Preparation Of Nanocellulose Aerogel And Study On Interfacial Water Evaporation Performance

Although the total amount of water resources in the world is very large,there are few fresh water resources for human society to survive and develop.Seawater desalination is an effective way to obtain fresh water resources.The traditional seawater desalination field requires complex and expensive equipment and consumes a lot of energy in the working process.Therefore,the effective use of clean and safe energy will be the top priority in the future development.Solar energy is a kind of clean renewable energy,inexhaustible,inexhaustible.Using solar energy to desalinize seawater is a green and sustainable strategy to obtain clean fresh water resources.So Solar Evaporator SE has been extensively studied.SE with material economy and stable structure has more practical application value.Therefore,in this paper,nanocellulose aerogel SE was prepared from two aspects of material and structure,and its photothermal properties were studied.（1）In this paper,carboxylated cellulose nanofibers（CNFs）were prepared by the TEMPO oxidation method,and graphene oxide（GO）was prepared from graphite by a modified Hummers oxidation method,and GO was reduced to reduced graphene oxide（RGO）.A hydrophilic and porous CNF aerogel was prepared from CNF as the base material,and the carbon-based material reduced graphene oxide was selected as the photothermal conversion material.The CNF/RGO aerogel obtained by gelation and further processing is used as SE,and the CNF aerogel prepared by ion crosslinking has a certain mechanical strength,which prevents the aerogel structure from being damaged by water molecules.The photothermal performance was studied,and the study showed that the evaporation performance of 3wt%CNF aerogel was the best,and the evaporation rate could reach 1.89 kg·m^-2·h^-1under the condition of 1sunlight intensity.（2）In order to further improve the mechanical strength and water resistance of CNF aerogel,it is reinforced by adding polyvinyl alcohol（PVA）,and the aerogel is modified by cross-linking with butane tetracarboxylic acid as a cross-linking agent.Chemically cross-linked CNF/PVA/RGO（CPR）aerogels were prepared as SE.The evaporation performance of aerogels with different contents of CNF,PVA and GO was explored.The study showed that with the increase of CNF content and the decrease of the amount of PVA,the evaporation performance was improved.When the GO concentration was 2mg/m L,the CPR evaporation rate is the highest,reaching an average rate 2.25kg·m^-2·h^-1under 1 sunlight illumination condition,and absorbs energy from the environ-ment during the evaporation process,and the evaporation efficiency exceeds 100%.Moreover,the aerogel has excellent salt resistance,and the evaporation performance remains basically unchanged after continuous work in a 20%high-concentration Na Cl solution for 12 hours.In addition,axial freezing and radial freezing were performed in liquid nitrogen environment to prepare SEs with two different orientation structures,respectively,and their salt resistance properties were studied.The results show that different freezing methods have different locations of salt deposition.At the same time,the two orientation structures have improved mechanical strength and stability.