Moisture Desorption Research Articles

Effect of water saturation in hardened mortar around a steel bar on corrosion considering exposure history

The corrosion rate of steel bar in carbonated concrete is dependent on the presence of water. However, there are few studies on corrosion rate considering the hysteresis behavior, which illustrates the difference between the water contents of concrete in the drying and wetting processes for the same RH. Therefore, this research was done to study the corrosion rate of hardened mortar exposed to various drying and wetting process. In the experiment, thin mortar specimens with an embedded steel plate were fabricated to represent changes in the water state around the steel bar in the mortar. Then, moisture desorption test using saturated specimens and moisture adsorption or dry-wet cycle test using dried specimens that is constant at 40 °C were carried out. The water saturation and corrosion rate were obtained by mass change of mortar specimen and weight loss of steel plate, respectively. The result shows that corrosion was barely observed in non-carbonated specimen but observed in carbonated specimen and the corrosion rate in moisture desorption process was larger than that in moisture adsorption process. In addition, arranging the relationship between water saturation and corrosion rate, constant relations can be seen being independent of process and as water saturation increased, corrosion rate increased by about 60 % and then became constant.

Physics-based prediction of moisture-capture properties of hydrogels

Moisture-capturing materials can enable potentially game-changing energy-water technologies such as atmospheric water production, heat storage, and passive cooling. Hydrogel composites recently emerged as outstanding moisture-capturing materials due to their low cost, high affinity for humidity, and design versatility. Despite extensive efforts to experimentally explore the large design space of hydrogels for high-performance moisture capture, there is a critical knowledge gap on our understanding behind the moisture-capture properties of these materials. This missing understanding hinders the fast development of novel hydrogels, material performance enhancements, and device-level optimization. In this work, we combine synthesis and characterization of hydrogel-salt composites to develop and validate a theoretical description that bridges this knowledge gap. Starting from a thermodynamic description of hydrogel-salt composites, we develop models that accurately capture experimentally measured moisture uptakes and sorption enthalpies. We also develop mass transport models that precisely reproduce the dynamic absorption and desorption of moisture into hydrogel-salt composites. Altogether, these results demonstrate the main variables that dominate moisture-capturing properties, showing a negligible role of the polymer in the material performance under all considered cases. Our insights guide the synthesis of next-generation humidity-capturing hydrogels and enable their system-level optimization in ways previously unattainable for critical water-energy applications.

A solar-driven hygroscopic aerogel using electrical impedance tomography for exploiting differentiated photothermal interfaces

Photothermal materials and structures are essential for the actual performance of interfacial solar-steam generation systems in atmospheric water harvesting (AWH) technologies. However, the absence of theoretical insights into water desorption, diffusion, and heat transfer at the photothermal interface can impede the development of efficient solar interfacial AWH technologies. To address this gap, we introduce an in-situ imaging approach utilizing the electrical impedance tomography (EIT) system to dynamically visualize the water desorption process within aerogels in real time. The visualization outcomes highlight that the effectiveness of moisture desorption in aerogels is influenced by critical factors, including heat concentration, the localization of heating and cooling, and minimal diffusion resistance. Furthermore, the microstructure and temperature disparities on different sides drive internal water movement and evaporation. The proposed design of the generalized EIT visualization detection system aims to reveal the desorption kinetics of highly efficient solar-driven AWH materials, paving the way for a new frontier in studying the interfacial solar-steam generation process.

Fabrication of functional diatomaceous earth with enhanced papain enzyme adsorption

Diatomaceous earth (DE) is a sedimentary rock comprising fossilized shells of diatoms, which are a type of algae. The shells of the diatoms are made of silicon dioxide, which is also the main component of DE. DE has excellent moisture absorption and desorption properties and is widely used as an adsorbent, abrasive, insulator, catalyst, and carrier in the stationary phase. It has also been widely studied for its application as a new silicon material in emerging growth fields, such as biosensors. However, because organic matter is adsorbed on the surface of DE, the organic matter must be removed to exploit the properties of mesoporous silica. In this study, the organic matter on the DE surface was removed by alkali treatment to expose the pores and increase the adsorption capacity. Additionally, papain was physisorbed onto DE using a rotator, and l-cysteine was added for papain activation. Under these optimised conditions, the activation of the papain enzyme was effective, resulting in improved DE performance. The adsorption power of DE was correlated with the amount of papain adsorbed, which, in turn, was correlated with its absorbance. Trichloroacetic acid was added to stop the reaction, and the absorbance was measured. The prepared samples were designated as papain/DE (P/DE) complexes. The final concentration of the P/DE was 1 mg/mL. In addition, cross-linked and non-cross-linked P/DE samples were prepared using N-hydroxysuccinimide and water-soluble carbodiimide in a 5:3 ratio and compared. The results showed that surface treatment and functionalisation of DE improved its functionality (enzyme activity), indicating its potential as a new DE material.

Hygroscopic and pH indicator-based polymer coating for fabrics with responsive discoloration

Humidity-induced discoloration from surface coating is promising, but the surface suffers from low stability, due to the lack of covalent interactions between pH indicator, hygroscopic components and fabrics. Here, we report a strategy to fabricate all-polymer-based, highly hygroscopic fabrics with humidity-induced discoloration and pH-induced discoloration simply by covalently coating/polymerizing a reactive pH indicator and a hygroscopic monomer onto fabrics. The resulting fabrics show remarkable and reversible discoloration from blue to yellow, upon increasing relative humidity. The high reusability of the discoloration has been verified by repeating moisture adsorption and desorption over 20 cycles, without obvious deterioration in the discoloration behavior. Moreover, the fabrics display discoloration behaviors upon contacting aqueous solutions and vapors at different pHs. The simple coating, significant and reversible color transition, and the high reusability enable the all-polymer-based, hygroscopic fabrics to be excellent candidates for humidity indication and pH indication.

Biomimetic Aerogel Composite for Atmospheric Water Harvesting.

Adsorption-based atmospheric water harvesting (AWH) with solar-driven photothermal desorption has become an effective means of solving freshwater scarcity in arid regions due to its low energy consumption and high efficiency. Moisture adsorption and desorption capacities are the most critical properties in AWH, and it is a challenge to improve the rate of moisture adsorption and desorption of composite adsorbents. Therefore, this paper reports a SA/carboxymethyl chitosan (CCS)/C/CaCl2-U composite aerogel adsorbents with simultaneously green, low-cost, degradable, and fast hygroscopicity and desorption kinetics. The composite adsorbent used water-soluble biomass materials sodium alginate (SA) and carboxymethyl chitosan (CCS) as the backbone of the aerogel, constructed a vertically aligned unidirectional pore structure by directional freezing, and introduced nanocarbon powder and moisture-absorbent salt calcium chloride (CaCl2) to improve the solar photothermal performance and water absorption, respectively. The results showed that the composite adsorbent had good water uptake capacity at 30-90% relative humidity (RH), the time to reach the water uptake of 1 g g-1 at 90% RH was only 2.5 h, and the final water uptake rate was up to 1.9 g g-1 within 12 h. Meanwhile, the composite sorbent can be heated and desorbed basically within 1 h at 80 °C and its evaporation efficiency is 1.3 times higher than that of the aerogel sorbent prepared by the conventional method when irradiated with 1000 W m-2 light intensity for 2 h. Therefore, the SA/CCS/C/CaCl2-U composite aerogel adsorbent of this study has a potential that can be applied in AWH due to its environmental friendliness, low cost, and faster hygroscopic desorption kinetics.

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.

Artificial-weathering test requirements for fire-retardant-treated wood to reproduce optimal chemical retention and moisture conditions

Despite the increasing outdoor use of fire-retardant-treated wood, methods for predicting its service life remain poorly established. With the aim of establishing a method to predict chemical losses from fire-retardant-treated (FRT) wood caused by humid atmospheres and rain outdoors, this study examined the preferable conditions for artificial-weathering tests and demonstrated the acceleration coefficients in these tests (i.e., the ratio of equivalent time to reach the same retention of chemicals in artificial weathering and outdoors) based on the EN927-6 standard. To determine the moisture absorption and desorption levels of FRT exposed to outdoor conditions, an outdoor exposure experiment was conducted. The moisture content was higher in the FRT wood than in untreated wood, regardless of the type of coating, and ranged between 11% (in March) and 50% (in September) of the untreated wood’s weight. EN927-6 artificial weathering tests were performed on two groups of specimens with initial moisture contents of 0% and 25%. Retention rates of fire-retardant chemicals after a 2520-h test were compared with those retrieved from 4-year outdoor exposure reported elsewhere. Comparison of these two experiments demonstrated that the acceleration coefficients were 4.1–11.3 in the case of specimens with 0% initial moisture content and 5.1–11.4 in the case of specimens with 25% initial moisture content. The higher initial moisture content produced a more uniform acceleration coefficient. Nevertheless, larger acceleration coefficients were derived from specimens with penetrating or semi-film-forming coatings in both cases. The relationships between the uniformity of this acceleration coefficient and the initial moisture content are discussed from the moisture absorption experiment under constant temperature and humidity and under condensation conditions.

Experimental investigation of a mixed desiccant solution of potassium formate and ionic liquid

Liquid desiccant technology is a promising energy-efficient alternative to conventional temperature and humidity control systems. In the quest to identify the optimal fluid for liquid desiccant systems, alternative desiccant solutions have been explored in terms of their feasibility and compatibility in dehumidification systems. This study proposes and characterises a new type of less expensive mixture of potassium formate (HCO2K) and 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). This novel desiccant solution was investigated in terms of corrosiveness to metals, moisture absorption and desorption ability, cost-effectiveness compared to conventional desiccant solutions. The corrosiveness of desiccant solutions to copper-nickel, copper and steel was tested at room temperature and at 60 °C. Experiments were conducted in a climatic chamber with temperatures of 25–31 °C and relative humidities of 80–90% for the absorption process and temperatures of 50–70 °C and relative humidities of 20–30% for the desorption process to assess the moisture absorption and desorption capacities and mass fraction variations of the desiccant solutions. The mixed desiccant of HCO2K/[EMIM][OAc] in the ratio 60/10% wt. showed a moisture absorption capacity of 0.146 gH2O/gsol (compared to 0.18 gH2O/gsol for aqueous lithium chloride at 33.3% wt.) for a temperature and relative humidity of the climatic chamber of 25 °C and 90%, respectively. Its low corrosiveness, good moisture absorption and desorption capacity and higher cost-effectiveness make it a promising alternative to conventional desiccants, such as aqueous solutions of lithium chloride.

The Effect of Wet and Dry Cycles on the Strength and the Surface Characteristics of Coromandel Lacquer Coatings

Research on the degradation mechanism of coating materials is crucial for the preservation of cultural heritage. The purpose of this study was to evaluate the protective effect of Coromandel coatings on wooden substrates by analyzing their dimensions, weight, adhesion strength, hydrophobicity, and glossiness. The results indicate that after five cycles, the radial moisture expansion rate of the wood specimen is 0.332%, while that of the lacquer specimen is 0.079%, representing 23.8% of the radial moisture expansion rate of untreated wood specimens. This performance is superior to that of the ash and pigment specimens. Across different experimental conditions, the change in the mass of the Coromandel specimens aligns with the trend in their dimensional changes, indicating that moisture absorption and desorption are the primary reasons for dimensional changes. The influence of temperature on mass and dimensional stability is significant only in terms of dry shrinkage rate. After wet and dry cycles at 40 °C, the adhesion strength of the Coromandel specimens decreases the most, with the ash specimens decreasing by 7.2%, the lacquer specimens by 3.2%, and the pigment specimens by 4.5%. Following wet and dry cycles at three different temperatures, the contact angle of the lacquer layers changes by less than 5%, with their contact angle values exceeding 120°. These data indicate that among the Coromandel coatings, the lacquer layer provides the best protection for the wooden substrate, while the ash coating is the most fragile. The degradation rate of the Coromandel specimens increases with rising temperatures. These findings emphasize the critical roles of humidity and temperature in protecting wooden coatings and aim to provide theoretical insights and practical significance for the preservation of wooden artifacts and the assessment of coating performance.

Wood dimensional stability enhancement by multivalent metal-cation-induced lignocellulosic microfibrils crosslinking

Wood is a hygroscopic material that responds to the moisture changes of the surrounding environment through swelling and shrinkage, making it dimensionally unstable. Here, we introduce a facile metal-ion-modification (MIM) approach to enhance the dimensional stability of wood. The MIM process involved swelling the wood samples with aqueous metal ion solutions and drying. The high valent metal cations, such as Fe3+, Al3+, and Zr4+, interacted with the hydrophilic groups (e.g., OH, COOH) present in the wood fibers, limiting their access to water and moisture, thereby enhancing the wood's hydrophobicity and dimensional stability. Evaluation of three wood species, southern yellow pine, poplar, and red oak, revealed water contact angles of 120–130° after MIM, indicative of enhanced surface hydrophobicity. Fe3+ treatment decreased southern yellow pine's swelling ratio from 6 % to 4 %. Fe3+-treated wood exhibited tangential anti-swelling efficiencies ranging from 39.83 % to 57.14 % and radial anti-swelling efficiencies from 34.74 % to 48.33 %, varying across wood species. The enhancement of wood dimensional stability can be attributed to the formation of irreversible coordination bonds between metal cations and lignocellulosic microfibrils in the wood cell wall. These bonds prevent the microfibrils from slipping in response to moisture absorption and desorption.

The Influence of Moisture Absorption and Desorption by the ABS Filament on the Properties of Additively Manufactured Parts Using the Fused Deposition Modeling Method.

This paper presents the results of research on the influence of the moisture content in a filament made of ABS polymer on the properties of products manufactured using FDM (fused deposition modeling). Tests were carried out on a standard printer, using the parameters recommended by the manufacturer and the literature on the subject. A special climatic chamber was used to condition the material. A negative impact of ABS filament moisture on the strength and dimensional accuracy of printed products and on the structure of their surface is demonstrated. When the range of the filament moisture is between 0.17% and 0.75%, the strength decreases by 25% and the sample thickness increases by 10%. It is also shown that this effect does not depend on the history of the polymer reaching a given moisture level, i.e., by absorbing moisture in the absorption process or releasing moisture in the desorption process.

Study on Preparation and Humidity-Control Capabilities of Vermiculite/Poly(sodium Acrylate-acrylamide) Humidity Controlling Composite.

This paper focuses on the preparation and evaluation of a novel humidity-control material, vermiculite/(sodium polyacrylate(AA)-acrylamide(AM)), using inverse suspension polymerization. Acrylic acid and acrylamide were introduced into the interlayer of modified vermiculite during the polymerization process, leading to the formation of a strong association with the modified vermiculite. The addition of vermiculite increased the specific surface area and pore volume of the composites. To investigate the moisture absorption and desorption properties of the composites, an orthogonal experiment and single-factor experiment were conducted to analyze the impacts of vermiculite content, neutralization degree, and the mass ratio of AA to AM. According to the control experiment, the addition of vermiculite was found to enhance the pore structure and surface morphology of the composite material, surpassing both vermiculite and PAA-AM copolymer in terms of humidity control capacity and rate. The optimal preparation conditions were identified as follows: vermiculite mass fraction of 4 wt%, a neutralization degree of 90%, and mAA:mAM = 4:1. The moisture absorption rate and moisture release rate of the composite material prepared under these conditions are 1.285 g/g and 1.172 g/g. The humidity control process of the composite material is governed by pseudo second-order kinetics, which encompasses the complete adsorption process. These results indicate that the vermiculite/PAA-AM composite humidity control material has excellent humidity control performance and is a simple and efficient humidity control method.

Using industrial waste in porous building materials for indoor humidity control

This study uses waste bricks and waste catalyst as raw materials in the synthesis of humidity control building materials with high structural strength. This paper explores the feasibility of producing porous humidity control materials (PHCM) through the billet sintering of waste brick with various quantities of waste catalyst (0 %–40 %) for indoor construction. N2 adsorption and desorption isotherms revealed that PHCM exhibits Type-IV adsorption with H3 hysteresis loops, indicating a network of interconnected mesopores with diameters ranging from 3 to 17 nm. Humidity control analysis revealed that increasing the waste catalyst content significantly enhanced the equilibrium moisture content and moisture adsorption and desorption capacity. This study determined that the adsorption of moisture within the PHCM relies on capillary condensation within the mesopores. Under 95 % relative humidity (RH), the highest equilibrium moisture content (2.97 kg/kg) and 12-h moisture adsorption capacity (72.41 g/m2) were obtained in specimens prepared at a sintering temperature of 1000 °C with a 40 % spent catalyst. This excellent adsorption capacity can be attributed to the high surface area of the waste catalyst, which increased the surface area of PHCM from 0.013 to 8.529 m2/g. This study demonstrates the benefits of synthesizing PHCM using waste bricks and catalysts in terms of porous properties, mechanical properties, and humidity control performance.

Moisture absorption and desorption characteristics and prediction model analysis of building thermal insulation materials

Understanding the isothermal moisture absorption and desorption characteristics of building thermal insulation materials and how they affect thermal conductivity, is curial for accurate building thermal design and energy-saving calculation. In this paper, five types of building thermal insulation materials are selected for investigation. First, the variation trend of the equilibrium mass moisture content of materials in different moisture absorption and desorption stages is studied employing the saturated salt solution method and the constant temperature and humidity box method, and the effect of temperature on the moisture absorption and desorption processes is evaluated. Additionally, the applicable model of the material in the moisture absorption and desorption process is obtained through a fitting analysis of the experimental data. Finally, the influence of the material’s moisture absorption and desorption characteristics on the thermal conductivity is analyzed using the transient thermal conductivity test method. The results highlight that there is a need to consider the moisture absorption and desorption processes to accurately determine the wet material thermal conductivity, and the hysteresis effect of the material in the moisture absorption and desorption processes is directly related to its microstructure and the relative humidity at the initial moisture desorption. At a temperature of 25 oC, the autoclaved aerated concrete exhibits its highest hysteresis rate of thermal conductivity during the moisture desorption process of third stage, reaching 13.2%.

Versatile and recyclable double-network PVA/cellulose hydrogels for strain sensors and triboelectric nanogenerators under harsh conditions

Versatile and recyclable conductive hydrogels with long-term environmental adaptability and mechanical stability have attracted tremendous attention in wearable smart electronics. Here, double-network (DN) polyvinyl alcohol (PVA)/cellulose hydrogels were constructed after introducing a conductive rigid cellulose/Zn2+/Ca2+ network into a soft PVA/borax network. The resultant hydrogels possessed good mechanical and self-adhesive properties, along with transparency, recyclability, and remarkable resistance to freezing. They showed 30-day non-drying properties due to the presence of hygroscopic salts through a dynamic moisture adsorption and desorption process. Dehydrated hydrogels can return to their original states via self-regeneration under high relative humidity. Hydrogel-based strain sensors retained good sensitivity and a wide sensing range during the wide working temperature ranging from −40 °C to 50 °C and after recycling. Additionally, conductive hydrogels were integrated into triboelectric nanogenerators (TENGs) functioning as energy harvesters for powering electronics. TENGs retained stable electrical outputs even under harsh conditions and after recycling. Hydrogels were also assembled into flexible self-powered biomechanical sensors and tactile sensors. Thermally reversible interactions in composite hydrogels enabled their good recyclability, thereby reducing economic costs and environmental impacts caused by e-wastes. This work demonstrates the great potential of versatile and recyclable hydrogels with good environmental and mechanical stability in wearable smart electronics under harsh conditions.

Research of fiberglass and basalt textile laminates on the kinetics of sorption and desorption of moisture after exposure to cold climate conditions

A two-stage kinetics of moisture sorption is obtained at a temperature of 23 °C and a humidity of 68 % in fiberglass laminates and basalt textile laminates exposed in a cold climate (Yakutsk) for 2 and 4 years. The adequacy of the relaxation model of anomalous moisture diffusion at the first stage of sorption is shown and an assessment of the increase in moisture content at the second stage is given. Keywords:textile laminate, moisture sorption kinetics, anomalous diffusion, approximation, structure and properties of the composite, climatic aging kychkinplasma@mail.ru

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.

Changes in Moisture Desorption Rate of Shelled Corn Layers in a Low-Temperature Deep-Bed Drying Column

To optimize grain drying processes, high-moisture shelled corn was dried in a device using a combination of three temperatures (45, 55 and 65 °C) and hot-air velocities (0.7, 1.1 and 1.3 m·s-1). The grain moisture and temperature, and the relative humidity (RH) of interstitial airflow were determined intelligently in grain layers of 7.5 to 32.5 cm with 5.0 cm intervals. The change in RH of interstitial airflow in grain layers of 7.5-27.5 cm with drying time all revealed the shape of a hyperbolic line and took turns to lag. These RH lines shortened with an increased drying temperature from 45 to 65 °C and hot-air velocity from 0.7 to 1.3 m·s-1. The temperature lines were raised and shortened with an increase in drying temperature and hot-air velocity. A modified moisture diffusion exponential equation was developed to analyze the moisture desorption rate of corn kernels. For the average sorption rate curve from grain layers of 2.5-32.5 cm at 1.3 m·s-1 of hot air, the transition points from adsorption to desorption occurred at 2.4 h, 2.7 h, and 3.0 h with drying temperatures of 65 and 45 °C, respectively, and represented the earliest and largest initial desorption rates among the three hot-air velocities. The moisture desorption rate of samples increased with increasing drying temperature. Compared with the average value of grain layers, at the same hot-air velocity, the kernel effective diffusivity (Deff) values dried at 55 °C were correspondingly higher than those dried at 45 and 65 °C. At the same drying temperature, the kernel Deff values tended to increase with an increase in hot-air velocity, whereas the activation energy decreased. These results suggested that an increase in drying temperature and hot-air velocity may considerably shorten adsorption time and increase desorption rates of shelled corn in deep bed drying.

Research Progress on Hygroscopic Agents for Atmospheric Water Harvesting Systems.

Adsorptive atmospheric water harvesting systems (AWHs) represent an innovative approach to collecting freshwater resources from the atmosphere, with a hygroscopic agent at their core. This method has garnered significant attention due to its broad applicability, strong recycling capacity, and sustainability. It is being positioned as a key technology to address global freshwater scarcity. The core agent's hygroscopic properties play a crucial role in determining the performance of the AWHs. This article provides a comprehensive review of the latest advancements in hygroscopic agents, including their adsorption mechanisms and classifications. This study of hygroscopic agents analyzes the performance and characteristics of relevant porous material composite polymer composites and plant composites. It also evaluates the design and preparation of these materials. Aiming at the problems of low moisture adsorption and desorption difficulty of the hygroscopic agent, the factors affecting the water vapor adsorption performance and the method of enhancing the hygroscopic performance of the material are summarized and put forward. For the effect of hygroscopic agents on the volume of water catchment devices, the difference in density before and after hygroscopicity is proposed as part of the evaluation criteria. Moisture absorption per unit volume is added as a performance evaluation criterion to assess the effect of hygroscopic agents on the volume of water collection equipment. The article identifies areas that require further research and development for moisture absorbers, exploring their potential applications in other fields and anticipating the future development direction and opportunities of moisture-absorbing materials. The goal is to promote the early realization of adsorptive atmospheric water harvesting technology for large-scale industrial applications.