Rapid Preparation And Performance Investigation Of Efficient Gel-based Solar Interface Evaporator

With the development of modern industry,the problem of shortage of fresh water resources has gradually come to the fore,and how to obtain fresh water resources has become an urgent problem to be solved.In recent years,solar interfacial photothermal vapor generation technology has shown a broad application prospect due to its high energy conversion efficiency and a series of other advantages.Starting from the solar interfacial photothermal solar generation technology,we firstly explain the background of desalination and the development of this technology,analyze the working mechanism of interfacial photothermal evaporation,introduce in detail the three main factors affecting the photothermal conversion efficiency:light absorbing materials,thermal management and water transmission,and finally introduce the materials constituting the solar interfacial photothermal solar generation system and discuss its application in depth.Based on the current development status and problems in this field,this paper presents the specific research contents and results as follows:1.The tannic acid-iron ion(TA-Fe³⁺)complex was systematically investigated as a photothermal conversion material and effective gelation factor,a preparation method without complex chemical synthesis was used to prepare solar interfacial evaporative photothermal hydrogels by mixing only polyvinyl alcohol（PVA）,agarose,Fe³⁺and TA.It was found that the TA-Fe³⁺complex has excellent photothermal conversion properties and strong gel-forming ability,and the prepared hydrogel has good plasticity and stability.The evaporation rate of this hydrogel evaporator can reach 1.875 kg·m^-2·h^-1 under the irradiation of one sun,corresponding to a conversion efficiency of 85.7%.In addition,the material has high stability in the cycle test and can be well purified for sewage as well as seawater,and the purified water can reach the standard of drinking water.The preparation of this intrinsic photothermal hydrogel provides a new way for the preparation of hydrogel-based interfacial evaporators,making them easy to prepare,eco-friendly and low-cost.2.High strength,high evaporation performance of PVA-agarose-CNT aerogel evaporators prepared by dip-coating and freeze-drying methods were systematically investigated.It was found that the crystalline PVA skeleton with excellent mechanical strength and the sparse agarose imparted excellent mechanical properties and hydrophilicity to the material,respectively,Carbon nanotubes（CNT）,a one-dimensional quantum material with a special structure,is composed of coaxial circular tubes with several to tens of layers of carbon atoms arranged in a hexagonal pattern,and has excellent mechanical,heat transfer,and optical conversion properties.The introduction of CNT on the aerogel surface substantially improves the absorption of light and gives the material excellent photothermal conversion properties.The evaporation rate and conversion efficiency of the prepared aerogel reached 1.88 kg·m^-2·h^-1 and 96.9%,respectively,while having a compressive strength of about 10 MPa at 80%strain,which exceeds the performance of many aerogel evaporators.Outdoor tests showed that the evaporation rate of the aerogel was 4.3 times higher than that of pure water,and the purified simulated seawater and organic effluent met drinking water standards.This study provides a simple method for preparing efficient,high-strength,low-cost aerogel evaporators that will have important applications in desalination and wastewater treatment.3.A porous photothermal hydrogel coating is proposed,which is rapidly prepared by mixing inexpensive raw materials such as sawdust（SD）,CNT and PVA.The crystalline PVA gives the coating a solid skeleton and the sawdust imparts a porous and loose structure to the coating,and the evaporator based on the hydrogel coating shows a fast water transport rate and efficient evaporation performance,as well as good mechanical properties and stability.The compressive stress of the wet hydrogel coating can be as high as 14.28 MPa at 80%strain.the evaporation rate of the hydrogel coating can reach 1.833 kg·m^-2·h^-1 under one sunlight intensity irradiation,corresponding to an energy conversion efficiency of 83.29%.The hydrogel coating can maintain high stability and good evaporation performance under various harsh conditions.Under outdoor conditions,the evaporation rate of the hydrogel coating-based evaporator is about 5.69 times higher than that of pure water,showing excellent evaporation performance under practical outdoor conditions.This work presents a fast,economical and scalable strategy to prepare high-performance photothermal hydrogel coatings,which will find sustainable practical applications in solar-powered water purification.