Moisture Sorption Capacity Research Articles

Research Progress on Moisture-Sorption Actuators Materials.

Actuators based on moisture-sorption-responsive materials can convert moisture energy into mechanical/electrical energy, making the development of moisture-sorption materials a promising pathway for harnessing green energy to address the ongoing global energy crisis. The deformability of these materials plays a crucial role in the overall energy conversion performance, where moisture sorption capacity determines the energy density. Efforts to boost the moisture absorption capacity and rate have led to the development of a variety of moisture-responsive materials in recent years. These materials interact with water molecules in different manners and have shown diverse application scenarios. Here, in this review, we summarize the recent progress on moisture-sorption-responsive materials and their applications. We begin by categorizing moisture-sorption materials-biomaterials, polymers, nanomaterials, and crystalline materials-according to their interaction modes with water. We then review the correlation between moisture-sorption and energy harvesting performance. Afterwards, we provide examples of the typical applications using these moisture-sorption materials. Finally, we explore future research directions aimed at developing next-generation high-performance moisture-sorption materials with higher water uptake, tunable water affinity, and faster water absorption.

Buffering moisture variation during cherry tomatoes preservation through deep eutectic solvent films

Moisture plays an important role in fruit preservation. In this study, deep eutectic solvents (DESs) were prepared and DES-based films with the property of buffering moisture variation were fabricated (CG10, CG50). Low-field nuclear magnetic resonance (LF-NMR) analyses and Raman spectra suggested that the water states in DESs and DES-based films transferred from a tight combination to a loose combination during the moisture sorption process. In addition, the moisture sorption capacity (Meq = 2.91) of the film suggested that CG50 possessed water storage capacity and a high effective diffusion coefficient (0.01 mm2 d−1) ensured the easy passing of water molecules through the DES-based films. Furthermore, the fruit preservation experiment using cherry tomatoes as a representative showed that DES-based films as a “buffer pool” not only could inhibit spoilage but also maintain the stable packaging RH, indicating the potential of DES-based films in moisture regulation.

Moisture sorption and its induced deformation of juvenile wood at different radial positions in poplar wood at the tissue scale

Juvenile wood exhibits significant variations in its properties across the radial direction, which responds strongly to water and can impact its applications in various scenarios. Wetwood, a specific presence in juvenile wood, is more prevalent in certain species. In this study, we focused on poplar (Populus x euramericana cv. 'San Martino') and analyzed the moisture content (M) and hygroscopic deformation of juvenile wood near the pith (wetwood) and in juvenile wood near the bark (normal wood) in real-time at the tissue scale (earlywood and latewood). To achieve this, we employed a dynamic vapor sorption analyzer in combination with a Dino-Lite Edge digital microscope. By utilizing the Guggenheim-Andersen-de Boer (GAB) model and the Kelvin equation, we examined the relationship between the bound water and hygroscopic deformation. The results revealed that the M in green condition of wetwood was significantly higher than that of normal wood. However, the disparity in moisture sorption capacity between wetwood and normal wood below the fiber saturation point contributed only minimally to this phenomenon. Regarding for hygroscopic deformation, it was observed that not all wetwood samples exhibited a greater shrinkage/swelling compared to normal wood samples. This variation can be attributed to structural factors, such as differences in microfibril angle, crystallinity, and cell wall ratios. Furthermore, it was found that the swelling ratio caused by 1 % of bound water (SwR-B) increased with rising relative humidity (RH) within the range of 0–90 % RH. However, the SwR-B stabilized or slightly decreased in the range of 90 %-95 % RH. This behavior is believed to be linked to the formation of capillary condensed water at higher humidity levels. Additionally, we found that the swelling ratio resulting from 1 % of polylayer water exceeded that caused by 1 % of monolayer water.

Radiative cooling assisted self-sustaining and highly efficient moisture energy harvesting

Harvesting electricity from ubiquitous water vapor represents a promising route to alleviate the energy crisis. However, existing studies rarely comprehensively consider the impact of natural environmental fluctuations on electrical output. Here, we demonstrate a bilayer polymer enabling self-sustaining and highly efficient moisture-electric generation from the hydrological cycle by establishing a stable internal directed water/ion flow through thermal exchange with the ambient environment. Specifically, the radiative cooling effect of the hydrophobic top layer prevents the excessive daytime evaporation from solar absorption while accelerating nighttime moisture sorption. The introduction of LiCl into the bottom hygroscopic ionic hydrogel enhances moisture sorption capacity and facilitates ion transport, thus ensuring efficient energy conversion. A single device unit (1 cm2) can continuously generate a voltage of ~0.88 V and a current of ~306 μA, delivering a maximum power density of ~51 μW cm−2 at 25 °C and 70% relative humidity (RH). The device has been demonstrated to operate steadily outdoors for continuous 6 days.

The Hygroscopic Properties and Sorption Isosteric Heat of Coix Seeds

Coix seeds are one of the most difficult-to-store cereal foods, and in order to maintain their quality during storage, the present study was conducted to determine the moisture adsorption and desorption isotherms of five varieties of coix seeds in the ranges of 10-35 °C and 11.3%-96.0% equilibrium relative humidity (ERH) using a static gravimetric method. The isotherms showed sigmoidal curves, and there was a hysteresis between adsorption and desorption isotherms. Six equilibrium moisture equations were used to fit the isotherms, and the Modified Chung-Pfost (MCPE), Modified Guggenheim-Anderson-deBoer (MGAB), Modified Henderson (MHE), Modified Oswin (MOE) and our developed modified Caurie (MCaurie) equations were suitable for fitting the data, among which MCPE was the best fitting equation. The monolayer water content decreased with increasing temperature, and the content of monolayer water, the density and layer number of adsorbed water, and the content of bound water for desorption were significantly higher than those of adsorption. The absolutely (ERH 65%) and relatively (ERH 70%) safe moisture contents (MC, wet basis, w.b.) of coix seeds were respectively 12.45%-12.82% and 13.15%-13.69% at 25 ℃. At equilibrium moisture content (EMC) less than 14.9% w.b., the desorption isosteric heats of coix seed were greater than the adsorption isosteric heats, and both decreased sharply in a hyperbolic form, approaching the latent heat of pure water at 14.9% w.b. The sorption isosteric heat of large-grain coix seed was slightly less than that of small-grain seed due to more cracks in the kernel back surface and more micropores in starch granular surface and resultantly more moisture sorption capacity. These results suggest that the desorptive and adsorptive behaviors of coix seeds should be differentiated for cooldown aeration, demoisturizing and remoisturizing operation, and the average isotherm can be used for common storage management.

Development and characterization of camel gelatin films: Influence of camel bone age and glycerol or sorbitol on film properties

This study developed and evaluated camel bone gelatin films (CBGFs) with glycerol or sorbitol as plasticizers. Gelatin extracted from the bones of camels (Camelus dromedarius) at ages ranging from 2.5 to 7 years was used. A comprehensive analysis was conducted, evaluating a range of properties including thickness, moisture sorption capacity, water vapor permeability (WVP), infrared spectral characteristics, light absorption behavior, solubility, as well as mechanical and thermal attributes. This thorough examination allowed for a nuanced understanding of the diverse characteristics exhibited by the camel gelatin samples across different age groups. The results indicated that camel age, glycerol, and sorbitol had a significant impact on the properties of the film (P < 0.05). Tensile strength ranged from 0.32 MPa to 3.99 MPa, while the percentage of elongation at break varied from 89.42 % to 2.68 %. Film color (lightness, L) ranged from 21.39 to 41.33. Glycerol and sorbitol plasticized films were 100 % water soluble. Moisture sorption increased with temperature (25 °C, 35 °C, and 45 °C), with sorbitol films retaining less water. WVP was low in films from old camel bones and high in glycerol-plasticized CBGF-2.5Y and CBGF-4.5Y. Thermal analysis showed a melting temperature between 158.60 °C and 174.10 °C, depending on bone age and plasticizer. These films demonstrate promise for use in food packaging, coatings, and pharmaceutical applications.

Self-assembly of MOF-801 into robust hierarchically porous monoliths for scale-up atmospheric water harvesting

MOFs are becoming one of the most promising sorbents for atmospheric water harvesting (AWH), but their powder form limits the scale-up application. Conventional shaping methods tend to deteriorate the sorption performance or weaken the mechanical strength of the sorbents. Here, monolithic MOF-801 was constructed by coupling sol–gel phase separation and acid-heat post-treatment method. The porosity can be optimized up to 59.7% by regulating the phase separation progress and gelation time, and the specific surface area and micropore volume can be optimized up to 977.8 m2 g−1 and 0.234 cm3 g−1 by the acid-heat post-treatment. The special properties ensured the monolithic MOF-801 with an excellent moisture sorption capacity of 1.2 times higher than that of the conventional MOF-801 powder in small batches and 1.4 times higher than that of the conventional compressed tablet in large batches at 30% RH. The monolithic MOF-801 had centimeter-scale morphology and good mechanical strength with compressive Young's modulus up to 61.3 MPa. This study provides a feasible strategy for achieving the monolithic shaping of MOFs for industrial-scale AWH.

Moisture Adsorption-Desorption Behaviour in Nanocomposite Copolymer Films.

Dehumidifying air via refrigerant cooling method consumes a tremendous amount of energy. Independent humidity control systems using desiccants have been introduced to improve energy efficiency. This research aimed to find an alternative to the commonly used solid desiccant, silica gel, which has weak physical adsorption properties. It also aimed to overcome the limitation of liquid desiccants that may affect indoor air quality and cause corrosion. This study reports on the synthesis of poly(vinyl alcohol-co-acrylic acid), P(VA-AA), through solution polymerisation by hydrolysing poly(vinyl acetate-co-acrylic acid), P(VAc-AA). This viable copolymer was then incorporated with graphene oxide (GO) at different concentrations (0 wt.%, 0.5 wt.%, 2 wt.% and 5 wt.%) to enhance the adsorption-desorption process. The samples were tested for their ability to adsorb moisture at different levels of relative humidity (RH) and their capability to maintain optimum sorption capacity over 10 repeated cycles. The nanocomposite film with 2% GO, P(VA-AA)/GO2, exhibited the highest moisture sorption capacity of 0.2449 g/g for 60-90% RH at 298.15 K, compared to its pristine copolymer, which could only adsorb 0.0150 g/g moisture. The nanocomposite desiccant demonstrated stable cycling stability and superior desorption in the temperature range of 318.15-338.15 K, with up to 88% moisture desorption.

Cellulose acetate/silica composites: Physicochemical and biological characterization

Cellulose acetate is of remarkable scientific interest, becoming more useful when is used in obtaining of the composite materials containing nanoparticles, as result of its improved properties. Thus, cellulose acetate/silica composite films obtained by casting the solutions of cellulose acetate (CA)/tetraethyl orthosilicate (TEOS) in different mixing ratios were analyzed in this paper. The impact of TEOS addition, and implicitly of the silica nanoparticles on the mechanical strength, water vapor sorption properties and antimicrobial activity of the cellulose acetate/silica films were mainly monitored. The results of the tensile strength tests were discussed in correlation with data obtained from Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. It was found that samples with low TEOS content show improved mechanical strength compared to samples with high amounts of TEOS. The microstructural characteristics of the studied films affect their moisture sorption capacity so that the weight of the adsorbed water increases with the addition of TEOS. These features are complemented with the antimicrobial activity against Staphylococcus aureus and Escherichia coli bacterial species. The obtained data show that the cellulose acetate/silica films, and especially those with low silica content have improved properties that can recommend them for applications in the biomedical field.

Moisture Sorption and Degradation of Polymer Filaments Used in 3D Printing.

Experimental research of the moisture sorption process of 12 typical filaments used for FFF was performed in atmospheres with a relative humidity from 16 to 97% at room temperature. Materials with high moisture sorption capacity were revealed. Fick's diffusion model was applied to all tested materials, and a set of sorption parameters was found. The solution of Fick's second equation for the two-dimensional cylinder was obtained in series form. Moisture sorption isotherms were obtained and classified. Moisture diffusivity dependence on relative humidity was evaluated. The diffusion coefficient was independent of the relative humidity of the atmosphere for six materials. It essentially decreased for four materials and grew for the other two. Swelling strain changed linearly with the moisture content of the materials and reached up to 0.5% for some of them. The degree of degradation of the elastic modulus and the strength of the filaments due to moisture absorption were estimated. All tested materials were classified as having a low (changes ca. 2-4% or less), moderate (5-9%), or high sensitivity to water (more than 10%) by their reduction in mechanical properties. This reduction in stiffness and strength with absorbed moisture should be considered for responsible applications.

Hygrothermal Properties Analysis of Bamboo Building Envelope with Different Insulation Systems in Five Climate Zones

Laminated bamboo lumber (BLL) and bamboo scrimber (BS) are potential environmentally friendly building materials, considering that they are hygroscopic materials and that their hygrothermal performance is closely related to the occupants’ comfort, their building durability, and building energy consumption. This study carried out material property tests on bamboo-based materials (BLL and BS) and analyzed hygrothermal performance simulations on bamboo exterior wall constructions in five major climatic zones using WUFI. Results show that BS had a greater heat storage capacity than BLL. However, BLL showed a relatively higher moisture sorption capacity, and BLL was more easily permeated by vapor than BS. The water content (WC) of 12 walls of BLL and BS was below 20%. BLL and BS met the requirements of the envelope, and the WC of BS was lower than that of BLL. Based on the results, the walls designed in this study are suitable for the corresponding climate zones. In the cold and severe climate zones especially, the external insulation system walls performed better than the internal insulation system. The external insulation system was recommended for these two climate zones. The design and simulation results of walls made of two types of bamboo-based materials provide a scientific basis for the application of the material.

Hygrothermal properties of insulation materials from rice straw and natural binders for buildings

Conversion agricultural straws to building insulation materials has attracted great interest due to their good hygrothermal properties and low carbon footprint. In this study, fully bio-sourced composite materials were designed based on rice straw and natural binders. Sodium alginate and chitosan were used as the binders. A crosslinking method was proposed to prevent the water-soluble issue of the composites using sodium alginate as the binder. The influence of fiber size, binder type and binder ratio on the hygrothermal properties of the composite materials made of rice straw were investigated. It was found that all the materials are insulating with their thermal conductivity values between 0.038 and 0.047 W/(m⋅K). The alginate-based composites had the higher water vapor permeability and moisture sorption capacity than the chitosan-based composites. Larger fiber size and lower binder ratio resulted in lower thermal conductivity and higher water vapor permeability. However, fiber size and binder ratio had a negligible effect on moisture sorption capacity of the composite materials. Additionally, the mold growth was investigated by exposing the composite materials to severe conditions, i.e., 93% RH and 97% RH at 20 °C. Mold proliferation was found to be easier and quicker in the surface of alginate-based composites compared to the chitosan-based composites.

Development and Characterization of a Microcrystalline Cellulose-based co-Processed Excipient using Design of Experiment Approach

The study aims to develop a co-processed excipient (CPE) containing microcrystalline cellulose (MCC) and crospovidone (CPV) using the wet massing technique. Preformulation studies were carried out on CPE to characterize its physicochemical properties. Optimization of the formulation of CPE was carried out using a mixture of experimental designs. The optimization study suggested a composite excipient containing MCC (99 %) and CPV (1 %). Solid state characterization of CPE revealed a material that is predominantly crystalline in nature. The particle size of CPE increased in comparison to starting material. FT-IR confirmed the compatibility of MCC and CPV when co-processed together to yield a single composite excipient. There was a decrease in moisture content and moisture sorption capacity of CPE when compared to MCC. Powder characterization revealed an improvement in bulk flow properties of CPE relative to MCC. In summary, the physicochemical properties obtained suggest that CPE will be a suitable tableting excipient in solid dosage formulation by direct compression.

Rheological performance of film-forming solutions and barrier properties of films fabricated from cold plasma-treated high methoxyl apple pectin and crosslinked by Ca2+: Impact of plasma treatment voltage

Sustainable and “green” technologies, such as cold plasma are gaining attention in recent times for improving the functional properties of hydrocolloids. Chemical modifications of hydrocolloids require several chemicals and solvents, which are not environment-friendly. The major objective of the study was to understand the impact of plasma treatment (170–230 V|15 min) on the rheology of film-forming solutions (FFS) and the barrier properties of pectin films. The film-forming properties of plasma-treated pectin were investigated in the presence of two plasticizers, namely, glycerol and polyethylene glycol (PEG) 400. The effects of cross-linking by CaCl2 on the rheology of FFS and barrier properties of the films were discussed. A voltage-dependent decrease in the apparent viscosity of FFS was observed. The viscoelastic properties of the FFS were enhanced due to cross-linking. Glycerol exhibited a better plasticizing effect than PEG. Cross-linking and increasing voltage synergistically contributed towards lower oxygen and carbon dioxide transmission rates. The moisture sorption rate and capacity of the films increased with the voltage of the treatment. The resistance to extension of the films made from glycerol and PEG decreased with voltage, with no significant change in extensibility. On the other hand, the cross-linking by Ca2+ and plasma treatment enhanced the resistance to extension for the films made from both the plasticizers. While the increasing hydrophilicity and opacity of the films were a major drawback of plasma modification, the increase in UV barrier property of the films was an advantage of the modification.

Extraction and Characterization of Pharmaceutical Grade Microcrystalline Cellulose From Bambara Nut (Voandzeia Subterranean (L) Thousars) Husk

Microcrystalline cellulose is a vital ingredient in the food, pharmaceutical, and cosmetics industries. In this study, Bambara nutshell microcrystalline cellulose (BNS-MCC) was prepared by acid hydrolysis modification of Bambara nutshell alpha-cellulose pulp. The sample was subjected to sodium hydroxide pulping (2.0% and 17.5% NaOH respectively) and a multistage pulping treatment using 3.5% nitric acid. The analysis results showed that the pulping method was effective for substantial removal of lignin with a 14.416% yield of alpha-cellulose pulp. The organoleptic and physicochemical properties of BNS-MCC were examined. The prepared BNS-MCC powder was examined using a Scanning Electron Microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR), and X-ray Diffractometer (XRD). The sample’s powder flow properties (true density, Hausner index, Carr’s index, angle of repose,powder porosity, loss on drying, and moisture sorption capacity) were (1.216g/mL, 1.34, 25.75%, 39.80o, 64.7%, and 46.81%). The results of the analysis of the BNS-MCC compared well with commercial grades and conformed to US Pharmacopeia (USP) and British Pharmacopeia specifications. This result shows that Bambara nutshells have potential application for pharmaceutical grade cellulose production used in direct compression tableting.

Hydration kinetics and phase evolution of Portland cement composites containing sodium-montmorillonite functionalized with a Non-Ionic surfactant

This study investigates the hydration behavior and phase evolution of portland cement composites containing montmorillonite (MT) with an objective to address the poor dispersion and improve physical features and chemical reactivity of MT through functionalization with a non-ionic surfactant (polyethylene glycol ether). After functionalization, the MT exhibited an enlarged layer spacing (122%), organic chemical bonds intercalated, improved dispersion in concrete pore solutions, reduced moisture sorption capacity. The cement composites containing the functionalized MT showed enhanced cement hydration, less portlandite, more calcium silicate hydrates (C-S-H) and aluminum-containing hydrates, a more densified microstructure, and higher strength than the composites with raw MT.

Polyzwitterionic Hydrogels for Efficient Atmospheric Water Harvesting.

Atmospheric water harvesting (AWH) is regarded as one of the promising strategies for freshwater production desirable to provide sustainable water for landlocked and arid regions. Hygroscopic materials have attracted widespread attention because of their water harvesting performance. However, the introduction of many inorganic salts often leads to aggregation and leakage issues in practical use. Here, polyzwitterionic hydrogels are developed as an effective AWH material platform. Via anti-polyelectrolyte effects, the hygroscopic salt coordinated with polymer chains could capture moisture and enhance the swelling property, leading to a strong moisture sorption capacity. The hydrogel shows superior AWH performance (0.62 g g-1 , 120 minutes for equilibrium at 30 % relative humidity) and produces 5.87 L kg-1 freshwater per day. It is anticipated that the polyzwitterionic hydrogels with unique salt-responsive properties could provide new insights into the design and synthesis of next-generation AWH materials.

Polyzwitterionic Hydrogels for Efficient Atmospheric Water Harvesting

AbstractAtmospheric water harvesting (AWH) is regarded as one of the promising strategies for freshwater production desirable to provide sustainable water for landlocked and arid regions. Hygroscopic materials have attracted widespread attention because of their water harvesting performance. However, the introduction of many inorganic salts often leads to aggregation and leakage issues in practical use. Here, polyzwitterionic hydrogels are developed as an effective AWH material platform. Via anti‐polyelectrolyte effects, the hygroscopic salt coordinated with polymer chains could capture moisture and enhance the swelling property, leading to a strong moisture sorption capacity. The hydrogel shows superior AWH performance (0.62 g g−1, 120 minutes for equilibrium at 30 % relative humidity) and produces 5.87 L kg−1 freshwater per day. It is anticipated that the polyzwitterionic hydrogels with unique salt‐responsive properties could provide new insights into the design and synthesis of next‐generation AWH materials.

Exploring cross-linked tragacanth as novel excipient-proof-of-concept

Background: Tragacanth, a natural gum, is frequently used as stabilizer for colloidal systems and as a binder in tablets. Materials from natural sources are in increasing demand to solve the current global environmental problems arising from synthesis involving petroleum-based substances. Objectives: In this context, we improved functionality of tragacanth through crosslinking and extended its application for directly compressed fast dissolving systems. Fast dissolving formulations upon settling on the tongue disintegrate promptly and release the medicament, thus making it especially suitable for paediatrics, geriatrics, bedbound, or incapacitated patients. Materials and Methods: Cross-linked tragacanth (CLT) was explored as a potent disintegrant and compared with sodium starch glycolate and Crospovidone for its effect on compressibility and release of metoclopramide hydrochloride from tablets made by direct compression and sublimation method. Formulations made using CLT were optimized for swelling capacity, absorption efficiency, and moisture sorption capacity. Results: The most appropriate controls for linkage of tragacanth were 1:0.4 proportion of tragacanth: Epichlorohydrin, at 105°C temperature for 45 min of reaction. Prepared formulations showed desired disintegration and wetting time. Formulations made using camphor showed porosity because of sublimation and favored rapid disintegration. Based on the drug release study, it is confirmed that formulation with 4% CLT and 20% camphor prepared by sublimation process exhibited highest drug release, i. e. 99.23% within 15 min. Conclusion: This study demonstrates the novel applicability of tragacanth as an effective natural superdisintegrant after cross-linking and provides a sustainable alternative to synthetic superdisintegrants while formulating the fast-disintegrating tablets.

Fe-Co controlled super-hygroscopic hydrogels toward efficient atmospheric water harvesting.

Extracting atmospheric moisture for freshwater production is an appealing way to mitigate the global water crisis. However, the low moisture sorption capacity and high desorption temperature are the major bottlenecks for efficient atmospheric water harvesting. Herein, we develop a transition metal super-hygroscopic hydrogel by an economical strategy, which is constructed through a facile coordination between metal salts and ethanolamine. When the empty electron orbital of the metal ion is coordinated with the lone electron pair of nitrogen or oxygen atom, the water active sorption site is formed. A single water layer is bonded on the sites by a coordination effect, followed by physical interaction with water to form multi-layer structures. The Fe and Co ions in the hydrogel function as dual sorption sites to capture moisture, which can harvest additional water by the synergistic effect of bimetals. As a result, the bimetal hydrogel contributes to a high water uptake of 5.22 g g-1 at 95% RH, triggering the desorption process by one solar intensity due to its low desorption temperature (≤50 °C).