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Special Issue "Research on Hydrometallurgical Separation Technology"

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A special issue of Separations (ISSN 2297-8739). This special issue belongs to the section "Analysis of Energies".

Deadline for manuscript submissions: 20 August 2022 | Viewed by 3396

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Prof. Dr. Keisuke Ohto
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Department of Chemistry and Applied Chemistry, Saga University, Saga city, 840-8502, Japan
Interests: metal separation; solvent extraction; ion -exchange; host–-guest chemistry; microreactor

Special Issue Information

Dear Colleagues,

The reservation of metallic resources has been an urgent global issue. In addition to mining, the recycling of critical metals and removal of hazardous elements have been at the focus of research for this purpose. Hydrometallurgical techniques such as solvent extraction and ion exchange has been extensively used for the recovery of critical metals and removal of hazardous elements. New challenges to design and prepare new reagents of extractants and adsorbents, to propose new concepts, and to establish new processes, and so on, continue for the efficient separation of metal resources.

This Special Issue aims to present readers with the hottest topics in hydrometallurgy. The issue invites contributions relating, but not limited, to fibers of membrane design and preparation, new precipitants, flotation and microreactor systems, applications of host compounds, treatment of environmental issues, and applications with a range of hydrometallurgical techniques.

Prof. Dr. Keisuke Ohto
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.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 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

New extractants and adsorbent
New concepts
New processes
Applications
Critical metals
Hazardous elements
Microreactor

Published Papers (5 papers)

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Research

Open AccessArticle

Separation of Microalgae by a Dynamic Bed of Magnetite-Containing Gel in the Application of a Magnetic Field

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Separations 2022, 9(5), 120; https://doi.org/10.3390/separations9050120 - 12 May 2022

Viewed by 287

Abstract

Microalgae are now known as potential microorganisms in the production of chemicals, fuel, and food. Since microalgae live in the sea and the river, they need to be harvested and separated and cultured for further usage. In this study, to separate microalgae, a bed of magnetite-containing gel (Mag gel, 190 µm) was packed in the column by the application of a magnetic field for the separative elution of injected microalgae (including mainly four species), cultured at Saga University in Japan. The applied magnetic field was set at a constant and dynamic-convex manner. At a constant magnetic field of 0.4–1.1 T, the elution percentage of the microalgae at less than 5 µm was 30–50%. At 1.1 T, the larger-sized microalgae were eluted at a percentage of 20%, resulting in the structural change of the bed by the applied magnetic field. In a convex-like change of the magnetic field at 1.1 T ⇄ 0.4 T, the smaller-sized microalgae were selectively eluted, whereas at 1.1 T ⇄ 0.8 T, the larger-sized microalgae were eluted. Dynamic convex-like changes by the magnetic field selectively eluted the microalgae, leading to the separation and the extraction of potential microalgae. Full article

(This article belongs to the Special Issue Research on Hydrometallurgical Separation Technology)

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Open AccessArticle

Comparative Extraction of Aluminum Group Metals Using Acetic Acid Derivatives with Three Different-Sized Frameworks for Coordination

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Separations 2021, 8(11), 211; https://doi.org/10.3390/separations8110211 - 08 Nov 2021

Viewed by 405

Abstract

We prepared acetic acid derivatives using three different frameworks, calix[4]arene, alkenyltrimethylol, and trihydroxytriphenylmethane, which differ in the number and size of their coordination sites. We further investigated the extraction properties for aluminum group metal ions. All three extraction reagents exhibited increased extraction compared with the corresponding monomeric compounds, owing to structural effects. The extraction reaction and extraction equilibrium constants were determined using a slope analysis. Their extraction abilities, separation efficiencies, and potential coordination modes are discussed using the extraction equilibrium constants, half-pH values, and spectroscopic data. The calix[4]arene and trihydroxytriphenylmethane derivatives demonstrated allosteric co-extraction of indium ions (In³⁺) with an unexpected stoichiometry of 1:2. Full article

(This article belongs to the Special Issue Research on Hydrometallurgical Separation Technology)

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Open AccessFeature PaperArticle

Selective Extraction of Platinum(IV) from the Simulated Secondary Resources Using Simple Secondary Amide and Urea Extractants

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Separations 2021, 8(9), 139; https://doi.org/10.3390/separations8090139 - 01 Sep 2021

Cited by 3 | Viewed by 587

Abstract

The recycling of rare metals such as platinum (Pt) from secondary resources, such as waste electronic and electrical equipment and automotive catalysts, is an urgent global issue. In this study, simple secondary amides and urea, N-(2-ethylhexyl)acetamide, N-(2-ethylhexyl)octanamide, and 1-butyl-3-(2-ethylhexyl)urea, which selectively extract Pt(IV) from a simulated effluent containing numerous metal ions, such as in an actual hydrometallurgical process, were synthesized and achieved efficient Pt(IV) stripping using only water. Comparison of Pt(IV) extraction behavior with a tertiary amide without N–H moieties suggests that the secondary amides and urea extractants effectively use hydrogen bonding to the hexachloroplatinate anion by N–H moieties. Examining the conditions for the third phase formation revealed that the secondary amide extractant with the longest alkyl chain can be used in the extraction process for a long time without forming any third phase, despite its lower Pt(IV) extraction capacity. The practical trial with simple compounds developed in this study should contribute to the development of Pt separation and purification processes. Full article

(This article belongs to the Special Issue Research on Hydrometallurgical Separation Technology)

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Open AccessFeature PaperArticle

New Concept for the Study of the Fluid Dynamics of Lithium Extraction Using Calix[4]arene Derivatives in T-Type Microreactor Systems

Yehezkiel Steven Kurniawan

Ramachandra Rao Sathuluri

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Separations 2021, 8(5), 70; https://doi.org/10.3390/separations8050070 - 20 May 2021

Cited by 1 | Viewed by 875

Abstract

Lithium extraction remains a challenge in the hydrometallurgy process due to its economic value and maldistribution sources. Employing calix[4]arene derivatives in solvent extraction techniques results in high selectivity and extraction capability, but a slow extraction rate. The slow kinetics of batch-wise extraction can be drastically accelerated by using a T-type microreactor system. Therefore, a combination of calix[4]arene and a microreactor system serves as an ideal platform for efficient lithium extraction. In this work, the fluid dynamics of lithium extraction using a monoacetic acid calix[4]arene derivative in a T-type microreactor system were studied. Increasing the O/A ratio increases the average length, surface area, and volume of the organic droplets, but decreases the specific surface area. In contrast, increasing the Reynolds number decreases the average length, surface area, and volume of the organic droplets, but increases the specific surface area. It was found that shorter diffusion distance, larger specific surface area, and faster vortex velocity were the factors that play the most pivotal roles in achieving great extraction rate enhancement in T-type microreactor systems compared to batch-wise systems. These findings represent an important new concept in the study of the fluid dynamics of lithium extraction using monoacetic acid calix[4]arene derivatives in T-type microreactor systems. Full article

(This article belongs to the Special Issue Research on Hydrometallurgical Separation Technology)

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Open AccessArticle

Selective Recovery of Platinum (IV) from HCl Solutions Using 2-Ethylhexylamine as a Precipitant

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Separations 2021, 8(4), 40; https://doi.org/10.3390/separations8040040 - 01 Apr 2021

Viewed by 732

Abstract

The selective separation and recovery of specific platinum-group metals (PGMs) from metal mixtures is a significant challenge owing to the similarity of these metals in terms of chemical and physical properties. Among the typical PGMs (Pd, Pt, and Rh), the selective recovery of Pt prior to the recovery of Pd and Rh is in high demand. In this study, we attempted the selective precipitation of Pt(IV) from mixed-metal HCl solutions using 2-ethylhexylamine (2EHA) as a precipitant and achieved the selective precipitation of Pt(IV) from Pd(II) and Rh(III) over a wide range of HCl concentrations. Selective precipitation of Pt(IV) was also achieved from HCl solutions with high levels of base metals, such as Al, Cu, Fe, and Zn. High yields of undegraded 2EHA remaining in the HCl solution after Pt(IV) precipitation were recovered using hydrophobic porous resins. X-ray photoelectron spectroscopy and thermogravimetric measurements revealed that the Pt(IV)-containing precipitate was an ion-pair comprising one [PtCl₆]²⁻ and two ammonium cations of 2EHA. The steric hindrance and high hydrophilicity of 2EHA suppressed the formation of Rh(III)- and Pd(II)-containing precipitates, respectively, resulting in the selective precipitation of Pt(IV). Full article

(This article belongs to the Special Issue Research on Hydrometallurgical Separation Technology)

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