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Minerals
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Ashes: Characterisation, Recovery and Utilization
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Ashes: Characterisation, Recovery and Utilization

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: closed (31 March 2024) | Viewed by 5043

Special Issue Editors

Dr. Bruno Valentim

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Guest Editor
Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências, Universidade do Porto and Instituto de Ciências da Terra, 4169-007 Porto, Portugal
Interests: organic petrology; ashes; spent LIB; circularity
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Elza Bontempi

E-Mail Website
Guest Editor
INSTM and Chemistry for Technologies Laboratory, Department of Mechanical and Industrial Engineering, University of Brescia, Via Branze 38, 25123 Brescia, Italy
Interests: spent lithium-ion batteries; raw materials recovery
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The main advantage of ashes is their readiness for utilization or processing because of their powder state. Additionally, in the case of combustion ashes, the heat removes almost all the organic elements and concentrates the inorganic ones as relics, amorphous materials or newly formed minerals.

As such, combustion ashes are important in civil construction applications, but also have potential as secondary raw materials as the source of rare earth elements, germanium, gallium, aluminium and other metals (in the case of ashes from coal and municipal solid waste), or to partially substitute primary raw materials such as phosphate rocks in the case of aviary manure ash or natural graphite in the case of coal char.

This Special Issue of Minerals is focused on ashes characterization, on the progress of their applications, and on the recovery of elements and materials from them.

We look forward to receiving your contributions.

Dr. Bruno Valentim
Prof. Dr. Elza Bontempi
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

  • fly ash and bottom ash
  • char, biochar, ferrospheres, cenospheres
  • ash formation and composition
  • volcanic, coal, municipal solid waste, biomass, sewage sludge and aviary ash
  • critical elements and materials from ash
  • concrete, zeolites and polymers from ash

Published Papers (4 papers)

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Research

16 pages, 1334 KiB  
Article
Comparison of the Analytical Performance of Inductively Coupled Plasma Mass Spectrometry and Instrumental Neutron Activation Analysis Techniques in the Elemental Analysis of Coal Fly Ash
by Ewelina Chajduk and Paweł Kalbarczyk
Minerals 2023, 13(12), 1484; https://doi.org/10.3390/min13121484 - 24 Nov 2023
Viewed by 792
Abstract
Inductively coupled plasma mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA) were applied to study the elemental content of coal combustion residues. Both methods’ analytical applicability and suitability for this type of material were described in detail. A certified reference material, fine [...] Read more.
Inductively coupled plasma mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA) were applied to study the elemental content of coal combustion residues. Both methods’ analytical applicability and suitability for this type of material were described in detail. A certified reference material, fine fly ash (CTA-FFA-1), was used to examine the capabilities and validation of both methods. A comparison study allowed for the modification of the procedures for these materials (previously elaborated in the Institute of Nuclear Chemistry and Technology), resulting in more accurate data with lower uncertainty. We highlighted that INAA and ICPs complemented each other in the analysis of coal and coal combustion residues. The digestion procedure was an integral part of the measurement and affected the environmental analysis results. Both methods were applied to the chemical characteristics of coal ashes from household furnaces. The hard coal was from Polish, Columbian, and Kazakh mines. The majority of elements had similar concentrations, independently of coal origin. Because ash from domestic coal combustion is used as a fertilizer or an anti-icing agent, we assessed the potential environmental impact via leaching experiments (according to PN-EN 12457-2). The potential risk of soil contamination due to ash dumping around the house and its surroundings was determined as insignificant (for the elements investigated). Full article
(This article belongs to the Special Issue Ashes: Characterisation, Recovery and Utilization)
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28 pages, 5812 KiB  
Article
Physicochemical Properties of Fe-Bearing Phases from Commercial Colombian Coal Ash
by Ana Cláudia Santos, Cláudia Cruz, Eric Font, David French, Alexandra Guedes, Karen Moreira, Helena Sant’Ovaia, Bruno J. C. Vieira, João C. Waerenborgh and Bruno Valentim
Minerals 2023, 13(8), 1055; https://doi.org/10.3390/min13081055 - 09 Aug 2023
Cited by 3 | Viewed by 1133
Abstract
High amounts of coal combustion products, such as fly ash and bottom ash, are generated every year; however, only 64% are used, which means that a significant part is landfilled despite containing valuable materials such as ferrospheres, which may be used as catalysts, [...] Read more.
High amounts of coal combustion products, such as fly ash and bottom ash, are generated every year; however, only 64% are used, which means that a significant part is landfilled despite containing valuable materials such as ferrospheres, which may be used as catalysts, substituting critical raw materials (e.g., platinoids). In commercial coals, pyrite contents are reduced as a pre-combustion S-emissions control measure, so low amounts of ferrospheres are expected in the respective ashes. However, given the large amounts of ash being generated from these coals, it may provide a reliable source of catalysts, with ferrospheres being easily recovered via magnetic separation. Several studies have been conducted regarding these morphotypes; however, there is a lack of investigation considering the ash derived from highly beneficiated coals and the variations with location and time. In this study, bottom ash, economizer grits, and fly ash samples from a Portuguese power plant burning Colombian commercial coal were fractionated using ferrite (Fe-MC fraction) and Nd (Nd-MC fraction) magnets, and a multi-technique approach was used to assess their properties (magnetic parameters, particle size distribution, mineralogy, particle morphology, microtexture, and chemical composition). The Fe-MC presented higher Fe concentrations (up to 44 wt.% Fe2O4) than the Nd-MC (up to 7 wt.% Fe2O4). Once it was a sequential process, Nd magnets essentially collected Fe-bearing aluminosilicate glass, and Fe-bearing minerals were residual when compared to the Fe-MC, where magnetite, magnesioferrite, hematite, and maghemite accounted for up to 30 wt.%. Among the Fe-MC, the sample collected from electrostatic precipitator fly ash (ESP FA), despite having a lower yield, presented higher Fe concentrations than the ones from bottom ash and economizer grits, which was related to the mode of occurrence of Fe-bearing phases: in the Fe-MC from ESP FA, discrete ferrospheres predominated, while in the remaining Fe-bearing phases, they were often embedded in aluminosilicate glass. All Fe-MC samples showed an increase of Fe-substituting elements (e.g., Mn and Ni) and their concentration tended to increase with decreasing particle size along with Fe. The integrated study of cross-sections enabled the identification of oxidation rims, martitization aspects, and the co-existence of hematite and magnesioferrite. Full article
(This article belongs to the Special Issue Ashes: Characterisation, Recovery and Utilization)
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15 pages, 2145 KiB  
Article
Long-Term Leaching Behavior and Geochemical Modeling of Cement Solidified Incineration Fly Ash Containing Waste Tires and Wood Biomass
by Jose Rodolfo Santiago, Tomoo Sekito and Yutaka Dote
Minerals 2023, 13(6), 823; https://doi.org/10.3390/min13060823 - 16 Jun 2023
Cited by 2 | Viewed by 1049
Abstract
Waste incineration is a widely used treatment method, and sustainable approaches are required to properly recycle large volumes of incineration ash to reduce environmental impacts and landfill space consumption. Studies have focused on the potential of recycling incineration ash as a replacement for [...] Read more.
Waste incineration is a widely used treatment method, and sustainable approaches are required to properly recycle large volumes of incineration ash to reduce environmental impacts and landfill space consumption. Studies have focused on the potential of recycling incineration ash as a replacement for natural aggregates in civil engineering applications, such as road construction. However, industrial waste incineration ash, such as waste tire incineration ash, contains hazardous heavy metals, such as lead and zinc that pose potential environmental threats. Moreover, few studies have investigated the leachability of these hazardous metals after long-term natural aging. This study investigates the long-term evolution of leachate chemistry, mineralogical transformation, and heavy metal fixation performance of a recycled roadbed material using ash from industrial waste incineration of waste tires and biomass (SFA). Additionally, field samples from a five-year pilot test site utilizing SFA were also examined. Regulatory leaching tests showed that the concentrations of Cd, Pb, As, T-Cr, and Ni were all below permissible limits even after five years of utilization. Long-term column leaching experiment results indicated that, compared to the total content of the SFA material, the leaching ratios of Pb, T-Cr, Cu, and Zn were 27%, 12%, 5%, and 0.1%, respectively. The SFA pH-stat leaching test results demonstrated that the mass release of the total content of heavy metals was relatively minimal, even under acidic pH conditions (pH < 4). Finally, profiles of pH and major ions in leachate from the column leaching experiment were simulated using HYDRUS HP1, implementing a dual-porosity modeling approach. In conclusion, despite containing hazardous heavy metals, SFA exhibits significantly low leaching rates over a long-term period. Full article
(This article belongs to the Special Issue Ashes: Characterisation, Recovery and Utilization)
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24 pages, 4497 KiB  
Article
Investigations on Single Minerals and Synthetic Ash Components for the Enrichment of Copper from Waste Incineration Bottom Ashes by Flotation
by Sebastian Keber, Marius Müller, Tobias Elwert and Daniel Goldmann
Minerals 2023, 13(3), 358; https://doi.org/10.3390/min13030358 - 03 Mar 2023
Viewed by 1251
Abstract
Currently, MSWI (municipal solid waste incineration) ashes are predominantly landfilled, although they can have copper contents comparable to those of low-grade ores. Based on a previously published characterization of MSWI-BA, this paper presents investigations on the identification of potential collectors for copper recovery [...] Read more.
Currently, MSWI (municipal solid waste incineration) ashes are predominantly landfilled, although they can have copper contents comparable to those of low-grade ores. Based on a previously published characterization of MSWI-BA, this paper presents investigations on the identification of potential collectors for copper recovery from MSWI-BA by flotation. The studies were conducted with single minerals (mainly copper oxide and sulfide) and synthetic slag components. Collector screening included thiourea-, thiophosphate-, and thiocarbamate-based collectors. In addition to commercial collector mixtures, pure ureas were also examined. At least one representative from each collector group was selected for the more in-depth studies: the thiourea S-n-dodecyle-iso-thiourea hydrochloride, the thiophosphate Danaflot 245, AERO 3473, and AERO MX-5160 as a mixture of a thiocarbamate and thiophosphates. Studies of the influence of collector concentration and pH were carried out with these. In addition, the contact angles of various metal oxides and the matrix composition with and without collector treatment were determined. Subsequently, flotation tests were carried out with mixtures of copper oxide and the individual matrix components (quartz, glass, cement, gypsum). AERO MX-5160 proved to be the most suitable collector, although alginic acid was added as a depressant due to a lack of selectivity towards gypsum. Full article
(This article belongs to the Special Issue Ashes: Characterisation, Recovery and Utilization)
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