Preparation Of Biomass Porous Materials And Its Study On Photothermal Conversion Performance In Wastewater

It is of great significance to construct a solar and thermal evaporation system driven by clean,safe and renewable solar energy as an energy source,which is an efficient,sustainable and inexpensive seawater desalination method.In recent years,the research of solar energy driven interface evaporation has focused on improving the evaporation efficiency of photothermal materials,and the design of oil distribution and salt resistance dual function of photothermal materials and its application in wastewater containing organic dyes.Therefore,from the perspective of practical application,this paper through the surface modification of photothermal materials,without affecting the water transmission,photothermal materials have hydrophilic hydrophobic,so that it can operate normally and efficiently in oily wastewater,and maintain high photothermal conversion efficiency.In addition,in terms of raw material selection and preparation methods,abundant and inexpensive biomass and inorganic materials are selected as raw materials,and simple preparation methods are used to promote their application.This paper prepared three kinds of photothermal materials,and with different methods,which has superhydrophilic/hydrophobic,superhydrophilic/oil/salt resistance,and constructed the corresponding solar interface evaporator,systematically studied their solar thermal evaporation properties before and after the modification.The results not only provide useful reference for the future preparation of hydrophilic hydrophobic photothermal materials,but also provide new research ideas for the design and optimization of solar interface evaporation photothermal conversion system.The main research contents and conclusions of the paper are as follows:(1)Take wood fiber as raw material,add it to sodium alginate(SA)solution mixed evenly,then freeze-dried to form a block aerogel,then cross-linked with Ca²⁺and freeze-linked the block again,freeze-dried the material after surface carbonization,and finally soak it in a sodium perfluoroic acid(SP)/nano Zn O/anhydrous ethanol mixture solution for oil thinning modification to obtain WF-SP.The test results show that the unmodified aerogel is loose and porous(porosity is 87%),and the aperture is interleaved and formed a stable three-dimensional structure,with low density(0.346 gcm^-3),low thermal conductivity(0.561 Wm^-1K^-1)and strong water transmission capacity.After surface carbonization,the light absorption rate of the material is higher than 90%,thus having excellent light absorption performance.According by photothermal evaporation experiments in pure water systems,the evaporation rate of WF-SP at 1.0 k Wm^-2solar-irradiation conditions is 1.42 kg m^-2h^-1,with the corresponding photothermal conversion efficiency of 84%.After showing the hydrophilic hydrophobic oil modification,the contact Angle of WF-SP to n-hexadecane is 131.7°,indicating that the material has excellent oil hydrophobic properties.When WF is 1.0 k Wm^-2,in the n-cetane=25:1,the oil conversion efficiency of the material is about 74%due to the blockage of part of the pore.(2)An ultra-hydrophilic,oil-sparse and salt-resistant photothermal material(EP-SP)was prepared from the cheap and easily available expanded perlite as raw material.The test results show that the EP-SP has a porosity of about 92%,an absorbance greater than90%,and a thermal conductivity of 0.068 W/m K.Under the simulated solar irradiation test conditions of 1 k W m^-2,the evaporation efficiency of EP-SP was 1.34 kg m^-2h^-1,and the photothermal conversion efficiency was 84.8%,and showed good salt resistance.At the same time,the contact angle of EP-SP and n-hexadecane can reach more than 134.8,indicating its excellent oil hydrophobic performance.The photothermal test results showed that the photothermal conversion efficiency of EP-SP in oily wastewater reached about 84.8%under the simulated solar irradiation test conditions of 1 k Wm^-2.(3)A new solar thermal material(BC-SP)with superhydrophilic-hydrophobic oil and can adsorb organic dyes is prepared from biomass carbon.The test results showed that the prepared BC-SP porosity was about 95%,with an absorbance greater than 90%,and a thermal conductivity of 0.065W/m K.Under the simulated solar irradiation tests at 1k W m^-2,the evaporation rate of BC-SP was 1.38 kg m^-2h^-1,and the photothermal conversion efficiency was 84.8%.In addition,the contact Angle of BC-SP and n-hexadecane can reach more than 141.8,indicating its excellent oil hydrophobic performance.The photothermal test results show that the average photothermal conversion efficiency of BC-SP in oily wastewater can reach about 85.1%under the simulated solar irradiation test conditions of 1k W m^-2.At the same time,BC-SP also has good adsorption performance on the dye.At the concentration of 10 ppm,the removal rate of BC-SP on methylene blue(MB),methyl orange(MO)and Congo red(CR)are99.66%,99.28%and 99.16%,respectively.