Structural Design And Performance Of Luffa Fabric-based High-efficiency Photothermal Evaporator

Solar interface evaporation technology can directly absorb solar energy and convert it into thermal energy to heat liquid water to produce water vapor,thus producing clean water.This process does not produce any pollution and is one of the effective ways to alleviate the shortage of fresh water resources.Due to their inherent high porosity,porous materials not only provides more effective evaporation area and improves the absorption of sunlight by enhancing light scattering,but also promotes water transport and sufficient vapor escape,which plays an important role in increasing the evaporation rate of photothermal water.The reported porous photothermal materials include synthetic gels,melamine foam and biomass materials.However,most of these materials suffer from complex preparation processes and difficulties in finished products,the mechanical properties are too poor and the structure is easily damaged,making it difficult to be useful in practical applications.Luffa has the advantages of high porosity,large specific surface area,good mechanical properties and low price,which makes it one of the ideal materials for photothermal substrates.This paper focuses on luffa as a photothermal substrate material,using polypyrrole with excellent photothermal properties as its modification,to build a luffa-based solar interface evaporator that can realize water regulation,an integrated structure photothermal evaporator that can realize seawater desalination and dye purification and a double-layer salt-resistant evaporation device that can be sized and realize high concentration salt water desalination are fabricated.By designing different system structures to make it applied in different practical fields,and studying the performance of photothermal evaporation of different structure evaporation devices.The specific research is as follows:(1)Preparation and photothermal performance of luffa-based solar interfacial evaporator.Using luffa,a biomass porous material,as a substrate,polypyrrole with excellent photothermal properties was polymerized on its fiber surface,and its light absorption performance,mechanical properties and stability were investigated.The luffa-based solar interface evaporator was designed by the combination with polyester filament columns and foamed polyethylene foam.The water supply system,heat management,photothermal conversion performance,and photothermal water evaporation performance of the evaporation device were tested and analyzed.The results show that the photothermal performance of the polypyrrole-modified luffa is excellent,and the evaporation rate of the luffa-based solar interface evaporator can reach 2.38 kg m^-2 h^-1 under one solar light intensity.Then the unique presence of water inside the lucerne fiber was observed by cryo-electron microscopy,revealing the evaporation principle,the water to be evaporated is made to form on the porous skeleton through its unique hydrophilic layered channels film state,which can effectively regulate the water content in the photothermal material.(2)Weave and performance of luffa fabric-based integrated photothermal water evaporation device.To solve the problem of integration and dimensionality of evaporation devices from biomass materials,a luffa fabric-based integrated photothermal water evaporation device was woven with polypyrrole modified luffa as weft yarn and cotton yarn as warp yarn,which improving the problem of size limitation of biomass materials.The evaporation device closely connects the water supply layer and the evaporation layer together to form a bridge evaporator,which can ensure sufficient water supply while reducing heat loss and increasing the evaporation area.The light absorption and photothermal conversion performance of luffa fabric before and after modification were tested and analyzed,and solar water evaporation experiments were conducted on the luffa fabric-based integrated evaporation device.The research results show that the light absorption and photothermal conversion performance of the polypyrrole-modified luffa fabric were significantly improved,and the evaporation rate of the luffa fabric-based integrated light and hot water evaporator is stable at about 1.89 kg m^-2 h^-1under the intensity of one sun,which can realize the purification of outdoor dye liquor wastewater.(3)Weaving and performance of luffa fabric-based double-layer salt-resistant interfacial evaporation devices.Polypyrrole-modified luffa was used as the substrate,which was hydrophobically modified using 1H,1H,2H,2H-perfluorooctyl trichlorosilane,and then its hydrophobicity and functional groups were investigated.The luffa fabric-based double-layer salt-resistant interfacial evaporation device was constructed using a double-layer tissue for weaving,with hydrophobic loofah as the upper weft yarn and nylon as the warp yarn;cotton yarn as the lower warp and weft yarn for weaving,and then combined with low thermal conductivity foamed polyethylene foam.The light absorption,photothermal conversion performance and structural stability of the evaporation device are tested.The evaporation rate of this evaporator in high concentration brine and the salt formation problem are investigated,and the effect of wind speed on the evaporation performance of the evaporator in the evaporation process is explored.The results show that this double-layer evaporation device has excellent photothermal performance and structural stability,and can effectively avoid the precipitation of salt on the surface of photothermal materials in the evaporation of highly concentrated brine.The evaporation rate is greatly improved by increasing the wind convection,and the water evaporation rate can be as high as 2.60 kg m^-2 h^-1 under a wind speed of 3 m/s and a solar light intensity.These studies provide some theoretical basis and technical support for the application of natural biomass materials with unique structures in the field of solar interfacial evaporation.