Reversible charging of the ice–water interface (original) (raw)
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Ice/Water Interface: Zeta Potential, Point of Zero Charge, and Hydrophobicity
Journal of Colloid and Interface Science, 1999
The ice/water interface is a common and important part of many biological, environmental, and technological systems. In contrast to its importance, the system has not been extensively studied and is not well understood. Therefore, in this paper the properties of the H 2 O ice/water and D 2 O ice/water interfaces were investigated. Although the zeta potential vs pH data points were significantly scattered, it was determined that the isoelectric point (iep) of D 2 O ice particles in water at 3.5°C containing 10 ؊3 M NaCl occurs at about pH 3.0. The negative values of the zeta potential, calculated from the electrophoretic mobility, seem to decrease with decreasing content of NaCl, while the iep shifts to a higher pH. The point of zero charge (pzc) of D 2 O ice and H 2 O ice, determined by changes in pH of 10 ؊4 M NaCl aqueous solution at 0.5°C after the ice particle addition, was found to be very different from the iep and equal to pH 7.0 ؎ 0.5. The shift of the iep with NaCl concentration and the difference in the positions of the iep and pzc on the pH scale point to complex specific adsorption of ions at the interface. Interestingly, similar values of iep and pzc were found for very different systems, such as hydrophilic ice and highly hydrophobic hexadecane droplets in water. A comparison of the zeta potential vs pH curves for hydrophilic ice and hydrophobic materials that do not possess dissociative functional groups at the interface (diamond, air bubbles, bacteria, and hexadecane) indicated that all of them have an iep near pH 3.5. These results indicate that the zeta potential and surface charge data alone cannot be used to delineate the electrochemical properties of a given water/moiety interface because similar electrical properties do not necessary mean a similar structure of the interfacial region. A good example is the aliphatic hydrocarbon/water interface in comparison to the ice/water interface. Although the experiments were carried out with care, both the zeta potential, measured with a precise ZetaPlus meter, and ⌬pH values (a measure of surface charge) vs pH were significantly scattered, and the origin of dissemination of the data points was not established. Differently charged ice particles and not fully equilibrium conditions at the ice/water interface may have been responsible for the dissemination of the data.
The journal of physical chemistry. B, 2014
We present a first-principles study of the properties of ordinary hexagonal ice (phase I(h)) and of its proton-ordered version (phase XI) under the action of static electric fields. We compute the mechanical response to the field in addition to the ionic current-voltage diagrams; we also analyze several other microscopic aspects of the proton transfer mechanism, with particular emphasis on the role played by the oxygen sublattice in driving molecular dissociation. We further study the topological aspects of the mechanical and electrical responses by orienting the external field along two different crystalline directions in both ice samples. At variance with ice Ih, ice XI displays an anisotropic behavior in the range of explored field intensities. In fact, when the direction of the field coincides with the ferroelectric axis, sustained molecular dissociation and proton transfer events are both observed just beyond a given field intensity; instead, the two processes exhibit different...
Investigation of the Proton-Exchange Processes at the Ice - Metal Interface
Le Journal de Physique Colloques, 1987
Resume-La presence dtune atmosphere dqhydrog&ne exerce une grande influence sur les courants continus de volume et de surface dans le cas d*un 6chantillon de glace maintenu entre des hlectrodes de Pd et d'alliages de Pd. La charge automatique de Pd et de ses alliages est peut-stre une possibilite pour produire une 6lectrode ohmique protonique permanente.
We present a first-principles study of the properties of ordinary hexagonal ice (phase I h ) and of its proton-ordered version (phase XI) under the action of static electric fields. We compute the mechanical response to the field in addition to the ionic current-voltage diagrams; we also analyze several other microscopic aspects of the proton transfer mechanism, with particular emphasis on the role played by the oxygen sublattice in driving molecular dissociation. We further study the topological aspects of the mechanical and electrical responses by orienting the external field along two different crystalline directions in both ice samples. At variance with ice I h , ice XI displays an anisotropic behavior in the range of explored field intensities. In fact, when the direction of the field coincides with the ferroelectric axis, sustained molecular dissociation and proton transfer events are both observed just beyond a given field intensity; instead, the two processes exhibit different activation thresholds when the field is oriented along another symmetry axis. The underlying mechanism of molecular dissociation appears to be the same in solid and liquid water independently of the direction of the field.
Using Mutual Charge Scheme to Measure Salinity of Ice
2015
For offshore measurements in Cold Regions, salinity of ice is also a critical parameter (together with many other parameters such as icing type, load, icing rate and melting rate) to be identified in order to optimize the performance of anti/de icing systems. Although there are some available sensory solutions in the market to measure real time salinity levels of water, however there are still not many real time techniques or solutions to measure the salinity of ice. In this research task, mutual charge transfer technique is utilized to measure the zero crossover values of different samples of ice and water with varying salt ratios. The aim of this paper is therefore to discuss the testing methodology and testing results.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
For a small volume (of about 10 −6 cm 3) of NaCl and other electrolyte solutions (C = 0.1 and 1 M) in thin (r = 5/10 m) single quartz capillaries, dependencies of the column length l of frozen solutions on the temperature t were measured using comparator IZA-2 in a thermostated chamber. At temperatures range t > −4 • C (for C = 0.1 M) and t > −8 • C (for C = 1 M) the l(t) dependencies are reversible and therefore correspond to establishment of an equilibrium between ice-1 and the solution. From the constants mass condition of the dissolved salt in a frozen column, the l(t) expression was derived, which includes thermodynamic relation between solution concentration in an equilibrium with ice, C s , and the temperature t for bulk systems. Deviations from the data known for bulk solutions were observed in thin capillaries when temperature t decreased to −3 • C (for 0.1 M NaCl) and to −6 • C for 1 M NaCl solution. This effect may be a result of strong adhesion of the ice column to capillary walls. In this case, some internal stresses arise in frozen solution resulting in a deviation from thermodynamic equilibrium conditions for bulk systems. When approaching the temperature of ice melting, adhesion forces decrease due to formation of a thin non-freezing water interlayer on the capillary wall. In this temperature range the experimental data are in agreement with the predictions for bulk systems. It was supposed that the observed deviation in thin capillaries may be caused by formation of an amorphous ice phase with higher density as compared with the ice-1 during rapid freezing, or by an effect of ice microlenses formation. Both effects will result in a deviation from the phase diagram corresponding to a bulk solution.
Chemistry of ice: Migration of ions and gases by directional freezing of water
Arabian Journal of Chemistry
Redistribution of anions and cations creates an electrical imbalance in ice grown from electrolyte solutions. Movement of acidic and basic ions in cooling solutions can permanently change the pH of frozen and unfrozen parts of the system, largely. The extent of pH change associated with freezing is determined by solute concentration and the extent of cooling. In the present work, redistribution of hydrogen, hydroxyl, carbonate, and bicarbonate ions was studied during directional freezing in batch aqueous systems. Controlled freezing was employed vertically as well as radially in acidic and basic solutions. In each case, the ions substantially migrated along with moving freezing front. Conductometry and pH-metry were employed to monitor the moving ions. Besides, some other experiments were carried out with molecular gases, such as oxygen, carbon dioxide, and chlorine and an azeotropic mixture like water–ethanol. Findings can be used to understand possible changes that can occur in preserving materials by freezing.
Industrial & Engineering Chemistry Research, 2008
MgCl 2 ) have been measured by a reliable differential temperature technique. The available experimental literature data on the freezing point depression in addition to the vapor pressure data of aqueous electrolyte solutions for NaCl, KCl, KOH, CaCl 2 , MgCl 2 , CaBr 2 , ZnCl 2 and ZnBr 2 have been used to optimize binary interaction parameters between salts and water. The fugacity of water in salt-free aqueous phase has been modeled by the Cubic-Plus-Association (CPA) equation of state. The Debye-Hückel electrostatic term has been used for taking into account the effect of salt on the fugacity of water when electrolytes are present. Model predictions are validated against independent experimental data generated in this work for both single and mixed electrolyte solutions and a good agreement between predictions and experimental data is observed, supporting the reliability of the developed model.
Proton Conduction in Water Ices under an Electric Field
We report on a first-principles study of the effects produced by a static electric field on proton conduction in ordinary hexagonal ice (phase I h ) and in its proton-ordered counterpart (phase XI). We performed ab initio molecular dynamics simulations of both phases and investigated the effects produced by the field on the structure of the material, with particular attention paid to the phenomenon of proton transfer. We observed that in ice I h molecules start to dissociate for field intensities around 0.25 V/Å, as in liquid water, whereas fields stronger than 0.36 V/Å are needed to induce a permanent proton flow. In contrast, in ice XI, electric fields as intense as 0.22 V/Å are already able to induce and sustain, through correlated proton jumps, an ionic current; this behavior suggests, somewhat counterintuitively, that the ordering of protons favors the autoprotolysis phenomenon. However, the same is not true for static conductivities. In fact, both crystalline phases show an ohmic behavior in the conduction regime, but the conductivity of ice I h turns out to be larger than that of ice XI. We finally discuss the qualitative and quantitative importance of the conspicuous concentration of ionic defects generated by intense electric fields in determining the value of the conductivity, also through a comparison with the experimental data available for saline ices.