Sorption Hysteresis Research Articles

Degradation assessment of archaeological oak (Quercus spp.) buried under oxygen-limited condition

Abstract The biological deterioration of archaeological wood under oxygen-limited conditions varies due to the limited activities of microorganisms. It is essential to expand the knowledge of the degradation types and the status of archaeological monuments for selecting the proper consolidates. The physical, chemical, and anatomical properties of approximately 600–650 year old archaeological oak collected from an archaeological site in Iasi-Romania were analysed to assess the quality and to identify the degradation types. The results were compared with similar tests on recently-cut oak. X-ray photoelectron spectroscopy (XPS) revealed the presence of more lignin-related peaks in the archaeological oak, which likely reflected the degradation of the wood carbohydrates as evidenced by the decreased oxygen-to-carbon ratio C ox/C non-ox. The differences in cellulose crystallinity were not significant suggesting that any cellulose degradation occurred in the amorphous regions. This was also reflected in the dynamic water vapor sorption analysis where the differences in sorption isotherms and hysteresis of archaeological and recently-cut oaks were marginal. Microscopic analysis of the oak cells illustrated bacterial degradation patterns, while the field emission scanning electron microscopy (FESEM) showed the presence of erosion bacteria in the archaeological oak collected from the site with low oxygen conditions.

Water sorption isotherms and hysteresis of cement paste at moderately high temperature, up to 80 °C

The constitutive models of concrete often consider water desorption isotherms to be near-equilibrium and significantly affected by moderately high temperature, 40–80°C, typically through microstructural changes. However literature data suggest that adsorption, not desorption, is near-equilibrium and moderate temperatures do not cause microstructural changes. This work supports the latter theory, through dynamic vapor sorption experiments on cement paste at 20–80°C. Samples were pre-conditioned at 60% relative humidity and 20°C, and isotherms were measured for several humidity ranges and testing rates. The results, corroborated by classical DFT simulations, indicate that adsorption is near-equilibrium and mostly unaffected by temperature, whereas desorption is out-of-equilibrium due to the ink-bottle effect at high humidity, and interlayer water at low humidity. Starting from the second cycle, desorption at higher temperatures features a shift of the cavitation pressure and overall a smaller hysteresis. A conceptual model of pore-specific temperature-dependent hysteresis is proposed to qualitatively explain the results.

Even Samples from the Same Waterlogged Wood Are Hygroscopically and Chemically Different by Simultaneous DVS and 2D COS-IR Spectroscopy

Waterlogged archaeological wood samples may degrade during long-term immersion in microbial-activity environments, which causes its biodegradation. Simultaneous dynamic vapor sorption (SDVS) and two-dimensional correlation infrared (2D COS-IR) spectroscopy reveal the degradation inhomogeneity of waterlogged fir wood from the Shengbeiyu shipwreck. The waterlogged and reference wood exhibit type II sorption isotherms. The equilibrium moisture contents of waterlogged archaeological fir wood from a decay region (WFD) were 22.5% higher than those of waterlogged archaeological fir wood from a sound region (WFS). WFD exhibits a higher measurable sorption hysteresis than WFS, implying greater variation in the surface moisture content in the WFD region compared to the WFS region, which may compromise the dimensional stability of the shipwreck. 2D COS-IR spectra confirmed the inhomogeneous degradation of the waterlogged wood via numerous mechanisms. The efficacy of SDVS and 2D COS-IR spectroscopy in the evaluation of the degradation state of waterlogged wood was demonstrated. This study verifies the existence of hygroscopic and chemical differences between visually similar samples from the same shipwreck.

Water in Wood: A Review of Current Understanding and Knowledge Gaps

Wood-water interactions are central to the utilization of wood in our society since water affects many important characteristics of wood. This topic has been investigated for more than a century, but new knowledge continues to be generated as a result of improved experimental and computational methods. This review summarizes our current understanding of the fundamentals of water in wood and highlights significant knowledge gaps. Thus, the focus is not only on what is currently known but equally important, what is yet unknown. The review covers locations of water in wood; phase changes and equilibrium states of water in wood; thermodynamics of sorption; terminology including cell wall water (bound water), capillary water (free water), fiber saturation point, and maximum cell wall moisture content; shrinkage and swelling; sorption hysteresis; transport of water in wood; and kinetics of water vapor sorption in the cell wall.

Sorption in C-S-H at the molecular level: Disjoining pressures, effective interactions, hysteresis, and cavitation

Sorption processes are critical for drying and durability of cement-based materials. By means of molecular simulations, we study the behavior of C-S-H upon sorption according to various pore sizes at ambient temperature. For interlayer distances between 10 and 26 Å, we determine the sorption isotherms, confining pressures, energy profiles, equilibrium basal distances, and metastable domains during drying and rewetting, respectively. We quantify the pore-size dependency of water cavitation and sorption hysteresis in C-S-H. Cavitation in C-S-H is heterogeneous due to the presence of hydrophobic sites in an overall hydrophilic surface. The critical pore sizes for hysteresis disappearance and reversibility of capillary condensation are provided for C-S-H. We discuss the lower limit of validity of the Kelvin–Cohan description of adsorption and desorption in C-S-H.

Moisture sorption isotherms and hysteresis of soybean grains

Knowledge of the relationship between the equilibrium moisture content of the product and the air that involves it is essential to guarantee product quality and preserve its characteristics during storage. This trend can be studied by sorption isotherms. Thus, this study aimed to obtain desorption and adsorption isotherms of soybean grains to determine the mathematical model that best fits the experimental data and analyze the hysteresis phenomenon. Soybean grains with a moisture content of 21.95% (db) were used to verify the desorption process. The grains were dried until 3.50% (db) for the adsorption process. The static-gravimetric method was employed to determine the equilibrium moisture content of the grain at different temperatures (10, 20, 30, 40, and 50°C) and relative humidity levels (0.10 to 0.92%). Eight mathematical models were fitted to the experimental data. The modified Halsey model satisfactorily represented the desorption and adsorption phenomena of soybean grains. The equilibrium moisture content of soybean grains increased along with an increment in water activity. The increase in temperature led to a reduction in the equilibrium moisture content of soybean grains at a constant water activity. The equilibrium moisture content values obtained by desorption are higher than those obtained by adsorption, indicating the hysteresis phenomenon at the studied temperature range. The isotherms obtained for the desorption and adsorption process were classified as type III because of the high oil content in soybean grains.

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Evaluation of color changes, wettability, and moisture sorption of heat-treated blue-stained radiata pine lumber

To improve the color and surface properties of blue-stained radiata pine, heat treatment was carried out at different temperatures and times. The color change, wettability, and dynamic moisture sorption of the wood were investigated. The results showed that, as the treatment temperature and duration time increased, the surface brightness of specimens gradually decreased, and the surface color became more reddish and blueish. In addition, the contact angle of distilled water at 0 s and 18 s gradually increased as the treatment temperature and time increased, which indicated a decrease in the surface wettability. The color of the blue-stained wood became more uniform with reduced surface wettability and hygroscopicity but increased sorption hysteresis after the treatment.

Cation exchange capacity and soil pore system play key roles in water vapour sorption

Understanding the controlling factors of soil water vapour sorption at different water activities (aw) is essential for accurate estimation of soil properties, such as cation exchange capacity (CEC) and specific surface area (SSA). The objective of this study was to identify the role of CEC and soil pore system in water vapour sorption and sorption hysteresis over a range of aw values. The CEC, SSA, pore volume, and water and nitrogen adsorption/desorption isotherms for eight soils with different clay contents and mineralogies were measured. Irrespective of aw and sorption direction, there was a significant correlation between water content and CEC, and the correlation varied with aw. The water content change was mainly related to CEC and SSAH2O for aw < ∼0.6, and to SSAN2 and pore volume for aw > ∼0.6. Similar to the forced closure phenomenon of the soil nitrogen desorption branch at a relative pressure (P/P0) of ∼ 0.45, the soil water vapour desorption branch also exhibited a sudden drop in the range of 0.2 < aw < 0.4. The water vapour sorption hysteresis for aw < ∼0.75 was mainly due to the difference in cation hydration during the adsorption and desorption process, and the hysteresis phenomena for aw > ∼0.75 was attributed to the different sizes of narrow pore necks and the connected pores.

Moisture sorption isotherms and hysteresis of cellulose, hemicelluloses and lignin isolated from birch wood and their effects on wood hygroscopicity

Moisture sorption isotherms and hysteresis of cellulose, hemicelluloses and lignin isolated from birch wood and their effects on wood hygroscopicity

Study on the moisture-induced swelling/shrinkage and hysteresis of Catalpa bungei wood across the growth ring

Abstract The moisture adsorption/desorption and swelling/shrinkage behavior of Catalpa bungei wood samples were documented in real-time at a mesoscopic scale using dynamic vapor sorption resolution combined with a Dino X Lite Digital Microscope. The results showed that earlywood, latewood, and growth ring samples exhibited varying water vapor sorption isotherms and hysteresis degrees throughout all relative humidity (RH) levels. The radial swelling/shrinkage strains in the separated earlywood (EW) and the growth ring earlywood (GR-E) were lower than that in separated latewood (LW) and growth ring latewood (GR-L) regions. The growth ring region (GR) containing earlywood and latewood tissues , presented an intermediate strain behavior. In contrast, GR-E’s swelling/shrinkage strains resemble LW, GR-L, and GR in the tangential direction. In particular, the GR swelling/shrinkage behavior resembled that of latewood regions, and GR-L had maximum swelling/shrinkage strains. This means that latewood dominated the swelling/shrinkage of the growth ring, promoted to a certain extent by earlywood. Strain hysteresis was observed when the swelling/shrinkage strain was considered an RH function. Latewood regions (LW, GR-L) showed more pronounced swelling hysteresis than earlywood regions (EW, GR-E) in the tangential and radial directions. Furthermore, at any relative humidity the change of the size of the specimen was immediately stabilized when the moisture content reached its equilibrium.

Integration of water sorption hysteresis for heat and mass transfer modeling

Integration of water sorption hysteresis for heat and mass transfer modeling

Ligated Solvent Influence on Interpenetration and Carbon Dioxide and Water Sorption Hysteresis in a System of 2D Isoreticular MOFs.

Four two-dimensional (2D), fluorinated metal-organic frameworks (MOFs), [Cu(hfipbb)(DMF)]n·0.5(DMF)n (1), [Cu(hfipbb)(DEF)]n (2), [Cu3(hfipbb)3(DMA)3]n·6(DMA)n·2(H2O)n (3), and [Cu2(hfipbb)2(DEA)2]n·2(DEA)n·2(H2O)n (4), have been synthesized where hfipbb = 4,4'-(hexafluoroisopropylidene)bis(benzoate), DMF = N,N'-dimethylformamide, DEF = N,N'-diethylformamide, DMA = N,N'-dimethylacetamide, and DEA = N,N'-diethylacetamide. The choice of either a formamide or acetamide solvent ligand leads to a 2D, doubly interpenetrated (1 and 2) or noninterpenetrated (3 and 4) MOF structure. Despite their lower potential void spaces, the doubly interpenetrated structures have superior carbon dioxide and hydrogen sorption properties. Their 195 K CO2 sorption isotherms display inflection points, followed by ∼3-fold increases in their sorption capacities and very large extents of hysteretic behavior. This shows that small changes in the identity of the ligated solvent ligand can affect whether the resulting MOF is interpenetrated or noninterpenetrated and so drastically affect the sorption properties. In addition, the activated phase of a fifth MOF, synthesized through DMF ligand exchange with water in 1 (1W), does not display an inflection point and subsequent increased CO2 sorption at 195 K, despite having the same degree of interpenetration, showing that even more subtle differences in the desolvated phases can lead to marked differences in their sorption behavior.

Synthesis of Mesoporous γ-Alumina Support for Water Composite Sorbents for Low Temperature Sorption Heat Storage

The efficiency of thermochemical heat storage is crucially determined by the performance of the sorbent used, which includes a high sorption capacity and a low regeneration temperature. The thermochemical salt hydrate– γ-alumina composite sorbents are promising materials for this application but lack systematic study of the influence of γ-alumina structural properties on the final storage performance. In this study, mesoporous γ-Al2O3 supports were prepared by solvothermal and hydrothermal synthesis containing a block copolymer (F-127) surfactant to design thermochemical CaCl2 and LiCl composite water sorbents. Altering the solvent in the synthesis has a significant effect on the structural properties of the γ-Al2O3 mesostructure, which was monitored by powder XRD, nitrogen physisorption, and SEM. Solvothermal synthesis led to a formation of mesoporous γ-Al2O3 with higher specific surface area (213 m2/g) and pore volume (0.542 g/cm3) than hydrothermal synthesis (147 m2/g; 0.414 g/cm3). The highest maximal water sorption capacity (2.87 g/g) and heat storage density (5.17 GJ/m3) was determined for W-46-LiCl containing 15 wt% LiCl for space heating, while the best storage performance in the sense of fast kinetics of sorption, without sorption hysteresis, low desorption temperature, very good cycling stability, and energy storage density of 1.26 GJ/m3 was achieved by W-46-CaCl2.

Influence of alkaline delignification time on the moisture uptake behaviour of hemp

The influence of the alkaline delignification of hemp on its moisture uptake has been studied under the project “Preparation and functionalization of hemp for textile substrates” focussed on the reduction of cotton imports for the manufacturing of clothing, household textiles and medical devices. The project looks for the partial replacement of cotton by hemp on the production of natural cellulosic textiles. Hemp fibres are alkaline delignified at different times to evaluate its effect on their moisture uptake behaviour to evaluate the ability of replacing cotton in the next-to-skin goods manufacturing. The paper gives three easy tools to analyse the moisture uptake behaviour by determining the sorption ratio, the hysteresis and the parameters of the isotherms fitted using three different models (GAB, Hailwood-Horrobin and Dent) to the absorption desorption isotherms. The samples of the original and delignified hemp have been subjected to moisture absorption/desorption trials from 5% to 95% RH at 25 °C. Sorption ratio and hysteresis reveal the greater influence of lignin on moisture uptake at low relative humidities, while at high, was cellulose which plays the most important role. The models fitted to the isotherms show that delignification decreases the size of the monolayer that, in desorption results always greater than in absorption. The energy constants of the monolayer for delignified fibres in absorption were higher than those for the original fibres, while the opposite occurred in desorption. Lignin caused great differences between absorption and desorption. The energy constants of the multilayer show a greater range of variation in delignified samples than in the original one, and results in absorption were higher than those in desorption. Delignification time of 3 h reached the highest cellulose content which best approached to the cellulose content of cotton causing that the moisture uptake behaviour drew near to it, especially at higher relative humidity.

In situ observation of shrinking and swelling of normal and compression Chinese fir wood at the tissue, cell and cell wall level

The shrinking and swelling of wood due to moisture changes are intrinsic material properties that control and limit the use of wood in many applications. Herein, hygroscopic deformations of normal and compression wood of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) were measured during desorption and absorption processes. The dimensional changes were observed in situ by an environmental scanning electron microscope and analyzed at different hierarchical levels (tissue, cell and cell wall). The relationship between moisture variation and hygroscopic deformation was measured. During initial desorption periods from 95 to 90 or 75% RH, an expansion of the lumen and a shrinkage of the cell wall were observed, revealing a non-uniform and directional deformation of single wood cells. The variation of shrinking or swelling at different hierarchical levels (tissue, cell and cell wall) indicates that the hygroscopic middle lamella plays a role in the deformation at the tissue level. Higher microfibril angles and helical cavities on the cell wall in compression wood correlate with a lower shrinking/swelling ratio. Normal wood showed a more pronounced swelling hysteresis than compression wood, while the sorption hysteresis was almost the same for both wood types. This finding is helpful to elucidate effects of micro- and ultrastructure on sorption. The present findings suggest that the sophisticated system of wood has the abilities to adjust the hygroscopic deformations by fine-tuning its hierarchical structures.

Full characterization of hygrothermal, mechanical and morphological properties of a recycled expanded polystyrene-based mortar

The construction sector is the most energy consuming one in the world, and it has a significant ecological impact. Indeed, concrete manufacturing overuses natural resources such as sand or gravel, and the need to use alternative building materials is urgent. Choosing adequate building materials takes an important part in the success of a high environmental quality project. This suggests using new alternative solutions, based on recycled materials or waste. However, their use being relatively recent, these materials properties are not widely known and there is lack of information concerning their hygrothermal and mechanical behavior.In this context, the present work aims then to highlight the experimental characterization of hygric, thermal, physical and mechanical properties of a recycled expanded polystyrene mortar, which is a relatively new building material, generally used for its thermal performances. Indeed, a complete characterization campaign was elaborated in this work, allowing a precise determination of the main properties of the material. The experimental characterization also included a usual cement paste made of the same cement as a reference material, in order to evaluate the polystyrene adding impact on the measured hygrothermal properties.Different methods of sorption isotherms determination were presented, and a better attention was devoted to the sorption hysteresis phenomenon characterization. The macroscopic hygrothermal properties, such as water vapor permeability, thermal conductivity and thermal capacity were also investigated function of the temperature and water content evolution. Mechanical strength was also determined, and SEM observations were performed to study the morphology of the material. Experimental results show that expanded polystyrene mortar exhibits a good thermal conductivity and thermal capacity, and a higher water vapor permeability. These results provide data for better forecast on the prediction of the hygrothermal and mechanical behavior of such material.

Biodegradable films from fishing industry waste: Technological properties and hygroscopic behavior

The objective was to evaluate the effect of glycerol on functional properties and sorption behavior of films elaborated with myofibrillar proteins of fish. Analyses of solubility, water vapor permeability (WVP), tensile strength (TS), elongation, and moisture sorption isotherms were performed. Films with lower glycerol concentrations (5, 10, and 15%) showed lower (p ≤ 0.05) permeability when compared to films with 30 and 40%. The increase in the glycerol concentration decreased the TS and increased the elongation of the lyophilized myofibrillary protein films (p ≤ 0.05). Glycerol significantly affected the solubility properties, with an increase of 95.96%. In the sorption process, the films presented curves types II and III, in which high concentrations of glycerol increased their water content. The sorption hysteresis decreased when the concentration of glycerol increased up to its disappearance in films with 40% glycerol. The GAB model was adequate to represent the sorption process of biodegradable films in the relative humidity range of 10–85% under the studied conditions. Films based on fish myofibrillar proteins in the presence of glycerol increase the water's binding capacity to mono and multilayers, and depending on the packaged food, like fresh produce, can preserve the moisture in the food, prolonging its shelf-life.

Probing the dynamics of water over multiple pore scales in cement by atomistic simulations

The presence of water in hydrated cement has significant effects on the properties of concrete. However, direct correlation of water with the macroscopic properties of concrete remains a major challenge. In this study, we use molecular dynamics simulations to determine the water dynamical properties in four pore environments of the calcium silicate hydrate (C–S–H) colloid model; interlayer pores, gel pores, connected pores and in the vicinity of a finite disk–like globule particles. It was revealed that the translational and rotational dynamics are decoupled, consequently, the translational dynamics govern the calculated T2 relaxation time at the surface. Based on NMR T2–T2 relaxation investigation, we showed an exchange between 1 and 4 nm connected pores. At short times, the adsorption/desorption of water from a 1 nm pore is limited to the edges, a behavior linked to water sorption hysteresis. The properties of water in the proximity of a finite C–S–H globule and confined in infinite pore models are comparable.

Influence of gelatinization degree and octenyl succinic anhydride esterification on the water sorption characteristics of corn starch

The effects of gelatinization degree (GD) and octenyl succinic anhydride (OSA) esterification in the sorption-desorption characteristics of normal corn starch (NCS) were studied. NCS was subjected to different GD (53, 70, and 96%) with an extruder and lyophilized. FTIR analysis revealed that GD increased the hydrated (995/1022 ratio) and decreased the short-range ordered (1022/1047 ratio). The equilibrium sorption-desorption curve of starches was obtained for water activities up to 0.95 and fitted with the Guggenheim-Anderson-de Boer (GAB) model. Gelatinization of corn starch decreased its water sorption capacity, increased its sorption hysteresis and decreased its monolayer moisture content. OSA treatment of NCS reduced the water sorption capacity, hysteresis, and monolayer moisture content as reflected by slight variations of these parameters with the GD. A principal component analysis showed that GD and OSA esterification are mutually independent treatments, which can provide different effects on the water sorption characteristics of NCS.