Hygroscopic Salts Research Articles

All‐Polymer Solid Desiccant With High Moisture Capture Capacity and Fast Sorption Kinetics

ABSTRACTDesiccants play crucial importance in both daily life and industrial production. The development of low‐cost and easy industrial scale production all‐polymer solid desiccants with high water adsorption capacity, low regeneration temperature, and fast sorption kinetics remains great challenges. Herein, we report a novel all‐polymer porous solid desiccant (APPSD) with high moisture capture capacity, low regeneration temperature, and fast sorption kinetics via a new zero‐waste, eco‐friendly, and easily scaled‐up process. The present APPSD could adsorb 0.8 g/g water vapor at 70% relative humidity (RH) within 1.5 h, and 1.9 g/g at 90% RH within 2.0 h at 25°C, exhibiting fast adsorption kinetics. The equilibrium moisture adsorptive capacity is as high as 2.16 g/g at 90% RH and 25°C, much higher than most reported solid polymer desiccants without hygroscopic salts under the same conditions. Amazingly, more than 92% of the absorbed water could be released at 40°C and 20% RH within 30 min, demonstrating extreme low regeneration temperature and high regeneration efficiency. Furthermore, almost no performance decline was observed during a 20‐cycle adsorption–desorption measurement, showing excellent recycling stability.

Low Evaporation Enthalpy Ionic Covalent Organic Frameworks for Efficient Atmospheric Water Harvesting at Low Humidity.

Herein, we introduce a series of ionic covalent organic frameworks (iCOFs) with a focus on addressing the challenge of water collection at low relative humidity levels below 25%. These iCOFs are characterized by numerous hydrophilic sites and high water stability, enabling efficient water vapor adsorption even at relatively low humidity levels. Through the use of various hygroscopic salt cations and precise control of ion concentration within the pores, the water state within the iCOFs pores can be effectively managed. Among the iCOFs, TB-COF-Li stands out with an impressive adsorption capacity of 0.24 g g-1 from 0 to 22% RH. Notably, due to its ionic porous structure, TB-COF-Li exhibits a significantly lower enthalpy of evaporation, measured at 967.04 J g-1, compared to bulk water with an enthalpy of 2387.4 J g-1. Moreover, under simulated conditions of 1.5 solar intensity at 60 °C, the majority of the adsorbed water can be rapidly desorbed without the need for additional energy input. This efficient desorption process contributes to a high water collection rate of 0.092 g g-1 h-1 in the final atmospheric water harvesting device. The development of these iCOFs offers a promising and cost-effective solution for obtaining fresh water in arid regions.

Low Evaporation Enthalpy Ionic Covalent Organic Frameworks for Efficient Atmospheric Water Harvesting at Low Humidity

Herein, we introduce a series of ionic covalent organic frameworks (iCOFs) with a focus on addressing the challenge of water collection at low relative humidity levels below 25%. These iCOFs are characterized by numerous hydrophilic sites and high water stability, enabling efficient water vapor adsorption even at relatively low humidity levels. Through the use of various hygroscopic salt cations and precise control of ion concentration within the pores, the water state within the iCOFs pores can be effectively managed. Among the iCOFs, TB‐COF‐Li stands out with an impressive adsorption capacity of 0.24 g g‐1 from 0 to 22% RH. Notably, due to its ionic porous structure, TB‐COF‐Li exhibits a significantly lower enthalpy of evaporation, measured at 967.04 J g‐1, compared to bulk water with an enthalpy of 2387.4 J g‐1. Moreover, under simulated conditions of 1.5 solar intensity at 60 °C, the majority of the adsorbed water can be rapidly desorbed without the need for additional energy input. This efficient desorption process contributes to a high water collection rate of 0.092 g g‐1 h‐1 in the final atmospheric water harvesting device. The development of these iCOFs offers a promising and cost‐effective solution for obtaining fresh water in arid regions.

Metal- and Halide-Free, Macroporous Hygroscopic Polymers for Efficient Atmospheric Water Harvesting.

Hygroscopic materials based on highly hygroscopic salts are promising for atmospheric water harvesting (AWH), but the metal- or halide-containing highly hygroscopic salts often have leakage and corrosion issues. Here, the design and synthesis of metal- and halide-free, highly hygroscopic, and macroporous polymers from [2-(acryloyloxy)ethyl]trimethylammonium chloride simply via in situ foaming, solidification, and ion exchange are reported. The resulting polymers exhibit highly interconnected macroporous structure, robust compression, and leakage-free performance, and they also demonstrate relatively high moisture adsorption capacities (up to 1.24gg-1 water at 85% relative humidity, accelerated adsorption rates, and efficient desorption. The polymers can harvest 0.76gg-1 water per adsorption-desorption cycle and show high reusability, without obvious deterioration over 10 cycles of adsorption, desorption, and water collection. With the incorporation of carboxylic multi-walled carbon nanotubes into the hygroscopic polymers, solar-driven AWH is realized, without the requirement of additional energy. On the whole, the metal- and halide-free, highly hygroscopic polymers exhibit the advantages of ease of preparation, energy saving, environmental protection, and economic sustainability for AWH.

Novel Sponge-Based Carbonaceous Hydrogel for a Highly Efficient Interfacial Photothermal-Driven Atmospheric Water Generator.

A high-performance atmospheric water generator based on continuous adsorption-desorption of liquid hygroscopic agents was constructed by applying interfacial photothermal evaporation technology to the field of atmospheric water harvesting. A three-dimensional carbon-containing sponge hydrogel photothermal conversion material with a porous channel structure was designed, which was prepared from melamine foam (MF) and carbon black (CB) cross-linked by sodium alginate (SA). The results showed that the evaporation rate of CB/SA@MF in pure water was 1.90 kg·m-2·h-1, and the photothermal conversion efficiency could reach 85.0%. The multistage pore structures and water transport channels in the A4 configuration device provided an excellent structural basis for material salt resistance and liquid hygroscopic agent regeneration. Using sponge-based CB/SA@MF hydrogel photothermal composites as the evaporation interface and liquid hygroscopic salts as the air-water trapping agent, an interfacial photothermal-driven atmospheric water generator successfully absorbed water at night and produced water during the day. Its water production could reach 2.84 kg·m-2·d-1. The cost of the atmospheric water generator was only $12, and the water quality obtained after 5 cycle tests met WHO/GB 5749-2022. This research was designed to collect fresh water from the air, bringing convenience to inland arid regions as well as remote and scattered areas with limited power resources.

A biocompatible, degradable, and recyclable photothermal actuator

The rise of disposable technology has led to a surge in waste, highlighting the urgency for sustainable alternatives such as biodegradable and transient devices in flexible electronics. Soft actuators, which emulate natural flexibility, are pivotal in this pursuit. However, current light-driven soft actuators degrade slowly and involve complex synthesis processes, potentially limiting market adoption. Addressing this, a new study proposes an innovative design using graphene oxide (GO) and sodium alginate (SA). These biocompatible, biodegradable materials dissolve readily in water, enabling recycling. When exposed to near-infrared (NIR) light, the actuator undergoes deformation and locomotion, aided by hygroscopic salt (LiCl) to enhance recovery. This approach integrates sustainable materials into soft actuator design, promising eco-friendly solutions for flexible electronics.

Microbial response to deliquescence of nitrate-rich soils in the hyperarid Atacama Desert

Abstract. Life in hyperarid regions has adapted to extreme water scarcity through mechanisms like salt deliquescence. While halite (NaCl) crusts have been intensively studied and identified as one of the last habitats under hyperarid conditions, other less common hygroscopic salt crusts remain unexplored. Here, we investigated newly discovered deliquescent soil surfaces in the Atacama Desert, containing substantial amounts of nitrates, to evaluate their habitability for microorganisms. We characterized the environment with respect to water availability and biogeochemistry. Microbial abundances and composition were determined by cell cultivation experiments, 16S rRNA gene sequencing, and membrane phospholipid fatty acid (PLFA) analysis, while microbial activity was assessed by analyzing adenosine triphosphate (ATP) and the molecular composition of organic matter. Our findings reveal that, while the studied hygroscopic salts provide temporary water, microbial abundances and activity are lower in the studied soil surfaces than in non-deliquescent soil surfaces. Intriguingly, the deliquescent crusts are enriched in geochemically degraded organic matter, indicated by the molecular composition. We conclude that high nitrate concentrations in the hyperarid soils suppress microbial activity but preserve eolian-derived biomolecules. These insights are important for assessing the habitability and searching for life in hyperarid environments on Earth and beyond.

Ammonium Dinitramide as a Prospective N-NO2 Synthon: Electrochemical Synthesis of Nitro-NNO-Azoxy Compounds from Nitrosoarenes.

In this study, the electrochemical coupling of nitrosoarenes with ammonium dinitramide is discovered, leading to the facile construction of the nitro-NNO-azoxy group, which represents an important motif in the design of energetic materials. Compared to known approaches to nitro-NNO-azoxy compounds involving two chemical steps (formation of azoxy group containing a leaving group and its nitration) and demanding expensive, corrosive, and hygroscopic nitronium salts, the presented electrochemical method consists of a single step and is based solely on nitrosoarenes and ammonium dinitramide. The dinitramide salt plays the roles of both the electrolyte and reactant for the coupling. Despite the fact that many side reactions can be expected due to the redox-activity of both the reagents and target products, under optimized conditions the synthesis is performed in an undivided cell under constant current conditions with high current density and can be easily scaled up without a reduction in the product yield. Moreover, the synthesized nitro-NNO-azoxy compounds are discovered to be potent fungicides active against a broad range of phytopathogenic fungi.

Testing and Characterization of Tubular Na-ZnCl2 Battery Cells for Stationary Energy Storage

The SALT battery (ZEBRA® battery) was first patented in 1978, and its technology is based on a liquid sodium (Na) anode in charged state, and a solid nickel (Ni) cathode in discharged state, having an electrolyte consisting of a molten nickel chloride/sodium chloride with sodium tetrachloroaluminate (NiCl2/NaCl-NaAlCl4) salt and a solid beta alumina (β''-Al2O3) electrolyte. The Na-NiCl2 cell operates at ~300°C to ensure a molten electrolyte and good Na+ conductivity, as the β''-Al2O3 also operates as a membrane allowing the Na+ ions to pass, but not the e-.Today, the technology is commercialized, and industrial production sites exist in Switzerland and China. The SALT batteries are used for railways as a back-up energy supply, and in electric vehicles for the mining and construction market. The Na current collector is also the cell housing, making sure that the SALT battery cell is completely hermitized to avoid any contact with air and humidity, as the electrolyte is hygroscopic salts. It is, however, important to reduce the amount of Critical Raw Materials (CRMs) utilizing more abundant materials to make it more competitive for future markets.In the SOLSTICE project, it has been investigated how the SALT battery can reduce and/or substitute Ni/NiCl2 with Zn/ZnCl2. The present work has covered characterization of a tubular Na-ZnCl2 battery cell, and measured the cell resistance by Electrochemical Impedance Spectroscopy (EIS), cell resistance when fully charged and discharged, as well as the post-mortem analyses, such as SEM and XRD. The study proved that Ni can be replaced by Zn in the full-size SALT battery cell, but the morphology still needs to be studied to optimize the chemistry. Acknowledgments: This work has been funded by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 963599.

Room-Temperature Ripening Enabled by Hygroscopic Salts for Hole-conductor-Free Printable Perovskite Solar Cells with Efficiency Over 20 .

Solution-processed perovskite films generally possess small grain sizes and high density of grain boundaries, which intensify non-radiative recombination of carriers and limit the power conversion efficiency (PCE) of solar cells. In this study, we report the room-temperature ripening enabled by the synergy of hygroscopic salts and moisture in air for efficient hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs). Treating perovskite films with proper hygroscopic salts in damp air induces obvious secondary recrystallization, which coarsens the grains size from hundreds of nanometers to several micrometers. It's proposed that the hygroscopic salt at grain boundaries could absorb moisture and form a complex which could not only serve as mass transfer channel but also assist in the dissolution of perovskite grains. This activates mass transfer between small grains and large grains since they possess different solubilities, and thus ripens the perovskite film. Consequently, p-MPSCs treated with the hygroscopic salt of NH4SCN show an improved power conversion efficiency of 20.13 % from 17.94 %, and maintain >98 % of the initial efficiency under maximum power point tracking at 55±5 °C for 350 hours.

Efficient atmospheric water harvesting enabled by hierarchically structured cellulose foam

The sorption-based atmospheric water harvesting technique is an appealing solution for addressing the challenge of freshwater shortages. In this study, a composite foam was fabricated by confining hygroscopic salt (CaCl2) into a Cr-based metal–organic framework (MIL-101), which was then integrated into a bacterial cellulose (BC) skeleton. The hierarchical structure, which contains micron- and nanoscale pores, enhances water storage, transport, and vapor evaporation throughout the whole water capture and release process. The pore confinement effect of MIL-101 and the interconnected BC network effectively restricted the leakage of the liquefied salt solution. Interestingly, the color of the CaCl2@MIL-101@BC foam changed from light green to dark green as the amount of absorbed water increased. This moisture-induced color darkening improves the light absorption ability during the water release stage under sunlight. At 30 % relative humidity, the foam can absorb up to 0.78 g g−1 of water per cycle (8 h) and desorb quickly under solar radiation. This makes foam a promising method for water production in arid areas.

Room‐Temperature Ripening Enabled by Hygroscopic Salts for Hole‐conductor‐Free Printable Perovskite Solar Cells with Efficiency Over 20 %

AbstractSolution‐processed perovskite films generally possess small grain sizes and high density of grain boundaries, which intensify non‐radiative recombination of carriers and limit the power conversion efficiency (PCE) of solar cells. In this study, we report the room‐temperature ripening enabled by the synergy of hygroscopic salts and moisture in air for efficient hole‐conductor‐free printable mesoscopic perovskite solar cells (p‐MPSCs). Treating perovskite films with proper hygroscopic salts in damp air induces obvious secondary recrystallization, which coarsens the grains size from hundreds of nanometers to several micrometers. It's proposed that the hygroscopic salt at grain boundaries could absorb moisture and form a complex which could not only serve as mass transfer channel but also assist in the dissolution of perovskite grains. This activates mass transfer between small grains and large grains since they possess different solubilities, and thus ripens the perovskite film. Consequently, p‐MPSCs treated with the hygroscopic salt of NH4SCN show an improved power conversion efficiency of 20.13 % from 17.94 %, and maintain >98 % of the initial efficiency under maximum power point tracking at 55±5 °C for 350 hours.

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.

Nanoporous Silica Lattice Coated with LiCl@PHEA for Continuous Water Harvesting from Atmospheric Humidity

AbstractRecently, atmospheric water harvesting (AWH) based on hygroscopic salt on an inorganic or organic carrier has attracted great attention because of its significant potential applications in the environment. The major technical challenges for practical applications are how to prevent the leakage of hygroscopic salt while achieving a high capacity for sorption of atmospheric water and a high sorption rate. Additionally, techniques for converting sorbed water (in the form of a lithium chloride (LiCl) solution) into clean water need to be developed. Here, a novel method for continuous atmospheric water harvesting, leveraging LiCl@PHEA hydrogels is introduced. Synthesized via one‐step UV polymerization in saturated LiCl solutions, these hydrogels exhibit remarkable air distension ability (>60 times), achieving high water sorption efficiency (11.18 gg−1 at 90% relative humidity in 30 min) with over 90 wt.% salt content and no leakage. This water collection system integrates a porous evaporator and a 3D‐printed silica substrate, ensuring an extraordinarily high evaporation rate (>11 kgm−2 h−1 under sunlight) and efficient water transmission. A prototype based on this achieves a record‐breaking collection rate of over 5 kgm−2 h−1, enabling large‐scale efficient atmospheric water harvesting. Additionally, continuous hydrogen production through electrolysis using the collected water (< 5 ppm of salts) is demonstrated.

Janus structured photothermal conversion materials prepared from carbonized corn straw particles for portable air water extraction devices

The utilization of photothermal conversion materials to enhance the desorption performance of hygroscopic salt solutions through interfacial photothermal effects presents a promising approach for the continuous extraction of water from the atmosphere. To improve the desorption efficiency of hygroscopic salt solutions, the objective of this research is to employ agricultural and forestry residues, such as corn straw, in conjunction with polyurethane sponges, for the production of an innovative Janus structure carbonized biomass photothermal conversion material. Compared to single-layer structured photothermal conversion materials, the pure water evaporation rate increased from 2.42 kg m-2 h-1 to 3.20 kg m-2 h-1 when utilizing the Janus structured photothermal conversion material. Remarkably, this material demonstrates outstanding resistance to salt, allowing it to endure 8 h evaporation cycles with 30 wt% NaCl without salt crystallization. Therefore, it is well-suited for the continuous desorption of liquid hygroscopic agents. Moreover, the portable air–water extraction device, which incorporates Janus structural photothermal conversion material to enhance the performance of 30 % LiCl, has been shown to effectively extract water in practical settings. It achieves a water intake rate of 1.74 L m-2 d-1 at 50 % humidity. This approach is distinguished by its simplicity, cost-effectiveness, and efficient utilization of solar energy resources, providing a promising solution to mitigate the shortage of fresh water resources.

Microbial preference for chlorate over perchlorate under simulated shallow subsurface Mars-like conditions

The Martian surface and shallow subsurface lacks stable liquid water, yet hygroscopic salts in the regolith may enable the transient formation of liquid brines. This study investigated the combined impact of water scarcity, UV exposure, and regolith depth on microbial survival under Mars-like environmental conditions. Both vegetative cells of Debaryomyces hansenii and Planococcus halocryophilus, alongside with spores of Aspergillus niger, were exposed to an experimental chamber simulating Martian environmental conditions (constant temperatures of about − 11 °C, low pressure of approximately 6 mbar, a CO2 atmosphere, and 2 h of daily UV irradiation). We evaluated colony-forming units (CFU) and water content at three different regolith depths before and after exposure periods of 3 and 7 days, respectively. Each organism was tested under three conditions: one without the addition of salts to the regolith, one containing sodium chlorate, and one with sodium perchlorate. Our results reveal that the residual water content after the exposure experiments increased with regolith depth, along with the organism survival rates in chlorate-containing and salt-free samples. The survival rates of the three organisms in perchlorate-containing regolith were consistently lower for all organisms and depths compared to chlorate, with the most significant difference being observed at a depth of 10–12 cm, which corresponds to the depth with the highest residual water content. The postulated reason for this is an increase in the salt concentration at this depth due to the freezing of water, showing that for these organisms, perchlorate brines are more toxic than chlorate brines under the experimental conditions. This underscores the significance of chlorate salts when considering the habitability of Martian environments.

A binary salt composite adsorbent material for solar-driven sorption-based atmospheric water harvesting

Solar-driven sorption-based atmospheric water harvesting (SSAWH) technology stands as a promising avenue for sourcing freshwater in arid and remote regions. For real-world large-scale applications, the effective water absorption capacity, broad humidity absorption range, and rapid desorption properties of adsorbent materials have been the main goals of the research area. In this context, we have developed a binary salt composite adsorbent material (PAMg-Li) for solar-driven water harvesting by integrating binary hygroscopic salts MgSO4 particles and LiCl particles, activated carbon fiber (ACF), and polyvinyl alcohol (PVA). The inherent porous structure and interconnected channels at micro and nano scales of PAMg-Li facilitate water absorption, and obtained satisfactory water absorption rate even at 30% relative humidity (RH). It has been shown to be able to achieve a high water storage capacity and realize water desorption under natural light. A home-made device based on PAMg-Li obtained a water evaporation rate of 0.084 kg/(m2·h) under solar radiation intensities ranging from 200 to 850 W/m2. The PAMg-Li material developed in this work can be a candidate for a more practical and effective choice for SSAWH.

A Semi-Interpenetrating Network Sorbent of Superior Efficiency for Atmospheric Water Harvesting and Solar-Regenerated Release.

Water is readily available nearly anywhere as vapor. Thus, atmospheric water harvesting (AWH) technologies are seen as a promising solution to support sustainable water production. This work reports a novel semi-interpenetrating network, which integrates poly(pyrrole) doped with a hygroscopic salt and 2D graphene-based nanosheets optimally assembled within an alginate matrix, capable of harvesting water from the atmosphere with a record intake of up to 7.15 gw/gs. Owing to the incorporated graphene nanosheets, natural sunlight was solely used to enable desorption, achieving an increase of the temperature of the developed network of up to 71 °C within 20 min, resulting in a water yield of 3.36 L/kgS in each cycle with quality well within the World Health Organization standard ranges. Notably, after 30 cycles of sorption and desorption, the composite hydrogel displayed unchanged water uptake and stability. This study demonstrates that atmospheric water vapor as a complementary source of water can be harvested sustainably and effectively at a minimal cost and without external energy input.

Preparation and properties of a metal-organic frameworks polymer material based on Sa-son seed gum capable of simultaneously absorbing liquid water and water vapor

Atmospheric water harvesting (AWH) technology has attracted significant attention as an effective strategy to tackle the global shortage of freshwater resources. Work has focused on the use of hydrogel-based composite adsorbents in water harvesting and water conservation. The approaches adopted to make use of hygroscopic inorganic salts which subject to a “salting out” effect. In this study, we report the first use of modified UIO-66-NH2 as a functional steric cross-linker and Sa-son seed gum was used as polymeric substrate to construct super hygroscopic hydrogels by free radical copolymerization. The maximum water uptake on SMAGs (572 cm3·g−1) outperforms pure UIO-66-NH2 (317 cm3·g−1). Simultaneously, our first attempt to use it for anti-evaporation applications in an arid environment (Lanzhou, China) simulating sandy areas. The evaporation rate of the anti-evaporation material treated with 0.20 % super moisture-absorbent gels (SMAGs) decreased by 6.1 % over 64 h period under natural condition in Lanzhou, China. The prepared material can not only absorb liquid water but also water vapor, which can provide a new way for water collection and conservation technology. The design strategy of this material has wide applications ranging from atmospheric water harvesting materials to anti-evaporation technology.

Advancing thermochemical storage: synthesis and characterization of cement-based composite materials

Thermal Energy Storage (TES) is crucial for sustainability of the energy sector, yet the development of cost-effective, robust materials remains a significant challenge. This study aims at exploring the synthesis and thermal characterization of cement-based composites for seasonal thermochemical energy storage, with the goal to harness the high energy density of hygroscopic salts while mitigating their limitations. We investigate composites with several cement matrices to improve salt-cement compatibility. Furthermore, we investigate the possible incorporation of porous low-cost compounds to enhance porosity and improve economic aspects. As far as the characterization aspects are concerned, we show experimental adsorption isotherms at different temperatures to estimate key material properties like isosteric heat and water uptake, along with the relevant figures of merit such as energy density. Our research leverages on adjustable porosity and affordability of cement as a host matrix for the ‘active phase’. We studied two synthesis approaches: traditional dry impregnation and an in-situ technique suitable for cements. The in-situ method, being straightforward and reproducible, permits greater control over salt content. Preliminary cost analysis positions these composites competitively in the market. Although we are still at sub-optimal stage, potential cost reduction of some less popular cement matrices suggests an opportunity for improvement.