Editorial

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Open AccessEditorial

Editorial for Special Issue “New Insights in Stability, Structure and Properties of Porous Materials”

by Annalisa Martucci and Giuseppe Cruciani

Minerals 2017, 7(5), 73; https://doi.org/10.3390/min7050073 - 11 May 2017

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Porous materials (such as zeolites, clay minerals, and assemblies of oxide nanoparticles) are of great importance for the progress in many technological and environmental fields, such as catalysis, adsorption, separation, and ion exchange, because of their unique pore topologies, tunable structures, and the [...] Read more.

Porous materials (such as zeolites, clay minerals, and assemblies of oxide nanoparticles) are of great importance for the progress in many technological and environmental fields, such as catalysis, adsorption, separation, and ion exchange, because of their unique pore topologies, tunable structures, and the possibility of introducing active reaction sites.[...] Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

Research

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4813 KiB

Open AccessArticle

Experimental Study of Montmorillonite Structure and Transformation of Its Properties under Treatment with Inorganic Acid Solutions

by Victoria V. Krupskaya, Sergey V. Zakusin, Ekaterina A. Tyupina, Olga V. Dorzhieva, Anatoliy P. Zhukhlistov, Petr E. Belousov and Maria N. Timofeeva

Minerals 2017, 7(4), 49; https://doi.org/10.3390/min7040049 - 23 Mar 2017

Cited by 160 | Viewed by 11418

Abstract

This paper discusses the mechanism of montmorillonite structural alteration and modification of bentonites’ properties (based on samples from clay deposits Taganskoye, Kazakhstan and Mukhortala, Buriatia) under thermochemical treatment (treatment with inorganic acid solutions at different temperatures, concentrations and reaction times). Treatment conditions were [...] Read more.

This paper discusses the mechanism of montmorillonite structural alteration and modification of bentonites’ properties (based on samples from clay deposits Taganskoye, Kazakhstan and Mukhortala, Buriatia) under thermochemical treatment (treatment with inorganic acid solutions at different temperatures, concentrations and reaction times). Treatment conditions were chosen according to those accepted in chemical industry for obtaining acid modified clays as catalysts or sorbents. Also, more intense treatment was carried out to simulate possible influence at the liquid radioactive site repositories. A series of methods was used: XRD, FTIR, ICP-AES, TEM, nitrogen adsorption, and particle size analysis. It allowed revealing certain processes: transformation of montmorillonite structure which appears in the leaching of interlayer and octahedral cations and protonation of the interlayer and –OH groups at octahedral sheets. In turn, changes in the structure of the 2:1 layer of montmorillonite and its interlayer result in significant alterations in the properties: reduction of cation exchange capacity and an increase of specific surface area. Acid treatment also leads to a redistribution of particle sizes and changes the pore system. The results of the work showed that bentonite clays retain a significant portion of their adsorption properties even after a prolonged and intense thermochemical treatment (1 M HNO₃, 60 °C, 108 h). Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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2049 KiB

Open AccessArticle

Temperature-Induced Desorption of Methyl tert-Butyl Ether Confined on ZSM-5: An In Situ Synchrotron XRD Powder Diffraction Study

by Elisa Rodeghero, Luisa Pasti, Elena Sarti, Giuseppe Cruciani, Roberto Bagatin and Annalisa Martucci

Minerals 2017, 7(3), 34; https://doi.org/10.3390/min7030034 - 28 Feb 2017

Cited by 14 | Viewed by 4416

Abstract

The temperature-induced desorption of methyl tert-butyl ether (MTBE) from aqueous solutions onto hydrophobic ZSM-5 was studied by in situ synchrotron powder diffraction and chromatographic techniques. This kind of information is crucial for designing and optimizing the regeneration treatment of such zeolite. The [...] Read more.

The temperature-induced desorption of methyl tert-butyl ether (MTBE) from aqueous solutions onto hydrophobic ZSM-5 was studied by in situ synchrotron powder diffraction and chromatographic techniques. This kind of information is crucial for designing and optimizing the regeneration treatment of such zeolite. The evolution of the structural features monitored by full profile Rietveld refinements revealed that a monoclinic (P2₁/n) to orthorhombic (Pnma) phase transition occurred at about 100 °C. The MTBE desorption process caused a remarkable change in the unit-cell parameters. Complete MTBE desorption was achieved upon heating at about 250 °C. Rietveld analysis demonstrated that the desorption process occurred without any significant zeolite crystallinity loss, but with slight deformations in the channel apertures. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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1919 KiB

Open AccessArticle

Strength Reduction of Coal Pillar after CO₂ Sequestration in Abandoned Coal Mines

by Qiuhao Du, Xiaoli Liu, Enzhi Wang and Sijing Wang

Minerals 2017, 7(2), 26; https://doi.org/10.3390/min7020026 - 17 Feb 2017

Cited by 25 | Viewed by 4818

Abstract

CO₂ geosequestration is currently considered to be the most effective and economical method to dispose of artificial greenhouse gases. There are a large number of coal mines that will be scrapped, and some of them are located in deep formations in China. [...] Read more.

CO₂ geosequestration is currently considered to be the most effective and economical method to dispose of artificial greenhouse gases. There are a large number of coal mines that will be scrapped, and some of them are located in deep formations in China. CO₂ storage in abandoned coal mines will be a potential option for greenhouse gas disposal. However, CO₂ trapping in deep coal pillars would induce swelling effects of coal matrix. Adsorption-induced swelling not only modifies the volume and permeability of coal mass, but also causes the basic physical and mechanical properties changing, such as elastic modulus and Poisson ratio. It eventually results in some reduction in pillar strength. Based on the fractional swelling as a function of time and different loading pressure steps, the relationship between volumetric stress and adsorption pressure increment is acquired. Eventually, this paper presents a theory model to analyze the pillar strength reduction after CO₂ adsorption. The model provides a method to quantitatively describe the interrelation of volumetric strain, swelling stress, and mechanical strength reduction after gas adsorption under the condition of step-by-step pressure loading and the non-Langmuir isothermal model. The model might have a significantly important implication for predicting the swelling stress and mechanical behaviors of coal pillars during CO₂ sequestration in abandoned coal mines. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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2262 KiB

Open AccessArticle

Use of Spent Zeolite Sorbents for the Preparation of Lightweight Aggregates Differing in Microstructure

by Wojciech Franus, Grzegorz Jozefaciuk, Lidia Bandura and Małgorzata Franus

Minerals 2017, 7(2), 25; https://doi.org/10.3390/min7020025 - 17 Feb 2017

Cited by 18 | Viewed by 5379

Abstract

Lightweight aggregates (LWAs) made by sintering beidellitic clay deposits at high temperatures, with and without the addition of spent zeolitic sorbents (clinoptilolitic tuff and Na-P1 made from fly ash) containing diesel oil, were investigated. Mineral composition of the aggregates determined by X-ray diffraction [...] Read more.

Lightweight aggregates (LWAs) made by sintering beidellitic clay deposits at high temperatures, with and without the addition of spent zeolitic sorbents (clinoptilolitic tuff and Na-P1 made from fly ash) containing diesel oil, were investigated. Mineral composition of the aggregates determined by X-ray diffraction was highly uniformized in respect of the initial composition of the substrates. The microstructure of the LWAs, which were studied with a combination of mercury porosimetry, microtomography, nitrogen adsorption/desorption isotherms and scanning electron microscopy, was markedly modified by the spent zeolites, which diminished bulk densities, increased porosities and pore radii. The addition of zeolites decreased water absorption and the compressive strength of the LWAs. The spent Na-P1 had a greater effect on the LWAs’ structure than the clinoptilolite. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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2338 KiB

Open AccessArticle

Effect of Silica Alumina Ratio and Thermal Treatment of Beta Zeolites on the Adsorption of Toluene from Aqueous Solutions

by Elena Sarti, Tatiana Chenet, Luisa Pasti, Alberto Cavazzini, Elisa Rodeghero and Annalisa Martucci

Minerals 2017, 7(2), 22; https://doi.org/10.3390/min7020022 - 15 Feb 2017

Cited by 13 | Viewed by 4646

Abstract

The adsorption of toluene from aqueous solutions onto hydrophobic zeolites was studied by combining chromatographic, thermal and structural techniques. Three beta zeolites (notated BEAs, since they belong to BEA framework type), with different SiO₂/Al₂O₃ ratios (i.e., 25, 38 [...] Read more.

The adsorption of toluene from aqueous solutions onto hydrophobic zeolites was studied by combining chromatographic, thermal and structural techniques. Three beta zeolites (notated BEAs, since they belong to BEA framework type), with different SiO₂/Al₂O₃ ratios (i.e., 25, 38 and 360), before and after calcination, were tested as adsorbents of toluene from aqueous media. This was performed by measuring the adsorbed quantities of toluene onto zeolites in a wide concentration range of solute. The adsorption data were fitted with isotherms whose models are based on surface heterogeneity of the adsorbent, according to the defective structure of beta zeolites. The thermal treatment considerably increases the adsorption of toluene, in the low concentration range, on all BEAs, probably due to surface and structural modifications induced by calcination. Among the calcined BEAs, the most hydrophobic zeolite (i.e., that with SiO₂/Al₂O₃ ratio of 360) showed the highest binding constant, probably due to its high affinity for an organophilic solute such as toluene. The high sorption capacity was confirmed by thermogravimetric analyses on BEAs, before and after saturation with toluene. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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3209 KiB

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The Influence of the Framework and Extraframework Content on the High Pressure Behavior of the GIS Type Zeolites: The Case of Amicite

by Rossella Arletti, Carlotta Giacobbe, Simona Quartieri and Giovanna Vezzalini

Minerals 2017, 7(2), 18; https://doi.org/10.3390/min7020018 - 05 Feb 2017

Cited by 4 | Viewed by 3836

Abstract

This paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction, of the high pressure behavior of the natural zeolite amicite [K₄Na₄(Al₈Si₈O₃₂)·10H₂O], the GIS-type phase with ordered (Si, Al) and [...] Read more.

This paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction, of the high pressure behavior of the natural zeolite amicite [K₄Na₄(Al₈Si₈O₃₂)·10H₂O], the GIS-type phase with ordered (Si, Al) and (Na, K) distribution. The experiments were carried out up to 8.13(5) GPa in methanol:ethanol:water = 16:3:1 (m.e.w.) and 8.68(5) GPa in silicone oil (s.o.). The crystal structure refinements of the patterns collected in m.e.w. were performed up to 4.71(5) GPa, while for the patterns collected in s.o. only the unit cell parameters were determined as a function of pressure. The observed framework deformation mechanism—similar to that reported for the other studied phases with GIS topology—is essentially driven by the distortion of the “double crankshaft” chains and the consequent changed shape of the 8-ring channels. The pressure-induced over-hydration observed in the experiment performed in aqueous medium occurs without unit cell volume expansion, and is substantially reversible. A comparison is made with the high pressure behavior of the other GIS-type phases, and the strong influence on compressibility of the chemical composition of both framework and extraframework species is discussed. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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Thermal Transformation of NH₄-Clinoptilolite to Mullite and Silica Polymorphs

by Antonio Brundu, Guido Cerri and Eleonora Sale

Minerals 2017, 7(1), 11; https://doi.org/10.3390/min7010011 - 19 Jan 2017

Cited by 10 | Viewed by 4703

Abstract

Clinoptilolite is a natural zeolite used for the abatement of ammonium in the treatment of urban wastewater. By considering that mullite was obtained through thermal treatment of NH₄-exchanged synthetic zeolites, this work aimed to evaluate if this phase can be obtained [...] Read more.

Clinoptilolite is a natural zeolite used for the abatement of ammonium in the treatment of urban wastewater. By considering that mullite was obtained through thermal treatment of NH₄-exchanged synthetic zeolites, this work aimed to evaluate if this phase can be obtained from NH₄-clinoptilolite. A material containing about 90 wt % of clinoptilolite, prepared using a Sardinian zeolite-rich rock, was NH₄-exchanged and subjected to treatments up to 1200 °C. After dehydration, de-ammoniation, and dehydroxylation processes, the clinoptilolite structure collapsed at 600 °C. An association of mullite, silica polymorphs, and glass, whitish in color, was obtained for treatments between 1000 and 1200 °C. The higher degree of crystallinity was reached after a 32 h heating at 1100 °C: mullite 22 wt %, cristobalite 59 wt %, tridymite 10 wt %, glass 9 wt %. It is possible to speed up the kinetics of the transformation by increasing the temperature to 1200 °C, obtaining the same amount of mullite in 2 h, but increasing the residual amorphous fraction (16 wt %). These results indicate that NH₄-clinoptilolite could represent a raw material of potential interest in the ceramic field, in particular in the production of acid refractory, opening scenarios for a possible reuse of clinoptilolite-based exchangers employed in ammonium decontamination. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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6243 KiB

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Characterization of a Fine-Grained Interstratification of Turbostratic Talc and Saponite

by Annett Steudel, Frank Friedrich, Rainer Schuhmann, Friedrich Ruf, Ulrich Sohling and Katja Emmerich

Minerals 2017, 7(1), 5; https://doi.org/10.3390/min7010005 - 05 Jan 2017

Cited by 14 | Viewed by 5671

Abstract

Interstratifications of talc and trioctahedral smectites from different provenances are used as indicators for geological environments and for geotechnical and technical applications. However, comprehensive layer characterization of these interstratifications is rare. Sample EX M 1694, a clay with red-beige appearance from the Madrid [...] Read more.

Interstratifications of talc and trioctahedral smectites from different provenances are used as indicators for geological environments and for geotechnical and technical applications. However, comprehensive layer characterization of these interstratifications is rare. Sample EX M 1694, a clay with red-beige appearance from the Madrid basin was studied by X-ray diffraction analysis, X-ray fluorescence analysis, Fourier transformation infrared spectroscopy, simultaneous thermal analysis, gas adsorption measurements, cation exchange capacity, and environmental scanning electron microscopy. More than 95% of particles in EX M 1964 belong to the clay fraction <2 µm. It contains 75% interstratification of 30% turbostratic talc, and 70% saponite type III and 25% turbostratic talc. The turbostratic talc(0.3)/saponite interstratification is characterized by a low number of layers per stack (3), small lateral dimension of layers (60–80 nm) and, accordingly, a high specific surface area (283 m²/g) with nearly equal surface area of micro- and mesopores. Thus, the studied material can be used as mined for adsorption, in contrast to acid-treated clays that produce hazardous waste during production. Low particle size of the interstratification drastically reduced thermal stability and dehydroxylation was superimposed by recrystallization of high temperature phases already at 816 °C, which is low for trioctahedral 2:1 layer minerals. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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Review

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Application of Mineral Sorbents for Removal of Petroleum Substances: A Review

by Lidia Bandura, Agnieszka Woszuk, Dorota Kołodyńska and Wojciech Franus

Minerals 2017, 7(3), 37; https://doi.org/10.3390/min7030037 - 08 Mar 2017

Cited by 107 | Viewed by 9589

Abstract

Environmental pollution with petroleum products has become a major problem worldwide, and is a consequence of industrial growth. The development of sustainable methods for the removal of petroleum substances and their derivatives from aquatic and terrestrial environments and from air has therefore become [...] Read more.

Environmental pollution with petroleum products has become a major problem worldwide, and is a consequence of industrial growth. The development of sustainable methods for the removal of petroleum substances and their derivatives from aquatic and terrestrial environments and from air has therefore become extremely important today. Advanced technologies and materials dedicated to this purpose are relatively expensive; sorption methods involving mineral sorbents are therefore popular and are widely described in the scientific literature. Mineral materials are easily available, low-cost, universal adsorbents and have a number of properties that make them suitable for the removal of petroleum substances. This review describes recent works on the use of natural, synthetic and modified mineral adsorbents for the removal of petroleum substances and their derivatives from roads, water and air. Full article

(This article belongs to the Special Issue New Insights in Stability, Structure and Properties of Porous Materials)

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