Metal Dissolution Research Articles

Sequential Selective Dissolution of Coinage Metals in Recyclable Ionic Media.

Coinage metals Cu, Ag, and Au are essential for modern electronics and their recycling from waste materials is becoming increasingly important to guarantee the security of their supply. Designing new sustainable and selective procedures that would substitute currently used processes is crucial. Here, we describe an unprecedented approach for the sequential dissolution of single metals from Cu, Ag, and Au mixtures using biomass-derived ionic solvents and green oxidants. First, Cu can be selectively dissolved in the presence of Ag and Au with a choline chloride/urea/H2O2 mixture, followed by the dissolution of Ag in lactic acid/H2O2. Finally, the metallic Au, which is not soluble in either solution above, is dissolved in choline chloride/urea/Oxone. Subsequently, the metals were simply and quantitatively recovered from dissolutions, and the solvents were recycled and reused. The applicability of the developed approach was demonstrated by recovering metals from electronic waste substrates such as printed circuit boards, gold fingers, and solar panels. The dissolution reactions and selectivity were explored with different analytical techniques and DFT calculations. We anticipate our approach will pave a new way for the contemporary and sustainable recycling of multi-metal waste substrates.

Sequential Selective Dissolution of Coinage Metals in Recyclable Ionic Media

AbstractCoinage metals Cu, Ag, and Au are essential for modern electronics and their recycling from waste materials is becoming increasingly important to guarantee the security of their supply. Designing new sustainable and selective procedures that would substitute currently used processes is crucial. Here, we describe an unprecedented approach for the sequential dissolution of single metals from Cu, Ag, and Au mixtures using biomass‐derived ionic solvents and green oxidants. First, Cu can be selectively dissolved in the presence of Ag and Au with a choline chloride/urea/H2O2 mixture, followed by the dissolution of Ag in lactic acid/H2O2. Finally, the metallic Au, which is not soluble in either solution above, is dissolved in choline chloride/urea/Oxone. Subsequently, the metals were simply and quantitatively recovered from dissolutions, and the solvents were recycled and reused. The applicability of the developed approach was demonstrated by recovering metals from electronic waste substrates such as printed circuit boards, gold fingers, and solar panels. The dissolution reactions and selectivity were explored with different analytical techniques and DFT calculations. We anticipate our approach will pave a new way for the contemporary and sustainable recycling of multi‐metal waste substrates.

Investigation of the effect of mechanical activation on nickel and cobalt extraction from laterite at atmospheric pressure by kinetics and leach residue analysis

ABSTRACT Nickel and cobalt extraction from laterite has been studied for years but has not been investigated enough by leach residue analysis. Also, the kinetic approach and leach residue analysis become important when mechanical activation improves nickel and cobalt extraction. Various kinetic assumptions were applied to understand the dissolution behaviour of Ni, Co, and Fe. The ore was activated mechanically in a planetary ball mill as a pre-treatment. The effects of liquid-to-solid ratio, acid ratio, leaching time, and temperature on the leaching of non-activated ore were studied to fix the parameters for the leaching of pre-treated ore. Leaching efficiencies of activated ore for 15 and 60 min exhibited better results at lower temperatures and shorter times than non-activated ore. Nickel extraction has 70% efficiency for 5 min leaching at 95°C in mechanically activated ore. Besides higher dissolution efficiency, apparent activation energy (Ea) decreased. Dissolution of metals from non-activated and activated ore was found to be mixed-controlled. Two different diffusion-controlled mechanisms that differ in the diffusion coefficient-time relationship were detected. An analysis of leach residue supported this finding.

Investigation on microstructure and mechanical properties of GH5188 superalloy TLP joints using nickel based alloy interlayer

GH5188 was bonded successfully with a commercial BNi-2 interlayer through transient liquid phase (TLP) diffusion bonding. The characteristic bonded joint was formed by following three characteristic zones: diffusion affected zone (DAZ) mainly consisting of boride precipitates, athermal solidification zone (ASZ) composed of multiple silica-boride phases and isothermal solidification zone (ISZ) containing γ solid solution phases. As the holding time increases, ISZ gradually replaced ASZ and a defect-free joints was obtained then. However, excessive holding time can cause ASZ to reappear because of the extravagant dissolution of the base metal. The joints’ shear strength from 574 MPa (1190 °C/5 min) increased to 777 MPa (1190 °C/60 min), and the fracture location shifted from ASZ to DAZ with the fracture mode transferred from cleavage fracture to mixed fracture.

Sustainable release of borate- and nitrate- electrolyte additives via metal-organic frameworks nanocapsules for stable lithium metal batteries

Constructing robust electrolyte interphase through inorganic electrolyte additives is an effective strategy to improve the electrochemical performance of lithium metal batteries (LMBs). However, the limited solubility of such additives in electrolyte hinders their further application. Herein, we apply metal–organic frameworks (MOFs) as nanocapsules to sustainably release lithium nitrate (LiNO3) and a novel salt of potassium tetraborate (K2B4O5(OH)4). LiNO3 is inclined to undergo reduction on lithium anode to form a nitride-rich solid electrolyte interphase (SEI) layer; while K2B4O5(OH)4 preferentially decomposes on high-voltage cathodes to create a boron-rich cathode electrolyte interphase (CEI) layer. Although both salts exhibit poor solubility in commercial carbonate electrolyte, they can be continuously consumed on the electrode surface and concurrently replenished from the nanocapsules during long-term cycling process. As a result, a compact lithium deposition is achieved and the dissolution of transition metals is restrained. Upon the sacrifice of LiNO3 and K2B4O5(OH)4, the lifespan of LMBs is remarkbly improved. The Li||LiNi0.5Co0.2Mn0.3 (NCM523) cells at 4.3 V and Li||LiNi0.6Co0.2Mn0.2 (NCM622) cells at 4.4 V can respectively deliver high capacity retentions of 87 % and 80.1 % for 200 cycles.

A Hydridoaluminate Additive Producing a Protective Coating on Ni‐Rich Cathode Materials in Lithium‐Ion Batteries

AbstractTo enhance the energy density of Li‐ion batteries, high‐capacity and high‐voltage cathode materials are needed. Recently, Ni‐rich layered oxides have attracted attention as they can offer ≈200 mAh g−1 when cycled up to 4.3 V. However, cycling these materials in their full capacity range often leads to excessive reactivity with the electrolyte, resulting in particle cracking, transition metal dissolution, and oxygen loss. In this study, the use of lithium hydridoaluminates as electrolyte additives is explored for lithium‐ion batteries based on nickel‐rich cathode materials. Being mild reducing agents, these additives act as HF scavengers, avoiding transition metal dissolution from the cathode. Additionally, their oxidation results in the formation of an Al‐rich protective layer on the cathode, which dampens the surface reactivity, preventing surface reconstruction and impedance build‐up. This study further stresses the important role of the cathode‐electrolyte interface phenomena on the capacity degradation of Ni‐rich cathode materials and provides a novel avenue for controlling this reactivity, thus extending their cycling life.

Addressing the Reuse of Deep Eutectic Solvents in Li-ion Battery Recycling: Insights Into Dissolution Mechanism, Metal Recovery, Regeneration and Decomposition.

Deep eutectic solvents (DESs) have garnered attention in Li-ion battery (LIB) recycling due to their declared eco-friendly attributes and adjustable metal dissolution selectivity, offering a promising avenue for recycling processes. However, DESs currently lack competitiveness compared to mineral acids, commonly used in industrial-scale LIB recycling. Current research primarily focuses on optimizing DES formulation and experimental conditions to maximize metal dissolution yields in standalone leaching experiments. While achieving yields comparable to traditional leaching systems is important, extensive DES reuse is vital for overall recycling feasibility. To achieve this, evaluating the metal dissolution mechanism can assist in estimating DES consumption rates and assessing process makeup stream costs. The selection of appropriate metal recovery and DES regeneration strategies is essential to enable subsequent reuse over multiple cycles. Finally, decomposition of DES components should be avoided throughout the designed recycling process, as by-products can impact leaching efficiency and compromise the safety and environmental friendliness of DES. In this review, these aspects are emphasized with the aim of directing research efforts away from simply pursuing the maximization of metal dissolution efficiency, towards a broader view focusing on the application of DES beyond the laboratory scale.

Release of nickel and chromium ions from stainless steel brackets as a result of long-term exposure to commonly used toothpaste

Background: Brackets in fixed orthodontic appliances are mostly made from metal or stainless steel. Maintaining oral hygiene by brushing the teeth with toothpaste during orthodontic treatment is important. One of the ingredients in toothpaste, sodium fluoride, can cause degradation of the stainless-steel surface, which has the potential to corrode or release metal elements. Purpose: the purpose of this study is to describe the Nickel and chromium ion release of stainless-steel brackets against toothpaste use in orthodontic treatment by means of narrative review. Review: The main corrosion products of stainless-steel brackets are nickel and chromium. Toothpaste detergents contain sodium lauryl sulfate, which can cause the release of nickel ions due to the presence of sodium ions, which can trigger redox reactions. In addition, the fluoride content will combine with hydrogen to produce hydrofluoric acid, which can damage the oxide layer on orthodontic wires, resulting in the release of metal ions such as nickel and chromium. The effects of the release of these ions can be carcinogenic, cause hypersensitivity reactions, and cause cytotoxicity. Corrosion causes the dissolution of filler metal, resulting in weakened bracket material and increased friction, leading to delayed tooth movement. Conclusion: Toothpaste can affect the release of nickel and chromium ions in stainless steel brackets in the presence of sodium and fluoride.

Synergistic effect of hydrogen bond and carbon coating to suppress the capacity and voltage fading in Li-Rich cathode

The voltage and capacity degradation of high-capacity Li-rich Mn-based (LRM) batteries during cycling have been a formidable barrier to their commercial application. In this study, a modified material coated with 15 nm-thick hydroxy-rich carbon layer (C-LRM) is synthesized by hydrothermal method, and C-LRM-PAA electrode is assembled by combining C-LRM with LiPAA binder. The strong hydrogen bond formed by the rich carboxyl group in LiPAA and the hydroxyl group in C-LRM makes the components of the C-LRM-PAA electrode closely connected to avoid electrode cracking, and the coating of the carbon layer avoids the cracking of the cathode particles. Consequently, this unique combination successfully inhibits transition metal dissolution, diminishes charge transfer impedance, and augments the lithium-ion diffusion coefficient, all of which contribute to suppressing the capacity and voltage attenuation. The electrochemical performance shows that after 200 cycles at 1C, the capacity retention rate increases from 40.8 % to 75.5 %, and the voltage decay rate decreases from 2.925 mV per cycle to 2.135 mV per cycle. This provides a new perspective for the electrode design of high energy density LRM batteries.

Multi-Objective Optimization of the Recovery of Base and Precious Metals from Waste Printed Circuit Boards by Two-Stage Hydrometallurgical Process Using Taguchi-Based Grey Relationship Analysis

This study focused on determining the optimum conditions for the maximum recovery of base and precious metals from printed circuit boards of end-of-life desktop computer motherboards using Taguchi-based grey relation analysis. In the first stage of the two-stage study, optimum conditions were investigated for the dissolution of base metals (copper and zinc) in waste printed circuit boards under high-pressure leaching. The dissolution of base metals was performed based on the L25 orthogonal array designed by Taguchi method. In the second step, designed according to Taguchi L9 orthogonal array to recover gold and silver from the solid remaining from the pressure-leaching process. Optimum combinations of parameters in both stages were determined using the multi-criteria optimization technique grey relationship analysis. In the experiments carried out in the determined optimum combinations, 99.62% of copper, 98.76% of zinc, 99.15 of silver and 85.82% of gold in waste printed circuit boards were recovered.Graphical

Influence of Process Parameters on the Mechanical Properties and Corrosion Resistance of Dissimilar Friction Stir Welded Joints of AA2024-O and AA6061-O Aluminum Alloys

The influence of the process parameters, traverse, and rotational speeds of dissimilar friction stir welded joints of AA2024-O and AA6061-O aluminum alloys on the corrosion resistance was evaluated. Potentiodynamic tests using a 3.5% NaCl solution, open circuit potential, and polarization curves showed the corrosion behavior for the different welding parameters. These data were correlated with those obtained by mechanical tests (microhardness, tensile, and fracture analysis) and microstructure analysis by optical and scanning electron microscopy. It was observed that the combined effect of the parameters influenced the variation of corrosion resistance. This was evidenced mainly by the improvement of corrosion resistance at 1200 rpm–65 mm·min−1, which was related to the tendency of grain size and heat input presented. The corrosive attacks on the welded joints presented greater affectations in the presence of base material 1 (AA6061-O) with higher metallic dissolution. Corrosion attacks abovementioned were presented in different forms, such as pitting, localized, and selective, and they were observed by scanning electron microscopy. Finally, in corrosive and mechanical terms, the best performing condition was 1200 rpm and 65 mm·min−1 compared to the low parameter of 840 rpm and 45 mm·min−1.

Quantitative study on the metal dissolution reaction with multivalent cations by a modified SECM mode: Pure Ti as a case

Metal corrosion exhibits coupled multi-reaction features, making it challenging to quantitatively study the dissolution reaction with variable-valent cations, particularly in valence quantification. This work develops a novel scanning electrochemical microscopy mode and applies it to Ti dissolution study in acidic fluorides. This mode identifies the potential-dependent corrosion reactions and quantifies the valence evolution of Ti from HER to transpassive regions. Results provide direct electrochemical evidence for soluble Ti(z≤3), for the first time, and revise the reported dissolution equation. The proposed mode overcomes the drawbacks of macro-electrochemical analysis based on coupling information and provides an effective quantitation method for anodic reactions.

Chitosan‐Decorated Alumina Hybrid Nanoparticles as Smart Scavengers of HF and Dissolved Transition Metals in Lithium‐Ion Batteries

AbstractLithium‐ion cells encompassing LiPF6 as the lithium salt and high‐voltage (LiNi0.5Mn1.5O4, LNMO) or high‐capacity (LiNi0.8Mn0.1Co0.1O2, NMC811) cathode materials are prone to transition metal (TM) dissolution caused by HF, whose formation is catalyzed by H2O traces. TM ions can shuttle to the anodic compartment, increasing the cell degradation rate. Accordingly, specific self‐healing strategies are helpful to develop scavengers able to eliminate HF and absorb TM ions so avoiding their shuttling. In this work, the fabrication and test of a bi‐functional, autonomous scavenging agent made of Al2O3 particles decorated is reported with chitosan. The nanometric Al2O3 core is a trap for HF by chemical bonding. The chitosan coating is acid‐sensitive, and the opening of such a capping layer is triggered in the presence of even small amounts of HF, leading to an efficient TM ion‐trapping. In addition, chitosan is biocompatible, biodegradable, and abundant, which is relevant for design‐for‐recycling scopes. With ≈200 ppm of water in the electrolyte, 12 wt% of scavenger causes, after 200 cycles at 1C, an increase of capacity retention from 73% to 88% for LNMO, and, impressively, from 46% to 84% for NMC811. This autonomous self‐healing mechanism is promising for application in next‐generation smart cells without requiring any external sensing.

Inclusion of Anion Additives in the Inner Solvation Shell to Regulate the Composition of Solid Electrolyte Interphase

AbstractAn innovative approach to electrolyte engineering in carbonate electrolytes is introduced by incorporating high donor number dual anion additives into the conventional electrolyte system (1 M NaPF6 EC:PC). The active engagement of anions in the primary solvation shell effectively hinders the reduction of solvent molecules by reducing the Lowest Unoccupied Molecular Orbital (LUMO) of Na+‐solvent‐anion complex as compared to the LUMO of pure solvents or Na+‐solvent complex. The participation of anions leads to the formation of a thinner and an inorganic‐rich Solid Electrolyte Interphase on the hard carbon anode enhancing Initial Coulombic Efficiency and significantly improving its kinetics. Moreover, the system with dual anion additives exhibits oxidative stability up to 4.5 V, effectively mitigating the undesired side reactions at high voltage operation of the layered sodium nickel manganese oxide cathode. The addition of dual anion additives proves instrumental in suppressing structural degradation and transition metal dissolution during the long cycling performance of the layered oxide cathode in a sodium‐ion full cell. The synergistic effects of this dual anion additive added electrolyte on both the anode and the cathode ultimately ensured prolonged cycling of the sodium‐ion full cell. The electrolyte engineering approach outlined in this study opens the door to advancing next‐generation high‐voltage sodium batteries.

Selective extraction of molybdenum from an industrial powdery tungsten-molybdenum mixture scraps through ultrasonic-assisted electrochemical dissolution mechanism

Extraction and recovery of W and Mo from waste scraps hold significant importance for sustainable resource utilization and environmental protection. Ultrasonic-assisted leaching was demonstrated to be a clean and efficient method for metal dissolution and separation, and the research emphasis of this work was focused on ultrasonic electrochemical behaviors. The HNO3 leaching behaviors of W and Mo under conventional and ultrasonic-assisted processes from powdery W-Mo mixture scraps generated in the powder metallurgy process were investigated. It’s demonstrated that Mo and W can be selectively separated by the regulation of lixiviant concentration and temperature, in which the Mo is converted into the soluble ions (MoO22+) while the W particle is kept in original metallic state and covered with insoluble WO3·H2O. Experiment results indicated that 96.38 % Mo and 8.03 % W were rapidly leached in 2 mol/L HNO3 within ultrasonic-assisted leaching for 10 min at 25 °C, showing a favorable pre-separation effect. Phase transformation and microstructure evolution of the leaching residues under conventional and ultrasonic-assisted leaching processes were analyzed. It’s suggested that Mo can precipitate in the form of molybdenum oxide hydrates, covering the unreacted particle surfaces and further hindering the Mo leaching, especially at higher temperature. This unfavorable situation can be relieved by the introduction of ultrasonic cavitation effect. Importantly, the electrochemical dissolution behaviors of pure W, pure Mo, and W-Mo alloy sheets in HNO3 solution were compared employing the potentiodynamic polarization and electrochemical impedance spectroscopy testing to reveal the ultrasonic intensifying mechanism in this study. Eventually, the ultrasonic electrochemical intensifying mechanism can be referential for the efficient dissolution of metal-based scraps for resource recycling.

Toward High Specific Energy and Long Cycle Life Li/Mn‐Rich Layered Oxide || Graphite Lithium‐Ion Batteries via Optimization of Voltage Window

Li/Mn‐rich layered oxide (LMR) cathode active materials promise exceptionally high practical specific discharge capacity (>250 mAh g−1) as a result of both conventional cationic and anionic oxygen redox. The latter requires electrochemical activation at high cathode potential (>4.5 V vs Li|Li+), though it is accompanied by capacity and voltage fade in the course of continuous release of lattice oxygen, layered‐to‐spinel phase transformation, redox couple shift, as well as transition metal dissolution, whereas the latter is particularly detrimental for graphite‐based anodes due to electrode crosstalk. Herein, the degradation is investigated in LMR || graphite full cells by systematically varying the voltage windows, analyzing electrochemical data and changes at the anode surface. Based on this, the optimal operational voltage window, i.e., upper and lower cutoff voltage (UCV and LCV), is elaborated to finally solve the dilemma of decent cycle life (at high UCVs) and insufficient LMR activation/capacity (at low UCV) and is shown to be superior via distinguishing between formation and postformation cycles of 4.5 and 4.3 V, respectively.

Cu-N Synergism Regulation to Enhance Anionic Redox Reversibility and Activity of Li- and Mn-Rich Layered Oxides Cathode.

Anionic redox chemistry enables extraordinary capacity for Li- and Mn-rich layered oxides (LMROs) cathodes. Unfortunately, irreversible surface oxygen evolution evokes the pernicious phase transition, structural deterioration, and severe electrode-electrolyte interface side reaction with element dissolution, resulting in fast capacity and voltage fading of LMROs during cycling and hindering its commercialization. Herein, a redox couple strategy is proposed by utilizing copper phthalocyanine (CuPc) to address the irreversibility of anionic redox. The Cu-N synergistic effect of CuPc could not only inhibit surface oxygen evolution by reducing the peroxide ion O2 2- back to lattice oxygen O2-, but also enhance the reaction activity and reversibility of anionic redox in bulk to achieve a higher capacity and cycling stability. Moreover, the CuPc strategy suppresses the interface side reaction and induces the forming of a uniform and robust LiF-rich cathode electrolyte, interphase (CEI) to significantly eliminate transition metal dissolution. As a result, the CuPc-enhanced LMRO cathode shows superb cycling performance with a capacity retention of 95.0% after 500 long-term cycles. This study sheds light on the great effect of N-based redox couple to regulate anionic redox behavior and promote the development of high energy density and high stability LMROs cathode.

Nutrient optimization in bioleaching: are we overdosing?

The general trend in biomining (i.e., bioleaching and biooxidation) is the use of media with high concentrations of the nutrients (nitrogen as ammonium, phosphorous as phosphate, and K), which are considered to be essential for microbial growth. The depletion of any of the nutrients would affect negatively the bioleaching (and biooxidation) capacity of the microorganisms, so the formulation of the different media ensures that there is a surplus of nutrients. However, some of these nutrients (e.g., phosphate, K) may be already present in the ore and are made available to the microorganisms when the ore is exposed to the low-pH media used during bioleaching. The effect of phosphate addition (109 mg/L) and depletion on the bioleaching of low-grade sulfidic ore alongside the determination of ammonium (i.e., 25 mg/L, 50 mg/L, 109 mg/L, 409 mg/L, and 874 g/L) requirements were studied. The results of the experiments presented showed that the addition of phosphate did not have any effect on the bioleaching of the low-grade sulfidic ore while the addition of ammonium was necessary to obtain higher redox potentials (>650 mV vs. Ag/AgCl) and higher metal (Co, Cu, Ni, and Zn) dissolutions. Temperature was the factor that shaped the microbial communities, at 30°C, the microbial community at the end of all the experiments was dominated by Acidithiobacillus sp. as well as at 42°C, except when nutrients were not added and Sulfobacillus sp. was the dominant microorganism. At 55°C, DNA recovery was unsuccessful, and at 60°C, the microbial communities were dominated by Sulfolobus sp. In conclusion, the amount of nutrients in bioleaching could be reduced significantly to achieve the redox potentials and metal dissolution desired in bioleaching without affecting the microbial communities and bioleaching efficiencies.

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes in a Localized High‐Concentration Electrolyte

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes in a Localized High‐Concentration Electrolyte

Precycling Strategy in Suitable Voltage to Improve the Stability of Interfacial Film and Suppress the Decline of LiNi0.6Mn0.2Co0.2O2 Cathode at Elevated Temperatures.

Layered ternary oxide LiNixMnyCo1-x-yO2 is a promising cathode candidate for high-energy lithium-ion batteries (LIBs). However, the capacity of LIBs is significantly restricted by several factors, including the repeated dissolution-regeneration of the interfacial film at high temperatures, the dissolution of transition metals, and the increase of impedance. Herein, a new precycling strategy in suitable voltage scope at room temperature is proposed to construct a uniform, thermally stable, and insoluble cathode-electrolyte interface (CEI), which helps to maintain stable cycling performances at high temperatures. Specifically, after 5 precycles in the range of 3.85-4.3 V at room temperature, a CEI layer containing numerous inorganic components and oligomers is formed on the surface of LiNi0.6Mn0.2Co0.2O2. Subsequently, the harmful side reactions are effectively suppressed, endowing the cell with an excellent capacity retention of 84.67% after 50 cycles at 0.5C and 55 °C, much higher than that of 65.61% under the conventional film-forming process conditions. This work emphasizes the crucial role of the precycling strategy in regulating the characteristics of CEI layer on the surface of cathode electrode, opening up a new avenue for the high-temperature application of positive electrodes of LIBs.