Water Vapor Adsorption Research Articles

An Exsolved Cu Nanocatalyst for Highly Efficient Methanol Steam Reforming

AbstractBaZr0.1Ce0.7Y0.2O3 (BZCY) perovskite with in‐situ exsolved metallic Cu catalyst acted as a catalyst for methanol steam reforming (MSR) for the first time. After reduction at 550 °C for 3 hours, fine and uniform metallic Cu nanoparticles were exsolved from the perovskite lattice with more active sites and oxygen vacancies on the surface. The reduced Ba0.9Zr0.1Ce0.7Y0.1Cu0.1O3 (BZCYCu) displayed a stable conversion of methanol above 99.9 % at 500 °C within 120 hours, with a negligible amount of CO in the outlet gas and no carbon species was detected on the surface of catalyst. The BZCYCu gained 7.4 % of their weight at 500 °C during the water vapor adsorption stage in temperature programmed water absorption experiment, which showed a considerable water adsorption capacity. Such a hygroscopicity could promote the catalytic methanol steam reforming and CO elimination. And metallic Cu has also been widely applied for the methanol steam reforming reaction due to their high activity and carbon resistance. The synergy of metallic Cu nanoparticles and perovskite substrate with more oxygen vacancies and well hydroscopicity improved the structural stability and ensured the catalytic activity of RBZCYCu catalysts.

Two Unprecedented Germanoniobate Frameworks Based on High-Nuclearity Peanut-Shaped {Ge12Nb38} Clusters.

By variation of the amount of GeO2, two organic-inorganic hybrid germanoniobate frameworks with 6-connected pcu and 10-connected bct topologies were constructed from peanut-shaped {α-Ge12Nb38} and {β-Ge12Nb38} clusters, respectively. The {α-Ge12Nb38} and {β-Ge12Nb38} clusters contain the most Ge centers of germanoniobates reported so far. The compounds exhibit proton conduction properties with a conductivity of 3.04 × 10-4 S·cm-3 for 1 and 1.62 × 10-4 S·cm-3 for 2 at 85 °C and 98% RH. The water vapor adsorption capacities for 1 and 2 are 5.86 and 4.40 mmol·g-1, respectively.

Insight into hydroxyl groups in anchoring Ir single–atoms on vacancy–deficient rutile TiO2 supports for selective catalytic oxidation of ammonia

High–performance catalysts are extremely required for controlling NH3 emission via selective catalytic oxidation (SCO), and the anchoring structural feature of active sites is a key prerequisite for developing them. This study confirms the importance of hydroxyl groups on vacancy–deficient reducible oxides as active groups. On the one hand, spontaneous atomic dispersion of active metal Ir is promoted by the abundant terminal hydroxyl groups. On the other hand, Ir cations anchor on the TiO2 surface through exchange with H+ in Ti–OH groups, and thus occupy the Brönsted acid sites. The adsorption strength of NH3 is another key factor affecting the reaction rate–determining step, namely NH3 dehydrogenation, which occurs at a faster rate in the coordinated L–NH3 rather than the ionic B–NH4+. Meanwhile, the coordinated L–NH3 significantly avoids the competitive adsorption of water vapor in the NH3–SCO reaction by reducing the number of hydrogen bonding. The TOF of preferred 0.8Ir/TiO2 sample is significantly higher than 0.2Ir/TiO2 sample, although Ir is almost always atomic dispersed. Finally, NH3 conversion is 85% in a wet circumstance (5% H2O) at 240 °C (GHSV = 85 000 h–1), with a N2 selectivity of up to 65% on 0.8Ir/TiO2 sample.

Water vapor transport properties of bio-based multilayer materials determined by original and complementary methods

To enhance PLA gas barrier properties, multilayer designs with highly polar barrier layers, such as nanocelluloses, have shown promising results. However, the properties of these polar layers change with humidity. As a result, we investigated water transport phenomena in PLA films coated with nanometric layers of chitosan and nanocelluloses, utilizing a combination of techniques including dynamic vapor sorption (DVS) and long-term water vapor adsorption–diffusion experiments (back-face measurements) to understand the influence of each layer on the behavior of multilayer films. Surprisingly, nanometric coatings impacted PLA water vapor transport. Chitosan/nanocelluloses layers, representing less than 1 wt.% of the multilayer film, increased the water vapor uptake of the film by 14.6%. The nanometric chitosan coating appeared to have localized effects on PLA structure. Moreover, nanocelluloses coatings displayed varying impacts on sample properties depending on their interactions (hydrogen, ionic bonds) with chitosan. The negatively charged CNF TEMPO coating formed a dense network that demonstrated higher resistance to water sorption and diffusion compared to CNF and CNC coatings. This work also highlights the limitations of conventional water vapor permeability measurements, especially when dealing with materials containing ultrathin nanocelluloses layers. It shows the necessity of considering the synergistic effects between layers to accurately evaluate the transport properties.

A comparative study of moisture adsorption on GO, MOF-5, and GO/MOF-5 composite for applications in atmospheric water harvesting.

Water scarcity is an alarming situation across the globe. Several methods have been reported in the literature to minimize the water shortage problem. Sorbent-based atmospheric water harvesting (SBAWH) is considered an energy-efficient, low-cost strategy, and sustainable approach. In the present study, the synthesis of graphene oxide (GO) was carried out using a modified Hummers' method, while the synthesis of MOF-5 and a GO/MOF-5 composite was carried out using a solvothermal approach. The synthesized materials were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The phase composition and crystallinity of all synthesized samples were confirmed by XRD analysis. SEM analysis provided information about the surface morphology of all synthesized samples. The adsorption of water vapors on surfaces of GO, MOF-5, and the GO/MOF-5 composite was evaluated by FTIR analysis. The negative charge was explored by the PZC technique on the surface of all synthesized materials. The water adsorption characteristics of GO, MOF-5, and the GO/MOF-5 composite were evaluated using an atmospheric water harvesting (AWH) plant. The maximum adsorption capacity of 542 mg g-1 was achieved by the MOF at 55% RH (relative humidity), while a low adsorption capacity of the MOF was observed at higher humidity values. This problem was overcome by making a GO/MOF-5 composite. GO imparts structural stability to the MOF-5 structure at higher humidity values. The maximum adsorption capacity of 1137 mg g-1 was achieved by the GO/MOF-5 composite at 75% RH. Several isotherm models, such as Langmuir, Freundlich, and Temkin, were applied to confirm the single-site occupation by water molecules and chemisorption behavior. Several thermodynamic properties were calculated, including isosteric heat (Q st), Gibbs free energy (ΔG), and sorption entropy (ΔS). The overall thermodynamics study confirms that the adsorption process is spontaneous and exothermic. In addition, second-order kinetics confirms that all synthesized material shows chemisorption behavior.

Exploring moisture adsorption on cobalt-doped ZnFe2O4 for applications in atmospheric water harvesting.

Sorption-based atmospheric water harvesting (SBAWH) is a highly promising approach for extracting water from the atmosphere thanks to its sustainability, exceptional energy efficiency, and affordability. In this work, ZnFe2O4 and Zn0.4Co0.6Fe2O4 were evaluated for moisture adsorption. The desired materials were synthesized by a surfactant-assisted sol-gel method. Synthesized samples were characterized using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), and point of zero charge (PZC). Crystallinity and phase composition were evaluated by XRD analysis. Several parameters were determined using XRD analysis: lattice parameter, unit cell volume, crystallite size, and bulk density. The morphology of synthesized materials was assessed via SEM, and unveiled the acquisition of consistent, homogeneous, and uniform crystals. Elemental composition was determined through EDX spectroscopy. Water adsorption on the surface was evaluated by FTIR spectroscopy. The magnetic properties of synthesized ZnFe2O4 and cobalt-doped ZnFe2O4 ferrites were investigated using VSM. The negative charge on the Zn0.4Co0.6Fe2O4 surface was explored using PZC. Adsorption studies on synthesized materials were conducted with the help of an atmospheric water harvesting (AWH) plant created by our team. Moisture adsorption isotherms of synthesized materials were determined using a gravimetric method under varying temperature and relative humidity (45-95%) conditions. The moisture content (Mc) of Zn0.4Co0.6Fe2O4 and ZnFe2O4 was 597 mg g-1 and 104 mg g-1, respectively. Key thermodynamic properties, including isosteric heat of adsorption (Qst), change in Gibbs free energy (ΔG), and change in sorption entropy (ΔS), were evaluated. Qst was negative, which confirmed the sorption of water vapors on the material surface. ΔG and ΔS indicated that water-vapor adsorption was spontaneous and exothermic. A second-order kinetics study was carried out on synthesized materials, demonstrating their chemisorption behavior. The latter was due to the oxygen defects created by replacement of Co2+ and Fe3+ at tetrahedral and octahedral sites. Water vapors in the atmosphere became attached to the surface and deprotonation occurred, and the hydroxyl ions were formed. Water vapor attached to these hydroxyl ions. A second-order kinetics study was carried out to confirm the chemisorption behavior of synthesized materials.

Cooling performance of a mhpa@mof based hybrid passive battery thermal management system for a module with large-capacity prismatic lithium-ion battery

Metal-organic frameworks are beginning to be employed in the thermal management system of lithium-ion batteries because of its high water absorption and enthalpy of phase change. However, its cooling performance is only preliminarily explored used in small cylindrical cells or a single large cell. The effect on multiple large-capacity cells has not be verified yet. In this study, a micro heat pipe arrays@MIL-101(Cr) hybrid battery thermal management system is proposed, and its cooling performance of different number of battery modules at different discharge rates is studied. Experimental results show that MIL-101(Cr) is evenly distributed, and the water vapor adsorption capacity reached 1.65 g/g. The maximum temperature of the micro heat pipe arrays@MIL-101(Cr) group was 36.42?C in the experiment of the four-cell battery pack at 1C discharge rate, which was 12.98?C lower than that of the natural cooling group and 3.05?C lower than that of the micro heat pipe arrays group. With the increase of the number of cells, the maximum temperature of the battery pack rises from 43.12?C to 47.37?C, and the temperature difference rises from 1.53?C to 5.57?C at 2C discharge rate. As the discharge rate increases, the maximum temperature of the battery consisting of four cells rises from 36.42?C to 47.37?C, and the maximum temperature difference rises from 2.87?C to 5.57?C, which suggests that the current micro heat pipe arrays@MOF based battery thermal management system be combined with an active thermal management system to ensure temperature control in high-rate and multi-battery modules.

Investigations on Water Vapor Adsorption–Desorption of Cementitious Materials and Its Induced Permeability under Isothermal Steady-State Flow

Investigations on Water Vapor Adsorption–Desorption of Cementitious Materials and Its Induced Permeability under Isothermal Steady-State Flow

In Ukrainian

The work is devoted to the investigation of the morphology and adsorption properties of powder composites based on biogenic hydroxyapatite modified by magnetite (1, 5, 25, 50 wt. %) of various types (synthesis methods) and chitosan. The morphology of the powders evaluated using SEM micrographs and AMIS software is characterized by a uniform distribution of particles size and shape. It was established that the use of magnetite synthesized by chemical precipitation in the amount of 1-5% allows to obtain composite materials with a particle size in a narrower size range. Analysis of the kinetics of adsorption-desorption processes showed that the adsorption of water vapor is directly related to the ratio of hydroxyapatite and magnetite, increasing with increasing magnetite content. In addition, it is shown that the adsorption process for composites modified by magnetite obtained by the chemical precipitation method proceeds uniformly, while for composites containing magnetite obtained by the thermal decomposition method, three consecutive stages of the adsorption process are characteristic: rapid linear increase in mass, gradual inhibition of the adsorption process and stabilization of the mass of the material. The evaluation of the increase in mass also indicates a connection with the ratio of hydroxyapatite and magnetite, increasing with increasing magnetite content, which confirms the presence of physicochemical processes of interaction of gas molecules with the active centers of the molecules of the studied materials. DTGA also shows that the type of magnetite in an amount of more than 25% significantly affects the mass loss of composites during heat treatment up to 1000 °C, which is related to the initial characteristics of the magnetite used. The presented results in combination with previously obtained physicomechanical and biochemical properties testify to the prospects of biogenic hydroxyapatite/magnetite/chitosan composite materials for medicine.

Characterization of Water Vapor Sorption Performance and Heat Storage of MIL-101 (Cr) Complex MgCl2, LiCl/LaCl3 System for Adsorptive Thermal Conversion.

Adsorption heat conversion systems can provide heating and cooling across time and space in a more environmentally friendly way. Porous materials are potential candidates for water-based adsorption thermal conversion, in which a metal-organic framework (MOF) has a larger specific surface area and porosity than other porous matrices. However, many MOFs with high saturated adsorption capacity have great deficiencies in performance at low water vapor partial pressure, which hinder their application in adsorption thermal conversion. To improve the water vapor adsorption performance of MIL-101 (Cr), different contents of magnesium chloride, lithium chloride, and lanthanum chloride are mixed into MIL-101 (Cr) by an impregnation method. The properties and structures of the materials are characterized by XRD, SEM, nitrogen adsorption tests, water vapor adsorption tests, TG, FTIR, and so on. The results show that the saturated water vapor adsorption capacity of the sample impregnated with salt increases by 1.5-2.3 times, up to 2.24 g/g, compared with that of the unimpregnated sample. When the partial pressure of water vapor is 0.3, the adsorption capacity increases by 5.3-7.5 times and reaches 0.68 g/g at most. The maximum heat storage density of impregnated samples can be increased by 866 J/g. Impregnated MgCl2 can greatly improve the adsorption and thermal conversion performance of MOF, and impregnated MgCl2 and the proper amount of LiCl can further improve the performance of the material system. Our experiments show that the composite impregnation of magnesium chloride and the proper amount of lithium chloride can improve the application performance of the MOF materials in the adsorption thermal conversion process.

Boosting N2O Decomposition by Fabricating the Cs-O-Co Structure over Co3O4 with Single-Layer Atoms of Cs.

Developing effective catalysts for N2O decomposition at low temperatures is challenging. Herein, the Cs-O-Co structure, as the active species fabricated by single-layer atoms of Cs over pure Co3O4, originally exhibited great catalytic activity of N2O decomposition in simulated vehicle exhaust and flue gas from nitric acid plants. A similar catalytic performance was also observed for Na, K, and Rb alkali metals over Co3O4 catalysts for N2O decomposition, illustrating the prevalence of alkali-metal-promotion over Co3O4 in practical applications. The catalytic results indicated that the TOF of Co3O4 catalysts loaded by 4 wt% Cs was nearly 2 orders of magnitude higher than that of pure Co3O4 catalysts at 300 °C. Interestingly, the conversions of N2O decomposition over Co3O4 catalysts doped by the same Cs loadings were significantly inhibited. Characterization results indicated that the primary active Cs-O-Co structure was formed by highly orbital hybridization between the Cs 6s and the O 2p orbital over the supported Co3O4 catalysts, where Cs could donate electrons to Co3+ and produce much more Co2+. In contrast, the doped Co3O4 catalysts were dominated by Cs2O2 species; meanwhile, CsOH species was generated by adsorbed water vapor led to a significant decrease in catalytic activity. In situ DRIFTS, rigorous kinetics, and DFT results elaborated the reaction mechanism of N2O decomposition, where the direct decomposition of adsorbed N2O was the kinetically relevant step over supported catalysts in the absence of O2. Meanwhile, the assistance of adsorbed N2O decomposition by activated oxygen was observed as the kinetically relevant step in the presence of O2. The results may pave a promising path toward developing alkali-metal-promotion catalysts for efficient N2O decomposition.

Hydrochromic film for dynamic information storage using cellulose nanofibers and silica nanoparticles

A hydrochromic composite film was fabricated by incorporating silica nanoparticles (SiNPs) with cellulose nanofibers (CNFs). The CNF/SiNP composite film underwent a reversible change in transparency in response to external moisture variation. The CNFs improved the dimensional stability of the CNF/SiNP composite film and induced morphological differences in SiNP agglomerates, which control the water vapor condensation in a porous film. The condensed water in the pores reduced the difference in refractive index over the CNF/SiNP film, enhancing its transparency. The selective transparency of the composite film was challenged by printing CNF/SiNP inks at different composition ratios. The differing susceptibility of the printed patterns to moisture provided selective transparency at specific patterns, which can store dynamic information such as QR or numerical codes by simple water vapor adsorption and desorption.

Modeling 4.3 billion years of water history on Phobos

Phobos, one of the Martian moonlets, has been the focus of long-standing scientific investigation, particularly regarding its origin: whether it was formed by a giant impact or a captured asteroid. In this study, we investigate the long-term internal evolution of Phobos over 4.3 billion years using a 3-dimensional thermal diffusion and water transport model, named ASTRA. The model newly implements reflected visible light and infrared radiation from Mars, orbital evolution of Phobos, water vapor adsorption on rock grain surfaces, and suppressed permeability due to the surface dust layer in addition to the previous study, allowing us to simulate different grain sizes of 1, 10, 100, and 1000 μm, adsorption coefficients of 1 and 10 kg m−3, and initial water contents of 0.1, 1 or 10 wt%.Our simulation results revealed that without the water vapor adsorption effect, the water inside Phobos would be lost over several billion years for an initial water content of 0.1 wt%. However, when water vapor adsorption was considered, scenarios emerge in which Phobos could retain water to the present day. In the case of a grain size of around 100 μm, Phobos could still continuously release water flux of 10−4–10−3 g s−1 for an initial water content of 0.1 wt%, and 10−2–1 g s−1 for an initial water content of >1 wt%. Furthermore, our research shows the possibility of subsurface condensed water ice in deep high latitude regions and the formation of a gas torus by escaping water-related molecules. If the future MMX mission can measure the water-related ions near the gas torus of Phobos with much >104 cm−2 s−1, the origin of Phobos is most likely the captured asteroid with an initial water content of >1%. For further detailed analysis, our results emphasize the importance of exploring surface soil parameters through soil sample return by the MMX mission.

Estimating the hydratable surface area of building materials from water vapour sorption

The specific surface area of a building material controls its physical, chemical, and biological functions and services, including its moisture regulating potential. The Hydratable Specific Surface Area (H-SSA) of a building material can be estimated from its primary water vapour adsorption and desorption isotherm at a given relative humidity (RH) value or range of RH. The concept is illustrated for 12 mineral and bio-based building materials. The estimated H-SSA for only 1 kg of some building materials can approach the area of a typical agricultural field (500,000 m2, 50 ha.), which helps explain and illustrate the great moisture regulating properties of many bio-based materials. The H-SSA appears useful to help characterize and classify building materials.

Advancement of visible light-driven photocatalytic degradation of dimethyl sulfide by Zn doped rGO/TiO2

In this study, visible light-driven photocatalytic degradation of dimethyl sulfide (DMS) by nanocomposite photocatalyst was achieved through doping TiO2 with reduced graphene oxide (rGO) and various contents of Zn via solvothermal method. Doping of Zn led to formation of oxygen defects and presence of Ti3+ which further promoted photocatalytic activity. After modification, formation of lower level band gap between VB and CB reduced required energy for electron excitation and accelerated light energy utilization. Besides, the presence of surface oxygen vacancies enhanced photocatalytic activity via adsorption of exoteric oxygen. The best DMS conversion (almost 50 %) was performed by 0.1rGO/Zn1TiO2 under typical indoor environment at 60 % RH. Declining of relative humidity to below 10 % improved photocatalytic degradation of DMS due to lower competitive adsorption of water vapor. The best fitting by Langmuir-Hinshelwood kinetics model 4 also supported the occurrence of competitive adsorption with water vapor. Moreover, detection of generated intermediates was used in development of proposed reaction mechanism. Thus, the discussion on DMS photocatalytic degradation over Zn/rGO/TiO2 could be comprehensively conducted from the preparation, characterization, stability test, proposed reaction mechanism, and kinetic study.

Gravimetric analysis of water vapor adsorption kinetics on hydrophilic and hydrophobic Si surfaces using microcantilevers

Understanding the nature of the adsorption of water molecules on a Si surface is of great interest in basic sciences as well as in broad range of industrial processes. Traditional techniques such as Fourier transform infrared spectroscopy cannot capture the adsorption phenomena on a larger surface area of Si. Herein, we report the adsorption kinetics of water molecules on hydrophilic and hydrophobic Si surfaces by means of a precision gravimetric method using microcantilevers (MC). Si MCs with hydrophilic and hydrophobic surfaces were synthesized by chemical route, and their resonance frequency with increasing Relative Humidity (RH) was measured. Shift in resonance frequency of MCs due to adsorption of water molecules was used to estimate the added mass on their surface. In hydrophilic MCs, added mass Vs RH data revealed three distinctive slopes, indicating variation in the molecular configuration of water molecules with increasing RH as predicted by spectroscopic techniques. These results are independently validated by measuring the adhesion force on the MC surface using force-distance curves. In contrast to this, in hydrophobic MCs, added mass due to adsorption was very low and found to increase marginally at higher RH values. An increase in MC surface roughness leading to the clustering of water molecules was shown to be the reason for these observations.

Efficient construction of calcium fluoride nanoaggregates for enhanced water vapor adsorption

Calcium fluoride (CaF2) is an ideal adsorbent for the dehydration of gaseous hydrogen fluoride (HF) containing water vapor. In this work, a novel CaF2 absorbent, spherical CaF2 nanoaggregates (NAs) with a closely packed structure, was proposed and efficiently fabricated by spray drying technology. As the building blocks of CaF2 NAs, the CaF2 nanoparticles (NPs) were prepared by the addition of excess calcium ions (Ca2+) or fluorine ions (F−) in the synthesis. The results indicated that the CaF2 NPs synthesized by excess Ca2+ and the corresponding NAs exhibited much better water vapor adsorption properties than their counterparts by excess F−, owing to higher zeta potentials. More importantly, whether excess Ca2+ or F−, CaF2 NAs had further enhanced water vapor adsorption capacity compared to primary CaF2 NPs, possibly owing to their unique nano-micro secondary structures and higher surface areas. This work has great potential in the development of high-performance absorbents for separating moisture from corrosive gas HF.

Preparation of porous membrane for moisture absorption from high‐humidity gases

AbstractSuitable air humidity is of great importance for human health, crop growth and the life of buildings. In this work, the polyvinylidene fluoride/calcium chloride (PVDF/CaCl2) porous membranes with rich pore structures for adsorption of high‐humidity gases were prepared using solvent evaporation‐induced phase separation. The results showed that the gap between the PVDF spherical crystals increased with the increase of CaCl2 content, which increased the porosity of the membrane. When the CaCl2 content reached 20 wt.%, the water vapor adsorption capacity of the PVDF/CaCl2 porous membrane was 0.876 and the initial adsorption rate was 0.050 g·g−1·min−1. At this point, the moisture vapor permeance of the membrane was the best at 0.04 g·m−2·h−1·Pa−1, and the dry strength of the PVDF/CaCl2 membrane was 0.397 MPa, which was 1.64 times that of the membrane without CaCl2. This work provides theoretical and technical guidance for the preparation of air dehumidification materials.Highlights The porosity of the membranes increased with increasing of calcium chloride content. The moisture vapor permeance of the M‐20 membrane was the best at 0.04 g·m−2·h−1·Pa−1. The dry strength of the M‐20 membrane was 1.64 times that of the M‐0 membrane.

Synthesis, Properties of MIL‐101(Al)‐NH2 Polymers Capable of Absorbing Vapor, Liquid Water Simultaneously

AbstractModified MIL‐101(Al)‐NH2 (MIL‐101(Al)‐NH2‐net) is used as a crosslinking agent and acrylic acid (AA) as a monomer, the MIL‐101(Al)‐NH2‐net grafted polyacrylic acid (MIL‐101(Al)‐NH2‐net‐g‐PAA (MAP)) composite water‐absorbent material is synthesized using the free radical polymerization method to study the application of composite absorbent materials in water collection. The structure and morphology of the composite water‐absorbent material are characterized using Fourier transform infrared spectrometry (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), Brunauer Emmett Teller (BET), and thermogravimetric analysis (TG), and the contents of ammonium persulfate (APS), MIL‐101(Al)‐NH2‐net, and neutralization degree of AA are optimized. Under optimal conditions, the water absorption ratios of the composite materials in distilled water, tap water, and 0.9% NaCl solution are 744, 169.5, and 85.5 g g−1. In addition, the properties of collecting water vapor are investigated. At 25 °C, 50% Relative Humidity (RH), 70% RH, and 90% RH, the MAP water vapor adsorption capacity is 0.0312, 0.5760, and 1.6856 g g−1, respectively. The water vapor adsorption of MIL‐101(Al)‐NH2 and MIL‐101(Al)‐NH2 self‐polymerization products are 0.025 and 0.1278 g g−1, respectively. The result showed that autopolymerization can improve the water vapor adsorption performance.

Transforming volcanic mud into mesoporous silica xerogel and its performance for efficient humidity adsorption

A high humidity level in the environment leads to the development of desiccants as hygroscopic material for adsorbing water vapor. Mesoporous silica xerogel, one of the solid adsorbents used for humidity adsorption, was synthesized from hazardous waste of volcanic mud via sol–gel methods by controlling the pH of the solution. The disordered amorphous silica was obtained, with the properties varied depending on the pH of the solution. Silica xerogel obtained at pH 8 exhibits the highest specific surface area of 576.527 m2g−1 and mesoporous surface area of 527.842 m2g−1. It also has the highest adsorption capacity of 18.90% gw/gads determined from the conventional method and 22.14% gw/gads from TG analysis. The performance for humidity adsorption exceeds the commercial silica with an efficiency of 0.9–7% gw/gads. This result indicates that the potential SiO2 extracted from volcanic mud can be commercialized as desiccants for humidity adsorption.