nach oben

2014 | Buch

Kapitel lesen Erstes Kapitel lesen

Transport and Reactivity of Solutions in Confined Hydrosystems

herausgegeben von: Lionel Mercury, Niels Tas, Michael Zilberbrand

Verlag: Springer Netherlands

Buchreihe : NATO Science for Peace and Security Series C: Environmental Security

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

Einloggen, um Zugang zu erhalten

Über dieses Buch

The present work reflects a multi-disciplinary effort to address the topic of confined hydrosystems developed with a cross-fertilization panel of physics, chemists, biologists, soil and earth scientists. Confined hydrosystems include all situations in natural settings wherein the extent of the liquid phase is limited so that the solid-liquid and/or liquid-air interfaces may be critical to the properties of the whole system. Primarily, this so-called “residual” solution is occluded in pores/channels in such a way that decreases its tendency to evaporation, and makes it long-lasting in arid (Earth deserts) and hyper-arid (Mars soils) areas. The associated physics is available from domains like capillarity, adsorption and wetting, and surface forces. However, many processes are still to understand due to the close relationship between local structure and matter properties, the subtle interplay between the host and the guest, the complex intermingling among static reactivity and migration pathway.

Expert contributors from Israel, Russia, Europe and US discuss the behaviour of water and aqueous solutes at different scale, from the nanometric range of carbon nanotubes and nanofluidics to the regional scale of aquifers reactive flow in sedimentary basins. This scientific scope allowed the group of participants with very different background to tackle the confinement topic at different scales. The book is organized according to four sections that include: i) flow, from nano- to mega-scale; ii) ions, hydration and transport; iii) in-pores/channels cavitation; iv) crystallization under confinement. Most of contributions relates to experimental works at different resolution, interpreted through classic thermodynamics and intermolecular forces. Simulation techniques are used to explore the atomic scale of interfaces and the migration in the thinnest angstrom-wide channels.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Interactions in Water Across Interfaces: From Nano to Macro-Scale Perspective

Abstract

In this work we first revisit the surface forces between two (model) mineral surfaces, mica, across an aqueous solution (KNO₃) over a broad range of concentrations. The significantly improved resolution available from the extended surface force apparatus (eSFA) allows the distinction of hydrated-ion structures. Above concentrations of 0.3 mM, hydrated-ion correlations give rise to multiple collective transitions (4 ± 1 Å) in the electrical double layers upon interpenetration. These features are interpreted as the result of hydrated-ion ordering (layering), and are responsible for hydration forces, in contrast to the traditional interpretation invoking water layering. At concentrations as low as 20 mM, attractive surface forces are measured in deviation to the DLVO theory. The estimated hydration number of the ions in the confined electrolyte is significantly below that of the bulk. A confined 1–3 nm thick ionic layer condensates at concentrations >100 mM, i.e. below bulk saturation. This study leads to new insights into crystal growth in nano-confinement that differs from the classical theory of crystallization. Finally, the impact of the properties of confined water or solution and in-pore crystallization on the macro-scale description of soil water distribution is discussed.

Rosa M. Espinosa-Marzal

Flow, from Nano- to Mega-Scale

Frontmatter

Chapter 2. Confined Water in Carbon Nanotubes and Its Applications

Abstract

Unique nanoscale transport properties of carbon nanotubes (CNTs) have inspired researchers for over a decade, initially with their analogies to various biological pores and later with the potential impact on water purification. Water can permeate through a nanometer-wide pipe of the CNT interior at rates far exceeding those predicted by Hagen-Poiseuille formulation and measured in nano conduits of different material, attributed to nano confinement, hydrophobicity, and smooth potential energy landscape. Also, chemical addition to the nanotube ends was found effective in electrostatic exclusion of ions without much loss of water permeability, suggesting the emergence of CNT membranes for desalination and purification of water resources. This article introduces Carbon Nanotube Nanofluidics by capturing important findings and progresses made in the early developments of the area.

Seul Ki Youn, Jakob Buchheim, Hyung Gyu Park

Chapter 3. Static and Dynamic Capillarity in Silicon Based Nanochannels

Abstract

In this chapter we review the fabrication of silicon based nanochannels and their use in capillarity studies. Static capillarity measurements of the pressure in isolated liquid plugs confined in hydrophilic nanochannels, confirm the existence of capillary negative pressure, quantitatively in accordance with the Young-Laplace equation. The negative pressure can be quantified through measurement of the elasto-capillary deformation of the channel capping due to the pressure difference with the atmospheric pressure. By measuring the capillary filling dynamics in nanochannels of uniform and accurately defined height, different (apparent) viscosity effects in confinement have been revealed. One effect (visible in insulating sub-100-nm channels) is likely to be related to the influence of the electrical double layer (an electroviscous effect), while the other effect (visible in conductive sub-50 nm channels) seems to be related to a decrease in the effective channel due to a thin immobile layer close to the polar or charged channel wall.

Niels Tas, Nataliya Brunets, Joost W. van Honschoten, Jeroen Haneveld, Henri V. Jansen

Chapter 4. Infrared-Thermodynamics Conversion as a Function of Temperature: Towards Confined Water

Abstract

An experimental method has been developed to calculate the thermodynamic properties of water from its vibrational properties, relevant to study (in near future) the properties of adsorbed or confined water. The infrared absorption of the intra-molecular OH stretching mode of liquid water has been measured over a wide range of temperature (from−10 to 90 °C). The corresponding large band has been decomposed into three Gaussian components standing for three different water connectivities (percolation model) that feature the liquid state as a function of temperature: network, intermediate, and multimer water. Measurements evidenced that the components are differently shifted with temperature, giving a quantitative insights into the internal energy change of liquid. A vibrational partition function has been used to calculate the corresponding thermodynamic properties, neglecting all energy components except the present intra-molecular vibrational mode. Interestingly, the vibrational free enthalpy thus computed differs of the total free enthalpy only by a multiplicative constant all along the thermal range.

Isabelle Bergonzi, Lionel Mercury

Chapter 5. Interchange of Infiltrating and Resident Water in Partially Saturated Media

Abstract

The interplay between resident water (“old water”) and infiltrating water (“new water”) in porous media is examined through experiments in an idealized 2D glass micromodel. The analysis is motivated by the recognition that two complementary processes occur as water migrates through the vadose zone: infiltration, when water advances downward through this zone, and drainage, which follows infiltration events (precipitation and irrigation) when air displaces water as the water migrates deeper into the subsurface. Residual water saturation after a cycle of drainage is controlled by pores and pore clusters that retain “old water”. During an infiltration cycle, “new water” flowing through the porous medium will intermittently connect to these clusters and then will leave a new pattern of disconnected clusters containing, presumably, both old and new water. In the micromodel experiments, image analysis is used to quantify the miscible interplay between old and new water over a cycle of imbibition by new water and drainage by air in a domain that is partially saturated with old water. We demonstrate that some old water remains in the system at long times within stable water pockets; these pockets may remain stable even after a second cycle of infiltration. An implication of this finding is that water scarcity under dry climate conditions may increase the influence of mixing of infiltrating and resident water on water quality, particularly in the uppermost aquifer layers.

Brian Berkowitz

Chapter 6. Impact of Heterogeneity on Evaporation from Bare Soils

Abstract

Heterogeneity in soil hydraulic properties has a significant impact on evaporation, and could be harnessed to reduce water losses and improve soil water conservation. This is illustrated through the consideration of the effect of Darcy scale heterogeneities resulting from horizontal layering. The impact of permeability gradient and thickness of layers has been investigated from evaporation experiments performed from homogeneous as well as horizontally multi-layered soil columns. Two main cases are distinguished depending on the sign of the permeability gradient, the unstable case when the permeability increases with depth and the stable case when, on the contrary, the permeability decreases with depth. The results indicate an interesting competition between stabilizing gravity effects and destabilizing or stabilizing permeability gradient effects and lead to the emergence of the concept of two-scale evaporation process.

Shmuel Assouline, Kfir Narkis, Stéphanie Veran-Tissoires, Manuel Marcoux, Marc Prat

Ions, Hydration, and Transport

Frontmatter

Chapter 7. Enhanced Ion Transport in 2-nm Silica Nanochannels

Abstract

Fluidic nanochannels with 1–2 nm in size are functional mimics of protein channels, and have recently attracted significant attention for exploring the transport of ions and molecules in confined liquids. Here we report ion transport in 2 nm deep nanochannels fabricated by standard semiconductor manufacturing processes. Ion transport in these nanochannels is dominated by surface charge until the ion concentration exceeds 100 mM. At low concentrations, proton mobility increases by a factor of four over its bulk value, possibly due to overlap of the two hydration layers adjacent to hydrophilic surfaces. The mobility of K+/Na + ions also increases as the bulk concentration decreases, although the reasons are not completely understood.

Chuanhua Duan

Chapter 8. Ionic and Molecular Transport Through Graphene Membranes

Abstract

New membrane materials have the potential to address some of the persistent challenges in water purification to improve the flux of water, selectivity to ions or contaminants, and fouling resistance. With its atomistic thickness and the ability to sustain nanometer-scale holes, graphene promises significant enhancement in the flux of water while offering potentially novel transport properties. In this work, the transport of ions and molecules through a single layer of graphene were measured as a first step towards realizing practical graphene membranes. Graphene grown by chemical vapor deposition (CVD) was transferred to a porous polycarbonate support membrane, and the diffusion of different salts and molecules was examined. While pressure-driven flow measurements revealed that the graphene covered the polycarbonate support membrane, diffusion experiments showed that it was permeable to salts, but not to larger molecules. This behavior was attributed to intrinsic defects in graphene in the 1–15 nm size range.

Rohit Karnik

Chapter 9. Molecular Structure and Dynamics of Nano-Confined Water: Computer Simulations of Aqueous Species in Clay, Cement, and Polymer Membranes

Abstract

Molecular-level knowledge of the thermodynamic, structural, and transport properties of water confined by interfaces and nanopores of various materials is crucial for quantitative understanding and prediction of many natural and technological processes, including carbon sequestration, water desalination, nuclear waste storage, cement chemistry, fuel cell technology, etc. Computational molecular modeling is capable to significantly complement the experimental investigations of such systems by providing invaluable atomic-scale information leading to improved understanding of the specific effects of the substrate structure and composition on the structure, dynamics and reactivity of interfacial and nano-confined aqueous solutions. This paper offers a brief overview of recent efforts to quantify some of these effects for individual H₂O molecules and hydrated ions confined at the interfaces and in nanopores of several typical hydrophilic and hydrophobic materials. The first molecular layer of aqueous solution at all substrates is often highly ordered, indicating reduced translational and orientational mobility of the H₂O molecules. This ordering cannot be simply described as “ice-like”, but rather resembles the behavior of supercooled water or amorphous ice, although with very significant substrate-specific variations.

Andrey G. Kalinichev

Chapter 10. Two Generalizations of the Theory of Seismoelectric Effect: Parameterization Providing Suitability of Frenkel’s Theory for Any Geometry of Soil’s Pore Space. The Role of Thermoosmosis in Seismoelectric Effect

Abstract

Seismic vibrations of water-saturated soils and rocks cause the fluid motion relative to the charged interface and thus to the flow potential. Thus a seismoelectrical wave is formed, in which the ratio of its sound and electrical components carries diverse information about water in soils and rocks. As a result electroseismic method is of importance for the problem of water resources and is widely used in hydrogeology. However, at present it is possible to explain only a small part of the information carried by the electroseismic signal. Empowering the method depends on the improvement of equipment and measurement as well as by means of the further development of the theory of seismoelectric effect. This paper makes two steps in the development of theory. First, it manages to express the seismoelectric field strength through the ζ-potential and through only the macroscopic parameters of Frenkel’s classic theory, which makes it suitable for any geometry of soil’s pore space. Second, for the first time the influence on the seismoelectric effect is considered of thermoosmotic flow arising under the action of temperature gradients which always accompany the sound wave.

Vladimir N. Shilov

In-Pores/Channels Cavitation

Frontmatter

Chapter 11. Evaporation-Induced Cavitation in Nanofluidic Channels: Dynamics and Origin

Abstract

In this chapter, we report a new mode of heterogeneous cavitation, i.e. evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures. The liquid menisci in nanochannels are observed to be pinned at the entrance while vapor bubbles form and expand inside during the evaporation. It is observed that the growth rate of the vapor bubbles is controlled by water evaporation at the channel entrance, which is actually significantly enhanced due to absence of vapor diffusion along the nanochannel. We also report previously unexplored bubble nucleation, growth, stability, translational symmetry and dynamics that seem to be unique at the nanoscale.

Chuanhua Duan

Chapter 12. Electrocavitation in Nanochannels

Abstract

A novel method has been developed to cavitate aqueous solutions, which is called electrocavitation. An axial voltage is applied in a nanochannel containing an aqueous solution with a stepwise conductivity gradient. A combination of electrical and viscous forces then generates a tension in the solution which, at sufficiently low pressures, causes it to cavitate. Measurement of the current during the experiment as well as optical observation provides knowledge on the time and axial position of cavitation, after which the pressure at the cavitation position can be calculated from a theoretical model in which also the ζ-potential is inserted, which is separately determined from electroosmotic flow experiments. It is found that generally the cavitation position coincides with the position of the conductivity step. In several experiments the cavitation pressure in successive experiments on the same channel became increasingly lower, suggesting a gradual removal of cavitation nuclei from the system. We calculated that pressures as low as −1630 bar ±10 % have been reached, close to theoretically predicted pressures for homogeneous cavitation. The platform performs reliably and can be easily controlled.

Daniel S. van Schoot, Kjeld G. H. Janssen, Niels R. Tas, Thomas Hankemeier, Jan C. T. Eijkel

Chapter 13. Stability and Negative Pressure in Bulk and Confined Liquids

Abstract

Negative pressure in liquids – especially in confined systems, like capillaries – often acts as a cohesive force between the solid walls, surrounding the liquid. These forces are responsible for various processes and phenomena, like sap transport in trees or mud stability/mud slides of granular systems (like soil). Due to the metastability of the liquids under negative pressure, different properties (including the limit of stability) cannot be measured directly because the metastable state might equilibrate back to stable ones (liquid + vapour) by cavitation, before the end of the measurement. Therefore it would be crucial to have an equation of state to describe the behavior of liquids (especially for water) in this region. We are going to present some result – comparing experimental data, molecular dynamic simulations and some analytical calculations -, showing which equations could be used in the metastable region and which should be the special pre-cautions taken during their use.

Attila R. Imre

Chapter 14. Experimental Superheating and Cavitation of Water and Solutions at Spinodal-Like Negative Pressures

Abstract

The superheated liquids are metastable with respect to their vapour, what means they can exist under arid conditions whatever the temperature: capillary liquid residing in arid soils (desert shrubs, Mars sub-surface, …), solutions in the deep Earth crust, or water involved in rapid disequilibrium events (terrestrial or submarine geysers). The superheating state changes the solvent properties of liquids, and so modifies phase transitions (solid–liquid, liquid–vapor) P-T-X conditions. The synthetic fluid inclusion (SFI) enables to fabricate micro-volumes of hand-made liquid dispersed inside quartz, which readily superheat. Volumes of SFI are intermediate between macro-systems, in which superheating is restricted to around −30–35 MPa with very short lifetime, and nanosystems, wherein confinement effects predominate and in which the host size is similar to the one of the critical nucleus of vapour phase (huge nucleation barrier). This volume-to-metastability relationship is still to be defined quantitatively, and we are targeting to combine thermometric classical measurements with spectrometric characterizations, enabling to establish the threshold between micro- and nano-systems precisely. Meanwhile, the experiments performed so far illustrate the diversity of contexts and situations that could be modelled by superheating issues.

Lionel Mercury, Kirill I. Shmulovich

Chapter 15. Plant Water Transport and Cavitation

Abstract

Water transport in the xylem of plants from the roots to leaves occurs under negative pressure. This makes the xylem sap vulnerable to cavitation. Cavitation is a common phenomenon in plants, and it induces major consequences on plant function by limiting the ability of the plant to extract water from drying soils and transport it to the leaves. Decreased water conductive capacity due to cavitation leads to decreased carbon assimilation rates by photosynthesis, and in extreme conditions, to plant mortality. Many plant species have the capability to refill xylem conduits, which have become air-filled due to cavitation.

Teemu Hölttä, John Sperry

Crystallization Under Confinement

Frontmatter

Chapter 16. Crystal Growth and Phase Equilibria in Porous Materials

Abstract

In numerous research areas there is considerable interest in the phase changes occurring in pore solutions. First, the pressure generated by crystal growth of salts in confined spaces of porous materials is generally recognized as a major damage mechanism. Second, dissolved salts strongly affect the moisture retention and transport properties of porous media. This report briefly reviews recent advances in the treatment of phase equilibria of salts in porous substrates. The first part deals with the theory of crystallization pressure. In the second part model approaches for the calculation of thermodynamic properties in mixed electrolyte solutions and the calculation of phase equilibria are discussed.

Michael Steiger

Chapter 17. Shaping the Interface – Interactions Between Confined Water and the Confining Solid

Abstract

The thermodynamics and kinetics of stressed solids with aqueous solutions in the grain interfaces are summarized. The main focus is on pressure solution and the connection to force of crystallization (crystallization pressure) is shown. The largest driving force of pressure solution, the work term, is linear in stress, all other contributions to the driving force are more than 3 orders of magnitude smaller. The minor driving forces (strain energy, surface tension, surface charges) are important for the transformation and stability of the interface structure and thereby the kinetics of pressure solution. Interface structure and stability may change strain rates up to 7 orders of magnitude.

Dag Kristian Dysthe

Chapter 18. Geochemistry of Capillary Hydrogeochemical Systems in Arid Environments

Abstract

In arid environments, porous media are unsaturated with water which is submitted to capillary constraints. The present chapter focuses on the geochemical impacts of such physical constraints and how theoretical analysis can help interpreting field or laboratory observations. The basic principles of capillary geochemistry suggest that the fate of contaminants, either organic or inorganic, can be significantly impacted in terms of reactive mass transfer in addition to flow and transport processes. All these mechanisms are closely interconnected, what makes the description of the behavior of such systems very complicated. An important work still has to be done in order to achieve such a goal: a number of mechanisms are not taken into account in the current state of development of the capillary geochemistry, namely mechanisms that occur in the thinnest confining geometries, like disjoining pressures, surface forces, etc.

Arnault Lassin, Lionel Mercury, Mohamed Azaroual

Chapter 19. Evaporation from a Porous Medium in the Presence of Salt Crystallization

Abstract

The interplay between salt transport, crystallization and evaporation from a porous medium is a topic rich in interesting open problems. This is illustrated through the consideration of a few of them from experiments with model porous media. We notably discuss the factors controlling the localization of crystallization spots at the evaporative surface of a porous medium and the impact of surface crystallization on evaporation kinetics.

Marc Prat

Chapter 20. Micro-CT Analysis to Explore Salt Precipitation Impact on Porous Media Permeability

Abstract

The concern for water scarcity as a future reality for a growing proportion of the planet is driving the need to understand in greater detail the role of water in ecosystem sustainability and resiliency. Pertinent to this conversation is the role that salt precipitation and salinization has on soil resources. This paper addresses this task by presenting results of a detailed study on the reduction in gas permeability of a porous media by subflorescent salt precipitation. Using high-resolution CT scanning and detailed Lattice Boltzman Modeling, the three dimensional distribution of salt was mapped and its effect on permeability was calculated. It was found that salt precipitate mass increases towards the soil surface and that the effect of subsurface precipitation on gas permeability was significant, potentially impacting gas exchange processes between atmosphere and vadose zone. In addition, results from the LBM were compared to estimates using the Koseny-Carman equation. A good correlation between these two methods indicates that the Koseny-Carman equation may be sufficient to calculate changes in permeability, providing a more accessible tool relative to the more complicated LBM approach. This study has made it clear that knowledge of the spatial distribution of salt precipitation is essential for any estimation of gas permeability changes due to subflorescence.

Noam Weisbrod, Uri Nachshon, Maria Dragila, Avrami Grader

Chapter 21. Reactive Transport in Heterogeneous Media

Abstract

We analyze the dynamics of reactive transport in heterogeneous media, emphasizing the nature of the chemical reactions and the role of small-scale fluctuations induced by the structure of the porous medium, which is the main component of geological formations. Our goal is the interpretation of the results of laboratory-scale experiments, for which detailed characterization of the system is possible. Modelling approaches have been based on continuum and particle tracking (PT) schemes, which differ in how the fluctuations are incorporated. We choose PT methods wherein space-time transitions are drawn from appropriate probability distributions that have been tested to account for anomalous (non-Fickian) transport. While PT methods have been employed for many years to describe conservative transport, their application to laboratory-scale reactive transport problems in the context of both Fickian and non-Fickian regimes is relatively recent. We concentrate on experimental observations of different types of reactions in heterogeneous media: (1) the dynamics of a bimolecular reactive transport (A + B → C) in passive (non-reactive) media, and (2) a multi-step chemical reaction, as exemplified in the process of dedolomitization involving both dissolution and precipitation. The fluctuations in a number of the key variables controlling the processes prove to have a dominant role; elucidation of this role forms the basis of the present study. An implication of these findings is that subtle changes in patterns of water flow, as a result of climate change or changes in land use, may have significant effects on water quality.

Harvey Scher, Brian Berkowitz

Chapter 22. Extraction of Water from the Atmosphere in Arid Areas by Employing Composites “A Salt Inside a Porous Matrix”

Abstract

This communication is addressed to sorptive extraction of water from the atmosphere in arid areas. The method includes (a) sorption of water vapour in an adsorber in the night-time when the air relative humidity is comparatively high, and (b) desorption of the stored water and its subsequent collection in a condenser in the day-time. New materials adapted to this process are highly welcome. Composites “a salt inside a porous matrix” (CSPMs) have enhanced water sorption capacity and their properties may be intently varied in a wide range. In this communication, we make a preliminary analysis of CSPMs application for extraction of water from the atmosphere. Firstly, a general scheme of the water extraction is described. Then, we form a mental representation of an ideal solid sorbent that is optimal for the extraction of water from the atmosphere. Finally, we discuss how to design a real CSPM with properties meeting the formulated requirements, what are roles of the salt and the matrix, etc.

Larisa Gordeeva, Yuri Aristov

Titel: Transport and Reactivity of Solutions in Confined Hydrosystems
herausgegeben von: Lionel Mercury
Niels Tas
Michael Zilberbrand
Verlag: Springer Netherlands
Electronic ISBN: 978-94-007-7534-3
Print ISBN: 978-94-007-7533-6
DOI: https://doi.org/10.1007/978-94-007-7534-3