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Minerals
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Structural Study on Ion Exchange Process of Clinoptilolite
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Structural Study on Ion Exchange Process of Clinoptilolite

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 3811

Special Issue Editors

Dr. Louiza Dimowa

E-Mail Website
Guest Editor
Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Interests: natural zeolites; ion exchange; XRD analyses; structural features of partially ion-exchanged zeolites; cation–water complexes; environmental science
Prof. Dr. Daniela Kovacheva

E-Mail Website
Guest Editor
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Interests: powder XRD analyses; crystal chemistry; inorganic materials; nanomaterials; Rietveld method for crystal structure refinement
Dr. Filip Ublekov

E-Mail Website
Guest Editor
Institute of Polymers, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Interests: organomodified montmorillonite; ion exchange; wide and small XRD analysis; polymer nanocomposites

Special Issue Information

Dear Colleagues,

This Special Issue aims to collect articles examining HEU-type zeolites: clinoptilolite and heulandite. Of main interest are the local cation–H2O complexes around the positions of the extra-framework cations, possible local water complexes, and the partial and full occupation of positions as determined by XRD structural refinement. Of additional interest is the influence of the properties of the cations (charge, dimensions, and hydration characteristics) in their distribution in the cavities of the zeolite. The consideration of real local complexes instead of the averaged structure obtained by X-ray diffraction is a prerequisite for understanding the crystal–chemical relations in the structures of HEU-type zeolites and their behavior in different natural and technological processes. Data and developments for clinoptilolite related to sorption, ion exchange, capacity, thermal behavior, etc., especially for toxic cations and analogs of radioactive cations are of particular interest due to their current practical importance related to ecology and environmental protection.

Dr. Louiza Dimowa
Prof. Dr. Daniela Kovacheva
Dr. Filip Ublekov
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • clinoptilolite
  • ion exchange
  • extra-framework cations
  • XRD powder diffraction
  • cation diffusion
  • heavy-metal sorption
  • cation selectivity
  • structural study
  • cation–water complexes

Published Papers (2 papers)

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Research

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13 pages, 1411 KiB  
Article
Structural Features and Thermal Behavior of Ion-Exchanged Clinoptilolite from Beli Plast Deposit (Bulgaria)
by Louiza Dimowa, Nadia Petrova, Yana Tzvetanova, Ognyan Petrov and Iskra Piroeva
Minerals 2022, 12(12), 1576; https://doi.org/10.3390/min12121576 - 08 Dec 2022
Cited by 3 | Viewed by 1016
Abstract
The structural features and the thermal behavior of natural, Na-, Ca-, K-, Mg-, and Cd-exchanged clinoptilolite from the Beli Plast deposit (Bulgaria) were studied. Purified clinoptilolite sample was preliminary prepared and ion-exchanged at 100 °C for six days. DSC-TG analyses were performed for [...] Read more.
The structural features and the thermal behavior of natural, Na-, Ca-, K-, Mg-, and Cd-exchanged clinoptilolite from the Beli Plast deposit (Bulgaria) were studied. Purified clinoptilolite sample was preliminary prepared and ion-exchanged at 100 °C for six days. DSC-TG analyses were performed for all studied forms. The effects in the DSC curves show differences with temperature due to release of weakly bound H2O molecules and strongly bound ones. The endotherm minima temperatures were between 78 and 115 °C decreasing in the sequence K- < Na- < Natural- < Ca- ≤ Mg- < Cd-clinoptilolite. The hydrate complexes around the exchanged cations also influenced the DSC curves. The cation-coordinating H2O molecules and the non-coordinating ones were determined by XRD structural refinement for all exchanged samples. The H2O molecules of the cation–hydrate complexes are released at higher temperatures than weakly bound ones and affected the DSC curves differently. The structural adjustments made by the Rietveld method, as well as the applied EDS analyzes for the chemical composition of the samples, allowed us to correlate these data to the thermal characteristics of the studied clinoptilolite samples. Full article
(This article belongs to the Special Issue Structural Study on Ion Exchange Process of Clinoptilolite)
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Review

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38 pages, 8478 KiB  
Review
Ion Exchange in Natural Clinoptilolite: Aspects Related to Its Structure and Applications
by Inocente Rodríguez-Iznaga, Marina G. Shelyapina and Vitalii Petranovskii
Minerals 2022, 12(12), 1628; https://doi.org/10.3390/min12121628 - 17 Dec 2022
Cited by 14 | Viewed by 2316
Abstract
Clinoptilolite is one of the most common, widespread and abundant zeolites in nature. Its availability, low cost, and outstanding ion exchange properties make clinoptilolite an excellent candidate for both direct use and various modifications to create new low-cost functional materials for sustainable development. [...] Read more.
Clinoptilolite is one of the most common, widespread and abundant zeolites in nature. Its availability, low cost, and outstanding ion exchange properties make clinoptilolite an excellent candidate for both direct use and various modifications to create new low-cost functional materials for sustainable development. Specific applications in which clinoptilolite is already being used include water treatment and heavy metal ion removal, agricultural purposes, storage and conversion of unwanted gaseous emissions into the atmosphere, production of catalysts and photocatalysts, bioactive materials, and a number of others. Unlike some other zeolites, clinoptilolite is difficult to synthesize, which is why most publications refer to this zeolite in its natural form, either directly from the deposit or after applying various processes to this mineral to improve its properties. Among the modification methods used, ion exchange stands out. This review is devoted to the study of ion exchange processes in natural clinoptilolite with two goals: first, as its strategic property for use in processes in which cation exchange is fundamentally necessary; second, as a way to modify it to create composite materials with predetermined desired properties. Full article
(This article belongs to the Special Issue Structural Study on Ion Exchange Process of Clinoptilolite)
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