Special Issue "Leaching Kinetics of Valuable Metals"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 31 March 2019

Special Issue Editor

Guest Editor
Dr. Stefano Ubaldini

Consiglio Nazionale delle Ricerche (CNR)—Istituto di Geologia Ambientale e Geoingegneria (IGAG), Area della Ricerca di Roma RM 1, Montelibretti, Via Salaria Km 29,300—C.P. 10, 00015 Monterotondo Stazione, Roma, Italy
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Interests: primary and secondary raw materials; low-grade georesources; metals recovery; precious metals; heavy metals; leaching; hydrometallurgy; bio-hydrometallurgy; bioprecipitation; electrowinning; remediation processes; environmental innovative technologies; industrial wastes; exhausted batteries; WEEE; minerals; wastewater; acid mine drainage

Special Issue Information

Dear Colleagues,

Leaching is a primary extractive operation in hydrometallurgical processing, by which a metal of interest is transferred from naturally-occurring minerals into an aqueous solution. In essence, it involves the selective dissolution of valuable minerals, where the ore, concentrate, or matte is brought into contact with an active chemical solution known as a leach solution.

Currently, the hydrometallurgical processes have a great application, not only in the mining sector—in particular, for the recovery of precious metals, such as gold and silver—but also in the environmental sector, for the recovery of toxic metals (such as copper, nickel, zinc, manganese, arsenic, cadmium, chromium, lead) from wastes of various types, and their reuse as valuable metals, after purification.

Therefore, there is an increasing need to develop novel solutions, to implement environmentally sustainable practices in the recovery of these valuable and precious metals, with particular reference to the critical metals, that are those included in materials that are indispensable to modern life and for which an exponential increase in consumption is already a reality or will be in a short-term perspective (antimony, indium, vanadium, rare hearts, etc.).

Consequently, the economics of the processes, which is closely linked to the kinetics of leaching, is of great importance.

For publication in this Special Issue, will be considered those articles that will contribute to the optimization of the kinetic conditions of innovative hydrometallurgical processes—economic and of low environmental impact—applied for the recovery of valuable and critical metals.

I hope you accept this invitation, and help us to make a high-impact and high-quality Special Issue on "Leaching Kinetics of Valuable Metals".

Dr. Stefano Ubaldini
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 papers will be 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. 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 1200 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

  • Primary and secondary raw materials
  • Low-grade georesources
  • Valuable metals
  • Precious metals
  • Heavy metals
  • Leaching
  • Hydrometallurgy
  • Environmental innovative technologies
  • Industrial wastes
  • WEEE

Published Papers (3 papers)

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Research

Open AccessArticle A Kinetic Study on the Preparation of AlNi Alloys by Aluminothermic Reduction of NiO Powders
Metals 2018, 8(9), 675; https://doi.org/10.3390/met8090675
Received: 9 July 2018 / Revised: 26 July 2018 / Accepted: 31 July 2018 / Published: 28 August 2018
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Abstract
In this work, the experimental results obtained during the preparation of Al-Ni and Al-Ni-Mg alloys using the aluminothermic reduction of NiO by submerged powder injection, assisted with mechanical agitation are presented and discussed. The analyzed variables were melt temperature, agitation speed, and initial
[...] Read more.
In this work, the experimental results obtained during the preparation of Al-Ni and Al-Ni-Mg alloys using the aluminothermic reduction of NiO by submerged powder injection, assisted with mechanical agitation are presented and discussed. The analyzed variables were melt temperature, agitation speed, and initial magnesium concentration in the molten alloy. For some of the experiments performed, it was found that the Ni concentration increased from 0 to about 3 wt-% after 90 min of treatment at constant temperature and constant agitation speed. In order to determine the values of the kinetic parameters of interest, such as the activation energy and the rate constants, the values of the results obtained were fitted to the kinetic formulae available. Moreover, the kinetics of the reaction were found to be governed by the diffusion of Al and Mg to the NiO boundary layer, where MgAl2O4 or Al2O3 were formed as the main reaction products. Finally, from a thermodynamic study of the system, the main reactions that took place are explained. Full article
(This article belongs to the Special Issue Leaching Kinetics of Valuable Metals)
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Open AccessArticle Uranium Removal from Groundwater by Permeable Reactive Barrier with Zero-Valent Iron and Organic Carbon Mixtures: Laboratory and Field Studies
Metals 2018, 8(6), 408; https://doi.org/10.3390/met8060408
Received: 31 March 2018 / Revised: 22 May 2018 / Accepted: 24 May 2018 / Published: 1 June 2018
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Abstract
Zhovty Vody city, located in south-central Ukraine, has long been an important center for the Ukrainian uranium and iron industries. Uranium and iron mining and processing activities during the Cold War resulted in poorly managed sources of radionuclides and heavy metals. Widespread groundwater
[...] Read more.
Zhovty Vody city, located in south-central Ukraine, has long been an important center for the Ukrainian uranium and iron industries. Uranium and iron mining and processing activities during the Cold War resulted in poorly managed sources of radionuclides and heavy metals. Widespread groundwater and surface water contamination has occurred, which creates a significant risk to drinking water supplies. Hydrogeologic and geochemical conditions near large uranium mine tailings storage facility (TSF) were characterized to provide data to locate, design and install a permeable reactive barrier (PRB) to treat groundwater contaminated by leachate infiltrating from the TSF. The effectiveness of three different permeable reactive materials was investigated: zero-valent iron (ZVI) for reduction, sorption, and precipitation of redox-sensitive oxyanions; phosphate material to transform dissolved metals to less soluble phases; and organic carbon substrates to promote bioremediation processes. Batch and column experiments with Zhovty Vody site groundwater were conducted to evaluate reactivity of the materials. Reaction rates, residence time and comparison with site-specific clean-up standards were determined. Results of the study demonstrate the effectiveness of the use of the PRB for ground water protection near uranium mine TSF. The greatest decrease was obtained using ZVI-based reactive media and the combined media of ZVI/phosphate/organic carbon combinations. Full article
(This article belongs to the Special Issue Leaching Kinetics of Valuable Metals)
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Open AccessArticle Neural Network Modeling for the Extraction of Rare Earth Elements from Eudialyte Concentrate by Dry Digestion and Leaching
Metals 2018, 8(4), 267; https://doi.org/10.3390/met8040267
Received: 8 March 2018 / Revised: 8 April 2018 / Accepted: 10 April 2018 / Published: 13 April 2018
Cited by 1 | PDF Full-text (8394 KB) | HTML Full-text | XML Full-text
Abstract
Eudialyte is a promising mineral for rare earth elements (REE) extraction due to its good solubility in acid, low radioactive, and relatively high content of REE. In this paper, a two stage hydrometallurgical treatment of eudialyte concentrate was studied: dry digestion with hydrochloric
[...] Read more.
Eudialyte is a promising mineral for rare earth elements (REE) extraction due to its good solubility in acid, low radioactive, and relatively high content of REE. In this paper, a two stage hydrometallurgical treatment of eudialyte concentrate was studied: dry digestion with hydrochloric acid and leaching with water. The hydrochloric acid for dry digestion to eudialyte concentrate ratio, mass of water for leaching to mass of eudialyte concentrate ratio, leaching temperature and leaching time as the predictor variables, and the total rare earth elements (TREE) extraction efficiency as the response were considered. After experimental work in laboratory conditions, according to design of experiment theory (DoE), the modeling process was performed using Multiple Linear Regression (MLR), Stepwise Regression (SWR), and Artificial Neural Network (ANN). The ANN model of REE extraction was adopted. Additional tests showed that values predicted by the neural network model were in very good agreement with the experimental results. Finally, the experiments were performed on a scaled up system under optimal conditions that were predicted by the adopted ANN model. Results at the scale-up plant confirmed the results that were obtained in the laboratory. Full article
(This article belongs to the Special Issue Leaching Kinetics of Valuable Metals)
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