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Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal...
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Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery

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

Deadline for manuscript submissions: 30 April 2026 | Viewed by 14519

Special Issue Editors

Prof. Dr. Sehliselo Ndlovu

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Guest Editor
Department of Mining and Geological Engineering, University of Arizona, Tucson, AZ, USA
Interests: hydrometallurgy; bioleaching; recycling; mineral processing; extractive metallurgy
Special Issues, Collections and Topics in MDPI journals
Dr. Mostafa Khodakarami

E-Mail Website
Guest Editor
Department of Chemical and Materials Engineering, University of Nevada, Reno, NV, USA
Interests: functional materials; colloids and interfaces; extractive metallurgy; wastewater treatment and resource recovery
Special Issues, Collections and Topics in MDPI journals
Dr. Thandazile Moyo

E-Mail Website
Guest Editor
Department of Energy and Mineral Engineering, John and Willie Leone Family Department of Energy and Mineral Engineering, Pennsylvania State University, University Park, PA, USA
Interests: circular economy in mineral extraction; sustainable development of mineral resources/responsible extraction; hydrometallurgy; electronic waste and battery recycling (urban mining); process mineralogy

Special Issue Information

Dear Colleagues,

We are pleased to invite authors to submit their manuscripts to a Special Issue on the latest advancements in the extraction of metals from a wide range of sources using hydrometallurgical techniques. We seek papers that address both traditional methods and innovative approaches to metal recovery, with an emphasis on sustainability, resilience, and efficiency. As the demand for critical metals continues to grow in response to the green energy transition and the circular economy, hydrometallurgy plays an increasingly vital role in meeting these challenges. We are particularly interested in papers that relate to the following:

  • The integration of traditional hydrometallurgical practices with emerging technologies to improve extraction efficiency and reduce environmental impact.
  • The exploration of sustainable solutions that enhance resource recovery from complex ores, secondary resources, and urban mining.
  • Addressing innovations in process optimization, energy efficiency, and a reduction in harmful emissions.
  • The investigation of the economic and environmental resilience of hydrometallurgical processes in a rapidly evolving industry.
  • Highlighting the role of hydrometallurgy in supporting the global green energy transition and ensuring a sustainable supply of critical materials.

This Special Issue will provide a platform for sharing cutting-edge research and advancing the development of hydrometallurgical processes that support a more sustainable and resilient future for metal recovery. We encourage researchers, industry experts, and practitioners to contribute original research articles, reviews, and case studies that reflect the diverse, evolving nature of this essential field.

Prof. Dr. Sehliselo Ndlovu
Dr. Mostafa Khodakarami
Dr. Thandazile Moyo
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 250 words) can be sent to the Editorial Office for assessment.

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

  • hydrometallurgy
  • sustainable extraction
  • circular economy
  • urban mining
  • environmental impact
  • innovative techniques
  • traditional approaches
  • resource efficiency
  • resource recovery

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Further information on MDPI's Special Issue policies can be found here.

Published Papers (7 papers)

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Research

Jump to: Review

20 pages, 11894 KB  
Article
A Novel Biomass-Derived Reductant for Nitric Acid Dissolution of Manganiferous Iron Ore: Comparative Assessment of Organic Reductants
by Soner Top, Mahmut Altiner, Huseyin Vapur, Sait Kursunoglu and Srecko Stopic
Minerals 2026, 16(1), 47; https://doi.org/10.3390/min16010047 - 31 Dec 2025
Cited by 2 | Viewed by 735
Abstract
This study investigates the selective dissolution of manganese from a manganiferous iron ore using nitric acid (HNO3) in the presence of various organic reductants. A series of leaching experiments was performed to evaluate the effects of temperature, reductant type, and leaching [...] Read more.
This study investigates the selective dissolution of manganese from a manganiferous iron ore using nitric acid (HNO3) in the presence of various organic reductants. A series of leaching experiments was performed to evaluate the effects of temperature, reductant type, and leaching time on Mn recovery, with particular emphasis on biomass (horse dung) and tartaric acid as novel reducing agents. The dissolution behaviour of Fe, Mn, Mg, Ca, and Al was systematically examined, revealing that Mn extraction was strongly enhanced in the presence of reductants, while Fe dissolution remained below 10% under all conditions. The maximum Mn dissolution exceeded 90% at 90 °C using biomass and reached nearly 85%–90% with tartaric acid at elevated temperatures. Kinetic studies were conducted by applying reaction order models and the shrinking core model. The results indicated that Mn dissolution in HNO3 medium is predominantly controlled by surface chemical reaction, with Arrhenius analysis yielding activation energies of 27.74 kJ/mol for biomass and 21.26 kJ/mol for tartaric acid. These relatively low values confirm the efficiency of organic reductants in facilitating Mn reduction and dissolution. To sum up, comparison of reductant efficiency revealed that, at the lowest concentrations, the dissolution of Mn followed the sequence glucose > sucrose > oxalic acid > tartaric acid > maleic acid > biomass > citric acid > acetic acid. At the highest concentrations, the trend shifted, with citric acid emerging as the most effective, followed by tartaric acid > oxalic acid > glucose > sucrose > maleic acid > biomass > acetic acid. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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15 pages, 2767 KB  
Article
Microwave-Induced Fracturing for Enhanced Permeability in Hard Rocks: A Novel Approach for In Situ Recovery in Mining
by Sahar Kafashi, Lionel Esteban, Andrej Bona and Aleksandar N. Nikoloski
Minerals 2025, 15(11), 1210; https://doi.org/10.3390/min15111210 - 17 Nov 2025
Viewed by 865
Abstract
Microwave fracturing and assisted mechanical breakage offer efficient and cost-effective rock excavation potential. However, these methods have not been well studied or understood for the deployment of in situ recovery (ISR) in mining, which could benefit from microwave-induced cracking to accelerate in situ [...] Read more.
Microwave fracturing and assisted mechanical breakage offer efficient and cost-effective rock excavation potential. However, these methods have not been well studied or understood for the deployment of in situ recovery (ISR) in mining, which could benefit from microwave-induced cracking to accelerate in situ leaching. This paper reports on investigations into the effects of microwaves on rock transport properties, specifically for in situ recovery applications. The research focused on microwave fragmentation of a synthetic ore with composition and particle size similar to many wet ore-bearing deposits, as well as hard lithium-bearing rock (spodumene) as a natural analogue, to assess changes in porosity and permeability after microwave treatment. The experiments involved exposing samples with varying water content to heating with different microwave energy levels, followed by examining the impact on the induced crack characteristics. All the samples were characterized by a suite of measurements before and after microwave treatment, including scanning electron microscopy (SEM), Nuclear Magnetic Resonance (NMR), nitrogen gas permeameter-porosimeter, and P-wave velocity measurements. The results showed a strong dependence of rock properties after microwave treatment on water content. At high water content (100%), NMR results showed a substantial increase in porosity, by nearly 17% and a dramatic 47-fold rise in permeability, from 0.65 mD to 311 mD. However, the treatment also caused partial melting of the sample, rendering it unsuitable for further testing, including permeability and P-wave velocity. At moderate water content (20%), permeability substantially increased (233–3404%), which was consistent with the observation of multiple cracks in SEM images. These changes led to low P-wave velocity values. This research provides crucial insights into microwave fracturing as a method for in situ recovery in mining. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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15 pages, 1918 KB  
Article
A Preliminary Study on the Solvent Extraction of Molybdenum and Rhenium from an Industrial Pregnant Leach Solution Using Alamine336 as the Extractant and the Ionic Liquid 1-Octyl-3-Methylimidazolium Bis(trifluoromethylsufonyl)imide as the Diluent
by Muhammad Hayat, Cristian Allendes, Alejandro Araya, Rene Cabezas, Julio Urzúa-Ahumada and Esteban Quijada-Maldonado
Minerals 2025, 15(11), 1204; https://doi.org/10.3390/min15111204 - 15 Nov 2025
Viewed by 1242
Abstract
A study on the selective solvent extraction (SX) of molybdenum (Mo) and rhenium (Re) from two industrial pregnant leach solutions (PLSs) was carried out using Alamine 336 as the extractant and the ionic liquid (IL) 1-octyl-3-methyl Imidazolium bis (trifluoromethylsulfonyl) imide [Omim][Tf2N] [...] Read more.
A study on the selective solvent extraction (SX) of molybdenum (Mo) and rhenium (Re) from two industrial pregnant leach solutions (PLSs) was carried out using Alamine 336 as the extractant and the ionic liquid (IL) 1-octyl-3-methyl Imidazolium bis (trifluoromethylsulfonyl) imide [Omim][Tf2N] as the diluent. One industrial PLS was rich in Mo (VI) (PLS-Mo) and the second one rich in Re (VII) (PLS-Re). Experiments were carried out in open vials in which the concentration of Alamine336 in the diluent, the aqueous-to-organic ratio (A/O), and the stripping with ammonium carbonate (NH42CO3) were carried out systematically. Results indicate that decreasing the aqueous-to-organic (A/O) ratio led to an enhancement in the extraction performances of both Mo (VI) and Re (VII), reaching recoveries of 95%–98% at an A/O ratio of 1:1. However, differences between PLSs became evident at higher ratios, as Re extraction declined more sharply than Mo. Third-phase formation was observed only in the Mo-containing PLS. The PLS–Re system did not exhibit the formation of a third phase due to a lower concentration of metal (1 g/L Mo). The use of ammonium carbonate for stripping led to enhanced recoveries, achieving 84.4% for Re and 46.8% for Mo. A total of 50 extraction-stripping cycles were carried out in this work. These demonstrated nearly total initial extraction, but performance decreased over the cycles because of insufficient stripping and solvent loading. Overall, [Omim][Tf2N] proved to be an effective and environmentally friendly alternative to conventional diluents for Mo and Re separation and recovery from industrial leach solutions. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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22 pages, 5351 KB  
Article
Hydrometallurgical Leaching of Copper and Cobalt from a Copper–Cobalt Ore by Aqueous Choline Chloride-Based Deep Eutectic Solvent Solutions
by Emmanuel Anuoluwapo Oke, Yorkabel Fedai and Johannes Hermanus Potgieter
Minerals 2025, 15(8), 815; https://doi.org/10.3390/min15080815 - 31 Jul 2025
Cited by 8 | Viewed by 3470
Abstract
The sustainable recovery of valuable metals such as Cu and Co from ores is a pressing need considering environmental and economic challenges. Therefore, this study evaluates the effectiveness of deep eutectic solvents (DESs) as alternative leaching agents for Cu and Co extraction. Four [...] Read more.
The sustainable recovery of valuable metals such as Cu and Co from ores is a pressing need considering environmental and economic challenges. Therefore, this study evaluates the effectiveness of deep eutectic solvents (DESs) as alternative leaching agents for Cu and Co extraction. Four DESs were prepared using choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and oxalic acid (OA), ethylene glycol (EG), urea (U) and thiourea (TU) as hydrogen bond donors (HBDs). Leaching experiments were conducted with DESs supplemented with 30 wt.% water at varying temperatures, various solid-to-liquid ratios, and time durations. The ChCl:OA DES demonstrated the highest leaching efficiencies among the DESs tested on pure CuO and CoO, achieving 89.2% for Cu and 92.4% for Co (60 °C, 400 rpm, 6 h, −75 + 53 µm particle size, and 1:10 solid-to-liquid ratio). In addition, the dissolution kinetics, analysed using the shrinking core model (SCM), showed that the leaching process was mainly controlled by surface chemical reactions. The activation energy values for Cu and Co leaching were 46.8 kJ mol−1 and 51.4 kJ mol−1, respectively, supporting a surface chemical control mechanism. The results highlight the potential of ChCl:OA as a sustainable alternative for metal recovery. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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19 pages, 11629 KB  
Article
Efficient Removal of Impurities from Refractory Oolitic Magnetite Concentrate via High-Pressure Alkaline Leaching and Ultrasonic Acid Leaching Process
by Mengjie Hu, Deqing Zhu, Jian Pan, Zhengqi Guo, Congcong Yang, Siwei Li and Wen Cao
Minerals 2025, 15(3), 220; https://doi.org/10.3390/min15030220 - 24 Feb 2025
Cited by 10 | Viewed by 1916
Abstract
Acid leaching is an effective method for dephosphorization; however, it is time-consuming and requires a high amount of acid consumption, resulting in increased production costs and environmental risks. This work aims to remove silicon, aluminum, and phosphorus from high-phosphorus oolitic magnetite concentrate through [...] Read more.
Acid leaching is an effective method for dephosphorization; however, it is time-consuming and requires a high amount of acid consumption, resulting in increased production costs and environmental risks. This work aims to remove silicon, aluminum, and phosphorus from high-phosphorus oolitic magnetite concentrate through high-pressure alkaline leaching and ultrasonic acid leaching. Compared with traditional acid leaching processes, the sulfuric acid dosage can be significantly reduced from 200 kg/t to 100 kg/t, and the pickling time is shortened from 60 min to 10 min. Thermodynamic and kinetic studies have demonstrated that acid leaching facilitates apatite dissolution at low temperatures, whereas the dephosphorization reaction is controlled mainly by diffusion. The application of ultrasonic waves leads to finer particle sizes and greatly increased specific surface areas, thereby accelerating the diffusion rate of the leaching agent. Furthermore, microscopic analysis revealed that under the influence of ultrasonic waves, numerous micro-fragments and pores form on particle surfaces due to cavitation effects and mechanical forces generated by ultrasonic waves. These factors promote both the reaction rates and diffusion processes of the leaching agent while enhancing the overall leaching efficiency. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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Review

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37 pages, 4734 KB  
Review
Leaching of Rhenium from Secondary Resources: A Review of Advances, Challenges, and Process Optimisation
by Ignacio Castillo, Mauricio Mura, Edelmira Gálvez, Felipe M. Galleguillos-Madrid, Eleazar Salinas-Rodríguez, Jonathan Castillo, Williams Leiva, Alvaro Soliz, Sandra Gallegos and Norman Toro
Minerals 2026, 16(1), 51; https://doi.org/10.3390/min16010051 - 31 Dec 2025
Viewed by 867
Abstract
Rhenium is one of the rarest and most strategically important metals, indispensable in high-temperature superalloys and platinum–rhenium catalysts used across the aerospace and petrochemical industries. Owing to its limited primary reserves, recovering rhenium from secondary sources, such as spent catalysts, superalloy residues, and [...] Read more.
Rhenium is one of the rarest and most strategically important metals, indispensable in high-temperature superalloys and platinum–rhenium catalysts used across the aerospace and petrochemical industries. Owing to its limited primary reserves, recovering rhenium from secondary sources, such as spent catalysts, superalloy residues, and metallurgical dusts, has become vital to ensuring supply security. This review examines technological developments between 1998 and 2025, focusing on how operational parameters, including temperature, leaching time, reagent concentration, and solid-to-liquid ratio, govern dissolution kinetics and overall process efficiency. Comparative evaluation of hydrometallurgical, alkaline, and hybrid processes indicates that modern systems can achieve recovery rates exceeding 98% through selective oxidation, alkaline activation, or combined pyro and hydrometallurgical mechanisms. Acid–chlorine leaching facilitates rapid, low-temperature dissolution; alkaline sintering stabilises rhenium as soluble perrhenates; and hybrid smelting routes enable the concurrent separation of rhenium and osmium. Sustainable aqueous systems employing nitric and ammonium media have also demonstrated near-complete recovery at ambient temperature under closed-loop recycling conditions. Collectively, these findings highlight a technological transition from energy-intensive, acid-based pathways towards low-impact, recyclable, and digitally optimised hydrometallurgical processes. The integration of selective oxidants, phase engineering, circular reagent management, and artificial intelligence-assisted modelling is defining the next generation of rhenium recovery, combining high extraction yields with reduced environmental impact and alignment with global sustainability goals. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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15 pages, 2876 KB  
Review
Permanent Cathode Technologies in Copper Electrowinning: Development and Status
by Kalin Naidoo and Kathryn C. Sole
Minerals 2025, 15(9), 957; https://doi.org/10.3390/min15090957 - 8 Sep 2025
Cited by 1 | Viewed by 4152
Abstract
The replacement of copper metal starter-sheet cathodes with the use of permanent cathode technology, in which the target metal is plated onto an inert blank template, has enabled significant benefits in the copper electrowinning process. These include the application of significantly higher current [...] Read more.
The replacement of copper metal starter-sheet cathodes with the use of permanent cathode technology, in which the target metal is plated onto an inert blank template, has enabled significant benefits in the copper electrowinning process. These include the application of significantly higher current density, which reduces tankhouse footprint and increases process intensity per unit area; improved operator safety with less reliance on manual electrode handling; and the implementation of process automation and robotics. Cathodes of >99.99% chemical purity and with a smooth and aesthetic surface morphology are consistently produced. This review considers the evolution and development of the permanent cathode process, its commercial adoption across the global copper industry, and the current technology status. Full article
(This article belongs to the Special Issue Innovations in Hydrometallurgy: Traditional and Emerging Approaches for Sustainable Metal Recovery)
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