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  • 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.

    更新日期:2018-01-07
  • 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.

    更新日期:2018-01-05
  • 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).

    更新日期:2018-01-05
  • 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.

    更新日期:2018-01-05
  • 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
    更新日期:2018-01-04
  • 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.

    更新日期:2017-12-31
  • 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.

    更新日期:2017-12-31
  • 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
  • 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.

    更新日期:2017-12-27
  • 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.

    更新日期:2017-12-27
  • 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
    更新日期:2017-12-20
  • 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
    更新日期:2017-12-20
  • 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.

    更新日期:2017-12-20
  • 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
    更新日期:2017-12-19
  • 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.

    更新日期:2017-12-19
  • 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
  • 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
  • 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.

    更新日期:2017-12-14
  • 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).

    更新日期:2017-12-14
  • 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.

    更新日期:2017-12-14
  • 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.

    更新日期:2017-12-14
  • 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.

    更新日期:2017-12-14
  • 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.

    更新日期:2017-12-14
  • 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.

    更新日期:2017-12-14
  • Surface organo-functionalization of palygorskite nanorods with γ-mercaptopropyltrimethoxysilane
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-08-16
    Peng Liu, Hongxing Wang, Changou Pan

    Palygorskite (Pal) nanorods have attracted more and more interests in polymer-based nanocomposites. Surface modification with silane is the main approach to improve their dispersibility in organic matrices. In the present work, the functionalization of Pal nanorods with silane was optimized in detail, aiming to the high dispersibility in organic matrices, including the reaction condition (temperature and time) and feeding ratio of silane (e.g. γ-mercaptopropyltrimethoxysilane, MPS). The morphology of the products was analyzed with TEM technique. Based on the characterization results and the sedimentation phenomena of their dispersions in toluene, the microstructure of the organo-functionalized palygorskite (OPAL) was established, in which locking effect and welding effect of silane were proposed.

    更新日期:2017-12-14
  • Variable charges of a red soil from different depths: Acid-base buffer capacity and surface complexation model
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-08-10
    Ying Wang, Pengfei Cheng, Fangbai Li, Tongxu Liu, Kuan Cheng, Jinling Yang, Ying Lu

    The soil variable charges play a unique role in many soil geochemical processes, particularly soil acidification. However, due to the complicated nature of soil particles, a fundamental understanding of the acid-base buffer capacities and mechanisms is still lacking. In the present study, red soil samples from different depths were examined. The element compositions, crystal structures, and surface groups were characterized by X-ray fluorescence, X-ray diffraction, and Fourier transform infrared spectroscopy, respectively. Thermogravimetric analysis was further conducted to examine the soil compositions and the organic matter content. Kaolinite, quartz, and hematite were identified as the dominant mineral components. As the depth of the soils increased, the contents of hematite and kaolinite increased, while the contents of quartz decreased. The weight loss of the soil samples from 200 to 400 °C indicated that the organic matter decreased substantially with increasing soil depth. Based on the potentiometric titration, the pHpzc was determined to range from 4.4 to 5.0. The surface complexation model (SCM) was used to further evaluate the acid-base properties of the soils by assuming two pKa for one surface site of the bulk soil. The results showed that the values of the model-derived pHpzc were well matched with those from the titration experiments; therefore, it is feasible to apply the SCM in examining the variable charges of the bulk soils. The calculated surface site concentration Hs, representing the soil buffer capacity, was positively correlated with the contents of the organic matter, implying that the organic matter of the soil plays an important role in the soil acid-base buffer capacity. From the extrapolated pHpzc, it can be proposed that kaolinite was the major soil mineral controlling the pHpzc of soils. This study would provide a quantitative approach for the soil acid-base buffer properties and a fundamental understanding of the underlying mechanisms.

    更新日期:2017-12-14
  • Discussion of “Optimization of carpet waste fibers and steel slag particles to reinforce expansive soil using response surface methodology” by M. Shahbazi, M. Rowshanzamir, S.M. Abtahi, S.M. Hejazi [Appl. Clay Sci., doi:10.1016/j.clay.2016.11.027]
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-08-01
    Amin Soltani

    Shahbazi et al. (2017) adopted the response surface methodology (RSM) technique to evaluate the combined efficiency of slag treatment and fiber reinforcement in the stabilization of an expansive soil mixture. The swell percent (Sp), swelling pressure (Ps), and unconfined compressive strength (qu) were represented as a function of three independent variables (i.e. slag content, fiber content, and fiber aspect ratio) by the second-order polynomial regression model, and ANOVA analysis was adopted to allocate a contribution percentage to each component of the regression model. It was noticed that the reported fitting parameters for Sp and Ps provided ambiguous predictions, and thus were recalculated to avoid any misleading information for readers. The statistical technique proposed by the authors is limited to allocating contribution factors to regressional components rather than evaluating the net favorable impact of each independent variable on the desired dependent variable. Therefore, the partial derivative sensitivity analysis approach was proposed as a simple and practical alternative to address the aforementioned uncertainty. The new approach presented in this discussion not only provides a unique contribution factor for each independent variable but also accounts for the combined favorable contribution offered by all three independent variables.

    更新日期:2017-12-14
  • Effect of acid activation of palygorskite on their toluene adsorption behaviors
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-07-26
    Jianxi Zhu, Ping Zhang, Yuebo Wang, Ke Wen, Xiaoli Su, Runliang Zhu, Hongping He, Yunfei Xi

    In this paper, acid-activated palygorskite (APalx) samples were prepared by a facile acid treatment method with different concentrations of HCl (0.5, 1, 3, 5 and 7 mol/L). The dynamic toluene adsorption performances of APalx were evaluated and the relevant adsorption mechanism was discussed. The prepared adsorbents were characterized using X-ray diffraction (XRD), elemental analysis, transmission electron microcopy (TEM), nitrogen adsorption-desorption isotherms and Fourier-transform infrared spectroscopy (FTIR). The results show that the palygorskite has a good resistant ability to acid attack, the structure still remains when the acid concentration is as high as 7 mol/L. Acid activation could significantly enhance the surface area (228, 250, 271, 273, 329 and 308 for Pal, APal0.5, APal1, APal3, APal5 and APal7, respectively) and porosity of palygorskite. APal5 has the best toluene adsorption capacity (90.4 mg/g) due to its highest SBET (329 m2/g) and Vmicro (0.055 cm3/g). The adsorption performance in terms of dynamic toluene adsorption capacities follows the order of Pal (44.6 mg/g) < APal0.5 (63.5 mg/g) < APal1 (71.3 mg/g) < APal7 (74.2 mg/g) < APal3 (75.1 mg/g) < APal5 (90.4 mg/g). APal5 can be readily regenerated by thermal desorption and has exhibited steady reproducibility after 6 cycles. These results have demonstrated that acid activation is a feasible and effective method for the structure and surface optimizing of palygorskite, enabling the APalx to become a promising candidate for the adsorption of volatile organic compounds in practical applications.

    更新日期:2017-12-14
  • Tracked changes of dolomite into Ca-Mg-Al layered double hydroxide
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-07-03
    Ning Mao, Chun Hui Zhou, John Keeling, Saverio Fiore, Hao Zhang, Liang Chen, Gui Chen Jin, Ting Ting Zhu, Dong Shen Tong, Wei Hua Yu

    Dolomite is a widespread carbonate mineral that has been investigated extensively over the past two centuries. Despite the high level of investigation, aspects of the environmental conditions of crystallization, diagenesis and dissolution remain elusive and the transformation of dolomite into other value-added products is still challenging. This work shows a novel, cleaner method to dissolve dolomite by taking advantage of the acidity from the hydrolysis of Lewis acid AlCl3 and as such the mineral can be efficiently converted into Ca-Mg-Al layered double hydroxide (LDH). The dolomite and the resulting Ca-Mg-Al LDH samples were characterized by powder X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composition of the products was measured by energy dispersive spectrometer-mapping (EDS-mapping), X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS). Particle sizes of the products were measured by a dynamic light scattering method. It is documented, for the first time, that dissolution of dolomite in AlCl3 aqueous solution is facilitated by hydrothermal treatment. Well-crystallized Ca-Mg-Al LDH crystals are achieved under (Ca + Mg): Al molar ratio = 1:1, pH = 10.5 via a simple co-precipitation method. The maximum utilization efficiencies of Ca2+, Mg2+ from dolomite to LDH are 36.3% and 95.5%, respectively. The possible mechanisms of LDH formation were: 1) the dolomite dissolved in the strong acid solution due to the hydrolysis of AlCl3 and thus provided Ca2+ and Mg2+; 2) with addition of NaOH, Al3+ cations precipitated to form Al(OH)3 (at 8.3 ≤ pH ≤ 9.3) and then part of the Al(OH)3 reacted with Ca2+ and Mg2+ to form the Ca-Mg-Al LDH; 3) at pH = 10.5, the Al(OH)3 was transformed as [AlO(OH)] and meanwhile Ca2+, Mg2+ and Al3+ took part in the formation of Ca-Mg-Al LDH; 4) when pH = 10.6, [AlO(OH)] reacted with NaOH to dissolve into [Al(OH)4]− and the [Al(OH)4]− finally co-precipitated with Ca2+ and Mg2+ to form the Ca-Mg-Al LDH during heating for drying.

    更新日期:2017-12-14
  • Solvothermal evolution of red palygorskite in dimethyl sulfoxide/water
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-06-19
    Zhifang Zhang, Wenbo Wang, Guangyan Tian, Qin Wang, Aiqin Wang

    Red clay deposit with palygorskite (Pal) as the main component is abundant on the earth, but it is not yet fully utilized in industrial fields because of its deep color. In this paper, we employed a facile one-step solvothermal process to treat red Pal using water, dimethyl sulfoxide (DMSO) and DMSO/water as solvents and studied the effect of this process on the structure, physico-chemical characteristics and color of red Pal. It was revealed that the brick-red Pal still remain its color unchanged after solvothermal reaction in water or DMSO solvent, but it converted to white after reaction in dimethyl sulfoxide (DMSO)/water mixture. When the volume ratio of DMSO to water is 2:1, the product has the best whiteness of 83.3%. The associated minerals such as quartz, feldspar and muscovite did not change significantly and the rod-like crystalline morphology of Pal still remains intact after solvothermal reaction. The leaching of Fe(III) in Pal, the dissolution of α-Fe2O3 and the reduction of Fe(III) by the dimethyl sulfide (the reaction product of DMSO with water) to Fe(II) contributed to the conversion of red Pal to white one. The conversion of brick-red Pal to white would lay a foundation for the applications of deep-colored clay minerals in the fields of chemical industries and composite materials.

    更新日期:2017-12-14
  • Self-supporting thin films of imogolite and imogolite-like nanotubes for infrared spectroscopy
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-06-16
    Yuanyuan Liao, Pierre Picot, Jean-Blaise Brubach, Pascale Roy, Sophie Le Caër, Antoine Thill

    Due to their narrow and well-defined structure, single wall nanotube, aluminosilicate nanotubes (imogolites) are excellent candidates to study how water is modified by either confinement or by the interface nature. A protocol is provided here to produce imogolite films that are ideally suited for infrared studies. Two types of imogolites were selected: a hydrophilic imogolite (IMO-OH) with inner surface fully covered with Si–OH hydrophilic groups and a hybrid imogolite (IMO-CH3) with inner surface fully covered with hydrophobic Si–CH3 groups. Films with different thicknesses were characterized by Small Angle X-ray Scattering (SAXS). The initial water content and the porosity of the films were estimated from ThermoGravimetric Analysis (TGA). Infrared spectroscopy was used to deduce the molar absorption coefficient of the bending mode that is significantly modified in confined water as compared to bulk water. Moreover, the interest of these films which allow avoiding extra-absorption features from the salt matrix or the supporting wafer is illustrated by an infrared study of the processes occurring in the IMO-OH film when it is heated from room temperature up to 350 °C. The evolution of the IR bands while heating shows the dehydration/dehydroxylation processes.

    更新日期:2017-12-14
  • Selective loading of 5-fluorouracil in the interlayer space of methoxy-modified kaolinite for controlled release
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-05-02
    Daoyong Tan, Peng Yuan, Faqin Dong, Hongping He, Shiyong Sun, Zongwen Liu

    Methoxy-modified kaolinite was used as a novel carrier for anticancer drug 5-fluorouracil (5FU). The selective loading of 5FU into the interlayer space of methoxy-modified kaolinite was achieved because the weakly bonded 5FU on the external surface was removed off by facile water rinse. The intercalated 5FU has strong affinity (electrostatic force and hydrogen bonding) with the interlayer surface of kaolinite, and its release was controlled because of the diffusion restriction of the kaolinite lamellar layers and the strong affinity between 5FU and kaolinite. The controlled release of 5FU from methoxy-modified kaolinite in simulated colonic fluid (pH 5.5) makes it be of potential use to administer an oral formulation of 5FU for colon specific delivery.

    更新日期:2017-12-14
  • Comment on “Measurement of the elastic properties of swelling clay minerals using the digital image correlation method on a single macroscopic crystal”, by S. Hedan, F. Hubert, D. Prêt, E. Ferrage, V. Valle, P. Cosenza [Applied Clay Science 116–117 (2015), 248–256, doi: 10.1016/j.clay.2015.04.002]
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2016-10-12
    Shengmin Luo, Dongwei Hou, Guoping Zhang

    Hedan et al. (2015) recently reported an interesting method for determining the elastic modulus of vermiculite, a representative swelling clay mineral. A platy natural macrocrystal of vermiculite was used in the study. The technique combining mechanical compression and digital image correlation (DIC) appears plausible. However, a fundamental issue related to the reported testing method, particularly the experimental setup and specimen geometry constraints, arises and is worth re-examination and discussion, because it may make the reported modulus inappropriate or inaccurate. In this short discussion, the stress distribution of a thin plate such as the tested vermiculite macrocrystal under uniaxial compression is analyzed, and the reported results are re-interpreted. It appears that the reported Young's modulus of 32.3 GPa is too high for the studied vermiculite.

    更新日期:2017-12-14
  • Synthesis of bentonite-supported Fe(II) and heteropolyacid (HPW) composite through a mechanochemical processing
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-06
    Guangtao Wei, Yunshang Li, Linye Zhang, Shuya Cai, Tong Zhu, Zhongmin Li, Jihua Mo

    In this work, a mechanochemical synthesis process was introduced as a facile method for producing bentonite-supported Fe(II) and heteropolyacid (HPW) composite, a catalyst used for photo-Fenton reaction and conventionally produced only by liquid-phase synthesis method. The composite was successfully synthesized under solid-phase condition in a ball mill through three stages of mechanical milling. The optimum synthesis conditions of composite were obtained, and the effects from the synthesis conditions on the catalytic activity of composite were discussed. The composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy disperse spectroscopy (EDS), fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The characterization results showed that the composite was a material with smooth surface, loose and clear layered structure, and had crystalline and amorphous phases in the microscopic scale. The characterization demonstrated the functional components of Fe(II) and HPW were successfully immobilized on the composite. Based on the characterization, the formation mechanism of composite in the mechanochemical synthesis was presented. The composite synthesized through the mechanochemical processing showed both high catalytic ability and excellent long-term stability in use. The results indicated that mechanochemical synthesis, as a green, simple and efficient preparation technology, was suitable for the industrial production of bentonite-supported Fe(II) and HPW composite.

    更新日期:2017-12-08
  • Comparison of adsorption and desorption of phosphate on synthesized Zn-Al LDH by two methods in a simulated soil solution
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-02
    Hadis Hatami, Amir Fotovat, Akram Halajnia

    Zinc aluminum layered double hydroxides (LDH) with Zn/Al molar ratios of 2 and 3 were synthesized by general (Zn2G-Al, Zn3G-Al) and modified (Zn2M-Al, Zn3M-Al) urea hydrolysis methods. The effects of time, pH, selectivity and initial phosphorous concentration were investigated on phosphate uptake by synthesized LDH in a simulated soil solution. Moreover, phosphate desorption from studied LDH was evaluated. Based on the results, nitrate containing Zn-Al LDH were synthesized by both methods. However, the presence of carbonate ion in the interlayer space of Zn3G-Al was recorded. The kinetics experiments indicated that the pseudo-second order model well described phosphate uptake on all LDH. The lowest uptake (1.09 mmol g− 1) was observed for Zn3G-Al likely due to Zn/Al molar ratio, the presence of carbonate in the interlayer space and incomplete phosphate intercalation mechanism. Phosphate adsorption isotherms of LDH were in agreement with Freundlich model. Although phosphate uptake decreased in the presence of other anions, the highest selectivity especially in the pure nitrate containing LDH were measured for phosphate anion. Phosphate uptake declined with increasing the pH from 6 to 8. The amounts of phosphate desorption from prepared LDH were between 23.2 and 36.3% suggesting that synthesized LDH may have potential to be used as a slow release phosphate fertilizer in soils.

    更新日期:2017-12-08
  • Mineral and textural transformations in aluminium-rich clays during ceramic firing
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-02
    Elisa Laita, Blanca Bauluz

    The aim of this study has been to analyse the mineralogical and textural transformations of a set of aluminium-rich shales of interest for refractory and ceramic uses, fired from 800 °C to 1300 °C. To that end, raw and fired samples were analysed by X-ray diffraction, transmitted light microscopy, field emission scanning electron microscopy, and transmission electron microscopy. Raw samples comprise variable proportions of illite, pyrophyllite, orthoclase, quartz, kaolinite, mixed-layer I-Sm, and organic matter. At temperatures below 800 °C, kaolinite, mixed-layer I-Sm, and organic matter are destabilized, indicating that they are the least stable phases in the firing process. Illite, pyrophyllite, and orthoclase remain until 1000 °C and show a broader stability field during firing than in natural environments. Quartz persists throughout the entire firing process, although it is partly replaced by vitreous phase. Hematite crystallizes at 900 °C. Vitrification begins at 1000 °C, marking the first significant textural change. From 1000 °C mullite starts to crystallize from the Si- and Al-rich vitreous phase. The mullite composition is not stoichiometric and probably as temperature increases Si is partially replaced by Al, Fe and Ti in the structure. Nevertheless, with the increase of the firing temperature, the mullite composition is closer to the theoretical composition and also to that of natural mullites. Furthermore its crystal thickness increases with temperature up to 70 nm.

    更新日期:2017-12-08
  • CEC input to evaluate the butyl diammonium dichloride as a swelling reducer in clay rich material
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-12-01
    Ann Bourgès, Stefan Simon

    Previous research suggest that repeated swelling of the clay minerals involve differential strain during wetting and drying cycles which may induce decay under a fatigue of the clay rich material. Scaling due to this process has been observed on some stone binding clay but also on earthen material used in architecture. Since recent years, research on the conservation of clay-rich sandstones lead to the development of bifunctional cationic surfactants as swelling reducers for sandstones with high hygric and hydric dilatation. In this paper, the butyl diammonium dichloride surfactant was experimented on earthen material to reduce important hygric dilatation which leads to fast and important decay of earthen material. It has been directly added into the clay mixture of molded adobe brick that was to be physically and mechanically tested. The aim is to further investigate the interaction of the surfactant with clay minerals. Series of experiments showed great impact on various physical-mechanical properties of the molded earthen mixtures. Some could have been expected according to the function of the surfactant, which is to block the micropores within the clay mineral structures, responsible for the swelling. Thus, the decrease of the specific surface area as well as the hygric dilatation is understandable. However, according to the concentration of surfactant used within the adobe mixture, other properties are also affected such as the ultrasonic velocity, the water uptake coefficient, the hydric shrinkage and the compressive strength. Therefore this paper underlines important influences in changes of properties of molded adobe according to the concentration of surfactant used, and the cation exchange capacity of the material. The paper will show a new approach consisting in adapting the concentration of surfactant as a function of cation exchange capacity (CEC) of the material.

    更新日期:2017-12-08
  • Stabilisation of soft soil using binary blending of high calcium fly ash and palm oil fuel ash
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-28
    Hassnen Jafer, William Atherton, Monower Sadique, Felicite Ruddock, Edward Loffill

    Lime and/or Ordinary Portland cement (OPC) are the traditional binders used in soft soil stabilisation. However, their manufacture has a negative impact on the environment. This paper reports the results of experimental work for the optimisation of a binary blended cementitious binder (BBCB) using two types of fly ash as an alternative for use in soft soil stabilisation. The optimum content of the high calcium fly ash (HCFA) was initially determined along with the effect of grinding activation on the performance of HCFA. Subsequently, the effect of palm oil fuel ash (POFA) pozzolanic reactivity on the engineering properties of soft soil, stabilised with HCFA, was investigated by producing different binary mixtures of HCFA and POFA. Based on the Atterberg limits and unconfined compressive strength (UCS) tests, the combination of POFA with HCFA results in a considerably lower plasticity index (PI) and higher compressive strength than those obtained from the soil treated with HCFA alone. Substantial changes in the microstructure and binders of the stabilised soil over curing time were evidenced by SEM imaging and XRD analysis. A solid and coherent structure was achieved after treatment with BBCB as evidenced by the formation of C single bond S single bond H, portlandite and ettringite as well as secondary calcite.

    更新日期:2017-12-08
  • Controlled release studies of boron and zinc from layered double hydroxides as the micronutrient hosts for agricultural application
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-28
    Patsaya Songkhum, Tuksadon Wuttikhun, Narong Chanlek, Pongtanawat Khemthong, Kritapas Laohhasurayotin

    Two forms of zinc-aluminium layered double hydroxides (ZnAl-LDH) with borate association (iZA and cZA) were prepared by ion-exchange process and in-situ co-precipitation. The received materials were examined using several characterization techniques, e.g. x-ray diffraction (XRD), scanning- and transmission-electron microscopy (SEM and TEM). The XRD diffractograms suggested that only monoborate ions (possibly trigonal and tetrahedral forms) were involved in the intercalation and adsorption. Elemental analyses, i.e. inductive coupled plasma-optical emission and atomic absorption spectroscopies, were used to determine the starting zinc and boron compositions, and the contents after the dissolution experiment in water, soil, and plant growth study. The iZA and cZA samples were found to controlled-release Zn and B contents which can be used as micronutrient sources in agricultural application. The releases of the two nutrients are suggested to initiate from the anionic-exchange of BO33 − and the transformation of Zn2 + from LDH basal plane. The plant experiments treated with these iZA and cZA exhibit improvements in plant growth, evidently attributed to the controlled and sustainable releases of boron and zinc for assisting macronutrient uptakes when used with the NPK fertilizer.

    更新日期:2017-12-08
  • Polyethyleneimine (PEI) loaded MgO-SiO2 nanofibers from sepiolite minerals for reusable CO2 capture/release applications
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-27
    Jing Ouyang, Wei Gu, Chenghui Zheng, Huaming Yang, Xiangchao Zhang, Yelin Jin, Jing Chen, Jinlong Jiang

    CO2 capture and storage (CCS) by advanced materials and technologies will play a significant role in reducing industrial or human caused CO2 emissions. In this article, a clay mineral based CO2 absorbent was prepared by impregnating polyethyleneimine (PEI) onto acid modified fibrous sepiolite. X-ray diffraction (XRD), Fourier transform microscopy (FTIR), thermogravimetric analysis (TGA), and N2 adsorption - desorption isotherms accompanied BET (Brunauer-Emmett-Teller) analysis were used to characterize the raw mineral and the prepared absorbents as well as their CO2 adsorption performances. After the acid treatment, the raw sepiolite changed into amorphous silica (SiO2) containing a small amount of MgO, but maintained their nanowire morphology, the SBET value of acid treated Sep was 4 times larger and pore volume was about 2 times higher than the raw mineral. The MgO-SiO2 nanowires and polyethyleneimine (PEI) successfully formed an organic-inorganic hybrid composite. A maximized adsorption capacity of 2.48 mmol/g at 75 °C was reached in CO2 adsorption/desorption measurement when the composite contained 50 wt% PEI. The product also showed an excellent adsorption repeatability, above 98% of the optimized CO2 adsorption capacity could be maintained after 10 circles tests, which confirmed that the fibrous MgO-SiO2 assembly optimal amount of PEI is a promising solid absorbent in CO2 gases controlling fields.

    更新日期:2017-12-08
  • Synthesis of Cu-BTC/Mt composites porous materials and their performance in adsorptive desulfurization process
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-27
    Fabien Habimana, Da Shi, Shengfu Ji

    This paper highlights the synthesis of Cu-BTC supported on Montmorillonite (Mt) to form Cu-BTC/Mt composite materials and examines their important role in adsorptive desulfurization process of fuel liquids. Cu-BTC/Mt composites were synthesized by solvothermal synthesis using varying Cu-BTC content (30%, 40% and 50%) and a well-known and constant amount of montmorillonite was used as support. The synthesized composites were then characterized using XRD, FT-IR, TEM and BET techniques. The adsorptive desulfurization performance of the as-prepared composite materials was investigated and their ability to remove thiophene from thiophene/n-octane model oil was studied under mild operating conditions namely: temperature near room temperature, atmospheric pressure and at different model oil/adsorbent mass ratio. Investigation results have shown that the 40%Cu-BTC/Mt composite sample has the best desulfurization performance for thiophene removal. After 6 h of desulfurization, under the reaction conditions of temperature of 30 °C and at a model oil/adsorbent mass ratio of 100:1, the percentage of sulfur removal was 76% while the adsorption desulfurization capacity reached 28.95 mgS/gMOF. The 40%Cu-BTC/Mt composite sample could be reused for at least five consecutive rounds. The adsorption kinetics fit well both the pseudo-first order rate equation and pseudo-second order rate equation models.

    更新日期:2017-12-08
  • Exploring the relationship between Th(IV) adsorption and the structure alteration of phlogopite
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-26
    Hanyu Wu, Shirong Qiang, Qiaohui Fan, Xiaolan Zhao, Peng Liu, Ping Li, Jianjun Liang, Wangsuo Wu

    The adsorption of Th(IV) and the structural transformation of phlogopite were explored using batch, extraction, and spectroscopic approaches in this study. The batch experiments showed that ion exchange, surface complexation, and precipitation were predominant for Th(IV) adsorption on phlogopite under the observed pH ranges. XRD patterns showed that phlogopite was indeed transforming into the vermiculite- and/or montmorillonite-like minerals during Th(IV) adsorption, which indicated that the adsorption of Th(IV) could enhance the weathering process of phlogopite. Such weathering process could be attributed to the intercalation of hydrated Th(IV) ions instead of K+ ions locating at the interlayer sites, and then induced the expansion of the interlayer with a d-spacing of ~ 14 Å. Higher temperature and initial Th(IV) concentration were benefit for the structural transformation, but the presence of alkaline cations inhibited the expansion process following the order of Rb+ > K+ > Na+ ≈ Li+, which is strictly consistent with their hydrated radii and energy. Fulvic acid (FA) affected the distribution of Th(IV) on phlogopite to a large extent, which induced different adsorption mechanisms for Th(IV) and the alteration process of phlogopite structure. The results clearly showed a positively relationship between the immobilization ability for Th(IV) and alteration degree of phlogopite structure, which is very important to understand the mutual interaction of radionuclides and micaceous minerals in the environment.

    更新日期:2017-12-08
  • Large-scale synthesis of sub-micro sized halloysite-composed CZA with enhanced catalysis performances
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-26
    Jing Ouyang, Zai Zhao, Huaming Yang, Yi Zhang, Aidong Tang

    Large scale synthesis of catalyst with intriguing performances is a hot issue in the fields of both chemical and material science. In this paper, sub-micro sized ceria-zirconia-alumina (CZA) oxide material and that composited with halloysite (Hal) were synthesized in multi-gram scale through a simple co-precipitation method. X-ray diffraction (XRD), N2 adsorption-desorption isotherms, transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy(XPS), and temperature-programmed H2 reduction (H2-TPR) were used to characterize the crystalline, textural, morphological characters, and reducibility of the products. Three-way catalytic performances of the supported products were tested in stoichiometric air/fuel condition. The samples were all composed of sub-mirco sized particles. Size of CZA was about 200 nm, while the hybrid material introduced with Hal (CZAH) showed a rod-like and sheet-like morphology consisted of agglomerated nanoparticles with size of about 100 nm. The adaption of PEG-4000 has guided the formation of nanoparticles and their self-assembly into nano-rods in the products. The Hal mineral in the composites retained their tubular morphology and penetrated into bulk of the CZA. The CZAH composite showed larger BET surface area, favorable pore structure, and better oxygen storage capacity than the CZA sample thanks to the introduction of Hal nanotubes. The supported Pd-Rh/CZAH showed the ignition temperature at about 210 °C, and converting efficiency reached near 100% for NOx and CO before 230 °C in TWC tests, which also showed the optimized catalytic performances than CZA matrix.

    更新日期:2017-12-08
  • Photocatalytic decolorization of cationic and anionic dyes over ZnO nanoparticle immobilized on natural Tunisian clay
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-26
    Haithem Bel Hadjltaief, Sameh Ben Ameur, Patrick Da Costa, Mourad Ben Zina, Maria Elena Galvez

    In the present work we describe a simple and low-cost method for the decolorization of textile dyeing and printing wastewaters, using ZnO as photocatalyst supported on natural Tunisian clay (ZnO/Clay). This composite ZnO/Clay material was synthesized through a sol–gel method. X-ray diffraction (XRD), Nitrogen Physisorption (BET), Infrared Spectroscopy (FTIR), Scanning Electronic Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HRTEM) linked with Energy Dispersive X-ray (EDX), were performed in order to explain the characteristics of the ZnO/Clay photocatalyst. The XRD patterns, pointing to the presence of ZnO of very small crystal sizes, i.e. highly dispersed on the clay surface. The photocatalytic activity of ZnO/Clay was assayed in the decolorization of a cationic dye (Malachite Green, MG) and anionic dyes (Red Congo, RC) in aqueous solution as models pollutants under UV irradiation. In addition, the effects of different parameters such as pH of the solution, catalyst dosage, concentration of the dyes, irradiation source, as well as the influence of the presence of inorganic ions were investigated. The ZnO/Clay photocatalyst exhibited high photocatalytic activity of MG and CR decolorization under simulated solar compared to UV irradiation. The recyclability of the ZnO/Clay photocatalyst was as well validated.

    更新日期:2017-12-08
  • A novel study on the influence of cork waste residue on metakaolin-zeolite based geopolymers
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-24
    Alcina Sudagar, Slavka Andrejkovičová, Carla Patinha, Ana Velosa, Amy McAdam, Eduardo Ferreira da Silva, Fernando Rocha

    The effect of industrial waste from the cork industry on the strength and adsorption properties of zeolite-metakaolin based geopolymers has been studied. Cork residue 20% by weight was added to geopolymers that contained 0%, 25%, 50%, 75% replacement of metakaolin by zeolite in the structure. The SiO2/Al2O3 and Na2O/Al2O3 molar ratios were kept at 1 to reduce the environmental impact of sodium silicate and sodium hydroxide to the minimum. The compressive strength evolution after 1, 14 and 28 days in water and the heavy metals (Cd2+, Cr3+, Cu2+, Pb2+, and Zn2+) adsorption of the geopolymers were determined. It was found that addition of zeolite and cork residue in minor amounts concurrently aided in increasing the compressive strength of geopolymers. The adsorption properties, however, were dominated by the presence of cork residue and metakaolin which resulted in increasing adsorption of all heavy metal cations with increasing metakaolin in the structure. The adsorption was well fitted by the Langmuir model with R2 > 0.98 and the trend of adsorption was found to be Pb2+ > Cd2+ > Cu2+, Zn2+ > Cr3+. The significant improvement in compressive strength, as well as adsorption capacity observed with the addition of cork waste residue, connotes that it can be efficient as filler in geopolymers.

    更新日期:2017-12-08
  • Heat-treated Dolomite-palygorskite clay supported MnOx catalysts prepared by various methods for low temperature selective catalytic reduction (SCR) with NH3
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-23
    Haiqing Zuo, Dongyao Xu, Wei Liu, Haijun Dan, Xianghui Liu, Shuang Lin, Pin Hou

    A series of manganese oxide catalysts loaded on thermally modified Dolomite-palygorskite clay (MnOx/M-DPC) were synthesized by adopting impregnation, precipitation and citric acid methods and investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR) at low temperature. The results showed that the precipitated sample was more active (with 83% NOx conversion at 120 °C) by comparing it with the other MnOx/M-DPC samples prepared by impregnation and citric acid methods. Almost all NOx were completely removed by using this sample in the studied temperature range between 180 °C and 300 °C. In addition, all samples offered high N2 selectivity (> 94%) in the whole temperature range, and their SCR performance were affected by H2O introduction and NO oxidation to NO2 in the absence of NH3, but dependent on reaction temperature. The studied samples were characterized by specific surface area, pore size distribution, X-ray diffraction (XRD), Scanning electron microscope (SEM), electron diffraction spectra (EDS) and X-ray photoelectron spectroscopy (XPS). The results of specific surface area and pore size distribution suggested that the surface area and pore structure of catalysts obtained from various preparation methods were different, resulting in great difference in the catalytic performance. The irregular multi-modal mesoporous structure played a crucial role in the high catalytic activity over the precipitated MnOx/M-DPC sample. In addition, the results from XRD, SEM, EDS and XPS analyses indicated that Mn3O4 phase, good dispersion of manganese oxide, higher concentration of Mn as well as higher surface Mn4 + species, high lattice oxygen content on the surface were also beneficial to the superior catalytic efficiency of the precipitated sample.

    更新日期:2017-12-08
  • Effects of heating on compositional, structural, and physicochemical properties of loess under laboratory conditions
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-23
    Fanyu Zhang, Ran Kong, Jianbing Peng

    Wildfires are swept-wing across the world is increasing in recent time, causing serious environmental, ecological and socioeconomic impacts due to alterations in soil properties. Currently, wildfires are increasing in landscapes over the Chinese Loess Plateau. This study examined the changes in loess properties at laboratory temperatures ranging from 20 to 1000 °C. Various tests were performed on the raw and heated loess, including mineral and chemical compositions, color, scanning electron microscopy (SEM), particle size distribution, bulk and particle densities, particle flow velocity, specific surface area (SSA) and cation exchange capacity (CEC), along with electric conductivity (CE) and pH of its 1:5 extracts. The test results showed that heating couldn't produce notable changes in various loess properties below 400 °C, although slight changes have been observed resulting from loss of physically free and absorbed water. In contrast, higher temperature heating can induce important changes in loess properties due to the formation of aggregation as a result of changes in structure and composition. The analysis of results indicated that there has a close relation between microscopic characteristics of heated samples and its macroscopic behaviors. These findings are important to an initial understanding of wildfire-induced alterations in loess properties and then can afford useful posthoc estimate to such as erosion and debris flow geohazard processing in the fire-affected loess areas.

    更新日期:2017-12-08
  • Adsorption of alkylamine cations on montmorillonite (001) surface: A density functional theory study
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-23
    Chenliang Peng, Yihang Zhong, Fanfei Min

    Hydrophobic aggregation in cationic surfactant dispersion is an effective method for the dewatering of clay-rich tailing. The effect of head groups type and alkyl chain length on the adsorption of alkylamine cations on montmorillonite (001) surface was investigated by density functional theory (DFT), sedimentation and measurement of contact angle and adsorption quantity. The results showed that the strongest active sites were located above the six-membered oxygen ring (SOR) of montmorillonite layer, around the H atoms on N atom in the head group for alkyl primary amine (CnPA+), secondary amine (CnSA+), tertiary amine (CnTA+) cations and around H atoms in the –CH3 groups for quaternary amine (CnQA+) cation. The alkylamine cations interacted with surfaces by electrostatic attraction and hydrogen bonding where PA+, SA+, and TA+ cations formed three, two and one NHn ⋯ Os hydrogen bonds with the montmorillonite (001) surface, respectively, while QA+ cations formed non-traditional CHc ⋯ Os hydrogen bonds. The adsorption energies of Cn alkylamine cations decreased with the increasing substitution degree of –CH3 groups to Hn atoms in the head group. Moreover, the adsorption energies increased with the n increasing from 12 to 16, but changed slightly when beyond 16. The experimental results were consistent with the theoretically calculated results.

    更新日期:2017-12-08
  • Particle arrangements in clay slurries: The case against the honeycomb structure
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-22
    Amer Deirieh, Irene Y. Chang, Michael L. Whittaker, Steven Weigand, Denis Keane, James Rix, John T. Germaine, Derk Joester, Peter B. Flemings

    The properties of clay slurries (porosity ~ 0.75) impact a wide range of materials such as commercial clay dispersions and sedimentary deposits. Their material behavior, and in particular the gelation of clay slurries, is thought to be governed by clay particle interactions. In the literature, such interactions are rarely directly probed, but rather inferred from structures observed by cryo-electron microscopy. For example, the honeycomb structure is a widely accepted textbook model that is used to rationalize the observed behavior of clay slurries. Using high-pressure freezing, cryo-electron microscopy, and cryo-synchrotron wide-angle X-ray scattering, this study shows that the honeycomb-structure is an artifact of sample preparation. When samples are high-pressure frozen, individual clay particles and aggregates of particles arrange in a random orientation rather than the closed-cell structure dominated by face-face and face-edge contacts observed in plunge frozen samples. These results substantially contribute to the understanding of the gelation mechanism and particle interactions in colloidal clay slurries, and provide valuable input parameters for meso-scale modeling efforts of clay dispersions and sedimentary deposits to upscale their mechanical properties to the macroscale.

    更新日期:2017-12-08
  • Co-Mn-Fe complex oxide catalysts from layered double hydroxides for decomposition of methylene blue: Role of Mn
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-21
    Daiqin Huang, Jianfeng Ma, Changhai Fan, Kai Wang, Wenchang Zhao, Mingguo Peng, Sridhar Komarneni

    Composite Co-Mn-Fe oxide catalysts were prepared by thermal decomposition of layered double hydroxide (LDH) or hydrotalcite-like precursors. A series of catalysts at different Mn/Fe ratios were obtained and characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) spectrometry, UV–vis diffuse reflectance spectroscopy and BET surface area analysis. The catalysts were tested for methylene blue (MB) dye decomposition under visible light illumination with and without the assistance of NaHSO3. When visible light illumination was used on the catalyst in the presence of NaHSO3, the degradation efficiency was greatly enhanced. All the Mn-containing samples showed much higher capability to degrade MB than that of MnO2 under the same conditions. The [0]CoMnFe-LDO sample which did not contain any Mn showed lower degrading ability than MnO2. In addition to determining the role of Mn and the Mn/Fe ratio of the complex oxide catalysts on the decomposition of MB, the stability and reusability of these complex oxide catalysts were also tested and found to be good.

    更新日期:2017-12-08
  • Performance studies of water-based drilling fluid for drilling through hydrate bearing sediments
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-20
    Madhukar Srungavarapu, Krishan Kumar Patidar, Akhilendra Kumar Pathak, Ajay Mandal

    Hydrate-bearing formation is a highly unconsolidated formation and being fragile, the hydrates get readily decomposed while drilling through it. To successfully drill through the hydrates, the drilling fluid should have low mud invasion, exhibit optimum properties for wellbore stability, prevent the formation of the hydrates in the annulus, choke lines, etc. Initial experiments were performed with the drilling fluid with the composition as artificial seawater, 3.0 wt% bentonite, 3.0 wt% barite, and 0.3 wt% carboxymethyl cellulose (CMC) (wt%). The rheological, filtration and gelling properties were determined. The synergistic effects of xanthan gum (XG) and CMC with different compositions were used to study rheological properties. The drilling fluid with desirable rheological properties was further studied at low temperatures and at high pressures. The drilling fluid was tested for hydrate inhibiting properties in a high-pressure autoclave vessel at 16.55 MPa and at 0 °C and further tested with increasing water cut at both static and dynamic conditions. The experimental results reveal that XG has better viscosifying properties while CMC has a better filtration loss properties. With the increase in the concentration of the both CMC and XG, there has been an increase in viscosity, yield point, gel strength and decrease in the filtration loss. The experimental results also show that the developed drilling fluid has good inhibiting properties under static conditions but with an increase in water cut the risk of formation of hydrates increases.

    更新日期:2017-12-08
  • Effects of dehydration and grinding on the mechanical shear behaviour of Ca-rich montmorillonite
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-20
    F. Dellisanti, A. Calafato, G.A. Pini, D. Moro, G. Ulian, G. Valdrè

    In order to investigate in detail the effects of dehydration and grinding on the mechanical shear behaviour of Ca-rich montmorillonite, a cycle of specific experimental shear deformation tests were performed on five typology of samples, preliminary controlled by thermal analysis (TG, DTA) and X-ray diffraction (XRD): (1) a natural Ca-montmorillonite containing about 5% of adsorbed water; (2) the same montmorillonite heated at 80 °C for 2 h to remove only the adsorbed water; (3) up to 250 °C for 2 h to remove also the interlayer water; (4) up to 340 °C for 2 h to complete the removal of interlayer water and start to introduce thermo-structural defects, and (5) the starting natural Ca-rich montmorillonite after hard ball-milling for 20 h to induce mechanical deformation and structural defects in the TOT layers. The five typologies of samples have been tested by a specifically designed and built shear box apparatus, under about 20 MPa condition of normal pressure. All samples, before and after the shear test, have been analysed by Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and XRD. A theoretical mechanical analysis based on the Maxwell model is proposed to explain the τ(ε) and τ( ε ̇ ) shear behaviour of the effects of the different type of dehydration and deformation of the material, that was finally discussed in the context of the microstructural OM, SEM and XRD data.

    更新日期:2017-12-08
  • Experimental study to examine the independent roles of lime and cement on the stabilization of a mountain soil: A comparative study
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-15
    L.K. Sharma, N.N. Sirdesai, K.M. Sharma, T.N. Singh

    The durability, efficiency and the integrity of structures built within or over mountain soils are mainly controlled by the geotechnical properties. It is therefore imperative to analyse these properties before the commencement of such projects, and upgrade them when and where required. The current study focusses on the addressing the problems associated with soil failure that occur during the construction and widening of roads and highways in the area of interest. The soil samples, which were collected from the study area, were stabilized using two types of readily-available additives, namely, lime and cement. The outcomes of the study indicate the dependence of the geotechnical and microstructural properties on the type of additive used. The comparative analysis suggests that the cement has a relatively higher influence on the mechanical behaviour of soil when compared to that of lime. Additionally, the compressive strength of the samples that had been cured for 28 days increased nearly four to six times than that of the untreated specimen, thereby suggesting the influence of curing time on the strength parameters. The increase in compressive strength can be attributed to the chemical transformations that occur in the soil on the addition of additives. The cation exchange and pozzolanic reactions resulted in the formation of cementitious compounds within the soil matrix, which was observed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis. The present study suggests that satisfactory strength can be achieved with the addition of 5% additives to the soil mixture, which will save the cost of stabilization subsequently.

    更新日期:2017-12-08
  • Sodium montmorillonite/ureasil-poly(oxyethylene) nanocomposite as potential adsorbent of cationic dye
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-15
    Yanisleidys Hernández Bermúdez, Laurianne Truffault, Sandra Helena Pulcinelli, Celso Valentim Santilli

    A sodium montmorillonite/ureasil-poly(oxyethylene) clay-polymer nanocomposite was prepared using the sol-gel reaction of a U-PEO hybrid precursor/clay mineral suspension, with the aim of developing a sorbent for the removal of cationic dyes from aqueous media. The structural characteristics of the nanocomposite were studied by FTIR, XRD, UV–Vis spectroscopy, and SAXS. The XRD results revealed intercalation of the U-PEO in the silicate interlayer spaces. FTIR spectra indicated the existence of strong interactions between methylene blue (MB) dye and the clay mineral silicate layers. Time-resolved SAXS measurements during MB adsorption showed a decrease of the montmorillonite (Mt) peak area and an increase of the half-height width of the peak, indicating that water uptake during dye adsorption caused a reduction of the Mt. crystallite size. UV–Vis adsorption experiments showed that the kinetics of MB adsorption followed a pseudo-first order process and that the steady state equilibrium adsorption capacity followed the Langmuir model. The results showed that the nanocomposite is potentially applicable as an adsorbent of dyes present in contaminated waters.

    更新日期:2017-12-08
  • Flocculation of aqueous kaolin suspension using a biodegradable flocculant system of poly (vinyl alcohol)-Acacia nilotica gum blends
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-14
    Tanbir Nasim, Abhijit Pal, Abhijit Bandyopadhyay

    Acacia nilotica gum (NG) was blended with high hydrolyzed grade biodegradable poly (vinyl alcohol) ( M n ¯ 14,000) in different mass proportions to produce a green and efficient flocculant for separartion of a low concentration of kaolin particles (3 mass%) from its suspension. Flocculation efficacy (settling time and turbidity number) was optimized with respect to flocculant dose, PVA-NG blend composition and pH of the medium. Results showed that PVA-NG73 (70% PVA and 30% NG) was the best performing flocculant at 25 ppm dose when the pH of the medium was maintained at 2.6. Zeta potential (both before and after addition of flocculant), hydrodynamic size, isoelectric point and reduced viscosity number were measured to explain the sedimentation rate and turbidity numbers. The floc size was measured and was found to be comparative to the rate of sedimentation. The amount of water absorbed and lost during operation was found to be proportional with the floc size. Impact of inorganic salts on sedimentation was investigated at a neutral pH which showed a faster settling potential of both bivalent and trivalent salts at an optimized concentration (0.3 M), at the best flocculant dose (25 ppm).

    更新日期:2017-12-08
  • Removal of acid orange 7 by surfactant-modified iron nanoparticle supported on palygorskite: Reactivity and mechanism
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-14
    Guixiang Quan, Lijuan Kong, Yeqing Lan, Jinlong Yan, Bin Gao

    To improve the hydrophobic property of iron nanoparticle (INP) coated on palygorskite (P), cationic surfactant cetyltrimethyl ammonium bromide (CTMAB) was used to modify its surface properties through ion exchange. The structure of the composited P-INP/CTMAB was characterized by various analytical methods. The results showed that the long chain of CTMAB was coated on the surface of P-INP without intercalation effect. The morphology of P-INP was thus not obviously changed after the modification, but the special specific surface area increased from 30.63 m2 g− 1 to 127.04 m2 g− 1. The decoloration and degradation efficiency of P-INP/CTMAB towards acid orange 7 (AO7) was examined under different pH value, temperature and dosage conditions. The results showed that the reaction was preferred to the acidic environment and its first-order reaction rate constant (kobs) linearly depended on the dosage. With suitable conditions, the removal rate of AO7 and total organic carbon (TOC) by P-INP/CTMAB reached about 98.4% and 59.21% after 2 h, respectively. These values were both higher than that of the unmodified composition P-INP, suggesting the synergistic effects in surface adsorption and the following removal reaction. The degradation intermediate products were investigated using HPLC-MS, and the potential degradation pathway of AO7 by P-INP/CTMAB was determined.

    更新日期:2017-12-08
  • Sintering of red ceramics from yellow Amazonian latosols incorporated with illitic and gibbsitic clay
    Appl. Clay. Sci. (IF 3.101) Pub Date : 2017-11-12
    Igor Alexandre Rocha Barreto, Marcondes Lima da Costa

    Latosols are part of the soil group with the widest geographic distribution in Brazil. This soil type consists of a yellowish to reddish clayey material, and it has been widely studied for its applicability to agriculture in tropical zones. Because of the wide distribution and mineral composition of latosols, it is important to evaluate the technical feasibility of using these materials for the production of red ceramics. The raw materials were characterized using X-ray diffraction, thermogravimetric and differential thermal analysis, inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, scanning electron microscopy, and a laser particle analyzer. To determine the physical and mechanical properties, 20 different mixtures of samples were produced with the latosols of Rondon do Pará and Mosqueiro combined with 0, 20, 30, and 40% illitic or gibbsitic clays; each composition was calcined at 950 and 1100 °C. The technological properties of the samples (linear shrinkage, water absorption, apparent porosity, apparent density, and flexural strength) were investigated. The Mosqueiro latosol consists of quartz and kaolinite with additional minerals of anatase and goethite, whereas the Rondon latosol contains kaolinite and quartz as the dominant minerals, as well as goethite, anatase, and gibbsite. Only the Mosqueiro latosol, without the addition of other materials, demonstrated technological aspects that were favorable for its use in the production of ceramic products. However, the addition of illitic and gibbsitic clays significantly improved the technological characteristics of the two latosols studied.

    更新日期:2017-12-08
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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