Solar Vaporization Research Articles

Realizing efficient solar evaporation and rapid lithium sorption by the halloysite nanotubes-based hydrogel

Solar-powered water treatment technology is gaining increasing importance as one solution to ameliorate water resource deficits. This study presents a novel approach of synergistically combining interface solar vaporization technology with low-cost sorption techniques to better enable resource recovery in the water treatment process. After preparation of a halloysite nanotube-based hydrogel, it was subjected to 1 sun illumination. The prepared hydrogel demonstrated an evaporation rate and evaporation efficiency of 2.97 kg/m2·h and 93.2%, respectively, with ideal salt and stain resistance. Under the synergistic effect of halloysite nanotubes (HNTs), the hydrogel efficiently sorbed Li+ at a rate and maximum capacity of 84.15% and 168.3 mg/g, respectively during the solar vaporization process. This study also discussed the main interactions between Li+ and hydrogel sorbents. The results of this study providing a novel and promising approach for concurrent water treatment and Li+ extraction.

Customized Microenvironments Spontaneously Facilitate Coupled Engineering of Real-Life Large-Scale Clean Water Capture and Pollution Remediation.

Harnessing abundant renewable resources and pollutants on a large scale to address environmental challenges, while providing sustainable freshwater, is a significant endeavour. This study presents the design of fully functional solar vaporization devices (SVD) based on organic-inorganic hybrid nanocomposites (CCMs-x). These devices exhibit efficient photothermal properties that facilitate multitargeted interfacial reactions, enabling simultaneous catalysis of sewage and desalination. The localized interfacial heating generated by the photothermal effect of CCMs-x triggers surface-dominated catalysis and steam generation. The CCMs-x SVD achieves a solar water-vapor generation rate of 1.41kg m-2 h-1 (90.8%), and it achieves over 95% removal of pollutants within 60min under one-sun for practical application. The exceptional photothermal conversion rate of wastewater for environmental remediation and water capture is attributed to customized microenvironments within the system. The integrated parallel reaction system in SVD ensures it is a real-life application in multiple scenarios such as municipal/medical wastewater and brine containing high concentrations. Additionally, the SVD exhibits long-term durability, antifouling functionality toward complex ionic contaminants. This study not only demonstrates a one-stone-two-birds strategy for large-scale direct production of potable water from polluted seawater, but also opens up exciting possibilities for parallel production of energy and water resources.

Orderly-assembled photothermal photonic crystals with multiple structural colors for high-performance interfacial solar desalination

The microstructure of photothermal materials plays a central role in interfacial solar evaporation, which is vital to solar absorption, thermal management, water and vapor transportation. Ordered structures constructed on cross-scale in a controllable fashion are potentially important for high-performance photothermic vaporization, and may provide fundamental insight into the correlation between microstructure and evaporation efficiency. Herein, the ordered photothermal materials featuring brilliant structural colors and spectral and thermal management are cross-scale assembled using unique colloidal photonic crystals (PCs) as the building block. Multidimensional ordered PC photothermal materials including PC layered nanofilms, microbeads and three-dimensional (3D) scaffolds are facially constructed by Langmuir-Blodgett, microfluidics and 3D printing techniques, respectively, exhibiting excellent internal light reflection and water wettability. As a result, the corresponding solar vaporization rates of 2.23, 2.14 and 2.0 kg m-2h−1 are achieved under 1 sun, greatly surpassing that in disordered PC films. Notably, the structural color originated from periodic-arranged PC structure shows a regulable and colorful appearance, in contrast to the monotonous black color in conventional broadband photothermal materials. The controllable methodology for ordered architecture construction inspires more novel nanostructured and multifunctional photothermal materials for solar evaporation materials.

Concentration of landfill leachate by solar driven surface vaporization performed on nanosecond-laser-treated titanium surface

The use of solar evaporators to concentrate landfill leachate is a sustainable approach for reducing wastewater volume and generating clean water. Recent studies have investigated numerous interfacial solar evaporators. However, achieving a high evaporation rate under low optical concentrations remains challenging. This research develops mono and bifacial titanium photo-thermal material for solar-based landfill leachate treatment. Its strong absorbency, photo-thermal, thermal insulation, and quick water delivery characteristics enable the fabricated material to reach a high evaporation rate, including 2.02 and 1.71 kg/h under one sun for double and single-sided panels, respectively. Under one sun for a single-sided panel, the photo-thermal conversion effectiveness reached nearly 80.00%, resulting in a high interfacial water evaporation efficiency of 86.00%. It was possible to easily position the fabricated photo-thermal panels at any angle and implement them to optimize irradiation from incidence light. In comparison with raw landfill leachate, the concentrated landfill leachate displayed high turbidity, total suspended solids, solid suspended concentration, and total dissolved solids. Additionally, in the purified water, 98.70%, 91.20%, and 99.70% removal efficiencies were obtained for Cr2+, Ni2+, and Fe2+. Besides, COD (chemical oxygen demand), TOC (total organic carbon), and NH3-N (ammonia nitrogen) were removed at 90.36%, 86.13%, and 69.3%, respectively. Based on the results of this study, the super-hydrophilic titanium photo-thermal material is a potential candidate solar absorber for simultaneously concentrating wastewater and producing clean water.

From Materials to Devices: Rationally Designing Solar Steam System for Advanced Applications

Solar-driven water vaporization for freshwater production attracts significant interest due to its potential for solving global water scarcity problems. In this review, the recent development of management strategies via diverse rational designs in terms of light, thermal, water, and anti-salt fouling for enhancement of overall vaporization efficiency, is summarized. For device design, a host-guest concept is raised for clearly elaborating the detailed function and interaction between the solar-thermal material and the substrates. In addition, the rising technologies derived from solar vaporization, such as energy generation, photocatalysis, dehumidification, salt harvesting, sterilization, and biofuel production, are also highlighted. This review provides a new horizon toward the development of solar technologies and practical applications.

Novel nanofluid based efficient solar vaporization systems with applications in desalination and wastewater treatment

The current work proposes a new strategy to improve solar evaporation efficiency and explore the real applications of volumetric solar evaporation device in desalination and wastewater treatment. Nanofluid based volumetric solar evaporation system is efficient to enhance the absorbance of solar irradiation. However, the solar evaporation efficiencies are relatively low. There is a need to investigate the fundamentals of the limitation and find a new strategy to improve the solar evaporation efficiency. In this paper, a novel device containing tungsten carbide nanofluids as work fluids is designed for the first time to reduce heat loss towards the bulk water, improve the stability of nanofluids, and avoid contamination of nanoparticles. The results show that tungsten carbide nanofluids of 0.3 wt% can harvest 99% of the incident solar energy within 1 cm penetration distance. The photothermal conversion efficiency is 97.7%. The novel device gives an evaporation rate of 1.235 kg m−2 h−1 and reached solar evaporation efficiency of 74.9% under 1-sun irradiation. The applications in desalination and wastewater treatment show that the ion rejection rate of seawater is higher than 99.99%, and the content of heavy metal ion is significantly lower than that in the World Health Organization drinking-water standard.

Metal organic framework enabled wood evaporator for solar-driven water purification

• Cu-CAT MOF was used as solar absorber for efficient water purification. • The superoleophobic MOF layer was integrated onto the bottom side of wood substrate. • The wood evaporator with a sandwich-like structure presents a good anti-oil-fouling property. • An evaporation rate of 1.80 kg m −2 h −1 under 1 sun illumination was obtained. By utilizing sunlight, the interfacial solar evaporation system is promising for seawater desalination, wastewater decontamination and electricity generation. Herein, a copper-based metal organic framework (Cu-CAT) was coated on wood sheets to form a wood evaporator, and the wood substrate with a low thermal conductivity is in charge of continuous water transportation. The Cu-CAT layer was attached tightly to both the top and bottom surfaces of the wood substrate. The black Cu-CAT at top surface affords a broadband and strong light absorption, while the underwater superoleophobic Cu-CAT layer presents a high oil repellence. Through optimizing the wood substrate thickness, the wood evaporator (Cu-CAT/Wood) with a wood thickness of 10 mm displayed an evaporation rate of 1.80 kg m −2 h −1 under simulated 1 sun illumination. Enabled by the Cu-CAT, the wood evaporator can be used for water purification from various sources (seawater, oil-, dye-, heavy metal- contaminated water and natural lake water). Importantly, the Cu-CAT/Wood could co-generate electricity induced by the solar vaporization process. This work will stimulate more studies on the structural designs of solar evaporators for drinkable water production and pollution abatement.

Improving the Performance of Direct Solar Collectors and Stills by Controlling the Morphology and Size of Plasmonic Core–Shell Nanoheaters

Plasmonic nanofluids, based on metal nanoparticles (NPs), has received tremendous attention for its potential to increase the efficiency of solar energy harvesting and harnessing systems. The ability to manage their optical absorption by tuning localized surface plasmon (LSP) bands is the reason why metal NPs are considered excellent nanoheaters with unique thermo-optic properties. In this work, we demostrate the influence of the tuning of plasmonic nanofluid absorption bands in different spectral regions, by modifying the morphology and size of the core–shell NPs, on the efficiency of plasmonic nanoheaters to heat fluids and generate steam. Five plasmonic nanofluids containing spherical Au@SiO2, rodlike Au@SiO2, with three different aspect ratios, and spherical SiO2@Au nanoshells were fabricated and characterized to study the local heating induced by plasmon-enhanced light absorption. Gains of up to 28.3 times in the nanofluid temperature increase in direct absorption solar collectors (DASCs) and 7.5 times in the amount of steam generated in the solar ethanol distillation were measured from control over LSP resonances of spherical and rodlike core–shell NPs. Energy distribution analysis shows that plasmonic nanofluids present an efficient energy transfer management, dedicating ∼72% of the absorbed energy to heating liquids at low levels of solar irradiance. However, at high solar irradiances, the good spectral matching between the plasmonic nanofluid LSP bands and the solar irradiance spectrum promotes strong local heating around the core–shell NPs, allowing local temperatures above the boiling point to be reached. Under these conditions, plasmonic nanofluids spend a small amount of energy to heat liquids and they transfer ∼83% of the absorbed energy to generate steam. Thus, a 7.7-fold increase in solar ethanol vaporization rate was achieved. The experimental results, understood from the optical properties of core–shell plasmonic NPs by using the Maxwell–Garnett theoretical model, corroborate the importance of fabricating nanoheaters with projected geometries to maximize the efficiency of solar collectors and stills.

Self-contained Janus Aerogel with Antifouling and Salt-Rejecting Properties for Stable Solar Evaporation.

Janus structural interfacial vaporization by separating the solar absorber from the bulk working fluid has attracted tremendous attention due to its low heat losses and high solar conversion efficiency for desalination, water purification, energy generation, etc. However, a totally separated double-deck structure with a discontinuous interfacial transition and inefficient photothermic materials undermines its long-term use and large-scale practical exploitation. Herein, a low-cost Janus monolithic chitosan aerogel with continuous aligned run-through microchannels has been demonstrated to have a highly efficient photothermic effect on seawater desalination and wastewater purification. The top solar absorber layer enhances broadband light absorption and photothermal conversion efficiency via the multiple internal reflection of incident light in the aligned microchannels. Moreover, the insulating/hydrophilic bottom layer promotes water transportation and heat localization, and simultaneously prevents salt/fouling accumulation. As a result, a long-term solar vaporization rate of ∼1.76 kg m-2 h-1 is achieved, corresponding to a light-to-vapor efficiency of ∼91% under 1 sun irradiation. Notably, the large-vessel microchannels throughout the aerogel and favorable swelling property provide sufficient water replenishment and storage for completely isolating self-contained evaporation, illustrating an enhanced and time-extended self-contained solar steam generation. Such a low-cost bilayer aerogel with remarkable cycling stability in various fluids offers potential opportunities for freshwater production in remote rural areas.

Superhydrophilic and oil-repellent porous material based on halloysite nanotubes and wood fibers for efficient solar steam generation

Solar steam generation (SSG) has emerged as one of the most efficient strategies for desalination and sewage treatment. In this work, we present an approach for the fabrication of a novel oil-repellent solar photothermal material (named as O-WF-HNTs), which is derived from wood fibers (WF) and halloysite nanotubes (HNTs) for efficient SSG. The porosity of the premodified sample (WF-HNTs) was about 89%, the light absorption was over 95%, and the thermal conductivity was 0.206 W m−1 k−1. Under the irradiation of 1.0 kW m−2, the solar energy conversion efficiency reaches up to 84% with better salt tolerance (the evaporation efficiency in 10% NaCl solution is 76%). After a surface modification, interestingly, the wettability of the as-resulted O-WF-HNTs changes to be hydrophilic and oil-repellent. The solar energy conversion efficiency of the O-WF-HNTs can reach as high as 79% in oily water under 1.0 kW m−2 illumination, while the untreated sample, i.e. WF-HNTs, only shows a very low solar energy conversion efficiency of 48% due to n-hexadecane blocks the channels of material and in turn hinders water transportation during solar vaporization. Compared with the existing photothermal materials, which usually suffer the shortcomings of either complicated preparation or oleophilic property, our materials take the advantages of a simple, cost-efficient, and scalable fabrication process with low-cost natural clay and wood fibers as raw materials, in particular oil-repellency which makes it possible for SSG even in oily water or sewage, thus the practical application of SSG is further broadened.

Novel oil-repellent photothermal materials based on copper foam for efficient solar steam generation

Solar steam generation (SSG) has emerged as one of renewable and environmentally friendly technologies for production of fresh water. Here, we demonstrate the preparation of a novel oil-repellent photothermal materials based on copper foam (CF) for efficient SSG. Only by a simple chemical oxidation treatment on CF (named as R–CF), the smooth CF skeleton changes to be rough, leading to an enhanced light absorption of up to 90% which is far higher than that of untreated CF (10–70%). By combination of its high porosity (89.6%) and high specific surface area (230 m2 g−1), the R–CF shows superior ability on SSG as well as salt-resistance, i.e., its evaporation efficiency in water and high saline solution reaches 85.25% and 70.19% under 1 kW m−2 irradiation, respectively. In addition, R–CF was further treated by a surface chemical modification to achieve hydrophilicity while oil-repellent wettability (named as OR-R-CF), enabling it solar vaporization even in oily water, e.g., an evaporation efficiency of 77.0% was obtained in oily water, which is great advantageous to those existing photothermal materials usually suffer the drawbacks of poor oil-repellent or anti-fouling property and thus shows significant potentials for practical SSG applications in both seawater and oily water.

Cost-effective and eco-friendly laser-processed cotton paper for high-performance solar evaporation

Recently, interfacial solar-driven evaporation has received tremendous attention due to its potential for enhancing solar thermal conversation ability via heat localization at the evaporation interface. Diverse materials and configurations have been explored to boost the evaporation using plastic foam as the thermal insulator at the cost of complex assembly and environmental threats. Herein, we demonstrate a biodegradable, cost-effective, and scalable three-dimensional (3D) cotton paper-based solar steam generator prepared by one-step laser-induced forward transfer in the ambient atmosphere. The as-prepared evaporator has excellent solar absorption ability. The defining advantages of this method are that it can easily form a 3D structure and it is free from hazardous raw material involvement and waste generation. With further novel design by using a natural air gap instead of artificial plastic material to insulate the steam generation area and the underlying bulk water, the as-prepared evaporation system can achieve a high evaporation rate of 1711 g m−2 h−1 with a corresponding efficiency of 83% under one sun illumination. Such solar vaporization functions offer new insights into the future development of high-performance solar steam generators through an environmentally friendly and cost-effective pathway.

Functional oil-repellent photothermal materials based on nickel foam for efficient solar steam generation

The production of fresh water by means of solar steam generation has emerged as one of frontier technologies for addressing the global water shortage issue. Here, we report the preparation of new photothermal materials by chemical modification of nickel foam with sulfur via a simple hydrothermal method for solar steam generation. The generation of nano nickel wire on the surface of skeleton of nickel foam by sulfur treatment could construct a much more dense network with hierarchical porous structure and hydrophilicity, which significantly enhance their light absorption (average 40–50% for untreated nickel foam while 91% for sulfur treated nickel foam (named as S–Ni foam) as well as water transportation. In the way, the as-prepared S–Ni foam possesses a high energy conversion efficiency of 83.6% under 1 kW m−2 irradiation. In view of most of reported photothermal materials which suffer the drawback of lose effectiveness in oily water, the S–Ni foam was further chemically modified with an anionic coordination between sodium perfluorooctanoate (PFO) and poly diallyl dimethyl ammonium (PDDA) chloride to achieve a strong hydrophilic-oleophobic wettability (named as OR-S-Ni foam). Such unique wettability endows the as-resulted OR-S-Ni foam excellent oil-repellent performance, making it possible solar vaporization even in water containing oils or organics contaminates, which should be of significantly technological significance for practical solar steam generation by largely extends its applications range.

A simple, mild and versatile method for preparation of photothermal woods toward highly efficient solar steam generation

Abstract Wood-based photothermal materials for solar steam generation have drawn great attentions in recent years. Until now, surface coating and surface carbonization have been developed to transform woods into photothermal materials. Although great achievements have been made, there are still some challenges. Firstly, carbonization needs high temperature and will deprive the wood's superhydrophilicity, which is disadvantage for the wood to against fouling of oil spills. Secondly, most black coatings such as carbon black will fall off the substrates due to the limited interaction between coating and substrates. Moreover, it is still difficult for surface carbonization and most surface coatings to turn woods with any shapes blackness, which will limit the structure design toward further improved solar steam generation performance. Herein, a simple, mild and versatile method without high temperature or any noble metals has been developed to transform various woods with any shapes into black materials for solar vaporization of water. The resultant wood exhibits high solar-to-evaporation efficiency (about 90%) under one sun illumination, outstanding stability (good acid-base resistance property, anti-rinsing at 3000r/min for 100 h, withstand cyclic frost-thaw for 100 times, withstand ultrasound treatment for 2 h), and desirable anti-crude oil-fouling performance, which is very attractive for its application in the ocean. Most importantly, structural designs can be easily realized via this method, leading to the significantly improved water evaporation rate from 1.34 kg m−2 h−1 to a record high rate of 1.85 kg m−2 h−1 for wood-based photothermal materials under one sun. This study represents a new avenue for fabrication and design of wood-based photothermal materials, and will contribute to the global effort in addressing world water and energy issues.

Ultrahigh-efficiency desalination via a thermally-localized multistage solar still

Passive vapor generation systems combining interfacial solar heating and vaporization enthalpy recycling enable high-efficient low-cost desalination.

A scalable, low-cost and robust photo-thermal fabric with tunable and programmable 2D/3D structures towards environmentally adaptable liquid/solid-medium water extraction

As a renewable and sustainable resource, solar energy exploited to conduct interfacial water evaporation has attracted considerable attention. However, conventional photo-thermal materials mainly focus on the issues of energy efficiency and multifunctionality, the lack of scalable, low-cost, flexible and washable features severely restrict the application from labs to industrialization. Significantly, owing to the low utilization of the spatial volume of the conventional two-dimensional (2D) evaporators, the development of editable and controllable 3D structures toward improved energy efficiency is highly desirable. Inspired by the traditional sewing clothes, herein, a functional photo-thermal fabrics with excellent scalable, washable and inexpensive features is designed to realize tunable and programmable 2D/3D structures, which enable the favorable in-plane and out-of-plane water extraction from liquid/solid medium. Since the polypyrrole (PPy) has favorable photo-thermal, stable features and strong interactions with the fibrous cotton, an in situ tunable oxypolymerization strategy was employed to construct PPy modified cotton fabric. The facile and robust approach enables the formation of a large-area PPy-modified cotton (PMC), which could function as a 2D generator for well-controlled in-plane water evaporation. Furthermore, the excellent sewable and editable features of the fabrics allow the programmable integration of these functional PMC building blocks into 3D system towards high-efficient out-of-plane solar vaporization. Specifically, the 3D design can adapt the photo-thermal fabrics to diverse environments with efficient purified water collection even from sand matrix.

Rationally Programmable Paper‐Based Artificial Trees Toward Multipath Solar‐Driven Water Extraction from Liquid/Solid Substrates

Solar vaporization, which is emerged as a promising candidate for harvesting solar energy in sewage purification and/or seawater desalination, has attracted increasing interests during the last few years. Although tremendous advances are made, it is still challenging to realize simple fabrication protocols, low‐cost, and rationally editable 3D structures toward multipath water extraction from liquid/solid media. Inspired by natural plants with hierarchical structures rooted in soils, herein, an artificial tree of carbon nanotubes (CNTs) film/paper hybrid with tunable transpiration toward multipath water extraction under solar illumination is rationally designed. In this system, an interfacial‐assisted transfer strategy is developed to alternatively transfer the self‐assembled CNT films at the air/water interface onto one side of arbitrary substrates in a uniform/patterned way. The paper‐based photothermal absorbers with favorable tailorability and foldability allow the transformation of the 2D evaporators to tree‐like 3D ones. The achieved 3D evaporators with specific structures can extract purified water ranging from conventional liquid phase (e.g., water) to solid phase (e.g., sand), which can significantly extend the application of water extraction.

Micro-/Macroscopically Synergetic Control of Switchable 2D/3D Photothermal Water Purification Enabled by Robust, Portable, and Cost-Effective Cellulose Papers.

Solar energy, as a renewable and sustainable resource, is considered to be a promising candidate for solving the water shortage through an interfacial solar-to-thermal conversion. Despite tremendous advances are achieved, it is still challenging for limited size, high-cost, and complicated fabrication protocols. More importantly, a favorable 2D/3D structure transformation to adapt to diverse conditions is considered to be very important. Inspired by the transformers with changeable geometries, herein, a large-area polypyrrole chemically functionalized cellulose paper (PPyP) with tunable microstructures and macroscopic geometries is developed via an in situ controlled oxypolymerization reaction. The resulted PPyP enables tunable 2D interfacial solar vaporization and even adapt itself to realization of 3D structures transformation for high-efficient water evaporation of up to 2.99 kg m-2 h-1 under 1 sun via an alternative kirigami/origami approach. Significantly, the PPyP can realize a switchable transformation between 2D and 3D structures to adapt diverse environments, demonstrating significant potentials in environmentally adaptable water purification.

Arched Bamboo Charcoal as Interfacial Solar Steam Generation Integrative Device with Enhanced Water Purification Capacity

AbstractInterfacial solar steam generation (ISSG) has received increasing attention in both industry and academia, and is considered a method with great potential for wastewater treatment and desalination. These practical applications require materials that fulfil several requirements: being low cost, being scalable in terms of processing, being environmentally friendly, and having a high, stable optical–thermal conversion efficiency of solar vaporization. Currently, biomass materials show very promising prospects for ISSG systems. Here, it is observed that bamboo charcoal (BC) possesses a series of unique advantages that make it a highly efficient ISSG device. The broadband light absorption and the arched and porous structural features of BC fulfil all the basic requirements of an ISSG device in localized heating, heat management, and water supply. The self‐contained arched BC device demonstrates high evaporation efficiency (84% under 1 sun radiation) and superb stability under strongly acidic, strongly alkaline, and intense light environment conditions. More importantly, the porous BC device can provide stable fresh water production that simultaneously promotes the purification of water via evaporation by heating. Finally, the low cost, environmentally sustainable, mechanically robust, and long‐term stable BC device is a potential opportunity for wastewater treatment and desalination in underdeveloped areas.

On the Perspective of Applying of a New Method for Wastewater Treatment Technology: Modification of the Third Traditional Stage with Two Units, One by Cultivating Microalgae and Another by Solar Vaporization

This Short Communication presents the concept of a new method for water/wastewater treatment technology using microalgae cultivation in effluents with the aims to treat, clean, and recycle waters using two units: the first one for cultivating microalgae and the second one through using sunlight and other types of renewable energy (wind photoelectric phenomena) modifying the physicochemical properties for vaporizing water that resulting from microalgae cultivation. The combined production of biomass by microalgae cultivation in polluted waters can allow achieving two main objectives: first, generate clean water and reuse it, and second, producing biomass, which may be used as resource for biofuels. Alternatively, it can be grown the microalgae using the CO2 produced by anaerobic digestion, while methane (CH4) as fuel after separation of biogases.