Application Of Photothermal Effect Of Carbon-based Materials In Water Treatment

Solar steam generation,as one of the most promising and sustainable methods to solve the global water shortage,has become more and more prominent.Using solar steam generation for desalination and wastewater treatment has great advantages in obtaining clean water.As the key of solar steam generation system,photothermal conversion materials have attracted great attention of researchers.Carbon based materials,including graphene based materials and biomass carbon materials,are the focus of current research due to their high solar energy absorption,low cost and easy to expand structure.In this paper,photothermal conversion materials were prepared by simple methods,and their performance in water treatment was studied.The main results are as follows:(1)The porous graphene composite foam was obtained by high temperature thermal reduction with a nickel foam as the substrate and uniformly coated with graphene oxide aqueous solution.The composite foam combines the broad spectrum absorption characteristics of reduced graphene oxide and the porous structure advantage of nickel foam,which can absorb about 89%solar energy effectively.Compared with the dense reduced graphene oxide film,the porous structure of the composite foam is more favorable for light harvesting.Moreover,the porous structure provides a channel for the overflow of steam,which is conducive to the improvement of water evaporation performance.Under one sun irradiation,the evaporation rate of water reaches 1.33 kg m^-2h^-1,and the solar steam conversion efficiency reaches83.4%.(2)A porous and super-hydrophilic photothermal film was prepared by using towel-gourd sponges as carbon source and self-assembled carbon film at the gas-liquid interface by constant volume injection method.The carbon film was transferred to the surface of commercial printing paper by capillary assisted transfer strategy.Under one sun irradiation,the evaporation rate of photothermal film was1.53 kg m^-2h^-1,and the evaporation efficiency was 95.9%.The excellent water evaporation performance of the sample makes it have good application in seawater desalination and wastewater treatment.(3)The feasibility of using concentrated acid dehydration method to prepare biomass carbon materials for solar steam generation was explored.Using fallen leaves as carbon source,carbon materials were prepared by concentrated acid dehydration method,and uniformly deposited on the surface of mixed cellulose ester membrane by vacuum filtration method.The mechanical stability and hydrophilicity of the photothermal film were improved by polyvinyl alcohol modification and oxygen plasma treatment.The photothermal conversion material 80FLPD6-MCEPO₂ was prepared to meet the needs of practical application.The porous carbon prepared by sulfuric acid dehydration method has high specific surface area and porosity,which is conducive to the escape of water vapor.The problem of salt accumulation on the evaporator surface is solved by adjusting the water transfer rate to match the input energy,and the high efficiency and stability of the evaporator are improved.Under one sun irradiation,the evaporation rate of photothermal film was 1.355 kg m^-2h^-1,and the evaporation efficiency was 85.1%.