Synthesis Of Porous Polymer Foam And Their Solar Interface Evaporation Performance

Water is an important fundamental substance of human life and development.However,with the rapid growth of the world's population and the improvement of modern industrialization,water pollution problem becomes serious increasingly.Human is facing a serious shortage of fresh water resources.Cost efficient desalination of seawater using clean energy has become the preferred way to obtain fresh water.Solar desalination technology can not only use green energy to produce clean water,but also alleviate the shortage of fossil energy.Solar interface steam generation does not need to heat the whole water,only uses solar energy to heat the water surface to produce steam through evaporator,which greatly improves the steam conversion efficiency.It is a big step forward and a research hotspot in solar steam generation.The design of evaporator is the basis and key problem of solar interface evaporation system.A wide range of photothermal materials have been created,including plasmonic metal,carbon-based materials,organic polymer materials,natural materials,hydrogels and so on.Great efforts have been made and significant progress has been achieved in the past few years.However,most of the evaporator materials have the disadvantages of high cost and poor stability,the salt in seawater may deposit on the surface of the evaporator,resulting in greatly reduced efficiency and even loss of desalination ability.So,the design and preparation of evaporators with low cost,excellent photothermal performance,good salt resistance and processability will be the research focus in the field of solar desalination in the future.In view of the problems of complex preparation process,high cost,poor energy conversion efficiency and salt resistance of existing evaporator materials.The subject takes cheap bulk chemicals as raw materials to prepare a series of organic porous polymer foams with low apparent density and thermal conductivity,using a simple one-pot synthesis or modification process.By adjusting the pore property,surface wetting property and optical absorption property of the foam materials,to achieve the coordination and enhancement of light absorption,water transport,heat insulation,light heat conversion and salt resistance.It provides high-performance and low-cost photo thermal conversion materials for solar desalination and industrial wastewater treatment,and provides new design ideas for large-scale production of evaporator.The main contents and conclusions are as follows:(1)The cross-linking monolithic ploymer porous foam was prepared based on cross-linked aromatic polymer(PDVB-PS)using styrene as monomer and divinylbenzene as cross-linking agent through a facile one-step hydrothermal method.The PDVB-PS foam possesses well-controlled porous structure,low apparent density and low thermal conductivity(0.038 W·m^-1·k^-1).After modification with sodium alginate and polypyrrole,the as-modified PDVB-PS(named as PPy-M-PDVB-PS)shows a superhydrophilic wettability(water contact angle?0°)and stronger light absorption(ca.90%).A high solar-vapor conversion efficiency of 87.6%for the PPy-M-PDVB-PS was obtained under 1-sun irradiation.(2)The superhydrophilic polymer porous foam(VMP)as salt-resistant photothermal materials,which was synthesized through a one-step hydrothermal method using styrene and 1-vinyl-3-ethylimidazolium tetrafluoroborate as monomers and N,N-methylenebisacrylamide as the cross-linking agent.The as-resulted VMP shows excellent mechanical properties,well-controlled porous structure(porosity is 73.81%),inherent low density and extremely low thermal conductivity(0.032 W·m^-1·K^-1),the PPy-VMP exhibits an excellent solar evaporation property,and the solar photothermal efficiency can reach more than88.3%under 1 k W m^-2 irradiation.Moreover,the introduction of ionic liquid moiety into VMP results in its interesting superhydrophilic wettability,which can accelerate water transportation and replenish the vaporized brine on the surface to prevent salt from adhering.(3)The superhydrophilic polymer porous foam(HPSS)was synthesized through a one-step hydrothermal method using sodium styrene sulfonate as monomer and N,N-methylenebisacrylamide as the cross-linking agent.Then Fe₃O₄ particles were in situ grown on the surface of HPSS,later the polypyrrole was polymerized on its surface by liquid-phase interfacial reaction to structure the binary light absorbing layer.HPSS/Fe₃O₄/PPy acts as interface evaporator,which has stronger photothermal conversion effect and stability compared with single absorption layer(HPSS/PPy).The solar photothermal efficiency of HPSS/Fe₃O₄/PPy can reach more than 94.7%under 1 sun irradiation.In the simulated seawater and high concentration salt solution,the stability of photothermal steam generation is still maintained.In addition,due to the magnetic property of HPSS/Fe₃O₄/PPy,the evaporator is easy to locate and recycle in practical application.(4)Black polyethylene foamed cotton(EPE-1)was used as raw material,it was modified by a mixed oxidation system composed of concentrated sulfuric acid,phosphorus pentoxide and potassium persulfate.The modified foam(M-EPE)keeps the mechanical properties and low thermal conductivity of the EPE-1.At the same time,it also exhibits superhydrophilic surface and the stronger absorption capability.When it was used as evaporator in solar driven interface evaporation system,the solar evaporation property of M-EPE influenced by foam thickness,pore size and pore type.The results show that:the inclined hole foam with thickness of 5 mm and aperture of 0.5 mm has the best evaporation performance.The solar photothermal efficiency of M-EPE-5 can reach more than93.8%under 1 sun irradiation.