Dissolution Of Metal Oxides Research Articles

Enhancing the anodic dissolution uniformity of dendritic-structured refractory high entropy alloys using a split electrolytic cell with a deep eutectic solvent

The attainment of uniform anodic dissolution in dendritic-structured refractory high entropy alloys (RHEAs) during the electropolishing process is essential for their utilization in high-precision components. Nevertheless, the intricate microstructures of these materials impede uniform dissolution, resulting in suboptimal surface quality. In this work, based on a choline chloride-based deep eutectic solvent and suitable polarization parameters selected by linear scanning voltammetry, a split electrolytic cell (SEC) was proposed to alter the traditional integrated electrolytic cell (IEC) to enhance the anodic dissolution uniformity of dendritic-structured RHEAs. A much smoother surface with Ra of 0.233 μm and a smaller height discrepancy of 0.8 μm was obtained, compared to those processed in IEC at the same condition. The non-uniform anodic dissolution was mainly attributed to the cathode-forming (hydroxide ion (OH−), dissolution of tungsten (W) in the dendrite region under the attack by OH−, and the formation of by-product, i.e., the water molecule. The positive impact of SEC on dissolution uniformity could be ascribed to its role in inhibiting OH− from interacting with the anode, as well as to the enhancement of solution acidity on the anode side, which facilitated the dissolution of metal oxides. The suggested reaction pathway was subsequently validated through experiments with controlled water concentration and assessing of electrochemical kinetics. Finally, the effects of SEC under different parameters were demonstrated. This work provides valuable insight into the precise, micro/nanoscale manufacturing and green electrochemical surface finishing of RHEAs in the future.

Strength, microstructure and bonding mechanism of borosilicate glass-to-SA105 carbon steel seals

The bonding strengths, microscopic characteristics and fracture properties of borosilicate glass-to-SA105 carbon steel seals were investigated, and two different glass-to-metal bonding mechanisms were compared. First, a mechanical interlocking mechanism was found via precipitates formed from chemical reactions at the interface of the seal bonded to unoxidized SA105 carbon steel. Second, a transitional layer mechanism was proven by the dissolution of metal oxides, which was on the surface of preoxidized SA105 carbon steel, into the glass. The bonding strength results showed that both mechanisms effectively contributed to the joining of dissimilar phases, but the effect of the latter mechanism was more prominent than that of the former mechanism. Various microstructures and chemical compositions of the surface oxide scales were obtained by applying different preoxidation conditions to SA105 carbon steel. Additionally, different sealing interfaces were reported through this process. The width of the interfacial transitional layer ranged from 0.5 μm to 1.5 μm, and the strength of the seal was closely related to this width. The sealing of SA105 carbon steel that was preoxidized at 800 °C for 30 min with a moderate width of the transitional layer had an optimal shear strength of 25.4 MPa. However, a wide transitional layer composed of the remaining oxide scales deteriorated the strength of the seal. In addition, fracture analysis of the seals after the shear test was conducted, and the intrinsic correlations between the macroscopic shear strength and microscopic bonding mechanism were established. The present work should provide a reference for the characterization of bonding strength in joining dissimilar materials.

Mechanism and technological method of leaching metals from waste lithium-ion batteries by synergistic action of natural organic reductants and mechanochemical method

In this study, litchi peel powder (LPP) was selected as a natural organic reductant to study the mechanism of green leaching of valuable metals from spent lithium-ion batteries (LIBs) by ball milling. LPP and cathode material were co-ball-milled(CBM) with water and then leached, LPP-assisted ball milling reduces the agglomeration tendency of the particles and increases the dispersion. Premixing by CBM makes the LPP and the cathode material fully contracted and tightly fused, and the mechanical force provides the activation energy of the reaction to accelerate the leaching. The leaching rates of Li, Co, Mn and Ni were 99.21 wt%, 96.52 wt%, 98.21 wt% and 94.79 wt% when LPP was added at 0.15 g and only 0.2 mol/L H3Cit was used. Compared with direct leaching, the amount of organic acids was reduced by 86.67 %. The proanthocyanidins contained in the LPP are the key to act as a reducing agent, and proanthocyanidins are the products of the combination of anthocyanins and glycosides. The natural phenolic and ester components in LPP are hydrolyzed into phenolic acids (protocatechulic acid, salicylic acid) and flavonoids (catechins) under the action of H3Cit, which accelerates the dissolution of metal oxides. The mechanism of natural organic reductant in auxiliary ball milling and organic acid leaching was clarified, which provided a new idea for the selection of ball milling auxiliary materials and proposed a economic and environmental protection method to leach valuable metals from spent LIBs.

Hydrological dynamics and manganese mineralization in the wake of the Sturtian glaciation

The Cryogenian Sturtian and Marinoan glaciations stand as the most extreme climate events in Earth history. Intriguingly, large-scale Mn carbonates characterize the nonglacial interlude of this period in South China. The formation mechanism of Mn carbonates and the potential correlation underlying this temporal association remain elusive. Here, we present an integrated petrographic and geochemical study of drill core materials intercepting the Mn-bearing Datangpo Formation. Rare earth element patterns of these Mn carbonates exhibit positive Ce anomalies and a lack of Y anomalies, which differ from those of modern seawater but resemble marine Mn-Fe oxides. These features, combined with negative carbonate carbon isotope compositions (δ13Ccarb as light as −9.9 ‰ VPDB), indicate the presence of oxide precursors and the incorporation of light carbon during Mn-carbonate precipitation. Phosphate oxygen isotope ratios (δ18Op) of HCl-extractable apatite reveal a ∼4 ‰ difference in the average δ18Op between Mn-rich and Mn-poor rocks. We propose that the more positive δ18Op of Mn-rich samples may result from the dominance of phosphate released by reductive dissolution of metal oxides or a heavier oxygen isotope signal of surrounding waters with which isotopic equilibrium has been reached. We further illustrate how marine invasions into coastal anoxic basins could have triggered the formation of Mn oxides and highlight the role of glaciation–deglaciation in the development of giant Mn deposits.

Optimization of on-site wastewater treatment efficiency and recovery based on nutrient mobility and adsorption kinetics modelling using HYDRUS-2D coupled with PHREEQC

A closed-loop on-site wastewater treatment system (OWT) was studied comprising steps of septic tank to remove organics (Biological Oxygen Demand (BOD)), biofiltration clarifier for biological removal of nitrogen (N), phosphorus (P) and BOD, reactive Polonite® filter for chemical adsorption and precipitation removal of dissolved P, and tidal flow constructed wetland (TFCW) sand filter for polishing the effluent to low P and N effluent Swedish standards. The field experimental data that have been used to optimize TFCW design in the numerical modelling using HYDRUS-2D coupled with and without PHREEQC indicated that the adsorption efficiency of the reactive Polonite® adsorbent was nearly double to that obtained in TFCW sand filters for PO4-P (95 %) and Total-P (85 %) removal in summer at a high temperature range (15.4–18.8 °C) and pH range (9.9–10.8). The weaker PO4-P (53 %) and Total-P (25 %) removal efficiency in winter was due to a low temperature (1.5–8.1 °C) and low pH (7.2–7.9). This decrease in pH was attributed to salinity in the domestic wastewater and dilution of rainwater. Modelling results revealed that the transport mechanisms and rate of P adsorption kinetics in the TFCW sand filters enhanced with calcium and iron flow from chemical dissolution in the preceding Polonite® adsorbent was increased with the increase in temperature. However, the P adsorption was less sensitive at high ferrihydrite (Fe(OH)3) dose, suggesting limited effects of cations dissolution and abundance of metal oxides and hydroxide ions at the mineral surface for anions exchange with phosphate for surface complexation. The strategy of combining field data and modelling provided valuable insights for assessing adaptability and optimizing TFCW design under variable fluxes and scenario effects of insulated/uninsulated and dilution by rainwater in cold-climate regions.

Ultrasound-assisted sustainable recycling of valuable metals from spent Li-ion batteries via optimisation using response surface methodology

In this study, the use of response surface methodology was proposed to optimise a novel green leaching process for recovering Li and Co from spent lithium-ion batteries (LIBs), assisted by ultrasonic irradiation and gluconic acid. This work investigated various parameters such as temperature, time, gluconic acid concentration, and ultrasound power (US power). To enhance the interpretability and optimisation of experimental data on metal leaching, the central composed design (CCD) was utilised to establish a predictive model. A statistical analysis using the analysis of variance (ANOVA) test was conducted to validate the quadratic model and determine the significant operating parameters, indicated by p-values (< 0.05). The model exhibited Adj R2 values of 0.98 for Li leaching and 0.96 for Co leaching, respectively. To confirm the results, additional characterisations of the solid residues were performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transformation infrared spectrometer (FT-IR/NIR). The leach liquor was subjected to precipitation and crystallisation methods to recover Li and Co. The purity of Li2CO3 and Co3O4 was confirmed to be ≥ 99% and ≥ 98.8%, respectively, through ICP-OES analysis. Finally, the recovered Li2CO3 and Co3O4 were utilised in a 1:1 molar ratio for regenerating new LiCoO2 cathode materials using a solid-state method. The resulting cathode materials exhibited high purity (≥ 99.43%) as confirmed by ICP-OES analysis. The obtained results demonstrate that ultrasound irradiation significantly enhanced the dissolution of metal oxides within the mixture. Furthermore, gluconic acid exhibited a dual function, acting as both an oxidising and reducing agent. Consequently, this process presents a promising and sustainable alternative for recycling valuable metals from spent LIBs.

Equilibrium, kinetics and thermodynamics of metal oxide dissolution based on CuO in a natural deep eutectic solvent

In the article, results of dissolution of metal oxides using a natural deep eutectic solvent (NDES or NADES) based on betaine, malic acid and ethylene glycol are presented. The obtained deep eutectic solvent was characterised by determining its physicochemical properties including density, viscosity as a function of temperature. The thermal stability of NADES was also determined. For CuO, equilibrium, kinetics, and thermodynamics of the oxide dissolution process in NADES and H2O were determined. Dissolution studies of selected metal oxides including ZnO, MgO, CaO, Fe2O3 in NADES and water were also carried out. It was found that the solubility of the metal oxides was 2 to 100 times higher in NADES compared to the solubility in water, despite the neutral pH of NADES. The study, using XRD and SEM methods, also shows changes in the morphology of particles subjected to dissolution in water and in NADES. The results indicate the possibility of extracting metal oxides by dissolution in NADES.

A study of thermophysical and physicochemical characteristic of the KALLA experiment facility

Activities are currently underway across the world to build heavy liquid metal-cooled reactors. For example, the ALFRED and BREST-OD-300 reactor designs use lead coolant, while the MYRRHA and SVBR-100 reactors use lead–bismuth coolant. The high corrosive and erosive activity of the coolant requires control of oxygen concentration and flow velocity. Due to the complex geometry of the reactors cooling circuit flow, numerical simulation methods are used extensively to justify the operation modes for liquid metal coolants. Correct justification of the complex oxygen transport processes in liquid metals requires the detailed physicochemical computational model, which takes into account the major reactions of oxygen with the coolant and the structural materials.This paper presents a physicochemical model, which includes the following processes: erosion, growth, and dissolution of the two-layer oxide film, precipitation and dissolution of metal oxides in the circuit with subsequent deposition in a filter, and inflow of oxygen by the mass exchanger. The physicochemical model was implemented using the model of passive scalar, which allows simulating the impurity transport in the coolant.Capabilities of the presented model are demonstrated based on the results of investigating thermohydraulic and physicochemical processes at the KALLA laboratory experimental facility. The duration of the simulation is 1000 hr.The spatial distributions of metal oxides concentrations, areas of enhanced erosive activity, as well as mass of oxides deposited in the filter and the amount of oxygen entering the circuit have been obtained. The surface distribution of the oxide film thickness on the test facility surfaces contacting the coolant has also been calculated.Accounting for thermocouples and the manufacturing technology made it possible to improve the accuracy of calculating the thermohydraulic characteristics of the coolant flow compared to earlier studies.

Front Cover: Enhanced Dissolution of Metal Oxides in Hydroxylated Solvents – Towards Application in Lithium‐Ion Battery Leaching (ChemSusChem 15/2023)

Front Cover: Enhanced Dissolution of Metal Oxides in Hydroxylated Solvents – Towards Application in Lithium‐Ion Battery Leaching (ChemSusChem 15/2023)

Enhanced Dissolution of Metal Oxides in Hydroxylated Solvents - Towards Application in Lithium-Ion Battery Leaching.

The recovery of critical metals from spent lithium-ion batteries (LIBs) is rapidly growing. Current methods are energy-intensive and hazardous, while alternative solvent-based strategies require more studies on their 'green' character, metal dissolution mechanism and industrial applicability. Herein, we bridged this gap by studying the effect of dilute HCl solutions in hydroxylated solvents to dissolve Co, Ni and Mn oxides. Ethylene glycol emerged consistently as the most effective solvent, dissolving up to four times more Co and Ni oxides than using aqueous acidic media, attributed to improved chloro-complex formation and solvent effects. These effects had a significant contribution compared to acid type and concentration. The highest Co dissolution (0.27 M) was achieved in 0.5 M HCl in 25 % (v/v) glycerol in water, using less acid and a significant amount of water compared to other solvent systems, as well as mild temperatures (40 °C). This solvent was applied to dissolve battery cathode material, achieving 100 % dissolution of Co and Mn and 94 % dissolution of Ni, following what was concluded to be a mixed mechanism. These results offer a simple alternative to current leaching processes, reducing acid consumption, enhancing atomic efficiency, and paving the way for optimized industrial hydrometallurgical processes leaning to 'greener' strategies.

In This Issue

Dissolution of redox-active metal oxides plays a fundamental role in the environment and technological applications. However, dissolution mechanisms remain poorly understood at nanoscale, particularly the interplay between acidic and reductive ...Iron-based redox-active minerals are ubiquitous in soils, sediments, and aquatic systems. Their dissolution is of great importance for microbial impacts on carbon cycling and the biogeochemistry of the lithosphere and hydrosphere. Despite its widespread ...

Realizing Metastable Cobaltite Perovskite via Proton-Induced Filling of Oxygen Vacancy Channels.

The interaction between transition-metal oxides (TMOs) and protons has become a key issue in magneto-ionics and proton-conducting fuel cells. Until now, most investigations on oxide-proton reactions rely on electrochemical tools, while the direct interplay between protons and oxides remains basically at simple dissolution of metal oxides by an acidic solution. In this work, we find classical TMO brownmillerite SrCoO2.5 (B-SCO) films with ordered oxygen vacancy channels experiencing an interesting transition to a metastable perovskite phase (M-SCO) in a weak acidic solution. M-SCO exhibits a strong ferromagnetism (1.01 μB/Co, Tc > 200 K) and a greatly elevated electrical conductivity (∼104 of pristine SrCoO2.5), which is similar to the prototypical perovskite SrCoO3. Besides, such M-SCO tends to transform back to B-SCO in a vacuum environment or heating at a relatively low temperature. Two possible mechanisms (H2O addition/active oxygen filling) have been proposed to explain the phenomenon, and the control experiments demonstrate that the latter mechanism is the dominant process. Our work finds a new way to realize cobaltite perovskite with enhanced magnetoelectric properties and may deepen the understanding of oxide-proton interaction in an aqueous solution.

Single Step Electrochemical Recovery and Regeneration of Cathode Materials

Sustainable battery production is a major challenge for the future of electrification. The rise in battery usage, particularly in portable electronics and electric vehicles, has led to a massive increase in the demand for critical battery materials. However, global supply has already begun to strain under the increased demand and projections predict that the global demand could easily surpass global supply in a matter of decades.Current battery recycling and recovery techniques for battery components involve multistep regenerative processes through either pyrometallurgical, hydrometallurgical, or direct recycling methods route. Our work demonstrates for the first time, the dissolution and electrochemical deposition of transition metal oxides in the same solvent for sustainable battery material usage and recovery for slurry cast and electroplated Li-ion battery cathodes. Ultra-dense, high-performing, binder and additive free cathodes are formed at the end of the recycling process.This discovery generates high quality energy dense battery cathodes from “end-of-life” batteries and paves the way towards a simplified recycling conditions for more sustainable battery production.

Effect of acid-base properties of zirconium dioxide on dissolution kinetics

The processes of metal extraction from ores, in which metals can often be found as part of oxides and sulphides, involve stages of chemical or electrochemical dissolution. Few publications can be found in the literature that describe detailed research studies looking into how the surface phenomena of d-metal oxides are linked to the acid-base properties and the dissolution mechanics. Consequently, it would be of relevance to establish kinetic relationships of the processes related to the extraction of metals from lean ores and secondary raw materials, leaching and beneficiation, surface etching and purification. This paper describes the results of a study that relied on potentiometric titration in an aqueous solution of potassium chloride to understand the dissolution kinetics of zirconium dioxide suspension. Titration curves were produced for different concentrations of the background electrolyte and pH values and a relationship was established between ZrO2 dissolution kinetics and pH of the medium. Acid-base equilibrium constants were calculated at the metal oxide/electrolyte solution interface. The obtained results were used to analyze the distribution of surface particles that form as a result of hydrogen ions adsorption and desorption. Interpretation of the experimental relationships was based on comparison with theoretical calculations. The authors simulated the dissolution process. The paper demonstrates that metal oxides dissolve in stages, and adsorption complexes form in the process, the composition of which is linked to the surface charge. These findings could be useful when studying the kinetics of d-metal oxides, as well as in practical applications related to the dissolution of transition metal oxides in electrolyte solutions.

Decomposition of Deep Eutectic Solvent Aids Metals Extraction in Lithium-Ion Batteries Recycling.

The application of deep eutectic solvents (DESs) to dissolve metal oxides in lithium-ion batteries (LIBs) recycling represents a green technological alternative to the mineral acids employed in hydrometallurgical recycling processes. However, DESs are much more expensive than mineral acids and must be reused to ensure economic feasibility of LIB recycling. To evaluate DES reusability, the role of the choline chloride-ethylene glycol DES decomposition products on metal oxides dissolution was investigated. The temperatures generally applied to carry on this DES leaching induced the formation of decomposition products that ultimately improved the ability to dissolve LIB metal oxides. The characterization of DES decomposition products revealed that the improved metal dissolution was mainly determined by the formation of Cl3 - , which was proposed to play a pivotal role in the oxidative dissolution of LIB metal oxides.

Demonstration of the model of physicochemical processes in heavy liquid metal cooled reactors in an example of the THEADES experiment simulation

Activities have been currently underway across the world to build heavy liquid metal-cooled reactors. Thus, for example, the ALFRED and BREST-OD-300 reactor designs use lead coolant, while the MYRRHA and CLEAR-I reactors use lead–bismuth coolant. The high corrosive and erosive activity of the coolant requires regulations oxygen concentration (1 ÷ 4E-6 wt.%) and flow velocity (0.5 ÷ 2.5 m/s). Due to the complex geometry of the reactor circulation circuit flow paths, numerical simulation methods are used extensively to justify scheduled modes of operation for liquid metal coolants. Correct justification of the complex oxygen transport processes in liquid metals requires the respective physicochemical computation model, which takes into account the main reactions of oxygen with the coolant and the structural materials.This paper presents a physicochemical model, which includes the following processes: erosion, growth, and dissolution of the two-layer oxide film, coagulation and dissolution of metal oxides in the circuit with subsequent deposition on filtering elements, and inflow from mass transfer apparatuses. StarCCM+, a commercial CFD code, was used as the tool in this study. The physicochemical model was implemented using models of passive impurities, which are used to simulate oxygen transport in the circulation circuit.Capabilities of the presented model were demonstrated based on the results of investigating thermohydraulic and physicochemical processes obtained at the THEADES experimental facility. The duration of the simulation was 1000 h.The distributions of impurity concentrations, increased erosive activity areas, as well as the total amount of oxides deposited on filter and the amount of oxygen entering the circuit have been obtained as a result of the calculations. The surface distribution of the oxide film thickness on the test facility surfaces contacting the coolant has also been calculated. These data can be extrapolated to reactor elements that operate under conditions that are similar to the considered experiment. For example, fuel assemblies.Simulation of thermocouples, as well as taking into account manufacturing technology made it possible to improve the accuracy of calculating the flow’s thermohydraulic characteristics as compared to earlier studies.

Modelling of the Erosive Dissolution of Metal Oxides in a Deep Eutectic Solvent—Choline Chloride/Sulfosalicylic Acid—Assisted by Ultrasonic Cavitation

Here we report on the results concerning the influence of ultrasound on the dissolution process of metal oxides CoO, Ni2O3 and Mn2O3 in choline chloride/sulfosalicylic acid as a deep eutectic solvent. The mechanism of dissolution under cavitation conditions with ultrasonic assistance is described. Theoretical research resulted in equations describing the dissolution process kinetics and linking its basic parameters. Optimal conditions for the most effective ultrasound application were found. Experimental data on dissolution kinetics of metal oxides in deep eutectic solvents was also obtained. It was discovered that experimental data correlates well with theoretical calculations, which confirms the correctness of developing a picture about the physicochemical nature of the process under study.

Speciation of Copper(II)-Betaine Complexes as Starting Point for Electrochemical Copper Deposition from Ionic Liquids.

The application of ionic liquids for the dissolution of metal oxides is a promising field for the development of more energy‐ and resource‐efficient metallurgical processes. Using such solutions for the production of valuable chemicals or electrochemical metal deposition requires a detailed understanding of the chemical system and the factors influencing it. In the present work, several compounds are reported that crystallize after the dissolution of copper(II) oxide in the ionic liquid [Hbet][NTf2]. Dependent on the initial amount of chloride, the reaction temperature and the purity of the reagent, copper crystallizes in complexes with varying coordination geometries and ligands. Subsequently, the influence of these different complex species on electrochemical properties is shown. For the first time, copper is deposited from the ionic liquid [Hbet][NTf2], giving promising opportunities for more resource‐efficient copper plating. The copper coatings were analyzed by SEM and EDX measurements. Furthermore, a mechanism for the decomposition of [Hbet][NTf2] in the presence of chloride is suggested and supported by experimental evidence.

The Initial Surface Structure of Co3O4 as a Factor of Influence on Kinetic Features of the Dissolution of the Solid Phase

Due to the depletion of natural reserves of cobalt-containing ores, it is urgent to optimize the processes of cobalt replenishment, based on the leaching of its compounds, processing of industrial waste, regeneration of cobalt compounds from catalysts. The kinetic characteristics of the dissolution of metal oxides are influenced by the initial state of their surface structure, which requires the accumulation of experimental material and individual targeted studies. The paper presents the results of an experimental study of the surface structure of industrial Co3O4 cobalt oxide samples. The studies were carried out by electron microscopy and X-ray phase analysis and revealed the size and shape of the Co3O4 particles and the nature of their surface distribution. The correspondence of experimental and theoretical data has been established, Co3O4 cobalt oxide has been identified as an α-form of the cubic crystal system. The data obtained are of interest in the study of the effect of the surface characteristics of the solid phase of Co3O4 cobalt oxide on the dissolution kinetics under the chemical and electrochemical influence

The effect of pH and hydrogen bond donor on the dissolution of metal oxides in deep eutectic solvents

pH and hydrogen bond donor type in DESs affects the solubility of metal oxides and selectivity of dissolution.