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Metals
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Processing and Characterization of Metal Containing Wastes
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Processing and Characterization of Metal Containing Wastes

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

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 32206

Special Issue Editor

Prof. Dr. Fernando Castro

E-Mail Website
Guest Editor
Department of Mechanical Engineering, Universidade do Minho, 4800-058 Guimarães, Portugal
Interests: wastes; extraction metallurgy; recycling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The metallurgical industry produces a high amount of wastes, most of which are rich in metals, in metallic form or in compounds. Whether in the extractive metallurgy phase or in the metal processing steps, the wastes generated may contain valuable metal elements. Other industrial activities also generate waste rich in metals. Such is the case, for example, of the residues generated in the surface treatment of materials, in the electrical and electronic industry, in the automotive industry, in the mining industry, and in chemistry, among many others. Moreover, at the end of life of products, metal scraps are often found, sometimes of simple composition, other times complex, requiring specific separation techniques.

Given the intrinsic value associated with metals and, in some cases, due to being considered critical materials because of their scarcity in nature and growing needs in specific applications, most metals contained in the wastes must be recovered, either through recycling processes or through more complex processes in which metals can be obtained in useful forms. On the other hand, it is common for wastes containing metals to present environmental hazards, necessitating treatments that are in compliance with the environmental protection principles, sometimes not aiming the recovery of metals but just the obtainment of less hazardous or inert products.

This Special Issue aims to address research on processes of metal recovery from wastes containing metals. Recycling processes, the use of physical and mechanical technologies, and chemical processes involving low or high temperatures are all of interest. Presentation of research on the inertization of hazardous wastes or similar processes is encouraged as well. This Issue also intends to include the presentation of studies on the characterization of wastes containing metals, not only to support the development of extraction, recycling, or inertization processes but also to further environmental and hazard assessments.

Prof. Dr. Fernando Castro
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 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 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

  • waste management
  • waste characterization
  • metal recycling
  • metal extraction processes
  • environmental assessment of wastes
  • critical and strategic metals
  • hydrometallurgy
  • pyrometallurgy
  • separation and sorting processes

Published Papers (5 papers)

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Research

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11 pages, 3744 KiB  
Article
Characterization of Galvanizing Flue Dust and Recycling Possibilities
by Jana Pirošková, Jakub Klimko, Jarmila Trpčevská, Martina Laubertová, Beatrice Plešingerová, Pavol Liptai, Tomáš Vindt and Dušan Oráč
Metals 2022, 12(5), 744; https://doi.org/10.3390/met12050744 - 27 Apr 2022
Cited by 1 | Viewed by 1870
Abstract
Waste generation is a part of every technological process, including galvanizing. The presented paper deals with the characterization of flue dust generated in the process of hot-dip galvanizing, and proposes possible methods for zinc recycling. The flue dust is released into the atmosphere [...] Read more.
Waste generation is a part of every technological process, including galvanizing. The presented paper deals with the characterization of flue dust generated in the process of hot-dip galvanizing, and proposes possible methods for zinc recycling. The flue dust is released into the atmosphere as a white fume above the zinc bath, which is caused by the decomposition of ammonium chloride and zinc chloride present in the flux. This dust is classified as hazardous waste and is a material with a particle size below 90 µm. In addition to zinc and iron compounds, it contains water vapor and oils. The presented elemental, phase, and other characteristic methods of flue dust are important for the subsequent selection of a suitable method for processing the material. At present, this waste is not processed separately due to its low production, which is approximately 0.3 kg per 1 tonne of galvanized steel. The proposed hydrometallurgical recycling method enables the processing of flue dust on a small scale and enables the recovery of high-purity zinc in the form of metallic zinc or zinc oxide. Full article
(This article belongs to the Special Issue Processing and Characterization of Metal Containing Wastes)
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20 pages, 3403 KiB  
Article
Influence of Cell Opening Methods on Electrolyte Removal during Processing in Lithium-Ion Battery Recycling
by Denis Manuel Werner, Thomas Mütze and Urs Alexander Peuker
Metals 2022, 12(4), 663; https://doi.org/10.3390/met12040663 - 13 Apr 2022
Cited by 5 | Viewed by 3368
Abstract
Lithium-ion batteries (LIBs) are an important pillar for the sustainable transition of the mobility and energy storage sector. LIBs are complex devices for which waste management must incorporate different recycling technologies to produce high-quality secondary (raw) materials at high recycling efficiencies (RE). This [...] Read more.
Lithium-ion batteries (LIBs) are an important pillar for the sustainable transition of the mobility and energy storage sector. LIBs are complex devices for which waste management must incorporate different recycling technologies to produce high-quality secondary (raw) materials at high recycling efficiencies (RE). This contribution to LIB recycling investigated the influence of different pretreatment strategies on the subsequent processing. The experimental study combined different dismantling depths and depollution temperatures with subsequent crushing and thermal drying. Therein, the removal of organic solvent is quantified during liberation and separation. This allows to evaluate the safety of cell opening according to the initial depollution status. These process steps play a key role in the recycling of LIBs when using the low-temperature route. Therefore, combinations of pretreatment and processing steps regarding technical and economic feasibility are discussed. Moreover, the process medium and equipment properties for a safe cell opening, the technical recycling efficiencies and their consequences on future industrial LIB waste management are pointed out. Full article
(This article belongs to the Special Issue Processing and Characterization of Metal Containing Wastes)
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27 pages, 2912 KiB  
Article
A Comparison of Methods for the Characterisation of Waste-Printed Circuit Boards
by Jonovan Van Yken, Ka Yu Cheng, Naomi J. Boxall, Chris Sheedy, Aleksandar N. Nikoloski, Navid R. Moheimani and Anna H. Kaksonen
Metals 2021, 11(12), 1935; https://doi.org/10.3390/met11121935 - 30 Nov 2021
Cited by 11 | Viewed by 3060
Abstract
Electronic waste is a growing waste stream globally. With 54.6 million tons generated in 2019 worldwide and with an estimated value of USD 57 billion, it is often referred to as an urban mine. Printed circuit boards (PCBs) are a major component of [...] Read more.
Electronic waste is a growing waste stream globally. With 54.6 million tons generated in 2019 worldwide and with an estimated value of USD 57 billion, it is often referred to as an urban mine. Printed circuit boards (PCBs) are a major component of electronic waste and are increasingly considered as a secondary resource for value recovery due to their high precious and base metals content. PCBs are highly heterogeneous and can vary significantly in composition depending on the original function. Currently, there are no standard methods for the characterisation of PCBs that could provide information relevant to value recovery operations. In this study, two pre-treatments, smelting and ashing of PCB samples, were investigated to determine the effect on PCB characterisation. In addition, to determine the effect of particle size and element-specific effects on the characterisation of PCBs, samples were processed using four different analytical methods. These included multi-acid digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, nitric acid digestion followed by X-ray fluorescence (XRF) analysis, multi-acid digestion followed by fusion digestion and analysis using ICP-OES, and microwave-assisted multi-acid digestion followed by ICP-OES analysis. In addition, a mixed-metal standard was created to serve as a reference material to determine the accuracy of the various analytical methods. Smelting and ashing were examined as potential pre-treatments before analytical characterisation. Smelting was found to reduce the accuracy of further analysis due to the volatilisation of some metal species at high temperatures. Ashing was found to be a viable pre-treatment. Of the four analytical methods, microwave-assisted multi-acid digestion offered the most precision and accuracy. It was found that the selection of analytical methods can significantly affect the accuracy of the observed metal content of PCBs, highlighting the need for a standardised method and the use of certified reference material. Full article
(This article belongs to the Special Issue Processing and Characterization of Metal Containing Wastes)
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13 pages, 8231 KiB  
Article
A New Added-Value Application for Steel Wire Drawing Mill Scale Waste in Stoneware Ceramic Products
by Inês Silveirinha Vilarinho, Ana Luisa Lopes, Jorge Carneiro, Carlos Pinto, João António Labrincha and Maria Paula Seabra
Metals 2021, 11(4), 661; https://doi.org/10.3390/met11040661 - 18 Apr 2021
Cited by 4 | Viewed by 3226
Abstract
Mill scale (MS) is a iron-rich waste generated in the wire drawing process with high iron content and is still mainly disposed in landfills. The scientific community has been studied its use in other applications such as pigments, concretes, among others. This work [...] Read more.
Mill scale (MS) is a iron-rich waste generated in the wire drawing process with high iron content and is still mainly disposed in landfills. The scientific community has been studied its use in other applications such as pigments, concretes, among others. This work aims to study a new added-value application for MS—the development of coloured ceramic pastes. For this purpose, the influence of the added amount (0, 1, 3, 5 and 10 wt.%), the pre-treatment (milling + sieving at 212 μμm), the maximum firing temperature (from 1043 to 1165 °C) and the type of furnace (laboratory/industrial) were analysed on the sample’s characteristics. A dark grey stoneware product was obtained through the incorporation of 10 wt.% of MS and leaching tests conducted at pilot scale with cups confirmed its immobilization in the ceramic matrix. Furthermore, it was proved that the firing temperature can be reduced by about 100 °C without affecting the specimen’s characteristics. This reduction leads to a considerable decrease in the energy consumption upon firing, inducing economic and environmental advantages. Therefore, this work provides a new added-value application for MS and contributes to the reduction of virgin raw materials consumption and development of more sustainable stoneware products. Full article
(This article belongs to the Special Issue Processing and Characterization of Metal Containing Wastes)
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Review

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40 pages, 3037 KiB  
Review
E-Waste Recycling and Resource Recovery: A Review on Technologies, Barriers and Enablers with a Focus on Oceania
by Jonovan Van Yken, Naomi J. Boxall, Ka Yu Cheng, Aleksandar N. Nikoloski, Navid R. Moheimani and Anna H. Kaksonen
Metals 2021, 11(8), 1313; https://doi.org/10.3390/met11081313 - 19 Aug 2021
Cited by 70 | Viewed by 19502
Abstract
Electronic e-waste (e-waste) is a growing problem worldwide. In 2019, total global production reached 53.6 million tons, and is estimated to increase to 74.7 million tons by 2030. This rapid increase is largely fuelled by higher consumption rates of electrical and electronic goods, [...] Read more.
Electronic e-waste (e-waste) is a growing problem worldwide. In 2019, total global production reached 53.6 million tons, and is estimated to increase to 74.7 million tons by 2030. This rapid increase is largely fuelled by higher consumption rates of electrical and electronic goods, shorter life cycles and fewer repair options. E-waste is classed as a hazardous substance, and if not collected and recycled properly, can have adverse environmental impacts. The recoverable material in e-waste represents significant economic value, with the total value of e-waste generated in 2019 estimated to be US $57 billion. Despite the inherent value of this waste, only 17.4% of e-waste was recycled globally in 2019, which highlights the need to establish proper recycling processes at a regional level. This review provides an overview of global e-waste production and current technologies for recycling e-waste and recovery of valuable material such as glass, plastic and metals. The paper also discusses the barriers and enablers influencing e-waste recycling with a specific focus on Oceania. Full article
(This article belongs to the Special Issue Processing and Characterization of Metal Containing Wastes)
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