Types Of Ionic Species Research Articles

Identifying the mechanisms behind the stability of silica nano- and micro-particles: Effects of particle size, electrolyte concentration and type of ionic species

Silica nanofluids have emerged as promising agents for various applications, such as water treatment, CO2 absorption, and chemical enhanced oil recovery (CEOR). However, their effectiveness can be hindered when transported through porous media, especially in challenging downhole environments. Aggregation of nanofluid suspensions can damage formation integrity, and brine fluids may unintentionally transport fine micro silica particles, warranting an in-depth examination of micro-particle behavior and stability. This study synthesized silica particles of different sizes (10 nm, 50 nm, 1 μm and 2 μm) and meticulously characterized them using advanced techniques of transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), thermal gravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. Subsequently, 560 combinations (in 5 series of 112 experiments) of micro- and nano-fluids in the presence of four different salts (NaCl, CaCl2, MgSO4 and MgCl2) were prepared. The stability and sedimentation of these combinations were investigated based on zeta potential, particle size, pH, electrical conductivity, and UV-spectrophotometry. The results indicated that sodium ions were effective for maintaining suspension stability at lower salt concentrations, while magnesium ions were preferred for higher salinities. Particle size increase led to instability at low salinities but stability at high salinities, where enthalpy dominated over entropy. Derjaguin-Landau-Verwey-Overbeek (DLVO) modeling accurately predicted particle interactions and aggregation tendencies. This investigation enhanced the understanding of the mechanisms governing silica particle stability through diverse analytical methods, addressing their limitations. The analysis of UV data over time revealed insights into sedimentation and aggregation kinetics. In summary, this study comprehensively explored the behavior and stability of silica particles in nano- and micro-fluids, shedding light on their performance in applications ranging from enhanced oil recovery to water treatment.

Impact of nanoplastic debris on the stability and transport of metal oxide nanoparticles: role of varying soil solution chemistry

The release of metal-based nanoparticles (MNPs) and nanoplastic debris (NPDs) has become ubiquitous in the natural ecosystem. Interaction between MNPs and NPDs may alter their fate and transport in the sub-surface environment and have not been addressed so far. Therefore, the present study has explored the role of NPDs on the stability and mobility of extensively used MNPs, i.e., CuO nanoparticles (NPs) under varying soil solutions (SS) chemistry. In the absence of NPDs, a very high aggregation of CuO NPs observed in SS extracted from black, lateritic, and red soils, which can be correlated with ionic strength (IS) and type of ionic species. The sedimentation rate (ksed(1/h)) for CuO NPs was >0.5 h−1 in the case of these SS. Interestingly, the stability and sedimentation behavior of CuO NPs varied significantly in the presence of NPDs. The ksed for CuO NPs decreased to half and found <0.25 h−1 in the presence of NPDs in all SS. C/C0 values in breakthrough curves increased drastically (black < alluvial < laterite < red) in presence of NPDs. Results suggest that the release of NPDs in the terrestrial ecosystem is a potential threat leading to increased mobility of MNPs in the environment.

Computational Study of Corrosion in Steel in Aqueous Solution: a Review

Corrosion affects most of the material strength and causes damages to the material and the structure. Corrosion has become a major problem of material stability and it is difficult to predict its phenomenon. It can happen in any environment and can deteriorate metallic material. Computational models have been implemented in order to study and predict the phenomenon and the evolution of the corrosion. This paper presents a critical review of the computational model from various softwares that have been developed to observe the growth and the behaviour of corrosion on the metallic material in aqueous solution. The metallic material undergoes redox reaction with the presence of oxygen and water to form corrosion. This paper reviews the corrosion model of steel at different pH, temperatures and types of ionic species. The pH of the aqueous solution is either acidic or alkaline which will determine the rate of corrosion by the ionic reaction in the electrolyte.

A quantitative phase-field model for crevice corrosion

A quantitative phase-field model is developed for the investigation of crevice corrosion of iron in salt water. Six types of ionic species and some associated chemical reactions have been considered. In addition to the transient distributions of ion concentrations and electric potential in the electrolyte, some physical and chemical properties related to corrosion, such as overpotential, pH value and corrosion rate, under different metal potentials are studied. Benchmarking of the phase-field model against a sharp interface model is conducted. The corrosion rates predicted by the models are in the same order of magnitudes with experimental results.

Special report: Chemical industry resilience amid tough pricing

A quantitative phase-field model is developed for the investigation of crevice corrosion of iron in salt water. Six types of ionic species and some associated chemical reactions have been considered. In addition to the transient distributions of ion concentrations and electric potential in the electrolyte, some physical and chemical properties related to corrosion, such as overpotential, pH value and corrosion rate, under different metal potentials are studied. Benchmarking of the phase-field model against a sharp interface model is conducted. The corrosion rates predicted by the models are in the same order of magnitudes with experimental results.

Ionic Current Rectification in a pH-Tunable Polyelectrolyte Brushes Functionalized Conical Nanopore: Effect of Salt Gradient.

The behavior of ionic current rectification (ICR) in a conical nanopore with its surface modified by pH-tunable polyelectrolyte (PE) brushes connecting two large reservoirs subject to an applied electric field and a salt gradient is investigated. Parameters including the solution pH, types of ionic species, strength of applied salt gradient, and applied potential bias are examined for their influences on the ionic current and rectification factor, and the mechanisms involved are investigated comprehensively. The ICR behavior depends highly on the charged conditions of the PE layer, the level of pH, the geometry of nanopore, and the thickness of the double layer. In particular, the distribution of ionic species and the local electric field near the nanopore openings play a key role, yielding profound and interesting results that are informative to device design as well as experimental data interpretation.

Diffusiophoresis of polyelectrolytes: Effects of temperature, pH, type of ionic species and bulk concentration

Extending previous analyses on rigid particles to non-rigid ones, we model the diffusiophoresis of a pH-regulated polyelectrolyte (PE) in a solution containing multiple ionic species. For the first time, the effects of temperature, pH, type of ionic species and bulk concentration are taken into account, and therefore, the conditions considered are more comprehensive and closer to reality than those of the available results in the literature. Numerical simulation is conducted to examine the diffusiophoretic behaviors of a PE under various conditions, and empirical relationships are developed for the dependence of its mobility on the factors mentioned above. We show that temperature and pH influence appreciably the charged conditions of a PE, the ionic diffusivities, and the fluid viscosity, yielding complicated and interesting behaviors that are informative to device design.

Analytical expressions for the electroosmotic flow in a charge-regulated circular channel

Abstract Analytical expressions are derived for the flow velocity and ionic current for the electroosmotic flow (EOF) in a charge-regulated circular channel, focusing on the effect of types of ions and their concentrations. We show that the mean flow velocity for those two cases can be different both quantitatively and qualitatively, implying that the true charged conditions can be inferred by appropriately designed experiments. The types of ionic species and their concentrations are also found to play a significant role. Both the EOF velocity and the current density increase with increasing ionic concentration, in general. However, the reverse trend is also observed at a sufficiently high ionic concentration.

Diffusiophoresis of a pH-regulated, zwitterionic polyelectrolyte in a solution containing multiple ionic species

The diffusiophoresis of a pH-regulated, zwitterionic polyelectrolyte (PE) simulating entities such as DNAs, proteins, and synthetic polymeric particles in a solution containing multiple ionic species is modeled theoretically. The results of numerical simulation reveal that the diffusiophoretic behavior of the PE is influenced significantly by its physicochemical properties, the solution pH, the bulk salt concentration, and the types of ionic species. In particular, both the magnitude and the sign of the PE mobility are influenced appreciably by the bulk salt concentration and the types of ionic species. We show that the induced electric field coming from the applied concentration gradient is weakened by the movement of H+ and OH−. This phenomenon is more appreciable when pH is away from the isoelectric point of a PE. The results obtained provide valuable and necessary information for the design of diffusiophoresis devices.

Establishing Sensitivity of Distribution Coefficient on Various Attributes of a Soil-Contaminant System

The distribution coefficient, kd, of a soil plays a vital role in controlling its interaction with contaminant(s). Studies conducted by earlier researchers, demonstrate that kd is quite sensitive to various attributes of the soil-contaminant system viz, ratio of the contaminant in the liquid form to the solid (soil) form, pH, the cation-exchange capacity; mineralogy and redox potential of the soil, temperature, types of ionic species, and concentration of the contaminant. Hence, it becomes difficult, if not impossible, to identify the parameters that have most significant influence on the kd. Such an exercisewould be helpful in minimizing the number of batch tests to be conducted for determining the kd of a soil-contaminant system, which otherwise is a very cumbersome task. To achieve this objective, application of the Taguchi method, which primarily helps in designing experiments, appears to be a panacea. With this in view and to demonstrate the potential of this meth- odology for identification of the dominating factor(s) to which kd is highly sensitive, the Taguchi method was employed (both static and dynamic analyses) for designing batch tests. Subsequently, five parameters—cation-exchange capacity of the soil, contaminant type (ionic species of contaminant), pH of soil-contaminant system, liquid to solid ratio and concentration of the contaminant—were selected and tem- perature was maintained as a noise parameter. In this paper, kd is demonstrated to be highly sensitive to the concentration of the contaminant, cation-exchange capacity of the soil, and ionic species of the contaminant, in a decreasing order. DOI: 10.1061/(ASCE)HZ.2153-5515 .0000199. © 2014 American Society of Civil Engineers.

Diffusiophoresis of a polyelectrolyte in a salt concentration gradient

The diffusiophoresis of a polyelectrolyte subject to an applied salt concentration gradient is modeled theoretically. The entirely porous type of particle is capable of simulating entities such as DNA, protein, and synthetic polymeric particles. The dependence of the diffusiophoretic behavior of the polyelectrolyte on its physical properties, and the types of ionic species and their bulk concentrations are discussed in detail. We show that in addition to the effects coming from the polarization of double layer and the difference in the ionic diffusivities, the polarization of the condensed counterions inside the polyelectrolyte might also be significant. The last effect, which has not been reported previously, reduces both the electric force and the hydrodynamic force acting on the polyelectrolyte. Both the direction and the magnitude of the diffusiophoretic velocity of the polyelectrolyte are found to highly depend upon its physical properties. These results provide valuable references for applications such as DNA sequencing and catalytic nano- or micromotors.

Adsorção de arsênio(V) pelo compósito magnético hidrotalcita: óxido de ferro

In this work, hydrotalcite, a layered double hydroxide, had its adsorption and ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe. The removal of As(V) by a HT-Fe adsorbent was evaluated under various conditions. The Kinetic process was well described by a pseudo-second order rate model. The maximum adsorption capacity, calculated with the Langmuir model showed to be dependent on pH, reaching values of 24.09, 10.19 and 7.44 mg g-1, respectively, for pH values of 4.0, 7.0 and 9.0. The inhibition by competition of anions is dependent on the type of ionic species.

Solution Properties of Inorganic Contamination in Mixed Solvents: Theory, Progress, and Limitations

Most of what is known about the environmental fate and transport of contaminants comes from studies of dilute, aqueous solutions. Theoretical and practical aspects of hydrophobic organic contaminants in aqueous mixtures of organic solvents are well developed, but relatively little attention has been paid to those situations where inorganic contaminants such as metals, water, and organic solvents occur simultaneously. The authors discuss changes in solution properties accompanying the addition of organic solvents. They review more than 500 references to available data on ion solvation, solubility, activity, acidity, pairing, and pH in electrolyte and electrolyte-free solvent mixtures and tabulate selected experimental values. Whenever available, equations developed to estimate these properties are given and their applications and limitations described. The implications of the progress in mixed-solvents solution chemistry on contaminant behavior and transport are described. Major limitations to the study of inorganic contamination in mixed solvents include the absence of complete and comprehensive data (e.g., type of ionic species, activity coefficients, solubility constants) that characterize solute and solvent properties in these mixtures and the indefinite number of possible solute and solvent combinations. The generation of models predicting such data from easily measured benchmark solute and solvent properties is a major challenge. The availability of such database and models may open the field for environmental engineers and soil scientists to study the basic chemical processes and mechanisms of metal contamination in complex multicomponent systems.

Electrokinetic Properties of Acid-Activated Montmorillonite Dispersions

In this study, the influence of pH, electrolyte concentration, and type of ionic species on the electrokinetic properties (zeta potential and electrokinetic charge density) of the acid-activated montmorillonite mineral have been investigated using the microelectrophoresis method. The electrokinetic properties of acid-activated montmorillonite dispersions have been determined in aqueous solutions of mono-, di-, and trivalent salts and divalent heavy metal salts. Zeta potential experiments have been performed to determine the point of zero charge (pzc) and potential determining ions (pdi). The zeta potential values of the acid-activated montmorillonite particles were negative and did not vary significantly within the pH range studied. Acid-activated montmorillonite dispersions do not have point of zero charge (pzc). The valence of the electrolytes has a great influence on the electrokinetic behavior of the suspension. A gradual decrease in the zeta potential (from −25 mV to −5 mV) occurs with the monovalent electrolytes when concentration increased. Divalent and heavy metal electrolytes have less negative z-potentials due to the higher valence of ions. A sign reversal of z-potential has been observed at AlCl3, FeCl3, and CrCl3 electrolytes (potential determining ions) and zeta potential values have had a positive sign at high electrolyte concentrations. The electrokinetic charge density of acid-activated montmorillonite has shown similar trends for variation in mono- and divalent electrolyte solutions. Up to concentrations of ca. 10−3 M, it has remained practically constant at approximately 0.5 × 10−3 C m−2 For higher concentrations of monovalent electrolytes more negative values (−16 × 10−3 C m−2) were observed. It has less negative values in divalent electrolyte concentrations according to monovalent electrolytes (−5 × 10−3 C m−2). For low concentrations of trivalent electrolytes, the electrokinetic charge density of montmorillonite particles is constant, but at certain concentrations it rapidly increased and changed its sign to positive.

Temperature and pH effects on biophysical and morphological properties of self‐assembling peptide RADA16‐I

It has been found that the self-assembling peptide RADA 16-I forms a beta-sheet structure and self-assembles into nanofibers and scaffolds in favor of cell growth, hemostasis and tissue-injury repair. But its biophysical and morphological properties, especially for its beta-sheet and self-assembling properties in heat- and pH-denatured conditions, remain largely unclear. In order to better understand and design nanobiomaterials, we studied the self-assembly behaviors of RADA16-I using CD and atomic force microscopy (AFM) measurements in various pH and heat-denatured conditions. Here, we report that the peptide, when exposed to pH 1.0 and 4.0, was still able to assume a typical beta-sheet structure and self-assemble into long nanofiber, although its beta-sheet content was dramatically decreased by 10% in a pH 1.0 solution. However, the peptide, when exposed to pH 13.0, drastically lost its beta-sheet structure and assembled into different small-sized globular aggregates. Similarly, the peptide, when heat-denatured from 25 to 70 degrees C, was still able to assume a typical beta-sheet structure with 46% content, but self-assembled into small-sized globular aggregates at much higher temperature. Titration experiments showed that the peptide RADA16-I exists in three types of ionic species: acidic (fully protonated peptide), zwitterionic (electrically neutral peptide carrying partial positive and negative charges) and basic (fully deprotonated peptide) species, called 'super ions'. The unordered structure and beta-turn of these 'super ions' via hydrogen or ionic bonds, and heat Brownian motion under the above denatured conditions would directly affect the stability of the beta-sheet and nanofibers. These results help us in the design of future nanobiomaterials, such as biosensors, based on beta-sheets and environmental changes. These results also help understand the pathogenesis of the beta-sheet-mediated neuronal diseases such as Alzheimer's disease and the mechanism of hemostasis.

Use of Ureasil gels to extract ions from aqueous solutions

Nanocomposite organic–inorganic gels synthesized through the sol–gel procedure by using Ureasil precursors can be employed as efficient sorbents for retaining metal cations and small anions from aqueous solutions. Sulfate or sulfonate as well as nitrate ions demonstrate a high affinity for Ureasils. High affinity was also demonstrated by trivalent metal cations. This affinity was explained by the presence of urea and of ether groups in Ureasils, which have the ability to complex many different types of ionic species.

The effects of electrolyte concentration, ion species and pH on the zeta potential and electrokinetic charge density of montmorillonite

AbstractIn this study, the influence of pH, electrolyte concentration and type of ionic species (such as LiCl, NaCl, KCl, RbCl, CsCl, CaCl2, AlCl3) on the electrokinetic properties (zeta potential and electrokinetic charge density) of montmorillonite has been quantified. The zeta potential of montmorillonite particles did not change significantly with change in pH. The valencies of the ions have proven to have a great influence on the electrokinetic behaviour of the suspension. There is a gradual decrease in the zeta potential (from —24 mV to —12 mV) with increase in monovalent electrolyte concentration (from 10-4 M to 10-1 M). At any monovalent electrolyte concentration, the magnitude of the zeta potential increased with the electrolytes in the order Li+ &gt; Na+ &gt; K+ &gt; Rb+ &gt; Cs+. The zeta potential of the montmorillonite minerals in CaCl2 solutions illustrated the same behaviour as the monovalent cations. Less negative values were obtained for the CaCl2 electrolyte (∼–10 mV) due to the greater valence of the ions. A sign reversal was observed at an AlCl3 concentration of 5 x 10-4 M, and, at greater concentrations, zeta potential values had a positive sign (∼20 mV).The electrokinetic charge density of montmorillonite showed similar trends of variation in mono and divalent electrolyte solutions. Up to concentrations of ∼10-3 M, it remained practically constant at ∼0.5 x 10-3Cm-2, while for greater electrolyte concentrations the negative charge produced more negative values (–16 x 10-3Cm-2). The electrokinetic charge density of montmorillonite particles was constant at low AlCl3 concentrations, but at certain concentrations it increased rapidly and changed sign to positive.

Matrix effects, internal energies and MS/MS spectra of molecular ions sputtered from surfaces

Desorption ionization (DI) involves the transfer of material from a condensed phase to a collision-free environment (ref. 1,2). Tandem mass spectrometry (ref. 3), used with desorption ionization, improves the signal-to-noise ratio for spectra of individual analytes present in complex matrices, provides evidence that fragmentation in DI is typically due to gas phase dissociations of energized but intact molecular ions after they have left the surface, and allows the compositions of desorbed ions to be characterized. A complementary approach to improving analytical performance and obtaining further information on the species and processes of desorption ionization is to be found in the examination of the sample in the presence of matrix materials. Some matrices act as reagents which yield an appropriate ionized form of the analyte (ref. 4), either during or prior to energization of the sample, while others serve to isolate analyte molecules and reduce intermolecular analyte reactions (ref. 5). Particularly complex matrices are those encountered when examining samples directly from chromatographic materials or in their natural state, for example, crude extracts of plant materials. Examples of analyses in these situations are given. Ammonium chloride acts as a valuable matrix material which, even at sample dilutions of 10 3, can cause an increase in both absolute secondary ion yields and in spectral persistence (ref. 6,7,8). This matrix has beneficial effects in SIMS, FAB and LD mass spectra and has the advantage of being totally transparent except under high flux conditions. It is shown to decrease ion internal energies, presumably by providing a sputtered ion with a shield of solvating molecules which are readily lost as NH 3 and HCl, thereby carrying away excess energy. Cluster ions [(NH 4) n+1Cl n] + are observed in FAB and shown by MS/MS to undergo ready desolvation. These cluster ions are remarkable for the absence or low intensity of clusters where the total number of anions and cations is a prime number and for the high intensity of clusters which may be made up of regular arrays of atoms, e.g., 3×3×3 or 3×3×5. A qualitative model of desorption ionization, advanced some years ago (ref. 9), accommodates the observations reported here using MS/MS and matrix effects. The chief features of this model are (i) isomerization (loss of identity) of the input energy, (ii) desorption of preformed ions or intact molecules, (iii) ion/molecule reactions such as cationization occurring in the selvedge region, (iv) dissociation of energetic (metastable) ions well-removed from the surface. In most cases just a few types of ionic species are sputtered from the surface and their unimolecular chemistry determines the chief features of the desorption ionization mass spectrum.

Effect of ion placement and structure on properties of plasticized polyelectrolytes

Abstract Exploratory studies of three polyelectrolytes containing several types of ionic species in different molecular environments were performed by dynamic mechanical, dielectric, and calorimetric methods. The materials were dimethyldiallyl-ammonium chloride (DMDAAC), 3-acrylamido-3-methylbutyl trimethylammonium chloride (AMBTAC) and sodium 2-acrylamido-2-methylpropanesulfonate (AMPS). It was found that the glass transition temperature of the polyanionic material is higher than that of polycationic materials, which correlates with the charge to internuclear distance (q/a) effect. In all of the materials studied, it was observed that the glass transition shifts to lower temperatures, and that the tan δ peak height increases with increasing plasticizer content. However, the general pattern of Tg depression is quite different for the polycationic polymers than for the anionics, as is shown by comparing the results of this work with several previous studies. For water-plasticized DMDAAC, which was studied ...