Preparation Of Polymer-based Photothermal Fabric And Study On Its Interface Photothermal-steam Conversion Performance

The rapid population growth and the massive discharge of domestic and industrial wastewater make the shortage of freshwater resources a global problem that needs to be solved urgently.The interface photothermal-steam conversion technology is one of the effective ways to solve this problem because of its simple,high-efficiency,low-cost,green and pollution-free characteristics.The conventional interface photothermal water evaporation system is mainly composed of photo-thermal materials and substrates.Among them,polydopamine,polypyrrole and other polymers have the advantages of being easy to bond with the substrate,good light absorption performance,biodegradability,etc.,and are regarded as potential light-absorbing materials;while the fibrous fabric substrate has high porosity and large specific surface area,soft and portable,changeable fabric structure,can be recycled,which is conducive to the escape of steam and water transmission during evaporation.Therefore,combining the advantages of the two can well solve the shortcomings of traditional evaporators such as complicated preparation methods,limited size and poor washability.In this thesis,the blended fabric is used as the substrate,and the fabric-based evaporator with excellent performance,flexibility and expandability is prepared by adjusting the micro-morphology of the polymer material and the macro-micro structure design of the entire evaporation device.The specific research is as follows:Firstly,the washable and corrosion-resistant high-elastic polyester/spandex blended fabric was used as the substrate,and polydopamine nanospheres（PDANSs）were grown on the surface of the fabric fiber by in-situ polymerization of dopamine,and the size of nanospheres was adjusted to prepare a multi-size polydopamine nanosphere-based two-dimensional photothermal fabric（PDANSs@fabric）.By characterizing the morphology,particle size,chemical composition of PDANSs@fabric,as well as testing its air permeability,hydrophilicity,photothermal,water evaporation and durability,the effect of the size of PDANSs on the performance of photothermal fabrics was studied.And explored the ability of the fabric-based evaporator to treat wastewater and seawater.The results show that as the size of PDANSs increases,the photothermal effect of the photothermal fabric first increases and then decreases.Under a single sunlight,the water evaporation rate of PDANSs@fabric with a spherical diameter of 650 nm is 1.48 kg m^-2 h^-1.Secondly,in order to further improve the light absorption capacity of the material in the infrared region,on the same fabric substrate mentioned above,by controlling the concentration of the methyl orange template,a polypyrrole nanowire array-based photothermal fabric（VPPy NWs-fabric）with efficient light absorption in the full spectrum range was prepared.Characterized the microscopic morphology and chemical composition of VPPy NWs-fabric,and explored its air permeability,hydrophilicity,photothermal,water evaporation and stability properties.The results show that the polypyrrole nanowire array structure can improve the light absorption of the material,and the light absorption rate is 97%in the range of 300-2500 nm.Under a single sunlight,the water evaporation rate of the polypyrrole array-based 2D photothermal fabric is up to 1.70 kg m^-2 h^-1.Finally,using the editable properties of the fabric,the two-dimensional polypyrrole array-based photothermal fabric prepared above is cut and sewn into a 3D cone（bionic）photothermal evaporator with different height-to-radius ratios.The effect of the height-to-radius ratio of the evaporator on its photothermal and water evaporation performance was studied,and the stability of the evaporator under the optimal parameters and its wastewater treatment and desalination capabilities were investigated.In addition,the mechanism of improving the steam conversion efficiency was analyzed.The results show that the optimal height-to-radius ratio of the evaporator is 3.Under a single sunlight,the water evaporation rate of the 3D photothermal fabric is as high as 2.32 kg m^-2 h^-1,and the evaporation mechanism is that the 3D evaporator can capture additional energy from the surrounding air,water,and recovered latent heat to promote water evaporation.