Complex Formation Of Ions Research Articles

Tailored proton conductive membranes of PVdF-co-HFP: Investigating the synergistic effects of ammonium tetrafluoroborate and phosphoric acid dopants on dielectric characteristics

This study investigates the structural, thermal, and dielectric properties of pure PVdF-co-HFP matrix and its composite electrolytes, PVdF-co-HFP/NH4BF4[x], both before and after PA doping, using FTIR, SEM, TGA, and dielectric analyses. FTIR spectra reveal characteristic vibrational bands, confirming the presence of various functional groups and phases. SEM images display a smooth and homogeneous surface morphology for pure PVdF-co-HFP, while the composite electrolytes exhibit irregular dispersion of NH4BF4 salt and rougher surfaces upon PA doping. TGA analysis shows that the onset of thermal degradation occurs at approximately 370 ℃ for pure PVdF-co-HFP, while PA-doped samples demonstrate higher decomposition temperatures, exceeding 400 ℃ due to hydrogen bonding and ionic complex formation. The presence of NH4BF4 and PA doping also affects the crystallinity of the PVdF-co-HFP matrix, notably shifting the transition temperatures of the alpha and beta phases. Ionic conductivity measurements indicate that PA doping significantly enhances conductivity by increasing charge carrier concentration and facilitating ion transport. PA-doped PVdF-co-HFP/NH4BF4[10] showed the highest conductivity reaching 1.68 × 10−3 S.cm−1 at 1 MHz and 400 K. Dielectric studies reveal frequency-dependent behavior, with dielectric constant (ε') and loss (ε") showing distinct trends influenced by salt concentration and PA doping. The dielectric tangent loss (tanδ) of PA-doped PVdF-co-HFP/NH4BF4 composite membranes exhibits frequency and temperature dependence. At higher temperatures, tanδ increases with frequency, showing a resonance peak that shifts towards higher frequencies. The study elucidates the impact of PA doping on the structural, thermal, and electrochemical performance of PVdF-co-HFP/NH4BF4 composites, providing insights for their potential applications in advanced electrolyte systems.

Development of an alternative method to quantify H2S: application in wine fermentation.

A colorimetric method for the quantification of hydrogen sulfide (H₂S) produced in microbial fermentations was developed using lead gelled alginate microparticles packed in glass columns. The formation of a lead sulfide complex, between H₂S and lead ion (Pb2+) immobilized on the microparticles, allowed simple and accurate quantification by colorimetry. The microparticle-loaded columns were calibrated and showed significant analytical sensitivity. The calibration curve of the system showed a correlation coefficient (r2) of 0.995 and a detection limit of 1.29 ± 0.02 μg L-1. The application of the columns in laboratory wine fermentations was able to detect variations in H2S production from 10.6 to 23.5 μg L-1 by increasing the sugar content in the medium, and from 10.6 to 3.2 μg L-1 with decreasing nitrogen content in the medium. Validation of the proposed method was carried out by determining H₂S in a vinic fermentation model, the results of which were compared with those obtained using a reference chemical method. The data obtained showed no statistically significant differences between the two methods, confirming the reliability and accuracy of the developed system. © 2024 Society of Chemical Industry.

A novel hydrogel composite of chitosan-phytic acid complex with PAAm: Characterization and adsorptive properties for UO22+and methylene blue

The composite of a polyelectrolyte combination of chitosan and phytic acid (CsPa) and its entrapped form in polyacrylamide (PAAmCsPa) were synthesized. The composites were characterized by a number of methods including ATR-FTIR, SEM-EDX, XRD and XPS. The adsorptive properties of CsPa and PAAmCsPa were analyzed and modelled for UO22+ and methylene blue (MB+). The results showed that the composites exhibited physico-chemical properties that were both inherited from the components as well as unique to them. The isotherms of UO22+ and MB+ were L-type Giles isotherms. The adsorption kinetics followed the pseudo-second-order model, in contrast to the Langmuir model, which predicts first-order kinetics for both species. According to the Weber-Morris model, the nature of the adsorption process was ion exchange and/or complex formation for both composites and ions. The thermodynamics showed that the adsorption process was endothermic (ΔH > 0), with increasing entropy (ΔS > 0) and spontaneous (ΔG < 0). The reusability tests of the composites for UO22+ adsorption showed that the composites were substantially reusable for 6 cycles. The composites were selective for UO22+ over MB+ ions, and UO22+ adsorption increased significantly when MB+ adsorbed composites were used. Reproducible measurements demonstrating the storability of the composites were obtained over a period of approximately one year.

Effects of Heterogeneous Mixing of Imidazolium-Based Ionic Liquids with Alcohols on Complex Formation of Ni(II) Ion.

Understanding the complex formation of metal ions in room-temperature ionic liquids (ILs) is essential for the application of ILs in solvent extraction. Nevertheless, the research on metal complex formation in ILs lags behind other applications. The complex formation equilibria may be influenced by specific interactions among the metal ion, ligand molecule, and IL cation and anion. In the present investigation, the complex formation of Ni2+ with ethanol (EtOH) and methanol (MeOH) molecules in ILs, 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([CNmim][TFSA], where N represents the alkyl chain lengths of 2 and 8) was discussed in terms of the microscopic interactions among alcohol molecules, [CNmim]+ and [TFSA]-, and the mesoscopic mixing states of alcohols in [CNmim][TFSA], with N = 2-12. The microscopic interaction of alcohol molecules with the imidazolium ring H atoms in the ILs was evaluated by using ATR-IR and 1H and 13C NMR spectroscopies. The self-hydrogen bonding of alcohol molecules was clarified from the O-H stretching vibration of alcohol molecules. MeOH molecules can be more strongly hydrogen-bonded with themselves than EtOH molecules due to the less steric hindrance and the weaker dispersion force of MeOH with the IL cation's alkyl chain. In fact, small-angle neutron scattering (SANS) experiments revealed the more heterogeneous mixing of MeOH with the ILs by the self-hydrogen bonding among MeOH molecules than EtOH. The longer the IL cation's alkyl chain, the more the MeOH clusters significantly form. In contrast, the formation of EtOH clusters becomes weaker with elongating the alkyl chain. Ultraviolet (UV)-visible spectroscopic measurements on Ni2+-[CNmim][TFSA]-alcohol solutions with N = 2 and 8 revealed that di-, tetra-, and hexa-alcohol-Ni2+ complexes are formed in both the ILs. With N = 2, the stabilities of Ni2+-EtOH and Ni2+-MeOH complexes are comparable in the IL. However, with N = 8, the complexes are more stable in the EtOH solutions than in the MeOH solutions. This is because the less heterogeneous mixing of EtOH molecules with the IL results in the larger enthalpic contribution in the complex formation, as shown by the thermodynamic parameters estimated by the van't Hoff plots on the stability constants at several temperatures.

Beyond transition block metals: exploring the reactivity of phosphine PTA and its oxide [PTA(O)] towards gallium(iii).

The water-soluble cage-like phosphine PTA (1,3,5-triaza-7-phosphaadamantane) and its phosphine oxide derivative [PTA(O)] (1,3,5-triaza-7-phosphaadamantane-7-oxide) were used to explore their reactivity towards two gallium(iii)-halide precursors, namely GaCl3 and GaI3, for the first time. By using various reaction conditions, a series of N-mono-protonated phosphine salts with [GaCl4]- or [I]- as counterions were obtained in all cases, while the formation of coordinated Ga-PTA and Ga-[PTA(O)] complexes was not observed. All compounds were characterized in solution using multinuclear NMR spectroscopy (1H, 13C{1H}, 31P{1H} and 71Ga) and in the solid state using FT-IR spectroscopy and X-ray crystal diffraction. The new Ga-phosphine salts resulted stable and highly soluble in aqueous solution at room temperature. Density functional theory (DFT) calculations were also performed to further rationalize the coordination features of PTA with Ga3+ metal ion, highlighting that the phosphorus-gallium bond is about twice weaker than the phosphorus-metal bond commonly established by PTA with transition metals such as gold. Furthermore, the mono-protonation of PTA (or [PTA(O)]) makes the formation of ionic gallium-PTA coordination complexes thermodynamically unstable, as confirmed experimentally by the formation of Ga-phosphine salts reported herein.

Controlling the formation of ionic complex vesicles through double-tailed surfactants.

Liposomes are often used in cosmetics since they are naturally derived and have excellent texture enhancing capabilities. However, when preparing them by using phospholipids with unsaturated acyl groups, they easily suffer from oxidative degradation. Accordingly, hydrogenated phospholipids are preferred, however, it is difficult to prepare stable liposomes due to its high gel-liquid crystalline phase transition temperature. On the other hand, although dialkyl dimethyl ammonium type cationic surfactants are widely known to form vesicles, they have rarely been used for skincare products except for water-in-oil type emulsion creams stabilized by organically modified clay minerals. We decided to overcome all of the problems above through ionic complex vesicles formed by double-tailed cationic and anionic surfactants. Distearyl dimethyl ammonium chloride (DSAC) and sodium dilauramidoglutamide lysine (DLGL) were selected as cationic and anionic surfactants, respectively. Differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SWAXS) measurements were performed to confirm the DSAC/DLGL/water ternary phase diagram. Newly developed ionic complex vesicle formation was confirmed by cryogenic transmission electron microscopy (cryo-TEM). The adsorbed cosmetic film structure on the skin invivo was evaluated through the polarized infrared external reflection (PIR-ER). Finally, a cosmetic lotion formula was developed and the vesicle size was determined by dynamic light scattering (DLS). DSC and SWAXS data indicated that stable vesicles could be obtained at a molar ratio of DLGL to DSAC = 6:4. At this molar ratio, multi lamellar vesicles with diameters less than 100 nm were observed through cryo-TEM. PIR-ER data revealed that the developed vesicles formed a highly perpendicular orientation to the human skin surface. We have succeeded in formulating a cosmetic lotion containing developed vesicles with a mean diameter of 63.2 nm, which was stable over 1 month at 0, 37, and 50°C. Our newly developed vesicles can be easily obtained through a coagulation process. Also, the adsorbed film structure supported by PIR-ER experiments implies that the developed lotion has an excellent texture that is the same as cosmetic lotions containing liposomes. Therefore, it's possible that this ionic complex vesicle could take the place of liposomes.

Experimental and dynamic molecular study of zinc extraction from sphalerite concentrate in ternary deep eutectic solvent

The utilization of deep eutectic solvents (DESs) as a novel class of solvents in metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20–1440 min, 40–100 °C, and 0–24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to improve efficiency substantially. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced zinc efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The sphalerite leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data were in the range of 0.87–0.97 for temperature of 40–100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.

Determination of glycyrrhizic acid as sweeteners by dual-wavelength overlapping resonance Rayleigh scattering

This study used cationic dyes methyl violet (MV) and neutral red (NR) as probes, based on dual-wavelength overlapping resonance Rayleigh scattering (RRS), and designed two highly sensitive methods for the determination of the natural sweetener glycyrrhizic acid (GZA). In the Clark-Lubs buffer solution, when only MV or NR was present in the solution, they formed supramolecular polymers through hydrogen bonding. When adding GZA at different concentrations, the formation of ionic association complexes led to a subsequent decrease in RRS intensity at two wavelengths in the MV − GZA system and NR − GZA system, and the amount of the decline was proportional to the GZA concentration. The linear ranges were determined as 0.1 − 0.6 mg/L and 0.1 − 0.7 mg/L, with correlation coefficients of 0.9972 and 0.9996, and limits of detection were 0.052 mg/L and 0.016 mg/L, respectively. For this study, reaction conditions were optimized, potential interfering substances were investigated, and the mechanisms behind RRS generation and intensity decrease were discussed. The proposed methods were sensitive, fast, time-saving and efficient, and have been successfully applied to licorice and dried ginger decoction analysis, yielding satisfactory results.

Investigation of electrochemical characteristics and nucleation mechanism of cerium influenced by F− in LiCl-KCl-CsCl melts

The present study investigated the influence of F− on the electrochemical characteristics and nucleation mechanism of cerium in LiCl-KCl-CsCl molten salts, a new electrolyte medium for pyroprocessing of spent nuclear fuel with lower melting point that reduces the temperature tolerance demand of operating equipment compared with LiCl-KCl melts. By employing different electrochemical techniques, the electrochemical reaction of Ce(III)/Ce in LiCl-KCl-CsCl melts containing F− was found to be a diffusion-controlled, electrochemical reversible and three electrons transfer redox reaction at 653 K (CCe(III) = 4.94 × 10−2 mol/kg). It was also discovered that exchange current density and the diffusion coefficient of Ce(III)/Ce dropped in the presence of F−, while shifting negatively the equilibrium potential and subsequently resulting in the change of thermodynamic characteristics. The electrodeposition mechanism of Ce was also studied, demonstrating that the nucleation mode of Ce successfully transformed into progressive nucleation when F− was added. The affected electrochemical characteristics and the mechanism of electrodeposition nucleation of Ce in LiCl-KCl-CsCl molten salts at lower temperatures were attributed to the stronger complex ion [CeCl5F]3− formed after the addition of F−, being illustrated by the mathematic analysis of the molten salt structure. The formation of complex ion [CeCl5F]3− provides a new solution to inhibit the dendrite growth issue in the pyroprocessing of spent nuclear fuel at lower temperatures.

Grain boundary complexion modification for interface stability in garnet based solid-state Li batteries

The garnet type solid-state electrolyte (SSE) encounters challenges related to poor interfacial contact with Li metal and dendrite penetration problem. This study addresses these issues by manipulating the surface property of garnet-based LLZTO (Li6.5La3Zr1.6Ta0.4O12) SSE. The manipulation is achieved by varying thickness of Al2O3 atomic layer deposition (ALD), followed by sintering. Research results show that the relative density, ionic conductivity, and hardness of LLZTO are improved while electronic conductivity is reduced due to the formation of multiple complexions at grain boundary (GB). The SSE pellets also demonstrate improved wettability with Li metal, leading to stable galvanostatic Li plating/stripping cycling with low polarization, which allows for batter battery performance than pristine one. The concept of modifying SSE through the grain boundary complexion modification by thin ALD coating for enhancing the dendrite tolerance with better electrochemical properties of SSE may open a new direction for solid state battery research.

Optical activation of implanted lanthanoid ions in aluminum nitride semiconductors by high temperature annealing

Lanthanoid (Ln)-doped aluminum nitride (AlN) semiconductors are one candidate for optoelectric devices and single photon sources, although their optical properties are less understood. We clarify the room temperature optical properties of Ln ion implanted single crystal AlN semiconductors and their changes upon thermal annealing by up to 1700 °C. Photoluminescence (PL), cathodoluminescence (CL), and time-resolved PL for praseodymium (Pr), europium (Eu), and neodymium (Nd) ion implanted AlN are analyzed. Recovery of implantation induced damages and thermal diffusion of implanted Ln ions by thermal annealing are also investigated. Our systematic studies reveal that there is a trade-off between optical activation of implanted Ln ions due to recovery of implantation damage and deactivation (quenching) due to complex formation and aggregation of Ln ions. The PL intensity of implanted Pr ions increases with increasing annealing temperature in the case of high-dose implantation (above 1020 cm-3), whereas it rather decreases in the case of low-dose implantation (below 4 × 1019 cm-3). However, the PL intensity is significantly reduced after annealing at 1700 °C in both cases, indicating that the quenching factor is dominant in this temperature range.

Novel Model for Predicting the Electrical Conductivity of Multisalt Electrolyte Solutions.

This study presents a novel model to predict the electrical conductivity of multisalt electrolyte solutions by incorporating corrections to the ideal behavior due to relaxation and electrophoretic effects. The performance of the model is evaluated by comparing its predictions with the experimental data of 24 multisalt aqueous solutions. The comparison reveals good agreement for solutions with an ionic strength below 1 mol/L without adjusting any parameter to fit to the experimental data. However, the model tends to overestimate the molar conductivity at higher ionic strengths. The discrepancy is attributed to the neglect of the solvent structure and the formation of ion pairs. It has been speculated how the accuracy of the developed model could be improved in relation to these limitations. Furthermore, the performance of the model is rigorously tested in systems with ion complex formation. It has been demonstrated that when the distribution of ion complexes is calculated from a thermodynamic model and then used to predict the electrical conductivity with the developed model, a satisfactory level of accuracy is attained for these systems.

Control over selectivity for demethylation in dolutegravir synthesis in microreactors: Kinetics and mechanisms

Demethylation of DTG-7 (i.e., an intermediate of an anti-HIV medication dolutegravir (DTG)) is the final step in the DTG synthesis, but its reaction network and kinetic investigations have not been reported yet. In this work, we established the reaction kinetic model of this system based on experimental data from microreactors, according with the demethylation mechanism of the complex ion formation and transformation examined by density functional theory (DFT) calculation. Due to limited solubility of the intermediate product (i.e., organolithium), various parameters were screened to reach a high DTG yield of 98.5 % at a residence time of 12 min without microreactor clogging. Detailed kinetic investigation of DTG-7 demethylation and ring-opening side reaction revealed that precise control over the temperature and residence time in the cascade microreactor system facilitated high selectivity and DTG yield with short residence times. Finally, an operating window was established for process optimization based on the kinetic model.

INFLUENCE OF CHEMICAL MODIFICATION ON THE COMPOSITION AND PROPERTIES OF ORGANOMINERAL COMPOSITE MATERIALS

The structure characteristic and polyfunctionality of humic substances makes it possible to obtain new products by chemical modification. The aim of this work is to study the regularities of sodium humate modification processes with phosphogypsum and phosphogypsum with polyacrylamide (PAA) mixture, to establish the composition and properties of obtained organomineral composite materials. Methods. Chemical analysis, infrared spectroscopy, differential thermal analysis and scanning electron microscopy. Results and discussion. The possibility of obtaining new types of products by modifying sodium humate with phosphogypsum and its mixture with PAA is shown. The dependence of the composition and properties of obtained organomineral composite materials on the modifier nature has been revealed. The chemical modification has been shown to increase the content of COOH groups to 0.24 mg-eq/g, phenolic OH groups to 1.83 mg-eq/g, total pores to 0.44 cm3/g, static exchange capacity to 27.25 mg-eq/g, P2O5 to 1.34%, nitrogen up to 1.71% and the humic acid yield - up to 42.83%. The reaction between sodium humate and phosphogypsum proceeds leads to an increase in the content of total, digestible and water-soluble forms of P2O5. Conclusion. It has been established that the use of phosphogypsum for humic substances modification contributes to the phosphorus production waste processing. Organo-mineral materials obtained by modifying sodium humate acquire growth-stimulating, fertilizing, reclamation, water-retaining, and sorption properties. The complexity and multi-component composition of synthesized compositions is determined by DTA, IR, SEM methods. It has been shown that when sodium humate is modified with phosphogypsum, ion exchange reactions and complex formation occur.

Noncovalent Host-Guest Complexes of Artemisinin with α-, β-, and γ- Cyclodextrin Examined by Structural Mass Spectrometry Strategies.

Cyclodextrins (CDs) are a family of macrocyclic oligosaccharides with amphiphilic properties, which can improve the stability, solubility, and bioavailability of therapeutic compounds. There has been growing interest in the advancement of efficient and reliable analytical methods that assist with elucidating CD host-guest drug complexation. In this study, we investigate the noncovalent ion complexes formed between naturally occurring dextrins (αCD, βCD, γCD, and maltohexaose) with the poorly water-soluble antimalarial drug, artemisinin, using a combination of ion mobility-mass spectrometry (IM-MS), tandem MS/MS, and theoretical modeling approaches. This study aims to determine if the drug can complex within the core dextrin cavity forming an inclusion complex or nonspecifically bind to the periphery of the dextrins. We explore the use of group I alkali earth metal additives to promote the formation of various noncovalent gas-phase ion complexes with different drug/dextrin stoichiometries (1:1, 1:2, 1:3, 1:4, and 2:1). Broad IM-MS collision cross section (CCS) mapping (n > 300) and power-law regression analysis were used to confirm the stoichiometric assignments. The 1:1 drug:αCD and drug:βCD complexes exhibited strong preferences for Li+ and Na+ charge carriers, whereas drug:γCD complexes preferred forming adducts with the larger alkali metals, K+, Rb+, and Cs+. Although the ion-measured CCS increased with cation size for the unbound artemisinin and CDs, the 1:1 drug:dextrin complexes exhibit near-identical CCS values regardless of the cation, suggesting these are inclusion complexes. Tandem MS/MS survival yield curves of the [artemisinin:βCD + X]+ ion (X = H, Li, Na, K) showed a decreased stability of the ion complex with increasing cation size. Empirical CCS measurements of the [artemisinin:βCD + Li]+ ion correlated with predicted CCS values from the low-energy theoretical structures of the drug incorporated within the βCD cavity, providing further evidence that gas-phase inclusion complexes are formed in these experiments. Taken together, this work demonstrates the utility of combining analytical information from IM-MS, MS/MS, and computational approaches in interpreting the presence of gas-phase inclusion phenomena.

Morphological transformation of perfluorinated sulfonic acid ionomer via ionic complex formation at a high entropy state

Proton exchange membranes (PEMs) act as conductors in PEM fuel cells (PEMFCs) to transport protons from the anode to the cathode in the membrane electrode assembly (MEA). Because protons are transported via the hydrophilic channels of the PEMs, the morphological control of these channels has been considered a key issue that influences their electrochemical performance. In this study, we propose a simple route that provides fast proton transport pathways via the morphological transformation of hydrophilic channels in a commercially available perfluorinated sulfonic acid (PFSA) ionomer, Nafion®. It is based on the formation of ionic complexes when metallic salts are added during the membrane fabrication process, instead of using PFSA ionomers with tuned chemical structures. The effectiveness of this strategy is theoretically verified by performing molecular simulations for the ionic cluster formation mechanism. The formation of the ionic complexes in a high entropy state is found to be advantageous in decreasing the distance between ionic clusters, improving proton transport efficiency resulting in higher proton conductivity and single cell performance without any additional chemical and processing step causing the production cost increase.

Separation of Phosphorus from Phosphorus-concentrated Steelmaking Slag

Since 10 million tons of steelmaking slag, which contains a few percent of phosphorus, are annually produced, the phosphorus amount in the slag is equivalent to the annual import volume of phosphorus rock in Japan. Therefore, the steelmaking slag is attracting attention as a potential phosphorus resources. Phosphorus-concentrated slag obtained by the dephosphorization reaction between high phosphorus hot metal and oxidizing slag at high temperature contains phosphorous comparable to that of phosphorus rock. However, because of high FeO concentration, it is difficult to use for phosphorus resources directly. In this work, the effects of pH, acid type and leaching method on the dissolution behavior of phosphorus from P-concentrated slag were investigated. As a result, phosphorus dissolution progressed at lower pH, and was promoted by the addition of citric acid, which is known as a chelate former. When nylon mill pot stirring with citric acid and alumina mill pot stirring with nitric acid were compared to impeller stirring, respectively. By combining nylon mill pot stirring and citrate leachate, phosphorus dissolution was accelerated, because the slag was pulverized during stirring and a formation of insoluble metal-phosphate was inhibited by the formation of complex ion between leached metal cation and citrate. When the slag was leached with alumina mill pot while controlling pH by nitric acid, the phosphorus dissolution ratio lowered since phosphorus ion and aluminum ion, which is supplied by the dissolution of pot and crushing ball during leaching, constructed secondary products with low solubility along with other dissolved ions.

Effect of grain boundary atomic density and temperature on symmetric tilt grain boundaries in tungsten: An atomistic study

The grain boundaries (GBs) play an important role in absorbing the point defects (interstitials and vacancies) generated by irradiation, and thus have significant effects on the resistance of materials to irradiation damage. In this work, considering the change of GB atomic density caused by absorbing point defects and irradiation temperature, 19 <110> symmetric tilt grain boundaries (STGBs) in tungsten were systematically studied with different GB atomic densities and different temperatures, based on the Molecular Dynamics simulations. The GBE difference caused by the change of GB atomic density, ΔGBE[n], are different for different STGBs. Our calculations show that the STGBs with large ΔGBE[n] are generally poor sinks for interstitials, while those with small ΔGBE[n] are generally strong sinks. The STGBs acting as strong sinks are generally those high-angle and high-GBE GBs. High temperature may lead to the formation of GB complexions containing local close-packed hexagonal (HCP) or face-centered cubic (FCC) structures at some special STGBs, which is not only related to the preferred lattice misorientations, but also associated with the symmetry of STGBs. These GB complexion transitions may reduce the GBEs of these special STGBs. Compared with GB atomic density, high temperature may significantly further promote the formation of local HCP or FCC structures at these special STGBs. Furthermore, a new GB structure analysis method based on the stacking of effective interstices was proposed to assess the absorption capacity of the 19 STGBs to interstitials. It was found that the absorption capacity of GBs to interstitials is negatively related to effective interstice density, while positively correlated with effective interstice size. This effective interstice analysis method offers a new way to assess the absorption capacity of GBs to interstitials, which is valuable in materials designing of irradiation resistance.

Maximum Impact of Ionic Strength on Acid-Catalyzed Reaction Rates Induced by a Zeolite Microporous Environment.

The intracrystalline ionic environment in microporous zeolite can remarkably modify the excess chemical potential of adsorbed reactants and transition states, thereby influencing the catalytic turnover rates. However, a limit of the rate enhancement for aqueous-phase dehydration of alcohols appears to exist for zeolites with high ionic strength. The origin of such limitation has been hypothesized to be caused by the spatial constraints in the pores via, e.g., size exclusion effects. It is demonstrated here that the increase in turnover rate as well as the formation of a maximum and the rate drop are intrinsic consequences of the increasingly dense ionic environment in zeolite. The molecularly sized confines of zeolite create a unique ionic environment that monotonically favors the formation of alcohol-hydronium ion complexes in the micropores. The zeolite microporous environment determines the kinetics of catalytic steps and tailors the impact of ionic strength on catalytic rates.

КОМПЛЕКСООБРАЗОВАНИЕ ИОНОВ ЖЕЛЕЗА С ГРИБНЫМИ МЕЛАНИНАМИ

The paper presents and discusses the results of experimental studies of the complex formation of iron ions with melanins isolated from forest beech chaga (faqus sylvatica) and birch chaga (betula), which exhibit high antioxidant activity. Melanins were isolated by alkaline extraction and precipitation in an acidic medium. To identify the isolated pigments, their IR and EPR spectra were recorded. The complex formation of iron ions with these melanins was studied by the method of gamma-resonance spectroscopy (GRS). It has been established that fungal melanins are able to effectively bind iron ions both in their two- and three-valence states. It is significant that fungal melanins, like melanins of animal and plant origin, are able to directly bind prooxidant Fe2+ ions and oxidize them to prooxidant inactive Fe3+ with subsequent complexation. The activity of these processes increases as the pH of the reaction medium increases and the suspension is illuminated with visible light.