Water Adsorption Properties Research Articles

Distribution of Water between Wheat Flour Components: A Dynamic Water Vapour Adsorption Study

The water adsorption properties of hard and soft wheat flours and flour components (starch, damaged starch, gluten, soluble pentosans, and insoluble pentosans) were determined at 25 °C using a controlled atmosphere microbalance. At different levels of relative humidity (from 10% to 95%), changes in sample mass (i.e., water gain) were continuously measured versus time and described using exponential models (R2≥0·994). Water adsorption isotherms were constructed for wheat flours and flour components and described using Guggenheim-Anderson-de Boer models (R2≥0·997). It was not possible to distinguish between the selected hard and soft wheat flours by their isotherms. The water-soluble pentosans had the highest water adsorption capacity. The theoretical distribution of water between the flour components (calculated using the Guggenheim-Anderson-de Boer parameters) was starch, 88%; gluten, 10%; and pentosans, 2%.

Template-Free Synthesis of AlPO 4 -H1 by Microwave Heating

Microwave heating enhanced the crystallization of aluminophosphate gels, and AlPO 4 -H1 was successfully obtained without using organic template reagents in a short reaction time. The use of amorphous aluminum hydroxide as an aluminum source and the addition of hydrochloric acid were found to be essentially important to obtain AlPO 4 -H1 as a single phase. Nitrogen and water adsorption properties were studied by measuring the adsorption isotherms.

Template-free synthesis of AlPO 4-H1, -H2, and -H3 by microwave heating

Aluminophosphate molecular sieves (AlPO 4's) were prepared by microwave heating without using organic template reagents. The microwave heating enhanced the crystallization of aluminophosphate gels, and AlPO 4-H1, -H2(AHT), and -H3(APC) were successfully obtained as single phases in a relatively short reaction time. The reaction conditions used for the crystallization of the three kinds of AlPO 4's were very similar to each other, but the use of different aluminum sources resulted in different structures; amorphous aluminum hydroxide, gibbsite, and boehmite were used for the preparation of AlPO 4-H1, -H2, and -H3, respectively. The crystallization temperatures were 125, 118, and 90 °C, respectively. The addition of hydrochloric acid was needed for the crystallization of AlPO 4-H1 and -H2. The addition of seed crystals and stirring the gels were found to be essential for the crystallization of AlPO 4-H3. Nitrogen and water adsorption properties were also measured.

Functional Property Changes in Heat Processed Soyabean (Glycine max) meal

The functional characteristics of soyabean subjected to roasting (solely or combined with blanching as a pre-treatment) were evaluated. The process reduced nitrogen solubility drastically within a pH range of 2-10, except at pH4. Foaming capacity was reduced by roasting and foams obtained for samples subjected to the highest roasting temperature without defatting had better stability than raw soyabean meal. Gelation capacity and emulsifying activity were also reduced but about one-third of the heat processed samples had better emulsion stability. Water absorption capacity of soyabean meal was increased by 5.10 – 45.2% due to the heat treatments while changes in fat absorption were inconsistent. The effect of roasting on the water adsorption properties of the product were minimal. The results confirmed the suitability of roasted soyabean meal for use in food systems requiring high water holding capacity. Keywords. Functional properties, Soyabean, heat treatment, roasting process, blanching. [Global Jnl Agric Res Vol.1(2) 2002: 93-100]

Cotton-Surfaced Nonwovens for Short-Wear-Cycle Apparel

Cotton-surfaced nonwovens have been developed with cotton on one side or both sides of a core structure in which the cotton content varies from 41–75% of the fabric weight. The thermally bonded two or three layered laminates are soft but strong and have a hand similar to cotton knits or hydroentangled fabrics. The fabrics have also demonstrated excellent wetting, wicking rates, water adsorption and water retention properties. Although these novel fabrics have notable flexibility and extensibility as produced, a post-treatment process provides the fabrics with instantaneous elastic recoveries ranging from 83–93% from an extension of 50%. The fabrics exhibit minimal linting characteristics and would be suitable as medical isolation gowns, head covers and shoe covers, bed sheets, pillow cases and for consumer applications such as disposable underwear, towels, wipers and personal hygiene products.

Studies on Water and Ammonia Programmed Thermodesorption of Mixed M(III)-vanadyl Phosphates

Hydrated M(III)-vanadyl phosphates (M (III)=Mn, Fe, Ga, Al) have been prepared and studied for water and ammonia adsorption properties by TG/DTA, NH3 TPD, FTIR and XRD techniques. The compounds have the same tetragonal layered structure of VOPO4 ⋅2H2 O, but shorter interlayer distances. Ammonia adsorption leads to intercalation of large amounts (0.19–0.39 mol/mol) of base between the layers of the materials, without displacement of water. The ammoniated phases obtained from these compounds have interlayer distances shorter than that of the corresponding precursors. In this connection an interaction mechanism NH3 -host is proposed. Treated at 450°C the materials adsorb ammonia only on the external surface because of the large decrease of the interlayer distance that prevents NH3 from entering the interlayer space. All M(III)-vanadyl phosphates present a wide distribution of strength of ammonia adsorbing sites.

WATER ADSORPTION PROPERTIES of COATED and NONCOATED POPCORNS

The addition of sugar for coating changed the sorption behavior of popcorn and made it more hygroscopic above a w value of 0.65. The isotherms for noncoated popcorn exhibited a slight sigmoid shape and for coated showed the shape characteristics of high sugar containing foods. The crossing of both popcorn samples was observed at 0.65 a w . The BET, the Smith and the GAB models were found to fit the adsorption data of noncoated popcorn; however, the BET and the Iglesias & Chirife models gave a good fit to the data of coated popcorn. The monolayer moisture content values estimated for both samples were considered to be correct values because of low standard error of estimates and their consistency with the literature values. The isosteric heat of noncoated popcorn was higher than the coated popcorn in the entire moisture content range considered for computation.

Model catalyst studies with single crystals and epitaxial thin oxide films

The paper describes recent results from our relatively new program to perform detailed studies of the catalytic properties of metal-oxide materials; in particular, to effect a determination of the active catalytic site(s) and the mechanism for reactions over this especially important class of heterogeneous catalysts. Issues of structure-sensitivity, poisoning and promotion, and competing reaction mechanisms are critical questions that need to be addressed in a detailed manner for catalysis by oxides. As just one important example, both surface (Langmui–Hinshelwood) and direct (Eley–Rideal) reaction mechanisms have been proposed for the selective catalytic reduction (SCR) reaction of nitrogen oxides (NO x ) over vanadia/titania catalysts. For this program, we are using a number of unique, state-of-the-art capabilities available in the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory; for example, the first molecular beam epitaxy (MBE) system dedicated to the growth of model metal-oxide films, and a unique moderate-pressure catalytic reactor/surface science apparatus. We describe the growth, characterization, and water adsorption properties of a thin Fe 3O 4(0 0 1) film grown on a lattice-matched MgO(0 0 1) substrate. Because our moderate pressure catalysis studies are preliminary at this point, we instead describe our previous results on the CO oxidation reaction over a Ru(0 0 0 1) model catalyst to demonstrate the utility of the experimental approach. We specifically discuss the possibility that this reaction occurs by an Eley–Rideal mechanism.

Structural properties and water adsorption behaviour of iron films grown on Cu(111)

Thin films of iron are deposited at 300 K on Cu(111). Up to four monolayers (ML), a pseudomorphic growth of iron films is observed by reflection high-energy electron diffraction (RHEED) leading to the formation of (111) planes of γ-fcc iron with a lattice parameter of 3.59 Å. Beyond that thickness, a progressive relaxation towards an α-bcc(110) plane is reported. For thicknesses of about 10 ML, the films are still strained as attested by a lattice parameter slightly smaller than that expected for bulk α-iron. By producing γ-(111) and α-(110) iron surfaces at will, water adsorption properties are investigated in the same conditions on both surfaces. After adsorption at 120 K, no dissociation is observed and the temperature-programmed desorption (TPD) spectra present two desorption peaks attributed to a first layer of chemisorbed molecular water and to multilayers of ice, respectively. The adsorption behaviour of water appears to be independent of the structure of the films. The exposure of the iron films to 250 L of oxygen at room temperature does not induce the dissociation of water on the oxidised surfaces as expected.

Water and dye adsorption properties of cactaceous material

Water and dye adsorption properties of cactaceous material

Adsorption of water on plutonium dioxide

Kinetic and equilibrium properties of water adsorption by plutonium dioxide are derived from gravimetric measurements in moist air at room temperature. In combination with mass–time data extracted from literature sources, the results provide a comprehensive picture of the adsorption process and its humidity dependence at 25 °C. Water is accommodated by a sequence of distinct steps involving five types of adsorbate–oxide interaction and accumulating ten molecular layers of water (approximately 2.1 mg H 2O/m 2 PuO 2 surface) at 100% relative humidity. The humidity-dependent first step and the second step involve half molecular layers of water and are attributed to dissociative chemisorption of water as OH. Like the second step, all subsequent processes are first order, but each involves a single molecular layer of H 2O. Kinetic and equilibrium results are applied in defining conditions for limiting the re-adsorption of water during handling operations and their relevance to the complex chemistry of the plutonium–oxygen system is outlined.

Water Adsorption Properties on Porous Silica Glass Surface Modified by Trimethylsilyl Groups

Nitrogen and water adsorption properties on the porous silica glass surfaces modified by different concentration of trimethylsilyl (TMS) groups were studied. The specific surface areas and parameterCvalues in the BET equation estimated from nitrogen adsorption decreased with increase in the surface concentration of the TMS groups and became constant values above 1.0 TMS group per nm2. The water adsorption property suggested that a highly silylated sample still represented hydrophilic character in initial adsorption process. Water molecules interact with the residual hydroxyl groups existing under the umbrellas of the TMS groups and form clusters. Above the concentration of 1.0 TMS group per nm2the capillary condensation of water vapor did not occur. The TMS groups interrupt to build a two-dimensional network of each cluster. The formation of multilayer adsorption of water molecules depends on the magnitude of hydrophilic patch areas which are surrounded by TMS groups.

Water adsorption properties of amorphous BaTiO 3 thin films

Amorphous barium titanate films were flash evaporated on silicon and studied with X-ray photoelectron spectroscopy. After water adsorption, the surface oxygen 1s photoelectron peak reveals the presence of hydroxyl groups. A thermal desorption experiment on a similar thin film evaporated on rhenium shows one peak of water partial pressure at about 480 K, which decreases after repeated cycles of adsorption and thermal desorption, suggesting that oxygen vacancies are filled up during desorption.

Large effect of leaching of DOC on water adsorption properties of a sandy soil

In this study, changes of adsorption properties of a sandy soil from a former sewage farm due to the leaching of dissolved organic carbon (DOC) were examined. The leaching of DOC at various pH levels was simulated in laboratory experiment using sodium hydroxide as the leaching agent. An increase of pH resulted in an increase of the amount of DOC in the studied soil. The removal of DOC altered the surface properties of the remaining solid. In particular, the surface area was reduced and the water vapour adsorption energy distribution function was shifted to lower energy ranges, thus showing the increase of the hydrophobic character of the soil. The intensity of these changes was more pronounced when the soil had been previously acidified.

Changes of mineralogical and surface properties of water dispersible clay after acid treatment of soils

AbstractMineralogical and water adsorption properties of water dispersible clays extracted from five soils of different typology after treatment with acid to different pH levels, were studied. The mineral composition, total and divalent iron content, surface areas and average adsorption energies of water dispersible clays were complicated functions of pH, reflecting the simultaneous effects of mineral destruction and aggregate disruption processes under influence of protons on soils. The magnetic susceptibilities of water dispersible clays were the lowest at pH 2 and roughly constant at higher pH values indicating the dissolution of crystalline forms of Fe below pH 3. The broadening of the peaks of adsorption energy distribution functions with decrease in pH is related to increasing formation of amorphous material from mineral phases.

An application of carbon-type semiconductors for the construction of a humidity-sensitive diode

This paper describes an application of carbon-type semiconductors for the construction of humidity-sensitive diodes. The sensing diodes consist of two semiconducting layers with different electronic properties deposited onto a quartz substrate by means of the spray pyrolysis method. The main electronic properties of carbons, i.e., electrical conductivity, and the type of majority current carriers were estimated by a suitable heat treatment. This resulted in the construction of humidity-sensitive diodes exhibiting a typical voltage-current diode-like behaviour in the presence of moisture. Some water adsorption and electronic properties of single carbon layers are also presented and discussed in terms of the amplification effect of the diode junction.

Synthesis And Water Sorption Properties Of Aluminophosphate (AlPO4) And Silicoaluminophosphate (Sapo) Molecular Sieves

ABSTRACTAluminophosphate (AlPO4–5, AlPO4–11, AlPO4–17, AlPO4–20) and silicoaluminophosphate (SAPO-5, SAPO- 11, SAPO-17, SAPO-20) molecular sieves of varying pore sizes (3–8 Å) were synthesized and their water adsorption and desorption properties were studied. Water sorption isotherms of AlPO4 molecular sieves were characterized by unusual isotherm shapes, that is, little or no initial adsorption followed by extreme adsorption leading to volume filling by hydrogen bonding and cooperative interaction in micropores, apparently due to the nonpolar nature of pore surfaces coupled with weak (reversible upon evacuation) chemisorption of water, and hysteresis loops extending to very low pressures. Although micropore filling in AlPO2's and isostructural SAPO's was completed almost at the same relative pressure (p/po), SAPO's exhibited less extreme adsorption isotherms as a result of their slightly more polar nature of pore surfaces compared to AlPO4's. Neither AlPO4apos;s nor SAPO's exhibited Brunauer Type I isotherms with water, contrary to a general expectation of the hydrophilic microporous solids.

Water adsorption properties of alumina pillared clay

Interlayers of montmorillonite were pillared with aluminum oxide and the water adsorption isotherms were measured on the samples calcined at temperatures ranging from 200 to 600°C. Although the nitrogen adsorption isotherms on the same samples were of the extreme Type I for Brunauer classification, the water adsorption isotherms did not fit either the Langmuir or the BET adsorption equations. The unusual shape of the isotherms can be interpreted in terms of hydrophobicity of the alumina pillared clays. The t-plot analysis of the adsorption isotherms revealed that the micropore filling with water was suppressed in the very low pressure region. From the t-plots, the slitwidth of the interlayer pores was estimated to be 7–8 Å, in good agreement with the pillar height obtained from the basal spacing. The low BET c-constant and the small isosteric heats of adsorption of water also suggest that the alumina pillared clays have hydrophobic properties.

Physico-chemical in vitro methods for determination of the skin compatibility of surfactants.

In order to reduce the number of animal tests there have been some efforts to establish in vitro methods for testing cosmetic products, especially for the skin compatibility of surfactants.The main principles of the published physico-chemical methods for in vitro testing of surfactants are summarized. They are mostly based on the interaction of surfactants with proteins and protein structures, e.g. isolated skin layers. Water binding capacity, adsorption, denaturation, solubilisation benetration and other properties have been investigated.The practical application of these methods implies thorough knowledge of their possibilities and limits. Thus the swelling behaviour of isolated pig epidermis has been studied in detail to develop an in vitro test for the skin compatibility of surfactants. The water uptake of epidermis strips in surfactant solutions was gravimetrically measured. Dependent on the surfactant structure the swelling values were different and characteristic. The effects of various types of surfactants and their mixtures are discussed and compared with skin irritation values of human and animal tests. Anionic surfactants displayed a satisfactory ranking correlation of swelling and irritation values.

Material Balance Depletion Models For Two-Phase Geothermal Reservoirs

Summary Material balance calculations, often referred to as "zero-dimensional" or "lumped element" reservoir evaluations, have been used extensively in petroleum and geothermal engineering. This paper presents a Havlena and Odeh-type material balance depletion model for two-phase reservoirs incorporating adsorption phenomena. A straight line formed between groups of thermodynamic and adsorption properties of water and the cumulative production history provides the initial fluid in place production history provides the initial fluid in place and the size of the vapor-dominated "steam cap." Adsorption phenomena were found to be the controlling mechanism phenomena were found to be the controlling mechanism in the depletion of vapor-dominated geothermal reservoirs. A material balance for vapor-dominated geothermal reservoirs, demonstrating the importance of adsorption phenomena, is presented also. A straight line provides the initial fluid in place. provides the initial fluid in place. Introduction The general approach to the material balance depletion model was first suggested by Schilthuis. The equation provides a volumetric balance between the expansion of provides a volumetric balance between the expansion of reservoir fluids as a result of the cumulative production. Havlena and Odeh, using the Schilthuis approach, developed linear expressions of the material balance equation for a variety of cases including undersaturated, gas-cap-drive and solution-gas-drive reservoirs. I present a similar development for the two-phase geothermal reservoir. Studies of reservoir and production behavior of vapor-dominated geothermal systems have focused on estimates of resource size. Whiting and Ramey presented an application of material and energy balances to geothermal steam production. Ramey applying conventional techniques for natural gas reservoirs, attempted to estimate the reserves of steam in place. Economides and Miller using the experimental results of Hsieh, in which the importance and magnitude of adsorption were demonstrated, introduced a new approach for material balance calculation of vapor-dominated systems. As I will show, desorption is the controlling mechanism in the depletion of vapor-dominated geothermal systems and the major variable in their material balance calculations. The Form of the Material Balance Equation for a Two-Phase Geothermal Reservoir As in the Havlena and Odeh approach, a volume balance in reservoir cubic feet [m3] may be written (in their work they used res bbl [res m3]): underground withdrawal equals expansion of liquid water, plus boiled-off water, plus expansion of steam cap, plus expansion of desorbed water, plus reduction in the PV. The reduction in PV will be neglected in the case of two-phase and vapor-dominated systems, as has been demonstrated for saturated reservoirs. Fig. 1 is a schematic of the two-phase geothermal model used in this analysis. Expansion of Liquid Water and Boiled-Off Water This term contains two components:liquid water expansion andboiled-off steam expansion. suppose that Wi lbm [kg] were present originally; then WiVli would be the initial volume while Wivl would be the volume at a lower pressure. Hence, the difference would provide the liquid expansion W i (vl-vli)................................(1) The boiled-off steam is taken here as the difference between the product of the initial liquid in place and the corresponding evaporation specific volumes at the given pressure interval. This is analogous to the product of the pressure interval. This is analogous to the product of the initial oil in place, the solution GOR, and the gas FVF in the Havlena and Odeh analysis. In both cases the difference depicts the expansion of the evolved gas. Wi (vlg-vlgi)...............................(2) Expansion of Steam Cap The total mass in the steam cap is taken as mWi, where m is expressed as the ratio of the mass of water in the vapor-dominated zone to the mass in the liquid-dominated zone. Then the expansion of the steam is given by mWi(vg-vgj).................................(3) Expansion of Desorbed Steam As presented by Economides and Miller, the volume occupied by desorbed fluid is given by mrM(Xi-X)vg.................................(4) where mr is the mass of rock, M is the molecular weight (18 in the case that no noncondensable gases exist in appreciable quantities), and Xj and X are the masses of adsorbed water in lbm-mol/lbm [gmol/g] of rock in the pressure increment. pressure increment. JPT P. 1305