Preparation And Adsorption Performance Of Biomass-Based Carbon Aerogels

The reckless discharge of industrial organic dyes and domestic oil pollution is seriously damaging people’s life,health and environmental safety.Therefore,it is of great importance to develop high performance novel adsorbents for water pollution treatment.Aerogel is considered to be the lightest material,and its large internal pore structure gives it a large specific surface area and special properties,making it an ideal material in the field of wastewater treatment.In addition,spiral carbon fiber has a special three-dimensional spiral structure,high specific surface area and excellent physicochemical properties,which also has a very broad prospect in the field of pollutant adsorption and removal.In this thesis,spiral carbon fibers were introduced into aerogel to form a novel spiral carbon fiber aerogel,and its performance in the field of oil-water separation and organic dye removal was systematically discussed.The main research contents are summarized as follows:(1)Based on the natural spiral duct structure inside waste tea leaves,spiral carbon fiber aerogels(SCFAs)were prepared by sol-gel method,freeze-drying technique,and high-temperature pyrolysis carbonization.It was shown that the three-dimensional aerogel prepared by the optimum mass ratio of bulk gel to water(1:9)has a typical three-dimensional helical network structure;After carbonization at 800°C,the samples formed amorphous and graphitized carbon;The carbonation temperature has a significant effect on its contact angle,and the contact angle increases with the increase of pyrolysis temperature,with a maximum contact angle of 134°;In addition,the specific surface area analysis shows that the surface area is 18.75 m~2/g and the average pore size is 7.63nm.(2)The adsorption performance of SCFAs on hydrophobic organic solvents with different viscosities(e.g.kerosene,pump oil,n-hexane,carbon tetrachloride,etc.)was investigated by surface wettability,adsorption kinetics and cycling stability.The results show that SCFAs-800 has excellent hydrophobic properties,can rapidly adsorb organic solvents and oils,reaches adsorption equilibrium within 30seconds,has higher adsorption performance than the other types of aerogel adsorbents,and has a peak adsorption capacity of 117 g/g for carbon tetrachloride;In addition,after 70%strain and 30 cycles of testing,the SCFAs-800 samples maintain their intact structure and retain more than 85%of the initial adsorption amount after 10 adsorption-desorption cycles.(3)Spiral carbon fiber aerogel cannot be successfully applied to the removal of hydrophilic organic pollutants because of its hydrophobic nature,so it is necessary to modify it by KOH activation to make it hydrophilic;Then the adsorption performance of porous spiral carbon fiber aerogels(PSCFAs)for hydrophilic organic pollutants such as methylene blue MB was further investigated.The study showed that pore filling is the main process of organic pollutant MB adsorption by porous spiral carbon fiber aerogels,and PSCFAs1-700-60 showed excellent adsorption performance on organic pollutant MB with a maximum adsorption capacity of 476 mg/g and a removal rate of up to 99.9%;The adsorption process is more consistent with the Langmuir model(R~2=0.99956-0.99977),which is a monolayer adsorption and a heat absorption reaction,in addition,the proposed second-order model(R~2=0.9987)is more consistent with the adsorption behavior of the sample on MB.The lower the p H value,the higher the concentration of salt ions,the more obvious the competition between H~+or salt ions and MB molecules for adsorption,which is not conducive to the removal of organic pollutants MB.