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Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Environmental Mineralogy and Biogeochemistry".

Deadline for manuscript submissions: closed (5 November 2023) | Viewed by 15526

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Special Issue Editors

Prof. Dr. Pierfranco Lattanzi

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Guest Editor

CNR-IGG, UOS Firenze, 50121 Firenze, Italy
Interests: ore deposits; hydrothermal fluids; environmental mineralogy and geochemistry
Special Issues, Collections and Topics in MDPI journals

Dr. Elisabetta Dore

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Guest Editor

Department of Chemical and Geological Sciences, Università degli Studi di Cagliari, 09124 Cagliari, Italy
Interests: environmental geochemistry and mineralogy; mine wastes; mine pollution; bio-geochemical barriers; remediation

Dr. Fabio Perlatti

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Guest Editor

1. National Mining Agency of Brazil (ANM), São Paulo 04040-033, Brazil
2. Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo (USP), Piracicaba 13418-900, Brazil
Interests: technosols; agromining; phytomining; recovery of mining areas; soil biogeochemistry; soil-rhizosphere-plants system; ecological restoration

Dr. Hendrik Gideon Brink

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Guest Editor

Department of Chemical Engineering, University of Pretoria, Pretoria 0002, South Africa
Interests: biochemical engineering; fermentation technology; biotechnology; bioprocess engineering; environmental engineering; water utilization engineering; waste valorization

Special Issue Information

Dear Colleagues,

One of the key aspects of sustainable development is the so called “ecological transition”, i.e., a change of the founding paradigms of our society to make human activities compatible with the global ecosystem. This change is motivated by the need to cope with emerging global challenges such as the impacts of climate change and increasing social disparity. A fundamental component of the ecological transition involves the shift from fossil-fuel-dominated energy production to renewable and less environmentally detrimental energy sources, such as solar, wind, and geothermal energy. On the other hand, all these alternative sources of energy have significant demands for mineral resources; in some cases more extensive than fossil-fuel-derived energy. These needs include historically important commodities such as iron (e.g, for the steel necessary to build up wind turbines), as well as less conventional, emerging materials (e.g., lithium, cobalt, rare earths), most of which are geochemically scarce. One can therefore conclude that this ecological transition would result in increased mining, with its accompanying historical record of severe environmental impacts and associated social opposition. The environmental and societal challenges associated with the increased demand for mining and therefore lower environmental impacts requires two words—Sustainable Mining. In the broadest sense, Sustainable Mining is a truly interdisciplinary activity calling for a wide variety of expertise, including: geological knowledge and exploration skills to unravel conventional and unconventional resources; development of more effective and environmental friendly extraction, beneficiation and metallurgical techniques; deep understanding of the long-term environmental impacts of extraction, processing and waste management activities; waste recycling as secondary sources; advances in reclamation planning to minimize the permanent effects and return mining lands for re-naturalization; or other uses. In this Special Issue, we welcome papers dealing with any facet of this wide spectrum of topics, with the ultimate goal of offering an up to date snapshot of the state of the art and of upcoming challenges. Although we expect mostly contributions based on geosciences and engineering, we do not exclude a priori manuscripts involving biology, health, and social issues.

Prof. Dr. Pierfranco Lattanzi
Dr. Elisabetta Dore
Dr. Fabio Perlatti
Dr. Hendrik Gideon Brink
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

sustainable mining
ecological transition
environmental impact
reclamation
waste management and recycling

Published Papers (11 papers)

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Editorial

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3 pages, 148 KiB

Open AccessEditorial

Editorial for the Special Issue “Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives”

by Hendrik Gideon Brink, Elisabetta Dore, Fabio Perlatti and Pierfranco Lattanzi

Minerals 2024, 14(4), 389; https://doi.org/10.3390/min14040389 - 8 Apr 2024

Viewed by 570

Abstract

A crucial aspect in the pursuit of sustainable development is the necessary shift toward an “ecological transition”, a transformation in societal paradigms to align human activities with the global ecosystem [...] Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

Research

Jump to: Editorial

19 pages, 8086 KiB

Open AccessArticle

Efficient Aqueous Copper Removal by Burnt Tire-Derived Carbon-Based Nanostructures and Their Utilization as Catalysts

by Iviwe Cwaita Arunachellan, Madhumita Bhaumik, Hendrik Gideon Brink, Kriveshini Pillay and Arjun Maity

Minerals 2024, 14(3), 302; https://doi.org/10.3390/min14030302 - 13 Mar 2024

Viewed by 826

Abstract

This research focuses on valorising waste burnt tires (BTs) through a two-phase oxidation process, leading to the production of onion-like carbon-based nanostructures. The initial carbonization of BTs yielded activated carbon (AC), denoted as “BTSA”, followed by further oxidation using the modified Hummer’s method to produce onion-like carbon designated as “BTHM”. Brunauer–Emmett–Teller (BET) surface area measurements showed 5.49 m²/g, 19.88 m²/g, and 71.08 m²/g for raw BT, BTSA, and BTHM, respectively. Additional surface functionalization oxidations were observed through Fourier-Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) analyses. Raman spectroscopy indicated an increased graphitic nature during each oxidation stage. BTHM was assessed in batch adsorption studies for cupric wastewater remediation, revealing a two-phase pseudo-first-order behaviour dominated by mass transfer to BTHM. The maximum adsorption capacity for Cu²⁺ on BTHM was determined as 136.1 mg/g at 25 °C. Langmuir adsorption isotherm best described BTHM at a solution pH of 6, while kinetics studies suggested pseudo-second-order kinetics. Furthermore, BTHM, laden with Cu²⁺, served as a catalyst in a model coupling reaction of para-idoanisole and phenol, successfully yielding the desired product. This study highlights the promising potential of BTHM for both environmental remediation and catalytic reuse applications to avoid the generation of secondary environmental waste by the spent adsorbent. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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14 pages, 2318 KiB

Open AccessArticle

The Raw Material Challenge of Creating a Green Economy

by Richard Jeremy Herrington

Minerals 2024, 14(2), 204; https://doi.org/10.3390/min14020204 - 17 Feb 2024

Viewed by 1300

Abstract

Clean technologies and infrastructure for our low-carbon, green future carry intense mineral demands. The ambition remains to recycle and reuse as much as we can; however, newly mined resources will be required in the near term despite the massive improvements in the reuse and recycling of existing end-of-use products and wastes. Growth trends suggest that mining will still play a role after 2050 since the demand for metals will increase as the developing world moves toward a per capita usage of materials comparable to that of the developed world. There are sufficient geological resources to deliver the required mineral commodities, but the need to mine must be balanced with the requirement to tackle environmental and social governance issues and to deliver sustainable development goals, ensuring that outcomes are beneficial for both the people and planet. Currently, the lead time to develop new mines following discovery is around 16 years, and this needs to be reduced. New approaches to designing and evaluating mining projects embracing social, biodiversity, and life cycle analysis aspects are pivotal. New frontiers for supply should include neglected mined wastes with recoverable components and unconventional new deposits. New processing technologies that involve less invasive, lower energy and cleaner methodologies need to be explored, and developing such methodologies will benefit from using nature-based solutions like bioprocessing for both mineral recovery and for developing sustainable landscapes post mining. Part of the new ambition would be to seek opportunities for more regulated mining areas in our own backyard, thinking particularly of old mineral districts of Europe, rather than relying on sources with potentially and less controllable, fragile, and problematic supply chains. The current debate about the potential of mining our deep ocean, as an alternative to terrestrial sources needs to be resolved and based on a broader analysis; we can then make balanced societal choices about the metal and mineral supply from the different sources that will be able to deliver the green economy while providing a net-positive deal for the planet and its people. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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18 pages, 8644 KiB

Open AccessArticle

Increase in Recovery Efficiency of Iron-Containing Components from Ash and Slag Material (Coal Combustion Waste) by Magnetic Separation

by Tatiana Aleksandrova, Nadezhda Nikolaeva, Anastasia Afanasova, Duan Chenlong, Artyem Romashev, Valeriya Aburova and Evgeniya Prokhorova

Minerals 2024, 14(2), 136; https://doi.org/10.3390/min14020136 - 26 Jan 2024

Viewed by 821

Abstract

This article presents the results of research aimed at optimizing the process of recovery of valuable components from ash and slag waste from thermal power plants. In this work, both experimental and theoretical studies were carried out to substantiate the use of magnetic separation methods for ash and slag waste processing. Ash and slag wastes were chosen as an object of research due to the presence of valuable components such as iron, aluminum, etc., in them. The research results showed that the method of magnetic separation, including high-gradient magnetic separation, can be effectively used in ash and slag waste processing. As a result, the topology of a magnetic beneficiation technological scheme has been proposed to obtain high-value-added products such as high-magnetic iron minerals, low-magnetic iron minerals, and aluminosilicate microspheres. By using magnetic separation in a weak magnetic field, magnetic microspheres containing high-magnetic iron minerals associated with intermetallics, ranging in size from 20 to 80 µm, were recovered. In the second stage of magnetic separation (high-gradient magnetic separation), an iron ore product with an iron content of 50% with a recovery of 92.07% could be obtained. By using scanning electron microscopy, it was found that the main part of microspheres, which contain low-magnetic iron minerals and aluminosilicates, with sizes from 2 to 15 microns, was recovered in the magnetic fraction. This paper proposes a new approach to the enrichment of ash and slag materials using magnetic separation, which will increase the efficiency of their processing and make the process environmentally sustainable. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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22 pages, 17066 KiB

Open AccessArticle

Unlocking Strategic and Critical Raw Materials: Assessment of Zinc and REEs Enrichment in Tailings and Zn-Carbonate in a Historical Mining Area (Montevecchio, SW Sardinia)

by Lorenzo Sedda, Giovanni De Giudici, Dario Fancello, Francesca Podda and Stefano Naitza

Minerals 2024, 14(1), 3; https://doi.org/10.3390/min14010003 - 19 Dec 2023

Viewed by 1093

Abstract

Mining wastes are often both a potential source of Strategic and Critical Raw Materials (SRMs and CRMs) and a threat to the environment. This study investigated the potential of mining wastes from the Montevecchio district of Sardinia, Italy, as a source of SRMs and CRMs. The tailings from Sanna mine processing plant were characterized by X-ray diffraction, Scanning Electron Microscopy, and Plasma Mass Spectometry, showing contents of 1.2 wt% of lead, 2.6 wt% of zinc, and about 600 mg/kg of Rare Earth Elements (REEs). White patinas formed in the riverbed, composed by Zn-bearing minerals (hydrozincite and zincite), also contain about 2900 mg/kg of REEs. Characterization of white patinas along the Rio Roia Cani evidenced that their precipitation from water also involves an uptake of Rare Earth Elements, enhancing their contents by an order of magnitude compared with tailings. The process of REEs concentration in Zn-bearing minerals of white patinas is a candidate as a tool for the economic recovery of these elements. These findings suggest that mining wastes from the Montevecchio district could be considered a potential resource for extracting SRMs and CRMs. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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18 pages, 2569 KiB

Open AccessFeature PaperArticle

Industrial Ceramics: From Waste to New Resources for Eco-Sustainable Building Materials

by Maura Fugazzotto, Paolo Mazzoleni, Isabella Lancellotti, Rachel Camerini, Pamela Ferrari, Maria Rosaria Tiné, Irene Centauro, Teresa Salvatici and Germana Barone

Minerals 2023, 13(6), 815; https://doi.org/10.3390/min13060815 - 15 Jun 2023

Cited by 2 | Viewed by 1502

Abstract

Today, the need to dispose of a huge amount of ceramic industrial waste represents an important problem for production plants. Contextually, it is increasingly difficult to retrieve new mineral resources for the realization of building materials. Reusing ceramic industrial waste as precursors for building blocks/binders, exploiting their aluminosilicate composition for an alkaline activation process, could solve the problem. This chemical process facilitates the consolidation of new binders/blocks without thermal treatments and with less CO₂ emissions if compared with traditional cements/ceramics. The alkali-activated materials (AAMs) are today thought as the materials of the future, eco-sustainable and technically advanced. In this study, six different kind of industrial ceramic waste are compared in their chemical and mineralogical composition, together with their thermal behaviour, reactivity in an alkaline environment and surface area characteristics, with the aim of converting them from waste into new resources. Preliminary tests of AAM synthesis by using 80%–100% of ceramic waste as a precursor show promising results. Workability, porosity and mechanical strengths in particular are measured, showing as, notwithstanding the presence of carbonate components, consolidated materials are obtained, with similar results. The main factors which affect the characteristics of the synthetized AAMs are the precursors’ granulometry, curing temperature and the proportions of the activating solutions. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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18 pages, 3901 KiB

Open AccessArticle

Fluvial Morphology as a Driver of Lead and Zinc Geochemical Dispersion at a Catchment Scale

by Patrizia Onnis, Patrick Byrne, Karen A. Hudson-Edwards, Tim Stott and Chris O. Hunt

Minerals 2023, 13(6), 790; https://doi.org/10.3390/min13060790 - 9 Jun 2023

Cited by 1 | Viewed by 1208

Abstract

Metal-mining exploitation has caused ecosystem degradation worldwide. Legacy wastes are often concentrated around former mines where monitoring and research works are mostly focused. Geochemical and physical weathering can affect metal-enriched sediment locations and their capacity to release metals at a catchment scale. This study investigated how fluvial geomorphology and soil geochemistry drive zinc and lead dispersion along the Nant Cwmnewyddion (Wales, UK). Sediments from different locations were sampled for geochemical and mineralogical investigations (portable X-ray fluorescence, scanning electron microscope, X-ray diffraction, and electron microprobe analysis). The suspended sediment fluxes in the streamwater were estimated at different streamflows to quantify the metal dispersion. Topographical and slope analysis allowed us to link sediment erosion with the exposure of primary sulphide minerals in the headwater. Zinc and lead entered the streamwater as aqueous phases or as suspended sediments. Secondary sources were localised in depositional stream areas due to topographical obstruction and a decrease in stream gradient. Sediment zinc and lead concentrations were lower in depositional areas and associated with Fe-oxide or phyllosilicates. Streamwater zinc and lead fluxes highlighted their mobility under high-flow conditions. This multi-disciplinary approach stressed the impact of the headwater mining work on the downstream catchment and provided a low-cost strategy to target sediment sampling via geomorphological observations. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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12 pages, 1648 KiB

Open AccessFeature PaperArticle

Tree Rings Record of Long-Term Atmospheric Hg Pollution in the Monte Amiata Mining District (Central Italy): Lessons from the Past for a Better Future

by Silvia Fornasaro, Francesco Ciani, Alessia Nannoni, Guia Morelli, Valentina Rimondi, Pierfranco Lattanzi, Claudia Cocozza, Marco Fioravanti and Pilario Costagliola

Minerals 2023, 13(5), 688; https://doi.org/10.3390/min13050688 - 18 May 2023

Cited by 3 | Viewed by 1617

Abstract

Trees may represent useful long-term monitors of historical trends of atmospheric pollution due to the trace elements stored along the tree rings caused by modifications in the environment during a tree’s life. Chestnut (Castanea sativa Mill.) tree trunk sections were used to document the yearly evolution of atmospheric Hg in the world-class mining district of Monte Amiata (MAMD; Central Italy) and were exploited until 1982. An additional source of Hg emissions in the area have been the active geothermal power plants. A marked decrease (from >200 µg/kg to <100 µg/kg) in Hg contents in heartwood tree rings is recorded, likely because of mine closure; the average contents (tens of µg/kg) in recent years remain higher than in a reference area ~150 km away from the district (average 4.6 µg/kg). Chestnut barks, recording present-day Hg pollution, systematically show higher Hg concentrations than sapwood (up to 394 µg/kg in the mining area). This study shows that tree rings may be a good record of the atmospheric Hg changes in areas affected by mining activity and geothermal plants and can be used as a low-cost biomonitoring method for impact minimization and optimal resource and land management. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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23 pages, 5853 KiB

Open AccessArticle

Ferric Hydroxide Recovery from Iron-Rich Acid Mine Water with Calcium Carbonate and a Gypsum Scale Inhibitor

by Tumelo Monty Mogashane, Johannes Philippus Maree, Munyaradzi Mujuru, Mamasegare Mabel Mphahlele-Makgwane and Kwena Desmond Modibane

Minerals 2023, 13(2), 167; https://doi.org/10.3390/min13020167 - 24 Jan 2023

Cited by 2 | Viewed by 1671

Abstract

The focus of this study was to improve the Reverse Osmosis Cooling (ROC) process by using CaCO₃ for neutralization and selective recovery of Fe(OH)₃ at pH 3.5. By using a specific inhibitor, ferric hydroxide was recovered separately from gypsum and other metals present in mine water. Ferric hydroxide was processed to pigment, a product that is imported and used as colorant in paints and tiles. In addition to pigment recovery, aluminum hydroxide and calcium carbonate can also be recovered from mine water. The following conclusions were made: (i) the rate of gypsum crystallization, in the absence of Fe³⁺, is influenced by the over saturation concentration in solution, the seed crystal concentration and temperature; (ii) gypsum crystallization from an over-saturated solution, in the presence of Fe(OH)₃ sludge, required an inhibitor dosage of 100 mg/L to keep gypsum in solution for a period of 30 min; (iii) gypsum crystallization from an over-saturated solution, in the presence of both Fe(OH)₃ sludge and CaCO₃ reactant, required a higher inhibitor dosage than 100 mg/L to keep gypsum in solution for a period of 30 min. A dosage of 200 mg/L kept gypsum in solution for the total reaction period; (iv) when only Fe(OH)₃ is present in the slurry, gypsum inhibition is more effective when Fe(OH)₃ sludge is allowed to settle after the initial mixing; (v) when both Fe(OH)₃ and CaCO₃ are present in the slurry, gypsum inhibition is more effective when the inhibitor is added over a period of time (10 min) rather than applying the total dosage at time zero; (vi) Fe(OH)₃ can be changed to yellow pigment (Goethite) by heating to 150 °C and to red pigment (Hematite) by heating to 800 °C. Pigment of nano particle size was produced; (vii) in the case of Na₂CO₃, the TDS increased from 12,660 mg/L in the feed to 13,684 mg/L due to the replacement of metal ions (Fe³⁺, Al³⁺, Fe²⁺, Mn²⁺ and Ca²⁺) with Na⁺ in solution. In the case where CaCO₃ was used for the removal of Fe³⁺ and Al³⁺, Ca(OH)₂ for the removal of Fe²⁺, Mn²⁺, and Na₂CO₃ for the removal of Ca²⁺, the TDS dropped from 12,661 mg/L to 2288 mg/L, due to gypsum precipitation. The alkali cost in the case of calcium alkalis amounted to ZAR29.43/m³ versus ZAR48.46/m³ in the case of Na₂CO₃. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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18 pages, 5903 KiB

Open AccessFeature PaperArticle

The Formation of Magnesite Ores by Reactivation of Dunite Channels as a Key to Their Spatial Association to Chromite Ores in Ophiolites: An Example from Northern Evia, Greece

by Giovanni Grieco, Alessandro Cavallo, Pietro Marescotti, Laura Crispini, Evangelos Tzamos and Micol Bussolesi

Minerals 2023, 13(2), 159; https://doi.org/10.3390/min13020159 - 21 Jan 2023

Viewed by 2012

Abstract

Ophiolite magnesite deposits are among the main sources of magnesite, a raw material critical for the EU. The present work focuses on magnesite occurrences at Kymasi (Evia Island, Greece), in close spatial association with chromitite within the same peridotite massif, and on the relationship between ultramafic rocks and late magnesite veins. Chromitite lenses are hosted within dunite, in contact with a partially serpentinized peridotite cut by magnesite veins. Close to the veins, the peridotite shows evidence of carbonation (forming dolomitized peridotite) and brecciation (forming a serpentinite–magnesite hydraulic breccia, in contact with the magnesite veins). Spinel mineral chemistry proved to be crucial for understanding the relationships between different lithologies. Spinels within partially serpentinized peridotite (Cr# 0.55–0.62) are similar to spinels within dolomitized peridotite (Cr# 0.58–0.66). Spinels within serpentinite–magnesite hydraulic breccia (Cr# 0.83–0.86) are comparable to spinels within dunite and chromitite (Cr# 0.79–0.84). This suggests that older weak zones, such as dunite channels, were reactivated as fluid pathways for the precipitation of magnesite. Magnesite stable isotope composition, moreover, points towards a meteoric origin of the oxygen, and to an organic source of carbon. The acquired data suggest the following evolution of Kymasi ultramafic rocks: (i) percolation of Cr-bearing melts in a supra-subduction mantle wedge within dunite channels; (ii) obduction of the ophiolitic sequence and peridotite serpentinization; (iii) uplift and erosion of mantle rocks to a shallow crustal level; (iv) percolation of carbon-rich meteoric waters rich at shallow depth, reactivating the dunite channels as preferential weak zones; and (v) precipitation of magnesite in veins and partial brecciation and carbonation of the peridotite host rock. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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21 pages, 9376 KiB

Open AccessArticle

Rapid Removal of Cr(VI) from Aqueous Solution Using Polycationic/Di-Metallic Adsorbent Synthesized Using Fe³⁺/Al³⁺ Recovered from Real Acid Mine Drainage

by Khathutshelo Lilith Muedi, Vhahangwele Masindi, Johannes Philippus Maree and Hendrik Gideon Brink

Minerals 2022, 12(10), 1318; https://doi.org/10.3390/min12101318 - 19 Oct 2022

Cited by 4 | Viewed by 1592

Abstract

The mining of valuable minerals from wastewater streams is attractive as it promotes a circular economy, wastewater beneficiation, and valorisation. To this end, the current study evaluated the rapid removal of aqueous Cr(VI) by polycationic/di-metallic Fe/Al (PDFe/Al) adsorbent recovered from real acid mine drainage (AMD). Optimal conditions for Cr(VI) removal were 50 mg/L initial Cr(VI), 3 g PDFe/Al, initial pH = 3, 180 min equilibration time and temperature = 45 °C. Optimal conditions resulted in ≥95% removal of Cr(VI), and a maximum adsorption capacity of Q = 6.90 mg/g. Adsorption kinetics followed a two-phase pseudo-first-order behaviour, i.e., a fast initial Cr(VI) removal (likely due to fast initial adsorption) followed by a slower secondary Cr(VI) removal (likely from Cr(VI) to Cr(III) reduction on the surface). More than 90% of adsorbed Cr(VI) could be recovered after five adsorption–desorption cycles. A reaction mechanism involving a rapid adsorption onto at least two distinct surfaces followed by slower in situ Cr(VI) reduction, as well as adsorption-induced internal surface strains and consequent internal surface area magnification, was proposed. This study demonstrated a rapid, effective, and economical application of PDFe/Al recovered from bona fide AMD to treat Cr(VI)-contaminated wastewater. Full article

(This article belongs to the Special Issue Sustainable Mining as the Key for the Ecological Transition: Current Trends and Future Perspectives)

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