Solar Water Evaporation Properties Of Carbon-based Nanofluids And Interface Materials

The fossil energy crisis,lack of fresh water resources,and increased water pollution are challenges to the world today.Application of solar water evaporation in seawater desalination and sewage treatment has the great advantage of saving energy and reducing pollution.Solar water evaporation uses light-to-heat conversion materials to convert light energy into heat energy and heat the water to evaporate it.Therefore,solar energy absorption/photothermal conversion,efficient use of heat energy,and sufficient water transportation are the keys to solar water evaporation systems.At present,solar water evaporation systems that are research hotspots mainly include volumetric evaporation systems that use nanofluids as absorbers,and interface evaporation systems that use photothermal materials floating on the water interface as absorbers.In this thesis,ATO@C?amorphous carbon-coated ATO nanoparticles?water-based nanofluid and ATO/C foam interfacial light-to-heat conversion material were prepared using antimony-doped tin oxide?ATO?aqueous nanofluids and glucose as raw materials.The performance of the volumetric evaporation system and interface evaporation system was studied.The results are as follows:1.Glucose and ATO were mixed in a certain ratio and placed in a 200?oven for hydrothermal treatment for 4 hours to obtain ATO@C aqueous nanofluids.The nanoparticles are spherical core@shell structures formed by wrapping a carbon shell on the surface of ATO nanoparticles.The particle has high stability and the size is20-30 nm.ATO@C nanofluids combine the absorption advantages of C in the visible region and ATO in the near infrared region.As the mass fraction increases,the solar absorption and light-to-heat conversion efficiency of the nanofluid increase.The nanofluid of 0.3wt%can absorb 99.9%of sunlight,and the light-to-heat conversion efficiency is 97.8%.Increasing the optical concentration can significantly enhance the evaporation rate of the nanofluids,but the water evaporation efficiency decreases instead.At one sun illumination,the water evaporation efficiency of the ATO@C nanofluids with a height of 5 cm is 45.9%.As the height of the nanofluid decreases,the heat loss decreases.The water evaporation efficiency of the nanofluids with a height of 1 cm is 92.9%.Since the penetration of sunlight decreases with the increase of the mass fraction,water evaporation of nanofluids can be regarded as interface evaporation with a thickness of 1 cm,which caused the thinking of the interface solar evaporator.2.ATO/C foam light-to-heat conversion material was prepared by a self-foaming method using glucose(C₆H₁₂O₆)as the carbon source and adding ATO.The ATO/C foam is mainly composed of amorphous carbon and ATO and the carbon content is greater than 70%.The foam has a broad band absorption characteristic in the solar spectral range.The porous structure allows the sample to float on the water surface,and promotes light absorption and water transport,which is conducive to enhancing water evaporation.The ATO/C foam contains C=O,OH and other groups,and has good hydrophilicity.In the case of adding an insulating layer,the water evaporation rate of ATO/C foam is 1.53 kg·m^-2·h^-1,and the evaporation efficiency is 96%.As the light intensity increases,the evaporation rate of the sample increases,but the evaporation efficiency decreases.The sample not only has excellent water evaporation performance,but also has good applications in seawater desalination and organic wastewater treatment.The condensate obtained by ATO/C foam treatment meets the national drinking water standard.