| Solar-driven interfacial evaporation technology uses solar energy to heat the evaporator surface water to produce water vapor with high photothermal efficiency,providing a promising avenue for efficiently obtaining clean water from brine.However,high evaporation rates are often accompanied by salt crystallization,and water evaporation can lead to salt formation on the evaporation system surface,reducing the evaporation rate.Salt crystallization is particularly severe as the salt solubility increases.Therefore,it remains a great challenge to maintain high evaporation rates when handling high concentrations of salt water.Carbon fiber is one of the few photothermal materials with excellent light absorption,low density,high thermal conductivity,high modulus and resistance to acid and alkali corrosion,and can be adapted to a variety of environmental desalination applications.However,carbon fiber has the problems of easy wire drawing and lateral breakage,and it is more difficult to realize compounding with various materials.The low surface polar performance also shows low water content,which cannot supply water in time when dealing with high concentration of brine,resulting in crystallized salt on the evaporator surface.In this thesis,using carbon fiber as the photothermal substrate material,by introducing different hydrophilic fibers and using different processing processes to prepare different photothermal structures,a carbon fiber-based high-efficiency interfacial photothermal vapor conversion device capable of satisfying salt water treatment was constructed:a carbon fiber-based Janus/superhydrophilic aerogel photothermal evaporator for long time treatment of high concentration salt water was prepared;an integrated carbon fiber evaporator was designed to prevent carbon fiber draw-off and achieve seawater We have designed an integrated carbon fiber-based double-layer fabric photothermal evaporator to prevent carbon fiber pulling and achieve seawater desalination and dye purification;we have woven a carbon fiber-based core sheath structure fabric photothermal evaporator that can achieve moisture regulation while processing concentrated salt water.The resulting device is capable of long-term stable solar brine desalination,and its photothermal and multifaceted performance has been discussed as follows:（1）Preparation of carbon fiber-based Janus/superhydrophilic photothermal aerogel evaporator and its performance study.The Janus aerogel with the top layer of carbon fiber and bottom layer of aramid was obtained by adding carboxymethyl cellulose dispersion,glutaraldehyde cross-linking,spacer fabric reinforcement,and then freeze-drying with waste carbon fiber powder and aramid powder as the substrate.The carbon fiber-based Janus/superhydrophilic photothermal aerogel evaporator was constructed by combining with perforated EPE foam.The prepared carbon fiber-based Janus/superhydrophilic photothermal aerogel evaporator has excellent hydrophilicity,high mechanical strength,good thermal insulation,low evaporation enthalpy(2113.91k J kg-1),high evaporation efficiency（98.93%）,high evaporation rate(1.85 kg m-2 h-1),and high salt resistance（15 wt%Na Cl solution）.And it can achieve continuous desalination of 15 wt%Na Cl solution for 5 consecutive days outdoors with consistently high mass loss rate(>7.2 kg m-2 for 10 consecutive hours).（2）Preparation of carbon fiber-based double-layer fabric photothermal evaporator and its photothermal performance study.In order to solve the problems of easy draw-off of carbon fiber and insufficient water supply,a double-layer structure photothermal fabric with carbon fiber photothermal layer on top and cotton yarn water supply layer on the bottom was woven by using black polyester yarn as warp yarn and carbon fiber and cotton yarn as weft yarn.By introducing water supply layer under the evaporator,carbon fiber and cotton yarn were firmly fixed by using preparation technology to prevent carbon fiber from dispersion while maintaining sufficient water supply.By combining with open-cell EPE foam,heat loss is prevented to the maximum.The evaporation rate of the carbon fiber-based double-layer fabric photothermal evaporator reaches 1.44 kg m-2 h-1,and could continuously process concentrated brine（10 wt%Na Cl solution）for 8 h and keep the evaporator surface clean.In addition,the carbon-fiber-based double-layer photothermal fabric evaporator can complete the conversion from seawater to drinking water and purify industrial waste dyes at a rate close to 100%,showing its excellent potential for practical applications.（3）Preparation of carbon fiber-based core-sheath structured photothermal fabric evaporator and its performance study.Carbon fibers were wrapped around the exterior of modal strands using a two-dimensional weaving machine to form a core-sheath structured photothermal yarn thread.The core-sheath structured photothermal yarn threads were used as warp yarns and carbon fibers were used as weft yarns for plain weaving on a loom,and the woven photothermal fabric was inserted into EPE foam in an arch shape to build a 3D structured carbon fiber-based core-sheath structured photothermal fabric evaporator.The prepared core-sheath structure photothermal yarn with core yarn strand number of 8 achieves the optimal evaporation rate(2.12 kg m-2 h-1)and salt resistance concentration（5 wt%Na Cl solution）were achieved for core sheath structure photothermal yarn with core yarn strand number 8.This photothermal fabric can be easily woven in a large scale integrated for practical outdoor photothermal desalination applications and can achieve close to 100%removal of major salt ions during the treatment of seawater,with no salt crystals precipitating on the evaporator surface and a vapor generation rate of～7.5 L m-2 day-1 under practical outdoor conditions of light for 7 consecutive days.The results show that the carbon fiber-based core sheath structured photothermal fabric evaporator opens a new path for seawater desalination and concentrated brine treatment. |
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