Preparation Of Janus Carbon Nanotube Coated Fabric And Study On Its Solar Water Evaporation Performance

In the context of the shortage of fresh water resources in the world,people use the rich seawater resources to obtain fresh water.However,the traditional seawater desalination technology has high energy consumption and complex equipment,which is not conducive to sustainable development.Therefore,it is necessary to seek new and simple water purification technology to reduce the loss of non-renewable energy.And solar seawater desalination technology is an emerging and potential solution at present.Owing to directly using solar energy to evaporate seawater,the technology is efficient,clean and environmentally friendly by using photothermal conversion materials to generate fresh water.In this paper,carbon nanotubes(CNTs)with wide spectrum absorption properties were used as photothermal conversion materials.The carbon nanotube coating was constructed on non-woven cotton by self-assembly method,and a stable light absorption layer was formed under the action of hydrogen bond.The Janus carbon nanotube coated fabric with asymmetric wettability was prepared by hydrophobic finishing on one side of the fabric by patterned spraying method.It improves the water transport performance of coated fabrics and realizes efficient solar water evaporation,which provides a new direction for exploring excellent photothermal evaporation materials.The research contents and methods of this paper mainly include the following four aspects:(1)Under the capillary induction of fiber,carbon nanotube coated fabric was successfully prepared by layer-by-layer self-assembly scheme.At the same time,the spectral absorption capacity of the fabric was characterized and analyzed to explore the effect of the number of self-assembly layers on the spectral absorption performance of the coated fabric.The experimental results showed that the carbon nanotubes were aligned on the fiber.In the wide spectral range of250?2500 nm,the light absorption of the five-layer carbon nanotube coated fabric is as high as94.5%,which proves that the fabric has excellent spectral absorption performance.(2)In the interface water evaporation system,the"skin core"structure was used to optimize the heat management and water transportation during water evaporation,so as to reduce the heat loss on the fabric surface during evaporation.Under the simulated light source,the water evaporation rate of carbon nanotube coated fabrics with different self-assembly layers was measured,the solar thermal conversion efficiency was calculated,and the water evaporation performance of coated fabrics was analyzed.Under one sun illumination(1 k W/m~2),the water evaporation rate of 5-layer carbon nanotube coated fabric is 1.63 kg·m^-2·h^-1,and the photothermal conversion efficiency is 83.3%.The effect of different light intensities on the water evaporation rate of carbon nanotube coated fabric was investigated by calibrating the light intensity with an optical power meter.Under two suns illumination,the water evaporation rate increases to 2.12kg·m^-2·h^-1.(3)Janus photothermal conversion fabric was prepared by setting the ratio gradient of hydrophobic area of 5%,10%,20%,30%and 40%.Single-side hydrophobic finishing of carbon nanotube coated fabric was accomplished by template masking method.According to the analysis of water contact angle,the contact angle of the hydrophobic surface is 127.2°,while the reverse side still maintain strong hydrophilicity.The water transport capacity of Janus photothermal conversion fabric was tested by dynamic water moisture management system,and the effects of different hydrophobic area ratios on the water transport performance of the fabric were studied.The experimental results showed that the optimal area ratio is 10%.At the same time,the water evaporation rate and photothermal conversion efficiency of Janus fabric are 1.78 kg·m^-2·h^-1 and90.2%respectively,and the solar water evaporation effect is significantly improved.(4)A portable seawater desalination device was designed to test the water evaporation performance of Janus photothermal conversion fabric in simulated seawater,analyze the purified water quality and evaluate its seawater desalination effect.The conductivity of water measured by conductivity meter decreased from 55.2 m S/cm to 52.3?S/cm,reaching the conductivity standard of natural drinking water,which proves that the Janus fabric has excellent solar seawater purification potential.