal the swelling property of the black cotton soil in Kenya
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-20
    Shiding Miao, Jianzhou Shi, Yanbin Sun, Peng Zhang, Zhaopu Shen, Hongen Nian, Jinqiu Huang, Xueqiu Wang, Peiping Zhang
  • Behavior of talc and mica in copper ore flotation
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-16
    Saeed Farrokhpay, Bulelwa Ndlovu, Dee Bradshaw

    Talc and mica are major gangue minerals in many base metal ores including sulfide ores. Talc is a naturally hydrophobic mineral, and therefore it is easily floatable. There have been many studies to overcome this problem, and depress talc with various reagents. In this study the flotation of a copper ore in the presence of talc and muscovite was studied. It was found that talc can affect copper flotation mainly via froth phase. The copper grade and recovery were affected in the presence of only 7% talc. On the other hand, muscovite influenced the pulp phase via affecting the pulp rheology. The copper flotation grade was reduced in the presence of high amount (30%) of muscovite due to the entrainment, but its effect on the copper recovery was negligible.

  • Effect of surface property of halloysite on the crystallization behavior of PBAT
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-16
    Xujuan Li, Daoyong Tan, Lan Xie, Hongjuan Sun, Shiyong Sun, Ganji Zhong, Penggang Ren
  • Anionic surfactant induced desorption of a cationic surfactant from mica
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-16
    Finian J. Allen, Chris L. Truscott, Rebecca J.L. Welbourn, Stuart M. Clarke

    The adsorption and desorption of a cationic surfactant, didodecyldimethylammonium bromide, from water onto a mica surface have been investigated using neutron reflectivity. The surfactant was observed to adsorb strongly as a bilayer that was tenacious to a sustained water wash, but on the addition of an anionic surfactant, sodium dodecyl sulfate, at its critical micelle concentration complete desorption was observed.

  • Preparation of nanocomposites for the removal of phenolic compounds from aqueous solutions
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-16
    Karina Abigail Hernández-Hernández, Javier Illescas, María del Carmen Díaz-Nava, Sonia Martínez-Gallegos, Claudia Muro-Urista, Rosa Elena Ortega-Aguilar, Efraín Rodríguez-Alba, Ernesto Rivera
  • Origin and paleoenvironmental significance of Fe single bond Mn nodules in the Holocene perialpine sediments of Geneva Basin, western Switzerland
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-15
    Branimir Šegvić, Stéphanie Girardclos, Giovanni Zanoni, Carlos Arbiol González, Tara Steimer-Herbet, Marie Besse
  • 更新日期:2018-02-15
  • Influence of ZnO on the activation of kaolinite-based coal waste: Pozzolanic activity and mineralogy in the pozzolan/lime system
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-14
    R. García-Giménez, R. Vigil de la Villa, S. Martínez-Ramírez, L. Fernández-Carrasco, M. Frías

    One inconvenience presented by the thermal activation of kaolinite-based wastes is their low content of metakaolinite, a highly pozzolanic product listed in current standards for the manufacture of commercial cements. The addition of a chemical activator during the thermal activation process is a priority line of research to increase the reactivity of the recycled metakaolinite. In this paper, an additional chemical activator, ZnO, is studied and its effect on both pozzolanic properties and the evolution of mineralogical phases in the thermal activation of coal waste with a reaction time of up to 90 days in the pozzolan/lime system. To do so, activation temperatures of between 550 °C/650 °C were selected and additions of chemical activator (ZnO) in percentages of between 0.0% and 3.0% by weight of coal waste, because it is an activator with a positive effect on a 100% natural kaolinite. The results showed that the incorporation of ZnO inhibited the reactivity of the recycled metakaolinite and in consequence, the capacity of the metakaolinite to react with the surrounding lime; even more so when the content of added chemical activator was raised, albeit with some exceptions, in the samples activated at 550 °C and 650 °C with 0.5% of chemical activator. In none of the cases under analysis was the chemical activator able to improve the properties of the metakaolinite in comparison with the properties of the reference sample activated only with temperature. The hydrated phases that appeared in the pozzolanic reaction were tetracalcium aluminate hydrate, stratlingite, monosulfoaluminate hydrate and LDH (phyllosilicate/carbonate).

  • Alginate clay hybrid composite adsorbents for the reclamation of industrial lean methyldiethanolamine solutions
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-14
    Anjali Achazhiyath Edathil, Priyabrata Pal, Fawzi Banat

    Alginate based clay hybrid composites were used as adsorbents for the removal of total organic acid anions (TOA) as heat stable salt (HSS) and heavy metal ions (chromium and iron) from industrial lean methyldiethanolamine (MDEA, 50 wt%) solvents. Spherical calcium alginate based hybrid (CAH) composites were prepared using three different filler clays such as sepiolite, montmorillonite and bentonite. To overcome the inherent iron leaching problem associated with clay minerals, an appropriate clay treatment method was utilized before preparing the hydrogel composite. The structure of the clay (before and after modification) and composites was characterized by XRD, whereas the sorption mechanism of the CAH hydrogel composites was conferred in combination with the results obtained from SEM, EDX and FTIR analyses. The effect of quantitative contributions of polymer, bead size, agitation speed, cross linker concentration, reaction time and filler weight% were studied using batch adsorption. The initial experiments confirmed that all the hybrid composites could superiorly separate HSS and heavy metal ions from lean MDEA solvents. 2.0 wt% clay containing composite hydrogels prepared by using 1 mm dropper in a CaCl2 solution of 1.5 M was found to have highest adsorption capacity. Thus, calcium alginate hybrid (CAH) composites showed efficient adsorption capacity for removing all the contaminants present in lean MDEA.

  • A facile preparation of superhydrophobic halloysite-based meshes for efficient oil–water separation
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-13
    Danyi Guo, Jiahui Chen, Kun Hou, Shouping Xu, Jiang Cheng, Xiufang Wen, Shuangfeng Wang, Chaoyun Huang, Pihui Pi

    A superhydrophobic halloysite-based mesh was facilely prepared by spraying epoxy/hexadecyltrimethoxysilane-halloysite nanotubes (HDTMS-HNTs) on stainless steel mesh. The as-prepared mesh was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical contact angle meter (OCA). The HNTs modified by HDTMS not only enhanced surface roughness, but also endowed hydrophobicity of the mesh. The mesh, with a static water contact angle of 154° and a sliding angle of 1.5°, was applied to separate a series of oil-water mixtures, such as n-hexane-water, isooctane-water and petroleum ether-water, with high separation efficiency of over 98%. The mesh still kept separation efficiency approximately 98.5% even after 25 separation cycles for n-hexane-water mixture separation. More importantly, the mesh is durable enough to withstand heat, chemical and mechanical challenges, such as hot water, strong alkaline, strong acid and sand abrasion, and high hydrostatic pressure. The as-prepared mesh will be a promising material in oil-water separation, because of the simple, economical and easily scalable preparation method and the excellent separation performance in radical oil-water separation.

  • Hydrothermal synthesis of zeolites using sanitary ware waste as a raw material
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-09
    Fátima García-Villén, Eduardo Flores-Ruíz, Cristóbal Verdugo-Escamilla, F. Javier Huertas

    Zeolites are extensively produced by hydrothermal treatment of different raw materials, such as kaolin. Sanitary ware (SW) is a kaolin-based ceramic ware usually found in sinks, urinals and bathtubs whose production is led by Spanish domestic clay product industry. SW production generates approximately 8% of solid waste in Spain, which increases landfills sizes and pose economic, social and technical problems. This study aims to evaluate the feasibility of solid waste of SW industry to produce zeolites once subjected to a conventional hydrothermal treatment during different times and temperatures. Ground SW was subjected to dissolution in a highly basic medium (NaOH 5 M) inside a Teflon-lined stainless steel reactors, at temperatures of 100, 150 and 200 °C for 1 to 30 days. X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize both the raw material and resultant mineral phases. Quartz and mullite present in SW transform into zeolites, as temperature and time increase. Mineral assemblage at 100 °C includes zeolite P, Na-faujasite and sodalite as major component and analcime, natrolite, and zeolite A as minor, which behave as metastable phases and their relative abundance depends on aging time. Analcime and cancrinite crystallization is favored by high temperature (150 °C to 200 °C) and increasing aging time produces analcime disappearance. Cancrinite is the dominant mineral after 30 days. Conventional SW waste is an optimal raw material for zeolites synthesis under high alkaline hydrothermal conditions. Combining time and temperature it is possible to drive crystallization towards a target phase.

  • Smectite in bentonite: Near infrared systematics and estimation of layer charge
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-02
    C. Tsiantos, V. Gionis, G.D. Chryssikos
  • Water adsorption and its impact on the pore structure characteristics of shale clay
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-01
    Dong Feng, Xiangfang Li, Xiangzeng Wang, Jing Li, Fengrui Sun, Zheng Sun, Tao Zhang, Peihuan Li, Yu Chen, Xu Zhang

    Water is considered ubiquitous within the shale reservoirs and mainly stored in the hydrophilic clay minerals. The water distribution characteristics and its effect on pore structure are important for the gas-in-place of shale systems. In this work, water vapor adsorption on montmorillonite (Mt), kaolinite (Kaol) and illite (Il) were performed to investigate the behaviors of water adsorption on shale clay. Subsequently, the moisture-equilibrated samples were conducted with N2 gas-adsorption techniques to investigate the effect of adsorbed water on pore structure characteristics, such as apparent pore size distribution (APSD), N2 BET specific surface area (N2-BET SSA) and pore volume (PV). The results show that the water uptake isotherms of our samples have the sigmoidal-shaped profiles and GAB model provides a good fit for the adsorption behavior. In addition, The APSD curves under different relative humidity (RH) conditions have validated the condensation effect and indicated that the small pores (approximately smaller than 5 nm) are blocked by the capillary water and will disappear on the APSD curves at RH of 98% while the large nanopores (> 5 nm) are covered with water film, these effects will lead dramatically decrease of N2-BET SSA. Taking Mt and Il samples as the examples, the N2-BET SSA has declined to 33.51% and 33.66% compared with the dry conditions when Sw approaches to 50%. Meanwhile, these effects also indicate that the gas storage for clay minerals is massively overestimating under dry condition, the contribution to methane adsorption might be negligible in the actual shale reservoir.

  • 更新日期:2018-02-02
  • Rheological and filtration properties of clay-polymer systems: Impact of polymer structure
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-01
    Hafiz Mudaser Ahmad, Muhammad Shahzad Kamal, Mamdouh A. Al-Harthi

    In this study, the effect of polymer structure, the degree of hydrolysis, chemical structure of monomer in the backbone, and charge distribution of monomer groups on rheological and filtration properties of Bentonite (Bent)/polymer dispersions were assessed. Two different water-soluble polymers were employed to investigate the rheological and filtration properties of Bent/polymer dispersions. The polymers evaluated are a copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid (AM-AMPS) (P1) and a terpolymer of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and N-Vinylpyrrolidone (AM-AMPS-NVP) (P2). The objective of this work was to study the rheological and filtration properties of Bent/polymer dispersions in deionized and salt water at different temperatures (25 °C and 85 °C). The steady shear rheological data was fitted to Herschel-Bulkley model to compute rheological parameters like yield stress, consistency index, and flow behavior index. The incorporation of polymers in Bent dispersions improved the rheological properties of the Bent dispersions. Addition of electrolyte in Bent/polymer dispersions led to a slight decrease in the rheological properties of all developed dispersions. The Bent/P2 dispersion revealed superior rheological properties compared to the other Bent and Bent/polymer dispersions in both deionized and salt water. TEM analysis of Bent/polymer dispersions was carried out to study the morphology of dispersions. LP/LT and HP/HT filtration experiments were performed in deionized and salt water at 25 °C and 85 °C, respectively, and results showed that Bent/P2 dispersion had minimum filtrate volume and filter cake thickness compared to the Bent dispersion. The permeability of filter cakes was determined using Darcy's law and filter cake morphologies were studied using SEM analysis. The excellent rheological and filtration properties of Bent/P2 dispersion was attributed to the presence of NVP monomer group in P2 polymer, which is stable towards elevated temperatures and high salinity environments. The exceptional filtration and rheological properties of P2 polymer make it a suitable candidate for the development of high-performance drilling fluids.

  • Halloysite nanotubes as a fine grained material for heavy metal ions removal in tropical biofiltration systems
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-01
    Andreas Aditya Hermawan, Jia Wei Chang, Pooria Pasbakhsh, Frank Hart, Amin Talei

    Biofiltration systems are landscape depressions or shallow basins used to slow and treat on-site stormwater runoff and are considered as one of the important components of a sustainable drainage system. Biofilters generally consist of two components: a filtration media which is sand-dominant and a top vegetated soil layer. The efficiency of a biofiltration system is normally assessed by two key parameters namely hydraulic conductivity and percentage removal of pollutants. In tropical areas like Malaysia where rainfall intensity is normally high, hydraulic conductivity of the biofiltration systems needs to be high enough to prevent ponding and possible flooding of the system. To date, several studies have been done on development and maintenance of such systems; however, few have studied such systems under tropical climates with heavy and intense rainfall which needs high hydraulic conductivity. The present study aims to identify proper soil filter media that not only can remove heavy metal ions efficiently but also has reasonably high hydraulic conductivity. For this, a soil column experimental set up was developed and the effectiveness of adding different fine grained materials such as fly ash, halloysite nanotubes (Hals) from two different origins (Imerys from NZ and HalloPure from I-Minerals, Idaho), and zeolite in sand-based soil media was assessed. To assure the validity of the results for each proposed filter media three replicates were prepared. The performance in removing heavy metal ions Fe(III), Mn(II), Cu(II), Zn(II), Ni(II), and Pb(II) was then evaluated for each soil composition using Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) test. Synthesized stormwater was used to provide consistency of pollutant concentration in experiments. The watering dosage was calculated based on hydrological data of a Malaysian catchment. Infiltration rate of each soil composition was also measured for further comparison. Results showed that increasing the percentage of fine materials can improve the heavy metal ions removal; however, the drawback would be significant decrease in infiltration rate. In general, Hals were found to fulfill the requirements for both high percentage removal and high infiltration rate compared to zeolite and fly ash. Moreover, the effect of aspect ratio, surface area, particle size and chemical composition of each fine material on its efficiency in heavy metal ions removal and infiltration rate were compared.

  • 更新日期:2018-02-02
  • Novel Cu-Zn-Al catalysts obtained from hydrotalcite-type precursors for middle-temperature water-gas shift applications
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-02-01
    C. Lucarelli, C. Molinari, R. Faure, G. Fornasari, D. Gary, N. Schiaroli, A. Vaccari
  • Functionalized halloysite nanotubes: Efficient carrier systems for antifungine drugs
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-01-19
    Marina Massaro, Ambra Campofelice, Carmelo Giuseppe Colletti, Giuseppe Lazzara, Renato Noto, Serena Riela
  • Comparison of organo-sepiolite modified by different surfactants and their rheological behavior in oil-based drilling fluids
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-01-06
    Jianle Weng, Zhijin Gong, Libing Liao, Guocheng Lv, Jianjie Tan

    Sepiolite modified by surfactants has been used in adsorption, catalysts, etc. While few studies focus on organo-sepiolite (OSep) which is used in oil-based drilling fluid. In this paper, a kind of cationic-anionic organo-sepiolite (CA-OSep) was prepared to be applied in oil-based drilling fluids. The structure and properties of OSep were characterized by X-ray diffraction, FTIR spectrum, thermal analysis and surface contact angle (SCA) analysis. The effect of dosage and chain length of surfactants, and the ratio of cationic to anionic surfactants on OSep were discussed as well as the rheological properties of OSep/diesel system. Cationic surfactant of long chains had better adhesion to the surface of sepiolite than surfactants of short chains. Compared with cationic organo-sepiolite (C-OSep), CA-OSep has an advantage in thermal stability. The apparent viscosity, plastic viscosity and yield value of oil-based drilling fluids with OSep as additives were further studied at different temperatures. Results indicated that organic surfactants had been adsorbed on the surface of sepiolite, and the CA-OSep had higher surface polarity and better thermal stability in 5# diesel oil than C-OSep. CA-OSep presented a new kind of potential rheological control additive for oil-based drilling fluids, and would exhibit excellent thermal stability.

  • Hydraulic and mechanical properties of compacted bentonite after 18 years in barrier conditions
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-01-05
    María Victoria Villar, Rubén Javier Iglesias, Carlos Gutiérrez-Álvarez, Beatriz Carbonell

    The FEBEX “in situ” test was performed at an underground laboratory in Grimsel (Switzerland) with the aim of studying the behaviour of components in the near-field of a nuclear waste repository. A gallery of 2.3 m in diameter was excavated through the granite and two heaters, simulating the thermal effect of the wastes, were placed inside, surrounded by a barrier of highly-compacted bentonite blocks. In 2015, after 18 years of operation, the experiment was dismantled. Some of the bentonite samples taken were tested in the laboratory to characterize, among others, their physical state and determine their permeability and swelling capacity. There were significant changes in water content and dry density across the bentonite barrier: their distribution was radial around the axis of the gallery, with the water content decreasing from the granite towards the axis of the gallery and the dry density following the inverse pattern. The swelling capacity of the samples was related to their position in the barrier. In the internal, drier part of the barrier an increase of the swelling capacity with respect to the reference bentonite was detected, whereas the samples from the external part swelled less than expected. This was attributed to the different salinity of the samples. The hydraulic conductivity was mainly related to the dry density of the samples and decreased with respect to the reference bentonite. This decrease was not related to the position of the samples and could be related to the microstructural reorganization of the bentonite during the 18-year operation –which brought about an average decrease in the pore size– and to the low hydraulic gradients applied to determine the permeability of the samples retrieved.

  • Preparation and characterization of the eco-friendly chitosan/vermiculite biocomposite with excellent removal capacity for cadmium and lead
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-01-05
    Liya Chen, Pingxiao Wu, Meiqing Chen, Xiaolin Lai, Zubair Ahmed, Nengwu Zhu, Zhi Dang, Yingzhi Bi, Tongyun Liu

    The chitosan/vermiculite biocomposite (CTS-VMT) was synthesized successfully with epichlorohydrin (ECH) cross-linking agent and used to remove cadmium and lead from the aqueous solution. CTS-VMT was characterized by FTIR, SEM, BET, TG-DTG, zeta potential and XPS. The effects of critical parameters including solution pH, contact time, initial heavy-metal concentration and adsorbent regeneration were investigated. Besides, adsorption mechanisms were also researched. The results indicated that chitosan molecule cannot intercalate into the interlayer space but cross link on the external surface of VMT. The maximum adsorption capacities for Cd(II) and Pb(II) were 58.48 mg g− 1 and 166.67 mg g− 1 at pH 4, respectively. The adsorption process fitted well the pseudo-second-order model and the adsorption isotherms could be correctly simulated by the Langmuir isotherm model. The zeta potential analyses put forward that electrostatic attraction existed in the adsorption process between the metal cations and CTS-VMT. However, the principal mechanism for adsorption on CTS-VMT was chelation according to the kinetic study and XPS analyses. Moreover, the desorption experiments revealed the prepared adsorbent tended to be regenerated by using HCl and the removal rations for four cycles were all > 90%. Therefore, the synthesized CTS-VMT in this study has the potential to be utilized as an eco-friendly adsorbent for removing Cd(II) and Pb(II).

  • Evaluation of a sand bentonite mixture as a shaft/borehole sealing material
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-01-05
    Haluk Akgün, Mustafa K. Koçkar

    The mechanical and hydrological characteristics of compacted sand bentonite mixtures with bentonite contents ranging from 5 to 40% were investigated in the laboratory in order to assess their use as a waste isolation material and to select an optimum sand bentonite mixture. Laboratory tests included compaction, compaction permeability, unconfined compression and direct shear tests which led to a recommendation to select a mixture with a bentonite content of 30% for the isolation of underground geological waste disposal repositories. This study complements the previous studies of the authors of this manuscript by determining the mechanical and hydrological properties of sand bentonite mixtures that possess bentonite contents > 30% to determine the geotechnical properties (i.e., unconfined compressive strength, Young's modulus, cohesion and angle of internal friction) and the mechanical behavior of these relatively high levels of bentonite mixtures for the first time in the literature.

  • Adsorption of fulvic and humic like acids on surfaces of clays: Relation with SUVA index and acidity
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2018-01-03
    Hervé Gouré-Doubi, Céline Martias, Agnès Smith, Nicolas Villandier, Vincent Sol, Vincent Gloaguen, Geneviève Feuillade
  • Preparation and characterization of a granular bentonite composite adsorbent and its application for Pb2+ adsorption
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-29
    Wei Mo, Qiuzhi He, Xiujuan Su, Shaojian Ma, Jinpeng Feng, Zhenli He

    Bentonite is an important clay for preparation of adsorbents for potential treatment of industrial effluents. However, due to its natural occurrence as fine particles and swelling after moisture absorption, bentonite is difficult to be separated from the liquid for regeneration purpose, which limits its application in effluent treatment. In this study, two different bentonite-polypropylene composites were synthesized, i.e., with and without pore-enlarging treatment. They both showed strong ability to resist hydraulic agitation damage with a small breakage rate in water. The obtained results from SEM and XRD characterization revealed that the compounding of bentonite with the polypropylene was a physical process, and the structural characteristics of bentonite particles were maintained in the new products. The granular composite adsorbents were effective in removing Pb2+ in aqueous solution. The suggested pore-enlarging treatment was verified as a successful operation to increase greatly the adsorption rate of contaminants on the granular bentonite composite.

  • A structural comparison of halloysite nanotubes of different origin by Small-Angle Neutron Scattering (SANS) and Electric Birefringence
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-29
    Giuseppe Cavallaro, Leonardo Chiappisi, Pooria Pasbakhsh, Michael Gradzielski, Giuseppe Lazzara

    The structure of halloysite nanotubes (Hal) from different mines was investigated by Small-Angle Neutron Scattering (SANS) and Electric Birefringence (EBR) experiments. The analysis of the SANS curves allowed us to correlate the sizes and polydispersity and the specific surfaces (obtained by a Porod analysis of the SANS data) of the nanotubes with their specific geological setting. Contrast matching measurements were performed on patch Hal (from Western Australia) in order to determine their experimental scattering length density for a more precise analysis. Further characterization of the mesoscopic structure of Hal was carried out by Electric Birefringence (EBR), which allowed to study the rotational mobility of Hal. From the obtained rotational diffusion coefficients of the different Hal we deduced their length via the Broersma theory, which compares well to TEM data. The analysis of both SANS and EBR data provided a bulk average information on the Hal structure in water, which, for instance, documented the markedly higher degree of well-definedness of the PT-Hal and the thinner tube walls present here. The attained systematic structural knowledge represents a step forward for the robust structural description of halloysites selected from four geological deposits and shows that Hal of different origin differ very markedly with respect to their mesoscopic structure.

  • Pd supported on Cu-doped Ti-pillared montmorillonite as catalyst for the Ullmann coupling reaction
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-27
    Kannan Vellayan, Beatriz González, Raquel Trujillano, Miguel A. Vicente, Antonio Gil
  • 更新日期:2017-12-27
  • Adsorption and characterization of palygorskite-isoniazid nanohybrids
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-24
    E. Carazo, A. Borrego-Sánchez, F. García-Villén, R. Sánchez-Espejo, C. Viseras, P. Cerezo, C. Aguzzi

    Studies of the equilibrium and thermodynamic aspects of the adsorption of isoniazid onto a pharmaceutical-grade palygorskite and features of the resultant clay drug nanohybrid systems were carried out. Equilibrium studies were performed in aqueous medium at different times and temperatures. The overall adsorption process was explained as the result of two simple processes: drug adsorption on the activated sites of palygorskite and a slight precipitation phase of drug molecules over the adsorbed monolayer. Formation of the nanohybrid was spontaneous, exothermic and exoentropic, obtaining an increase in the thermodynamic stability of the system (ΔH = − 48,82 kJ/mol; ΔS = − 0.14 kJ/mol K). A full and comprehensive study of the solid state characterization corroborated the effective interaction between the components. Total amount of INH loaded was about 20% w/w. FTIR spectra revealed the interaction via water bridges between the endocyclic N of the drug and surface OH groups of palygorskite. Surface charge studies confirmed the non-electrostatic nature of the interactions.

  • Microbial community changes induced by uranyl nitrate in bentonite clay microcosms
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-23
    Margarita Lopez-Fernandez, Ramiro Vilchez-Vargas, Fadwa Jroundi, Nico Boon, Dietmar Pieper, Mohamed L. Merroun

    Deep geological repository (DGR) is one of the internationally accepted options to dispose radioactive wastes. Bentonite formations from Almeria, Spain, were selected as reference material for artificial barriers for the future Spanish repository. However, the safety of this long-term disposal could be compromised not only by physicochemical factors but also by microbial processes. The highly radioactive waste must be safely stored at least for 100,000 years for the radioactivity to decrease to similar levels to those of natural uranium. To simulate a scenario where the mobilization of radionuclides from the repository to the host formations may occur, long-term microcosms were studied. After being exposed to uranyl nitrate for 5 months, the response of the bentonite microbial community to the addition of this radionuclide was evaluated. High throughput 16S rRNA gene sequencing revealed that the structure of the microbial community after the uranyl nitrate treatment differs to that of the control microcosms. The microbial diversity was dominated by Firmicutes and Proteobacteria. Moreover, after the uranyl nitrate treatment OTUs annotated as Paracoccus and Bacillus were highly enriched. The mineralogy of bentonites was not affected by the uranyl nitrate treatment as was demonstrated by X-ray diffraction analysis. In addition, the study of uranium-bacteria interaction revealed the ability of isolates to biomineralize uranium as uranium phosphate mineral phases. Thus, the changes induced by the release of uranium in the microbial population may also affect the mobility of this radionuclide, making it less mobile and therefore less harmful for this environment.

  • Nanotubes in nanofibers: Antibacterial multilayered polylactic acid/halloysite/gentamicin membranes for bone regeneration application
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-19
    Malgorzata Karolina Pierchala, Maziyar Makaremi, Hui Li Tan, Janarthanan Pushpamalar, Saravanan Muniyandy, Atefeh Solouk, Sui Mae Lee, Pooria Pasbakhsh
  • Biopharmaceutical improvement of praziquantel by interaction with montmorillonite and sepiolite
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-19
    Ana Borrego-Sánchez, Esperanza Carazo, Carola Aguzzi, César Viseras, C. Ignacio Sainz-Díaz
  • Comparative adsorption of tetracyclines on biochars and stevensite: Looking for the most effective adsorbent
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-19
    Rafael Antón-Herrero, Carlos García-Delgado, María Alonso-Izquierdo, Gabriel García-Rodríguez, Jaime Cuevas, Enrique Eymar

    Tetracyclines are one of the most widely used class of veterinary and human antibiotics. The conventional treatment of wastewater based on activated sludge is not effective to remove antibiotics and their residues are still biologically active, which represents a problem in terms of bacterial resistance. The main objective of this work is to assess ability of stevensite and two biochars to adsorb three tetracycline antibiotics from water. Batch adsorption experiments were carried out to test the ability of these materials to adsorb tetracyclines. Then desorption experiments were performed to determine the adsorption strength on stevensite. In order to elucidate the adsorption mechanism of tetracyclines on stevensite, cation exchange analysis and spectroscopic analyses by IR and XRD were performed. The adsorption of tetracyclines on stevensite was tested on continuous system with water artificially contaminated. Finally, the designed filter was validated with tetracyclines spiked wastewater. The two biochars and stevensite were able to adsorb between 60 and 100% of the tetracyclines present in the batch system. Stevensite was the material with the highest tetracyclines removal capacity (around 100% at low concentrations of tetracyclines). Biochars showed less affinity for tetracyclines adsorption (70%). Tetracyclines desorption from stevensite reached values lower than 10% for low tetracyclines concentrations. The IR spectroscopy suggested that cation exchange is the main mechanism of tetracyclines adsorption on clay and also proved the role of amide and amine groups in this adsorption. The cation exchange mechanism was confirmed by displacement of Ca and Mg from stevensite. A continuous wastewater flow through a system composed by stevensite leaved this system with no tetracyclines, indicating water purification by tetracyclines adsorption in clay.

  • Kinetics of release and antibacterial activity of salicylic acid loaded into halloysite nanotubes
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-19
    L. Ghezzi, A. Spepi, M. Agnolucci, C. Cristani, M. Giovannetti, M.R. Tiné, C. Duce
  • Characterisation of Andalusian peats for skin health care formulations
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-18
    Fátima García-Villén, Rita Sánchez-Espejo, Esperanza Carazo, Ana Borrego-Sánchez, Carola Aguzzi, Pilar Cerezo, César Viseras

    Composition and properties of three different peat strata from “El Padul” peatbog have been studied and peat pastes have been formulated to prepare skin health care products. As for composition, the main phase of each stratum was constituted of smectites (outer stratum), organic matters (intermediate) or carbonates (inner). Pristine strata and their aqueous dispersed systems were characterized for such properties (pH, rheology and cooling kinetics) that are considered determinant in view of their topical application. Main phases of each stratum influenced pH and rheology but not cooling kinetics. Combination of the strata in different w/w ratios led to peat pastes with improved performance for skin administration.

  • Porous clay heterostructures intercalated with multicomponent pillars as catalysts for dehydration of alcohols
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-14
    Lucjan Chmielarz, Andrzej Kowalczyk, Monika Skoczek, Małgorzata Rutkowska, Barbara Gil, Piotr Natkański, Marcelina Radko, Monika Motak, Radosław Dębek, Janusz Ryczkowski
  • 更新日期:2017-12-14
  • Concentration-dependent and simultaneous sorption and desorption of pyrene and fluorene on major soil minerals in sub-Saharan Africa
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-09
    Paul N. Diagboya, Bamidele I. Olu-Owolabi, Ezekiel D. Dikio, Kayode O. Adebowale
  • 更新日期:2017-12-14
  • Adsorption of ammonium by different natural clay minerals: Characterization, kinetics and adsorption isotherms
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-11
    Aref Alshameri, Hongping He, Jianxi Zhu, Yunfei Xi, Runliang Zhu, Lingya Ma, Qi Tao

    This research presented six natural clay minerals (NCM) evaluated for the effectiveness of NH4+ adsorption from aqueous solution. For the first time, the NH4+ adsorption capacities of kaolinite, halloysite, montmorillonite, vermiculite, palygorskite, and sepiolite were examined and compared in the same study. All the NCM were fully characterized by XRD, SEM/EDS, XRF,FTIR, CEC, zeta potential and nitrogen adsorption-desorption isotherms to better understand the adsorption mechanism-property relationship. Adsorption kinetics showed that the adsorption behavior followed the pseudo-second-order kinetic model. The adsorption isotherms fitted by the Langmuir model illustrated that among all the NCM studied, vermiculite (50.06 mg/g) and montmorillonite (40.84 mg/g) showed the highest ammonium adsorption capacities. Our results revealed that the cation exchange is the main mechanism for the NH4+ adsorption. Additionally, negatively charged surface, water absorption process and surface morphology of NCM might also contribute to the high adsorption capacity for the NH4+. The maximum adsorption capacities for all NCM were rapidly obtained within 30 min with a dosage of 0.3 g/25 mL at pH of 7. The results illustrated that the NCM have significant potential as economic, safe and effective adsorbent materials for the NH4+ adsorption from the aqueous solution.

  • Thermal properties of some Egyptian kaolin pastes for pelotherapeutic applications: Influence of particle geometry on thermal dosage release
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-11
    Mahmoud E. Awad, Alberto López-Galindo, Rita Sánchez-Espejo, Mahmoud M. El-Rahmany, César Viseras Iborra

    The present study aims to evaluate the potentiality of 7 selected structural highly ordered kaolinite-rich samples from Egyptian Carboniferous sedimentary deposits (located at Abu Zenima district, west central Sinai peninsula) to use them in medicinal semisolid formulations as peloids. The effect of particle geometry and kaolinite crystallite size are studied to check their influence on thermal dosage performance. The studied samples exhibit a variable mineralogy. Kaolinite is the main constituent (ranging from 81 to 94%), followed by quartz (up to 14%), lesser amounts of anatase and halite, and traces of hematite, magnetite, alunite and gypsum. The kaolinite order “Hinckley Index” varies from 1.28 to 1.50. 1:1 (w/w) kaolin mud pastes were prepared with purified water in Eppendorf tubes using a touch vibration vortex mixer for 2 min. The cooling kinetics of pastes were measured by using a differential scanning calorimetry equipment (Shimadzu DSC-50Q). Specific heats were calculated, following Cara et al. (2000). The granulometry and geometric surface area were measured by laser diffraction (Mastersizer 2000LF, Malvern Instruments) in the range 0.02 and 1500 μm. All analyzed samples showed a clear predominance of particles under 4 μm (ranging from 82 to 94%), with median size (D50) ranging from 0.93 to 1.35 μm. The heat retention time during cooling from 50 °C to 32 °C reached up to 30.82 min, oscillating around an average of 28.72 min, and the temperature corresponding to the minimal dosage time (T20) was not exceed below 34.7 °C. A good correlation (R2 = 0.875) was found between heat retention time and specific heats. There is no correlation between kaolinite content and thermal properties, but R2 values around 0.6 are found with granulometry (finer the particles, greater the heat retention time t32 and the specific heat). Even if sample H5 (Gabal Hazbar deposit) is not the richest in kaolinite, it exhibits the best thermal dosage performance, in accordance with the granulometry (D50 = 0.93 μm), and geometric surface area (3.73 m2/g).

  • Assessment of the effect of mineralogy on the geotechnical parameters of clayey soils: A case study for the Orta County, Çankırı, Turkey
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-09-19
    Haluk Akgün, Asuman Günal Türkmenoğlu, Arzu Arslan Kelam, Karim Yousefi-Bavil, Gökalp Öner, Mustafa Kerem Koçkar

    The purpose of this study is to investigate and relate the geotechnical parameters with the mineralogical properties of the Miocene and Plio-Quaternary (Pliocene to Quaternary) lacustrine and fluvial sediments, particularly clayey soils in the Orta County, Çankırı. The study area is located about 110 km northeast of Ankara which is the capital city of the Republic of Turkey and Orta is a small county of Çankırı. The study area is a structural depression in the northern part of the Orta plain which is filled by fault-controlled continental sedimentation. In order to correlate the geotechnical and mineralogical characteristics and to establish a relation between these properties, comprehensive geotechnical laboratory studies have been performed. For correlation purposes, disturbed and undisturbed soil samples were collected from twenty-two locations of the study area. On these samples, mineralogical (i.e., methylene blue absorption, specific surface area determination, X-ray powder diffraction (XRD) and scanning electron microscope (SEM-EDAX)) analysis and geotechnical (i.e., sieve analysis, hydrometer, Atterberg (consistency) limits, oedometer and swelling) tests were implemented. By the aid of the statistical analysis, cross-correlation of the soil properties was established by the regression analyses performed. In particular, the plasticity index was correlated with cation exchange capacity, specific surface area, clay content, percent of fines, smectite and smectite/kaolinite ratio (SKR). There was a direct relationship between PI and smectite percentage as well as between PI and SKR. Additionally, the liquid limit was correlated with the clay content and the effect of the specific surface area on the swelling characteristics was studied. The effects of the mineralogical properties of the Orta clays together with the geological history on geotechnical parameters were investigated by considering the relationships mentioned. The results of the study revealed that the mineralogical characteristics had a significant effect on the geotechnical behavior of clayey soils of the Orta County which was demonstrated by regression analyses. Finally it was identified that the geotechnical properties of clayey soils can be approximated and more reliably determined if the mineralogical character and composition of clay is accurately investigated and well developed.

  • Effects of charge density on the hydration of siloxane surface of montmorillonite: A molecular dynamics simulation study
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-09-18
    Wei Shen, Lin Li, Huijun Zhou, Qing Zhou, Meng Chen, Jianxi Zhu

    The physicochemical properties of clay minerals strongly depend on their hydration characteristics which therefore have drawn great concerns from different research communities. In the present work, the effects of charge density of montmorillonite (Mt) on the hydration characteristics of its interlayer spaces, particularly the siloxane surface, were studied using classical molecular dynamics (MD) simulations. Four Mt. models with various octahedral charges are established, and these charges are compensated with tetramethylammonium cation (TMA). The simulation results showed that water molecules within the hydration layer of siloxane surface will donate hydrogen atoms to form H-bond with the surface oxygen atoms, while those surrounding TMA only slightly have their oxygen atoms point towards TMA. In addition, water molecules prefer to first hydrate the siloxane surface and then the TMA as the water content increases. These findings indicate that water molecules have stronger hydration interaction with siloxane surface than with TMA, and TMA can be ideal counterbalance cation in terms of studying the hydration characteristics of siloxane surface. Charge density can significantly influence the hydration of TMA-Mt. Although increasing charge density will not lead to the formation of stronger H-bond (i.e., no obvious reduction of H-bond length) between water molecules and siloxane surface, water molecules are more likely to be drawn to the siloxane surface and form more H-bonds between them. Subsequently, the hydration energy increases and the mobility of water molecules decreases as the charge density rises. These findings show that charge density can evidently influence the hydrophobicity of siloxane surface, which may further influence its interaction with organic species, e.g., the adsorption of organic contaminants.

  • Photocatalytic microreactors based on nano TiO2-containing clay colloidosomes
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-09-01
    Sen Lin, Shiyong Sun, Kexuan Shen, Daoyong Tan, Hongping Zhang, Faqin Dong, Xiaoxin Fu

    Photocatalytic microcompartments have attracted increasing interests in the field of photocatalytic degradation. This work focused on the construction and characterization of a novel photocatalytic microsystem comprising polydopamine-modified TiO2 nanoparticles (NPs) dispersed in clay-based colloidosomes, utilizing partially hydrophobic montmorillonite particles as building blocks for colloidosome membrane assembly. Assessment of photocatalytic activity was performed by photocatalytic degradation of methylene blue and rhodamine B, with the small molecule dyes decomposing within the compartmentalized microsystems. Encapsulation of TiO2 NPs within the clay colloidosomes enhanced the efficiency of photocatalytic degradation. The results showed a selective degradation of methylene blue in the presence of rhodamine B, with associated λMB/λRhB of 2.04. The present study indicates that photocatalytic semiconductor NPs encapsulated in clay colloidosomes form a promising microsystem with great potential for application in environmental remediation.

  • Synthesis of palygorskite-supported Mn1 − xCexO2 clusters and their performance in catalytic oxidation of formaldehyde
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-08-31
    Can Wang, Haibo Liu, Tianhu Chen, Chengsong Qing, Xuehua Zou, Jingjing Xie, Xiaori Zhang

    Nano-scale Mn1 − xCexO2 catalysts supported on palygorskite (PG) with different dopant fractions were prepared by the co-precipitation method and applied in the catalytic oxidation of formaldehyde (HCHO). The obtained samples were characterized using BET, XRD, Raman spectroscopy, TEM, EDS, and H2-TPR to illustrate the physicochemical properties of the catalysts. After the introduction of cerium, the growth of manganese oxide was inhibited. However, an increase of the Ce/(Ce + Mn) ratio from 0.1 to 0.5 increased the particle size from 2.87 to 6.86 nm. A remarkable interface (grain boundaries) between MnO2 and CeO2 was observed, especially for low cerium molar fractions (0.1–0.4). The doping of cerium significantly enhanced the activity of manganese oxide for HCHO oxidation at 100–180 °C. The Mn0.9Ce0.1/PG catalyst exhibited the best activity, and HCHO was completely converted to CO2 and H2O at 160 °C. The characterization results indicated that smaller particle size, surface-adsorbed oxygen species and abundant oxygen vacancies accounted for the high catalytic activity of the Mn0.9Ce0.1/PG catalyst for HCHO conversion. In addition, the Mn0.9Ce0.1/PG catalyst also displayed high stability in lifetime testing and excellent water-resistant performance. The experimental results suggest that palygorskite-supported Mn0.9Ce0.1 is a promising catalyst for the catalytic oxidation of formaldehyde at low temperatures.

  • Investigation of adsorption of 5-Chlorouracil onto montmorillonite: An IR and Raman spectroscopic study
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-08-23
    Sevim Akyuz, Tanil Akyuz

    In this study, the adsorption of 5-Chlorouracil (5-ClU) on natural montmorillonite from Anatolia was investigated using FT-IR and Raman spectroscopy. The 5-ClU is a thymine antagonist and has some antitumor properties. The comparison of the vibrational spectra of the adsorbed 5-ClU with those of the free molecule provided data on the nature and characteristics of the clay organic complexes. The intercalation of 5-ClU within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacing. Vibrational spectroscopy indicates that adsorbed 5-ClU molecules on montmorillonite are coordinated to exchangeable cations, directly or indirectly through water bridges.

Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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