scholarly journals Nanoparticle Size Effect on Water Vapour Adsorption by Hydroxyapatite

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 1005 ◽  
Author(s):  
Urszula Szałaj ◽  
Anna Świderska-Środa ◽  
Agnieszka Chodara ◽  
Stanisław Gierlotka ◽  
Witold Łojkowski
Keyword(s):  
Physical Adsorption ◽  
Adsorbed Water ◽  
Nanoparticle Size ◽  
Ambient Atmosphere ◽  
Hydroxyapatite Nanoparticles ◽  
Fitting Method ◽  
Relative Air Humidity ◽  
Vapour Adsorption ◽  
Adsorption Of Water ◽  
Water Vapour Adsorption

Handling and properties of nanoparticles strongly depend on processes that take place on their surface. Specific surface area and adsorption capacity strongly increase as the nanoparticle size decreases. A crucial factor is adsorption of water from ambient atmosphere. Considering the ever-growing number of hydroxyapatite nanoparticles applications, we decided to investigate how the size of nanoparticles and the changes in relative air humidity affect adsorption of water on their surface. Hydroxyapatite nanoparticles of two sizes: 10 and 40 nm, were tested. It was found that the nanoparticle size has a strong effect on the kinetics and efficiency of water adsorption. For the same value of water activity, the quantity of water adsorbed on the surface of 10 nm nano-hydroxyapatite was five times greater than that adsorbed on the 40 nm. Based on the adsorption isotherm fitting method, it was found that a multilayer physical adsorption mechanism was active. The number of adsorbed water layers at constant humidity strongly depends on particles size and reaches even 23 layers for the 10 nm particles. The amount of water adsorbed on these particles was surprisingly high, comparable to the amount of water absorbed by the commonly used moisture-sorbent silica gel.

scholarly journals Evolution of Pore Characteristics for Bentonite Modified by an Ionic Soil Stabilizer during Hydration Processes

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Wei Huang ◽  
Zili Feng ◽  
Huanran Fu ◽  
Wei Xiang
Keyword(s):  
Nitrogen Adsorption ◽  
Adsorbed Water ◽  
Crystal Layer ◽  
Basal Surface ◽  
Pore Characteristics ◽  
Soil Stabilizer ◽  
Pore Structures ◽  
Vapour Adsorption ◽  
Adsorption Of Water ◽  
Water Vapour Adsorption

An ionic soil stabilizer (ISS) is used to reinforce clay soils because the ISS can regulate the hydration processes and microstructures of clays. To evaluate the regulation of ISS, natural bentonite was modified by ISS at different concentrations in this research. Water vapour adsorption and X-ray diffraction (XRD) were carried out to interpret the hydration mechanism of bentonite. Meanwhile, an associated analysis between hydration pore structures and hydration mechanisms was implemented through variation of pore characteristic tests at different relative humidities (RHs) to distinguish multiscale pore adsorption of water during the corresponding hydration process. In addition, the pore characteristics were studied via XRD, nitrogen adsorption, and mercury injection tests. Finally, the origins that adsorbed water and pore structures changed by adding ISS were discussed. The results showed that for calcium bentonite, the cations hydrated first in the range of 0 < RH < 0.45 ~ 0.55 , accompanied by the expansion of micropores. Then, adsorption occurred on the basal surface of the crystal layer in the range of 0.45 ~ 0.55 < RH < 0.8 ~ 0.9 , with water mainly adsorbed into the mesopores. With further hydration when RH > 0.8 ~ 0.9 , diffused double layer (DDL) water ceaselessly entered the macropores. Both adsorbed water and multiscale pore size decreased when ISS was added to bentonite. The origins of the reduction were the regulation of ISS to exchangeable cations and the basal surface of the crystal layer.

Differential heat of water adsorption for montmorillonite, kaolinite and allophane

Clay Minerals ◽  
1989 ◽  
Vol 24 (3) ◽  
pp. 505-512 ◽  
Author(s):  
S. Iwata ◽  
F. Izumi ◽  
A. Tsukamoto
Keyword(s):  
Water Vapour ◽  
Water Adsorption ◽  
Adsorption Process ◽  
Dominant Role ◽  
Equilibrium Constants ◽  
Adsorbed Water ◽  
Differential Heat ◽  
Clay Surface ◽  
Vapour Adsorption ◽  
Water Vapour Adsorption

AbstractDifferential heat of water vapour adsorption for Cs+-saturated montmorillonite, kaolinite and allophane was measured over a low relative humidity range from 10−4 to 10−1. Two interactions (clay surface atom-water and counterion-water) are mainly involved in the water vapour adsorption process. To assess the affinity of water to the clay surface, the amounts of adsorbed water and the differential heat due to Cs+ were estimated from equilibrium constants in the gas phase reactions. It is tentatively concluded that (i) a dominant role of water adsorption due to the Cs+-water interaction in the adsorption process is evident only for montmorillonite; (ii) the affinity of water to the clay surface is strongest for allophane and weakest for montmorillonite.

scholarly journals Application of the Simplified Equation for Micropore Size Distribution to the Study of Water Vapour Adsorption on Activated Carbon

1995 ◽  
Vol 12 (3) ◽  
pp. 203-209 ◽  
Author(s):  
R.N. Nickolov ◽  
D.R. Mehandjiev
Keyword(s):  
Activated Carbon ◽  
Size Distribution ◽  
Water Vapour ◽  
Adsorbed Water ◽  
Relative Pressure ◽  
Micropore Size Distribution ◽  
Vapour Adsorption ◽  
Water Vapour Adsorption ◽  
Water Values ◽  
Micropore Size

Water vapour adsorption on activated carbon has been investigated by an analysis of the nitrogen isotherms determined on carbon samples after their initial wetting at the same relative pressure followed by freezing. The simplified equation for micropore size distribution has been used. A relatively narrow range of pre-adsorbed water values has been found, within which the microporous space of the initial activated carbon changes as a result not only of filling but also of elimination (blocking) of parts of the texture.

scholarly journals Changes in the size of the apparent surface area and adsorption energy of the rye roots by low pH and the presence of aluminium ions induced

2016 ◽  
Vol 30 (3) ◽  
pp. 375-381 ◽  
Author(s):  
Alicja Szatanik-Kloc
Keyword(s):  
Surface Area ◽  
Water Vapour ◽  
Adsorption Energy ◽  
High Energy ◽  
Root Surface ◽  
Low Ph ◽  
Vapour Adsorption ◽  
Average Water ◽  
Water Vapour Adsorption ◽  
Adsorption Desorption

Abstract The plant reactions on Al-stress include i.a. change of the surface area of the roots, which in the physicochemistry of plants characterizes the transport of water and ions through the root. The object of this study is the specific surface area of the roots of plants which are tolerant to aluminium, such as rye. Plants of rye were grown in a nutrient solution for 14 days at pH 4.5 in the presence of Al3+ ions of concentration 10, 20, and 40 mg dm−3. The control plants were grown continuously at pH 7 or pH 4.5 without Al3+. The apparent surface area and adsorption energy of the plants roots were determined from water vapour adsorption – desorption data. The apparent surface area of roots growing in the aluminium was (with respect to control) statistically significantly lower. There were no statistically significant differences in the apparent surface area of the roots which grew in pH 7, pH 4.5 without Al3+. The average water vapour adsorption energy of the root surface, under stress conditions decreased. In the roots grown in the presence of Al+3, there was a slight decrease in high energy adsorption centres and an increase in the amount of low-energy centres.

Study of the reaction CaSO4.½H2O (β-hemihydrate) = CaSO4 (β-soluble anhydrite)+½H2O in the temperature range 20–100° C

1965 ◽  
Vol 34 (268) ◽  
pp. 327-345 ◽  
Author(s):  
J. D. C. McConnell
Keyword(s):  
Water Vapour ◽  
Vapour Pressure ◽  
Physical Adsorption ◽  
Linear Increase ◽  
Water Vapour Pressure ◽  
Hydration Reaction ◽  
Temperature Range ◽  
Dehydration Reactions ◽  
Adsorption Of Water ◽  
Hydration And Dehydration

SummaryA thermogravimetric vacuum microbalance has been used to study the reaction between β-soluble anhydrite and water vapour in the temperature range 20–100° C. Equilibrium water-vapour pressures for the hydration reaction in this temperature range were determined directly and have been compared with available data obtained by Kelly, Southard, and Anderson (1941) in the temperature range 80–120° C. The kinetics of the hydration and dehydration reactions have also been studied in a series of isothermal experiments with varying water-vapour pressure. These experiments indicate that in a vapour-pressure range close to the equilibrium value very low rates for both hydration and dehydration are observed. Outside this range of vapour pressures both hydration and dehydration rates increase suddenly and show an approximately linear increase with imposed water-vapour pressure.At low temperatures (25° C) the dehydration reaction has an associated activation energy of approximately 10 kcal mole−1. In the same temperature range additional, physical adsorption of water vapour by the specimen was noted.

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