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The use of solar-driven interfacial evaporation for seawater desalination and wastewater treatment is a promising solution to the pressing freshwater crisis. However, the challenge of developing low-cost, easy-to-make, scalable, and high-performance evaporators for efficient steam generation and stable desalination remains enormous. Herein, a cellulose-based carbon paper (CBCP) with outstanding flexibility and structural stability was successfully prepared by a simple and scalable strategy. The formation of ice crystals during the freeze-drying process effectively enlarges and links the pores among cellulose-based fibers, which would facilitate the evaporation and salt-rejecting capability of the as-obtained photothermal paper. The hierarchical porous structure, high light absorption, and excellent solar-thermal conversion capability give CBCP superior interfacial evaporation performance to produce clean water from a wide range of water sources, including real seawater, high salt wastewater, and dye-contained wastewater. The evaporator achieves a high evaporation rate of 1.25 kg m−2 h−1 (energy conversion efficiency of 80.6%) for real seawater under one sun irradiation and has good salt-rejecting capability. During 10 evaporation cycles (100 h in total), the obtained evaporation rate keeps constant around 1.31 kg m−2 h−1. In addition, about 7.7 kg m−2 of freshwater was produced from seawater per day in the outdoor evaporation test. These significant advantages will give CBCP great potential for practical solar-assisted desalination and wastewater purification. [ABSTRACT FROM AUTHOR]

Purification of seawater and wastewater by solar-driven interfacial evaporation is a promising way to alleviate water scarcity. However, the high cost, complex fabrication methods, and short service life of the materials limit their practical application. Herein, a novel three-dimensional (3D) photothermal aerogel composited of vermiculite nanosheets and polyvinyl alcohol (PVA) precursors have been prepared via freeze-drying and treated by quick pyrolysis for highly efficient solar-driven interfacial evaporation. The vermiculite nanosheets exfoliated from natural clay were used as the skeletal support of the composite aerogels, which are cheap and abundant natural materials. The introduced PVA improves the mechanical properties and produces carbon derivatives after pyrolysis, enhancing the light absorption capacity. The as-prepared aerogels have hierarchical porous structures, impressive mechanical properties, great light absorption capacity, and outstanding salt-rejection ability. The optimized aerogel not only exhibits a high evaporation rate of 2.64 kg m−2 h−1 (normalized to top and side surfaces) under 1.0 sun irradiation with excellent cost-effectiveness at 361.64 g h−1 $−1 but also shows superior performance in treating high-salt (15.0 wt%) brine water and organic dye-contained wastewater. The proposed method provides an attractive and effective way to prepare photothermal aerogels for efficient solar steam generation for mitigating water scarcity issues. • 3D clay-based solar evaporators for desalination were made. • Scalable and low-cost PVPA was prepared via a simple and quick pyrolysis strategy. • The as-prepared PVPA shows excellent evaporation performance and reusability. • The PVPA can treat different concentrations of brine and dye-contained wastewater. [ABSTRACT FROM AUTHOR]

With the rapid development of agriculture, controlling phosphorus emissions is a pressing challenge for preventing water eutrophication. A graphite-promoted cyclopentane (CP) hydrate-based desalination was proposed to remove K 3 PO 4 from effluents. It was found via the in situ optical microscopy that the reaction temperature and the concentration of feeding K 3 PO 4 solution significantly affect the morphologies and amount of the as-produced CP hydrate crystals. The lower reaction temperature produces more crystals with irregular shapes, while fewer crystals formed in K 3 PO 4 solution with higher concentration. The reaction temperature, time and feeding concentration-dependent desalination and salt enrichment performances were studied. It was found that desalination efficiency linearly increases with the elevated reaction temperature ranging from − 2 °C to 3 °C; however, water recovery declines with temperature. The temperature-dependent water recovery is due to the strong driving force for hydrate formation at low temperatures. The time-dependent water recovery shows a three-stage feature, including exponential growth, linear increase, and stable stages, owing to the interaction between the driving force of supercooling and the increasing K 3 PO 4 concentration during the reaction processes. The desalination efficiency shows an inverted volcanic shape with the increased concentration of feeding K 3 PO 4 solution. The pre-melting effect plays a critical role in improving desalination efficiency at high K 3 PO 4 concentrations. A maximum desalination efficiency of 85.0% was reached for treating an artificial solution with salinity as high as 42452 mg/L. Both desalted water and concentrated phosphorus-containing solution can be recovered by this method, which is attractive for producing freshwater with potential for recovery of resources. [Display omitted] • A method using cyclopentane hydrate formation was proposed to extract freshwater and enrich K 3 PO 4. • An impressive water recovery over 50% can be obtained in 2 h. • This method can treat an artificial solution with salinity as high as 42452 mg/L. [ABSTRACT FROM AUTHOR]

• High water recovery can be obtained via cyclopentane hydrate formation. • Halide ions have different capability in hindering hydrate formation. • High purity fresh water can be produced via multi-stage hydrate desalination. Hydrate-based desalination is an attractive and energy-effective method. In order to obtain high water recovery and purity, the desalination and Li+ enrichment performance were examined using single-stage desalination via graphite-promoted cyclopentane (CP) hydrate formation. LiCl, LiBr and LiI aqueous solutions with concentration ranging from 0.01 to 0.6 mol/L were used as brine. The rate for CP hydrate formation is determined by concentration, independent of the type of used salts. Halide ions were found to have the different capability in hindering CP hydrate-based desalination, with an order of Cl− < Br− < I−. The desalination efficiency was improved with increased concentration. Water recovery of 40% can be obtained in 1 h reaction, demonstrating the high efficiency of hydrate-based desalination. The desalination efficiency remains constant at around 70% over 24 h reaction, which can be dramatically enhanced by multi-stage desalination. The graphite powder, as the promoter for hydrate formation shows impressive recycling stability. The finding in this study would be of great help for developing effective desalination processes to produce fresh water and enrich high-value salts via CP hydrates. [ABSTRACT FROM AUTHOR]

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. • The "brick-concrete" structures were used to optimize the pore sizes of the 3D photothermal evaporators. • The functions of MSAs in water transport and hydrogen bond activization were systematically analyzed. • The as-prepared MSAs show excellent evaporation performance and reusability. [ABSTRACT FROM AUTHOR]

Abstract Desalination via hydrate processes is promising in producing freshwater at low energy cost. However, it is a great challenge to instantaneously produce and form large amount of hydrates in short time, particularly with salts presence. In this study, we used cheap and easily separated graphite particles to promote hydrate based desalination. The added graphite can promote the formation of hydrate, greatly shortening the induction time. The desalination efficiency was also enhanced due to the introduced graphite. Combined graphite and stirring, both the desalination efficiency and water conversion ratio were boosted. The impact of particle sizes of graphite on hydrate formation was found to be different at static state and stirring. The proposed hydrate based desalination is almost independent on treated volume. Additionally, this method can use the nature chilling, which is potential in further reducing the energy cost of desalination via hydrate. The findings in this study would help rationally choose and design promoting agents and hydrate processes for facilitating hydrate formation and desalination via hydrates. Highlights • Introduction of graphite boosted the hydrate formation rate. • Graphite increased desalination efficiency and water conversion ratio. • The particle size of graphite played critical roles in enhancing desalination via hydrate process. [ABSTRACT FROM AUTHOR]