The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Makoto Ogawa - One of the best experts on this subject based on the ideXlab platform.
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formation of cadmium sulfide and zinc sulfide mixture in the interlayer space of Montmorillonite
European Journal of Inorganic Chemistry, 2015Co-Authors: Jirabhorn Kabilaphat, Nithima Khaorapapong, Areeporn Ontam, Makoto OgawaAbstract:Cadmium sulfide and zinc sulfide (CdS and ZnS) were incorporated in sodium and cetyltrimethylammonium Montmorillonites by the precipitation of sulfides from soluble metal sources in the presence of Montmorillonites. The resulting hybrids were characterized by XRD, themogravimetric/differential thermal analysis (TG-DTA), TEM, Raman spectroscopy, and UV/Vis and photoluminescence spectroscopy. The absorption onsets owing to CdS and ZnS in cetyltrimethylammonium-Montmorillonite appeared in a shorter wavelength region (311–520 nm) relative to that (309–484 nm) of the two semiconductors in sodium Montmorillonite, thus reflecting the difference in the particle sizes of CdS and ZnS in the hybrids. The appearance of the broad emission bands combined with the bands centered at 469, 451, 440, and 431 nm owing to CdS and ZnS were attributed to the existence of both CdS and ZnS in the products. The difference in the emission intensity of the hybrids is discussed in terms of the role of the cetyltrimethylammonium cation. The unique optical properties of the two products were thought to occur through the interactions of sulfides with their environment (Montmorillonite and cetyltrimethylammonium cation).
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in situ complexation of 8 hydroxyquinoline and 4 4 bipyridine with zinc ii in the interlayer space of Montmorillonite
Applied Clay Science, 2014Co-Authors: Patcharaporn Pimchan, Nithima Khaorapapong, Minoru Sohmiya, Makoto OgawaAbstract:Abstract A series of mixed-ligand zinc complexes was prepared by coordination of 8-hydroxyquinoline and 4,4′-bipyridine to interlayer zinc(II) ion of Montmorillonite through solid–solid reactions at room temperature. The intercalation of the ligands and the in situ formation of the mixed-ligand zinc complexes in the interlayer spaces of Montmorillonite were confirmed by powder XRD, TG-DTA, as well as FT-IR, UV-Vis and photoluminescence spectroscopies. The intense photoluminescence of zinc(8-hydroxyquinoline)(4,4′-bipyridine)-Montmorillonite hybrids appeared at 503 nm while photoluminescence of zinc(4,4′-bipyridine)(8-hydroxyquinoline)-Montmorillonite hybrids was seen at 511 nm. The blue- and red-shifts of the luminescent bands of the hybrids compared with that of zinc(8-hydroxyquinoline) 2 -Montmorillonite (506 nm) suggested that the different types and/or microstructure of the mixed-ligand zinc complexes formed in the interlayer spaces of Montmorillonite. The photoluminescence intensities of the as-prepared mixed-ligand zinc complexes in Montmorillonite decreased in the order of zinc(8-hydroxyquinoline)(4,4′-bipyridine) 2 -Montmorillonite > zinc(8-hydroxyquinoline)(4,4′-bipyridine)-Montmorillonite > zinc(4,4′-bipyridine)(8-hydroxyquinoline) 2 -Montmorillonite > zinc(4,4′-bipyridine)(8-hydroxyquinoline)-Montmorillonite > zinc(8-hydroxyquinoline)-Montmorillonite. The sequence of ligand loading affected the molecular structure and/or packing of the formed complex to control the photoluminescence efficiencies of the hybrids.
Zhongxin Luo - One of the best experts on this subject based on the ideXlab platform.
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enhanced removal of bisphenol a from aqueous solution by organo Montmorillonites modified with novel gemini pyridinium surfactants containing long alkyl chain
Chemical Engineering Journal, 2016Co-Authors: Qiang Yang, Zhongxin Luo, Manglai Gao, Senfeng YangAbstract:Abstract To utilize the π–π interaction and the hydrophobic affinity of modifiers with long alkyl chain in the interlayer of Montmorillonites for effective removal of bisphenol A (BPA) from aqueous solution, organo-Montmorillonites modified with novel Gemini pyridinium surfactants containing both the aromatic ring and long alkyl chain, 1,1′-didodecyl-4,4′-trimethylene bispyridinium bromide (BPy-12-3-12) and 1,1′-dihexadecyl-4,4′-trimethylene bispyridinium bromide (BPy-16-3-16) were designed and prepared in this study. The raw Montmorillonite and organo-Montmorillonites (BPy-12-3-12-Mt and BPy-16-3-16-Mt) were specified with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA). The main effect factors which played a significant role in removal of BPA from aqueous solution, such as the amount of modifier, alkyl chain length, contact time and solution pH were investigated in detail. The experimental results indicated that the maximum adsorption capacities of BPA obtained from Langmuir isotherms were 222.2 mg/g for BPy-12-3-12-Mt and 208.3 mg/g for BPy-16-3-16-Mt at pH 6, suggesting that organoclays with shorter alkyl chain presented higher affinity for BPA. This may be due to the combined contribution of π–π interaction and hydrophobic interaction, especially π–π interaction played a dominated role in BPA adsorption. Additionally, the experimental data were best fitted with the Langmuir isotherm model. The obtained kinetics data for BPA adsorption onto the organoclays were described well by the pseudo-second-order model. Thermodynamic parameters demonstrated that the adsorption process of BPA was spontaneous and exothermic in nature.
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the characterization of organo Montmorillonite modified with a novel aromatic containing gemini surfactant and its comparative adsorption for 2 naphthol and phenol
Chemical Engineering Journal, 2015Co-Authors: Senfeng Yang, Manglai Gao, Zhongxin Luo, Qiang YangAbstract:Abstract A novel aromatic-containing gemini surfactant, bis-N,N,N,-hexadecyldimethyl- p -phenylenediammonium dibromide (BHPD) was used to modify Na-Montmorillonite for the first time. The surface and structure of the resultant organoclays were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), elemental analysis (EA) and Zeta potential. The results showed that interlayer space of the Na-Montmorillonite was significantly expanded at relatively low concentration of BHPD. The comparative study for the adsorption of 2-naphthol and phenol from aqueous solution was performed on the resultant organo-Montmorillonites. The results suggested that the adsorption amount of 2-naphthnol was much higher than that of phenol under the same condition, which may be attributed to the stronger hydrophobicity of 2-naphthol and its higher delocalized π-electron density. The important factors, such as the amount of modifier, contact time, temperature and pH in the solution, were also taken into consideration. Additionally, the kinetics and thermodynamics parameters were investigated, it was found that the reaction process was completed in a short time, the experimental data fitted very well with the pseudo-second-order kinetic model, and the equilibrium adsorption data were proved to be in good agreement with the Freundlich isotherm model. Thermodynamic parameters Gibbs free energy (Δ G °), the enthalpy (Δ H °) and the entropy change of sorption (Δ S °) demonstrated that the adsorption of 2-naphthol and phenol was a spontaneous and exothermic process.
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the removal of p nitrophenol from aqueous solutions by adsorption using gemini surfactants modified Montmorillonites
Chemical Engineering Journal, 2013Co-Authors: Guanghai Xue, Manglai Gao, Zhongxin LuoAbstract:Abstract Montmorillonites modified by two gemini surfactants (1,3-bis(dodecyldimethylammonio)-propane dibromide (BDP) and 1,3-bis(dodecyldimethylammonio)-2-hydroxypropane dichloride (BDHP)) via ion exchange were used to remove p-nitrophenol (PNP) from aqueous solutions. The organo-Montmorillonites were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. The effects of the concentration of modified agent, adsorbent mass, pH and contact time were investigated in detail. The results showed that as the concentration of modified agent increased, the adsorption amount increased accordingly and reached maximum adsorption when the concentration of modified agent approached and exceeded 1.0CEC. The removal percentages of PNP increased with the increasing of adsorbent mass at constant initial PNP concentration (100 mg/L). The results revealed that the adsorption of PNP increases with an increase in pH. The adsorption kinetics was found to follow the pseudo-second-order kinetic model and the equilibrium data fitted the Langmuir, Redlich–Peterson and Temkin equations better than Freundlich equation for both BDP modified Montmorillonite (BDP-Mt) and BDHP modified Montmorillonite (BDHP-Mt). The results also showed that BDHP-Mt containing one hydroxyl in the gemini surfactant molecule was more effective than BDP-Mt for the sorption of PNP from aqueous solutions. Thus, a new idea was provided for the selection of high efficient modified agent, i.e., hydroxyl-containing gemini surfactants. The negative values of ΔG° and ΔH° obtained from thermodynamic study of adsorption process indicated the spontaneous and exothermic nature of the two processes.
Jianxi Zhu - One of the best experts on this subject based on the ideXlab platform.
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adsorption of phenol and cu ii onto cationic and zwitterionic surfactant modified Montmorillonite in single and binary systems
Chemical Engineering Journal, 2016Co-Authors: Qingze Chen, Jianxi Zhu, Runliang Zhu, Qi Tao, Godwin A AyokoAbstract:Abstract Organo-Montmorillonites (OMts) modified by cationic surfactant (hexadecyltrimethylammonium bromide, C16) and zwitterionic surfactant (hexadecyldimethyl (3-sulphonatopropyl) ammonium, Z16) were used to remove phenol and Cu(II) from aqueous solution. The OMts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), Fourier-transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and C, H, and N elemental analyses. Besides the independent adsorption of single contaminants, simultaneous and sequential adsorption of phenol and Cu(II) onto OMts were also investigated. The organic carbon contents of the two OMts were similar but the basal spacing of Z16 modified Montmorillonite (Z16-Mt) was larger than that of C16 modified Montmorillonite (C16-Mt) indicating a higher packing density of surfactant and hydrophobicity in C16-Mt with a slight higher adsorption capacity toward phenol. On the other hand, C16-Mt showed much lower capacity in adsorbing Cu(II) as compared with raw Montmorillonite. On the contrary, the adsorption capacity of Z16-Mt toward Cu(II) was comparable with that of raw Montmorillonite. The equilibrium data of phenol and Cu(II) were fitted satisfactorily with Linear and Langmuir models, respectively. In the sequential adsorption system, the adsorption of one contaminant was not affected by the other pre-adsorbed one; desorption of pre-adsorbed contaminant was also investigated. For both two contaminants, one did not affect the adsorption of the other one onto Z16-Mt and C16-Mt in the simultaneous system. Z16-Mt could rapidly and efficiently remove both phenol and Cu(II) simultaneously. The adsorption kinetics followed the Pseudo-second order model. The results of this work might provide novel information for developing new effective adsorbents toward organic contaminants and heavy metals.
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restricting layer collapse enhances the adsorption capacity of reduced charge organoclays
Applied Clay Science, 2014Co-Authors: Runliang Zhu, Jianxi Zhu, Junbo Zhao, Lifang Zhu, Qi TaoAbstract:Abstract By restricting layer collapse, and increasing the exposure of siloxane surfaces, in the interlayer space of organoclays, their capacity for adsorbing hydrophobic organic contaminants has been enhanced. The organoclays were prepared by replacing a proportion (20–80%) of the Li + ions, occupying interlayer sites in Montmorillonite, with tetramethylammonium (TMA) ions. The TMA-exchanged samples were then heated at 200 °C for 12 h to induce migration of most interlayer Li + ions into the silicate layers, and as a result of which the layer charge was reduced. Finally, the remaining Li + cations in the reduced-charge Montmorillonite were exchanged with TMA. The structural and adsorptive characteristics of the novel reduced-charge organoclays (N-TMA-Mt) are compared with those of their traditional counterparts (T-TMA-Mt), obtained by direct intercalation of TMA into reduced-charge Montmorillonites. As layer charge decreased, both the specific surface area and adsorption capacity (for nitrobenzene) of T-TMA-Mt increased to a maximum, and then declined. In the case of N-TMA-Mt, however, both parameters increased as layer charge decreased. When the layer charge of N-TMA-Mt decreased to approximately 60% of the value for the original Montmorillonite, the adsorption capacity of the sample was greater than that of T-TMA-Mt. XRD analysis indicates that the layer structure of N-TMA-Mt is more rigid than that of T-TMA-Mt. The above results indicate that the pre-exchanged TMA cations in the interlayer space of N-TMA-Mt act as pillars, restricting layer collapse (during thermal treatment), and increasing the exposure of siloxane surfaces. As a result, the capacity of N-TMA-Mt for adsorbing hydrophobic organic contaminants is superior to that of traditional organoclays.
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studies on the solid acidity of heated and cation exchanged Montmorillonite using n butylamine titration in non aqueous system and diffuse reflectance fourier transform infrared drift spectroscopy
Pacific Rim Conference on Multimedia, 2013Co-Authors: Hongmei Liu, Dong Liu, Peng Yuan, Daoyong Tan, Jingong Cai, Jianxi Zhu, Zhiguang SongAbstract:The effects of heating and cation exchange on the solid acidity of Montmorillonite were investigated using n-butylamine titration in non-aqueous system and diffuse reflectance Fourier transform infrared spectroscopy. The number of total, Bronsted, and Lewis acid sites showed the same modulation tendency with increasing heating temperature, reaching a maximum at 120 °C and subsequently decreasing until it reaches a minimum at 600 °C. The Lewis acid sites result from unsaturated Al3+ cations, and their number increased with the heating temperature due to the dehydration and dehydroxylation of Montmorillonite. The generation and evolution of Bronsted acidity were mainly related to interlayer-polarized water molecules. Water adsorbed on the unsaturated Al3+ ions also acted as a Bronsted acid. The acid strength of the Bronsted acid sites was dependent on the polarization ability of the exchangeable cation, the amount of interlayer water, and the degree of dissociation of the interlayer water coordinated to exchangeable cations. All cation-exchanged Montmorillonites exhibited different numbers of acid sites and various distributions of acid strength. Bronsted acidity was predominant in Al3+-exchanged Montmorillonite, whereas the Na+- and K+-exchanged Montmorillonites showed predominantly Lewis acidity. Moreover, Mg2+- and Li+-exchanged Montmorillonites exhibited approximately equal numbers of Bronsted and Lewis acid sites. The Bronsted acidity of cation-exchanged Montmorillonite was positively correlated with the charge-to-radius ratios of the cations, whereas the Lewis acidity was highly dependent on the electronegativity of the cations. The acid strengths of Al3+- and Mg2+-exchanged Montmorillonites were remarkably higher than those of monovalent cation-exchanged Montmorillonites, showing the highest acid strength (H0 ≤ −3.0). Li+- and Na+-exchanged Montmorillonites exhibited an acid strength distribution of −3.0 < H0 ≤ 4.8, with the acid strength ranging primarily from 1.5 to 3.3 in Li+-exchanged Montmorillonite, whereas only weaker-strength acid sites (1.5 < H0 ≤ 4.8) were present in K+-exchanged Montmorillonite. The results of the catalysis experiments indicated that Montmorillonite promoted the thermal decomposition of the model organic. The catalytic activity showed a positive correlation with the solid acidity of Montmorillonite and was affected by cation exchange, which occurs naturally in geological processes.
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the influence of alkyl chain length on surfactant distribution within organo Montmorillonites and their thermal stability
Journal of Thermal Analysis and Calorimetry, 2012Co-Authors: Jianxi Zhu, Peng Yuan, Wei Shen, Qing Zhou, Dong LiuAbstract:Organically modified clay minerals with high thermal stability are critical for synthesis and processing of clay-based nanocomposites. Two series of organo-Montmorillonites have been synthesized using surfactants with different alkyl chain length. The organo-Montmorillonites were characterized by X-ray diffraction and differential thermogravimetry, combining with molecule modelling. For surfactant with relatively short alkyl chain, the resultant organo-Montmorillonite displays a small maximum basal spacing (ca. 1.5 nm) and most surfactants intercalate into Montmorillonite interlayer spaces as cations with a small amount of surfactant molecules loaded in the interparticle pores with “house-of-cards” structure. However, for surfactant with relatively long alkyl chain, the resultant organo-Montmorillonite displays a large maximum basal spacing (ca. 4.1 nm) and the loaded surfactants exist in three formats: intercalated surfactant cations, intercalated surfactant molecules (ionic pairs), and surfactant molecules in interparticle pores. The surfactant molecules (ionic pairs) in interparticle pores and interlayer spaces will be evaporated around the evaporation temperature of the neat surfactant while the intercalated surfactant cations will be evaporated/decomposed at higher temperature.
Hongping He - One of the best experts on this subject based on the ideXlab platform.
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organoclays prepared from Montmorillonites with different cation exchange capacity and surfactant configuration
Applied Clay Science, 2010Co-Authors: Hongping He, Peng Yuan, Yanhong QingAbstract:Abstract Organically modified Montmorillonites (‘organo-Montmorillonites’) have attracted a great deal of interest because of their wide applications in industry and environmental protection. We have synthesized organo-Montmorillonites using Montmorillonites with different cation exchange capacities (CEC) and surfactants with different alkyl chain number and chain length. The organo-Montmorillonites were characterized by X-ray diffraction (XRD) and differential thermogravimetry (DTG). The basal spacing of the organo-Montmorillonites increased with surfactant loading, while the maximum basal spacing increased as the alkyl chain length of the surfactant increased. For the same surfactant, the maximum basal spacing of the organo-Montmorillonites was little influenced by the CEC of the Montmorillonite component. The level of surfactant loading required to reach the maximum basal spacing, however, strongly depended on the CEC. For a given alkyl chain length, the maximum basal spacing increased when the chain number increased from one to two. These findings are important to the preparation of low-cost organoclays for industrial applications.
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thermal characterization of surfactant modified Montmorillonites
Clays and Clay Minerals, 2005Co-Authors: Hongping He, Dan Yang, Zhe Ding, Pen Yuan, Yunfei Xi, Ray L. FrostAbstract:The thermal stability of surfactant-modified clay plays a key role in the synthesis and processing of organoclay based nanocomposites. Differential thermal analysis (DTA), thermogravimetric measurement (TG) and differential scanning calorimetry (DSC) were used in this study to characterize the thermal stability of hexadecyltrimethylammonium bromide (HDTMAB) modified Montmorillonites prepared at different surfactant concentrations. DSC shows that the molecular environment of the surfactant within the Montmorillonite galleries is unique from that in the bulk state. The endothermic peak at 70-100 oC in the DTA curves of the modified Montmorillonites is attributed to both the surfactant phase transformation and the loss of free and interlayer water. With an increase of surfactant packing density, the amount of water residing in the modified Montmorillonite decreases gradually, reflecting the improvement of the hydrophobic property for organoclay. However, the increase of the surfactant packing density within the galleries leads to the decrease of the thermal stability of the organoclays. With an increase of initial surfactant concentration for the preparation of organoclays, the surfactant packing density increases gradually to a "saturated" state. It was found that the cationic surfactant was introduced into the Montmorillonite interlayer not only by cation exchange but also by physical adsorption.
Jeanfrancois Gerard - One of the best experts on this subject based on the ideXlab platform.
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supercritical co2 ionic liquid mixtures for modification of organoclays
Journal of Colloid and Interface Science, 2011Co-Authors: Sebastien Livi, Jeanfrancois Gerard, Jannick DuchetrumeauAbstract:The use of supercritical CO2 as solvent in the modification of Montmorillonite by imidazolium and phosphonium ionic liquids bearing long alkyl chains (C18) known for their excellent thermal stability is described. The objective is to combine the environmentally friendly character of ionic liquids and supercritical carbon dioxide for the organophilic treatment of lamellar silicates. Dialkyl imidazolium and alkyl phosphonium salts were synthesized to be used as new surfactants for cationic exchange of layered silicates. Then, the synthesized phosphonium (MMT-P) or imidazolium (MMT-I) modified Montmorillonites, cationically exchanged under supercritical carbon dioxide with or without co-solvent, have been analyzed by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and compared to Montmorillonites treated by conventional cationic exchange.
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influence of the intercalated cations on the surface energy of Montmorillonites consequences for the morphology and gas barrier properties of polyethylene Montmorillonites nanocomposites
Journal of Colloid and Interface Science, 2007Co-Authors: Emilie Picard, H Gauthier, Jeanfrancois Gerard, Eliane EspucheAbstract:Abstract Organically modified Montmorillonites obtained by cation exchange from the same natural layered silicate were studied. The surface properties of the pristine and a series of organically modified clays were determined by inverse gas chromatography and the water adsorption mechanisms were studied by a gravimetric technique coupled with a microcalorimeter. A significant increase of the specific surface area, a decrease of the water adsorption, and a decrease of the dispersive component of the surface energy were observed when the sodium cations of the natural Montmorillonite were exchanged for a quaternary ammonium. Slighter differences in surface properties were observed, on the other hand, between the different types of organically modified Montmorillonites. Indeed, similar dispersive components of the surface energy were determined on the organoclays. Nevertheless, the specific surface area increased in the range 48–80 m2/g with increasing d-spacing values and the presence of specific groups attached to the quaternary ammonium, such as phenyl rings or hydroxyl groups, led to some specific behaviors, i.e., a more pronounced base character and a higher water adsorption at high activity, respectively. Differences in interlayer cation chain organization, denoted as crystallinity, were also observed as a function of the nature of the chains borne by the quaternary ammonium. In a later step, polyethylene-based nanocomposites were prepared with those organically modified Montmorillonites. The clay dispersion and the barrier properties of the nanocomposites were discussed as a function of the Montmorillonite characteristics and of the matrix/Montmorillonite interactions expected from surface energy characterization.
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Barrier properties of nylon 6-Montmorillonite nanocomposite membranes prepared by melt blending : Influence of the clay content and dispersion state. Consequences on modelling
Journal of Membrane Science, 2007Co-Authors: Emilie Picard, Jeanfrancois Gerard, Alexandre Vermogen, Eliane EspucheAbstract:Polyamide 6-Montmorillonites membranes have been prepared and studied for a large range of clay content (from 0 to 18wt.%). The barrier properties of these systems have been determined for different diffusing molecules varying by their kinetic diameter and their interaction capacity. The relative permeability has been found to be independent on the diffusing molecule showing that a tortuosity effect is at the origin of the improved barrier properties. The crystalline morphology of the polyamide matrix has been shown to be only slightly dependent on the nanocomposite composition. Consequently, the permeation properties have been related to the clay content and dispersion. From a quantitative description of the Montmorillonite particle dispersion, the ability of different geometrical models to describe the experimental relative permeability data is discussed. This modelling leads to the conclusion that it is necessary to consider the polydispersity of the impermeable filler shapes and to take into account the presence of surfactant located at the inorganic surface to appropriately model the transport properties of the nanocomposites in a large range of nanoclay contents.
