| The shortage of freshwater resources has become one of the most pressing global challenges,especially in densely populated cities and resource-poor rural areas.To solve this problem,many methods of seawater desalination and wastewater purification have been developed and improved.Among them,solar energy as a green and sustainable renewable energy source,has received more and more attention in recent years.The development of efficient photothermal conversion materials and proper design of structure,which can absorb light energy and convert it into heat energy for water desalination and purification,is an effective way to alleviate the global freshwater crisis.In this work,the cotton fabric(CF)was used as the base material,the impurities on the surface of the cotton fabric are first removed by pretreatment and the surface is etched to increase the specific surface area,and then the treated cotton fabric is immersed in the dispersed carboxylated multi-walled carbon nanotubes(MWCNTs-COOH)solution.Under the conditions of high temperature and high pressure,the carboxylated multi-walled carbon nanotubes are uniformly deposited on the surface of the fiber,thereby preparing the MWCNTs-COOH/CF photothermal conversion material with good absorbance and photothermal effect.Then,a jellyfish-type solar photothermal evaporator for seawater desalination was designed through the structure of the bionic jellyfish.The MWCNTs-COOH/CF photothermal material was used as the main body of the jellyfish for photothermal evaporation,and the hydrophilic cotton yarns(CYs)as tentacles to transport water to the top of the main evaporation layer.This design separates the evaporation layer from the main water,effectively suppresses the heat loss and improves the evaporation efficiency.Scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS),moisture management tester(MMT)and other test methods were used to observe and characterize the structure and performance of the prepared MWCNTs-COOH/CF photothermal conversion material.The research results show that in the 6.67 g/L MWCNTs-COOH solution,the MWCNTs-COOH/CF photothermal conversion material prepared after high temperature and high-pressure treatment can achieve 90.84% optical absorption in the wavelength range of 300~2500 nm,and its evaporation rate is 1.18 kg m-2 h-1 under 1 sun radiation intensity.It is expected to provide a new solution for the acquisition of fresh water in practical applications.In order to reduce production costs and achieve large-scale commercial applications,dopamine-modified boron nitride(BN-PDA)is used later in this paper to replace part of carboxylated multi-walled carbon nanotubes.Using the potential difference between modified boron nitride and carboxylated multi-walled carbon nanotubes in different p H solutions,an attempt was made to prepare MWCNTs-COOH/BN-PDA/CF photothermal conversion materials using self-assembly method at room temperature instead of the previous high temperature and high-pressure method.Moreover,the solar photothermal evaporator is different from the previous one in that it uses polystyrene(PS)foam as a support and insulation material,and explores its application in the field of wastewater purification.Through the structure observation and performance characterization of fabrics assembled with different layers,it is found that as the number of assembled layers increases,the absorbance and thermal conductivity of MWCNTs-COOH/BN-PDA/CF fabrics continue to increase.The 10-layer composite fabric can achieve 93.50% optical absorption in the wavelength of 300~2500 nm,and the thermal conductivity can reach 123.88% of the original fabric;In terms of evaporation rate and photothermal conversion efficiency,the 10-layer composite fabric can reach 1.55 kg m-2 h-1 and 83.66% under 1 sun radiation intensity.Furthermore,the results of MMT,stress-strain test and cycle capability test show that the multilayer structured composite fabric has good moisture management,tensile strength and robustness.In this paper,two fabric-based photothermal conversion materials were successfully prepared and showed good photothermal conversion effects in outdoor tests.They are expected to be promissing candidates to solve the shortage of fresh water in remote,off-grid or water-polluted areas. |
PDF Full Text Request