Ions Of Different Charge Research Articles

Simulation of Magnetic Separation of Metal Ions in Aqueous Electrolytes

The magnetic separation of metal ions provides an alternative solution to traditional separation techniques such as pyrometallurgy, hydrometallurgy, biometallurgy or electrodialysis. Compared to traditional techniques that either use large amounts of chemicals (usually inorganic acids combined with reducing agent), produce large amounts of sludge as solid waste, consume a large amount of energy, or are difficult to separate ions of different charges [1], the magnetic separation of the metal ions can separate ions based on their magnetic susceptibility. This method is environmentally friendly [2] and consumes a small amount of energy (particularly when the system is designed using permanent magnets instead of electromagnets). The goal of this presentation is twofold. First, we derive the set of transport equations that need to be used to simulate the magnetic separation of metal ions in aqueous solutions. Then, we use these transport equations to simulate the magnetic separation process in various magnetic systems and predict the efficiency of magnetic separation of different systems.The mathematical model developed here is based on coupling the three-dimensional Navier-Stokes equations for flow transport with the drift (migration)-diffusion equations of ion transport [3] in the presence of magnetic field gradients. Both the drift-diffusion model and the Navier-Stokes equations include the magnetic force term as an additional driving force. By solving the entire system of equations self-consistently we analyze the effect of the diffusivity, concentration gradients, magnetic field gradients and fluid velocity over the capturing properties of the system. A detailed presentation of the mathematical model, underlying assumptions of the model, limiting cases, numerical implementation in three-dimensional structures, and simulations results will be presented at the meeting. In addition, we will present predictions for the magnetic separation of Li, Fe, Ni, Mn, and Co from the solution phase. Fortunately, these ions have significantly different magnetic susceptibility, which vary over more than 3 orders of magnitude, and which allows for the efficient extraction and separation of the elements from the solution and from each other.

Prediction of Peptide Ion Distribution in Positive Electrospray Ionization

We have investigated the possibility of predicting the distribution of ions of different charge during electrospray ionization of peptides in mass spectrometric experiments using neural networks. Three independent data sets obtained on the same equipment and deposited in ProteomeXchange (PXD032141, PXD051750, PXD019263) were used as training and test samples. A set of fractional values for 1+ to 5+ ions was calculated as predicted values for each of the newly identified peptides. Four different sets of peptide descriptions were used as independent variables, including both the spectrum of amino acid residues and the physicochemical properties of the amino acid residues. Sixty-four variants of neural networks were analyzed, varying the input description, number and type of layers, activation and loss functions. The coefficient of determination and a set of Euclidean, Sørensen, Chebyshev, and Cosine metrics were considered as measures of prediction quality. For the best selected variants, the error did not exceed 10% in 80% of the cases. This accuracy may be sufficient for a preliminary estimation of the probability of detecting a peptide ion of a given charge.

Impact of Silica-Modification and Oxidation on the Crystal Structure of Magnetite Nanoparticles

At present, the widespread use of iron oxide nanoparticles, including for commercial purposes, requires strict preservation of their phase composition during their application. The choice of nanoparticle modifier and modification conditions is decisive due to their high sensitivity to oxygen in the case of using real conditions (O2, pH change, etc.). In this work, we studied the change in the phase composition of magnetite nanoparticles after modification with 3-aminopropyltriethoxysilane (APTES) and oxidation with nitric acid in order to estimate the protective potential of the silica shell. After modification by APTES and oxidation with nitric acid, the nonstoichiometric nature of the magnetite nanoparticles according to XRD data increased, which indicates an increase in transition forms compared to the initial sample (magnetite content decreased to 27% and 24%, respectively). In contrast, Mössbauer spectroscopy data detected a decrease in the nonstoichiometric index due to APTES modification conditions, but strong oxidation after exposure to nitric acid. It also showed that by analyzing the data of the diffraction analysis and Mössbauer spectroscopy for the same sample, one can obtain information not only about the ionic composition of “magnetite”, but also about the distribution of iron ions of different charges over the crystalline and amorphous parts of the preparation.

Calculating the closest approach parameter for ethyl lactate-based ATPS

Aqueous Two-Phase Systems (ATPS) is a powerful separation technique for biotechnological compounds, such as pigments, proteins and flavonoids. Nowadays, ATPS generally include dissolved salts, which cause phase immiscibility and promote solute partition. Therefore, to accurately model the liquid-liquid equilibria (LLE) of these systems, specific terms for the long-range interactions in thermodynamic models are needed. A well-known hypothesis for this purpose is the Pitzer-Debye-Hückel (PDH) term, which requires the knowledge of the closest approach parameter (ρ), i.e., an adjustable parameter. The aim of this work was calculating this parameter supposing total dissociation of the salts in ethyl lactate-based ATPS. In this new approach, ρ became specific for each chemical species and its physical meaning (related to the distance between ions of different charges) was preserved. This method was applied in the LLE modelling of 7 ethyl lactate + organic or inorganic salts + water systems measured by the group, using the PDH term coupled with the UNIversal QUAsi-Chemical (UNIQUAC) model, whose junction is generally known as PDH+UNIQUAC, and compared with classical UNIQUAC and with previous works. The new approach accurately described the experimental liquid-liquid equilibria (LLE) data and presented smaller composition deviations than UNIQUAC.

Effects of hexamethylenetetramine (HMTA) on the aqueous solution structure, dynamics and ion solvation scenario: A concentration and temperature dependent study with potential HMTA models

The local hydrogen bonding structure of water and its dynamics in hexamethylenetetramine (HMTA) solution is investigated by using classical molecular dynamics simulations. In this study, we have compared two potential HMTA models with different Lennard-Jones (L-J) combination rules. We have considered five different concentrations of HMTA, ranging from pure water to 6.181 m HMTA at 298 K, whereas to calculate the temperature dependence from 298 K to 353 K, we have used 4.187 m concentration of HMTA. From the radial distribution function, it is observed that the addition of HMTA facilitates structural making of water, whereas our calculated values of the tetrahedral order parameter and asphericity of water suggests disordered structure with increasing HMTA concentration. Also there is a significant development of self-aggregation among water and HMTA molecules at higher concentration of HMTA. The self-diffusion coefficient values of water and HMTA is found to be decreased with increasing HMTA concentration in the solution, whereas at concentrations below 1.0 m, it matches well with the experimental observations. Our calculated activation energy of diffusion for HMTA (4.10 ± 0.2 kcal/g mol for Model-II), is very close to the experimental observation (4.34–4.44 kcal/g mol). The structure of the hydration shell of ions of different charges and sizes is also investigated in the presence of HMTA. For all the models, it is observed that the structural and dynamical properties of water and the hydration shell of ion shows negligible difference with varying concentration and temperature. In contrast, the ion−HMTA correlations are model dependent. It is suggested that the HMTA model-I (AM) is the suitable model for representing ion-solvation structure and dynamics particularly at lower concentrations of aqueous-HMTA solution.

Kinetics and mechanism of the oxidative degradation of sofosbuvir by N-bromosuccinimide in aqueous medium

The kinetics of the electron transfer in sofosbuvir (Sofo) using N-bromosuccinimide (NBS) in aqueous medium has been studied spectrophotometrically over the (10–30) °C range, (0.1–0.5) mol dm−3 ionic strength, pH = 6.0–8.0 range over a range of NBS and Sofo concentrations. The rate of reaction was first order dependence on both [NBS] and [Sofo] and decreased with increasing [H+] over the range studied suggesting that the deprotonated form of sofosbuvir is more reactive than its conjugate acid. The hydrogen atom attached to the nitrogen atom of pyrimidine dione ring has a highly acidic character due to withdrawing effect of the adjacent two carbonyl groups and so the sofosbuvir acted as an acid. The rate decreased with increasing the ionic strength of the reaction mixture and supported that the reaction took place between two ions of different charges.

Brine ions impacts on water-oil dynamic interfacial properties considering asphaltene and maltene constituents

Smart water flooding is one of the most promising methods for Enhanced Oil Recovery (EOR). However, the exact mechanism beyond is still unknown and the comprehensive knowledge for optimization of the composition of the ions needed for an effective flooding process is not available. In this manner, the interactions of different ions present in the aqueous phase with those components of the oil that can have a certain affinity to water (e.g. asphaltene and maltene) are of great importance. In this research work, the effects of monovalent and divalent ions of different charges (Na+, Cl−, Ca2+, Mg2+, and SO42-) on dynamic interfacial properties of the water/oil system have been studied using profile analysis tensiometry (PAT) experimental method. It is demonstrated that participation of the ions from the water phase into the electrostatic interactions with oil, depends on the surface charge of different components of the oil that adsorb at interface. For a better understanding of this matter, separate solutions of the extracted asphaltene in toluene and maltene (de-asphalted oil using heptane) were prepared and used for comparative studies. The results illustrate a major role for the cations, while changes of the anions show negligible effects in our case studies. Among the cations, Mg2+ and Ca2+ show very significant effects on interfacial properties of the related brine-oil interface while Na+ shows negligible effects. The results also demonstrate more significant interaction of the resin components with divalent cations (Mg2+ and Ca2+) in comparison with the asphaltene components. In particular, Mg2+ shows a stronger interaction with both resin and asphaltene molecules in comparison with Ca2+. The measured interfacial elasticity results provide us very helpful complementary data for better understanding of the approximate size and concentration of the adsorbed molecules/aggregates, that support these findings well.

The Prediction of the Ion Fraction of the Peptide with Selected Charge in Mass Spectrometry with Positive Electrospray Ionization

The possibility of prediction of selected ion fraction in the total peptide fraction obtained during mass spectrometry with positive ionization by electrospray was investigated on the basis of the amino acid sequence. The data obtained in the MS / MS experiment [Ramus et al., 2015] using the standardized UPS1 kit (48 highly purified human proteins) and deposited in ProteomeXchange (identifier PXD001819) were used as the initial data set. For each of the identified peptides belonging to one of the proteins of the UPS kit, a list of detected ions of different charge was formed. The sum of the peak intensities detected for the primary ion was used as a measure of quantity. Since the ratio of the peptide fractions of ions with different charges does not depend on the concentration in the experimental sample, the total sample was assembled by combining the data obtained for different dilutions of UPS1. A set of equations of prediction of the fraction of 1+, 2+, and 3+ ions has been constructed. This computational analysis has shown applicability of the proposed for prediction of the ion fraction of the peptide with selected charge in mass spectrometry with positive electrospray ionization.

Behaviour of cis- and trans-N-methylformamide in liquid mixture: Dynamical properties at varying pressure and temperature, and ion solvation scenario

Classical molecular dynamics simulations have been carried out to investigate dynamical properties of cis-trans mixture of liquid N-methylformamide at eight different temperatures (278–423 K) and four pressures ranging from 0.1 MPa to 300 MPa. At 298 K and 0.1 MPa, it is observed that cis-NMF is impeded by approximately 4.12% in its diffusion rate than trans-NMF. Higher pressures evoke slower dynamics concomitantly with enhanced caging effect, which is appreciable in case of cis-NMF. Calculated activation energy values for diffusion (13.465 ± 0.21–15.641 ± 0.51 kJ/mol) are in agreement with experimental observations, particularly at 0.1 MPa. Unlike self-diffusion behaviour, the orientational relaxation time of NH bond vector follows Arrhenius behaviour even at lower temperature and higher pressure. Hydrogen bonding patterns are observed to be different for H-bonds involving amide-hydrogen of either trans-NMF or cis-NMF molecules and overall interaction probability is boosted by the participation of cis-NMF conformers. Solvation scenario of ions of different charge and size in cis/trans-NMF mixture has also been explored. It is found that cations favour oxygen of cis-NMF and anions are attracted towards hydrogen sites of trans-NMF while intermediately-sized potassium and bromide ions may deviate in their preferences from the usual trend.

Study of the stability and homogeneity of water in oil emulsions of heavy oil

Water-in-oil (W/O) emulsions are present in applications from well drilling to refining and cause diverse problems. The present paper details the results of a study of the stability and homogeneity of W/O emulsions of a heavy oil using the optical microscopy technique. The W/O emulsions used previously dehydrated heavy oil with the addition of increasing volumes of 10, 20, 30, 35 and 40% w/v of deionized water and formation water, under mechanical stirring at 2500, 5000, 10,000 and 15,000 rpm. Moreover, a saturated sodium chloride solution was added to the oil in the contents at 10, 20 and 30% w/v under stirring at 5000 rpm, in order to verify the influence of the electrolyte type on the stability of the emulsions. The W/O emulsions were subjected to a gravitational separation test to verify stability and photomicrographs of the emulsions were analyzed to evaluate the homogeneity and the droplet size distribution (DSD). The results showed that the prepared emulsions were stable and homogeneous even after aging for 30 days and after being subjected to heating. This stability may be related to the high content of resins and asphaltenes in the studied oil. The emulsions prepared with formation water showed higher DSD values than those prepared with saturated NaCl solution and deionized water. This distinction of droplet sizes can be related to the presence of ions of different charges in the formation water.

Describing Ion Exchange at Membrane Electrodes for Ions of Different Charge

AbstractIt is well‐documented in the literature that the Nikolsky‐Eisenman equation cannot accurately describe the equilibrium of ion exchange at membrane electrodes for ions of different charge. Despite this, unfortunately, it is still widely used owing to the complexity of the more rigorous formalism developed by Bakker et al. in 1994. Here, different available approaches are presented in a unified manner and compared. This includes two different approximations that are equally appropriate for cases of low level of interference where the extent of ion‐exchange is comparatively small, one of which is introduced here for the first time. The comparison also considers the permutated form of the Nikolsky‐Eisenman equation, where the primary ion is treated as the interfering ion and vice versa. As the permutated form gives a deviation from the thermodynamic model that is opposite that of the regular Nikolsky‐Eisenman equation, the two can be combined to give a semi‐empirical equation that is surprisingly close to the thermodynamic model and that comprises a single equation for any charge combination. The different choices presented here may be helpful to solve more complex theoretical problems, as for example in the modeling of the time dependence of the electrode response by numerical simulation where the interfacial step condition is a unique and difficult feature of the calculation.

Multiturn beam injection system

The system of accumulation of charged particles in the process of beam injection is considered. The number of accumulated particles in this system is limited either by the maximum accumulated beam intensity or restrictions on the energy spread of particles in the beam. This system allows one to separate and accumulate ions of different charges. The number of accumulated turns may exceed 102.

ELECTRICAL CONDUCTANCE STUDIES ON ION EXCHANGE MEMBRANE USING CONTACT-DIFFERENCE METHOD

Comparisons of contact-difference and contact methods for the measurement of membrane conductivity were made. It was found that the conductivity of the ion exchange membrane at infinite dilution can be accurately measured only by contact-difference method (CDM) in equilibrium with highly diluted electrolyte solutions. The dependence of the measured specific electrical conductivity and impedance of ion exchange membranes on the concentration, temperature, charges of counter ions and frequency of an electric field was discussed. Good agreement was found between the experimentally determined activation energy of ion-exchange membranes in the form of ions of different charges and the calculated activation energy using ab initio quantum chemical method.

SOLAR ENERGETIC PARTICLE DRIFTS AND THE ENERGY DEPENDENCE OF 1 au CHARGE STATES

ABSTRACT The event-averaged charge state of heavy ion solar energetic particles (SEPs), measured at 1 au from the Sun, typically increases with the ions’ kinetic energy. The origin of this behavior has been ascribed to processes taking place within the acceleration region. In this paper we study the propagation through interplanetary space of SEP Fe ions, injected near the Sun with a variety of charge states that are uniformly distributed in energy, by means of a 3D test particle model. In our simulations, due to gradient and curvature drifts associated with the Parker spiral magnetic field, ions of different charge propagate with very different efficiencies to an observer that is not magnetically well connected to the source region. As a result we find that, for many observer locations, the 1 au event-averaged charge state , as obtained from our model, displays an increase with particle energy E, in qualitative agreement with spacecraft observations. We conclude that drift-associated propagation is a possible explanation for the observed distribution of versus E in SEP events, and that the distribution measured in interplanetary space cannot be taken to represent that at injection.

Poisson-Fermi Modeling of the Ion Exchange Mechanism of the Sodium/Calcium Exchanger.

The ion exchange mechanism of the sodium/calcium exchanger (NCX) crystallized by Liao et al. in 2012 is studied using the Poisson-Fermi theory developed by Liu and Eisenberg in 2014. A cycle of binding and unbinding is proposed to account for the Na(+)/Ca(2+) exchange function of the NCX molecule. Outputs of the theory include electric and steric fields of ions with different sizes, correlations of ions of different charges, and polarization of water, along with number densities of ions, water molecules, and interstitial voids. We calculate the electrostatic and steric potentials of the four binding sites in NCX, i.e., three Na(+) binding sites and one Ca(2+) binding site, with protein charges provided by the software PDB2PQR. The energy profiles of Na(+) and Ca(2+) ions along their respective Na(+) and Ca(2+) pathways in experimental conditions enable us to explain the fundamental mechanism of NCX that extrudes intracellular Ca(2+) across the cell membrane against its chemical gradient by using the downhill gradient of Na(+). Atomic and numerical details of the binding sites are given to illustrate the 3 Na(+):1 Ca(2+) stoichiometry of NCX. The protein NCX is a catalyst. It does not provide (free) energy for transport. All energy for transport in our model comes from the ions in surrounding baths.

Binding Sites of the Ca/Na Exchanger NCX Analyzed with Poisson Fermi Theory

The calcium sodium transporter NCX is a Y shaped branched channel in the structure crystallized by Liao et al. (2012) with well-defined binding sites. It seems unlikely that mechanism can be understood until structure is extended by estimates of binding free energies. It seems that existing molecular dynamics cannot cope with trace concentrations and movements of calcium. The number density of ionizable side chains is extremely high and so theory must include finite size ions and large electric and steric free energies. We use Fermi-Poisson theory (Liu and Eisenberg, 2014) that deals successfully with bulk solutions and several channel types. Outputs of theory include electric and steric fields of ions with different sizes; correlations of ions of different charge, and polarization of water, along with number densities of ions, water molecules and interstitial voids. These vary with conditions. They are not assumed.We calculate electrostatic and steric potentials of three Na+ and one Ca2+ binding site of the Liao structure with charges from PDB2PQR software. Atomic and numerical details of binding sites illustrate the ion-exchange mechanism and its energetic endpoints. Energy profiles of Na+ and Ca2+ ions along their pathways give insight into the mechanism of coupling by which NCX moves intracellular Ca2+ uphill against its chemical gradient, while Na+ moves downhill. But the mechanism and energetics of the conformation change of the transporter protein NCX remain a fascinating mystery.NCX does not use energy beyond ion gradients and electric and steric fields described consistently by Poisson-Fermi theory. Its conformation change is that of catalysis, not pumping, in the dictionary sense of ‘pumping’. Poisson-Fermi can describe energetic end points, although a kinetic model of conformation remains outside its grasp.

Electrochemical Properties of Polypyrrole Doped by Alternating Polymer Micelles

AbstractMicelles composed of alternating polymer – poly(maleic anhydride alt‐1‐octadecene) (crosslinked and hydrolyzed) of diameter close to 200 nm were incorporated to polypyrrole films in course of potentiostatic polymerization. In this way a novel composite material was obtained with quite unique properties compared to typical polypyrrole. In the present case micelles possessing negatively charged carboxyl groups served as counter ions. The presence of micelles determines nontypical properties of the films such as separate potential ranges corresponding either to cation‐ and anion‐exchange or to low concentration of mobile ions. Factors affecting sensitivity to ions of different charges are discussed. Due to presence of carboxyl groups in the micelles, the obtained films exhibit pH sensitivity, both in potentiometric and voltammetric measurements mode.

Hydration properties of Cm(iii) and Th(iv) combining coordination free energy profiles with electronic structure analysis

The hydration structure of two actinoid ions of different charge, Cm(III) and Th(IV), was investigated. Density Functional Theory, DFT-based molecular dynamics and the single sweep method were used to obtain free energy landscapes of ion-water coordination. Free energy curves as a function of the ion-water coordination number were obtained for both ions. The number of water molecules in the first coordination shell of Cm(III) varies between 8 and 10. For Th(IV), on the other hand, the 9-fold structure is stable and only the 10-fold structure seems to be accessible with a small but non-negligible free energy barrier. Finally, by combining molecular dynamics simulations with electronic structure calculations, we showed that the differences between Cm(III) and Th(IV) are mainly due to electrostatic effects. Cm(III) is less charged and it has fewer water molecules in its first shell, while Th(IV) has more water molecules because of a stronger electrostatic interaction.

‘Shell’ model for impurity spreading from a localized source

In fusion devices strongly localized intensive sources of impurities may arise unexpectedly, e.g., if the wall is excessively demolished by hot plasma particles, or can be created deliberately through impurity injection done for diverse purposes. The spreading of impurities from such sources, both along and perpendicular to the magnetic field, is affected by Coulomb collisions with background particles, ionization, acceleration by electric field, etc. Simultaneously the plasma itself can be significantly disturbed by these interactions. To describe self-consistently the impurity spreading process and the electron density response, three-dimensional fluid equations for the particle, parallel momentum and energy balances of various ion species are solved by reducing them to one-dimensional equations for the time evolution of the radial profiles of several parameters which allow finding the main characteristics of solutions: the maximum densities of impurity ions of different charges, the dimensions along and across the magnetic field of ‘shells’, i.e. the cross-sections of the regions occupied with these particles by magnetic surfaces, and characteristic temperatures of impurity ions. The results of modelling of the penetration process for carbon impurity into a relatively cold edge of ohmic TEXTOR plasma and of argon into hot H-mode plasma in JET are presented.

ChemInform Abstract: From Composites to Solid Solutions: Modeling of Ionic Conductivity in the CaF2—BaF2 System.

By using calcium fluorite and barium fluorite as test materials, we demonstrated that homovalent can greatly affect ionic conductivity through locally changing the defect density. Whilst this doping is a state-of-the-art effect in the case of dopants that replace native ions of different charge (heterovalent dopants), it is a rather surprising effect at a first glance for substitutional dopants of the same charge; here, the phenomenon is not electrostatic, but elastic in nature. As a consequence of size mismatch, the smaller Ca atoms in the BaF(2) lattice favored the formation of interstitial sites that were located close to the Ca atoms, whilst doping larger Ba species into the CaF(2) phase favored vacancy formation. In terms of conductivity, and in agreement with the different mobilities, the first doping effect was favorable, whilst the other decreased conductivity. The concentration effects were formalized by a heterogeneous Frenkel reaction that was distinguished from the mean Frenkel reaction by additional (elastic) trapping that became more pronounced the lower the temperature. It was very revealing to relate this phenomenon to CaF(2)-BaF(2) multilayers and composites. In very general terms, these effects in the solid solutions were understood as being the atomistic limit of the interfacial charge-transfer that occurred at the hetero-interface of the crystallites or films, and reflected the transition from heterogeneous doping (higher-dimensional doping) to homogeneous doping (zero-dimensional doping).