Oxidation Of Salts Research Articles

Reducing noble metal content in water electrolysis catalysts: A study on high-entropy oxides

This study presents the development of high-entropy oxide (HEO) catalysts based on Iridium-Ruthenium oxides (IrRuOx) for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWEs). By incorporating 3d transition metals such as Fe, Co, and Ni, we achieved catalysts with enhanced performance and stability. Using density functional theory (DFT) calculations, we predicted that HEOs possess a more favorable electronic structure for catalytic reactions. The synthesized rutile-type HEO catalyst (RuIrFeCoNi)O2, created via a molten salt oxidation method, exhibited a low overpotential of 261 mV and excellent cycling stability, maintaining a stable voltage of 1.73 V at 1 A cm−2 over 100 hours of electrolysis. This innovative approach not only reduces noble metal content but also leverages multimetallic synergistic effects to optimize the catalytic performance and stability, offering a promising avenue for the industrial application of acidic water electrolysis in PEMWEs.

Hydroxyl functionalized hexagonal boron nitride quantum dots as nanozyme for pesticides sensing through dual colorimetric and fluorometric platform: A combined experimental and theoretical study

The Hydroxyl-functionalized hexagonal boron nitride quantum dots (h-BN QDs) were synthesized using a hydrothermal technique in a water medium, exhibiting stability in water for over 90 days. The present study demonstrates two simple fluorescence and colorimetric techniques for sensing organophosphorus (OP) and organochloride (OC) pesticides (atrazine, simazine and chlorpyrifos) in an aqueous medium using hydroxyl-functionalized h-BN QDs. The sensing capability of h-BN QDs for these pesticides was determined to be in the range of 5–10 µM using both techniques. The hydroxyl groups on the surface of the QDs enhanced dispersibility and enabled peroxidase-like catalytic activity in acidic conditions. The radical generation using hydroxyl-functionalized h-BN QDs in the presence of H2O2 upon 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) oxidation plays a significant role in the peroxidase reaction. The hydrogen bonding and π-π interactions between the pesticide molecules and ABTS can enhance the pesticide sensing performance. The limit of detection (LOD) using ABTS for atrazine, simazine, and chlorpyrifos was 6.11, 6.56, and 2.47 µM, respectively. Fluorescence sensing, based on a turn ON/OFF mechanism, demonstrated high specificity and sensitivity with LODs of 5.59, 6.45, and 8.08 µM for the same pesticides. The DFT studies revealed non-covalent bonding, such as hydrogen bonding, π-π interactions between the pesticides and the h-BN QDs, indicating binding affinities and stabilization energies of the complexes which can detect pesticides effectively. Atrazine exhibited higher binding affinity towards h-BN QDs, followed by simazine and chlorpyrifos. The h-BN QDs provide a new insight into bonding with pesticides, enhancing the peroxidase mimetic and fluorescence activity.

Structural, magnetic and electrocatalytic properties of rock salt oxide nanofibers (Ni0.2Mg0.2Zn0.2Cu0.2-xCo0.2+x)O produced by air-heated solution blow spinning (A-HSBS) for oxygen evolution reaction

Structural, magnetic and electrocatalytic properties of rock salt oxide nanofibers (Ni0.2Mg0.2Zn0.2Cu0.2-xCo0.2+x)O produced by air-heated solution blow spinning (A-HSBS) for oxygen evolution reaction

Enhanced high-temperature corrosion resistance of Cr-modified phosphate/aluminum powder composite coatings: Mechanisms and thermodynamic insights

Phosphate composite coatings are regarded as one of the tangible solutions for surface protection in salt spray environments, benefiting from their cost-effectiveness and prominent structure stability upon high-temperature exposure. However, rapid curing of these coatings often leads to crack formation, and the underlying corrosion mechanisms in service conditions remain insufficiently understood, limiting their practical applications. In this study, we developed chromium-incorporated phosphate/aluminum powder composite (Cr-P/Al) coatings and evaluated their corrosion resistance under alternating conditions of salt spray corrosion and oxidation at 450 °C. By integrating experimental results, ab initio calculations, and thermodynamic analysis, we demonstrate that the incorporation of Cr significantly enhances the performance of the P/Al coatings. The structural evolution was first revealed that Cr’s modification reduced tensile stress and prevented cracks in the coating. A mixed layer of amorphous oxides and phosphates forms on the surface of the Al powder, providing robust binding strength. A novel corrosion mechanism was identified that Cl2 and volatile chlorides facilitated the removal of Cl-. This process is more ineffective with Cr-P/Al coating, as amorphous Cr oxide has low reactivity at a high log[p(Cl2)] and low log[p(O2)] compared with amorphous Mg and Fe oxide, thereby enhancing the corrosion resistance of the coating. These coating densification methods and corrosion protection mechanisms provide a critical foundation for the future application of phosphate composite coatings.

Effect of feeding amount on tail gas and waste salt obtained from molten salt oxidation process of cation exchange resins

ABSTRACT The effective treatment of spent radioactive ion exchange resins generated during the operation of nuclear facilities is of great significance to reduce its potential hazards to the environment. This work innovatively provides a simple and low-cost molten salt oxidation (MSO) system includes air intake, feeding, waste salt discharge and exhaust gas treatment and analysis system for disposal of spent cation exchange resins (CERs). By studying three feeding amounts that injection of 25 g, 125 g and 1250 g CERs in 10 times under air conditions, the oxidation efficiency of CERs in MSO system was further evaluated. The scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) results indicated the sulfur can be trapped in the melt. Sulfur in functional group can be converted to Na2S and KLi(SO4) via Li2CO3-Na2CO3-K2CO3, which is proved by XRD patterns. The experimental results presented that degradation rates of CERs are 99.31%, 99.80%, and 99.91% in different feeding amounts, respectively. Furthermore, the volume reduction of residue gathered by feeding 1250 g CERs in 10 times was the highest, which can reach 9.19. Therefore, the bench-scale MSO system is a potential and promising treatment for spent CERs volume reduction.

Novel assessment of molten salt oxidation for cation exchange resin treatment: Effective neutralization of sulfurous gas with Li2CO3-Na2CO3-K2CO3 system

The conventional thermal treatment of cation exchange resin substantially releases sulfurous gases, causing significant equipment corrosion and air pollution. In contrast, the Li2CO3-Na2CO3-K2CO3 as an alkaline molten system effectively neutralizes sulfur gas and mitigates waste gas production inherent in thermal oxidation methods. In the molten salt oxidation process, the volume concentration of SO2 was reduced by 81.7 % compared to that in the traditional thermal oxidation process, and this method reduces the generation of hazardous gases such as CO, CH4, and C2H6. The integration of online gas mass spectrometry and phase stability diagrams for carbonate and sulfur interception products demonstrate excellent thermodynamic stability during the molten salt oxidation (MSO) process. Moreover, a more accurate assessment of the acid gas neutralization capacity of the molten salt system is provided, and the acid gas neutralization capacity of the Li2CO3-Na2CO3-K2CO3 carbonate system can reach 82.58 % at 800 °C. The predominant contributors to acid gas neutralization are Na2CO3 and K2CO3, as evidenced by waste salt composition and ternary phase diagrams. The stable presence of Li2CO3 throughout the MSO process contributes to the lowering of the melting point of the carbonate system to 393 °C.

Improvement of ionic conductivity of solid polymer electrolyte based on Cu−Al bimetallic metal-organic framework fabricated through molecular grafting

A composite solid electrolyte comprising a Cu−Al bimetallic metal-organic framework (CAB), lithium salt (LiTFSI) and polyethylene oxide (PEO) was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes. Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.% CAB (PL-CAB-10%) exhibits high ionic conductivity (8.42×10−4 S/cm at 60 °C), high Li+ transference number (0.46), wide electrochemical window (4.91 V), good thermal stability, and outstanding mechanical properties. Furthermore, PL-CAB-10% exhibits excellent cycle stability in both Li−Li symmetric battery and Li/PL-CAB- 10%/LiFePO4 asymmetric battery setups. These enhanced performances are primarily attributable to the introduction of the versatile CAB. The abundant metal sites in CAB can react with TFSI− and PEO through Lewis acid–base interactions, promoting LiTFSI dissociation and improving ionic conductivity. Additionally, regular pores in CAB provide uniformly distributed sites for cation plating during cycling.

The efficient oxidation of waste resins via ternary alkali carbonate: Mechanisms of the Fe3+/Co2+-catalysis for enhanced fixing organic sulfur, iron and cobalt

The development of a highly efficient and cost-effective strategy for the fixation of organic sulfur, as well as radioactive metal nuclides holds great significance in the treatment of organic contaminants. Herein, ternary molten carbonate (Li2CO3-Na2CO3-K2CO3) was used for treating simulated waste resins containing Fe3+ and Co2+ (Fe-Co-CERs). The FT-IR and XPS analysis showed that the significant conversion process of organic sulfur in molten Li2CO3-Na2CO3-K2CO3 was sulfonic acid group (−SO3-) → sulfuryl group (−SO2-) → sulfur bond (−S-). The TG-DTG curves and the activation energy (E) revealed Fe3+ and Co2+ possess self-catalysis during the oxidation of Fe-Co-CERs, wherein distinctly facilitated the decomposition of −SO3- and −S- structures. The produced SO2 was further absorbed by molten carbonate to generate sulfate, which was confirmed by the observed increase in SO42- and the corresponding decrease of CO32–. The conversion of LiNaSO4 to K3Na(SO4)2 revealed that Li2CO3 is to function as a sulfur catcher at temperatures below 400 °C, which then as a crucial heat transfer medium at temperatures above 400 °C. The predominant forms of Fe and Co at 700 °C were primarily Co8FeS8, FeS, and CoS, which underwent oxidation to form CoFe2O4 and CoSO4 at 800 °C. The retention rate of S, Fe and Co reached 94.36 %, 97.48 % and 98.35 %, respectively. This molten salt oxidation (MSO) strategy exhibits promising potential for the treatment of organic contaminants containing sulfur and multiple metal elements.

An Electrochemical Phase Field Model Applied to Molten Salt Dealloying Corrosion of Ni-Alloys

Metal alloys in contact with molten salts are known to corrode via a dealloying process, wherein the less-noble alloy elements (e.g. Cr) are selectively oxidized and dissolved, leaving behind a corroded structure that is enriched in the more-noble elements (e.g. Ni). In some cases, this can lead to molten salt infiltration into the alloy through discrete channels along specific microstructural features (e.g. grain boundaries). However, in other cases the dealloying process promotes a more full-scale attack of the alloy, generating a fine-scale ligament structure. This process can severely degrade the alloy’s structural integrity, which limits the practicality of these material systems in otherwise promising applications (e.g. molten salt-cooled power reactors).The thermokinetic conditions for dealloying corrosion depend on the salt chemistry and the metal microstructure, which together inform the reaction process occurring at their interface. The salt chemistry and oxidant content set the electrochemical potential for selective oxidation of the less-noble elements. The associated oxidation rate is expected to depend on the presence of an interfacial structure (e.g. double layer) and also on the transport rates of reactants towards the interface (e.g. species diffusion in the metal and oxidizer transport in the salt) and reaction products away from the interface (cation transport in the salt). The corrosion rate and morphology will also depend strongly on the rate of transport laterally along the metal-salt interface, since the reorganization of the more-noble species (Ni) towards ligament formation facilitates the attack of the alloy by the corrosive agent. It has been hypothesized that molten salts enhance this rate of solute diffusion along the metal interface.In this work, we propose an electrochemical phase field model to predict the microstructural evolution of model Ni-alloys undergoing dealloying corrosion in molten fluoride salts. The model incorporates metal oxidation and dissolution via experimentally determined redox potentials and activity coefficients for metal species in the molten salt. We show that the corrosion rate and development of pores is strongly dependent on solute transport rates within the metal and also along their solid-liquid interface. In particular, we reveal a mechanism in which grain boundaries couple with the solid-liquid corrosion front to promote rapid dealloying and molten salt attack. Oxidant content in the salt and double-layer formation at the interface are discussed for their roles in setting the electrochemical potential and reaction rate at the metal-salt interface. Finally, we discuss how the model leverages insights from atomistic modeling and highlight key knowledge gaps in the mesoscale modeling of electrochemical molten salt corrosion.

Bionanomining: bioengineered CuO nanoparticles from mining and organic waste for photo-catalytic dye degradation.

The novel bioengineered CuO nanoparticles were successfully synthesized directly using green chemistry, the nontoxic and renewable aqueous extract of waste papaya peel (Carica papaya) as a precursor. The XRD analysis indicated a monoclinic phase of CuO nanoparticles and a size of 20nm, and the optical absorption analysis showed a peak in the 264nm range. In TEM, the morphology of the NPs was observed to be almost spherical with a particle size of 15nm. The CuO nanoparticles showed good efficiency in the degradation of methylene, obtaining up to 50% in 40min using 6mg in 60ml of MB at 10mg/L. The novel presented in this work derives from using rock minerals, from which we have directly obtained copper salt and copper oxide nanoparticles. This process not only utilizes ecological green chemistry but also offers an economic advantage by directly producing nanoparticles from the mineral instead of purchasing costly pure chemical reagents and employing novel nanomaterials to purify wastewater.

Mechanical Properties of Adjacent Pile Bases in Collapsible Loess under Metro Depot

Metro transit construction has begun to develop rapidly in northwest China because of the acceleration of urbanization. Accordingly, metro depots are also regarded as an essential auxiliary facility for stopping, operation, and maintenance of trains. Meanwhile, many commercial buildings are constructed over metro depots to improve the utilization rate of land due to the increasingly scarce urban land resources, known as transit-oriented development (TOD). These buildings have a large covered area and transfer concentrated loads to the bases. Therefore, pile bases under metro depots have the bearing characteristics of undertaking large concentrated loads, while lesser loads are placed on the soil between the adjacent pile bases. Additionally, the main ground in northwest China is collapsible loess, so the collapsibility should also be considered. Based on the above background, this research performed static loading tests with and without immersion in a reduced scale of adjacent pile bases under a metro depot in Xi’an. The remolding process of natural loess could destroy its structure and the anisotropy of natural loess could also affect the test results. Therefore, four kinds of artificial collapsible loess with different mass ratios of barite powder, kaolin, river sand, cement, industrial salt, and calcium oxide were made by the free-drop method. This method could make the artificial loess simulate the structure of natural loess reasonably. Then, the artificial loess with the most similar properties to intact loess was selected by comparison. Finally, static loading tests with this artificial loess were implemented. The results showed that the ultimate bearing capacity was 4.5 kN. At the same time, the axial force decreased along depth, since the pile shaft friction was positive, and the load sharing ratio of pile tip force increased to 0.58 when the load exceeded 4.5 kN in the situation without immersion; the settlement of pile bases increased significantly after immersion, while the negative shaft friction occurred at the depth of −8 cm~−35 cm, and the load sharing ratio of pile tip force reached 0.92.

Carrier-driving CO2 separation by amine-rich membranes with intercalated graphene oxide

Amine-rich facilitated transport membranes (FTMs) attract great interest in intensifying the membrane-based CO2 separation processes. The high-molecular-weight polyvinylamine (PVAm) polymers containing fixed-site carriers of the amino groups were used to prepare highly CO2-permeable membranes. The sterically hindered PVAm polymers of poly(N-methyl-N-vinylamine) and poly(N-isopropyl-N-vinylamine) were obtained by functionalization of PVAm to provide superior CO2 solubility. By loading the mobile carriers of amino acid salt (AAS) and CO2-philic graphene oxide (GO), the prepared FTMs render enhanced CO2 permeance and CO2/N2 selectivity. The d-spacing of 8.8 Å and the ultramicropores of 3.5 Å from GO nanosheets provide the combination of both selective surface flow and molecular sieving mechanisms to achieve improved CO2 permeance and CO2/N2 selectivity. In addition, the intercalation of GO hinders N2 transport through the membrane due to a longer pathway, while the mobile carriers of AAS introduced into the PVAm matrix facilitate CO2 transport through the selective layer. Therefore, the CO2/N2 selectivity of the prepared FTMs was significantly enhanced to 171 based on the intensified carrier-driving transport mechanism. It can be concluded that amine-rich membranes based on both fixed and mobile carriers of the amino groups together with intercalated GO can synergistically improve the CO2/N2 separation performance, and be potentially applied for CO2 capture from flue gas.

ZnO enhanced molten Na2CO3-K2CO3 system for simulated waste resins treatment: Efficient conversion and fixation of organic sulfur and iron(III)

The radioactive spent resins from pressurized water nuclear power plant always contain a significant proportion of 55Fe, which invariably leads to the release of radionuclides and acidic gases if not treated promptly. Herein, an efficient ZnO enhanced molten salt oxidation (MSO) method was established for the removal and fixation of organic sulfur and Fe in simulated radioactive resins containing Fe3+ (Fe-CERs). The existence of Fe3+ facilitates the reaction with O2 to form Fe2O3, which contributes to the fracture of organic skeleton. The comparative study was conducted to explore the impact of ZnO on the oxidation behavior of Fe and S at 600–800 °C. The introduction of ZnO caused the continuous formation of ZnS at 600–700 °C, and the conversion of ZnO at 800 °C indirectly promotes the retention rate of S (85.42 %). The potential conversion of Zn0.73Fe0.27S to ZnS may occur within the temperature range of 700 °C to 800 °C. Additionally, the predominant presence of carbon in residues at approximately 700 °C could exert a stimulating effect on the sulfidation process of Fe2O3 and inhibit the formation of SO2. The coexistence of Fe2O3, carbon and ZnO effectively diminishes H2S and SO2 amounts while further enhancing the fixation of S and Fe. The increase generation of K2SO4, FeS and Fe3O4 leads to a high formation rate of SO42- (79.36 %) and a great retention efficiency of Fe (96.23 %) at 800 °C. The proposed novel MSO method holds promising potential for applications in the treatment of organic contaminants.

An Experimental Approach to Assess Fluorine Incorporation into Disordered Rock Salt Oxide Cathodes.

Disordered rock salt oxides (DRX) have shown great promise as high-energy-density and sustainable Li-ion cathodes. While partial substitution of oxygen for fluorine in the rock salt framework has been related to increased capacity, lower charge-discharge hysteresis, and longer cycle life, fluorination is poorly characterized and controlled. This work presents a multistep method aimed at assessing fluorine incorporation into DRX cathodes, a challenging task due to the difficulty in distinguishing oxygen from fluorine using X-ray and neutron-based techniques and the presence of partially amorphous impurities in all DRX samples. This method is applied to "Li1.25Mn0.25Ti0.5O1.75F0.25" prepared by solid-state synthesis and reveals that the presence of LiF impurities in the sample and F content in the DRX phase is well below the target. Those results are used for compositional optimization, and a synthesis product with drastically reduced LiF content and a DRX stoichiometry close to the new target composition (Li1.25Mn0.225Ti0.525O1.85F0.15) is obtained, demonstrating the effectiveness of the strategy. The analytical method is also applied to "Li1.33Mn0.33Ti0.33O1.33F0.66" obtained via mechanochemical synthesis, and the results confirm that much higher fluorination levels can be achieved via ball-milling. Finally, a simple and rapid water washing procedure is developed to reduce the impurity content in as-prepared DRX samples: this procedure results in a ca. 10% increase in initial discharge capacity and a ca. 11% increase in capacity retention after 25 cycles for Li1.25Mn0.25Ti0.50O1.75F0.25. Overall, this work establishes new analytical and material processing methods that enable the development of more robust design rules for high-energy-density DRX cathodes.

Effect of Cr on the high-temperature corrosion of dissimilar AISI 904L and Inconel 625 joints employed in the coal-fired thermal power plant tubes

ABSTRACT The hot corrosion behaviours of 5-mm-thick plates of dissimilar AISI 904L and Inconel 625 weldments produced by continuous current gas tungsten arc welding process using Ni-Cr-Mo-enriched filler wires (ERNiCrMo-4 and ERNiCrCoMo-1) were investigated. Optical microscopy was used to examine the microstructure of these weldments. The corrosion performance of the weldments and base metals was determined in the mixture of K2SO4 + 60% NaCl molten salt (MS) and air oxidation conditions at 700°C for 50 cycles. The thermogravimetric plots derived the corrosion kinetics of the weldments. The microstructure and the elemental analysis of the scales formed on the corroded samples were evaluated by scanning electron microscopy and energy-dispersive spectroscopy. The phases developed on the oxide layers during the corrosion were analysed using X-ray diffraction. The fusion zones of ERNiCrCoMo-1 weldment and AISI 904L base metal were vulnerable to degradation in the MS environment, causing severe cracks and spallation compared to ERNiCrCoMo-1 weldment.

Understanding the catalysis of chromium trioxide added magnesium hydride for hydrogen storage and Li ion battery applications

This study explores how the chemical interaction between magnesium hydride (MgH2) and the additive CrO3 influences the hydrogen/lithium storage characteristics of MgH2. We have observed that a 5 wt.% CrO3 additive reduces the dehydrogenation activation energy of MgH2 by 68 kJ/mol and lowers the required dehydrogenation temperature by 80 °C. CrO3 added MgH2 was also tested as an anode in an Li ion battery, and it is possible to deliver over 90% of the total theoretical capacity (2038 mAh/g). Evidence for improved reversibility in the battery reaction is found only after the incorporation of additives with MgH2. In depth characterization study by X-ray diffraction (XRD) technique provides convincing evidence that the CrO3 additive interacts with MgH2 and produces Cr / MgO byproducts. Gibbs free energy analyses confirm the thermodynamic feasibility of conversion from MgH2/CrO3 to MgO/Cr, which is well supported by the identification of Cr(0) in the powder by X ray photoelectron spectroscopy (XPS) technique. Through high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) we found evidence for the presence of 5 nm size Cr nanocrystals on the surface of MgO rock salt nanoparticles. There is also convincing ground to consider that MgO rock salt accommodates Cr in the lattice. These observations support the argument that creation of active metal – metal dissolved rock salt oxide interface may be vital for improving the reactivity of MgH2, both for the improved storage of hydrogen and lithium.

Detritiation of the Organic Material in the MSO Process

Tritium is a radioactive isotope of hydrogen, and due to its limited supply and related high price, it is necessary to recover it from tritiated materials via detritiation technologies. The number of tritiated materials arises during fusion. Tritium from fusion reactors is deposited in the outer layer of plasma-facing materials, which must be dealt with during maintenance or decommissioning processes. A second source of waste is laboratory equipment that could be contaminated with tritium. High-temperature treatment in an oxidation environment can achieve the release of tritium from metals or organic materials. The tritiated vapor is then captured in a series of water bubblers and reprocessed into pure T2. One of the high-temperature methods is molten salt oxidation (MSO), which uses high temperatures, alkaline salt, and an oxidative environment for flameless oxidation of different types of waste. This work aimed to simulate the detritiation processes of tritiated organic materials in MSO technology. First, a series of experiments with D2O absorbed in ion resins was conducted. The organic waste was decomposed within the molten salt, and the flue gas was measured to determine the oxidation efficiency. The D2O was captured in a series of water bubblers, and the water was then analyzed with attenuated total reflectance (ATR)–Fourier transform infrared spectroscopy (FTIR). The results showed that all deuterium in the form of D2O was caught in the first water bubbler. The capture efficiency ranged from 22.32% to 61.13%. The lower efficiency capture can be explained as D2O in water can form a HDO molecule and its correct determination is problematic. The second type of experiment was carried out with T2O with an activity of 851 Bq and with tritiated oil with an activity of 2495 Bq. The T2O was added to the set amount of ion resins and dosed into MSO. A peristaltic pump dosed the tritiated oil. The flue gas was measured to determine oxidation efficiency, and the T2O was captured within the water bubblers. The water was analyzed with liquid scintillation spectroscopy. The capture efficiency ranged between 76.42% to 97.87%. The results showed that this technology is suitable for the detritiation of tritiated organic materials.

Enhanced molten salt oxidation effect of nuclear grade cation exchange resin in lithium containing catalytic salt system

The Cation ion-exchange resins (CERs) can be effectively oxidized in molten Li2CO3-Na2CO3-K2CO3, but the high price of Li2CO3 requires further clarification of its necessity in the molten salt oxidation (MSO) process of CERs. In this paper, Li+ ions are introduced into CERs by ion exchange, and the direct oxidation of pure CERs and Li+ doped CERs and the MSO process of Li+ doped CERs in Na2CO3-K2CO3 (Li+ in CERs), pure CERs in Li2CO3-Na2CO3-K2CO3 (Li+ in molten salt) and pure CERs in Na2CO3-K2CO3 (without Li+) were compared. Thermo-gravimetric analyzer (TGA) and gas mass spectrometry data illustrate that the introduction of Li+ can increase the peak content of CO2 and SO2 and reduce the mass of residue. Fourier transform infrared spectroscopy (FT-IR) results reflect that the presence of Li+ can advance the temperature of resin skeleton destruction. Scanning electron microscope (SEM) displays the fracture degree of CERs is more severe in Li2CO3-Na2CO3-K2CO3 than other two systems. X-ray diffraction spectrum (XRD) and the content of carbonate and sulfate are used to analyze the composition of waste salt after MSO. Compared with other two systems, the content of sulfate produced by adsorption of SO2 and residual carbonate are the highest in Li2CO3-Na2CO3-K2CO3. Thermodynamic calculation using HSC chemistry 6.0 evidences that in Li2CO3-Na2CO3-K2CO3, Li2O produced by decomposition of Li2CO3 can provide oxygen ions, while Na2CO3 and K2CO3 can absorb SO2. Changing the oxidation temperature and oxidation time in different systems, the destruction and removal efficiency (DRE) of CERs are comprised. The DRE of Li+ in molten salt can achieve 99.99 % of CERs at a lower oxidation temperature and less oxidation time than other salt systems. In summary, the superiority of Li2CO3 in ternary salts is difficult to replace at present.

Characteristics of Molten Salt Gasification of Waste PVC

Molten salt oxidation is a robust thermal process with the inherent capability to catalytically oxidize the organic compounds while retaining the inorganic ingredients in salt bath. In the present study, molten salt gasification was used for the disposal of waste PVC. The characteristics of molten salt gasification of PVC under different temperatures and air equivalence ratios (ERs) on the gasification characteristics, chlorine retention efficiency, PCDD/F generation, and the distribution of heavy metals such as Cu, Pb, and Zn were investigated. The results showed that increasing the temperature and ER could effectively enhance the yield of gasification gas and carbon conversion efficiency. The highest gasification efficiency of 41.2% was achieved at 750 °C and ER = 0.4, with a gas yield of 0.442 Nm3/kg PVC. Molten carbonates showed an absorption and retention efficiency of more than 99.5% for chlorine under all conditions. Increasing temperature resulted in a significant reduction in the generation of PCDD/F. At 750 °C, the PCDD/F generation was less than 19 pg/g PVC with an I-TEQ of less than 1.4 pg/g PVC, and the ER had a minor effect on PCDD/F. During the molten salt gasification process, most of the heavy metals, such as Cu, Pb, and Zn, were retained in the salt bath.

Enabling High-Performance Layered Li-Rich Oxide Cathodes by Regulating the Formation of Integrated Cation-Disordered Domains.

Layered Li-rich oxide cathode materials are capable of offering high energy density due to their cumulative cationic and anionic redox mechanism during (de)lithiation process. However, the structural instability of the layered Li-rich oxide cathode materials, especially in the deeply delitiated state, results in severe capacity and voltage degradation. Considering the minimal isotropic structural evolution of disordered rock salt oxide cathode during cycling, cation-disordered nano-domains have been controllably introduced into layered Li-rich oxides by co-doping of d0-TM and alkali ions. Combining electrochemical and synchrotron-based advanced characterizations, the incorporation of the phase-compatible cation-disordered domains can not only hinder the oxygen framework collapse along the c axis of layered Li-rich cathode under high operation voltage but also promote the Mn and anionic activities as well as Li+ (de)intercalation kinetics, leading to remarkable improvement in rate capability and mitigation of capacity and voltage decay. With this unique layered/rocksalt intergrown structure, the intergrown cathode yields an ultrahigh capacity of 288.4mAhg-1 at 0.1C, and outstanding capacity retention of ≈90.0% with obviously suppressed voltage decay after 100 cycles at 0.5, 1, and 2C rate. This work provides a new direction toward advanced cathode materials for next-generation Li-ion batteries.