Free Cations Research Articles

Variability and driving factors of the soil saturated hydraulic conductivity along the horizontal and vertical directions in the upper catchment of Benggang

Benggang is a unique soil erosion landform in the subtropical hilly granite area of South China that seriously endangers the local ecology and environment. In this study, a developing Benggang in South China was selected to explore the spatial variability and the driving factors of the soil saturated hydraulic conductivity (Ks). The results demonstrated that the soil properties of Benggang landforms varied with the soil layer depth and slope position. Only the sand content increased with decreasing distance from the collapsing wall, while the soil organic matter (SOM) content, free iron oxide (Fed) content and cation exchange capacity (CEC) exhibited the opposite trend. Particularly, these parameters exhibited the most significant variation between the middle slope (MS) and lower slope (LS) I and II positions. The Ks values at the LS positions were significantly higher than those at the upper slope (US) and middle slope (MS) positions, and the Ks values first decreased and then increased as the soil layer depth increased. Among the slope positions, the variation in Ks values followed the order of LS II > LS I > US > MS. The Ks values in different directions exhibited notable multifractal characteristics, and the heterogeneity was stronger in the vertical direction than in the horizontal direction. The soil Ks values significantly differed between the different directions at four slope positions, and the values along the vertical direction were higher than those along the horizontal direction at the US and MS sites. However, the values along the horizontal direction were higher than those along the vertical direction at the LS I and LS II sites. Especially at the LS II site, the difference in the soil Ks values between the two directions was extremely significant (P < 0.01). The correlation coefficient values between Ks and the number, area ratio and mean volume of soil macropores were > 0.8. Path analysis revealed that the mean volume of macropores was the main factor affecting the Ks variation. The difference in the soil Ks values at the LS positions could effectively explain the mechanism of headward erosion on the Benggang slope. This study provides a theoretical basis for Benggang erosion control and the prevention of soil erosion in South China.

Unimolecular Benzodioxole-based Photoinitiators for Free Radical and Cationic Photopolymerization Under LED Light Irradiation

Compared to amines as coinitiators applied in photopolymerization, benzodioxole derivatives exhibit similar reactivity but less yellowing and lower toxicity. In this paper, a series of unimolecular type II photoinitiators, containing coumarins as chromophores and benzodioxoles as coinitiators, were synthesized. The substituents with different electron donating/withdrawing abilities were designed for systematical investigation of structure-property relationship. Under LED irradiation, the novel photoinitiators can induce not only free radical polymerization of acrylate monomers, but also cationic polymerization of epoxy monomers via radical promoted cationic polymerization mechanism.

Cultivable bacteria in the supraglacial lake formed after a glacial lake outburst flood in northern Pakistan.

Recently, a supraglacial lake formed as a result of a glacial lake outburst flood (GLOF) in the Dook Pal Glacier. Lake debris and meltwater samples were collected from the supraglacial lake to determine bacterial diversity. Geochemical analyses of samples showed free amino acids (FAAs), anions, cations, and heavy metals. Comparable viable bacterial counts were observed in meltwater and debris samples. Using R2A media, a total of 52 bacterial isolates were identified: 40 from debris and 12 from meltwater. The relative abundance of Gram-positive (80.8%) bacteria was greater than Gram-negative (19.2%). Molecular identification of these isolates revealed that meltwater was dominated by Firmicutes (41.6%) and Proteobacteria (41.6%), while lake debris was dominated by Firmicutes (65.0%). The isolates belonged to 14 genera with the greatest relative abundance in Bacillus. Tolerance level of isolates to salts was high. Most of the Gram-positive bacteria were eurypsychrophiles, while most of the Gram-negative bacteria were stenopsychrophiles. Gram-negative bacteria displayed a higher minimum inhibitory concentration of selected heavy metals and antibiotics than Gram-positive. This first-ever study of culturable bacteria from a freshly formed supraglacial lake improves our understanding of the bacterial diversity and antibiotic resistance released from the glaciers as a result of GLOF.

English

The report focused on the extraction of oilseeds of Desbordesia glaucescens (Engl.) Tiegh. from Gabon as well as on the phytochemical study and evaluation of the anti-free radical activity of the extracts obtained. The extraction was carried out by cold maceration with solvents of increasing polarities: hexane, tricholroethylene, acetone, ethanol and distilled water. The anti-free radical activity was measured by scavenging the free radical cation of 2,2&#39;-azinobis [3-ethylbenzothiazolin-6-sulfonic acid] (ABTS &bull; +) with gallic acid as the standard antioxidant. Total extraction yields were in the order of 82.31%. Phytochemical tests demonstrated the presence of secondary metabolites of alkaloids, tannins, polyphenolstypes, reducing compounds, free anthracene derivatives, anthraquinones, total sugars, coumarins, free quinones, sterols and terpenes, carotenoids, flavonoids, cardiac glycosides, mucilages, saponins and leucoanthocyanins. The results of the anti-free radical activity showed that the polar extracts were much more anti-free of the free radicals than the non-polar extracts. The aqueous extract was the most active with an IC50 of 10 &micro;g. mL-1, followed by ethanolic extract with IC50 of 14 &micro;g. mL-1 and acetone extract with IC50 of 150 &micro;g. mL-1. Cyclohexane and trichlorethylene extracts were more or less inactive. Gallic acid, the standard antioxidant, showed an IC50 of 0.37 &micro;g. mL-1. Key words: Desbordesia glaucescens, oil seeds, extracts, phytochemical tests, anti-radical activity, ABTS test.

Thermodynamic and Kinetic Features of Bi3+ Complexes with the Azamacrocycles H4BATA and H4DOTA

AbstractIn current research, we determined the stability constants and kinetic properties of Bi3+ complexes with the benzoazacrown ligand H4BATA along with the H4DOTA ligand. Correct determination of the stability constants is possible when equilibrium with the free forms of the cation is observed. Unlike potentiometric titration, it is possible to apply the free‐ion selective radiotracer extraction (FISRE) method with highly stable complexes at low pH values, where the true equilibrium with the free cation forms in the solution is achieved. FISRE clarified the stability constants of Bi3+ complexes with H4BATA towards higher values. According to the UV spectroscopy data, the H4BATA ligand binds Bi3+ at room temperature within a few minutes at pH 1. We also defined the acid‐assisted mechanism of complex dissociation, where monoprotonated and deprotonated forms of the complex were found to be inert. In summary, the H4BATA ligand is highly suitable for use as a component of bismuth‐based radiopharmaceuticals.

Why Does Ethaline Apparently Behave as an Ideal Binary Mixture?

Phase diagram mixtures of the salt choline chloride (ChCl) with ethylene glycol (EG) surprisingly seem to behave as ideal binary nonelectrolyte mixtures [Agieienko, V.; Buchner, R. Phys. Chem. Chem. Phys.2022, 24, 5265]. To shed some light on this conundrum, results of broad-band dielectric relaxation spectroscopy (DRS) and quantum-chemical calculations are reported for solutions of ChCl, choline iodide (ChI), and chlorocholine chloride (ClChCl), in EG up to saturation at 298.15 K. The data revealed that all three solutes are only weakly solvated in the sense that on average per equivalent of solute only one EG OH-group is dynamically affected. While contact ion pairs are significant for solute concentrations of ≲1 M, free cation concentrations are rather low. Instead, over the entire concentration range a large fraction of the dipolar cations could not be detected by DRS. We argue that the latter are embedded in large solute aggregates, explaining thus the phase diagram of ChCl + EG and the very low ionicity of all systems.

Impact of Ion-Ion Correlated Motion on Salt Transport in Solvated Ion Exchange Membranes.

The influence of dynamical ion-ion correlations and ion pairing on salt transport in ion exchange membranes remain poorly understood. In this study, we use the framework of Onsager transport coefficients within atomistic molecular dynamics simulations to study the impact of ion-ion correlated motion on salt transport in hydrated polystyrene sulfonate membranes and compare with the results from aqueous salt solutions. At sufficiently high salt concentrations, cation-anion dynamical correlations exert a significant influence on both salt diffusivities and conductivities. Anion-anion distinct correlations, arising from the imbalance between the concentration of free (mobile) cations and anions, and the retarding effect of the fixed charge groups on cations, proves to be an additional important feature for polymer membranes. Our results demonstrate that dynamical correlations should become an important consideration in experimental measurements of salt diffusivities and conductivities for non-dilute salt solutions in polymer membranes.

The Transition (vs ΔpKa) from Triple Ions to Free Cations in Poor Protic Ionic Liquids Made from Weak Acids

In mixtures of amines with carboxylic acids, the limited ionicity at 1:1 stoichiometric mixtures is due to insufficient ionization and/or ion pairing in low-dielectric environments. Higher conductivities have historically been seen at 5:1 acid:base mixing ratios, where simulations have revealed large (and thus more stable) ions: homoassociated anions (AH)2A−(HA)3 and cationic triple ions B+(AH)A− (HA)2B+. Recent work in understanding the Gibbs energies for degree-of-ionization equilibria hints that there may be an onset, for systems with an acid-base pKa difference increasing towards 10, for the formation of free (unpaired) protonate-amine ions BH+. The speed (gradual? sudden?) of such an onset with increasing ΔpKa is explored in this work, with the aim of better understanding the limited ionicity phenomenon in protic ionic liquids.

The Transition (vs ΔpKa) from Triple Ions to Free Cations in Poor Protic Ionic Liquids Made from Weak Acids

In mixtures of amines with carboxylic acids, the limited ionicity at 1:1 stoichiometric mixtures is due to insufficient ionization or ion pairing in low-dielectric environments. Higher conductivities have historically been seen at roughly 4:1 acid/base mixing ratios, where simulations have revealed large (and thus more stable) ions: homoassociated anions (AH)(AH)(A−)(HA)(HA) and cationic triple ions (BH+)(AH)(A−)(HA)(HB+). Recent work in understanding the Gibbs energies for degree-of-ionization equilibria hints that there may be an onset, for systems with an acid-base pKa difference increasing towards 10, for the formation of free (unpaired) protonate-amine cations BH+. The transition with increasing ΔpKa is explored in this work, to aid in the prediction of ionicity and conductivity of protic ionic liquids.

Influence Factors in the Wide Application of Alkali-Activated Materials: A Critical Review about Efflorescence.

Applications related to alkali-activated materials (AAMs) have received much attention due to their excellent mechanical properties and low-energy production. Although much research has focused on developing AAMs, their application is still limited. One of the primary reasons is the efflorescence. Not only does efflorescence affect the material aesthetics, but it also affects the mechanical performance, leading to a decrease in material quality. This paper first summarizes the current research on AAMs efflorescence. The formation process of efflorescence is divided into three parts: alkaline cation leaching, air carbonation, and efflorescence formation. Furthermore, the influences caused by different factors, including raw materials, curing conditions, AAMs modalities, etc., on the efflorescence are proposed. This paper highlights the solutions for efflorescence by avoiding free alkaline cation leaching and preventing air carbonation. The advantages and disadvantages of efflorescence are discussed in-depth, showing that it can be exploited under certain conditions, such as in wastewater treatment. This paper has important implications for the practical preparation and application of AAMs.

Interfacial characteristics and mechanical behaviors of geopolymer binder with steel slag aggregate: Insights from molecular dynamics

As a promising sustainable building material, geopolymer/steel-slag composite materials have been poorly known in the field of the interfacial characteristics of geopolymer/steel-slag interface, especially at the molecular level. Herein, in this work, molecular dynamics simulation was employed to reveal the interfacial characteristics and mechanical behaviors of geopolymer binder with steel slag aggregate. The molecular models of two geopolymer binders (C-A-S-H and N-A-S-H) and three main minerals of steel slag aggregate (Ca 2 SiO 4 , Ca 2 Fe 2 O 5 and CaCO 3 ) were constructed and carried out. Then the wetting characteristics of different mineral surfaces, interfacial characteristics, interaction mechanisms and mechanical behaviors of various geopolymer/steel-slag interfacial systems were elucidated and compared. It is found that the Ca 2 SiO 4 , Ca 2 Fe 2 O 5 and CaCO 3 of steel slag aggregate show strong hydrophilicity , attracting water molecules to accumulated on its mineral surface and promoting the diffusion of Ca 2+ and Na + at the interface. The interaction energy of geopolymer/steel-slag systems is mainly composed of electrostatic interaction energy. Thanks to the accumulation of water molecules on the mineral surface, the stronger hydrogen bond interaction occurs at the interface of the geopolymer/steel-slag system. The free metal cations from mineral surfaces and geopolymer binder respectively are coordinated with the accumulated water molecules to emerge hydrated ions , forming composite ionic clusters to stabilize the interfacial interaction . Mechanically, the interaction systems with C-A-S-H binder possess stronger interfacial tensile strength and shear strength. Steel slag with higher Ca 2 SiO 4 content can effectively form strong interfacial bonding , lowering the risk of interfacial tensile failure, whereas steel slag containing more Ca 2 Fe 2 O 5 can reduce occurrence possibility of shearing damage. CaCO 3 formed by carbonization of steel slag, is conductive to strengthening the interfacial interaction with geopolymer binder. • MD simulation can reveal the interfacial behaviors of geopolymer/steel-slag. • The interfacial interaction of geopolymer/steel-slag is mainly composed of electrostatic interaction. • The water molecules at the interface produce hydrogen bond interaction. • The water molecules, Ca 2+ and Na + migrate to the interface to form hydrated ions.

A Cu(II)-organic framework with hxl topology as an efficient adsorbent for methylene blue

The present work demonstrates the synthesis of a Cu-pyrazinedicarboxylate derived coordination polymer (CP), {[Cu(pzdca)2](Me2NH2)2}n (HT-2) (H2pzdca = 2,3-Pyrazindicarboxylic acid). The coordination polymer has been characterized using FTIR, PXRD, TGA, SEM and single crystal X-ray analysis. HT-2 crystallizes in a monoclinic system with the P21/c space group. The asymmetrical unit of HT-2, [Cu(pzdca)](Me2NH2) is composed of single Cu ion, one coordinated linker (pdca2−) and one free dimethyl aminium cation. The coordination sphere of the CP is anionic which is counter balanced by two dimethyl ammonium cations. The crystallography indicates that the structure around Cu2+ ion is octahedral and the topological analysis discloses that the valence-bonded MOFs for the HT-2 results in underlying 2,4-c net with the hxl topology. The present polymer has been assessed for environmental remediation as an adsorbent for hazardous aromatic dyes. The HT-2 effectively adsorbs the cationic dye (MB) from the mixture of the cationic (MB) and anionic (MO) dyes under ambient temperature and pH. Thus, the present CP is an intriguing example of the structure-property relationship for tuning the adsorption capacities towards hazardous environmental pollutants.

Vibrational Study of Mono and Diprotonated Species of Potent Anti-acid Ranitidine Hydrochloride Combining DFT with SQMFF Calculations

Structural and vibrational studies of mono (M) and diprotonated (D) species of ranitidine hydrochloride (RH) have been performed by combining B3LYP/6-31G* calculations with the scaled quantum mechanical force field (SQMFF) methodology. Four M structures in the gas phase and aqueous solution and two D E/Z and Z/E isomers in solution were considered. The M and D free base, cationic, and hydrochloride species show higher dipole moment values and expansion of volumes in solution, while higher solvation energies are predicted for both D (E/Z) and (Z/E) species. NBO and AIM studies suggest high stabilities of D (Z/E) cationic and hydrochloride species in solution. Gap values show that the M and D species are the most reactive in both media. M and two D forms were completely assigned, and their force constants were reported. The D hydrochloride (E/Z) form shows two IR bands at 2718 and 2625 cm-1 assigned to νN6-H34 and νN5-H44 stretching modes where the formation of O3-H34···N6 bond justifies the strong shifting of N6-H34 stretching mode towards lower wavenumbers. The IR bands at 2563, 2515, and 2475 cm-1 assigned to the two D species, together with the absence of an intense band at 1764 cm-1, show clearly that M species is not present in the solid phase, but the two D hydrochloride (E/Z) and (Z/E) species.

Study of capacitance type flexible electronic devices based on polyacrylamide and reduced graphene oxide composite hydrogel

Flexible electronic devices can transform various external stimuli into electrical signals, and have broad prospects in wearable devices, soft machines, artificial intelligence and other fields. However, the flexible electronic materials based on hydrogel lack mechanical strength and stability. Meanwhile, the electrodes in hydrogels are also easily corroded by electrolytes. In this work, the capacitive sensor based on polyacrylamide-rGO (PAM-rGO) composite hydrogel was studied to solve these problems. Due to the effect of hydrogen bonds, the reduced graphene oxide (rGO) can greatly enhance the mechanical strength of hydrogels. At the same time, the hydrogel is encapsulated in the capacitor, and the stability of the capacitor increases due to the decrease of the water loss of the hydrogel. The PAM-rGO composite hydrogel did not contain free anion and cation, the corrosion of the electrode decreased and the service life was prolonged. The wearable device of PAM-rGO composite hydrogel sensor performed well in tensile and compression stimulation tests, and the linear relationship reached 0.998 and 0.992 in turn, showing potential applications in the field of flexible electronic devices.

Feasibility study on using CO2-rich industrial waste gas replacement for shale gas exploration based on adsorption characteristics

Clean utilization of CO2-rich industrial waste gas (CO2-rich IWG) is of great significance to realize carbon neutralization. Due to the strong adsorption capacity of clay and organic matter in shale to CO2, it has a good potential for CO2-rich IWG storage and replacement. So, the feasibility of using CO2-rich IWG replacement for shale gas exploration from the perspective of adsorption was studied. A shale composite model was constructed based on the adsorption experiments, and the molecular simulation results were fitted with experiments for the model reliability. Then, the slit models of different minerals were constructed to study the adsorption mechanisms. Finally, the competitive adsorption mechanisms of different components with CH4 were revealed. The results show that the overall adsorption capacity on shale minerals are ranked as HF > CO2 > SO2 > H2S > NO2 > CH4 > CO；Hydrogen bond and electrostatic force are the main adsorption modes of HF, and electrostatic force between negatively charged atoms of gas molecule and mineral surface is the main adsorption modes of CO2, SO2 and H2S. That of NO2, CH4 and CO is the weak van der Waals force. In the competition with CH4, the absolute adsorption capacity of gas decreases, but the relative adsorption capacity increases. The relative adsorption capacities of HF, CO2, H2S and SO2 increase by 35, 26, 15 and 12 times, respectively. During competitive adsorption, negatively charged atoms in HF, CO2, H2S and SO2 are more likely to bind with free cations on the surface of illite and smectite, and generate electrostatic repulsion for C atoms in CH4, leading to the weakening or even disappearance of CH4 adsorption capacity.

Insight into the dual effect of water on lignin dissolution in ionic liquids.

The dual regulation of water on lignin in ionic liquids was studied at the molecular level by molecular dynamics simulation. The simulation results show that a small amount of water will destroy the ion association in ionic liquids, that is, it will produce more free anions and cations. The free ions around lignin are conducive to the dissolution of lignin. On the contrary, excess water will seriously solvate anions and cations. By changing the number of lignin clusters, it is more intuitive to observe that the dissolution of lignin in ILs containing a small amount of water is stronger than that in pure IL, however, the dissolution ability of lignin is reduced after adding a large amount of water in ILs. It is concluded that with the increase of water content, water changes from co-solvent to anti-solvent in the dissolution process. This study provides ideas for the design of IL-water system for economic pretreatment of biomass.

Free Radical-Cationic Hybrid System Passivation Film for the Surface of Hot-Dip Aluminum-Zinc Coated Steel Plate

3-Ethyl-3-benzoxy-methyl oxacyclobutane (TCM 104) and 3,4-epoxy-cyclohexyl carboxylic acid-3',4'-epoxy-cyclohexyl methyl ester (UVR 6110) as active diluents, a mixture of modified epoxy-acrylate and modified polyester acrylate in a certain proportion of oligomer, triaryl sulfonium hexafluorophosphate as cationic photoinitiator, irgacure 184 as free radical photoinitiator, and high-pressure mercury lamp as radiation source, and then the compound formula of free radical and cation hybrid photo-curing were prepared and further coated on the hot-dipped aluminum-zinc steel plate. After curing, the passivation film was characterized by neutral salt spray testing, FT-IR spectroscopy and electrochemical properties along with other relative evaluation criterions. The passivation film of this hybrid system can be cured at an energy of 600 mJ/cm2, and its performances are comparable to those of current water-based passivators.

Modified Compositions of Micelle–Clay and Liposome–Clay Composites for Optimal Removal from Water of Bacteria and Hydrophobic Neutral Chemicals

The efficiency in water treatment by granulated complexes formed from the clay bentonite with (i) micelles of the cations of octadecyltrimethyl-ammonium (ODTMA) or (ii) liposomes of didodecyldimethyl-ammonium (DDAB) was investigated. The bentonite–ODTMA complexes were synthesized in three variations: I. mass ratio of 68/32, which resulted in an excess of positive charge of half of the clay cation exchange capacity and is denoted “ordinary”; II. complexes having higher loads of ODTMA, denoted “enriched”; and III. “neutral”. These variations were designed to optimize the efficiency and reduce the costs of water treatment. “Ordinary” and “neutral” complexes of DDAB were also synthesized. The “ordinary” complex of ODTMA was shown to be efficient in the removal of anionic/hydrophobic molecules and bacteria. The “enriched” complexes were more active in removal of bacteria from water by filtration due to the higher release of free ODTMA cations, which causes biostatic/biocidal effects. The corresponding “ordinary” and “neutral” complexes of ODTMA and DDAB yielded the same efficiency in removal from water of the neutral and hydrophobic herbicides, S-metolachlor (i) and alachlor (ii), respectively. Model calculations, which considered sorption/desorption and convection yielded simulations and predictions of filtration results of the herbicides. The neutral complexes are advantageous since their production saves about 1/3 of the amount of ODTMA or DDAB, which constitutes the expensive component in the respective composite.

Effect of Heat on Antioxidant Capacity of Black Radish (&lt;i&gt;Raphanus sativus&lt;/i&gt; L. var &lt;i&gt;niger&lt;/i&gt;) Root

The aim of this study was to identify the influence of drying temperature on total phenolic content and antioxidative efficacy of black radish root and to investigate heat stability of antioxidant capacity of its juice. Hot water extracts from the roots dried at four different temperatures were rich in total phenolics and characterized for DPPH free radical and ABTS radical cation scavenging activity, and reducing power. The best oven drying temperature corresponding to maximum value of total phenolic content and antioxidant potential was 70C. Antiradical activity and reducing power of the juice remained after pasteurization at 95C for 2 min.

Study on the structural properties of refining slags by molecular dynamics with deep learning potential

The CaO-Al2O3 is the most important basis of the multicomponent slag in the steel making industry. The microstructure of molten CaO-Al2O3 systems affects the physical, chemical, and metallurgic properties of refining slags. It is significant to establish a computational method to accurately describe the microstructure of the slag at the atomic level and speculate the properties of large slag models. In this paper, the effect of compositions on the structure of molten CaO-Al2O3 systems was studied by ab initio molecular dynamics, deep learning theory, and deep potential molecular dynamics. The structures of various molten slags were simulated by ab initio molecular dynamics, which accurately describes the interactions between atoms. The potential functions were obtained by deep learning theory. The properties of the large slag models were simulated by molecular dynamics with deep learning potential. As the molar fraction of CaO increases from 0.5 to 0.7, the combination of O and Al mainly forms [AlO4]-5, [AlO3]-3, and [AlO5]-7. Ca presents mainly as free cations in the molten CaO-Al2O3 system. In addition, the diffusion coefficient of Ca decreases from 9.0 × 10-10 m2/s to 5.4 × 10-10 m2/s. The diffusion coefficients of Al and O slightly decrease and are close to 1.1 × 10-10 m2/s and 3.0 × 10-10 m2/s, respectively. It is deduced that the dissolution of CaO provides free O2– and promotes the formation of [AlOn]-b and increases the polymerization degree, which causes deterioration of the fluidity of molten CaO-Al2O3 slags as XCaO increases from 0.5 to 0.7.