Effect Of Montmorillonite Content Research Articles

Effect of montmorillonite content and sodium chloride solution on the residual swelling pressure of an expansive clay

Expansive clays may continue to swell even after obtaining fully saturated condition due to the continuing montmorillonite hydration process. Expansive clays in this case, if confined, will generate swelling pressure, which is termed as residual swelling pressure in this study. The residual swelling pressure poses significant impact on the long-term safety and stability of adjacent geotechnical infrastructure. Despite its significance, currently, there are very limited studies on the residual swelling pressure. In this paper, the influence of (1) the montmorillonite content and (2) sodium chloride (NaCl) concentration in the pore water on the residual swelling pressure of a compacted expansive clay was evaluated using constant-volume swelling tests. Scanning electron microscopy analyses were applied to investigate the influence of NaCl solution on the microstructure of the compacted expansive clay. Tests results showed that the residual swelling pressure increases with montmorillonite content and dry density of specimen and decreases with an increase in the NaCl concentration. The NaCl in the pore water used for compacting the clay influences the particle orientation and arrangement. High NaCl concentrated solution contributes to soil structures with higher integrity that exhibit lower residual swelling pressure. An equation is developed to interpret and predict the residual swelling pressure of expansive soils considering their montmorillonite content and dry density. The proposed equation is verified using experimental data determined in this study as well as data obtained from the literature.

Effect of montmorillonite content in natural Saudi Arabian clay on its adsorptive performance for single aqueous uptake of Cu(II) and Ni(II)

The effect of montmorillonite content on adsorptive performance of natural Saudi Arabian clay for aqueous uptake of Cu(II) and Ni(II) was investigated under kinetic and equilibrium batch studies. The clay and bentonite used were characterized using scanning electron microscopy (SEM), Brunauer-Emmet-Teller (BET), cationic exchange capacity (CE), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) techniques. The clay was composed of kaolinite and muscovite with lower quartz and calcite contents, while the bentonite was mainly montmorillonite mineral possessing surface area of 20.83 and 44.27 m2/g, respectively. Increase in montmorillonite content in the clay significantly, resulted in decrease in Cu(II) adsorption capacity while increasing the capacity for Ni(II) adsorption. Equilibrium time was found to increase considerably as the montmorillonite content was increased and was higher for the clay compared to the bentonite with 16.38 and 8.66 mg/g maximum adsorption capacities for the metal ions, respectively. For both metal ions and the different montmorillonite content, the experimental data predominantly, fitted pseudo-second-order model (R2 = 0.96–0.999) while both Langmuir and Freundlich isotherm models described well the two ions removal mechanisms (R2 = 0.91–0.99). The two metal ions exhibited divergent behaviors for having distinctive affinities towards the clay and bentonite surfaces, respectively. This suggests that proportion of montmorillonite in clay adsorbents is susceptible to influence different metal ions removal from water in different manner.

Effect of montmorillonite content on frictional velocity dependence of clay-rich fault at wet condition with a large fault displacement

Effect of montmorillonite content on frictional velocity dependence of clay-rich fault at wet condition with a large fault displacement

Effect of montmorillonite content on mechanical and hydraulic properties of bentonite and its numerical modelling

Abstract Recently, the hydraulic/mechanical/chemical (HMC) analytical method has been studied with the aim of evaluating the long-term performance of Trans-Uranium (TRU) geological repositories. In this particular research, the hydraulic/mechanical modelling of bentonite materials for HMC analyses has been studied, with bentonite materials considered as the engineered barrier. It is said that the bentonite material in the TRU disposal facilities is altered chemically by cement leachate. Moreover, there is a concern that chemical alteration changes the expansion characteristics and water permeability of the bentonite material. In this paper, using past test results, the influence of montmorillonite content and the exchange of sodium and calcium ions on mechanical and hydraulics behaviour is examined. Hydraulic/mechanical mathematical modelling is also presented, describing the mechanical behaviour of bentonite from an initially unsaturated state while also taking into account the hydraulic and mechanical characteristics of bentonite mentioned above. We also simulate the saturation process from an initially unsaturated state in a TRU disposal facility, which is modelled one-dimensionally.

Effect of Montmorillonite Content on Nucleation of Polypropylene

In this article, the effect of montmorillonite (MMT) concentration on the nucleation of polypropylene (PP) was investigated. The PP/MMT nanocomposites containing various content of MMT (0.075-3.0 wt%) were prepared by a melt blending process using an internal mixer, followed by compression molding into sheets. The nucleation effect of MMT was characterized by X-ray diffraction (XRD), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) techniques. XRD results indicated that the PP nanocomposites loaded with less than 1.5 wt% of MMT formed an exfoliated structure. DSC results showed that the crystallization temperature (Tc) of PP/MMT nanocomposites were higher than that of neat PP. Tc also increased with increasing MMT content, indicating that MMT was effective in nucleating PP crystal. WAXD patterns revealed that the addition of MMT did not affect the crystal structure of PP. Mechanical property tests showed that the tensile and impact strengths of the PP/MMT nanocomposites were better than those of neat PP when the MMT content was lower than 1.5 wt%.

Swelling behavior of sulfonated polyacrylamide nanocomposite hydrogels in electrolyte solutions: comparison of theoretical and experimental results

Nanocomposite hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide/sodium montmorillonite with chromium triacetate as ionic cross-linker. The effect of montmorillonite content on equilibrium swelling in NaCl and CaCl2 solutions, ultimate storage modulus and effective cross-link density was evaluated. The limiting storage modulus of the nanocomposite (NC) hydrogels dropped by increasing montmorillonite content up to 1,000 ppm, and then it increased by further montmorillonite loading. A mechanism is proposed for the formation of PAMPS/Na+-MMT/Cr3+ NC hydrogels. According to this mechanism, the drop in limiting storage modulus of the NC gels at low Na+-MMT concentration is due to ionic interactions between the negative layers of sodium montmorillonite and Cr3+, leading to decreased cross-link density. However, the increase of the limiting storage modulus of the NC gels at high clay concentration results from the strong interactions between the polyacrylamide chains and clay platelets. The equilibrium swelling ratio of the NC networks decreased with increase of montmorillonite content in both aqueous NaCl and CaCl2 solutions. In addition, the experimental swelling data of these NC hydrogels were described by a modified Flory–Rehner theory. The modified model was sensitive to montmorillonite concentration and it described adequately the swelling data for NC gels in NaCl solutions. Nevertheless, theoretical predictions showed some deviations from experimental results for swelling of NC hydrogels in CaCl2 solutions.

Effect of montmorillonite content in nanocomposites of segmented polyurethanes with poly(2-alkyl-2-oxazoline) sequences

A series of polyurethane/montmorillonite (PU/MMT) nanocomposites, based on poly(tetramethyleneglycol) (PTMG), α,ω-dihydroxylated poly(2-alkyl-2-oxazoline) (PROZO), [4,4’-methylenebis-(phenyl isocyanate)] (MDI) or [4,4’-methylenebis-(cyclohexyl isocyanate)] (H12MDI) and montmorillonite (MMT), were investigated. The amount of added clay ranged from 3 up to 10% by weight. The influence of the MMT weight fraction in the polymer matrix on the morphology and thermal, dynamic mechanical and tensile properties was characterized by scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectrophotometry, differential scanning callorimetry, thermogravimetric analysis and dynamic—mechanical analysis. The results of the investigations were used to rank the nanocomposites according to their properties in relation to the polyurethane matrix structure and MMT content. It was evidenced that the silicate layers were preferentially, but not exclusively, attracted to the hydrophilic polar PROZO domains, their level of dispersion being controlled through specific intermolecular interactions and the filler loading amount. Introducing clay in the polyurethane matrix resulted in an increase of both tensile strength and thermal stability. Their non-monotonic dependence on clay content was explained by considering that concomitant and contrasting effects develop as the clay amount increases: an improvement of the filler—matrix interactions and a reduction of the matrix labile physical crosslinking degree by hydrogen bonding coupled with a lower dispersion homogeneity. For high inorganic filler amount aggregated clay particles together with regions with mixture of exfoliated and intercalated morphologies were revealed.

Montmorillonite-alginate composites as a drug delivery system: Intercalation and In vitro release of diclofenac sodium

Diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method. The structure and surface morphology of the synthesized composite beads were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Diclofenac release kinetics of the composite in simulated intestinal fluid medium (pH 7.4) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac-montmorillonite-alginate composites bead was investigated by UV/Vis spectrophotometer. Diclofenac encapsulation efficiency in the montmorillonite-alginate composites bead increases with an increase in the montmorillonite content. The control release of diclofenac from diclofenac-montmorillonite-alginate composites beads was observed to be better as compared to diclofenac-alginate beads.

Effect of montmorillonite content and the type of its modifier on the thermal properties and flammability of polyimideamide nanocomposite fibers

The effects of montmorillonite (MMT) content (1, 3, 5%) and the type of its modifiers on the thermal properties and flammability of PIA nanocomposite fibers have been assessed. Sodium montmorrilonite was modified with aminododecane acid and octadecylamine. Samples of PIA nanocomposite containing commercial MMT: Nanomer PGW from Nanocor were also included in the comparative analysis. It has been found that the glass transition temperature (T g) of the fibers under investigation depends on the type of MMT’s modifier. On the other hand this parameter does not affect the thermal stability of fibers defined with T 5 and T 50 indicators since the thermal decomposition of modifiers takes place at lower temperatures. The results of testing the flammability of PIA nanocomposite fibers containing 3% of variously modified MMT allow one to include them among flame-retardant fibers.