Water Vapor Uptake Research Articles

Microtubular PEDOT-Coated Bricks for Atmospheric Water Harvesting.

Atmospheric water harvesting is a promising technology for alleviating global water scarcity. Current water sorption materials efficiently capture water vapor from ubiquitous air; however, they are difficult to scale up due to high costs, complex device engineering, and intensive energy consumption. Fired red brick, a low-cost masonry construction material, holds the potential for developing large-scale functional architectures. Here, we utilize fired red brick for atmospheric water harvesting by integrating a microtubular coating of the conducting polymer PEDOT within its inorganic microstructure. This microtubular polymer coating affords hygroscopicity and high surface area for water nucleation, enables capillary forces to promote water transport, and enhances the water harvesting efficiency. Our brick composite achieves a maximum water vapor uptake of ∼200 wt % versus polymer mass at 95% relative humidity, decreasing to ∼15 wt % at 40% relative humidity. Facile water release is demonstrated via thermal, electrical, and illuminative heating. This proof-of-concept study demonstrates the potential of masonry construction materials for large-scale atmospheric water harvesting.

High-resolution neutron imaging reveals kinetics of water vapor uptake into a sessile water droplet

•High-resolution neutron imaging visualizes the evaporation of a sessile droplet •The neutron imaging traces a deuterated component in the evaporating droplet •FTIR spectroscopy and diffusion-based model support the neutron imaging observation The spatiotemporal distribution of multiple components and phases governs their evaporation and condensation at the liquid-vapor interface. However, in situ methods to characterize the distribution remain challenging, despite the significance of understanding the ubiquitous mass transport phenomena. Here, we introduce high-resolution neutron imaging as a versatile method to quantify the composition of a sessile droplet in situ, under evaporation and condensation. To prove the concept, we perform a neutron transmittance analysis of a sessile heavy water (D2O) droplet and measure the fraction change of H2O to D2O by the sorption of ambient H2O vapor during the evaporation. Our observations are consistent with ex situ Fourier transform infrared spectroscopy measurements and our diffusion-based numerical model. Our results demonstrate that, with deuterated components having a physicochemical similarity with their hydrogenated counterparts, high-resolution neutron imaging can trace composition changes in nonequilibrium phenomena, such as evaporation and condensation. The spatiotemporal distribution of multiple components and phases governs their evaporation and condensation at the liquid-vapor interface. However, in situ methods to characterize the distribution remain challenging, despite the significance of understanding the ubiquitous mass transport phenomena. Here, we introduce high-resolution neutron imaging as a versatile method to quantify the composition of a sessile droplet in situ, under evaporation and condensation. To prove the concept, we perform a neutron transmittance analysis of a sessile heavy water (D2O) droplet and measure the fraction change of H2O to D2O by the sorption of ambient H2O vapor during the evaporation. Our observations are consistent with ex situ Fourier transform infrared spectroscopy measurements and our diffusion-based numerical model. Our results demonstrate that, with deuterated components having a physicochemical similarity with their hydrogenated counterparts, high-resolution neutron imaging can trace composition changes in nonequilibrium phenomena, such as evaporation and condensation.

Tunable temperature-responsive permeable composite films using polyethylene glycol as a phase change material

Poly(ether-block-amide) (PEBAX)/polyethylene glycol (PEG) (PEBAX/PEG) composite films were successfully prepared, via solution casting methods, for use as temperature-responsive permeable composite films. Their morphologies, thermal properties, and permeabilities were investigated as a function of PEG content. The introduction of high molecular weight PEG into PEBAX results in enhancement of thermal stability in the composite films. As the PEG content was increased, water vapor uptake increased, but the vapor diffusion rate decreased because of effects related to chemical affinity and crystallinity. All PEBAX/PEG composite films exhibited a jump in permeability at temperatures near the PEG phase transition temperature, and this depends on PEG content. This indicates that considerable gas passed through the composite films at temperatures near the PEG phase transition temperature, and this can be controlled by introducing different amounts of PEG. Our result can provide the insights into the further development of self-venting materials using temperature-responsive permeable materials for food, agricultural, and biomedical packaging.

Water sorption on coal: effects of oxygen-containing function groups and pore structure

Coal-water interactions have profound influences on gas extraction from coal and coal utilization. Experimental measurements on three coals using X-ray photoelectron spectroscopy (XPS), low-temperature nitrogen adsorption and dynamic water vapor sorption (DVS) were conducted. A mechanism-based isotherm model was proposed to estimate the water vapor uptake at various relative humidities, which is well validated with the DVS data. The validated isotherm model of sorption was further used to derive the isosteric heat of water vapor sorption. The specific surface area of coal pores is not the determining parameter that controls water vapor sorption at least during the primary adsorption stage. Oxidation degree dominates the primary adsorption, and which togethering with the cumulative pore volume determine the secondary adsorption. Higher temperature has limited effects on primary adsorption process.The isosteric heat of water adsorption decreases as water vapor uptake increases, which is found to be close to the latent heat of bulk water condensation at higher relative humidity. The results confirmed that the primary adsorption is controlled by the stronger bonding energy while the interaction energy between water molecules during secondary adsorption stage is relatively weak. However, the thermodynamics of coal-water interactions are complicated since the internal bonding interactions within the coal are disrupted at the same time as new bonding interactions take place within water molecules. Coal has a shrinkage/swelling colloidal structure with moisture loss/gain and it may exhibit collapse behavior with some collapses irreversible as a function of relative humidity, which further plays a significant role in determining moisture retention.

Shining New Light on the Kinetics of Water Uptake by Organic Aerosol Particles.

The uptake of water vapor by various organic aerosols is important in a number of applications ranging from medical delivery of pharmaceutical aerosols to cloud formation in the atmosphere. The coefficient that describes the probability that the impinging gas-phase molecule sticks to the surface of interest is called the mass accommodation coefficient, αM. Despite the importance of this coefficient for the description of water uptake kinetics, accurate values are still lacking for many systems. In this Feature Article, we present various experimental techniques that have been evoked in the literature to study the interfacial transport of water and discuss the corresponding strengths and limitations. This includes our recently developed technique called photothermal single-particle spectroscopy (PSPS). The PSPS technique allows for a retrieval of αM values from three independent, yet simultaneous measurements operating close to equilibrium, providing a robust assessment of interfacial mass transport. We review the currently available data for αM for water on various organics and discuss the few studies that address the temperature and relative humidity dependence of αM for water on organics. The knowledge of the latter, for example, is crucial to assess the water uptake kinetics of organic aerosols in the Earth's atmosphere. Finally, we argue that PSPS might also be a viable method to better restrict the αM value for water on liquid water.

Effect of degree of sulfonation on the performance of adsorbent SAPO-34/S-PEEK composite coatings for adsorption heat pumps

A composite adsorbent coating on Al6061 aluminum substrate, based on SAPO34 zeolite filler and sulfonate poly (ether-ether ketone) (S-PEEK) matrix is proposed for sustainable energy saving technologies. The effect of sulfonation degree on the mechanical and physical chemical properties of the composite coating was assessed by synthesizing four batches with a degree of sulfonation of the matrix ranging from about 40%–50%. The degree of sulfonation was measured by titration and confirmed by thermogravimetry and FTIR analysis. For each batch of S-PEEK four coatings at increasing SAPO-34 filler content (in the range 80−95 wt.%) were realized. The composite coatings were homogenous and almost defect free. The mechanical performances, evaluated by scratch and pull-off tests, highlighted that all batches exhibited a suitable behavior for adsorption heat pumps application in mobile systems. Best results were observed by using a relatively high sulfonation time of S-PEEK. Obtained coating exhibited indeed very good adhesive and cohesive properties as well as high water vapor uptakes.

Engineering hydrophobic carbon sponge from metal−organic complexes@melamine foam composite for advanced volatile organic compounds adsorption

In this work, highly hydrophobic carbon sponges with large specific surface area were successfully prepared (denoted as HHCS-1, HHCS-2 and HHCS-3). By simply increasing temperature and decreasing heating rate, the carbon sponge showed unique sphere structures at the points of each connection. Moreover, the unique sphere structure changes from no obvious fold to obvious fold. HHCS-3 with the largest surface area of 2926.2 m2 g−1 exhibited superior adsorption performance for methanol, acetone and toluene, and the largest saturated adsorption capacity reached as high as 172, 365 and 429 mg g−1. The ultralow water vapor absorption rate indicates that HHCSs have excellent hydrophobicity and water vapor uptakes are only 7.62%, 6.71% and 6.25% at the relative humidity of 50%. When water vapor was introduced into toluene gas (RH = 50%), the toluene-saturated adsorption capacities are only reduced by 7.2−8.6% compared with under dry conditions. The adsorption capacity of toluene on the HHCSs is higher than that of methanol and acetone. Kinetic adsorption models show that the adsorption of methanol, acetone and toluene onto HHCSs mainly depends on surface adsorption.

A metal-OH group modification strategy to prepare highly-hydrophobic MIL-53-Al for efficient acetone capture under humid conditions

A series of highly-hydrophobic MIL-53-Al (MIL = Materials of Institut Lavoisier) frameworks synthesized via decoration of the Al-OH groups by alkyl phosphonic acid were developed as adsorbents for removing acetone from humid gas streams. The newly prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), N2 adsorption-desorption and thermogravimetric analysis (TGA). Their adsorption behaviors toward acetone vapor under dry and wet conditions were studied subsequently. Results showed that alkyl phosphonic acid was successfully grafted into MIL-53-Al skeleton through coordinating interaction with Al3+ generating MIL-53-Al@Cx (x = 12, 14, 18). The MIL-53-Al@Cx exhibited similar crystal structure and thermal stability to parent MIL-53-Al. Furthermore, the modified materials showed significantly enhanced hydrophobicity. The water vapor uptake of MIL-53-Al@C14 decreased by 72.55% at 75% relative humidity (RH). Dynamic adsorption experiments demonstrated that water vapor had almost no effect on the acetone adsorption performance of MIL-53-Al@C14. Under the condition of 90% RH, the acetone adsorption capacity of MIL-53-Al@C14 was 102.98% higher than that of MIL-53-Al. Notably, MIL-53-Al@C14 presented excellent adsorption reversibility and regeneration performance in 10 adsorption-desorption cycles. Taken together, the strategy of metal-OH group modification is an attractive way to improve the acetone adsorption performance over metal-organic frameworks (MOFs) under humid conditions. Besides, MIL-53-Al@C14 would be deemed as a promising candidate for capturing acetone in high moisture environment.

Preparation of metal organic frameworks/graphene oxide composite membranes for water capturing from air

Water capturing from air is a promising technology to solve the shortage of freshwater resources. In this paper, metal organic framework (MOF-801)/graphene oxide (GO) composite membranes were prepared for efficient water capturing from air, and the effects of drying methods of membranes, MOF-801 contents, adsorption kinetics, and membranes reusability were investigated. The results showed that the natural-dried MOF-801/GO membranes displayed higher water vapor uptake than that of freeze-dried. The water vapor uptake of the membranes rose with the increased MOF-801 contents, and reached 0.23 g g−1 (or 73 g m−2) at 30 % relative humidity and 17 ℃ for the MOF-801/GO (mass ratio of 3:1) membranes. The adsorption kinetics showed that the water vapor uptake rose quickly at first, and attained plateau after 4 h. The MOF-801/GO membranes displayed dehumidification rate of 98.68 % and excellent reusability, demonstrating great potential in water capturing from air.

Energy Efficient Ultrahigh Flux Separation of Oily Pollutants from Water with Superhydrophilic Nanoscale Metal–Organic Framework Architectures

AbstractThe rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar‐like Co‐CAT‐1 metal–organic framework (MOF) crystallites on gold‐coated woven stainless steel meshes with large, 50 μm apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity‐driven, highly efficient oil–water separation featuring water fluxes of up to nearly one million L m−2 h−1. Water physisorption experiments reveal the hydrophilic nature of Co‐CAT‐1 with a total water vapor uptake at room temperature of 470 cm3 g−1. Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF‐based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L−1 of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on‐surface extreme wetting properties, yielding energy‐efficient water‐selective large‐aperture membranes.

Energy Efficient Ultrahigh Flux Separation of Oily Pollutants from Water with Superhydrophilic Nanoscale Metal-Organic Framework Architectures.

The rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar‐like Co‐CAT‐1 metal–organic framework (MOF) crystallites on gold‐coated woven stainless steel meshes with large, 50 μm apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity‐driven, highly efficient oil–water separation featuring water fluxes of up to nearly one million L m−2 h−1. Water physisorption experiments reveal the hydrophilic nature of Co‐CAT‐1 with a total water vapor uptake at room temperature of 470 cm3 g−1. Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF‐based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L−1 of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on‐surface extreme wetting properties, yielding energy‐efficient water‐selective large‐aperture membranes.

Surface properties of Ca, Ti‐doped CeO2 and their influence on the reverse water‐gas shift reaction

AbstractCeO2‐based materials can be found in a variety of catalytic processes, including the reverse water‐gas shift (RWGS) reaction. Nevertheless, the interaction of molecular gases with the surfaces of such materials is still not clear. Recently, some progress was reported on the incorporation of neodymium (Nd) and calcium (Ca) into ceria and their effect on H2O and CO2 adsorption. Titanium (Ti), which has a much smaller ionic radius, has the ability to change the interaction landscape, both as a co‐dopant to Ca and as a sole dopant in the CeO2 system. In this study, the interactions of environmental gases (i.e., water vapor and CO2) on the surface of Ti‐doped CeO2 and Ca,Ti co‐doped CeO2 were investigated. Ti addition to CeO2 was shown to decrease water vapor uptake by up to 25% all while maintaining similar heats of adsorption. In the case of CO2 adsorption, Ti addition to CeO2 had lowered the uptake by more than 50% as well as lowering the heat of adsorption. Co‐doping with Ti and Ca showed small decrease in H2O uptake accompanied with increased heat of adsorption. For CO2, the changes to the uptake and energetics were small and did not indicate a specific trend. The RWGS catalytic performance showed improvement by the addition of Ti in certain levels. The relationship between the doping, surface properties, gas‐surface interactions, and catalytic performance is discussed.

Modelling a tropical-like cyclone in the Mediterranean Sea under present and warmer climate

Abstract. This study focuses on a single Mediterranean hurricane (hereafter medicane), to investigate its response to global warming during the middle of the 21st century and assesses the effects of a warmer ocean and a warmer atmosphere on its development. Our investigation uses the state-of-the-art regional climate model WRF to produce the six-member, multi-physics ensembles. Results show that our model setup simulates a realistic cyclone track and the transition from an initial disturbance to a tropical-like cyclone with a deep warm core. However, the simulated transition occurs earlier than for the observed medicane. The response of the medicane to future climate change is investigated with a pseudo global warming (PGW) approach. This is the first application of the PGW framework to medicanes. The PGW approach adds a climate change delta (defined as difference between future and present climate) to WRF's boundary conditions which is obtained for all prognostic variables using the mean change in an ensemble of CMIP5 simulations. A PGW simulation where the climate change delta is added to all prognostic variables (PGWALL) shows that most of the medicane characteristics moderately intensify, e.g. surface wind speed, uptake of water vapour, and precipitation. However, the minimum sea level pressure (SLP) is almost identical to that under present climate conditions. Two additional PGW simulations were undertaken; One simulation adds the projected change in sea surface and skin temperature only (PGWSST) while the second simulation adds the PGW changes to only atmospheric variables (PGWATMS); i.e. we use present-day sea surface temperatures. These simulations show opposing responses of the medicane. In PGWSST, the medicane is more intense than PGWALL as indicated by lower SLP values, the stronger surface wind, and the more intense evaporation and precipitation. In contrast, the medicane in PGWATMS still transitions into a tropical-like cyclone with a deep warm core, but the PGWATMS medicane weakens considerably (SLP, surface wind, and rainfall decrease). This difference can be explained by an increase in water vapour driven by the warmer ocean surface (favourable for cumulus convection). The warmer and drier atmosphere in PGWATMS tends to inhibit condensation (unfavourable for cumulus convection). The warmer ocean and warmer atmosphere have counteracting effects which leads to only a modest enhancement of the medicane by global warming. The novel approach in this study provides new insights into the different roles of warming of the ocean and atmosphere in medicane development.

Leaf water δ18O reflects water vapour exchange and uptake by C3 and CAM epiphytic bromeliads in Panama.

The distributions of CAM and C3 epiphytic bromeliads across an altitudinal gradient in western Panama were identified from carbon isotope (δ13C) signals, and epiphyte water balance was investigated via oxygen isotopes (δ18O) across wet and dry seasons. There were significant seasonal differences in leaf water (δ18Olw), precipitation, stored 'tank' water and water vapour. Values of δ18Olw were evaporatively enriched at low altitude in the dry season for the C3 epiphytes, associated with low relative humidity (RH) during the day. Crassulacean acid metabolism (CAM) δ18Olw values were relatively depleted, consistent with water vapour uptake during gas exchange under high RH at night. At high altitude, cloudforest locations, C3 δ18Olw also reflected water vapour uptake by day. A mesocosm experiment with Tillandsia fasciculata (CAM) and Werauhia sanguinolenta (C3) was combined with simulations using a non-steady-state oxygen isotope leaf water model. For both C3 and CAM bromeliads, δ18Olw became progressively depleted under saturating water vapour by day and night, although evaporative enrichment was restored in the C3 W. sanguinolenta under low humidity by day. Source water in the overlapping leaf base 'tank' was also modified by evaporative δ18O exchanges. The results demonstrate how stable isotopes in leaf water provide insights for atmospheric water vapour exchanges for both C3 and CAM systems.

Defining sulfonation limits of poly(ether-ether-ketone) for energy-efficient dehumidification

Unprecedented water vapor uptake of 320% was demonstrated with SPEEK at an unexpectedly low degree of sulfonation of 19% due to the high S–S distance.

Antioxidant and hydrophobic Cotton fabric resisting accelerated ageing

Antioxidant fabrics are excellent shields against oxidative damage by free radicals and can be used in clothing, packaging, cosmetics and preservation. In this study, we developed antioxidant and hydrophobic cotton fabrics using ecofriendly materials and processes. The fabrics were functionalized with a double layer coating. Pristine cotton fabrics were coated with a food grade antioxidant (butylated hydroxytoluene, BHT) incorporated biodegradable polyester (polycaprolactone, PCL). This coating was shielded with an acetoxy functional biocompatible hydrophobic silicone coating. The hydrophobic shielding prevented potential loss of the antioxidant due to interaction with water or ambient humidity over time. Coated fabrics were exposed to extreme peroxidative (concentrated H2O2) and UV light damage conditions using an ad hoc protocol for simulating decades of atmospheric ageing. Chemical changes on the cotton surface and potential oxidation and preventive mechanisms were studied using spectroscopy. Treated fabrics also displayed very low water vapor uptake and remained breathable with no visible color change. Mechanical properties of the original fabric were preserved after the treatment.

The Contrail Mitigation Potential of Aircraft Formation Flight Derived from High-Resolution Simulations

Formation flight is one potential measure to increase the efficiency of aviation. Flying in the upwash region of an aircraft’s wake vortex field is aerodynamically advantageous. It saves fuel and concomitantly reduces the carbon foot print. However, CO2 emissions are only one contribution to the aviation climate impact among several others (contrails, emission of H2O and NOx). In this study, we employ an established large eddy simulation model with a fully coupled particle-based ice microphysics code and simulate the evolution of contrails that were produced behind formations of two aircraft. For a large set of atmospheric scenarios, these contrails are compared to contrails behind single aircraft. In general, contrails grow and spread by the uptake of atmospheric water vapour. When contrails are produced in close proximity (as in the formation scenario), they compete for the available water vapour and mutually inhibit their growth. The simulations demonstrate that the contrail ice mass and total extinction behind a two-aircraft formation are substantially smaller than for a corresponding case with two separate aircraft and contrails. Hence, this first study suggests that establishing formation flight may strongly reduce the contrail climate effect.

Enhancing water adsorption capacity of acorn nutshell based activated carbon for adsorption thermal energy storage application

Adsorption thermal energy storage plays a vital role in supporting the availability of renewable energy. Activated carbons produced from local waste biomass have been attracting considerable attention in adsorption technology due to their unique properties and sustainability. However, their limitation in water vapor uptake hinders the practical application of this material. In this work, acorn nutshells were utilized as a base material to produce activated carbon. Air oxidation was performed as a versatile and low-cost technique to enhance the material’s properties and water adsorption capacity. By applying air oxidation as a post-treatment during material production, the amount of active functional groups and the water adsorption on activated carbon has been successfully enhanced. From the theoretical calculation, it is found that activated carbon–water working pairs shown promising performance to be used for adsorption thermal energy storage applications. The adsorption of water vapor on the post-treated-activated carbon releases the isosteric heat between 2400 kJ/kg to 2500 kJ/kg. Moreover, this study’s working pair can be driven by a temperature of less than 50 °C. From the results, it is confirmed that by controlling the adsorbent’s surface properties, activated carbon–water working pairs can be a promising way to provide alternative material and reduce the energy demand for driving the system.

Effect of nanoclay on the properties of rosin derivative cross‐linked green composite based on chicken feather fiber and modified vegetable oil

AbstractFully biodegradable composites based on waste chicken feather fiber (CF), functionalized epoxidized soybean oil (ESO), rosin derivative and various nanoclay percentages were prepared via compression molding. Rosin derivative was synthesized as a substitute of styrene/divinylbenzene. Nuclear magnetic resonance and Fourier transform infrared spectroscopy confirmed the synthesized rosin derivatives structures. Delamination and distribution of silicate layers were studied by X‐ray diffraction and transmission electron microscopy. Scanning electron microscopy was used to analyse compatibility among modified ESO and rosin. FTIR study revealed the interaction between resin, CF, rosin derivative, and nanoclay. The nanoclay loaded composites showed better mechanical properties than the nanoclay free composite. The thermal stability of nanoclay loaded composites were also found to be enhanced. Composites loaded with nanoclay (3 wt%) revealed the least chemical resistance, volumetric swelling and water vapor uptake capacity.

Biodegradable Hydrophilic Film of Crosslinked PVA/Silk Sericin for Seed Coating: The Effect of Crosslinker Loading and Polymer Concentration

Biodegradable polymers are already used in many industries due to their environmental benefits, however their use in agriculture is not yet widespread. Herein, a new biodegradable film of crosslinked poly(vinyl alcohol) (PVA)/silk sericin (SS) was explored and used to coat seeds in order to protect seeds from environmental risk factors with the aim to enhance germination. Films of PVA/SS with different loadings of dimethylurea (DMU, crosslinker) and with different concentrations of PVA were fabricated using an organic solvent free casting process. These crosslinked films were characterized for their thickness, morphology, functional groups, mechanical properties, hydrophilicity and swelling. The results found that the crosslinked film composed of 20% w/w DMU, 10% w/v PVA and 2% w/v SS had good mechanical and physical properties due to higher DMU contents promoting greater crosslinking via hydrogen bonding. This film composition was used to coat on lablab bean seeds by a spray rotary coating machine. Coated and non-coated seeds were compared for their imbibition, water vapor uptake and germination. The coated seeds showed higher imbibition and water vapor uptake than non-coated seeds due to the hydrophilic properties of PVA and SS, which helps to promote higher % germination of the coated seeds. This new biodegradable hydrophilic film of crosslinked PVA/SS has potential for use in seed coating technology.