Effect Of Different Cations Research Articles

Adsorption studies of methylene blue on cation-modified graphene oxide and graphene oxide/MXene membranes

Membranes prepared from graphene oxide (GO) have greater advantages over traditional materials for water treatment, while MXene is a good candidate for pollutant removal. However, the effect of different cations introduced into the prepared GO membranes on their adsorption performance must be further explored. In this study, a series of cation-modified GO and GO/MXene membranes were prepared based on the self-assembly of GO. Na+-modified membranes were found to be more effective at removing methylene blue (MB) than multivalent cation-modified GO membranes. However, the cation-modified GO/MXene membranes improved the MB adsorption efficiency, and the higher the ionic valence, the more pronounced the effect. In addition, the effects of the pH, temperature, contact time and initial concentration of MB on the adsorption performance of the membranes were investigated. The best removal of MB was achieved under neutral conditions, and the adsorption process was consistent with quasi-secondary kinetics and Langmuir isotherm models. The fitting results of the Langmuir isotherm model showed that the maximum adsorption capacities of the cation-modified GO membranes for MB were 654.9, 319.8, and 246.3 mg/g, respectively. The maximum adsorption capacities of the cation-modified GO/MXene membranes for MB were 687.3, 497.6, and 772.4 mg/g, respectively. Furthermore, the results of the intraparticle diffusion model revealed that the entire adsorption process was controlled by both external and internal diffusion. The thermodynamic analysis results indicated that the entire adsorption process was a heat-absorbing process and could proceed spontaneously. That the findings suggest that the Na+-modified GO and Al3+-modified GO/MXene membranes demonstrate the best adsorption effects and are promising adsorbents for MB removal.

Understanding the electronic structure and transport properties of A-site SrTiO3-δ ceramics with enhanced configuration entropy

Since SrTiO3 is attractive due to its versatile electronic properties ranging from dielectric to semiconducting behavior, the effect of systematic co-substitution of various A-site cations on the electronic structure and transport properties of oxygen-deficient SrTiO3-δ bulk ceramics was analyzed. The materials were synthesized by reverse co-precipitation method and densified by spark plasma sintering (SPS) in a vacuum, followed by a post-thermal treatment in a reducing atmosphere (5 % H2/Ar). The phase purity was confirmed by X-ray diffraction (XRD), different microstructures were revealed by scanning electron microscopy (SEM), and characterization in terms of electrical conductivity (σel) and Seebeck coefficient (S) were performed. The largest power factor was obtained with Sr0.25Ca0.25Na0.25La0.25TiO3-δ by maintaining electrical conductivity while increasing the Seebeck coefficient. Density Functional Theory (DFT) calculations were applied to obtain information on band structures, the projected density of states (PDOS), and electron density differences (EDD). Band structures indicated that oxygen deficiency essentially changed the conductive nature of the studied materials by shifting the Fermi level to the conductive zone, while PDOS plots define the role of each element located at the A site. The electronic structure is affected to the greatest extent in the cases when Nd and Pr are present at the A-site. However, the obtained experimental and computational (DFT) results could not completely match and explain all phenomena since understanding the effect of different cations at A-site on oxygen vacancy formation seems to be a challenging task, and therefore, some hypotheses are proposed. This work attempts to understand the role of a particular cation at A-site on the electronic band structure and its relevance to the formation of oxygen vacancies, thereby providing valuable insights for future high-entropy perovskite titanates with improved transport properties.

Preparation of PVDF-nSiO2/PVSQ high-flux composite membrane by chemical grafting and separation of composite brine by membrane distillation

The large-scale application of membrane distillation (MD), an important method for desalting seawater, is limited due to membrane fouling. In this study, ethyl orthosilicate (TEOS) was polymerized to obtain different nSiO2 particles. Vinyl triethoxysilane (VTES) was hydrolysed and polycondensation was used to produce spherical polyethylene-sesquioxane (PVSQ) microparticles, which were modified to construct micro/nano particles. Then grafted on the surface of polyvinylidene fluoride (PVDF) composite membrane. The low-surface-energy hydrophobic groups present on the surfaces of the vinyl and ethoxy particles greatly enhanced the membrane hydrophobicity. The particle size of nSiO2 can change the properties of the membrane. The separation performance of the membrane was tested by direct contact membrane distillation (DCMD). In the separation of a constant concentration of feed solution (3.5 wt% NaCl), the membrane flux was relatively stable at 23.8 kg·m−2·h−1, and the salt interception rate reached 99.99 %. In the subsequent separation of a salt/humic acid solution, the flux remained stable and the good anti-fouling performance indicating that this system outperformed the unmodified membrane. Finally, the effect of different cations on the water diffusivity was studied using a molecular simulation method. Both Ca2+ and Mg2+ reduced the diffusion coefficient of water. However, when these two ions were present simultaneously, Ca2+ inhibited the binding of Mg2+ to water, and the diffusion coefficient of water increased. This study provides a novel approach for preparing hydrophobic membranes for the separation of complex brines.

Combined DFT and ionic model computational study of the effect of alkali metal cations on the structure, bonding and properties of molten cryolites, M3AlF6 (M = li, Na, K, Rb, and Cs)

ABSTRACT Ionic melts, in the form of ionic liquids and molten salts, are important in many technological aspects such as metal production and energy applications. Cryolite melts constitute an important family especially for the industrial production of Al. The present computational study aims to analyse the effect of different cations on the structure and properties of Al (III) fluorocomplexes in cryolite melts. Cation effects are discussed as the ion pair interactions due to alkali metal cations of cryolite compounds M3AlF6 with M= Li, Na, K, Rb, or Cs for various microclusters using ionic interaction model (IM) and DFT calculations. DFT results for different ion complexes are compared with the energy calculations using a pseudoclassical model for isolated clusters. QTAIM and ELF analyses were performed to understand the nature of interactions in detail. A link between open-shell interactions and decreased ionic conductivity is proposed within the series of K, Rb, and Cs. Environmental effects, such as temperature and presence of other ions, are investigated in detail by DFT analysis.

Rheology and characterization of sulfated agarans from the edible epiphytic red alga, Vertebrata lanosa (truffle seaweed)

The effect of different cations (K+, Ca2+ and Ba2+) on the gel forming properties of sulfated polysaccharides isolated from the red epiphytic alga, Vertebrata lanosa, using a successive cold (25 °C) and hot (95 °C) alkaline extraction process is presented. The elucidation of their monomeric composition using a two-step reductive hydrolysis and structural analyses (1D and 2D NMR) revealed d-galactose (G) linked to 3,6-anhydro-l-galactose (LA) and also sulfated 3,6-anhydro-l-galactose (L6S) as the major monomers with some amounts of glucose, β-d-xylose, 6-O-methyl-d-galactose (G6M), 2-O-methyl-l-anhydrogalactose (LA2M) and l-arabinofuranose. This composition implied the presence of both diads of agaran types, funoran and porphyran in polysaccharides from Vertebrata lanosa. Similar to funorans, their gelation, was highly influenced in the presence of Ba2+ ions compared to other tested salts. 0.2 M of BaCl2 in the hot extracted fractions recorded storage modulus (Gʹ) to up to ∼80 Pa and increased complex viscosity to 16,000 mPa s compared to the <5 Pa storage modulus from pristine solutions with no added salts. Sulfate amount contained within these fractions ranged up to ∼30% with less than 1 % (gallic acid equivalent, GAE) total phenolic compounds. Some of these fraction, nonetheless, have shown good α-amylase and reactive oxygen species (ROS) inhibition activities thus suggesting a nutraceutical potential of hydrocolloids from this algal species.

Characterization of ionically crosslinked mango peel pectin-based films: Effect of different cations on the improved properties of film

Mango peels are often dumped as waste, producing severe environmental issues. This study investigated the physicochemical properties of mango peel pectin and its based films prepared by crosslinking with cations. The results showed that pectin obtained from mango peel is high-methoxy pectin and consists of aggregates of linear homogalacturonan. Thin films were prepared with the extracted mango peel pectin crosslinked with Ca2+, Zn2+, and Cu2+, respectively, and were characterized. The crosslinking improved the properties of the pectin-based film, including tensile strength, hydrophobic properties, and thermal stability. Fourier transform infrared spectroscopy techniques and X-ray diffraction exhibited the nature of inter-molecular interactions between ions and pectin in films, while scanning electron microscope showed the observable differences in the microstructure. These results showed that the crosslinking of pectin with cations would provide new insight for preparing a pectin-based film with excellent properties.

Adsorption of the hydrophobic organic pollutant hexachlorobenzene to phyllosilicate minerals

Hexachlorobenzene (HCB), a representative of hydrophobic organic chemicals (HOC), belongs to the group of persistent organic pollutants (POPs) that can have harmful effects on humans and other biota. Sorption processes in soils and sediments largely determine the fate of HCB and the risks arising from the compound in the environment. In this context, especially HOC–organic matter interactions are intensively studied, whereas knowledge of HOC adsorption to mineral phases (e.g., clay minerals) is comparatively limited. In this work, we performed batch adsorption experiments of HCB on a set of twelve phyllosilicate mineral sorbents that comprised several smectites, kaolinite, hectorite, chlorite, vermiculite, and illite. The effect of charge and size of exchangeable cations on HCB adsorption was studied using the source clay montmorillonite STx-1b after treatment with nine types of alkali (M+: Li, K, Na, Rb, Cs) and alkaline earth metal cations (M2+: Mg, Ca, Sr, Ba). Molecular modeling simulations based on density functional theory (DFT) calculations to reveal the effect of different cations on the adsorption energy in a selected HCB-clay mineral system accompanied this study. Results for HCB adsorption to minerals showed a large variation of solid–liquid adsorption constants Kd over four orders of magnitude (log Kd 0.9–3.3). Experiments with cation-modified montmorillonite resulted in increasing HCB adsorption with decreasing hydrated radii of exchangeable cations (log Kd 1.3–3.8 for M+ and 1.3–1.4 for M2+). DFT calculations predicted (gas phase) adsorption energies (− 76 to − 24 kJ mol−1 for M+ and − 96 to − 71 kJ mol−1 for M2+) showing a good correlation with Kd values for M2+-modified montmorillonite, whereas a discrepancy was observed for M+-modified montmorillonite. Supported by further calculations, this indicated that the solvent effect plays a relevant role in the adsorption process. Our results provide insight into the influence of minerals on HOC adsorption using HCB as an example and support the relevance of minerals for the environmental fate of HOCs such as for long-term source/sink phenomena in soils and sediments.

Effect of Different Cations on Ion-Transport Behavior in Polymer Gel Electrolytes Intended for Application in Flexible Electrochemical Devices

Effect of Different Cations on Ion-Transport Behavior in Polymer Gel Electrolytes Intended for Application in Flexible Electrochemical Devices

A novel synthetic strategy towards NaCl-type NixCo1−xO solid solution nanoplatelets encapsulated in N-doped carbon for enhanced lithium-ion storage

NaCl-type Ni-Co oxide solid solution is expected to be a promising alternative anode material for lithium-ion batteries. However, the synthesis of solid solutions with well-defined morphology and homogeneity is still challenging. Based on a novel NixCo1−x(OH)(OCH3)@polydopamine intermediate and its topotactic thermolysis, a unique synthetic route towards NixCo1−xO solid solution (0 <x ≤ 0.5) encapsulated in N-doped carbon (NixCo1−xO@N-C) was introduced. NixCo1−x(OH)(OCH3) nanoplatelets were firstly synthesized with a solvothermal method and used as the precursor for a NixCo1−x(OH)(OCH3)@polydopamine intermediate. Thermolytic decomposition of metastable NixCo1−x(OH)(OCH3)@polydopamine results in the formation of NaCl-type NixCo1−xO and conformal carbon coating. The resulting NixCo1−xO@N-C shows a well-defined two-dimensional (2D) platelet-morphology and homogenous elemental distribution. Benefited from a tunable Ni/Co ratio, the lithium-storage performance of NixCo1−xO@N-C can be optimized, thereby achieving a high specific capacity of 949 mA h g−1 at the current density of 0.2 A g−1, a great rate capability (530 mA h g−1 at 2 A g−1), as well as excellent long-term cyclability (563 mA h g−1 at 2 A g−1 after 500 cycles) for Ni1/6Co5/6O@N-C. Such a remarkable performance could be attributed to the synergistic effect of different cations, the 2D nanoplatelet structure, the robust conductive carbon coating, and a high pseudocapacitive contribution.

Effect of Ca2+, Mg2+, Ba2+ and Sr2+ cations on calcium carbonate scaling formation in oil-gas well: Based on density functional theory study and molecular dynamics simulation

The effect of different cations (Ca2+, Mg2+, Ba2+ and Sr2+) adsorption on carbonate type scaling formation was studied by using CASTEP and Forcite module based on density functional theory and molecular dynamics, respectively. By calculating the adsorption energy of cations adsorbed on four adsorption sites (top, hollow, short-range bridge and long-range bridge) of (2 × 1 × 1)CaCO3 (1 –1 0) surface, the most stable adsorption site was determined. On this basis, the banding mechanism of O atom and cation was studied by analyzing the state density of different cations adsorbed model. It has been shown that the Mg2+ cation adsorbed at top site of O atom on CaCO3(1 –1 0) surface was the most stable one according to the adsorption energy calculation results. Under the condition of multiple type of cations co-existence at the same ionic concentration, Mg2+ and Ba2+ would preferably combined with CO32– to form magnesium carbonate and barium carbonate scaling, causing the crystal growth process of calcium carbonate scaling inhibited. The converse is equally true that the existence of Sr2+ is more conducive to the calcium carbonate scaling crystal growth. The radial distribution function analysis indicated that the bonding strength between Mg2+ and O atom on CaCO3 (1 –1 0) surface is the largest, weakening followed Ba2+, Ca2+ and Sr2+ successively. Density of state study indicated that adsorption of Mg2+ cation on CaCO3 (1 –1 0) surface is mainly due to the interaction between 2p orbit of O atoms and 3s orbit of Mg2+ cation.

Antibacterial behavior of oxynitride glasses as a glassy grain boundary phase for silicon nitride‐based ceramics

AbstractSilicon nitride‐based ceramics have provided significant advantages due to their high chemical resistance, high elastic modulus, and combination of hardness and fracture toughness (depending on self‐reinforcement). Over the past two decades, a significant amount of interest has been generated for the bio‐applications of these materials. However, the effect of the grain boundary phase on such applications is still not very well understood. In this study, the effect of different cations on biological (such as antibacterial and cytocompatibilty) and material properties (like wetting angles and isoelectric points [IEP]) of oxynitride glasses, mimicking the grain boundary phase in Si3N4 and SiAlON ceramics, were investigated. Results revealed that the antibacterial behavior and mammalian cell viability were inversely correlated in glasses with rare‐earth cation additions. Ca was the best cation when the two properties (bacterial response and cell proliferation) were considered together, and, thus should be further studied for a wide range of applications.

CO2 methanation on Ni-Ce0.8M0.2O2 (M=Zr, Sn or Ti) catalyst: Suppression of CO via formation of bridging carbonyls on nickel

The effect of different cations (M=Zr, Sn or Ti) doping on ceria supported nickel (Ni-Ce0.8M0.2O2) catalysts and their performance in the CO2 methanation reaction has been investigated. Among the prepared catalysts, the Ni-CeO2 (CN) catalyst exhibited the best catalytic performance with a CO2 conversion of 62.9% at 400 °C. The selectivity on Ni-Ce0.8Zr0.2O2 (CZN) remained above 98.4% from 200 to 400 °C. As confirmed by in-situ DRIFTS, the dissociative adsorption of H2 mainly proceeds on Ni, by-product CO is mainly assigned to the releasing of weak-binding linearly adsorbed CO on nickel, which is from the hydrogenation of formates with adsorbed H. The CO-suppressing effect is attributed to the strong adsorption of carbon monoxide on nickel via the forming of bridging carbonyls. It was found that CO2 is adsorbed on the catalysts to form carbonate, bicarbonate and formate species. The formate species could be further hydrogenated by dissociated H and then finally release methane.

Thermodynamics and phase separation phenomenon of polyoxyethylene sorbitan monolaurate in micellar solutions containing inorganic salts

Abstract The phase separation behavior of polyoxyethylene sorbitan monolaurate (1.000 mmol/L) was investigated in aqueous micellar solution containing inorganic salt, especially the high concentration of different cationic chlorides including NaCl, KCl, MgCl2, CaCl2, BaCl2 and AlCl3. The continuous decrease in the cloud point (CP) was observed on adding the univalent cationic chlorides (NaCl and KCl). While the addition of multivalent cationic chlorides initially depress the phase separation and then promote the solvation of surfactant in water phase. The relationship between the reciprocal of CP and the concentration of inorganic salt is found to well linearize in the range of a certain concentration of inorganic salt. The dependence of related constant terms in the obtained equations on the nature of inorganic ions was theoretically discussed. The ionic charge vs. atom radium ratio was also used to probe the difference in the effect of different cations on the phase separation. In the framework of phase separation model, the obtained thermodynamic parameters indicate that the process of phase separation is non-spontaneous and the entropy makes an overwhelming contribution.

Complex-precipitation using functionalized chiral ionic liquids with L-proline anion and chromatographic analysis for enantioseparation of racemic amino acids.

As one kind of functionalized green medium, chiral ionic liquids (CILs) have been widely applied in fields of asymmetric catalysis, enantioseparation, and so on. In this study, four kinds of amino acid-based CILs were synthesized by using trimethylamine, N-methylpyrrolidine, N-methylimidazole, and tropine as cationic nucleus, respectively. Then their specific optical rotation and solubility in common solvents were determined for further resolution application. The effect of different cations in these CILs was explored on the separation of racemic phenylalanine in complex-precipitation way. Moreover, various factors were systematically investigated for their effects on resolution efficiency, including the type of additive copper salts, the molar ratio of Cu (II) to CIL, pH value, the amount of racemic phenylalanine, and temperature. Under the appropriate conditions, L-phenylalanine mainly existed in solid phase and could be separated from its enantiomers in liquid phase. Furthermore, the mechanism of resolution was studied by thermogravimetric analysis, infrared spectrum, and molecular simulation. The resolution system has characteristics of no organic solvent, fast separation speed, simple resolution process, and easy scale-up.

Radiation induced crosslinking of polyacrylamide incorporated low molecular weights natural polymers for possible use in the agricultural applications

Superabsorbent hydrogels based on polyacrylamide (PAAm) and Na-alginate (Alg) or chitosan (CS) were synthesized by γ-rays. The effect of dose and copolymer composition on gel content and water absorbency of PAAm/Alg, PAAm/CS and PAAm/Alg/CS hydrogels were studied. The gel content and water absorbency follows the order PAAm/Alg>PAAm/Alg/CS>PAAm/CS. The effect of different cations, fertilizers, buffers on water absorbency of the hydrogels was investigated. Water retention capability of swollen hydrogels as a function of time was studied. PAAm/Alg hydrogel has a high water retention capability. An application of the prepared hydrogels in agricultural fields was performed using maize plants. The results showed that the presence of hydrogels had growth promotion effect on quality and quantity of maize plants. The plants treated by PAAm/Alg hydrogels showed 50% increase in the grain yield suggesting their possible use as a soil conditioner and a water reservoir for plant-soil system.

The role of cations in copper flotation in the presence of bentonite

The previous study demonstrated that bentonite had a deleterious effect on copper flotation by increasing pulp viscosity, but this deleterious effect could be mitigated by sea water (Zhang et al., 2015a). In this study, the effect of different cations, Na+, K+, Mg2+ and Ca2+ with the same anion, Cl−, on the rheology of a copper-gold ore in the presence of bentonite and copper flotation was investigated. It was found that the improvement of copper flotation in the presence of bentonite was generally dependent on the reduction of pulp viscosity by these cations. Divalent cations, Mg2+ and Ca2+, had a more significant effect on pulp viscosity and therefore copper flotation than monovalent cation, Na+, K+. These cations also interacted with bentonite, with residual cations modifying the froth property. However, this modification was less significant in copper flotation in the presence of bentonite where pulp viscosity played a critical role.

Biopolymer Production Kinetics of Mixed Culture Using Wastewater Sludge as a Raw Material and the Effect of Different Cations on Biopolymer Applications in Water and Wastewater Treatment.

Thirteen extracellular polymeric substances (EPS) producing bacterial strains were cultivated (as mixed culture) in the sterilized sludge (suspended solids of 25 g/L) and the batch fermentation was carried out. Mixed culture revealed a high specific growth rate of 0.35/hr. The EPS production rate was higher up to 24 hours, which gradually decreased with further incubation. The kinetic estimates demonstrated growth-associated EPS production. Broth EPS revealed higher flocculation activity when combined with different cations (Ca(2+), Mg(2+), Fe(3+), and Al(3+)) in river water (≥90%), municipal wastewater (≥90%), and brewery wastewater (≥80%), respectively. A low dose (5 to 40 mg/L) of trivalent cations was required to achieve higher flocculation compared to the divalent cations (50 to 250 mg/L). Flocculation performance of EPS was comparable to Magnafloc-155 (chemical polymer) and, hence, it could be used as a flocculant.

Selective and Sensitive Electrochemical Determination of Trace Amounts of Mercury Ion in Some Real Samples Using an Ion Imprinted Polymer Nano-Modifier

A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, sensitive and highly selective determination of mercury (II) ion using square wave stripping voltammetry. The carbon paste electrode was modified by an ion imprinted polymer. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, −0.600 V vs. Ag/AgCl; deposition time, 250 s; resting time, 10 s; SW frequency, 80 Hz; pulse amplitude, 70 V; dc voltage step height, 5.8 mV), the detection limit was found to be 0.04 ng mL−1 for the determination of Hg2+ ion over a wide linear range from 0.20 to 1600.0 ng mL−1. The effect of different cations and anions on the determination of the target ion was studied, and it was found that the electrode is highly selective for the determination of Hg2+ ion. Furthermore, the present method was successfully applied to the determination of Hg2+ in water and some foodstuff samples.

English

English

Implication of zeta potential and surface free energy in the description of agricultural soil quality: Effect of different cations and humic acids on degraded soils

Here we present results of our study about the effect of natural organic matter in the adsorptions processes of commercial humic acid (HA) on the physicochemical properties, stability, and structure of an agricultural olive soil. Our soil belongs to the loamy texture class and gives a medium-low chemical fertility. Its organic carbon content is very low (0.40%), which could be explained by the Mediterranean climate type in which the soil developed. From the fine earth mineralogy, we conclude that smectite was the most abundant mineral in our soil.We first demonstrated that HA effectively adsorbs onto soil, mainly at basic pH. Electrophoresis measurements of soil particle suspensions as a function of pH in the presence and absence of humic acid clearly demonstrate the adsorption of negatively charged entities onto smectite in the soil. This effect is more significant when the soil contains natural organic matter, which confirms the mordant character of this matter in native soil.Analysis of surface free energy components leads to the conclusion that humic acid molecules impart a significant electron donor character to the soil particles, which in turn decreases their hydrophilicity. All collected data were used to interpret the final soil structure. Our results are consistent with fabric images obtained by scanning electron microscopy of natural samples that present the major aggregation state. Interpretation of these results can be explained by a combination of electrical and thermodynamic interaction, electrostatic forces, double-layer repulsion, van der Waals attraction, and hydrophilic/hydrophobic repulsion/attraction.