Deliquescence Of Salts Research Articles

Influences of saltwater immersion on properties of wood-cellulosic paper.

The saltwater immersion method was developed to inhibit mould growth on flood- or tsunami-damaged paper. Commercially available fine paper used for printing and writing showed decreased tensile indices after saltwater immersion. The salt remaining in the paper tended to increase the moisture content because of the salt deliquescence and moisture in the air. The tensile index was restored by removing salt from the paper. Crystallization and distribution of salt in interfibre pores were also considered to influence interfibre rebonding. The difference in the fibre responses to saltwater depended on the relationship between nano-scaled pores in the fibre walls, osmotic pressure, and the degree of sizing, which resulted in low water retention values. More of the starch applied as a surface sizing agent was dissolved or dispersed during distilled water immersion than saltwater immersion. This loosened the fibre network, which was a factor that decreased the sizing degree of the paper.

Salt deliquescence drives photosynthesis in the hyperarid Atacama Desert

Endolithic cyanobacteria are found in halite nodules in the hyperarid core of the Atacama Desert. Using Pulse Amplitude Modulated Fluorometry, we show here that photosynthetic systems of these cyanobacteria become active when the relative humidity rises above 70% and the salt becomes wet by way of deliquescence. This is the first evidence of active metabolism in the hyperarid core of the Atacama, and supports the view of a microbial community sustained by deliquescence. Our results expand the water activity envelope of life on Earth.

Sea salt deliquescence and crystallization in atmosphere: an in situ investigation using x‐ray phase contrast imaging

X‐ray phase contrast imaging (PCI) based on synchrotron radiation was introduced for the first time as an in situ imaging way to investigate sea salt phase change, i.e. deliquescence and crystallization in atmospheric environment. A performance on the deliquescence of pure NaCl, which is the dominant component in sea salt, demonstrated that this technique can directly observe the change of core particle and differentiate the outer water layer clearly in solid‐aqueous system of ~100 µm scale. The imaging results showed that sea salt particle deliquesced on a large scale of relative humidity (RH) between 34 and 97% RH as a solid–liquid drop, while no clear deliquescence RH was observed during the process. According to the drop size growth curve, sea salt deliquescence can be divided into three steps, namely water accumulating step (34–75% RH), bulk melting step (75–86% RH) and delay dissolving step (>86% RH), which are most probably dominated by grouped components as MgCl2/CaCl2/MgSO4, NaCl and Na2SO4/KCl/K2SO4, respectively. Instead at a sole RH, the crystallization of sea salt solution occurred at a range of 46–58% RH, which well agreed with the theory proposed by Ge et al. The aqueous‐solid condition provided by sea salt deliquescence and crystallization may greatly enhance the heterogeneous chemical reactions in atmosphere. Copyright © 2012 John Wiley & Sons, Ltd.

Damage in porous media: role of the kinetics of salt (re)crystallization

We present multiscale experiments assessing the impact of the recrystallization dynamics of sodium sulfate and sodium chloride on damage observed in sandstone during humidity cycling. The deliquescence of both salts leads to the formation of homogeneous salt solutions which, upon drying, can reach high concentrations before (re)crystallization. For sodium chloride that has only a single crystalline phase, precipitation manifests itself as the fast growth of a small number of nuclei which grow to larger sizes in time. For sodium sulfate, with different crystalline phases, we observe that kinetically the precipitation of the thenardite (the anhydrous phase with the higher solubility) appears to be favored. The comparison of these results with those obtained when rewetting of crystals is done with liquid leads to the conclusion that the size of crystals that precipitate upon recrystallization is an important ingredient for explaining the damage observed in stones, besides the crystallization pressure that is usually invoked.

Study on temperature and humidity environment of grotto 72 at the Mogao Grottoes in Dunhuang, China

AbstractThis article presents research on destructive environmental mechanisms affecting the murals in the Mogao Grottoes, specifically Grotto 72, from a meteorological perspective. Analysis of outside monitoring data during 1999‐2008 shows that condensation of moisture and/or salt deliquescence on the mural affects a high percentage of the internal grotto, whereas the interchange of moisture between the interior grotto and the surrounding air accounts for a relatively small effect. But high humidity was the threat to the mural, so the planting of the shelterbelts was a new threat to the mural due to irrigation of shelterbelts. The higher relative humidity (RH) produced by shelterbelts in front of the grottoes is only weakly related to local precipitation but is highly correlated with the times of water irrigation of those shelterbelts. The intra‐seasonal variability of temperature and RH on the mural surface is relatively stable because temperature inversion frequently occurs in the internal grotto and is favourable for maintenance of stable air stratification that is beneficial to the preservation of the wall paintings. Using ridge regression estimation of the period data, coupling equations of the change of temperature and humidity on the mural surface, the internal grotto air and the external environment are obtained. The real‐time dynamics of temperature and humidity are thus analysed and reported here, offering a scientific basis for establishing a long‐term monitoring network in the Mogao Grottoes. Copyright © 2012 Royal Meteorological Society

Hypersaline “wet patches” in Taylor Valley, Antarctica

Spatially isolated patches of soil located in Taylor Valley, McMurdo Dry Valleys, Antarctica, are sites of elevated salt content and soil moisture. During Antarctic spring, in the absence of snow melt, visibly wet (reduced albedo) patches of soil are present at the surface. The soil pore fluids are hypersaline and have average water activity of 0.74 (the water activity of a solution determines the equilibrium vapor pressure of that solution), and are an order of magnitude more saline than average soils in the Dry Valleys. These salty soils are 3–5 times more water rich than average soils. Geochemical and meteorological analyses show that these wet patches are sites of direct vapor emplacement into soil pore fluids that may ultimately be sourced by the deliquescence of soil salts. These wet patches represent a non‐precipitation, non‐groundwater source for water into Antarctic permafrost.

Laboratory studies of perchlorate phase transitions: Support for metastable aqueous perchlorate solutions on Mars

Perchlorate salts, recently discovered on Mars, are known to readily absorb water vapor from the atmosphere and deliquesce into the aqueous phase at room temperature. Here we study the deliquescence (crystalline solid to liquid transition) and efflorescence (liquid to crystalline solid transition) of perchlorate salts at low temperatures relevant to Mars. A Raman microscope and environmental cell were used to determine the deliquescence relative humidity (DRH) and efflorescence relative humidity (ERH) of NaClO 4 and Mg(ClO 4) 2 as a function of temperature and hydration state. We find that the deliquescence of anhydrous NaClO 4 is only slightly dependent on temperature and occurs at ~ 38% RH. The DRH of NaClO 4·H 2O increases with decreasing temperature from 51% at 273 K to 64% at 228 K. The DRH of Mg(ClO 4) 2·6H 2O also increases with decreasing temperature from 42% at 273 K to 64% at 223 K. The efflorescence of both NaClO 4 and Mg(ClO 4) 2 salt solutions occurs at a lower RH than deliquescence due to the kinetic inhibition of crystallization. For all temperatures studied, the ERH values of NaClO 4 and Mg(ClO 4) 2 are 13% and 19%, respectively. These results indicate perchlorate salts can exist as metastable, supersaturated solutions over a wide range of RH and temperature conditions. Summer diurnal temperature and relative humidity cycles at low latitudes on Mars could allow the surface salts to be aqueous for several hours per day.

Multiform structures with silicon nanopillars by cesium chloride self-assembly and dry etching

We develop a novel method to fabricate multiform structures of Si nanopillars (diameters > 40 nm, aspect ratio > 10, coverage ratio > 35%) by dry etch with self-assembled cesium chloride (CsCl) nanoislands as mask. The pillars can cover structures of lateral size 1 μm and unpolished Si wafer, enabling uneven surface to be textured by nanopillars without complex process or expensive polishing. Planar micro-patterns and tridimensional localization of nanopillars have been easily realized, useful for integrating nanopillars to devices. By figuring out substrate influences, fast formation of CsCl islands within 1 min has been achieved for the first time, making CsCl process flow to be possibly controlled within 30 min. Based on the deliquescence of salt, CsCl self-assembly is simple, widely tunable and compatible, which endows the approaches great practical potential.

Nanopillars by cesium chloride self-assembly and dry etching

We introduce a method combining cesium chloride self-assembly and inductively coupledplasma to fabricate nanopillars with uniform coverage over an entire 4 inch prepatterned siliconwafer. This method can produce pillars with average diameters ranging from 50 nm to1.5 µm, aspect ratios up to 13 and coverage ratios above 35%. Cesium chloride self-assemblyutilizes the deliquescence of salt, with advantages of excellent tunability, high aspect ratioand potential for micro/nano mixed structures, which makes this technologypromising in the areas of MEMS, solar cells, batteries, light emitting diodes, etc.

Water Vapor Absorption in Porous Media Polluted by Calcium Nitrate Studied by Time Domain Nuclear Magnetic Resonance

Nuclear magnetic resonance relaxation analysis of liquid water (1)H nuclei in real porous media, selected for their similar composition (carbonate rocks) and different pore space architecture, polluted with calcium nitrate, is presented to study the kinetics of water condensation and salt deliquescence inside the pore space. These phenomena are responsible for deterioration of porous materials when exposed to environmental injury by pollution in a humid atmosphere. The theory is well described for simple pore geometries, but it is not yet well understood in real porous media with wide distributions of pore sizes and connections. The experiment is performed by following in time the formation of liquid water inside the pore space by T(1) and T(2) relaxation time distributions. The distributions allow one to see the effects of both the salt concentration and the pore space structure on the amount of water vapor condensed and its kinetics. It is shown that, for a given lithotype, even with different amounts of pollutant, the rate-average relaxation time T(1ra) tends to increase monotonically with NMR signal, proportional to the amount of liquid water. T(1ra) is often inversely associated with surface-to-volume ratio. This suggests a trend toward the filling of larger pores as amounts of liquid water increase, but it does not indicate a strict sequential filling of pores in order of size and starting with the smallest; in fact, relaxation time distributions show clearly that this is not the case. Increased amounts of salt lead to both markedly increased rates and markedly increased amounts of water absorption. NMR measurements of amounts of water, together with relaxation time distributions, give the possibility of information on the effect of pollution in porous materials exposed to humid atmospheres but sheltered from liquid water, even before the absorption of large amounts of moisture and subsequent damage. These phenomena are of importance also in other fields, such as the exploitation of geothermal energy.

General Corrosion Behavior of N06022 in Super Concentrated Brines at Temperatures Higher than 100°C

AbstractAlloy 22 (N06022) is a highly corrosion resistant nickel based alloy. Extensive research has been conducted in the last eight years on the corrosion behavior of Alloy 22, mainly regarding its resistance to localized corrosion. Less attention has been paid to the general corrosion resistance in highly concentrated brines that may result from the deliquescence of salts contained in dust. Salts such as mixtures of NaCl, KCl, CaCl2, NaNO3, and KNO3 may deliquesce at temperatures above 100°C through absorption of moisture from the air. Electrochemical tests were used to assess the general corrosion behavior of Alloy 22 in brines with chloride and nitrate concentrations ranging from 8 molal to 100 molal in the temperature range 100 to 160°C. The effect of mixed anions and cations was also studied. Results show that, even for short-term immersion periods, the corrosion rate of Alloy 22 in high temperatures super concentrated brines is generally below 10 μm/year.

Evaluating the influence of mixture composition on the kinetics of salt damage in wall paintings using time lapse video imaging with direct data annotation

This paper presents an examination of the timescale of phase transition behaviour of a series of salts known to cause damage to wall paintings and other cultural property. The rate of deliquescence and crystallisation of single salts (nitromagnesite and halite) under different RH regimes, and the extent to which this was affected when mixed with other salts (niter, nitratite and gypsum), was investigated. The study was conducted using simple conventional techniques (mass measurements over time) and also using an innovative new method: timelapse video imaging with online data annotation. The results demonstrate the synergy gained from combining video imaging with environmental data in reference to time in the study of salt phase changes: where it revealed new information concerning the kinetics of deliquescence and crystallisation. The implications of these results for the implementation of environmental control measures within historic buildings are discussed.

Boiling Temperature and Reversed Deliquescence Relative Humidity Measurements for Mineral Assemblages in the NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O System

Boiling temperature measurements have been made at ambient pressure for saturated ternary solutions of NaCl + KNO3 + H2O, NaNO3 + KNO3 + H2O, and NaCl + Ca(NO3)2 + H2O over the full composition range, along with those of the single salt systems. Boiling temperatures were also measured for the four component NaCl + NaNO3 + KNO3 + H2O and five component NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O mixtures, where the solute mole fraction of Ca(NO3)2, x{Ca(NO3)2}, was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO3 + H2O system is ≈134.9 ∘C; for the NaNO3 + KNO3 + H2O system is ≈165.1 ∘C at x(NaNO3) ≈ 0.46 and x(KNO3) ≈ 0.54; and for the NaCl + Ca(NO3)2 + H2O system is 164.7 ± 0.6 ∘C at x{NaCl} ≈ 0.25 and x{Ca(NO3)2} ≈ 0.75. The NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O system forms molten salts below their maximum boiling temperatures and the temperatures corresponding to the cessation of boiling (dry-out temperatures) of these liquid mixtures were determined. These dry-out temperatures range from ≈300 ∘C when x{Ca(NO3)2} = 0 to ≥ 400 ∘C when x{Ca(NO3)2} = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO3 + KNO3 and NaCl + NaNO3 + KNO3 salt mixture from 120 to 180 ∘C at ambient pressure. The NaNO3 + KNO3 salt mixture has a MDRH of 26.4% at 120 ∘C and 20.0% at 150 ∘C. This salt mixture also absorbs water at 180 ∘C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO3 + KNO3 salt mixture was found to have a MDRH of 25.9% at 120 ∘C and 10.5% at 180 ∘C. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control brine composition due to the deliquescence of salts formed in dust deposited on waste canisters in the proposed nuclear repository at Yucca Mountain, Nevada.

Water uptake by aerosol: Water activity in supersaturated potassium solutions and deliquescence as a function of temperature

Atmospheric aerosol models often calculate water uptake by particles based on information on salt deliquescence and electrolyte mixing rules. Therefore improvements in deliquescence predictions and in the water-activity relations used in mixing rules can improve estimates of size distributions. The primary goals of this work are to derive equations for the variation in the mutual deliquescence relative humidity (MDRH) with temperature ( T) for a particle containing an arbitrary number of hydrated and anhydrous salts and to extend the range of validity of water–activity relations reported for binary solutions of KNO 3, KCl, KBr, and K 2SO 4 to greater supersaturations. Equations for MDRH( T) are derived based on the equilibrium conditions that define deliquescence and the Gibbs-Duhem relation. MDRH is calculated from solubility data and the ZSR mixing rule to generate reference values for the equations and to evaluate their reliability. The ZSR mixing rule is also used to predict concentrations of KNO 3, KCl, KBr, and K 2SO 4 in highly supersaturated binary solutions. Polynomial fits are presented that relate water activity to concentration for these solutions. The deliquescence equations derived here predict MDRH( T) for hydrate systems with sufficient accuracy for temperature excursions of about 25 K. MDRH( T) usually follows the trend of DRH( T) for the most soluble salt in the system, while the temperature dependence of saturation concentration can be neglected for some salt systems. A linear temperature dependence for saturation concentration appears necessary to capture MDRH( T) for systems containing Ca(NO 3) 2·4H 2O and CaCl 2·6H 2O. Consideration of deliquescence for a representative sea-salt system indicates that minor hydrated components have an important influence on the uptake of water by sea-salt particles and should be considered in equilibrium aerosol models. Results of this study improve estimates of water uptake by atmospheric particles containing hydrates and potassium salts.

Formation of Microcrystals, Micropuddles, and Other Spatial Inhomogenieties in Surface Reactions under Ambient Conditions: An Atomic Force Microscopy Study of Water and Nitric Acid Adsorption on MgO(100) and CaCO3(101̄4)

In this study, atomic force microscopy (AFM) is used to image freshly cleaved MgO(100) and CaCO3(104) as these surfaces undergo reaction with water and nitric acid under ambient conditions of temperature, pressure, and relative humidity. The reaction of water and nitric acid results in the formation of hydroxylated and nitrated surfaces, respectively. It is clear from the AFM images that there are spatial inhomogenieties and surface features that form on micrometer and nanometer length scales as these reactions proceed. These features, which include hillocks, patches, microcrystallites, and micropuddles, are due to surface and phase segregation as a result of facile ion mobility in the presence of adsorbed water. In addition, instabilities and oscillations in the AFM images provide an indication of liquid formation and the deliquescence (i.e., a solid to liquid-phase transition) of nitrate salts as a function of relative humidity.

Salt damage to brick kiln walls in Japan: spatial and seasonal variation of efflorescence and moisture content

To clarify the mechanism of salt fretting of a brick building, monthly observations were made over one year at a two-storey brick kiln in central Japan. Products of weathering that had fallen were collected and weighed; salts were identified using XRD and the moisture content of the brick was measured at its surface using a portable infrared optical moisture meter. Gypsum (CaSO4·2H2O) was found at the bottom of the first floor wall in the warm and humid season. Thenardite (Na2SO4) is dominant on the first floor wall; it is abundant in the cold and dry season but sparse in the warm and humid season. Magnesium sulphate is dominant on the second floor wall; epsomite (MgSO4·7H2O) was observed in the dry-to-wet season and hexahydrite (MgSO4·6H2O) in the wet-to-dry season. Seasonal changes in salt abundance result from the temperature dependence of the solubilities and equilibrium relative humidities (ERH) of each salt. The amount of brick decay material due to salt weathering is much greater from the second floor wall than from the first floor wall and is greater from spring to the end of summer. These seasonal and spatial variations of the rate of brick decay can be explained by a combination of factors: (1) the types of salt, (2) efflorescence or sub-florescence and (3) salt deliquescence.

The effect of nitric acid uptake on the deliquescence and efflorescence of binary ammoniated salts in the upper troposphere

[1] Thermodynamic equilibrium model calculations are used to show that HNO3 can lower the relative humidity barrier to deliquesce binary ammoniated salts in the upper troposphere, particularly in aerosol solutions with an (NH4)2SO4 composition. Also in the case of (NH4)2SO4 or NH4HSO4 there is no abrupt change in the physical state of the thermodynamic system (instantaneous change of a dry salt particle into an aqueous solution) at the deliquescent point, which is typical for such a phase transition. Model results show that HNO3 dissolution in ammoniated aerosol solutions can prevent the efflorescence of (NH4)2SO4 and NH4HSO4 salts in favor of (NH4)3H(SO4)2 (letovicite) crystallization. Future laboratory experiments, where binary ammoniated salts are studied at cold temperatures in the presence of both HNO3 and H2O, are needed to confirm the results of our model calculations.

Nucleated deliquescence of salt

We have studied deliquescence on the (001) face of single crystals of NaCl and find that it is a nucleated phenomenon. The phase transition occurs only after the relative humidity exceeds that found over the saturated solution by at least 5%. The contrast between our observations and previous measurements using salt powders or crystallites leads us to the conclusion that deliquescence is controlled by the differences in energy required to solvate ions from the smooth (001) face and from the defect-rich surfaces of particulate samples.

Waste Package Environment for the Yucca Mountain Site Characterization Project

ABSTRACTEnvironmental parameters that would affect the degradation of engineered materials, including waste packages and drip shields, in the potential high level nuclear waste repository at Yucca Mountain, Nevada are being characterized as part of the Yucca Mountain Project. These parameters include: temperature, relative humidity, range of water chemistry, deliquescence of salts, pH, and electrochemical potential (Eh). The likelihood of various brine compositions forming on the engineered components under repository conditions, and the implications, is discussed. Relative humidity controls the ionic strength and composition of the aqueous solutions, and hence strongly influences the corrosion processes that could occur. Studies are underway to more fully characterize the redox state of aqueous solutions in contact with engineered system components.

Deliquescence and recrystallization of salts in the Dead Sea Scrolls

In the traditional manufacture of the parchment of the Dead Sea Scrolls, considerable amounts of soluble salts were applied. These salts were examined by X-ray diffraction, X-ray fluorescence and polarized light microscopy. Dynamic aspects of deliquescence and recrystallization of the salts were examined with the environmental scanning electron microscope. The presence of these salts may have considerable significance for the conservation of the Dead Sea Scrolls.