Non-modified Clay Research Articles

Equilibrium, kinetic and thermodynamic studies of copper adsorption onto poly(n-vinylpyrrolidone) modified clay

ABSTRACTWe demonstrated in this study the removal of copper ions from aqueous solutions by a new and cost efficiency adsorbent based on poly(N-vinylpyrrolidone) modified sodium bentonite. The X-ray diffraction analysis confirmed that the poly(N-vinylpyrrolidone) is well intercalated in the clay inter-sheets. Adsorption of copper was analyzed by the atomic absorption spectroscopy technical.Quantitative removal of copper in aqueous solution and the optimum conditions in batch experimental set-up were attained by following searching effects such as contact time, initial metal concentration, pH and temperature.The elimination of this pollutant by this a new composite reached 3.27 mg.g−1, which is more important than the amount of copper adsorbed by the non-modified clay (1.5 mg.g−1). The experimental results showed that the equilibrium and shaking time was attained within 05 min. The better retention capacity of copper was obtained at pH between 4 and 5.8.Equilibrium data were well fitted with the Langmuir, Freundlich and Elovich models.Also, the pseudo first order and pseudo-second-order were also applied. The experimental data follow well the pseudo-second-order kinetics. The thermodynamic of this new adsorbent of copper shows spontaneous and exothermic process with a negative value of ΔS.

Allyl phosphonium salt-modified clay for photocured coatings: Influence on the properties of polyester acrylate-based coatings

In this study, bentonite clay was modified with a phosphonium salt and this modified clay was used to prepare polyester acrylate based coatings to improve their flame retardancy and mechanical properties. Photocured composites were prepared with 1, 2, and 3 wt% phosphonium salt modified clay and for comparison 1 wt% nonmodified clay containing composites were also prepared. Modified clay displayed good dispersion properties due to its increased basal spacing. Composites were characterized by FT-IR and XRD measurements. According to XRD results, it was found that the modified clay was exfoliated in the composites. Furthermore, we investigated the effect of allyl phosphonium salt modified clay on the thermal, mechanical, and flame retardant properties of polyester acrylate based composites coatings. When compared with neat clay containing coatings, modified clay containing photocured coatings exhibited increased modulus and enhanced thermal properties due to increased crosslinking density. Moreover, the presence of the phosphonium salt enhanced the flame retardancy of the polyester based coatings. POLYM. COMPOS., 36:946–954, 2015. © 2014 Society of Plastics Engineers

Effects of modified and non-modified clay on the rheological behavior of high density polyethylene

HDPE nanocomposites containing 2.5, 5 and 10wt.% of non-modified and modified clays (NMC and MC) were prepared by melt extrusion in a twin screw extruder. Compression molded samples were prepared. Transmission electron microscopy (TEM) indicated a partial intercalation of the modified clay nanofiller within the HDPE matrix comparing to that of non-modified clay. The moduli of nanocomposites increased with increase in nanofiller concentration; but this increase was greater in the low frequency region. The non-modified clay had a greater increase in the elastic behavior, while the modified clay increased viscose behavior because of more interactions with the matrix and partial intercalation. The rheological behaviors of both HDPE/NMC and HDPE/MC nanocomposites are more sensitive to nanoparticles’ concentration at low frequencies. The HDPE/MC nanocomposites showed semi-circle shapes comparing to HDPE/NMC nanocomposites. While the Cole–Cole plot of HDPE/NMC nanocomposite had more departure of semi-circle shape. The agglomerated particles could concentrate the imposed stress so the yield stress reached at lower shear rates comparing to pure HDPE and HDPE filled 2.5wt.% NMC nanocomposite. Study of suspension models showed that the Eilers-Van Dijck and Einsten models fitted to almost experimental data satisfactorily.

In vitro toxicological assessment of clays for their use in food packaging applications

Montmorillonite based clays have a wide range of applications that are going to contribute to increase human exposure to these materials. One of the most promising uses of clays is the development of reinforced food contact materials that results in nanocomposites with improved barrier properties. Different organoclays have been developed introducing modifiers in the natural clay which is commercially available. However, the toxicological aspects of these materials have been scarcely studied so far. In the present study, the cytotoxic effects of a non-modified clay (Cloisite Na+) and an organoclay (Cloisite 30B) have been investigated in the hepatic cell line HepG2. Only Cloisite 30B showed cytotoxicity. In order to elucidate the toxic mechanisms underlying these effects, apoptosis, inflammation, oxidative stress and genotoxicity biomarkers were assayed. Moreover, a morphology study with light and electron microscopy was performed. Results showed genotoxic effects and glutathione decrease. The most relevant ultraestructural alterations observed were mitochondrial degeneration, dilated endomembrane systems, heterophagosomes formation, fat droplets appearance and presence of nuclear lipid inclusions. Cloisite 30B, therefore, induces toxic effects in HepG2 cells. Further research is needed to assess the risk of this clay on the human health.

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.

Effect of Blended Montomollironite on Crystallization of Poly(vinylidene fluoride)

The effect of blend of nano-clay on Poly(vinylidene fluoride) (PVDF) crystallization was examined in PVDF/organo-clay (organically modified clay) nanocomposites and PVDF/natural-clay (non-modified clay) composites. These two types of composite materials were prepared by a melt compounding method using a twin-screw extruder. The composites were characterized by X-ray diffraction (XRD) and Differential Scanning Calorimeter (DSC) measurement. We found that the PVDF crystallizes as β-form crystal on clay surface of both composite systems. Results for films made by slow cooling from melt are one important evidence that crystallization mechanism of β-form PVDF in these nanocomposites is epitaxial growth on the surface of clay platelets. In addition, we predict PVDF crystallization behaviors which depend on degree of supercooling by comparing quenched and slowly cooled samples of the composite systems.