| The shortage of freshwater resources is one of the most serious threats to global development.Without damaging the current freshwater system,seawater desalination technology is one of the easy ways to provide high-quality freshwater.With the development of the traditional desalination technologies,such as RO and MED,the desalination system based on solar-driven interfacial evaporation desalination(SDID)has shown strong potential in water purification for its high efficiency,low cost,green energy,sustainability and scalability.Nevertheless,the salting deposition will weaken the light absorption capacity,thereby reducing the continuous evaporation efficiency of the SDID.Therefore,building the effective photothermal materials and the reasonable evaporation device are the serious challenge in the current.Based on fiber materials with large specific surface area and adjustable wettability,combine the wide spectrum adsorption of carbon materials,this paper has prepared evaporation devices with strong photo-thermal conversion,heat management and thermal limiting capabilities,efficient transport channels of water and low heat conductivity,achieving continuous and efficient evaporation efficiency through the collaborative design and construction of multi-level structure and spatial dimensions.The main contents are as follows:(1)The D-PAN@PDA@Ag core-shell nanocomposite fibrous membrane with super-thick PDA shell was uniformly established by electrospinning and polymerization,showing the advantages of broad-spectrum absorption,high specific surface area,good flexibility and mechanical properties,super hydrophilicity and scalability.Combining with the space separated photothermal evaporator and D-PAN@PDA@Ag fibrous membrane,it provides a good water transport channel and avoids salt resistant deposition,providing the good thermal concentration and thermal limitation performance in the process of seawater desalination.The evaporation rate and energy conversion efficiency reached 1.91 kg m-2 h-1 and 85.5%under 1-sun irradiation,showing a continuous and stable performance of photothermal interfaciai desalination.At the same time,the interaction mechanism between PDA molecule and the water molecule is explored through experimental analysis and theoretical calculation,which also provides a new idea for the construction of photothermal fibrous membrane materials.(2)In order to further improve the light absorption rate and optimize the construction of the evaporator,polyurethane-carbon nanotube(TPU-CNT,TPC)fibrous membrane was prepared by electrospinning.Combined with carbon black(CB)material,the Janus TPC@CB sponge was prepared by gas expansion method and the adjustment of surface wetting property.In the process of SDID,the hydrophobic CB layer on the foam surface provides efficient light absorption(98%),and the microporous hydrophilic TPC sponge composed of interconnected thin fibrous layers at the bottom provides a fast water transport channel and good thermal insulation performance,so that the heat converted by photothermal CB materials can be concentrated to the thin layer of water on the top,achieving self-floating and self-spreading performance and simplifying the design of devices,which is useful to the needs of practical SDID applications.The thermal conductivity of Janus TPC@CB sponges under dry and wet conditions are 0.0398 W m-1 K-1 and 0.115 W m-1 K-1 respectively,showing good thermal insulation performance.The evaporation rate of Janus TPC@CB sponge evaporator is 1.80 kg m-2 h-1,and the energy conversion efficiency is 97.2%under the 1-sun irradiation.This method was expected to achieve low-cost liquid zero discharge treatment of wastewater,and prospects for the application of seawater desalination and wastewater treatment.(3)In order to break the time limitation of sunlight irradiation in SDID,the flexibility CC-CNT photothermal material was prepared by in-situ growth method.The interface evaporator based on CC-CNT material not only has efficient wide spectrum absorption,but also has good electrical conductivity,realizing salt-resistance effect and all-weather evaporation with photo thermal and electrothermal synergistic effects.The research shows that CC-CNT materials have been successfully prepared through optimization of conditions and structural characterization.In the structure of Janus CC-CNT evaporator,the hydrophilic commercial fibrous cloth was used for efficient transmission of water,and the PS foam with low thermal conductivity provides thermal insulation,and the photothermal seawater evaporation performance and the photothermal/electrothermal synergistic seawater evaporation performance has been investigated respectively.The evaporation rate of the evaporator is 1.67 kg m-2 h-1 and the energy conversion efficiency is 88.9%under the sunlight of one time.When the voltage of 1.8 V is applied to 1-sun irradiation system,the evaporation rate is up to 3.29 kg m-2 h-1.In addition,using solar cells as the supplement of power,the constructed evaporative reflux device can continuously collect clean water at a high rate of 5.70 kg m-2 d-1.This research has provided a new method to build high-performance evaporation devices and expand the practical application of efficient solar desalination. |
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