Dissolution Of Elements Research Articles

A well-matched MgNiO2 surface heterointerface layer to enhance the cycling stability of cobalt-free Li-rich Mn-based cathode materials

The instability of lattice oxygen and the resulting chain reactions mainly originate at the interface between the electrolyte and the outmost surface of Li-rich Mn-based cathode materials (LRM). Although many research works are focused on improving the cycling performances of LRM by surface protection, the issue of voltage fading is still severing. To overcome the challenge, the MgNiO2 surface heterointerface layer is constructed on the surface of cobalt-free LRM to form a heterointerface in this work, which can suppress side reactions at the interface, inhibit the dissolution of Mn elements, enhance the lattice oxygen stability, and stabilize the crystal structure. Benefiting from the above merits, the voltage fading value of the modified sample has been decreased by 28.2%. And the specific capacity retention of the modified sample (92.9%) is significantly higher than that of the pristine sample (80.9%). This work provides a valuable idea for optimizing the surface to improve the electrochemical performance of high-specific capacity Li-rich cathode materials.

Characterization of hollow glass microspheres with potential for regional climate intervention to preserve snow and ice surfaces

Cold regions including the Arctic are warming fast, resulting in increased losses of snow and ice cover. A climate intervention approach, where hollow glass microspheres (HGMs) are applied on snow and ice surfaces such as Artic sea ice has been suggested for ice preservation. HGMs are commercial materials, typically in the 10–200 μm diameter size range. They are very lightweight, highly reflective materials with a high crush strength. It is suggested that through that reflectivity, their application onto snow and ice surfaces can increase the albedo, and thus stabilize snow and ice covers, for example aid the formation of multiyear sea ice. In this study we tested the stability and behaviour of different HGMs under stress conditions to gain knowledge on their potential environmental fate. Stability tests, measured as maintenance of positive buoyancy, during sediment interaction, repeated freezing and thawing and prolonged exposure in seawater showed differences in environmental stability of the tested materials with stability depending on wall thickness and surface integrity. None of the tested materials seemed to be very susceptible to biofouling under the conditions tested. However, leaching of elements, especially Si was observed for some materials, potentially indicating dissolution of the HGMs in seawater over time. Further studies are needed to determine the element dissolution from HGMs and other potential environmental implications such as impacts on organisms. Although this paper is directed towards using HGMs in a local climate intervention application the findings may be of general interest for other uses of HGM materials.

Investigating the possibility of PCCP mortar coating leaching and the impact on drinking water quality

AbstractThe objective of this article was to investigate the potential for the dissolution and leaching of certain chemical elements from the protective mortar coatings of prestressed concrete cylinder pipe (PCCP) into drinking water in the event of leakage and how this might affect the overall quality of the water delivered to consumers. The mortars as linings are also typically used for renovation of old pipes. Samples from three frequently used mortar coating mixtures underwent immersion in water after 28 days of curing and were monitored for 430 days. The water was tested for pH levels and the presence of aluminum, chromium, lead, and iron, in accordance with the standards set for human consumption in Moroccan and other countries such as Australia, Canada, and the United States, as well as organizations such as the European Union and World Health Organization. The results indicate that the highest levels of aluminum, iron, chromium, and lead leaching occurred after the initial contact with water, gradually declining over time. Furthermore, the inclusion of silica fume and fly ash in the coating increases the potential for chemical element leaching. Additionally, preinstallation pipeline washing demonstrates its effectiveness in reducing the leaching of chemical elements into drinking water in the event of leakages. The overall results suggest that the likelihood of contamination of drinking water by leaching of chemical elements from the mortar coating in case of a leakage appears to be negligible under the studied conditions.

Dissolution of Rare Earth Elements Concentrate from Xenotime Sand with Strong Acids

Rare Earth Elements (REE) concentrate from the processing of xenotime minerals still contains a mixture of REE and its impurities, so it requires a further separation process to purify the content of each element. The first step to separating each element of REE is to dissolve the REE concentrate in strong acid as a feed for the liquid-liquid extraction or ion exchange column process. The REE concentrate was dissolved in 3 variations of strong acids, namely hydrochloric acid, nitric acid, and sulfuric acid. XRF and FTIR analyses were done before and after the dissolution process. The results showed that sulfuric acid is the best dissolution reagent for the total rare earth elements (71.75%) but is less selective for separating light REE, heavy REE, and their impurities. Better selectivity for separating light REE and heavy REE is shown by dissolution with nitric acid with dissolution levels of 37.32% and 81.91%, respectively. Meanwhile, hydrochloric acid showed the lowest dissolution results for the total element of REE (63.14%) but had the best selectivity to prevent the dissolving of radioactive elements. The results of the FTIR analysis showed that REE-chloride, REE-nitrate, and REE-sulfate bonds had been formed in each dissolving filtrate.

Elemental dissolution characteristics of granite and gabbro under high-temperature water-rock interactions

In the process of developing hot dry rock (HDR) through enhanced geothermal systems (EGS), it is necessary to inject circulating water to complete thermal energy extraction. However, the injected water will react with the high-temperature rock and produce mineral dissolution, which can destroy the artificial reservoir and affect the development of geothermal energy. To explore the influence of temperature on the solution composition and mineral dissolution after water-rock reaction, this study conducted water-rock interaction experiments on gabbro and granite at different heat treatment temperatures. Subsequently, the changes of solution composition and mineral dissolution with temperature after the reaction were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and XRD. The results demonstrated that Si, Na, Ca, K, Al, and Mg did not enter the aqueous solution at the same dissolution rate. Si was the primary solute in the solution, mainly resulting from the dissolution of quartz, and the dissolution rates of metallic elements were lower. In the granite-water interaction system, metallic elements such as Na, K, Ca, and Al showed a tendency to enter the solution at low temperatures, i.e., 150–180 °C, and the dissolution rate of Si reached its peak when the water was close to the supercritical state. With the increase in temperature, the dissolution rates of Si and metallic elements showed an initial increasing trend followed by a decrease. When water is in the subcritical to the supercritical state, abrupt fluctuations in the physical properties of water can strongly affect the dissolution of minerals or rocks. The results of this study provide insights into rock corrosion fatigue and mineral scaling in EGS water environment.

Element dissolution from Zn-bearing rocks treated with chemical and biotic agents: A prospective circular economy strategy for metal recovery from secondary resources

Calamine susceptibility to dissolution requires a detailed experimental evaluation to uncover an alternative management option for these materials. This study aimed to investigate the (bio)leaching behaviours of Zn/Pb-bearing calamines to quantify their potential as a Zn resource. Chemical treatments, including the application of mineral (H2SO4, HCl and HNO3) and organic acids (citric and oxalic acids), along with biotic treatments involving the bacteria Acidithiobacillus thiooxidans and Pseudomonas fluorescens, were used to analyse the mobilisation mechanisms, namely acidification and complexation. The results showed that HCl and HNO3 were the most efficient chemical agents, with an extraction efficiency as high as 39 % (Zn). A. thiooxidans extracted the largest amount of Zn (40 %), which proves that the efficiency of the biotic process can be nearly the same as that of the chemical process. However, the main mechanism governing element mobility was the pH factor. This study shows the potential of calamines as prospective materials for the recovery of Zn and other elements (Ge, Tl), even in those treatment conditions that require further optimisation.

Ultrasound application in alkaline pretreatment process of spodumene to improve particle floatability

Selective surface dissolution was found to be important in spodumene flotation. In this study, we proposed to introduce ultrasound into the pretreatment process to accelerate particle vibration and cavitation, as well as the migration of mineral surface components to solution. Micro-flotation results showed that the flotation recovery of spodumene can be 86.08% by ultrasound pretreatment, but only 39.30% by traditional mechanical agitation pretreatment. Compared with traditional mechanical agitation, ultrasonic pretreatment can shorten the pretreatment process, reduce the dosage of agents, reduce the mechanical agitation speed, and improve the efficiency of the pretreating process. Inductively coupled plasma analysis showed that, in the ultrasonic system, the amount of Li, Al, and Si species in the solution was twice as much as those in the traditional preprocessing system. Moreover, the scanning electron microscope results demonstrated a larger surface dissolution area in the ultrasonic system. X-Ray photoelectron spectroscopy results showed that the atomic concentration of Si species on the spodumene surface decreased, whereas the relative atomic concentrations of Li and Al species increased, indicating that the ultrasound effect strengthened the selective dissolution of elements on the mineral surface. The high-resolution spectra of O 1s showed that more collectors are adsorbed on the mineral surface treated by ultrasonic pretreatment.

Tailored electronic structure of Ir in high entropy alloy for highly active and durable bi-functional electrocatalyst for water splitting under acidic environment.

Proton exchange membrane water electrolysis (PEMWE) requires an efficient and durable bi-functional electrocatalyst for HER and OER. Herein, we design Ir-based electrocatalyst using high entropy alloy (HEA) platform of ZnNiCoIrX with two elements (X: Fe and Mn). A facile dealloying in vacuum system enables the construction of nanoporous structure with high crystallinity using Zn as a sacrificial element. Especially, Mn incorporation into HEAs tailors the electronic structure of Ir site, resulting in the d-band center being far away from Fermi level. Downshift of the d-band center weakens the adsorption energy with reaction intermediates, which is beneficial for catalytic reactions. Despite low Ir content, ZnNiCoIrMn delivers only 50mV overpotential for HER at -50mA cm-2 and 237mV overpotential for OER at 10mA cm-2 . Furthermore, ZnNiCoIrMn shows almost constant voltage for HER and OER for 100h and high stability number of 3.4×105 nhydrogen nIr -1 and 2.4×105 noxygen nIr -1 , demonstrating exceptional durability of HEA platform. The compositional engineering of ZnNiCoIrMn limits the diffusion of elements by high entropy effects and simultaneously tailors electronic structure of active Ir sites, resulting in the modified cohesive and adsorption energies, all of which can suppress the dissolution of elements. This article is protected by copyright. All rights reserved.

NS-ZnO@P–Zn nanocomposites catalysts with superior photodegradation of methyl orange through in-situ oxidation and pH-mediated dealloying of equiatomic Al50Zn50 precursors

Mediation of solution pH play a vital role of the formation of porous architectures and dealloying the amphoteric Al50Zn50 precursors. Simultaneous active dissolution of Al and Zn elements in the equiatomic AlZn precursors occurs in dealloying solution pH 1, and porous AlZn structure tend to form due to faster dissolution of Al atoms. Rough porous Zn architectures without ZnO form in dealloying solution pH 13.3 accompanying with prevailed Al dissolution. In bulk solution pH 13, nanocomposites consisting of spindle-shaped ZnO on porous Zn (NS–ZnO@P–Zn) form due to near-electrode pH decrease down to stable pH range of ZnO species basing on in-situ pH monitoring results. In-situ oxidation and dealloying of Al50Zn50 precursors under pH mediation can govern the formation of NS-ZnO@P–Zn nanocomposites. Photodegradation performances of methyl orange by NS-ZnO@P–Zn catalysts under visible-light irradiation are much better than porous AlZn and porous Zn catalysts. NS-ZnO@P–Zn nanocomposites with band-gap of 3.10 eV exhibit superior photodegradation efficiency due to photo-induced charge separation.

Experimental Study of the Activation Effect of Oxalic Acid on the Dissolution of Rare Earth Elements in the Typical Diagenetic Minerals of Coal Seams

Rare earth elements (REEs) are considered to be one of the most important metal raw materials, and coal seams are one of the potential sources of REEs. As a low-molecular-weight organic acid, oxalic acid has a strong ability to migrate and dissolve minerals. The coal seam is formed by herbaceous plants and contains more oxalic acid, which may affect the enrichment and transport of REEs during coal formation. Based on the provenance minerals and enrichment carriers of REEs in the coal seam, granite and its weathered minerals (plagioclase, kaolinite, montmorillonite, and quartz) were selected for oxalic acid leaching experiments, to clarify the activation ability of oxalic acid for REEs in coal seams. Experimental results have shown that oxalic acid dissolves minerals and leads to the dissolution and migration of REEs. The higher the concentration of oxalic acid, the stronger the dissolution ability. Each element has a similar dissolution ability in high-concentration oxalic acid solutions, while the ionic radius and electronegativity can cause abnormal distribution of individual elements. The REE dissolution ability in different minerals is controlled by the crystal structure, and the re-adsorption of minerals inhibits the dissolution of REEs in low-concentration oxalic acid solutions. In addition, comparative analysis of REE distribution characteristics in natural water shows that the dissolution and migration of REEs are complexly affected by many factors in addition to pH and fluid environment. Therefore, the activation effect of oxalic acid on REEs in coal seams needs to be further studied.

Study on effect of chloride and temperature on corrosion behavior of CoCrFeMnNi high entropy alloy

The effect of chloride ion concentration and solution temperature on the corrosion behavior of CoCrFeMnNi high entropy alloy (HEA) was studied by electrochemical measurements, atomic force microscope (AFM) and immersion test. The result shows that increasing [Cl-]/[OH-] ratio or solution temperature enhances the electrochemical reaction ability, weakens the protection of passive film, and generates more severe pitting corrosion. The negative impact of temperature on the corrosion behavior of the HEA is more obvious than that of chloride concentration. A synergistic effect is produced between solution temperature and chloride ion concentration, which significantly destructs the denseness of passive film, and greatly decreases the anti-corrosion properties of the HEA. The pits occurred on the HEA could be ascribed to the selective dissolution of Fe, Co and Ni elements.

Effects of NiCl2 and FeCl2 additives on the anodic dissolution behaviours of Inconel 600 in molten LiCl–KCl salts

The anodic dissolution behaviour of Inconel 600 must be elucidated to design an efficient decontamination process for used nuclear steam generator tubes with radioactive nuclide depositions in their surface microcracks. We investigated the effects of NiCl2 and FeCl2 additives in LiCl–KCl eutectic salts on the microstructural changes in Inconel 600 during electrolytic decontamination. A Cr–Fe depletion layer formed on Inconel 600 via Ni reduction at the position where alloying elements oxidised. In the FeCl2-added salt, the selective dissolution of active alloying elements through the grain boundary produced a cavity-cluster layer whose shape was changed using applied electrochemical methods.

Porous V2O3/C composite electrodes derived from V-MOF with advanced performance for Zn-ion battery

Vanadium oxides are promising cathode materials for Zn-ion batteries. However, they are always suffered from inferior performance because of intrinsic sluggish kinetics, poor conductivity and surface elements dissolution. In this work, porous composite of V2O3 nanoparticles embedded in carbon framework is fabricated by pyrolysis of a Vanadium-base MOF. Attributing to the abundant pores, high specific area and conductive carbon framework, the obtained hierarchical composite delivers a high specific capacity of 240 mAh g−1 at 0.5 A g−1 although the content of carbon is up to 50%, and exhibits a good rate performance with 86.6% retention when the current densities increased from 0.5 to 4 A g−1. Moreover, the cycling performance of the composite is much better than that of commercial V2O3.

Double function-layers construction strategy promotes the cycling stability of LiCoO2 under high temperature and high voltage

Lithium cobalt oxide (LCO), as a popular commercial material, can release higher capacity by increasing the charging voltage. However, deep delithiation leads to the dissolution of elements and structural disorder. Meanwhile, high-temperature performance is still in urgent need to be improved in practical application. Here, we use LiNO3, NaF and H3BO3 as raw materials to construct the outer LiF-rich layer and the inner B, F gradient doped hierarchical nanostructures through stirring and calcination. The electrochemically stable LiF-rich surface helps to form a favorable cathode electrolyte interphase (CEI) layer to prevent electrolyte penetration. The gradient doping of B and F in the subsurface region increases the stability of the lattice at high temperature and high potential. The unique structure enables treated LCO to demonstrate stable cycling under high voltage (4.6 V) with a capacity retention of 93.2% after 800 cycles and displayed 95.2% retention for 100 cycles under high temperature (45 °C). The postmortem analyses after long cycles prove the strategy of surface modification helps to protect the structure and reduce adverse reactions. This study provides a simple and extendable method for improving the cycling stability of cathodes at high temperature and high voltage.

Operando kinetics of hydrogen evolution and elemental dissolution Ⅱ: A time resolved mass-charge balance during the anodic dissolution of magnesium with variable iron content

The rates of hydrogen evolution, magnesium (Mg) dissolution and electron exchange were monitored individually, in situ, and in real time during anodic and cathodic polarization of Mg in 0.1 M NaCl. Under all conditions, the anodic charge correlated with Mg2+ dissolution while hydrogen formation was independent and led to insoluble Mg(II) formation. Increased iron (Fe) impurity promoted hydrogen evolution, but was not necessary for the negative difference effect. These results suggest that electrochemical dissolution occurred across an intact Mg(II)-based film, while hydrogen evolution occurred in regions where the film breaks down induced by anodic polarization.

The analysis on creep failure mechanism of nickel-based single crystal superalloys deposited with different molten salts

The creep properties of nickel-based single crystal superalloys under the effect of the Na2SO4 salt and the mixed salts of Na2SO4 and NaCl (75 % Na2SO4 + 25 % NaCl) are investigated in this paper, respectively. The failure mechanism influenced by the γ/γ′ phase evolution and element dissolution is fully discussed through the elemental distribution analysis and the fractographic analysis by Scanning Electron Microscope (SEM) with energy-dispersive spectrometer (EDS). The results show that the existence of NaCl and Na2SO4 result in the appearance of the tearing ridge and the cleavage-like plane, respectively. Thus, the failure of the specimen deposited with Na2SO4 is mainly the cleavage-like fracture, and that of the specimen deposited with mixed salts presents a mixed mode of cleavage-like plane and tearing ridge. According to the EDS analysis, the failure mechanisms of nickel-based single crystal superalloys deposited with different molten salts are determined by its corrosive behaviors. The Na2SO4 is overrun by the sulfidation and oxidation reactions on surface of specimen due to its lower diffusion rate, so the sulphidation attack almost appears on surface and the further permeation is hardly observed. While the existence of NaCl in mixed salts leads to the generation of volatile metal chlorides, which directly promotes the substrate to be exposed in corrosive environment. Therefore, the declination of effective cross-section is the only reason for the fracture of nickel-based single crystal superalloys deposited with Na2SO4, and the mixed mode is presented on the fracture of the specimens deposited with mixed salts.

Efficient Leaching Process of Valuable Elements from Gibbsite Ore Materials in Talet Seleim, Southwestern, Sinai, Egypt Using Green and Ecofriendly Lixiviant Agent: Optimization, Kinetic and Thermodynamic Study

Here, valuable elements in Talet Seleim, Southwestern, Sinai, Egypt was leaching using methanesulfonic acid (MSA) as an environmental-friendly and ecofriendly lixiviant agent. The effects of methane sulfonic acid (MSA) concentration, time of leaching reaction, temperature, liquid/solid ratio (L/S) and stirring speed on dissolution of valuable elements in MSA were studied. The optimized conditions for dissolution of various metals were: methane sulfonic acid concentration; 150g/L, dissolution time; 300 min, temperature; 363K, liquid to solid ratio; 4 ml/g and stirring speed; 400 rpm/min. The dissolution efficiency of Zn, Cu, Ni and Pb are 81.8%, 79.47%, 76.6%, and 70.7%, respectively under the optimal conditions. Different mathematical kinetic models for the dissolution process in MSA were studied since it is very important for economic metal dissolution. The experimental data were best fitted by fitted by pseudo-second-order homogeneous reaction model, whilst lead (Pb) was best fitted the diffusion through the product or ash layer. The activation energies of the dissolution processes of different metals were evaluated. Overall, the MSA leaching system provides an efficient, clean and environmental-friendly method for dissolution of valuable metals. It can be a promising alternative for inorganic acids.

Suppressing the Surface Amorphization of Ba0.5Sr0.5Co0.8Fe0.2O3-δ Perovskite toward Oxygen Catalytic Reactions by Introducing the Compressive Stress.

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite has been recognized as a promising oxygen evolution reaction (OER) catalyst due to its superior intrinsic catalytic activity. However, BSCF suffers from serious degradation during the OER process due to its surface amorphization caused by the segregation of A-site ions (Ba2+ and Sr2+). Herein, we construct a novel BSCF composite catalyst (BSCF-GDC-NR) by anchoring the gadolinium-doped ceria oxide (GDC) nanoparticles on the surface of a BSCF nanorod by a concentration-difference electrospinning method. Our BSCF-GDC-NR has greatly improved bifunctional oxygen catalytic activity and stability toward both oxygen reduction reaction (ORR) and OER compared with the pristine BSCF. The improvement of the stability can be related to that anchoring GDC on BSCF effectively suppresses the segregation and dissolution of A-site elements in BSCF during the preparation and catalytic processes. The suppression effects are ascribed to the introduction of compressive stress between BSCF and GDC, which greatly inhibits the diffusions of Ba and Sr ions. This work can give a guidance for developing the perovskite oxygen catalysts with high activity and stability.

A tough Janus-faced CEI film for high voltage layered oxide cathodes beyond 4.6 V

Cathode electrolyte interphase (CEI) film is suffering from electrochemical disintegration and physical disturbance caused by particles’ volumetric variation while layered oxide cathodes are operated at high voltage. However, most CEI design strategies only focus on the electrochemical stability of the film. Herein a novel tough Janus-faced CEI film with excellent high-voltage stability and ultrahigh Young's modulus ∼ 30 Gpa is in-situ constructed by succinonitrile (SN) and cyclohexylbenzene (CHB) additives. SN is adsorbed on electrode particles due to the coordinative interaction with transition metals, then CHB is electrochemically polymerized generating an outer layer subsequently. This Janus-faced film not only prevents the decomposition of electrolyte and the irreversible phase transition on particles surface, but also suppresses the particles cracking and Co element dissolution. With the multiply protection of this film, the cyclic performances of LiCoO2 and LiNi0.8Co0.1Mn0.1O2 cathodes are remarkably improved, over 500 & 600 cycles at the high voltages of 4.6 & 4.7 V vs. Li+/Li, respectively. This work not only provides a novel design of functional CEI film, but also throws light on other electrochemical protection fields such as metal corrosion.

Optimizing Surface Composition and Structure of FeWO4 Photoanodes for Enhanced Water Photooxidation

AbstractPhotoelectrochemical water splitting is a promising approach to produce green hydrogen using solar energy. A primary bottleneck remains the lack of efficient photoanodes to catalyze the sluggish water photooxidation reaction. Engineering photoabsorbers with a narrow bandgap and suitable band edge can boost the photoelectrochemical performance. Herein, nanostructured iron tungstate (FeWO4) photoanodes are engineered directly on a fluorine doped tin oxide glass substrate via a scalable and ultra‐fast flame synthesis route in 13 seconds. Physiochemical, optoelectronic, and electrochemical properties of these photoanodes are systematically investigated. The key roles of charge transport, transfer, and dissolution of W and Fe ions from the FeWO4 matrix within long‐term performance are revealed. Optimal FeWO4 photoanode with a bandgap of 1.82 eV and a FeOOH/NiOOH co‐catalyst coating shows an improved water photooxidation performance, reaching a photocurrent density of 0.23 mA cm−2 at 1.4 V versus reversible hydrogen electrode in 1 m potassium hydroxide. It further demonstrates relatively good photostability, maintaining ≈96% of photocurrent density after 1‐hour continuous photooxidation, albeit some trace of Fe, W and Ni elements dissolution. Insights on the photooxidation performance of nanostructured FeWO4 provide promising directions for the engineering of small band‐gap catalysts for a variety of photoelectrochemical applications.