Selective Extraction Of Metals Research Articles

Thermogravimetry as a research tool for the development of an ammonium sulphate roasting process for selective metal extraction from minerals

AbstractThe ammonium sulphate roasting process involves reacting mineral-bearing materials with ammonium sulphate via a solid–solid roasting process and subjecting the resulting roast residue to aqueous leaching. This process enables the simultaneous, non-selective co-extraction of strategic metals from the starting materials. However, effective separation of the extracted metals is often mandatory to produce quality products of high purity. In this study, the combined application of thermogravimetric analysis, X-ray powder diffraction and inductively coupled plasma optical emission spectrometry confirmed the non-selectivity of the process when applied to a South African diamond mine residue residue roasted with ammonium sulphate in a 1:2 mass ratio (m/m) at 450 °C for 2 h, with magnesium, iron and aluminium being co-extracted into water-soluble metal sulphates. Thermogravimetry was then applied to develop a multi-step, multi-temperature selective roasting process using mixtures of pure commercial metal sulphate salts. The first step of the modified process successfully separated iron and aluminium sulphates from magnesium-sulphates in the roast residues by thermally decomposing soluble iron and aluminium sulphates into insoluble oxides via calcination at 750 °C for 2 h. This temperature was lower than the one at which magnesium sulphates convert into magnesium oxide. In the second and final step, iron and aluminium were recovered from the oxide minerals via solid–solid re-roasting with ammonium sulphate at 450 °C for 1 h, causing the oxides to revert back to their water-soluble sulphate forms. The effectiveness of the modified process was subsequently verified using a diamond mine residue, showing that the soluble iron and aluminium contents in the magnesium-bearing leachate could be reduced by over 90%.

Application of Polymer-Embedded Tetrabutylammonium Bromide (TBAB) Membranes for the Selective Extraction of Metal Ions from Aqueous Solutions.

The selective extraction of metals from aqueous solutions is a very important stage in the hydrometallurgical processing of metallic waste. Leach solutions are usually a multicomponent mixture. The main impurity of aqueous solutions obtained after leaching using inorganic acids is iron. In this work, the membrane separation of iron(III) from nickel(II), cobalt(II), and lithium(I) was studied. The facilitated transport of metal ions using polymer inclusion membranes (PIMs) with tetrabutylammonium bromide (TBAB) as an ion carrier under various conditions was analyzed in detail. Several factors, such as the ion carrier concentration in the membrane as well as the effect of the inorganic acid concentration in the source/receiving phases on the kinetic parameters, were investigated. The results show that ionic liquid TBAB is a very selective ion carrier of Fe(III) towards Ni(II), Co(II), and Li(I).

Synthesis and Characterisation of PVC-based non-plasticised polymer inclusion membranes for selective metal extraction

ABSTRACT Polymer Inclusion Membranes (PIMs) are one of the most capable systems for metal separation from multi-metallic solutions. This process offers some advantages over other commercial purification techniques in terms of selectivity in the recovery of metal ions, simultaneous extraction and stripping, long-term stability, and is also eco-friendly. This study involves the synthesis, characterisation, and application of polyvinyl chloride-based Polymer Inclusion Membrane. The possible challenges associated with membrane fabrication have also been highlighted. 5-nonylsalicylaldoxime (ACORGA M5640) is used for the synthesis of PIMs. Synthesised membranes with different ratios of polyvinyl chloride to carrier were characterised by various techniques including scanning electron microscopy, atomic probe microscopy, and Fourier transform infrared spectroscopy, to understand the morphology/chemistry. Moreover, the thermal stability was also investigated by thermal gravimetric analysis (TGA). And finally, a contact angle measurement was done to check its hydrophobicity and wettability. Further, it was found that 98% of copper was recovered from the multi-metallic e-waste solution. Opportunities and future aspects of synthesised membranes have also been discussed.

Integration of wastewater electro-electrodialysis and CO2 capture for sustainable LIB recycling: Process design and economic analyses

Hydrometallurgy-based recycling processes for spent lithium-ion batteries (LIB) can be conducted under mild operating conditions while achieving a high metal recovery rate. However, due to the excessive use of chemicals during operation, issues associated with operating costs and pollution of disposed wastewater hinder large-scale application. The disposed wastewater contains highly concentrated ions that can be reutilized via electro-electrodialysis (EED). In addition, regenerated base can be utilized as a CO2 absorbent, which produces soda ash that can be directly utilized for metal precipitation in the recycling process. Thus, this paper proposes a novel integrated system of wastewater EED and CO2 capture for sustainable LIB recycling. This system includes selective metal recovery of cathode material, wastewater EED, and CO2 capture and utilization. Based on the simulation results, system performance was evaluated considering the regenerated chemical concentration and its impact on the metal recovery rate. The complete regeneration of 2.04 M sulfuric acid and 1.09 M caustic soda solutions could be accomplished from the waste liquid. In recycling capacity of 50,000 ton/year, 0.33 kg of CO2 could be captured per 1 kg of LCO cathode material, and 99% selective metal extraction could be accomplished during battery recycling using the regenerated chemicals. To clarify economic performance, the levelized cost of recycling was analyzed in different market scenarios for chemicals. The proposed system can accomplish full regeneration of wastewater via EED with a 21.90% lower levelized cost of recycling compared with the conventional system. The results of simulation and economic analysis demonstrate the potential performance of the proposed system in terms of sustainability and economic feasibility in current LIB recycling industry.

A Multifocal Study Investigation of Pyrolyzed Printed Circuit Board Leaching

Electric waste from numerous devices that are put out of use every day has some form of printed circuit board that contains precious and valuable metals in their components. In order to extract these metals, the printed circuit boards were crushed and pyrolyzed into powder. The fine pyrolyzed printed circuit board (PPCB) powder was separated into fractions, and the fine metallic fraction was used as a raw material for metal leaching extraction. In order to better understand how various metal species react in leaching media, several leaching agents were used (sulfuric acid, nitric acid, glycine, and acid mine drainage-AMD) alone, and with the addition of hydrogen peroxide. Additionally, the influence of the S/L ratio and leaching temperature were investigated in sulfuric acid leaching solutions, as this is the one most widely used. In one case, the reactor was heated in a thermal bath, while in the other, it was heated in an ultrasonic bath. Lastly, several experiments were conducted with a (consecutive) two-pronged leaching approach, with and without applied pretreatment. The aim of this paper is to give a multifocal and detailed approach to how metals such as Al, Cu, Co, Zn, Sn, and Ca behave when extracted from fine PPCB powder. However, some attention is given to Nd, Pd, Pb, and Ba as well. One of the main findings is that regardless of the pretreatment or the sequence of leaching media applied, consecutive two-pronged leaching cannot be used for selective metal extraction. However, AMD was found to be suitable for selective leaching with very limited applications.

Sequential flue gas utilization for sustainable leaching and metal precipitation of spent lithium-ion battery cathode material: Process design and techno-economic analysis

The growing use of lithium nickel manganese cobalt oxide (NCM) batteries has necessitated increased recovery of cathode materials for sustainable battery recycling given the limited metal source, and to mitigate the negative environmental impact of battery disposal. Acid leaching and the use of precipitants are essential for selective metal extraction in the recycling process. However, the excessive use of chemicals degrades the economic performance of the recycling process. In this study, we propose and simulate a novel lithium-ion battery (LIB) recycling system through sequential SOX, NOX, and CO2 utilization of industrial flue gas in the following four processes: sulfuric acid and nitric acid regeneration from SOX, NOX, acid leaching of cathode materials, Na2CO3 regeneration from sulfur and nitric-free flue gas, selective precipitation. In the sequential flue gas capture and utilization, the H2O2 is used as a wet absorbent for both desulfurization and denitrification, and produces 3.3 M H2SO4 and 7.18 M HNO3. NaOH is used for CO2 utilization, and 2.32 M of Na2CO3 is produced. We expected that the sequential flue gas utilization reduced the acids and precipitant consumption in the battery recycling process, which was more advantageous than the conventional recycling process by 2.70%.

Carbon mineralization with concurrent critical metal recovery from olivine

Carbon dioxide utilization for enhanced metal recovery (EMR) during mineralization has been recently developed as part of CCUS (carbon capture, utilization, and storage). This paper describes fundamental studies on integrating CO2 mineralization and concurrent selective metal extraction from natural olivine. Nearly 90% of nickel and cobalt extraction and mineral carbonation efficiency are achieved in a highly selective, single-step process. Direct aqueous mineral carbonation releases Ni2+ and Co2+ into aqueous solution for subsequent recovery, while Mg2+ and Fe2+ simultaneously convert to stable mineral carbonates for permanent CO2 storage. This integrated process can be completed in neutral aqueous solution. Introduction of a metal-complexing ligand during mineral carbonation aids the highly selective extraction of Ni and Co over Fe and Mg. The ligand must have higher stability for Ni-/Co- complex ions compared with the Fe(II)-/Mg- complex ions and divalent metal carbonates. This single-step process with a suitable metal-complexing ligand is robust and utilizes carbonation processes under various kinetic regimes. This fundamental study provides a framework for further development and successful application of direct aqueous mineral carbonation with concurrent EMR. The enhanced metal extraction and CO2 mineralization process may have implications for the clean energy transition, CO2 storage and utilization, and development of new critical metal resources.

Selective extraction performance of Ni, Cu, Co, and Mn adopted by a coupled leaching of low-grade Ni-sulfide ore and polymetallic Mn-oxide ore in sulphuric acid solutions

The coupled leaching of ocean polymetallic nodule and low-grade nickel sulphide ore in sulphuric acid solution was investigated, especially in performance on selective extraction of Ni, Cu, Co, and Mn. This work can be divided into three parts. First, the advantageous selective metal extraction conditions, parallel to the optimal coupled leaching conditions, were measured by coupled leaching tests which adopted the Ni, Mn, Cu, Co, and Fe dissolution efficiency. Under the optimal conditions, the extraction ratios of Ni, Mn, Cu, Co, and Fe are 96.8%, 97.3%, 92.2%, 97.9%, and 28.9%, respectively. Second, electrochemical tests revealed that multi-metal simultaneous extraction from two ores depends on the reduction-oxidation dissolution of a corrosion cell of the nodule cathode and the sulphide ore anode. The results showed that acidity and Fe3+ ion affected dissolution of both ores significantly; high valence manganese oxide reduction takes precedence which is in control of the Ni, Mn, Cu, and Co dissolution of the nodule; Ni, Cu, and Co extraction from the nickel ore is a course of sulphide minerals oxidative conversion which significantly affected by Fe2+-containing sulphide oxidation. Third, the separation performance of iron substance in the solution was determined by the transformation of minerals phases of the leached residues, showing that Fe-bearing minerals dissolved to Fe3+ ion then precipitated as iron vitriol or oxide during the selectively coupled leaching. The selectively coupled leaching of low-grade multi-metallic sulphide ore and oxide ore mainly rests with the transformation of Fe-containing species in the system.

Electrochemical determination of Pb2+ and Cd2+ with a poly(pyrrole-1-carboxylic acid) modified electrode

• Pyrrole-1-carboxylic acid (Py-CO 2 ) was synthesized and applied for modification of pencil graphite electrodes (PGE). • Electropolymerization of Py-CO 2 created a sensing film for selective metal extraction and determination. • The modified electrode, PPy-CO 2 @PGE, provided excellent sensitivity and selectivity for detection of Pb 2+ and Cd 2+ . • Accurate analysis of Pb 2+ and Cd 2+ in several natural water sources was demonstrated and independently verified. A pencil graphite electrode (PGE) was modified by the electropolymerization of pyrrole-1-carboxylic acid (Py-CO 2 ) to form a sensing film of poly(pyrrole-1-carboxylic acid) (PPy-CO 2 ) for the sensitive determination of Pb 2+ and Cd 2+ by differential pulse anodic stripping voltammetry (DPASV). The porous structure of the PPy-CO 2 film uniformly distributes a carboxylate group throughout the coating to selectively coordinate and preconcentrate metal ions. The polymer film was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and energy dispersive X-ray (EDS) and Fourier transform infrared (FTIR) spectroscopy. Under the optimized conditions (analyte solution pH: 6.0, extraction time: 15 min, reduction potential: −1.1 V and reduction time: 160 s), a linear relationship between peak current and metal concentration was obtained from 0.1 to 1 nM for Pb 2+ and Cd 2+ with detection limits of 0.018 and 0.023 nM, respectively. Simultaneous analysis of Pb 2+ and Cd 2+ was performed in the presence of the possible interfering ions Cr 3+ , Bi 3+ , Cu 2+ , Fe 2+ , Zn 2+ and Co 2+ and in complex matrices. The performance of the PPy-CO 2 @PGE demonstrated excellent intra-day repeatability, long-term reproducibility over a seven-week period and was utilized for the determination of Pb 2+ and Cd 2+ in a variety of natural water samples with the results independently verified by inductively coupled plasma-mass spectrometry.

Highly efficient re-cycle/generation of LiCoO2 cathode assisted by 2-naphthalenesulfonic acid

The explosively growing demand for electrical energy is generating a great deal of spent lithium-ion batteries (LIBs). Therefore, a simple and effective strategy for the sustainable recycling of used batteries is urgently needed to minimize chemical consumption and to reduce the associated environmental pollution. In this work, 2-naphthalenesulfonic acid is innovatively proposed for the highly-selective recovery of valuable metals. Impressively, lithium and cobalt are simultaneously separated through a single-step process, in which 99.3% of lithium is leached out as Li+ enriched solutions while 99% of cobalt is precipitated as cobalt-naphthalenesulfonate. The obtained lithium enriched solutions are recovered as Li2CO3. The cobalt-naphthalenesulfonate with high purity (99%) is ready to be transformed into Co3O4, and then generated into LiCoO2 by reacting with the above-obtained Li2CO3. The cathode material LiCoO2 with micro/nanostructures exhibits excellent electrochemical properties. Characterization results confirm the coordination structure of the extracted cobalt complex (Co(NS)2•6H2O). Finally, compared to other selective metal extraction techniques, this strategy avoids additional separation and purification processes, thus improving the recycling efficiency. Overall, this route can be extended to selectively extract valuable metals from other types of cathode materials in spent LIBs as a sustainable approach.

DETERMINATION OF METALS AND RADIONUCLIDES BY NEWEST FUNCTIONALIZED REAGENTS IN LIQUID MEDIA

The conditions for the formation of metal complexes (aluminium, radionuclides) in solutions are considered. The properties of solid extractants (TVEX) and their application for the selective extraction of metals and radionuclides are discussed. The extraction of 90Sr, 90Y, 137Cs and U(VI) radionuclides from aqueous TVEX solutions impregnated with calixarenes C45 and CIP67 has been studied. The use of surfactants in combination with OAR (PA) is a typical example of the fact that the analytical capabilities of even well-known reagents are far from exhausted, and the use of functionalized reagents can significantly improve the basic analytical characteristics of metal detection.

Facile indium recovery from waste liquid crystal displays: Chloride-facilitated indium electroreduction and stepwise Cu/MoO2 and indium electrodeposition

With a huge amount of waste liquid crystal displays (LCDs) generated annually, their proper recycling raises continuous concern to realize pollution control (heavy metal and liquid crystal) and resource recovery (indium). However, due to their multi-metal feature, traditional hydrometallurgy lacks of sufficient selectivity, which makes the recycling route lengthy, costly, and generate more waste. Electrodeposition acts as a promising technique for selective metal extraction from multi-metal system due to its high selectivity and electron as clean reagent. To fully develop its application in metal recovery, stepwise Cu/MoO2 and In electrodeposition from In-Cu-Mo-Fe waste LCD leachate is explored in depth. Electrochemical behavior analysis shows Cu and MoO2 can be first electrodeposited for their higher electroreduction potential. Cl- plays a key role in accelerating indium electroreduction kinetics, which largely shortens the extraction time without the sacrifice of current efficiency. This accelerating effect is attributed to the increased concentration of electroactive species or collision frequency. Under optimized condition, 99.41% of indium (> 99% purity) can be electrodeposited within 13 h with high current efficiency. This study provides a cleaner approach for waste LCDs recycling and gives implications for the potential application of electrochemical technique in e-waste recycling.

Selective metal extraction by biologically produced siderophores during bioleaching from low-grade primary and secondary mineral resources

Siderophores are a class of biogenic macromolecules that have high affinities for metals in the environment, thus could be exploited for alternate sustainable metal recovery technologies. Here, we assess the role of siderophores in the extraction and complexation of metals from an iron oxide-rich metallurgical processing residue and a low-grade primary Ni ore. Evaluation of the biological siderophore production by three pseudomonads, P. fluorescens, P. azotoformans and P. putida identified that P. putida could generate the highest siderophore yield, which was characterized as a hydroxamate and catecholate mixed-type pyoverdine PyoPpC-3B. Key physicochemical parameters involved in raw siderophore mediated metal extraction were identified using a fractional factorial design of experiments (DOE) and subsequently employed in purified PyoPpC-3B leaching experiments. Further targeted experiments with hydroxamate and catecholate functional analogues of PyoPpC-3B confirmed their marked ability to competitively or selectively leach and chelate hard metal ions, including Al(OH)4-, Mn2+ and Zn2+. Interestingly, complexation of Mn and Zn ions exceeded the natural affinity of pyoverdine for Fe3+, thus despite the low metal recoveries from the materials tested in this study, this work provides important new insights in siderophore-metal interactions.

Liquid metals dealloying as a general approach for the selective extraction of metals and the fabrication of nanoporous metals: A review

Liquid metal dealloying, a method of etching based on different solubilities of each component of the alloy into the liquid metal, has been extensively developed for metallurgical and structural materials applications. This review discusses the development on liquid metal dealloying for recycling alloy scraps and the fabrication of nano-porous materials. Extracting and recycling the valuable metal from alloy scraps by liquid metal dealloying can be more efficient and environmentally friendlier comparing to traditional alloy treatment processes for metal recovery. Manufacturing of nano-porous materials by liquid metal dealloying, not only can meet the need for efficient production of less noble metal nano-porous materials, but also can precisely control the morphology of the nano-pores by adjusting the dealloying conditions. This review demonstrates that liquid metal dealloying opens new avenues for the recycling of alloy scraps and for the fabrication of nano-porous metals, in addition to a wide variety of other promising applications.

Selective liquid phase micro-extraction of metal chloro-complexes from saline waters using ionic liquids

Existing methods for the extraction of priority metallic pollutants as Ag, Cd, Cu, Ni and Zn from saline waters present limited efficacy due to the high complexity of the water matrix, which affects metals speciation. There is a lack of reagents for the efficient extraction of the metal chlorocomplexes formed at the natural pH of saline waters, requiring tedious and reagent consuming processes. To develop a simple method for the efficient micro-extraction of metallic chlorocomplexes in saline waters, two task specific ionic liquids (TSILs) are proposed. The TSILs methyltrioctilammonium hexylsulfanyl acetate ([N1888][C6SAc]) and methyltrioctilphosphonium hexylsulfanyl acetate ([P1888][C6SAc]) have been supported on a solvent bar micro-extraction (SBME) device and applied to the micro-extraction of Ag, Cd, Cu, Ni and Zn from seawater, as well as inland and marshland salt-pan waters. The extraction efficacy was related with the formation of negatively charged chlorocomplexes, being higher for Cd, Ag and Zn than for Cu and Ni. Concluding, the proposed methodology can be considered as a valuable and simple tool for the selective extraction of metals from saline and hypersaline natural waters.

Thermal stability and specific heats of coordinating ionic liquids

Ionic liquids (ILs) have been revealed as promising solvents, namelly for the selective extraction of metals from aqueous solutions. ILs extractive properties can be trimmed but to do that in a programmed and educated way it is necessary to know their basic properties. The range of temperature in which they can be used as solvents as well as their specific heat, necessary to perform thermodynamic calculations with them, are fundamental properties needed to achieve this desideratum. Thus, the goal of this work has been the study of the thermal stability and specific heats of five ionic liquids that proved to be good extractive solvents.

Morphology, Modification and Characterisation of Electrospun Polymer Nanofiber Adsorbent Material Used in Metal Ion Removal

Among a wide range of technologies available to separate metal ions, adsorption is a major treatment technique for removing or recovering metals from aqueous solutions. Electrospun nanofiber adsorbents have attracted research consideration due to the distinctive properties such as their high surface area, high porosity and high adsorption capacity which makes nanofibers a good choice for selective metal recovery applications. Thus, the modification of electrospun nanofiber adsorbents by functionalisation with suitable ligands for selective metal extraction is a growing area of scientific research aiming to improve the selectivity of the adsorption process. This study reviews and summarises available information related to the different nanofiber modification processes for increasing adsorption efficiency, functionality and selectivity of modified nanofiber adsorbents as well as improving their durability and stability during use. The surface properties of an adsorbent is an essential control factor for its metal ion adsorption efficiency. The various techniques available for characterisation of specific properties of nanofiber adsorbents are also considered. Lastly, the recovery of the metal ions after adsorption by regenerating adsorbent materials and understanding the kinetics of nanofiber adsorption processes is summarised and recommendations made for further studies in order to address existing weaknesses of these materials.

A formulator’s cut of the phase prism for optimizing selective metal extraction

Solvent-based liquid-liquid extraction and stripping is the key separation method at the basis of all hydrometallurgical processes, such as those used to retrieve strategic metals from ores or waste material. During formulation of an efficient extraction system, chemical engineers often encounter instabilities and the formation of undesired phases. In order to avoid the appearance of those in practice, we propose a simple and convenient approach of the phase diagram, based on mole ratio of cations as the variable that controls interfacial curvature. The proposed formulator’s cut through the Gibbs phase prism is more adapted than fish-cuts or similar ones in the case of extraction and stripping formulation optimized against variation in the feed composition.

Preparation of hollow mesoporous carbon spheres and their performances for electrochemical applications

Hollow carbon materials have received intensive attention for energy storage/conversion applications due to their attractive properties of high conductivity, high surface area, large void and short diffusion pathway. In this work, a novel hollow mesoporous material based on carbide-derived carbon (CDC) is presented. CDC is a new class of carbon material synthesized by the selective extraction of metals from metal carbides. With a two-stage extraction procedure of carbides with chlorine, firstly hybrid core-shell carbon particles were synthesized, i.e. mesoporous/graphitic carbon shells covering microporous/amorphous carbon cores. The amorphous cores were then selectively removed from particles by a careful oxidative treatment utilizing its low thermal characters while the more stable carbon shells remained, thus resulting hollow particles. The characterization methods (e.g. N2 sorption, Raman spectroscopy, temperature-programmed oxidation and SEM) proved the successful synthesis of the aspired material. In electric double-layer capacitor (EDLC) testing, this novel hollow core material showed a remarkable enhancement of EDLC’s rate handling ability (75% at a high scan rate) with respect to an entirely solid-mesoporous material. Furthermore, as a fuel cell catalyst support the material showed higher Pt mass activity (a factor of 1.8) compared to a conventional carbon support for methanol oxidation without noticeably decreasing activity in a long-term testing. Therefore, this carbon nanostructure shows great promises as efficient electrode materials for energy storage and conversion systems.

Directions for improvement of mechanochemical processes of utilizing ore tailings

Аbstract. The article is devoted to the problem of waste-free extraction of metals from the tailings of primary ore processing. It represents a generalized approach of development of a mechanochemical technology of metal extraction by leaching in disintegrator and includes a summary of existing views on the problem, an analysis of prospects of the technology and the real steps taken in this direction. In the article, the theory and practice of mechanochemical extraction of metals from ores is examined and the assessment of the existing state of subject matter is given. The essence of the problem is that for the expansion of applications of the recommended technology, it must be improved. The article includes an introduction, a purpose statement and the results of improvement on the level of patents in Russian Federation. The article highlights the problems of increasing the speed and fullness of the extraction of metals remaining after primary processing by traditional beneficiation methods, provides arguments and scientific description of the new methods of intensification of metal leaching in a disintegrator. Particular attention is paid to the effectiveness of combination of the methods of interaction with a mineral in order to increase the degree of extraction which allows to reduce operating costs. The essence of the above is the following: the scope of application of the breakthrough technology of waste-free metal extraction from deadstock poor raw materials can be improved by the use of new and prospective technologies based on the increase of process energetics. The main significance of the study lies in the experimental confirmation of the phenomenon of wastefree metal extraction into bulk concentrate by repeated activation in a disintegrator. The study’s advantage is the argument for the need of development of the new technology in order to gain economic, environmental and strategic benefits. The study is pioneering. It opens up a cluster of new problems, for example, selective extraction of metals from a collective solution, optimizing the resistance of the working body of disintegrator, utilizing master solutions, etc.