Preparation And Application Of Biomass Carbon-based Photothermal Materials

The solar thermal driven water evaporation system uses green,stable and sustainable sunlight as the energy source.The photothermal conversion material absorbs sunlight and converts it into heat energy,so that the water temperature inside the material rises to produce low-temperature steam.In sea water desalination,sewage treatment,sterilization and hydropower co-generation,solar thermal driven water evaporation systems have broad application prospects.The materials in the high-efficiency light-heat-driven water evaporation system should have the characteristics of high light absorption,hydrophilic porous structure and high heat utilization,and should also be suitable for a variety of liquid treatments.In order to obtain efficient,stable and multifunctional photothermal conversion materials,we prepared sulfuric acid hydrothermally carbonized sugarcane and chitosan（CS）/polyurethane（PU）dual network aerogels,and studied the effect of interface evaporation area on photothermal conversion.The research results are as follows:The sugarcane with abundant yield is selected as the biomass carbon source,and the porous biomass carbon material is prepared by the hydrothermal carbonization method.The carbonized sugarcane prepared by the hydrothermal method in 2 M sulfuric acid solution has a multi-level microscopic morphology,a large number of micron-sized carbon balls are attached to the thin-walled cell wall,and the absorptance in the range of 200-2500 nm reaches 95.36%.At the same time,sulfuric acid hydrothermally carbonized sugarcane has abundant hydrophilic groups with a contact angle of 0°.The evaporation rate is 2.32 kg m^-2h^-1 under 1 sun,and the heat utilization rate reaches 95%.Sulfuric acid hydrothermally carbonized sugarcane has a good desalination ability for ordinary concentration of seawater.The ion removal rate of Na⁺,K⁺,Ca²⁺and Mg²⁺reaches 99.9%.The produced fresh water meets the standards of the World Health Organization.At the same time,the adsorption capacity for methyl orange under light is 29.57 mg g^-1,which can work stably in strong acid,strong alkali and dye wastewater.It also has an average evaporation rate of 1.66 kg m^-2 h^-1in a closed outdoor condensate collection device.Using waste bagasse produced in the sugar industry as a biomass carbon source,a carbon-based light-absorbing material was prepared by a high-temperature pyrolysis method,and the carbonized bagasse was added to the CS/PU sponge-based aerogel.The effect of carbonization temperature on the composition of bagasse was explored.When the pyrolysis temperature is 500°C,cellulose and lignin were almost completely decomposed.The addition amount of carbonized bagasse will also affect the evaporation performance of the aerogel.When the addition amount is 1%,CB500/CS/PU aerogel has the best photothermal conversion performance,and the light absorption rate in the wavelength range of 200-2500nm is 98.2%.The evaporation rate is 2.04 kg m^-2 h^-1 under 1sun.In addition,PU sponge-based aerogel can also be applied to ordinary seawater desalination and alkaline wastewater treatment,and has strong evaporation stability.The area of the evaporation interface has a huge impact on the evaporation performance of light and hot water.As the ratio of the evaporation area on the side of the sample to the projected area（side/projection）increases,the water evaporation rate increases.The side/projection ratio increases,the moisture inside the sample is more easily transported to the evaporation interface,and the evaporation speed is faster.The heat of photothermal conversion is used by the water evaporation phase change process,and the surface temperature of the sample is lower,which makes less convection and radiation loss between the sample and the air.