Vapor phase adsorption of trichloroethane using organically modified montmorillonite

The vapor of 1,1,1-trichloroethane (TCA) was adsorbed to organically modified montmorillonite (organoclay). Hexadecyltrimethylammonium (HDTMA) was used to modify the surface of the clay and three types of organoclays with different HDTMA loadings were prepared. In adsorption experiments, the three types of organoclays, along with the non-modified (washed) clay were used. TCA was adsorbed from gaseous phase (nitrogen) by using a fixed adsorption bed. The adsorption breakthrough curves and the adsorption isotherms were determined at three different temperatures (24, 34, and 44 °C). The adsorption data were modeled with the Langmuir and BET isotherm equations. It was found that the isotherms of non-modified clay exhibited a favorable Type I behavior, which implies that the adsorption capacity is strongly dependent on vapor concentration at low concentration ranges. In regards to the organoclays, isotherms showed a marginally favorable Type II behavior with a reduced adsorption capacity at low concentrations, and exhibited a linear increase at elevated vapor concentrations. The temperature effect on the adsorption capacities of non-modified clay and organoclays exhibited different patterns. Desorption of TCA from clays was also performed by using pure nitrogen. The desorption rate constant k was in the order of 10^?4 min^?1 for all types of clay.     

Orientation of montmorillonite clay in dicyclopentadiene/organically modified clay dispersions and nanocomposites

Highly delaminated dispersions of the organically modified clay I‐28 (Nanocor, Inc.) in liquid dicyclopentadiene (DCPD) were prepared. In situ ring‐opening metathesis polymerization of I‐28/DCPD nanodispersions generated I‐28/poly(DCPD) nanocomposites. When clay/DCPD dispersions were cured under shear, alignment of clay platelets, tactoids, and small particles was captured. This orientation was confirmed by X‐ray diffraction and transmission electron microscopy. The Herman's orientation parameters were calculated for the oriented nanocomposites. Viscosities of these liquid nanodispersions exhibited thixotropic flow behavior, prior to curing. The time‐dependent viscosity effects became more pronounced with an increase in delamination. Initial viscosities increased with progressive clay platelet generation during delamination and nanodispersion within the liquid monomer. Viscosity can be used to follow clay exfoliation/delamination. Etching the surface of a 2 wt % I‐28 clay/poly(DCPD) nanocomposite with oxygen plasma eroded the matrix, exposing clay tactoids protruding from the surface. These surfaces were examined by SEM and energy dispersive X‐ray spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2743–2751, 2006     

Effect of organically modified montmorillonite clay on the properties of hydroxyl terminated polydimethyl siloxane

Hydroxyl-terminated poly(dimethylsiloxane) cured by a mixture of methyl tris (methyl ethyl ketoxime) silane and 3-aminopropyl triethoxy silane system is known for satisfactory mechanical properties and chemical resistance. The effect of nanoclay on this poly(dimethyl siloxane) (PDMS) system is explored in this study. Organically modified clay (montmorillonite) nanocomposites of PDMS were processed by solution blending followed by cross linking. The effect of nanoclay content on the mechanical, barrier, thermal and dynamic mechanical properties of the nanocomposites were investigated in detail. X-ray diffraction studies reveal exfoliated nature of the nanoclay layers in the composites. The mechanical properties, such as tensile strength and elongation at break of PDMS, improved substantially on reinforcement with nanoclay. The maximum enhancement in properties occurred at a nanoclay content of 2-3%. Cross-link density increased with increase in nanoclay concentration up to 3% and decreased with further addition. The barrier properties were not significantly altered by the incorporation of nanoclay. Initial decomposition temperatures marginally increased at lower loading levels of nanoclay, whereas a reverse trend is observed at higher loadings. The glass transition temperature remains practically the same for all the compositions. The study demonstrates that nanoclay addition is an effective method for improving the properties of PDMS.     

Exfoliation of organically modified montmorillonite driven by molecular diffusion in maleated polypropylene

This work is focused on the factors influencing the intercalation of maleated polypropylene (PPMA) into organically modified montmorillonite (OMMT). Two kinds of PPMA were used to explore the optimal candidate for effective intercalation into OMMT. The grafting degree of maleic anhydride and the viscosity of PPMA have effects on the diffusion of polymer molecules. Moreover, the loading level of surfactant was varied to optimize the modification of montmorillonite because the appropriate loading level can provide a balance between interlayer distance and steric hindrance. The kind of surfactant changes the interaction between OMMT and PPMA, and accordingly the intercalation of PPMA is different, resulting in the discrepancy of the intercalation of PPMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Experimental and MD simulation study on the physical and mechanical properties of organically modified montmorillonite clay and compatibilized linear low density polyethylene nanocomposites

Understanding the interfacial interactions plays a key role in controlling mechanical and physical properties of polymer/clay nanocomposites (PCNs). In this work, the surface interactions between constituents of experimentally prepared PCNs which are the pristine linear low density polyethylene (PE) chains, PE compatibilizers, montmorillonite clay surface layer, and surfactants were studied quantitatively by employing molecular dynamics simulation technique. The interaction energy between the polymer and the clay was found to be inversely proportional with the volume of the surfactant which decreases the electrostatic interactions between the compatibilizer and the hydrophilic clay surface. However, the van der Waals (vdW) interactions between alkyl tails of surfactants and the PE chains increase with the tail length of the surfactants. The most attractive interaction was between the surfactant's head group and the clay surface. We showed that there existed fine balance between the electrostatic and vdW type forces on the stability and the enhanced properties of the PE–organoclay nanocomposites. Calculated interaction energies were then correlated to the experimentally measured mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45817.     

Optimization of kinetic data for two‐stage batch adsorption of Pb(II) ions onto tripolyphosphate‐modified kaolinite clay

BACKGROUND: Most adsorption studies consider only the adsorption of pollutants onto low cost adsorbents without considering how equilibrium and kinetic data can be optimized for the proper design of adsorption systems. This study considers the optimization of kinetic data obtained for the removal of Pb(II) from aqueous solution by a tripolyphosphate modified kaolinite clay adsorbent. RESULTS: Modification of kaolinite clay with pentasodium tripolyphosphate increases its cation adsorption capacity (CEC) and specific surface area (SSA) from 7.81 to 78.9 meq (100 g)^?1 and 10.56 to 13.2 m² g^?1 respectively. X‐ray diffraction patterns for both unmodified and tripolyphosphate‐modified kaolinite clay suggest the modification is effective on the surface of the clay mineral. Kinetic data from the batch adsorption of Pb(II) onto the tripolyphosphate‐modified kaolinite clay adsorbent were optimized to a two‐stage batch adsorption of Pb(II) using the pseudo‐second‐order kinetic model. Mathematical model equations were developed to predict the minimum operating time for the adsorption of Pb(II). Results obtained suggest that increasing temperature and decreasing percentage Pb(II) removal by the adsorbent enhanced operating time of the adsorption process. The use of two‐stage batch adsorption reduces contact time to 6.7 min from 300 min in the single‐stage batch adsorption process for the adsorption of 2.5 m³ of 500 mg L^?1 Pb(II) under the same operating conditions. CONCLUSION: Results show the potential of a tripolyphosphate‐modified kaolinite clay for the adsorption of Pb(II) from aqueous solution and the improved efficiency of a two‐stage batch adsorption process for the adsorption of Pb(II) even at increased temperature. Copyright © 2009 Society of Chemical Industry     

Removal of the persistent pollutant chlorobenzene by adsorption onto activated montmorillonite

The potential of activated bentonite was assessed for adsorption of chlorobenzene from aqueous solution. The bentonite used was treated by chemical and thermal activation over 100–500 °C. The thermal activation increased the adsorption capacity more strongly than chemical activation which consists to acid and hydrogen peroxide treatment. The removal is dominated by adsorption at low initial concentrations and low temperatures and favourable in acidic media. The dependence of the adsorption on pH appears to be related to the solubility of chlorobenzene. Thermodynamic parameters such as ΔH°, ΔS°, ΔG° and Ea have been calculated. The adsorption process is spontaneous and exothermic in nature. The Freundlich isotherm described the adsorption data over the concentration range (20–270 °C).     

Isothermal degradation of poly(3‐hydroxybutyrate)/organically modified montmorillonite nanocomposites

Polymer nanocomposites consisted of biodegradable poly(3‐hydroxybutyrate) (PHB) and organically modified montmorillonite Cloisite25A (OMMT), prepared by the solution‐casting method, were isothermally degraded for 120 min at 230, 235, 240, and 245°C in the nitrogen atmosphere. The addition of OMMT increases the thermal stability of PHB, and the most pronounced effect has the addition of 7 wt% of OMMT. Kinetic analysis was performed using reduced time plots and model‐free isoconversional methods. The empirical kinetic triplets (E, A, and g(α)) for the isothermal degradation of pure PHB and PHB/OMMT nanocomposites were determined. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Optimization by response surface methodology (RSM) for toluene adsorption onto prepared acid activated clay

Adsorption of toluene onto acid activated clay was carried out. Modified clay was prepared by acid attack (H₂SO₄) on raw material. Response surface methodology based on a 2‐level, 4‐variables central composite orthogonal design was used to evaluate the effects of important parameters on the adsorption of toluene on to activated clay. Temperature (53.8–96.2°C), contact time (0.57–6.93 h), mass ratio of liquid/solid (3.38–7.62) and strength of acid (7.75–57.24%) were chosen as process variables for the optimization. Of these parameters, temperature reaction and time had greater impact on toluene adsorption than did the other parameters. Analysis of variance (ANOVA) shows a good agreement between theoretical analysis and experimental data. The validity of model is verified by an experiment at the optimum conditions. The optimum conditions for the maximum adsorption of toluene onto activated clay are: temperature of 96.2°C, a contact time of 6.93 h, a liquid/solid ratio of 5.98 and strength of acid of 32.94%. Since the predicted values and the actual experimental value obtained for the maximum adsorption of toluene are within 95% confidence intervals, the final model is considered valid and has satisfactory predictive ability.     

Synthesis of exfoliated polyamide 6,6/organically modified montmorillonite nanocomposites by in situ interfacial polymerization

Polyamide 6,6 (PA 6,6)/organically modified montmorillonite (OMMT) nanocomposites were prepared by a novel method, using direct interfacial polymerization of an aqueous hexamethylene diamine and a nonaqueous adipoyl chloride in dichloromethane solution containing different amounts of OMMT dispersed nanoparticles. The state of dispersion of OMMT in the PA 6,6 matrix was investigated by means of X‐ray diffraction, as well as transmission electronic microscopy. The results indicated that the OMMT nanoparticles were dispersed homogeneously and nearly exfoliated in the PA 6,6 matrix. The random arrangement of clay platelets in the PA 6,6 matrix, exfoliation, and intercalation of clays between the PA 6,6 matrix were distinguished. The amount of the incorporated OMMT in the PA 6,6 matrix was determined by means of TGA technique. Furthermore it was found that addition of a small amount of OMMT dramatically improved the thermal stability of PA 6,6. The TGA thermograms of all the synthesized nanocomposite samples showed an interesting unexpected lag in the weight loss at high temperatures, which could be another evidence for formation of fully exfoliated nanocomposites structures, with improved thermal stability. Nucleating effect of the OMMT nanoparticles and their influence on crystallization behavior of PA 6,6 was confirmed by DSC. Finally it is concluded that the in situ interfacial polycondensation is a suitable method for synthesis of nanocomposites with well dispersed structures and enhanced properties. POLYM. COMPOS., 28:733–738, 2007. © 2007 Society of Plastics Engineers     

Development of high‐performance epoxy/clay nanocomposites by incorporating novel phosphonium modified montmorillonite

Novel organoclays were synthesized by several kinds of phosphonium cations to improve the dispersibility in matrix resin of composites and accelerate the curing of matrix resin. The possibility of the application for epoxy/clay nanocomposites and the thermal, mechanical, and adhesive properties were investigated. Furthermore, the structures and morphologies of the epoxy/clay nanocomposites were evaluated by transmission electron microscopy. Consequently, the corporation of organoclays with different types of phosphonium cations into the epoxy matrix led to different morphologies of the organoclay particles, and then the distribution changes of silicate layers in the epoxy resin influenced the physical properties of the nanocomposites. When high‐reactive phosphonium cations with epoxy groups were adopted, the clay particles were well exfoliated and dispersed. The epoxy/clay nanocomposite realized the high glass‐transition temperature (T_g) and low coefficient of thermal expansion (CTE) in comparison with those of neat epoxy resin. On the other hand, in the case of low‐reactive phoshonium cations, the dispersion states of clay particles were intercalated but not exfoliated. The intercalated clay did not influence the T_g and CTE of the nanocomposite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of intercalated ladder‐like poly(vinylsilsesquioxanes)/organically modified montmorillonite nanocomposites

In this paper, ladder‐like poly(vinylsilsesquioxanes) (LPVS)/organically modified montmorillonite (OMT) nanocomposites have been synthesized by ultrasonic dispersion and solution blending method. The structures of nanocomposites are characterized by small angle X‐ray scattering (SAXS) and high‐resolution transmission electronic microscopy (TEM). These results indicate that LPVS have already entered the galleries of OMT layers and intercalated LPVS/OMT nanocomposites have been formed. The effects of different reaction conditions, including solution concentration and the advantage of ultrasonic dispersion, are discussed. The intercalated nanocomposite is further treated at 250.0°C for 2 h in order to eliminate surfactant in OMT. On the basis of the SAXS and TGA results, it has been found that the treated product remains in its intercalated structure and presents better thermal stability, which provides potential usage in polymer composites. POLYM. COMPOS., 27: 660–664, 2006. © 2006 Society of Plastics Engineers     

Polymer–montmorillonite clay nanocomposites. Part 1: Complexation of montmorillonite clay with a vinyl monomer

An organo‐clay complex was formed by the exchange reaction of a quaternary ammonium salt of a derivatized styrene monomer with Na⁺‐montmorillonite clay. The binding of the derivatized styrene monomer with the montmorillonite clay was confirmed by FTIR and the diffused reflectance analysis. The increase of the d‐spacing of the derivatized styrene‐N⁺–montmorillonite clay complex to 1.47 nm, measured by X‐ray diffraction, indicates that a monolayer of the monomer is adsorbed between adjacent montmorillonite layers. A molecular modeling of the monomer suggested a benzene ring tilted to the c‐axis of the montmorillonite clay. The carbon content of the styrene‐N⁺–montmorillonite clay of 11.02 % suggested a complete surface coverage of the clay by the monomer and a surface coverage of 0.74 nm² per exchange site of the montmorillonite. Copyright © 2004 Society of Chemical Industry     

Fe2O3改性蒙脱土对邻苯二酚的高效去除机理

蒙脱土及其改性后的吸附材料在环境领域广泛应用。本文研究了蒙脱土（MT-Na）及其Fe₂O₃改性后（MT-Fe₂O₃）用于去除不同pH条件溶液中的邻苯二酚。与MT-Na相比，MT-Fe₂O₃对邻苯二酚表现出更快速和高效的去除效果。随着pH升高，MT-Na从溶液中除去邻苯二酚增加，而MT-Fe₂O₃表现出相反的现象。双室一级去除动力学模型拟合结果表明，MT-Na的快室去除邻苯二酚来自于吸附，慢室去除主要是来自于降解；MT-Fe₂O₃快室主要是吸附和最初的降解，随着降解中间产物在表面的生成，阻碍了邻苯二酚在颗粒上的吸附，减缓了降解速率，表现为慢室去除。Fe₂O₃诱导生成的·OH是MT-Fe₂O₃高效去除邻苯二酚的主要因素。区分黏土颗粒去除邻苯二酚过程中的吸附和降解的贡献，将有助于更加准确地评估黏土颗粒的环境功效和描述邻苯二酚的环境行为。     

Featured structures of fire residue of high‐impact polystyrene/organically modified montmorillonite nanocomposites during burning

The structures and constituents of fire residue of high‐impact polystyrene/organically modified montmorillonite (HIPS/OMMT) nanocomposite during burning was investigated using scanning electron microscopy, thermogravimetric analysis, X‐ray diffraction analysis, and elementary analysis techniques and based on quenched samples obtained during the cone calorimeter test. It was found that during burning the HIPS/OMMT nanocomposite tends to form a two‐layer structure of fire residue on the surface of material. This two‐layer structure contains a thin and condensed skin layer at the top and a loose and expanded cellular layer under the skin layer. The skin structure contains many small sizes of voids, while the cellular structure includes a large number of large‐size voids. Both the skin and cellular layers are composed of mainly montmorillonite platelets, which are aggregated to form a nanoscale network structure, in which certain amounts of carbonaceous char components are trapped during burning but decompose above approximately 550°C in the presence of oxygen. Finally, an idealized model was put forward to explain the featured structures of fire residues for the nanocomposite studied. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of the loading levels of organically modified montmorillonite on the flame‐retardant properties of asphalt

The flame‐retardant properties of asphalt for some building applications are very important. In this study, we mainly focused on the influence of organically modified montmorillonite (OMMT) on the flame‐retardant and other properties of asphalt in a large content range and explored suitable contents of OMMT for modified asphalts. Modified asphalts with different contents of OMMT from 2 to 15 wt % were prepared by melt blending. The X‐ray diffraction results revealed that the intercalated structure was formed in the OMMT‐modified asphalt. Rubber processing analysis results indicated the formation of a filler–network structure in the OMMT‐modified asphalt. The limiting oxygen index and cone calorimetry results suggested that OMMT could be used as efficient and ideal flame retardants of asphalt. The results also reveal that excess OMMT contents (i.e., >10 wt %) depredated the flame‐retardant performance of the modified asphalt. We analyzed the mechanism by taking into account of the features of the modified agent for OMMT. The experimental data showed that the viscosity, softening point, and penetration index of the OMMT‐modified asphalt increased with increasing OMMT content, but the ductility decreased slightly when the OMMT content was not beyond 7 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 10.1002/app.40972.     

Effect of silane grafting on the microstructure of high‐density polyethylene/organically modified montmorillonite nanocomposites

Organically modified montmorillonite (org‐MMT) and high‐density polyethylene (HDPE) grafted with silane groups (HDPE‐g‐silane) were melt compounded to give HDPE‐g‐silane‐blend‐org‐MMT nanocomposites. X‐ray diffractometry was performed to investigate the intercalation effect. Transmission electron microscopy was applied to observe the dispersion of org‐MMT layers in HDPE matrices. The results indicate that an intercalated structure can be easily obtained in HDPE‐g‐silane‐blend‐org‐MMT nanocomposites. Furthermore, positron annihilation lifetime spectroscopy was used to characterize the microstructure of the composites. It is found that the ortho‐positron (o‐Ps) intensity for HDPE‐g‐silane is decreased by approximately 10% with a narrower lifetime distribution than that for HDPE. With increasing org‐MMT concentration, the o‐Ps intensity I₃ increases for HDPE‐g‐silane‐blend‐org‐MMT nanocomposites; however, for HDPE‐blend‐org‐MMT composites I₃ decreases. It is found that HDPE composites with good dispersion can be obtained following appropriate modification of the HDPE. And silane grafting has an effect on the free volume of the HDPE nanocomposites. Copyright © 2007 Society of Chemical Industry     

Optimization of processing parameters for the synthesis of low‐density polyethylene/organically modified montmorillonite nanocomposites using X‐ray diffraction with experimental design

The influence of the processing parameters on the synthesis of low‐density polyethylene (LDPE)/organically modified montmorillonite (OMM) nanocomposite films was studied using experimental design. Intercalation in the nanocomposites was analysed using X‐ray diffraction and verified using atomic force microscopy. Four direct melt processing parameters were studied to obtain surface maps of intercalation in the nanocomposites: concentration of OMM (clay‐%), concentration of Polybond^® 3149 (compatibilizer‐%), mixing temperature (T_mix) and mixing time. An ANOVA validated the polynomial function, and intercalation maps from response surface methodology (RSM) were obtained. The clay‐% parameter had the most significant effect, and T_mix showed no significant effect on intercalation (p < 0.05). A strong synergic interaction between clay‐% and compatibilizer‐% was observed, which is not possible to detect using univariate experiments. RSM provides a powerful tool for choosing the best processing conditions that lead to formulations with the highest intercalations by considering the main factors and their interactions. © 2013 Society of Chemical Industry     

Morphology and properties of silane‐modified montmorillonite clays and clay/PBT composites

Commercially available organoclay (Closite 30B) was modified by using 3‐aminopropyltriethoxysilane (APS) via a silylation reaction. Sodium clay (Closite Na) was treated by APS directly as a control. Such modified clays were further melt‐compounded with polybutylene terephthalate (PBT). The morphology and properties of the modified organoclays were characterized with X‐ray diffraction (XRD), transmission electrical microscopy (TEM), Infra‐red spectroscopy, contact angle measurement, and thermogravimetric analysis (TGA). The effects of modified clays on the crystallization behavior of PBT were characterized by differential scanning calorimetry. The basal spacing of Closite Na was enlarged from 1.01 to 1.41 nm after APS treatment, indicating that the APS was intercalated into the clay intergalleries as a monolayer. The basal spacing of Closite 30B increased slightly after APS treatment, partially resulted from the reactions between the APS and hydroxyl groups on the intercalant of Closite 30B. Closite 30B was found to be exfoliated disorderly after melt‐compounded with PBT. The APS‐modified Closite 30B only dispersed as swollen elliptical clay aggregates, in which the silicate layers were orderly intercalated. TGA results showed that the decomposition temperature at 5% weight loss of Closite 30B was increased from 250 to 270°C after APS treatment. A significant increase in the degree of crystallinity of PBT was observed in the exfoliated PBT/30B composite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Removal of fulvic acid from aqueous media by adsorption onto modified vermiculite

Clay minerals are low cost materials that can be structurally modified and exploited for removal of natural organic matter from freshwaters. The present study shows that vermiculites modified by ion exchange with hexadecyltrimethylammonium or intercalation with poly(hydroxy iron) cations are potential adsorbents for removal of fulvic acid, whereas the adsorption on the raw clay mineral is negligible. The efficiency of the modified vermiculite was evaluated by measuring adsorption isotherms by the batch technique using initial fulvic acid concentrations between 2.5 and 50.0 mg L^− 1, with one hour of contact time. At least 94% of the fulvic acid initially present in a 20 mg L^− 1 solution was sorbed onto either the intercalated poly(hydroxy iron) cations or the organically modified vermiculite. Up to an initial concentration of 5.0 mg L^− 1 the adsorption is irreversible, and no quantifiable fulvic acid was measured in the desorption experiments. For initial fulvic acid concentrations between 10.0 and 50.0 mg L^− 1, desorption was between 2.3% and 4.9% for Fe(III) intercalated vermiculite, and between 1.4% and 9.2% for the organoclay. The adsorption percentages on intercalated poly(hydroxy iron) cations increased upon lowering pH and increasing the ionic strength, indicating the occurrence of strong binding mechanisms such as ligand exchange. Adsorption percentage of fulvic acid onto the organoclay also increased with lowering of pH, but in this case the adsorption percentages showed a small decrease at high ionic strength, suggesting that electrostatic attraction plays an important role in the adsorption process.