Special Issue "Natural Zeolites"

A special issue of Minerals (ISSN 2075-163X).

Deadline for manuscript submissions: closed (31 December 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Sergey Churakov

1. Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland;
2. Paul Scherrer Institut, Head of Laboratory for Waste Management, OFLA/203a, CH-5232 Villigen PSI, Switzerland
Website | E-Mail
Interests: atomistic simulation of minerals and natural fluids; reactive transport in micro- and meso- porous materials; mineral reactivity
Guest Editor
Dr. Georgia Cametti

Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland
Website | E-Mail
Interests: crystal chemistry of natural zeolites; single crystal x-ray refinement; temperature driven phase transitions in microporous materials

Special Issue Information

Dear Colleagues,

In the past few decades, the interest in natural zeolites has continuously increased due to their low cost, abundancy, and, most important, wide range of industrial applications. They are, not only employed as effective sorbents in environmental remediation and in purification processes, such as wastewater treatment and soil depollution, but also as catalysts for chemical synthesis or drug delivery. Thus, the research on the minerals of zeolite group is continuously growing and new aspects concerning the structural and chemical features in wide range of conditions and also the novel approaches towards use oriented change of their structural properties and catalytic capacity are of particular relevance.

The aim of this Special Issue is to bring together state-of-the-art research papers and reviews covering different aspects of the zeolite’s crystal structure and chemistry, their thermal behaviour, as well as surface properties. This Special Issue welcomes papers reporting innovative approaches for the characterization of zeolite structure and their properties as well as studies dealing with industrial and medical applications of zeolites using both experimental and theoretical modelling methods. Special emphasis will be given to the research on environmental related-studies. Studies on both natural and synthetic systems will be considered.

Prof. Dr. Sergey Churakov
Dr. Georgia Cametti
Guest Editors

Manuscript Submission Information

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Keywords

  • structural investigations of zeolites
  • cation exchange
  • catalysts
  • theoretical crystal structure modelling

Published Papers (7 papers)

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Research

Open AccessArticle Real-Time Observation of Fibrous Zeolites Reactivity in Contact with Simulated Lung Fluids (SLFs) Obtained by Atomic Force Microscope (AFM)
Minerals 2019, 9(2), 83; https://doi.org/10.3390/min9020083
Received: 27 December 2018 / Revised: 13 January 2019 / Accepted: 22 January 2019 / Published: 29 January 2019
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Abstract
Inhalation of fibrous erionite particles has been linked to malignant mesothelioma. Accordingly, erionite is considered the most carcinogenic mineral. The reactivity and the nature of erionite biotoxicity has been the subject of intensive research. Despite very close chemical and structural relationships between erionite [...] Read more.
Inhalation of fibrous erionite particles has been linked to malignant mesothelioma. Accordingly, erionite is considered the most carcinogenic mineral. The reactivity and the nature of erionite biotoxicity has been the subject of intensive research. Despite very close chemical and structural relationships between erionite and offretite, the reactivity of offretite in lung fluids remains unknown. In this paper, the interaction of erionite and offretite surfaces with simulated lung fluids was investigated by means of in situ atomic force microscope (AFM). To simulate different environments in the lungs, artificial lysosomal fluid (ALF) and Gamble’s solution were used. In ALF (4.15 < pH < 4.31) the dissolution of erionite and offretite surfaces was detected, as well as an evident removal of particles (mainly attributed to impurities) from the crystal faces. Instead, the growth of a layer of a yet unknown phase on the surface of both zeolites was observed during the interaction with Gamble’s solution (7.4 < pH < 8.48). The thickness of this layer reached a few tens of nanometers and covered all the observed areas. The understanding of the observed processes is of paramount importance, since they could be potentially involved in the mechanisms triggering the toxicological effects of erionite fibres. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle Basic Treatment in Natural Clinoptilolite for Improvement of Physicochemical Properties
Minerals 2018, 8(12), 595; https://doi.org/10.3390/min8120595
Received: 30 September 2018 / Revised: 14 November 2018 / Accepted: 23 November 2018 / Published: 14 December 2018
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Abstract
Natural zeolites are low in cost and exhibit interesting properties for applications in adsorption and catalysis. However, the fact that they are natural materials, not obtained in pure form, and can incorporate various compensating ions can compromise their properties and restrict their use. [...] Read more.
Natural zeolites are low in cost and exhibit interesting properties for applications in adsorption and catalysis. However, the fact that they are natural materials, not obtained in pure form, and can incorporate various compensating ions can compromise their properties and restrict their use. As their textural and chemical properties are of great relevance for adsorption and catalysis applications, this work aims to study the modification of the natural zeolite clinoptilolite to obtain materials with better physicochemical properties. Clinoptilolite was treated with NaOH under various conditions. The treated material was characterized by X-ray diffraction, X-ray fluorescence, N2 adsorption and desorption at 77 K, CO2 adsorption at 273 K, and pyridine adsorption. The treatment allowed the removal of silicon from the material, improving the textural properties and preserving the structural Al. With the removal of Si, the Si/Al ratio decreased, and consequently, the number of acid and adsorptive sites increased. In addition, statistical planning revealed that the concentration of NaOH is the parameter that most influences the improvement of the textural properties. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle A Further Investigation of NH4+ Removal Mechanisms by Using Natural and Synthetic Zeolites in Different Concentrations and Temperatures
Minerals 2018, 8(11), 499; https://doi.org/10.3390/min8110499
Received: 10 September 2018 / Revised: 24 October 2018 / Accepted: 25 October 2018 / Published: 1 November 2018
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Abstract
We investigated the ammonium removal abilities of natural and synthetic zeolites with distinct Si/Al ratios and various surface areas to study how adsorption and ion exchange processes in zeolites perform under different ammonium concentrations and different temperatures. Five zeolites—natural mordenite, chabazite, erionite, clinoptilolite, [...] Read more.
We investigated the ammonium removal abilities of natural and synthetic zeolites with distinct Si/Al ratios and various surface areas to study how adsorption and ion exchange processes in zeolites perform under different ammonium concentrations and different temperatures. Five zeolites—natural mordenite, chabazite, erionite, clinoptilolite, and synthetic merlinoite—were immersed in 20, 50, and 100 mg/kg ammonium solutions. The results demonstrate that zeolites under high ammonium concentrations (100 mg/kg) possess higher physical adsorption capacity (0.398–0.468 meq/g), whereas those under lower ammonium concentrations (20 mg/kg) possess greater ion exchange properties (64–99%). The ion exchange ability of zeolites is extremely dependent on the cation content of the zeolites, and the cation content is affected by the Si/Al ratio. The surface area of zeolites also has a partial influence on its physical adsorption ability. When the surface area is less than 100 m2/g, the adsorption ability of zeolite increases obviously with surface area; however, adsorption ability is saturated as the surface area becomes larger than this critical value of 100 m2/g. When we placed the zeolites in 50 mg/kg ammonium concentration at different temperatures (5–50 °C), we found that the zeolites exhibited the highest ammonium removal ability at 30 °C and the potassium release was enhanced at 30–40 °C. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle Case Studies for Clean Technology Development in the Chemical Industry Using Zeolite Based Catalysts
Minerals 2018, 8(10), 462; https://doi.org/10.3390/min8100462
Received: 11 September 2018 / Revised: 4 October 2018 / Accepted: 12 October 2018 / Published: 17 October 2018
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Abstract
This paper deals with the practical implementation of cleaner technologies in the chemical industry, using two case studies as an illustration. The first case study deals with the removal of NOx and N2O gases over an iron-doped ZSM-5 catalyst developed for [...] Read more.
This paper deals with the practical implementation of cleaner technologies in the chemical industry, using two case studies as an illustration. The first case study deals with the removal of NOx and N2O gases over an iron-doped ZSM-5 catalyst developed for tail gas treatment in nitric acid manufacturing. The aim for this case study was to investigate the efficiency of the zeolitic catalyst in the DeNOx process and to compare its catalytic activity with the conventional vanadia-titania. By the experiments carried out, it can be concluded that the new technological developments could significantly contribute to a decrease in environmental pollution. The second case study focuses on zeolite-based catalysts prepared from zeolitic tuff by the impregnation method, for biodiesel production from waste sunflower vegetable oil. The effects of operating and processing variables such as reaction temperature and time were investigated. The results showed that the highest biodiesel yield was 96.7% at an 11.5 MeOH/oil molar ratio, in the presence of 6.4 wt % catalyst at a 50 °C reaction temperature and reaction time of 2 h. The properties of the biodiesel that was produced, such as the viscosity, meet the required specifications of standard JUS EN14214. The common feature of the two different case studies is that both technologies use zeolite catalysts, namely naturally-occurring zeolitic tuff and synthetic ZSM type zeolite catalyst. The examples shown emphasize the importance of the zeolites in clean chemical technologies, which contribute to the protection of the environment. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle Adsorption of N2, NO2 and CO2 on Epistilbite Natural Zeolite from Jalisco, Mexico after Acid Treatment
Minerals 2018, 8(5), 196; https://doi.org/10.3390/min8050196
Received: 15 February 2018 / Revised: 3 May 2018 / Accepted: 4 May 2018 / Published: 5 May 2018
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Abstract
Emissions of carbon dioxide (CO2) and nitrogen dioxide (NO2) in recent years has been increased considerably. One way to reduce the concentration of these greenhouse gases in the atmosphere is adsorptive capture. This paper describes the main results of [...] Read more.
Emissions of carbon dioxide (CO2) and nitrogen dioxide (NO2) in recent years has been increased considerably. One way to reduce the concentration of these greenhouse gases in the atmosphere is adsorptive capture. This paper describes the main results of adsorption of N2, NO2, and CO2 on epistilbite, both natural and on samples that were chemically treated at various concentrations of HCl. Data on the adsorption of CO2 and NO2 were evaluated by the Freundlich and Langmuir equations. Additionally, the thermodynamic parameters of adsorption were calculated, including the degree of interaction of the zeolite samples with gases by gradually changing the isosteric heat capacities of adsorption. The acid treatment improves the adsorption capacity of epistilbite with respect to NO2 and CO2, due the replacement of large extra-framework cation by small H+ ions. The improvement in the distribution of pore sizes in epistilbite samples was calculated by the method of Barrett-Joyner-Halenda. The sample H1 that was prepared in a moderately concentrated acid showed the best behavior in the CO2 adsorption processes, while the natural EPIN material preferably adsorbs NO2. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle Insights into Adsorption of Chlorobenzene in High Silica MFI and FAU Zeolites Gained from Chromatographic and Diffractometric Techniques
Minerals 2018, 8(3), 80; https://doi.org/10.3390/min8030080
Received: 9 January 2018 / Revised: 7 February 2018 / Accepted: 19 February 2018 / Published: 26 February 2018
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Abstract
In this work, the capability of two commercial high silica zeolites (HSZs), namely ZSM-5 and Y, for the removal of chlorobenzene (CB) from water was investigated by combining chromatographic and diffractometric techniques. The adsorption isotherms and kinetics of CB on ZSM-5 and Y [...] Read more.
In this work, the capability of two commercial high silica zeolites (HSZs), namely ZSM-5 and Y, for the removal of chlorobenzene (CB) from water was investigated by combining chromatographic and diffractometric techniques. The adsorption isotherms and kinetics of CB on ZSM-5 and Y zeolites were determined from batch tests. The adsorption kinetics were very fast; the time to reach equilibrium was less than 10 min. The equilibrium data of CB on the two HSZs showed dissimilarities that are particularly evident in the adsorption data concerning the low concentration range, where Y zeolite is characterized by low adsorption. On the contrary, at higher solution concentrations the adsorption capacity of Y is higher than that of ZSM-5. The crystalline structures of Y and ZSM-5 saturated with CB were investigated by X-ray diffraction (XRD) techniques. Rietveld refinement analyses of XRD data allowed for quantitative probing of the structural modifications of both zeolites after CB adsorption and provided insight into the preferred zeolite adsorption sites in both microporous materials. The refined framework–extraframework bond distances confirm that interactions between the selected organic contaminant and hydrophobic zeolites are mediated via co-adsorbed H2O. The occurrence of H2O–CB–framework oxygen oligomers explains variations in both the unit cell parameters and the shape of the channels, clearly confirming that water plays a very relevant role in controlling the diffusion and adsorption processes in hydrophobic zeolites. Full article
(This article belongs to the Special Issue Natural Zeolites)
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Open AccessArticle Thermal Stability of Woolly Erionite-K and Considerations about the Heat-Induced Behaviour of the Erionite Group
Minerals 2018, 8(1), 28; https://doi.org/10.3390/min8010028
Received: 30 December 2017 / Revised: 15 January 2018 / Accepted: 17 January 2018 / Published: 19 January 2018
Cited by 4 | PDF Full-text (5445 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The thermal behavior of a woolly erionite-K sample (Lander County, NV, USA), chemical formula (Ca2.03Na0.73K2.52Mg0.26)[Al8.22Si27.78O71.80]·35.94H2O, was investigated in the 303–1173 K thermal range by in situ X-ray [...] Read more.
The thermal behavior of a woolly erionite-K sample (Lander County, NV, USA), chemical formula (Ca2.03Na0.73K2.52Mg0.26)[Al8.22Si27.78O71.80]·35.94H2O, was investigated in the 303–1173 K thermal range by in situ X-ray powder diffraction. Present data suggest a general thermally-induced volume contraction whose magnitude increases as S i S i + A l ratio becomes smaller. An inverse correlation between S i S i + A l ratio and Tdehydr is observed because higher S i S i + A l ratio values are associated to lower dehydration temperatures. A positive dependence exists between S i S i + A l ratio and Tbreak. A higher Si content results in a greater thermal stability, in agreement with the general trend observed in zeolites. On the contrary, no correlation has been found between Tbreak and weighted ionic potential (Z/r)wt as suggested by reference data. Heating produces a general depletion of the Ca1, Ca2, Ca3, and K1 sites, which is counterbalanced by an increase of the K2 site scattering, even though the latter is not populated at RT. No “internal ion exchange” mechanism was apparently acting in the present sample differently from other erionite samples analysed in the past. At 303 K approximately 20 e allocated at the OW H2O sites might be assigned to (extra-framework) EF cations. Such fraction increases due to their migration from the extra-framework cation sites following the same mechanism reported in reference data. Full article
(This article belongs to the Special Issue Natural Zeolites)
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