Atmospheric Water Harvesting Research Articles

Leveraging Isoreticular Principle to Elucidate the Key Role of Inherent Hydrogen-Bonding Anchoring Sites in Enhancing Water Sorption Cyclability of Zr(IV) Metal-Organic Frameworks.

Water adsorption/desorption cyclability of porous materials is a prerequisite for diverse applications, including atmospheric water harvesting (AWH), humidity autocontrol (HAC), heat pumps and chillers, and hydrolytic catalysis. However, unambiguous molecular insights into the correlation between underlying building blocks and the cyclability are still highly elusive. In this work, by taking advantage of the well-established isoreticular synthetic principle in Zr(IV) metal-organic frameworks (Zr-MOFs), we show that the inherent density of hydrogen atoms in the organic skeleton can play a key role in regulating the water sorption cyclability of MOFs. The ease of isoreticular practice of Zr-MOFs enables the successful syntheses of two pairs of isostructural Zr-MOFs (NU-901 and NU-903, NU-950 and SJTU-9) from pyrene- or benzene-cored carboxylate linkers, which feature scu and sqc topological nets, respectively. NU-901 and NU-950 comprised of pyrene skeletons carrying more hydrogen-bonding anchoring sites show distinctly inferior cyclability as compared with NU-903 and SJTU-9 built of benzene units. Single-crystal X-ray crystallography analysis of the hydrated structure clearly unveils the water molecule-involved interactions with the hydrogen-bonding donors of benzene moieties. Remarkably, NU-903 and SJTU-9 isomers exhibit outstanding water vapor sorption capacities as well as working capacities at the desired humidity range with potential implementations covering indoor humidity control and water harvesting. Our findings uncover the importance of hydrogen-bonding anchoring site engineering of organic scaffold in manipulating the framework durability toward water sorption cycle and will also likely facilitate the rational design and development of highly robust porous materials.

Double-ended vacuum tube collector based solar powered atmospheric water harvesting by using composite desiccant material ‘Jute/CaCl₂’

ABSTRACT Amidst increasing fresh water crisis, sorption based solar powered atmospheric water harvesting (SPAWH) offers a promising solution to this problem. The available sorption based systems use composite desiccants that are expensive and artificially processed, which restricts their scalability and practical implementation. Moreover, the required desorption temperature available from the system is also low. The proposed system develops and experimentally investigates a novel composite desiccant material synthesized using anhydrous CaCl₂ impregnated in Jute (intrinsic host material), which is cheap and naturally available. To desorb the composite desiccant, 4.86 m2 double-ended vacuum tube collector is used, which produces peak hot air temperature of 134.2°C. The developed system using 12 kg composite of Jute/CaCl₂ harvests 5850 ml/day of water at 0.086 $/L cost with 13.93% thermal and 8.66% exergy efficiency. The results of the water analysis verify that the harvested water is of good quality and is safe for use.

Thermoelectrically Regulating Heat Flux in Metal−Organic Framework Monoliths for High-Yield Atmospheric Water Harvesting in Arid Regions

Thermoelectrically Regulating Heat Flux in Metal−Organic Framework Monoliths for High-Yield Atmospheric Water Harvesting in Arid Regions

Experimental comparison of solar‐powered adsorption‐based atmospheric water harvesting using air‐to‐air & water‐to‐air heat exchanger for condensation

AbstractAdsorption‐focused technologies for atmospheric water harvesting is of great importance. Most of the available systems in the literature use glass as a condenser, which gets heated up. This restricts vapor condensation to harvest less water and hampers the system's scalability. The effectiveness of the proposed solar atmospheric water harvesting system, which uses an air‐to‐air fin‐tube heat exchanger to condense the vapors, is experimentally evaluated in this work. In order to assess the system's effectiveness using a water‐to‐air fin‐tube heat exchanger, a comparison study is also carried out. The experimental setup consists of evacuated tube solar air heater having 8.46 m2 area and 15 kg silica gel adsorbent. The performance metrics for comparison include adsorption & regeneration rate, thermal, overall and exergy efficiency, along with economic analyses. The system harvests 1890 mL/day of water using air‐to‐air heat exchanger at cost of 0.19 $/l, achieving thermal, overall & exergy efficiencies of 21.66%, 2.24%, and 6.51%, respectively. On the other hand, the water‐to‐air heat exchanger based system harvests maximum of 2680 mL/day of water at a cost of 0.14 $/l, achieving thermal, overall & exergy efficiencies of 25.65%, 3.34%, and 9.13%, respectively. Moreover, the produced water is confirmed to be safe for consumption.

Challenging POPular opinion: Porous organic polymers for atmospheric water harvesting

As humanity faces growing water scarcity in many parts of the world, innovative solutions are imperative to achieve equitable access to safe drinking water for all. Atmospheric water harvesting (AWH) is a highly promising solution to water scarcity, comprising water adsorption directly from air using hydrophilic adsorbents, followed by collection upon desorption. Porous organic polymers exhibit distinct advantages for AWH, including broad tailorability, desirable porous properties, and outstanding chemical and thermal stability. This perspective outlines the current state-of-the-art in porous organic materials for AWH, distinguishing between reticular and amorphous materials, to discern key properties and outline future design principles. We also outline key performance metrics and provide a guide for the characterisation of such porous organic materials for those seeking to enter the field of AWH.

Hierarchical Silica Composites for Enhanced Water Adsorption at Low Humidity.

To combat water scarcity in remote areas around the world, adsorption-based atmospheric water harvesting (AWH) has been proposed as a technology that can be used alongside existing water production capabilities. However, commonly used adsorbents either have low water adsorption loadings or are difficult to regenerate. In this work, we developed two novel hierarchical silica-salt composites that both exhibit high water adsorption loadings under dry and humid conditions. The total water vapor loading, kinetics, and heats of water adsorption for both silica-salt composites were investigated. As hierarchical silicas have tunable pores and large pore volumes, these materials serve as effective host matrixes for the hygroscopic salt LiCl. Our results suggest that hierarchical pores play a significant role in water adsorption: micropores and some smaller mesopores act as "storage" sites for hygroscopic salt, whereas larger mesopores and macropores increase the accessibility of water vapor into the silica. Using this mix of pores, we achieved greater than 0.4 g H2O/g composite at 10% RH and 27 °C. Additionally, we found that the salt-impregnated silica and bare silica had the same heat of adsorption: 80-90 kJ/mol. The results suggest that the H-bond interactions are similar for both systems and that the primary mechanism at play here is water cluster adsorption/desorption. Despite the similar energies, the LiCl-containing materials exhibited considerably slower kinetics than bare silica materials. Of equal importance to the adsorption capacity and kinetics of these composites is their mechanical stability. To assess their mechanical stability, high-energy ball milling of silica was conducted to create more uniform particle sizes. However, reduced particle sizes came at a cost─the BET surface areas and pore volumes were drastically decreased after more than 1 h of ball milling. Findings from this study suggest that short-term ball milling may be a viable large-scale option to reduce particle size in silica materials without sacrificing significant performance.

Recent Advances of Bio-Based Hydrogel Derived Interfacial Evaporator for Sustainable Water and Collaborative Energy Storage Applications.

Solar interfacial evaporation strategy (SIES) has shown great potential to deal with water scarcity and energy crisis. Biobased hydrogel derived interfacial evaporator can realize efficient evaporation due to the unique structure- properties relationship. As such, increasing studies have focused on water treatment or even potential accompanying advanced energy storage applications with respect of efficiency and mechanism of bio-based hydrogel derived interfacial evaporation from microscale to molecular scale. In this review, the interrelationship between efficient interfacial evaporator and bio-based hydrogel is first presented. Then, special attention is paid on the inherent molecular characteristics of the biopolymer related to the up-to-date studies of promising biopolymers derived interfacial evaporator with the objective to showcase the unique superiority of biopolymer. In addition, the applications of the bio-based hydrogels are highlighted concerning the aspects including water desalination, water decontamination atmospheric water harvesting, energy storage and conversion. Finally, the challenges and future perspectives are given to unveil the bottleneck of the biobased hydrogel derived SIES in sustainable water and other energy storage applications.

Innovative 3D-printed surfaces for efficient water harvesting from air

PurposeThe purpose of this study is to develop nature-inspired 3D surfaces for atmospheric water harvesting.Design/methodology/approachInitially, cylindrical-shaped protrusions were produced utilizing a 3D printer to obtain a surface with a high surface area. Subsequently, an electrospraying technique was employed to coat the tips of these hydrophobic protrusions with hydrophilic nano-scale particles and fibers, utilizing polyamide 6 (PA6) or PA6/chitosan (CH) blends. In the next stage of the study, the impact of protrusion shape was investigated by fabricating surfaces with cylindrical, conical and tree-shaped protrusions. Following the production of 3D surfaces, PA6 was electrosprayed onto the protrusions to achieve varied wettability patterns on the 3D surface. Finally, the water collection rates and capacities of the surfaces were evaluated.FindingsWater collection tests demonstrated that PA6-coated surfaces exhibited greater water collection capacity compared to untreated surfaces. Furthermore, the addition of CH enhanced the water collecting efficiency of the 3D surface. It was found that the shape of the protrusions significantly influenced water collection capacity. Particularly, cone-shaped protrusions exhibited the highest water collecting capability among the different shapes tested.Originality/valueIn this study, 3D printing and electrospraying techniques were combined to create 3D surfaces characterized by high surface area, along with hydrophilic and hydrophobic regions to produce superior surfaces for atmospheric water harvesting.

Spontaneous water oozing of a soft drain bed via energy-free atmospheric water harvesting

Atmospheric water harvesting has emerged as an efficient strategy for addressing the global challenge of freshwater scarcity. However, the in being energy-consuming water-collecting process has obstructed its practicality. In this work, a soft drain bed, which was composed of hydrophilic cloth and hygroscopic gel, has been demonstrated to capture atmospheric water effectively, followed by converting it into liquid water spontaneously and sustainably, under all-weather humidity conditions. Under the optimal working condition of 30°C with a relative humidity level of 75%, the bed can provide a spontaneous water oozing ability of 1.25g (liquid water)/hour within the 8h of working time. More importantly, after 5 working cycles, 80% of the oozing ability can be reserved, suggesting the high potential for practical freshwater supply application. The proposed design strategy is expected to provide new hints for the development of future energy-saving decentralized freshwater supply systems.

Techno-Economic Analysis of Atmospheric Water Harvesting Across Climates.

Drinking water scarcity is a global challenge as groundwater and surface water availability diminishes. The atmosphere is an alternative freshwater reservoir that has universal availability and could be harvested as drinking water. In order to effectively perform atmospheric water harvesting (AWH), we need to (1) understand how different climate regions (e.g., arid, temperate, and tropical) drive the amount of water that can be harvested and (2) determine the cost to purchase, operate, and power AWH. This research pairs thermodynamics with techno-economic analysis to calculate the water productivity and cost breakdown of a representative condensation-based AWH unit with water treatment. We calculate the monthly and annual levelized cost of water from AWH as a function of climate and power source (grid electricity vs renewable energy from solar photovoltaics (PV)). In our modeled unit, AWH can provide 1744-2710 L/month in a tropical climate, 394-1983 L/month in a temperate climate, and 37-1470 L/month in an arid climate. The levelized cost of water of AWH powered by the electrical grid is $0.06/L in a tropical climate, $0.09/L in a temperate climate, and $0.17/L in an arid climate. If off-grid solar PV was purchased at the time of purchasing the AWH unit to power the AWH, the costs increase to $0.40/L in an arid climate, $0.17/L in a temperate climate, and $0.10/L in a tropical climate. However, if using existing solar PV there are potential cost reductions of 4.25-5-fold between purchasing and using existing solar PV, and 2-3-fold between using the electrical grid and existing solar PV, with the highest cost reductions occurring in the tropical climate. Using existing solar PV, the levelized cost of AWH is $0.09/L in an arid climate, $0.04/L in a temperate climate, and $0.02/L in a tropical climate.

Green Synthesis of Polyurethane Sponge-Grafted Calcium Alginate with Carbon Ink Aerogel with High Water Vapor Harvesting Capacity for Solar-Driven All-Weather Atmospheric Water Harvesting.

Atmospheric water harvesting (AWH) technology is a new strategy for alleviating freshwater scarcity. Adsorbent materials with high hygroscopicity and high photothermal conversion efficiency are the key to AWH technology. Hence, in this study, a simple and large-scale preparation for a hygroscopic compound of polyurethane (PU) sponge-grafted calcium alginate (CA) with carbon ink (SCAC) was developed. The PU sponge in the SCAC aerogel acts as a substrate, CA as a moisture adsorber, and carbon ink as a light adsorber. The SCAC aerogel exhibits excellent water absorption of 0.555-1.40 g·g-1 within a wide range of relative humidity (40-80%) at 25 °C. The SCAC aerogel could release adsorbed water driven by solar energy, and more than 92.17% of the adsorbed water could be rapidly released over a wide solar intensity range of 1.0-2.0 sun. In an outdoor experiment, 57.517 g of SCAC was able to collect 32.8 g of clean water in 6 h, and the water quality meets the drinking water standards set by the World Health Organization. This study suggests a new approach to design promising AWH materials and infers the potential practical application of SCAC aerogel-based adsorbents.

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In article number EOM2_12473, Xueli Yan and co‐workers report the fabrication of a nano‐sized octahedral N‐doped MOF‐801 adsorbent through a facile one‐pot process for high‐yield solar‐powered atmospheric water harvesting in dry environment. The success relies on N‐doping‐induced mixed‐linkers of 2,3‐diaminobutanedioic acid and fumaric acid to form unique pore structures of MOFs. image

Compact rapid cycling fuel-fired atmospheric water harvesting device for all-day water production

Compact rapid cycling fuel-fired atmospheric water harvesting device for all-day water production

Assessment of Atmospheric Water Harvesting Potential in Tagaytay City and Dasmariñas City, Cavite, Philippines

This study aimed to assess the atmospheric water harvesting potential in two areas in Cavite: Dasmarinas City and Tagaytay City. A device was designed and assembled to collect atmospheric water data from the two locations during dry and wet seasons. The variation in the amount of atmospheric water collected was analyzed.Climatic parameters were also observed and its relationship to the amount of atmospheric water was established. Results showed that the difference between atmospheric water collection in Tagaytay City and Dasmariñas City, as well as between the wet and dry seasons, was present but not notably statistically significant. Collection at night, specifically during the time frame of 12:00 am to 6:00 am, produces more atmospheric water than collection during the day where the lowest quantity was obtained during the time frame of 12:00 pm to 6:00 pm. During the dry season, more atmospheric water was collected at the onset compared to a wet season where more atmospheric water was collected at the end.Additionally, relative humidity has a moderate and direct correlation to atmospheric water quantity while temperature and wind speed have a very weak and indirect correlation. The predictive model performs well and produces relatively accurate results. Moreover, the collected atmospheric water samples passed the physical drinking-water quality parameters such as turbidity, total dissolved solids, and color ranging from 0.10 to 0.40 NTU, 4 to 12 mg/L, and less than 2 CU, respectively. It also passed the chemical drinking-water quality parameters such as levels of cadmium and lead, and pH ranging from 0 to less than 0.00049 mg/L, 0 to less than 0.0038 mg/L, and 6.5 to 7.5, respectively. However, total coliforms were present in the samples, thus, an adequate treatment and cleaning process must be developed for the atmospheric water harvesting device.

Design of a Compact Multicyclic High-Performance Atmospheric Water Harvester for Arid Environments.

Water scarcity remains a grand challenge across the globe. Sorption-based atmospheric water harvesting (SAWH) is an emerging and promising solution for water scarcity, especially in arid and noncoastal regions. Traditional approaches to AWH such as fog harvesting and dewing are often not applicable in an arid environment (<30% relative humidity (RH)), whereas SAWH has demonstrated great potential to provide fresh water under a wide range of climate conditions. Despite advances in materials development, most demonstrated SAWH devices still lack sufficient water production. In this work, we focus on the adsorption bed design to achieve high water production, multicyclic operation, and a compact form factor (high material loading per heat source contact area). The modeling efforts and experimental validation illustrate an optimized design space with a fin-array adsorption bed enabled by high-density waste heat, which promises 5.826 Lwater kgsorbent -1 day-1 at 30% RH within a compact 1 L adsorbent bed and commercial adsorbent materials.

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.

Vertically aligned sheet-like structural aerogel incorporated with expanded graphite for efficient solar desalination and atmospheric water harvesting

Solar desalination and atmospheric water harvesting are economically friendly techniques for obtaining freshwater. However, developing aerogels capable of simultaneously achieving long-term stable operation of efficient solar desalination and atmospheric water harvesting remains challenging. The aramid fiber (AF)-reinforced vertically aligned sheet-like structural aerogel incorporated with expanded graphite was prepared through a sequential process involving freeze-drying, carbonization, and tannin surface modification. The aerogel can serve directly as a seawater desalination evaporator and function as an atmospheric water harvester through LiCl loading. The vertical sheet-like structure of the aerogel enables the evaporator to exhibit a high evaporation rate, reaching 2.4 kg m-2h-1 under 1 kW m-2 simulated solar radiation. The high specific surface area allows the aerogel to load a large amount of LiCl, resulting in a water absorption capacity as high as 3.29 g g-1 (90 % RH), and it can release 80 % of the adsorbed water within 120 min under only 0.5 kW m-2 simulated solar radiation. The laminar void structure of EG can restrict the movement of LiCl, preventing its leakage and ensuring stable water harvesting performance. The water evaporator and harvester both demonstrated excellent stability during cycling tests. Additionally, due to the reinforcing effect of AF, the compression strength of the aerogel reaches as high as 110.9 kPa. The prepared aerogel has promising prospects for freshwater acquisition.

Tailoring the covalent organic frameworks based polymer materials for solar-driven atmospheric water harvesting

Atmospheric water harvesting through reticular materials is an innovation that has the potential to change the world. Here, this study offers a technique for creating a solar-powered hygroscopic polymer material for atmospheric water harvesting with the reticular materials. The results show that the porous hygroscopic polymer materials can achieve high performance with high vapor capture (up to ac. 28.8–49.7 mg/g at 28–38 %RH and 25 ℃), rapid photothermal conversion efficiency (up to 32.2 ℃ within 15 min under 1000 W/m−2 light at 25 ℃), a low desorption temperature (lower than 40 ℃), and an effective water release rate. Besides, the material also has excellent water-retention properties, which can effectively store desorbed liquid water in polymer networks for use by vegetation during water demand periods. The strategy opens new avenues for atmospheric water-harvesting materials, which will hopefully solve the global crisis of freshwater shortages.

A Sulfonated Covalent Organic Framework for Atmospheric Water Harvesting.

We report a sulfonated covalent organic framework (COF) capable of atmospheric water harvesting in arid conditions. The isothermal water uptake profile of the framework was studied, and the network displayed steep water sorption at low relative humidity (RH) in temperatures of up to 45 °C, reaching a water uptake of 0.12 g g-1 at 10 % RH and even 0.08 g g-1 at just 5 % RH, representing some of the most extreme conditions on the planet. We found that the inclusion of sulfonate moieties shifted uptake in the water isotherm profiles to lower RH compared to non-sulfonated equivalents, demonstrating well the benefits of including these hydrophilic sites for water uptake in hot, arid locations. Repeated uptake and desorption cycles were performed on the material without significant detriment to its adsorption performance, demonstrating the potential of the sulfonated COF for real-world implementation.

Rape Pollen‐Based Composite Sorbent with Thermo‐Responsive and Photothermal Properties for Atmospheric Water Harvesting

AbstractSorption‐based atmospheric water harvesting (SAWH) has great potential for clean water acquisition and renewable energy use. Adsorption and desorption properties of sorbents play a crucial role in SAWH systems. However, most sorbents with high adsorption capacities are hindered by either slow sorption/desorption kinetics or poor regeneration performance. Here, a highly efficient block copolymer composite sorbent with dual functions of thermo‐responsive and photothermal properties is designed based on rape pollens. This sorbent has a hierarchical porous structure, in which the outermost layer of poly‐pyrrole enables it to convert light energy into heat and the second layer of poly(N‐isopropylacrylamide) imparts thermo‐responsive properties to improve the desorption ability. Meanwhile, confined LiCl improves its sorption capacity and cavities of the pollen can store captured moisture to avoid liquid leakage. This sorbent can sorb moisture to more than 144% of its own weight within 3 h under 20 °C&amp;80% relative humidity (RH) and 82% of captured water can be released within 0.5 h under 1 sun. The water harvester using this sorbent can realize an exceptional water productivity of up to 2.21gwater gsorbent−1 day−1 only by three continuous water adsorption‐desorption cycles in a day. The high‐performance sorbent smooths the path for efficiently extracting water from the atmosphere to tackle water scarcity.