The relations between the origin and some basic physical and chemical properties of bentonite rocks illustrating on the example of Sarmatian bentonite site at Sajóbábony (HU)

Five bentonite samples (35–47% montmorillonite) from a Sarmatian sediment series with bentonite sites around Sajóbábony (Hungary) were studied. Some of these samples were tuffogenic bentonite (sedimentary), the others were bentonitized tuff with volcano sedimentary origin. The mineral composition, particle size distribution, specific surface area, cation exchange capacity, acid–base properties of the edge sites, swelling, adsorption and migration rate of different substances were studied. We found that some characteristic properties of bentonites are mainly determined by montmorillonite content but others depend on the origin. The montmorillonite content determines the cation exchange capacity and caesium ion sorption properties. These properties depend on the layer charges of montmorillonite.The origin of bentonite determines the particle size distribution, consequently the specific surface area determined by BET method and acid–base properties of the edge sites. The quantity of the edge sites mainly depends on the specific surface area.The swelling and migration of a non-adsorbing ion in bentonite shows no direct relations to the montmorillonite content or the origin. These processes are influenced by several factors.As a consequence, the properties and the application possibilities of bentonites are not determined alone by the montmorillonite content, the origin has also an important role.The paper studies a special Hungarian bentonite site so in this respect it has local significance. However, the consequences, that is the effort about the search of relation between the bentonites and their properties, are general and valid for other bentonites, too.     

Stabilization of natural anthocyanin by intercalation into montmorillonite

Because of its non-toxicity, naturally occurring anthocyanin has a potential for the utilization as a harmless coloring material. Its color instability under alkaline condition or light irradiation limits its practical use. Anthocyanin can be stabilized by the intercalation into montmorillonite. The anthocyanin–montmorillonite maintains the original color at basic condition of even pH 11. The intercalated anthocyanin also exhibits enhanced stability against visible light irradiation compared with the anthocyanin simply adsorbed on the external surface of the mineral particles. The stability enhancement is attributed to the electrostatic host–guest interaction and to steric protection from the attack of atmospheric oxygen. The intercalated complex can be a candidate of an environmentally friendly coloring material.     

Effect of heating of organo-montmorillonites under different atmospheres

We studied the influence of heating on the behaviour of two organo-montmorillonites paying particular attention to the possible degradation effects of the organic modifier under different atmospheres. Hoffmann elimination and anucleophilic substitution on the nitrogen led to rapid degradation of the modifier. As confirmed by deconvoluted FTIR spectra, the presence of oxygen accelerated the degradation rate. The degradation products of the modifier (α-olefins transforming into various carboxyl compounds if oxygen is present) initially increased the basal spacing, followed by a collapse of the particle layers when the decomposition products migrated toward the surface and eventually volatilized.     

膨润土提纯工艺研究

膨润土作为新兴的非金属矿物,广泛应用于食品、化工、医药等多个领域,高纯膨润土更是具有高附加值。针对膨润土提纯工艺及方法进行了概括,指出了不同方法的工艺设备、提纯原理、分离效果及现存问题。对其各工艺方法研究的主要进展进行了讨论,归纳了膨润土提纯常用工艺的类型、影响因素以及应用的广泛性。并在此基础上,对高纯膨润土制备的研究前景进行了展望。     

国内外膨润土的资源特点及市场现状

总结了膨润土的组成和结构特征、矿床和矿石类型以及资源分布情况,介绍了膨润土的性能和应用途径,分析了国内外膨润土市场的现状和发展趋势,最后对我国膨润土的开发利用提出了一些建议。     

Kinetics and thermodynamics of Mn(II) removal from aqueous solutions onto Mg-Zn-Al LDH/montmorillonite nanocomposite

This study deals with the removal of Mn(II) from aqueous solutions by Mg-Zn-Al LDH/montmorillonite nanocomposite. LDH adsorbent was prepared by co-precipitation method and the composite was prepared by physical mixing of LDH and MMT using high-shear action. The data revealed that the maximum adsorption efficiency were 24.5, 26.4 and 28.9?mg/g at adsorbent mass of 0.25?g/L, pH of 6.0, initial Mn(II) concentration of 80?mg/L, stirring rate of 160?rpm, contact time of 75?min and different temperatures of 298, 308 and 318?K, respectively. Langmuir and Freundlich models were used to optimize the adsorption process and pseudo-first order and pseudo-second order models were used to evaluate the adsorption kinetics of Mn(II) ions onto Mg-Zn-Al (LDH)/MMT nanocomposite. The data indicated that Langmuir model fits the experimental data better than Freundlich model and pseudo-second order model is sufficient to depict the kinetics of Mn(II) onto Mg-Zn-Al (LDH)/MMT composite. Also, the data obtained from thermodynamics study; Gibbs free energy (ΔG°), Enthalpy change (ΔH°), and Entropy change (ΔS°) revealed that the adsorption process is spontaneous, endothermic and randomness at the solid-solution interface during the process of adsorption.     

Controllable preparation of graphitic carbon nitride nanosheets via confined interlayer nanospace of layered clays

This work described the size-controllable preparation of novel graphitic carbon nitride nanosheets using the interlayer space of smectite clays as a confined nanoreactor through cyanamide condensation. The prepared solids were characterized by X-ray diffraction, FT-IR, SEM and TEM. Results revealed that when ammonium-saponite was used, graphitic carbon nitride with an average crystal size of about 4.8 nm, the particle size of 50-100 nm and a C/N = 1.931 was obtained. When montmorillonite was used, graphitic carbon nitride with a crystal size of approximate 6.0 nm, the particle size of 100-150 nm and a C/N = 0.959 was yielded. The space-confined preparation of carbon nitride using layered clay minerals not only changes the texture of the resultant carbon nitride, but also alters the composition of products owing to the change of the whole reaction scheme to yield some new species. Such controllability over the size can be ascribed to the difference of the interlayer space and the cation exchange capacity of saponite and montmorillonite.     

Morphological and thermomechanical characterization of thermoplastic starch/montmorillonite nanocomposites

A combination of starch and clay for the preparation of nanocomposite materials is proposed. In this work, starch was plasticized by pequi (Caryocar brasiliense) oil, and thermoplastic starch (TPS)/montmorillonite (MMT) nanocomposites were analyzed by X-ray diffraction (XRD), thermogravimetry (TG), thermomechanical analyses (TMA) and scanning electron microscopy (SEM). Exfoliated and intercalated nanocomposites were found to be dependent on MMT content. Exfoliation is the predominant mechanism of clay dispersion for low filler loading. Increase of the clay loading (>5 wt.%) causes intercalation. The introduction of low content (?5 wt.%) of MMT improves the thermal stability and the stiffness of the materials. There is a limit content of clay that can be added to improve the thermal and thermomechanical properties of the composites. Beyond that value the composite presents properties below the original polymer.     

试论晋西北N2红粘土的膨胀性及其影响

本文在分析晋西北地区Ｎ２红粘土膨胀特性其机理的基础上，结合万家寨引黄工程实践，研究和讨论了Ｎ２红粘土对工程建筑尤其是地下工程建筑产生的影响。