Preparation Of Tungsten Based Photothermal Materials And Application In Water Evaporation

With the development of science and technology and the improvement of human living standards,the living environment has been seriously damaged.The solution of environmental problem is the urgent matter of human development.Among all the environmental problems,water shortage is one of the most important challenges facing mankind,which poses an increasingly serious threat to sustainable economic development and social progress.Rapid population growth,climate change and the indiscriminate discharge of industrial and domestic pollution have exacerbated the shortage of fresh water resources.Continuous population growth,climate change and the indiscriminate discharge of industrial and domestic pollution have exacerbated the shortage of fresh water.As we all know,although there are abundant water resources on earth,97%of them are sea water,but this water is not suitable for direct drinking,nor for domestic or industrial use.Therefore,it is of great significance to develop efficient and convenient water purification technology to extract fresh water from seawater,industrial wastewater and domestic sewage.The existing seawater purification technologies include thermal steam compression,reverse osmosis,multistage distillation and electrodialysis.But they all have certain shortcomings,these technologies cost a lot of money,high energy consumption,easy to pollute the environment.This is not applicable to remote areas and some poor and underdeveloped countries.Therefore,solving the contradiction between water purification efficiency and energy consumption has become an urgent problem for sustainable freshwater production.Solar driven water evaporation technology is a new,green and efficient way to solve the above problems.Solar driven water evaporation relies on photothermal materials with excellent photothermal conversion performance,but most of the existing photothermal materials still have many shortcomings,such as low photothermal conversion efficiency and poor photothermal stability.At the same time,the photothermal film used for solar driven water evaporation has the disadvantages of complex preparation,low water evaporation efficiency and high cost,which limit its application in practical life and production.In view of the above problems,this paper prepared a series of tungsten-based photothermal materials,through ion doping or hydrogen reduction to enhance the photothermal conversion performance,deposited on the surface of different hydrogel film,constructed three different water evaporator,seawater desalination and wastewater purification.The specific research content is as follows:(1)Nickel tungstate was synthesized by hydrothermal method and reduced in hydrogen/argon atmosphere to obtain tungsten nickel alloy(NiW).The photothermal film was synthesized by mixing alloy with Bing and Agar by casting method.Due to the excellent photothermal properties of NiW and the porous structure of photothermal film,NiW@Bing@Agar has better water evaporation performance.The water evaporation performance of different photothermal films in water was tested by adjusting the ratio of Agar and Bing concentration.At the same time,the photothermal membrane can also be used for seawater desalination,purification of heavy metal ion solution and purification of dye wastewater.(2)On the basis of nickel tungstate,Fe-doped and reduced in hydrogen/argon atmosphere,ternary nickel-iron-tungsten(FeNi₃@W)alloy was obtained.FeNi₃@W@PVA-PA 1.25 hydrogel photothermal film was constructed by physical stirring method.The hydrogel can realize efficient interfacial water evaporation under the irradiation of a simulated sunlight.FeNi₃@W@PVA-PA 1.25 hydrogel photothermal membrane can also remove toxic heavy metal ions and dyes from industrial wastewater by solar energy driven water evaporation technology,and has shown excellent performance in seawater desalination.On the basis of nickel tungstate,copper doping,in the hydrogen/argon mixture of its reduction treatment,to obtain ternary nickel-tungsten-Copper(Cu_0.4W_0.6@Ni₁₇W₃)alloy.The alloy was mixed with gelatin and agar to produce Cu_0.4W_0.6@Ni₁₇W₃@Gelatin@Agar photothermal film by casting method.The photothermal film not only has excellent light absorption performance,but also has stable porous structure.Cu_0.4W_0.6@Ni₁₇W₃@Gelatin-Agar photothermal film has excellent water evaporation ability,and the photothermal conversion efficiency of the film can be effectively increased by optimizing the mixing ratio of gelatin-agar.The photothermal membrane can be applied to the purification of wastewater containing heavy metal ions or dyes and seawater purification.In addition,in the process of seawater desalination,the photothermal film has good salt resistance,which proves that it has great application potential in seawater desalination.