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Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery,...
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Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Extractive Metallurgy".

Deadline for manuscript submissions: 25 July 2026 | Viewed by 4005

Editor

Prof. Dr. Željko Kamberović

E-Mail Website
Guest Editor
Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade, Serbia
Interests: extractive metallurgy; hydrometallurgy; hydro-electrorefining; recycling technologies; metal recovery; resource efficiency; waste valorization; sustainable materials management; circular economy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The global demand for critical and strategic metals continues to rise, driven by technological innovation and the transition to a low-carbon economy. Hydrometallurgy provides a versatile, efficient, and environmentally sustainable pathway for metal extraction and recovery from both primary ores and secondary sources, including industrial residues, e-waste, and end-of-life products.

This Special Issue aims to present the latest scientific and technological advancements across all stages of hydrometallurgical processing. Topics of interest include novel approaches to feed characterization, pretreatment, innovative leaching techniques (e.g., bioleaching, mechanochemical activation, ionic liquids), selective extraction and separation processes, recovery methods, and advanced raffination strategies. Emphasis will be given to process intensification, circular economy practices, environmental performance, and industrial scalability.

Contributions from both academia and industry are welcome, including original research articles, reviews, and case studies that highlight breakthroughs in process development, modeling, and real-world applications. By fostering interdisciplinary dialogue and integrating fundamental research with technological practice, this Special Issue seeks to promote sustainable hydrometallurgical solutions for the metal industries of the future.

Prof. Dr. Željko Kamberović
Guest Editor

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-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals 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 2600 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
  • metal recovery
  • leaching processes
  • extraction and separation
  • raffination and purification
  • secondary raw materials
  • critical raw materials
  • green technologies
  • sustainable metallurgy
  • circular economy in hydrometallurgy

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Published Papers (6 papers)

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Research

Jump to: Review

29 pages, 2228 KB  
Article
Pseudo-Closed-Loop Metallurgy and Quality-Adjusted Circularity of Secondary Copper: A Conceptual Framework
by Vesna Alivojvodić, Natalija Dolić, Jelena Zarić Kovačević and Nela Vujović
Metals 2026, 16(6), 663; https://doi.org/10.3390/met16060663 - 15 Jun 2026
Viewed by 348
Abstract
Mass-based circularity indicators, such as ISO 59020:2024, quantify material recovery as a share of total throughput but do not account for chemical composition or functional performance, as a consequence of their sector-agnostic design. In copper metallurgical systems, trace tramp elements (e.g., As, Sb, [...] Read more.
Mass-based circularity indicators, such as ISO 59020:2024, quantify material recovery as a share of total throughput but do not account for chemical composition or functional performance, as a consequence of their sector-agnostic design. In copper metallurgical systems, trace tramp elements (e.g., As, Sb, Bi, Fe, Sn, Ni) present in WEEE-derived scrap, anode slimes, and refinery residues can significantly reduce electrical conductivity. Even at nominal purities of ≥99.7 wt.% Cu, conductivity may drop to 85.0–88.0% IACS, as illustrated by selected reported cases—a level of functional degradation that remains undetected by mass-based accounting. Analysis of Grade A cathode standards (EN 1978:2022, LME Cu-CATH-1, ASTM B115-10:2021) shows that impurity limits as low as 2 ppm (Bi) constrain the achievable share of secondary feed in closed-loop recycling. For a specific flash-smelting–refinery configuration, modeling indicates that secondary feed shares above approximately 30% may lead to impurity accumulation beyond the stated specification constraints unless low-impurity primary copper is introduced. This study introduces the Quality-Adjusted Circularity Indicator (QACI), a conceptual, specification-constrained indicator framework that applies a dilution factor fdil derived from a binary blending mass balance to adjust ISO 59020:2024 inflow-based circularity indicators using a feed-composition blending constraint anchored to Grade A specification limits. The QACI functions as a feed-composition screening indicator operating at the anode blending stage and does not represent a correction of the full electrorefining system. Parametric scenario analysis across six stylized impurity configurations shows that, at identical mass-based circularity (Cmass = 25%), the QACI ranges from 7.1% to 25.0%. This corresponds to a 1.3- to 3.5-fold difference between the mass-based and quality-adjusted indicator values under the stated feed-composition assumptions, illustrating the potential overestimation introduced when feed-quality constraints are not considered. This ratio quantifies the divergence between two indicator values under stylized conditions and should not be interpreted as a directly measured fold-difference in actual loop-closure performance. Positioned within the ISO 59020:2024 Annex C complementary method space, the QACI is positioned as a first-order screening approach of existing circularity metrics that may inform future research discussion of quality-differentiated approaches in EU secondary metals policy. Full article
(This article belongs to the Special Issue Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination)
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20 pages, 5340 KB  
Article
Microfluidic-Intensified Two-Stage Tannin Precipitation of Germanium to Reduce Tannin Consumption
by Ziyu Zhao, Dongli Li, Yibo Luo, Min Feng, Lixin Sun, Xian Zhou and Shaohua Ju
Metals 2026, 16(6), 644; https://doi.org/10.3390/met16060644 - 11 Jun 2026
Viewed by 255
Abstract
To address the challenges of low germanium recovery and high reagent consumption during precipitation from strongly acidic solutions, this study developed a two-stage tannin process intensified by microfluidic mixing and systematically examined the synergistic effects of tannin dosage and pH on coordination chemistry. [...] Read more.
To address the challenges of low germanium recovery and high reagent consumption during precipitation from strongly acidic solutions, this study developed a two-stage tannin process intensified by microfluidic mixing and systematically examined the synergistic effects of tannin dosage and pH on coordination chemistry. First-stage recovery rose from 45.23% to 91.28% as the tannin ratio increased from 5- to 15-fold, confirming that sufficient ligand promotes dense chelate formation. Optimising pH to 2.0–2.5 deprotonated tannin hydroxyls, enabling electrostatic–chelation synergy with Ge(OH)3+ and yielding 79.88% recovery—a 20.28% improvement over pH 1.5. The staged second-stage process proved particularly effective: at pH 1.5, a “5-fold primary + 15-fold secondary” scheme achieved 92.04% total recovery with only 13.22-fold cumulative tannin, a 46.81% increase over the single-stage 5-fold treatment; at pH 2.5, a “5-fold + 10-fold” combination reached 95.44% recovery with just 8.67-fold reagent. Microfluidic processing refined particle size and intensified the Ge–O vibration at 864 cm−1, indicating more stable coordination. Economic analysis reveals that efficiency plateaus beyond a 17-fold cumulative dosage, making staged addition the cost-effective choice. By harmonising staged coordination with enhanced mass transfer, this approach resolves the inherent conflict between precipitation depth and reagent overuse, delivering a sustainable strategy for germanium recovery. Full article
(This article belongs to the Special Issue Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination)
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15 pages, 7085 KB  
Article
Hydrothermal Synthesis of Hierarchical Boehmite from Co-Processed Stainless Steel Dust and Aluminum Dross Residue
by Hongda Yao, Nan Wang, Min Chen and Xiaoqing Chen
Metals 2026, 16(5), 455; https://doi.org/10.3390/met16050455 - 22 Apr 2026
Viewed by 440
Abstract
Stainless steel dust and aluminum dross are large-volume solid wastes in the metallurgical industry. Synergistic treatment of these wastes recovers some metals but yields an Al-rich residue (Al2O3 > 50%) that represents both a resource loss and an environmental threat [...] Read more.
Stainless steel dust and aluminum dross are large-volume solid wastes in the metallurgical industry. Synergistic treatment of these wastes recovers some metals but yields an Al-rich residue (Al2O3 > 50%) that represents both a resource loss and an environmental threat if untreated. In this work, boehmite (γ-AlOOH) was synthesized via a hydrothermal route using the Al-rich residue as the aluminum source. The aim was to valorize this waste stream while comprehensively evaluating the product’s phase, morphology, pore characteristics, efficacy and underlying mechanism for Cr(VI) removal from aqueous solutions. The hydrothermal process was optimized as pH = 11.0, under which high-purity and well-crystallized γ-AlOOH was successfully prepared without harmful by-products. The product had uniform particle size distribution without obvious agglomeration, with a specific surface area of 156.7 m2/g, pore volume of 0.60 cm3/g and average pore diameter of 14.6 nm. The boehmite synthesized at pH 11.0 achieved a Cr(VI) removal efficiency of 31.28% and a maximum adsorption capacity of 15.64 mg/g. This study provides a new path for the resource utilization of high-aluminum residue, with both environmental and economic benefits and potential application value. Full article
(This article belongs to the Special Issue Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination)
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28 pages, 13315 KB  
Article
Thermodynamic and Kinetic Analysis of Lead Leaching from Pretreated Pb–Ag Jarosite Sludge by Chloride Solution
by Dimitrije Anđić, Miroslav Sokić, Aleksandar Jovanović, Nataša Gajić, Jovana Djokić, Marija Koprivica and Željko Kamberović
Metals 2026, 16(4), 367; https://doi.org/10.3390/met16040367 - 26 Mar 2026
Viewed by 691
Abstract
Waste products of zinc hydrometallurgy, such as Pb–Ag jarosite sludge, represent a significant environmental problem due to toxic properties associated with elevated lead content. At the same time, this material has economic value, making its valorization beneficial from both ecological and financial perspectives. [...] Read more.
Waste products of zinc hydrometallurgy, such as Pb–Ag jarosite sludge, represent a significant environmental problem due to toxic properties associated with elevated lead content. At the same time, this material has economic value, making its valorization beneficial from both ecological and financial perspectives. This study investigates the chloride leaching of pretreated Pb–Ag jarosite sludge, which underwent sulphation roasting followed by water leaching. The experiments were conducted with a constant solid/liquid ratio of 1:20, a stirring rate of 150 rpm, and using a 4 mol dm3 MgCl2 solution as the leaching agent, while temperature (40–80 °C) and leaching time (up to 120 min) were varied. The results showed that temperature significantly affects the lead leaching degree, with the highest (95%) achieved at 80 °C after 60 min. Kinetic analysis revealed a diffusion-controlled mechanism, with an activation energy of 18.40 kJ mol−1. Due to the characteristics of the leaching curve, the process was divided into four segments, with corresponding activation energies determined for each segment (16.48, 11.80, 13.88, and 20.50 kJ mol−1). The proposed MgCl2 system enables efficient lead leaching with a reduced amount of leaching agent, thus representing a more sustainable approach to the valorization of Pb–Ag jarosite sludge. Full article
(This article belongs to the Special Issue Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination)
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17 pages, 3334 KB  
Article
Roasting of Spodumene with Calcite at Atmospheric Pressure—Implications of Trace Potassium
by Enrique Garcia-Franco, María-Pilar Martínez-Hernando, Roberto Paredes, Yolanda Sanchez-Palencia, Pedro Mora and Marcelo F. Ortega
Metals 2026, 16(1), 59; https://doi.org/10.3390/met16010059 - 2 Jan 2026
Viewed by 1391
Abstract
Lithium is an essential material for lightweight batteries. Traditional mining of soluble salts expanded to include the extraction of hard rocks, which requires their solubilization through roasting. Among hard lithium rocks, spodumene has recently received attention from the scientific community. Its metallurgical processing [...] Read more.
Lithium is an essential material for lightweight batteries. Traditional mining of soluble salts expanded to include the extraction of hard rocks, which requires their solubilization through roasting. Among hard lithium rocks, spodumene has recently received attention from the scientific community. Its metallurgical processing can be classified according to the type of reagents, as well as the operating temperature and pressure. The use of calcium carbonate as a natural alkali avoids aggressive chemicals such as sulfuric acid or caustic soda. In this article, 0.5 g of jewelry-grade spodumene was loaded into a ceramic crucible with 2.5 g of reducing agent in a tandem of roasting at 1050 °C-1 bar-30 min and leaching with neutral water at 90 °C-1 bar-20 min at a water/clinker mass ratio of 25. Measurements by XRD, ICP-OES, and SEM-EDX suggest a pathway of spodumene cracking because of poor contact with the reductant. Potassium present in the crucible acts as a flux and encapsulates spodumene crystals, causing lithium to end up bound to silica. While lithium metasilicate is barely soluble in water, leaching potassium aluminate hoards in the liquid. The empirical observations were supported with thermodynamic spontaneity studies, which required compiling the mineral properties based on open reference tabulations. Full article
(This article belongs to the Special Issue Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination)
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Review

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17 pages, 1192 KB  
Review
On the Use of Amino Acids to Leach Precious Metals from Primary and Secondary Resources
by Simbarashe Fashu, Aaron Mukuya and Quinton Kanhukamwe
Metals 2026, 16(7), 724; https://doi.org/10.3390/met16070724 - 1 Jul 2026
Viewed by 198
Abstract
During hydrometallurgical processing of precious metals, the leaching process is the critical stage mainly contributing to environmental pollution problems. The most important process variables affecting leaching kinetics are temperature, lixiviant concentration, solid-to-liquid ratio, presents of catalysts and synergists, and the type of oxidant. [...] Read more.
During hydrometallurgical processing of precious metals, the leaching process is the critical stage mainly contributing to environmental pollution problems. The most important process variables affecting leaching kinetics are temperature, lixiviant concentration, solid-to-liquid ratio, presents of catalysts and synergists, and the type of oxidant. There are significant efforts to replace harmful lixiviants with environmentally friendly solvents in leaching of precious metals during hydrometallurgical processing of precious metals. Of the different lixiviants researched, amino acids demonstrate much potential to compete with traditional lixiviants like cyanide and aqua regia. We have reviewed the chemistry and performance of amino acids in leaching of precious metals from primary and secondary resources and compared them with traditional approaches. The use of different approaches to enhance the leaching kinetics including starved cyanide, addition of strong oxidant, addition of synergists and catalysts, concentration and temperature were reviewed. Commonly used amino acids were reported and the future for commercialization of amino acids for precious metal leaching was discussed. The use of amino acids in absence of cyanide requires the use of strong oxidants and further research is still necessary on green amino acid–oxidant combinations capable of leaching secondary resources and producing high leaching efficiencies at a low cost. Full article
(This article belongs to the Special Issue Advances in Hydrometallurgy of Metals: Sources, Pretreatment, Leaching, Extraction, Recovery, Raffination)
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