High Evaporation Rates Research Articles

Natural-inspired hierarchic double-Janus solar evaporator for stable clean water production from high-salinity emulsions

Interfacial solar evaporation shows great potential in clean water production, emulsions separation, and high-salinity brine treatment. However, it remains challenging for the evaporators to maintain a high evaporation rate in the high-salinity emulsions due to the co-pollution of salt and oil. Herein, we first proposed a hierarchic double-Janus solar evaporator (HDJE) with a hydrophobic salt-rejecting top layer and oil-rejecting bottom layer. Compared to the traditional one, HDJE could treat industrial high-salinity oil-in-water emulsions stably for over 70 h, with a stable average evaporation rate of 1.73 kg m−2 h−1 and a high purification efficiency of up to 99.8 % for oil and ions. It was also verified that HDJE could be used for high-efficiency purification of oily concentrated seawater outdoor. An average water production rate of 3.59 kg m−2 d−1 and a TOC removal ratio of over 98 % was obtained. In conclusion, this study provides a novel way to effectively dispose of high-salinity oily wastewater.

3D macroporous MXene/sodium alginate aerogels with “brick-concrete” structures for highly efficient solar-driven water purification

Interfacial water evaporation, powered by solar energy, holds great promise to extract freshwater from seawater on a global scale. It has the potential to address the world's water scarcity challenges using renewable energy. While the ideal design of evaporator materials is critical to the interfacial vaporization desalination, tailoring the structures and compositions of solar evaporators and figuring out the structure/composition-performance relationship of evaporators remains unexplored. Herein, 3D macroporous “brick-concrete” MXene/sodium alginate aerogel (MSA) evaporators were designed and fabricated with constant MXene content and varying polymer loading. The as-made MSAs show sodium alginate-dependent evaporating performance with an optimum evaporation rate of 3.28 kg m−2 h−1 (1 sun). This exceptional rate is attributed to several factors, including enhanced light absorption, optimized pore sizes, reduced enthalpy of evaporation and improved water transport. The water molecule states and hydrogen bonding network in the aerogels can be tuned by their compositions, resulting in the reduced evaporation enthalpy, the monolithic structures with controlled thermal conductivity facilitate the exploitation of environmental energy, leading to the high evaporation rate. Our study not only establishes design principles for achieving superior evaporation performance, but also sheds light on the relationship between structures, compositions, and performance of solar evaporators.

Logistic curve modelling of sea surface temperature and latent heat flux variability in the Tropical Indian Ocean

The Tropical Indian Ocean (TIO) is one of the most vulnerable regions to climate change due to its unique ocean-atmosphere interactions. The region is characterized by warm temperatures, high evaporation rates, and strong convection, making it particularly vulnerable to greenhouse gases. This susceptibility leads to an overall trend of warming across the Earth's surface and atmosphere, intensifying sea surface temperatures (SST) and increasing evaporation rates, consequently influencing Surface Latent Heat Flux (SLHF). The strong influence of both SST and SLHF on atmospheric circulation and precipitation patterns makes them critical factors in determining the region's climate, particularly in monsoon-dominated regions. Analysis reveals a consistent upward trend in both SST and SLHF in the central region of TIO. To model this, standard Logistic Curve Model (LCM) has been applied to these parameters averaged over the central region of the TIO. The model is run for a period of 20 years from 2001 to 2020, grouped into four lustrums. The LCM-derived SST and SLHF are in good consistent with observed datasets during the above periods with, correlation coefficients ranging from 0.92 to 0.96 for SST and 0.86–0.90 for SLHF. Extending the model spatially across the entire TIO region explains the ability to project fluctuations in SST and SLHF values across different seasons. These findings highlight the model's relevance for capturing short-term, long-term, and seasonal variability of the parameters, providing important insights into regional climate dynamics.

Polymer foam fabricated via surfactant foaming method enables high-performance solar interfacial evaporation

Solar interfacial evaporation is considered as a low energy consumption, low cost, and sustainable desalination technology. However, its practical application is still limited by complex preparation processes and low photothermal conversion efficiency. In this work, we report novel polymer foam (Agar/SA/GO-Ag composite foam). It is prepared by simple and convenient surfactant foaming and in-situ reduction methods and consists of graphene oxide (GO) and silver nanoparticles (Ag NPs) (photothermal conversion medium) as well as Agar and sodium alginate (SA) (basic skeleton) for use in solar-powered interfacial evaporation systems. The prepared foam has excellent wettability and achieves 96.7% light absorption in the full spectrum range. A high evaporation rate of 2.55 kg·m−2·h−1 and a high evaporation efficiency of 97.3% were obtained under the conditions of simulated sunlight (1.0 kW·m−2). Moreover, the foam exhibits good reusability in a 10-cycle test without obvious attenuation in evaporation performance. Foam is used for seawater desalination and wastewater purification, and the treated water meets the water quality standards of the World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA). In short, this work demonstrates a sustainable strategy for low-cost and efficient solar-powered clean water production.

A Trimode Self-Cleaning Composite Membrane with an Eco-friendly Substrate for Energy-Saving Wastewater Recycling

A separation membrane with low or clean energy costs is urgently required for energy-saving and long-term service since electric energy generated from burning non-renewable resources will gradually cause a burden to the environment. At present, the conventional membrane being used in one mode is critical for a variety of scenarios in real life, which suffers from a trade-off effect, short service life, being difficult to recycle after damage. Herein, we report a trimode purification membrane composed of an eco-friendly polycaprolactone (PCL) substrate and functional graphene dioxide/polyaniline (GO/PANI) particles. Due to the photothermal transfer and photocatalytic properties of GO/PANI blend, the composite membrane can absorb 97.44% solar energy to handle natural seawater or mixed wastewater, which achieves a high evaporation rate of 1.47 kg m−2 h−1 in solar-driven evaporation mode. For the photocatalytic adsorption–degradation mode, 93.22% of organic dyes can be adsorbed and degraded after 12 h irradiation under 1 kW m−2. Moreover, electric-driven cross-flow filtration mode as a supplement also shows effective rejection over 99% for organic dyes with a high flux over 40 L m−2 h−1 bar−1. The combination of solar-driven evaporation, photocatalytic adsorption–degradation, and electric-driven cross-flow filtration demonstrates a prospective and sustainable strategy to generating clean water from sewages.Graphical A trimode self-cleaning composite membrane of bio-degradable substrate PCL and functional particles GO/PANI were successfully fabricated, which can purify natural seawater or mixed wastewater stably in solar-driven evaporation mode, handle organic dyes by reduction–oxidation chemical transformation in photothermal adsorption–degradation mode, and be applied in cross-flow filtration mode driven by electric as a supplement for rainy, cloudy days, or at night.

Temperature-Dependent Structural Properties of Nickel and Cobalt Selenite Hydrates as Solar Water Evaporators.

Solar water evaporation offers a promising solution to address global water scarcity, utilizing renewable energy for purification and desalination. Transition-metal selenite hydrates (specifically nickel and cobalt) have shown potential as solar absorbers with high evaporation rates of 1.83 and 2.34 kg∙m-2∙h-1, but the reported discrepancy in evaporation rate deserves further investigation. This investigation aims to clarify their thermal stability for applications and determine the underlying mechanisms responsible for the differences. Nickel and cobalt selenite hydrate compositions were synthesized and investigated via thermogravimetric analysis, X-ray diffraction, and Raman spectroscopy to assess their temperature-induced structural and compositional variations. The results reveal distinct phase transitions and structural alterations under various temperature conditions for these two photothermal materials, providing valuable insights into the factors influencing water transportation and evaporation rates.

Recycling waste carbon fibers for solar-driven clean water production by one-step electrochemical process

Waste carbon fibers (WCF), as a co-product of carbon-based textile material, presented a high recycling value. However, it is difficult to utilize the short carbon fibers by traditional process, recycling and using these WCF effectively has thus attracted increasing attention. Herein, we propose a novel strategy that utilizes simultaneous electrochemical exfoliation and deposition processes to convert WCF into photothermal materials. Stainless steel felt (SS) was selected as the substrate to verify this strategy. Through this strategy, the reduced graphene oxide-coated SS (rGO-SS) was obtained. The 2D solar-driven interfacial evaporator based on rGO-SS enabled stable evaporation in actual wastewater with an excellent rate of 1.44 ∼ 1.50 kg m−2 h−1 under 1 sun. Additionally, by constructing a 3D evaporation structure, rGO-SS performed a high evaporation rate of ∼16.88 kg m−2 h−1 under 1 sun. Finally, this work proposes a novel method for the waste carbon fibers and gives new insights into fabricating a novel solar-driven interfacial evaporator.

Metal-Loaded Synthetic Melanin via Oxidative Polymerization of Neurotransmitter Norepinephrine Exhibiting High Photothermal Conversion.

Polydopamine (PDA)-derived melanin-like materials exhibit significant photothermal conversion owing to their broad-spectrum light absorption. However, their low near-infrared (NIR) absorption and inadequate hydrophilicity compromise their utilization of solar energy. Herein, we developed metal-loaded poly(norepinephrine) nanoparticles (PNE NPs) by predoping metal ions (Fe3+, Mn3+, Co2+, Ca2+, Ga3+, and Mg2+) with norepinephrine, a neuron-derived biomimetic molecule, to address the limitations of PDA. The chelation between catechol and metal ions induces a ligand-to-metal charge transfer (LMCT) through the formation of donor-acceptor pairs, modulating the light absorption behavior and reducing the band gap. Under 1 sun illumination, the Fe-loaded PNE coated wood evaporator achieved a high seawater evaporation rate and efficiency of 1.75 kg m-2 h-1 and 92.4%, respectively, owing to the superior hydrophilicity and photothermal performance of PNE. Therefore, this study offers a comprehensive exploration of the role of metal ions in enhancing the photothermal properties of synthetic melanins.

Issues of Water Resources in Saudi Arabia: Past, Present, and Future

The present paper addresses a comprehensive historical assessment of water consumption, demand, and supply in Saudi Arabia, along with future projections regarding water balance, in terms of demand and supply by source in various sectors. Being an arid region, Saudi Arabia experiences scorching heat, low precipitation, a high rate of potential evaporation, and the absence of permanent water bodies over the territory. Groundwater contributes almost 61% of total available water, while the recharge rate is negligible. However, few widyan (ephemeral streams) systems exists to satisfy water demand, which could contribute to approximately one year of domestic water consumption if managed efficiently. The study also predicts water consumption scenarios for the next three consecutive development plans, i.e., the 10th plan (2015–2019), 11th plan (2020–2024), and 12th plan (2025–2029). The analysis shows that water consumption may decline significantly in the future, if the present rate of decline continues. Scenario I, if the current rate is assumed, provides a decrease in consumption of 14.36, 12.66, and 11.15 BCM for 10th, 11th, and 12th plans, respectively. Moreover, the domestic and industrial sectors will consume more water in the future. In the same way, scenarios II and III represent a decline in total water consumption, along with that of agriculture, while domestic and industrial water usage would increase, thus improving environmental sustainability.

Biopolymer Hydrogel-Based Salt-Resistant Evaporator for Solar-Energy-Driven Desalination and Water Purification.

Interfacial solar steam generation (ISSG) has recently received much attention as a low-carbon-footprint and high-energy-efficient strategy for seawater desalination and wastewater treatment. However, achieving the goals of a high evaporation rate, ecofriendliness, and high tolerance to salt ions in brine remains a bottleneck. Herein, a novel hydrogel-based evaporator for effective solar desalination was synthesized on the basis of sodium alginate (SA) and carboxymethyl chitosan (CMCS) incorporating a carbon nanotube (CNT)-wrapped melamine sponge (MS) through a simple dipping-drying-cross-linking process. The hydrogel-based evaporator reaches a high evaporation rate of 2.18 kg m-2 h-1 in 3.5 wt % brine under 1 sun irradiation. Furthermore, it demonstrated excellent salt ion rejection in high-concentration salt water. Simultaneously, it exhibits excellent purification functionality toward heavy metals and organic dyes. This study provides a simple and efficient strategy for seawater desalination and wastewater treatment.

All-weather-available down carbon fiber hydrogel with enhanced mechanical properties for simultaneous efficient clean water generation and dye adsorption from dye wastewater

Solar-driven photothermal conversion can produce clean water from dye wastewater while leaving the dye in the evaporation medium. Herein, a biomass-based composite hydrogel via down-fiber carbon (DFC) aerogel modified with chitosan-polyvinyl alcohol (CS-PVA) hydrogel was designed to address the aforementioned problem. The CS-PVA@DFC hydrogel integrated the capacity of simultaneous clean water production/dye adsorption during the day and continuous dye adsorption during the night. Furthermore, the modification of the CS-PVA hydrogel endowed the composite hydrogel with enhanced compression stress of 190.07 kPa (76.03 times that of DFC aerogel of 2.50 kPa) and impressive resilient recovery. Moreover, the CS-PVA@DFC hydrogel possessed solar light absorption of 99.56 % and strengthened water replenishment capacity due to the high porosity and CS-PVA hydrophilic network structure. The CS-PVA@DFC hydrogel demonstrated a stable, high evaporation rate of 2.34 kg·m−2·h−1 and simultaneous dye adsorption capacity of 70.39 % for treating methyl orange dye solution within 5 h. Additionally, the 24-h outdoor test showed that the CS-PVA@DFC hydrogel possessed excellent clean water production capacity during the daytime (reaching 4.17 kg·m−2·h−1 at 1:00p.m.) and continuous satisfactory dye adsorption capacity all day (89.68 %). These findings will inspire researchers seeking opportunities to improve the mechanical properties of aerogel and its application for treating wastewater, especially wastewater with harmful dyes.

A robust and low-cost blended-fiber-based evaporator with high efficiency for solar desalination

The solar-driven interfacial evaporation (SDIE) is a clean and efficient technology to mitigate freshwater shortages. A robust and low-cost evaporator is essential for the practical implementation of SDIE systems. Herein, we design a fantastic blended-fiber-based evaporator using weaving techniques. This mixture fabric is crafted using polyethylene terephthalate fibers and linen threads. It makes full use of the excellent light absorption, tensile strength, and corrosion resistance of polyethylene terephthalate fibers. Meanwhile, the mixture fabric reserves exceptional air permeability and water supply capability of linen thread. We optimize the density of the mixture fabric by adjusting the reed count and the weft count. It is found that the combination of the 40 reed and a single weft yarn produces the most effective and stable evaporator. The optimized mixture fabric makes a good trade-off between the water supply to the evaporator and solar-thermal evaporation. As a result, the evaporator achieves a high evaporation rate and efficiency (~1.53kg/m2/h, ~ 90%) under 1 sun illumination, which surpasses most of the existing two-dimensional evaporators based on metal nanomaterials, polymers, carbon-based materials, and fabrics. Our work opens a new horizon for the development of efficient, scalable, flexible, low-cost, corrosion-resistant, and stable evaporators.

(Ca0.25La0.5Dy0.25)CrO3 Ceramic Fiber@Biomass-Derived Carbon Aerogel with Enhanced Solute Transport Channels for Highly Efficient Solar Interface Evaporation.

The use of solar interface evaporation for seawater desalination or sewage treatment is an environmentally friendly and sustainable approach; however, achieving efficient solar energy utilization and ensuring the long-term stability of the evaporation devices are two major challenges for practical application. To address these issues, we developed a novel ceramic fiber@bioderived carbon composite aerogel with a continuous through-hole structure via electrospinning and freeze-casting methods. Specifically, an aerogel was prepared by incorporating perovskite oxide (Ca0.25La0.5Dy0.25)CrO3 ceramic fibers (CCFs) and amylopectin-derived carbon (ADC). The CCFs exhibited remarkable photothermal conversion efficiencies, and the ADC served as a connecting agent and imparted hydrophilicity to the aerogel due to its abundant oxygen-containing functional groups. After optimizing the composition and microstructure, the (Ca0.25La0.5Dy0.25)CrO3 ceramic fiber@biomass-derived carbon aerogel demonstrated remarkable properties, including efficient light absorption and rapid transport of water and solutes. Under 1 kW m-2 light intensity irradiation, this novel material exhibited a high temperature (48.3 °C), high evaporation rate (1.68 kg m-2 h-1), and impressive solar vapor conversion efficiency (91.6%). Moreover, it exhibited long-term stability in water evaporation even with highly concentrated salt solutions (25 wt%). Therefore, the (Ca0.25La0.5Dy0.25)CrO3 ceramic fiber@biomass-derived carbon aerogel holds great promise for various applications of solar interface evaporation.

Sandwiched solar interfacial evaporation system: Integrating phase change material/hydrogel/NiCo2O4 nanoflower for superior desalination

Solar-driven interfacial evaporation is a kind of sustainable and eco-friendly method of water treatment to alleviate the global water crisis. Here we demonstrate a novel sandwiched solar interfacial evaporator integrating phase change material (PCM), sodium alginate hydrogel (SA), and NiCo2O4 nanoflower featuring superb evaporation and glorious thermal energy management to achieve efficient energy utilization and long-term evaporation stability. After being combined with filter paper, NiCo2O4 nanoflower composites are adopted as the light absorber on the top layer, which can achieve an absorption of about 96.5 % in the full spectral range. SA hydrogel has been used as an intermediate layer for rapid water supply to the evaporation interface and to prevent salt deposition. Under one sun irradiation (1 kW m−2), the evaporator exhibits a high evaporation rate (1.94 kg m-2h−1) and excellent endurance in the treatment of high salt-concentration water. In particular, benefiting from the rational combination of PCM, the water production reached up to 12.13 kg m−2, which is 2.23 kg m-2higher than that of the evaporator without PCM under natural solar irradiation for 9 h. This work presents a promising concept for maximally utilizing intermittent solar irradiation energy and prolonged salt-free deposition desalination.

Recent Advances in High-Rate Solar-Driven Interfacial Evaporation.

Recent advances in solar-driven interfacial evaporation (SDIE) have led to high evaporation rates that open promising avenues for practical utilization in freshwater production and industrial application for pollutant and nutrient concentration, and resource recovery. Breakthroughs in overcoming the theoretical limitation of 2D interfacial evaporation have allowed for developing systems with high evaporation rates. This study presents a comprehensive review of various evaporator designs that have achieved pure evaporation rates beyond 4kgm-2h-1, including structural and material designs allowing for rapid evaporation, passive 3D designs, and systems coupled with alternative energy sources of wind and joule heating. The operational mechanisms for each design are outlined together with discussion on the current benefits and areas for improvement. The overarching challenges encountered by SDIE concerning the feasibility of direct integration into contemporary practical settings are assessed, and issues relating to sustaining elevated evaporation rates under diverse environmental conditions are addressed.

A multistage assembled laminar membrane for solar thermal conversion and nighttime electricity production

Interfacial solar-driven evaporation technology has great potential to address freshwater shortages. Despite significant progress in developing efficient evaporators, the challenge of evaporation rates of two-dimensional evaporators still needs to be solved. In addition, interfacial solar-driven evaporation relies on solar energy to trigger the evaporation of thin water layers at the water–air interfaces. It thus may be at risk of interruption in the absence of sunlight. To overcome these challenges, we have intelligently assembled different functional components to form a multistage assembled laminar membrane used for interfacial solar-driven evaporation during the day and power generation at night. Specifically, solar evaporation achieved a high evaporation rate of 1.78 kg m−2h−1 under single solar irradiation. Desalination and water purification capabilities were also demonstrated. More notably, the membrane also showed its worth as an electrical generator in overcast weather or nights, delivering a voltage of 309 mV and a current of 2 μA. The voltage and current can be multiplied by connecting four membranes in series and parallel to 1.1 V and 8.8 μA, respectively. This powers a calculator directly and stores excess electricity in a capacitor, which can be as high as 2 V in 2000 s. This innovation shows promising applications in next-generation freshwater production and power generation.

Root-based solar interfacial evaporation setup for efficient volumetric reduction of concentrated slurry waste

Although solar interfacial evaporation stands as a promising application for seawater desalination, it has been scarcely studied for volumetric reduction of particle-containing wastewater. Taking inspiration from trees, this work presents a novel approach of root-based solar-interfacial evaporation for accelerated drying of slurries. By varying the total surface area of the roots, the water conduction rate was maximized under different intensities of solar radiation. The optimal setup displayed a high evaporation rate of 1.15 kg/(m2h1) under 1 sun irradiation. Additionally, the evaporator dried the slurry to 75 wt% solid concentration at this high evaporation rate. The setup could remove water further till solid concentration above 90 wt% in a total 40-h duration. The decrease in slurry evaporation rates observed at higher solid concentration was attributed to the break-up of continuous water capillary bridges present between the particles in the slurries. Long duration evaporation experiments for over 100 h of continuous operation displayed 75 % evaporation efficiency, underlining the feasibility of this setup for long-term usage. Large-scale outdoor experiments, scaling to 625 cm2, exhibited high evaporation rates comparable to the smaller setups, confirming the feasibility of this setup for large-scale volumetric reduction.

Development of physically based modelling of bubble behaviour for subcooled boiling applications

A methodology for the modelling of phase change phenomena in two-phase flow is presented, based on interface capturing simulation and the mechanistic modelling of interfacial heat and mass transfer. The volume of fluid approach is adopted, utilising a compressive scheme to maintain interface sharpness, allowing a continuum representation of mass and heat source terms to be used. The methodology is verified against analytical solutions for both evaporation and condensation phase change problems, demonstrating excellent agreement even in the case of a large phase density ratio and high rate of evaporation.

Synergistic effects of hydrophilic function group and micropores on water evaporation in a novel carbon hydrogels for efficient solar steam generation

Solar steam generation (SSG) using hydrogels is emerging as a promising technology for clean water production. Herein, a novel oxygen-doped microporous carbon hydrogel (OPCH), rich in hydrophilic groups and micropores, has been synthesized from microalgae to optimize SSG. OPCH outperforms hydrogels with hydrophobic porous carbon or nonporous hydrophilic biochar, significantly reducing water's evaporation enthalpy from 2216.06 to 1107.88 J g−1 and activating 42.3 g of water per 100 g for evaporation, resulting in an impressive evaporation rate of 2.44 kg m−2 h−1 under one sun. A detailed investigation into the synergistic effects of hydrophilic groups and micropores on evaporation via a second derivative thermogravimetry method revealed two types of bonded water contributing to enthalpy reduction. Molecular dynamics simulations provided further insights, revealing that the hydrophilic micropores considerably decrease both the number and the lifetime of hydrogen bonds among water molecules. This dual effect not only reduces the energy barrier for evaporation but also enhances the kinetic energy needed for the phase transition, significantly boosting the water evaporation process. The sustained high evaporation rates of OPCH, observed across multiple cycles and under varying salinity conditions, underscore its potential as a highly efficient and sustainable solution for SSG applications.

A novel hierarchical chromium black membrane prepared by electroplating for desalination

Solar-driven interfacial evaporation (SDIE), a technology for local solar energy conversion through photothermal materials, has been greatly developed. The metal oxide semiconductors have excellent photothermal conversion performance and are considered the most promising materials for photothermal conversion. Hierarchical structure with large surface area is beneficial to improve the photothermal conversion efficiency through the light-trapping effect and reduces the evaporation enthalpy of water. Herein, chromium black (Cr, Cr2O3, CrO3-x) photothermal membranes (CBPM) with ganoderma-like hierarchical structure were prepared by electrochemical oxidation. Due to the small interlayer spacing of the ganoderma-like structure, the light absorption of CBPM (M7) can reach 78.53 %, which in turn promotes the conversion of solar energy due to the low thermal conductivity of the chromium black layer, resulting in a high evaporation rate of 1.64 kg m−2 h−1. The solar-to-vapor conversion efficiency is up to 90.39 % under 1 sun irradiation. Meanwhile, the superhydrophilicity of the membrane is conducive to salt redissolution at night, so there was not much performance degradation after 24 cycles. This study provides a new solution for water treatment using chromium black as a photothermal material with great potential for solar production of fresh water.