Water Sorption Isotherms Research Articles

Development of a honey-based powder ingredient using a mixture design: Botanical origin effect and hydration properties

The aim of this research was to develop and characterize a high honey content powder with good functional, sensory and hydration properties. A four-responses (hygroscopicity, solubility, cohesiveness and global sensory acceptability) D-optimal mixture design by Design Expert was used. Three factors were selected for the freeze-drying process: honey (60–80%), gum arabic – GA(0–40%) and whey protein concentrate – WPC (0–40%). Three optimal formulations (physicochemical–OPCP–, sensory–OSP– and combined–OCP–) with 72–74% of honey and different GA:WPC ratios were studied. The model prediction was successfully confirmed for the optimal points. Hydration and antioxidant characteristics were evaluated in optimal formulations for honey of three different botanical origins (Eucalyptus, Citrus and Prairie). Water sorption isotherms were sigmoid shape type II for all samples, with a slight difference at high aw for OSP. Flowability (4.5–16.3Ci), hygroscopicity (19.5–24.4 g/100 g), and solubility (87.1–94.6%), were within typical ranges. The botanical origin showed little influence in the physicochemical characteristics but showed differences in the antiradical activity (Prairie honey showed the highest values). These honey powders could be used in a variety of products in the food industry, as food ingredients or directly as a natural sweetener, promoting and diversifying honey consumption.

Comparative analysis of water condensate porosity using mercury intrusion porosimetry and nitrogen and water adsorption techniques in porous building stones

Condensate porosity in porous materials has a significant influence on comfort, energy consumption, and material’s strength and durability. The variation of the moisture content of the material for a given variation of relative humidity describes the moisture storage capacity and has to be determined experimentally through the water sorption isotherm. However, the characterisation of sorption isotherm is very time-consuming, mostly for high relative humidity conditions, which may cause experimental errors and reproducibility problems.This paper aims to estimate experimental water condensate porosity using mercury intrusion porosimetry and nitrogen adsorption technique considering pores smaller than 0.1 μm for a wide range of porous sedimentary rock types with different petrographic characteristics. Particularly for nitrogen adsorption characterisation, we interpolated the pore volume using BJH method applied to the desorption branch. In the water adsorption test, condensate porosity is obtained with the maximum adsorbed water at RH = 100%.The ratio between water condensate porosity and total porosity in the studied porous stones is important and varies from 2 to 38%. Nitrogen adsorption technique provides the best estimation of condensate porosity (R2 = 0.979) and an effective estimation of water condensate porosity. The correlation between condensate porosity using MIP is moderate (R2 = 0.892) and presents a wider dispersion for all the range of condensate porosity. A mathematical expression that fits the shape and curvature of the water isotherm was also analysed in terms of pore structure. These studies are scarce for porous stones and our results provide valuable information for these widely used construction and building material.

Application of Molecular Sieves for Drying Transformers Insulated with Mineral Oil, Natural Ester, or Synthetic Ester

A high level of moisture in the insulation system of power transformers is often the cause of their failure. This can be prevented by drying a transformer in its place of installation. In the article the application of molecular sieves (MS) in the drying process of the transformer insulation system was analyzed. The water sorption isotherms of 3A MS in mineral oil, natural ester, and synthetic ester at 35 °C were determined, which was not described in the literature before. An evaluation of the influence of temperature on the drying dynamics of electro-insulating liquids using MS was also carried out. The drying dynamics were tested at three temperatures, i.e., 35 °C, 50 °C, and 65 °C, which allowed to analyze the effect of temperature on a short-term or continuous drying process. The tests showed that 3A MS’s ability to adsorb water varied depending on the type of electro-insulating liquid. The determined water sorption isotherms, described by means of Langmuir adsorption model, make it possible to calculate the amount of MS needed for drying transformers with different liquid insulation. The research and analyses show the MS’s great potential for the drying of transformer insulation systems.

Improvement of Barrier Properties of Biodegradable Polybutylene Succinate/Graphene Nanoplatelets Nanocomposites Prepared by Melt Process.

Polybutylene Succinate (PBS)/Graphene nanoplatelets (GnP) nanocomposites over a range of GnP from 0 to 1.35 wt.%. were prepared by a melt process. A mixture of individual graphene nanosheets and aggregates was obtained by the addition of GnP in the PBS matrix. The presence of these fillers did not significantly modify the morphology, crystalline microstructure of the matrix or its thermal stability. However, a slight reinforcement effect of PBS was reported in the presence of GnP. The water sorption isotherm modelling with Guggenheim, Andersen and De Boer (GAB) equation and Zimm-Lundberg theory allowed a phenomenological analysis at the molecular scale. The presence of GnP did not modify the water sorption capacity of the PBS matrix. From a kinetic point of view, a decrease of the diffusion coefficient with the increasing GnP content was obtained and was attributed to a tortuosity effect. The influence of water activity was discussed over a range of 0.5 to 1 and 0 to 0.9 for water and dioxygen permeability. Improvement of the barrier properties by 38% and 35% for water and dioxygen permeability respectively were obtained.

Application of Corn Fibers from Harvest Residues in Biocomposite Films

Agro-industrial residues are difficult to dispose of or reuse; however, it can be used to generate goods such as biodegradable packaging. The aim was to isolate and characterize fibers from corn stalks, husks, and cobs, and apply them in starch composite films (control, 5 g 100 g−1, 10 g 100 g−1, 15 g 100 g−1 and 20 g 100 g−1). The cellulose fibers were isolated by alkaline treatment and characterized by its morphology, crystallinity, and chemical structure, showing materials with different lengths and diameters, and intermediate crystallinity. The composite films were evaluated by morphological characteristics, water-solubility, water vapor permeability, chemical structure, mechanical properties, and sorption isotherms. Generally, fibers reinforcement decreased moisture adsorption. The tensile strength and Young's modulus increased adding straw fiber (5 g 100 g−1 and 10 g 100 g−1) and stalk and cob fibers (5 g 100 g−1). The use of cellulose fibers in films is important to expand and improve the current lack of biodegradable packaging.

Water Sorption and Transport in Shales: An Experimental and Simulation Study

AbstractUnderstanding water uptake and drainage in shales has important implications for both hydrocarbon extraction and hydraulic fracturing fluid disposal. This study reports gravimetric water sorption isotherms and kinetics of water transport in shales. Moisture mass transport profiles during water uptake and drainage processes were numerically simulated. Quantitative parameters characterizing the water transport properties were calculated and their dependences on water saturation were analyzed. An approach was proposed to evaluate the permeability of shales using dynamic water sorption. The reliability of the estimated results was verified by the experimental values using gas permeability measurements.The apparent diffusion coefficients of water sorption on shales were found to be between 1.0 × 10−12 and 1.5 × 10−11 m2/s. The apparent diffusion coefficient first increases with water saturation and remains stable at a moderately saturated condition. However, this coefficient decreases for shales with high water saturation. Apparent diffusion coefficients for the sorption process are almost equal to those for the desorption process, except at the moderate saturation condition. Liquid water (including adsorbed water) contributes more than 80% to the water transport, whereas water vapor mainly contributes to shales with low water saturation. The liquid water permeability determined by water sorption is consistent with the crushed‐rock permeability measured by gas expansion. A further reasonable agreement is achieved between the analytical gas permeability, as a function of water saturation, and the experimental gas phase permeability. Water sorption kinetics provide an indirect method for assessing the water transport properties as a function of water saturation when direct measurements are not available.

Evaluation of water sorption isotherm, glass transistion temperature, vitamin C and color stability of mango peel powder during storage

The purpose of this work was to study the physical and chemical stability of the mango peel powder produced by hot-air drying. Sorption isotherms at 25 °C and glass transition temperatures (Tg) of the samples in equilibrium at different aw were determined. The degradation of vitamin C and color parameter b* was evaluated along storage under controlled conditions (relative humidity = 60%, temperature = 10, 25 and 35 °C) during 180 days. GAB model well-described water adsorption of the product, showing a monolayer moisture content (Xm) of 0.1260 g water/g dry solids and a critical aw of 0.56. The Gordon-Taylor model predicted the plasticizing effect of water on glass transition temperature, since Tg of the powders kept at different relative humidity conditions decreased as water activity increased. No visual signs of agglomeration and darkening were observed for samples stored at aw ≤ 0.529. The powders are a source of calcium and rich in potassium, copper, magnesium and manganese. The concentration of inorganic contaminants and pesticide residues were below the maximum allowed limits. The degradation of vitamin C and color parameter b* followed the first and zero-order kinetic models, respectively. The study indicated good stability for the powders along the storage at 10 and 25 °C, which can be incorporated into different food products, showing high retention of vitamin C, phenolic compounds, antioxidant activity and maintenance of color characteristics.

Thermal and mass transfer properties of a shrinkable industrial sludge: experimental determination and modeling approach

ABSTRACT In this study the thermo-physical and mechanical properties of an industrial sludge like shrinkage coefficient, density, water activity, apparent moisture diffusivity, effective thermal conductivity and heat capacity are determined experimentally. These properties constitute a major part of the required input data to model the sludge drying. The sludge shrinks linearly until reaching a critical water content X cr = 23% and then maintains a constant volume until the end of drying. Therefore, the density increases with decreasing the water content until the critical value (X cr = 23%) then it decreases until the end of drying. The Henderson equation seems to be the most appropriate statistical model to describe the water sorption isotherm of the sludge. The apparent moisture diffusivity is determined from the numerical solution of Richard’s law of diffusion with shrinkage. The results show that the effective thermal conductivity and the heat capacity decrease with the reduction of the water content from 2.60 W m−1 K−1 and 2.52 J g−1 K−1 for a wet sludge to 1.71 W m−1 K−1 and 0.78 J g−1 K−1 for a dry sludge respectively. The relationships between thermo-physical / mechanical properties and the water content / temperature of the sludge are established to be introduced in the created numerical drying model.

Defective Zr-Fumarate MOFs Enable High-Efficiency Adsorption Heat Allocations.

Adsorption-driven heat transfer devices incorporating an efficient "adsorbent-water" working pair are attracting great attention as a green and sustainable technology to address the huge global energy demands for cooling and heating. Herein, we report the improved heat transfer performance of a defective Zr fumarate metal-organic framework (MOF) prepared in a water solvent (Zr-Fum HT). This material exhibits an S-shaped water sorption isotherm (P/P0 = 0.05-0.2), excellent working capacity (0.497 mLH2O mL-1MOF) under adsorption-driven cooling/chiller working conditions (Tadsorption(ads) = 30 °C, Tcondensation(con) = 30 °C, and Tdesorption(des) = 80 °C), very high coefficient of performances for both cooling (0.83) and heating (1.76) together with a relatively low driving temperature at 80 °C, a remarkable heat storage capacity (423.6 kW h m-3MOF), and an outstanding evaporation heat (343.8 kW h m-3MOF). The level of performance of the resultant Zr-Fum HT MOF is above those of all existing benchmark water adsorbents including MOF-801 previously synthesized in the N,N-dimethylformamide solvent under regeneration at 80 °C which is accessible from the solar source. This is coupled with many other decisive advantages including green synthesis and high proven chemical and mechanical robustness. The microscopic water adsorption mechanism of Zr-Fum HT at the origin of its excellent water adsorption performance was further explored computationally based on the construction of an atomistic defective model online with the experimental data gained from a subtle combination of characterization techniques.

Application of Dynamic Temperature-Humidity Chamber for Measuring Moisture Sorption Isotherms of Biomaterials as Compared to the Conventional Isopiestic Method

Measurement of water activity and moisture sorption isotherms of foods and biomaterials are important to determine the state of water. In this work, a dynamic temperature-humidity (DTH) controlled chamber was used to measure water sorption isotherm and compared with the conventional isopiestic method. Temperature and relative humidity of DTH chamber can be controlled in the range of -15 to 100°C and 0 to 98%, respectively; thus, measurement of water activity at any point can be measured within the above ranges. The DTH chamber method showed high reproducibility as compared with the conventional isopiestic method when measured isotherms of cellulose, lignin, and hemicellulase were compared at 30°C. Finally, isotherm data of cellulose, lignin, and hemicellulase were generated in the temperature range of 10-90°C using DTH chamber, and these were modelled by BET and GAB equations. The model parameters were correlated with the temperature.

Effects of composition and temperature on water sorption in overmature Wufeng-Longmaxi shales

Water sorption provides a great approach to understand water-shale interaction. In this research, water sorption isotherms of fourteen Wufeng-Longmaxi shale samples collected from the eastern Sichuan Basin of China were generated and then interpreted by classical sorption models. The sorption behavior of water and its relationship with pore structure, organic/inorganic composition, and temperature (278–333 K) were explored using organic geochemistry, mineralogy, and gas physical sorption. Brunauer-Emmett-Teller theory functions well for these isotherms but generates ambiguous model parameters, suggesting that multilayer sorption concept is not suitable for water sorption. Dent model distinguishes between primary and secondary sorption, and the resulting specific surface area (ADent(H2O)) is not comparable to the nitrogen-determined specific surface area (ABET(N2)). However, ADent(H2O)/ABET(N2) linearly decreases with increasing ABET(N2), and water saturation is negatively correlated with total pore volume. These observations collectively support the surface-chemistry-controlled clustering mechanism for water sorption. Clay minerals dominate water sorption at low relative pressure because they provide more hydrophilic sorption sites for water cluster formation and growth. Nevertheless, organic matter becomes increasingly important with increasing relative pressure, primarily because a specific-sized organic pore has higher filling pressure than the same-sized clay pore resulting in more pronounced condensation in organic pores at high relative pressure. The water desorption branch shifts to higher relative pressure with increasing temperature and thus, the hysteresis loop shrinks, indicating a mechanism of capillary evaporation similar to wetting fluid nitrogen. The water adsorption branch is insensitive to temperature change, reflecting a temperature-independent clustering mechanism between 278 K and 333 K. The enthalpy of adsorption of collected shale samples is smaller than that of lower-maturity shales but close to that of condensation of bulk water. Based on this finding, we argue that higher-maturity shales have weaker interaction with water, which gives rise to lower temperature sensitivity of water sorption. Therefore, in the future, detailed investigations should revolve around water sorption behavior and its response to temperature in shales with different thermal maturities.

Modelling the Proton-Conductive Membrane in Practical Polymer Electrolyte Membrane Fuel Cell (PEMFC) Simulation: A Review.

Theoretical models used to describe the proton-conductive membrane in polymer electrolyte membrane fuel cells (PEMFCs) are reviewed, within the specific context of practical, physicochemical simulations of PEMFC device-scale performance and macroscopically observable behaviour. Reported models and their parameterisation (especially for Nafion 1100 materials) are compiled into a single source with consistent notation. Detailed attention is given to the Springer–Zawodzinski–Gottesfeld, Weber–Newman, and “binary friction model” methods of coupling proton transport with water uptake and diffusive water transport; alongside, data are compiled for the corresponding parameterisation of proton conductivity, water sorption isotherm, water diffusion coefficient, and electroosmotic drag coefficient. Subsequent sections address the formulation and parameterisation of models incorporating interfacial transport resistances, hydraulic transport of water, swelling and mechanical properties, transient and non-isothermal phenomena, and transport of dilute gases and other contaminants. Lastly, a section is dedicated to the formulation of models predicting the rate of membrane degradation and its influence on PEMFC behaviour.

Physicochemical Properties of Potato Starch Nanoparticles Produced by Anti‐Solvent Precipitation

AbstractThis work aims to understand the physicochemical properties of potato starch nanoparticles (SNPs) obtained by anti‐solvent precipitation. Moisture content, water activity, color, morphology, thermal behavior (differential scanning calorimetry), swelling factor, solubility in water, water sorption isotherms, rheological properties, and stability in water are analyzed and compared using native potato starch (PS) as control. The resulting SNPs after anti‐solvent precipitation have a particle size between 50 and 150 nm, smaller than those observed in PS (between 10 and 100 µm). SNPs behave as an amorphous material without gelatinization stage where the swelling factor is drastically reduced, while the solubility increased dramatically at low temperatures when compared with PS. The Guggenheim–Anderson–de Boer model from the isotherms data allows a calculation of the surface area, obtaining values of 105 and 211 m2 g−1 for PS and SNPs, respectively. The high surface area in SNPs is associated with an increase in the proportion of hydroxyl groups active for water adsorption throughout its structure. Both samples show Newtonian fluid behavior; however, SNPs solutions prove to be much more stable at room temperature than PS solution.

An analytical framework for estimating drying shrinkage strain of OPC based hardened cement paste

A new analytical framework that relies on minimal inputs and combines a number of existing techniques to estimate reversible drying shrinkage strain of OPC-based materials is presented. This includes a multiscale framework for estimating water (de)sorption isotherm (WSI), an analytical homogenization technique to estimate bulk modulus, and a multi-mechanism based drying shrinkage formulation. The minimal inputs needed are the cement composition, microstructural information and mechanical properties of hydrated phases of hardened cement paste. A pore network model that forms the core module of the multiscale WSI provides a quantitative basis for the drying shrinkage formulation. The unique feature of the framework is that only two calibration parameters are involved: (i) a geometric parameter used in the pore network model, and (ii) a constant in the disjoining pressure relationship, which is set to unity mainly due to a lack of knowledge. Importantly, there is no need to calibrate these parameters for every experiment. Results from the framework are compared against shrinkage data from literature that encompass both virgin materials (samples that have never been dried prior to the test) and non-virgin materials. A reasonably good correspondence has been achieved with respect to the non-virgin materials, whereas, the results for the virgin materials are examined mainly to gain qualitative understanding of the role of the microstructure on irreversible deformation and thus to propose a phenomenological model.

On the calculation of thermodynamic parameters in sorption calorimetric experiments

The sorption calorimetry method developed by Wadsö and co-workers is one of the most successful methods for studying the enthalpy of vapor sorption by solids and gels. A unique feature of this method is a simultaneous measurement of the water sorption isotherm and the sorption enthalpy. The accuracy of the enthalpy measurements in sorption calorimetric experiments can be affected by diffusion of water vapour through the injection channel tube and potentially through small leaks in the sorption cell. At high water activities this leads to an apparent drift of the measured enthalpies towards endothermic values. In this work we propose an improvement of the enthalpy calculation method, that eliminates these effects and substantially improves the accuracy of the enthalpy measurements. The new method is successfully tested on previously published sorption calorimetric data and can be recommended for use in future experiments.

Effect of pH on the physicochemical characteristics and the surface chemical composition of camel and bovine whey protein’s powders

This study investigated the effect of pH on the denaturation extent, the surface chemical composition, the water sorption isotherm and the glass transition temperature of camel and bovine whey protein’s powders. The LC-MS analysis indicated that the β-Lactoglobulin was the most denatured protein in bovine whey powders regardless the pH value, while this protein was totally absent in camel whey. The α-Lactalbumin was relatively heat stable after drying and predominated the powder surface (X-ray photoelectron spectroscopy results) in both camel and bovine whey powders regardless the pH (neutral (6.7) or acidic (4.3 and 4.6)). Analysis of the water sorption isotherms indicated that decreasing the pH induced the increase of the water activity of lactose crystallization for camel and bovine whey powders. Finally, decreasing the pH led to the decrease of the glass transition temperature of camel and bovine whey powder (at 0.13, 0.23, and 0.33 of water activity).

Mathematical modelling of water sorption isotherms and thermodynamic properties of Cucumis melo L. seeds

Moisture sorption isotherms for Cucumis melo L. seeds are determined at different temperatures of 30, 40 and 60 °C with the standard gravimetric-static method. The isotherm curves exhibited a type II behavior according to BET classification. For desorption and adsorption isotherms, equilibrium moisture content decreases with increasing of temperature at constant water activity. Moreover, the sorption isotherms exhibit hysteresis effect. Several models were applied to fit the relationship between equilibrium moisture content and the environment conditions data for melon seeds. The results examination indicates that Peleg model is able to reproduce experimental data within an acceptable precision. Additionally, sorption isotherms data were used to determine the thermodynamic properties such as net isosteric heat of sorption which was evaluated through direct use of moisture isotherms by applying the Clausius–Clapeyron equation. Increase in the equilibrium moisture content generated the decrease of net isosteric heat of sorption. As well, microscopic analysis shows a significant effect of desorption/adsorption process on microstructure of the seed.

Water Activity Role on Dried Agaricus Bisporus L. Lipid Oxidation During Storage Time

The aim is to determine the influence of water activity on dried Agaricus bisporus lipid oxidation stored for 180 days at a temperature of 25�C. Water sorption isotherms were determined using desiccators methods. Agaricus bisporus samples were equilibrated on saturated salt solutions in a range of water activity from 0.1 to 0.753. The equilibrium moisture content was obtained when there was no appreciable change in sample weight. GAB model was tested to determine the monolayer of Agaricus bisporus, m0, and there were monitored peroxide value, acidity value and refraction index as a function of Agaricus bisporus moisture (0.032 and 0.062 g water g-1 Agaricus bisporus) during the period of storage and the influence of Agaricus bisporus moisture on lipid oxidation.

Effect of Glass Transition Temperature Range on the Caking Behavior of Freeze-dried Carbohydrate Blend Powders

Glass transition temperature (Tg) and degree of caking for maltodextrin with added plasticizers (glucose, maltose, and sorbitol) were investigated. Onset and offset Tgs were evaluated by differential scanning calorimetry. From the onset and offset Tg-curves and water sorption isotherm, each critical water activity (awc) value was determined (water activity at each Tg = 25 °C). The awc range between onset Tg and offset Tg was extended by the addition of plasticizers. The degree of caking increased at a water activity just above awc of onset Tg, and completely caked at a water activity just below awc of offset Tg. Effect of aw on the degree of caking became more gradual with the addition of plasticizers because of the extended awc range. According to the dependence of viscosity on temperature and water activity, a predictive model for the caking of amorphous powders was proposed based on the onset and offset Tg curves.

Effect of biodegradable active packaging with zeolites on fresh broccoli florets.

Most of the food packaging is mainly petroleum-based, and new forms of food packaging have emerged, such as active, intelligent, and biodegradable packaging to extend the shelf life of fresh vegetables. The aim was to develop a biodegradable active packaging and senescence indicator label for fresh broccoli florets (Brassica oleracea L. var. italica), to increase shelf life and to monitor the decay of the vegetable. The biodegradable active packagings (BAP) were produced by blown extrusion containing zeolite as ethylene scavenger, and their mechanical properties, water vapor permeability, and water sorption isotherms were determined. Fresh broccoli florets were packed in perforated and non-perforated BAP and stored at 12°C, and their weight loss, vitamin C content, color, and texture were evaluated during the storage. BAPs were efficient in reducing the metabolism of fresh broccoli florets stored at 12°C, preserving the color, and vitamin C content for 7days. The senescence indicator labels were able to detect CO2 in packages without perforations.