| At present,the shortage of fresh water resources has become a global problem.Seawater desalination is one of the important methods to solve this problem.A variety of seawater desalination technologies have been developed today,but there are some problems in actual production that make it difficult to apply further.As a new type of desalination technology,solar seawater desalination can effectively avoid the problems caused by traditional methods,and is considered to be one of the future development directions of seawater desalination technology.Among them,the development of photothermal film is the research focus of solar seawater desalination technology.Researchers have developed a variety of l photothermal films(such as titanium dioxide nanoparticles,graphene,etc.).The l photothermal film floats on the water surface,which greatly improves the rate of water evaporation.In order to further improve the heat utilization efficiency,people have developed a composite structure of photothermal film,such as double aerogel.However,during the process of water evaporation,salt is easily deposited on the upper surface of the film,which reduces the efficiency.Direct contact of the lower surface of the film with water will also cause considerable heat loss.In order to solve this problem,based on polypyrrole and silver oxide photothermal materials,a photothermal conversion film was prepared.I have developed an indirect-contact evaporation device by hanging the photothermal film in the air and the two ends of the film are immersed in water.It can efficiently evaporate seawater and avoid depositing salt particles on its surface.The main work contents are as follows:(1)(1)Polypyrrole photothermal cotton used for solar water desalinationFirst,disperse ammonium persulfate solution and pyrrole solution with good dispersibility,then immerse the hydrophilic cotton cloth in the ammonium persulfate solution,take out the cotton cloth,add the pyrrole solution uniformly on the cotton cloth,and then react at low temperature A photothermal film uniformly coated with polypyrrole(PPy)is obtained.Cotton-PPy has good hydrophilicity and can transport water efficiently.The film has strong spectral absorption capacity and can absorb ~ 96.97% of sunlight.Under simulated sunlight,the Cotton-PPy photothermal film can quickly rise from 25 ? to 70.1 ? in 150 s,which is higher than the temperature increase of the blank cotton cloth(31.6 ?)under the same conditions.Cotton-PPy photothermal film was used to construct a suspended indirect contact evaporation device.Under simulated sunlight(1.0 k W m-2),the water evaporation rate reached 1.939 kg m-2 h-1.During the evaporation process,water will flow down the cotton cloth to collect at the lowest point of the cotton cloth,and the water will take away the salt on the surface of the cotton cloth to avoid the deposition of salt particles.After repeating the evaporation operation more than 20 times,the surface structure,light absorption capacity and water evaporation rate of the film remained stable,showing excellent cycle stability.The Cotton-PPy photothermal film developed in this paper is low in cost and extremely easy to clean,and has great application potential in the application of seawater desalination.(2)Silver oxide photothermal cotton used for solar water desalinationUsing redox reaction,equipped with silver nitrate solution and sodium borohydride solution,the silver nitrate solution was evenly added dropwise on the surface of cotton cloth soaked with sodium borohydride solution to obtain light and heat uniformly coated with silver oxide(Ag2O)film.At the same time,the silver oxide thermal cotton(Cotton-Ag2O)exhibits a broad spectrum absorption,which can absorb ~ 84.96% of sunlight.Cotton-Ag2 O photothermal film was used to construct a suspended indirect contact evaporation device.Under simulated sunlight(1.0 k W m-2),the water evaporation rate reached 1.874 kg m-2 h-1.When light and heat evaporate,the water flows along the cotton cloth to drip at the lowest part of the cotton cloth for collection.The flow of water prevents the salt particles from depositing on the membrane surface.The film after repeated operations still maintains the original structure and water evaporation performance,and is still stable after repeated 20 times.Cotton-Ag2 O photothermal film developed in this paper is low in cost and easy to wash,and has great application prospects in the application of seawater desalination. |
PDF Full Text Request