Dynamic Vapor Sorption Research Articles

Effect of hygro-mechanical treatment combined with saturated steam on bamboo cell wall: Structural, chemical, and hygroscopic properties

Bamboo has shown great potential in various fields such as construction, furniture, and decoration due to its fast growth rate, short degradation cycle, strong carbon sequestration ability, and excellent mechanical properties. The effects of hygro-mechanical treatment combined with saturated steam (SC treatment) on bamboo cell walls are less studied. This study explored the effects of SC treatment at different temperatures (140°C, 160°C, 180°C) on the cell wall structure, chemical composition, and hygroscopic properties of bamboo. The study utilized Fourier transform infrared spectroscopy (FTIR) and Confocal Raman microscopy (CRM) to analyze the chemical properties of bamboo, X-ray diffraction (XRD) to analyze the crystal structure, Small Angle X-ray Scattering (SAXS) to analyze the microstructure, Brunauer-Emmett-Teller (BET) to analyze porosity, and Dynamic Vapor Sorption (DVS) to assess humidity adsorption. The lignin and hemicellulose in the bamboo were degraded under saturated steam treatment, leading to reduced stability of the bamboo fiber structure. Compression under these conditions severely damages the orderly arrangement of the fiber structure, resulting in a decrease in the microfibril orientation. The reduction in orientation significantly affected the moisture transfer rate in bamboo and the micromechanical properties of the fiber cells. Simultaneously, the reduction of lignin and hemicellulose decreases the hygroscopic properties of bamboo. The results of this study indicate that SC treatment significantly improves the crystallinity and dimensional stability of bamboo while reducing its porosity, hygroscopicity, and micromechanical properties. Among the three experimental groups, the 160°C saturation steam-compression treatment was considered the best method for significantly improving bamboo performance while maintaining structural integrity.

A Nature-Inspired Design for Sequestering Polycyclic Aromatic Hydrocarbons in Asphalt-Surfaced Areas

Asphalts for pavement and roofing are known to emit volatile organic compounds (VOCs), contributing to air pollution, including the formation of ozone and secondary organic aerosols, which further worsen air quality. These emissions become more pronounced with higher sun intensity and higher temperature, accelerating the loss of essential components and the aging of bitumen. Consequently, the durability and functionality of bitumen are compromised. In this study, we investigate the efficacy of nitrogen-carrying functional groups in biochar at retaining VOCs in bitumen and prolonging the service life of asphalt surfaces. Biochar derived by hydrothermal liquefaction of red microalgae, rich in N-functional groups, is compared with low-N biochar obtained through acid-washing. Laboratory tests demonstrate that bitumen modified with high-N biochar exhibits greater resistance to aging after 200 h of ultraviolet radiation exposure compared to bitumen modified with low-N biochar. The values of an aging index based on the crossover modulus and an aging index based on the crossover frequency indicate greater susceptibility to aging in neat bitumen compared to biochar-modified bitumen, and bitumen modified with high-N biochar showed the lowest aging index. Compared to neat bitumen, measurements of carbonyl and sulfoxide as aging indicators showed an improvement of 12.9% for high-N biochar in slowing bitumen aging, while low-N biochar provided only a 3.1% improvement. Dynamic vapor sorption analysis showed 35% less mass loss in bitumen with high-N biochar compared to bitumen with low-N biochar. These improvements can be attributed to the increased retention of VOCs in bitumen facilitated by the N-functional groups in high-N biochar. Modeling with density functional theory shows the mechanisms by which biochar rich in N-functional groups exhibits enhanced adsorption of VOCs. This modeling highlights the importance of biochar's nitrogen functional groups in biochar's electronic structure and molecular structure in retaining VOCs in the bitumen matrix. The study outcomes promote sustainability and resource conservation in the construction industry and align with goals of carbon neutrality.

Detection of helical water flows in sub-nanometer channels

Nanoscale flows of liquids can be revealed in various biological processes and underlie a wide range of nanofluidic applications. Though the integral characteristics of these systems, such as permeability and effective diffusion coefficient, can be measured in experiments, the behaviour of the flows within nanochannels is still a matter of speculation. Herein, we used a combination of quadrupolar solid-state NMR spectroscopy, computer simulation, and dynamic vapour sorption measurements to analyse water diffusion inside peptide nanochannels. We detected a helical water flow coexisting with a conventional axial flow that are independent of each other, immiscible, and associated with diffusion coefficients that may differ up to 3 orders of magnitude. The trajectory of the helical flow is dictated by the screw-like distribution of ionic groups within the channel walls, while its flux is governed by external water vapour pressure. Similar flows may occur in other types of nanochannels containing helicoidally distributed ionic groups and be exploited in various nanofluidic lab-on-a-chip devices.

Leucine as a Moisture-Protective Excipient in Spray-Dried Protein/Trehalose Formulation

The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate properties, stability, and ultimately bioavailability of the final product. More specifically, Leu has been proposed to form a shell on the surface of spray-dried (SD) particles. The aim of this study was to explore the potential of Leu in the SD protein/trehalose (Tre) formulation to control the water uptake and moisture-induced recrystallization of amorphous Tre, using lysozyme (LZM) as a model protein. LZM/Tre (1:1, w/w) was dissolved in water with varied amounts of Leu (0 - 40%, w/w) and processed by spray-drying. The solid form, residual moisture content (RMC), hygroscopicity, and morphology of SD LZM/Tre/Leu powders were evaluated, before and after storage under 22°C/55% RH conditions for 90 and 180 days. The X-ray powder diffraction results showed that Leu was in crystalline form when the amount of Leu in the formulation was at least 20% (w/w). Thermo-gravimetric analysis and scanning electron microscopy results showed that 0%, 5%, and 10% (w/w) Leu formulations led to comparable RMC and raisin-like round particles. In contrast, higher Leu contents resulted in a lower RMC and increased surface corrugation of the SD particles. Dynamic vapor sorption analysis showed that partial recrystallization of amorphous Tre to crystalline Tre·dihydrate occurred in the 0% Leu formulation. However, adding as little as 5% (w/w) Leu inhibited this recrystallization during the water sorption/desorption cycle. In addition, after storage, the formulations with higher Leu contents showed reduced water uptake. Instead of observing recrystallization of amorphous Tre in 0%, 5%, and 10% (w/w) Leu formulations, recrystallization of amorphous Leu was noted in the 5% and 10% (w/w) Leu formulations after storage. In summary, our study demonstrated that the addition of Leu has the potential to reduce water uptake and inhibit moisture-induced recrystallization of amorphous Tre in the SD protein/Tre powder system.

Eutectic mixtures containing the active pharmaceutical ingredient ezetimibe: Phase diagrams, solid state characterization and dissolution profiles

Cardiovascular disease represents the leading cause of death worldwide, according to the World Health Organization (WHO) report. One of the treatment strategies is the use of the drug ezetimibe (EZT). This drug is a cholesterol absorption inhibitor with low aqueous solubility, which affects its therapeutic efficacy. The purpose of this paper was to obtain eutectic materials of EZT with methylparaben (MPB), salicylic acid (SCA) and nicotinamide (NTM) coformers, and to study their phase diagrams, dissolution properties and hygroscopicity to assess possible enhancements. Phase and Tamman diagrams were constructed using differential scanning calorimetry (DSC) results. The eutectic materials were characterized by powder X-ray diffraction (PXRD) and polarized light optical microscopy (OM). The hygroscopicity of the materials was assessed at different relative humidities (RH) through dynamic vapor sorption (DVS). The dissolution study was conducted with the materials in powder form, with paddle dissolution, rotating at 50 rpm, in 900 mL of aqueous buffer solution at pH 6.8 and 37 °C. The phase diagrams demonstrated that EZT formed eutectic systems with eutectic molar fractions of 0.59, 0.67 and 0.69 for EZT-SCA, EZT-NTM and EZT-MPB, respectively. The three eutectic materials are characterized as microcrystalline conglomerates of their components. In terms of the hygroscopic behavior of EZT at different RHs, eutectic materials demonstrated lower susceptibility to monohydrate formation compared to the anhydrous form. In dissolution studies, EZT-SCA and EZT-MPB solubilized EZT in amounts 22 % higher than the pure drug in 15 min. On the other hand, EZT-NTM eutectic suppressed the dissolution of EZT down to 56 % at the same time. The results indicated the possibility of obtaining materials with enhanced properties using eutectic mixtures, with improved dissolution rates and hygroscopic stability.

Process development in Quality‐by‐Design paradigm for anti‐solvent aided crystallization: impact of crystallization parameters on particle morphology and dissolution behaviour of Dexlansoprazole active pharmaceutical ingredient

AbstractBACKGROUNDIn this work, a process development study for the crystallization step of dexlansoprazole API has been demonstrated under the Quality‐by‐Design (QbD) paradigm. Dexlansoprazole (crystalline) samples prepared under different crystallization conditions of reactor temperature and addition time of anti‐solvent were subjected to solid‐state characterization with variety of analytical techniques, including X‐ray powder diffraction (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic vapour sorption (DVS), scanning electron microscopy (SEM), particle size distribution (PSD) by laser diffraction and intrinsic dissolution rate (IDR).RESULTSThe crystalline samples were observed to have identical polymorphic phase integrity but differed in their physical characteristics. The particle size distribution and microscopy data collectively elucidated the particle growth kinetics and the extent of agglomeration could be correlated to crystallization conditions, namely reactor temperature and addition time of anti‐solvent. The intrinsic dissolution rate of samples was in good agreement with the morphological properties.CONCLUSIONAn empirical model has been proposed for intrinsic dissolution rate correlating with crystallization process parameters. In conclusion, it was possible to elucidate the impact of crystallization parameters on the solid‐state behaviour of dexlansoprazole for development of appropriate pharmaceutical dosage forms. © 2024 Society of Chemical Industry (SCI).

Colyophilized Sugar-Polymer Dispersions for Enhanced Processing and Storage Stability.

Sucrose and trehalose pharmaceutical excipients are employed to stabilize protein therapeutics in a dried state. The mechanism of therapeutic protein stabilization is dependent on the sugars being present in an amorphous solid-state. Colyophilization of sugars with high glass transition polymers, polyvinylpyrrolidone (PVP), and poly(vinylpyrrolidone vinyl acetate) (PVPVA), enhances amorphous sugar stability. This study investigates the stability of colyophilized sugar-polymer systems in the frozen solution state, dried state postlyophilization, and upon exposure to elevated humidity. Binary systems of sucrose or trehalose with PVP or PVPVA were lyophilized with sugar/polymer ratios ranging from 2:8 to 8:2. Frozen sugar-PVPVA solutions exhibited a higher glass transition temperature of the maximally freeze-concentrated amorphous phase (Tg') compared to sugar-PVP solutions, despite the glass transition temperature (Tg) of PVPVA being lower than PVP. Tg values of all colyophilized systems were in a similar temperature range irrespective of polymer type. Greater hydrogen bonding between sugars and PVP and the lower hygroscopicity of PVPVA influenced polymer antiplasticization effects and the plasticization effects of residual water. Plasticization due to water sorption was investigated in a dynamic vapor sorption humidity ramping experiment. Lyophilized sucrose systems exhibited increased amorphous stability compared to trehalose upon exposure to the humidity. Recrystallization of trehalose was observed and stabilized by polymer addition. Lower concentrations of PVP inhibited trehalose recrystallization compared to PVPVA. These stabilizing effects were attributed to the increased hydrogen bonding between trehalose and PVP compared to trehalose and PVPVA. Overall, the study demonstrated how differences in polymer hygroscopicity and hydrogen bonding with sugars influence the stability of colyophilized amorphous dispersions. These insights into excipient solid-state stability are relevant to the development of stabilized biopharmaceutical solid-state formulations.

Hydric Environment and Chemical Composition Shape Non-avian Reptile Eggshell Absorption.

The amniotic egg fulfils a critical role in reproduction by serving as an interface between the external environment and the embryo. Because non-avian reptiles are rarely incubated, they must be heated by, and absorb water from, the oviposition site for the developing embryo. The mechanisms by which they absorb sufficient, but not excess, water and how these mechanisms vary with local habitat is largely unknown, despite its significance to their evolution. Here, we first performed histology, Fourier-transform infrared spectroscopy and dynamic vapor sorption experiments to elucidate the mechanisms of eggshell absorption for 56 reptile species. Then, we used phylogenetic comparative analysis to test the hypothesis that the absorptive capacity of reptile eggshells increases with aridity of the environment. We found that water absorption increases in the presence of a superficial mucopolysaccharide layer and decreases with increased calcium content. We found that eggs from arid environments have highly absorbent eggshells, but only in species with weakly calcified shells. Our results suggest that reptile eggshells have over evolutionary time tuned absorptive capacity to environmental moisture level. Since these eggs often must sustain conflicting constraints, they may serve as inspirations for new biomimetic materials, such as water filtering membranes or humidity sensors.

A drug–drug cocrystal strategy to regulate stability and solubility: A case study of temozolomide/caffeic acid

Temozolomide (TMZ) is a common clinical drug widely used to treat glioblastoma multiforme and gradual astrocytoma. Despite its widespread use in cancer treatment, issues remain with the solubility and stability of TMZ, which can be addressed by synthesizing novel pharmaceutical cocrystals. This study sought to enhance the physiochemical properties of TMZ. To this end, a pioneering pharmaceutical cocrystal of TMZ and caffeic acid (CAF), 2TMZ–CAF·0·5H2O (2:1:0.5) was synthesized and characterized using a solution method. The cocrystal structure was analyzed by molecular surface electrostatic potential (MESP), Hirshfeld surface analysis, and 2D fingerprinting. They were further characterized by single crystal X-ray diffraction, power X-ray diffraction, proton nuclear magnetic resonance, thermogravimetry-differential scanning calorimetry, dynamic vapor sorption, and Fourier transform infrared spectroscopy. Furthermore, the hygroscopicity, stability, and solubility of the TMZ–CAF cocrystal were investigated to evaluate their pharmaceutical applicability. In the asymmetric unit of the novel synthesized cocrystal, two complementary molecules of TMZ and CAF were found, forming planar hydrogen bonding pairs such as O–H···O, N–H···O, and O–H···N. Moreover, the cocrystals exhibited excellent stability compared to TMZ alone and regulated solubility during accelerated stabilization and dissolution processes. Hence, the cocrystals boast characteristics that can circumvent the rapid release of TMZ. In conclusion, the newly synthesized 2TMZ–CAF·0·5H2O cocrystals demonstrate enhanced physiochemical properties, including improved stability and solubility, compared to pure TMZ. This suggests potential utility in drug delivery systems. Additionally, the findings underscore the growing importance of pharmaceutical cocrystals in drug development, with implications for advancing cancer treatment and drug formulation strategies.

New Cocrystals of Ligustrazine: Enhancing Hygroscopicity and Stability.

Ligustrazine (TMP) is the main active ingredient extracted from Rhizoma Chuanxiong, which is used in the treatment of cardiovascular and cerebrovascular diseases, with the drawback of being unstable and readily sublimated. Cocrystal technology is an effective method to improve the stability of TMP. Three benzoic acid compounds including P-aminobenzoic acid (PABA), 3-Aminobenzoic acid (MABA), and 3,5-Dinitrobenzoic acid (DNBA) were chosen for co-crystallization with TMP. Three novel cocrystals were obtained, including TMP-PABA (1:2), TMP-MABA (1.5:1), and TMP-DNBA (0.5:1). Hygroscopicity was characterized by the dynamic vapor sorption (DVS) method. Three cocrystals significantly improved the hygroscopicity stability, and the mass change in TMP decreased from 25% to 1.64% (TMP-PABA), 0.12% (TMP-MABA), and 0.03% (TMP-DNBA) at 90% relative humidity. The melting points of the three cocrystals were all higher than TMP, among which the TMP-DNBA cocrystal had the highest melting point and showed the best stability in reducing hygroscopicity. Crystal structure analysis shows that the mesh-like structure formed by the O-H⋯N hydrogen bond in the TMP-DNBA cocrystal was the reason for improving the stability of TMP.

Measurement of Water Uptake and States in Nafion Membranes Using Humidity-Controlled Terahertz Time-Domain Spectroscopy.

Perfluorinated sulfonic acid ionomers are well known for their unique water uptake properties and chemical/mechanical stability. Understanding their performance-stability trade-offs is key to realizing membranes with optimal properties. Terahertz time-domain spectroscopy has been demonstrated to resolve water states inside industrially relevant membranes, producing qualitatively agreeable results to conventional gravimetric analysis and prior demonstrations. Using the proposed humidity-controlled terahertz time-domain spectroscopy, here we quantify this detailed water information inside commercially available Nafion membranes at various humidities for direct comparison against literature values from dynamic vapor sorption, differential scanning calorimetry, and Fourier transform infrared spectroscopy on selected samples. Using this technique therefore opens up opportunities for rapid future parameter space investigation for membrane optimization.

Hygrothermal Properties and Performance of Bio-Based Insulation Materials Locally Sourced in Sweden.

In recent years, there has been a paradigm shift in the building sector towards more sustainable, resource efficient, and renewable materials. Bio-based insulation derived from renewable resources, such as plant or animal fibres, is one promising group of such materials. Compared to mineral wool and polystyrene-based insulation materials, these bio-based insulation materials generally have a slightly higher thermal conductivity, and they are significantly more hygroscopic, two factors that need to be considered when using these bio-based insulation materials. This study assesses the hygrothermal properties of three bio-based insulation materials: eelgrass, grass, and wood fibre. All three have the potential to be locally sourced in Sweden. Mineral wool (stone wool) was used as a reference material. Hygrothermal material properties were measured with dynamic vapour sorption (DVS), transient plane source (TPS), and sorption calorimetry. Moisture buffering of the insulation materials was assessed, and their thermal insulation capacity was tested on a building component level in a hot box that exposed the materials to a steady-state climate, simulating in-use conditions in, e.g., an external wall. The tested bio-based insulation materials have significantly different sorption properties to stone wool and have higher thermal conductivity than what the manufacturers declared. The hot-box experiments showed that the insulating capacity of the bio-based insulators cannot be reliably calculated from the measured thermal conductivity alone. The results of this study could be used as input data for numerical simulations and analyses of the thermal and hygroscopic behaviour of these bio-based insulation materials.

Mechanochemically Induced Solid-State Transformations of Levofloxacin.

Levofloxacin hemihydrate (LVXh) is a complex fluoroquinolone drug that exists in both hydrated and anhydrous/dehydrated forms. Due to the complexity of such a compound, the primary aim of this study was to investigate the amorphization capabilities and solid-state transformations of LVXh when exposed to mechanical treatment using ball milling. Spray drying was utilized as a comparative method for investigating the capabilities of complete LVX amorphous (LVXam) formation. The solid states of the samples produced were comprehensively characterized by powder X-ray diffraction, thermal analysis, infrared spectroscopy, Rietveld method, and dynamic vapor sorption. The kinetics of the process and the quantification of phases at different time points were conducted by Rietveld refinement. The impact of the different mills, milling conditions, and parameters on the composition of the resulting powders was examined. A kinetic investigation of samples produced using both mills disclosed that it was in fact possible to partially amorphize LVXh upon mechanical treatment. It was discovered that LVXh first transformed to the anhydrous/dehydrated form γ (LVXγ), as an intermediate phase, before converting to LVXam. The mechanism of LVXam formation by ball milling was successfully revealed, and a new method of forming LVXγ and LVXam by mechanical forces was developed. Spray drying from water depicted that complete amorphization of LVXh was possible. The amorphous form of LVX had a glass transition temperature of 80 °C. The comparison of methods highlighted that the formation of LVXam is thus both mechanism- and process-dependent. Dynamic vapor sorption studies of both LVXam samples showed comparable stability properties and crystallized to the most stable hemihydrate form upon analysis. In summary, this work contributed to the detailed understanding of solid-state transformations of essential fluoroquinolones while employing greener and more sustainable manufacturing methods.

Hygroscopicity in Epoxy Powder Composites

Epoxy powders offer a low-cost way of manufacturing thick-section composite parts, such as those found in wind and tidal turbines. Currently, their processing cycle includes a lengthy drying stage (≥15 h) to remove ambient moisture. This drying stage prevents void defect formation and, thereby, a reduction in mechanical properties; however, it constitutes up to 60% of the processing time. Little research has been published which studies the drying stage or its optimisation. In the present work, experimental and simulated analyses are used to investigate the effects of hygroscopicity in epoxy powder composites. Tests are performed to quantify the void content of dried and undried laminates and to measure its impact on transverse flexural strength. Dynamic vapour sorption analysis is used to study the sorption behaviour of the epoxy powder. It is shown that the epoxy powder is slightly hygroscopic (1.36 wt%) and exhibits sorption behaviour that is characteristic of glassy polymers. This results in up to 4.8% voids (by volume) if processed in an undried state, leading to a 43% reduction in transverse flexural strength. A modified linear driving force model is fitted to the desorption data and then implemented in existing process-simulation tools. The drying of a thick epoxy powder composite section is simulated to investigate the influence of powder sintering on the duration of the drying stage. Process simulations reveal that a standard drying cycle prematurely sinters the powder, which inhibits moisture release. By maintaining the powder state, simulations show that the drying cycle can be reduced to 5 h.

Unraveling UVB effects: Catalase activity and molecular alterations in the stratum corneum

AimUltraviolet B (UVB) radiation can compromise the functionality of the skin barrier through various mechanisms. We hypothesize that UVB induce photochemical alterations in the components of the outermost layer of the skin, known as the stratum corneum (SC), and modulate its antioxidative defense mechanisms. Catalase is a well-known antioxidative enzyme found in the SC where it acts to scavenge reactive oxygen species. However, a detailed characterization of acute UVB exposure on the activity of native catalase in the SC is lacking. Moreover, the effects of UVB irradiation on the molecular dynamics and organization of the SC keratin and lipid components remain unclear. Thus, the aim of this work is to characterize consequences of UVB exposure on the structural and antioxidative properties of catalase, as well as on the molecular and global properties of the SC matrix surrounding the enzyme. ExperimentsThe effect of UVB irradiation on the catalase function is investigated by chronoamperometry with a skin covered oxygen electrode, which probes the activity of native catalase in the SC matrix. Circular dichroism is used to explore changes of the catalase secondary structure, and gel electrophoresis is used to detect fragmentation of the enzyme following the UVB exposure. UVB induced alterations of the SC molecular dynamics and structural features of the SC barrier, as well as its water sorption behavior, are investigated by a complementary set of techniques, including natural abundance 13C polarization transfer solid-state NMR, wide-angle X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and dynamic vapor sorption microbalance. FindingsThe findings show that UVB exposure impairs the antioxidative function of catalase by deactivating both native catalase in the SC matrix and lyophilized catalase. However, UVB radiation does not alter the secondary structure of the catalase nor induce any observable enzyme fragmentation, which otherwise could explain deactivation of its function. NMR measurements on SC samples show a subtle increase in the molecular mobility of the terminal segments of the SC lipids, accompanied by a decrease in the mobility of lipid chain trans-gauche conformers after high doses of UVB exposure. At the same time, the NMR data suggest increased rigidity of the polypeptide backbone of the keratin filaments, while the molecular mobility of amino acid residues in random coil domains of keratin remain unaffected by UVB irradiation. The FTIR data show a consistent decrease in absorbance associated with lipid bond vibrations, relative to the main protein bands. Collectively, the NMR and FTIR data suggest a small modification in the composition of fluid and solid phases of the SC lipid and protein components after UVB exposure, unrelated to the hydration capacity of the SC tissue. To conclude, UVB deactivation of catalase is anticipated to elevate oxidative stress of the SC, which, when coupled with subtle changes in the molecular characteristics of the SC, may compromise the overall skin health and elevate the likelihood of developing skin disorders.

Effect of Heat Treatment on Hygroscopicity of Chinese Fir (Cunninghamia lanceolata [Lamb.] Hook.) Wood

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p < 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content.

Modeled versus Experimental Salt Mixture Behavior under Variable Humidity.

This study investigates the kinetics of salt mixture crystallization under relative humidity (RH) conditions, varying between 15 and 95% (at 20 °C), to inform applications in built heritage preservation, geology, and environmental sciences. We focused on commonly found, sulfate-rich and calcium-rich salt mixtures containing five to six ions, Cl-, NO3-, Na+, and K+, including or excluding less common Mg2+, and including either an excess of SO42- or Ca2+, with respect to gypsum. Using time-lapse micrographs and dynamic vapor sorption, we explore how crystallization and dissolution behavior depend on RH and mixture composition under constant temperature. A range of RH change rates were studied to simulate realistic weather events. Microstructural analyses through environmental scanning electron microscopy (ESEM) confirmed the crystal habit corresponding with RH transitions. Phases predicted from thermodynamic modeling (ECOS/RUNSALT) were confirmed using micro-Raman spectroscopy, X-ray diffraction (XRD), and elemental mapping via energy-dispersive X-ray spectroscopy (EDX). We identify a strong correlation between phase transition kinetics and RH change rates, with crystallization deviating by -15% and dissolution by +7% from modeled values under rapid (several seconds) and slow (several days) RH changes. These insights are important for preservation strategies in built heritage, salt deposition, and dissolution mechanisms in diverse geological and realistic environmental contexts, laboratory experiments, future modeling efforts, and the understanding of stone decay in general.

Simultaneous impregnation and microencapsulation of CaCl2 using silica gel and methyl cellulose for thermal energy storage applications

Thermal energy storage utilizing the adsorption of moisture from air is a promising energy storage technology due to its high energy density and minimum heat losses. Salt hydrates and salt hydrate composites, such as calcium chloride (CaCl2) and CaCl2-based composites, have shown favourable energy storage properties in this area of research. However, these materials have shown issues with stability due to swelling and deliquescence. In this work, CaCl2 was stabilized using three methods: impregnation into silica gel, encapsulation in methyl cellulose, and both impregnation and encapsulation stabilization techniques used simultaneously. Therefore, three CaCl2-based composites were synthesized. For the first composite, silica gel was impregnated with CaCl2. For the second composite, CaCl2 was encapsulated by methyl cellulose. For the third composite, silica gel was impregnated with CaCl2 and the CaCl2 was encapsulated with methyl cellulose. These samples were structurally characterized using scanning electron microscopy as well as Brunauer-Emmett-Teller (BET) to determine surface area, pore size distribution and nitrogen adsorption isotherms at 77 K. Water vapour adsorption isotherms were also determined at 25 °C for different relative humidities by dynamic vapor sorption (DVS). Similarly, LiCl-based composites were also synthesized and examined in this work, but issues of deliquescence, swelling, and agglomeration made the materials impractical to work with. To determine the prepared materials’ thermal energy storage performance, 2–6 g of each sample was tested in a lab-scale apparatus. This process uses the exothermic adsorption of moisture from ambient air in an open thermal energy storage system. The CaCl2 impregnated silica gel that was encapsulated in methyl cellulose showed reasonably high stability and energy storage performance after 3 hydration and dehydration cycles with minimum agglomeration. An energy storage density of 241 kWh/m3 (0.87 GJ/m3) and specific energy of 630 Wh/kg (2268 kJ/kg) was achieved with this material for 90% inlet relative humidity after a regeneration at 90 °C.

Moisture-induced limited recrystallization may not reduce the dissolution of amorphous solid dispersions: A case of nitrendipine

As a promising strategy, amorphous solid dispersion (ASD) technology has been widely studied and employed. However, moisture affects the physical stability of ASD, leading to phase separation and recrystallization. This study aims to investigate the moisture-induced physical instability of the nitrendipine (NTD) ASD systems from apparent phenomenon to molecular mechanism. The critical relative humidity (CRH) of the ASD was identified as 50% RH through a dynamic vapor sorption study. After being stored above the CRH, ASDs exhibited obvious phase separation and recrystallization, owing to water competition hydrogen bond as evidenced by molecular docking. After 75% RH exposure, the ASD underwent obvious recrystallization thereafter the dissolution was reduced. However, the dissolution of ASD samples stored at 60% RH did not decrease obviously. This study helps to understand the environment humidities for ASD physical stability and gives hints at the relation between recrystallization and dissolution in the ASD system.

Effect of the pore structure characteristics of coal samples on the dynamic adsorption of water vapor

In order to study the dynamic adsorption process of water vapor in the pore structure of different coal samples (YJL for lignite, SEK for bituminous coal and BJ for anthracite). The pore structure characteristics of the three coal samples were analyzed by mercuric pressure method, liquid nitrogen adsorption method and infrared spectroscopy. Further, the water vapor adsorption capacity of the three coal samples under different humidity conditions was determined by dynamic water vapor sorption (DVS) experiments. In addition, the monolayer adsorption and multilayer adsorption at different humidity were calculated using the Dent model. The results showed that YJL had the largest surface pore volume and oxygen functional group parameter (IO = 12.41), and its water vapor adsorption capacity was also the highest. However, under high humidity conditions, the presence of a large number of pore throats in the YJL coal samples hindered multilayer adsorption, resulting in a water vapor adsorption percentage of only 18.07 %. On the other hand, SEK has a small oxygen functional group parameter (IO = 5.81), poor pore connectivity, and a certain pore throat structure, resulting in a low water vapor adsorption capacity of SEK coal samples, with a water vapor adsorption proportion of only 23.76 %. BJ coal has a large pore volume and a large number of oxygen functional groups on the surface (IO = 8.84), which has a good pore connectivity and the least number of pore throats structure, resulting in a water vapor adsorption ratio is higher at 87.38 %. On this basis, cylindrical and wedge-shaped pore models of coal samples were constructed, and molecular dynamics simulations were carried out to investigate the adsorption characteristics of water vapor in these pore models. The results show that the adsorption process of water molecules in coal develops continuously with “initial-water chain-water bridge-water lock”. By summarizing and analyzing the above experimental results, four control mechanisms of coal pore characteristics affecting water vapor adsorption were clarified. These findings are of great significance for studying the movement of water vapor in coal seams and understanding the degree of water confinement caused by hydraulic control measures.