Topical Collection "Clays and Other Industrial Mineral Materials"

A topical collection in Minerals (ISSN 2075-163X). This collection belongs to the section "Clays and Engineered Mineral Materials".

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Editors

Department of Geology and Geochemistry, Universidad Autónoma of Madrid, 28049 Madrid, Spain
Interests: geology and geochemistry of clays; special clays applications; sepiolite–palygorskite; bentonite; Talc–kerolite; clays and health; mineral characterization
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Department of Inorganic Chemistry, Universidad de Malaga, 29071 Malaga, Spain
Interests: kaolin; smectite group of minerals; sepiolite; palygorskite; pelotherapy; advanced, clay-based materials; pharmaceutical uses of adsorption processes; new technologies
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Department of Geology & Geoenvironment, National and Kapodistrian University of Athens (NKUA), 157 84 Athens, Greece
Interests: raw materials characterization; industrial minerals in environmental applications; economic geology; green geochemistry; mineralogy; cementitious and construction materials; industrial clays; fillers–filters–absorbents; microporous raw materials; marine aggregates; raw materials policy; mine waste reuse; environmental impacts; ecosystems; geoarchaeology; natural heritage
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Topical Collection Information

Dear Colleagues,

Industrial minerals form an exceptionally varied group of raw materials that cover virtually all needs of modern human life, although their presence is often invisible. Industrial minerals can be defined as those minerals that, due to their physical and/or chemical properties, are used in industrial processes. From a compositional point of view, industrial mineral materials include both silicates (e.g., zeolites and clays) and nonsilicates (e.g., chromite and barite). No doubt, it can be said that clay minerals and clays, whether in their natural state or modified, are outstanding materials in the field of industrial mineral materials. They are abundant, relatively cheap to obtain, and mostly friendly from an industrial and health viewpoint.

Clay is a textural term referring to natural rock, sediment, and/or alteration products mainly made up of very fine-grained clay mineral phyllosilicates. Clay minerals, whether natural or synthetic, show economically interesting physical and chemical properties directly related to their structure and composition. Both the layer charge and small particle size of the clay minerals give place to suitable properties such as plasticity, sorption, rheology, and ion exchange, among others.

Taking into account their origin, clay minerals can be detrital and authigenic. Detrital clay minerals are inherited and thus reflect the sediment source (provenance). Authigenic clay minerals are, in a broad sense, “formed or generated in place”, whether related to soil processes, sedimentary deposition or diagenesis; in addition, authigenic clays are also formed under low-grade metamorphic conditions and/or the influence of hydrothermal events.

When they are classified as industrial minerals, a distinction is made between common clays, which usually consist of an association of several clay minerals, and special clays, which are typically formed of just one clay mineral and include kaolin, bentonite, sepiolite and palygorskite.

This collection aims to cover several broad objectives. It will be focused mainly on the study of industrial clays and clay minerals, but it also will deal with other industrial minerals. Approaches to these industrial mineral materials can be focused on: 1) geology, 2) mineralogy and geochemistry, 3) mineral genesis, 4) physical and physicochemical properties, 5) industrial and environmental applications, and 6) methods for their characterization.

We look forward to your submissions.

Prof. Dr. Manuel Pozo Rodríguez
Prof. Dr. Francisco Franco
Prof. Dr. Michael G. Stamatakis
Collection Editors

Manuscript Submission Information

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Keywords

  • Clays
  • Clay minerals
  • Industrial mineral materials
  • Geology
  • Mineralogy
  • Geochemistry
  • Genesis
  • Properties
  • Applications
  • Common clays
  • Special clays
  • Bentonite
  • Kaolin and related clays
  • Sepiolite
  • Palygorskite

Published Papers (7 papers)

2022

Jump to: 2021, 2020

Article
Development and Characterization of Na2CO3-Activated Mozambican Bentonite: Prediction of Optimal Activation Conditions Using Statistical Design Modeling
Minerals 2022, 12(9), 1116; https://doi.org/10.3390/min12091116 - 01 Sep 2022
Cited by 2 | Viewed by 873
Abstract
A calcium bentonite clay from Boane region (Mozambique) was subjected to an Na2CO3 activation process. The methylene blue test together with energy-dispersive X-ray spectroscopy (EDX) analysis indicated the successful ion exchange of Ca2+ by Na+ ions since the [...] Read more.
A calcium bentonite clay from Boane region (Mozambique) was subjected to an Na2CO3 activation process. The methylene blue test together with energy-dispersive X-ray spectroscopy (EDX) analysis indicated the successful ion exchange of Ca2+ by Na+ ions since the cation exchange capacity (CEC) increased from 67.5 to 74 meq/100 g and the Na/Ca ratio from 2.91 up to 15.8, as the concentration of Na2CO3, activation temperature, and activation time were varied from 2 to 6 wt.%, from 25 to 65 °C, and from 2 to 4 h, respectively. However, the increase in the CEC did not follow the same trend as the increase in the Na/Ca ratio, and for the case of Na2CO3 concentration, the increase in the CEC was limited. The X-ray diffraction (XRD) patterns also confirmed that Ca-rich bentonite was effectively modified into Na-bentonite since after the activation, the d(001) decreased from 1.52 nm to 1.30 nm. The statistical design of the experiments showed that as well as the time and the temperature × time linear interactive effect, all the other independent factors and their interactive effects had a significant influence on the CEC. The response surface methodology (RSM) indicated that higher values of the CEC can be obtained under the optimal activation conditions of 4 wt.% Na2CO3, at a temperature of 45 °C, and with an activation time of 3 h. A statistical model was used to predict the CEC, and the R2 value was 0.99529, which denotes a satisfactory result in predicting the CEC. Full article
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Article
Desorption of REEs from Halloysite and Illite: A Link to the Exploitation of Ion-Adsorption RE Ore Based on Clay Species
Minerals 2022, 12(8), 1003; https://doi.org/10.3390/min12081003 - 08 Aug 2022
Cited by 2 | Viewed by 1073
Abstract
The adsorption/desorption characteristics for light and heavy rare earth elements (REEs) on halloysite and illite (which are beneficial for the utilization of ion-adsorption RE ore) were systematically investigated and compared. Additionally, halloysite and illite were fully charactered by XRD, SEM, microscope, zeta potential, [...] Read more.
The adsorption/desorption characteristics for light and heavy rare earth elements (REEs) on halloysite and illite (which are beneficial for the utilization of ion-adsorption RE ore) were systematically investigated and compared. Additionally, halloysite and illite were fully charactered by XRD, SEM, microscope, zeta potential, nitrogen adsorption–desorption isotherms and buffer pH to build the relationship between adsorption/desorption mechanisms and the minerals’ properties. The results of experiments show that the adsorption rate of halloysite is higher than illite, although they are both very fast and follow the pseudo-second-order kinetic model. The adsorption capacity of halloysite and illite increases with an increase in adsorption pH and remains constant when pH is higher than 4. Due to the narrow interlamellar spacing of halloysite and the fact that it is a nanotube, RE ions are adsorbed only through electrostatic attraction, whereas the adsorption and desorption pH have a significant effect on the recovery of RE ions from illite, because of the diverse adsorption mechanism. The results illustrated that the structure and surface properties of clays are also the key factors that affect RE ions leaching. Full article
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Article
Sepiolite and Other Authigenic Mg-Clay Minerals Formation in Different Palustrine Environments (Madrid Basin, Spain)
Minerals 2022, 12(8), 987; https://doi.org/10.3390/min12080987 - 03 Aug 2022
Viewed by 976
Abstract
Lithofacies belonging to mud-flat and palustrine deposits (lake margin) in the Miocene of the Madrid Basin (Spain) have been studied. Four lithofacies corresponding to mud flat (1 and 3) and palustrine (2 and 4) deposits have been differentiated. Units 1 and 3 consist [...] Read more.
Lithofacies belonging to mud-flat and palustrine deposits (lake margin) in the Miocene of the Madrid Basin (Spain) have been studied. Four lithofacies corresponding to mud flat (1 and 3) and palustrine (2 and 4) deposits have been differentiated. Units 1 and 3 consist mainly of mudstones and carbonates (calcretes and diolocretes). The clay fraction is dominated by trioctahedral smectite (up to 79%) with illite and kaolinite as minor components. The d(060) spacing value shows reflections at 1.52 and 1.50 Å indicating also the presence of dioctahedral phyllosilicates. Unit 2 consists predominantly of lutites (claystones), locally with carbonate and chert nodules. The clay fraction is dominated by sepiolite (up to 96%) with variable contents of smectite and subordinate illite. The d(060) spacing value shows reflections at 1.51 and 1.52 Å indicating trioctahedral clay minerals. Unit 4 consists mostly of carbonates (limestones) with mudstone and lutite inserts. The clay fraction shows different contents of sepiolite, palygorskite and dioctahedral smectite. The analysis of a selection of trace elements (Cr, Co, Th, La, Sc) has allowed us to determine the characteristics of the source area as dioritic, somewhat different from those of the nearby materials from the Batallones sector. Sepiolite shows FWHM values ranging between 0.68 and 1.10 (2θ), indicating “low crystallinity sepiolite”. Differences in the conditions of formation of magnesian smectite and palygorskite have been observed in the mud-flat and palustrine deposits. The formation of sepiolite mainly by neoformation in palustrine deposits with different hydrochemistry is remarkable, leading to differences in fibre size and crystallinity of the fibrous clay mineral. Authigenic transformation processes from previous Al-rich phases would be responsible for the formation of saponite and palygorskite in mud flat and palustrine environments, with different pH conditions. Full article
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Article
Coal Sludge Permeability Assessment Based on Rowe Cell Consolidation, and Filtration Investigations
Minerals 2022, 12(2), 212; https://doi.org/10.3390/min12020212 - 07 Feb 2022
Cited by 1 | Viewed by 1062
Abstract
In this paper, an attempt has been made to investigate the possibility of using coal sludge to seal a landfill site by presenting the results of their compressibility and permeability tests. Coal sludge is a fine-grained waste from the coal enrichment process, and [...] Read more.
In this paper, an attempt has been made to investigate the possibility of using coal sludge to seal a landfill site by presenting the results of their compressibility and permeability tests. Coal sludge is a fine-grained waste from the coal enrichment process, and its permeability is also highly dependent on its degree of consolidation. The tests were carried out in a Rowe Cell, making it possible to determine the water permeability coefficient more precisely by determining the degree of the material consolidation during testing. The test was carried out using backpressure conditions. The test procedure in the Rowe Cell consisted of the following three steps: saturation, consolidation, and filtration. The coal sludge was taken directly from the filter presses as a by-product of the fines’ coal enrichment process. The paper presents the results of the individual stages performed in a Rowe Cell. The consolidation coefficient was determined using three different methods (Casagrande, Taylor, and Robbinson methods). The permeability coefficient was measured by the indirect and the direct method, the results of both were compared. The results (k < 10−9 m/s) indicated that the value of the permeability coefficient responds to the value for isolating barrier materials. Full article
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2021

Jump to: 2022, 2020

Article
A Novel Calcium Oxalate/Sepiolite Composite for Highly Selective Adsorption of Pb(II) from Aqueous Solutions
Minerals 2021, 11(6), 552; https://doi.org/10.3390/min11060552 - 23 May 2021
Cited by 4 | Viewed by 1866
Abstract
Synthesizing functional nanomaterials from naturally abundant clay has always been of vital importance for resource utilization, however, the lack of new methods to effectively utilize low-grade clay presents a significant challenge. Herein, a calcium oxalate/sepiolite nanocomposite (SMN-x) was prepared by using the water [...] Read more.
Synthesizing functional nanomaterials from naturally abundant clay has always been of vital importance for resource utilization, however, the lack of new methods to effectively utilize low-grade clay presents a significant challenge. Herein, a calcium oxalate/sepiolite nanocomposite (SMN-x) was prepared by using the water bath heating method to convert the associated calcium carbonate in low-grade sepiolite into calcium oxalate. The developed composite was subsequently used to remove Pb(II) from the aqueous solutions. The SMN-3 adsorbent prepared by heating in a water bath at 90 °C for 3 h (with a high specific surface area of 234.14 m2·g−1) revealed the maximum Pb(II) adsorption capacity of 504.07 mg·g−1 at pH 5, which was about five times higher than that of sepiolite (105.57 mg·g−1). Further, the SMN-3 adsorbent possessed a much higher selectivity for Pb(II) as compared to the other metal ions. Moreover, the residue was noted to be stable and safe. The adsorption kinetics and isotherms conformed to the quasi-second-order kinetic and Langmuir models. During the adsorption process, ion exchange was noted to the main mechanism, however, it was also accompanied by electrostatic attraction. This study provides a novel strategy for the sustainable development of simple and efficient adsorbents by utilizing low-grade clay minerals. Full article
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2020

Jump to: 2022, 2021

Article
Sustainable Reuse of Coal Mine Waste: Experimental and Economic Assessments for Embankments and Pavement Layer Applications in Morocco
Minerals 2020, 10(10), 851; https://doi.org/10.3390/min10100851 - 26 Sep 2020
Cited by 17 | Viewed by 3425
Abstract
This paper deals with the potential reuse of coal mine waste rocks (CMWR) as an alternative material for road construction to conserve the natural resources and sustainable management of mining waste. The investigation was conducted through the determination of the chemical, mineralogical, geotechnical [...] Read more.
This paper deals with the potential reuse of coal mine waste rocks (CMWR) as an alternative material for road construction to conserve the natural resources and sustainable management of mining waste. The investigation was conducted through the determination of the chemical, mineralogical, geotechnical properties, and acid mine drainage formulation of CMWR as well as economic feasibility. This waste was used either alone for embankments and mixed with stabilizing agents fly ash (FA) and hydraulic road binder (HRB) for pavement applications. The experimental results confirmed that weathered CMWR can be successfully used alone as a sustainable alternative material for the embankment. Furthermore, the use of stabilizing agents in the following ratio CMWR:FA:HRB = 80:20:5 allow the use of CMWR in road sub-base layers for high-traffic pavements. Also, the environmental investigations showed that CMWR does not present any potential contaminating risk on the surrounding environment and most of the pyrite particles were already oxidized. Therefore, the environmental impact of acid mine drainage produced by pyritic waste throughout its life cycle can be neglected. Finally, an economic case study confirmed the workability of CMWR reuse in a radius of 29 km around their dumps by resulting in a lower cost compared with conventional materials. Full article
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Article
Application of Evolved Gas Analysis Technique for Speciation of Minor Minerals in Clays
Minerals 2020, 10(9), 824; https://doi.org/10.3390/min10090824 - 18 Sep 2020
Cited by 6 | Viewed by 3240
Abstract
Mineralogical characterization of clays used in manufacturing of traditional ceramic products is critical for guarantee the quality of the final product, but also for assessing the environmental impact of the industrial process in terms of atmospheric emissions. In fact, the presence of impurities [...] Read more.
Mineralogical characterization of clays used in manufacturing of traditional ceramic products is critical for guarantee the quality of the final product, but also for assessing the environmental impact of the industrial process in terms of atmospheric emissions. In fact, the presence of impurities even in low-level concentrations can have a big impact. So, it is very important to carry out an accurate mineral quantification of those minerals which are related to carbon dioxide and acid emissions (hydrogen fluoride, hydrogen chloride or sulfur dioxide). The development of hyphenated techniques coupling thermal analysis equipment with mass spectrometry and Fourier-transform infrared spectroscopy provides more valuable information and lower limit quantification than other primary techniques, such as X-ray diffraction or infrared spectroscopy. The main objective of this work is to develop an analytical procedure using evolved gas analysis to identify and quantify minerals such as chlorides, sulfides, carbonaceous materials and minor clay minerals. In addition to this, the study includes the analysis of acid emissions during the ceramic firing treatment even if they are present at low quantitative levels. This methodology was applied to reference materials so that it allows the identification of sulfur, chlorine, fluorine and carbonaceous compounds in concentrations lower than 1%. Full article
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