Preparation Of 3D Wood Photothermal Conversion Device And Its Enhancement Of Seawater Desalination

The shortage of fresh water resources has become increasingly prominent,and desalination has become an effective method to alleviate the crisis of fresh water resources shortage.Solar interface light-to-heat conversion technology has high potential for development in the field of seawater desalination due to its high energy conversion efficiency.The fabrication of interfacial light-to-heat conversion devices using natural renewable wood is an important means to realize the low cost and sustainability of the technology,but the low evaporation efficiency of wood-based devices limits its large-scale application.In order to improve the evaporation performance of wood structure devices and broaden the field of wood in seawater desalination,this study prepared three kinds of tannic acid/iron complex wood photothermal conversion devices with different structures by chemical modification and structural design,using bio-derived tannic acid as light absorbing material and delignification wood as base material.The main research contents and conclusions are as follows:（1）Construction of photothermal conversion wood with three-dimensional structure.By treating poplar veneer with sodium hydroxide（Na OH）and sodium sulfite（Na₂SO₃）,delignification wood was obtained.Three kinds of V-shaped,conical and flower-shaped tannic acid/iron complex wood evaporation devices were designed and fabricated successfully by means of cutting and loading tannic acid complex.By optimizing the solution concentration ratio and device Angle of tannic acid/iron complex photothermal conversion device,the optimal experimental parameters are as follows:tannic acid/iron complex concentration of 4%,V-shaped device Angle of 40°.Under these conditions,the wood photothermal conversion device has high performance of seawater evaporation.（2）Formation mechanism of 3D structure photothermal conversion wood.Through the analysis of microstructure,wood-TA-Fe³⁺maintained the pore structure of wood after chemical modification and had capillary action.Chemical composition analysis and contact Angle test confirmed that alkaline sodium sulfite treatment successfully removed part of the lignin in wood,effectively improve the hydrophilicity and flexibility,providing a basis for three-dimensional structure shaping.At the same time,the absorption rate of tannic acid/iron complex wood was more than 90%in the wavelength range of 200nm to 800 nm.The absorption capacity of tannic acid/iron complex wood was significantly higher than that of untreated wood,and the surface temperature was about 16℃higher at one solar intensity.The reason is mainly due to the complexation of tannic acid and iron ion,forming d-d transition to promote light absorption.In addition,together with the internal porous structure of wood itself,tannic acid/iron complex wood has excellent thermal management ability.（3）Seawater evaporation and desalination properties of 3D structure photothermal conversion wood.The evaporation and desalination performance of three kinds of photothermal devices were tested under one solar illumination intensity.The evaporation rate and photothermal conversion efficiency of V-shaped evaporation devices reached 2.52 kg m^-2 h^-1 and 101.4%,respectively.The evaporation rate of conical evaporator can reach 1.79 kg m^-2 h^-1,about 1.6 times that of 2D evaporator,and the photothermal conversion efficiency reaches 109%.The special structure of tannic acid/iron complex wood plant photothermal evaporation device has an excellent evaporation rate of 1.98 kg m^-2 h^-1 and ultra-high photothermal conversion efficiency of 116%,exceeding the limit value of photothermal conversion efficiency.At the same time,in the cyclic stability test,the three kinds of photothermal conversion devices show outstanding stability.In addition,the main concentration of metal ions(Na⁺,Mg²⁺,K⁺,Ca²⁺)in seawater after desalination meets the drinking water standards stipulated by the World Health Organization,showing excellent desalination performance.The preparation conditions of 3D wood photothermal conversion devices are simple and mild,which provides a new way for wood based interfacial evaporation.